WO2026021419A1

WO2026021419A1 - Method, apparatus, and medium for video processing

Info

Publication number: WO2026021419A1
Application number: PCT/CN2025/109779
Authority: WO
Inventors: Cunhui DONG; Wenjie Zhang; Yuwen He; Li Zhang
Original assignee: Douyin Vision Co Ltd; ByteDance Inc
Current assignee: Douyin Vision Co Ltd; ByteDance Inc
Priority date: 2024-07-23
Filing date: 2025-07-22
Publication date: 2026-01-29
Anticipated expiration: 2027-01-23

Abstract

Embodiments of the present disclosure provide a solution for video processing. A method for video processing is proposed. The method comprises: obtaining, for a conversion between a current block within a current frame of the video and a bitstream of the video, a reference quantization parameter (QP) for the current block; determining first information regarding whether the current block involves a scene cut; determining a target QP for the current block based on the reference QP and the first information; and performing the conversion based on the target QP.

Description

METHOD, APPARATUS, AND MEDIUM FOR VIDEO PROCESSING

FIELDS

Embodiments of the present disclosure relates generally to video processing techniques, and more particularly, to video coding.

BACKGROUND

In nowadays, digital video capabilities are being applied in various aspects of peoples’ lives. Multiple types of video compression technologies, such as motion picture expert group (MPEG) -2, MPEG-4, international telecommunication union -telecommunication standardization sector (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) standard, versatile video coding (VVC) standard, have been proposed for video encoding/decoding. However, coding quality of video coding techniques is generally expected to be further improved.

SUMMARY

Embodiments of the present disclosure provide a solution for video processing.

In a first aspect, a method for video processing is proposed. The method comprises: obtaining, for a conversion between a current block within a current frame of the video and a bitstream of the video, a reference quantization parameter (QP) for the current block; determining first information regarding whether the current block involves a scene cut; determining a target QP for the current block based on the reference QP and the first information; and performing the conversion based on the target QP.

Based on the method in accordance with the first aspect of the present disclosure, the QP used for the current block is determined by considering the information regarding whether the current block involves a scene cut. Compared with the conventional solution, the proposed method can advantageously enable QP adjustment for a block involving scene cut. Thereby, the blockness artifact for such a block involving scene cut can be mitigated and thus subjective quality of video coding can be improved.

In a second aspect, an apparatus for video processing is proposed. The apparatus comprises a processor and a non-transitory memory with instructions thereon. The instructions upon execution by the processor, cause the processor to perform a method in accordance with the first aspect of the present disclosure.

In a third aspect, a non-transitory computer-readable storage medium is proposed. The non-transitory computer-readable storage medium stores instructions that cause a processor to perform a method in accordance with the first aspect of the present disclosure.

In a fourth aspect, another non-transitory computer-readable recording medium is proposed. The non-transitory computer-readable recording medium stores a bitstream of a video which is generated by a method performed by an apparatus for video processing. The method comprises: obtaining a reference quantization parameter (QP) for a current block of the video; determining first information regarding whether the current block involves a scene cut; determining a target QP for the current block based on the reference QP and the first information; and generating the bitstream based on the target QP.

In a fifth aspect, a method for storing a bitstream of a video is proposed. The method comprises: obtaining a reference quantization parameter (QP) for a current block of the video; determining first information regarding whether the current block involves a scene cut; determining a target QP for the current block based on the reference QP and the first information; generating the bitstream based on the target QP; and storing the bitstream in a non-transitory computer-readable recording medium.

This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

Through the following detailed description with reference to the accompanying drawings, the above and other objectives, features, and advantages of example embodiments of the present disclosure will become more apparent. In the example embodiments of the present disclosure, the same reference numerals usually refer to the same components.

Fig. 1 illustrates a block diagram of an example video coding system in accordance with some embodiments of the present disclosure;

Fig. 2 illustrates a block diagram of an example video encoder in accordance with some embodiments of the present disclosure;

Fig. 3 illustrates a block diagram of an example video decoder in accordance with some embodiments of the present disclosure;

Fig. 4 illustrates an overview of an example encoding process according to HEVC standard;

Fig. 5 illustrates a flowchart of a method for video processing in accordance with some embodiments of the present disclosure; and

Fig. 6 illustrates a block diagram of a computing device in which various embodiments of the present disclosure can be implemented.

Throughout the drawings, the same or similar reference numerals usually refer to the same or similar elements.

DETAILED DESCRIPTION

Principle of the present disclosure will now be described with reference to some embodiments. It is to be understood that these embodiments are described only for the purpose of illustration and help those skilled in the art to understand and implement the present disclosure, without suggesting any limitation as to the scope of the disclosure. The disclosure described herein can be implemented in various manners other than the ones described below.

In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skills in the art to which this disclosure belongs.

References in the present disclosure to “one embodiment, ” “an embodiment, ” “an example embodiment, ” and the like indicate that the embodiment described may include a particular feature, structure, or characteristic, but it is not necessary that every embodiment includes the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an example embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

It shall be understood that although the terms “first” and “second” etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and similarly, a second element could be termed a first element, without departing from the scope of example embodiments. As used herein, the term “and/or” includes any and all combinations of one or more of the listed terms.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a” , “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” , “comprising” , “has” , “having” , “includes” and/or “including” , when used herein, specify the presence of stated features, elements, and/or components etc., but do not preclude the presence or addition of one or more other features, elements, components and/or combinations thereof.
Example Environment

Fig. 1 is a block diagram that illustrates an example video coding system 100 that may utilize the techniques of this disclosure. As shown, the video coding system 100 may include a source device 110 and a destination device 120. The source device 110 can be also referred to as a video encoding device, and the destination device 120 can be also referred to as a video decoding device. In operation, the source device 110 can be configured to generate encoded video data and the destination device 120 can be configured to decode the encoded video data generated by the source device 110. The source device 110 may include a video source 112, a video encoder 114, and an input/output (I/O) interface 116.

The video source 112 may include a source such as a video capture device. Examples of the video capture device include, but are not limited to, an interface to receive video data from a video content provider, a computer graphics system for generating video data, and/or a combination thereof.

The video data may comprise one or more pictures. The video encoder 114 encodes the video data from the video source 112 to generate a bitstream. The bitstream may include a sequence of bits that form a coded representation of the video data. The bitstream may include coded pictures and associated data. The coded picture is a coded representation of a picture. The associated data may include sequence parameter sets, picture parameter sets, and other syntax structures. The I/O interface 116 may include a modulator/demodulator and/or a transmitter. The encoded video data may be transmitted directly to destination device 120 via the I/O interface 116 through the network 130A. The encoded video data may also be stored onto a storage medium/server 130B for access by destination device 120.

The destination device 120 may include an I/O interface 126, a video decoder 124, and a display device 122. The I/O interface 126 may include a receiver and/or a modem. The I/O interface 126 may acquire encoded video data from the source device 110 or the storage medium/server 130B. The video decoder 124 may decode the encoded video data. The display device 122 may display the decoded video data to a user. The display device 122 may be integrated with the destination device 120, or may be external to the destination device 120 which is configured to interface with an external display device.

The video encoder 114 and the video decoder 124 may operate according to a video compression standard, such as the High Efficiency Video Coding (HEVC) standard, Versatile Video Coding (VVC) standard and other current and/or further standards.

Fig. 2 is a block diagram illustrating an example of a video encoder 200, which may be an example of the video encoder 114 in the system 100 illustrated in Fig. 1, in accordance with some embodiments of the present disclosure.

The video encoder 200 may be configured to implement any or all of the techniques of this disclosure. In the example of Fig. 2, the video encoder 200 includes a plurality of functional components. The techniques described in this disclosure may be shared among the various components of the video encoder 200. In some examples, a processor may be configured to perform any or all of the techniques described in this disclosure.

In some embodiments, the video encoder 200 may include a partition unit 201, a prediction unit 202 which may include a mode select unit 203, a motion estimation unit 204, a motion compensation unit 205 and an intra-prediction unit 206, a residual generation unit 207, a transform unit 208, a quantization unit 209, an inverse quantization unit 210, an inverse transform unit 211, a reconstruction unit 212, a buffer 213, and an entropy encoding unit 214.

