Encoder, decoder, encoding method, decoding method, bit stream generation device, and transmission method

Abstract

To provide an encoder of which the throughput can be reduced.SOLUTION: In a first operating mode, an encoder 100 derives a first motion vector in a unit of a prediction block in a merge mode (S112) and performs a first motion compensation process that generates a prediction image by referring to a spatial gradient of luminance in an image generated by performing motion compensation using the first motion vector (S113); and in a second operating mode, derives motion vectors at a plurality of control points, derives a second motion vector in a unit of a sub-block for each sub-block obtained by splitting the prediction block (S114) and performs a second motion compensation process that generates a prediction image without referring to a spatial gradient of luminance in an image generated by performing motion compensation using the second motion vector (S115).SELECTED DRAWING: Figure 15

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] Conventionally, H.265 exists as a standard for encoding moving images. H.265 is also known as HEVC (High Efficiency Video Coding). [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] In such encoding and decoding methods, it is desirable to be able to reduce the amount of processing.

[0005] An object of the present disclosure is to provide a decoding device, an encoding device, a decoding method, or an encoding method that can reduce the amount of processing. [Means for solving the problem]

[0006] An encoding device according to one embodiment of the present disclosure includes a circuit and a memory, and the circuit performs motion compensation processing using the memory. The motion compensation processing includes a first operating mode and a second operating mode. In the first operating mode, a first motion vector is derived in a merge mode for each prediction block obtained by dividing an image included in a moving image, and a first motion compensation processing is performed to generate a prediction image by referring to a spatial gradient of luminance in an image generated by motion compensation using the first motion vector. In the second operating mode, motion vectors of multiple control points of the prediction block are derived based on motion vectors of blocks spatially adjacent to the prediction block, and a second motion vector for bidirectional prediction is derived for each sub-block obtained by dividing the prediction block into multiple sub-blocks using the motion vectors of the multiple control points. The second motion compensation processing is performed to generate a prediction image without referring to a spatial gradient of luminance in an image generated by motion compensation using the second motion vector.

[0007] An encoding device according to one embodiment of the present disclosure includes a circuit and a memory, and the circuit performs motion compensation processing using the memory. The motion compensation processing includes a first operating mode and a second operating mode. In the first operating mode, a first motion vector is derived for each prediction block into which an image included in a moving image is divided, and a first motion compensation processing is performed to generate a prediction image by referring to a spatial gradient of luminance in an image generated by motion compensation using the first motion vector. In the second operating mode, motion vectors of multiple control points of the prediction block are derived based on motion vectors of blocks spatially adjacent to the prediction block, and a second motion vector is derived for each sub-block into which the prediction block is divided using the motion vectors of the multiple control points, and a second motion compensation processing is performed to generate a prediction image without referring to a spatial gradient of luminance in an image generated by motion compensation using the second motion vector.

[0008] An encoding device according to one embodiment of the present disclosure includes a circuit and a memory, and the circuit performs motion compensation processing using the memory. The motion compensation processing includes a first operating mode and a second operating mode. In the first operating mode, a first motion vector is derived for each prediction block into which an image included in a moving image is divided, and a first motion compensation processing is performed to generate a prediction image by referring to a spatial gradient of luminance in an image generated by motion compensation using the first motion vector. In the second operating mode, motion vectors of multiple control points of the prediction block are derived based on motion vectors of blocks spatially adjacent to the prediction block, and a second motion vector for bidirectional prediction is derived for each sub-block into which the prediction block is divided using the motion vectors of the multiple control points, and a second motion compensation processing is performed to generate a prediction image without referring to a spatial gradient of luminance in an image generated by motion compensation using the second motion vector. The second operating mode further includes multiple motion compensation modes in which the motion vectors of the multiple control points used to derive the second motion vector are different.

[0009] A decoding device according to one embodiment of the present disclosure comprises a circuit and a memory, and the circuit performs motion compensation processing using the memory, the motion compensation processing including a first operating mode and a second operating mode, in which in the first operating mode, a first motion vector is derived for each prediction block into which an image included in a moving image is divided, and a first motion compensation processing is performed to generate a prediction image by referring to a spatial gradient of luminance in an image generated by motion compensation using the first motion vector, and in the second operating mode, motion vectors of multiple control points of the prediction block are derived based on motion vectors of blocks spatially adjacent to the prediction block, and a second motion vector for bidirectional prediction is derived for each sub-block into which the prediction block is divided using the motion vectors of the multiple control points, and a second motion compensation processing is performed to generate a prediction image without referring to a spatial gradient of luminance in an image generated by motion compensation using the second motion vector, and the second operating mode further includes multiple motion compensation modes in which the motion vectors of the multiple control points used to derive the second motion vector are different.

[0010] These comprehensive or specific aspects may be realized as a system, an apparatus, a method, an integrated circuit, a computer program, or a non-transitory recording medium such as a computer-readable CD-ROM, or may be realized as any combination of a system, an apparatus, a method, an integrated circuit, a computer program, and a recording medium. [Effects of the Invention]

[0011] The present disclosure can provide a decoding device, an encoding device, a decoding method, or an encoding method that can reduce the amount of processing. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a block diagram showing a functional configuration of a coding device according to the first embodiment. [Figure 2] FIG. 2 is a diagram showing an example of block division according to the first embodiment. [Figure 3]FIG. 3 is a table showing the transformation basis functions corresponding to each transformation 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 ALF. [Figure 4C] FIG. 4C is a diagram showing another example of the shape of the filter used in 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 using the OBMC process. [Figure 5C] FIG. 5C is a conceptual diagram for explaining an outline of the predicted image correction process using 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 outline of the motion vector derivation process in the merge mode. [Figure 9C] FIG. 9C is a conceptual diagram for explaining an outline of the DMVR process. [Figure 9D] FIG. 9D is a diagram for explaining an outline of a predicted image generation 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. [Figure 11] FIG. 11 is a flowchart of the inter-picture prediction process according to the first comparative example. [Figure 12] FIG. 12 is a flowchart of the inter-picture prediction process according to the second comparative example. [Figure 13] FIG. 13 is a flowchart of the inter prediction process according to the first embodiment. [Figure 14] FIG. 14 is a flowchart of an inter-picture prediction process according to a variation of the first embodiment. [Figure 15] FIG. 15 is a flowchart of the encoding process and the decoding process according to the modification of the first embodiment. [Figure 16] FIG. 16 is a conceptual diagram illustrating the template FRUC method according to the first embodiment. [Figure 17] FIG. 17 is a conceptual diagram illustrating the bilateral FRUC scheme according to the first embodiment. [Figure 18] FIG. 18 is a flowchart showing the operation of deriving a motion vector by the FRUC method according to the first embodiment. [Figure 19] FIG. 19 is a conceptual diagram showing the BIO processing according to the first embodiment. [Figure 20] FIG. 20 is a flowchart showing the BIO processing according to the first embodiment. [Figure 21] FIG. 21 is a block diagram showing an example of implementation of the encoding device according to the first embodiment. [Figure 22] FIG. 22 is a block diagram showing an example of implementation of the decoding device according to the first embodiment. [Figure 23] FIG. 23 is a diagram showing the overall configuration of a content supply system that realizes a content distribution service. [Figure 24] FIG. 24 is a diagram showing an example of a coding structure for scalable coding. [Figure 25] FIG. 25 is a diagram showing an example of a coding structure for scalable coding. [Figure 26]FIG. 26 is a diagram showing an example of a display screen of a web page. [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 illustrating an example of a smartphone. [Figure 29] FIG. 29 is a block diagram showing an example of the configuration of a smartphone. DETAILED DESCRIPTION OF THE INVENTION

[0013] An encoding device according to one embodiment of the present disclosure includes a circuit and a memory, and the circuit uses the memory to derive a first motion vector by a first inter-frame prediction method that uses the degree of compatibility between two reconstructed images of two areas in two different pictures, for each prediction block into which an image included in a moving image is divided, and performs a first motion compensation process that generates a predicted image for each prediction block by referring to a spatial gradient of luminance in an image generated by motion compensation using the derived first motion vector.

