WO2013147497A1 - Method for applying sample adaptive offset in scalable video coding, and apparatus using the method - Google Patents

Description

Application Method of Sample Adaptive Offset in Scalable Video Coding and Apparatus Using the Same

TECHNICAL FIELD The present invention relates to video compression techniques, and more particularly, to a method and apparatus for applying a sample adaptive offset (SAO) in scalable video coding.

Recently, the demand for high resolution and high quality images is increasing in various applications. As an image has a high resolution and high quality, the amount of information on the image also increases.

As information volume increases, devices with various performances and networks with various environments are emerging.

With the emergence of devices of varying performance and networks of different environments, the same content is available in different qualities.

In detail, as the video quality of the terminal device can be supported and the network environment is diversified, in general, video of general quality may be used in one environment, but higher quality video may be used in another environment. .

For example, a consumer who purchases video content on a mobile terminal can view the same video content on a larger screen and at a higher resolution through a large display in the home.

In recent years, broadcasts having a high definition (HD) resolution are being serviced, and many users are already accustomed to high resolution and high definition video.Ultra High Definition (UHD) has more than four times the resolution of an HDTV. I am also interested in the services of the company.

Therefore, in order to provide various video services required by users in various environments according to the quality, based on a high-efficiency encoding / decoding method for high-capacity video, the quality of the image, for example, the image quality, the resolution of the image, the size of the image, It is necessary to provide scalability in the frame rate of video and the like.

An object of the present invention is to provide a method and apparatus for improving the quality of an upper layer by applying a filter using information of a lower layer in scalable video coding.

An object of the present invention is to provide a method and apparatus for effectively applying SAO to an upper layer by using information of SAO applied to a lower layer in scalable video coding.

An object of the present invention is to provide a method and apparatus for effectively transmitting information of SAO applied to an upper layer by using information of SAO applied to a lower layer in scalable video coding.

According to the SAO method in scalable video coding disclosed in the present specification, SAO is applied to an upper layer based on information on SAO applied to a lower layer.

The encoding apparatus transmits SAO indication information for specifying the SAO applied to the upper layer to the decoding apparatus.

The decoding apparatus may receive the SAO indication information and specify the SAO to be applied to the upper layer by using the received SAO indication information and the SAO applied to the lower layer.

The encoding apparatus and the decoding apparatus may specify the SAO to be applied to the upper layer by using the information about the SAO applied to the lower layer.

In addition, information (syntax element) indicating SAO to be applied to the upper layer may be transmitted using information indicating SAO applied to the lower layer.

According to the present invention, the quality of the upper layer can be improved by applying a filter using information of the lower layer in scalable video coding.

According to the present invention, SAO can be effectively applied to an upper layer by using information of SAO applied to a lower layer in scalable video coding.

According to the present invention, in scalable video coding, the information of the SAO applied to the upper layer can be effectively transmitted using the information of the SAO applied to the lower layer.

1 is a block diagram schematically illustrating a video encoding apparatus supporting scalability according to an embodiment of the present invention.

2 is a block diagram schematically illustrating a video decoding apparatus supporting scalability according to an embodiment of the present invention.

3 is a block diagram illustrating an example of inter-layer prediction in an encoding apparatus and a decoding apparatus that perform scalable coding according to the present invention.

4 is a diagram schematically illustrating an example of a method of applying a band offset.

5 is a diagram schematically illustrating another example of a method of applying a band offset.

6 is a diagram schematically illustrating a category of edge offsets.

FIG. 7 is a diagram for briefly explaining an example of applying an XOR operation to SAO information of a lower layer and SAO information of an upper layer according to the present invention.

8 is a diagram for briefly explaining another example of applying an XOR operation to SAO information of a lower layer and SAO information of a higher layer according to the present invention.

9 is a flowchart schematically illustrating a method of applying SAO to an upper layer and transmitting SAO information according to the present invention.

10 is a flowchart schematically illustrating a method of receiving SAO indication information indicating SAO to be applied to a higher layer and applying SAO to a higher layer according to the present invention.

As the present invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the invention to the specific embodiments. The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the spirit of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as "comprise" or "have" are intended to indicate that there is a feature, number, step, action, component, part, or combination thereof described on the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

On the other hand, each of the components in the drawings described in the present invention are shown independently for the convenience of description of the different characteristic functions in the video encoding apparatus / decoding apparatus, each component is a separate hardware or separate software It does not mean that it is implemented. For example, two or more of each configuration may be combined to form one configuration, or one configuration may be divided into a plurality of configurations. Embodiments in which each configuration is integrated and / or separated are also included in the scope of the present invention without departing from the spirit of the present invention.

Hereinafter, with reference to the accompanying drawings, it will be described in detail a preferred embodiment of the present invention. Hereinafter, the same reference numerals are used for the same components in the drawings, and redundant description of the same components is omitted.

In a video coding method that supports scalability (hereinafter, referred to as 'scalable coding'), input signals may be processed in layers. Depending on the layer, the input signals (input images) may have at least one of resolution, frame rate, bit-depth, color format, and aspect ratio. Can be.

In the present specification, scalable coding includes scalable encoding and scalable decoding.

In scalable encoding / decoding, prediction between layers is performed by using differences between layers, that is, based on scalability, thereby reducing overlapping transmission / processing of information and increasing compression efficiency.

1 is a block diagram schematically illustrating a video encoding apparatus supporting scalability according to an embodiment of the present invention.

Referring to FIG. 1, the encoding apparatus 100 includes an encoder 105 for layer 1 and an encoder 135 for layer 0.

Layer 0 may be a base layer, a reference layer, or a lower layer, and layer 1 may be an enhancement layer, a current layer, or an upper layer.

The encoding unit 105 of the layer 1 includes a prediction unit 110, a transform / quantization unit 115, a filtering unit 120, a decoded picture buffer (DPB) 125, an entropy coding unit 130, and a MUX (Multiplexer, 165). ).

The encoding unit 135 of the layer 0 includes a prediction unit 140, a transform / quantization unit 145, a filtering unit 150, a DPB 155, and an entropy coding unit 160.

The prediction units 110 and 140 may perform inter prediction and intra prediction on the input image. The prediction units 110 and 140 may perform prediction in predetermined processing units. The performing unit of prediction may be a coding unit (CU), a prediction unit (PU), or a transform unit (TU).

For example, the prediction units 110 and 140 may determine whether to apply inter prediction or intra prediction in a CU unit, determine a mode of prediction in a PU unit, and perform prediction in a PU unit or a TU unit. have. Prediction performed includes generation of a prediction block and generation of a residual block (residual signal).

Through inter prediction, a prediction block may be generated by performing prediction based on information of at least one picture of a previous picture and / or a subsequent picture of the current picture. Through intra prediction, prediction blocks may be generated by performing prediction based on pixel information in a current picture.

As a mode or method of inter prediction, there are a skip mode, a merge mode, a motion vector predtiction (MVP) method, and the like. In inter prediction, a reference picture may be selected with respect to the current PU that is a prediction target, and a reference block corresponding to the current PU may be selected within the reference picture. The prediction unit 160 may generate a prediction block based on the reference block.

The prediction block may be generated in integer sample units or may be generated in integer or less pixel units. In this case, the motion vector may also be expressed in units of integer pixels or units of integer pixels or less.

In inter prediction, motion information, that is, information such as an index of a reference picture, a motion vector, and a residual signal, is entropy encoded and transmitted to a decoding apparatus. When the skip mode is applied, residuals may not be generated, transformed, quantized, or transmitted.

In intra prediction, the prediction mode may have 33 directional prediction modes and at least two non-directional modes. The non-directional mode may include a DC prediction mode and a planner mode (Planar mode). In intra prediction, a prediction block may be generated after applying a filter to a reference sample.

The PU may be a block of various sizes / types, for example, in the case of inter prediction, the PU may be a 2N × 2N block, a 2N × N block, an N × 2N block, an N × N block (N is an integer), or the like. In the case of intra prediction, the PU may be a 2N × 2N block or an N × N block (where N is an integer). In this case, the PU of the N × N block size may be set to apply only in a specific case. For example, the NxN block size PU may be used only for the minimum size CU or only for intra prediction. In addition to the above-described PUs, PUs such as N × mN blocks, mN × N blocks, 2N × mN blocks, or mN × 2N blocks (m <1) may be further defined and used.