In other examples, the video encoder 200 may include more, fewer, or different functional components. In an example, the prediction unit 202 may include an intra block copy (IBC) unit. The IBC unit may perform prediction in an IBC mode in which at least one reference picture is a picture where the current video block is located.

Furthermore, although some components, such as the motion estimation unit 204 and the motion compensation unit 205, may be integrated, but are represented in the example of Fig. 2 separately for purposes of explanation.

The partition unit 201 may partition a picture into one or more video blocks. The video encoder 200 and the video decoder 300 may support various video block sizes.

The mode select unit 203 may select one of the coding modes, intra or inter, e.g., based on error results, and provide the resulting intra-coded or inter-coded block to a residual generation unit 207 to generate residual block data and to a reconstruction unit 212 to reconstruct the encoded block for use as a reference picture. In some examples, the mode select unit 203 may select a combined inter and intra prediction (CIIP) mode in which the prediction is based on an inter prediction signal and an intra prediction signal. The mode select unit 203 may also select a resolution for a motion vector (e.g., a sub-pixel or integer pixel precision) for the block in the case of inter-prediction.

To perform inter prediction on a current video block, the motion estimation unit 204 may generate motion information for the current video block by comparing one or more reference frames from buffer 213 to the current video block. The motion compensation unit 205 may determine a predicted video block for the current video block based on the motion information and decoded samples of pictures from the buffer 213 other than the picture associated with the current video block.

The motion estimation unit 204 and the motion compensation unit 205 may perform different operations for a current video block, for example, depending on whether the current video block is in an I-slice, a P-slice, or a B-slice. As used herein, an “I-slice” may refer to a portion of a picture composed of macroblocks, all of which are based upon macroblocks within the same picture. Further, as used herein, in some aspects, “P-slices” and “B-slices” may refer to portions of a picture composed of macroblocks that are not dependent on macroblocks in the same picture.

In some examples, the motion estimation unit 204 may perform uni-directional prediction for the current video block, and the motion estimation unit 204 may search reference pictures of list 0 or list 1 for a reference video block for the current video block. The motion estimation unit 204 may then generate a reference index that indicates the reference picture in list 0 or list 1 that contains the reference video block and a motion vector that indicates a spatial displacement between the current video block and the reference video block. The motion estimation unit 204 may output the reference index, a prediction direction indicator, and the motion vector as the motion information of the current video block. The motion compensation unit 205 may generate the predicted video block of the current video block based on the reference video block indicated by the motion information of the current video block.

Alternatively, in other examples, the motion estimation unit 204 may perform bi-directional prediction for the current video block. The motion estimation unit 204 may search the reference pictures in list 0 for a reference video block for the current video block and may also search the reference pictures in list 1 for another reference video block for the current video block. The motion estimation unit 204 may then generate reference indexes that indicate the reference pictures in list 0 and list 1 containing the reference video blocks and motion vectors that indicate spatial displacements between the reference video blocks and the current video block. The motion estimation unit 204 may output the reference indexes and the motion vectors of the current video block as the motion information of the current video block. The motion compensation unit 205 may generate the predicted video block of the current video block based on the reference video blocks indicated by the motion information of the current video block.

In some examples, the motion estimation unit 204 may output a full set of motion information for decoding processing of a decoder. Alternatively, in some embodiments, the motion estimation unit 204 may signal the motion information of the current video block with reference to the motion information of another video block. For example, the motion estimation unit 204 may determine that the motion information of the current video block is sufficiently similar to the motion information of a neighboring video block.

In one example, the motion estimation unit 204 may indicate, in a syntax structure associated with the current video block, a value that indicates to the video decoder 300 that the current video block has the same motion information as the another video block.

In another example, the motion estimation unit 204 may identify, in a syntax structure associated with the current video block, another video block and a motion vector difference (MVD) . The motion vector difference indicates a difference between the motion vector of the current video block and the motion vector of the indicated video block. The video decoder 300 may use the motion vector of the indicated video block and the motion vector difference to determine the motion vector of the current video block.

As discussed above, video encoder 200 may predictively signal the motion vector. Two examples of predictive signaling techniques that may be implemented by video encoder 200 include advanced motion vector prediction (AMVP) and merge mode signaling.

The intra prediction unit 206 may perform intra prediction on the current video block. When the intra prediction unit 206 performs intra prediction on the current video block, the intra prediction unit 206 may generate prediction data for the current video block based on decoded samples of other video blocks in the same picture. The prediction data for the current video block may include a predicted video block and various syntax elements.

The residual generation unit 207 may generate residual data for the current video block by subtracting (e.g., indicated by the minus sign) the predicted video block (s) of the current video block from the current video block. The residual data of the current video block may include residual video blocks that correspond to different sample components of the samples in the current video block.

In other examples, there may be no residual data for the current video block, for example in a skip mode, and the residual generation unit 207 may not perform the subtracting operation.

The transform unit 208 may generate one or more transform coefficient video blocks for the current video block by applying one or more transforms to a residual video block associated with the current video block.

After the transform unit 208 generates a transform coefficient video block associated with the current video block, the quantization unit 209 may quantize the transform coefficient video block associated with the current video block based on one or more quantization parameter (QP) values associated with the current video block.

The inverse quantization unit 210 and the inverse transform unit 211 may apply inverse quantization and inverse transforms to the transform coefficient video block, respectively, to reconstruct a residual video block from the transform coefficient video block. The reconstruction unit 212 may add the reconstructed residual video block to corresponding samples from one or more predicted video blocks generated by the prediction unit 202 to produce a reconstructed video block associated with the current video block for storage in the buffer 213.

After the reconstruction unit 212 reconstructs the video block, loop filtering operation may be performed to reduce video blocking artifacts in the video block.

The entropy encoding unit 214 may receive data from other functional components of the video encoder 200. When the entropy encoding unit 214 receives the data, the entropy encoding unit 214 may perform one or more entropy encoding operations to generate entropy encoded data and output a bitstream that includes the entropy encoded data.

Fig. 3 is a block diagram illustrating an example of a video decoder 300, which may be an example of the video decoder 124 in the system 100 illustrated in Fig. 1, in accordance with some embodiments of the present disclosure.

The video decoder 300 may be configured to perform any or all of the techniques of this disclosure. In the example of Fig. 3, the video decoder 300 includes a plurality of functional components. The techniques described in this disclosure may be shared among the various components of the video decoder 300. In some examples, a processor may be configured to perform any or all of the techniques described in this disclosure.

In the example of Fig. 3, the video decoder 300 includes an entropy decoding unit 301, a motion compensation unit 302, an intra prediction unit 303, an inverse quantization unit 304, an inverse transform unit 305, a reconstruction unit 306 and a buffer 307. The video decoder 300 may, in some examples, perform a decoding pass generally reciprocal to the encoding pass described with respect to video encoder 200.

The entropy decoding unit 301 may retrieve an encoded bitstream. The encoded bitstream may include entropy coded video data (e.g., encoded blocks of video data) . The entropy decoding unit 301 may decode the entropy coded video data, and from the entropy decoded video data, the motion compensation unit 302 may determine motion information including motion vectors, motion vector precision, reference picture list indexes, and other motion information. The motion compensation unit 302 may, for example, determine such information by performing the AMVP and merge mode. AMVP is used, including derivation of several most probable candidates based on data from adjacent PBs and the reference picture. Motion information typically includes the horizontal and vertical motion vector displacement values, one or two reference picture indices, and, in the case of prediction regions in B slices, an identification of which reference picture list is associated with each index. As used herein, in some aspects, a “merge mode” may refer to deriving the motion information from spatially or temporally neighboring blocks.

The motion compensation unit 302 may produce motion compensated blocks, possibly performing interpolation based on interpolation filters. Identifiers for interpolation filters to be used with sub-pixel precision may be included in the syntax elements.