[0014] According to this, the encoding device performs the motion vector derivation process and the first motion compensation process by the first inter-picture prediction method on a prediction block basis, thereby reducing the amount of processing compared to when these processes are performed on a sub-block basis. Furthermore, the first motion compensation process, which generates a prediction image by referring to the spatial gradient of luminance, can achieve correction on a unit smaller than the prediction block unit, thereby suppressing a decrease in encoding efficiency when processing is not performed on a sub-block basis. Therefore, the encoding device can reduce the amount of processing while suppressing a decrease in encoding efficiency.

[0015] For example, the circuit may further use the memory to derive a second motion vector for each of the prediction blocks by a second inter-frame prediction method that uses a degree of match between a target prediction block and a reconstructed image of an area included in a reference picture, perform a second motion compensation process for each of the prediction blocks to generate a prediction image by referring to a spatial gradient of luminance in an image generated by motion compensation using the second motion vector, and generate an encoded bitstream that includes information for identifying the second motion vector.

[0016] This allows the processing unit of the motion compensation process to be the same when the first inter prediction method is used and when the second inter prediction method is used, thereby facilitating the implementation of the motion compensation process.

[0017] For example, the two regions in the first inter-frame prediction method may be (1) a region in a target picture adjacent to a target prediction block and a region in a reference picture, or (2) two regions in two different reference pictures.

[0018] A decoding device according to one embodiment of the present disclosure includes a circuit and a memory, and the circuit uses the memory to derive a first motion vector by a first inter-frame prediction method that uses the degree of compatibility between two reconstructed images of two areas in two different pictures, for each prediction block into which an image included in a moving image is divided, and performs a first motion compensation process that generates a predicted image for each prediction block by referring to a spatial gradient of luminance in an image generated by motion compensation using the derived first motion vector.

[0019] According to this, the decoding device performs the motion vector derivation process and the first motion compensation process by the first inter-picture prediction method on a prediction block basis, thereby reducing the amount of processing compared to when these processes are performed on a sub-block basis. Furthermore, the first motion compensation process that generates a prediction image by referring to the spatial gradient of luminance can achieve correction on a unit smaller than the prediction block unit, thereby suppressing a decrease in coding efficiency that occurs when processing is not performed on a sub-block basis. Therefore, the decoding device can reduce the amount of processing while suppressing a decrease in coding efficiency.

[0020] For example, the circuit may further use the memory to obtain, from the coded bitstream, information for specifying a second motion vector for each of the prediction blocks, derive the second motion vector for each of the prediction blocks by a second inter-frame prediction method using the information, and perform a second motion compensation process for each of the prediction blocks to generate a predicted image by referring to a spatial gradient of luminance in an image generated by motion compensation using the derived second motion vector.

[0021] This allows the processing unit of the motion compensation process to be the same when the first inter prediction method is used and when the second inter prediction method is used, thereby facilitating the implementation of the motion compensation process.

[0022] For example, the two regions in the first inter-frame prediction method may be (1) a region in a target picture adjacent to a target prediction block and a region in a reference picture, or (2) two regions in two different reference pictures.

[0023] An encoding method according to one embodiment of the present disclosure derives a first motion vector by a first inter-frame prediction method that uses the degree of compatibility between two reconstructed images of two areas in two different pictures, for each prediction block obtained by dividing an image included in a moving image, and performs motion compensation processing that generates a predicted image for each prediction block by referring to the spatial gradient of luminance in an image generated by motion compensation using the derived first motion vector.

[0024] According to this, the coding method performs the motion vector derivation process and the first motion compensation process by the first inter-picture prediction method in units of prediction blocks, thereby reducing the amount of processing compared to when these processes are performed in units of sub-blocks. Furthermore, the first motion compensation process that generates a prediction image by referring to the spatial gradient of luminance can achieve correction in units smaller than the prediction block unit, thereby suppressing a decrease in coding efficiency when processing is not performed in units of sub-blocks. Therefore, the coding method can reduce the amount of processing while suppressing a decrease in coding efficiency.

[0025] A decoding method according to one embodiment of the present disclosure derives a first motion vector by a first inter-frame prediction method that uses the degree of compatibility between two reconstructed images of two areas in two different pictures, for each prediction block obtained by dividing an image included in a moving image, and performs motion compensation processing that generates a predicted image for each prediction block by referring to the spatial gradient of luminance in an image generated by motion compensation using the derived first motion vector.

[0026] According to this, the decoding method performs the motion vector derivation process using the first inter-picture prediction method and the first motion compensation process on a prediction block basis, thereby reducing the amount of processing compared to performing these processes on a sub-block basis, for example. Furthermore, the first motion compensation process that generates a prediction image by referring to the spatial gradient of luminance can achieve correction on a unit smaller than the prediction block unit, thereby suppressing a decrease in coding efficiency that occurs when processing is not performed on a sub-block basis. Therefore, the decoding method can reduce the amount of processing while suppressing a decrease in coding efficiency.

[0027] An encoding device according to one embodiment of the present disclosure includes a circuit and a memory, and the circuit uses the memory to, in a first operating mode, derive a first motion vector for each prediction block into which an image included in a moving image is divided, and perform a first motion compensation process for each prediction block to generate a prediction image by referring to a spatial gradient of luminance in an image generated by motion compensation using the derived first motion vector, and in a second operating mode, perform a second motion compensation process for each sub-block into which the prediction block is divided, and generate a prediction image by each sub-block without referring to a spatial gradient of luminance in an image generated by motion compensation using the second motion vector.

[0028] According to this, in the first operating mode, the encoding device performs the motion vector derivation process and the first motion compensation process on a prediction block basis, thereby reducing the amount of processing compared to performing these processes on a subblock basis, for example. Furthermore, the first motion compensation process, which generates a prediction image by referring to the spatial gradient of luminance, can achieve correction on a unit smaller than the prediction block unit, thereby suppressing a decrease in encoding efficiency that occurs when processing is not performed on a subblock basis. Furthermore, in the second operating mode, the encoding device performs the motion vector derivation process and the second motion compensation process on a subblock basis. Here, the second motion compensation process does not refer to the spatial gradient of luminance, so the processing amount is smaller than that of the first motion compensation process. Furthermore, by having these two operating modes, the encoding device can improve encoding efficiency. In this way, the encoding device can reduce the amount of processing while suppressing a decrease in encoding efficiency.

