RU2827439C1 - Cross-component adaptive loop filtering for video encoding - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: invention relates to image processing. Result is achieved by the fact that by generating a plurality of syntax elements related to an adaptive loop filter (ALF), image header records for the CCALF are introduced, which determine common CCALF data, and all slices can then inherit this common information. Said plurality of syntax elements related to ALF comprises a first syntax element which indicates whether an adaptive ALF loop filter is enabled at the sequence level, and first syntax element is signalled at sequence parameter set (SPS) level, and a second syntax element which indicates whether an inter-component adaptive loop filter is enabled at the sequence level, and the second syntax element is signalled at the SPS level.

EFFECT: improved inter-component adaptive contour filtering and syntax elements for cross-component adaptive loop filter (CCALF).

19 cl, 21 dwg, 1 tbl

Description

FIELD OF TECHNOLOGY TO WHICH THE INVENTION RELATES

Embodiments of the present application (disclosure) generally relate to the field of image processing and, more particularly, to a cross-component adaptive loop filter (CC-ALF) as an in-loop filter or as a post-loop filter and a high-level syntax for cross-component ALF (CCALF).

LEVEL OF TECHNOLOGY

Image coding (encoding and decoding) is used in a wide range of digital imaging applications, such as digital broadcast television, video transmission over the Internet and mobile networks, real-time conversation applications such as video chat, video conferencing, DVD and Blu-ray discs, video content acquisition and editing systems, and video cameras in security applications.

Since the development of the block-based hybrid approach to video coding in the H.261 standard in 1990, new video coding techniques and tools have been developed that form the basis of new video coding standards. One of the goals of most video coding standards has been to achieve a reduction in bit rate compared to its predecessor without sacrificing image quality. Other video coding standards include MPEG-1 video, MPEG-2 video, ITU-T H.262/MPEG-2, ITU-T H.263, ITU-T H.264/MPEG-4 Part 10, Advanced Video Coding (AVC), ITU-T H.265, High Efficiency Video Coding (HEVC), ITU-T H.266/Versatile Video Coding (VVC), and extensions such as scalable and/or three-dimensional (3D) extensions to these standards.

Block-based image coding schemes have in common that edge artifacts may appear along the edges of the blocks. These artifacts arise due to the independent coding of the coding blocks. These edge artifacts are often easily visible to the user. The goal of block-based image coding is to reduce edge artifacts below a visibility threshold. This is done by performing edge filtering such as deblocking filter, SAO, and adaptive loop filter (ALF). The order of the filtering process is deblocking filter, then SAO, and then ALF. In addition, a cross-component adaptive loop filter (CC-ALF) is additionally used.

Specifically for the cross-component adaptive loop filter (CC-ALF), the luma sample values are used to refine each chroma component. The process must be performed on both the Cb and Cr components, cross-component adaptive loop filtering can be computationally expensive and therefore can add additional pipeline latency, especially for hardware implementations.

ESSENCE OF THE INVENTION

In view of the above-mentioned problems, the present disclosure is directed to improving inter-component adaptive loop filtering and syntax elements for CCALF. The present disclosure may, among other things, relate to the problem of providing a device, encoder, decoder and related methods that can perform inter-component adaptive loop filtering with reduced signaling overhead, in particular, the slice header overhead (in terms of the number of bits) can be reduced, thus filtering can be more efficient.

Examples of the present disclosure provide devices and methods for encoding and decoding an image that can improve encoding performance, thereby increasing the efficiency of video signal encoding. The disclosure is described in detail in the examples and claims contained in this file.

Embodiments of the present application provide encoding and decoding devices and methods according to the independent claims, so that the complexity of the inter-component ALF can be reduced and the performance of the inter-component adaptive loop filter (CC-ALF) as an embedded loop filter or a post-loop filter can be improved accordingly.

The above and other objectives can be achieved by means of the subject matter of the independent claims. Additional forms of implementation are apparent from the dependent claims, the description and the figures.

Specific embodiments are set forth in the attached independent claims, and other embodiments are set forth in the dependent claims.

According to a first aspect, the disclosure relates to an encoding method implemented by an encoding device, comprising:

performing a filtering process (such as a cross-component filtering process) by applying a cross-component adaptive loop filter (CC-ALF);

generating a bit stream including a plurality of syntactic elements related to the CC-ALF (such as M syntactic elements related to the CC-ALF, and M>=1, and M is an integer), wherein said plurality of syntactic elements related to the CC-ALF indicate information related to the CC-ALF,

wherein said plurality of syntax elements related to the CC-ALF are signaled at any one or more of a video parameter set (VPS) layer, a sequence parameter set (SPS) layer, a picture parameter set (PPS) layer, a picture header, a slice header, or a tile header; or

wherein said plurality of syntactic elements related to the CC-ALF are signaled at the sequence parameter set (SPS) level and/or in the image header.

This bit stream can be reduced in size while providing appropriate information in the bit stream structure for those layers where the present application is actually applied or to which it relates, and this allows inter-component adaptive loop filtering to be performed with reduced signaling overhead, thus filtering can be more efficient and an increase in coding efficiency is achieved.

According to a second aspect, the disclosure relates to a decoding method implemented by a decoding device comprising:

parsing one or more syntax elements from a video bitstream, wherein the syntax elements indicate information related to a cross-component adaptive loop filter (CC-ALF), wherein the syntax elements are obtained from any one or more of a video parameter set (VPS) layer, a sequence parameter set (SPS) layer, a picture parameter set (PPS) layer, a picture header, a slice header, or a tile header of the bitstream; or wherein the syntax elements are obtained from a sequence parameter set (SPS) layer and/or a picture header; and

performing a filtering process (such as a cross-component filtering process) by applying CC-ALF based on syntax elements or based on the values of syntax elements.

This method can make it possible to obtain relevant information from a bit stream during decoding when the bit stream is reduced in size, providing improved data compression, and it makes it possible to perform inter-component adaptive loop filtering with reduced signaling overhead, thus the filtering can be more efficient and an increase in coding efficiency is achieved.

According to a third aspect, the invention relates to a device for decoding video data. The device comprises: a processing circuit for implementing the method according to the first aspect of the disclosure.

According to a fourth aspect, the invention relates to a device for encoding video data. The device comprises: a processing circuit for implementing the method according to the second aspect of the invention.

The method according to the first aspect of the present disclosure may be implemented by the device according to the third aspect of the disclosure. Additional features and forms of implementation of the method according to the third aspect of the disclosure correspond to the features and forms of implementation of the device according to the first aspect of the disclosure.

The method according to the second aspect of the invention can be implemented using the device according to the fourth aspect of the invention. Additional features and forms of implementation of the method according to the fourth aspect of the disclosure correspond to the features and forms of implementation of the device according to the second aspect of the disclosure.

According to a fifth aspect, the disclosure relates to a device for decoding a video stream, including a processor and a memory. The memory stores instructions that cause the processor to perform the method according to the first aspect.

According to a sixth aspect, the disclosure relates to a device for encoding a video stream, including a processor and a memory. The memory stores instructions that cause the processor to perform the method according to the second aspect.

According to the seventh aspect, a computer-readable data carrier is proposed, on which instructions are stored, the execution of which results in the fact that said one or more processors are configured to encode video data. The instructions cause one or more processors to perform the method according to the first or second aspect or any possible embodiment of the first or second aspect.

According to an eighth aspect, the invention relates to a computer program comprising program code for performing the method according to the first or second aspect or any possible embodiment of the first or second aspect when executed on a computer.

The present disclosure provides a coding method implemented by an encoding device, the method comprising:

application of the CC-ALF intercomponent adaptive contour filter to refine the color component;

generating a bit stream including a plurality of syntactic elements related to the ALF (syntactic elements related to the CC-ALF, used below), wherein said plurality of syntactic elements related to the CC-ALF indicate information related to the ALF (information related to the CC-ALF, used below);

wherein said plurality of syntactic elements related to the CC-ALF are signaled at any one or more of the sequence parameter set (SPS), picture header or slice header level;

wherein said plurality of syntax elements related to the CC-ALF comprises a first syntax element that indicates whether or not an adaptive loop filter (ALF) comprising an inter-component adaptive loop filter is enabled at the sequence level, and the first syntax element is signaled at the SPS level, and a second syntax element that indicates whether or not the inter-component adaptive loop filter is enabled at the sequence level, and the second syntax element is signaled at the SPS level.

Although it is generally indicated here that the first and second syntax elements are signaled at the SPS level, this does not mean that the signaling of at least the second syntax element is unconditional. Rather, this embodiment also covers implementations in which the second syntax element is signaled, for example, based on the value of the first syntax element and/or depending on the value of another syntax element, as will be further described below.

The first syntax element may be referred to as sps_alf_enabled_flag in the following, while the second syntax element may be referred to as sps_ccalf_enabled_flag. However, this is merely a name used herein. The invention is not limited by the specific name of the first or second syntax element or any other syntax element mentioned herein.

It can be understood that CC-ALF is a special kind of ALF, CC-ALF can depend on whether ALF is enabled or not, so the first syntax element, i.e. sps_alf_enabled_flag, also applies to CC-ALF, and therefore the syntax elements related to CC-ALF can be used below. Similarly, the information specified by the first syntax element, i.e. sps_alf_enabled_flag, also applies to CC-ALF, so the information related to CC-ALF can be used below.

In this way, information that can be used for all images in a sequence can be efficiently transmitted at the SPS layer, reducing the bitstream size by reducing the amount of redundant information and allowing inter-component adaptive loop filtering to be performed with reduced signaling overhead, thus filtering can be more efficient and improving coding efficiency.

In one embodiment, said plurality of syntax elements related to CC-ALF comprises a third syntax element, when the second syntax element indicates that CC-ALF is included, wherein the third syntax element is signaled in the header of the image, and the third syntax element indicates whether CC-ALF is included for the current image containing a plurality of slices.

This third syntax element can also be referred to as pic_ccalf_enabled_flag. In this embodiment, the relevant CC-ALF information related to the entire image can be transmitted while maintaining a small bitstream size. For example, Slice 1..Slice N share the same CCALF information, so the common information can be directly inherited from the image header instead of each slice header transmitting them redundantly.

In a further embodiment, said plurality of syntax elements related to CC-ALF comprises a fourth syntax element, when the second syntax element indicates that CC-ALF is enabled, wherein the fourth syntax element is signaled in the header of the picture, and the fourth syntax element indicates whether CC-ALF is enabled for the color component Cb for the current picture of the video sequence associated with the bitstream.

The fourth syntax element can, for example, be designated as pic_cross_component_alf_cb_enabled_flag. However, this is not mandatory. The fourth syntax element can effectively signal CC-ALF for the Cb color component while keeping the amount of redundant information, for example in the slice header, small.

In addition, it may be provided that if the fourth syntax element has a value of 1, this indicates that CC-ALF for the color component Cb is enabled for the current image, and/or if the fourth syntax element has a value of 0, this indicates that CC-ALF for the color component Cb is disabled for the current image.

In one embodiment, said plurality of syntax elements related to the CC-ALF comprises a fifth syntax element, when the fourth syntax element indicates that the CC-ALF for the color component Cb is enabled for the current picture, wherein the fifth syntax element is signaled in the header of the picture, and the fifth syntax element indicates a set of parameters to which the color component Cb of all slices in the current picture belongs. This syntax element may be designated as pic_cross_component_alf_cb_aps_id. This, however, is simply a name and is not construed as limiting the present disclosure. This embodiment may allow sets of signaling parameters that are provided for all slices of the picture already at the picture level, thereby reducing the amount of redundant information.

In addition, it can be provided that said plurality of syntax elements associated with CC-ALF comprises a seventh syntax element, when the second syntax element indicates that CC-ALF is enabled, wherein the seventh syntax element is signaled in the image header, and the seventh syntax element indicates whether CC-ALF is enabled for the Cr color component for the current image of the video sequence associated with the bitstream. This syntax element can, for example, be designated as pic_cross_component_alf_cr_enabled_flag without limiting the present disclosure. With this syntax element, it is possible to reliably signal the inclusion of CC-ALF for the Cr color components.

In addition, it may be provided that if the seventh syntax element has a value of 1, this indicates that CC-ALF for the color component Cr is enabled for the current image, and/or if the seventh syntax element has a value of 0, this indicates that CC-ALF for the color component Cr is disabled for the current image.

In one embodiment, said plurality of syntax elements associated with CC-ALF comprises an eighth syntax element, wherein the seventh syntax element indicates that CC-ALF for the Cr color component is enabled for the current image, wherein the eighth syntax element is signaled in the image header, and the eighth syntax element indicates a set of parameters that is associated with the Cr color component of all slices in the current image. The eighth syntax element may be designated as pic_cross_component_alf_cr_aps_id, although this is only one example. This syntax element may provide information about the corresponding parameters that will be used during filtering.

In addition, it may be provided that the fourth syntax element, the fifth syntax element, the sixth syntax element, the seventh syntax element, the eighth syntax element and the ninth syntax element are signaled when the third syntax element indicates that CC-ALF is enabled for the current picture of the video sequence associated with the bitstream. If CC-ALF is disabled, these elements may be set to default values and will still be signaled in the bitstream. Alternatively, if CC-ALF is disabled, these syntax elements may not be signaled in the bitstream, thereby reducing its size, since unused information is excluded from the bitstream.

In a further embodiment, said plurality of syntax elements related to CC-ALF comprises a tenth syntax element, when the second syntax element indicates that CC-ALF is enabled, wherein the tenth syntax element is signaled in the slice header, and the tenth syntax element indicates whether CCALF is enabled for the Cb color component for the current slice of the current picture of the video sequence associated with the bitstream. This syntax element may, without the intention of limiting the present disclosure, be called slice_cross_component_alf_cb_enabled_flag. In this way, an efficient signaling of whether CC-ALF should be enabled for the Cb color components can be provided.

In addition, it may be provided that if the tenth syntax element has the value 1, this indicates that CCALF for color component Cb is enabled for the current slice, and/or if the tenth syntax element has the value 0, this indicates that CCALF for color component Cb is disabled for the current slice.

In a further embodiment, said plurality of syntax elements related to the CC-ALF comprises an eleventh syntax element, when the tenth syntax element indicates that the CC-ALF for the color component Cb is enabled for the current slice, wherein the tenth syntax element is signaled in the slice header and the tenth syntax element indicates a set of parameters referenced by the color component Cb of the current slice. This syntax element may be designated as pic_cross_component_alf_cb_aps_id, although this is not intended to limit the present disclosure.

In a further embodiment, said plurality of syntax elements related to CC-ALF comprises a twelfth syntax element, when the second syntax element indicates that CC-ALF is enabled, wherein the twelfth syntax element is signaled in the slice header, and the twelfth syntax element indicates whether CCALF is enabled for the color component Cr for the current slice of the current picture of the video sequence associated with the bitstream. The twelfth syntax element may, for example, be designated as slice_cross_component_alf_cr_enabled_flag.

In a further embodiment, it is provided that if the twelfth syntax element has a value of 1, this indicates that CCALF for the color component Cr is enabled for the current slice, and/or if the twelfth syntax element has a value of 0, this indicates that CCALF for the color component Cr is disabled for the current slice.

It may also be envisaged that said plurality of syntax elements related to the CC-ALF comprises a thirteenth syntax element, when the twelfth syntax element indicates that the CC-ALF for the color component Cr is enabled for the current slice, wherein the thirteenth syntax element is signaled in the slice header and the thirteenth syntax element indicates the parameter set referenced by the color component Cr of the current slice. For example, the thirteenth syntax element may be designated asslice_cross_component_alf_cr_aps_id. This can effectively provide information about the parameter to be used for filtering related to the color component Cr.

It may be provided that the second syntax element is signaled if the first syntax element has the first value, or the second syntax element is signaled conditionally at least based on the value of the first syntax element. If ALF is not included (as signaled by the first syntax element), CC-ALF will also not be included. By not providing the second syntax element in this case, the bitstream size can be further reduced.

In one embodiment, said plurality of syntax elements related to the CC-ALF comprises a fourteenth syntax element signaled at the SPS level, wherein the fourteenth syntax element indicates the type of input in the CC-ALF. The fourteenth syntax element may be designated ChromaArrayType, although this does not limit the present disclosure.

More specifically, the second syntax element is signaled when the first syntax element has the first value and the fourteenth syntax element has the second value. The second value may be any value other than a specific value that indicates that CC-ALF should not be enabled.

In yet another specific embodiment, the second syntax element is signaled when the first syntax element has a value equal to 1 and the fourteenth syntax element has a value not equal to 0.

For any of the above embodiments, it may be provided that the CC-ALF operates as part of an adaptive loop filtering process and uses the luminance sample values to refine at least one chrominance component.

The present disclosure further provides a decoding method implemented by a decoding device, the method comprising:

parsing a plurality of syntax elements associated with a cross-component adaptive loop filter, CC-ALF, from a bitstream, wherein said plurality of syntax elements, wherein said plurality of syntax elements related to the CC-ALF are obtained from any one or more of a sequence parameter set (SPS) level, a picture header, or a slice header;

wherein said plurality of syntax elements related to the CC-ALF comprises a first syntax element that indicates whether or not an adaptive loop filter (ALF) comprising an inter-component adaptive loop filter is enabled at the sequence level, and the first syntax element is signaled at the SPS level, and a second syntax element that indicates whether or not the inter-component adaptive loop filter is enabled at the sequence level, and the second syntax element is signaled at the SPS level;

performing a CC-ALF process using at least one of said plurality of CC-ALF related syntax elements.

Although it is generally indicated here that the first and second syntax elements are provided at the SPS level, this does not mean that at least the second syntax element is provided in the bitstream unconditionally. Rather, this embodiment also covers implementations in which the second syntax element is part of the bitstream, for example, based on the value of the first syntax element and/or depending on the value of another syntax element, as will be further described below.

The first syntax element may be referred to as sps_alf_enabled_flag in the following, while the second syntax element may be referred to as sps_ccalf_enabled_flag. However, this is merely a name used herein. The invention is not limited by the specific name of the first or second syntax element or any other syntax element mentioned herein.

In this way, information that can be used, for example, for all images in a sequence can be efficiently provided to the decoder at the SPS level, reducing the size of the bitstream by reducing the amount of redundant information, and this allows inter-component adaptive loop filtering to be performed with reduced signaling overhead, thus filtering can be more efficient and an increase in coding efficiency is achieved.

It may be provided that said plurality of syntax elements related to CC-ALF comprises a third syntax element when a second syntax element indicating that CC-ALF is enabled is received, wherein the third syntax element is received from a header of the image and the third syntax element indicates whether CC-ALF is enabled for the current image comprising a plurality of slices. This third syntax element may also be referred to as pic_ccalf_enabled_flag. In this embodiment, relevant CC-ALF information related to the entire image may be provided while maintaining a small bitstream size.

In a further embodiment, said plurality of syntax elements related to CC-ALF comprises a fourth syntax element when the second syntax element is received indicating that CC-ALF is enabled, wherein the fourth syntax element is obtained from a picture header and the fourth syntax element indicates whether CC-ALF is enabled for the Cb color component for the current picture of the video sequence. The fourth syntax element may, for example, be designated as pic_cross_component_alf_cb_enabled_flag. However, this is not mandatory. The fourth syntax element may effectively cause the decoder to enable CC-ALF for the Cb color component, while keeping the amount of redundant information, for example, in the slice header, small.

In a further embodiment, it may be provided that if the fourth syntax element has a value of 1, this indicates that CC-ALF for the color component Cb is enabled for the current image, and/or if the fourth syntax element has a value of 0, this indicates that CC-ALF for the color component Cb is disabled for the current image.

In addition, said plurality of syntax elements related to the CC-ALF may comprise a fifth syntax element, when the fourth CC-ALF syntax element for the color component Cb is resolved for the current image, wherein the fifth syntax element is obtained from the image header and the fifth syntax element indicates a set of parameters that is associated with the color component Cb of all slices in the current image. This syntax element may be designated as pic_cross_component_alf_cb_aps_id. This, however, is simply a name and is not construed as limiting the present disclosure. This embodiment may provide the ability to provide sets of parameters that are provided for all slices of an image already at the image level, thereby reducing the amount of redundant information.

In a further embodiment, said plurality of syntax elements associated with CC-ALF comprises a seventh syntax element when the second syntax element is received indicating that CC-ALF is enabled, wherein the seventh syntax element is obtained from a picture header and the seventh syntax element indicates whether CC-ALF is enabled for the Cr color component for the current picture of the video sequence associated with the bitstream. This syntax element may, for example, be designated as pic_cross_component_alf_cr_enabled_flag without limiting the present disclosure. With this CC-ALF syntax element, the decoder can reliably determine whether CC-ALF is enabled for the Cr color components.

It may be provided that if the seventh syntax element has a value of 1, this indicates that CC-ALF for the Cr color component is enabled for the current image, and/or if the seventh syntax element has a value of 0, this indicates that CC-ALF for the Cr color component is disabled for the current image.

In a further embodiment, said plurality of syntax elements associated with the CC-ALF comprises an eighth syntax element, when a seventh syntax element is received, indicating that the CC-ALF for the color component Cr is enabled for the current image, wherein the eighth syntax element is obtained from the image header, and the eighth syntax element indicates a set of parameters that is associated with the color component Cr of all slices in the current image. The eighth syntax element may be designated as pic_cross_component_alf_cr_aps_id, although this is only one example. This syntax element may provide information about the corresponding parameters that will be used during filtering.

In addition, it may be provided that the fourth syntax element, the fifth syntax element, the sixth syntax element, the seventh syntax element, the eighth syntax element and the ninth syntax element are obtained when the third syntax element indicating that CC-ALF is enabled for the current picture of the video sequence associated with the bitstream is obtained.

In one embodiment, said plurality of syntax elements related to CC-ALF comprises a tenth syntax element, when a second syntax element is received, indicating that CC-ALF is enabled, wherein the tenth syntax element is obtained from a slice header, and the tenth syntax element indicates whether CCALF is enabled for the Cb color component for the current slice of the current picture of the video sequence associated with the bitstream. This syntax element may, without the intention of limiting the present disclosure, be called slice_cross_component_alf_cb_enabled_flag. In this way, the decoder can determine whether CC-ALF should be enabled for the Cb color components.

In addition, it may be provided that if the tenth syntax element has the value 1, this indicates that CCALF for color component Cb is enabled for the current slice, and/or if the tenth syntax element has the value 0, this indicates that CCALF for color component Cb is disabled for the current slice.

In one embodiment, said plurality of syntax elements related to CC-ALF comprises an eleventh syntax element when a tenth syntax element is received indicating that CC-ALF for color component Cb is enabled for the current slice, wherein the tenth syntax element is received from the slice header, and the tenth syntax element indicates a set of parameters referenced by the color component Cb of the current slice. This syntax element may be designated as pic_cross_component_alf_cb_aps_id, although this is not intended to limit the present disclosure.

It may be envisaged that said plurality of syntax elements related to CC-ALF comprises a twelfth syntax element when the second syntax element indicating that CC-ALF is enabled is received, wherein the twelfth syntax element is received from a slice header and the twelfth syntax element indicates whether CCALF is enabled for the color component Cr for the current slice of the current picture of the video sequence associated with the bitstream. The twelfth syntax element may, for example, be designated as slice_cross_component_alf_cr_enabled_flag.

In a more specific embodiment, if the twelfth syntax element has a value of 1, this indicates that CCALF for the Cr color component is enabled for the current slice, and/or if the twelfth syntax element has a value of 0, this indicates that CCALF for the Cr color component is disabled for the current slice.

In addition, it can be provided that said plurality of syntax elements related to CC-ALF comprises a thirteenth syntax element when a twelfth syntax element is received indicating that CC-ALF for the color component Cr is enabled for the current slice, wherein the thirteenth syntax element is obtained from the slice header and the thirteenth syntax element indicates a set of parameters referred to by the color component Cr of the current slice. For example, the thirteenth syntax element can be designated as slice_cross_component_alf_cr_aps_id. This can effectively provide information about the parameter that will be used for filtering related to the color component Cr.

In one embodiment, the second syntax element is obtained if the first syntax element has a first value, or the second syntax element is obtained based at least on the value of the first syntax element.

In addition, it may be provided that said plurality of syntax elements related to the CC-ALF comprises a fourteenth syntax element obtained from the SPS layer, wherein the fourteenth syntax element indicates the type of input in the CC-ALF. The fourteenth syntax element may be designated ChromaArrayType, although this does not limit the present disclosure.

More specifically, a second syntactic element may be obtained when the first syntactic element has a first value and the fourteenth syntactic element has a second value. This second value may be any value that is different from, or may be used to indicate, the value that CC-ALF should not be included.

More specifically, it may be provided that the second syntactic element is obtained when the first syntactic element has a value equal to 1 and the fourteenth syntactic element has a value not equal to 0.

For any of the above embodiments, it may be further provided that the CC-ALF operates as part of an adaptive loop filtering process and uses the luminance sample values to refine at least one chrominance component.

This disclosure also applies to

a device for encoding video data, comprising:

video data memory; and

a video encoder, wherein the video encoder is configured to: apply an inter-component adaptive loop filter CC-ALF for refining the chrominance component; generate a bit stream including a plurality of syntactic elements related to the CC-ALF, wherein said plurality of syntactic elements related to the CC-ALF indicate information related to the CC-ALF; wherein said plurality of syntactic elements related to the CC-ALF are signaled at any one or more of a sequence parameter set (SPS), a picture header or a slice header level; wherein said plurality of syntax elements related to the CC-ALF comprises a first syntax element that indicates whether or not an adaptive loop filter (ALF) comprising an inter-component adaptive loop filter is enabled at the sequence level, and the first syntax element is signaled at the SPS level, and a second syntax element that indicates whether or not the inter-component adaptive loop filter is enabled at the sequence level, and the second syntax element is signaled at the SPS level. In this case, the advantages of the above-mentioned encoding methods are provided to coders for encoding, for example, video.

This disclosure also applies to

a device for decoding video data, comprising:

video data memory; and

a video decoder, wherein the video decoder is configured to: parse a plurality of syntax elements associated with a cross-component adaptive loop filter, CC-ALF, from a bitstream, wherein said plurality of syntax elements, wherein said plurality of syntax elements related to the CC-ALF are obtained from any one or more of a sequence parameter set (SPS) level, a picture header or a slice header; wherein said plurality of syntax elements related to the CC-ALF comprise a first syntax element that indicates whether or not an adaptive loop filter (ALF) comprising the cross-component adaptive loop filter is enabled at a sequence level, and the first syntax element is signaled at a SPS level, and a second syntax element that indicates whether or not the cross-component adaptive loop filter is enabled at a sequence level, and the second syntax element is signaled at a SPS level; and performing the CC-ALF process using at least one of said plurality of syntax elements related to the CC-ALF.

This takes advantage of the reduced bitstream size while still providing reliable video decoding.

In addition, an encoder for encoding video is provided, comprising a processing circuit for performing a method according to any of the above embodiments. In this case, the advantages of the above-mentioned encoding methods are provided to encoders for encoding, for example, video.

In addition, a decoder is provided for decoding the bit stream, wherein the decoder comprises a processing circuit for performing the method according to any of the above-mentioned embodiments. In this case, the advantages of a reduced bit stream size are realized in reliable video decoding.

Also provided within the scope of this disclosure is a computer-readable storage medium comprising computer-executable instructions that, when executed by a computing device, cause the computing device to perform the method according to any of the above embodiments.

The present disclosure further provides an encoded bitstream for a video signal by including a plurality of syntax elements related to a CC-ALF, wherein said plurality of syntax elements related to the CC-ALF indicate information related to the CC-ALF;

wherein said plurality of syntactic elements related to the CC-ALF are signaled at any one or more of the sequence parameter set (SPS), picture header or slice header level;

wherein said plurality of syntax elements related to the CC-ALF comprises a first syntax element that indicates whether or not an adaptive loop filter (ALF) comprising an inter-component adaptive loop filter is enabled at the sequence level, and the first syntax element is signaled at the SPS level, and a second syntax element that indicates whether or not the inter-component adaptive loop filter is enabled at the sequence level, and the second syntax element is signaled at the SPS level.

The bitstream can be reduced in size while still providing information to be used for decoding when CC-ALF is used reliably.

The details of one or more embodiments are set forth in the accompanying drawings and the following description. Other features, objects and advantages will be apparent from the description, drawings and claims.

BRIEF DESCRIPTION OF DRAWINGS

The following embodiments of the invention are described in more detail with reference to the accompanying figures and drawings, in which:

Fig. 1A is a block diagram showing an example of a video coding system capable of implementing embodiments of the invention;

Fig. 1B is a block diagram showing another example of a video coding system capable of implementing embodiments of the invention;

Fig. 2 is a block diagram showing an example of a video encoder capable of implementing embodiments of the invention;

Fig. 3 is a block diagram showing an example of the structure of a video decoder capable of implementing embodiments of the invention;

Fig. 4 is a block diagram illustrating an example of an encoding device or a decoding device;

Fig. 5 is a block diagram illustrating another example of an encoding device or a decoding device;

Fig. 6 includes Fig. 6a, 6b and 6c, where (6a) is the placement of the CC ALF relative to the other loop filters (6b and 6c) is a diamond-shaped filter;

Fig. 7 is a diagram illustrating all slice headers that are required to carry CCALF data in the prior art;

Fig. 8 is a diagram illustrating an example of the enhanced CC-ALF syntax elements;

Fig. 9A is a conceptual diagram illustrating the nominal vertical and horizontal relative locations of discrete luma and chroma samples;

Fig. 9B is a schematic diagram illustrating co-located luminance blocks and chrominance blocks;

Fig. 10 is a block diagram showing an exemplary structure of a content delivery system 3100 that implements a content delivery service;

Fig. 11 is a block diagram showing the structure of an exemplary terminal device;

Fig. 12 is a block diagram showing an example of an encoder;

Fig. 13 is a block diagram showing an example of a decoder;

Fig. 14 shows a flow chart of a video encoding method according to one embodiment;

Fig. 15 shows a flow chart of a video decoding method according to one embodiment.

Fig. 16 is a schematic representation of a data structure 5000, i.e., a video bitstream 500.

The following identical reference numbers refer to identical or at least functionally equivalent functions unless explicitly stated otherwise.

DETAILED DESCRIPTION OF IMPLEMENTATION OPTIONS

The following definition is for reference:

coding block:BlockMxN discrete samples for some values of M and N, so that the divisionCTBoncoding blocks isdivision.

coding tree block (CTB)):BlockNxN discrete samples for some value of N such that the divisioncomponentonCTBis division.

coding tree unit (CTU):CTBsamplesbrightness, two correspondingCTBsamplescolors images,consisting of three arrays of samples, orCTBmonochrome samplesimages or images, encoded using three separate color planes andsyntactic structures,used for encoding samples.

coding unit (CU): Coding blockbrightness samples,two correspondingcoding blocksamplescolors images, which has three sample arrays, or a monochrome sample coding blockimagesor images,which is encoded using three separate color planes And syntactic structures, used to encode samples.

component: An array or a single sample from one of the three arrays (a luma array and two chroma arrays ) that make up an image in 4:2:0, 4:2:2, or 4:4:4 color format, or an array or a single sample from an array that makes up an image in monochrome format.

In the following description, reference is made to the accompanying drawings, which form a part of this disclosure and which show, by way of illustration, specific aspects of embodiments of the invention or specific aspects in which embodiments of the present invention can be used. It is understood that embodiments of the present invention can be used in other aspects and include structural or logical changes not shown in the figures. Therefore, the following detailed description should not be taken in a limiting sense, and the scope of the present invention is defined by the appended claims.