The motion compensation unit 302 may use the interpolation filters as used by the video encoder 200 during encoding of the video block to calculate interpolated values for sub-integer pixels of a reference block. The motion compensation unit 302 may determine the interpolation filters used by the video encoder 200 according to the received syntax information and use the interpolation filters to produce predictive blocks.

The motion compensation unit 302 may use at least part of the syntax information to determine sizes of blocks used to encode frame (s) and/or slice (s) of the encoded video sequence, partition information that describes how each macroblock of a picture of the encoded video sequence is partitioned, modes indicating how each partition is encoded, one or more reference frames (and reference frame lists) for each inter-encoded block, and other information to decode the encoded video sequence. As used herein, in some aspects, a “slice” may refer to a data structure that can be decoded independently from other slices of the same picture, in terms of entropy coding, signal prediction, and residual signal reconstruction. A slice can either be an entire picture or a region of a picture.

The intra prediction unit 303 may use intra prediction modes for example received in the bitstream to form a prediction block from spatially adjacent blocks. The inverse quantization unit 304 inverse quantizes, i.e., de-quantizes, the quantized video block coefficients provided in the bitstream and decoded by entropy decoding unit 301. The inverse transform unit 305 applies an inverse transform.

The reconstruction unit 306 may obtain the decoded blocks, e.g., by summing the residual blocks with the corresponding prediction blocks generated by the motion compensation unit 302 or intra-prediction unit 303. If desired, a deblocking filter may also be applied to filter the decoded blocks in order to remove blockiness artifacts. The decoded video blocks are then stored in the buffer 307, which provides reference blocks for subsequent motion compensation/intra prediction and also produces decoded video for presentation on a display device.

Some example embodiments of the present disclosure will be described in detailed hereinafter. It should be understood that section headings are used in the present document to facilitate ease of understanding and do not limit the embodiments disclosed in a section to only that section. Furthermore, while certain embodiments are described with reference to Versatile Video Coding or other specific video codecs, the disclosed techniques are applicable to other video coding technologies also. Furthermore, while some embodiments describe video coding steps in detail, it will be understood that corresponding steps decoding that undo the coding will be implemented by a decoder. Furthermore, the term video processing encompasses video coding or compression, video decoding or decompression and video transcoding in which video pixels are represented from one compressed format into another compressed format or at a different compressed bitrate.
1. Brief Summary
The present disclosure is related to video coding technologies. Specifically, it is related to the subjective quality
optimization in video coding. It may be applied to existing video encoders, such as x264, x265, HM, VVenC, VTM and others. It may also be applicable to future video coding encoders or video codecs.
2. Introduction
2.1 High Efficiency Video Coding (HEVC) standard
Fig. 4 depicts the block diagram of a hybrid video encoder, including block partitions that split the video picture
into CTUs. For each CTU, it is divided into several blocks, called coding units, using quad-tree and binary tree structures. For each coding unit, block-based intra or inter prediction is performed, and the resulting residues are transformed and quantized. Finally, Context-Adaptive Binary Arithmetic Coding (CABAC) entropy coding is employed for bitstream generation.
2.2 Subjective quality of video
The subjective quality of video refers to the audience's subjective feelings and evaluation of video quality. It is
affected by many factors, such as clarity, blockness artifact, ringing artifact, temporal flicking and so on. Clarity refers to whether the texture in the video is clear. The loss of clarity is mainly caused by the loss of high-frequency part of transform coefficient during video coding. Blockness artifact refers to obvious block boundaries in frames. The main reason is that the frame is divided into coding units during video coding, and adjacent coding units may use different coding parameters. So there are differences between neighboring units. The ringing artifact refers to the oscillation at the edge of the object, like ripples. It is mainly caused by the loss of the high-frequency part of the transform coefficient in coding. Temporal flicker refers to discontinuities when a video is played, such as brightness flickering, flickering at the edges of objects, etc. This is mainly due to the fact that the frames of the video are not jointly processed.
2.3 Deblocking filter and sample adaptive offset (SAO)
The deblocking filter and SAO are two post-processing methods in video coding, which are used to alleviate
blockness artifact and ringing artifact, respectively. The deblocking filter analyzes the differences between adjacent pixels along the boundary of different coding units, and applies low-pass filtering of different strengths to different areas according to the difference in pixels, thereby smoothing these boundaries and reducing the visual perception of blockness artifact. SAO can adaptively analyze the characteristics of each coding unit and apply corresponding pixel offset values according to the characteristics. SAO can cut the peaks and fill the valleys of pixels, thereby reducing the ringing artifact of videos.
3. Problems
The subjective quality optimization in video coding has following problems:
1. There is deblocking filter in common video coding standards, but the deblocking filter can only modify up
to 3 pixels of the boundary, it cannot very well solve the blockness artifact of large coding unit.
2. There are some methods of adjusting quantization parameter (QP) to reduce blockness artifact, such as
adaptive quantization (AQ) . However, it only bases on variance of pixels, which causes a waste of bit.
3. To alleviate the blockness artifact, too much attention is paid to QP adjustment, which will lead to a
significant increase in bit rate. Blockness artifact can be further mitigated by focusing on other modules of encoding.
4. In most commonly used encoders, lambda and QP have a one-to-one correspondence. When QP is large,
lambda will also be large, resulting in poor predictions during mode selection, which will seriously affect the subjective quality.
4. Detailed Solutions
To solve the above problems and some other problems not mentioned, methods as summarized below are
disclosed. These solutions should be considered as examples to explain the general concepts and should not be interpreted in a narrow way. Furthermore, these solutions can be applied individually or combined in any manner.
1. Blockness artifact optimization based on QP adjustment
a. QP adjustment based on block-level scene cutting and gradient: blocks with scene cutting and flat
texture are more likely to appear blockness artifact, so the QP is reduced. For example, the intra-frame cost intraCost and inter-frame cost interCost of the current block are calculated through pre-analysis. If the intraCost is less than the interCost and the gradient grad is small, the QP is reduced to reduce the blockness artifact and improve the subjective quality. Specifically, it can be achieved through the following five steps:
i. Calculate the intraCost of the current block and its four neighbor blocks by pre-analysis,
which are recorded as intraCostCurr , intraCostTop , intraCostLeft , intraCostRight, intraCostBottom. Calculate the interCost of the current block and its four neighboring blocks by pre-analysis, which are recorded as interCostCurr, interCostTop, interCostLeft, interCostRight, interCostBottom.
ii. Calculate the gradient of the current block and its four neighboring blocks, which are
recorded as gradCurr, gradTop, gradLeft, gradRight, gradBottom.
iii. If a block satisfies intraCost≤ fIntraInterFactor× interCost, then the block is
considered as a scene cutting block. The fIntraInterFactor can be related to the gradient. For example, fIntraInterFactor is calculated as:
fIntraInterFactor = max (0, 1 + (0.4 -grad) )

