Coding device, decoding device, and bit stream generation device

Abstract

To provide a coding device to which a filter that nips a block boundary and has an asymmetrical characteristic is applied.SOLUTION: The coding device includes: performing multiplication for a first block by using a plurality of first brightness filter coefficients as a multiplication value and multiplication for a second block by using a plurality of second brightness filter coefficients as a multiplication value, and thereby performing filter processing to a first boundary between the first block and the second block (S112); performing multiplication for a third block by using a plurality of first color difference filter coefficient as a multiplication value and multiplication for a fourth block by using a plurality of second collor difference filter coefficient as a multiplication value, and thereby performing the filtering processing to a second boundary between the third block and the fourth block, and selecting the plurality of first brightness filter coefficients and the plurality of second brightness filter coefficients asymmetrically with respect to the first boundary (S111); and selecting the plurality of first color difference filter coefficients and the plurality of second color difference filter coefficient symmetrically with respect to a second boundary.SELECTED DRAWING: Figure 13

Description

[Technical field]

[0001] The present disclosure relates to an encoding device, a decoding device, an encoding method, and a decoding method. [Background technology]

[0002] A video coding standard called High-Efficiency Video Coding (HEVC) has been standardized by the Joint Collaborative Team on Video Coding (JCT-VC). [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] H.265(ISO / IEC 23008-2 HEVC(High Efficiency Video Coding)) Summary of the Invention [Problem to be solved by the invention]

[0004] Further improvements in such encoding and decoding techniques are required.

[0005] Therefore, an object of the present disclosure is to provide an encoding device, a decoding device, an encoding method, or a decoding method that can achieve further improvements. [Means for solving the problem]

[0006] An encoding device according to an embodiment of the present disclosure includes a processing circuit and a memory connected to the processing circuit, and the processing circuit uses the memory to perform multiplication for a first block using a plurality of first luminance filter coefficients as multiplier values, and to perform multiplication for a second block using a plurality of second luminance filter coefficients as multiplier values, thereby changing values ​​of a plurality of luminance pixels in the first block and the second block, to perform a filter process on a first boundary between the first block and the second block, to perform multiplication for a third block using a plurality of first chrominance filter coefficients as multiplier values, and to perform multiplication for a fourth block using a plurality of second chrominance filter coefficients as multiplier values. a filtering process is performed on a second boundary between the third block and the fourth block by changing values ​​of a plurality of chrominance pixels in the third block and the fourth block by performing a filtering process on the second boundary between the third block and the fourth block, the plurality of first luma filter coefficients and the plurality of second luma filter coefficients are selected asymmetrically with respect to the first boundary, the plurality of first luma filter coefficients and the plurality of second luma filter coefficients are selected based on a prediction mode of the first block and a prediction mode of the second block and a quantization parameter, and the plurality of first chrominance filter coefficients and the plurality of second chrominance filter coefficients are selected symmetrically with respect to the second boundary.

[0007] A decoding device according to an aspect of the present disclosure includes a processing circuit and a memory connected to the processing circuit, and the processing circuit uses the memory to perform multiplication for a first block using a plurality of first luma filter coefficients as multiplier values, and to perform multiplication for a second block using a plurality of second luma filter coefficients as multiplier values, thereby changing values ​​of a plurality of luma pixels in the first block and the second block, to perform a filter process on a first boundary between the first block and the second block, perform multiplication for a third block using a plurality of first chroma filter coefficients as multiplier values, and perform multiplication for a fourth block using a plurality of second chroma filter coefficients as multiplier values. and performing a filtering process on a second boundary between the third block and the fourth block by changing values ​​of a plurality of chrominance pixels in the third block and the fourth block, wherein the plurality of first luminance filter coefficients and the plurality of second luminance filter coefficients are selected asymmetrically with respect to the first boundary, the plurality of first luminance filter coefficients and the plurality of second luminance filter coefficients are selected based on a prediction mode of the first block and a prediction mode of the second block and a quantization parameter, and the plurality of first chrominance filter coefficients and the plurality of second chrominance filter coefficients are selected symmetrically with respect to the second boundary.

[0008] Furthermore, these general or specific aspects may be realized by a system, a method, an integrated circuit, a computer program, or a recording medium such as a computer-readable CD-ROM, or may be realized by any combination of a system, a method, an integrated circuit, a computer program, and a recording medium. Effect of the Invention

[0009] The present disclosure can provide an encoding device, a decoding device, an encoding method, or a decoding method that can achieve further improvements. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a block diagram showing a functional configuration of a coding device according to the first embodiment. [Diagram 2] FIG. 2 is a diagram showing an example of block division according to the first embodiment. [Diagram 3] FIG. 3 is a table showing the transform basis functions corresponding to each transform type. [Figure 4A] FIG. 4A is a diagram showing an example of the shape of a filter used in ALF. [Figure 4B] FIG. 4B is a diagram showing another example of the shape of the filter used in the ALF. [Figure 4C] FIG. 4C is a diagram showing another example of the shape of the filter used in the ALF. [Figure 5A] FIG. 5A is a diagram showing 67 intra prediction modes in intra prediction. [Figure 5B] FIG. 5B is a flowchart for explaining an outline of the predicted image correction process by the OBMC process. [Figure 5C] FIG. 5C is a conceptual diagram for explaining an overview of the predicted image correction process by the OBMC process. [Figure 5D] FIG. 5D is a diagram showing an example of FRUC. [Figure 6] FIG. 6 is a diagram for explaining pattern matching (bilateral matching) between two blocks along a motion trajectory. [Figure 7] FIG. 7 is a diagram for explaining pattern matching (template matching) between a template in a current picture and a block in a reference picture. [Figure 8] FIG. 8 is a diagram for explaining a model assuming uniform linear motion. [Figure 9A] FIG. 9A is a diagram for explaining derivation of a motion vector for each sub-block based on motion vectors of a plurality of adjacent blocks. [Figure 9B] FIG. 9B is a diagram for explaining an overview of the motion vector derivation process in the merge mode. [Figure 9C] FIG. 9C is a conceptual diagram for explaining an overview of the DMVR process. [Figure 9D]FIG. 9D is a diagram for explaining an outline of a predicted image generating method using luminance correction processing by LIC processing. [Figure 10] FIG. 10 is a block diagram showing a functional configuration of a decoding device according to the first embodiment. As shown in FIG. [Figure 11] FIG. 11 is a flowchart of the deblocking filter process according to the first embodiment. [Figure 12] FIG. 12 is a diagram showing an example of a pixel arrangement on a block boundary according to the first embodiment. [Figure 13] FIG. 13 is a flowchart of the deblocking filter process according to the first embodiment. [Figure 14] FIG. 14 is a flowchart of the deblocking filter process according to the second embodiment. [Figure 15] FIG. 15 is a diagram showing the relationship between pixel positions in a block and errors according to the second embodiment. In FIG. [Figure 16] FIG. 16 is a flowchart of the deblocking filter process according to the third embodiment. [Figure 17] FIG. 17 is a diagram illustrating a transform basis of DCT-II according to the third embodiment. [Figure 18] FIG. 18 is a diagram illustrating a transformation base of the DST-VII according to the third embodiment. [Figure 19] FIG. 19 is a flowchart of the deblocking filter process according to the fourth embodiment. [Figure 20] FIG. 20 is a flowchart of the deblocking filter process according to the fifth embodiment. [Figure 21] FIG. 21 is a diagram showing an example of weights based on the intra prediction direction and the direction of a block boundary according to the fifth embodiment. [Figure 22] FIG. 22 is a flowchart of the deblocking filter process according to the sixth embodiment. [Diagram 23] FIG. 23 is a diagram showing an example of weights based on the quantization parameters according to the sixth embodiment. [Figure 24]FIG. 24 is a diagram showing the overall configuration of a content supply system that realizes a content distribution service. [Diagram 25] FIG. 25 is a diagram showing an example of a coding structure in scalable coding. [Figure 26] FIG. 26 is a diagram showing an example of a coding structure in scalable coding. [Figure 27] FIG. 27 is a diagram showing an example of a display screen of a web page. [Figure 28] FIG. 28 is a diagram showing an example of a display screen of a web page. [Figure 29] FIG. 29 is a diagram illustrating an example of a smartphone. [Diagram 30] FIG. 30 is a block diagram showing an example of the configuration of a smartphone. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] In the deblocking filter process of H.265 / HEVC, which is one of the image coding methods, a filter with symmetric characteristics is applied across the block boundary. As a result, when the error distribution is discontinuous, for example when the error of pixels located on one side of the block boundary is small and the error of pixels located on the other side of the block boundary is large, the efficiency of error reduction may decrease due to symmetric filtering. Here, the error is the difference in pixel values ​​between the original image and the reconstructed image.

[0012] An encoding device according to one aspect of the present disclosure includes a processor and a memory, and the processor uses the memory to determine asymmetric filter characteristics across a block boundary and perform deblocking filter processing using the determined filter characteristics.

[0013] According to this, the encoding device may be able to reduce errors by performing filtering with asymmetric filter characteristics across block boundaries.

[0014] For example, in determining the filter characteristics, the asymmetric filter characteristics may be determined so that the effect of the deblocking filter process is greater for pixels that are more likely to have an error from the original image.

[0015] This allows the encoding device to increase the effect of the filter process on pixels with large errors, which may further reduce the errors of the pixels. Also, the encoding device allows the encoding device to reduce the effect of the filter process on pixels with small errors, which may prevent the errors of the pixels from increasing.

[0016] For example, in determining the filter characteristics, the asymmetric filter characteristics may be determined by changing the filter coefficients of a reference filter asymmetrically across the block boundary.

[0017] For example, in determining the filter characteristics, asymmetric weights may be determined across the block boundary, and in the deblocking filter process, a filter calculation using filter coefficients may be performed, and the change in pixel value before and after the filter calculation may be weighted by the determined asymmetric weights.

[0018] For example, in determining the filter characteristics, an asymmetric offset value may be determined across the block boundary, and in the deblocking filter process, a filter operation using a filter coefficient may be performed, and the determined asymmetric offset value may be added to the pixel value after the filter operation.

[0019] For example, in determining the filter characteristics, an asymmetric reference value is determined across the block boundary, and in the deblocking filter process, a filter calculation is performed using a filter coefficient, and if the amount of change in pixel value before and after the filter calculation exceeds the reference value, the amount of change may be clipped to the reference value.

[0020] For example, in determining the filter characteristics, a condition for determining whether or not to perform the deblocking filter process may be set asymmetrically across the block boundary.

[0021] A decoding device according to one aspect of the present disclosure includes a processor and a memory, and the processor uses the memory to determine asymmetric filter characteristics across a block boundary and perform deblocking filter processing using the determined filter characteristics.

[0022] According to this, the decoding device may be able to reduce errors by performing filtering with asymmetric filter characteristics across a block boundary.

[0023] For example, in determining the filter characteristics, the asymmetric filter characteristics may be determined so that the effect of the deblocking filter process is greater for pixels that are more likely to have an error from the original image.

[0024] This allows the decoding device to increase the effect of the filter process on pixels with large errors, which may further reduce the errors of the pixels. Also, the decoding device allows the decoding device to reduce the effect of the filter process on pixels with small errors, which may prevent the errors of the pixels from increasing.

[0025] For example, in determining the filter characteristics, the asymmetric filter characteristics may be determined by changing the filter coefficients of a reference filter asymmetrically across the block boundary.

[0026] For example, in determining the filter characteristics, asymmetric weights may be determined across the block boundary, and in the deblocking filter process, a filter calculation using filter coefficients may be performed, and the change in pixel value before and after the filter calculation may be weighted by the determined asymmetric weights.

[0027] For example, in determining the filter characteristics, an asymmetric offset value may be determined across the block boundary, and in the deblocking filter process, a filter operation using a filter coefficient may be performed, and the determined asymmetric offset value may be added to the pixel value after the filter operation.

[0028] For example, in determining the filter characteristics, an asymmetric reference value is determined across the block boundary, and in the deblocking filter process, a filter calculation is performed using a filter coefficient, and if the amount of change in pixel value before and after the filter calculation exceeds the reference value, the amount of change may be clipped to the reference value.

[0029] For example, in determining the filter characteristics, a condition for determining whether or not to perform the deblocking filter process may be set asymmetrically across the block boundary.

[0030] An encoding method according to an aspect of the present disclosure determines filter characteristics that are asymmetric across a block boundary, and performs deblocking filtering using the determined filter characteristics.

[0031] According to this, the coding method may be able to reduce errors by performing filtering with asymmetric filter characteristics across block boundaries.

[0032] A decoding method according to an aspect of the present disclosure determines filter characteristics that are asymmetric across a block boundary, and performs a deblocking filter process having the determined filter characteristics.

[0033] According to this, the decoding method may be able to reduce errors by performing filtering with asymmetric filter characteristics across a block boundary.

[0034] An encoding device according to one aspect of the present disclosure includes a processor and a memory, and the processor uses the memory to determine asymmetric filter characteristics across a block boundary based on pixel values ​​across the block boundary, and performs deblocking filter processing using the determined filter characteristics.

[0035] According to this, the encoding device may be able to reduce errors by performing filtering with asymmetric filter characteristics across a block boundary, and may be able to determine appropriate filter characteristics based on pixel values ​​across a block boundary.

[0036] For example, the filter characteristics may be determined based on the difference between the pixel values.

[0037] For example, in determining the filter characteristics, the difference in the filter characteristics across the block boundary may be increased as the difference in the pixel values ​​increases.

[0038] This allows the encoding device to potentially prevent unnecessary smoothing from being performed when, for example, a block boundary coincides with the edge of an object in an image.

[0039] For example, in determining the filter characteristics, the difference in pixel values ​​may be compared with a threshold based on a quantization parameter, and if the difference in pixel values ​​is greater than the threshold, the difference in filter characteristics on either side of the block boundary may be made larger than if the difference in pixel values ​​is smaller than the threshold.

[0040] This enables the encoding device to determine filter characteristics that take into account the effect of the quantization parameter on the error.

[0041] For example, in determining the filter characteristics, the difference in the filter characteristics across the block boundary may be made smaller as the difference in the pixel values ​​increases.

[0042] This allows the decoding device to suppress the smoothing from being weakened due to asymmetry when, for example, block boundaries are subjectively noticeable, potentially suppressing degradation of subjective performance.

[0043] For example, the filter characteristics may be determined based on the variance of the pixel values.

[0044] A decoding device according to one aspect of the present disclosure includes a processor and a memory, and the processor uses the memory to determine asymmetric filter characteristics across a block boundary based on pixel values ​​across the block boundary, and performs deblocking filter processing using the determined filter characteristics.

[0045] According to this, the decoding device may be able to reduce errors by performing filtering with asymmetric filter characteristics across a block boundary, and may be able to determine appropriate filter characteristics based on the difference in pixel values ​​across a block boundary.

[0046] For example, the filter characteristics may be determined based on the difference between the pixel values.

[0047] For example, in determining the filter characteristics, the difference in the filter characteristics across the block boundary may be increased as the difference in the pixel values ​​increases.

[0048] This allows the decoding device to increase the effect of the filter process on pixels with large errors, which may further reduce the errors of the pixels. Also, the decoding device allows the decoding device to reduce the effect of the filter process on pixels with small errors, which may prevent the errors of the pixels from increasing.

[0049] For example, in determining the filter characteristics, the difference in pixel values ​​may be compared with a threshold based on a quantization parameter, and if the difference in pixel values ​​is greater than the threshold, the difference in filter characteristics on either side of the block boundary may be made larger than if the difference in pixel values ​​is smaller than the threshold.

[0050] This enables the decoding device to determine filter characteristics that take into account the effect of the quantization parameter on the error.

[0051] For example, in determining the filter characteristics, the difference in the filter characteristics across the block boundary may be made smaller as the difference in the pixel values ​​increases.

[0052] This allows the decoding device to potentially suppress unnecessary smoothing when, for example, a block boundary coincides with the edge of an object in an image.

[0053] For example, the filter characteristics may be determined based on the variance of the pixel values.

[0054] An encoding method according to an aspect of the present disclosure determines filter characteristics that are asymmetric across a block boundary based on pixel values ​​across the block boundary, and performs deblocking filter processing with the determined filter characteristics.

[0055] According to this, the encoding method may be able to reduce errors by performing filtering with asymmetric filter characteristics across a block boundary, and may determine appropriate filter characteristics based on the difference in pixel values ​​across the block boundary.

[0056] A decoding method according to an aspect of the present disclosure determines filter characteristics that are asymmetric across a block boundary based on pixel values ​​across the block boundary, and performs deblocking filter processing with the determined filter characteristics.

[0057] According to this, the decoding method may be able to reduce errors by performing filtering with asymmetric filter characteristics across a block boundary, and may determine appropriate filter characteristics based on differences in pixel values ​​across a block boundary.

[0058] An encoding device according to one aspect of the present disclosure includes a processor and a memory, and the processor uses the memory to determine asymmetric filter characteristics across a block boundary based on an angle between the prediction direction of intra prediction and the block boundary, and performs deblocking filter processing using the determined filter characteristics.