In addition, the prediction units 110 and 140 may perform prediction on the layer 1 by using the information of the layer 0. In the present specification, a method of predicting information of a current layer using information of another layer is referred to as inter-layer prediction for convenience of description.

Information of the current layer that is predicted using information of another layer (ie, predicted by inter-layer prediction) may include texture, motion information, unit information, predetermined parameters (eg, filtering parameters, etc.).

In addition, information of another layer used for prediction for the current layer (ie, used for inter-layer prediction) may include texture, motion information, unit information, and predetermined parameters (eg, filtering parameters).

As an example of inter-layer prediction, in inter-layer unit parameter prediction, unit (CU, PU, and / or TU) information of a base layer is derived and used as unit information of an enhancement layer, or based on unit information of a base layer. Unit information of the treatment layer may be determined.

In addition, the unit information may include information at each unit level. For example, in the case of CU information, information about a partition (CU, PU and / or TU) may include information on transform, information on prediction, and information on coding. In the case of PU information, information on a PU partition and information on prediction (eg, motion information, information on a prediction mode, etc.) may be included. The information about the TU may include information about a TU partition, information on transform (transform coefficient, transform method, etc.).

In addition, the unit information may include only the partition information of the processing unit (eg, CU, PU, TU, etc.).

Interlayer motion prediction, another example of interlayer prediction, is also called interlayer inter prediction. According to inter-layer inter prediction, prediction of a current block of layer 1 (current layer or enhancement layer) may be performed using motion information of layer 0 (reference layer or base layer).

In case of applying inter-layer inter prediction, motion information of a reference layer may be scaled.

As another example of inter-layer prediction, inter-layer texture prediction is also called inter-layer intra prediction or intra base layer (BL) prediction. In inter-layer texture prediction, the texture of the reference block in the reference layer may be used as a prediction value for the current block of the enhancement layer. In this case, the texture of the reference block may be scaled by upsampling.

In another example of inter-layer prediction, inter-layer parameter prediction may derive a parameter used in the base layer to reuse it in the enhancement layer or predict a parameter for the enhancement layer based on the parameter used in the base layer.

As an example of interlayer prediction, interlayer texture prediction, interlayer motion prediction, interlayer unit information prediction, and interlayer parameter prediction have been described. However, the interlayer prediction applicable to the present invention is not limited thereto.

For example, the prediction unit may use inter-layer residual prediction, which predicts the residual of the current layer using residual information of another layer as inter-layer prediction, and performs prediction on the current block in the current layer based on the residual layer.

In addition, the prediction unit is an interlayer prediction interlayer that performs prediction on the current block in the current layer by using a difference (difference image) image between the reconstructed picture of the current layer and the resampled picture of another layer as the interlayer prediction. Differential prediction may also be performed.

The transform / quantization units 115 and 145 may perform transform on the residual block in transform block units to generate transform coefficients and quantize the transform coefficients.

The transform block is a block of samples and is a block to which the same transform is applied. The transform block can be a transform unit (TU) and can have a quad tree structure.

The transform / quantization units 115 and 145 may generate a 2D array of transform coefficients by performing transform according to the prediction mode applied to the residual block and the size of the transform block. For example, if intra prediction is applied to a residual block and the block is a 4x4 residual array, the residual block is transformed using a discrete sine transform (DST), otherwise the residual block is transformed into a discrete cosine transform (DCT). Can be converted using.

In addition, the transform / quantization units 115 and 165 may fixedly use a specific transform regardless of the prediction mode and the size of the transform block. For example, the transform / quantization units 115 and 165 may apply only DST to all transform blocks. Also, the transform / quantization units 115 and 165 may apply only DCT to all transform blocks.

The transform / quantization unit 115 and 145 may quantize the transform coefficients to generate quantized transform coefficients.

The transform / quantization units 115 and 145 may transfer the quantized transform coefficients to the entropy coding units 130 and 160. In this case, the transform / quantization unit 145 may rearrange the two-dimensional array of quantized transform coefficients into one-dimensional arrays according to a predetermined scan order and transfer them to the entropy coding units 130 and 160. In addition, the transform / quantizers 115 and 145 may transfer the reconstructed block generated based on the residual and the predictive block to the filtering units 120 and 150 for inter prediction.

Meanwhile, the transform / quantization units 115 and 165 may skip transform and perform quantization only or omit both transform and quantization as necessary. For example, the transform / quantization unit 115 or 165 may omit the transform for a block having a specific prediction method or a specific size block, or a block of a specific size to which a specific prediction block is applied.

The entropy coding units 130 and 160 may perform entropy encoding on the quantized transform coefficients. Entropy encoding may use, for example, an encoding method such as Exponential Golomb, Context-Adaptive Binary Arithmetic Coding (CABAC), or the like.

The filtering units 120 and 150 may apply a deblocking filter, an adaptive loop filter (ALF), and a sample adaptive offset (SAO) to the reconstructed picture.

The deblocking filter may remove distortion generated at the boundary between blocks in the reconstructed picture. The adaptive loop filter (ALF) may perform filtering based on a value obtained by comparing the reconstructed image with the original image after the block is filtered through the deblocking filter. The SAO restores the offset difference from the original image on a pixel-by-pixel basis to the residual block to which the deblocking filter is applied, and is applied in the form of a band offset and an edge offset.

The filtering units 120 and 150 may apply only the deblocking filter, only the deblocking filter and the ALF, or may apply only the deblocking filter and the SAO without applying all of the deblocking filter, ALF, and SAO.

The DPBs 125 and 155 may receive the reconstructed block or the reconstructed picture from the filtering units 125 and 150 and store the received reconstruction picture. The DPBs 125 and 155 may provide a reconstructed block or picture to the predictors 110 and 140 that perform inter prediction.

Information output from the entropy coding unit 160 of layer 0 and information output from the entropy coding unit 130 of layer 1 may be multiplexed by the MUX 165 and output as a bitstream.

Meanwhile, for the convenience of description, the encoding unit 105 of the layer 1 has been described as including the MUX 165. However, the MUX is separate from the encoding unit 105 of the layer 1 and the encoding unit 135 of the layer 0. It may be a device or a module of.

2 is a block diagram schematically illustrating a video decoding apparatus supporting scalability according to an embodiment of the present invention.

Referring to FIG. 2, the decoding apparatus 200 includes a decoder 210 of layer 1 and a decoder 250 of layer 0.

Layer 0 may be a base layer, a reference layer, or a lower layer, and layer 1 may be an enhancement layer, a current layer, or an upper layer.

The decoding unit 210 of the layer 1 includes an entropy decoding unit 215, a reordering unit 220, an inverse quantization unit 225, an inverse transform unit 230, a prediction unit 235, a filtering unit 240, and a memory. can do.

The decoding unit 250 of the layer 0 may include an entropy decoding unit 255, a reordering unit 260, an inverse quantization unit 265, an inverse transform unit 270, a filtering unit 280, and a memory 285. .

When the bitstream including the image information is transmitted from the encoding device, the DEMUX 205 may demultiplex the information for each layer and deliver the information to the decoding device for each layer.

The entropy decoding units 215 and 255 may perform entropy decoding corresponding to the entropy coding scheme used in the encoding apparatus. For example, when CABAC is used in the encoding apparatus, the entropy decoding units 215 and 255 may also perform entropy decoding using CABAC.

Information for generating a prediction block among the information decoded by the entropy decoding units 215 and 255 is provided to the prediction units 235 and 275, and a residual value of which entropy decoding is performed by the entropy decoding units 215 and 255. That is, the quantized transform coefficients may be input to the reordering units 220 and 260.

The reordering units 220 and 260 may rearrange the information of the bitstreams entropy decoded by the entropy decoding units 215 and 255, that is, the quantized transform coefficients, based on the reordering method in the encoding apparatus.

For example, the reordering units 220 and 260 may rearrange the quantized transform coefficients of the one-dimensional array into the coefficients of the two-dimensional array. The reordering units 220 and 260 may generate a two-dimensional array of coefficients (quantized transform coefficients) by performing scanning based on the prediction mode applied to the current block (transform block) and / or the size of the transform block.