iv. If the gradient grad of a block is less than the threshold Thr, it is considered as a flat
block. The threshold Thr is related to the QP of the block. For example,
Thr = max (0.05, 0.4 + (QP -36) * 0.6) .
v. Determine whether the current block satisfies both step (iii) and (iv) conditions. If the
current block satisfies the conditions, determine whether there are neighbor blocks that meet the conditions. If there are neighbor blocks that meet the conditions, reduce the QP of the current block. The adjustment of QP is related to the QP of the current block and the gradient of the current block. For example,
QPNew = max (30, QPOld- (10 + (1 -GradCurr) * 2) ) .
2. Blockness artifact optimization based on pre-processing and QP adjustment
a. Blur and adjust QP to alleviate blockness artifact, which will not increase bitrate.
b. For the current coding frame, blurring is first performed for the whole frame or non-important
region, such as the edge region of the frame or the region of non-interest, to reduce the encoding bit rate, and then QP is reduced for the whole frame or important region, such as the center region of the frame or the region of interest, to alleviate blockness artifact. For example, the current encoding frame is first blurred by a Gaussian kernel, and then QP is reduced by 2 to align the bit rate.
c. The top and bottom part of picture is blurred to reduce the bitrate. The saving bitrate will be applied
to those important regions such as ROI by reducing QP for those regions.
3. Blockness artifact optimization based on mode decision
a. Reduce the selection probability of intra and skip to avoid blockness artifact. For example, when
conducting mode decision, the mode costs of intra and skip are enlarged, such as the costNew =costOld× factor, where factor is set to 1.2.
b. Reduce the selection probability of large block to avoid blockness artifact. For example, when
conducting mode decision, the cost of large block is enlarged, such as the costNew = costOld *blockSize / (32 * 32) , where blockSize is the area of the block.
c. Add the cost of blockness artifact when conducting mode decision. For example, add the cost of
inter-block continuity to the cost of the current mode, that is, costNew = costOld +costConsist. One way to calculate costConsist is sum of absolute difference (SAD) of P_i and Q_i, where P_i is the pixel value of the current block bordering the neighbor block, and Q_i is the pixel value of the neighbor block bordering the current block.
4. Subjective quality optimization based on lambda adjustment
a. When the QP of the current block is relatively large, in order to ensure that the subjective quality is
not too bad, the lambda corresponding to the QP is reduced. For example, when the QP is greater than 45, lambdaNew = lambdaOld× 0.8.
b. When the QP of the current block is relatively large, in order to ensure that the subjective quality is
not too bad, the lambda corresponding to the QP is trimmed. For example, when QP is greater than 45, its lambda is set to the lambda corresponding to QP equal to 45.
c. For subjective quality optimization, a new QP-lambda model is built, which meets the conditions:
the lambda growth rate is reduced in the high QP. For example: lambda = pow (2.0, (QP-12) /3.0) /QP, and pow (A, B) represents A^B.
General Aspects
5. The above bullets could be applied to any scenarios, not limited to one scenario.
6. The above bullets could be applied to rate control module.

More details of the embodiments of the present disclosure will be described below which are related to subjective quality optimization in video coding. The embodiments of the present disclosure should be considered as examples to explain the general concepts and should not be interpreted in a narrow way. Furthermore, these embodiments can be applied individually or combined in any manner.

As used herein, the term “block” may represent a coding tree block (CTB) , a coding tree unit (CTU) , a coding block (CB) , a coding unit (CU) , a prediction unit (PU) , a transform unit (TU) , a prediction block (PB) , a transform block (TB) , a subblock, a tile, a slice, a subpicture, a video processing unit comprising multiple samples/pixels, and/or the like. A block may be rectangular or non-rectangular. Moreover, the term “frame” may be a picture of the video.

Fig. 5 illustrates a flowchart of a method 500 for video processing in accordance with some embodiments of the present disclosure. The method 500 may be implemented during a conversion between a current block within a current frame of the video and a bitstream of the video. As shown in Fig. 5, the method 500 starts at 502 where a reference quantization parameter (QP) for the current block is determined. For example, the reference QP for the current block may determined according to any existing QP deriving scheme, and this is not described in details herein.

At 504, first information regarding whether the current block involves a scene cut is determined. As used herein, the term “scene cut” may refer to a significant content change, such as the cut from one scene to the other.

In some embodiments, in order to determining the first information, a first cost for applying an intra prediction mode on the current block and a second cost for applying an inter prediction mode on the current block may be determined. The first cost may also be referred to as an intra cost, and the second cost may also be referred to as a inter cost. For example, the first cost and/or the second cost may be determined based on a rate-distortion cost function. In addition, the first information may be determined based on the first cost and the second cost.

For example, the second cost may be scaled with a scaling factor. If the first cost is smaller than the scaled second cost, it may be determined that the current block involves a scene cut. If the first cost is larger than the scaled second cost, it may be determined that the current block does not involve a scene cut. In one example embodiment, if the first cost is equal to the scaled second cost, it may be determined that the current block involves a scene cut. In another example embodiment, if the first cost is equal to the scaled second cost, it may be determined that the current block does not involve a scene cut.

In some embodiments, the scaling factor may be determined based on a gradient of the current block. For example, a gradient of a sample may be determined based on an absolute difference between a value of the sample and a value of at least one neighboring sample, and the gradient of the current block may be determined as a sum of gradient of each sample of the current block. By way of example rather than limitation, the scaling factor may be determined as follows:
fIntraInterFactor = max (0, 1 + (0.4 -gradCurr) ) ,
where fIntraInterFactor represents the scaling factor, gradCurr represents the gradient of the current block,
and max () represents a max function that returns the largest value in a set of values. It should be understood that the possible implementations of the gradient calculation and scaling factor derivation described here are merely illustrative and therefore should not be construed as limiting the present disclosure in any way.

At 506, a target QP for the current block is determined based on the reference QP and the first information. In some embodiments, in order to determine the target QP, second information regarding whether to adjust the reference QP may be determined based on the first information, and the target QP may be determined based on the second information and the reference QP. This will be described in detail below.

At 508, the conversion is performed based on the target QP. In some embodiments, the conversion may include encoding the current block into the bitstream. Alternatively or additionally, the conversion may include decoding the current block from the bitstream. It should be understood that the above illustrations and/or examples are described merely for purpose of description. The scope of the present disclosure is not limited in this respect.

In view of the above, the QP used for the current block is determined by considering the information regarding whether the current block involves a scene cut. Compared with the conventional solution, the proposed method can advantageously enable QP adjustment for a block involving scene cut. Thereby, the blockness artifact for such a block involving scene cut can be mitigated and thus subjective quality of video coding can be improved.

In some embodiments, for determining the second information, if the current block involves a scene cut, it may be determined that the reference QP may be to be adjusted. If the current block does not involve a scene cut, it may be determined that the reference QP may be not adjusted.

In some alternative embodiments, in order to determine the second information, third information indicating whether a texture of the current block is flat may be determined, and the second information may be determined based on the first information and the third information.

In some embodiments, in order to determine the third information, a gradient of the current block may be determined. If the gradient of the current block is smaller than a gradient threshold, it may be determined that the texture of the current block is flat. If the gradient of the current block is larger than the gradient threshold, it may be determined that the texture of the current block is not flat. In one example embodiment, if the gradient of the current block is equal to the gradient threshold, it may be determined that the texture of the current block is flat. Alternatively, if the gradient of the current block is equal to the gradient threshold, it may be determined that the texture of the current block is not flat.

In some embodiments, the gradient threshold may be determined based on the reference QP for the current block. By way of example rather than limitation, the gradient threshold may be determined as follows:
Thr = max (0.05, 0.4 + (QP -36) *0.6) ,
where Thr represents the gradient threshold, QP represents the reference QP for the current block, and
max () represents a max function that returns the largest value in a set of values. It should be understood that the specific values recited herein are intended to be examples rather than limiting the scope of the present disclosure.

In some embodiments, for determining the second information, if the current block involves a scene cut and the texture of the current block is flat, it may be determined that the reference QP may be to be adjusted. If the current block does not involve a scene cut or the texture of the current block is not flat, it may be determined that the reference QP may be not adjusted. By additionally considering the texture characteristics of the current block, the QP adjustment decision for the current block can be made more accurately, and thus the subjective quality of video coding can be further improved.

In some further embodiments, for determining the second information, if the current block does not involve a scene cut or the texture of the current block is not flat, it may be determined that the reference QP may be not adjusted. If the current block involves a scene cut and the texture of the current block is flat, the following operations may be performed: determining whether at least one neighboring block of the current block involves a scene cut; determining whether a texture of the at least one neighboring block of the current block is flat; and if the at least one neighboring block involves a scene cut and the texture of the at least one neighboring block is flat, it may be determined that the reference QP may be to be adjusted; or if all of the at least one neighboring block does not involve a scene cut or the texture of all of the at least one neighboring block is not flat, it may be determined that the reference QP may be not adjusted. In some embodiments, the at least one neighboring block of the current block may comprise a block left to the current block, a block right to the current block, a block above the current block, a block below the current block, and/or the like.