[0059] According to this, the encoding device may be able to reduce errors by performing filtering with asymmetric filtering characteristics across a block boundary, and may determine appropriate filtering characteristics based on an angle between the prediction direction of intra prediction and the block boundary.

[0060] For example, in determining the filter characteristics, the closer the angle is to perpendicular, the greater the difference in the filter characteristics on either side of the block boundary.

[0061] This allows the encoding device to increase the effect of the filter process on pixels with large errors, which may further reduce the errors of the pixels. Also, the encoding device allows the encoding device to reduce the effect of the filter process on pixels with small errors, which may prevent the errors of the pixels from increasing.

[0062] For example, in determining the filter characteristics, the difference in the filter characteristics on either side of the block boundary may be made smaller as the angle approaches horizontal.

[0063] This allows the encoding device to increase the effect of the filter process on pixels with large errors, which may further reduce the errors of the pixels. Also, the encoding device allows the encoding device to reduce the effect of the filter process on pixels with small errors, which may prevent the errors of the pixels from increasing.

[0064] A decoding device according to one aspect of the present disclosure includes a processor and a memory, and the processor uses the memory to determine asymmetric filter characteristics across a block boundary based on an angle between the prediction direction of intra prediction and the block boundary, and performs deblocking filter processing using the determined filter characteristics.

[0065] According to this, the decoding device may be able to reduce errors by performing filtering with asymmetric filter characteristics across a block boundary, and may be able to determine appropriate filter characteristics based on an angle between the prediction direction of intra prediction and the block boundary.

[0066] For example, in determining the filter characteristics, the closer the angle is to perpendicular, the greater the difference in the filter characteristics on either side of the block boundary.

[0067] This allows the decoding device to increase the effect of the filter process on pixels with large errors, which may further reduce the errors of the pixels. Also, the decoding device allows the decoding device to reduce the effect of the filter process on pixels with small errors, which may prevent the errors of the pixels from increasing.

[0068] For example, in determining the filter characteristics, the difference in the filter characteristics on either side of the block boundary may be made smaller as the angle approaches horizontal.

[0069] This allows the decoding device to increase the effect of the filter process on pixels with large errors, which may further reduce the errors of the pixels. Also, the decoding device allows the decoding device to reduce the effect of the filter process on pixels with small errors, which may prevent the errors of the pixels from increasing.

[0070] An encoding method according to one aspect of the present disclosure determines asymmetric filter characteristics across a block boundary based on an angle between the prediction direction of intra prediction and the block boundary, and performs deblocking filtering processing with the determined filter characteristics.

[0071] According to this, the coding method may be able to reduce errors by performing filtering with asymmetric filtering characteristics across a block boundary, and may determine appropriate filtering characteristics based on an angle between the prediction direction of intra prediction and the block boundary.

[0072] A decoding method according to one aspect of the present disclosure determines asymmetric filter characteristics across a block boundary based on an angle between the prediction direction of intra prediction and the block boundary, and performs deblocking filtering processing with the determined filter characteristics.

[0073] According to this, the decoding method may be able to reduce errors by performing filtering with asymmetric filtering characteristics across a block boundary, and may determine appropriate filtering characteristics based on an angle between the prediction direction of intra prediction and the block boundary.

[0074] An encoding device according to one aspect of the present disclosure includes a processor and a memory, and the processor uses the memory to determine asymmetric filter characteristics across a block boundary based on the position of a target pixel within a block, and performs a deblocking filter process on the target pixel having the determined filter characteristics.

[0075] According to this, the encoding device may be able to reduce errors by performing filtering with asymmetric filter characteristics across block boundaries, and may be able to determine appropriate filter characteristics based on the position of a target pixel within a block.

[0076] For example, the filter characteristics may be determined such that the effect of the filtering process is greater for pixels farther away from reference pixels for intra prediction.

[0077] This allows the encoding device to increase the effect of the filter process on pixels with large errors, which may further reduce the errors of the pixels. Also, the encoding device allows the encoding device to reduce the effect of the filter process on pixels with small errors, which may prevent the errors of the pixels from increasing.

[0078] For example, the filter characteristics may be determined such that the effect of the deblocking filtering process on a lower right pixel is greater than the effect of the deblocking filtering process on an upper left pixel.

[0079] This allows the encoding device to increase the effect of the filter process on pixels with large errors, which may further reduce the errors of the pixels. Also, the encoding device allows the encoding device to reduce the effect of the filter process on pixels with small errors, which may prevent the errors of the pixels from increasing.

[0080] A decoding device according to one aspect of the present disclosure includes a processor and a memory, and the processor uses the memory to determine asymmetric filter characteristics across a block boundary based on the position of a target pixel within a block, and performs a deblocking filter process on the target pixel having the determined filter characteristics.

[0081] According to this, the decoding device may be able to reduce errors by performing filtering with asymmetric filter characteristics across a block boundary, and may be able to determine appropriate filter characteristics based on the position of a target pixel within a block.

[0082] For example, the filter characteristics may be determined such that the effect of the filtering process is greater for pixels farther away from reference pixels for intra prediction.

[0083] This allows the decoding device to increase the effect of the filter process on pixels with large errors, which may further reduce the errors of the pixels. Also, the decoding device allows the decoding device to reduce the effect of the filter process on pixels with small errors, which may prevent the errors of the pixels from increasing.

[0084] For example, the filter characteristics may be determined such that the effect of the deblocking filtering process on a lower right pixel is greater than the effect of the deblocking filtering process on an upper left pixel.

[0085] This allows the decoding device to increase the effect of the filter process on pixels with large errors, which may further reduce the errors of the pixels. Also, the decoding device allows the decoding device to reduce the effect of the filter process on pixels with small errors, which may prevent the errors of the pixels from increasing.

[0086] An encoding method according to one aspect of the present disclosure determines asymmetric filter characteristics across a block boundary based on the position of a target pixel within a block, and performs a deblocking filter process on the target pixel having the determined filter characteristics.

[0087] According to this, the encoding method may be able to reduce errors by performing filtering with asymmetric filter characteristics across block boundaries, and may determine appropriate filter characteristics based on the position of a target pixel within a block.

[0088] A decoding method according to one aspect of the present disclosure determines asymmetric filter characteristics across a block boundary based on the position of a target pixel within a block, and performs a deblocking filter process on the target pixel having the determined filter characteristics.

[0089] According to this, the decoding method may be able to reduce errors by performing filtering with asymmetric filter characteristics across a block boundary, and may determine appropriate filter characteristics based on the position of a target pixel within a block.

[0090] An encoding device according to one aspect of the present disclosure includes a processor and a memory, and the processor uses the memory to determine asymmetric filter characteristics across a block boundary based on a quantization parameter, and performs deblocking filter processing using the determined filter characteristics.

[0091] According to this, the encoding device may be able to reduce errors by performing filtering with asymmetric filter characteristics across block boundaries, and may be able to determine appropriate filter characteristics based on a quantization parameter.

[0092] For example, in determining the filter characteristics, the filter characteristics may be determined such that the effect of the deblocking filter process increases as the quantization parameter increases.

[0093] This allows the encoding device to increase the effect of the filter process on pixels with large errors, which may further reduce the errors of the pixels. Also, the encoding device allows the encoding device to reduce the effect of the filter process on pixels with small errors, which may prevent the errors of the pixels from increasing.

[0094] For example, in determining the filter characteristics, the filter characteristics may be determined so that the change in influence accompanying the change in the quantization parameter of the upper left pixel is greater than the change in influence accompanying the change in the quantization parameter of the lower right pixel.

[0095] This allows the encoding device to increase the effect of the filtering process on pixels with large errors, potentially making it possible to further reduce errors in those pixels.

[0096] A decoding device according to one aspect of the present disclosure includes a processor and a memory, and the processor uses the memory to determine asymmetric filter characteristics across a block boundary based on a quantization parameter, and performs deblocking filter processing using the determined filter characteristics.

[0097] According to this, the decoding device may be able to reduce errors by performing filtering with asymmetric filter characteristics across a block boundary, and may be able to determine appropriate filter characteristics based on a quantization parameter.

[0098] For example, in determining the filter characteristics, the filter characteristics may be determined such that the effect of the deblocking filter process increases as the quantization parameter increases.

[0099] This allows the decoding device to increase the effect of the filter process on pixels with large errors, which may further reduce the errors of the pixels. Also, the decoding device allows the decoding device to reduce the effect of the filter process on pixels with small errors, which may prevent the errors of the pixels from increasing.

[0100] For example, in determining the filter characteristics, the filter characteristics may be determined so that the change in influence accompanying the change in the quantization parameter of the upper left pixel is greater than the change in influence accompanying the change in the quantization parameter of the lower right pixel.

[0101] This allows the decoding device to increase the effect of the filtering process on pixels with large errors, potentially making it possible to further reduce errors in those pixels.

[0102] An encoding method according to an aspect of the present disclosure may determine filter characteristics that are asymmetric across a block boundary based on a quantization parameter, and perform a deblocking filter process having the determined filter characteristics.

[0103] According to this, the coding method may be able to reduce errors by performing filtering with asymmetric filter characteristics across block boundaries, and may also be able to determine appropriate filter characteristics based on a quantization parameter.

[0104] A decoding method according to an aspect of the present disclosure determines filter characteristics that are asymmetric across a block boundary based on a quantization parameter, and performs deblocking filtering using the determined filter characteristics.

[0105] According to this, the decoding method may be able to reduce errors by performing filtering with asymmetric filter characteristics across a block boundary, and may also be able to determine appropriate filter characteristics based on a quantization parameter.

[0106] These comprehensive or specific aspects may be realized as a system, a method, an integrated circuit, a computer program, or a recording medium such as a computer-readable CD-ROM, or may be realized as any combination of a system, a method, an integrated circuit, a computer program, and a recording medium.

[0107] Hereinafter, the embodiment will be described in detail with reference to the drawings.

[0108] The embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, component arrangement and connection forms, steps, and order of steps shown in the following embodiments are merely examples and are not intended to limit the scope of the claims. Furthermore, among the components in the following embodiments, components that are not described in an independent claim showing a top concept are described as optional components.

[0109] (Embodiment 1) First, an overview of the first embodiment will be described as an example of an encoding device and a decoding device to which the processes and / or configurations described in each aspect of the present disclosure can be applied. However, the first embodiment is merely an example of an encoding device and a decoding device to which the processes and / or configurations described in each aspect of the present disclosure can be applied, and the processes and / or configurations described in each aspect of the present disclosure can also be implemented in encoding devices and decoding devices different from the first embodiment.

[0110] When applying the processing and / or configurations described in each aspect of the present disclosure to the first embodiment, for example, any of the following may be performed.

[0111] (1) For the encoding device or the decoding device of the first embodiment, among the multiple components constituting the encoding device or the decoding device, components corresponding to the components described in each aspect of the present disclosure are replaced with the components described in each aspect of the present disclosure.

[0112] (2) In the encoding device or decoding device of the first embodiment, any modification such as addition, replacement, or deletion of functions or processes performed by some of the components constituting the encoding device or decoding device is made, and then the components corresponding to the components described in each aspect of the present disclosure are replaced with the components described in each aspect of the present disclosure.

[0113] (3) Adding a process to the method implemented by the encoding device or decoding device of the first embodiment, and / or replacing or deleting some of the processes included in the method, and then replacing the process corresponding to the process described in each aspect of the present disclosure with the process described in each aspect of the present disclosure.

[0114] (4) Some of the components constituting the encoding device or decoding device of the first embodiment may be implemented in combination with components described in each aspect of the present disclosure, components having some of the functions of the components described in each aspect of the present disclosure, or components performing some of the processing performed by the components described in each aspect of the present disclosure.

[0115] (5) Implementing a component having some of the functions of some of the multiple components constituting the encoding device or decoding device of embodiment 1, or a component that performs some of the processing performed by some of the multiple components constituting the encoding device or decoding device of embodiment 1, in combination with a component described in each aspect of the present disclosure, a component having some of the functions of the component described in each aspect of the present disclosure, or a component that performs some of the processing performed by the component described in each aspect of the present disclosure.

[0116] (6) In the method implemented by the encoding device or the decoding device of the first embodiment, among a plurality of processes included in the method, a process corresponding to a process described in each aspect of the present disclosure is replaced with a process described in each aspect of the present disclosure.

[0117] (7) Some of the processes included in the method implemented by the encoding device or the decoding device of the first embodiment may be implemented in combination with the processes described in each aspect of the present disclosure.

[0118] It should be noted that the manner of implementing the processes and / or configurations described in each aspect of the present disclosure is not limited to the above examples. For example, the processes and / or configurations may be implemented in a device used for a purpose other than the video / image encoding device or video / image decoding device disclosed in the first embodiment, or the processes and / or configurations described in each aspect may be implemented independently. Furthermore, the processes and / or configurations described in different aspects may be implemented in combination.

[0119] [Outline of the encoding device] First, a description will be given of an overview of a coding device according to embodiment 1. Fig. 1 is a block diagram showing a functional configuration of a coding device 100 according to embodiment 1. The coding device 100 is a video / image coding device that codes a video / image on a block-by-block basis.

[0120] As shown in FIG. 1, the encoding device 100 is a device that encodes an image on a block-by-block basis, and includes a division unit 102, a subtraction unit 104, a transformation unit 106, a quantization unit 108, an entropy encoding unit 110, an inverse quantization unit 112, an inverse transformation unit 114, an addition unit 116, a block memory 118, a loop filter unit 120, a frame memory 122, an intra prediction unit 124, an inter prediction unit 126, and a prediction control unit 128.

[0121] The encoding device 100 is realized by, for example, a general-purpose processor and a memory. In this case, when the software program stored in the memory is executed by the processor, the processor functions as the division unit 102, the subtraction unit 104, the transformation unit 106, the quantization unit 108, the entropy coding unit 110, the inverse quantization unit 112, the inverse transformation unit 114, the addition unit 116, the loop filter unit 120, the intra prediction unit 124, the inter prediction unit 126, and the prediction control unit 128. The encoding device 100 may also be realized as one or more dedicated electronic circuits corresponding to the division unit 102, the subtraction unit 104, the transformation unit 106, the quantization unit 108, the entropy coding unit 110, the inverse quantization unit 112, the inverse transformation unit 114, the addition unit 116, the loop filter unit 120, the intra prediction unit 124, the inter prediction unit 126, and the prediction control unit 128.

[0122] Each component included in the encoding device 100 will be described below.

[0123] [Divided part] The division unit 102 divides each picture included in the input video into a plurality of blocks, and outputs each block to the subtraction unit 104. For example, the division unit 102 first divides a picture into blocks of a fixed size (e.g., 128x128). These fixed-size blocks may be called coding tree units (CTUs). The division unit 102 then divides each of the fixed-size blocks into blocks of a variable size (e.g., 64x64 or less) based on recursive quadtree and / or binary tree block division. These variable-size blocks may be called coding units (CUs), prediction units (PUs), or transform units (TUs). Note that in this embodiment, it is not necessary to distinguish between CUs, PUs, and TUs, and some or all of the blocks in a picture may be the processing units of CUs, PUs, and TUs.

[0124] Fig. 2 is a diagram showing an example of block division according to embodiment 1. In Fig. 2, solid lines represent block boundaries based on quadtree block division, and dashed lines represent block boundaries based on binary tree block division.

[0125] Here, the block 10 is a square block of 128x128 pixels (128x128 block). This 128x128 block 10 is first divided into four square 64x64 blocks (quadtree block division).

[0126] The top-left 64x64 block is further divided vertically into two rectangular 32x64 blocks, and the left 32x64 block is further divided vertically into two rectangular 16x64 blocks (binary tree block division). As a result, the top-left 64x64 block is divided into two 16x64 blocks 11 and 12 and a 32x64 block 13.

[0127] The top right 64x64 block is divided horizontally into two rectangular 64x32 blocks 14, 15 (binary tree block division).

[0128] The bottom left 64x64 block is divided into four square 32x32 blocks (quadtree block division). Of the four 32x32 blocks, the top left and bottom right blocks are further divided. The top left 32x32 block is divided vertically into two rectangular 16x32 blocks, and the right 16x32 block is further divided horizontally into two 16x16 blocks (binary tree block division). The bottom right 32x32 block is divided horizontally into two 32x16 blocks (binary tree block division). As a result, the bottom left 64x64 block is divided into a 16x32 block 16, two 16x16 blocks 17, 18, two 32x32 blocks 19, 20, and two 32x16 blocks 21, 22.

[0129] The bottom right 64x64 block 23 is not split.

[0130] 2, the block 10 is divided into 13 variable-sized blocks 11 to 23 based on recursive quad-tree and binary tree block division. Such division is sometimes called QTBT (quad-tree plus binary tree) division.

[0131] In Fig. 2, one block is divided into four or two blocks (quadtree or binary tree block division), but the division is not limited to this. For example, one block may be divided into three blocks (ternary tree block division). Division including such ternary tree block division is sometimes called MBT (multi type tree) division.

[0132] [Subtraction section] The subtraction unit 104 subtracts a prediction signal (prediction sample) from an original signal (original sample) for each block divided by the division unit 102. That is, the subtraction unit 104 calculates a prediction error (also called a residual error) of a block to be coded (hereinafter, referred to as a current block). Then, the subtraction unit 104 outputs the calculated prediction error to the conversion unit 106.