[0029] For example, the circuit may derive the first motion vector for each prediction block using a first inter prediction method in the first operation mode, and derive the second motion vector for each sub-block using a second inter prediction method different from the first inter prediction method in the second operation mode.

[0030] For example, the second inter prediction method may be an inter prediction method that uses a degree of compatibility between two reconstructed images of two regions in two different pictures.

[0031] This allows inter-picture prediction to be performed on a sub-block basis, which is highly effective in improving coding efficiency by calculating motion vectors on a sub-block basis, thereby improving coding efficiency.

[0032] For example, the first inter-picture prediction method may be one of (1) a third inter-picture prediction method that uses the degree of conformance between a reconstructed image of an area in a target picture adjacent to a target prediction block and a reconstructed image of an area in a reference picture, and (2) a fourth inter-picture prediction method that uses the degree of conformance between two reconstructed images of two areas in two different reference pictures, and the second inter-picture prediction method may be the other of the third inter-picture prediction method and the fourth inter-picture prediction method.

[0033] For example, the first inter prediction method may be the third inter prediction method, and the second inter prediction method may be the fourth inter prediction method.

[0034] This allows inter-picture prediction to be performed on a sub-block basis, which is highly effective in improving coding efficiency by calculating motion vectors on a sub-block basis, thereby improving coding efficiency.

[0035] For example, the first inter-frame prediction method may be an inter-frame prediction method that uses a degree of match between a target prediction block and a reconstructed image of an area included in a reference picture, and an encoded bitstream may be generated that includes information for identifying the derived first motion vector.

[0036] A decoding device according to one embodiment of the present disclosure includes a circuit and a memory, and the circuit uses the memory to, in a first operating mode, derive a first motion vector for each prediction block into which an image included in a moving image is divided, and perform a first motion compensation process for each prediction block to generate a prediction image by referring to a spatial gradient of luminance in an image generated by motion compensation using the derived first motion vector, and in a second operating mode, perform a second motion compensation process for each sub-block into which the prediction block is divided, and generate a prediction image for each sub-block without referring to a spatial gradient of luminance in an image generated by motion compensation using the second motion vector.

[0037] According to this, in the first operating mode, the decoding device performs the motion vector derivation process and the first motion compensation process on a prediction block basis, thereby reducing the amount of processing compared to performing these processes on a sub-block basis, for example. Furthermore, the first motion compensation process, which generates a prediction image by referring to the spatial gradient of luminance, can achieve correction on a unit smaller than the prediction block unit, thereby suppressing a decrease in coding efficiency that occurs when processing is not performed on a sub-block basis. Furthermore, in the second operating mode, the decoding device performs the motion vector derivation process and the second motion compensation process on a sub-block basis. Here, the second motion compensation process does not refer to the spatial gradient of luminance, so the processing amount is smaller than that of the first motion compensation process. Furthermore, by having these two operating modes, the decoding device can improve coding efficiency. In this way, the encoding device can reduce the amount of processing while suppressing a decrease in coding efficiency.

[0038] For example, the circuit may derive the first motion vector for each prediction block using a first inter prediction method in the first operation mode, and derive the second motion vector for each sub-block using a second inter prediction method different from the first inter prediction method in the second operation mode.

[0039] For example, the second inter prediction method may be an inter prediction method that uses a degree of compatibility between two reconstructed images of two regions in two different pictures.

[0040] This allows inter-picture prediction to be performed on a sub-block basis, which is highly effective in improving coding efficiency by calculating motion vectors on a sub-block basis, thereby improving coding efficiency.

[0041] For example, the first inter-picture prediction method may be one of (1) a third inter-picture prediction method that uses the degree of conformance between a reconstructed image of an area in a target picture adjacent to a target prediction block and a reconstructed image of an area in a reference picture, and (2) a fourth inter-picture prediction method that uses the degree of conformance between two reconstructed images of two areas in two different reference pictures, and the second inter-picture prediction method may be the other of the third inter-picture prediction method and the fourth inter-picture prediction method.

[0042] For example, the first inter prediction method may be the third inter prediction method, and the second inter prediction method may be the fourth inter prediction method.

[0043] This allows inter-picture prediction to be performed on a sub-block basis, which is highly effective in improving coding efficiency by calculating motion vectors on a sub-block basis, thereby improving coding efficiency.

[0044] For example, in the first inter-frame prediction method, information for identifying the first motion vector in units of the prediction block may be obtained from the coded bitstream, and the first motion vector may be derived using the information.

[0045] In one embodiment of the encoding method of the present disclosure, in a first operating mode, a first motion vector is derived for each prediction block obtained by dividing an image included in a moving image, and a first motion compensation process is performed for each prediction block to generate a predicted image by referring to the spatial gradient of luminance in an image generated by motion compensation using the derived first motion vector; and in a second operating mode, a second motion compensation process is performed for each sub-block obtained by dividing the prediction block, and a second motion compensation process is performed for each sub-block to generate a predicted image without referring to the spatial gradient of luminance in an image generated by motion compensation using the second motion vector.

[0046] According to this, in the first operating mode, the coding method performs the motion vector derivation process and the first motion compensation process on a prediction block basis, thereby reducing the amount of processing compared to performing these processes on a sub-block basis. Furthermore, the first motion compensation process, which generates a prediction image by referring to the spatial gradient of luminance, can achieve correction on a unit smaller than the prediction block unit, thereby suppressing a decrease in coding efficiency that occurs when processing is not performed on a sub-block basis. Furthermore, in the second operating mode, the coding method performs the motion vector derivation process and the second motion compensation process on a sub-block basis. Here, the second motion compensation process does not refer to the spatial gradient of luminance, so the processing amount is smaller than that of the first motion compensation process. Furthermore, by having these two operating modes, the coding method can improve coding efficiency. In this way, the coding method can reduce the amount of processing while suppressing a decrease in coding efficiency.

[0047] A decoding method according to one embodiment of the present disclosure, in a first operating mode, derives a first motion vector for each prediction block into which an image included in a moving image is divided, and performs a first motion compensation process for each prediction block to generate a predicted image by referring to the spatial gradient of luminance in an image generated by motion compensation using the derived first motion vector; and in a second operating mode, derives a second motion vector for each sub-block into which the prediction block is divided, and performs a second motion compensation process for each sub-block to generate a predicted image without referring to the spatial gradient of luminance in an image generated by motion compensation using the second motion vector.

[0048] According to this, in the first operation mode, the decoding method performs the motion vector derivation process and the first motion compensation process on a prediction block basis, thereby reducing the amount of processing compared to performing these processes on a sub-block basis, for example. Furthermore, the first motion compensation process, which generates a prediction image by referring to the spatial gradient of luminance, can achieve correction on a unit smaller than the prediction block unit, thereby suppressing a decrease in coding efficiency that occurs when processing is not performed on a sub-block basis. Furthermore, in the second operation mode, the decoding method performs the motion vector derivation process and the second motion compensation process on a sub-block basis. Here, the second motion compensation process does not refer to the spatial gradient of luminance, so the processing amount is smaller than that of the first motion compensation process. Furthermore, by having these two operation modes, the decoding method can improve coding efficiency. In this way, the coding method can reduce the amount of processing while suppressing a decrease in coding efficiency.