For example, information regarding whether at least one neighboring block of the current block involves a scene cut and information regarding whether a texture of the at least one neighboring block of the current block is flat may be determined in the same manner as the current block, which has been described in detail above. By additionally considering these information of the neighboring block (s) of the current block, the QP adjustment decision for the current block can be made more accurately, and thus the subjective quality of video coding can be further improved.

In some embodiments, if the reference QP is not adjusted, the reference QP may be determined as the target QP. In this case, the QP for the current block is not adjusted. Alternatively, if the reference QP is to be adjusted, the target QP may be determined based on a result of adjusting the reference QP. By way of example rather than limitation, the target QP may be determined as follows:
QPNew = max (30, QPOld - (10 + (1 -gradCurr) *2) ) ,
where QPNew represents the target QP, QPOld represents the reference QP, and gradCurr represents the
gradient of the current block. It should be understood that the above examples are described merely for purpose of description. The scope of the present disclosure is not limited in this respect.

In some embodiments, a blur operation may be performed on at least part of the current frame. For example, the at least part of the current frame may comprise one of the following: the entire current frame, a region of non-interest within the current frame, an edge region of the current frame, a top part and a bottom part of the current frame, or the like. By way of example rather than limitation, the blur operation may be performed with a Gaussian kernel or the like.

In this case, if the current block is comprised in a target region of the current frame, the target QP may be determined based on a result of reducing the reference QP. If the current block is not comprised in the target region, the target QP may be determined without reducing the reference QP. For example, the target region of the current frame may comprise one of the following: the entire current frame, a center region within the current frame, a region of interest (ROI) within the current frame, or the like. Thereby, the subjective quality of the target region can be improved while without increasing the bitrate.

In some embodiments, at 508, a target weighting factor may be determined for a rate term used to determine a rate-distortion (RD) cost. In addition, a rate-distortion optimization (RDO) process may be performed based on the target weighting factor, and the conversion may be performed based on a result of the RDO process.

By way of example rather than limitation, the RD cost may be determined as follows:
J = D + λ *R,
where J represents the RD cost, D represents a distortion term, R represents a rate term, and λ represents
the weighting factor. The distortion term D is used to quantify the fidelity between the original block and corresponding reconstructed block, and the rate term D is used to measure number of bits required to signal coding parameters. It is seen that changing the value of λ enables tradeoffs between rate decreases and distortion increases.

In some embodiments, in order to determine the target weighting factor, a reference weighting factor may be determined based on the target QP. If the target QP is smaller than the QP threshold, the reference weighting factor may be determined as the target weighting factor. If the target QP is larger than a QP threshold, the target weighting factor may be determined based on a result of reducing the reference weighting factor. For example, the target weighting factor may be determined as follows:
lambdaNew = lambdaOld × alpha,
where lambdaNew represents the target weighting factor, lambdaOld represents the reference weighting
factor, and alpha represents a scaling factor smaller than 1. It should be understood that the above examples are described merely for purpose of description. The scope of the present disclosure is not limited in this respect.

In one example embodiment, if the target QP is equal to the QP threshold, the target weighting factor may be determined based on a result of reducing the reference weighting factor. Alternatively, if the target QP is equal to the QP threshold, the reference weighting factor may be determined as the target weighting factor.

In some alternative embodiments, in order to determine the target weighting factor, a reference weighting factor may be determined based on the target QP. If the target QP is larger than a QP threshold and the reference weighting factor is larger than a weighting factor upper limit, the weighting factor upper limit is determined as the target weighting factor. If the target QP is smaller than the QP threshold or the reference weighting factor is smaller than the weighting factor upper limit, determining the reference weighting factor as the target weighting factor.

In some further embodiments, the target weighting factor may be determined based on the target QP according to a predetermined model, and a growth rate of the target weighting factor may be negatively correlated with the target QP in the predetermined model. By way of example rather than limitation, the predetermined model may be as follows:
lambda = 2 (QP-12) /3 /TQP,
where lambda represents the target weighting factor, and TQP represents the target QP. It should be
understood that the above examples are described merely for purpose of description. The scope of the present disclosure is not limited in this respect.

In some embodiments, a third cost for applying an intra mode or a skip mode on the current block may be determined. In addition, the third cost may be adjusted by increasing the third cost, and mode decision for the current block is performed based on the adjusted first cost. Thereby, a selection probability of intra mode and skip mode can be reduced, so as to mitigate or even avoid blockness artifact.

By way of example rather than limitation, the third cost may be adjusted as follows:
cost3New = cost3Old× beta,
where cost3New represents the adjusted third cost, cost3Old represents the third cost, and beta represents
a scaling factor larger than 1. It should be understood that the above examples are described merely for purpose of description. The scope of the present disclosure is not limited in this respect.

In some embodiments, a fourth cost for a first block obtained by partitioning the current frame may be determined. In addition, the fourth cost may be adjusted based on a size of the first block, and the adjusted fourth cost is positively correlated with the size. Furthermore, mode decision for the current frame may be performed based on the adjusted fourth cost. Thereby, a selection probability of a large block can be reduced, so as to mitigate or even avoid blockness artifact.

By way of example rather than limitation, the fourth cost may be adjusted as follows:
cost4New = cost4Old *bSize / (32 *32) ,
where cost4New represents the adjusted fourth cost, cost4Old represents the fourth cost, and bSize
represents the size of the first block. It should be understood that the above examples are described merely for purpose of description. The scope of the present disclosure is not limited in this respect.

In some embodiments, a fifth cost for applying a coding mode on the current block may be determined. In addition, the fifth cost may be adjusted based on a blockness artifact cost for the current block. By way of example rather than limitation, the adjusted fifth cost may be determined based on a sum of the fifth cost and the blockness artifact cost. Moreover, mode decision for the current block may be performed based on the adjusted fifth cost. For example, the blockness artifact cost for the current block may be determined based on a difference metric between values of samples within the current block that border an adjacent block of the current block and values of samples within the adjacent block that border the current block. By way of example rather than limitation, the difference metric may be sum of absolute difference (SAD) , mean-squared error (MSE) , or the like. Thereby, the blockness artifact cost can be taken into consideration in the mode decision process, so as to mitigate or even avoid blockness artifact.

In should be understood that the proposed method may be applicable for different video coding standards, different application scenarios, and different rate control schemes. The scope of the present disclosure is not limited in this respect.

In view of the above, the solutions in accordance with some embodiments of the present disclosure can advantageously improve coding quality.

According to further embodiments of the present disclosure, a non-transitory computer-readable recording medium is provided. The non-transitory computer-readable recording medium stores a bitstream of a video which is generated by a method performed by an apparatus for video processing. The method comprises: obtaining a reference quantization parameter (QP) for a current block of the video; determining first information regarding whether the current block involves a scene cut; determining a target QP for the current block based on the reference QP and the first information; and generating the bitstream based on the target QP.

According to still further embodiments of the present disclosure, a method for storing bitstream of a video is provided. The method comprises: obtaining a reference quantization parameter (QP) for a current block of the video; determining first information regarding whether the current block involves a scene cut; determining a target QP for the current block based on the reference QP and the first information; generating the bitstream based on the target QP; and storing the bitstream in a non-transitory computer-readable recording medium.

Implementations of the present disclosure can be described in view of the following clauses, the features of which can be combined in any reasonable manner.

Clause 1. A method for video processing, comprising: obtaining, for a conversion between a current block within a current frame of the video and a bitstream of the video, a reference quantization parameter (QP) for the current block; determining first information regarding whether the current block involves a scene cut; determining a target QP for the current block based on the reference QP and the first information; and performing the conversion based on the target QP.

Clause 2. The method of clause 1, wherein determining the first information comprises: determining a first cost for applying an intra prediction mode on the current block; determining a second cost for applying an inter prediction mode on the current block; and determining the first information based on the first cost and the second cost.

Clause 3. The method of clause 2, wherein determining the first information based on the first cost and the second cost comprises: scaling the second cost with a scaling factor; and in accordance with that the first cost is smaller than the scaled second cost, determining that the current block involves a scene cut; or in accordance with that the first cost is larger than the scaled second cost, determining that the current block does not involve a scene cut.