[0133] The original signal is an input signal to the encoding device 100, and is a signal representing an image of each picture constituting a moving image (for example, a luminance (luma) signal and two color difference (chroma) signals). Hereinafter, the signal representing the image may also be referred to as a sample.

[0134] [Conversion section] The transform unit 106 transforms the prediction error in the spatial domain into transform coefficients in the frequency domain, and outputs the transform coefficients to the quantization unit 108. Specifically, the transform unit 106 performs, for example, a predetermined discrete cosine transform (DCT) or discrete sine transform (DST) on the prediction error in the spatial domain.

[0135] The transform unit 106 may adaptively select a transform type from among a plurality of transform types, and transform the prediction errors into transform coefficients using a transform basis function corresponding to the selected transform type. Such a transform may be called an explicit multiple core transform (EMT) or an adaptive multiple transform (AMT).

[0136] The multiple transform types include, for example, DCT-II, DCT-V, DCT-VIII, DST-I, and DST-VII. Figure 3 is a table showing the transform basis functions corresponding to each transform type. In Figure 3, N indicates the number of input pixels. The selection of the transform type from among the multiple transform types may depend on, for example, the type of prediction (intra prediction and inter prediction) or the intra prediction mode.

[0137] Such information indicating whether EMT or AMT is applied (e.g., called an AMT flag) and information indicating the selected transformation type are signaled at the CU level. Note that the signaling of such information does not need to be limited to the CU level, and may be at other levels (e.g., sequence level, picture level, slice level, tile level, or CTU level).

[0138] Furthermore, the transform unit 106 may retransform the transform coefficients (transformation results). Such retransformation may be called AST (adaptive secondary transform) or NSST (non-separable secondary transform). For example, the transform unit 106 performs retransformation for each subblock (e.g., 4x4 subblock) included in a block of transform coefficients corresponding to intra-prediction errors. Information indicating whether or not to apply NSST and information regarding a transform matrix used in NSST are signaled at a CU level. Note that signaling of these pieces of information does not need to be limited to the CU level, and may be at other levels (e.g., sequence level, picture level, slice level, tile level, or CTU level).

[0139] Here, a separable transformation is a method in which the transformation is performed multiple times by separating the input into directions equal to the number of dimensions, and a non-separable transformation is a method in which when the input is multidimensional, two or more dimensions are treated as one dimension and the transformation is performed together.

[0140] For example, one example of a non-separable transformation is when the input is a 4x4 block, it is treated as a single array with 16 elements, and a 16x16 transformation matrix is ​​used to transform the array.

[0141] Another example of a non-separable transformation is the Hypercube Givens Transform, which treats a 4x4 input block as a single array with 16 elements and then performs Givens rotations on that array multiple times.

[0142] [Quantization section] The quantization unit 108 quantizes the transform coefficients output from the transform unit 106. Specifically, the quantization unit 108 scans the transform coefficients of the current block in a predetermined scanning order, and quantizes the transform coefficients based on a quantization parameter (QP) corresponding to the scanned transform coefficients. Then, the quantization unit 108 outputs the quantized transform coefficients of the current block (hereinafter, referred to as quantized coefficients) to the entropy coding unit 110 and the inverse quantization unit 112.

[0143] The predetermined order is an order for quantization / dequantization of the transform coefficients. For example, the predetermined scanning order is defined as ascending (low to high) or descending (high to low) frequency order.

[0144] The quantization parameter is a parameter that defines the quantization step (quantization width). For example, if the value of the quantization parameter increases, the quantization step also increases. In other words, if the value of the quantization parameter increases, the quantization error increases.

[0145] [Entropy coding part] The entropy coding unit 110 generates a coded signal (coded bit stream) by variable-length coding the quantized coefficients input from the quantization unit 108. Specifically, the entropy coding unit 110, for example, binarizes the quantized coefficients and arithmetically codes the binary signal.

[0146] [Dequantization section] The inverse quantization unit 112 inverse quantizes the quantized coefficients input from the quantization unit 108. Specifically, the inverse quantization unit 112 inverse quantizes the quantized coefficients of the current block in a predetermined scanning order. Then, the inverse quantization unit 112 outputs the inverse quantized transform coefficients of the current block to the inverse transform unit 114.

[0147] [Inverse conversion section] The inverse transform unit 114 restores the prediction error by inverse transforming the transform coefficients that are input from the inverse quantization unit 112. Specifically, the inverse transform unit 114 restores the prediction error of the current block by performing an inverse transform on the transform coefficients that corresponds to the transform performed by the transform unit 106. Then, the inverse transform unit 114 outputs the restored prediction error to the adder unit 116.

[0148] Note that the restored prediction error does not match the prediction error calculated by the subtraction unit 104 because information has been lost due to quantization. That is, the restored prediction error includes a quantization error.

[0149] [Addition section] The adder 116 reconstructs the current block by adding the prediction error input from the inverse transformer 114 and the prediction sample input from the prediction control unit 128. The adder 116 then outputs the reconstructed block to the block memory 118 and the loop filter unit 120. The reconstructed block is sometimes called a local decoded block.

[0150] [Block memory] The block memory 118 is a storage unit for storing blocks that are referenced in intra prediction and are in a picture to be coded (hereinafter, referred to as a current picture). Specifically, the block memory 118 stores the reconstructed blocks output from the adder 116.

[0151] [Loop filter section] The loop filter unit 120 applies a loop filter to the block reconstructed by the adder unit 116, and outputs the filtered reconstructed block to the frame memory 122. The loop filter is a filter (in-loop filter) used in the encoding loop, and includes, for example, a deblocking filter (DF), a sample adaptive offset (SAO), and an adaptive loop filter (ALF).

[0152] In ALF, a least squared error filter is applied to remove coding artifacts. For example, for each 2x2 sub-block in the current block, one filter is selected from among multiple filters based on local gradient direction and activity.

[0153] Specifically, first, sub-blocks (e.g., 2x2 sub-blocks) are classified into a plurality of classes (e.g., 15 or 25 classes). The classification of the sub-blocks is performed based on the gradient direction and activity. For example, a classification value C (e.g., C=5D+A) is calculated using a gradient direction value D (e.g., 0 to 2 or 0 to 4) and a gradient activity value A (e.g., 0 to 4). Then, based on the classification value C, the sub-blocks are classified into a plurality of classes (e.g., 15 or 25 classes).

[0154] The gradient direction value D is derived, for example, by comparing gradients in multiple directions (e.g., horizontal, vertical, and two diagonal directions), and the gradient activity value A is derived, for example, by adding gradients in multiple directions and quantizing the sum.

[0155] Based on the result of such classification, a filter for the sub-block is determined from among a plurality of filters.

[0156] The shape of the filter used in the ALF is, for example, a circularly symmetric shape. FIGS. 4A to 4C are diagrams showing a number of examples of the shape of the filter used in the ALF. FIG. 4A shows a 5×5 diamond-shaped filter, FIG. 4B shows a 7×7 diamond-shaped filter, and FIG. 4C shows a 9×9 diamond-shaped filter. Information indicating the shape of the filter is signaled at the picture level. Note that the signaling of the information indicating the shape of the filter does not need to be limited to the picture level, and may be at other levels (for example, the sequence level, slice level, tile level, CTU level, or CU level).

[0157] The on / off of ALF is determined, for example, at the picture level or the CU level. For example, whether or not to apply ALF is determined for luminance at the CU level, and whether or not to apply ALF is determined for chrominance at the picture level. Information indicating whether or not to apply ALF is signaled at the picture level or the CU level. Note that the signaling of information indicating whether or not to apply ALF is not limited to the picture level or the CU level, and may be at another level (for example, the sequence level, the slice level, the tile level, or the CTU level).

[0158] The coefficient sets of multiple selectable filters (e.g., up to 15 or 25 filters) are signaled at the picture level. Note that the signaling of the coefficient sets does not need to be limited to the picture level, but may be at other levels (e.g., sequence level, slice level, tile level, CTU level, CU level, or sub-block level).

[0159] [Frame memory] The frame memory 122 is a storage unit for storing reference pictures used in inter prediction, and may be called a frame buffer. Specifically, the frame memory 122 stores the reconstructed block filtered by the loop filter unit 120.

[0160] [Intra prediction section] The intra prediction unit 124 generates a prediction signal (intra prediction signal) by performing intra prediction (also called intra-screen prediction) of the current block with reference to a block in the current picture stored in the block memory 118. Specifically, the intra prediction unit 124 generates an intra prediction signal by performing intra prediction with reference to samples (e.g., luminance values, chrominance values) of blocks adjacent to the current block, and outputs the intra prediction signal to the prediction control unit 128.

[0161] For example, the intra prediction unit 124 performs intra prediction using one of a plurality of predefined intra prediction modes. The plurality of intra prediction modes includes one or more non-directional prediction modes and a plurality of directional prediction modes.

[0162] The one or more non-directional prediction modes include, for example, a planar prediction mode and a DC prediction mode defined in the H.265 / High-Efficiency Video Coding (HEVC) standard (Non-Patent Document 1).

[0163] The multiple directional prediction modes include, for example, 33 prediction modes defined in the H.265 / HEVC standard. The multiple directional prediction modes may include 32 prediction modes in addition to the 33 directions (a total of 65 directional prediction modes). FIG. 5A is a diagram showing 67 intra prediction modes (2 non-directional prediction modes and 65 directional prediction modes) in intra prediction. The solid arrows represent the 33 directions defined in the H.265 / HEVC standard, and the dashed arrows represent the additional 32 directions.

[0164] In addition, in the intra prediction of the chrominance block, the luminance block may be referenced. That is, the chrominance component of the current block may be predicted based on the luminance component of the current block. Such intra prediction may be called CCLM (cross-component linear model) prediction. An intra prediction mode of the chrominance block that refers to such a luminance block (for example, called a CCLM mode) may be added as one of the intra prediction modes of the chrominance block.

[0165] The intra prediction unit 124 may correct pixel values ​​after intra prediction based on the gradient of reference pixels in the horizontal / vertical directions. Intra prediction with such correction may be called position dependent intra prediction combination (PDPC). Information indicating whether or not PDPC is applied (e.g., called a PDPC flag) is signaled, for example, at a CU level. Note that the signaling of this information does not need to be limited to the CU level, and may be at other levels (e.g., sequence level, picture level, slice level, tile level, or CTU level).

[0166] [Inter prediction section] The inter prediction unit 126 generates a prediction signal (inter prediction signal) by performing inter prediction (also called inter prediction) of the current block with reference to a reference picture stored in the frame memory 122 and different from the current picture. The inter prediction is performed in units of the current block or a sub-block (e.g., 4x4 block) in the current block. For example, the inter prediction unit 126 performs motion estimation in the reference picture for the current block or the sub-block. Then, the inter prediction unit 126 generates an inter prediction signal of the current block or the sub-block by performing motion compensation using motion information (e.g., a motion vector) obtained by the motion estimation. Then, the inter prediction unit 126 outputs the generated inter prediction signal to the prediction control unit 128.

[0167] The motion information used for the motion compensation is signaled. For the signaling of the motion vector, a motion vector predictor may be used, i.e. the difference between the motion vector and the motion vector predictor may be signaled.

[0168] In addition, the inter prediction signal may be generated using not only the motion information of the current block obtained by motion search, but also the motion information of the adjacent block. Specifically, the inter prediction signal may be generated for each sub-block in the current block by performing weighted addition of the prediction signal based on the motion information obtained by motion search and the prediction signal based on the motion information of the adjacent block. Such inter prediction (motion compensation) may be called OBMC (overlapped block motion compensation).

[0169] In such an OBMC mode, information indicating the size of a sub-block for OBMC (e.g., called OBMC block size) is signaled at the sequence level. Also, information indicating whether or not to apply the OBMC mode (e.g., called OBMC flag) is signaled at the CU level. Note that the signaling level of these pieces of information does not need to be limited to the sequence level and CU level, and may be other levels (e.g., picture level, slice level, tile level, CTU level, or sub-block level).

[0170] The OBMC mode will now be described in more detail. Figures 5B and 5C are a flowchart and a conceptual diagram for explaining an overview of the predicted image correction process in the OBMC process.

[0171] First, a predicted image (Pred) is obtained by normal motion compensation using a motion vector (MV) assigned to a block to be coded.

[0172] Next, the motion vector (MV_L) of the already-encoded left adjacent block is applied to the block to be encoded to obtain a predicted image (Pred_L), and the predicted image is weighted and superimposed with Pred_L to perform a first correction of the predicted image.

[0173] Similarly, the motion vector (MV_U) of the already-encoded adjacent block above is applied to the block to be encoded to obtain a predicted image (Pred_U), and the predicted image that has been corrected the first time is weighted and overlaid with Pred_U to perform a second correction of the predicted image, which is then used as the final predicted image.

[0174] Although a two-stage correction method using the left adjacent block and the upper adjacent block has been described here, it is also possible to configure a method in which more than two stages of correction are performed using the right adjacent block or the lower adjacent block.

[0175] The area in which overlapping is performed does not have to be the entire pixel area of ​​the block, but may be only a part of the area near the block boundary.

[0176] Note that although the above describes the process of correcting a predicted image from one reference picture, the process is similar when correcting a predicted image from multiple reference pictures. After obtaining corrected predicted images from each reference picture, the obtained predicted images are then overlaid to obtain the final predicted image.

[0177] The block to be processed may be a prediction block unit, or a sub-block unit obtained by further dividing the prediction block.

[0178] As a method of determining whether or not to apply OBMC processing, for example, there is a method of using obmc_flag, which is a signal indicating whether or not to apply OBMC processing. As a specific example, in an encoding device, it is determined whether or not the encoding target block belongs to an area with complex motion, and if it belongs to an area with complex motion, a value of 1 is set as obmc_flag and encoding is performed by applying OBMC processing, and if it does not belong to an area with complex motion, a value of 0 is set as obmc_flag and encoding is performed without applying OBMC processing. On the other hand, in a decoding device, by decoding obmc_flag described in a stream, whether or not to apply OBMC processing is switched according to the value, and decoding is performed.

[0179] In addition, the motion information may be derived on the decoding device side without being signaled. For example, a merge mode defined in the H.265 / HEVC standard may be used. Also, for example, the motion information may be derived by performing motion estimation on the decoding device side. In this case, the motion estimation is performed without using pixel values ​​of the current block.

[0180] Here, a mode in which motion estimation is performed on the decoding device side will be described. This mode in which motion estimation is performed on the decoding device side is sometimes called a pattern matched motion vector derivation (PMMVD) mode or a frame rate up-conversion (FRUC) mode.

[0181] An example of the FRUC process is shown in FIG. 5D. First, a list of multiple candidates (which may be the same as the merge list) each having a predicted motion vector is generated by referring to the motion vectors of encoded blocks spatially or temporally adjacent to the current block. Next, a best candidate MV is selected from multiple candidate MVs registered in the candidate list. For example, an evaluation value of each candidate included in the candidate list is calculated, and one candidate is selected based on the evaluation value.

[0182] Then, based on the motion vector of the selected candidate, a motion vector for the current block is derived. Specifically, for example, the motion vector of the selected candidate (best candidate MV) is derived as it is as the motion vector for the current block. Also, for example, the motion vector for the current block may be derived by performing pattern matching in the surrounding area of ​​the position in the reference picture corresponding to the motion vector of the selected candidate. That is, a search is performed in the surrounding area of ​​the best candidate MV in the same manner, and if there is an MV with a better evaluation value, the best candidate MV may be updated to the MV, and the MV may be set as the final MV of the current block. It is also possible to configure the system without performing this process.

[0183] The same processing may be performed when processing is performed in sub-block units.

[0184] The evaluation value is calculated by finding a difference value of the reconstructed image by pattern matching between an area in a reference picture corresponding to the motion vector and a predetermined area. The evaluation value may be calculated using information other than the difference value.

[0185] As the pattern matching, a first pattern matching or a second pattern matching is used. The first pattern matching and the second pattern matching are sometimes called bilateral matching and template matching, respectively.

[0186] In the first pattern matching, pattern matching is performed between two blocks in two different reference pictures that are along the motion trajectory of the current block. Therefore, in the first pattern matching, an area in another reference picture along the motion trajectory of the current block is used as a predetermined area for calculating the evaluation value of the above-mentioned candidate.

[0187] FIG. 6 is a diagram for explaining an example of pattern matching (bilateral matching) between two blocks along a motion trajectory. As shown in FIG. 6, in the first pattern matching, two motion vectors (MV0, MV1) are derived by searching for a pair of two blocks that are along the motion trajectory of a current block (Cur block) and are in two different reference pictures (Ref0, Ref1) that best match each other. Specifically, for the current block, a difference is derived between a reconstructed image at a designated position in a first coded reference picture (Ref0) designated by a candidate MV and a reconstructed image at a designated position in a second coded reference picture (Ref1) designated by a symmetric MV obtained by scaling the candidate MV by a display time interval, and an evaluation value is calculated using the obtained difference value. It is preferable to select the candidate MV with the best evaluation value among a plurality of candidate MVs as the final MV.