For example, it is understood that the disclosure related to the described method may also be true for the corresponding device or system adapted to perform the method, and vice versa. For example, if one or a plurality of specific method steps are described, the corresponding device may include one or a plurality of blocks, such as functional blocks, to perform the described one or a plurality of method steps (for example, one block performing one or a plurality of steps, or a plurality of blocks, each of which performs one or more of said plurality of steps), even if such one or more blocks are not explicitly described or illustrated in the figures. On the other hand, for example, if a specific device is described based on one or a plurality of blocks, such as functional blocks, the corresponding method may include one step to perform the functionalities of one or a plurality of blocks (for example, one step performing the functionalities of one or a plurality of blocks, or a plurality of steps, each of which performs the functionalities of one or more of said plurality of blocks), even if such one or a plurality of steps are not explicitly described or illustrated in the figures. Furthermore, it is understood that features of various exemplary embodiments and/or aspects described herein may be combined with one another unless otherwise specifically stated.

Video coding generally refers to the processing of a sequence of images that form a video or a video sequence. Instead of the term "image", the terms "frame" or "picture" may be used synonymously in the field of video coding. Video coding (or coding in general) comprises two parts: video encoding and video decoding. Video coding is performed at the source side and generally comprises processing (e.g. by compression) of the original video images to reduce the amount of data required to represent the video images (for more efficient storage and/or transmission). Video decoding is performed at the receiver (destination) side and generally comprises the inverse processing compared to the encoder to restore the video images. Embodiments that refer to "coding" video images (or images in general) should be understood as referring to "coding" or "decoding" video images or the corresponding video sequences. The combination of the encoding part and the decoding part is also called CODEC (Coding and Decoding).

In lossless video coding, the original video images can be reconstructed, i.e. the reconstructed video images have the same quality as the original video images (provided there is no transmission loss or other data loss during storage or transmission). In lossy video coding, additional compression is performed, for example by quantization, to reduce the amount of data representing the video images that cannot be fully reconstructed at the decoder, i.e. the quality of the reconstructed video images is lower or worse than the quality of the original video images.

Several video coding standards belong to the group of "hybrid lossy video codecs" (i.e. they combine spatial and temporal prediction in the sample domain and 2D transform coding to apply quantization in the transform domain). Each picture of a video sequence is typically partitioned into a set of non-overlapping blocks, and coding is typically performed at the block level. In other words, at the encoder, video is typically processed, i.e. encoded, at the block (video block) level, such as using spatial (intra-picture) prediction and/or temporal (inter-picture) prediction to form a prediction block, the prediction block is subtracted from the current block (the block currently being/to be processed) to obtain a residual block, the residual block is transformed, and this residual block is quantized in the transform domain to reduce the amount of data (compression) to be transmitted, while at the decoder, the inverse of the processing compared to the encoder is applied to the coded or compressed block to reconstruct the current block for presentation. In addition, the encoder duplicates the decoder's processing loop so that they both will produce identical predictions (e.g. intra-frame and inter-frame predictions) and/or reconstructions for processing, i.e. encoding, subsequent blocks.

In the following embodiments, the video coding system 10, video encoder 20 and video decoder 30 are described based on Figs. 1-3.

Fig. 1A is a schematic block diagram illustrating an example coding system 10, such as a video coding system 10 (or coding system 10 for short), that can use the techniques of the present application. A video encoder 20 (or encoder 20 for short) and a video decoder 30 (or decoder 30 for short) of the video coding system 10 represent examples of devices that can be configured to perform the techniques in accordance with the various examples described in the present application.

As shown in Fig. 1A, the encoding system 10 comprises a source device 12 configured to provide encoded image data 21, for example, to a recipient device 14 for decoding the encoded image data 13.

The source device 12 may comprise an encoder 20 and may additionally, i.e. optionally, comprise an image source 16, a preprocessor (or pre-processing unit) 18, such as an image preprocessor 18, and a communication interface or communication unit 22.

The image source 16 may comprise or be any type of image capture device, such as a camera for capturing a real world image, and/or any type of image generating device, such as a computer graphics processor for generating a computer animated image, or any type of other device for receiving and/or providing a real world image, a computer generated image (e.g., screen content, a virtual reality (VR) image), and/or any combination thereof (e.g., an augmented reality (AR) image). The image source may be any type of memory or storage in which any of the above-mentioned images are stored.

In contrast to the preprocessor 18 and the processing performed by the pre-processing unit 18, the image or image data 17 may also be referred to as a raw image or unprocessed image data 17.

The preprocessor 18 may be configured to receive (raw) image data 17 and to perform preprocessing of the image data 17 to obtain a preprocessed image 19 or preprocessed image data 19. The preprocessing performed by the preprocessor 18 may, for example, comprise cropping, color format conversion (for example, from RGB to YCbCr), color correction or noise reduction. It can be understood that the preprocessing unit 18 may be an optional component.

The video encoder 20 may be configured to receive pre-processed image data 19 and provide encoded image data 21 (further details will be described below, e.g. based on Fig. 2).

The communication interface 22 of the source device 12 may be configured to receive the encoded image data 21 and transmit these encoded image data 21 (or any further processed version thereof) via the communication channel 13 to another device, such as the recipient device 14 or any other device, for storage or direct recovery.

The receiving device 14 may comprise a decoder 30 (for example, a video decoder 30) and may additionally, i.e. optionally, comprise a communication interface or communication unit 28, a postprocessor 32 (or postprocessor 32) and a display device. 34.

The communication interface 28 of the receiving device 14 may be configured to receive the encoded image data 21 (or any further processed version thereof), for example, directly from the source device 12 or from any other source, for example, a storage device, for example a memory device for encoded image data, and provide the encoded image data 21 to the decoder 30.

The communication interface 22 and the communication interface 28 may be configured to transmit or receive the encoded image data 21 or the encoded data 13 via a direct communication link between the source device 12 and the destination device 14, such as a direct wired or wireless connection, or via any type of network, such as a wired or wireless network or any combination thereof, or any private and public network, or any combination thereof.

The communication interface 22 may, for example, be configured to pack the encoded image data 21 into an appropriate format, such as into packets, and/or to process the encoded image data using any type of transmission coding or processing for transmission over a communication channel or communication network.

The communication interface 28, which is analogous to the communication interface 22, may, for example, be configured to receive the transmitted data and process the transmission data using any type of appropriate decoding or processing and/or decompression of the transmission to obtain the encoded image data 21.

Both or at least one of the communication interface 22 and the communication interface 28 can be configured as unidirectional communication interfaces, as shown by the arrow for the communication channel 13 in Fig. 1A, pointing from the source device 12 to the destination device 14, or bidirectional communication interfaces, and can be configured, for example, to send and receive messages, for example, to establish a connection, to confirm and exchange any other information related to the communication link and/or data transmission, for example, the transmission of encoded image data.

The decoder 30 may be configured to receive the encoded image data 21 and provide decoded image data 31 or a decoded image 31 (further details will be described below, for example, based on Fig. 3 or Fig. 5).

The post-processor 32 of the receiving device 14 may be configured to post-process the decoded image data 31 (also referred to as reconstructed image data), such as the decoded image 31, to obtain post-processed image data 33, such as the post-processed image 33. The post-processing performed by the post-processing unit 32 may comprise, for example, color format conversion (for example, from YCbCr to RGB), color correction, cropping or resampling, or any other processing, such as for preparing the decoded image data 31 for display, such as by means of the display device 34.

The display device 34 of the receiving device 14 can be configured to receive the image data 33 after processing for displaying the image, for example, to a user or a viewer. The display device 34 can be or contain a display of any type for presenting the reconstructed image, for example, an integrated or external display or monitor. The displays can, for example, contain liquid crystal displays (LCD), organic light-emitting diode (OLED) displays, plasma displays, projectors, micro-LED displays, liquid crystals on silicon (LCoS), a digital light processor (DLP) or another display of any type.

Although Fig. 1A illustrates the source device 12 and the destination device 14 as separate devices, embodiments of the devices may also comprise both or both functionalities, the source device 12 or the corresponding functionality and the destination device 14 or the corresponding functionality. In such embodiments, the source device 12 or the corresponding functionality and the destination device 14 or the corresponding functionality may be implemented using the same hardware and/or software or using separate hardware and/or software or any combination thereof.

The source device and/or the destination device may be further implemented using special hardware and/or software. For example, one or both of these devices may be implemented using specially designed hardware for implementing one or more of the functionalities mentioned above and below. Alternatively or additionally, one or more of the functionalities described above and below may be implemented using specially designed software that may be executed on general-purpose hardware, such as processors. In addition, combinations of the above are also envisaged, where the source device and/or the destination device may be implemented using a combination of specially dedicated hardware for implementing one or more functions and software for implementing one or more other functions.

As will be apparent from the description of the specific element, the presence and (exact) division of functionality of the various blocks or functions in the source device 12 and/or the destination device 14, as shown in Fig. 1A, may vary depending on the actual device and application.

Coder20 (for example, video encoder 20) or decoder 30(eg video decoder 30) or both the encoder 20 and the decoder 30 may be implemented via a processing circuit as shown in Fig. 1B, such as one or more microprocessors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), discrete logic, hardware, dedicated video coding, or any combinations thereof. The encoder 20 may be implemented via a processing circuit 46 to implement various blocks as discussed with respect to the encoder 20 of Fig. 2 and/or any other encoder system or subsystem described herein. The decoder 30 may be implemented via a processing circuit 46 to implement various blocks as discussed with respect to the decoder 30 of Fig. 3 and/or any other decoder system or subsystem described herein. The processing circuit may be configured to perform various operations, which will be described below. As shown in Fig. 5, if the techniques are partially implemented in software, the device may store instructions for the software on a suitable non-transitory computer-readable storage medium and may execute the instructions in hardware using one or more processors to perform the techniques of this disclosure. Any of the video encoder20and video decoder30may be integrated as part of a combined encoder/decoder (CODEC) in a single device, such as shown in Fig. 1B.

The source device 12 and the destination device 14 may comprise any of a wide range of devices, including any type of portable or stationary devices, such as laptops or notebook computers, mobile phones, smartphones, tablets or tablet computers, cameras, desktop computers, set-top boxes, televisions, display devices, digital media players, game consoles, video streaming devices (such as content service servers or content delivery servers), a broadcast receiving device, a broadcast transmitting device or the like, and may use any type of operating system or do without it. In some cases, the source device 12 and the destination device 14 may be equipped for wireless communication. Thus, the source device 12 and the destination device 14 may be wireless communication devices.

In some cases, the video coding system 10 illustrated in Fig. 1A is merely an example, and the techniques of the present application may be applied to video coding settings (such as video encoding or video decoding) that do not necessarily involve the transmission of any data between encoding and decoding devices. In other examples, data is retrieved from local memory, streamed over a network, or the like. A video coding device may encode and store data in memory, and/or a video decoding device may retrieve and decode data from memory. In some examples, encoding and decoding are performed by devices that do not communicate with each other, but simply encode data into memory and/or retrieve and decode data from memory.

For convenience of description, embodiments of the present invention are described herein, for example, with reference to High Efficiency Video Coding (HEVC) or to the Universal Video Coding (VVC) reference software, a next-generation video coding standard being developed by the Joint Collaborative Video Coding Group (JCT-VC) of the ITU-T Video Coding Experts Group (VCEG) and the ISO/IEC Moving Picture Experts Group (MPEG). A person skilled in the art will understand that embodiments of the present invention are not limited to HEVC or VVC.

Encoder and encoding method

Fig. 2 shows a block diagram of an example video encoder 20 that may be configured to implement the techniques of the present disclosure. In the example of Fig. 2, video encoder 20 comprises an input 201 (or input interface 201), a residual calculation unit 204, a transform processing unit 206, a quantization unit 208, an inverse quantization unit 210 and an inverse transform processing unit 212, a restoration unit 214, a loop filter unit 220, a decoded picture buffer (DPB) 230, a mode selection unit 260, an entropy encoding unit 270 and an output 272 (or output interface 272). The mode selection unit 260 may include an inter-picture prediction unit 244, an intra-picture prediction unit 254 and a separation unit 262. The inter-picture prediction unit 244 may include a motion estimation unit and a motion compensation unit (not shown). The video encoder 20 shown in Fig. 2 may also be referred to as a hybrid video encoder or a video encoder according to a hybrid video codec.

The residual calculation unit 204, the transform processing unit 206, the quantization unit 208, the mode selection unit 260 may relate to the formation of a forward signal path of the encoder 20, while the inverse quantization unit 210, the inverse transform processing unit 212, the restoration unit 214, the buffer 216, the loop filter 220, the decoded picture buffer (DPB) 230, the inter-frame prediction unit 244, and the intra-frame prediction unit 254 may relate to the formation of a reverse signal path of the video encoder 20, wherein the reverse signal path of the video encoder 20 corresponds to the signal path of the decoder (see the video decoder 30 in Fig. 3). The inverse quantization unit 210, the inverse transform processing unit 212, the restoration unit 214, the loop filter 220, the decoded picture buffer (DPB) 230, the inter-frame prediction unit 244 and the intra-frame prediction unit 254 also belong to the formation of the “built-in decoder” of the video encoder 20.

Images and image separation (images and blocks)

The encoder 20 may be configured to receive, for example via the input 201, an image 17 (or image data 17), for example an image from a sequence of images forming a video or a video sequence. The received image or image data may also be a pre-processed image 19 (or pre-processed image data 19). For simplicity, the following description refers to the image 17. The image 17 may also be referred to as the current image or the image to be encoded (in particular, in video encoding, to distinguish the current image from other images, for example previously encoded and/or decoded images of the same video sequence, i.e. a video sequence that also contains the current image).

A (digital) image is or can be viewed as a two-dimensional array or matrix of samples with intensity values. A sample in an array may also be referred to as a pixel (short for picture element) or a pel (picture element). The number of samples in the horizontal and vertical directions (or axes) of the array or image determines the size and/or resolution of the image. Three color components are typically used to represent color, i.e. an image can be represented by or include three arrays of samples. In the RBG format or color space, an image contains a corresponding array of red, green, or blue samples. However, in video coding, each pixel is typically represented in a luma and chroma format or color space, such as YCbCr, which contains a luma component denoted by Y (sometimes L is also used instead) and two chroma components (color difference components) denoted by Cb and Cr. The Y component of luminance (or luma for short) represents the brightness or intensity of the gray level (e.g. as in a grayscale image), while the two components of chrominance (Cb and Cr) represent the chromaticity or color information components. Accordingly, an image in YCbCr format contains an array of luma samples with the (Y) values of the luma samples and two arrays of chrominance samples with the (Cb and Cr) values of the chrominance. Images in RGB format can be converted or transformed to YCbCr format and vice versa, a process also known as color conversion or conversion. If the image is monochrome, it may contain only an array of luma samples. Accordingly, an image may be, for example, an array of luma samples in monochrome format or an array of luma samples and two corresponding arrays of chrominance samples in 4:2:0, 4:2:2 and 4:4:4 color formats.

Embodiments of video encoder 20 may comprise a picture partitioning unit (not shown in Fig. 2) configured to partition picture 17 into a plurality of (typically non-overlapping) picture blocks 203. These blocks may also be referred to as root blocks, macroblocks (H.264/AVC) or coding tree blocks (CTB) or coding tree units (CTU) (H.265/HEVC and VVC). The picture partitioning unit may be configured to use the same block size for all pictures in a video sequence and a corresponding grid defining the block size, or to vary the block size between pictures or subsets or groups of pictures and to partition each picture into corresponding blocks.

In further embodiments, the video encoder may be configured to receive directly a block 203 of the image 17, such as one, several or all of the blocks forming the image 17. The block 203 of the image may also be referred to as the current block of the image or the block of the image to be encoded.

Like the image 17, the image block 203 is again or can be considered as a two-dimensional array or matrix of samples with intensity values (sample values), although of a smaller size than the image 17. In other words, the block 203 can contain, for example, one array of samples (for example, a brightness array in the case of a monochrome image 17, or a brightness or chrominance array in the case of a color image) or three arrays of samples (for example, a brightness and two chrominance arrays in the case of a color image 17) or any other number and/or type of arrays depending on the color format used. The number of samples in the horizontal and vertical direction (or axis) of the block 203 determines the size of the block 203. Accordingly, the block can be, for example, an MxN (M-column by N-row) array of discrete samples or an MxN array of transformation coefficients.

The embodiments of the video encoder 20 shown in Fig. 2 may be configured to encode the image 17 block by block, such that encoding and prediction are performed for each block 203.

Embodiments of video encoder 20, as shown in Fig. 2, may be further configured to divide and/or encode an image using slices (also referred to as video slices), wherein an image may be divided or encoded using one or more slices (typically without overlapping), and each slice may comprise one or more blocks (e.g., CTUs) or one or more groups of blocks (e.g., tiles (H.265/HEVC and VVC) or bricks (VVC)).

Embodiments of video encoder 20, as shown in Fig. 2, may be further configured to divide and/or encode an image using groups of slices/tiles (also called tile groups) and/or tiles (also called video tiles, in which an image may be divided or encoded using one or more groups of slices/tiles (typically non-overlapping), and each group of slices/tiles may contain, for example, one or more blocks (e.g., CTUs) or one or more tiles, where each tile may, for example, have a rectangular shape and may contain one or more blocks (e.g., CTUs), such as full or fractional blocks.

Calculating the remainder

The residual calculating unit 204 may be configured to calculate the residual block 205 (also referred to as the residual 205) based on the image block 203 and the prediction block 265 (further details about the prediction block 265 are given below), for example by subtracting the sample values of the prediction block 265 from the sample values of the image block 203, sample by sample (pixel by pixel), to obtain the residual block 205 in the sample domain.

Transformation

The transform processing unit 206 may be configured to apply a transform, such as a discrete cosine transform (DCT) or a discrete sine transform (DST), to the sample values of the residual block 205 to obtain transform coefficients 207 in the transform domain. The transform coefficients 207 may also be referred to as residual transform coefficients and represent the residual block 205 in the transform domain.

The transform processing unit 206 may be configured to apply integer approximations of the DCT/DST, such as the transforms defined for H.265/HEVC. Compared to the orthogonal DCT transform, such integer approximations are typically scaled by a certain factor. In order to preserve the norm of the residual block that is processed by the forward and inverse transforms, additional scaling factors are applied as part of the transform process. The scaling factors are typically selected based on certain constraints, such as scaling factors that are powers of two for shift operations, bit depth of the transform coefficients, trade-offs between precision and implementation costs, etc. Specific scaling factors are, for example, specified for the inverse transform, such as by the inverse transform processing unit 212 (and the corresponding inverse transform, such as by the inverse transform processing unit 312 in the video decoder 30), and corresponding scaling factors for the forward transform, such as by the transform processing unit 206, can be specified as appropriate in the encoder 20.

Embodiments of video encoder 20 (respectively transform processing unit 206) may be configured to output transform parameters, such as the type of transform or transforms, for example, directly or encoded or compressed via entropy encoding unit 270, so that, for example, video decoder 30 can receive and use the transform parameters for decoding.

Quantization

The quantization unit 208 may be configured to quantize the transform coefficients 207 to obtain quantized coefficients 209, for example by applying scalar quantization or vector quantization. The quantized coefficients 209 may also be referred to as quantized transform coefficients 209 or quantized residual coefficients 209.

The quantization process may reduce the bit depth associated with some or all of the transform coefficients 207. For example, an n-bit transform coefficient may be rounded to an m-bit transform coefficient during quantization, where n is greater than m. The degree of quantization may be changed by adjusting the quantization parameter (QP). For example, for scalar quantization, a different scaling may be applied to achieve finer or coarser quantization. Smaller quantization step sizes correspond to finer quantization, while larger quantization step sizes correspond to coarser quantization. The applicable quantization step size may be specified by the quantization parameter (QP). The quantization parameter may, for example, be an index for a predetermined set of applicable quantization step sizes. For example, small quantization parameters may correspond to fine quantization (small quantization step sizes), and large quantization parameters may correspond to coarse quantization (large quantization step sizes), or vice versa. Quantization may include division by a quantization step size, and the corresponding and/or inverse dequantization, for example by the inverse quantization unit 210, may include multiplication by the quantization step size. Embodiments in accordance with some standards, such as HEVC, may be configured to use a quantization parameter to determine the quantization step size. Typically, the quantization step size may be calculated based on the quantization parameter using a fixed point approximation of an equation that includes division. Additional scaling factors may be introduced for quantization and dequantization to restore the norm of the residual block that may have been changed due to the scaling used in the fixed point approximation of said equation for the quantization step size and the quantization parameter. In one exemplary implementation, the scaling of the inverse transform and the dequantization may be combined. Alternatively, customized quantization tables may be used and signaled from the encoder to the decoder, for example in a bitstream. Quantization is a lossy operation, with losses increasing as the quantization step size increases.

Embodiments of video encoder 20 (respectively quantization unit 208) may be configured to output quantization parameters (QP), for example directly or encoded via entropy encoding unit 270, so that, for example, video decoder 30 can receive and apply quantization parameters for decoding.

Inverse quantization

The inverse quantization unit 210 may be configured to apply the inverse quantization of the quantization unit 208 to the quantized coefficients to obtain dequantized coefficients 211, for example by applying the inverse quantization scheme applied by the quantization unit 208, based on or using the same quantization step size as the quantization unit 208. The dequantized coefficients 211 may also be referred to as dequantized residual coefficients 211 and correspond - although they are typically not identical to the transform coefficients due to quantization loss - to the transform coefficients 207.

Inverse transformation

The inverse transform processing unit 212 may be configured to apply an inverse transform of the transform applied by the transform processing unit 206, such as an inverse discrete cosine transform (DCT) or an inverse discrete sine transform (DST) or other inverse transforms, to obtain a reconstructed residual block 213 (or corresponding dequantized coefficients 213) in the sample domain. The reconstructed residual block 213 may also be referred to as a transform unit 213.

Recovery

The reconstruction unit 214 (e.g., the adder or summer 214) may be configured to add the transform unit 213 (i.e., the reconstructed residual block 213) to the prediction unit 265 to obtain the reconstructed block 215 in the sample domain, for example by adding, sample by sample, a sample value of the reconstructed residual block 213 and a sample value of the prediction unit 265.

Filtration

The loop filter unit 220 (or shortened "loop filter" 220) may be configured to filter the reconstructed block 215 to obtain the filtered block 221 or, in general, to filter the reconstructed samples to obtain filtered sample values. The loop filter unit, for example, is configured to smooth pixel transitions or otherwise improve the quality of the video. The loop filter unit 220 may comprise one or more loop filters, such as a deblocking filter, an adaptive sample offset (SAO) filter, or one or more other filters, such as an adaptive loop filter (ALF), a noise suppression filter (NSF), or any combination thereof. In an example, the loop filter unit 220 may comprise a deblocking filter, SAO, and ALF. The order of the filtering process may be a deblocking filter, SAO, and ALF. In another example, a process called Luminance Mapping with Chroma Scaling (LMCS) is added (namely, an adaptive mapper in the loop). This process is performed before deblocking. In another example, the deblocking filter process can also be applied to internal sub-block edges, such as affine sub-block edges, ATMVP sub-block edges, sub-block transform (SBT) edges, and internal sub-section (ISP) edges.

To effectively remove blocking artifacts that occur for large "blocks", VVC uses a deblocking filter with a larger number of taps. Here, the term "blocks" is used in a very general sense and can refer to a "transform block (TB), prediction block (PB), or coding unit (CU) block". The filter with a larger number of taps is applied to both the luma and chroma components. The longer tap filter for the luma components modifies a maximum of 7 samples for each row of samples perpendicular and adjacent to the edge, and is applied to blocks of size >=32 samples in the deblocking direction, i.e., for vertical edges, the block width must be >=32 samples, and for horizontal edges, the block height must be >=32 samples.

The chroma filter with a large number of taps is applied to chroma blocks when both blocks adjacent to a given edge have a size >=8 samples, and it changes a maximum of three samples on both sides of the edge. Therefore, for vertical edges, the block width of both blocks adjacent to the edge must be >=8 samples, and for horizontal edges, the block height of both blocks adjacent to the edge must be >=8 samples. Although the loop filter block 220 is shown in Fig. 2 as a loop filter, in other configurations, the loop filter block 220 can be implemented as a post-loop filter. The filtered block 221 can also be referred to as a filtered reconstructed block 221.

Embodiments of video encoder 20 (respectively loop filter unit 220) may be configured to output loop filter parameters (such as SAO filter parameters or ALF filter parameters or LMCS parameters), for example, directly or encoded by entropy encoding unit 270, so that, for example, decoder 30 can receive and apply the same loop filter parameters or corresponding loop filters for decoding.

Decoded image buffer

The decoded picture buffer (DPB) 230 may be a memory that stores reference pictures or, in general, reference picture data for encoding video data by the video encoder 20. The DPB 230 may be formed by any of a variety of memory devices, such as a dynamic random access memory (DRAM), including synchronous DRAM (SDRAM), magnetoresistive RAM (MRAM), resistive RAM (RRAM) or other types of memory devices. The decoded picture buffer (DPB) 230 may be configured to store one or more filtered blocks 221. The decoded picture buffer 230 may be further configured to store other previously filtered blocks, such as previously reconstructed and filtered blocks 221, of the same current picture or different pictures, such as previously reconstructed pictures, and may provide complete previously reconstructed, i.e. decoded, pictures (and corresponding reference blocks and samples) and/or partially reconstructed current picture (and corresponding reference blocks and samples), for example, for inter-picture prediction. Decoded picture buffer (DPB) 230 can also be configured to store one or more unfiltered reconstructed blocks 215 or, in general, unfiltered reconstructed samples, for example if reconstructed block 215 is not filtered by loop filter unit 220, or any other additionally processed version of reconstructed blocks or samples.

Mode selection (separation and prediction)

The mode selection unit 260 comprises a splitting unit 262, an inter-prediction unit 244 and an intra-prediction unit 254 and is configured to receive or obtain original image data, such as an original block 203 (the current block 203 of the current image 17), and reconstructed image data, such as filtered and/or unfiltered reconstructed samples or blocks of the same (current) image and/or from one or a plurality of previously decoded images, such as from a decoded image buffer 230 or other buffers (for example, a linear (line) buffer, not shown). The reconstructed image data is used as reference image data for prediction, such as inter-prediction or intra-prediction, to obtain a prediction block 265 or a predictor 265.

The mode selection unit 260 may be configured to determine or select a split for the current block prediction mode (including no split) and a prediction mode (for example, an intra or inter frame prediction mode) and to generate a corresponding prediction block 265, which is used to calculate the residual block 205 and to reconstruct the reconstructed block 215.

Embodiments of the mode selection unit 260 may be configured to select a partition and a prediction mode (e.g., from those supported by or available to the mode selection unit 260) that provide the best match, or in other words, the minimum residual (minimum residual means the best compression for transmission or storage), or the minimum signaling overhead (minimum signaling overhead means the best compression for transmission or storage), or that takes into account or balances both factors. The mode selection unit 260 may be configured to determine the partition and prediction mode based on rate/distortion optimization (RDO), that is, to select the prediction mode that provides the minimum distortion at a certain rate. Terms such as "best", "minimum", "optimal", etc. in this context do not necessarily refer to the all-encompassing "best", "minimum", "optimal", etc., but may also refer to the fulfillment of a selection or termination criterion, such as when a value exceeds or falls below a threshold, or other constraints potentially leading to "suboptimal selection" but reducing complexity and processing time.

In other words, the partitioning unit 262 may be configured to partition an image from a video sequence into a sequence of coding tree units (CTUs), and the CTU 203 may be further partitioned into smaller block partitions or sub-blocks (which again form blocks), for example, iteratively using a quadrant partition (QT), a binary partition (BT) or a ternary tree partition (TT) or any combination thereof, and to perform, for example, a prediction for each of the partitions of the block or sub-blocks, wherein the mode selection comprises selecting a tree structure of the partitioned block 203, and the prediction modes are applied to each of the partitions or sub-blocks of the block.

The following explains in more detail the separation (e.g., by means of the separation unit 260) and the prediction processing (by means of the inter-frame prediction unit 244 and the intra-frame prediction unit 254) performed by the exemplary video encoder 20.

Separation

The partitioning unit 262 may be configured to partition an image from a video sequence into a sequence of coding tree units (CTUs), and the partitioning unit 262 may partition (or divide) the coding tree unit (CTU) 203 into smaller parts, such as smaller blocks of a square or rectangular size. For an image that has three arrays of samples, the CTU consists of an N×N block of luma samples together with two corresponding blocks of chroma samples. The maximum allowable size of a luma block in a CTU is specified as 128×128 in the development of universal video coding (VVC), but in the future it may be specified as a value different from 128×128, such as 256×256. The CTUs of an image may be clustered/grouped as groups of slices/tiles, tiles or bricks. A tile covers a rectangular area of an image, and a tile may be divided into one or more bricks. A brick consists of multiple rows of CTUs within a tile. A tile that is not divided into multiple bricks may be called a brick. However, a brick is a true subset of a tile and is not called a tile. VVC supports two tile group modes, namely slice/tile group raster scan mode and rectangular slice mode. In tile group raster scan mode, a slice/tile group contains a sequence of tiles in a tiled raster scan of an image. In rectangular slice mode, a slice contains a number of image bricks that together form a rectangular region of the image. The bricks of a rectangular slice are arranged in the order of the slice's raster scan bricks. These smaller blocks (which may also be referred to as subblocks) may be further divided into even smaller sections. It is also called a tree split or hierarchical tree splitting, in which a root block, for example at the root level 0 of the tree (hierarchy level 0, depth 0), may be recursively split, for example divided into two or more blocks of the next lower level of the tree, for example nodes at level 1 of the tree (hierarchy level 1, depth 1), whereby these blocks may be split again into two or more blocks of the next lower level, for example level 2 of the tree (hierarchy level 2, depth 2), and so on until the split is terminated, for example due to the fulfillment of a termination criterion, such as reaching the maximum tree depth or the minimum block size. Blocks that are not further split are also called leaf blocks or leaf nodes of the tree. A tree using two-partition splitting is called a binary tree (BT), a tree using three-partition splitting is called a ternary tree (TT), and a tree using four-partition splitting is called a quadtree (QT).

For example, a coding tree unit (CTU) may be or contain a CTB of luma samples, two corresponding CTBs of chroma samples of an image that has three arrays of samples, or a CTB of samples of a monochrome image or an image that is encoded using three separate color planes and syntax structures used to encode the samples. Accordingly, a coding tree block (CTB) may be an N×N block of samples for some value of N, so that dividing a component into a CTB is a split. A coding unit (CU) may be or contain a coding block of luma samples, two corresponding coding blocks of chroma samples of an image that has three arrays of samples, or a coding block of samples of a monochrome image or an image that is encoded using three separate color planes and syntax structures used to encode the samples. Accordingly, a coding block (CB) may be an M×N block of samples for some values of M and N, so that dividing a CTB into coding blocks is a split.

In embodiments such as those according to HEVC, a coding tree unit (CTU) may be divided into CUs using a quadtree structure designated as a coding tree. The decision on whether to code an image region using inter-frame (temporal) or intra-frame (spatial) prediction is made at the leaf CU level. Each leaf CU may be further divided into one, two or four PUs according to a PU division type. Within one PU, the same prediction process is applied, and the relevant information is transmitted to a PU-based decoder. After obtaining a residual block by applying a prediction process based on a PU division type, the leaf CU may be divided into transform units (TUs) according to another quadtree structure similar to the coding tree for the CU.