[0049] Furthermore, these comprehensive or specific aspects may be realized as a system, an apparatus, a method, an integrated circuit, a computer program, or a non-transitory recording medium such as a computer-readable CD-ROM, or may be realized as any combination of a system, an apparatus, a method, an integrated circuit, a computer program, and a recording medium.

[0050] Hereinafter, the embodiments will be specifically described with reference to the drawings.

[0051] The embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, component placement and connection configurations, steps, and step order 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 the independent claims that represent the highest concepts are described as optional components.

[0052] (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.

[0053] 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.

[0054] (1) For the encoding device or decoding device of the first embodiment, among the multiple components constituting the encoding device or 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. (2) Any modification, such as addition, replacement, or deletion, of the functions or processes performed by some of the components constituting the encoding device or decoding device of the first embodiment may be made to the encoding device or decoding device, and then components corresponding to the components described in each aspect of the present disclosure may be replaced with the components described in each aspect of the present disclosure. (3) The method implemented by the encoding device or decoding device of the first embodiment may be modified by adding a process and / or replacing or deleting some of the processes included in the method, and then replacing the process described in each aspect of the present disclosure with the process described in each aspect of the present disclosure. (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. (5) A component having some of the functions of some of the components constituting the encoding device or decoding device of the first embodiment, or a component that performs some of the processing performed by some of the components constituting the encoding device or decoding device of the first embodiment, is implemented in combination with a component described in each aspect of the present disclosure, a component having some of the functions of the components described in each aspect of the present disclosure, or a component that performs some of the processing performed by the components described in each aspect of the present disclosure. (6) In the method implemented by the encoding device or decoding device of the first embodiment, among the multiple processes included in the method, processes corresponding to the processes described in each aspect of the present disclosure are replaced with the processes described in each aspect of the present disclosure. (7) Some of the processes included in the method implemented by the encoding device or decoding device of the first embodiment may be implemented in combination with the processes described in each aspect of the present disclosure.

[0055] 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, they may be implemented in a device used for a purpose different from the video / image encoding device or video / image decoding device disclosed in Embodiment 1, 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.

[0056] [Outline of the encoding device] First, an overview of a coding device according to Embodiment 1 will be described. 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.

[0057] 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.

[0058] The encoding device 100 is realized by, for example, a general-purpose processor and memory. In this case, when a 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. Alternatively, the encoding device 100 may 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.

[0059] Each component included in the encoding device 100 will be described below.

[0060] [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 are sometimes 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 are sometimes called coding units (CUs), prediction units (PUs), or transform units (TUs). Note that in this embodiment, there is no need to distinguish between CUs, PUs, and TUs, and some or all of the blocks in a picture may serve as the processing units of CUs, PUs, and TUs.

[0061] 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.

[0062] 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).

[0063] 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.

[0064] The top right 64x64 block is divided horizontally into two rectangular 64x32 blocks 14 and 15 (binary tree block division).

[0065] The lower-left 64x64 block is divided into four square 32x32 blocks (quadtree block decomposition). Of the four 32x32 blocks, the upper-left and lower-right blocks are further divided. The upper-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 decomposition). The lower-right 32x32 block is divided horizontally into two 32x16 blocks (binary tree block decomposition). As a result, the lower-left 64x64 block is divided into 16x32 block 16, two 16x16 blocks 17 and 18, two 32x32 blocks 19 and 20, and two 32x16 blocks 21 and 22.

[0066] The bottom right 64x64 block 23 is not split.

[0067] 2, block 10 is divided into 13 variable-sized blocks 11 to 23 based on recursive quad-tree and binary tree block division. This type of division is sometimes called QTBT (quad-tree plus binary tree) division.

[0068] 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.

[0069] [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 referred to as a residual) 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.

[0070] 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 an image may also be referred to as a sample.

[0071] [Conversion section] The transform unit 106 transforms the spatial domain prediction errors into frequency domain transform coefficients 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 spatial domain prediction errors.

[0072] 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 is sometimes called an explicit multiple core transform (EMT) or an adaptive multiple transform (AMT).

[0073] The multiple transform types include, for example, DCT-II, DCT-V, DCT-VIII, DST-I, and DST-VII. Fig. 3 is a table showing transform basis functions corresponding to each transform type. In Fig. 3, N represents the number of input pixels. Selection of a transform type from among these multiple transform types may depend, for example, on the type of prediction (intra prediction or inter prediction) or the intra prediction mode.

[0074] Information indicating whether EMT or AMT is applied (e.g., referred to as an AMT flag) and information indicating the selected transformation type are signaled at the CU level. Note that 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).

[0075] Furthermore, the transform unit 106 may retransform the transform coefficients (transform results). Such retransformation may be referred to as an adaptive secondary transform (AST) or a non-separable secondary transform (NSST). For example, the transform unit 106 performs retransformation for each sub-block (e.g., 4x4 sub-block) included in a block of transform coefficients corresponding to intra-prediction errors. Information indicating whether or not to apply NSST and information regarding the transform matrix used for NSST are signaled at the CU level. Note that signaling of this information does not need to be limited to the CU level, and may be at other levels (e.g., the sequence level, picture level, slice level, tile level, or CTU level).

[0076] 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 all at once.

[0077] 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 the transformation process is performed on that array using a 16x16 transformation matrix.

[0078] Similarly, a non-separable transformation is one that treats a 4x4 input block as a single array with 16 elements and then performs multiple Givens rotations on that array (Hypercube Givens Transform).

[0079] [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 quantization parameters (QP) corresponding to the scanned transform coefficients. The quantization unit 108 then 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.

[0080] The predetermined order is an order for quantizing / dequantizing the transform coefficients. For example, the predetermined scanning order is defined as an ascending order (low frequency to high frequency) or a descending order (high frequency to low frequency).

[0081] The quantization parameter is a parameter that defines the quantization step (quantization width). For example, as the value of the quantization parameter increases, the quantization step also increases. In other words, as the value of the quantization parameter increases, the quantization error also increases.

[0082] [Entropy coding section] 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.

[0083] [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. The inverse quantization unit 112 then outputs the inverse quantized transform coefficients of the current block to the inverse transform unit 114.

[0084] [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.

[0085] 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.

[0086] [Adder] 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.

[0087] [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.

[0088] [Loop filter section] The loop filter unit 120 applies a loop filter to the block reconstructed by the adder 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).

[0089] ALF applies a least squares error filter to remove coding artifacts, for example, for each 2x2 sub-block in the current block, one filter selected from multiple filters based on local gradient direction and activity.

[0090] Specifically, first, sub-blocks (e.g., 2x2 sub-blocks) are classified into a plurality of classes (e.g., 15 or 25 classes). The sub-blocks are classified 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).