[0188] Under the assumption of continuous motion trajectories, the motion vectors (MV0, MV1) pointing to two reference blocks are proportional to the temporal distances (TD0, TD1) between the current picture (Cur Pic) and the two reference pictures (Ref0, Ref1). For example, if the current picture is located between two reference pictures in time and the temporal distances from the current picture to the two reference pictures are equal, the first pattern matching derives bidirectional motion vectors that are mirror-symmetric.

[0189] In the second pattern matching, pattern matching is performed between a template in the current picture (a block adjacent to the current block in the current picture (e.g., an upper and / or left adjacent block)) and a block in the reference picture. Therefore, in the second pattern matching, a block adjacent to the current block in the current picture is used as a predetermined area for calculating the evaluation value of the above-mentioned candidate.

[0190] Fig. 7 is a diagram for explaining an example of pattern matching (template matching) between a template in a current picture and a block in a reference picture. As shown in Fig. 7, in the second pattern matching, a motion vector of a current block is derived by searching in a reference picture (Ref0) for a block that best matches a block adjacent to a current block (Cur block) in a current picture (Cur Pic). Specifically, for the current block, a difference is derived between a reconstructed image of both or either of the left adjacent and upper adjacent coded areas and a reconstructed image at the same position in a coded reference picture (Ref0) specified by a candidate MV, an evaluation value is calculated using the obtained difference value, and a candidate MV with the best evaluation value among a plurality of candidate MVs is selected as a best candidate MV.

[0191] Information indicating whether such a FRUC mode is applied (e.g., when the FRUC flag is true) is signaled at the CU level. Also, when the FRUC mode is applied (e.g., when the FRUC flag is true), information indicating a pattern matching method (first pattern matching or second pattern matching) (e.g., when the FRUC mode flag is true) is signaled at the CU level. Note that the signaling of such information does not need to be limited to the CU level, and may be at other levels (e.g., sequence level, picture level, slice level, tile level, CTU level, or subblock level).

[0192] Here, a mode in which a motion vector is derived based on a model assuming uniform linear motion will be described. This mode is sometimes called a BIO (bi-directional optical flow) mode.

[0193] FIG. 8 is a diagram for explaining a model assuming uniform linear motion. In FIG. x ,v y) denotes a velocity vector, and τ0 and τ1 denote the temporal distance between the current picture (CurPic) and two reference pictures (Ref0, Ref1), respectively. (MVx0,MVy0) denotes a motion vector corresponding to the reference picture Ref0, and (MVx1,MVy1) denotes a motion vector corresponding to the reference picture Ref1.

[0194] At this time, the velocity vector (v x ,v y Under the assumption of uniform linear motion of the object, (MVx0,MVy0) and (MVx1,MVy1) are respectively (v x τ0,v y τ0) and (-v x τ1,-v y τ1), and the following optical flow equation (1) holds:

[0195]

number

[0196] Here, I (k) denotes the luminance value of reference image k (k=0,1) after motion compensation. This optical flow equation indicates that the sum of (i) the time derivative of the luminance value, (ii) the product of the horizontal velocity and the horizontal component of the spatial gradient of the reference image, and (iii) the product of the vertical velocity and the vertical component of the spatial gradient of the reference image is equal to zero. Based on a combination of this optical flow equation and Hermite interpolation, block-wise motion vectors obtained from a merge list or the like are corrected pixel by pixel.

[0197] Note that the decoding device may derive a motion vector using a method other than the method based on a model assuming uniform linear motion. For example, a motion vector may be derived for each sub-block based on the motion vectors of multiple adjacent blocks.

[0198] Here, a mode in which a motion vector is derived for each sub-block based on the motion vectors of a plurality of adjacent blocks will be described. This mode is sometimes called an affine motion compensation prediction mode.

[0199] FIG. 9A is a diagram for explaining derivation of a motion vector for each sub-block based on the motion vectors of multiple adjacent blocks. In FIG. 9A, the current block includes 16 4x4 sub-blocks. Here, a motion vector v0 of the upper left corner control point of the current block is derived based on the motion vectors of the adjacent blocks, and a motion vector v1 of the upper right corner control point of the current block is derived based on the motion vectors of the adjacent sub-blocks. Then, using the two motion vectors v0 and v1, the motion vectors (v x ,v y ) is derived.

[0200]

number

[0201] Here, x and y respectively indicate the horizontal and vertical positions of the sub-block, and w indicates a predetermined weighting factor.

[0202] Such affine motion compensation prediction mode may include several modes with different methods of deriving the motion vectors of the upper left and upper right corner control points. Information indicating such affine motion compensation prediction mode (e.g., called affine flag) is signaled at the CU level. Note that the signaling of the information indicating this affine motion compensation prediction mode does not need to be limited to the CU level, and may be at other levels (e.g., sequence level, picture level, slice level, tile level, CTU level, or subblock level).

[0203] [Predictive control unit] The prediction control unit 128 selects either the intra-prediction signal or the inter-prediction signal, and outputs the selected signal to the subtraction unit 104 and the addition unit 116 as a prediction signal.

[0204] Here, an example of deriving a motion vector for a picture to be coded in the merge mode will be described. Fig. 9B is a diagram for explaining an overview of a motion vector derivation process in the merge mode.

[0205] First, a prediction MV list is generated in which prediction MV candidates are registered. The prediction MV candidates include spatially adjacent prediction MVs, which are MVs held by multiple coded blocks located spatially around the block to be coded, temporally adjacent prediction MVs, which are MVs held by nearby blocks projected onto the position of the block to be coded in the coded reference picture, joint prediction MVs, which are MVs generated by combining the MV values ​​of spatially adjacent prediction MVs and temporally adjacent prediction MVs, and zero prediction MVs, which are MVs with a value of zero.

[0206] Next, one prediction MV is selected from the multiple prediction MVs registered in the prediction MV list, and is determined as the MV for the block to be coded.

[0207] Furthermore, the variable length coding unit writes merge_idx, which is a signal indicating which predicted MV has been selected, into the stream and codes it.

[0208] Note that the predicted MVs registered in the predicted MV list described in Figure 9B are just an example, and the number may be different from the number shown in the figure, the configuration may not include some of the types of predicted MVs shown in the figure, or the configuration may include additional predicted MVs other than the types of predicted MVs shown in the figure.

[0209] Note that the final MV may be determined by performing DMVR processing, which will be described later, using the MV of the block to be coded derived in the merge mode.

[0210] Here, an example of determining the MV using the DMVR process will be described.

[0211] FIG. 9C is a conceptual diagram for explaining an overview of the DMVR process.

[0212] First, the optimal MVP set for the block to be processed is set as a candidate MV, and reference pixels are obtained from the first reference picture, which is a processed picture in the L0 direction, and the second reference picture, which is a processed picture in the L1 direction, according to the candidate MV, and a template is generated by taking the average of each reference pixel.

[0213] Next, the template is used to search the surrounding areas of the candidate MVs of the first and second reference pictures, and the MV with the smallest cost is determined as the final MV. The cost value is calculated using the difference value between each pixel value of the template and each pixel value of the search area, the MV value, etc.

[0214] The outline of the processing described here is basically the same for the encoding device and the decoding device.

[0215] Note that other processing may be used instead of the processing described here, as long as it is processing that can search the vicinity of the candidate MV and derive the final MV.

[0216] Here, a mode in which a predicted image is generated using LIC processing will be described.

[0217] FIG. 9D is a diagram for explaining an outline of a predicted image generating method using luminance correction processing by LIC processing.

[0218] First, a MV for obtaining a reference image corresponding to a block to be coded from a reference picture that is a coded picture is derived.

[0219] Next, for the block to be coded, the luminance pixel values ​​of the coded surrounding reference areas adjacent to the left and above and the luminance pixel values ​​at the equivalent positions in the reference picture specified by the MV are used to extract information indicating how the luminance values ​​have changed between the reference picture and the picture to be coded, and a luminance correction parameter is calculated.

[0220] A luminance correction process is performed on a reference image in a reference picture specified by the MV using the luminance correction parameter, thereby generating a predicted image for the block to be coded.

[0221] It should be noted that the shape of the peripheral reference region in FIG. 9D is just an example, and other shapes may be used.

[0222] Although the process of generating a predicted image from one reference picture has been described here, the process is similar when generating a predicted image from multiple reference pictures, and a luminance correction process is performed in a similar manner on the reference images obtained from each reference picture before generating a predicted image.

[0223] As a method of determining whether or not to apply LIC processing, for example, there is a method of using lic_flag, which is a signal indicating whether or not to apply LIC processing. As a specific example, in an encoding device, it is determined whether or not the encoding target block belongs to an area where a luminance change occurs, and if it belongs to an area where a luminance change occurs, a value of 1 is set as lic_flag and encoding is performed by applying LIC processing, and if it does not belong to an area where a luminance change occurs, a value of 0 is set as lic_flag and encoding is performed without applying LIC processing. On the other hand, a decoding device decodes lic_flag described in a stream, and switches whether or not to apply LIC processing depending on the value and performs decoding.

[0224] Another method of determining whether to apply LIC processing is, for example, a method of determining according to whether LIC processing is applied to surrounding blocks.As a specific example, when the block to be coded is in merge mode, determine whether the surrounding coded blocks selected when deriving MV in merge mode processing have been coded by applying LIC processing, and switch whether to apply LIC processing according to the result and perform coding.In addition, in this example, the process in decoding is exactly the same.

[0225] [Overview of the Decryption Device] Next, a description will be given of an overview of a decoding device capable of decoding the coded signal (coded bit stream) output from the above coding device 100. Fig. 10 is a block diagram showing a functional configuration of a decoding device 200 according to the first embodiment. The decoding device 200 is a video / image decoding device that decodes a video / image on a block-by-block basis.

[0226] As shown in FIG. 10, the decoding device 200 includes an entropy decoding unit 202, an inverse quantization unit 204, an inverse transform unit 206, an addition unit 208, a block memory 210, a loop filter unit 212, a frame memory 214, an intra prediction unit 216, an inter prediction unit 218, and a prediction control unit 220.

[0227] The decoding device 200 is realized by, for example, a general-purpose processor and a memory. In this case, when the software program stored in the memory is executed by the processor, the processor functions as the entropy decoding unit 202, the inverse quantization unit 204, the inverse transform unit 206, the addition unit 208, the loop filter unit 212, the intra prediction unit 216, the inter prediction unit 218, and the prediction control unit 220. The decoding device 200 may also be realized as one or more dedicated electronic circuits corresponding to the entropy decoding unit 202, the inverse quantization unit 204, the inverse transform unit 206, the addition unit 208, the loop filter unit 212, the intra prediction unit 216, the inter prediction unit 218, and the prediction control unit 220.

[0228] Each component included in the decoding device 200 will be described below.

[0229] [Entropy Decoding Part] The entropy decoding unit 202 entropy decodes the coded bit stream. Specifically, the entropy decoding unit 202 arithmetically decodes the coded bit stream into a binary signal, for example. The entropy decoding unit 202 then debinarizes the binary signal. As a result, the entropy decoding unit 202 outputs quantized coefficients to the inverse quantization unit 204 on a block-by-block basis.

[0230] [Dequantization section] The inverse quantization unit 204 inverse quantizes the quantized coefficients of a block to be decoded (hereinafter, referred to as a current block) that is input from the entropy decoding unit 202. Specifically, the inverse quantization unit 204 inverse quantizes each quantized coefficient of the current block based on a quantization parameter corresponding to the quantized coefficient. Then, the inverse quantization unit 204 outputs the inverse quantized quantized coefficients (i.e., transform coefficients) of the current block to the inverse transform unit 206.

[0231] [Inverse conversion section] The inverse transform unit 206 restores the prediction error by inverse transforming the transform coefficients input from the inverse quantization unit 204 .

[0232] For example, if the information interpreted from the encoded bitstream indicates that EMT or AMT is to be applied (e.g., the AMT flag is true), the inverse transform unit 206 inverse transforms the transform coefficients of the current block based on the interpreted information indicating the transform type.

[0233] Also for example, if the information interpreted from the coded bitstream indicates to apply NSST, then inverse transform unit 206 applies an inverse re-transform to the transform coefficients.

[0234] [Addition section] The adder 208 reconstructs the current block by adding the prediction error, which is an input from the inverse transformer 206, and the prediction sample, which is an input from the prediction control unit 220. The adder 208 then outputs the reconstructed block to the block memory 210 and the loop filter unit 212.

[0235] [Block memory] The block memory 210 is a storage unit for storing blocks that are referenced in intra prediction and are in a picture to be decoded (hereinafter, referred to as a current picture). Specifically, the block memory 210 stores the reconstructed block output from the adder 208.

[0236] [Loop filter section] The loop filter unit 212 applies a loop filter to the block reconstructed by the adder unit 208, and outputs the filtered reconstructed block to a frame memory 214, a display device, or the like.

[0237] If the information indicating ALF on / off read from the encoded bitstream indicates ALF on, one filter is selected from among multiple filters based on the local gradient direction and activity, and the selected filter is applied to the reconstructed block.

[0238] [Frame memory] The frame memory 214 is a storage unit for storing reference pictures used in inter prediction, and may be called a frame buffer. Specifically, the frame memory 214 stores the reconstructed blocks filtered by the loop filter unit 212.

[0239] [Intra prediction section] The intra prediction unit 216 generates a prediction signal (intra prediction signal) by performing intra prediction with reference to a block in the current picture stored in the block memory 210 based on an intra prediction mode interpreted from the encoded bit stream. Specifically, the intra prediction unit 216 generates an intra prediction signal by performing intra prediction with reference to samples (e.g., luminance values, chrominance values) of blocks adjacent to the current block, and outputs the intra prediction signal to the prediction control unit 220.

[0240] Note that, when an intra prediction mode that references a luminance block in intra prediction of a chrominance block is selected, the intra prediction unit 216 may predict the chrominance component of the current block based on the luminance component of the current block.

[0241] Furthermore, when information interpreted from the encoded bitstream indicates the application of PDPC, the intra prediction unit 216 corrects pixel values ​​after intra prediction based on the gradients of reference pixels in the horizontal / vertical directions.

[0242] [Inter prediction section] The inter prediction unit 218 predicts the current block by referring to a reference picture stored in the frame memory 214. The prediction is performed in units of the current block or sub-blocks (e.g., 4x4 blocks) in the current block. For example, the inter prediction unit 218 generates an inter prediction signal of the current block or sub-block by performing motion compensation using motion information (e.g., motion vectors) interpreted from the encoded bitstream, and outputs the inter prediction signal to the prediction control unit 220.

[0243] In addition, when the information interpreted from the encoded bitstream indicates that the OBMC mode is to be applied, the inter prediction unit 218 generates an inter prediction signal using not only the motion information of the current block obtained by motion search, but also the motion information of adjacent blocks.

[0244] Also, if the information interpreted from the encoded bitstream indicates that the FRUC mode is applied, the inter prediction unit 218 derives motion information by performing motion search according to the pattern matching method (bilateral matching or template matching) interpreted from the encoded bitstream. Then, the inter prediction unit 218 performs motion compensation using the derived motion information.

[0245] In addition, when the BIO mode is applied, the inter prediction unit 218 derives a motion vector based on a model assuming uniform linear motion. In addition, when information interpreted from the encoded bitstream indicates that an affine motion compensation prediction mode is applied, the inter prediction unit 218 derives a motion vector on a sub-block basis based on the motion vectors of multiple adjacent blocks.

[0246] [Predictive control unit] The prediction control unit 220 selects either the intra-prediction signal or the inter-prediction signal, and outputs the selected signal to the addition unit 208 as a prediction signal.

[0247] [Deblocking filter processing] Next, the deblocking filter processing performed in the encoding device 100 and the decoding device 200 configured as above will be specifically described with reference to the drawings. Note that, although the operation of the loop filter unit 120 provided in the encoding device 100 will be mainly described below, the operation of the loop filter unit 212 provided in the decoding device 200 is also similar.

[0248] As described above, when encoding an image, the encoding device 100 calculates a prediction error by subtracting a prediction signal generated by the intra prediction unit 124 or the inter prediction unit 126 from an original signal. The encoding device 100 generates a quantized coefficient by performing an orthogonal transform process and a quantization process on the prediction error. Furthermore, the encoding device 100 restores the prediction error by inverse quantizing and inverse orthogonal transforming the obtained quantized coefficient. Here, since the quantization process is a lossy process, the restored prediction error has an error (quantization error) with respect to the prediction error before transformation.

[0249] The deblocking filter process performed by the loop filter unit 120 is a type of filter process that is performed for the purpose of reducing the quantization error. The deblocking filter process is applied to block boundaries to remove block noise. In the following, the deblocking filter process is also simply referred to as filter process.

[0250] Fig. 11 is a flowchart showing an example of the deblocking filter process performed by the loop filter unit 120. For example, the process shown in Fig. 11 is performed for each block boundary.