The inverse quantizers 225 and 265 may generate transform coefficients by performing inverse quantization based on the quantization parameter provided by the encoding apparatus and the coefficient values of the rearranged block.

The inverse quantizers 225 and 265 may transfer the entropy decoded residual to the inverse transformers 230 and 270 without dequantizing the entropy decoded residual according to a predetermined condition or a quantization scheme in the encoding apparatus.

The inverse transform units 230 and 270 may perform inverse transform on the transform performed by the transform unit of the encoding apparatus. The inverse transform units 230 and 270 may perform inverse DCT and / or inverse DST on a discrete cosine transform (DCT) and a discrete sine transform (DST) performed by an encoding apparatus.

The DCT and / or DST in the encoding apparatus may be selectively performed according to a plurality of pieces of information, such as a prediction method, a size of a current block, and a prediction direction, and the inverse transformers 230 and 270 of the decoding apparatus may perform transform information performed in the encoding apparatus. Inverse transformation may be performed based on.

For example, the inverse transform units 230 and 270 may apply inverse DCT and inverse DST according to a prediction mode / block size. For example, the inverse transformers 230 and 270 may apply an inverse DST to a 4x4 luma block to which intra prediction is applied.

In addition, the inverse transform units 230 and 270 may fixedly use a specific inverse transform method regardless of the prediction mode / block size. For example, the inverse transform units 330 and 370 may apply only inverse DST to all transform blocks. In addition, the inverse transform units 330 and 370 may apply only inverse DCT to all transform blocks.

The inverse transformers 230 and 270 may generate a residual or residual block by inversely transforming the transform coefficients or the block of the transform coefficients.

The inverse transformers 230 and 270 may also skip the transformation as needed or in accordance with the manner encoded in the encoding apparatus. For example, the inverse transforms 230 and 270 may omit the transform for a block having a specific prediction method or a specific size or a block of a specific size to which a specific prediction block is applied.

The prediction units 235 and 275 may perform prediction on the current block based on prediction block generation related information transmitted from the entropy decoding units 215 and 255 and previously decoded blocks and / or picture information provided by the memories 245 and 285. A prediction block can be generated.

When the prediction mode for the current block is an intra prediction mode, the prediction units 235 and 275 may perform intra prediction on the current block based on pixel information in the current picture.

When the prediction mode for the current block is the inter prediction mode, the prediction units 235 and 275 may perform information on the current block based on information included in at least one of a previous picture or a subsequent picture of the current picture. Inter prediction may be performed. Some or all of the motion information required for inter prediction may be derived from the information received from the encoding apparatus and correspondingly.

When the skip mode is applied as the mode of inter prediction, residual is not transmitted from the encoding apparatus, and the prediction block may be a reconstruction block.

Meanwhile, the prediction unit 235 of layer 1 may perform inter prediction or intra prediction using only information in layer 1, or may perform inter layer prediction using information of another layer (layer 0).

For example, the predictor 235 of the layer 1 may perform prediction on the current block by using one of the motion information of the layer 1, the texture information of the layer 1, the unit information of the layer 1, and the parameter information of the layer 1. In addition, the prediction unit 235 of the layer 1 may perform prediction on the current block by using a plurality of pieces of information of the motion information of the layer 1, the texture information of the layer 1, the unit information of the layer 1, and the parameter information of the layer 1. have.

The predictor 235 of the layer 1 may receive motion information of the layer 1 from the predictor 275 of the layer 0 to perform motion prediction. Inter-layer motion prediction is also called inter-layer inter prediction. By inter-layer motion prediction, prediction of a current block of a current layer (enhanced layer) may be performed using motion information of a reference layer (base layer). The prediction unit 335 may scale and use motion information of the reference layer when necessary.

The predictor 235 of the layer 1 may receive texture information of the layer 1 from the predictor 275 of the layer 0 to perform texture prediction. Texture prediction is also called inter layer intra prediction or intra base layer (BL) prediction. In inter-layer texture prediction, the texture of the reference block in the reference layer may be used as a prediction value for the current block of the enhancement layer. In this case, the texture of the reference block may be scaled by upsampling.

The predictor 235 of the layer 1 may receive unit parameter information of the layer 1 from the predictor 275 of the layer 0 to perform unit parameter prediction. By unit parameter prediction, unit (CU, PU, and / or TU) information of the base layer may be used as unit information of the enhancement layer, or unit information of the enhancement layer may be determined based on unit information of the base layer.

The predictor 235 of the layer 1 may receive parameter information regarding the filtering of the layer 1 from the predictor 275 of the layer 0 to perform parameter prediction. By parameter prediction, the parameters used in the base layer can be derived and reused in the enhancement layer, or the parameters for the enhancement layer can be predicted based on the parameters used in the base layer.

The adders 290 and 295 may generate reconstruction blocks using the prediction blocks generated by the predictors 235 and 275 and the residual blocks generated by the inverse transformers 230 and 270. In this case, the adders 290 and 295 can be viewed as separate units (restore block generation unit) for generating the reconstruction block.

Blocks and / or pictures reconstructed by the adders 290 and 295 may be provided to the filtering units 240 and 280.

The filtering units 240 and 280 may apply deblocking filtering, sample adaptive offset (SAO), and / or ALF to the reconstructed blocks and / or pictures.

The filtering units 240 and 280 may not apply all of the deblocking filter, ALF, and SAO, and may apply only the deblocking filter, only the deblocking filter and the ALF, or may apply only the deblocking filter and the SAO.

Referring to the example of FIG. 2, the filtering unit 240 of the layer 1 performs filtering on the reconstructed picture by using parameter information transmitted from the predicting unit 235 of the layer 1 and / or the filtering unit 280 of the layer 1. It can also be done. For example, in layer 1, the filtering unit 240 may apply filtering to or between layers using the parameters predicted from the parameters of the filtering applied in the layer 0.

The memories 245 and 285 may store the reconstructed picture or block to use as a reference picture or reference block. The memories 245 and 285 may output the stored reconstructed picture through a predetermined output unit (not shown) or a display (not shown).

In the example of FIG. 2, the reordering unit, the inverse quantization unit, and the inverse transform unit have been described. However, as in the encoding procedure of FIG. It can also be configured.

In the example of FIGS. 1 and 2, the prediction unit has been described, but for better understanding, the prediction unit of layer 1 may be different from the interlayer prediction unit that performs prediction using information of another layer (layer 0). It may also be regarded as including an inter / intra predictor for performing prediction without using the information of).

3 is a block diagram illustrating an example of inter-layer prediction in an encoding apparatus and a decoding apparatus that perform scalable coding according to the present invention.

Referring to FIG. 3, the predictor 300 of layer 1 includes an inter / intra predictor 340 and an interlayer predictor 350.

The prediction unit 300 of the layer 1 may perform interlayer prediction necessary for the prediction of the layer 1 from the information of the layer 0.

For example, the interlayer prediction unit 350 may receive interlayer prediction information from the prediction unit 320 and / or the filtering unit 330 of the layer 0 to perform interlayer prediction necessary for the prediction of the layer 1.

The inter / intra prediction unit 340 of the layer 1 may perform inter prediction or intra prediction using the information of the layer 1 without using the information of the layer 0.

In addition, the inter / intra predictor 340 of the layer 1 may perform prediction based on the information of the layer 0 using the information transmitted from the interlayer predictor 350.

In addition, the filtering unit 310 of the layer 1 may perform the filtering based on the information of the layer 0, or may perform the filtering based on the information of the layer 0. Information of the layer 0 may be transferred from the filtering unit 330 of the layer 0 to the filtering unit 310 of the layer 1, or may be transferred from the interlayer prediction unit 350 of the layer 1 to the filtering unit 310 of the layer 1. It may be.

The information transmitted from the layer 0 to the interlayer prediction unit 330 may be at least one of information about a unit parameter of the layer 0, motion information of the layer 0, texture information of the layer 0, and filter parameter information of the layer 0. have.

For convenience of explanation, assume a sub-prediction unit that predicts each inter-layer information in the inter-layer prediction unit 350.

For example, the interlayer predictor 350 may include a texture predictor 360, a motion predictor 370, a unit information predictor 380, and a parameter predictor 390.