[0091] The gradient direction value D is derived by, for example, comparing gradients in multiple directions (e.g., horizontal, vertical, and two diagonal directions), and the gradient activity value A is derived by, for example, adding gradients in multiple directions and quantizing the sum.

[0092] Based on the result of such classification, a filter for the sub-block is determined from among a plurality of filters.

[0093] The filter shape used in ALF is, for example, a circularly symmetric shape. FIGS. 4A to 4C are diagrams showing several examples of filter shapes used in ALF. FIG. 4A shows a 5x5 diamond-shaped filter, FIG. 4B shows a 7x7 diamond-shaped filter, and FIG. 4C shows a 9x9 diamond-shaped filter. Information indicating the filter shape is signaled at the picture level. Note that signaling of the information indicating the filter shape does not need to be limited to the picture level, and may be at other levels (e.g., sequence level, slice level, tile level, CTU level, or CU level).

[0094] Whether ALF is turned on or off is determined, for example, at the picture level or the CU level. For example, whether ALF is applied to luminance is determined at the CU level, and whether ALF is applied to chrominance is determined at the picture level. Information indicating whether ALF is turned on or off is signaled at the picture level or the CU level. Note that signaling of information indicating whether ALF is turned on or off does not need to be 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).

[0095] 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 also be at other levels (e.g., sequence level, slice level, tile level, CTU level, CU level, or sub-block level).

[0096] [Frame memory] The frame memory 122 is a storage unit for storing reference pictures used in inter prediction, and is sometimes called a frame buffer. Specifically, the frame memory 122 stores the reconstructed blocks filtered by the loop filter unit 120.

[0097] [Intra prediction section] The intra prediction unit 124 generates a prediction signal (intra prediction signal) by performing intra prediction (also referred to as intra-picture prediction) of the current block with reference to blocks in the current picture stored in the block memory 118. Specifically, the intra prediction unit 124 generates the 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.

[0098] 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.

[0099] 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).

[0100] The multiple directional prediction modes include, for example, the 33 prediction modes defined in the H.265 / HEVC standard. Note that the multiple directional prediction modes may also include 32 prediction modes in addition to the 33 directions (65 directional prediction modes in total). Fig. 5A is a diagram showing 67 intra prediction modes (2 non-directional prediction modes and 65 directional prediction modes) in intra prediction. Solid arrows represent the 33 directions defined in the H.265 / HEVC standard, and dashed arrows represent the additional 32 directions.

[0101] Note that a luminance block may be referenced in intra prediction of a chrominance block. That is, the chrominance component of the current block may be predicted based on the luminance component of the current block. This type of intra prediction is sometimes called CCLM (cross-component linear model) prediction. An intra prediction mode of a chrominance block that references such a luminance block (e.g., called a CCLM mode) may be added as one of the intra prediction modes for the chrominance block.

[0102] The intra prediction unit 124 may correct pixel values ​​after intra prediction based on gradients of reference pixels in the horizontal / vertical directions. Intra prediction involving such correction is sometimes called PDPC (position dependent intra prediction combination). Information indicating whether PDPC is applied (e.g., called a PDPC flag) is signaled, for example, at the CU level. Note that 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).

[0103] [Inter prediction section] The inter prediction unit 126 generates a prediction signal (inter prediction signal) by performing inter prediction (also referred to as inter prediction) on the current block with reference to a reference picture stored in the frame memory 122 that is different from the current picture. The inter prediction is performed in units of the current block or sub-blocks (e.g., 4x4 blocks) within the current block. For example, the inter prediction unit 126 performs motion estimation on the current block or sub-block within the reference picture. The inter prediction unit 126 then generates an inter prediction signal for the current block or sub-block by performing motion compensation using motion information (e.g., a motion vector) obtained by the motion estimation. The inter prediction unit 126 then outputs the generated inter prediction signal to the prediction control unit 128.

[0104] The motion information used for 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.

[0105] Note that an inter-prediction signal may be generated using not only the motion information of the current block obtained by motion estimation, but also the motion information of adjacent blocks. Specifically, an inter-prediction signal may be generated for each sub-block in the current block by weighting and adding a prediction signal based on the motion information obtained by motion estimation and a prediction signal based on the motion information of adjacent blocks. Such inter-prediction (motion compensation) may be called OBMC (overlapped block motion compensation).

[0106] In such an OBMC mode, information indicating the size of a sub-block for OBMC (e.g., called an OBMC block size) is signaled at the sequence level. Also, information indicating whether the OBMC mode is applied (e.g., called an OBMC flag) is signaled at the CU level. Note that the signaling level of this information is not limited to the sequence level and the CU level, and may be other levels (e.g., the picture level, slice level, tile level, CTU level, or sub-block level).

[0107] The OBMC mode will now be described in more detail. Figures 5B and 5C are a flowchart and a conceptual diagram for explaining an outline of the predictive image correction process using the OBMC process.

[0108] First, a predicted image (Pred) is obtained by normal motion compensation using a motion vector (MV) assigned to the block to be coded.

[0109] Next, the motion vector (MV_L) of the coded left adjacent block is applied to the block to be coded to obtain a predicted image (Pred_L), and the predicted image is weighted and superimposed with Pred_L to perform the first correction of the predicted image.

[0110] Similarly, the motion vector (MV_U) of the already coded upper adjacent block is applied to the block to be coded 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.

[0111] 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 correction is performed more than two times using the right adjacent block or the lower adjacent block.

[0112] The area to be superimposed does not have to be the pixel area of ​​the entire block, but may be only a part of the area near the block boundary.

[0113] Although the process of correcting a predicted image from one reference picture has been described here, 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 further superimposed to form the final predicted image.

[0114] The target block to be processed may be a prediction block unit or a sub-block unit obtained by further dividing the prediction block.

[0115] As a method for determining whether to apply OBMC processing, for example, there is a method using obmc_flag, which is a signal indicating whether to apply OBMC processing. As a specific example, an encoding device determines whether a block to be encoded belongs to an area with complex motion, and if it belongs to an area with complex motion, sets the value of obmc_flag to 1 and performs encoding using OBMC processing, and if it does not belong to an area with complex motion, sets the value of obmc_flag to 0 and performs encoding without applying OBMC processing. On the other hand, a decoding device decodes obmc_flag described in a stream, and switches whether to apply OBMC processing depending on the value, and performs decoding.

[0116] Alternatively, 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. Alternatively, 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.

[0117] 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.

[0118] An example of the FRUC process is shown in Figure 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 coded blocks spatially or temporally adjacent to the current block. Next, a best candidate MV is selected from the 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.

[0119] Then, a motion vector for the current block is derived based on the motion vector of the selected candidate. Specifically, for example, the motion vector of the selected candidate (best candidate MV) is derived as the motion vector for the current block as is. Also, for example, the motion vector for the current block may be derived by performing pattern matching in a peripheral area of ​​a position in a reference picture corresponding to the motion vector of the selected candidate. That is, a search is performed in a similar manner in a peripheral area of ​​the best candidate MV, and if an MV with a better evaluation value is found, the best candidate MV may be updated to the MV and used as the final MV for the current block. Note that a configuration may be adopted in which this process is not performed.