[0251] First, the loop filter unit 120 calculates a block boundary strength (Bs) to determine the behavior of the deblocking filter process (S101). Specifically, the loop filter unit 120 determines Bs using the prediction mode or the properties of the motion vector of the block to be filtered. For example, if at least one of the blocks sandwiching the boundary is an intra-prediction block, Bs is set to 2. If at least one of the conditions (1) to (3) is satisfied, namely (1) at least one of the blocks sandwiching the boundary contains a dominant orthogonal transform coefficient, (2) the difference between the motion vectors of both blocks sandwiching the block boundary is equal to or greater than a threshold, and (3) the number of motion vectors or the reference image of both blocks sandwiching the block boundary are different, Bs is set to 1. If none of the conditions (1) to (3) is satisfied, Bs is set to 0.

[0252] Next, the loop filter unit 120 determines whether the set Bs is greater than a first threshold value (S102). If Bs is equal to or less than the first threshold value (No in S102), the loop filter unit 120 does not perform filtering (S107).

[0253] On the other hand, if the set Bs is greater than the first threshold (Yes in S102), the loop filter unit 120 calculates the pixel variation d of the boundary region using pixel values ​​in the blocks on both sides of the block boundary (S103). This process will be explained with reference to Fig. 12. If the pixel values ​​of the block boundary are defined as shown in Fig. 12, the loop filter unit 120 calculates, for example, d = |p30-2 x p20 + p10| + |p33-2 x p23 + p13| + |q30-2 x q20 + q10| + |q33-2 x q23 + q13|.

[0254] Next, the loop filter unit 120 judges whether the calculated d is greater than a second threshold (S104). If d is equal to or less than the second threshold (No in S104), the loop filter unit 120 does not perform filtering (S107). Note that the first threshold and the second threshold are different.

[0255] If the calculated d is greater than the second threshold (Yes in S104), the loop filter unit 120 determines the filter characteristics (S105) and performs filtering with the determined filter characteristics (S106). For example, a 5-tap filter of (1, 2, 2, 2, 1) / 8 is used. That is, for p10 shown in FIG. 12, the calculation (1×p30+2×p20+2×p10+2×q10+1×q20) / 8 is performed. Here, during filtering, clipping is performed so that the displacement falls within a certain range to avoid excessive smoothing. The clipping here refers to threshold processing in which, for example, when the threshold of the clipping is tc and the pixel value before filtering is q, the pixel value after filtering can only be within the range of q±tc.

[0256] Hereinafter, an example will be described in which an asymmetric filter is applied across a block boundary in the deblocking filtering process by the loop filter unit 120 according to this embodiment.

[0257] Fig. 13 is a flowchart showing an example of a deblocking filter process according to the present embodiment. Note that the process shown in Fig. 13 may be performed for each block boundary, or may be performed for each unit pixel including one or more pixels.

[0258] First, the loop filter unit 120 acquires coding parameters and determines asymmetric filter characteristics across a block boundary using the acquired coding parameters (S111). In the present disclosure, it is assumed that the acquired coding parameters characterize, for example, an error distribution.

[0259] Here, the filter characteristics are parameters used to control filter coefficients and filter processing, etc. The coding parameters may be any parameters that can be used to determine the filter characteristics. The coding parameters may be information indicating the error itself, or may be information or parameters related to the error (e.g., information that determines the magnitude of the error).

[0260] In the following description, a pixel that is determined to have a large or small error based on the encoding parameters, that is, a pixel that is likely to have a large or small error, will also be referred to simply as a pixel with a large or small error.

[0261] Here, it is not necessary to perform the determination process each time, but the process may be performed according to a predetermined rule that associates the encoding parameters with the filter characteristics.

[0262] It should be noted that even if a pixel is statistically likely to have a small error, it may have a larger error than a pixel that is likely to have a large error when viewed on a pixel-by-pixel basis.

[0263] Next, the loop filter unit 120 executes a filter process having the determined filter characteristics (S112).

[0264] Here, the filter characteristics determined in step S111 do not necessarily have to be asymmetric, and a symmetric design is also possible. In the following, a filter having asymmetric filter characteristics across a block boundary is also referred to as an asymmetric filter, and a filter having symmetric filter characteristics across a block boundary is also referred to as a symmetric filter.

[0265] Specifically, the filter characteristics are determined taking into consideration two points: that pixels determined to have a small error are less likely to be influenced by surrounding pixels with large errors, and that pixels determined to have a large error are more likely to be influenced by surrounding pixels with small errors. In other words, the filter characteristics are determined so that the larger the error, the greater the influence of the filter process. For example, the filter characteristics are determined so that the larger the error, the greater the change in pixel value before and after filter process. This makes it possible to prevent pixels that are likely to have a small error from deviating from the true value due to large value fluctuations. Conversely, for pixels that are likely to have a large error, the error can be reduced by fluctuating the value under the strong influence of pixels with small errors.

[0266] In the following, a factor that changes the displacement caused by a filter is defined as a filter weight. In other words, a weight indicates the degree of influence of the filter process on a symmetric pixel. Increasing the weight means that the influence of the filter process on the pixel in question increases. In other words, it means that the pixel value after the filter process is more susceptible to the influence of other pixels. Specifically, increasing the weight means determining the filter characteristics so that the amount of change in pixel value before and after the filter process increases, or so that the filter process is more easily performed.

[0267] That is, the loop filter unit 120 increases the weight for pixels with larger errors. Note that increasing the weight for pixels with larger errors does not necessarily mean changing the weight continuously based on the error, but also includes changing the weight stepwise. That is, the weight for a first pixel only needs to be smaller than the weight for a second pixel that has a larger error than the first pixel. The same expression is used hereinafter.

[0268] In addition, it is not necessary that the weight of a pixel having a larger error is larger in the finally determined filter characteristic. In other words, the loop filter unit 120 may modify the reference filter characteristic determined by the conventional method, for example, so that the weight of a pixel having a larger error tends to be larger.

[0269] A number of specific methods for changing the weights asymmetrically will be described below. Note that any of the methods described below may be used, or a combination of a number of methods may be used.

[0270] As a first technique, the loop filter unit 120 reduces the filter coefficient for a pixel with a larger error. For example, the loop filter unit 120 reduces the filter coefficient for a pixel with a larger error and increases the filter coefficient for a pixel with a smaller error.

[0271] For example, an example of deblocking filter processing performed on pixel p1 shown in FIG. 12 will be described. In the following, a filter determined by, for example, a conventional method without applying this method is called a reference filter. The reference filter is a 5-tap filter perpendicular to the block boundary and extends over (p3, p2, p1, q1, q2). The filter coefficient is (1, 2, 2, 2, 1) / 8. It is also assumed that the error of block P is likely to be large, and the error of block Q is likely to be small. In this case, the filter coefficient is set so that block P with a large error is easily influenced by block Q with a small error. Specifically, the filter coefficient used for pixels with a small error is set to be large, and the filter coefficient used for pixels with a large error is set to be small. For example, (0.5, 1.0, 1.0, 2.0, 1.5) / 6 is used as the filter coefficient.

[0272] As another example, 0 may be used as the filter coefficient for pixels with small error. For example, (0,0,1,2,2) / 5 may be used as the filter coefficient. That is, the filter tap may be changed. Conversely, a filter coefficient that is currently 0 may be changed to a value other than 0. For example, (1,2,2,2,1,1) / 9 may be used as the filter coefficient. That is, the loop filter unit 120 may extend the filter tap to the side with small error.

[0273] The reference filter does not have to be a filter symmetrical about the target pixel, such as the above (1,2,2,2,1) / 8. In such a case, the loop filter unit 120 further adjusts the filter. For example, the filter coefficient of the reference filter used for the pixel at the left end of the Q block is (1,2,3,4,5) / 15, and the filter coefficient of the reference filter used for the pixel at the right end of the block P is (5,4,3,2,1) / 15. That is, in this case, filter coefficients that are inverted left and right are used between pixels sandwiching the block boundary. Such filter characteristics that are inversion symmetrical about the block boundary can also be called "filter characteristics that are symmetrical about the block boundary". In other words, filter characteristics that are asymmetrical about the block boundary are filter characteristics that are not inversion symmetrical about the block boundary.

[0274] Also, as described above, when the error in block P is large and the error in block Q is small, the loop filter unit 120 changes, for example, the filter coefficients of the reference filter used for the rightmost pixel of block P from (5,4,3,2,1) / 15 to (2.5,2.0,1.5,2.0,1.0) / 9.

[0275] In this way, in the deblocking filter process, a filter whose filter coefficients change asymmetrically across a block boundary is used. For example, the loop filter unit 120 determines a reference filter having filter characteristics symmetric across a block boundary according to a predetermined criterion. The loop filter unit 120 changes the reference filter so that it has filter characteristics asymmetric across the block boundary. Specifically, the loop filter unit 120 at least one of increasing the filter coefficient of at least one pixel with a small error and decreasing the filter coefficient of at least one pixel with a large error among the filter coefficients of the reference filter.

[0276] Next, a second method of changing weights asymmetrically will be described. First, the loop filter unit 120 performs a filter operation using a reference filter. Next, the loop filter unit 120 performs asymmetric weighting across a block boundary on a reference change amount Δ0, which is a change amount of pixel value before and after the filter operation using the reference filter. In the following, for the sake of distinction, the process using the reference filter is called a filter operation, and a series of processes including the filter operation and the subsequent correction process (for example, asymmetric weighting) is called a filter process (deblocking filter process).

[0277] For example, for pixels with small errors, the loop filter unit 120 calculates a post-correction change amount Δ1 by multiplying the reference change amount Δ0 by a coefficient smaller than 1. For pixels with large errors, the loop filter unit 120 calculates a post-correction change amount Δ1 by multiplying the reference change amount Δ0 by a coefficient larger than 1. Next, the loop filter unit 120 generates a post-filter pixel value by adding the post-correction change amount Δ1 to the pixel value before the filter operation. Note that the loop filter unit 120 may perform only one of the processing for pixels with small errors and the processing for pixels with large errors.

[0278] For example, as in the above, it is assumed that the error in block P is large and the error in block Q is small. In this case, the loop filter unit 120 calculates the post-correction change amount Δ1 for pixels included in block Q with small error by, for example, multiplying the reference change amount Δ0 by 0.8. Also, the loop filter unit 120 calculates the post-correction change amount Δ1 for pixels included in block P with large error by, for example, multiplying the reference change amount Δ0 by 1.2. In this way, it is possible to reduce the fluctuation in the value of pixels with small error. Also, it is possible to increase the fluctuation in the value of pixels with large error.

[0279] In addition, the ratio of the coefficient multiplied by the reference change amount Δ0 of a pixel with a small error to the coefficient multiplied by the reference change amount Δ0 of a pixel with a large error may be selected to be 1:1. In this case, the filter characteristics are symmetrical on both sides of the block boundary.

[0280] The loop filter unit 120 may calculate the coefficient by which the reference change amount Δ0 is multiplied by a constant by multiplying the reference coefficient. In this case, the loop filter unit 120 uses a larger constant for pixels with large errors than for pixels with small errors. As a result, the amount of change in pixel value for pixels with large errors increases, and the amount of change in pixel value for pixels that are likely to have small errors decreases. For example, the loop filter unit 120 uses a constant of 1.2 or 0.8 for pixels adjacent to the block boundary, and a constant of 1.1 or 0.9 for pixels one pixel away from the pixel adjacent to the block boundary. The reference coefficient is calculated by, for example, (A×(q1−p1)−B×(q2−p2)+C) / D. Here, A, B, C, and D are constants. For example, A=9, B=3, C=8, and D=16. Also, p1, p2, q1, and q2 are pixel values ​​of pixels having the positional relationship shown in FIG. 12 across the block boundary.

[0281] Next, a third method of changing weights asymmetrically will be described. The loop filter unit 120 performs a filter operation using the filter coefficients of the reference filter, as in the second method. Next, the loop filter unit 120 adds an offset value that is asymmetric across the block boundary to the pixel value after the filter operation. Specifically, the loop filter unit 120 adds a positive offset value to the pixel value of a pixel with a large error so that the value of the pixel with a large error approaches the value of a pixel that is likely to have a small error and the displacement of the pixel with a large error increases. In addition, the loop filter unit 120 adds a negative offset to the pixel value of a pixel with a small error so that the value of the pixel with a small error does not approach the value of a pixel with a large error and the displacement of the pixel with a small error decreases. As a result, the amount of change in pixel value for a pixel with a large error increases, and the amount of change in pixel value for a pixel with a small error decreases. Note that the loop filter unit 120 may perform only one of the processing for a pixel with a small error and the processing for a pixel with a large error.

[0282] For example, for a pixel included in a block with a large error, the loop filter unit 120 calculates a post-correction change amount Δ1 by adding a positive offset value (e.g., 1) to the absolute value of the reference change amount Δ0. Also, for a pixel included in a block with a small error, the loop filter unit 120 calculates a post-correction change amount Δ1 by adding a negative offset value (e.g., -1) to the absolute value of the reference change amount Δ0. Next, the loop filter unit 120 generates a post-filter pixel value by adding the post-correction change amount Δ1 to the pixel value before the filter operation. Note that the loop filter unit 120 may add an offset value to the pixel value after the filter operation, instead of adding an offset value to the change amount. Also, the offset value does not have to be symmetrical across the block boundary.

[0283] Furthermore, when a filter tap extends from a block boundary over a plurality of pixels, the loop filter unit 120 may change only the weight for a specific pixel, or may change the weight for all pixels. Furthermore, the loop filter unit 120 may change the weight according to the distance from the block boundary to the target pixel. For example, the loop filter unit 120 may make the filter coefficients applied to the first two pixels from the block boundary asymmetric, and make the filter coefficients applied to the subsequent pixels symmetric. Furthermore, the filter weights may be common to a plurality of pixels, or may be set for each pixel.

[0284] Next, a fourth method of asymmetrically changing weights will be described. The loop filter unit 120 performs a filter calculation using the filter coefficients of a reference filter. Next, when a change amount Δ in pixel values ​​before and after the filter calculation exceeds a clip width that is a reference value, the loop filter unit 120 clips the change amount Δ to the clip width. The loop filter unit 120 sets the clip width asymmetrically across the block boundary.

[0285] Specifically, the loop filter unit 120 makes the clip width for pixels with large errors larger than the clip width for pixels with small errors. For example, the loop filter unit 120 makes the clip width for pixels with large errors a constant multiple of the clip width for pixels with small errors. As a result of changing the clip width, the values ​​of pixels with small errors cannot change significantly. Also, the values ​​of pixels with large errors can change significantly.

[0286] The loop filter unit 120 may adjust the absolute value of the clip width instead of specifying the ratio of the clip width. For example, the loop filter unit 120 fixes the clip width for pixels with large errors to twice the predetermined reference clip width. The loop filter unit 120 sets the ratio between the clip width for pixels with small errors and the clip width for pixels with small errors to 1.2:0.8. Specifically, for example, the reference clip width is 10, and the change amount Δ before and after the filter operation is 12. In this case, if the reference clip width is used as is, the change amount Δ is corrected to 10 by threshold processing. On the other hand, if the target pixel is a pixel with large error, for example, the reference clip width is multiplied by 1.5. As a result, the clip width becomes 15, so threshold processing is not performed and the change amount Δ becomes 12.

[0287] Next, a fifth method of asymmetrically changing weights will be described. The loop filter unit 102 sets the condition for determining whether or not to perform filtering asymmetrically across the block boundary. Here, the condition for determining whether or not to perform filtering is, for example, the first threshold value or the second threshold value shown in FIG. 11.

[0288] Specifically, the loop filter unit 120 sets conditions for pixels with large errors so that filtering is more likely to be performed, and sets conditions for pixels with small errors so that filtering is less likely to be performed. For example, the loop filter unit 120 sets a threshold for pixels with small errors higher than the threshold for pixels with large errors. For example, the loop filter unit 120 sets a threshold for pixels with small errors to a constant multiple of the threshold for pixels with large errors.

[0289] Furthermore, the loop filter unit 120 may not only specify the ratio of the thresholds but also adjust the absolute values ​​of the thresholds. For example, the loop filter unit 120 may fix the threshold for pixels with small errors to twice the predetermined reference threshold, and set the ratio between the threshold for pixels with small errors and the threshold for pixels with large errors to 1.2:0.8.

[0290] Specifically, suppose the reference threshold for the second threshold in step 104 is 10, and d calculated from pixel values ​​in the block is 12. If the reference threshold is used as the second threshold as is, it is determined that filtering is to be performed. On the other hand, if the target pixel is a pixel with a small error, for example, a value 1.5 times the reference threshold is used as the second threshold. In this case, the second threshold becomes 15, which is larger than d. As a result, it is determined that filtering is not to be performed.

[0291] Furthermore, the constants indicating the weights based on the errors used in the first to fifth techniques may be values ​​that are predetermined or may be variable in the encoding device 100 and the decoding device 200. Specifically, the constants are coefficients multiplied by the filter coefficients or the filter coefficients of the reference filter in the first technique, coefficients multiplied by the reference change amount Δ0 or constants multiplied by the reference coefficients in the second technique, offset values ​​in the third technique, constants multiplied by the clip width or the reference clip width in the fourth technique, and constants multiplied by the threshold or the reference threshold in the fifth technique.

[0292] When the constant is variable, information indicating the constant may be included in a bitstream as a parameter for each sequence or slice, for example, and transmitted from encoding device 100 to decoding device 200. Note that the information indicating the constant may be information indicating the constant itself, or information indicating a ratio or difference from a reference value.