Clause 4. The method of clause 3, wherein the scaling factor is determined based on a gradient of the current block.

Clause 5. The method of clause 4, wherein the scaling factor is determined as follows:
fIntraInterFactor = max (0, 1 + (0.4 -gradCurr) ) ,
wherein fIntraInterFactor represents the scaling factor, gradCurr represents the gradient of the current
block, and max () represents a max function that returns a largest value in a set of values.

Clause 6. The method of any of clauses 1-5, wherein determining the target QP comprises: determining, based on the first information, second information regarding whether to adjust the reference QP;and determining the target QP based on the second information and the reference QP.

Clause 7. The method of clause 6, wherein determining the second information comprises: in accordance with that the current block involves a scene cut, determining that the reference QP is to be adjusted, or in accordance with that the current block does not involve a scene cut, determining that the reference QP is not adjusted.

Clause 8. The method of clause 6, wherein determining the second information comprises: determining third information indicating whether a texture of the current block is flat; and determining the second information based on the first information and the third information.

Clause 9. The method of clause 8, wherein determining the third information comprises: determining a gradient of the current block; and in accordance with that the gradient of the current block is smaller than a gradient threshold, determining that the texture of the current block is flat; or in accordance with that the gradient of the current block is larger than the gradient threshold, determining that the texture of the current block is not flat.

Clause 10. The method of clause 9, wherein the gradient threshold is determined based on the reference QP for the current block.

Clause 11. The method of clause 10, wherein the gradient threshold is determined as follows:
Thr = max (0.05, 0.4 + (QP -36) *0.6) ,
wherein Thr represents the gradient threshold, QP represents the reference QP for the current block, and
max () represents a max function that returns a largest value in a set of values.

Clause 12. The method of any of clauses 8-11, wherein determining the second information based on the first information and the third information comprises: in accordance with that the current block involves a scene cut and the texture of the current block is flat, determining that the reference QP is to be adjusted; or in accordance with that the current block does not involve a scene cut or the texture of the current block is not flat, determining that the reference QP is not adjusted.

Clause 13. The method of any of clauses 8-11, wherein determining the second information based on the first information and the third information comprises: in accordance with that the current block does not involve a scene cut or the texture of the current block is not flat, determining that the reference QP is not adjusted; or in accordance with that the current block involves a scene cut and the texture of the current block is flat, performing the following operations: determining whether at least one neighboring block of the current block involves a scene cut; determining whether a texture of the at least one neighboring block of the current block is flat; and in accordance with that the at least one neighboring block involves a scene cut and the texture of the at least one neighboring block is flat, determining that the reference QP is to be adjusted; or in accordance with that all of the at least one neighboring block does not involve a scene cut or the texture of all of the at least one neighboring block is not flat, determining that the reference QP is not adjusted.

Clause 14. The method of clause 13, wherein the at least one neighboring block of the current block comprises at least one of the following: a block left to the current block, a block right to the current block, a block above the current block, or a block below the current block.

Clause 15. The method of any of clauses 6-14, wherein determining the target QP based on the second information and the reference QP comprises: in accordance with that the reference QP is not adjusted, determining the reference QP as the target QP; or in accordance with that the reference QP is to be adjusted, determining the target QP based on a result of adjusting the reference QP.

Clause 16. The method of clause 15, wherein in accordance with that the reference QP is to be adjusted, the target QP is determined as follows:
QPNew = max (30, QPOld - (10 + (1 -gradCurr) *2) ) ,
wherein QPNew represents the target QP, QPOld represents the reference QP, and gradCurr represents
the gradient of the current block.

Clause 17. The method of any of clauses 1-16, wherein a blur operation is performed on at least part of the current frame, and in accordance with that the current block is comprised in a target region of the current frame, the target QP is determined based on a result of reducing the reference QP, or in accordance with that the current block is not comprised in the target region, the target QP is determined without reducing the reference QP.

Clause 18. The method of clause 17, wherein the target region of the current frame comprises one of the following: the entire current frame, a center region within the current frame, or a region of interest (ROI) within the current frame.

Clause 19. The method of any of clauses 17-18, wherein the at least part of the current frame comprises one of the following: the entire current frame, a region of non-interest within the current frame, an edge region of the current frame, or a top part and a bottom part of the current frame.

Clause 20. The method of any of clauses 17-19, wherein the blur operation is performed with a Gaussian kernel.

Clause 21. The method of any of clauses 1-20, wherein performing the conversion based on the target QP comprises: determining, based on the target QP, a target weighting factor for a rate term used to determine a rate-distortion (RD) cost; performing a rate-distortion optimization (RDO) process based on the target weighting factor; and performing the conversion based on a result of the RDO process.

Clause 22. The method of clause 21, wherein determining the target weighting factor comprises: determining a reference weighting factor based on the target QP; in accordance with that the target QP is larger than a QP threshold, determining the target weighting factor based on a result of reducing the reference weighting factor; or in accordance with that the target QP is smaller than the QP threshold, determining the reference weighting factor as the target weighting factor.

Clause 23. The method of clause 22, wherein in accordance with that the target QP is larger than the threshold, the target weighting factor is determined as follows:
lambdaNew = lambdaOld × alpha,
wherein lambdaNew represents the target weighting factor, lambdaOld represents the reference weighting
factor, and alpha represents a scaling factor smaller than 1.

Clause 24. The method of clause 21, wherein determining the target weighting factor comprises: determining a reference weighting factor based on the target QP; in accordance with that the target QP is larger than a QP threshold and the reference weighting factor is larger than a weighting factor upper limit, determining the weighting factor upper limit as the target weighting factor; or in accordance with that the target QP is smaller than the QP threshold or the reference weighting factor is smaller than the weighting factor upper limit, determining the reference weighting factor as the target weighting factor.

Clause 25. The method of clause 21, wherein the target weighting factor is determined based on the target QP according to a predetermined model, and a growth rate of the target weighting factor is negatively correlated with the target QP in the predetermined model.

Clause 26. The method of clause 25, wherein the predetermined model is as follows:
lambda = 2 (QP-12) /3 /TQP,
wherein lambda represents the target weighting factor, and TQP represents the target QP.

Clause 27. The method of any of clauses 1-26, further comprising: determining a third cost for applying an intra mode or a skip mode on the current block; adjusting the third cost by increasing the third cost; and performing mode decision for the current block based on the adjusted first cost.

Clause 28. The method of clause 27, wherein the third cost is adjusted as follows:
cost3New = cost3Old× beta,
wherein cost3New represents the adjusted third cost, cost3Old represents the third cost, and beta
represents a scaling factor larger than 1.

Clause 29. The method of any of clauses 1-28, further comprising: determining a fourth cost for a first block obtained by partitioning the current frame; adjusting the fourth cost based on a size of the first block, the adjusted fourth cost being positively correlated with the size; and performing mode decision for the current frame based on the adjusted fourth cost.

Clause 30. The method of clause 29, wherein the fourth cost is adjusted as follows:
cost4New = cost4Old *bSize / (32 *32) ,
wherein cost4New represents the adjusted fourth cost, cost4Old represents the fourth cost, and bSize
represents the size of the first block.

Clause 31. The method of any of clauses 1-30, further comprising: determining a fifth cost for applying a coding mode on the current block; adjusting the fifth cost based on a blockness artifact cost for the current block; and performing mode decision for the current block based on the adjusted fifth cost.

Clause 32. The method of clause 31, wherein the blockness artifact cost for the current block is determined based on a difference metric between values of samples within the current block that border an adjacent block of the current block and values of samples within the adjacent block that border the current block.

Clause 33. The method of clause 31, wherein the adjusted fifth cost is determined based on a sum of the fifth cost and the blockness artifact cost.

Clause 34. The method of any of clauses 1-33, wherein the method is applicable for different video coding standards, different application scenarios, and different rate control schemes.

Clause 35. The method of any of clauses 1-34, wherein the conversion includes encoding the current block into the bitstream.