When the reference block of the reference layer is reconstructed, the texture predictor 360 may use the texture of the reference block in the reference layer as a prediction value for the current block of the enhancement layer. In this case, the texture predictor 360 may be scaled by upsampling the texture of the reference block.

The motion predictor 370 may predict the current block of layer 1 (the current layer or the enhancement layer) by using the motion information of the layer 0 (the reference layer or the base layer). In this case, the motion predictor 370 may scale the motion information of the reference layer.

The unit information predictor 380 derives unit (CU, PU, and / or TU) information of the base layer and uses the unit information of the enhancement layer based on the unit information of the base layer or uses the unit information of the enhancement layer based on the unit information of the base layer. You can decide.

The parameter predictor 390 may derive the parameters used in the base layer to reuse them in the enhancement layer or predict the parameters for the enhancement layer based on the parameters used in the base layer.

As an example of interlayer prediction, interlayer texture prediction, interlayer motion prediction, interlayer unit information prediction, and interlayer parameter prediction have been described. However, the interlayer prediction applicable to the present invention is not limited thereto.

For example, the inter-layer prediction unit may further include a sub-prediction unit for performing inter-layer residual prediction and / or a sub-prediction unit for performing inter-layer differential prediction. Inter-layer difference prediction may be performed.

When the configuration of FIG. 3 is a configuration of an encoding apparatus, in layer 1, the prediction unit 300 may correspond to the prediction unit 110 of FIG. 1, and the filtering unit 310 may include the filtering unit 120 of FIG. 1. It can correspond to. In layer 0, the predictor 320 may correspond to the predictor 140 of FIG. 1, and the filter 330 may correspond to the filter 150 of FIG. 1.

In addition, if the configuration of FIG. 3 is a configuration of a decoding apparatus, in layer 1, the prediction unit 300 may correspond to the prediction unit 235 of FIG. 2, and the filtering unit 310 is the filtering unit 240 of FIG. 2. ) Can be used. In layer 0, the predictor 320 may correspond to the predictor 275 of FIG. 2, and the filter 330 may correspond to the filter 280 of FIG. 2.

As described above, in scalable video coding, inter-layer prediction for predicting information of a current layer using information of another layer may be performed.

In scalable video coding, inter-layer prediction takes advantage of the fact that the base layer and the current layer (enhanced layer) are likely to be similar. Similarly, it is likely that the filter applied to the base layer and the filter applied to the current layer are similar.

Therefore, a method of reusing filter information (eg, filter parameter) of the base layer to the current layer or transmitting or predicting filter information of the current layer based on the filter information of the base layer may be used.

In detail, in the above-described in-loop filters, the SAO information on the current layer may be transmitted based on the SAO information of the base layer or the SAO information may be applied to the current layer using the SAO information of the base layer.

In the base layer, it may be determined whether the SAO is applicable at the sequence parameter level, and whether or not the SAO may be applied in units of coding tree units (CTUs). The CTU means the highest CU among the CUs of the tree structure and may be a large coding unit (LCU). In the present specification, the CTU and the LCU are mixed and described as necessary so that the invention can be easily understood.

SAO includes a band offset and an edge offset. When SAO is applied, a band offset or an edge offset may be applied in units of samples.

The encoding apparatus may transmit information indicating whether to apply the band offset or the edge offset to the decoding apparatus. In this case, the encoding apparatus may instruct SAO to be performed in the current CTU by using SAO information of already processed CTUs around the current CTU. For example, when the information signaled from the encoding device indicates that the SAO information of the neighboring CTU is to be used, the decoding device may perform SAO in the current CTU using the SAO information of the left CTU or the upper CTU of the current CTU.

The value of the offset to apply may be signaled from the encoding device to the decoding device. The offset value may be determined for each CTU according to the category. In addition, the offset value may be signaled using respective information (syntax element) indicating the magnitude and the sign.

The band offset divides the pixel value into 32 bands, according to the pixel histogram, and then applies an offset for four consecutive bands. In the case of applying a band offset, the encoding apparatus determines four bands to apply the band offset, and indicates the offsets for the four bands and indicates the first of four bands (ie, the position of the start band). Start band information) may be transmitted.

4 is a diagram schematically illustrating an example of a method of applying a band offset.

Referring to FIG. 4, the pixel value range 400 of all pixels is uniformly divided into 32 bands.

The encoding apparatus indicates four consecutive bands (K, K + 1, K + 2, K + 3) to apply the band offset. The encoding device may specify four bands to which the band offset is to be applied by specifying the position of the start band 410.

The decoding apparatus may specify four consecutive bands K, K + 1, K + 2, and K + 3 to which the band offset is to be applied based on the received information. The decoding apparatus may receive information (start band information) specifying the start band 410 from the encoding apparatus. In this case, information specifying the location of the start band may be transmitted at the SAO syntax level.

The decoding apparatus may specify four consecutive bands including the start band 410 and apply a band offset to the four specified bands. The band offset to be applied may be determined for each band (category).

The encoding apparatus may transmit information specifying the offset value to be applied to each of the four bands to the decoding apparatus, and the decoding apparatus derives the offset value specified by the received information for each band, and the pixels belonging to each band. An offset value corresponding to may be applied. In this case, the offset value may be divided into information indicating a size and information indicating a sign and transmitted from the encoding apparatus to the decoding apparatus.

The decoding apparatus may apply an offset corresponding to a band to which the corresponding pixel belongs to a pixel belonging to four bands to which the band offset is applied.

Instead of applying the band offset to four consecutive bands, the band offset may be divided into a center band and a peripheral band to apply the offset to any one of the two band groups.

5 is a diagram schematically illustrating another example of a method of applying a band offset.

Referring to FIG. 5, the pixel value range 400 of all pixels is evenly divided into 32 bands.

A total of 32 bands may be divided into 16 central bands 510 and 16 bands 520-1 and 520-2.

The encoding apparatus may determine which band group among the center band 510 and the peripheral bands 520-1 and 520-2 to apply the offset to. In the case of applying the band offset, the encoding apparatus indicates information indicating which band group among the center band 510 and the peripheral bands 520-1 and 520-2 to apply the offset and an offset value to be applied for each band. Information may be transmitted to the decoding apparatus.

The decoding apparatus may receive information indicating the band group (center band or peripheral band) to which the offset is to be applied and information indicating the offset value for each band from the encoding apparatus. In the case of applying the band offset, the decoding apparatus may apply the offset value allocated to the band to which the pixel belongs to the pixel based on the received information.

The edge offset is divided into four classes of edges of the image as a whole in a block to which SAO is applied, for example, a CTU. For example, the class can be divided into four types: vertical edge, horizontal edge, 45 degree edge support, and 135 degree edge.

For each class, the encoding apparatus and the decoding apparatus may apply an offset value according to the corresponding category by dividing the pixel value of the pixel to which the edge offset is applied to the pixel value of the neighboring pixel into four categories. .

The categories are 1) if the pixel value of the target pixel is larger than the two surrounding pixels, 2) if the pixel value of the target pixel is equal to one pixel around and smaller than the other pixel, 3) the pixel value of the target pixel is one 4) If the pixel value of the target pixel is the same as the pixel and larger than the other pixel, it may be 4 categories.

6 is a diagram schematically illustrating a category of edge offsets.

When applying an edge offset. The category of the current pixel (target pixel) may be determined using two neighboring pixels of the current pixel. In this case, two neighboring pixels compared to determine a category may be determined according to a class to which a block to which SAO is applied, for example, a CTU.

For example, the vertical edge may be two pixels above and below the target pixel, the horizontal edge may be the left and right pixels, and the 45-degree edge may be the upper left and lower right pixels of the target pixel. In the case of an edge, the pixels may be lower left and upper right pixels.

In FIG. 6, C denotes a current pixel, and C-1 and C + 1 denote peripheral pixels of the current pixel. Depending on the direction (class) of the edge, C-1 and C + 1 may be left and right pixels of the current pixel, top and bottom pixels of the current pixel, or may be peripheral pixels of the current pixel in a diagonal direction.

Referring to FIG. 6, (6a) shows a case where two neighboring pixels of the current pixel have a larger value than the current pixel as the first category of the edge offset.