In embodiments, for example, according to the latest video coding standard currently under development, which is referred to as universal video coding (VVC), a combined nested multi-type quadtree tree using a segmentation structure of binary and ternary partitions, for example, is used to partition a coding tree unit. In the coding tree structure, in the coding tree unit, the CU may have either a square or a rectangular shape. For example, the coding tree unit (CTU) is first partitioned by a quaternary tree. Then, the leaf nodes of the quaternary tree can be further partitioned by a multi-type tree structure. There are four types of partitioning in the multi-type tree structure: vertical binary partitioning (SPLIT_BT_VER), horizontal binary partitioning (SPLIT_BT_HOR), vertical ternary partitioning (SPLIT_TT_VER), and horizontal ternary partitioning (SPLIT_TT_HOR). The leaf nodes of the multi-type tree are called coding units (CUs), and unless the CU is too large for the maximum transform length, this segmentation is used to predict and process the transform without any further partitioning. This means that in most cases, CUs, PUs, and TUs have the same block size in the multi-type tree nested block structure quadtree. An exception occurs when the maximum supported transform length is less than the width or height of the color component of the CU. VVC develops a unique mechanism for signaling the partitioning of the partitioning information in the multi-type tree nested block structure quadtree. In the signaling mechanism, the coding tree unit (CTU) is considered as the root of the quaternary tree and is first partitioned by the quaternary tree structure. Each leaf node of the quaternary tree (when it is large enough to allow it) is then further partitioned by the multi-type tree structure. In the multi-type tree structure, the first flag (mtt_split_cu_flag) indicating whether the node is further split is signaled; when the node is further split, the second flag (mtt_split_cu_vertical_flag) indicating the split direction is signaled, and then the third flag (mtt_split_cu_binary_flag) indicating whether the split is binary or triple split is signaled. Based on the values of mtt_split_cu_vertical_flag and mtt_split_cu_binary_flag, the multi-type tree splitting mode (MttSplitMode) of the CU can be obtained by the decoder based on a predefined rule or table. It should be noted that for a certain design, such as a pipeline processing scheme with 64×64 luma blocks and 32×32 chroma blocks in VVC hardware decoders, TT splitting is prohibited when the width or height of the luma coding block is greater than 64, since shown in Figure 6. TT splitting is also prohibited when the width or height of the chroma coding block is greater than 32. The pipeline processing scheme will split the image into virtual pipeline data units (VPDUs), which are defined as non-overlapping image blocks. In hardware decoders, consecutive VPDUs are processed by several pipeline stages simultaneously. The VPDU size is roughly proportional to the buffer size in most pipeline stages, so it is important to keep the VPDU size small. In most hardware decoders, the VPDU size can be set equal to the maximum transform block (TB) size. However, in VVC, ternary tree (TT) and binary tree (BT) splitting can result in larger VPDUs.

Furthermore, it should be noted that when a portion of a tree node block exceeds the lower or right boundary of the image, the tree node block is forcibly split until all discrete samples of each coded CU are within the image boundaries.

As an example, the Intra Sub-Partitions (ISP) tool can divide intra-predicted luminance blocks vertically or horizontally into 2 or 4 subdivisions depending on the block size.

In one example, mode selection unit 260 of video encoder 20 may be configured to perform any combination of the partitioning methods described herein.

As described above, video encoder 20 is configured to determine or select the best or optimal prediction mode from a set of (e.g., predetermined) prediction modes. The set of prediction modes may comprise, for example, intra-frame prediction modes and/or inter-frame prediction modes.

Intraframe prediction

The set of intra-frame prediction modes may comprise 35 different intra-frame prediction modes, such as non-directional modes such as the DC (or average) mode and the planar mode, or directional modes such as defined in HEVC, or may comprise 67 different intra-frame prediction modes, such as non-directional modes such as the DC (or average) mode and the planar mode, or directional modes such as defined for VVC. For example, several conventional angular intra-frame prediction modes are adaptively replaced by wide-angle intra-frame prediction modes for non-square blocks, such as defined in VVC. As another example, in order to avoid division operations for DC prediction, only the longer side is used to calculate the average value for non-square blocks. In addition, the intra-frame prediction results of the planar mode may be further modified using the position-dependent intra-frame prediction combination (PDPC) method.

The intra-frame prediction block 254 is configured to use the reconstructed discrete samples of adjacent blocks of the same current image to form the intra-frame prediction block 265 according to the intra-frame prediction mode of the set of intra-frame prediction modes.

The intra-frame prediction unit 254 (or, in general, the mode selection unit 260) is further configured to output the intra-frame prediction parameters (or, in general, information indicating the selected intra-frame prediction mode for the block) to the entropy coding unit 270 in the form of a syntax element 266 for inclusion in the encoded image data 21 so that, for example, the video decoder 30 can receive and use the prediction parameters for decoding.

Interframe prediction

The set (or possible) of inter-prediction modes depends on the available reference pictures (i.e. previously at least partially decoded pictures, e.g. stored in DBP 230) and other inter-prediction parameters, e.g. whether the entire reference picture or only a part, e.g. a window search area around the area of the current block, of the reference picture is used to find the best match of the reference block, and/or e.g. whether pixel interpolations, e.g. half/half-pixel, quarter-pixel and/or 1/16 pixel interpolation, are applied or not.

In addition to the above prediction modes, skip mode, direct mode and/or other inter-frame prediction mode may be used.

For example, in the advanced merge prediction mode, the merge candidate list in this mode is constructed by including the following five types of candidates in order: Spatial MVP from neighboring spatial CUs, Temporal MVP from co-located CUs, History-based MVP from the FIFO table, Pairwise average MVP, and zero MVs. And the decoder-side motion vector refinement based on bilateral agreement (DMVR) can be applied to improve the MV accuracy of the merge mode. The MVD fusion mode (MMVD) comes from the motion vector difference fusion mode. The MMVD flag is signaled immediately after sending the skip flag and the merge flag to indicate whether the MMVD mode is used for the CU. And the adaptive motion vector resolution (AMVR) scheme at the CU level can be applied. AMVR allows the MVD of the CU to be encoded with different accuracy. Depending on the prediction mode for the current CU, the MVD of the current CU can be adaptively selected. When a CU is encoded in fusion mode, the combined inter/intra prediction (CIIP) mode can be applied to the current CU. A weighted averaging of the inter and intra prediction signals is performed to obtain the CIIP prediction. Affine motion compensation prediction, the affine motion field of a block is described by the motion information of two checkpoint motion vectors (4 parameters) or three checkpoint motion vectors (6 parameters). Sub-block-based temporal motion vector prediction (SbTMVP), which is similar to temporal motion vector prediction (TMVP) in HEVC, but predicts the motion vectors of CU subunits within the current CU. Bidirectional optical flow (BDOF), previously called BIO, is a simpler version that requires much less computation, especially in terms of the number of multiplications and the multiplier size. Triangular partition mode, in this mode, the CU is uniformly divided into two triangular partitions using either diagonal partition or anti-diagonal partition. In addition, the dual prediction mode is extended beyond simple averaging to provide a weighted averaging of two prediction signals.

The inter-picture prediction unit 244 may include a motion estimation (ME) unit and a motion compensation (MC) unit (both not shown in Fig. 2). The motion estimation unit may be configured to receive or obtain an image block 203 (the current image block 203 of the current image 17) and a decoded image 231, or at least one or a plurality of previously reconstructed blocks, such as reconstructed blocks of one or a plurality of other/different previously decoded images 231, for motion estimation. For example, the video sequence may comprise the current image and the previously decoded images 231, or, in other words, the current image and the previously decoded images 231 may be part of or form a sequence of images forming the video sequence.

The encoder 20 may, for example, be configured to select a reference block from said plurality of reference blocks of the same or different images from a plurality of other images and to provide the reference image (or reference image index) and/or an offset (spatial offset) between the position (x, y coordinates) of the reference block and the position of the current block as inter-frame prediction parameters to the motion estimation block. This offset is also called a motion vector (MV).

The motion compensation unit may be configured to receive, for example, an inter-prediction parameter and to perform inter-prediction based on or using the inter-prediction parameter to obtain the inter-prediction block 265. The motion compensation performed by the motion compensation unit may include receiving or generating a prediction block based on a motion vector/block determined by motion estimation, possibly performing interpolations with sub-pixel accuracy. The interpolation filtering may generate additional pixel samples from known pixel samples, thus potentially increasing the number of candidate prediction blocks that can be used to code the image block. After receiving the motion vector for the PU of the current image block, the motion compensation unit may determine the location of the prediction block pointed to by the motion vector in one of the reference image lists.

The motion compensation unit may also generate syntax elements associated with blocks and video slices for use by the video decoder 30 when decoding image blocks of a video slice. In addition to or as an alternative to slices and corresponding syntax elements, tile groups and/or tiles and corresponding syntax elements may be generated or used.

Entropy coding

The entropy coding unit 270 may be configured to apply, for example, an entropy coding algorithm or scheme (e.g., a variable length coding (VLC) scheme, a context-adaptive VLC (CAVLC) scheme, an arithmetic coding scheme, binarization, context coding), adaptive binary arithmetic coding (CABAC) based on the context-adaptive binary arithmetic coding (SBAC) syntax, probability interval partitioning entropy coding (PIPE) or another entropy coding methodology or method) or bypass (without compression) the quantized coefficients 209, the inter-frame prediction parameters, the intra-frame prediction parameters, the loop filter parameters and/or other syntax elements to obtain coded image data 21 that can be output via the output 272, for example, in the form of an encoded bitstream 21, so that, for example, the video decoder 30 can receive and use parameters for decoding. The bit stream can, for example, have a form as indicated further in Fig. 16 below. Thus, the embodiments described in connection with this figure are considered to be included also in the bit stream 21 described here. In addition, any structure of the bit stream mentioned here can be provided as a bit stream 21 in the sense of this embodiment. The coded bit stream 21 can be transmitted to the video decoder 30 or stored in memory for subsequent transmission or retrieval by the video decoder 30.

Other changes in the structure of the video encoder 20 may be used to encode the video stream. For example, the encoder 20, which is not based on a transform, may quantize the residual signal directly without the transform processing unit 206. In another implementation, the encoder 20 may have a quantization unit 208 and an inverse quantization unit 210 combined into a single unit.

Decoder and decoding method

Fig. 3 shows an example of a video decoder 30 that may be configured to implement the techniques of the present disclosure. The video decoder 30 may be configured to receive encoded image data 21 (e.g., encoded bitstream 21), such as encoded by the encoder 20, to obtain a decoded image 331. The encoded image data or bitstream comprises information for decoding the encoded image data, such as data that represents image blocks of a coded video slice (and/or tiles or groups of tiles) and associated syntax elements.

In the example of Fig. 3, decoder 30 comprises an entropy decoding unit 304, an inverse quantization unit 310, an inverse transform processing unit 312, a restoration unit 314 (e.g., an adder 314), a loop filter 320, a decoded picture buffer (DPB) 330, a mode applying unit 360, an inter-prediction unit 344, and an intra-prediction unit 354. Inter-prediction unit 344 may be or include a motion compensation unit. Video decoder 30 may, in some examples, perform a decoding step that is generally the reverse of the encoding step described with respect to video encoder 100 in Fig. 2.

As explained with respect to the encoder 20, the inverse quantization unit 210, the inverse transform processing unit 212, the reconstruction unit 214, the loop filter 220, the decoded picture buffer (DPB) 230, the inter-picture prediction unit 344 and the intra-picture prediction unit 354 are also referred to as forming an “on-chip decoder” of the video encoder 20. Accordingly, the inverse quantization unit 310 may be identical in function to the inverse quantization unit 110, the inverse transform processing unit 312 may be identical in function to the inverse transform processing unit 212, the reconstruction unit 314 may be identical in function to the reconstruction unit 214, the loop filter 320 may be identical in function to the loop filter 220, and the decoded picture buffer 330 may be identical in function to the decoded picture buffer 230. Therefore, the explanations provided for the corresponding blocks and functions of the video encoder 20 apply accordingly to the corresponding blocks and functions of the video decoder 30.

Entropy Decoding

The entropy decoding unit 304 may be configured to parse the bit stream 21 (or, in general, the encoded image data 21) and perform, for example, entropy decoding of the encoded image data 21 to obtain, for example, quantized coefficients 309 and/or decoded coding parameters (not shown in Fig. 3), such as any or all inter-prediction parameters (e.g., a reference image index and a motion vector), an intra-prediction parameter (e.g., an intra-prediction mode or index), transform parameters, quantization parameters, loop filter parameters and/or other syntax elements. The entropy decoding unit 304 may be configured to apply decoding algorithms or schemes corresponding to the coding schemes as described in relation to the entropy coding unit 270 of the encoder 20. The entropy decoding unit 304 may be further configured to provide the inter-frame prediction parameters, the intra-frame prediction parameter and/or other syntax elements to the mode applying unit 360 and other parameters to other units of the decoder 30. The video decoder 30 may receive syntax elements at the video slice level and/or the video block level. In addition to or as an alternative to slices and corresponding syntax elements, tile groups and/or tiles and corresponding syntax elements may be received and/or used.

Inverse quantization

The inverse quantization unit 310 may be configured to receive quantization parameters (QP) (or, in general, information related to inverse quantization) and quantized coefficients from the encoded image data 21 (e.g., by means of parsing and/or decoding, e.g., by means of the entropy decoding unit 304) and to apply, based on the quantization parameters, inverse quantization with respect to the decoded quantized coefficients 309 to obtain dequantized coefficients 311, which may also be referred to as transform coefficients 311. The inverse quantization process may include using a quantization parameter determined by the video encoder 20 for each video block in the video slice (or tile or group of tiles) to determine a degree of quantization and, similarly, a degree of inverse quantization to be applied.

Inverse transformation

The inverse transform processing unit 312 may be configured to receive the dequantized coefficients 311, also referred to as the transform coefficients 311, and to apply a transform to the dequantized coefficients 311 in order to obtain reconstructed residual blocks 213 in the sample domain. The reconstructed residual blocks 213 may also be referred to as transform blocks 313. The transform may be an inverse transform, such as an inverse DCT, an inverse DST, an inverse integer transform, or a conceptually similar process to the inverse transform. The inverse transform processing unit 312 may be further configured to receive transform parameters or corresponding information from the encoded image data 21 (e.g., by parsing and/or decoding, such as by means of the entropy decoding unit 304) in order to determine a transform to be applied to the dequantized coefficients 311.

Recovery

The reconstruction unit 314 (for example, the addition unit or adder 314) may be configured to add the reconstructed residual block 313 with the prediction unit 365 to obtain the reconstructed block 315 in the sample domain, for example by adding the sample values of the reconstructed residual block 313 and the sample values of the prediction unit 365.

Filtration

The loop filter unit 320 (either in the encoding loop or after the encoding loop) can be configured to filter the reconstructed block 315 to obtain a filtered block 321, for example, to smooth pixel transitions or otherwise improve the quality of the video. The loop filter unit 320 can comprise one or more loop filters, such as a deblocking filter, an adaptive sampling offset (SAO) filter, or one or more other filters, such as an adaptive loop filter (ALF), a noise suppression filter (NSF), or any combination thereof. In an example, the loop filter unit 220 can comprise a deblocking filter, a SAO filter, and an ALF filter. The order of the filtering process can be a deblocking filter. In another example, a process called luminance mapping with chroma scaling (LMCS) is added (namely, an adaptive converter in the loop). This process is performed before deblocking. In another example, the deblocking filter process may also be applied to internal sub-block edges, such as affine sub-block edges, ATMVP sub-block edges, sub-block transform (SBT) edges, and internal sub-section (ISP) edges. Although loop filter unit 320 is shown in Fig. 3 as a loop filter, in other configurations, loop filter unit 320 may be implemented as a post-loop filter.

The JVET-P0080 and JVET-O0630 offer a new in-loop filter called the inter-component ALF filter, which is also referred to here as CC-ALF or CCALF. CC-ALF operates as part of the adaptive loop filtering process and uses the luminance sample values to refine each chroma component (i.e. the Cr or Cb component, for example, the first chroma component is precisely the Cb component and the second chroma component is precisely the Cr component). CC-ALF operates by applying a diamond-shaped filter to the luminance component for each chroma sample of the chroma component, and then the filtered output value is then used as a correction for the output of the ALF chroma process.

The Cross-Component Adaptive Loop Filter (CC-ALF) can be used as a loop filter and as a post-processing step respectively.

Decoded image buffer

The decoded video blocks 321 of the image are then stored in a decoded picture buffer 330, which stores the decoded pictures 331 as reference pictures for subsequent motion compensation for other pictures and/or for display output, respectively.

The decoder 30 may be configured to output the decoded image 311, such as via an output 312, for presentation or viewing to a user.

Prediction

The inter-prediction unit 344 may be identical to the inter-prediction unit 244 (in particular, the motion compensation unit), and the intra-prediction unit 354 may be identical to the inter-prediction unit 254 in function, and makes decisions on division or partitioning and performs prediction based on the division and/or prediction parameters or corresponding information received from the encoded image data 21 (for example, by parsing and/or decoding, for example, by means of the entropy decoding unit 304). The mode applying unit 360 may be configured to perform prediction (intra-prediction or inter-prediction) for each block based on the reconstructed images, blocks or corresponding samples (filtered or unfiltered) to obtain a prediction block 365.

When the video slice is encoded as an intra-frame-coded (I) slice, the intra-frame prediction unit 354 of the mode applying unit 360 is configured to generate a prediction block 365 for a block of an image of the current video slice based on a signaled intra-frame prediction mode and data from previously decoded blocks of the current image. When the video image is encoded as an inter-frame-coded (i.e. B or P) slice, the inter-frame prediction unit 344 (e.g., a motion compensation unit) of the mode applying unit 360 is configured to generate prediction blocks 365 for a video block of the current video slice based on motion vectors and other syntax elements received from the entropy decoding unit 304. For inter-frame prediction, the prediction blocks can be generated from one of the reference pictures within one of the reference picture lists. Video decoder 30 may construct reference frame lists, List 0 and List 1, using default construction methods based on reference pictures stored in DPB 330. The same or similar may be applied to or through embodiments using tile groups (e.g. video tile groups) and/or tiles (e.g. video tiles) in addition to or alternatively to slices (e.g. video slices), for example, video may be coded using I, P or B tile groups and/or tiles.

The mode applying unit 360 may be configured to determine prediction information for a video block of the current video slice by parsing motion vectors or related information and other syntax elements, and uses the prediction information to generate prediction blocks for the current video block, deciphered. For example, the mode applying unit 360 uses some of the received syntax elements to determine a prediction mode (e.g., intra-frame or inter-frame prediction) used to code the video blocks of the video slice, a type of the inter-frame prediction slice (e.g., a B slice, a P slice, or a GPB slice), construction information for one or more reference picture lists for the slice, motion vectors for each inter-frame coded video block of the slice, an inter-frame prediction status for each inter-frame coded video block of the slice, and other information for decoding the video blocks in the current video slice. The same or similar may be applied to or through embodiments using tile groups (e.g. video tile groups) and/or tiles (e.g. video tiles) in addition to or alternatively to slices (e.g. video slices), for example video may be encoded using I, P or B tile groups and/or tiles.

Embodiments of video decoder 30, as shown in Fig. 3, may be configured to divide and/or decode an image using slices (also referred to as video slices), wherein an image may be divided into or decoded using one or more slices (typically without overlapping), and each slice may comprise one or more blocks (e.g., CTUs) or one or more groups of blocks (e.g., tiles (H.265/HEVC and VVC) or bricks (VVC)).

Embodiments of video decoder 30, as shown in Fig. 3, may be configured to divide and/or decode an image using groups of slices/tiles (also called tile groups) and/or tiles (also called video tiles, wherein an image may be divided into or decoded using one or more groups of slices/tiles (typically non-overlapping), and each group of slices/tiles may contain, for example, one or more blocks (e.g., CTUs) or one or more tiles, wherein each tile may, for example, have a rectangular shape and may contain one or more blocks (e.g., CTUs), such as full or fractional blocks.

Other embodiments of video decoder 30 may be used to decode encoded image data 21. For example, decoder 30 may create an output video stream without loop filter unit 320. For example, decoder 30, which is not based on transform, may perform inverse quantization of the residual signal directly without inverse transform processing unit 312 for certain blocks or frames. In another implementation, video decoder 30 may have inverse quantization unit 310 and inverse transform processing unit 312, combined into one unit.

It should be understood that in the encoder 20 and the decoder 30, the result of processing of some current stage can be further processed and then output to the next stage. For example, after interpolation filtering, obtaining a motion vector or contour filtering, an additional operation such as truncation (Clip) or shift (Shift) can be performed on the result of processing of interpolation filtering, obtaining a motion vector or contour filtering.

It should be noted that additional operations can be applied to the obtained motion vectors of the current block (including but not limited to motion vectors of the affine mode checkpoint, motion vectors of a sub-block in the affine, planar, ATMVP modes, time motion vectors, and the like). For example, the value of a motion vector is limited to a predetermined range according to its representative bit. If the representative bit of the motion vector is bitDepth (bit depth), then the range is -2^(bitDepth-1) ~ 2^(bitDepth-1)-1, where "^" means exponentiation. For example, if bitDepth is set to 16, the range is -32768 ~ 32767; if bitDepth is set to 18, the range is -131072~131071. For example, the value of the resulting motion vector (e.g., MV of four 4×4 subblocks in one 8×8 block) is constrained so that the maximum difference between the integer parts of the MV of the four 4×4 subblocks does not exceed N pixels, e.g., is no more than 1 pixel. Here, two methods of constraining the motion vector according to bitDepth are presented.

Fig. 4 is a schematic diagram of a video encoding device 400 according to an embodiment of the present disclosure. The video encoding device 400 is suitable for implementing the disclosed embodiments that are described in this document. In an embodiment, the video encoding device 400 may be a decoder, such as video decoder 30 of Fig. 1A, or an encoder, such as video encoder 20 of Fig. 1A.

The video encoding device 400 comprises input ports 410 (or input ports 410) and receiver units 420 (Rx) for receiving data; a processor, logic unit or central processing unit (CPU) 430 for processing data; transmitter units 440 (Tx) and output ports 450 (or output ports 450) for transmitting data; and memory 460 for storing data. The video encoding device 400 may also comprise optical-to-electrical (OE) signal conversion components and electrical-to-optical (EO) signal conversion components connected to the input ports 410, receiver units 420, transmitter units 440 and output ports 450 to provide input or output of optical or electrical signals.

The processor 430 is implemented by hardware and software. The processor 430 can be implemented as one or more CPU chips, cores (for example, as a multi-core processor), FPGA, ASIC and DSP. The processor 430 communicates with the input ports 410, the receiver units 420, the transmitter units 440, the output ports 450 and the memory 460. The processor 430 includes an encoding module 470. The encoding module 470 implements the disclosed embodiments described above. For example, the encoding module 470 implements, processes, prepares or provides various encoding operations. Therefore, the inclusion of the encoding module 470 provides a significant improvement in the functionality of the video encoding device 400 and provides a transformation of the video encoding device 400 into another state. Alternatively, encoding module 470 is implemented as instructions stored in memory 460 and executed by processor 430.

Memory 460 may comprise one or more disks, tape drives, and solid-state drives and may be used as an overflow data storage device for storing programs when such programs are selected for execution and for storing instructions and data that are read during execution of programs. Memory 460 may be, for example, volatile and/or non-volatile and may be read-only memory (ROM), random access memory (RAM), ternary associative memory (TCAM), and/or static random access memory (SRAM).

Fig. 5is a simplified block diagram of the device500, which can be used as one or both of the source device 12 and the destination device 14 of Fig. 1 according to an exemplary embodiment.

The processor 502 in the device 500 may be a central processor. Alternatively, the processor 502 may be any other type of device or a plurality of devices capable of manipulating or processing information that currently exists or will be developed in the future. Although the disclosed implementations may be practiced with a single processor, as shown, for example, with the processor 502, speed and efficiency advantages may be achieved by using more than one processor.

Memory 504 in device 500 may be a read-only memory (ROM) or a random access memory (RAM) device in the implementation. Memory 504 may be a memory device of any other suitable type of device. Memory 504 may include code and data 506, which are accessed by processor 502 using bus 512. Memory 504 may further include an operating system 508 and application programs 510, wherein application programs 510 include at least one program that allows processor 502 to perform the methods described in this document. For example, application programs 510 may include applications 1 through N, which further include a video encoding application that performs the methods described in this document.

The device 500 may also include one or more output devices, such as a display 518. The display 518 may be, in one example, a touch display that combines a display with a touch element capable of receiving touch inputs. The display 518 may be connected to the processor 502 via a bus 512.

Although shown here as a single bus, the bus 512 of the device 500 may consist of multiple buses. In addition, the secondary storage 514 may be directly connected to other components of the device 500 or may be accessible via a network and may comprise a single embedded unit, such as a memory card, or multiple units, such as multiple memory cards. Thus, the device 500 may be implemented in a wide variety of configurations.

Detailed Description of Embodiments of the Present Disclosure

Video coding can be performed based on a color space and a color format. For example, color video plays an important role in multimedia systems, where different color spaces are used to represent color efficiently. A color space specifies color as numerical values using several components. A popular color space is the RGB color space, in which color is represented as a combination of the values of the three primary color components (i.e., red, green, and blue). The YCbCr color space is widely used for color video compression, as described in A. Ford and A. Roberts, “Colour space converts,” University of Westminster, London, Tech. Rep., August 1998.

YCbCr can be easily converted from the RGB color space by a linear transformation, and the redundancy between the different components, namely the inter-component redundancy, is significantly reduced in the YCbCr color space. One of the advantages of YCbCr is its backward compatibility with black-and-white television, since the Y signal carries luminance information. In addition, the chroma bandwidth can be reduced by subsampling the Cb and Cr components in a 4:2:0 chroma sampling format with a significantly smaller subjective impact than subsampling in the RGB color space. Because of these advantages, YCbCr is the main color space for video compression. There are other color spaces, such as YCoCg, used in video compression. In this disclosure, regardless of the actual color space used, the luminance (or L or Y) and the two chromins (Cb and Cr) are used to represent the three color components in the video compression scheme.

For example, when the sampling structure of the chroma format is 4:2:0 sampling, each of the two chroma arrays has half the height and half the width of the luma array. The nominal vertical and horizontal relative positions of the luma and chroma samples in the images are shown in Fig. 9A. Fig. 9B illustrates an example of 4:2:0 sampling. Fig. 9B illustrates an example of a combined luma block and chroma block. If the video format is YUV4:2:0, then there is one 16x16 luma block and two 8x8 chroma blocks.

In particular, the coding block or transform block contains a luminance block and two chrominance blocks.

As shown, the luma block contains four times as many samples as the chroma block. Specifically, the chroma block contains N samples by N samples, while the luma block contains 2N samples by 2N samples. Therefore, the luma block has four times the resolution of the chroma block. For example, when the YUV4:2:0 format is used, the luma samples can be reduced by a factor of four (e.g., the width by a factor of two and the height by a factor of two). YUV is a color encoding system that uses a color space in terms of the luma components Y and the two chroma components U and V.

Image Title:

The concept of image header was recently introduced in the VVC standard (as presented in JVET-P1006, P0095, P0120, P0239). See section 7.3.2.6 in JVET-P2001-VE for information on the image header syntax.

The current VVC draft proposes to transmit the mandatory picture header concept once for each picture as the first VCL NAL unit of the picture. The current VVC draft also moves several syntax elements currently present in the slice header into this picture header. Syntax elements that functionally only need to be transmitted once per picture are moved into the picture header instead of being transmitted multiple times for a given picture, e.g., syntax elements in the slice header are transmitted once per slice. Moving syntax elements out of the slice header is advantageous because the computations required to process the slice header can limit overall throughput.

For the adaptive loop filter (ALF), the following syntax elements (ALF-specific syntax elements) were introduced into the image header:

7.3.2.6 RBSP Image Header Syntax

picture_header_rbsp( ) { Descriptor …… if( sps_alf_enabled_flag ) { pic_alf_enabled_present_flag u(1) if( pic_alf_enabled_present_flag ) { pic_alf_enabled_flag u(1) if( pic_alf_enabled_flag ) { pic_num_alf_aps_ids_luma u(3) for( i = 0; i < pic_num_alf_aps_ids_luma; i++ ) pic_alf_aps_id_luma [ i ] u(3) if( ChromaArrayType != 0 ) pic_alf_chroma_idc u(2) if( pic_alf_chroma_idc ) pic_alf_aps_id_chroma u(3) } } } ……

Here, the syntax elements are pic_alf_enabled_present_flag, pic_alf_enabled_flag, pic_num_alf_aps_ids_luma, pic_alf_aps_id_luma[i], pic_alf_chroma_idc, pic_alf_aps_id_chroma. These syntax elements are provided in the image header, where their presence potentially depends on other syntax elements that have been previously or otherwise reported. For example, sps_alf_enabled_flag and ChromaArrayType are such other syntax elements.

In the following, any syntactic element designated by a descriptor in the table and/or highlighted in bold is a syntactic element that is signaled or provided in the current syntax structure.

The following syntax changes have been made to the slice header for ALF.

7.3.7.1 General Slice Header Syntax

slice_header( ) { Descriptor …… if( sps_alf_enabled_flag && !pic_alf_enabled_present_flag ) { slice_alf_enabled_flag u(1) if( slice_alf_enabled_flag ) { slice_num_alf_aps_ids_luma u(3) for( i = 0; i < slice_num_alf_aps_ids_luma; i++ ) slice_alf_aps_id_luma [ i ] u(3) if( ChromaArrayType != 0 ) slice_alf_chroma_idc u(2) if( slice_alf_chroma_idc ) slice_alf_aps_id_chroma u(3) } } ……..

The semantics of ALF image header records and slice header records are as follows:

pic_alf_enabled_present_flag equal to 1 indicates that pic_alf_enabled_flag, pic_num_alf_aps_ids_luma, pic_alf_aps_id_luma[i], pic_alf_chroma_idc, and pic_alf_aps_id_chroma are present in PH. pic_alf_enabled_present_flag equal to 0 indicates that pic_alf_enabled_flag, pic_num_alf_aps_ids_luma, pic_alf_aps_id_luma[i], pic_alf_chroma_idc, and pic_alf_aps_id_chroma are not present in PH. When pic_alf_enabled_present_flag is absent, it is assumed to be 0.

pic_alf_enabled_flag equal to 1 indicates that the adaptive contour filter is enabled for all slices associated with the PH, and can be applied to the Y, Cb, or Cr color component of the slices. pic_alf_enabled_flag equal to 0 indicates that the adaptive contour filter can be disabled for one, some, or all slices associated with the PH. If pic_alf_enabled_flag is absent, it is assumed to be 0.

pic_num_alf_aps_ids_luma specifies the number of ALF APS that PH-related slices belong to.

pic_alf_aps_id_luma [i] specifies the adaptation_parameter_set_id of the i-th ALF APS to which the luma component of PH-related slices belongs.

The alf_luma_filter_signal_flag value of an APS NAL unit with aps_params_type equal to ALF_APS and Adaptation_parameter_set_id equal to pic_alf_aps_id_luma[i] shall be equal to 1.

pic_alf_chroma_idc equal to 0 indicates that the adaptive contour filter is not applied to the Cb and Cr color components. pic_alf_chroma_idc equal to 1 indicates that the adaptive contour filter is applied to the Cb color component. pic_alf_chroma_idc equal to 2 indicates that the adaptive contour filter is applied to the Cr color component. pic_alf_chroma_idc equal to 3 indicates that the adaptive contour filter is applied to the Cb and Cr color components. When pic_alf_chroma_idc is absent, it is assumed to be 0.

pic_alf_aps_id_chroma specifies the id_adaptation_parameter_set_id of the ALF APS referenced by the chroma component of PH-related slices.