[0293] In addition, examples of methods for changing a coefficient or constant depending on an error include a method of changing it linearly, a method of changing it quadratically, a method of changing it exponentially, or a method of using a lookup table showing the relationship between an error and a constant.

[0294] Also, when the error is equal to or greater than the reference value, or when the error is equal to or less than the reference value, a fixed value may be used as the constant. For example, the loop filter unit 120 may set the variable to a first value when the error is equal to or less than a predetermined range, set the variable to a second value when the error is equal to or greater than the predetermined range, and continuously change the variable from the first value to the second value according to the error when the error is within the predetermined range.

[0295] Furthermore, when the error exceeds a predetermined reference, the loop filter unit 120 may use a symmetric filter (reference filter) instead of the asymmetric filter.

[0296] Furthermore, when using a lookup table or the like, loop filter unit 120 may store both tables for cases where the error is large and cases where the error is small, or may store only one of the tables and calculate the other constant from the contents of that table in accordance with a predetermined rule.

[0297] As described above, the encoding device 100 and the decoding device 200 according to this embodiment can reduce errors in reconstructed images by using an asymmetric filter, thereby improving the encoding efficiency.

[0298] This aspect may be implemented in combination with at least a part of other aspects of the present disclosure. Also, some of the processes, some of the configurations of the device, and some of the syntax described in the flowcharts of this aspect may be implemented in combination with other aspects.

[0299] (Embodiment 2) Specific examples of encoding parameters that characterize the above-mentioned error distribution will be described in the second to sixth embodiments. In the present embodiments, the loop filter unit 120 determines filter characteristics according to the position of the target pixel within the block.

[0300] 14 is a flowchart showing an example of the deblocking filter process according to the present embodiment. First, the loop filter unit 120 acquires information indicating the position of the target pixel in the block as an encoding parameter characterizing the error distribution. Based on the position, the loop filter unit 120 determines filter characteristics that are asymmetric across the block boundary (S121).

[0301] Next, the loop filter unit 120 executes a filter process having the determined filter characteristics (S122).

[0302] Here, pixels farther from the reference pixels for intra prediction are more likely to have a larger error than pixels closer to the reference pixels for intra prediction. Therefore, the loop filter unit 120 determines filter characteristics such that the amount of change in pixel value before and after the filtering process increases for pixels farther from the reference pixels for intra prediction.

[0303] For example, in the case of H.265 / HEVC or JEM, the pixel closest to the reference pixel is the pixel located at the upper left in the block, and the pixel closest to the reference pixel is the pixel located at the lower right in the block, as shown in Fig. 15. Therefore, the loop filter unit 120 determines the filter characteristics such that the weight of the lower right pixel in the block is greater than the weight of the upper left pixel.

[0304] Specifically, the loop filter unit 120 determines filter characteristics for pixels far from the reference pixels of intra prediction so that the influence of the filter process is increased, as described in the first embodiment. That is, the loop filter unit 120 increases the weight of pixels far from the reference pixels of intra prediction. Here, increasing the weight means, as described above, performing at least one of the following: (1) decreasing the filter coefficient; (2) increasing the filter coefficient of pixels on either side of a boundary (i.e., pixels close to the reference pixels of intra prediction); (3) increasing the coefficient multiplied by the amount of change; (4) increasing the offset value of the amount of change; (5) increasing the clip width; and (6) correcting the threshold so that the filter process is easily performed. On the other hand, the loop filter unit 120 determines filter characteristics for pixels close to the reference pixels of intra prediction so that the influence of the filter process is reduced. That is, the loop filter unit 120 decreases the weight of pixels close to the reference pixels of intra prediction. Here, reducing the weight means, as described above, doing at least one of the following: (1) increasing the filter coefficient; (2) decreasing the filter coefficient of pixels on either side of a boundary (i.e., pixels close to the reference pixel for intra prediction); (3) decreasing the coefficient by which the change amount is multiplied; (4) decreasing the offset value of the change amount; (5) decreasing the clip width; and (6) modifying the threshold value so that the filter process is less likely to be performed.

[0305] It is to be noted that the above process may be performed when intra prediction is used, and not for blocks where inter prediction is used, but since the properties of intra prediction blocks may also be influenced by inter prediction, the above process may also be performed for inter prediction blocks.

[0306] Furthermore, the loop filter unit 120 may change the weighting by arbitrarily specifying a position in a particular block. For example, as described above, the loop filter unit 120 may increase the weighting of the pixel in the lower right of the block and decrease the weighting of the pixel in the upper left of the block. Note that the loop filter unit 120 may change the weighting by arbitrarily specifying a position in the block, not limited to the upper left and lower right.

[0307] 15, at adjacent block boundaries in the horizontal direction, the error of the left block is large and the error of the right block is large. Therefore, loop filter unit 120 may increase the weight of the left block and decrease the weight of the right block for adjacent block boundaries in the horizontal direction.

[0308] Similarly, at the boundary between adjacent blocks in the vertical direction, the error of the upper block is large and the error of the lower block is small. Therefore, for the boundary between adjacent blocks in the vertical direction, loop filter unit 120 may increase the weight of the upper block and decrease the weight of the lower block.

[0309] Furthermore, the loop filter unit 120 may change the weight according to the distance from the reference pixel of intra prediction. Furthermore, the loop filter unit 120 may determine the weight in block boundary units or in pixel units. The farther away from the reference pixel, the larger the error is likely to be. Therefore, the loop filter unit 120 determines the filter characteristics so that the gradient of the weight becomes steeper the farther away from the reference pixel. Furthermore, the loop filter unit 120 determines the filter characteristics so that the gradient of the weight on the upper side of the right side of the block is gentler than the gradient of the weight on the lower side.

[0310] This aspect may be implemented in combination with at least a part of other aspects of the present disclosure. Also, some of the processes, some of the configurations of the device, and some of the syntax described in the flowcharts of this aspect may be implemented in combination with other aspects.

[0311] (Embodiment 3) In this embodiment, the loop filter unit 120 determines the filter characteristics according to the orthogonal transform basis.

[0312] 16 is a flowchart showing an example of the deblocking filter process according to the present embodiment. First, the loop filter unit 120 acquires information indicating an orthogonal transform base used for a current block as an encoding parameter characterizing an error distribution. Based on the orthogonal transform base, the loop filter unit 120 determines filter characteristics that are asymmetric across a block boundary (S131).

[0313] Next, the loop filter unit 120 executes a filter process having the determined filter characteristics (S132).

[0314] The encoding device 100 selects one of a plurality of candidates for an orthogonal transform base, which is a transform base used when performing an orthogonal transform. The plurality of candidates include, for example, a base in which the 0th-order transform base of DCT-II or the like is flat, and a base in which the 0th-order transform base of DCT-VII or the like is not flat. Fig. 17 is a diagram showing the transform bases of DCT-II. Fig. 18 is a diagram showing the transform bases of DCT-VII.

[0315] The zero-order basis of DCT-II is constant regardless of the position in the block. In other words, when DCT-II is used, the error in the block is constant. Therefore, when both blocks on either side of the block boundary are transformed by DCT-II, the loop filter unit 120 performs filtering using a symmetric filter, not an asymmetric filter.

[0316] On the other hand, the zeroth order basis of DST-VII has a larger value as the distance from the left or top block boundary increases. In other words, the error is likely to increase as the distance from the left or top block boundary increases. Therefore, the loop filter unit 120 uses an asymmetric filter when at least one of two blocks on either side of a block boundary has been transformed by DST-VII. Specifically, the loop filter unit 120 determines the filter characteristics so that the effect of the filter process is smaller for pixels with smaller values ​​in a block of a lower order basis (e.g., zeroth order).

[0317] Specifically, when both blocks on either side of a block boundary are converted by DST-VII, the loop filter unit 120 determines the filter characteristics so that the effect of the filter process is greater for the bottom right pixel in the block by the above-mentioned method, and also determines the filter characteristics so that the effect of the filter process is greater for the top left pixel in the block.

[0318] Also, when DST-VII and DCT-II are adjacent to each other vertically, the loop filter unit 120 determines the filter characteristics so that the filter weight for the lower pixel of the upper block in which DST-VII is used, which is adjacent to the block boundary, is larger than the filter weight for the upper pixel of the lower block in which DCT-II is used. However, the difference in amplitude of the low-order basis in this case is smaller than the difference in amplitude of the low-order basis when DST-VIIs are adjacent to each other. Therefore, the loop filter unit 120 sets the filter characteristics so that the gradient of the weight in this case is smaller than the gradient of the weight when DST-VIIs are adjacent to each other. For example, the loop filter unit 120 sets the weight to 1:1 (symmetric filter) when DCT-II and DCT-II are adjacent, sets the weight to 1.3:0.7 when DST-VII and DST-VII are adjacent, and sets the weight to 1.2:0.8 when DST-VII and DCT-II are adjacent.

[0319] This aspect may be implemented in combination with at least a part of other aspects of the present disclosure. Also, some of the processes, some of the configurations of the device, and some of the syntax described in the flowcharts of this aspect may be implemented in combination with other aspects.

[0320] (Embodiment 4) In this embodiment, the loop filter unit 120 determines the filter characteristics according to pixel values ​​on either side of a block boundary.

[0321] 19 is a flowchart showing an example of the deblocking filter process according to the present embodiment. First, the loop filter unit 120 acquires information indicating pixel values ​​in blocks sandwiching a block boundary as an encoding parameter characterizing an error distribution. The loop filter unit 120 determines filter characteristics that are asymmetric across the block boundary based on the pixel values ​​(S141).

[0322] Next, the loop filter unit 120 executes a filter process having the determined filter characteristics (S142).

[0323] For example, the loop filter unit 120 increases the difference in filter characteristics across the block boundary as the pixel value difference d0 increases. Specifically, the loop filter unit 120 determines the filter characteristics so that the difference in the effect of the filter process increases. For example, the loop filter unit 120 sets the weights to 1.4:0.6 when d0>(quantization parameter)×(constant) is satisfied, and sets the weights to 1.2:0.8 when the above relationship is not satisfied. That is, the loop filter unit 120 compares the pixel value difference d0 with a threshold based on the quantization parameter, and increases the difference in filter characteristics across the block boundary when the pixel value difference d0 is greater than the threshold, compared to when the pixel value difference d0 is smaller than the threshold.

[0324] As another example, the loop filter unit 120 may increase the difference in filter characteristics across the block boundary as the average value b0 of the variances of pixel values ​​in both blocks on either side of the block boundary increases. Specifically, the loop filter unit 120 may determine filter characteristics such that the difference in the influence of the filter process increases. For example, the loop filter unit 120 may set the weights to 1.4:0.6 when b0>(quantization parameter)×(constant) is satisfied, and may set the weights to 1.2:0.8 when the above relationship is not satisfied. In other words, the loop filter unit 120 may compare the variance b0 of pixel values ​​with a threshold based on the quantization parameter, and increase the difference in filter characteristics across the block boundary when the variance b0 of pixel values ​​is greater than the threshold, compared to when the variance b0 of pixel values ​​is smaller than the threshold.

[0325] Which of the adjacent blocks should have a larger weight, that is, which block has a larger error, can be specified by the method of the above-mentioned second or third embodiment, or the method of the below-mentioned sixth embodiment. That is, the loop filter unit 120 determines asymmetric filter characteristics on either side of the block boundary according to a predetermined rule (for example, the method of the second, third or sixth embodiment). Next, the loop filter unit 120 changes the determined filter characteristics based on the pixel value difference d0 so that the difference between the filter characteristics on either side of the block boundary becomes larger. That is, the loop filter unit 120 increases the ratio or difference between the weight of a pixel with a large error and the weight of a pixel with a small error.

[0326] Here, if the pixel value difference d0 is large, this may be the case when the block boundary coincides with the edge of an object in the image. In such a case, by reducing the difference in filter characteristics on either side of the block boundary, unnecessary smoothing can be prevented.

[0327] Conversely, the loop filter unit 120 may reduce the difference in filter characteristics across the block boundary as the pixel value difference d0 increases. Specifically, the loop filter unit 120 determines the filter characteristics so that the difference in the influence of the filter process decreases. For example, the loop filter unit 120 sets the weights to 1.2:0.8 when d0>(quantization parameter)×(constant) is satisfied, and sets the weights to 1.4:0.6 when the above relationship is not satisfied. The weights may be set to 1:1 (symmetric filter) when the above relationship is satisfied. That is, the loop filter unit 120 compares the pixel value difference d0 with a threshold based on the quantization parameter, and reduces the difference in filter characteristics across the block boundary when the pixel value difference d0 is greater than the threshold, compared to when the pixel value difference d0 is smaller than the threshold.

[0328] For example, a large pixel value difference d0 means that block boundaries are more noticeable. In such a case, by reducing the difference in filter characteristics on either side of the block boundary, it is possible to prevent the smoothing effect from being weakened by an asymmetric filter.

[0329] Note that these two processes may be performed simultaneously. For example, the loop filter unit 120 may use a first weight when the pixel value difference d0 is less than a first threshold, use a second weight with a difference greater than the first weight when the pixel value difference d0 is equal to or greater than the first threshold and less than a second threshold, and use a third weight with a difference smaller than the second weight when the pixel value difference d0 is equal to or greater than the second threshold.

[0330] Furthermore, the pixel value difference d0 may be the difference between pixel values ​​on either side of the boundary, or the average or variance of the pixel value differences. For example, the pixel value difference d0 is calculated by (A×(q1-p1)-B×(q2-p2)+C) / D, where A, B, C, and D are constants. For example, A=9, B=3, C=8, and D=16. Furthermore, p1, p2, q1, and q2 are pixel values ​​of pixels on either side of the block boundary, which are in the positional relationship shown in FIG. 12.

[0331] The pixel value difference d0 and the weight may be set on a pixel-by-pixel basis, on a block boundary basis, or on a block group basis including multiple blocks (for example, on an LCU (Largest Coding Unit) basis).

[0332] This aspect may be implemented in combination with at least a part of other aspects of the present disclosure. Also, some of the processes, some of the configurations of the device, and some of the syntax described in the flowcharts of this aspect may be implemented in combination with other aspects.

[0333] (Embodiment 5) In this embodiment, the loop filter unit 120 determines the filter characteristics according to the intra-prediction direction and the block boundary direction.

[0334] 20 is a flowchart showing an example of a deblocking filter process according to the present embodiment. First, the loop filter unit 120 acquires information indicating an angle between the prediction direction of intra prediction and a block boundary as an encoding parameter characterizing an error distribution. The loop filter unit 120 determines filter characteristics that are asymmetric across the block boundary based on the angle (S151).

[0335] Next, the loop filter unit 120 executes a filter process having the determined filter characteristics (S152).

[0336] Specifically, the loop filter unit 120 increases the difference in filter characteristics across the block boundary as the angle approaches vertical, and decreases the difference in filter characteristics across the block boundary as the angle approaches horizontal. More specifically, when the intra-prediction direction is closer to vertical to the block boundary, the filter characteristics are determined so that the difference in filter weights for pixels on both sides of the block boundary increases, and when the intra-prediction direction is closer to horizontal to the block boundary, the filter characteristics are determined so that the difference in filter weights for pixels on both sides of the block boundary decreases. Figure 21 is a diagram showing an example of weights for the relationship between the intra-prediction direction and the direction of the block boundary.

[0337] Which of the adjacent blocks should have a larger weight, that is, which block has a larger error, can be specified by the method of the above-mentioned second or third embodiment, or the method of the below-mentioned sixth embodiment. That is, the loop filter unit 120 determines asymmetric filter characteristics on either side of the block boundary according to a predetermined rule (for example, the method of the second, third or sixth embodiment). Next, the loop filter unit 120 changes the determined filter characteristics based on the intra prediction direction and the direction of the block boundary so that the difference between the filter characteristics on either side of the block boundary becomes large.

[0338] Furthermore, the encoding device 100 and the decoding device 200 specify the intra prediction direction using, for example, an intra prediction mode.

[0339] In addition, when the intra prediction mode is the planar mode or the DC mode, the loop filter unit 120 may not consider the direction of the block boundary. For example, when the intra prediction mode is the planar mode or the DC mode, the loop filter unit 120 may use a predetermined weight or a weight difference regardless of the direction of the block boundary. Alternatively, when the intra prediction mode is the planar mode or the DC mode, the loop filter unit 120 may use a symmetric filter.

[0340] This aspect may be implemented in combination with at least a part of other aspects of the present disclosure. Also, some of the processes, some of the configurations of the device, and some of the syntax described in the flowcharts of this aspect may be implemented in combination with other aspects.

[0341] (Embodiment 6) In this embodiment, the loop filter unit 120 determines the filter characteristics according to a quantization parameter indicating the width of quantization.

[0342] 16 is a flowchart showing an example of the deblocking filter process according to the present embodiment. First, the loop filter unit 120 acquires information indicating a quantization parameter used in quantizing the current block as an encoding parameter characterizing an error distribution. The loop filter unit 120 determines filter characteristics that are asymmetric across the block boundary based on the quantization parameter (S161).

[0343] Next, the loop filter unit 120 executes a filter process having the determined filter characteristics (S162).