(6b) represents a second category of edge offset, in which one of two peripheral pixels of the current pixel has the same value as the current pixel, and the other pixel has a larger value than the current pixel.

(6c) represents a third category of edge offset, in which one pixel of two neighboring pixels of the current pixel has the same value as the current pixel, and the other pixel has a smaller value than the current pixel.

(6d) indicates a case where two peripheral pixels of the current pixel have a smaller value than the current pixel as the fourth category of the edge offset.

In FIG. 6, an edge offset is divided into four categories as an example. However, an edge offset is divided into five categories by adding a case in which two neighboring pixels of the current pixel have the same value as the current pixel. It may be.

The offset value applied to the edge offset may be derived according to the category of the current pixel when two peripheral pixels of the current pixel are selected according to the class, and a category is determined according to the relationship with the selected pixel.

In the case of applying the edge offset, the encoding apparatus may transmit information indicating to apply the edge offset and offset information according to the category to the decoding apparatus. For example, the encoding apparatus may transmit information specifying the offset value for each category to the decoding apparatus.

When applying the edge offset, the decoding apparatus may apply the offset to the target pixel according to the category to which the target pixel belongs. For example, the decoding apparatus may derive an offset value to be applied to the current picture according to the category of the current picturer based on the information about the offset value received from the encoding rule.

The offset value may be divided into information indicating a magnitude and information indicating a sign and transmitted from the encoding device to the decoding device.

When applying the SAO, the encoding apparatus may transmit a SAO type index that specifies which of the above-described edge offset and band offset to be applied to the decoding apparatus.

Table 1 shows an example of the SAO type index that specifies the SAO to be applied.

TABLE 1

In the example using Table 1, the encoding apparatus may transmit whether to apply SAO, band offset, or edge offset to the decoding apparatus through the SAO type index.

The decoding apparatus does not apply SAO when the received SAO type index is 0, and applies a band offset when the received SAO type index is 1. If the received SAO type index is 2, the edge offset may be applied.

In the embodiment of Table 1, the SAO type index indicates whether to apply a band offset or an edge offset. Therefore, when the band offset is applied, the information indicating the start band and the information indicating the offset value may be transmitted separately, and when the edge offset is applied, the information indicating the edge class and the offset value may be transmitted separately. have.

Meanwhile, unlike Table 1, the SAO type index may indicate both the class of the edge offset and the application band of the band offset.

Table 2 shows another example of the SAO type index that specifies the SAO to apply.

TABLE 2

Table 2 shows a SAO type index when SAO is performed by applying the band offset described in FIG. 5 and the edge offset described in FIG. 6.

In the embodiment of Table 2, the encoding apparatus uses the SAO type index from 0 to 6 to apply the SAO, edge offset, or band offset, as well as the class and band of the edge offset. Up to the application band of the offset can be indicated.

The decoding apparatus may perform SAO as indicated by the received SAO type index.

As described above, the SAO applied in the base layer and the SAO applied in the enhancement layer are likely to be similar. For example, if the class of the edge offset in the lower layer (base layer) was an edge of 90 degrees, the probability of being the 90 degree edge class of the edge offset in the current layer is higher than that of another class.

However, since the probability that the SAO property of the current layer is not the same as the SAO property of the base layer cannot be excluded, instead of applying the SAO information of the base layer to the current layer as it is, between the SAO information of the base layer and the SAO information of the current layer. Consider the method of increasing the coding efficiency by utilizing the difference of.

According to the present invention, among the limited candidates based on the SAO applied to the base layer, information indicating the SAO to be applied in the enhancement layer may be signaled.

For example, enhancement layer SAO candidates to be applied to an enhancement layer may be configured as SAOs similar to SAO applied to a base layer. The encoding apparatus may signal which of the enhancement layer SAO candidates to apply to the enhancement layer. The decoding apparatus may apply the SAO candidate signaled from the encoding apparatus to the current layer (enhanced layer).

When the edge offset is applied, the index of the class (edge type) for the enhancement layer may be readjusted, and the order of categories in the enhancement layer may be readjusted. For example, the highest ranking index (lowest index) may be assigned to the same edge type as that of the base layer. Furthermore, the ranking of indexes for edge types similar to the edge type of the base layer may be increased.

In addition, a method of reducing a transmission bit amount and increasing compression efficiency by signaling a difference value between the information of the SAO applied to the base layer and the information of the SAO applied to the current layer may be used.

Hereinafter, a method of applying SAO to an enhancement layer using SAO information of a base layer according to the present invention will be described in detail with reference to the drawings and tables.

(Example 1) SAO candidate configuration of an enhancement layer

In this embodiment, SAO candidates that can be applied to an enhancement layer may be limited to SAOs similar to those of SAO applied to a base layer.

For example, when (i) an edge offset is applied, (i) an edge type applied in the base layer may define a class of edge offset for the enhancement layer. Or (ii) the edge offset to the enhancement layer as two edge types: an edge type applied to the base layer and an edge type applied to the base layer by 45 degrees, or an edge type rotated 135 degrees to the edge type applied to the base layer. You can also qualify the class of. Or (iii) three edge types, one edge type applied to the base layer and two edge types similar to the edge type applied to the base layer (45 degree rotated edge type and 135 degree rotated edge type). You can also qualify the class.

In this case, which of (i) to (iii) to use may be predetermined between the encoding device and the decoding device. In addition, the encoding apparatus may determine which scheme (i) to (iii) to use, and may transmit information indicating the determined scheme to the decoding apparatus.

The encoding apparatus may specify an edge type (class) by indicating only to apply an edge offset in the case of (i) of applying a single edge type at the edge offset of the enhancement layer. In the case of (ii) and (iii) of applying a plurality of edge types in the edge offset of the enhancement layer, the encoding apparatus may separately signal which edge type to apply.

Meanwhile, instead of using all four classes (0 degree edge, 90 degree edge, 45 degree edge, 135 degree edge) for the edge offset in the enhancement layer, the category of the edge offset may be defined. For example, (a) the same category as the category applied in the base layer may be applied to the enhancement layer. Or (b) limit and use candidates to categories applied to the base layer and categories before or after the categories applied to the base layer, or (c) to limit candidates to two categories before and after the category applied to the base layer and the category applied to the base layer. Can also be used.

In this case, which method (a) to (c) is to be used may be predetermined between the encoding device and the decoding device. In addition, the encoding apparatus may determine which scheme (a) to (b) to use, and may transmit information indicating the determined scheme to the decoding apparatus.

In the case of (a) of applying a single category, if the edge offset is applied to the enhancement layer, the decoding apparatus may use the category applied to the base layer. In the case of (b) and (c) applying a plurality of categories, if an edge offset is applied to the enhancement layer, the decoding apparatus may apply any of the candidate categories according to the relationship between the current pixel (target pixel) and the surrounding pixel. Can be determined.

Example 2 Using the Difference Value of SAO Information

When using Table 1, applying an edge offset, information specifying the edge type (class) may be transmitted separately.

In this case, the edge type of the upper layer (current layer) is likely to be the same as or similar to the edge type of the lower layer (eg, the base layer). For example, if the edge type of the lower layer is a horizontal edge, the edge type of the current layer also has a high probability of being a horizontal edge and a diagonal edge more than a probability of being a vertical edge.

In the case of using Table 2, the SAO type has 7 types from 0 to 6. In the example of Table 2, if the SAO type of the lower layer (e.g., base layer) is a vertical (90 degree) edge of 2, the upper layer (current layer) is likely to have characteristics of vertical edges similar to the lower layer. The highest and subsequent diagonal edges (45-degree edge or 135-degree edge) are most likely to have characteristics, and the horizontal edge is unlikely to have a characteristic.

Therefore, when transmitting information indicating the edge type or SAO type of the current layer, the difference between the edge type of the lower layer and the edge type of the current layer or the difference between the SAO type of the lower layer and the SAO type of the current layer is determined. By transmitting, the bits required for transmission can be reduced and the compression rate can be improved.

For example, in an embodiment to which Table 1 applies, if the value of the index indicating the edge type of the base layer is i _B and the value of the index indicating the edge type of the current layer is i _C , the encoding apparatus may determine i _C and i _B. The difference value i _C -i _B may be signaled. The decoding apparatus adds the difference value between a i _B i and _C received from the encoding device to the i _B may derive an edge-type of the current layer.