The alf_chroma_filter_signal_flag of an APS NAL unit that has aps_params_type equal to ALF_APS and Adaptation_parameter_set_id equal to pic_alf_aps_id_chroma must be equal to 1.

slice_alf_enabled_flag equal to 1 indicates that the adaptive edge filter is enabled and can be applied to the Y, Cb, or Cr color component in the slice. slice_alf_enabled_flag equal to 0 indicates that the adaptive edge filter is disabled for all color components in the slice. If absent, slice_alf_enabled_flag is assumed to be pic_alf_enabled_flag.

slice_num_alf_aps_ids_luma specifies the number of ALF APSs referenced by the slice. When slice_alf_enabled_flag is 1 and slice_num_alf_aps_ids_luma is not present, the value of slice_num_alf_aps_ids_luma is assumed to be equal to the value of pic_num_alf_aps_ids_luma.

slice_alf_aps_id_luma [i] specifies the adaptation_parameter_set_id of the i-th ALF APS referenced by the slice's luma component. The TemporalId of an APS NAL unit having aps_params_type equal to ALF_APS and adaptation_parameter_set_id equal to slice_alf_aps_id_luma[i] must be less than or equal to the TemporalId of the coded slice NAL unit. When slice_alf_enabled_flag is 1 and slice_alf_aps_id_luma[i] is absent, the value of slice_alf_aps_id_luma[i] is assumed to be equal to the value of pic_alf_aps_id_luma[i].

The alf_luma_filter_signal_flag value of an APS NAL unit that has aps_params_type equal to ALF_APS and Adaptation_parameter_set_id equal to slice_alf_aps_id_luma[i] must be equal to 1.

slice_alf_chroma_idc equal to 0 specifies that the adaptive contour filter is not applied to the Cb and Cr color components. slice_alf_chroma_idc equal to 1 specifies that the adaptive contour filter is applied to the Cb color component. slice_alf_chroma_idc equal to 2 specifies that the adaptive contour filter is applied to the Cr color component. slice_alf_chroma_idc equal to 3 specifies that the adaptive contour filter is applied to the Cb and Cr color components. When slice_alf_chroma_idc is absent, it is assumed to be equal to pic_alf_chroma_idc.

slice_alf_aps_id_chroma specifies the id_adaptation_parameter_set_id of the ALF APS referenced by the slice's chroma component. The TemporalId of an APS NAL unit that has aps_params_type equal to ALF_APS and adaptation_parameter_set_id equal to slice_alf_aps_id_chroma must be less than or equal to the TemporalId of the coded slice NAL unit. When slice_alf_enabled_flag is 1 and slice_alf_aps_id_chroma is absent, slice_alf_aps_id_chroma is assumed to be equal to pic_alf_aps_id_chroma.

The alf_chroma_filter_signal_flag value of an APS NAL unit that has aps_params_type equal to ALF_APS and an Adaptation_parameter_set_id equal to slice_alf_aps_id_chroma must be equal to 1.

As described above, when all slices have the same ALF filtering data, then instead of transmitting the ALF filtering data separately in each of the slice headers, the common ALF filtering data for all slices is transmitted only once in the image header and as a result, all slices inherit the ALF filtering data from the image header. This reduces the overhead of the slice header (in terms of number of bits).

The present disclosure collects all common syntax elements of CCALF, which are signaled in the header of each image slice and are defined in the image header. The present disclosure attempts to extend the same principle of ALF signaling to the inter-component ALF (CCALF) as well. Currently, for CCALF, each of the slice headers must convey the following information in a common way:

7.3.7.1 General Slice Header Syntax

slice_header( ) { Descriptor …… if( ChromaArrayType != 0 ) slice_cross_component_alf_cb_enabled_flag u(1) if( slice_cross_component_alf_cb_enabled_flag ) { slice_cross_component_alf_cb_aps_id u(3) slice_cross_component_cb_filters_signalled_minus1 ue(v) } if( ChromaArrayType != 0 ) slice_cross_component_alf_cr_enabled_flag u(1) if( slice_cross_component_alf_cr_enabled_flag ) { slice_cross_component_alf_cr_aps_id u(3) slice_cross_component_cr_filters_signalled_minus1 ue(v) } ……..

Therefore, each slice must convey all of the above syntactic elements, even if the information is the same in all slices in a given image.

Therefore, in order to reduce the overhead of the slice header, the present invention defines image header entries also for CCALF.

1.1 Technical problems solved by the present invention

The present disclosure introduces image header entries for CCALF to reduce slice overhead. As shown in Fig. 7, slices 1 through N contain the same CCALF filter information 7001. Therefore, each slice header must transmit the same data, which leads to redundancy and overhead in signaling the slice bits. As shown in Fig. 8, to eliminate this redundancy in the CCALF data, image header entries 8001 for CCALF are introduced that define common CCALF data (as well as information related to CCALF), and all slices can then inherit this common information 8002. Therefore, this eliminates redundancy in signaling and reduces the overhead of parsing slice headers.

1.2 Embodiments of the technical implementation of this disclosure

It should be noted that each of the following embodiments, disclosed as "alternative", may be provided in combination with any of the other (alternative) embodiments and may be specifically implemented using any of the above-described devices, such as an encoder and/or decoder, as mentioned in the above figures.

1.2.1 Alternative embodiment 1

The first step introduces a new Sequence Parameter Set (SPS) syntax element called the "second syntax element" (denoted below, for example, by sps_ccalf_enabled_flag), which controls whether CCALF is enabled or not. The syntax is shown below: The second syntax element (sps_ccalf_enabled_flag) completely separates the ALF operation from the CCALF operation and therefore allows ALF and CCALF to be enabled or disabled separately at the sequence level.

7.3.2.3 RBSP Sequence Parameter Set Syntax

seq_parameter_set_rbsp( ) { Descriptor …… sps_alf_enabled_flag u(1) sps_ccalf_enabled_flag u(1) …….

Here, sps_alf_enabled_flag is an example of a first syntax element that is also provided in the SPS level syntax. The first and second syntax elements may be signaled independently of each other, as shown in the table above. However, as for example provided in Alternative Embodiment 5 below, the second syntax element may also be signaled depending on, for example, the value that the first syntax element has or takes.

The new image header entries (in bold and italics) are shown below:

7.3.2.6 RBSP Image Header Syntax

picture_header_rbsp( ) { Descriptor …….. if( sps_alf_enabled_flag ) { pic_alf_enabled_present_flag u(1) if( pic_alf_enabled_present_flag ) { pic_alf_enabled_flag u(1) if( pic_alf_enabled_flag ) { pic_num_alf_aps_ids_luma u(3) for( i = 0; i < pic_num_alf_aps_ids_luma; i++ ) pic_alf_aps_id_luma [ i ] u(3) if( ChromaArrayType != 0 ) pic_alf_chroma_idc u(2) if( pic_alf_chroma_idc ) pic_alf_aps_id_chroma u(3) } } } if( sps_ccalf_enabled_flag ) { pic_ccalf_enabled_present_flag u(1) if( pic_ccalf_enabled_present_flag ) { pic_ccalf_enabled_flag u(1) if( pic_ccalf_enabled_flag ) { if( ChromaArrayType != 0 ) pic_cross_component_alf_cb_enabled_flag u(1) if( pic_cross_component_alf_cb_enabled_flag ) { pic_cross_component_alf_cb_aps_id u(3) pic_cross_component_cb_filters_signalled_minus1 ue(v) } if( ChromaArrayType != 0 ) pic_cross_component_alf_cr_enabled_flag u(1) if( pic_cross_component_alf_cr_enabled_flag ) { pic_cross_component_alf_cr_aps_id u(3) pic_cross_component_cr_filters_signalled_minus1 ue(v) } } } ……

Here, additional syntax elements are introduced into the image header, where these additional syntax elements can only be present if the first and/or second syntax elements take on certain values. This is indicated by the "if" syntax, depending on the value of the first syntax element and/or the second syntax element.

In particular, a third syntax element may be provided in the image header (here denoted as pic_ccalf_enabled_flag ) depending on the value of the second syntax element. This syntax element can specify (as explained below) whether CCALF should be enabled for the current image.

The fourth syntax element (e.g. pic_cross_component_alf_cb_enabled_flag ) may be additionally provided in the image header depending on the second syntax element.

Depending on, for example, the value of the second syntax element and/or the value of the third syntax element and/or the fourth syntax element , a fifth syntax element such as pic_cross_component_alf_cb_aps_id may be provided. In addition, a sixth syntax element may be provided in the image header. the syntactic element, denoted here as pic_cross_component_cb_filters_signalled_minus1 , potentially also depending on the second syntactic element, and/or the third syntactic element, and/or the fourth syntactic element.

In parallel to this, a seventh syntax element, designated above as pic_cross_component_alf_cr_enabled_flag , may be provided, depending on the second syntax element and/or the third syntax element.

Depending on, for example, the value of the seventh syntax element, but potentially also depending on the second syntax element and/or the third syntax element, an eighth element (e.g. pic_cross_component_alf_cr_aps_id ) and/or a ninth syntax element may be provided. (e.g. pic_cross_component_cr_filters_signalled_minus1 ).

The meaning of syntactic elements one through nine, and the meaning of syntactic elements ten through fourteen, additionally indicated below, will be explained later.

The syntax of a slice header is as follows:

7.3.7.1 General Slice Header Syntax

slice_header( ) { Descriptor ……. if( sps_alf_enabled_flag && !pic_alf_enabled_present_flag ) { slice_alf_enabled_flag u(1) if( slice_alf_enabled_flag ) { slice_num_alf_aps_ids_luma u(3) for( i = 0; i < slice_num_alf_aps_ids_luma; i++ ) slice_alf_aps_id_luma [ i ] u(3) if( ChromaArrayType != 0 ) slice_alf_chroma_idc u(2) if( slice_alf_chroma_idc ) slice_alf_aps_id_chroma u(3) } if( sps_ccalf_enabled_flag && ! pic_ccalf_enabled_present_flag) { slice_ccalf_enabled_flag u(1) if( slice_ccalf_enabled_flag ) { if( ChromaArrayType != 0 ) slice_cross_component_alf_cb_enabled_flag u(1) if( slice_cross_component_alf_cb_enabled_flag ) { slice_cross_component_alf_cb_aps_id u(3) slice_cross_component_cb_filters_signalled_minus1 ue(v) } if( ChromaArrayType != 0 ) slice_cross_component_alf_cr_enabled_flag u(1) if( slice_cross_component_alf_cr_enabled_flag ) { slice_cross_component_alf_cr_aps_id u(3) slice_cross_component_cr_filters_signalled_minus1 ue(v) } } …..

As noted above, in some embodiments, additional syntax elements provided in the slice header syntax may be provided only if the first and/or second syntax element and/or one or more additional syntax elements provided in the image header take corresponding values.

In particular, as shown above, the tenth syntactic element, such as slice_cross_component_alf_cb_enabled_flag , may be provided depending on the value of the second syntax element and potentially also depending on a fourteenth syntax element (optionally provided at the SPS level and designated here as ChromaArrayType) that is not equal to 0. In addition, an eleventh syntax element, designated above as slice_cross_component_alf_cb_aps_id , may be provided depending on the value of the second syntax element and/or depending on the value of the tenth syntax element.

Accordingly, a twelfth syntax element, such as slice_cross_component_alf_cr_enabled_flag , may be provided depending on the value of the second syntax element and potentially also depending on the fourteenth syntax element not being equal to 0. In addition, a thirteenth syntax element, which is designated above as slice_cross_component_alf_cr_aps_id , may be provided depending on the value of the second syntax element and/or depending on the value of the twelfth syntax element.

However, it is also intended that the syntactic elements (in particular the tenth through thirteenth syntactic elements) present in the slice header may be present regardless of the value of other syntactic elements, such as the second syntactic element or the fourteenth syntactic element. In particular, it may be envisaged that the syntactic elements related to the CC-ALF in the slice header (e.g. the tenth through thirteenth syntactic elements) take a default value if the first syntactic element, the second syntactic element, or another syntactic element indicates that the CC-ALF is not included.

The semantics of the newly introduced syntactic elements is as follows:

The second syntax element is designated here as sps_ccalf_enabled_flag . This is provided only as an example and does not limit the disclosure. In embodiments, a value of 0 for the second syntax element indicates that the inter-component adaptive loop filter is disabled for the current video sequence. A value of 1 for the second syntax element indicates that the inter-component adaptive loop filter is enabled for the current video sequence.

pic_ccalf_enabled_present_flagequal to 1 indicates that pic_ccalf_enabled_flag, pic_cross_component_alf_cb_enabled_flag, pic_cross_component_alf_cb_aps_id, pic_cross_component_alf_cb_filter_count_minus1, pic_cross_component_alf_cr_enabled_flag, pic_cross_component_alf_cr_aps_id, and count_minus1 are represented in PH (picture header). pic_alf_enabled_present_flag equal to 0 indicates that pic_ccalf_enabled_flag, pic_cross_component_alf_cb_enabled_flag, pic_cross_component_alf_cb_aps_id, pic_cross_component_alf_cb_filter_count_minus1, pic_cross_component_alf_cr_enabled_flag, pic_cross_component_alf_cr_aps_id, and pic_cross_component_alf_cr_filter_count_minus1 are not present in PH. When pic_ccalf_enabled_present_flag is absent, it is assumed to be 0.

The third syntax element (here denoted as pic_ccalf_enabled_flag ) value of 1 indicates that the inter-component adaptive contour filter is enabled for all slices associated with the PH and can be applied to the Cb or Cr color component of the slices. The third syntax element value of 0 indicates that the inter-component adaptive contour filter can be disabled for one, some, or all slices associated with the PH (image header). If absent, the third syntax element value can be assumed to be 0.

The fourth syntax element was mentioned above and can be indicated here by pic_cross_component_alf_cb_enabled_flag . The value of the fourth syntax element equal to 0 indicates that the cross-component Cb filter is not applied to the Cb color component of all slices associated with PH. When the value of the fourth syntax element equals to 1, it indicates that the cross-component Cb filter is applied to the Cb color component of all slices associated with PH. When the fourth syntax element is absent, it is assumed to be 0.

The fifth syntactic element can be denoted here bypic_cross_component_alf_cb_aps_id.Fifth The syntax element specifies the id_adaptation_parameter_set_id, which is the Cb color component of all slices associated with the PH.

The sixth syntax element can be indicated here by pic_cross_component_cb_filters_signalled_minus1. The value of the sixth syntax element plus 1 specifies the number of cross-component Cb filters of all slices associated with the PH. The value of the sixth syntax element must be in the range from 0 to 3.

When the fourth syntax element is 1, the bitstream conformance requirement is that the sixth syntax element must be less than or equal to the value of alf_cross_component_cb_filters_signalled_minus1 in the ALF APS referenced by the fifth syntax element of the current image.

The seventh syntax element mentioned above is denoted as pic_cross_component_alf_cr_enabled_flag. The value of the seventh syntax element equal to 0 indicates that the cross-component Cr filter is not applied to the Cr color component of all slices associated with PH. The value of the seventh syntax element equal to 1 indicates that the cross-component Cr filter is applied to the Cr color component of all slices associated with PH. When the seventh syntax element is absent, it is assumed to be 0.

The eighth syntax element was also mentioned and is named as pic_cross_component_alf_cr_aps_id as an example. The value of the eighth syntax element is intended to specify the adaptation_parameter_set_id, which is the color component Cr of all slices associated with PH.

Moreover, a ninth syntactic element is mentioned, which can be designated aspic_cross_component_cr_filters_signalled_minus1. Meaning The ninth syntax element plus 1 specifies the number of inter-component filters Cr of all slices associated with PH. The value of the ninth syntax element must be in the range from 0 to 3.

When the value of the seventh syntax element is 1, a conformance requirement of the bitstream is that the value of the ninth syntax element must be less than or equal to the value of alf_cross_component_cr_filters_signalled_minus1 in the ALF APS referenced by the eighth syntax element of the current image.

The semantics of the syntactic elements of the CCALF slice header are further specified as follows:

slice_ccalf_enabled_flag equal to 1 indicates that the inter-component adaptive contour filter is enabled and can be applied to the Cb or Cr color component in the slice. slice_alf_enabled_flag equal to 0 indicates that the inter-component adaptive contour filter is disabled for all color components in the slice. If absent, slice_ccalf_enabled_flag is assumed to be equal to the third syntax element.

The tenth syntax element mentioned above can be designated as slice_cross_component_alf_cb_enabled_flag , and it can be provided that the value of the tenth syntax element equal to 0 indicates that the Cb cross-component filter is not applied to the Cb color component. The tenth syntax element equal to 1 indicates that the Cb cross-component filter is applied to the Cb color component. When the tenth syntax element is absent, it is assumed to be equal to the fourth syntax element (e.g., pic_cross_component_alf_cb_enabled_flag ).

The eleventh syntactic element mentioned above can be referred to asslice_cross_component_alf_cb_aps_id. Meaning The eleventh syntax element specifies the adaptation_parameter_set_id, which is referenced by the slice's Cb color component.

When the tenth syntax element has a value of 1, the conformance requirement of the bitstream is that for all slices of the current ALF image, the APS referenced by the eleventh syntax element must be the same.

When the tenth syntactic element is 1 and the eleventh syntactic element is absent, the value of the eleventh syntactic element is assumed to be equal to the value of the fifth syntactic element.

slice_cross_component_cb_filters_signalled_minus1 plus 1 specifies the number of Cb cross-component filters. The value of slice_cross_component_cb_filters_signalled_minus1 must be between 0 and 3.

When the tenth syntax element is 1, a bitstream conformance requirement is that slice_cross_component_cb_filters_signalled_minus1 must be less than or equal to the value of alf_cross_component_cb_filters_signalled_minus1 in the ALF APS referenced by the eleventh of the current slice.

When the tenth syntax element is 1 and the eleventh is missing, the value of slice_cross_component_cb_filters_signalled_minus1 is considered equal to the value of pic_cross_component_cb_filters_signalled_minus1.

The mentioned twelfth syntax element can be referred to as slice_cross_component_alf_cr_enabled_flag. A value of 0 for the twelfth syntax element indicates that the Cr cross-component filter is not applied to the Cr color component. A value of 1 for the twelfth syntax element indicates that the adaptive cross-component contour filter is applied to the Cr color component. When the twelfth syntax element is absent, it is assumed to be equal to the seventh syntax element, such as pic_cross_component_alf_cr_enabled_flag .

A thirteenth syntax element was mentioned, which can be further referred to as slice_cross_component_alf_cr_aps_id. The value of the thirteenth syntax element specifies the id_adaptation_parameter_set_id referenced by the slice's Cr color component.

When the value of the twelfth syntax element is 1, the conformance requirement of the bitstream is that for all slices of the current ALF picture, the APS referenced by the thirteenth syntax element must be the same.

When the value of the twelfth syntactic element is 1 and the thirteenth syntactic element is absent, the value of the thirteenth syntactic element is assumed to be equal to the value of the eighth syntactic element.

slice_cross_component_cr_filters_signalled_minus1plus 1 specifies the number of cross-component Cr filters. The value of slice_cross_component_cr_filters_signalled_minus1 must be in the range from 0 to 3.

When the twelfth syntax element is 1, a conformance requirement of the bitstream is that slice_cross_component_cr_filters_signalled_minus1 must be less than or equal to the value of alf_cross_component_cr_filters_signalled_minus1 in the ALF APS referenced by the thirteenth syntax element of the current slice.

When the twelfth syntax element is 1 and the thirteenth syntax element is absent, the value of slice_cross_component_cr_filters_signalled_minus1 is assumed to be equal to the value of pic_cross_component_cr_filters_signalled_minus1.

Implementation option 2:

In option 2, the second syntax element at the SPS level (e.g. sps_ccalf_enabled_flag) is no longer introduced, so the first syntax element (e.g. sps_alf_enabled_flag) also controls the application of the ccalf filter.

The syntax for alternative 2 is as follows:

7.3.2.6 RBSP Image Header Syntax

picture_header_rbsp( ) { Descriptor …….. if( sps_alf_enabled_flag ) { pic_alf_enabled_present_flag u(1) if( pic_alf_enabled_present_flag ) { pic_alf_enabled_flag u(1) if( pic_alf_enabled_flag ) { pic_num_alf_aps_ids_luma u(3) for( i = 0; i < pic_num_alf_aps_ids_luma; i++ ) pic_alf_aps_id_luma [ i ] u(3) if( ChromaArrayType != 0 ) pic_alf_chroma_idc u(2) if( pic_alf_chroma_idc ) pic_alf_aps_id_chroma u(3) } } pic_ccalf_enabled_present_flag u(1) if( pic_ccalf_enabled_present_flag ) { pic_ccalf_enabled_flag u(1) if( pic_ccalf_enabled_flag ) { if( ChromaArrayType != 0 ) pic_cross_component_alf_cb_enabled_flag u(1) if( pic_cross_component_alf_cb_enabled_flag ) { pic_cross_component_alf_cb_aps_id u(3) pic_cross_component_cb_filters_signalled_minus1 ue(v) } if( ChromaArrayType != 0 ) pic_cross_component_alf_cr_enabled_flag u(1) if( pic_cross_component_alf_cr_enabled_flag ) { pic_cross_component_alf_cr_aps_id u(3) pic_cross_component_cr_filters_signalled_minus1 ue(v) } } } ……

In this second embodiment, a second syntax element, which may be sps_ccalf_enabled_flag, may be provided at the SPS level. In this embodiment, it may be indicated whether CCALF should be included or not based on an additional syntax element, such as pic_ccalf_enabled_present_flag, which indicates whether CCALF is present, that additional syntax elements related to CCALF, and from which it can be further obtained that CCALF should be included for the current picture to which pic_ccalf_enabled_present_flag refers.

The syntax of a slice header is as follows:

7.3.7.1 General Slice Header Syntax

slice_header( ) { Descriptor ……. if( sps_alf_enabled_flag && !pic_alf_enabled_present_flag ) { slice_alf_enabled_flag u(1) if( slice_alf_enabled_flag ) { slice_num_alf_aps_ids_luma u(3) for( i = 0; i < slice_num_alf_aps_ids_luma; i++ ) slice_alf_aps_id_luma [ i ] u(3) if( ChromaArrayType != 0 ) slice_alf_chroma_idc u(2) if( slice_alf_chroma_idc ) slice_alf_aps_id_chroma u(3) } if( sps_alf_enabled_flag && ! pic_ccalf_enabled_present_flag) { slice_ccalf_enabled_flag u(1) if( slice_ccalf_enabled_flag ) { if( ChromaArrayType != 0 ) slice_cross_component_alf_cb_enabled_flag u(1) if( slice_cross_component_alf_cb_enabled_flag ) { slice_cross_component_alf_cb_aps_id u(3) slice_cross_component_cb_filters_signalled_minus1 ue(v) } if( ChromaArrayType != 0 ) slice_cross_component_alf_cr_enabled_flag u(1) if( slice_cross_component_alf_cr_enabled_flag ) { slice_cross_component_alf_cr_aps_id u(3) slice_cross_component_cr_filters_signalled_minus1 ue(v) } } …..

As can be seen from the above, the presence of syntax elements in the slice header, such as slice_ccalf_enabled_flag, slice_cross_component_alf_cb_enabled_flag, slice_cross_component_alf_cb_aps_id, slice_cross_component_cb_filters_signalled_minus1, slice_cross_component_alf_cr_enabled_flag, slice_cross_component_alf_cr_aps_id and slice_cross_component_cr_filters_signalled_minus1 , and/or the tenth through thirteenth syntax elements already mentioned above, may depend on the first syntax element provided at the SPS level, such as sps_alf_enabled_flag , and the syntax element provided in the image header, such as pic_ccalf_enabled_present_flag , and possibly an additional syntax element provided in the slice header, such as slice_ccalf_enabled_flag .

Implementation option 3:

Another alternative for CCALF image header entries is as follows: In this alternative, pic_alf_enabled_present_flag, pic_alf_enabled_flag controls the CCALF image header entries and the CCALF slice header entries respectively.

7.3.2.6 RBSP Image Header Syntax

picture_header_rbsp( ) { Descriptor …….. if( sps_alf_enabled_flag ) { pic_alf_enabled_present_flag u(1) if( pic_alf_enabled_present_flag ) { pic_alf_enabled_flag u(1) if( pic_alf_enabled_flag ) { pic_num_alf_aps_ids_luma u(3) for( i = 0; i < pic_num_alf_aps_ids_luma; i++ ) pic_alf_aps_id_luma [ i ] u(3) if( ChromaArrayType != 0 ) pic_alf_chroma_idc u(2) if( pic_alf_chroma_idc ) pic_alf_aps_id_chroma u(3) if( ChromaArrayType != 0 ) pic_cross_component_alf_cb_enabled_flag u(1) if( pic_cross_component_alf_cb_enabled_flag ) { pic_cross_component_alf_cb_aps_id u(3) pic_cross_component_cb_filters_signalled_minus1 ue(v) } if( ChromaArrayType != 0 ) pic_cross_component_alf_cr_enabled_flag u(1) if( pic_cross_component_alf_cr_enabled_flag ) { pic_cross_component_alf_cr_aps_id u(3) pic_cross_component_cr_filters_signalled_minus1 ue(v) } /* end of pic_alf_enabled_flag */ } /* end of pic_alf_enabled_present_flag */ } /* end of sps_alf_enabled_flag */ ……

The syntax of a slice header is as follows:

7.3.7.1 General Slice Header Syntax

slice_header( ) { Descriptor ……. if( sps_alf_enabled_flag && !pic_alf_enabled_present_flag ) //clarification: if sps_alf_enabled_flag is true (and) if pic_alf_enabled_present_flag is false)//{ slice_alf_enabled_flag u(1) if( slice_alf_enabled_flag ) { slice_num_alf_aps_ids_luma u(3) for( i = 0; i < slice_num_alf_aps_ids_luma; i++ ) slice_alf_aps_id_luma [ i ] u(3) if( ChromaArrayType != 0 ) slice_alf_chroma_idc u(2) if( slice_alf_chroma_idc ) slice_alf_aps_id_chroma u(3) if( ChromaArrayType != 0 ) slice_cross_component_alf_cb_enabled_flag u(1) if( slice_cross_component_alf_cb_enabled_flag ) { slice_cross_component_alf_cb_aps_id u(3) slice_cross_component_cb_filters_signalled_minus1 ue(v) } if( ChromaArrayType != 0 ) slice_cross_component_alf_cr_enabled_flag u(1) if( slice_cross_component_alf_cr_enabled_flag ) { slice_cross_component_alf_cr_aps_id u(3) slice_cross_component_cr_filters_signalled_minus1 ue(v) } } /* end of slice_alf_enabled_flag loop */ } /* end of sps_alf_enabled_flag && !pic_alf_enabled_present_flag */ …..

It can be seen that !(0)=1 or !(1)=0.

Implementation option 4:

Since there is a constraint in the current CCALF design that slice_cross_component_alf_cb_aps_id, slice_cross_component_alf_cr_aps_id must be the same in all slices, there is no point in repeating this syntax element in the slice header, but only signaling pic_cross_component_alf_cb_aps_id and pic_cross_component_alf_cr_aps_id in the picture header. Then it can be inferred that the values of the syntax elements slice_cross_component_alf_cb_aps_id and slice_cross_component_alf_cr are the same as the values of pic_cross_component_alf_cb_aps_id and pic_cross_component_alf_cr_aps_id. In this way, the information amount in the bitstream can be further reduced.

Possible syntax is as follows:

7.3.2.6 RBSP Image Header Syntax

picture_header_rbsp( ) { Descriptor …….. if( sps_alf_enabled_flag ) { pic_alf_enabled_present_flag u(1) if( pic_alf_enabled_present_flag ) { pic_alf_enabled_flag u(1) if( pic_alf_enabled_flag ) { pic_num_alf_aps_ids_luma u(3) for( i = 0; i < pic_num_alf_aps_ids_luma; i++ ) pic_alf_aps_id_luma [ i ] u(3) if( ChromaArrayType != 0 ) pic_alf_chroma_idc u(2) if( pic_alf_chroma_idc ) pic_alf_aps_id_chroma u(3) } } } if( sps_ccalf_enabled_flag ) { pic_cross_component_alf_cb_aps_id u(3) pic_cross_component_alf_cr_aps_id u(3) pic_ccalf_enabled_present_flag u(1) if( pic_ccalf_enabled_present_flag ) { pic_ccalf_enabled_flag u(1) if( pic_ccalf_enabled_flag ) { if( ChromaArrayType != 0 ) pic_cross_component_alf_cb_enabled_flag u(1) if( pic_cross_component_alf_cb_enabled_flag ) { pic_cross_component_cb_filters_signalled_minus1 ue(v) } if( ChromaArrayType != 0 ) pic_cross_component_alf_cr_enabled_flag u(1) if( pic_cross_component_alf_cr_enabled_flag ) { pic_cross_component_cr_filters_signalled_minus1 ue(v) } } } ……

Here, additional syntax elements that belong to CCALF (i.e. at least syntax elements containing the element ccalf or cross_component_alf or cc_alf ) are provided depending on the value of a second syntax element signaled at the SPS level, i.e. in this embodiment sps_ccalf_enabled_flag .

In particular, depending on the value of the second syntax element, a third syntax element such as pic_ccalf_enabled_flag may be provided in the image header, where this third syntax element may indicate whether CCALF is enabled for slices of the current image.

Additionally, the image header may contain a fourth syntax element , such as pic_cross_component_alf_cb_enabled_flag , and a seventh syntax element, such as pic_cross_component_alf_cb_enabled_flag , may be provided, depending on the value of the second syntax element.

The syntax for a slice header can be as follows:

7.3.7.1 General Slice Header Syntax

slice_header( ) { Descriptor ……. if( sps_alf_enabled_flag && !pic_alf_enabled_present_flag ) { slice_alf_enabled_flag u(1) if( slice_alf_enabled_flag ) { slice_num_alf_aps_ids_luma u(3) for( i = 0; i < slice_num_alf_aps_ids_luma; i++ ) slice_alf_aps_id_luma [ i ] u(3) if( ChromaArrayType != 0 ) slice_alf_chroma_idc u(2) if( slice_alf_chroma_idc ) slice_alf_aps_id_chroma u(3) } if( sps_ccalf_enabled_flag && ! pic_ccalf_enabled_present_flag) { slice_ccalf_enabled_flag u(1) if( slice_ccalf_enabled_flag ) { if( ChromaArrayType != 0 ) slice_cross_component_alf_cb_enabled_flag u(1) if( slice_cross_component_alf_cb_enabled_flag ) { slice_cross_component_cb_filters_signalled_minus1 ue(v) } if( ChromaArrayType != 0 ) slice_cross_component_alf_cr_enabled_flag u(1) if( slice_cross_component_alf_cr_enabled_flag ) { slice_cross_component_cr_filters_signalled_minus1 ue(v) } } …..

Also for this embodiment, it may be provided that the syntax elements in the slice header that relate to CCALF are provided depending on the value of a second syntax element provided at the SPS level and/or depending on the value of one or more syntax elements related to CCALF provided in the picture header, for example pic_ccalf_enabled_present_flag .

slice_cross_component_alf_cb_aps_idAlways can be considered the same as the valuepic_cross_component_alf_cb_aps_id.

slice_cross_component_alf_cr_aps_idAlways can be considered the same as the valuepic_cross_component_alf_cr_aps_id.