[0344] Here, the greater the quantization parameter, the greater the possibility of an error occurring. Therefore, loop filter unit 120 determines filter characteristics such that the greater the quantization parameter, the greater the effect of filtering.

[0345] Fig. 23 is a diagram showing an example of weighting for a quantization parameter. As shown in Fig. 23, the loop filter unit 120 increases the weighting for the upper left pixel in a block as the quantization parameter increases. On the other hand, the loop filter unit 120 reduces the increase in the weighting for the lower right pixel in the block as the quantization parameter increases. In other words, the loop filter unit 120 determines the filter characteristics such that the change in the effect of the filtering process associated with the change in the quantization parameter for the upper left pixel is greater than the change in the effect of the filtering process associated with the change in the quantization parameter for the lower right pixel.

[0346] Here, the upper left pixel in the block is more susceptible to the effect of the quantization parameter than the lower right pixel in the block, so by performing the above-described process, the error can be appropriately reduced.

[0347] Furthermore, the loop filter unit 120 may determine the weight of each of the two blocks on either side of the boundary based on the quantization parameter of the block, or may calculate the average value of the quantization parameters of the two blocks and determine the weights of the two blocks based on the average value. Alternatively, the loop filter unit 120 may determine the weights of two blocks based on the quantization parameter of one block. For example, the loop filter unit 120 uses the above-mentioned method to determine the weight of one block based on the quantization parameter of the one block. Next, the loop filter unit 120 determines the weight of the other block based on the determined weight and in accordance with a predetermined rule.

[0348] Alternatively, loop filter unit 120 may use a symmetric filter when the quantization parameters of the two blocks are different or when the difference between the quantization parameters of the two blocks exceeds a threshold.

[0349] 23, the weights are set using a linear function, but any function other than a linear function or a table may be used. For example, a curve showing the relationship between the quantization parameter and the quantization step (quantization width) may be used.

[0350] Furthermore, when the quantization parameter exceeds a threshold, the loop filter unit 120 may use a symmetric filter instead of an asymmetric filter.

[0351] Furthermore, when the quantization parameter is described with decimal point accuracy, the loop filter unit 120 may perform an operation such as rounding up, rounding down, or the like on the quantization parameter and use the calculated quantization parameter in the above process. Alternatively, the loop filter unit 120 may perform the above process taking into account decimal points.

[0352] As described above, in the second to sixth embodiments, a plurality of methods for determining an error have been described individually, but two or more of these methods may be combined. In this case, the loop filter unit 120 may weight the two or more combined elements.

[0353] The following describes modified examples.

[0354] Encoding parameters other than the above-described examples may be used. For example, the encoding parameters may be the type of orthogonal transform (Wavelet, DFT, lapped transform, etc.), the block size (width and height of the block), the direction of the motion vector, the length of the motion vector, or the number of reference pictures used in inter prediction, and information indicating the characteristics of the reference filter. They may also be used in combination. For example, the loop filter unit 120 may use an asymmetric filter only when the length of the block boundary is 16 pixels or less and the pixel to be filtered is close to the reference pixel of the intra prediction, and may use a symmetric filter in other cases. As another example, asymmetric processing may be performed only when a predetermined type of filter among multiple filter candidates is used. For example, an asymmetric filter may be used only when the displacement by the reference filter is calculated by (A×(q1-p1)-B×(q2-p2)+C) / D. Here, A, B, C, and D are constants. For example, A=9, B=3, C=8, and D=16. Also, p1, p2, q1, and q2 are pixel values ​​of pixels having the positional relationship shown in FIG. 12 across the block boundary.

[0355] Furthermore, the loop filter unit 120 may perform the above processing on one of the luminance signal and the color difference signal, or may perform the above processing on both. Furthermore, the loop filter unit 120 may perform a common process on the luminance signal and the color difference signal, or may perform different processes on the luminance signal and the color difference signal. For example, the loop filter unit 120 may use different weights for the luminance signal and the color difference signal, or may determine the weights according to different rules.

[0356] Moreover, the various parameters used in the above processes may be determined by the encoding device 100, or may be preset fixed values.

[0357] Moreover, whether to perform the above processing or not, or the contents of the above processing may be switched in a predetermined unit. The predetermined unit is, for example, a slice unit, a tile unit, a wavefront division unit, or a CTU unit. The contents of the above processing are a parameter indicating which of the above-mentioned multiple methods is to be used, or a weight, or a parameter for determining these.

[0358] Furthermore, the loop filter unit 120 may limit the area in which the above processing is performed to a CTU boundary, a slice boundary, or a tile boundary.

[0359] Furthermore, the number of filter taps may differ between the symmetric filter and the asymmetric filter.

[0360] Furthermore, the loop filter unit 120 may determine whether or not to perform the above-mentioned processing, or change the content of the above-mentioned processing, depending on the frame type (I frame, P frame, B frame).

[0361] Furthermore, the loop filter section 120 may determine whether or not to perform the above processing, or the content of the above processing, depending on whether or not a specific processing has been performed in the previous or subsequent stage.

[0362] In addition, the loop filter unit 120 may perform different processing depending on the type of prediction mode used for the block, or may perform the above processing only for blocks using a specific prediction mode. For example, the loop filter unit 120 may perform different processing for blocks using intra prediction, blocks using inter prediction, and merged blocks.

[0363] Furthermore, the encoding device 100 may encode filter information, which is a parameter indicating whether or not to perform the above processing, or the content of the above processing. That is, the encoding device 100 may generate an encoded bitstream including the filter information. This filter information may include information indicating whether or not to perform the above processing on a luminance signal, information indicating whether or not to perform the above processing on a chrominance signal, or information indicating whether or not to make the processing different for each prediction mode.

[0364] Furthermore, the decoding device 200 may perform the above-mentioned processing based on filter information included in the encoded bitstream. For example, the decoding device 200 may determine whether to perform the above-mentioned processing or the content of the above-mentioned processing based on the filter information.

[0365] This aspect may be implemented in combination with at least a part of other aspects of the present disclosure. Also, some of the processes, some of the configurations of the device, and some of the syntax described in the flowcharts of this aspect may be implemented in combination with other aspects.

[0366] (Embodiment 7) In each of the above embodiments, each of the functional blocks can usually be realized by an MPU, a memory, etc. Furthermore, the processing by each of the functional blocks is usually realized by a program execution unit such as a processor reading and executing software (programs) recorded on a recording medium such as a ROM. The software may be distributed by downloading, etc., or may be recorded on a recording medium such as a semiconductor memory and distributed. Of course, each functional block can also be realized by hardware (dedicated circuitry).

[0367] Furthermore, the processes described in each embodiment may be realized by centralized processing using a single device (system), or may be realized by distributed processing using multiple devices. The processor that executes the above program may be either single or multiple. That is, centralized processing or distributed processing may be performed.

[0368] The aspects of the present disclosure are not limited to the above-described examples, and various modifications are possible, which are also included within the scope of the aspects of the present disclosure.

[0369] Further, here, application examples of the video coding method (image coding method) or video decoding method (image decoding method) shown in each of the above embodiments and a system using the same will be described. The system is characterized by having an image coding device using the image coding method, an image decoding device using the image decoding method, and an image coding / decoding device equipped with both. Other configurations in the system can be appropriately changed depending on the case.

[0370] [Usage example] 24 is a diagram showing the overall configuration of a content supply system ex100 that realizes a content distribution service. The area where communication services are provided is divided into cells of a desired size, and base stations ex106, ex107, ex108, ex109, and ex110, which are fixed wireless stations, are installed in each cell.

[0371] In this content supply system ex100, devices such as a computer ex111, a game machine ex112, a camera ex113, a home appliance ex114, and a smartphone ex115 are connected to the Internet ex101 via an Internet service provider ex102 or a communication network ex104, and base stations ex106 to ex110. The content supply system ex100 may be configured to connect any of the above elements in combination. Each device may be directly or indirectly connected to each other via a telephone network or short-distance wireless communication, without going through the base stations ex106 to ex110, which are fixed wireless stations. In addition, the streaming server ex103 is connected to each device such as a computer ex111, a game machine ex112, a camera ex113, a home appliance ex114, and a smartphone ex115 via the Internet ex101, etc. In addition, the streaming server ex103 is connected to a terminal in a hot spot in an airplane ex117, etc., via a satellite ex116.

[0372] Instead of the base stations ex106 to ex110, wireless access points or hot spots may be used. The streaming server ex103 may be directly connected to the communication network ex104 without going through the Internet ex101 or the Internet service provider ex102, or may be directly connected to an airplane ex117 without going through a satellite ex116.

[0373] The camera ex113 is a device capable of taking still images and videos, such as a digital camera. The smartphone ex115 is a smartphone, a mobile phone, or a PHS (Personal Handyphone System) that is compatible with a mobile communication system generally called 2G, 3G, 3.9G, 4G, and 5G in the future.

[0374] The home appliance ex118 is a refrigerator or an appliance included in a home fuel cell cogeneration system.

[0375] In the content supply system ex100, a terminal having a photographing function is connected to a streaming server ex103 via a base station ex106 or the like, thereby enabling live distribution and the like. In live distribution, a terminal (such as a computer ex111, a game machine ex112, a camera ex113, a home appliance ex114, a smartphone ex115, and a terminal in an airplane ex117) performs the encoding process described in each of the above embodiments on still image or video content photographed by a user using the terminal, multiplexes the video data obtained by the encoding with audio data obtained by encoding audio corresponding to the video, and transmits the obtained data to the streaming server ex103. That is, each terminal functions as an image encoding device according to one aspect of the present disclosure.

[0376] Meanwhile, the streaming server ex103 streams the transmitted content data to the requesting client. The client is a computer ex111, a game machine ex112, a camera ex113, a home appliance ex114, a smartphone ex115, a terminal in an airplane ex117, or the like, capable of decoding the encoded data. Each device that receives the distributed data decodes and plays back the received data. That is, each device functions as an image decoding device according to one aspect of the present disclosure.

[0377] [Distributed processing] The streaming server ex103 may be a plurality of servers or computers that process, record, and distribute data in a distributed manner. For example, the streaming server ex103 may be realized by a CDN (Contents Delivery Network), and content distribution may be realized by a network that connects a large number of edge servers distributed around the world. In a CDN, an edge server that is physically close to the client is dynamically assigned according to the client. The content is cached and distributed to the edge server, thereby reducing delays. In addition, when an error occurs or the communication state changes due to an increase in traffic, the processing can be distributed among multiple edge servers, the distribution entity can be switched to another edge server, or distribution can be continued by bypassing the part of the network where a failure has occurred, thereby realizing high-speed and stable distribution.

[0378] In addition to the distributed processing of the distribution itself, the encoding processing of the captured data may be performed by each terminal, may be performed by the server side, or may be shared among the terminals. As an example, in the encoding processing, a processing loop is generally performed twice. In the first loop, the complexity of the image or the amount of code is detected for each frame or scene. In the second loop, processing is performed to maintain the image quality and improve the encoding efficiency. For example, the terminal performs the first encoding processing, and the server side that receives the content performs the second encoding processing, thereby improving the quality and efficiency of the content while reducing the processing load on each terminal. In this case, if there is a request to receive and decode almost in real time, the data encoded once by the terminal can be received and played back by other terminals, making it possible to perform more flexible real-time distribution.

[0379] As another example, the camera ex113 etc. extracts features from an image, compresses data related to the features as metadata, and transmits the compressed data to the server. The server performs compression according to the meaning of the image, for example, by determining the importance of an object from the features and switching the quantization precision. The feature data is particularly effective in improving the precision and efficiency of motion vector prediction when the server performs recompression. Alternatively, the terminal may perform simple encoding such as VLC (variable length coding), and the server may perform encoding with a large processing load such as CABAC (context-adaptive binary arithmetic coding).

[0380] As another example, in a stadium, a shopping mall, a factory, etc., there may be a plurality of video data in which almost the same scene has been shot by a plurality of terminals. In this case, using the plurality of terminals that shot the video and, as necessary, other terminals and servers that did not shoot the video, coding processing is assigned to each of them, for example, in units of GOPs (Group of Pictures), in units of pictures, or in units of tiles obtained by dividing a picture, for distributed processing. This reduces delays and realizes better real-time performance.

[0381] In addition, since the multiple video data are of almost the same scene, the server may manage and / or instruct the video data shot by each terminal to be mutually referenced. Alternatively, the server may receive the encoded data from each terminal and change the reference relationship between the multiple data, or correct or replace the pictures themselves and re-encode them. This makes it possible to generate a stream with improved quality and efficiency for each piece of data.

[0382] The server may also perform transcoding to change the encoding format of the video data before distributing it. For example, the server may convert an MPEG-based encoding format into a VP-based encoding format, or convert H.264 into H.265.

[0383] In this way, the encoding process can be performed by a terminal or one or more servers. Therefore, in the following, descriptions such as "server" or "terminal" are used to indicate the entity performing the processing, but some or all of the processing performed by the server may be performed by the terminal, and some or all of the processing performed by the terminal may be performed by the server. The same applies to the decoding process.

[0384] [3D, multi-angle] In recent years, it has become common to integrate and use images or videos of different scenes or the same scene taken from different angles by multiple devices such as cameras ex113 and / or smartphones ex115 that are almost synchronized with each other. The videos taken by the devices are integrated based on the relative positional relationship between the devices that is obtained separately, or on areas where feature points included in the videos match.

[0385] The server may not only encode 2D video, but also encode still images automatically or at a time specified by the user based on scene analysis of the video and transmit them to the receiving terminal. If the server can obtain the relative positional relationship between the shooting terminals, the server may generate a 3D shape of the scene based on not only 2D video but also images of the same scene captured from different angles. The server may separately encode 3D data generated by point clouds, etc., or may generate images to be transmitted to the receiving terminal by selecting or reconstructing images from images captured by multiple terminals based on the results of recognizing or tracking people or objects using the 3D data.

[0386] In this way, the user can enjoy a scene by selecting any video corresponding to each shooting terminal, or can enjoy content in which a video from any viewpoint is cut out from 3D data reconstructed using multiple images or videos. Furthermore, sound may be collected from multiple different angles, just like the video, and the server may multiplex the sound from a specific angle or space with the video and transmit it in accordance with the video.

[0387] In recent years, content that associates the real world with a virtual world, such as Virtual Reality (VR) and Augmented Reality (AR), has also become popular. In the case of VR images, the server creates viewpoint images for the right eye and the left eye, respectively, and may perform encoding that allows reference between each viewpoint video using Multi-View Coding (MVC) or the like, or may encode them as separate streams without mutual reference. When decoding the separate streams, it is preferable to play them in synchronization with each other so that a virtual three-dimensional space is reproduced according to the user's viewpoint.

[0388] In the case of an AR image, the server superimposes virtual object information in the virtual space on camera information in the real space based on the three-dimensional position or the movement of the user's viewpoint. The decoding device may obtain or hold virtual object information and three-dimensional data, generate a two-dimensional image according to the movement of the user's viewpoint, and smoothly connect them to create superimposed data. Alternatively, the decoding device may transmit the movement of the user's viewpoint to the server in addition to a request for virtual object information, and the server may create superimposed data according to the movement of the viewpoint received from the three-dimensional data held by the server, encode the superimposed data, and deliver it to the decoding device. Note that the superimposed data has an α value indicating the transparency in addition to RGB, and the server may set the α value of the part other than the object created from the three-dimensional data to 0, etc., and encode the data in a state in which the part is transparent. Alternatively, the server may generate data in which a predetermined value of RGB value is set to the background like a chromakey, and the part other than the object is the background color.

[0389] Similarly, the decoding process of the distributed data may be performed by each client terminal, or may be performed by the server side, or may be shared among them. As an example, a certain terminal may once send a reception request to the server, and the content corresponding to the request may be received by other terminals, decoded, and the decoded signal may be transmitted to a device having a display. By distributing the processing and selecting appropriate content regardless of the performance of the communication-enabled terminals themselves, data with good image quality can be reproduced. In another example, while large-sized image data is received by a TV or the like, a part of the area, such as tiles into which the picture is divided, may be decoded and displayed on the viewer's personal terminal. This allows the viewer to share the overall picture while checking his / her own area of ​​responsibility or the area he / she wants to check in more detail at hand.

[0390] In the future, it is expected that content will be seamlessly received by switching appropriate data for the currently connected communication using delivery system standards such as MPEG-DASH under circumstances where multiple short-distance, medium-distance, or long-distance wireless communication is available, regardless of whether indoors or outdoors. This allows users to freely select and switch in real time not only their own terminals but also decoding devices or display devices such as displays installed indoors and outdoors. In addition, decoding can be performed while switching the decoding device and the display device based on the user's location information, etc. This makes it possible to move while displaying map information on the wall or part of the ground of a neighboring building where a displayable device is embedded while moving to a destination. It is also possible to switch the bit rate of the received data based on the accessibility of the encoded data on the network, such as when the encoded data is cached on a server that can be accessed from the receiving terminal in a short time, or when it is copied to an edge server in a content delivery service.