Clause 36. An apparatus for video processing comprising a processor and a non-transitory memory with instructions thereon, wherein the instructions upon execution by the processor, cause the processor to perform a method in accordance with any of clauses 1-35.

Clause 37. A non-transitory computer-readable storage medium storing instructions that cause a processor to perform a method in accordance with any of clauses 1-35.

Clause 38. A non-transitory computer-readable recording medium storing a bitstream of a video which is generated by a method performed by an apparatus for video processing, wherein the method comprises: obtaining a reference quantization parameter (QP) for a current block of the video; determining first information regarding whether the current block involves a scene cut; determining a target QP for the current block based on the reference QP and the first information; and generating the bitstream based on the target QP.

Clause 39. A method for storing a bitstream of a video, comprising: obtaining a reference quantization parameter (QP) for a current block of the video; determining first information regarding whether the current block involves a scene cut; determining a target QP for the current block based on the reference QP and the first information; generating the bitstream based on the target QP; and storing the bitstream in a non-transitory computer-readable recording medium.
Example Device

Fig. 6 illustrates a block diagram of a computing device 600 in which various embodiments of the present disclosure can be implemented. The computing device 600 may be implemented as or included in the source device 110 (or the video encoder 114 or 200) or the destination device 120 (or the video decoder 124 or 300) .

It would be appreciated that the computing device 600 shown in Fig. 6 is merely for purpose of illustration, without suggesting any limitation to the functions and scopes of the embodiments of the present disclosure in any manner.

As shown in Fig. 6, the computing device 600 includes a general-purpose computing device 600. The computing device 600 may at least comprise one or more processors or processing units 610, a memory 620, a storage unit 630, one or more communication units 640, one or more input devices 650, and one or more output devices 660.

In some embodiments, the computing device 600 may be implemented as any user terminal or server terminal having the computing capability. The server terminal may be a server, a large-scale computing device or the like that is provided by a service provider. The user terminal may for example be any type of mobile terminal, fixed terminal, or portable terminal, including a mobile phone, station, unit, device, multimedia computer, multimedia tablet, Internet node, communicator, desktop computer, laptop computer, notebook computer, netbook computer, tablet computer, personal communication system (PCS) device, personal navigation device, personal digital assistant (PDA) , audio/video player, digital camera/video camera, positioning device, television receiver, radio broadcast receiver, E-book device, gaming device, or any combination thereof, including the accessories and peripherals of these devices, or any combination thereof. It would be contemplated that the computing device 600 can support any type of interface to a user (such as “wearable” circuitry and the like) .

The processing unit 610 may be a physical or virtual processor and can implement various processes based on programs stored in the memory 620. In a multi-processor system, multiple processing units execute computer executable instructions in parallel so as to improve the parallel processing capability of the computing device 600. The processing unit 610 may also be referred to as a central processing unit (CPU) , a microprocessor, a controller or a microcontroller.

The computing device 600 typically includes various computer storage medium. Such medium can be any medium accessible by the computing device 600, including, but not limited to, volatile and non-volatile medium, or detachable and non-detachable medium. The memory 620 can be a volatile memory (for example, a register, cache, Random Access Memory (RAM) ) , a non-volatile memory (such as a Read-Only Memory (ROM) , Electrically Erasable Programmable Read-Only Memory (EEPROM) , or a flash memory) , or any combination thereof. The storage unit 630 may be any detachable or non-detachable medium and may include a machine-readable medium such as a memory, flash memory drive, magnetic disk or another other media, which can be used for storing information and/or data and can be accessed in the computing device 600.

The computing device 600 may further include additional detachable/non-detachable, volatile/non-volatile memory medium. Although not shown in Fig. 6, it is possible to provide a magnetic disk drive for reading from and/or writing into a detachable and non-volatile magnetic disk and an optical disk drive for reading from and/or writing into a detachable non-volatile optical disk. In such cases, each drive may be connected to a bus (not shown) via one or more data medium interfaces.

The communication unit 640 communicates with a further computing device via the communication medium. In addition, the functions of the components in the computing device 600 can be implemented by a single computing cluster or multiple computing machines that can communicate via communication connections. Therefore, the computing device 600 can operate in a networked environment using a logical connection with one or more other servers, networked personal computers (PCs) or further general network nodes.

The input device 650 may be one or more of a variety of input devices, such as a mouse, keyboard, tracking ball, voice-input device, and the like. The output device 660 may be one or more of a variety of output devices, such as a display, loudspeaker, printer, and the like. By means of the communication unit 640, the computing device 600 can further communicate with one or more external devices (not shown) such as the storage devices and display device, with one or more devices enabling the user to interact with the computing device 600, or any devices (such as a network card, a modem and the like) enabling the computing device 600 to communicate with one or more other computing devices, if required. Such communication can be performed via input/output (I/O) interfaces (not shown) .

In some embodiments, instead of being integrated in a single device, some or all components of the computing device 600 may also be arranged in cloud computing architecture. In the cloud computing architecture, the components may be provided remotely and work together to implement the functionalities described in the present disclosure. In some embodiments, cloud computing provides computing, software, data access and storage service, which will not require end users to be aware of the physical locations or configurations of the systems or hardware providing these services. In various embodiments, the cloud computing provides the services via a wide area network (such as Internet) using suitable protocols. For example, a cloud computing provider provides applications over the wide area network, which can be accessed through a web browser or any other computing components. The software or components of the cloud computing architecture and corresponding data may be stored on a server at a remote position. The computing resources in the cloud computing environment may be merged or distributed at locations in a remote data center. Cloud computing infrastructures may provide the services through a shared data center, though they behave as a single access point for the users. Therefore, the cloud computing architectures may be used to provide the components and functionalities described herein from a service provider at a remote location. Alternatively, they may be provided from a conventional server or installed directly or otherwise on a client device.

The computing device 600 may be used to implement video encoding/decoding in embodiments of the present disclosure. The memory 620 may include one or more video coding modules 625 having one or more program instructions. These modules are accessible and executable by the processing unit 610 to perform the functionalities of the various embodiments described herein.

In the example embodiments of performing video encoding, the input device 650 may receive video data as an input 670 to be encoded. The video data may be processed, for example, by the video coding module 625, to generate an encoded bitstream. The encoded bitstream may be provided via the output device 660 as an output 680.

In the example embodiments of performing video decoding, the input device 650 may receive an encoded bitstream as the input 670. The encoded bitstream may be processed, for example, by the video coding module 625, to generate decoded video data. The decoded video data may be provided via the output device 660 as the output 680.

While this disclosure has been particularly shown and described with references to example embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present application as defined by the appended claims. Such variations are intended to be covered by the scope of this present application. As such, the foregoing description of embodiments of the present application is not intended to be limiting.

Claims

A method for video processing, comprising:

obtaining, for a conversion between a current block within a current frame of the video and a bitstream of the video, a reference quantization parameter (QP) for the current block;

determining first information regarding whether the current block involves a scene cut;

determining a target QP for the current block based on the reference QP and the first information; and

performing the conversion based on the target QP.
The method of claim 1, wherein determining the first information comprises:

determining a first cost for applying an intra prediction mode on the current block;

determining a second cost for applying an inter prediction mode on the current block; and

determining the first information based on the first cost and the second cost.
The method of claim 2, wherein determining the first information based on the first cost and the second cost comprises:

scaling the second cost with a scaling factor; and

in accordance with that the first cost is smaller than the scaled second cost, determining that the current block involves a scene cut; or

in accordance with that the first cost is larger than the scaled second cost, determining that the current block does not involve a scene cut.
The method of claim 3, wherein the scaling factor is determined based on a gradient of the current block.
The method of claim 4, wherein the scaling factor is determined as follows:

fIntraInterFactor = max (0, 1 + (0.4 -gradCurr)) ,

wherein fIntraInterFactor represents the scaling factor, gradCurr represents the gradient of the current block, and max () represents a max function that returns a largest value in a set of values.
The method of any of claims 1-5, wherein determining the target QP comprises:

determining, based on the first information, second information regarding whether to adjust the reference QP; and