Another possible syntax is as follows:

7.3.2.6 RBSP Image Header Syntax

picture_header_rbsp( ) { Descriptor …….. if( sps_alf_enabled_flag ) { pic_alf_enabled_present_flag u(1) if( pic_alf_enabled_present_flag ) { pic_alf_enabled_flag u(1) if( pic_alf_enabled_flag ) { pic_num_alf_aps_ids_luma u(3) for( i = 0; i < pic_num_alf_aps_ids_luma; i++ ) pic_alf_aps_id_luma [ i ] u(3) if( ChromaArrayType != 0 ) pic_alf_chroma_idc u(2) if( pic_alf_chroma_idc ) pic_alf_aps_id_chroma u(3) } } pic_cross_component_alf_cb_aps_id u(3) pic_cross_component_alf_cr_aps_id u(3) pic_ccalf_enabled_present_flag u(1) if( pic_ccalf_enabled_present_flag ) { pic_ccalf_enabled_flag u(1) if( pic_ccalf_enabled_flag ) { if( ChromaArrayType != 0 ) pic_cross_component_alf_cb_enabled_flag u(1) if( pic_cross_component_alf_cb_enabled_flag ) { pic_cross_component_alf_cb_aps_id u(3) pic_cross_component_cb_filters_signalled_minus1 ue(v) } if( ChromaArrayType != 0 ) pic_cross_component_alf_cr_enabled_flag u(1) if( pic_cross_component_alf_cr_enabled_flag ) { pic_cross_component_alf_cr_aps_id u(3) pic_cross_component_cr_filters_signalled_minus1 ue(v) } } } ……

In the syntax according to the above table, the presence of the syntax elements related to CCALF depends on the value of the first syntax element provided at the SPS level, such as sps_alf_enabled_flag. The second syntax element, such as sps_ccalf_enabled_flag, may or may not be provided at the SPS level in this embodiment.

The syntax for a slice header can be as follows:

7.3.7.1 General Slice Header Syntax

slice_header( ) { Descriptor ……. if( sps_alf_enabled_flag && !pic_alf_enabled_present_flag ) { slice_alf_enabled_flag u(1) if( slice_alf_enabled_flag ) { slice_num_alf_aps_ids_luma u(3) for( i = 0; i < slice_num_alf_aps_ids_luma; i++ ) slice_alf_aps_id_luma [ i ] u(3) if( ChromaArrayType != 0 ) slice_alf_chroma_idc u(2) if( slice_alf_chroma_idc ) slice_alf_aps_id_chroma u(3) } if( sps_alf_enabled_flag && ! pic_ccalf_enabled_present_flag) { slice_ccalf_enabled_flag u(1) if( slice_ccalf_enabled_flag ) { if( ChromaArrayType != 0 ) slice_cross_component_alf_cb_enabled_flag u(1) if( slice_cross_component_alf_cb_enabled_flag ) { slice_cross_component_cb_filters_signalled_minus1 ue(v) } if( ChromaArrayType != 0 ) slice_cross_component_alf_cr_enabled_flag u(1) if( slice_cross_component_alf_cr_enabled_flag ) { slice_cross_component_cr_filters_signalled_minus1 ue(v) } } …..

slice_cross_component_alf_cb_aps_idAlways is meant to be the same as the meaningpic_cross_component_alf_cb_aps_id.

slice_cross_component_alf_cr_aps_idAlways is meant to be the same as the meaningpic_cross_component_alf_cr_aps_id.

Another possible syntax is as follows:

RBSP Image Header Syntax

picture_header_rbsp( ) { Descriptor …….. if( sps_alf_enabled_flag ) { pic_cross_component_alf_cb_aps_id u(3) pic_cross_component_alf_cr_aps_id u(3) pic_alf_enabled_present_flag u(1) if( pic_alf_enabled_present_flag ) { pic_alf_enabled_flag u(1) if( pic_alf_enabled_flag ) { pic_num_alf_aps_ids_luma u(3) for( i = 0; i < pic_num_alf_aps_ids_luma; i++ ) pic_alf_aps_id_luma [ i ] u(3) if( ChromaArrayType != 0 ) pic_alf_chroma_idc u(2) if( pic_alf_chroma_idc ) pic_alf_aps_id_chroma u(3) if( ChromaArrayType != 0 ) pic_cross_component_alf_cb_enabled_flag u(1) if( pic_cross_component_alf_cb_enabled_flag ) { pic_cross_component_cb_filters_signalled_minus1 ue(v) } if( ChromaArrayType != 0 ) pic_cross_component_alf_cr_enabled_flag u(1) if( pic_cross_component_alf_cr_enabled_flag ) { pic_cross_component_cr_filters_signalled_minus1 ue(v) } /* end of pic_alf_enabled_flag */ } /* end of pic_alf_enabled_present_flag */ } /* end of sps_alf_enabled_flag */ ……

The syntax of a slice header is as follows:

7.3.7.1 General Slice Header Syntax

slice_header( ) { Descriptor ……. if( sps_alf_enabled_flag && !pic_alf_enabled_present_flag ) { slice_alf_enabled_flag u(1) if( slice_alf_enabled_flag ) { slice_num_alf_aps_ids_luma u(3) for( i = 0; i < slice_num_alf_aps_ids_luma; i++ ) slice_alf_aps_id_luma [ i ] u(3) if( ChromaArrayType != 0 ) slice_alf_chroma_idc u(2) if( slice_alf_chroma_idc ) slice_alf_aps_id_chroma u(3) if( ChromaArrayType != 0 ) slice_cross_component_alf_cb_enabled_flag u(1) if( slice_cross_component_alf_cb_enabled_flag ) { slice_cross_component_cb_filters_signalled_minus1 ue(v) } if( ChromaArrayType != 0 ) slice_cross_component_alf_cr_enabled_flag u(1) if( slice_cross_component_alf_cr_enabled_flag ) { slice_cross_component_cr_filters_signalled_minus1 ue(v) } } /* end of slice_alf_enabled_flag loop */ } /* end of sps_alf_enabled_flag && !pic_alf_enabled_present_flag */ …..

In this embodiment , it is assumed that slice_cross_component_alf_cb_aps_id always matches the value of pic_cross_component_alf_cb_aps_id .

In this embodiment, the twelfth syntactic element is such How slice_cross_component_alf_cr_aps_id, is always considered to be the same as the value of the eighth syntactic element, such aspic_cross_component_alf_cr_aps_id).

Implementation option 5:

Another alternative syntax might be as follows: In this syntax, the CCALF parameters are conditionally signaled based on the value of a second syntax element, as mentioned above. This second syntax element may be supplied or may contain a flag such as sps_ccalf_enabled_flag.

RBSP Sequence Parameter Set Syntax

seq_parameter_set_rbsp( ) { Descriptor sps_decoding_parameter_set_id u(4) sps_video_parameter_set_id u(4) sps_max_sublayers_minus1 u(3) sps_reserved_zero_4bits u(4) sps_ptl_dpb_hrd_params_present_flag u(1) if( sps_ptl_dpb_hrd_params_present_flag ) profile_tier_level( 1, sps_max_sublayers_minus1 ) gdr_enabled_flag u(1) sps_seq_parameter_set_id u(4) chroma_format_idc u(2) if(chroma_format_idc = = 3) separate_colour_plane_flag u(1) ref_pic_resampling_enabled_flag u(1) pic_width_max_in_luma_samples ue(v) pic_height_max_in_luma_samples ue(v) sps_log2_ctu_size_minus5 u(2) subpics_present_flag u(1) if( subpics_present_flag ) { sps_num_subpics_minus1 u(8) for( i = 0; i <= sps_num_subpics_minus1; i++ ) { subpic_ctu_top_left_x [ i ] u(v) subpic_ctu_top_left_y [ i ] u(v) subpic_width_minus1 [ i ] u(v) subpic_height_minus1 [ i ] u(v) subpic_treated_as_pic_flag [ i ] u(1) loop_filter_across_subpic_enabled_flag [ i ] u(1) } } sps_subpic_id_present_flag u(1) if( sps_subpics_id_present_flag ) { sps_subpic_id_signalling_present_flag u(1) if( sps_subpics_id_signalling_present_flag ) { sps_subpic_id_len_minus1 ue(v) for( i = 0; i <= sps_num_subpics_minus1; i++ ) sps_subpic_id [ i ] u(v) } } bit_depth_minus8 ue(v) min_qp_prime_ts_minus4 ue(v) sps_weighted_pred_flag u(1) sps_weighted_bipred_flag u(1) log2_max_pic_order_cnt_lsb_minus4 u(4) sps_poc_msb_flag u(1) if( sps_poc_msb_flag ) poc_msb_len_minus1 ue(v) if( sps_max_sublayers_minus1 > 0 ) sps_sublayer_dpb_params_flag u(1) if( sps_ptl_dpb_hrd_params_present_flag ) dpb_parameters( 0, sps_max_sublayers_minus1, sps_sublayer_dpb_params_flag ) long_term_ref_pics_flag u(1) inter_layer_ref_pics_present_flag u(1) sps_idr_rpl_present_flag u(1) rpl1_same_as_rpl0_flag u(1) for( i = 0; i < !rpl1_same_as_rpl0_flag ? 2 : 1; i++ ) { num_ref_pic_lists_in_sps [ i ] ue(v) for( j = 0; j < num_ref_pic_lists_in_sps[ i ]; j++) ref_pic_list_struct( i, j ) } if( ChromaArrayType != 0 ) qtbtt_dual_tree_intra_flag u(1) log2_min_luma_coding_block_size_minus2 ue(v) partition_constraints_override_enabled_flag u(1) sps_log2_diff_min_qt_min_cb_intra_slice_luma ue(v) sps_log2_diff_min_qt_min_cb_inter_slice ue(v) sps_max_mtt_hierarchy_depth_inter_slice ue(v) sps_max_mtt_hierarchy_depth_intra_slice_luma ue(v) if( sps_max_mtt_hierarchy_depth_intra_slice_luma != 0 ) { sps_log2_diff_max_bt_min_qt_intra_slice_luma ue(v) sps_log2_diff_max_tt_min_qt_intra_slice_luma ue(v) } if( sps_max_mtt_hierarchy_depth_inter_slice != 0 ) { sps_log2_diff_max_bt_min_qt_inter_slice ue(v) sps_log2_diff_max_tt_min_qt_inter_slice ue(v) } if( qtbtt_dual_tree_intra_flag ) { sps_log2_diff_min_qt_min_cb_intra_slice_chroma ue(v) sps_max_mtt_hierarchy_depth_intra_slice_chroma ue(v) if( sps_max_mtt_hierarchy_depth_intra_slice_chroma != 0 ) { sps_log2_diff_max_bt_min_qt_intra_slice_chroma ue(v) sps_log2_diff_max_tt_min_qt_intra_slice_chroma ue(v) } } sps_max_luma_transform_size_64_flag u(1) sps_joint_cbcr_enabled_flag u(1) if( ChromaArrayType != 0 ) { same_qp_table_for_chroma u(1) numQpTables = same_qp_table_for_chroma ? 1: ( sps_joint_cbcr_enabled_flag ? 3: 2 ) for( i = 0; i < numQpTables; i++ ) { qp_table_start_minus26 [ i ] se(v) num_points_in_qp_table_minus1 [ i ] ue(v) for( j = 0; j <= num_points_in_qp_table_minus1[ i ]; j++ ) { delta_qp_in_val_minus1 [ i ][ j ] ue(v) delta_qp_diff_val [ i ][ j ] ue(v) } } } sps_sao_enabled_flag u(1) sps_alf_enabled_flag u(1) if( sps_alf_enabled_flag && ChromaArrayType != 0 ) sps_ccalf_enabled_flag u(1) sps_transform_skip_enabled_flag u(1) if( sps_transform_skip_enabled_flag ) sps_bdpcm_enabled_flag u(1) if( sps_bdpcm_enabled_flag && chroma_format_idc == 3 ) sps_bdpcm_chroma_enabled_flag u(1) sps_ref_wraparound_enabled_flag u(1) if( sps_ref_wraparound_enabled_flag ) sps_ref_wraparound_offset_minus1 ue(v) sps_temporal_mvp_enabled_flag u(1) if( sps_temporal_mvp_enabled_flag ) sps_sbtmvp_enabled_flag u(1) sps_amvr_enabled_flag u(1) sps_bdof_enabled_flag u(1) if( sps_bdof_enabled_flag ) sps_bdof_pic_present_flag u(1) sps_smvd_enabled_flag u(1) sps_dmvr_enabled_flag u(1) if( sps_dmvr_enabled_flag) sps_dmvr_pic_present_flag u(1) sps_mmvd_enabled_flag u(1) sps_isp_enabled_flag u(1) sps_mrl_enabled_flag u(1) sps_mip_enabled_flag u(1) if( ChromaArrayType != 0 ) sps_cclm_enabled_flag u(1) if( chroma_format_idc == 1 ) { sps_chroma_horizontal_collocated_flag u(1) sps_chroma_vertical_collocated_flag u(1) } sps_mts_enabled_flag u(1) if( sps_mts_enabled_flag ) { sps_explicit_mts_intra_enabled_flag u(1) sps_explicit_mts_inter_enabled_flag u(1) } sps_sbt_enabled_flag u(1) sps_affine_enabled_flag u(1) if( sps_affine_enabled_flag ) { sps_affine_type_flag u(1) sps_affine_amvr_enabled_flag u(1) sps_affine_prof_enabled_flag u(1) if( sps_affine_prof_enabled_flag ) sps_prof_pic_present_flag u(1) } if( chroma_format_idc == 3 ) { sps_palette_enabled_flag u(1) sps_act_enabled_flag u(1) } sps_bcw_enabled_flag u(1) sps_ibc_enabled_flag u(1) sps_ciip_enabled_flag u(1) if( sps_mmvd_enabled_flag ) sps_fpel_mmvd_enabled_flag u(1) sps_triangle_enabled_flag u(1) sps_lmcs_enabled_flag u(1) sps_lfnst_enabled_flag u(1) sps_ladf_enabled_flag u(1) if( sps_ladf_enabled_flag ) { sps_num_ladf_intervals_minus2 u(2) sps_ladf_lowest_interval_qp_offset se(v) for( i = 0; i < sps_num_ladf_intervals_minus2 + 1; i++ ) { sps_ladf_qp_offset [ i ] se(v) sps_ladf_delta_threshold_minus1 [ i ] ue(v) } } sps_scaling_list_enabled_flag u(1) sps_loop_filter_across_virtual_boundaries_disabled_present_flag u(1) if( sps_loop_filter_across_virtual_boundaries_disabled_present_flag ) { sps_num_ver_virtual_boundaries u(2) for( i = 0; i < sps_num_ver_virtual_boundaries; i++ ) sps_virtual_boundaries_pos_x [ i ] u(13) sps_num_hor_virtual_boundaries u(2) for( i = 0; i < sps_num_hor_virtual_boundaries; i++ ) sps_virtual_boundaries_pos_y [i] u(13) } if( sps_ptl_dpb_hrd_params_present_flag ) { sps_general_hrd_params_present_flag u(1) if( sps_general_hrd_params_present_flag ) { general_hrd_parameters( ) if( sps_max_sublayers_minus1 > 0 ) sps_sublayer_cpb_params_present_flag u(1) firstSubLayer = sps_sublayer_cpb_params_present_flag ? 0 :
sps_max_sublayers_minus1 ols_hrd_parameters( firstSubLayer, sps_max_sublayers_minus1 ) } } field_seq_flag u(1) vui_parameters_present_flag u(1) if( vui_parameters_present_flag ) vui_parameters( ) /* Specified in ITU-T H.SEI | ISO/IEC 23002-7 */ sps_extension_flag u(1) if( sps_extension_flag ) while(more_rbsp_data( ) ) sps_extension_data_flag u(1) rbsp_trailing_bits( ) }

As can be seen from the table above, the second syntax element sps_ccalf_enabled_flag is provided depending on the value of the first syntax element sps_alf_enabled_flag and, optionally, depending on a fourteenth syntax element, such as ChromaArrayType. In particular, the second syntax element may, in some embodiments, be signaled if the fourteenth syntax element takes on a value other than zero.

7.3.2.3 RBSP Sequence Parameter Set Syntax

seq_parameter_set_rbsp( ) { Descriptor …… sps_alf_enabled_flag u(1) if(sps_alf_enabled_flag && ChromaArrayType != 0 ) sps_ccalf_enabled_flag u(1) …….

Note: ChromaArrayType != 0, that is, this is not a brightness component, but a chroma component Cb, Cr.

ChromaArrayType specifies the chroma sampling relative to the luma sampling, as specified in the following table.

ChromaArrayType Color format 0 Monochrome 1 4:2:0 2 4:2:2 3 4:4:4

In a monochrome sample, there is only one array of samples, which is nominally considered the luminance array.

In 4:2:0 sampling, each of the two chroma arrays is half the height and half the width of the luma array.

In 4:2:2 sampling, each of the two chroma arrays has the same height and half the width of the luma array.

With 4:4:4 sampling, each of the two chroma arrays has the same height and width as the luma array.

As shown in the table above, the second syntax element is provided if the first syntax element is true, that is, when the first syntax element is sps_alf_enabled_flag and specifies that ALF should be enabled. In addition, the second syntax element is provided if the fourteenth syntax element has a value other than 0.

1.1.1.1 RBSP Sequence Parameter Set Syntax

seq_parameter_set_rbsp( ) { Descriptor sps_decoding_parameter_set_id u(4) sps_video_parameter_set_id u(4) sps_max_sublayers_minus1 u(3) sps_reserved_zero_4bits u(4) sps_ptl_dpb_hrd_params_present_flag u(1) if( sps_ptl_dpb_hrd_params_present_flag ) profile_tier_level( 1, sps_max_sublayers_minus1 ) gdr_enabled_flag u(1) sps_seq_parameter_set_id u(4) chroma_format_idc u(2) if(chroma_format_idc = = 3) separate_colour_plane_flag u(1) ref_pic_resampling_enabled_flag u(1) pic_width_max_in_luma_samples ue(v) pic_height_max_in_luma_samples ue(v) sps_log2_ctu_size_minus5 u(2) subpics_present_flag u(1) if( subpics_present_flag ) { sps_num_subpics_minus1 u(8) for( i = 0; i <= sps_num_subpics_minus1; i++ ) { subpic_ctu_top_left_x [ i ] u(v) subpic_ctu_top_left_y [ i ] u(v) subpic_width_minus1 [ i ] u(v) subpic_height_minus1 [ i ] u(v) subpic_treated_as_pic_flag [ i ] u(1) loop_filter_across_subpic_enabled_flag [ i ] u(1) } } sps_subpic_id_present_flag u(1) if( sps_subpics_id_present_flag ) { sps_subpic_id_signalling_present_flag u(1) if( sps_subpics_id_signalling_present_flag ) { sps_subpic_id_len_minus1 ue(v) for( i = 0; i <= sps_num_subpics_minus1; i++ ) sps_subpic_id [ i ] u(v) } } bit_depth_minus8 ue(v) min_qp_prime_ts_minus4 ue(v) sps_weighted_pred_flag u(1) sps_weighted_bipred_flag u(1) log2_max_pic_order_cnt_lsb_minus4 u(4) sps_poc_msb_flag u(1) if( sps_poc_msb_flag ) poc_msb_len_minus1 ue(v) if( sps_max_sublayers_minus1 > 0 ) sps_sublayer_dpb_params_flag u(1) if( sps_ptl_dpb_hrd_params_present_flag ) dpb_parameters( 0, sps_max_sublayers_minus1, sps_sublayer_dpb_params_flag ) long_term_ref_pics_flag u(1) inter_layer_ref_pics_present_flag u(1) sps_idr_rpl_present_flag u(1) rpl1_same_as_rpl0_flag u(1) for( i = 0; i < !rpl1_same_as_rpl0_flag ? 2 : 1; i++ ) { num_ref_pic_lists_in_sps [ i ] ue(v) for( j = 0; j < num_ref_pic_lists_in_sps[ i ]; j++) ref_pic_list_struct( i, j ) } if( ChromaArrayType != 0 ) qtbtt_dual_tree_intra_flag u(1) log2_min_luma_coding_block_size_minus2 ue(v) partition_constraints_override_enabled_flag u(1) sps_log2_diff_min_qt_min_cb_intra_slice_luma ue(v) sps_log2_diff_min_qt_min_cb_inter_slice ue(v) sps_max_mtt_hierarchy_depth_inter_slice ue(v) sps_max_mtt_hierarchy_depth_intra_slice_luma ue(v) if( sps_max_mtt_hierarchy_depth_intra_slice_luma != 0 ) { sps_log2_diff_max_bt_min_qt_intra_slice_luma ue(v) sps_log2_diff_max_tt_min_qt_intra_slice_luma ue(v) } if( sps_max_mtt_hierarchy_depth_inter_slice != 0 ) { sps_log2_diff_max_bt_min_qt_inter_slice ue(v) sps_log2_diff_max_tt_min_qt_inter_slice ue(v) } if( qtbtt_dual_tree_intra_flag ) { sps_log2_diff_min_qt_min_cb_intra_slice_chroma ue(v) sps_max_mtt_hierarchy_depth_intra_slice_chroma ue(v) if( sps_max_mtt_hierarchy_depth_intra_slice_chroma != 0 ) { sps_log2_diff_max_bt_min_qt_intra_slice_chroma ue(v) sps_log2_diff_max_tt_min_qt_intra_slice_chroma ue(v) } } sps_max_luma_transform_size_64_flag u(1) sps_joint_cbcr_enabled_flag u(1) if( ChromaArrayType != 0 ) { same_qp_table_for_chroma u(1) numQpTables = same_qp_table_for_chroma ? 1: ( sps_joint_cbcr_enabled_flag ? 3: 2 ) for( i = 0; i < numQpTables; i++ ) { qp_table_start_minus26 [ i ] se(v) num_points_in_qp_table_minus1 [ i ] ue(v) for( j = 0; j <= num_points_in_qp_table_minus1[ i ]; j++ ) { delta_qp_in_val_minus1 [ i ][ j ] ue(v) delta_qp_diff_val [ i ][ j ] ue(v) } } } sps_sao_enabled_flag u(1) sps_alf_enabled_flag u(1) if( sps_alf_enabled_flag && ChromaArrayType != 0 ) sps_ccalf_enabled_flag u(1) sps_transform_skip_enabled_flag u(1) if( sps_transform_skip_enabled_flag ) sps_bdpcm_enabled_flag u(1) if( sps_bdpcm_enabled_flag && chroma_format_idc == 3 ) sps_bdpcm_chroma_enabled_flag u(1) sps_ref_wraparound_enabled_flag u(1) if( sps_ref_wraparound_enabled_flag ) sps_ref_wraparound_offset_minus1 ue(v) sps_temporal_mvp_enabled_flag u(1) if( sps_temporal_mvp_enabled_flag ) sps_sbtmvp_enabled_flag u(1) sps_amvr_enabled_flag u(1) sps_bdof_enabled_flag u(1) if( sps_bdof_enabled_flag ) sps_bdof_pic_present_flag u(1) sps_smvd_enabled_flag u(1) sps_dmvr_enabled_flag u(1) if( sps_dmvr_enabled_flag) sps_dmvr_pic_present_flag u(1) sps_mmvd_enabled_flag u(1) sps_isp_enabled_flag u(1) sps_mrl_enabled_flag u(1) sps_mip_enabled_flag u(1) if( ChromaArrayType != 0 ) sps_cclm_enabled_flag u(1) if( chroma_format_idc == 1 ) { sps_chroma_horizontal_collocated_flag u(1) sps_chroma_vertical_collocated_flag u(1) } sps_mts_enabled_flag u(1) if( sps_mts_enabled_flag ) { sps_explicit_mts_intra_enabled_flag u(1) sps_explicit_mts_inter_enabled_flag u(1) } sps_sbt_enabled_flag u(1) sps_affine_enabled_flag u(1) if( sps_affine_enabled_flag ) { sps_affine_type_flag u(1) sps_affine_amvr_enabled_flag u(1) sps_affine_prof_enabled_flag u(1) if( sps_affine_prof_enabled_flag ) sps_prof_pic_present_flag u(1) } if( chroma_format_idc == 3 ) { sps_palette_enabled_flag u(1) sps_act_enabled_flag u(1) } sps_bcw_enabled_flag u(1) sps_ibc_enabled_flag u(1) sps_ciip_enabled_flag u(1) if( sps_mmvd_enabled_flag ) sps_fpel_mmvd_enabled_flag u(1) sps_triangle_enabled_flag u(1) sps_lmcs_enabled_flag u(1) sps_lfnst_enabled_flag u(1) sps_ladf_enabled_flag u(1) if( sps_ladf_enabled_flag ) { sps_num_ladf_intervals_minus2 u(2) sps_ladf_lowest_interval_qp_offset se(v) for( i = 0; i < sps_num_ladf_intervals_minus2 + 1; i++ ) { sps_ladf_qp_offset [ i ] se(v) sps_ladf_delta_threshold_minus1 [ i ] ue(v) } } sps_scaling_list_enabled_flag u(1) sps_loop_filter_across_virtual_boundaries_disabled_present_flag u(1) if( sps_loop_filter_across_virtual_boundaries_disabled_present_flag ) { sps_num_ver_virtual_boundaries u(2) for( i = 0; i < sps_num_ver_virtual_boundaries; i++ ) sps_virtual_boundaries_pos_x [ i ] u(13) sps_num_hor_virtual_boundaries u(2) for( i = 0; i < sps_num_hor_virtual_boundaries; i++ ) sps_virtual_boundaries_pos_y [i] u(13) } if( sps_ptl_dpb_hrd_params_present_flag ) { sps_general_hrd_params_present_flag u(1) if( sps_general_hrd_params_present_flag ) { general_hrd_parameters( ) if( sps_max_sublayers_minus1 > 0 ) sps_sublayer_cpb_params_present_flag u(1) firstSubLayer = sps_sublayer_cpb_params_present_flag ? 0 :
sps_max_sublayers_minus1 ols_hrd_parameters( firstSubLayer, sps_max_sublayers_minus1 ) } } field_seq_flag u(1) vui_parameters_present_flag u(1) if( vui_parameters_present_flag ) vui_parameters( ) /* Specified in ITU-T H.SEI | ISO/IEC 23002-7 */ sps_extension_flag u(1) if( sps_extension_flag ) while(more_rbsp_data( ) ) sps_extension_data_flag u(1) rbsp_trailing_bits( ) }

1.1.1.2 RBSP Syntax of Image Parameter Set

pic_parameter_set_rbsp( ) { Descriptor pps_pic_parameter_set_id ue(v) pps_seq_parameter_set_id u(4) pic_width_in_luma_samples ue(v) pic_height_in_luma_samples ue(v) conformance_window_flag u(1) if( conformance_window_flag ) { conf_win_left_offset ue(v) conf_win_right_offset ue(v) conf_win_top_offset ue(v) conf_win_bottom_offset ue(v) } scaling_window_flag u(1) if( scaling_window_flag ) { scaling_win_left_offset ue(v) scaling_win_right_offset ue(v) scaling_win_top_offset ue(v) scaling_win_bottom_offset ue(v) } output_flag_present_flag u(1) mixed_nalu_types_in_pic_flag u(1) pps_subpic_id_signalling_present_flag u(1) if( pps_subpics_id_signalling_present_flag ) { pps_num_subpics_minus1 ue(v) pps_subpic_id_len_minus1 ue(v) for( i = 0; i <= pps_num_subpic_minus1; i++ ) pps_subpic_id [ i ] u(v) } no_pic_partition_flag u(1) if( !no_pic_partition_flag ) { pps_log2_ctu_size_minus5 u(2) num_exp_tile_columns_minus1 ue(v) num_exp_tile_rows_minus1 ue(v) for( i = 0; i <= num_exp_tile_columns_minus1; i++ ) tile_column_width_minus1 [i] ue(v) for( i = 0; i <= num_exp_tile_rows_minus1; i++ ) tile_row_height_minus1 [ i ] ue(v) rect_slice_flag u(1) if(rect_slice_flag) single_slice_per_subpic_flag u(1) if( rect_slice_flag && !single_slice_per_subpic_flag ) { num_slices_in_pic_minus1 ue(v) tile_idx_delta_present_flag u(1) for( i = 0; i < num_slices_in_pic_minus1; i++ ) { slice_width_in_tiles_minus1 [ i ] ue(v) slice_height_in_tiles_minus1 [ i ] ue(v) if( slice_width_in_tiles_minus1[ i ] = = 0 &&
slice_height_in_tiles_minus1[ i ] = = 0 ) { num_slices_in_tile_minus1 [ i ] ue(v) numSlicesInTileMinus1 = num_slices_in_tile_minus1[ i ] for( j = 0; j < numSlicesInTileMinus1; j++ ) slice_height_in_ctu_minus1 [ i++ ] ue(v) } if( tile_idx_delta_present_flag && i < num_slices_in_pic_minus1 ) tile_idx_delta [ i ] se(v) } } loop_filter_across_tiles_enabled_flag u(1) loop_filter_across_slices_enabled_flag u(1) } entropy_coding_sync_enabled_flag u(1) if( !no_pic_partition_flag | | entropy_coding_sync_enabled_flag ) entry_point_offsets_present_flag u(1) cabac_init_present_flag u(1) for( i = 0; i < 2; i++ ) num_ref_idx_default_active_minus1 [ i ] ue(v) rpl1_idx_present_flag u(1) init_qp_minus26 se(v) log2_transform_skip_max_size_minus2 ue(v) cu_qp_delta_enabled_flag u(1) pps_cb_qp_offset se(v) pps_cr_qp_offset se(v) pps_joint_cbcr_qp_offset_present_flag u(1) if( pps_joint_cbcr_qp_offset_present_flag ) pps_joint_cbcr_qp_offset_value se(v) pps_slice_chroma_qp_offsets_present_flag u(1) pps_cu_chroma_qp_offset_list_enabled_flag u(1) if( pps_cu_chroma_qp_offset_list_enabled_flag ) { chroma_qp_offset_list_len_minus1 ue(v) for( i = 0; i <= chroma_qp_offset_list_len_minus1; i++ ) { cb_qp_offset_list [ i ] se(v) cr_qp_offset_list [ i ] se(v) if( pps_joint_cbcr_qp_offset_present_flag ) joint_cbcr_qp_offset_list [ i ] se(v) } } pps_weighted_pred_flag u(1) pps_weighted_bipred_flag u(1) alf_present_in_ph_flag u(1) deblocking_filter_control_present_flag u(1) if( deblocking_filter_control_present_flag ) { deblocking_filter_override_enabled_flag u(1) pps_deblocking_filter_disabled_flag u(1) if( !pps_deblocking_filter_disabled_flag ) { pps_beta_offset_div2 se(v) pps_tc_offset_div2 se(v) } } constant_slice_header_params_enabled_flag u(1) if( constant_slice_header_params_enabled_flag ) { pps_dep_quant_enabled_idc u(2) for( i = 0; i < 2; i++ ) pps_ref_pic_list_sps_idc [i] u(2) pps_mvd_l1_zero_idc u(2) pps_collocated_from_l0_idc u(2) pps_six_minus_max_num_merge_cand_plus1 ue(v) pps_max_num_merge_cand_minus_max_num_triangle_cand_plus1 ue(v) } picture_header_extension_present_flag u(1) slice_header_extension_present_flag u(1) pps_extension_flag u(1) if( pps_extension_flag ) while(more_rbsp_data( ) ) pps_extension_data_flag u(1) rbsp_trailing_bits( ) }