In addition, in an embodiment of applying Table 2, if the value of the index indicating the SAO type of the base layer is i _{SAO_B} and the value of the index indicating the SAO type of the current layer is i _{SAO_C} , the encoding apparatus may determine i _{SAO_C} and i _{SAO_B} . A difference value (i _{SAO_C} -i _{SAO_B} ) may be signaled. The decoding apparatus adds the difference value between the i and i _{SAO_B SAO_C} received from the encoding device to the i _{SAO_B} can lead to edge-type of the current layer.

For example, if the SAO type of the lower layer (base layer) is 2 (90 degree edge of the edge offset) and the SAO type of the current layer (upper layer) is 3 (135 degree edge of the edge offset), then the encoding device may The difference 1 may be transmitted to the decoding apparatus.

The decoding apparatus may obtain the SAO type 3 of the current layer by adding the received value 1 to the SAO type 2 of the lower layer.

Example 3 Application of Difference Value Applying XOR Operation

When the SAO information of the upper layer (current layer) is transmitted based on the SAO information of the lower layer, an XOR (exclusive or) operation may be applied.

FIG. 7 is a diagram for briefly explaining an example of applying an XOR operation to SAO information of a lower layer and SAO information of an upper layer according to the present invention. In FIG. 7, a case where the SAO information is the SAO type of Table 2 will be described as an example.

Referring to FIG. 7, an XOR operation 730 is performed on the SAO type 710 of the lower layer (base layer) and the SAO type 720 of the upper layer (enhancement layer).

The encoding device transmits SAO information 740. In this case, the transmitted SAO information 740 is a value obtained by performing an XOR operation on the SAO type 710 of the base layer and the SAO type 720 of the enhancement layer.

The decoding apparatus may receive the SAO information 740 and inversely apply an XOR operation to derive the SAO type of the enhancement layer.

In the example of FIG. 7, the table 2 has been described in consideration of an example of applying the table 2. However, even when using the table 1, SAO information may be transmitted by applying the XOR operation.

In this case, SAO information transmitted to the decoding apparatus may be generated by applying an XOR operation between the edge type of the base layer and the edge type of the enhancement layer instead of the SAO type.

Example 4 Application of Gray Code Conversion

In the case of using the XOR operation, even if the difference between the base layer SAO information and the SAO information of the enhancement layer is small, the result of the XOR operation may be large.

For example, in the example of applying Table 2, if the SAO type of the base layer is 3 (135 degree edge of the edge offset) and the SAO type of the enhancement layer is 4 (45 degree edge of the edge offset), The difference is 1, but the result of the XOR operation is 7.

Therefore, the XOR operation may be performed after converting the SAO value of each layer to a gray code (gray code). The conversion to gray code converts two consecutive binary values one bit apart.

8 is a diagram for briefly explaining another example of applying an XOR operation to SAO information of a lower layer and SAO information of a higher layer according to the present invention. In FIG. 8, a case where the SAO information is the SAO type of Table 2 will be described as an example.

Referring to FIG. 8, the encoding apparatus converts the SAO type 810 of the lower layer (base layer) from the gray coder 820 to gray code before performing the XOR operation, and the SAO type of the upper layer (enhanced layer). 830 is converted from the gray coder 840 to the gray code.

The encoding apparatus performs XOR operation 850 on the SAO type value of the base layer and the enhancement layer SAO type value converted to gray code.

The encoding device transmits SAO information 860. In this case, the transmitted SAO information 860 is a value obtained by performing an XOR operation on the gray code-converted SAO type value of the base layer and the gray code-converted SAO type value of the enhancement layer.

In the example of FIG. 8, the example in which Table 2 is applied has been described. However, even when Table 1 is used, SAO information may be transmitted by applying gray code conversion and XOR operation.

In this case, the XOR operation is applied to the decoding apparatus by applying an XOR operation between a value obtained by converting an index indicating the edge type of the base layer to gray code instead of a SAO type and a value converting the index indicating the edge type of the enhancement layer into gray code. SAO information transmitted may be generated.

(Example 5) Reordering SAO Information

In the present embodiment, the index table indicating the SAO information of the upper layer may be rearranged according to the type (SAO type, class or category) of the SAO applied to the lower layer.

For example, when using Table 1 to specify the SAO type and separately signal the edge type (class) of the edge offset, the index indicating the edge type applied to the lower layer may be adjusted to a lower value (higher rank). .

If the SAO type of the lower layer was a modified edge as an edge offset, the SAO type of the upper layer is also likely to be an edge in the same direction or a diagonal direction as the lower layer. Therefore, in the SAO type table for the upper layer, efficiency can be improved by having vertical edges and diagonal edges appear in front of the table (low index).

In addition, when specifying the SAO type using Table 2, the index indicating the SAO type applied to the lower layer may be adjusted to a lower value (higher rank).

Specifically, in the case of specifying the SAO type using Table 1, if the SAO type applied to the lower layer (base layer) is i _{SAO_L} , the SAO type table to be applied to the upper layer (enhanced layer) indicates i _{SAO_L} . You can adjust the value of the index to a lower value. That is, i _{SAO_L} can be raised to a higher position (higher rank) than the position in Table 1.

For example, if the SAO type applied to the lower layer is an edge offset of 135 degrees, the corresponding index is 3 in Table 1, but in the upper layer, 1 may be assigned as the SAO type index.

In this case, it can be applied by increasing the edges of the angle similar to i _{SAO_B} , for example, 90 degrees edge or 135 degrees edge. For example, in Table 1, if an index is assigned in the order of 0 degree edge, 90 degree edge, 135 degree edge, and 45 degree edge, but 135 degree edge is applied in the lower layer, 135 degree edge, 90 degree edge, 0 degree in the upper layer Indexes may be assigned in the order of edge, 45 degree edge.

Even in an embodiment using Table 2, the edge type applied to the lower layer may be adjusted to have a higher priority or a lower index in the upper layer.

Table 3 is a table specifying the classes of edge offsets available in the example of applying Table 2.

TABLE 3

In Table 3, if the index is assigned in the order of 0 degree edge, 90 degree edge, 135 degree edge, and 45 degree edge, but the 135 degree edge is applied in the lower layer, the upper layer reorders the table as shown in Table 4 or Table 5. This can be applied to specify the class of edge offset.

TABLE 4

TABLE 5

The encoding apparatus may apply SAO to the base layer (lower layer) and reorder the SAO application table (eg, Table 1 or Table 2) as described above based on the applied SAO type (edge type). The encoding apparatus may signal an index indicating a SAO type (edge type) to be applied to an upper layer (enhanced layer) in the reordered SAO application table.

The decoding apparatus may apply SAO to the base layer (lower layer) and reorder the SAO application table (eg, Table 1 or Table 2) as described above based on the applied SAO type (edge type). The decoding apparatus receives an index indicating the SAO type (edge type) to be applied to the upper layer (enhanced layer) from the encoding apparatus, and selects the SAO type (edge type) indicated by the index received on the reordered SAO application table. It can be applied to the upper layer (enhancement layer).

(Example 6) Signaling of Inter Layer SAO

In the case of applying the SAO to the enhancement layer, any one of the above-described embodiments may be applied to the entire video, and the SAO method to be applied to the enhancement layer may be adaptively selected from the above-described embodiments.

In the case of adaptively selecting a SAO method to be applied to an enhancement layer, the encoding apparatus uses the SAO information of the base layer as a method of using some / or all of the above-described embodiments and the SAO information of the base layer. Information indicating which scheme to use among the configured SAO candidates may be signaled.

The decoding apparatus may select the SAO method indicated by the information transmitted by the encoding apparatus from among the SAO candidates and apply it to the enhancement layer (current layer).

The indicator indicating whether to use the SAO information of the base layer is called base_pred_sao_param_flag in this embodiment. In this example, although flag is shown for convenience of description, since one of a plurality of SAO methods may be indicated through base_pred_sao_param_flag, base_pred_sao_param_flag may be a kind of index or indicator. Accordingly, base_pred_sao_param_flag may also be referred to as base_pred_sao_param_idc.