[0391] [Scalable Coding] The switching of contents will be described using a scalable stream compressed and coded by applying the video coding method shown in each of the above embodiments, as shown in FIG. 25. The server may have multiple streams with the same content but different qualities as individual streams, but may be configured to switch contents by taking advantage of the characteristics of a temporal / spatial scalable stream realized by coding in layers as shown in the figure. In other words, the decoding side can freely switch between low-resolution content and high-resolution content by determining which layer to decode according to an internal factor such as performance and an external factor such as the state of the communication band. For example, if you want to continue watching a video you were watching on your smartphone ex115 while on the move on a device such as an Internet TV after you get home, the device can decode the same stream up to a different layer, reducing the burden on the server side.

[0392] Furthermore, as described above, in addition to the configuration that realizes scalability in which pictures are coded for each layer and an enhancement layer exists above a base layer, the enhancement layer may include meta-information based on image statistics, etc., and the decoding side may generate high-quality content by super-resolving pictures of the base layer based on the meta-information. Super-resolution may be either an improvement in the signal-to-noise ratio at the same resolution or an increase in resolution. The meta-information includes information for specifying linear or nonlinear filter coefficients used in the super-resolution process, or information for specifying parameter values ​​in the filter process, machine learning, or least squares calculation used in the super-resolution process.

[0393] Alternatively, a picture may be divided into tiles or the like according to the meaning of an object in an image, and the decoding side may select a tile to decode to decode only a part of the area. Also, by storing the attribute of an object (person, car, ball, etc.) and its position in a video (coordinate position in the same image, etc.) as meta information, the decoding side can identify the position of a desired object based on the meta information and determine the tile containing the object. For example, as shown in FIG. 26, the meta information is stored using a data storage structure different from pixel data such as an SEI message in HEVC. This meta information indicates, for example, the position, size, or color of a main object.

[0394] Meta information may also be stored in units consisting of multiple pictures, such as streams, sequences, or random access units, etc. This allows the decoding side to obtain the time when a specific person appears in the video, and by combining this with picture-by-picture information, it is possible to identify the picture in which an object exists and the position of the object within the picture.

[0395] [Web page optimization] FIG. 27 is a diagram showing an example of a display screen of a web page in a computer ex111 or the like. FIG. 28 is a diagram showing an example of a display screen of a web page in a smartphone ex115 or the like. As shown in FIG. 27 and FIG. 28, a web page may include multiple link images that are links to image content, and the appearance of the web page differs depending on the device used to view the page. When multiple link images are visible on the screen, the display device (decoding device) displays a still image or I-picture that each content has as a link image, displays a video such as a gif animation using multiple still images or I-pictures, or receives only the base layer to decode and display the video, until the user explicitly selects the link image, or until the link image approaches the center of the screen or the entire link image enters the screen.

[0396] When a link image is selected by a user, the display device gives top priority to decoding the base layer. If the HTML constituting the web page contains information indicating that the content is scalable, the display device may decode up to the enhancement layer. In order to ensure real-time performance, before selection or when the communication bandwidth is very tight, the display device decodes and displays only forward-reference pictures (I-pictures, P-pictures, and B-pictures with forward reference only), thereby reducing the delay between the decoding time of the first picture and the display time (the delay from the start of decoding the content to the start of display). The display device may also ignore the reference relationship between pictures and roughly decode all B-pictures and P-pictures with forward reference, and perform normal decoding as the number of received pictures increases over time.

[0397] [Automatic driving] Furthermore, when transmitting and receiving still image or video data such as 2D or 3D map information for automatic driving or driving assistance of a vehicle, the receiving terminal may receive weather or construction information as meta information in addition to image data belonging to one or more layers, and may associate and decode these. Note that the meta information may belong to a layer, or may simply be multiplexed with the image data.

[0398] In this case, since a car, drone, or airplane including a receiving terminal moves, the receiving terminal can realize seamless reception and decoding while switching between base stations ex106 to ex110 by transmitting the location information of the receiving terminal at the time of a reception request. Also, the receiving terminal can dynamically switch how much meta information to receive or how much to update map information according to the user's selection, the user's situation, or the state of the communication band.

[0399] In this manner, in the content supply system ex100, the client can receive, decode, and play back encoded information transmitted by the user in real time.

[0400] [Distribution of personal content] Furthermore, the content supply system ex100 allows not only high-quality, long-duration content from video distributors, but also low-quality, short-duration content from individuals via unicast or multicast distribution. It is expected that such personal content will continue to increase in the future. To improve the quality of personal content, the server may perform editing processing before encoding processing. This can be achieved, for example, by the following configuration.

[0401] During shooting, in real time or after accumulating, the server performs recognition processing such as shooting errors, scene search, semantic analysis, and object detection from the original image or encoded data. Then, based on the recognition result, the server manually or automatically corrects out-of-focus or camera shake, deletes less important scenes such as scenes that are less bright than other pictures or are out of focus, emphasizes object edges, changes color, and performs other editing. The server encodes the edited data based on the editing result. It is also known that if the shooting time is too long, the viewer rating will decrease, and the server may automatically clip not only scenes of less importance as described above but also scenes with little movement based on the image processing result so that the content will be within a specific time range depending on the shooting time. Alternatively, the server may generate a digest based on the result of the semantic analysis of the scene and encode it.

[0402] In addition, there are cases where personal contents contain images that infringe copyrights, moral rights, portrait rights, etc., and the scope of sharing may exceed the intended scope, which may be inconvenient for individuals. Therefore, for example, the server may change the image to an unfocused image of a person's face on the periphery of the screen, or the inside of a house, and encode it. The server may also recognize whether the image to be encoded contains a face of a person other than a person registered in advance, and if so, may perform processing such as blurring the face. Alternatively, as pre-processing or post-processing of encoding, the user may specify a person or background area that he or she wishes to process in the image from the viewpoint of copyright, etc., and the server may replace the specified area with another image or blur the focus. If it is a person, the image of the face part can be replaced while tracking the person in the video.

[0403] In addition, since viewing of personal content with a small amount of data requires real-time performance, the decoding device first receives the base layer as a top priority, and performs decoding and playback, although this depends on the bandwidth. The decoding device may receive an enhancement layer during this time, and when playback is looped or otherwise played two or more times, play high-quality video including the enhancement layer. In this way, if the stream is scalably encoded, it is possible to provide an experience in which the video is rough when not selected or when viewing begins, but the stream gradually becomes smarter and the image quality improves. In addition to scalable encoding, a similar experience can be provided even if a rough stream played the first time and a second stream encoded with reference to the first video are configured as one stream.

[0404] [Other use cases] Moreover, these encoding or decoding processes are generally processed in an LSIex500 possessed by each terminal. The LSIex500 may be a single chip or may be configured with multiple chips. Note that software for encoding or decoding moving images may be incorporated into some kind of recording medium (such as a CD-ROM, a flexible disk, or a hard disk) that can be read by the computer ex111 or the like, and the encoding or decoding process may be performed using the software. Furthermore, if the smartphone ex115 has a camera, video data captured by the camera may be transmitted. The video data in this case is data that has been encoded by the LSIex500 possessed by the smartphone ex115.

[0405] The LSIex500 may be configured to download and activate application software. In this case, the terminal first determines whether the terminal supports the encoding method of the content or has the ability to execute a specific service. If the terminal does not support the encoding method of the content or does not have the ability to execute a specific service, the terminal downloads a codec or application software, and then acquires and plays the content.

[0406] Furthermore, at least one of the video encoding device (image encoding device) or video decoding device (image decoding device) of each of the above embodiments can be incorporated into a digital broadcasting system, not limited to the content supply system ex100 via the Internet ex101. Since multiplexed data in which video and audio are multiplexed is carried and transmitted over broadcasting radio waves using a satellite or the like, there is a difference in that it is more suitable for multicast compared to the content supply system ex100, which has a configuration that is easy to use for unicast, but similar applications are possible with regard to the encoding process and decoding process.

[0407] [Hardware configuration] FIG. 29 is a diagram showing a smartphone ex115. FIG. 30 is a diagram showing a configuration example of the smartphone ex115. The smartphone ex115 includes an antenna ex450 for transmitting and receiving radio waves to and from the base station ex110, a camera unit ex465 capable of taking videos and still images, and a display unit ex458 for displaying the video captured by the camera unit ex465 and the decoded data of the video received by the antenna ex450. The smartphone ex115 further includes an operation unit ex466 such as a touch panel, an audio output unit ex457 such as a speaker for outputting audio or sound, an audio input unit ex456 such as a microphone for inputting audio, a memory unit ex467 capable of storing encoded data such as captured video or still images, recorded audio, received video or still images, and e-mail, or decoded data, and a slot unit ex464 which is an interface unit with a SIMex468 for identifying a user and authenticating access to various data including a network. In addition, an external memory may be used instead of the memory unit ex467.

[0408] In addition, a main control unit ex460, which comprehensively controls the display unit ex458 and the operation unit ex466, etc., is connected to a power supply circuit unit ex461, an operation input control unit ex462, a video signal processing unit ex455, a camera interface unit ex463, a display control unit ex459, a modulation / demodulation unit ex452, a multiplexing / separation unit ex453, an audio signal processing unit ex454, a slot unit ex464, and a memory unit ex467 via a bus ex470.

[0409] When the power key is turned on by a user's operation, the power supply circuit unit ex461 starts up the smartphone ex115 into an operational state by supplying power to each unit from the battery pack.

[0410] The smartphone ex115 performs processes such as telephone calls and data communications under the control of a main control unit ex460 having a CPU, a ROM, and a RAM. During a telephone call, a voice signal collected by a voice input unit ex456 is converted into a digital voice signal by a voice signal processing unit ex454, which is then subjected to spectrum spreading processing by a modulation / demodulation unit ex452, and the digital-to-analog conversion processing and frequency conversion processing by a transmission / reception unit ex451 is then transmitted via an antenna ex450. In addition, the received data is amplified, and subjected to frequency conversion processing and analog-to-digital conversion processing, and the spectrum inverse spreading processing by a modulation / demodulation unit ex452 is then performed, and the analog voice signal is converted into an analog voice signal by a voice signal processing unit ex454, which is then output from a voice output unit ex457. During a data communication mode, text, still images, or video data is sent to the main control unit ex460 via an operation input control unit ex462 by operating an operation unit ex466 or the like of the main unit, and transmission and reception processing is performed in the same manner. When transmitting video, still images, or video and audio in the data communication mode, the video signal processing unit ex455 compresses and encodes the video signal stored in the memory unit ex467 or the video signal input from the camera unit ex465 by the moving image encoding method shown in each of the above embodiments, and sends the encoded video data to the multiplexing / separation unit ex453. The audio signal processing unit ex454 also encodes the audio signal collected by the audio input unit ex456 while the camera unit ex465 is capturing the video or still images, and sends the encoded audio data to the multiplexing / separation unit ex453. The multiplexing / separation unit ex453 multiplexes the encoded video data and the encoded audio data by a predetermined method, and performs modulation and conversion processing in the modulation / demodulation unit (modulation / demodulation circuit unit) ex452 and the transmission / reception unit ex451, and transmits the data via the antenna ex450.

[0411] When receiving a video attached to an e-mail or chat, or a video linked to a web page, etc., in order to decode the multiplexed data received via the antenna ex450, the multiplexing / separation unit ex453 separates the multiplexed data into a bit stream of video data and a bit stream of audio data by separating the multiplexed data, and supplies the encoded video data to the video signal processing unit ex455 via the synchronization bus ex470, and supplies the encoded audio data to the audio signal processing unit ex454. The video signal processing unit ex455 decodes the video signal by a video decoding method corresponding to the video encoding method shown in each of the above embodiments, and displays the video or still image contained in the linked video file on the display unit ex458 via the display control unit ex459. The audio signal processing unit ex454 also decodes the audio signal, and audio is output from the audio output unit ex457. Note that since real-time streaming is widespread, there may be cases where audio playback is socially inappropriate depending on the user's situation. Therefore, as an initial value, a configuration in which only video data is played without playing audio signals is preferable. The audio may be played in sync only when the user performs an operation such as clicking on the video data.

[0412] In addition, although the smartphone ex115 has been described as an example here, three types of implementation formats are possible for the terminal: a transmitting / receiving terminal having both an encoder and a decoder, a transmitting terminal having only an encoder, and a receiving terminal having only a decoder. Furthermore, in the digital broadcasting system, multiplexed data in which audio data and the like are multiplexed with video data is received or transmitted, but the multiplexed data may include text data related to the video in addition to audio data, or the video data itself may be received or transmitted instead of the multiplexed data.

[0413] Although the main control unit ex460 including the CPU controls the encoding or decoding process, terminals often have a GPU. Therefore, a configuration may be used in which a wide area is processed collectively by utilizing the performance of the GPU using a memory shared by the CPU and GPU, or a memory whose addresses are managed so that they can be used in common. This can shorten the encoding time, ensure real-time performance, and achieve low latency. In particular, it is efficient to perform the processing of motion search, deblocking filter, SAO (Sample Adaptive Offset), and transformation and quantization collectively in units such as pictures by the GPU, rather than by the CPU.

[0414] This aspect may be implemented in combination with at least a part of other aspects of the present disclosure. Also, some of the processes, some of the configurations of the device, and some of the syntax described in the flowcharts of this aspect may be implemented in combination with other aspects. [Industrial Applicability]

[0415] The present disclosure is applicable to an encoding device, a decoding device, an encoding method, and a decoding method. [Explanation of symbols]

[0416] 100 Encoding device 102 Division 104 Subtraction section 106 Conversion unit 108 Quantization section 110 Entropy coding unit 112, 204 Inverse quantization section 114, 206 Inverse conversion unit 116, 208 Addition section 118, 210 Block Memory 120, 212 Loop filter section 122, 214 frame memory 124, 216 Intra prediction section 126, 218 Inter prediction section 128, 220 Predictive control unit 200 Decryption device 202 Entropy Decoding Unit

Claims

1. A processing circuit; a memory coupled to the processing circuit; The processing circuitry uses the memory to: performing a multiplication for a first block using a plurality of first luminance filter coefficients as multiplication values ​​and performing a multiplication for a second block using a plurality of second luminance filter coefficients as multiplication values, thereby changing values ​​of a plurality of luminance pixels in the first block and the second block, thereby performing a filtering process on a first boundary between the first block and the second block; performing multiplication for a third block using a plurality of first chrominance filter coefficients as multiplication values ​​and performing multiplication for a fourth block using a plurality of second chrominance filter coefficients as multiplication values, thereby changing values ​​of a plurality of chrominance pixels in the third block and the fourth block, thereby performing a filtering process on a second boundary between the third block and the fourth block; the plurality of first luminance filter coefficients and the plurality of second luminance filter coefficients are selected asymmetrically about the first boundary; the first luma filter coefficients and the second luma filter coefficients are selected based on a prediction mode of the first block and a prediction mode of the second block and a quantization parameter; the plurality of first chrominance filter coefficients and the plurality of second chrominance filter coefficients are selected symmetrically with respect to the second boundary; Encoding device.

2. A processing circuit; a memory coupled to the processing circuit; The processing circuitry uses the memory to: performing a multiplication for a first block using a plurality of first luminance filter coefficients as multiplication values ​​and performing a multiplication for a second block using a plurality of second luminance filter coefficients as multiplication values, thereby changing values ​​of a plurality of luminance pixels in the first block and the second block, thereby performing a filtering process on a first boundary between the first block and the second block; performing multiplication for a third block using a plurality of first chrominance filter coefficients as multiplication values ​​and performing multiplication for a fourth block using a plurality of second chrominance filter coefficients as multiplication values, thereby changing values ​​of a plurality of chrominance pixels in the third block and the fourth block, thereby performing a filtering process on a second boundary between the third block and the fourth block; the plurality of first luminance filter coefficients and the plurality of second luminance filter coefficients are selected asymmetrically about the first boundary; the first luma filter coefficients and the second luma filter coefficients are selected based on a prediction mode of the first block and a prediction mode of the second block and a quantization parameter; the plurality of first chrominance filter coefficients and the plurality of second chrominance filter coefficients are selected symmetrically with respect to the second boundary; Decryption device.

3. A processing circuit; a memory coupled to the processing circuit; The processing circuitry uses the memory to: generating parameters for causing a decoding device to execute a deblocking filter process; including said parameters in a bitstream; The deblocking filter process includes: performing a multiplication for a first block using a plurality of first luminance filter coefficients as multiplication values ​​and performing a multiplication for a second block using a plurality of second luminance filter coefficients as multiplication values, thereby changing values ​​of a plurality of luminance pixels in the first block and the second block, thereby performing a filtering process on a first boundary between the first block and the second block; performing multiplication for a third block using a plurality of first chrominance filter coefficients as multiplication values ​​and performing multiplication for a fourth block using a plurality of second chrominance filter coefficients as multiplication values, thereby changing values ​​of a plurality of chrominance pixels in the third block and the fourth block, thereby performing a filtering process on a second boundary between the third block and the fourth block; the plurality of first luminance filter coefficients and the plurality of second luminance filter coefficients are selected asymmetrically about the first boundary; the first luma filter coefficients and the second luma filter coefficients are selected based on a prediction mode of the first block and a prediction mode of the second block and a quantization parameter; the plurality of first chrominance filter coefficients and the plurality of second chrominance filter coefficients are selected symmetrically with respect to the second boundary; Bitstream generator.

Images