General syntax for constraint information

general_constraint_info( ) { Descriptor general_progressive_source_flag u(1) general_interlaced_source_flag u(1) general_non_packed_constraint_flag u(1) general_frame_only_constraint_flag u(1) intra_only_constraint_flag u(1) max_bitdepth_constraint_idc u(4) max_chroma_format_constraint_idc u(2) frame_only_constraint_flag u(1) no_qtbtt_dual_tree_intra_constraint_flag u(1) no_partition_constraints_override_constraint_flag u(1) no_sao_constraint_flag u(1) no_alf_constraint_flag u(1) no_ccalf_constraint_flag u(1) no_joint_cbcr_constraint_flag u(1) no_ref_wraparound_constraint_flag u(1) no_temporal_mvp_constraint_flag u(1) no_sbtmvp_constraint_flag u(1) no_amvr_constraint_flag u(1) no_bdof_constraint_flag u(1) no_dmvr_constraint_flag u(1) no_cclm_constraint_flag u(1) no_mts_constraint_flag u(1) no_sbt_constraint_flag u(1) no_affine_motion_constraint_flag u(1) no_bcw_constraint_flag u(1) no_ibc_constraint_flag u(1) no_ciip_constraint_flag u(1) no_fpel_mmvd_constraint_flag u(1) no_triangle_constraint_flag u(1) no_ladf_constraint_flag u(1) no_transform_skip_constraint_flag u(1) no_bdpcm_constraint_flag u(1) no_qp_delta_constraint_flag u(1) no_dep_quant_constraint_flag u(1) no_sign_data_hiding_constraint_flag u(1) no_mixed_nalu_types_in_pic_constraint_flag u(1) no_trail_constraint_flag u(1) no_stsa_constraint_flag u(1) no_rasl_constraint_flag u(1) no_radl_constraint_flag u(1) no_idr_constraint_flag u(1) no_cra_constraint_flag u(1) no_gdr_constraint_flag u(1) no_aps_constraint_flag u(1) while( !byte_aligned( ) ) gci_alignment_zero_bit f(1) num_reserved_constraint_bytes u(8) for( i = 0; i < num_reserved_constraint_bytes; i++ ) gci_reserved_constraint_byte [i] u(8) }

7.3.3.2 General syntax of constraint information

general_constraint_info( ) { Descriptor …. no_alf_constraint_flag u(1) if (!no_alf_constraint_flag) no_ccalf_constraint_flag u(1)

NOTES:

!(0)=1

!(1)=0

7.3.2.4 RBSP Syntax of Image Parameter Set

RBSP Image Header Syntax

picture_header_rbsp( ) { Descriptor non_reference_picture_flag u(1) gdr_pic_flag u(1) no_output_of_prior_pics_flag u(1) if( gdr_pic_flag ) recovery_poc_cnt ue(v) ph_pic_parameter_set_id ue(v) if( sps_poc_msb_flag ) { ph_poc_msb_present_flag u(1) if( ph_poc_msb_present_flag ) poc_msb_val u(v) } if( sps_subpic_id_present_flag && !sps_subpic_id_signalling_flag ) { ph_subpic_id_signalling_present_flag u(1) if( ph_subpics_id_signalling_present_flag ) { ph_subpic_id_len_minus1 ue(v) for( i = 0; i <= sps_num_subpics_minus1; i++ ) ph_subpic_id [ i ] u(v) } } if( !sps_loop_filter_across_virtual_boundaries_disabled_present_flag ) { ph_loop_filter_across_virtual_boundaries_disabled_present_flag u(1) if( ph_loop_filter_across_virtual_boundaries_disabled_present_flag ) { ph_num_ver_virtual_boundaries u(2) for( i = 0; i < ph_num_ver_virtual_boundaries; i++ ) ph_virtual_boundaries_pos_x [i] u(13) ph_num_hor_virtual_boundaries u(2) for( i = 0; i < ph_num_hor_virtual_boundaries; i++ ) ph_virtual_boundaries_pos_y [i] u(13) } } if( separate_colour_plane_flag == 1 ) colour_plane_id u(2) if( output_flag_present_flag ) pic_output_flag u(1) pic_rpl_present_flag u(1) if( pic_rpl_present_flag ) { for( i = 0; i < 2; i++ ) { if( num_ref_pic_lists_in_sps[ i ] > 0 && !pps_ref_pic_list_sps_idc[ i ] &&
( i = = 0 | | ( i = = 1 && rpl1_idx_present_flag ) ) ) pic_rpl_sps_flag [ i ] u(1) if( pic_rpl_sps_flag[ i ] ) { if( num_ref_pic_lists_in_sps[ i ] > 1 &&
( i = = 0 | | ( i = = 1 && rpl1_idx_present_flag ) ) ) pic_rpl_idx [ i ] u(v) } else ref_pic_list_struct( i, num_ref_pic_lists_in_sps[ i ] ) for( j = 0; j < NumLtrpEntries[ i ][ RplsIdx[ i ] ]; j++ ) { if( ltrp_in_slice_header_flag[ i ][ RplsIdx[ i ] ] ) pic_poc_lsb_lt [ i ][ j ] u(v) pic_delta_poc_msb_present_flag [ i ][ j ] u(1) if( pic_delta_poc_msb_present_flag[ i ][ j ] ) pic_delta_poc_msb_cycle_lt [ i ][ j ] ue(v) } } } if( partition_constraints_override_enabled_flag ) { partition_constraints_override_flag u(1) if( partition_constraints_override_flag ) { pic_log2_diff_min_qt_min_cb_intra_slice_luma ue(v) pic_log2_diff_min_qt_min_cb_inter_slice ue(v) pic_max_mtt_hierarchy_depth_inter_slice ue(v) pic_max_mtt_hierarchy_depth_intra_slice_luma ue(v) if( pic_max_mtt_hierarchy_depth_intra_slice_luma != 0 ) { pic_log2_diff_max_bt_min_qt_intra_slice_luma ue(v) pic_log2_diff_max_tt_min_qt_intra_slice_luma ue(v) } if( pic_max_mtt_hierarchy_depth_inter_slice != 0 ) { pic_log2_diff_max_bt_min_qt_inter_slice ue(v) pic_log2_diff_max_tt_min_qt_inter_slice ue(v) } if( qtbtt_dual_tree_intra_flag ) { pic_log2_diff_min_qt_min_cb_intra_slice_chroma ue(v) pic_max_mtt_hierarchy_depth_intra_slice_chroma ue(v) if( pic_max_mtt_hierarchy_depth_intra_slice_chroma != 0 ) { pic_log2_diff_max_bt_min_qt_intra_slice_chroma ue(v) pic_log2_diff_max_tt_min_qt_intra_slice_chroma ue(v) } } } } if( cu_qp_delta_enabled_flag ) { pic_cu_qp_delta_subdiv_intra_slice ue(v) pic_cu_qp_delta_subdiv_inter_slice ue(v) } if( pps_cu_chroma_qp_offset_list_enabled_flag ) { pic_cu_chroma_qp_offset_subdiv_intra_slice ue(v) pic_cu_chroma_qp_offset_subdiv_inter_slice ue(v) } if( sps_temporal_mvp_enabled_flag ) pic_temporal_mvp_enabled_flag u(1) if(!pps_mvd_l1_zero_idc ) mvd_l1_zero_flag u(1) if( !pps_six_minus_max_num_merge_cand_plus1 ) pic_six_minus_max_num_merge_cand ue(v) if( sps_affine_enabled_flag ) pic_five_minus_max_num_subblock_merge_cand ue(v) if( sps_fpel_mmvd_enabled_flag ) pic_fpel_mmvd_enabled_flag u(1) if( sps_bdof_pic_present_flag ) pic_disable_bdof_flag u(1) if( sps_dmvr_pic_present_flag ) pic_disable_dmvr_flag u(1) if( sps_prof_pic_present_flag ) pic_disable_prof_flag u(1) if( sps_triangle_enabled_flag && MaxNumMergeCand >= 2 &&
!pps_max_num_merge_cand_minus_max_num_triangle_cand_plus1 ) pic_max_num_merge_cand_minus_max_num_triangle_cand ue(v) if ( sps_ibc_enabled_flag ) pic_six_minus_max_num_ibc_merge_cand ue(v) if( sps_joint_cbcr_enabled_flag ) pic_joint_cbcr_sign_flag u(1) if( sps_sao_enabled_flag ) { pic_sao_enabled_present_flag u(1) if( pic_sao_enabled_present_flag ) { pic_sao_luma_enabled_flag u(1) if(ChromaArrayType != 0 ) pic_sao_chroma_enabled_flag u(1) } } if( sps_alf_enabled_flag && alf_present_in_ph_flag ) { pic_alf_enabled_present_flag u(1) if( pic_alf_enabled_present_flag ) { pic_alf_enabled_flag u(1) if( pic_alf_enabled_flag ) { pic_num_alf_aps_ids_luma u(3) for( i = 0; i < pic_num_alf_aps_ids_luma; i++ ) pic_alf_aps_id_luma [ i ] u(3) if( ChromaArrayType != 0 ) pic_alf_chroma_idc u(2) if( pic_alf_chroma_idc ) pic_alf_aps_id_chroma u(3) } if( ChromaArrayType != 0 ) if (sps_ccalf_enabled_flag) { pic_cross_component_alf_cb_enabled_flag u(1) if( pic_cross_component_alf_cb_enabled_flag ) { pic_cross_component_alf_cb_aps_id u(3) pic_cross_component_cb_filters_signalled_minus1 ue(v) } if( ChromaArrayType != 0 )
pic_cross_component_alf_cr_enabled_flag u(1) if( pic_cross_component_alf_cr_enabled_flag ) { pic_cross_component_alf_cr_aps_id u(3) pic_cross_component_cr_filters_signalled_minus1 ue(v) } } } } if (!pps_dep_quant_enabled_flag) pic_dep_quant_enabled_flag u(1) if( !pic_dep_quant_enabled_flag ) sign_data_hiding_enabled_flag u(1) if( deblocking_filter_override_enabled_flag ) { pic_deblocking_filter_override_present_flag u(1) if( pic_deblocking_filter_override_present_flag ) { pic_deblocking_filter_override_flag u(1) if( pic_deblocking_filter_override_flag ) { pic_deblocking_filter_disabled_flag u(1) if( !pic_deblocking_filter_disabled_flag ) { pic_beta_offset_div2 se(v) pic_tc_offset_div2 se(v) } } } } if( sps_lmcs_enabled_flag ) { pic_lmcs_enabled_flag u(1) if( pic_lmcs_enabled_flag ) { pic_lmcs_aps_id u(2) if( ChromaArrayType != 0 ) pic_chroma_residual_scale_flag u(1) } } if( sps_scaling_list_enabled_flag ) { pic_scaling_list_present_flag u(1) if( pic_scaling_list_present_flag ) pic_scaling_list_aps_id u(3) } if( picture_header_extension_present_flag ) { ph_extension_length ue(v) for( i = 0; i < ph_extension_length; i++) ph_extension_data_byte [ i ] u(8) } rbsp_trailing_bits( ) }

pic_parameter_set_rbsp( ) { Descriptor …. if (sps_alf_enabled_flag) alf_present_in_ph_flag u(1) deblocking_filter_control_present_flag u(1) if( deblocking_filter_control_present_flag ) { …….

alf_present_in_ph_flag equal to 1 specifies that syntax elements for ALF inclusion may be present in PH (picture headers) belonging to PPS. alf_present_in_ph_flag equal to 0 specifies that syntax elements for ALF inclusion may be present in slice headers belonging to PPS.

7.3.2.6 RBSP Image Header Syntax

picture_header_rbsp( ) { Descriptor …….. if( sps_alf_enabled_flag && alf_present_in_ph_flag) { pic_alf_enabled_flag u(1) if( pic_alf_enabled_flag ) { pic_num_alf_aps_ids_luma u(3) for( i = 0; i < pic_num_alf_aps_ids_luma; i++ ) pic_alf_aps_id_luma [ i ] u(3) if( ChromaArrayType != 0 ) pic_alf_chroma_idc u(2) if( pic_alf_chroma_idc ) pic_alf_aps_id_chroma u(3) if( sps_ccalf_enabled_flag ) { pic_cross_component_alf_cb_enabled_flag u(1) if( pic_cross_component_alf_cb_enabled_flag ) { pic_cross_component_alf_cb_aps_id u(3) } pic_cross_component_alf_cr_enabled_flag u(1) if( pic_cross_component_alf_cr_enabled_flag ) { pic_cross_component_alf_cr_aps_id u(3) } } /* end of sps_ccalf_enabled_flag */ } /* end of pic_alf_enabled_flag */ } /* end of (sps_alf_enabled_flag && alf_present_in_ph_flag) */ ……

As shown in the table above, the presence of additional CCALF-related syntax elements in the image header, such as the fourth syntactic element (e.g.pic_cross_component_alf_cb_enabled_flag) and the seventh syntactic element (For example, pic_cross_component_alf_cr_enabled_flag), may depend on the presence and/or meaning of a second syntactic element. The presence of a fifth syntactic element, such aspic_cross_component_alf_cb_aps_id,may then depend on the second syntactic element and/or the presence and/or meaning of a fourth syntactic element, while the presence and/or meaning of an eighth syntactic element, such aspic_cross_component_alf_cr_aps_id, may depend on the presence and/or meaning of the second syntactic element and/or the presence and/or meaning of the seventh syntactic element.

7.3.7.1 General Slice Header Syntax

slice_header( ) { Descriptor ……. if( sps_alf_enabled_flag && !alf_present_in_ph_flag) { slice_alf_enabled_flag u(1) if( slice_alf_enabled_flag ) { slice_num_alf_aps_ids_luma u(3) for( i = 0; i < slice_num_alf_aps_ids_luma; i++ ) slice_alf_aps_id_luma [ i ] u(3) if( ChromaArrayType != 0 ) slice_alf_chroma_idc u(2) if( slice_alf_chroma_idc ) slice_alf_aps_id_chroma u(3) if( sps_ccalf_enabled_flag) { slice_cross_component_alf_cb_enabled_flag u(1) if( slice_cross_component_alf_cb_enabled_flag ) { slice_cross_component_alf_cb_aps_id u(3) } slice_cross_component_alf_cr_enabled_flag u(1) if( slice_cross_component_alf_cr_enabled_flag ) { slice_cross_component_alf_cr_aps_id u(3) } } /* end of sps_ccalf_enabled_flag */ } /* end of slice_alf_enabled_flag */ } /* end of (sps_alf_enabled_flag && !alf_present_in_ph_flag) */ …..

In the table above, additional syntactic elements related to CCALF may further depend on the presence and/or value of a second syntactic element. For example, a tenth syntactic element such asslice_cross_component_alf_cb_enabled_flag,may be provided depending on the second syntactic element. Depending on the presence and/or value of this tenth syntactic element and/or the second syntactic element, the eleventh syntactic element may be provided,such asslice_cross_component_alf_cb_aps_id. In addition, the slice header may contain a twelfth syntactic element may be provided, such asslice_cross_component_alf_cr_enabled_flag, depending on the value of the second syntactic element. Depending on the presence and/or value of the twelfth syntactic element and/or depending on the second syntactic element in the slice header, there may be a thirteenth syntactic element is provided, such asslice_cross_component_alf_cr_aps_id.

NOTES:

!(0)=1

!(1)=0

if(sps_alf_enabled_flag && !alf_present_in_ph_flag) means "if sps_alf_enabled_flag is true (and) if alf_present_in_ph_flag is false)"

Slice Header Syntax

General syntax of a slice header.

slice_header( ) { Descriptor slice_pic_order_cnt_lsb u(v) if( subpics_present_flag ) slice_subpic_id u(v) if( rect_slice_flag | | NumTilesInPic > 1 ) slice_address u(v) if( !rect_slice_flag && NumTilesInPic > 1 ) num_tiles_in_slice_minus1 ue(v) slice_type ue(v) if( !pic_rpl_present_flag &&( ( nal_unit_type != IDR_W_RADL && nal_unit_type !=
IDR_N_LP ) | | sps_idr_rpl_present_flag ) ) { for( i = 0; i < 2; i++ ) { if( num_ref_pic_lists_in_sps[ i ] > 0 && !pps_ref_pic_list_sps_idc[ i ] &&
( i = = 0 | | ( i = = 1 && rpl1_idx_present_flag ) ) ) slice_rpl_sps_flag [ i ] u(1) if( slice_rpl_sps_flag[ i ] ) { if( num_ref_pic_lists_in_sps[ i ] > 1 && ( i = = 0 | | ( i = = 1 && rpl1_idx_present_flag ) ) ) slice_rpl_idx [ i ] u(v) } else ref_pic_list_struct( i, num_ref_pic_lists_in_sps[ i ] ) for( j = 0; j < NumLtrpEntries[ i ][ RplsIdx[ i ] ]; j++ ) { if( ltrp_in_slice_header_flag[ i ][ RplsIdx[ i ] ] ) slice_poc_lsb_lt [ i ][ j ] u(v) slice_delta_poc_msb_present_flag [ i ][ j ] u(1) if( slice_delta_poc_msb_present_flag[ i ][ j ] ) slice_delta_poc_msb_cycle_lt [ i ][ j ] ue(v) } } } if( pic_rpl_present_flag | | ( ( nal_unit_type != IDR_W_RADL && nal_unit_type !=
IDR_N_LP ) | | sps_idr_rpl_present_flag ) ) { if( ( slice_type != I && num_ref_entries[ 0 ][ RplsIdx[ 0 ] ] > 1 ) | |
( slice_type = = B && num_ref_entries[ 1 ][ RplsIdx[ 1 ] ] > 1 ) ) { num_ref_idx_active_override_flag u(1) if(num_ref_idx_active_override_flag) for( i = 0; i < ( slice_type == B ? 2: 1 ); i++ ) if( num_ref_entries[ i ][ RplsIdx[ i ] ] > 1 ) num_ref_idx_active_minus1 [ i ] ue(v) } } if( slice_type != I ) { if( cabac_init_present_flag ) cabac_init_flag u(1) if( pic_temporal_mvp_enabled_flag ) { if( slice_type = = B && !pps_collocated_from_l0_idc ) collocated_from_l0_flag u(1) if( ( collocated_from_l0_flag && NumRefIdxActive[ 0 ] > 1 ) | |
( !collocated_from_l0_flag && NumRefIdxActive[ 1 ] > 1 ) ) collocated_ref_idx ue(v) } if( ( pps_weighted_pred_flag && slice_type = = P ) | |
(pps_weighted_bipred_flag && slice_type == B)) pred_weight_table( ) } slice_qp_delta se(v) if( pps_slice_chroma_qp_offsets_present_flag ) { slice_cb_qp_offset se(v) slice_cr_qp_offset se(v) if( sps_joint_cbcr_enabled_flag ) slice_joint_cbcr_qp_offset se(v) } if( pps_cu_chroma_qp_offset_list_enabled_flag ) cu_chroma_qp_offset_enabled_flag u(1) if( sps_sao_enabled_flag && !pic_sao_enabled_present_flag ) { slice_sao_luma_flag u(1) if( ChromaArrayType != 0 ) slice_sao_chroma_flag u(1) } if( sps_alf_enabled_flag && !alf_present_in_ph_flag pic_alf_enabled_present_flag ) { slice_alf_enabled_flag u(1) if( slice_alf_enabled_flag ) { slice_num_alf_aps_ids_luma u(3) for( i = 0; i < slice_num_alf_aps_ids_luma; i++ ) slice_alf_aps_id_luma [ i ] u(3) if( ChromaArrayType != 0 ) slice_alf_chroma_idc u(2) if( slice_alf_chroma_idc ) slice_alf_aps_id_chroma u(3) } if (sps_ccalf_enabled_flag) { if( ChromaArrayType != 0 ) slice_cross_component_alf_cb_enabled_flag u(1) if( slice_cross_component_alf_cb_enabled_flag ) { slice_cross_component_alf_cb_aps_id u(3) slice_cross_component_cb_filters_signalled_minus1 ue(v) } if( ChromaArrayType != 0 ) slice_cross_component_alf_cr_enabled_flag u(1) if( slice_cross_component_alf_cr_enabled_flag ) { slice_cross_component_alf_cr_aps_id u(3) slice_cross_component_cr_filters_signalled_minus1 ue(v) } } } } if( deblocking_filter_override_enabled_flag &&
!pic_deblocking_filter_override_present_flag ) slice_deblocking_filter_override_flag u(1) if( slice_deblocking_filter_override_flag ) { slice_deblocking_filter_disabled_flag u(1) if( !slice_deblocking_filter_disabled_flag ) { slice_beta_offset_div2 se(v) slice_tc_offset_div2 se(v) } } if( entry_point_offsets_present_flag && NumEntryPoints > 0 ) { offset_len_minus1 ue(v) for( i = 0; i < NumEntryPoints; i++ ) entry_point_offset_minus1 [i] u(v) } if( slice_header_extension_present_flag ) { slice_header_extension_length ue(v) for( i = 0; i < slice_header_extension_length; i++) slice_header_extension_data_byte [ i ] u(8) } byte_alignment( ) }

In the table above, some elements are shown crossed out. This means that in the first embodiment, these elements may be present. In an alternative embodiment, these elements may be omitted, leaving the remaining syntax as it is. For example, the ChromaArrayType element may not be provided. Accordingly, any dependency on this element, including the conditional presence of other syntax elements, may be provided in the first embodiment. In an alternative embodiment, this dependency does not exist, resulting, for example, in the syntax elements being present in any case, while in an alternative embodiment they are present only if ChromaArrayType has a specific value.

Similarly, syntax elements such as slice_cross_component_cr_filters_signalled_minus1 and slice_cross_component_cb_filters_signalled_minus1 may not be provided at all (regardless of whether a syntax element such as ChromaArrayType is present).

The semantics of the newly introduced syntactic elements is as follows:

A value of 0 for the second syntax element, such as (sps_ccalf_enabled_flag) , indicates that the cross-component adaptive loop filter is disabled. A value of 1 for the first syntax element indicates that the cross-component adaptive loop filter is enabled. This can also have the opposite meaning, i.e. if the second syntax element has a value of 1, CCALF can be disabled, whereas if the second syntax element has a value of 0, CCALF can be enabled.

A no_ccalf_constraint_flag value of 1 specifies that the first syntax element (for example, sps_ccalf_enabled_flag) must be 0. A no_ccalf_constraint_flag value of 0 imposes no such constraint.

In embodiments, the filtering process is detailed below.

For the embodiments discussed above, some general remarks are made below regarding the meaning of particular syntax elements and the consequences of these syntax elements taking on certain values. The disclosure below is intended to cover any of the embodiments given above, in particular, alternative embodiments 1 through 5.

8.8 In-circuit filtration process

8.8.1 General Provisions

……

4. When the first syntax element (designated sps_alf_enabled_flag above) is 1, the following applies:

When the second syntax element (e.g. sps_ccalf_enabled_flag) is 1, the array of reconstructed image samples (before the adaptive loop filter) SL' is set equal to the array of reconstructed image samples S _L .

The adaptive loop filtering process as specified in 8.8.5.1 is called with the array of reconstructed image samples S _L and, when the fourteenth syntax element (in the tables above it is designated as ChromaArrayType) not equal to 0, the arrays S _Cb and S _Cr as input, and the modified reconstructed array of image samples S' _L and, when the fourteenth syntax element is not equal to 0, the arrays S' _Cb and S' _Cr after the adaptive loop filter as output.

The array S′ _L and, when the fourteenth syntax element is not equal to 0, the arrays S′ _Cb and S′ _Cr are assigned to the array S _L , and, when the fourteenth syntax element is not equal to 0, to the arrays S _Cb and S _Cr (which represent the decoded image), respectively.

When the second syntax element (for example, sps_ccalf_enabled_flag) is 1, the following applies:

The process of inter-component adaptive loop filtering, as specified in section xxxx, is called with the array of reconstructed image samples S _L and, when the fourteenth syntax element (e.g., ChromaArrayType) is not equal to 0, the arrays S _Cb and S _Cr as input data and the modified reconstructed array of image samples S' _L and, when the fourteenth syntax element is not equal to 0, the arrays S' _Cb and S' _Cr after the inter-component adaptive loop filter as output data.

The array S′ _L and, when the fourteenth syntax element is not equal to 0, the arrays S′ _Cb and S′ _Cr are assigned to the array S _L , and, when the fourteenth syntax element is not equal to 0, to the arrays S _Cb and S _Cr (which represent the decoded image), respectively.

It should be noted that the present invention is not limited to the alternatives presented here, but rather the invention in a very general form allows conditionally signaling CCALF data present in a slice header in an image header. The main advantage of using CCALF data in an image header is that the signaling overhead in the slice header is reduced.

The invention also covers the case where a particular CCALF syntax element signaled in a slice header has the same meaning in all slices (e.g. due to some bitstream conformance requirements), then that particular syntax element is no longer signaled in the slice header, but rather is signaled only once in the picture header associated with all slices.

The Cross-Component Adaptive Loop Filter (CC-ALF) can be used as a loop filter and as a post-processing step respectively.

CC-ALF uses the luma sample values to refine each chroma component. CC_ALF is applied to the luma samples to obtain a correction factor for filtering the chroma samples.

The JVET-P0080 and JVET-O0630 introduce a new in-loop filter called the inter-component ALF. The CC-ALF operates as part of the adaptive loop filtering process and uses the luma sample values to refine each chroma component (Cr or Cb component). The tool is driven by information in the bitstream, and this information includes both (a) the filter coefficients for each chroma component and (b) a mask that controls the application of the filter to blocks of samples. The filter coefficients are reported in the adaptation parameter set (APS), and the block sizes and mask are reported at the slice level.

It can be understood that Mask is a bit (0 or 1). Here mask indicates whether the block of samples should be filtered or not (mask=1 means it is filtered) and (mask=0 means it is not filtered). Basically, APS contains coefficients for ALF and other information.

The general appearance of the CC-ALF is shown in Fig. 6(a), Fig. 6(b) and Fig. 6(c). This general design can be applied to any of the above-mentioned embodiments that relate to the problems related to the CC-ALF. In particular, it is assumed that what is described herein is covered by each of the alternative embodiments 1 through 5.

The location of the filter is shown in Fig. 6a (see left side). The shape of the filter is shown in Fig. 6b and 6c.

CC-ALF works by applying a linear diamond filter (Figures 6b and 6c) to the luma channel for each chroma component, which is expressed as

Where

(x, y) - the specified location of the i-th color component;

(xC, yC) - brightness location based on (x, y);

Si - support for luminance filter for chroma component I;

ci(x ₀ ,y ₀ ) - filter coefficients.

It should be noted that there is a first chroma component (e.g., chroma component cb) when i=1 for chroma component i, and there is a second chroma component (e.g., chroma component cr) when i=2 for chroma component i.

The main characteristics of CC-ALF include:

Brightness position ? around which the support region is centered is calculated based on the spatial scaling factor between the luma and chroma planes. Basically, CCALF uses luma samples to refine chroma samples. Therefore, the filter is applied to the luma samples, and then a correction factor for chroma is derived.

All filter coefficients are transferred to APS and have 8-bit dynamic range.

APS can be referenced in the slice header.

The CC-ALF coefficients used for each slice chroma component are also stored in a buffer corresponding to the temporal sublayer. Reuse of these sets of sublayer temporal filter coefficients is simplified by slice-level flags. It can be seen that the temporal sublayers are mainly determined based on reference information.

The application of CC-ALF filters is controlled by a variable block size and signaled by a context-coded flag received for each block of samples. The block size together with the CC-ALF enable flag is received at the slice level for each chroma component.

Border padding for horizontal virtual borders uses repetition. The rest of the borders use the same padding type as regular ALF.

Fig. 8 is a block diagram showing the image header entries for CCALF that define the common CCALF data, and all slices can then inherit this common information compared to Fig. 7.

Fig. 16 is a schematic diagram of a data structure 5000, the data structure 5000 may represent a portion of the bitstream 21 generated by the encoder in Fig. 2 and received by the decoder in Fig. 3. The data structure 5000 (i.e., the video bitstream 5000) may comprise a VPS 5005; an SPS 5010; a PPS 5015; and at least four slices 5020, 5025, 5030 and 5035. Slice 5020 may contain header 5040 and data 5045. Slices 5025, 5030, 5035 are similar to slice 5020. Data 5045 may contain at least three blocks 5050, 5055 and 5060, that is, an encoded representation of at least three blocks 5050, 5055 and 5060. Although four slices 5020-5035 are shown, video bitstream 5000 contains any suitable number of slices. Although three blocks 5050-5060 are shown, data 5045 contains any suitable number of blocks. In addition, each remaining slice 5025, 5030, 5035 also contains blocks. Thus, while the video bitstream 5000 contains, for example, an encoded representation of multiple blocks, the video bitstream 5000 contains one SPS 5010 and significantly fewer slice headers than blocks. It is understood that the bitstream including a plurality of syntax elements related to the CC-ALF can also be shown in Fig. 16. As shown by the syntax above and below, the plurality of syntax elements related to the CC-ALF are clearly defined. In addition, the process of encoding or decoding the bitstream is clearly indicated in the syntax and/or semantics noted above and below.

The bitstream shown here may be obtained by encoding a video sequence using any of the embodiments described above. In particular, this bitstream may be obtained or may include syntax elements and, in particular, syntax elements related to CC-ALF, as explained in the above alternative embodiments 1-5.

Fig. 14 shows a block diagram of a method 4200 for encoding, for example, video. This method can be implemented, for example, using the encoder according to Fig. 12, but any other encoder and encoding device disclosed in this document can also be used to perform this method.

The encoding method 4200 comprises applying 4201 an inter-component adaptive loop filter CC-ALF for refining a chrominance component and generating 4202 a bitstream including a plurality of syntax elements related to the CC-ALF, wherein said plurality of syntax elements related to the CC-ALF indicate information related to the CC-ALF. In the bitstream generated in step 4202, said plurality of syntax elements related to the CC-ALF are signaled at any one or more of a sequence parameter set (SPS) level, a picture header or a slice header. Said plurality of syntax elements related to CC-ALF comprises a first syntax element that indicates whether or not an adaptive loop filter (ALF) comprising an inter-component adaptive loop filter is enabled at the sequence level, and the first syntax element is signaled at the SPS level, and a second syntax element that indicates whether or not the inter-component adaptive loop filter is enabled at the sequence level, and the second syntax element is signaled at the SPS level.

Fig. 15 shows a block diagram of a method 4300 for decoding, for example, video from a bitstream, etc. This method 4300 can be implemented, for example, using the decoder according to Fig. 13. Also, any other decoder and decoding device disclosed in this document can be used to perform the method 4300.

The method 4300 comprises parsing 4301 a plurality of syntax elements related to a cross-component adaptive loop filter, CC-ALF, from a bitstream, wherein said plurality of syntax elements related to the CC-ALF are obtained from any one or more of a sequence parameter set (SPS) level, a picture header or a slice header. Said plurality of syntax elements related to the CC-ALF comprises a first syntax element that indicates whether an adaptive loop filter (ALF) comprising a cross-component adaptive loop filter is enabled or not at a sequence level, and the first syntax element is signaled at a SPS level, and a second syntax element that indicates whether the cross-component adaptive loop filter is enabled or not at a sequence level, and the second syntax element is signaled at a SPS level. The method 4300 further comprises a step 4302 of performing a CC-ALF process using at least one of said plurality of syntax elements related to the CC-ALF.

In one embodiment, an encoding method implemented by an encoding device is provided, comprising:

performing a filtering process (such as a cross-component filtering process) by applying a cross-component adaptive loop filter (CC-ALF);

generating a bit stream including a plurality of syntactic elements related to the CC-ALF (such as M syntactic elements related to the CC-ALF, and M>=1, and M is an integer), wherein said plurality of syntactic elements related to the CC-ALF indicate information related to the CC-ALF,

wherein said plurality of syntax elements related to the CC-ALF are signaled at any one or more of a video parameter set (VPS) level, a sequence parameter set (SPS) level, a picture parameter set (PPS) level, a picture header, a slice header or a tile header; or wherein said plurality of syntax elements related to the CC-ALF are signaled at a sequence parameter set (SPS) level and/or in a picture header.

By means of this method, a bitstream can be provided whose size is reduced, since information relating to, for example, all slices of an image can be provided in the image header only once.

In one embodiment, said plurality of syntax elements related to CC-ALF comprises: a first syntax element (e.g., a first indicator, such as sps_ccalf_enabled_flag or sps_alf_enabled_flag), wherein the first syntax element (e.g., a first indicator, such as sps_ccalf_enabled_flag) is signaled at the sequence parameter set (SPS) level. This indicator may indicate whether ALF or CC-ALF or both can be enabled or not for the entire sequence.