Table 6 is a SAO scheme table that can be used to indicate the SAO to be applied in the enhancement layer according to the present embodiment.

TABLE 6

Referring to Table 6, the encoding apparatus may transmit a base_pred_sao_param_flag indicating how to perform SAO of the enhancement layer (current layer) using the SAO information of the base layer to the decoding apparatus.

base_pred_sao_param_flag indicates in Table 6 how to apply the enhancement layer (current layer) using the SAO information of the base layer.

The decoding apparatus may receive base_pred_sao_param_flag from the encoding apparatus and perform SAO on the enhancement layer using a method indicated by base_pred_sao_param_flag in Table 6.

In the example using Table 6, if the value of base_pred_sao_param_flag is 00, SAO is applied to the enhancement layer without using SAO information of another layer (eg, the base layer). In this case, parameters for SAO of the enhancement layer may be transmitted from the encoding device to the decoding device.

If the value of base_pred_sao_param_flag is 01, SAO information of the base layer is used, but as in the third embodiment, SAO may be performed on the enhancement layer based on the signaled information by applying an XOR operation. The specific method is as described in Example 3.

If the value of base_pred_sao_param_flag is 10, SAO information of the base layer is used, but SAO for the enhancement layer may be performed based on the signaled information by applying gray code conversion and XOR operation as in the fourth embodiment. The specific method is as described in Example 4.

If the value of base_pred_sao_param_flag is 11, SAO information of the base layer is used, but SAO information may be rearranged and applied to the enhancement layer as in the fifth embodiment. The specific method is as described in Example 5.

In Table 6, Table 1 may be used or Table 2 may be used in each method indicated by base_pred_sao_param_flag.

base_pred_sao_param_flag may be transmitted through extended syntax.

Table 7 shows an example of an adaptive parameter set (APS) in scalable extension as an example of a syntax structure in which base_pred_sao_param_flag is transmitted.

TABLE 7

Referring to Table 7, when the value of base_pred_sao_param_flag is not 0, sao_data_byte_count is transmitted to skip past data without parsing.

Meanwhile, base_pred_sao_param_flag may be signaled by using the SAO syntax in scalable extension in the scalable extension without using the APS in the scalable extension.

Table 8 briefly illustrates base_pred_sao_param_flag signaled in SAO syntax structure in scalable extension.

TABLE 8

In the example of Table 8, base_pred_sao_param_flag may indicate how to perform SAO of the enhancement layer (current layer) using SAO information of the base layer in the same manner as in the example of Table 6.

In addition, unlike the example of Table 6, in the example of Table 8, base_pred_sao_param_flag may be simply used as a flag indicating whether to use the SAO parameter of the base layer for SAO of the enhancement layer. In this case, if the value of base_pred_sao_param_flag is 0, the SAO parameter of the lower layer (for example, the base layer) is not applied to the upper layer (for example, the enhancement layer). If the value of base_pred_sao_param_flag is 1, the lower layer (for example, the base layer) SAO parameter of may be applied to SAO of a higher layer (eg, an enhancement layer) as it is.

9 is a flowchart schematically illustrating a method of applying SAO to an upper layer and transmitting SAO information according to the present invention.

Here, for the convenience of description, the encoding apparatus will be described as performing the operation of FIG. 9.

Referring to FIG. 9, the encoding apparatus applies SAO to an upper layer (S910). The encoding apparatus may apply the SAO to the upper layer based on the information about the SAO applied to the lower layer.

In this case, the information on the SAO applied to the lower layer may be related to which SAO type is applied to the lower layer or to which edge type edge offset is applied to the lower layer.

The encoding apparatus may determine the SAO to be applied to the upper layer by giving priority to the SAO applied to the lower layer.

For example, when determining the SAO to be applied to the upper layer on the lookup table shown in Table 2, the encoding apparatus may reassign the index so that the SAO type applied to the lower layer has a low index. Alternatively, when determining the SAO to be applied to the upper layer on the lookup table shown in Table 3, the encoding apparatus may reallocate the index such that the edge type (class) applied to the lower layer has a low index.

In addition, the encoding apparatus may limit candidates of SAO to be applied to a higher layer to a predetermined number or range. For example, when six SAO types are applied to a lower layer as shown in Table 2, the encoding apparatus prioritizes the SAO types applied to the lower layer or takes fewer than six SAO types in consideration of the statistical frequency of the SAO types. It can be limited to candidates applicable to. The encoding apparatus may determine the SAO type to apply to the upper layer among the limited candidates.

In addition, when four edge types are applied to the lower layer as shown in Table 3, the encoding apparatus prioritizes the edge type applied to the lower layer or takes more than four edge types in consideration of the statistical frequency of the edge type. It can also be limited to candidates applicable to. The encoding apparatus may determine an edge type to apply to the upper layer among the limited candidates.

Subsequently, the encoding apparatus may transmit SAO information (S920). The encoding apparatus may transmit information indicating SAO applied to the upper layer, that is, SAO indication information, to the decoding apparatus.

The SAO indication information may include difference value information indicating a difference between the SAO applied to the lower layer and the SAO applied to the upper layer. Accordingly, the SAO applied to the upper layer may be specified by the difference value included in the SAO applied to the lower layer and the SAO indication information.

In this case, the difference value may be a difference between the SAO type applied to the lower layer and the SAO type applied to the upper layer in the example using Table 2. In addition, in the case of using Table 1, the difference value may be a difference between an edge type (class) applied to a lower layer and an edge type (class) applied to an upper layer.

Meanwhile, the SAO indication information may be information generated by performing an XOR operation on the information indicating the SAO applied to the lower layer and the information indicating the SAO applied to the upper layer. In this case, the information indicating the SAO may be a SAO type or an edge type.

In addition, the encoding apparatus may gray code convert the information indicating the SAO applied to the lower layer, and gray code convert the information indicating the SAO applied to the upper layer, and then perform XOR operation on the gray code converted values to generate SAO indication information. It may be.

When the SAO type or the edge type is reassigned in step S910, the encoding apparatus may indicate the SAO applied to the upper layer based on the indices to which the SAO indication information is reassigned.

In addition, the encoding apparatus may indicate whether the SAO indication information is generated by the XOR operation, the gray code conversion and the XOR operation, or the reallocated SAO type / edge type included in or separately from the SAO indication information. Information indicating whether or not may be transmitted.

In FIG. 9, the above-described embodiments of the present disclosure have been described together, but it should be noted that the contents corresponding to the embodiments may be separately implemented or may be simultaneously implemented in some cases.

10 is a flowchart schematically illustrating a method of receiving SAO indication information indicating SAO to be applied to a higher layer and applying SAO to a higher layer according to the present invention.

For convenience of description, the decoding apparatus will be described as performing the operation of FIG. 10.

Referring to FIG. 10, the decoding apparatus receives SAO indication information from the encoding apparatus (S1010). The SAO indication information indicates the SAO applied to the upper layer.

The SAO indication information may include difference value information indicating a difference between the SAO applied to the lower layer and the SAO applied to the upper layer. Accordingly, the SAO applied to the upper layer may be specified by the difference value included in the SAO applied to the lower layer and the SAO indication information.

In this case, the difference value may be a difference between the SAO type applied to the lower layer and the SAO type applied to the upper layer in the example using Table 2. In addition, in the case of using Table 1, the difference value may be a difference between an edge type (class) applied to a lower layer and an edge type (class) applied to an upper layer.

Meanwhile, the SAO indication information may be information generated by performing an XOR operation on the information indicating the SAO applied to the lower layer and the information indicating the SAO applied to the upper layer. In this case, the information indicating the SAO may be a SAO type or an edge type.

In addition, the SAO indication information may be generated by gray code converting the information indicating the SAO applied to the lower layer, and gray code converting the information indicating the SAO applied to the upper layer, and then performing XOR operation on the gray code converted values. have.

The index indicating the SAO type or edge type that can be applied to the upper layer can be reassigned based on the SAO applied to the lower layer. In this case, the SAO indication information indicates the SAO applied to the upper layer based on the reassigned indexes. You may.

Also, included in or separately from the SAO indication information, indicates whether the SAO indication information is generated by XOR operation, gray code conversion and XOR operation, or indicates a reallocated SAO type / edge type. Information may be transmitted.