determining the target QP based on the second information and the reference QP.
The method of claim 6, wherein determining the second information comprises:

in accordance with that the current block involves a scene cut, determining that the reference QP is to be adjusted, or

in accordance with that the current block does not involve a scene cut, determining that the reference QP is not adjusted.
The method of claim 6, wherein determining the second information comprises:

determining third information indicating whether a texture of the current block is flat; and

determining the second information based on the first information and the third information.
The method of claim 8, wherein determining the third information comprises:

determining a gradient of the current block; and

in accordance with that the gradient of the current block is smaller than a gradient threshold, determining that the texture of the current block is flat; or

in accordance with that the gradient of the current block is larger than the gradient threshold, determining that the texture of the current block is not flat.
The method of claim 9, wherein the gradient threshold is determined based on the reference QP for the current block.
The method of claim 10, wherein the gradient threshold is determined as follows:
Thr = max (0.05, 0.4 + (QP -36) *0.6) ,

wherein Thr represents the gradient threshold, QP represents the reference QP for the current block, and max () represents a max function that returns a largest value in a set of values.
The method of any of claims 8-11, wherein determining the second information based on the first information and the third information comprises:

in accordance with that the current block involves a scene cut and the texture of the current block is flat, determining that the reference QP is to be adjusted; or

in accordance with that the current block does not involve a scene cut or the texture of the current block is not flat, determining that the reference QP is not adjusted.
The method of any of claims 8-11, wherein determining the second information based on the first information and the third information comprises:

in accordance with that the current block does not involve a scene cut or the texture of the current block is not flat, determining that the reference QP is not adjusted; or

in accordance with that the current block involves a scene cut and the texture of the current block is flat, performing the following operations:

determining whether at least one neighboring block of the current block involves a scene cut;

determining whether a texture of the at least one neighboring block of the current block is flat; and

in accordance with that the at least one neighboring block involves a scene cut and the texture of the at least one neighboring block is flat, determining that the reference QP is to be adjusted; or

in accordance with that all of the at least one neighboring block does not involve a scene cut or the texture of all of the at least one neighboring block is not flat, determining that the reference QP is not adjusted.
The method of claim 13, wherein the at least one neighboring block of the current block comprises at least one of the following:

a block left to the current block,

a block right to the current block,

a block above the current block, or

a block below the current block.
The method of any of claims 6-14, wherein determining the target QP based on the second information and the reference QP comprises:

in accordance with that the reference QP is not adjusted, determining the reference QP as the target QP; or

in accordance with that the reference QP is to be adjusted, determining the target QP based on a result of adjusting the reference QP.
The method of claim 15, wherein in accordance with that the reference QP is to be adjusted, the target QP is determined as follows:
QPNew = max (30, QPOld - (10 + (1 -gradCurr) *2)) ,

wherein QPNew represents the target QP, QPOld represents the reference QP, and gradCurr represents the gradient of the current block.
The method of any of claims 1-16, wherein a blur operation is performed on at least part of the current frame, and

in accordance with that the current block is comprised in a target region of the current frame, the target QP is determined based on a result of reducing the reference QP, or

in accordance with that the current block is not comprised in the target region, the target QP is determined without reducing the reference QP.
The method of claim 17, wherein the target region of the current frame comprises one of the following:

the entire current frame,

a center region within the current frame, or

a region of interest (ROI) within the current frame.
The method of any of claims 17-18, wherein the at least part of the current frame comprises one of the following:

the entire current frame,

a region of non-interest within the current frame,

an edge region of the current frame, or

a top part and a bottom part of the current frame.
The method of any of claims 17-19, wherein the blur operation is performed with a Gaussian kernel.
The method of any of claims 1-20, wherein performing the conversion based on the target QP comprises:

determining, based on the target QP, a target weighting factor for a rate term used to determine a rate-distortion (RD) cost;

performing a rate-distortion optimization (RDO) process based on the target weighting factor; and

performing the conversion based on a result of the RDO process.
The method of claim 21, wherein determining the target weighting factor comprises:

determining a reference weighting factor based on the target QP;

in accordance with that the target QP is larger than a QP threshold, determining the target weighting factor based on a result of reducing the reference weighting factor; or

in accordance with that the target QP is smaller than the QP threshold, determining the reference weighting factor as the target weighting factor.
The method of claim 22, wherein in accordance with that the target QP is larger than the threshold, the target weighting factor is determined as follows:
lambdaNew = lambdaOld × alpha,

wherein lambdaNew represents the target weighting factor, lambdaOld represents the reference weighting factor, and alpha represents a scaling factor smaller than 1.
The method of claim 21, wherein determining the target weighting factor comprises:

determining a reference weighting factor based on the target QP;

in accordance with that the target QP is larger than a QP threshold and the reference weighting factor is larger than a weighting factor upper limit, determining the weighting factor upper limit as the target weighting factor; or

in accordance with that the target QP is smaller than the QP threshold or the reference weighting factor is smaller than the weighting factor upper limit, determining the reference weighting factor as the target weighting factor.
The method of claim 21, wherein the target weighting factor is determined based on the target QP according to a predetermined model, and a growth rate of the target weighting factor is negatively correlated with the target QP in the predetermined model.
The method of claim 25, wherein the predetermined model is as follows:
lambda = 2 ^(QP-12) ^/3 /TQP,

wherein lambda represents the target weighting factor, and TQP represents the target QP.
The method of any of claims 1-26, further comprising:

determining a third cost for applying an intra mode or a skip mode on the current block;

adjusting the third cost by increasing the third cost; and

performing mode decision for the current block based on the adjusted first cost.
The method of claim 27, wherein the third cost is adjusted as follows:
cost3New = cost3Old× beta,

wherein cost3New represents the adjusted third cost, cost3Old represents the third cost, and beta represents a scaling factor larger than 1.
The method of any of claims 1-28, further comprising:

determining a fourth cost for a first block obtained by partitioning the current frame;

adjusting the fourth cost based on a size of the first block, the adjusted fourth cost being positively correlated with the size; and

performing mode decision for the current frame based on the adjusted fourth cost.
The method of claim 29, wherein the fourth cost is adjusted as follows:
cost4New = cost4Old *bSize / (32 *32) ,

wherein cost4New represents the adjusted fourth cost, cost4Old represents the fourth cost, and bSize represents the size of the first block.
The method of any of claims 1-30, further comprising:

determining a fifth cost for applying a coding mode on the current block;

adjusting the fifth cost based on a blockness artifact cost for the current block; and

performing mode decision for the current block based on the adjusted fifth cost.
The method of claim 31, wherein the blockness artifact cost for the current block is determined based on a difference metric between values of samples within the current block that border an adjacent block of the current block and values of samples within the adjacent block that border the current block.
The method of claim 31, wherein the adjusted fifth cost is determined based on a sum of the fifth cost and the blockness artifact cost.
The method of any of claims 1-33, wherein the method is applicable for different video coding standards, different application scenarios, and different rate control schemes.
The method of any of claims 1-34, wherein the conversion includes encoding the current block into the bitstream.
An apparatus for video processing comprising a processor and a non-transitory memory with instructions thereon, wherein the instructions upon execution by the processor, cause the processor to perform a method in accordance with any of claims 1-35.
A non-transitory computer-readable storage medium storing instructions that cause a processor to perform a method in accordance with any of claims 1-35.
A non-transitory computer-readable recording medium storing a bitstream of a video which is generated by a method performed by an apparatus for video processing, wherein the method comprises:

obtaining a reference quantization parameter (QP) for a current block of the video;

determining first information regarding whether the current block involves a scene cut;

determining a target QP for the current block based on the reference QP and the first information; and

generating the bitstream based on the target QP.
A method for storing a bitstream of a video, comprising:

obtaining a reference quantization parameter (QP) for a current block of the video;

determining first information regarding whether the current block involves a scene cut;

determining a target QP for the current block based on the reference QP and the first information;

generating the bitstream based on the target QP; and

storing the bitstream in a non-transitory computer-readable recording medium.