In a further embodiment, the first syntax element (e.g., a first indicator such as sps_ccalf_enabled_flag) indicates whether or not the cross-component adaptive loop filter (CC-ALF) is enabled at the sequence level, or

wherein the first syntax element (e.g. the first indicator such as sps_alf_enabled_flag) indicates whether the adaptive loop filter (ALF) containing the cross-component adaptive loop filter (CC-ALF) is enabled or not at the sequence level. With this first syntax element, the adaptive loop filter modes can be specifically provided at the sequence level for all images or parts of a sequence.

In addition, it can be provided that the first syntax element (such as sps_ccalf_enabled_flag or sps_alf_enabled_flag) is set to the first value ("true" or 1) or the first syntax element has the first value ("true" or 1). With this value it can be indicated whether ALF and/or CC-ALF are enabled, preferably using only one bit value.

In one embodiment, said plurality of CC-ALF related syntax elements further comprises:

a second syntax element (e.g., a second indicator such as pic_ccalf_enabled_present_flag) if the first syntax element (e.g., sps_ccalf_enabled_flag or sps_alf_enabled_flag) is set to the first value ('true' or 1) or the first syntax element has the first value ('true' or 1) in which the second syntax element (such as pic_ccalf_enabled_present_flag) is signaled in the image header; or

the ninth syntactic element (e.g. the ninth indicator, such aspic_alf_enabled_present_flag) if the first syntax element (such as sps_ccalf_enabled_flag or sps_alf_enabled_flag) is set to the first value ('true' or 1) or the first syntax element has the first value ('true' or 1), and the ninth syntax element (such aspic_alf_enabled_present_flag) is signaled in the image header.

That the second syntax element is provided if the first syntax element is set to the first value (and accordingly for the ninth syntax element) may be understood as meaning that the corresponding syntax element is provided alone or at least once if the first syntax element has the first value and is not provided in any other case. This embodiment may, however, provide that the second and ninth syntax elements are provided or present regardless of the value of the first syntax element. This meaning may be applied to the presence or absence of all additional syntax elements mentioned herein, provided that these syntax elements are considered to be present if another syntax element takes a specific value.

The second and ninth syntax elements can be used to specify whether ALF and/or CC-ALF are enabled for image slices using reduced bits.

In one embodiment, the second syntax element (e.g., a second indicator such as pic_ccalf_enabled_present_flag) indicates whether the third syntax element and/or the fourth set of syntax elements are present in the image header.

In addition, it may be envisaged that said set of syntactic elements related to CC-ALF additionally comprises:

a third syntactic element (e.g. a third indicator such aspic_ccalf_enabled_flag or pic_alf_enabled_flag), if the second syntax element (such as pic_ccalf_enabled_present_flag) or the ninth syntax element (such aspic_alf_enabled_present_flag) is set to the first value ('true' or 1), or the second syntactic element or the ninth syntactic element has the first value ('true' or 1), and the third syntactic element(suchHow pic_ccalf_enabled_flag or pic_alf_enabled_flag) is signaled in the image header.

In a further embodiment, a third syntax element (e.g., a third indicator such as pic_ccalf_enabled_flag ) indicates whether the cross-component adaptive contour filter (CCALF) is enabled for all slices associated with the picture header or not, or

wherein the third syntax element (e.g. the third indicator such as pic_alf_enabled_flag ) indicates whether the adaptive loop filter containing the cross-component adaptive loop filter (CCALF) is enabled for all slices associated with the image header or not. In this way, the information about the application of ALF or CC-ALF can be conveyed for all slices of the image using a reduced amount of information.

In a further embodiment, said plurality of CC-ALF related syntax elements further comprises:

a fourth set of syntax elements if the third syntax element (e.g., a third indicator such as pic_ccalf_enabled_flag or pic_alf_enabled_flag ) is set to the first value ('true' or 1) or the third syntax element has the first value ('true' or 1), where the fourth set of syntax elements is signaled in the image header (e.g., at the image header level), or the fourth set of syntax elements is carried by image header elements.

In particular, in one embodiment, the fourth set of syntax elements comprises:

if( ChromaArrayType != 0 ) pic_cross_component_alf_cb_enabled_flag u(1) if(pic_cross_component_alf_cb_enabled_flag ) { pic_cross_component_alf_cb_aps_id u(3) } if( ChromaArrayType != 0 ) pic_cross_component_alf_cr_enabled_flag u(1) if( pic_cross_component_alf_cr_enabled_flag ) { pic_cross_component_alf_cr_aps_id u(3) } }

Additionally or alternatively, it may be provided that the fourth set of syntactic elements comprises:

if( ChromaArrayType != 0 ) pic_cross_component_alf_cb_enabled_flag u(1) if(pic_cross_component_alf_cb_enabled_flag ) { pic_cross_component_alf_cb_aps_id u(3) pic_cross_component_cb_filters_signalled_minus1 ue(v) } if( ChromaArrayType != 0 ) pic_cross_component_alf_cr_enabled_flag u(1) if( pic_cross_component_alf_cr_enabled_flag ) { pic_cross_component_alf_cr_aps_id u(3) pic_cross_component_cr_filters_signalled_minus1 ue(v) } }

In addition, additionally or alternatively, the fourth set of syntactic elements contains:

if( ChromaArrayType != 0 ) pic_cross_component_alf_cb_enabled_flag u(1) if( pic_cross_component_alf_cb_enabled_flag ) { pic_cross_component_cb_filters_signalled_minus1 ue(v) } if( ChromaArrayType != 0 ) pic_cross_component_alf_cr_enabled_flag u(1) if( pic_cross_component_alf_cr_enabled_flag ) { pic_cross_component_cr_filters_signalled_minus1 ue(v) }

In the above embodiments, relevant information about the filters to be applied may be provided for all slices already in the image header, potentially reducing the bitstream size.

In a further embodiment, it is provided that for all slices of the same image, the same CC-ALF related information (such as aps_ids) is inherited from the image header. Thus, there is no need to additionally include the information provided in the image header in slice headers, etc., thereby potentially reducing the amount of information provided in the bitstream.

In one embodiment, said plurality of CC-ALF related syntax elements comprises:

a first syntax element (e.g., a first indicator such as sps_ccalf_enabled_flag or sps_alf_enabled_flag), wherein the first syntax element (e.g., a first indicator such as sps_ccalf_enabled_flag) is signaled at the sequence parameter set (SPS) level,

a second syntax element (e.g. a second indicator such as pic_ccalf_enabled_present_flag) if the first syntax element (such as sps_ccalf_enabled_flag or sps_alf_enabled_flag) is set to the first value ('true' or 1) or has the first value ('true' or 1), and the second syntax element (such as pic_ccalf_enabled_present_flag) is signaled in the image header.

In addition, the said set of syntactic elements related to CC-ALF may contain:

the fifth syntactic element (e.g. the fifth indicator, such asslice_ccalf_enabled_flagorslice_alf_enabled_flag) if the first syntax element (such as sps_ccalf_enabled_flag or sps_alf_enabled_flag) is set to the first value ('true' or 1) or has the first value ('true' or 1) , and if the second syntax element (such as pic_ccalf_enabled_present_flag or pic_alf_enabled_present_flag) is set to the second value ('false' or 0) or has the second value ('false' or 0), where the fifth syntactic element (such asslice_ccalf_enabled_flagorslice_alf_enabled_flag) is signaled in the slice header.

It may also be envisaged that said set of syntactic elements related to CC-ALF additionally comprises:

a sixth set of syntax elements, if the fifth syntax element (e.g., a fifth indicator such as slice_ccalf_enabled_flag or slice_alf_enabled_flag ) is set to the first value ('true' or 1) or the fifth syntax element has the first value ('true' or 1), where the sixth set of syntax elements is signaled in the slice header or the sixth set of syntax elements is carried by slice header records. This set of syntax elements may, for example, indicate parameters to be used in ALF or CC-ALF. By providing this set, potentially dependent on the value of the fifth syntax element, the size of the bitstream may be further reduced.

In particular, it may be envisaged that the sixth set of syntactic elements contains:

if( ChromaArrayType != 0 ) slice_cross_component_alf_cb_enabled_flag u(1) if(slice_cross_component_alf_cb_enabled_flag ) { slice_cross_component_alf_cb_aps_id u(3) } if( ChromaArrayType != 0 ) slice_cross_component_alf_cr_enabled_flag u(1) if( slice_cross_component_alf_cr_enabled_flag ) { slice_cross_component_alf_cr_aps_id u(3) } }

Additionally or alternatively, it may be provided that the sixth set of syntactic elements comprises:

if( ChromaArrayType != 0 ) slice_cross_component_alf_cb_enabled_flag u(1) if( slice_cross_component_alf_cb_enabled_flag ) { slice_cross_component_alf_cb_aps_id u(3) slice_cross_component_cb_filters_signalled_minus1 ue(v) } if( ChromaArrayType != 0 ) slice_cross_component_alf_cr_enabled_flag u(1) if( slice_cross_component_alf_cr_enabled_flag ) { slice_cross_component_alf_cr_aps_id u(3) slice_cross_component_cr_filters_signalled_minus1 ue(v) }

In addition, it may be envisaged that the sixth set of syntactic elements contains:

if( ChromaArrayType != 0 ) slice_cross_component_alf_cb_enabled_flag u(1) if( slice_cross_component_alf_cb_enabled_flag ) { slice_cross_component_cb_filters_signalled_minus1 ue(v) } if( ChromaArrayType != 0 ) slice_cross_component_alf_cr_enabled_flag u(1) if( slice_cross_component_alf_cr_enabled_flag ) { slice_cross_component_cr_filters_signalled_minus1 ue(v) }

In a further embodiment, said plurality of CC-ALF related syntax elements further comprises:

a seventh syntax element (for example, a seventh indicator such as pic_cross_component_alf_cb_aps_id) and an eighth syntax element (for example, an eighth indicator such as pic_cross_component_alf_cr_aps_id) if the first syntax element (such as sps_ccalf_enabled_flag or sps_alf_enabled_flag) is set to the first value ('true' or 1) or has the first value ('true' or 1).

In one embodiment, said plurality of CC-ALF related syntax elements further comprises:

a seventh syntax element (e.g., a seventh indicator such as pic_cross_component_alf_cb_aps_id) and an eighth syntax element (e.g., an eighth indicator such as pic_cross_component_alf_cr_aps_id) if the first syntax element (such as sps_ccalf_enabled_flag or sps_alf_enabled_flag) is set to the first value ('true' or 1) or has the first value ('true' or 1), and if the ninth syntax element (such as pic_alf_enabled_present_flag ) is set to the first value ('true' or 1) or has the first value ('true' or 1).

In one embodiment, said plurality of CC-ALF related syntax elements further comprises:

the seventh syntactic element (e.g. the seventh indicator, such aspic_cross_component_alf_cb_aps_id), the eighth syntax element (e.g. the eighth indicator, such as pic_cross_component_alf_cr_aps_id), and the second syntax element (e.g.pic_ccalf_enabled_present_flag),if the first syntax element (e.g. sps_ccalf_enabled_flag or sps_alf_enabled_flag) is set to the first value ('true' or 1) or has the first value ('true' or 1) , and if the ninth syntax element (For example, pic_alf_enabled_present_flag) is set to the first value ('true' or 1) or has the first value ('true' or 1).

It may also be envisaged that said set of syntactic elements related to CC-ALF additionally comprises:

a seventh syntax element (e.g., a seventh indicator such as pic_cross_component_alf_cb_aps_id), an eighth syntax element (e.g., an eighth indicator such as pic_cross_component_alf_cr_aps_id), and a ninth syntax element (e.g., pic_alf_enabled_present_flag) if the first syntax element (e.g., sps_ccalf_enabled_flag or sps_alf_enabled_flag) is set to the first value ('true' or 1) or has the first value ('true' or 1).

Moreover, in one embodiment, the CC-ALF is employed to perform filtering processing on one or more luminance samples of a luminance component of a current image block to refine a chroma sample (such as each chroma sample) of a chroma component of the current image block.

In particular, it may be envisaged that the CC-ALF is configured to refine each chrominance component using the luminance sample values.

In one embodiment, CC-ALF operates as part of an adaptive loop filtering process.

It may also be envisaged that the image block contains a luminance block and color blocks,

wherein the first chroma block represents a first chroma component (such as a Cb component) of the image block, and the second chroma block represents a second chroma component (such as a Cr component) of the image block.

The present disclosure also relates to an encoding method implemented by an encoding device comprising:

determining whether the cross-component ALF (CC-ALF) is enabled or not;

generating a bitstream including one or more syntactic elements (e.g. a syntactic element related to CC-ALF, such how pic_ccalf_enabled_flag, pic_cross_component_alf_cb_enabled_flag or pic_cross_component_alf_cr_enabled_flag), wherein said one or more syntax elements indicate whether inter-component ALF (CC-ALF) is enabled or not at the image header level and corresponding information related to CC-ALF, wherein the syntax elements are signaled at the image header level. In this way, relevant information for subsequent decoding can be provided with a reduced size in the bitstream.

It may also be provided that the CC-ALF is used to perform filtering processing on one or more luminance samples of the luminance component of the current image block to refine a chroma sample (e.g., each chroma sample) of the chroma component of the current image block.

In one embodiment, the method further comprises:

performing filtering processing of a luminance component of a current image block that belongs to the image using the CC-ALF filter, wherein one or more luminance samples of the luminance component of the current image block are used to refine at least one chroma sample (for example, each chroma sample) of the chroma component of the current image block.

It may also be envisaged that the CC-ALF is configured to refine each chrominance component using the luminance sample values.

In a further embodiment, CC-ALF operates as part of an adaptive loop filtering process.

It may also be envisaged that the image block contains a luminance block and color blocks,

wherein the first chroma block represents a first chroma component (such as a Cb component) of the image block, and the second chroma block represents a second chroma component (such as a Cr component) of the image block.

The present disclosure further relates to a decoding method implemented by a decoding device, the method comprising:

parsing one or more syntax elements from a video bitstream, wherein said one or more syntax elements indicate information related to a cross-component adaptive loop filter (CC-ALF), wherein said one or more syntax elements are obtained from any one or more of a video parameter set (VPS) layer, a sequence parameter set (SPS) layer, a picture parameter set (PPS) layer, a picture header, a slice header, or a tile header of the bitstream; or wherein said one or more syntax elements are obtained from a sequence parameter set (SPS) layer and/or a picture header; and

performing a filtering process (such as a cross-component filtering process) by applying CC-ALF based on syntactic elements or based on the values of syntactic elements.

Information that may be necessary to determine the filtering method to be applied and how it is applied may be provided along with it in a bitstream that is reduced in size but still allows reliable decoding.

The present disclosure further describes a decoding method implemented by a decoding device, wherein the method comprises:

parsing a plurality of syntax elements from a video bitstream, wherein the syntax elements are obtained from any one or more of a video parameter set (VPS) layer, a sequence parameter set (SPS) layer, a picture parameter set (PPS) layer, a picture header, a slice header, or a tile header of the bitstream; or wherein the syntax elements are obtained from a sequence parameter set (SPS) layer and/or a picture header;

determining information related to a cross-component adaptive loop filter (CC-ALF) based on one or more syntactic elements from said plurality of syntactic elements, wherein

performing a filtering process (such as a cross-component filtering process) by applying the CC-ALF based on the information related to the CC-ALF.

Information that may be necessary to determine the filtering method to be applied and how it is applied may be provided along with it in a bitstream that is reduced in size but still allows reliable decoding.

It may be envisaged that said one or more syntax elements or said plurality of syntax elements (such as syntax elements related to CC-ALF) comprise: a first syntax element (for example a first indicator such as sps_ccalf_enabled_flag or sps_alf_enabled_flag), wherein the first syntax element (for example a first indicator such as sps_ccalf_enabled_flag) is obtained from a sequence parameter set (SPS) level.

In particular, it may be further provided that the first syntax element (e.g. the first indicator, such as sps_ccalf_enabled_flag) indicates whether the cross-component adaptive loop filter (CC-ALF) is enabled at the sequence level, or

wherein the first syntax element (e.g., the first indicator, such as sps_alf_enabled_flag) indicates whether or not the adaptive loop filter (ALF) containing the cross-component adaptive loop filter (CC-ALF) is enabled at the sequence level.

In this way, information about which filtering method should be applied can be provided with a reduced amount of information to the decoder in the bitstream.

In one embodiment, the first syntax element (such as sps_ccalf_enabled_flag or sps_alf_enabled_flag) is output as the first value ('true' or 1), or the first syntax element has the first value ('true' or 1).

It may also be envisaged that said plurality of syntactic elements (such as syntactic elements related to CC-ALF) additionally comprise:

a second syntax element (such as a second indicator such as pic_ccalf_enabled_present_flag) if the first syntax element (such as sps_ccalf_enabled_flag or sps_alf_enabled_flag) is derived as the first value ('true' or 1) or the first syntax element has the first value ('true' or 1) in which the second syntax element (such as pic_ccalf_enabled_present_flag) is obtained from the image header; or

a ninth syntax element (e.g. a ninth indicator such as pic_alf_enabled_present_flag) if the first syntax element (such as sps_ccalf_enabled_flag or sps_alf_enabled_flag) is output as the first value ('true' or 1) or the first syntax element has the first value ('true' or 1), and the ninth syntax element (such as pic_alf_enabled_present_flag ) is obtained from the image header.

In a further embodiment, the second syntax element (e.g., a second indicator such as pic_ccalf_enabled_present_flag) indicates whether the third syntax element and/or the fourth set of syntax elements are present in the image header.

The said set of syntactic elements (such as syntactic elements related to CC-ALF) may further comprise:

a third syntactic element (e.g. a third indicator such aspic_ccalf_enabled_flagor pic_alf_enabled_flag) if the second syntax element (such as pic_ccalf_enabled_present_flag) or the ninth syntax element (such aspic_alf_enabled_present_flag) is output as the first value ('true' or 1), or the second syntactic element or the ninth syntactic element has the first value ('true' or 1), and the third syntactic element (such aspic_ccalf_enabled_flag or pic_alf_enabled_flag) is obtained from the image title.

In particular, it may be provided that a third syntax element (e.g. a third indicator such as pic_ccalf_enabled_flag) indicates whether the cross-component adaptive contour filter (CCALF) is enabled for all slices associated with the picture header or not, or

where the third syntax element (e.g. the third indicator such as pic_alf_enabled_flag) indicates whether the adaptive loop filter containing the cross-component adaptive loop filter (CCALF) is enabled for all slices associated with the image header or not.

In one embodiment, said plurality of syntax elements (such as syntax elements related to CC-ALF) further comprise:

a fourth set of syntax elements if the third syntax element (e.g., a third indicator such as pic_ccalf_enabled_flag or pic_alf_enabled_flag ) is output as the first value ('true' or 1) or the third syntax element has the first value ('true' or 1) and the fourth set of syntax elements is obtained from the image header (e.g., at the image header level) or the fourth set of syntax elements is carried by image header elements.

This set of syntax elements may be provided only if the third syntax element takes or is derived as the first value and may not be present otherwise, or the values of the set of syntax elements may be set to a default value, such as 0, if the third syntax element takes another value. In both cases, reliable provision of relevant decoding information can be ensured with a reduced bitstream size.

In particular, the fourth set of syntactic elements may contain:

if( ChromaArrayType != 0 ) pic_cross_component_alf_cb_enabled_flag u(1) if(pic_cross_component_alf_cb_enabled_flag ) { pic_cross_component_alf_cb_aps_id u(3) } if( ChromaArrayType != 0 ) pic_cross_component_alf_cr_enabled_flag u(1) if( pic_cross_component_alf_cr_enabled_flag ) { pic_cross_component_alf_cr_aps_id u(3) } }

Alternatively or additionally, the fourth set of syntactic elements may contain:

if( ChromaArrayType != 0 ) pic_cross_component_alf_cb_enabled_flag u(1) if(pic_cross_component_alf_cb_enabled_flag ) { pic_cross_component_alf_cb_aps_id u(3) pic_cross_component_cb_filters_signalled_minus1 ue(v) } if( ChromaArrayType != 0 ) pic_cross_component_alf_cr_enabled_flag u(1) if( pic_cross_component_alf_cr_enabled_flag ) { pic_cross_component_alf_cr_aps_id u(3) pic_cross_component_cr_filters_signalled_minus1 ue(v) } }

In a further embodiment, the fourth set of syntax elements may comprise:

if( ChromaArrayType != 0 ) pic_cross_component_alf_cb_enabled_flag u(1) if( pic_cross_component_alf_cb_enabled_flag ) { pic_cross_component_cb_filters_signalled_minus1 ue(v) } if( ChromaArrayType != 0 ) pic_cross_component_alf_cr_enabled_flag u(1) if( pic_cross_component_alf_cr_enabled_flag ) { pic_cross_component_cr_filters_signalled_minus1 ue(v) }

It may be envisaged that for all slices of the same picture the same CC-ALF related information (such as aps_ids) is inherited from the picture header. In this way the amount of information provided in the bitstream to indicate to the decoder the CC-ALF related information for the picture slices may be reduced.

In one embodiment, said plurality of syntax elements (such as syntax elements related to CC-ALF) comprise:

a first syntax element (e.g., a first indicator such as sps_ccalf_enabled_flag or sps_alf_enabled_flag), where the first syntax element (e.g., a first indicator such as sps_ccalf_enabled_flag) is obtained from the sequence parameter set (SPS) level,

a second syntax element (e.g. a second indicator such as pic_ccalf_enabled_present_flag) if the first syntax element (such as sps_ccalf_enabled_flag or sps_alf_enabled_flag) is inferred as the first value ('true' or 1) or has the first value ('true' or 1), where the second syntax element (such as pic_ccalf_enabled_present_flag) is obtained from the image header.

In a further embodiment, said plurality of syntax elements (such as syntax elements related to CC-ALF) further comprise:

a fifth syntax element (e.g. a fifth indicator such as slice_ccalf_enabled_flag or slice_alf_enabled_flag ) if the first syntax element (such as sps_ccalf_enabled_flag or sps_alf_enabled_flag ) is output as the first value ('true' or 1) or has the first value ('true' or 1) , and if the second syntax element (such as pic_ccalf_enabled_present_flag or pic_alf_enabled_present_flag ) is output as the second value ('false' or 0) or has the second value ('false' or 0), where the fifth syntax element (such as slice_ccalf_enabled_flag or slice_alf_enabled_flag ) is obtained from the slice header.

It may be envisaged that said set of syntactic elements (such as syntactic elements related to CC-ALF) additionally comprise:

a sixth set of syntax elements if the fifth syntax element (e.g., the fifth indicator such as slice_ccalf_enabled_flag or slice_alf_enabled_flag ) is output as the first value ('true' or 1), or the fifth syntax element has the first value ('true' or 1), and the sixth set of syntax elements is obtained from the slice header, or the sixth set of syntax elements is carried by slice header records.

In particular, it may be envisaged that the sixth set of syntactic elements contains:

if( ChromaArrayType != 0 ) slice_cross_component_alf_cb_enabled_flag u(1) if(slice_cross_component_alf_cb_enabled_flag ) { slice_cross_component_alf_cb_aps_id u(3) } if( ChromaArrayType != 0 ) slice_cross_component_alf_cr_enabled_flag u(1) if( slice_cross_component_alf_cr_enabled_flag ) { slice_cross_component_alf_cr_aps_id u(3) } }

Alternatively or additionally, it may be provided that the sixth set of syntactic elements comprises:

if( ChromaArrayType != 0 ) slice_cross_component_alf_cb_enabled_flag u(1) if( slice_cross_component_alf_cb_enabled_flag ) { slice_cross_component_alf_cb_aps_id u(3) slice_cross_component_cb_filters_signalled_minus1 ue(v) } if( ChromaArrayType != 0 ) slice_cross_component_alf_cr_enabled_flag u(1) if( slice_cross_component_alf_cr_enabled_flag ) { slice_cross_component_alf_cr_aps_id u(3) slice_cross_component_cr_filters_signalled_minus1 ue(v) }

Similarly, it can be envisaged that the sixth set of syntactic elements contains:

if( ChromaArrayType != 0 ) slice_cross_component_alf_cb_enabled_flag u(1) if( slice_cross_component_alf_cb_enabled_flag ) { slice_cross_component_cb_filters_signalled_minus1 ue(v) } if( ChromaArrayType != 0 ) slice_cross_component_alf_cr_enabled_flag u(1) if( slice_cross_component_alf_cr_enabled_flag ) { slice_cross_component_cr_filters_signalled_minus1 ue(v) }

In one embodiment, said plurality of syntax elements (such as syntax elements related to CC-ALF) further comprise:

a seventh syntax element (for example, a seventh indicator such as pic_cross_component_alf_cb_aps_id ) and an eighth syntax element (for example, an eighth indicator such as pic_cross_component_alf_cr_aps_id ) if the first syntax element (such as sps_ccalf_enabled_flag or sps_alf_enabled_flag ) is inferred to be the first value ('true' or 1) or has the first value ('true' or 1).

It may also be envisaged that said plurality of syntactic elements (such as syntactic elements related to CC-ALF) additionally comprise:

a seventh syntax element (e.g., a seventh indicator such as pic_cross_component_alf_cb_aps_id) and an eighth syntax element (e.g., an eighth indicator such as pic_cross_component_alf_cr_aps_id) if the first syntax element (such as sps_ccalf_enabled_flag or sps_alf_enabled_flag) is output as the first value ('true' or 1) or has the first value ('true' or 1), and if the ninth syntax element (such as pic_alf_enabled_present_flag ) is output as the first value ('true' or 1) or has the first value ('true' or 1).

In another embodiment, said plurality of syntax elements (such as syntax elements related to CC-ALF) further comprise:

the seventh syntactic element (e.g. the seventh indicator, such aspic_cross_component_alf_cb_aps_id), the eighth syntax element (e.g. the eighth indicator, such as pic_cross_component_alf_cr_aps_id), and the second syntax element (e.g.pic_ccalf_enabled_present_flag),if the first syntax element (e.g. sps_ccalf_enabled_flag or sps_alf_enabled_flag ) is output as the first value ('true' or 1) or has the first value ('true' or 1) , and if the ninth syntax element (For example, pic_alf_enabled_present_flag) is output as the first value ("true" or 1) or has the first value ("true" or 1).

It may also be envisaged that said plurality of syntactic elements (such as syntactic elements related to CC-ALF) additionally comprise:

a seventh syntax element (e.g., a seventh indicator such as pic_cross_component_alf_cb_aps_id), an eighth syntax element (e.g., an eighth indicator such as pic_cross_component_alf_cr_aps_id), and a ninth syntax element (e.g., pic_alf_enabled_present_flag) if the first syntax element (e.g., sps_ccalf_enabled_flag or sps_alf_enabled_flag ) is inferred to be the first value ('true' or 1) or has the first value ('true' or 1).

In one embodiment, the CC-ALF is used to perform filtering processing on one or more samples of a luminance component of a current image block to refine a chroma sample (e.g., each chroma sample) of a chroma component of the current image block.

CC-ALF can be designed to refine each chrominance component using luminance sample values.

It can also be envisaged that CC-ALF operates as part of an adaptive loop filtering process.

In one embodiment, the image block comprises a luminance block and chroma blocks,

wherein the first chroma block represents a first chroma component (such as a Cb component) of the image block, and the second chroma block represents a second chroma component (such as a Cr component) of the image block.

The present disclosure further relates to a decoding method implemented by a decoding device comprising:

parsing from the video bitstream one or more syntactic elements (e.g. M syntactic elements related to CC-ALF, where M is an integer and M>=1, for example, pic_ccalf_enabled_flag,pic_cross_component_alf_cb_enabled_flag or pic_cross_component_alf_cr_enabled_flag), wherein said one or more syntax elements indicate whether or not inter-component ALF (CCALF) is included at the image header level, and corresponding information related to CCALF, wherein said one or more syntax elements are obtained from the image header level.

performing a filtering process (such as a cross-component filtering process) by applying CC-ALF in response to determining that CC-ALF is enabled.

This method can appropriately apply CC-ALF during decoding, allowing the bitstream size to be reduced.

In one embodiment, the CC-ALF is used to perform filtering processing on one or more samples of a luminance component of a current image block to refine a chroma sample (e.g., each chroma sample) of a chroma component of the current image block.

It may also be envisaged that the CC-ALF is configured to refine each chrominance component using the luminance sample values.

In a further embodiment, CC-ALF operates as part of an adaptive loop filtering process.

Embodiments may further provide that the image block comprises a luminance block and chroma blocks,

wherein the first chroma block represents a first chroma component (such as a Cb component) of the image block, and the second chroma block represents a second chroma component (such as a Cr component) of the image block.

The present disclosure further provides an apparatus for encoding video data, comprising:

video data memory; and

video encoder, wherein the video encoder is designed with the ability to:

performing a filtering process (such as a cross-component filtering process) by applying a cross-component adaptive loop filter (CC-ALF);

forming a bit stream for a video signal by including a plurality of syntax elements (such as syntax elements related to a CC-ALF), wherein said plurality of syntax elements indicate information related to the CC-ALF,

wherein said plurality of syntax elements related to the CC-ALF are obtained from any one or more of a video parameter set (VPS) level, a sequence parameter set (SPS) level, a picture parameter set (PPS) level, a picture header, a slice header, or a tile header; or

wherein said set of syntactic elements related to CC-ALF is obtained from the sequence parameter set (SPS) level and/or the image header.

This device can implement encoding that results in a bitstream that is reduced in size.

In addition, a device for decoding video data is provided, comprising:

video data memory; and

a video decoder, wherein the video decoder is configured to:

parsing a plurality of syntax elements from a video bitstream, wherein said plurality of syntax elements are obtained from any one or more of a video parameter set (VPS) layer, a sequence parameter set (SPS) layer, a picture parameter set (PPS) layer, a picture header, a slice header or a tile header of the bitstream, or wherein said plurality of syntax elements are obtained from a sequence parameter set (SPS) layer and/or a picture header of the bitstream;

determining information related to a cross-component adaptive loop filter (CC-ALF) based on one or more syntactic elements from said plurality of syntactic elements; and

performing a filtering process (such as a cross-component filtering process) by applying the CC-ALF based on the information related to the CC-ALF.

This decoder can perform robust decoding by requiring a reduced-size bitstream to obtain information related to the filter to be applied during decoding.

The present disclosure further provides an encoder comprising a processing circuit for performing the method according to any of the above embodiments.

The present disclosure also relates to a decoder, wherein the decoder comprises a processing circuit for performing the method according to any of the above embodiments.

In addition, a computer program product is provided containing a program code for performing the method in accordance with any of the above embodiments.

The present disclosure further relates to a decoder, wherein the decoder comprises:

one or more processors; and

a non-volatile computer-readable storage medium coupled to the processors and storing a program for execution by the processors, wherein the program, when executed by the processors, configures the decoder to perform the method according to any of the above embodiments.

In addition, the present disclosure provides an encoder comprising:

one or more processors; and

a non-volatile computer-readable storage medium coupled to the processors and storing a program for execution by the processors, wherein the program, when executed by the processors, configures the encoder to perform the method according to any of the above embodiments.

In addition, a non-volatile recording medium is provided that includes an encoded bit stream decoded by an image decoding device, the bit stream is formed by dividing a frame of a video signal or an image signal into a plurality of blocks and includes a plurality of syntax elements (such as syntax elements related to a CC-ALF), wherein said plurality of syntax elements indicate information related to a CC-ALF,

wherein said plurality of syntax elements (such as syntax elements related to CC-ALF) are obtained from any one or more of a video parameter set (VPS) level, a sequence parameter set (SPS) level, a picture parameter set (PPS) level, a picture header, a slice header, or a tile header, or

wherein said plurality of syntax elements (such as syntax elements related to CC-ALF) are obtained from at least one of a sequence parameter set (SPS) level or an image header.