The decoding apparatus applies SAO to an upper layer (S1020). The decoding apparatus may apply the SAO to the upper layer based on the received SAO indication information and the information about the SAO applied to the lower layer.

The information about the SAO applied to the lower layer may be related to which SAO type is applied to the lower layer or to which edge type edge offset is applied to the lower layer.

If the SAO indication information includes difference value information indicating a difference between the SAO applied to the lower layer and the SAO applied to the upper layer, the SAO applied to the higher layer is determined by the difference value included in the SAO indication information applied to the lower layer. Can be specified. The decoding apparatus may apply the specified SAO to the upper layer.

As described above, the difference value may be a difference in SAO type or a difference in edge type.

SAO to be applied to the upper layer may be determined by giving priority to SAO applied to the lower layer.

For example, when determining the SAO to be applied to the upper layer on the lookup table shown in Table 2, the index may be reassigned so that the SAO type applied to the lower layer has a lower index. Alternatively, when determining the SAO to be applied to the upper layer on the lookup table shown in Table 3, the index may be reassigned so that the edge type (class) applied to the lower layer has a lower index.

In this case, the decoding apparatus may reassign the index for the SAO to be applied to the upper layer, and then apply the SAO type or edge type corresponding to the index indicated by the SAO indication information to the upper layer.

In addition, candidates of SAO to be applied to a higher layer may be limited to a predetermined number or range. For example, when six SAO types are applied to the lower layer as shown in Table 2, less than six SAO types may be applied to the upper layer by giving priority to the SAO type applied to the lower layer or considering the statistical frequency of the SAO types. Can be limited to candidates. The decoding apparatus may apply the SAO type specified by the SAO indication information and the SAO applied to the lower layer among the limited candidates to the upper layer.

In addition, when four edge types are applied to the lower layer as shown in Table 3, less than four edge types may be applied to the upper layer by giving priority to the edge type applied to the lower layer or considering the statistical frequency of the edge types. It may be limited to candidates. The decoding apparatus may apply the SAO indication information and the SAO type specified by the SAO applied to the lower layer among the limited candidates to the upper layer.

In FIG. 10, the above-described embodiments of the present disclosure have been described together, but it should be noted that the contents corresponding to the embodiments may be separately implemented or may be simultaneously implemented in some cases.

In the present specification, for convenience of description, the information is transmitted from the encoding apparatus and the decoding apparatus receives the description, but the present invention is not limited thereto. In the present specification, the transmission / reception of information may mean transmission / reception on a network, and may mean storage on a recording medium and acquisition from a recording medium.

In addition, in the present specification, in order to facilitate understanding of the present invention, the upper / lower layer, the current / reference layer, and the enhancement / base layer are mixed, but in the present specification, the upper layer, the current layer, and the enhancement layer may use the same layer. The lower layer, the reference layer, and the base layer may also mean the same layer.

In the present specification, for convenience of description, an array of samples reconstructed at a specific time point (for example, a picture order count (POC) or an access unit (AU)) for each layer in a multi-layer structure in which scalable video coding is supported is referred to as a 'picture. '

In this regard, the entire sample array reconstructed or reconstructed at a specific time in the decoded and output layer (current layer) may be called a picture and may be distinguished from the reconstructed or reconstructed sample array of the referenced layer. The sample array reconstructed or reconstructed at a specific time point in the referenced layer may be referred to as a representation, a reference layer picture, a reference layer sample array, a reference layer texture, or the like. In this case, one decoded picture reconstructed in the current layer may be output for one AU.

In the exemplary system described above, the methods are described based on a flowchart as a series of steps or blocks, but the invention is not limited to the order of steps, and certain steps may occur in a different order or concurrently with other steps than those described above. Can be. In addition, the above-described embodiments include examples of various aspects. Accordingly, it is intended that the present invention cover all other replacements, modifications and variations that fall within the scope of the following claims.

Claims (20)

As a SAO method in scalable video coding,
Applying the SAO to the upper layer based on the information about the SAO applied to the lower layer; And
And transmitting SAO indication information indicating SAO applied to the upper layer. The method of claim 1, wherein the SAO indication information includes information indicating a difference between a SAO applied to the lower layer and a SAO applied to the upper layer.
The SAO method applied to the upper layer is characterized by the information on the SAO applied to the lower layer and the SAO indication information. The SAO method of claim 2, wherein the SAO indication information includes information indicating a difference between a SAO type applied to the lower layer and a SAO type applied to the upper layer. The SAO method of claim 2, wherein the SAO indication information includes information indicating a difference between a class of an edge offset applied to the lower layer and a class of an edge offset applied to the upper layer. The method of claim 1, wherein the SAO indication information,
Information indicating the SAO type applied to the lower layer; and
SAO method, characterized in that the information generated by performing an XOR (Exclusive OR) operation indicating the SAO type applied to the upper layer. The method of claim 1, wherein the SAO indication information,
A value obtained by gray code converting information indicating a SAO type applied to the lower layer; and
And the information indicating the SAO type applied to the upper layer is information generated by performing an XOR operation on a gray code converted value. The method of claim 1, wherein in applying the SAO to the upper layer,
Reallocates indexes indicating SAO types such that the SAO type applied to the lower layer has a low index,
And transmitting the SAO indication information by using the reassigned indexes to transmit information indicating the SAO type applied to the upper layer. The method of claim 1, wherein in applying the SAO to the upper layer,
Reallocates an index indicating the class of the edge offset such that the class of the edge offset applied to the lower layer has a low index,
And transmitting the SAO indication information by using the reassigned indexes to transmit information indicating a class of an edge offset applied to the upper layer. The method of claim 1, wherein in applying the SAO to the upper layer, one of the upper layer edge type candidates is selected and applied.
And the upper layer edge type candidates are composed of some edge types among the edge types available in the lower layer. As a sample adaptive offset (SAO) method in scalable video coding,
Receiving SAO indication information indicating SAO applied to an upper layer; And
And applying the SAO to the upper layer based on the SAO indication information and the SAO information applied to the lower layer. The method of claim 10, wherein the SAO indication information includes information indicating a difference between a SAO applied to the lower layer and a SAO applied to the upper layer.
The SAO method applied to the upper layer is characterized by the information on the SAO applied to the lower layer and the SAO indication information. The SAO method of claim 2, wherein the SAO indication information includes information indicating a difference between a SAO type applied to the lower layer and a SAO type applied to the upper layer. The SAO method of claim 2, wherein the SAO indication information includes information indicating a difference between a class of an edge offset applied to the lower layer and a class of an edge offset applied to the upper layer. The method of claim 1, wherein the SAO indication information,
Information indicating the SAO type applied to the lower layer; and
SAO method, characterized in that the information generated by performing an XOR (Exclusive OR) operation indicating the SAO type applied to the upper layer. The method of claim 1, wherein the SAO indication information,
A value obtained by gray code converting information indicating a SAO type applied to the lower layer; and
And the information indicating the SAO type applied to the upper layer is information generated by performing an XOR operation on a gray code converted value. The method of claim 1, wherein in applying the SAO to the upper layer,
Reallocates indexes indicating SAO types such that the SAO type applied to the lower layer has a low index,
And transmitting the SAO indication information by using the reassigned indexes to transmit information indicating the SAO type applied to the upper layer. The method of claim 1, wherein in applying the SAO to the upper layer,
Reallocates an index indicating the class of the edge offset such that the class of the edge offset applied to the lower layer has a low index,
And transmitting the SAO indication information by using the reassigned indexes to transmit information indicating a class of an edge offset applied to the upper layer. The method of claim 1, wherein in applying the SAO to the upper layer, one of the upper layer edge type candidates is selected and applied.
And the upper layer edge type candidates are composed of some edge types among the edge types available in the lower layer. A first filter unit applying SAO to a lower layer;
A second filter unit which applies the SAO to the upper layer based on the information about the SAO applied to the lower layer,
And transmitting SAO indication information indicating SAO applied to the upper layer to a decoding device. A first filter unit applying SAO to a lower layer;
A second filter unit which applies the SAO to the upper layer based on the information about the SAO applied to the lower layer,
SAO indication information indicating SAO applied to the upper layer is transmitted from an encoding device.

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