[0120] The same processing may be performed when processing is performed in sub-block units.

[0121] The evaluation value is calculated by finding the difference between the reconstructed image and a predetermined area by pattern matching between the area in the reference picture corresponding to the motion vector. The evaluation value may be calculated using other information in addition to the difference.

[0122] As the pattern matching, first pattern matching or second pattern matching is used. The first pattern matching and second pattern matching are sometimes called bilateral matching and template matching, respectively.

[0123] 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 that is along the motion trajectory of the current block is used as a predetermined area for calculating the evaluation value of the candidate.

[0124] FIG. 6 is a diagram illustrating 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 the most closely matched pair of two blocks along the motion trajectory of a current block (Cur block) in two different reference pictures (Ref0, Ref1). Specifically, for the current block, a difference is derived between a reconstructed image at a specified position in a first coded reference picture (Ref0) specified by a candidate MV and a reconstructed image at a specified position in a second coded reference picture (Ref1) specified by a symmetric MV obtained by scaling the candidate MV by the display time interval, and an evaluation value is calculated using the obtained difference value. The candidate MV with the best evaluation value among multiple candidate MVs may be selected as the final MV.

[0125] Under the assumption of continuous motion trajectories, motion vectors (MV0, MV1) pointing to two reference blocks are proportional to the temporal distances (TD0, TD1) between a current picture (CurPic) and two reference pictures (Ref0, Ref1). For example, if the current picture is located between two reference pictures temporally 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.

[0126] 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, the block adjacent to the current block in the current picture is used as a predetermined area for calculating the evaluation value of the candidate.

[0127] 7 is a diagram illustrating 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 a reference picture (Ref0) for a block that best matches a block adjacent to a current block (Cur block) in the current picture (Cur Pic). Specifically, a difference is derived between a reconstructed image of both or either of the coded areas adjacent to the left and / or above the current block and a reconstructed image at the same position in the coded reference picture (Ref0) specified by a candidate MV, an evaluation value is calculated using the obtained difference value, and the candidate MV with the best evaluation value among the multiple candidate MVs is selected as the best candidate MV.

[0128] Information indicating whether such a FRUC mode is applied (e.g., called an FRUC flag) is signaled at the CU level. Furthermore, 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., called an FRUC mode flag) is signaled at the CU level. Note that signaling of this information does not need to be limited to the CU level, and may be at other levels (e.g., the sequence level, the picture level, the slice level, the tile level, the CTU level, or the sub-block level).

[0129] Here, we will explain a mode in which motion vectors are derived based on a model that assumes uniform linear motion. This mode is sometimes called BIO (bi-directional optical flow) mode.

[0130] FIG. 8 is a diagram for explaining a model assuming uniform linear motion. In FIG. 8, (v x ,v y) denotes a velocity vector, and τ0 and τ1 denote the temporal distance between the current picture (Cur Pic) and two reference pictures (Ref0 and Ref1), respectively. (MVx0,MVy0) denotes a motion vector corresponding to reference picture Ref0, and (MVx1,MVy1) denotes a motion vector corresponding to reference picture Ref1.

[0131] At this time, the velocity vector (v x ,v y ), (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:

[0132]

number

[0133] where 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.

[0134] Note that the decoding device may derive motion vectors using a method other than that based on a model assuming constant-velocity linear motion. For example, a motion vector may be derived for each sub-block based on the motion vectors of multiple adjacent blocks.

[0135] Here, a mode in which a motion vector is derived for each sub-block based on the motion vectors of multiple neighboring blocks will be described. This mode is sometimes called an affine motion compensation prediction mode.

[0136] FIG. 9A is a diagram for explaining the derivation of motion vectors 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, the 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 the 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 vector (v x ,v y ) is derived.

[0137]

number

[0138] Here, x and y respectively indicate the horizontal and vertical positions of the sub-block, and w indicates a predetermined weighting coefficient.

[0139] Such an affine motion compensation prediction mode may include several modes in which the methods of deriving the motion vectors of the upper-left and upper-right corner control points are different. Information indicating such an affine motion compensation prediction mode (e.g., called an 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., the sequence level, the picture level, the slice level, the tile level, the CTU level, or the sub-block level).

[0140] [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.

[0141] Here, an example of deriving a motion vector for a picture to be coded in merge mode will be described. Fig. 9B is a diagram for explaining an overview of the motion vector derivation process in merge mode.

[0142] 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 spatially located around the block to be coded, temporally adjacent prediction MVs, which are MVs held by blocks in the vicinity of the block to be coded projected onto the coded reference picture, joint prediction MVs, which are MVs generated by combining the MV values ​​of the spatially adjacent prediction MVs and the temporally adjacent prediction MVs, and zero prediction MVs, which are MVs with a value of zero.

[0143] Next, one prediction MV is selected from the plurality of prediction MVs registered in the prediction MV list, and is determined as the MV for the block to be coded.

[0144] Furthermore, the variable length coding unit encodes the stream by describing merge_idx, which is a signal indicating which predicted MV has been selected.

[0145] 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 predicted MVs other than the types of predicted MVs shown in the figure.

[0146] The final MV may be determined by performing the DMVR process, which will be described later, using the MV of the block to be coded derived in the merge mode.

[0147] Here, an example of determining the MV using the DMVR process will be described.

[0148] FIG. 9C is a conceptual diagram for explaining an outline of the DMVR process.

[0149] 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 averaging each reference pixel.

[0150] Next, the template is used to search the surrounding areas of the candidate MVs in 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 between each pixel value of the template and each pixel value of the search area, the MV value, etc.

[0151] The outline of the processing described here is basically the same for the encoding device and the decoding device.

[0152] 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.

[0153] Here, a mode for generating a predicted image using LIC processing will be described.

[0154] FIG. 9D is a diagram for explaining an outline of a predicted image generation method using luminance correction processing by LIC processing.

[0155] First, an MV for obtaining a reference image corresponding to a block to be coded is derived from a reference picture that is a coded picture.

[0156] 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.

[0157] A predicted image for the block to be coded is generated by performing luminance correction processing on a reference image in a reference picture specified by the MV using the luminance correction parameters.

[0158] The shape of the peripheral reference region in FIG. 9D is an example, and other shapes may be used.

[0159] 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.

[0160] One method for determining whether to apply LIC processing is to use lic_flag, which is a signal indicating whether to apply LIC processing. As a specific example, an encoding device determines whether 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, sets the value of lic_flag to 1 and performs encoding by applying LIC processing, and if it does not belong to an area where a luminance change occurs, sets the value of lic_flag to 0 and performs encoding without applying LIC processing. On the other hand, a decoding device decodes lic_flag described in the stream, and switches whether to apply LIC processing depending on the value, and performs decoding.

[0161] As another method for determining whether to apply LIC processing, for example, there is also a method for determining whether LIC processing has been applied to surrounding blocks.As a specific example, when the block to be coded is in merge mode, it is determined whether the surrounding coded blocks selected when deriving MV in merge mode processing have been coded using LIC processing, and depending on the result, whether to apply LIC processing is switched and coded.In addition, in this example, the process in decoding is exactly the same.