The present disclosure also relates to a device comprising:

a non-volatile computer-readable medium on which instructions are stored that, when executed by one or more processors, cause said one or more processors to perform operations for generating image data corresponding to a video bitstream, wherein the image data comprises:

a plurality of images in a video bitstream, including an image containing N slices; and

image header associated with N image slices,

wherein one or more of or each of the N slices contains a plurality of blocks of samples encoded using entropy,

in this case, CC-ALF filtering information or CC-ALF filter parameters are inherited by N slices from the image header or N slices inherit ALF filtering data from the image header.

In accordance with any of the above embodiments, it may be further provided that

The values of slice_cross_component_alf_cr_aps_id and slice_cross_component_alf_cb_aps_id are the same as the values of pic_cross_component_alf_cb_aps_id and pic_cross_component_alf_cr_aps_id.

In a further embodiment, pic_cross_component_alf_cb_aps_id and pic_cross_component_alf_cr_aps_id are obtained from the image header.

It can also be provided that a syntax element related to CCALF occurs only once in the image header associated with all N slices.

In one embodiment, N is a positive integer greater than 1.

In one embodiment, a method for encoding a video bitstream is provided, implemented by an encoding device, wherein the encoding method comprises:

generating a bitstream for a video signal by including a plurality of syntax elements (e.g., a syntax element related to ALF, such as sps_alf_enabled_flag, and/or a syntax element related to CCALF, such as sps_ccalf_enabled_flag), wherein said plurality of syntax elements comprise a cross-component adaptive loop filter (CC-ALF) enable flag (e.g., sps_ccalf_enabled_flag) and

wherein the CC-ALF related parameters are signaled conditionally based at least on the value of the CC-ALF enable flag (such as sps_ccalf_enabled_flag).

This can provide a bitstream that contains the relevant information for decoding, but has a reduced size.

Furthermore, according to the present disclosure, a method for decoding a video bitstream is provided, implemented by a decoding device, wherein the decoding method comprises:

obtaining (S110) a plurality of syntax elements from a video bitstream;

wherein said plurality of syntax elements comprises a cross-component adaptive loop filter (CC-ALF) enable flag (such as sps_ccalf_enabled_flag), and

whereby the CC-ALF related parameters are signaled conditionally based at least on the value of the CCALF enable flag (such as sps_ccalf_enabled_flag).

This method allows reliable decoding even when the bitstream size is reduced.

In one embodiment, in the case where one or more conditions are satisfied, a CCALF enable flag (such as sps_ccalf_enabled_flag) is signaled at the bitstream sequence parameter set (SPS) level, wherein the one or more conditions comprise: when the value of a first flag (such as sps_alf_enabled_flag) that is signaled at the bitstream sequence parameter set (SPS) level has an enabling value (such as a first value, for example, "true" or 1), and

where the CCALF enable flag indicates whether the cross-component adaptive loop filter (CCALF) is enabled at the sequence level or the SPS level.

Syntax elements may also be provided to contain a third flag (such asalf_present_in_ph_flag), and the third flag signals the Picture Parameter Set (PPS) level of the bitstream, and the third flag indicates whether one or more syntax elements for ALF inclusion are present in the PH (Picture Headers), referring to the PPS, or not.

It can also be envisaged that the third flag (alf_present_in_ph_flag), equal to 1, indicates that the syntax elements for ALF inclusion may be present in PH (picture headers) belonging to the PPS. The third flag (alf_present_in_ph_flag), equal to 0, indicates the syntax elements for ALF inclusion that may be present in slice headers belonging to the PPS.

In one embodiment, it is provided that if the value of the first flag (such as sps_alf_enabled_flag) is an enabling value (such as a first value, such as "true" or 1), and the value of the third flag (alf_present_in_ph_flag) is an enabling value (such as a first value, such as "true" or 1), and

if the value of the CCALF enable flag (e.g.sps_ccalf_enabled_flag) is the enabling value (e.g. the first value, e.g. "true" or 1), the parameters related to cross-component adaptive loop filtering (CCALF) (e.g. the syntax elements for enabling CCALF) are signaled at the picture_header level of the bitstream.

In another embodiment, it is provided that if the value of the first flag (such as sps_alf_enabled_flag) is an enabling value (such as the first value, such as "true" or 1), and the value of the third flag (alf_present_in_ph_flag) is a disabling value (such as the second value, such as "false" or 0), and

if the value of the CCALF enable flag (e.g.sps_ccalf_enabled_flag) is The enabling value (e.g. the first value, such as "true" or 1), parameters related to cross-component adaptive loop filtering (CCALF) (e.g. syntax elements to enable CCALF) are reported at the slice_header level of the bitstream.

In a further embodiment, a CC-ALF enable flag (such as sps_ccalf_enabled_flag) equal to 0 indicates that the inter-component adaptive loop filter is disabled; or

A CC-ALF enable flag (such as sps_ccalf_enabled_flag) equal to 1 indicates that the inter-component adaptive loop filter is enabled.

In addition, it may be envisaged that syntactic elements contain:

a second flag (such as no_ccalf_constraint_flag ) equal to 1 indicates that the CCALF enable flag (such as sps_ccalf_enabled_flag ) is 0; or a second flag (such as no_ccalf_constraint_flag ) equal to 0 imposes no such constraint.

In one embodiment, the method further comprises:

performing a filtering process (such as an inter-component adaptive loop filtering process) on the reconstructed image (such as the reconstructed array of luminance samples S _L , the reconstructed array of chrominance samples S _Cb and/or the reconstructed array of chrominance samples S _Cr ) to obtain a filtered reconstructed image (such as a modified reconstructed array of luminance samples S' _L , a modified reconstructed array of chrominance samples S' _Cb and/or a modified reconstructed array of chrominance samples S' _Cr ).

The present disclosure further provides an encoded bitstream for a video signal by including a plurality of syntax elements (e.g., a syntax element related to ALF, such as sps_alf_enabled_flag, and/or a syntax element related to CCALF, such as sps_ccalf_enabled_flag), wherein said plurality of syntax elements comprise a cross-component adaptive loop filter (CCALF) enable flag (e.g., sps_ccalf_enabled_flag) and

whereby CCALF-related parameters are signaled conditionally based at least on the value of the CCALF enable flag (such as sps_ccalf_enabled_flag).

The bitstream can be reduced in size while still providing information to be used for decoding when CC-ALF is used reliably.

Fig. 12 shows an embodiment of an encoder 4000. The encoder 4000 can be implemented using any processing circuit, designated here by 4001, for performing a video encoding method. In particular, the processing circuit 4001 can be configured to apply an inter-component adaptive loop filter CC-ALF for refining a chrominance component. The processing circuit can be further configured to generate a bitstream including a plurality of syntax elements related to the CC-ALF, wherein said plurality of syntax elements related to the CC-ALF indicate information related to the CC-ALF, wherein said plurality of syntax elements related to the CC-ALF are signaled at any one or more of a sequence parameter set (SPS) layer, a picture header or a slice header.

Said set of syntax elements related to CC-ALF in this context comprises a first syntax element that indicates whether or not an adaptive loop filter (ALF) comprising an inter-component adaptive loop filter is enabled at the sequence level, and the first syntax element is signaled at the SPS level, and a second syntax element that indicates whether or not the inter-component adaptive loop filter is enabled at the sequence level, and the second syntax element is signaled at the SPS level.

The encoder may further comprise a receiver 4002 for receiving video to be encoded and a transmitter 4003 for transmitting a bitstream containing at least said plurality of syntax elements.

Fig. 13 shows an embodiment of a decoder 4100. The decoder 4100 can be implemented using any processing circuit 4101 for performing a method for decoding video. In particular, the processing circuit 4101 can be configured to parse a plurality of syntax elements associated with a cross-component adaptive loop filter, CC-ALF, from a bitstream, wherein said plurality of syntax elements related to the CC-ALF are obtained from any one or more of a sequence parameter set (SPS) layer, a picture header, or a slice header.

In particular, said plurality of syntax elements related to CC-ALF comprises a first syntax element that indicates whether or not an adaptive loop filter (ALF) comprising an inter-component adaptive loop filter is enabled at the sequence level, and the first syntax element is signaled at the SPS level, and a second syntax element that indicates whether or not the inter-component adaptive loop filter is enabled at the sequence level, and the second syntax element is signaled at the SPS level.

The processing circuit may be further configured to perform the CC-ALF process using at least one of said plurality of syntax elements related to the CC-ALF.

Moreover, the decoder 4100 may comprise a receiver 4102 for receiving the bit stream. In addition, the decoder may comprise a transmitter 4103 for outputting the decoded video, for example, to an output device not shown here.

The following explains the applications of the encoding method and the decoding method as shown in the above embodiments and the system using them.

Fig. 10 is a block diagram showing a content delivery system 3100 for implementing a content distribution service. This content delivery system 3100 includes a capture device 3102, a terminal device 3106 and optionally includes a display 3126. The capture device 3102 communicates with the terminal device 3106 via a communication line 3104. The communication line may include the communication channel 13 described above. The communication line 3104 includes, but is not limited to, WIFI, Ethernet, cable, wireless communication (3G/4G/5G), USB or any combination thereof, or the like.

The capture device 3102 generates data and can encode the data using the encoding method shown in the above embodiments. Alternatively, the capture device 3102 can distribute the data to a streaming server (not shown in the Figures), and the server encodes the data and transmits the encoded data to the terminal device 3106. The capture device 3102 includes, but is not limited to, a camera, a smartphone or tablet, a computer or laptop, a videoconferencing system, a PDA, a vehicle-mounted device, or a combination of any of them, or the like. For example, the capture device 3102 can include the source device 12 described above. When the data includes video, the video encoder 20 included in the capture device 3102 can actually perform video encoding processing. When the data includes audio (i.e., speech), the audio encoder included in the capture device 3102 can actually perform audio encoding processing. For some practical scenarios, the capture device 3102 distributes the encoded video and audio data by multiplexing them together. For other practical scenarios, such as in a videoconferencing system, the encoded audio data and the encoded video data are not multiplexed. The capture device 3102 distributes the encoded audio data and the encoded video data to the terminal device 3106 separately.

In the content delivery system 3100, the terminal device 310 receives and reproduces the encoded data. The terminal device 3106 may be a device capable of receiving and retrieving data, such as a smartphone or tablet 3108, a computer or laptop 3110, a network video recorder (NVR) / digital video recorder (DVR) 3112, a TV 3114, a set-top box (STB) 3116, a video conferencing system 3118, a video surveillance system 3120, a personal digital assistant (PDA) 3122, a vehicle-mounted device 3124, or a combination thereof, or the like, capable of decoding the above-mentioned encoded data. For example, the terminal device 3106 may include the recipient device 14 described above. When the encoded data includes video, the video decoder 30 included in the terminal device is given priority for performing the video decoding. When the encoded data includes audio, the audio decoder included in the terminal device is given priority to perform the audio decoding processing.

For a terminal device with its own display, such as a smartphone or tablet 3108, a computer or laptop 3110, a network video recorder (NVR) / digital video recorder (DVR) 3112, a TV 3114, a personal digital assistant (PDA) 3122 or a device installed on a vehicle 3124, the terminal device can transmit decoded data to its display. For a terminal device not equipped with a display, such as an STB 3116, a videoconferencing system 3118 or a video surveillance system 3120, a contact is established therein with an external display 3126 for receiving and displaying decoded data.

When each device in this system performs encoding or decoding, an image encoding device or an image decoding device may be used, as shown in the above-mentioned embodiments.

Fig. 11 is a diagram showing the structure of an exemplary terminal device 3106. After the terminal device 3106 receives a stream from the capture device 3102, the protocol processing unit 3202 analyzes the transmission protocol of said stream. The protocol includes, but is not limited to, the real-time streaming protocol (RTSP), the hypertext transfer protocol (HTTP), the HTTP Live streaming protocol (HLS), MPEG-DASH, the real-time transport protocol (RTP), the real-time messaging protocol (RTMP), or any combination thereof, or the like.

After the protocol processing unit 3202 processes the stream, a stream file is formed. The file is output to the demultiplexing unit 3204. The demultiplexing unit 3204 can separate the multiplexed data into encoded audio data and encoded video data. As described above, in other practical scenarios, for example, in a videoconferencing system, the encoded audio data and the encoded video data are not multiplexed. In this situation, the encoded data is transmitted to the video decoder 3206 and the audio decoder 3208 without using the demultiplexing unit 3204.

By means of demultiplexing processing, an elementary stream (ES) of video, an audio ES and, optionally, subtitles are generated. The video decoder 3206, which includes the video decoder 30 described in the above-mentioned embodiments, decodes the video ES using the decoding method as shown in the above-mentioned embodiments to generate a video frame and supplies this data to the synchronization unit 3212. The audio decoder 3212 decodes the audio ES to generate an audio frame and supplies this data to the synchronization unit 3212. Alternatively, the video frame may be stored in a buffer (not shown in Fig. Y) before being supplied to the synchronization unit 3212. Similarly, the audio frame may be stored in a buffer (not shown in Fig. Y) before being supplied to the synchronization unit 3212.

The synchronization unit 3212 synchronizes the video frame and the audio frame and supplies the video/audio to the video/audio display 3214. For example, the synchronization unit 3212 synchronizes the presentation of video and audio information. The information can be encoded in a syntax using time stamps regarding the presentation of the encoded audio and video data, as well as time stamps regarding the delivery of the data stream itself.

If subtitles are included in the stream, the subtitle decoder 3210 decodes the subtitles and synchronizes them with the video frame and the audio frame and transmits the video/audio/subtitles to the video/audio/subtitle display 3216.

The present invention is not limited to the above-mentioned system, and either the image encoding device or the image decoding device in the above-mentioned embodiments may be included in another system such as an automobile system.

Mathematical operators

The mathematical operators used in this application are similar to those used in the C programming language. However, the results of integer division and arithmetic shift operations are defined more precisely, and additional operations such as exponentiation and real-valued division are defined. The numbering and counting conventions specify a 0-based convention, such that "first" is equivalent to 0, "second" is equivalent to 1, and so on.

Arithmetic operators

The following arithmetic operators are defined as follows:

+ Addition - Subtraction (as a two-argument operator) or negation (as a unary prefix operator) * Multiplication, including matrix multiplication x ^y Exponentiation. Defines x to the power of y. In other contexts, this notation is used as a superscript that should not be interpreted as exponentiation. / Integer division with result truncated toward zero. For example, 7/4 and -7 / -4 are truncated to 1, and -7/4 and 7 / -4 are truncated to -1. ÷ Used to indicate division in mathematical equations where truncation or rounding is not intended. Used to indicate division in mathematical equations where truncation or rounding is not intended. Summation f( i ), where i takes all integer values from x to y inclusive. x % y Modulo operation. The remainder of dividing x by y, defined only for integers x and y, where x >= 0 and y > 0.

Logical operators

The following logical operators are defined as follows:

x && y Boolean logical "and" for x and y

x || y Boolean logical "or" for x and y

!Boolean logical "not"

x?y:z If x is TRUE or not 0, evaluate to y; otherwise evaluate to z.

Relational operators

The following relational operators are defined as follows:

>More

>=Greater than or equal to

<Less

<=Less than or equal to

= =Equal

!=Not equal

When a comparison operator is applied to a syntax element or variable that is assigned the value "na" (not applicable), the value "na" is treated as a distinct value for the syntax element or variable. The value "na" is not considered equal to any other value.

Bitwise operators

The following bitwise operators are defined as follows:

&Bitwise and. When operating on integer arguments, operates on the two's complement representation of the integer value. When operating on a binary argument that has fewer bits than another argument, the shorter argument is expanded by adding the more significant bits that are 0.

|Bitwise "or". When operating on integer arguments, operates on the two's complement representation of the integer value. When operating on a binary argument that has fewer bits than the other argument, the shorter argument is expanded by adding the more significant bits that are 0.

^When operating on integer arguments, operates on the two's complement representation of the integer value. When operating on a binary argument that contains fewer bits than another argument, the shorter argument is expanded by adding the more significant bits that are 0.

x >> y Arithmetic right shift of the two's complement integer representation of x by y binary digits. This function is defined only for nonnegative integer values y. The bits shifted to the most significant bits (MSB) as a result of a right shift have a value equal to the MSB of x before the shift operation.

x << y Left arithmetic shift of the two's complement integer representation of x by y binary digits. This function is defined only for non-negative integer values of y. Bits shifted into the least significant bits (LSB) as a result of a left shift have the value 0.

Assignment operators

The following arithmetic operators are defined as follows:

=Assignment operator

++Increment, i.e. x++ is equivalent to x = x+ 1; when used in an array index, evaluates to the value of the variable before the increment operation.

--Decrement, i.e. x- is equivalent to x = x- 1; when used in an array index, evaluates the variable to the value before the decrement operation.

+=Increment by the specified amount, i.e. x+=3 is equivalent to x=x+3, and x+=(-3) is equivalent to x=x+(-3)

-=Decrease by the specified amount, i.e. x-=3 is equivalent to x=x-3, and x-=(-3) is equivalent to x=x-(-3).

Range designation

The following notation is used to specify a range of values:

x=y..z x takes integer values from y to z inclusive, where x, y and z are integers and z is greater than y.

Mathematical functions

The following mathematical functions are defined:

Abs(x)=

Asin(x) is the arcsine trigonometric function, operating on an argument x that is in the range -1.0 to 1.0 inclusive, with an output value in the range -π÷2 to π÷2 inclusive, in units of radians.

Atan(x) is an arctangent trigonometric function operating on an argument x, with an output value in the range -π÷2 to π÷2 inclusive, in units of radians.

Atan2(y, x)=

Ceil(x) is the smallest integer greater than or equal to x.

Clip1Y(x)=Clip3( 0, ( 1 << BitDepthY ) - 1, x )

Clip1C(x)=Clip3( 0, ( 1 << BitDepthC ) - 1, x )

Clip3(x, y, z)=

Cos(x) is the trigonometric cosine function, operating with argument x in units of radians.

Floor(x) is the largest integer less than or equal to x.

GetCurrMsb(a, b, c, d)=

Ln(x) is the natural logarithm of x (logarithm to the base e, where e is the constant of the base of the natural logarithm, equal to 2.718 281 828…).

Log2(x) - logarithm of x to base 2

Log10(x) is the logarithm of x to the base 10.

Min(x, y)=

Max(x, y)=

Round( x )=Sign( x ) * Floor( Abs( x ) + 0.5)

Sign(x)=

Sin(x) is the trigonometric sine function, operating with argument x in units of radians.

Sqrt(x)=

Swap(x, y)=(y, x)

Tan(x) is a trigonometric tangent function that operates on an argument x in units of radians.

Order of priority of operations

When the order of precedence in an expression is not explicitly indicated by parentheses, the following rules apply:

-- Operations with higher priority are executed before any operation with lower priority.

-- Operations with the same priority are performed sequentially from left to right.

The table below lists the priority of operations from highest to lowest; a higher position in the table indicates a higher priority.

For those operators that are also used in the C programming language, the order of precedence used in this description is the same as in the C programming language.

Table: Priority of operations from highest (at the top of the table) to lowest (at the bottom of the table)

operations (with operands x, y and z) "x++", "x--" "!x", "-x" (as unary prefix operator) xy "x*y", "x/y", "x÷y", " ", "x%y" "x+y", "xy" (as an operator with two arguments), " " "x<<y", "x>>y" "x<y", "x<=y", "x>y", "x>=y" "x==y", "x!=y" "x&y" "x|y" "x&&y" "x||y" "x?y:z" "x..y" "x=y", "x+=y", "x-=y"

Text description of logical operations

In the text, the definition of logical operations, which would be mathematically described in the following form:

if( condition 0 )

definition 0

else if( condition 1 )

definition 1

… else /* informative comment on the remaining condition */

definition of n

can be described as follows:

… as specified below / … the following applies:

- If condition 0, definition 0

- Otherwise, If condition 1, definition 1

- …

-- Otherwise (informative comment on the remaining condition), definition n.

Each "if ... Else, if ... Else, ..." clause in the text is introduced by the words "... as specified below" or "... the following applies" followed immediately by "if ...". The final clause of an "if ... Else, if ... Else, ..." clause is always "Otherwise, ...". Alternating "if ... Else, if ... Else, ..." clauses can be identified by matching "... as specified below" or "... the following applies" with a final "Otherwise, ...".

In the text, the definition of logical operations, which would be mathematically described in the following form:

if( condition 0a && condition 0b )

definition 0

else if( condition 1a | | condition 1b )

definition 1

…

else

definition of n

can be described as follows:

… as specified below / … the following applies:

-- If all of the following conditions are true, definition 0:

- condition 0a

- condition 0b

-- Otherwise, if one or more of the following conditions are true, Definition 1:

- condition 1a

- condition 1b

- …

- Otherwise, the definition of n

In the text, the definition of logical operations, which would be mathematically described in the following form:

if( condition 0 )

definition 0

if( condition 1 )

definition 1

can be described as follows:

When condition is 0, definition is 0

When condition 1, definition 1

Although embodiments of the present invention have been primarily described in terms of video coding, it should be noted that embodiments of encoding/decoding system 10, encoder 20 and decoder 30 (and, accordingly, system 10), as well as other embodiments described herein, may also be configured to process or encode/decode a still image, i.e., process or encode/decode a single image independently of any preceding or following image, as in video coding/decoding. In general, only the inter-frame prediction units 244 (encoder) and 344 (decoder) may not be available in case the encoding/decoding for image processing is limited to one image 17. All other functionalities (also referred to as tools or technologies) of the video encoder 20 and the video decoder 30 may be equally used for still image processing, such as residual calculation 204/304, transform 206, quantization 208, inverse quantization 210/310, (inverse) transform 212/312, splitting 262/362, intra-frame prediction 254/354 and/or loop filtering 220, 320 and entropy encoding/decoding 270 and entropy decoding 304.

Embodiments, such as the encoder 20 and the decoder 30, as well as the functions described herein, such as with respect to the encoder 20 and the decoder 30, can be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions can be stored on a computer-readable medium or transmitted via a communication medium in the form of one or more instructions or code and executed by a hardware processing unit. Computer-readable media can include computer-readable media that correspond to a tangible medium, such as a storage medium, or a communication medium, including any medium that enables transmission of a computer program from one place to another, such as according to a communication protocol. Thus, computer-readable media can typically correspond to (1) tangible computer-readable storage media that are non-transitory, or (2) a communication medium, such as a signal or a carrier wave. The storage media may be any available media that can be accessed by one or more computers or one or more processors to retrieve instructions, code, and/or data structures for implementing the techniques described in this disclosure. The computer program product may include a computer-readable medium.

By way of example, and not limitation, such computer-readable media may comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, flash memory, or any other medium that can be used to store desired program code in the form of instructions or data structures and can be accessed by a computer. In addition, any connection is properly called a computer-readable medium. For example, if instructions are transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave communications, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave communications are included within the definition of medium. However, it should be understood that computer-readable media and storage media do not include connections, carrier waves, signals, or other transient media, but instead are directed to non-transitory, tangible storage media. The term "disc" as used herein includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk, and Blu-ray disc, where discs typically reproduce data magnetically and discs reproduce data optically using lasers. Combinations of the above should also be included within the scope of computer-readable media.

The instructions may be executed by one or more processors, such as one or more digital signal processors (DSP), general-purpose microprocessors, application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other equivalent integrated or discrete logic circuits. Accordingly, the term "processor" as used herein may refer to any of the above-mentioned structures or any other structure suitable for implementing the techniques described herein. Furthermore, in some aspects, the functionality described herein may be provided within specialized hardware and/or software units configured to encode and decode, or included in a combined codec. Furthermore, the techniques may be fully implemented in one or more circuits or logic elements.

The methods of this disclosure may be implemented in a variety of devices or hardware components, including a wireless telephone, an integrated circuit (IC), or a set of ICs (e.g., a chipset). This disclosure describes various components, modules, or blocks to highlight functional aspects of devices capable of performing the disclosed technologies, but does not necessarily require implementation by different hardware blocks. Rather, as described above, the various blocks may be combined into a codec hardware block or provided by a plurality of interacting hardware blocks, including one or more processors, as described above, together with suitable software and/or firmware.

Claims (37)

1. A method (4200) of encoding, implemented by an encoding device, comprising: application (4201) of the CC-ALF intercomponent adaptive contour filter to refine the color component; generating (4202) a bit stream including a plurality of syntactic elements related to the ALF, wherein said plurality of syntactic elements related to the ALF indicate information related to the ALF; wherein said plurality of syntactic elements related to the ALF are signaled at any one or more of the sequence parameter set (SPS), picture header, or slice header level; wherein said plurality of syntax elements related to the ALF comprises a first syntax element that indicates whether or not an adaptive loop filter (ALF) is enabled at the sequence level, and the first syntax element is signaled at the SPS level, and a second syntax element that indicates whether or not an inter-component adaptive loop filter is enabled at the sequence level, and the second syntax element is signaled at the SPS level. 2. The method according to claim 1, wherein said plurality of syntax elements related to ALF comprises a third syntax element, when the second syntax element indicates that CC-ALF is included, wherein the third syntax element is signaled in the header of the image, and the third syntax element indicates whether CC-ALF is included for the current image containing a plurality of slices. 3. The method according to claim 1 or 2, wherein said plurality of syntax elements related to ALF comprises a fourth syntax element, when the second syntax element indicates that CC-ALF is included, wherein the fourth syntax element is signaled in the header of the image, and the fourth syntax element indicates whether CC-ALF is included for the color component Cb for the current image of the video sequence associated with the bitstream. 4. The method according to claim 3, wherein if the fourth syntax element has a value of 1, this indicates that CC-ALF for color component Cb is enabled for the current image, and/or if the fourth syntax element has a value of 0, this indicates that CC-ALF for color component Cb is disabled for the current image. 5. The method according to any one of claims 1 to 4, wherein said plurality of syntax elements associated with CC-ALF comprises a seventh syntax element, when the second syntax element indicates that CC-ALF is enabled, wherein the seventh syntax element is signaled in the header of the picture and the seventh syntax element indicates whether CC-ALF is enabled for the color component Cr for the current picture of the video sequence associated with the bitstream. 6. A decoding method (4300) implemented by a decoding device, comprising: parsing (4301) a plurality of adaptive loop filter, ALF, syntax elements associated with a bitstream, wherein said plurality of ALF-related syntax elements are obtained from any one or more of a sequence parameter set (SPS) level, a picture header, or a slice header; wherein said plurality of syntax elements related to the ALF comprises a first syntax element that indicates whether an adaptive loop filter (ALF) is enabled or not at the sequence level, and the first syntax element is signaled at the SPS level, and a second syntax element that indicates whether a cross-component adaptive loop filter, CC-ALF, is enabled or not at the sequence level, and the second syntax element is signaled at the SPS level; and performing (4302) the CC-ALF process using at least one of said plurality of syntactic elements related to ALF. 7. The method of claim 6, wherein said plurality of syntax elements related to ALF comprises a third syntax element when a second syntax element is received indicating that CC-ALF is included, wherein the third syntax element is obtained from an image header, and the third syntax element indicates whether CC-ALF is included for the current image containing a plurality of slices. 8. The method according to claim 6 or 7, wherein said plurality of syntax elements related to ALF comprises a fourth syntax element when a second syntax element is received indicating that CC-ALF is included, wherein the fourth syntax element is received from a header of an image and the fourth syntax element indicates whether CC-ALF is included for the color component Cb for the current image of the video sequence. 9. The method according to claim 8, wherein if the fourth syntax element has a value of 1, this indicates that CC-ALF for color component Cb is enabled for the current image, and/or if the fourth syntax element has a value of 0, this indicates that CC-ALF for color component Cb is disabled for the current image. 10. The method according to claim 8 or 9, wherein said plurality of syntax elements related to ALF comprises a fifth syntax element when the fourth CC-ALF syntax element for the color component Cb is included for the current image, wherein the fifth syntax element is obtained from the image header and the fifth syntax element indicates a set of parameters that is associated with the color component Cb of all slices in the current image. 11. The method according to any one of claims 6-10, wherein said plurality of syntax elements associated with CC-ALF comprises a seventh syntax element when a second syntax element is received indicating that CC-ALF is enabled, wherein the seventh syntax element is obtained from a header of a picture, and the seventh syntax element indicates whether CC-ALF is enabled for the color component Cr for the current picture of the video sequence associated with the bitstream. 12. The method according to claim 10, wherein if the seventh syntax element has a value of 1, this indicates that CC-ALF for the color component Cr is enabled for the current image, and/or if the seventh syntax element has a value of 0, this indicates that CC-ALF for the color component Cr is disabled for the current image. 13. The method according to claim 10 or 11, wherein said plurality of syntax elements associated with the CC-ALF comprises an eighth syntax element when a seventh syntax element is received indicating that the CC-ALF for the color component Cr is enabled for the current image, wherein the eighth syntax element is obtained from the image header, and the eighth syntax element indicates a set of parameters that is associated with the color component Cr of all slices in the current image. 14. The method according to any one of claims 7-12, wherein the fourth syntax element, the fifth syntax element, the sixth syntax element, the seventh syntax element, the eighth syntax element and the ninth syntax element are obtained when a third syntax element indicating that CC-ALF is enabled for the current picture of the video sequence associated with the bitstream is obtained. 15. The method according to any one of claims 6 to 13, wherein said plurality of syntax elements related to CC-ALF comprises a tenth syntax element when a second syntax element is received indicating that CC-ALF is enabled, wherein the tenth syntax element is obtained from a slice header and the tenth syntax element indicates whether CCALF is enabled for the color component Cb for the current slice of the current picture of the video sequence associated with the bitstream. 16. The method according to any one of paragraphs 6-15, wherein the second syntactic element is obtained if the first syntactic element has the first value, or wherein the second syntactic element is obtained conditionally based at least on the value of the first syntactic element. 17. A device for encoding video data, comprising: video data memory; and video encoder, wherein the video encoder is designed with the ability to: application of the CC-ALF intercomponent adaptive contour filter to refine the color component; and forming a bit stream including a plurality of syntactic elements associated with an adaptive loop filter, ALF, wherein said plurality of syntactic elements related to the ALF indicate information related to the ALF; wherein said plurality of syntactic elements related to the ALF are signaled at any one or more of the sequence parameter set (SPS), picture header, or slice header level; wherein said plurality of syntax elements related to the ALF comprises a first syntax element that indicates whether or not an adaptive loop filter (ALF) is enabled at the sequence level, and the first syntax element is signaled at the SPS level, and a second syntax element that indicates whether or not an inter-component adaptive loop filter is enabled at the sequence level, and the second syntax element is signaled at the SPS level. 18. A device for decoding video data, comprising: video data memory; and a video decoder, wherein the video decoder is configured to: parsing a plurality of syntactic elements related to an adaptive loop filter, ALF, from a bitstream, wherein said plurality of syntactic elements related to ALF are obtained from any one or more of a sequence parameter set (SPS) level, a picture header, or a slice header; wherein said plurality of syntax elements related to the ALF comprises a first syntax element that indicates whether an adaptive loop filter (ALF) is enabled or not at the sequence level, and the first syntax element is signaled at the SPS level, and a second syntax element that indicates whether a cross-component adaptive loop filter, CC-ALF, is enabled or not at the sequence level, and the second syntax element is signaled at the SPS level; and performing the CC-ALF process using at least one of said plurality of syntactic elements related to ALF. 19. A computer-readable storage medium containing computer-executable instructions that, when executed by a computing device, cause the computing device to perform the method of any one of paragraphs 1-16.

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