[0162] [Overview of the decoding device] Next, an overview will be given of a decoding device capable of decoding the coded signal (coded bitstream) output from the above coding device 100. Fig. 10 is a block diagram showing the functional configuration of a decoding device 200 according to Embodiment 1. The decoding device 200 is a video / image decoding device that decodes video / images on a block-by-block basis.

[0163] 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.

[0164] The decoding device 200 is realized by, for example, a general-purpose processor and memory. In this case, when a 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. Alternatively, the decoding device 200 may 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.

[0165] Each component included in the decoding device 200 will be described below.

[0166] [Entropy Decoding] The entropy decoding unit 202 entropy-decodes the coded bitstream. Specifically, the entropy decoding unit 202 arithmetically decodes the coded bitstream into a binary signal. 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.

[0167] [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. The inverse quantization unit 204 then outputs the inverse quantized coefficients (i.e., transform coefficients) of the current block to the inverse transform unit 206.

[0168] [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 .

[0169] 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.

[0170] Also, for example, if the information decoded from the coded bitstream indicates that NSST is to be applied, then inverse transform unit 206 applies an inverse re-transform to the transform coefficients.

[0171] [Adder] The adder 208 reconstructs the current block by adding the prediction error input from the inverse transformer 206 and the prediction sample 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.

[0172] [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 blocks output from the adder 208.

[0173] [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.

[0174] If the information indicating ALF on / off read from the encoded bitstream indicates that ALF is on, one filter is selected from multiple filters based on the local gradient direction and activity, and the selected filter is applied to the reconstructed block.

[0175] [Frame memory] The frame memory 214 is a storage unit for storing reference pictures used in inter prediction, and is sometimes called a frame buffer. Specifically, the frame memory 214 stores the reconstructed blocks filtered by the loop filter unit 212.

[0176] [Intra prediction section] The intra prediction unit 216 generates a prediction signal (intra prediction signal) by performing intra prediction based on the intra prediction mode interpreted from the encoded bitstream, by referring to blocks in the current picture stored in the block memory 210. Specifically, the intra prediction unit 216 generates the intra prediction signal by performing intra prediction by referring 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.

[0177] 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.

[0178] Furthermore, when information interpreted from the coded 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 and vertical directions.

[0179] [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) within the current block. For example, the inter prediction unit 218 generates an inter prediction signal for the current block or sub-block by performing motion compensation using motion information (e.g., motion vectors) interpreted from the coded bitstream, and outputs the inter prediction signal to the prediction control unit 220.

[0180] In addition, if 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.

[0181] Furthermore, if the information interpreted from the coded bitstream indicates that the FRUC mode is to be 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 coded bitstream. Then, the inter prediction unit 218 performs motion compensation using the derived motion information.

[0182] Furthermore, when the BIO mode is applied, the inter prediction unit 218 derives a motion vector based on a model assuming constant-velocity linear motion. Furthermore, when information interpreted from the coded bitstream indicates that the affine motion compensation prediction mode is to be applied, the inter prediction unit 218 derives a motion vector for each sub-block based on the motion vectors of multiple adjacent blocks.

[0183] [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.

[0184] [Comparative Example] Before describing the inter-screen prediction process according to this embodiment, an example of the inter-screen prediction process when the method of this embodiment is not used will be described.

[0185] First, comparative example 1 will be described. Fig. 11 is a flowchart of inter prediction processing in units of prediction blocks in a video encoding method and a video decoding method according to comparative example 1. The processing shown in Fig. 11 is repeatedly performed in units of prediction blocks, which are the processing units of the inter prediction processing. Note that, although the following mainly describes the operation of the inter prediction unit 126 included in the encoding device 100, the operation of the inter prediction unit 218 included in the decoding device 200 is also similar.

[0186] When the FRUC control information indicates 0 (0 in S101), the inter prediction unit 126 derives a motion vector (MV) for each prediction block according to a normal inter prediction method (S102). Here, the normal inter prediction method is a conventional method that does not use the FRUC method, and is, for example, a method in which a motion vector is derived on the encoding side, and information indicating the derived motion vector is transmitted from the encoding side to the decoding side.

[0187] Next, the inter prediction unit 126 performs motion compensation for each prediction block using the motion vector for each prediction block, thereby obtaining an inter prediction image (S103).

[0188] On the other hand, when the FRUC control information indicates 1 (1 in S101), the inter predictor 126 derives a motion vector for each prediction block according to the template FRUC method (S104).Then, the inter predictor 126 derives a motion vector for each sub-block obtained by dividing the prediction block according to the template FRUC method (S105).

[0189] On the other hand, when the FRUC control information indicates 2 (2 in S101), the inter predictor 126 derives a motion vector for each prediction block according to the bilateral FRUC method (S106). Thereafter, the inter predictor 126 derives a motion vector for each sub-block obtained by dividing the prediction block according to the bilateral FRUC method (S107).

[0190] Then, the inter prediction unit 126 derives a motion vector for each sub-block according to the template FRUC method or the bilateral FRUC method, and then performs motion compensation for each sub-block using the derived motion vector for each sub-block to obtain an inter-screen predicted image (S108).

[0191] In this way, FRUC processing can track small movements by deriving motion vectors for each block and then correcting the motion vectors for each sub-block. This improves coding efficiency. However, it may not be able to adequately handle blocks where deformation occurs on a pixel-by-pixel basis.

[0192] Next, comparative example 2 will be described. Fig. 12 is a flowchart of inter prediction processing in units of prediction blocks in a video encoding method and a video decoding method according to comparative example 2. In comparative example 2, BIO processing is used as motion compensation processing. That is, in the processing shown in Fig. 12, steps S103 and S108 in the processing shown in Fig. 11 are changed to steps S103A and S108A.

[0193] When the FRUC control information indicates 0 (0 in S101), the inter prediction unit 126 derives a motion vector for each prediction block according to a normal inter prediction method (S102). Next, the inter prediction unit 126 obtains an inter prediction image by performing motion compensation by BIO processing for each prediction block using the motion vector for each prediction block (S103A).

[0194] On the other hand, when the FRUC control information indicates 1 (1 in S101), the inter predictor 126 derives a motion vector for each prediction block according to the template FRUC method (S104).Then, the inter predictor 126 derives a motion vector for each sub-block obtained by dividing the prediction block according to the template FRUC method (S105).

[0195] On the other hand, when the FRUC control information indicates 2 (2 in S101), the inter predictor 126 derives a motion vector for each prediction block according to the bilateral FRUC method (S106). Thereafter, the inter predictor 126 derives a motion vector for each sub-block obtained by dividing the prediction block according to the bilateral FRUC method (S107).

[0196] Then, the inter prediction unit 126 derives a motion vector for each sub-block according to the template FRUC method or the bilateral FRUC method, and then performs motion compensation by BIO processing for each sub-block using the derived motion vector for each sub-block to obtain an inter-screen predicted image (S108A).

[0197] In this way, in Comparative Example 2, the inter prediction unit 126 can correct the predicted image on a pixel-by-pixel basis by performing the BIO process after the FRUC process, which may improve the coding efficiency even for blocks that are subject to deformation.

[0198] On the other hand, there is a problem that the processing volume increases because both FRUC processing and BIO processing are performed.

[0199] In addition, while normal inter-frame prediction performs BIO processing on a prediction block basis, FRUC performs BIO processing on a sub-block basis. As such, the units of the motion vectors that are input into BIO processing differ between normal inter-frame prediction and FRUC, which creates the problem of needing to implement two types of BIO processing functions.

[0200] [Inter-screen prediction processing] The inter prediction process performed by the inter prediction unit 126 according to this embodiment will be described. The inter prediction unit 126 can perform at least two types of motion vector derivation methods in the inter prediction process: a normal inter prediction method and a FRUC method. In the normal inter prediction method, information about the motion vector of the block to be processed is coded into a stream. In the FRUC method, information about the motion vector of the block to be processed is not coded into a stream, and a motion vector is derived using a reconstructed image of the processed area and a processed reference picture by a method common to both the coding side and the decoding side.

[0201] The inter prediction unit 126 further performs BIO processing, which involves performing motion compensation on the processed reference picture for each prediction block using a motion vector to obtain a prediction image, deriving a local motion estimate by obtaining a luminance gradient value, and generating a corrected prediction image using the derived local motion estimate. In the FRUC method, the inter prediction unit 126 performs processing on a prediction block basis to derive a motion vector on a prediction block basis. In the BIO processing, the inter prediction unit 126 always inputs a motion vector on a prediction block basis, regardless of which motion vector derivation method is used, and generates a prediction image using a common process on a prediction block basis.

[0202] The inter prediction process by the inter prediction unit 126 according to this embodiment will be described below. Fig. 13 is a flowchart of the inter prediction process for each prediction block in the video coding method and video decoding method according to this embodiment. The process shown in Fig. 13 is repeatedly performed for each prediction block, which is the processing unit of the inter prediction process. Note that, although the operation of the inter prediction unit 126 included in the coding device 100 will be mainly described below, the operation of the inter prediction unit 218 included in the decoding device 200 is also similar.

[0203] When the FRUC control information indicates 0 (0 in S101), the inter prediction unit 126 derives a motion vector for each prediction block according to the normal inter prediction method (S102), similar to the process shown in Fig. 12. Next, the inter prediction unit 126 obtains an inter prediction image by performing motion compensation by BIO processing for each prediction block using the motion vector for each prediction block (S103A).

[0204] On the other hand, when the FRUC control information indicates 1 (1 in S101), the inter prediction unit 126 derives a motion vector for each prediction block according to the template FRUC method (S104). When the FRUC control information indicates 2 (2 in S101), the inter prediction unit 126 derives a motion vector for each prediction block according to the bilateral FRUC method (S106). Note that, in the process shown in Fig. 13, unlike the process shown in Fig. 12, the inter prediction unit 126 does not derive a motion vector for each sub-block when the FRUC method is used.

[0205] Then, the inter prediction unit 126 derives a motion vector for each prediction block according to the template FRUC method or the bilateral FRUC method, and then obtains an inter prediction image by performing motion compensation by BIO processing for each prediction block using the derived motion vector for each prediction block (S103A).

[0206] As described above, in this embodiment, the inter prediction unit 126 derives a motion vector for each prediction block regardless of whether the FRUC control information indicates the normal inter prediction method, the template FRUC method, or the bilateral FRUC method. Then, the inter prediction unit 126 performs BIO processing for each prediction block. That is, in all cases, the processing unit is the prediction block unit, and the processing unit is the same.

[0207] Note that the numbers of the FRUC control information shown above are merely examples, and other numbers may be used. Also, only one of the template FRUC method and the bilateral FRUC method may be used. Furthermore, common processing may be used during encoding and decoding.

[0208] Here, in Comparative Example 2 shown in FIG. 12, both sub-block-based FRUC processing, which corrects motion vectors on a sub-block basis, and BIO processing, which corrects predicted images on a pixel-by-pixel basis, are performed. Both sub-block-based FRUC processing and BIO processing are processes that perform correction in units finer than predicted blocks, and have similar properties and effects. In the process shown in FIG. 13, these processes are consolidated into BIO processing. Furthermore, in the process shown in FIG. 13, the FRUC processing on a sub-block basis, which requires a large amount of processing, is not performed, thereby reducing the amount of processing. Furthermore, the BIO processing when the FRUC method is used is also changed from sub-block-based to predicted block-based, thereby reducing the amount of processing.

[0209] In this way, the processing according to this embodiment shown in FIG. 13 may be able to improve the coding efficiency even for blocks that are subject to deformation, while suppressing an increase in the amount of processing compared to Comparative Example 2 shown in FIG. 12.

[0210] Furthermore, in the process according to the present embodiment shown in Fig. 13, regardless of the value of the FRUC control information, BIO processing is performed using a motion vector for each prediction block as an input, which eliminates the need for BIO processing using a motion vector for each sub-block as an input, as compared to Comparative Example 2 shown in Fig. 12. This allows for simplification of implementation.

[0211] Note that the BIO processing in step S103A does not need to be completely identical among multiple motion vector derivation methods. That is, the BIO processing used may be different in one or each of the cases where the normal inter prediction method, the template FRUC method, and the bilateral FRUC method are used.

[0212] Furthermore, for at least one of the plurality of motion vector derivation methods, the BIO process of step S103A may be replaced with another process (including a variation of the BIO process) that generates a predicted image while correcting the predicted image in units of pixels or units smaller than the predicted block. In this case, too, the two processes having the same characteristics as described above can be integrated into one process, which may reduce the increase in processing volume compared to Comparative Example 2 and improve coding efficiency even for blocks that undergo deformation.

[0213] Furthermore, for at least one of the multiple motion vector derivation methods, the BIO process in step S103A may be replaced with another process that uses a motion vector for each prediction block as input and corrects the predicted image while generating a predicted image. In this case, the above-mentioned process of using a motion vector for each sub-block as input is also unnecessary, making it possible to simplify implementation.

[0214] Furthermore, whether or not to perform BIO processing may be switched. For example, the inter prediction unit 126 may perform the processing shown in Fig. 13 when BIO processing is performed, and may perform the processing shown in Fig. 11 when BIO processing is not performed. Alternatively, even when BIO processing is not performed, the inter prediction unit 126 may not need to perform motion vector derivation processing on a sub-block basis, as in Fig. 13. In other words, the inter prediction unit 126 may perform processing in which the processing of step S108A shown in Fig. 13 is replaced with motion compensation processing on a prediction block basis that does not include BIO processing.

[0215] [Variation of Inter-Screen Prediction Processing] A modified example of the inter prediction process according to this embodiment will be described below. Fig. 14 is a flowchart of the inter prediction process in the video coding method and video decoding method according to the modified example of this embodiment. The process shown in Fig. 14 is repeatedly performed for each prediction block, which is the processing unit of the inter prediction process.

[0216] When the FRUC control information indicates 0 (0 in S101), the inter prediction unit 126 derives a motion vector for each prediction block according to the normal inter prediction method (S102), similar to the process shown in Fig. 13. Next, the inter prediction unit 126 obtains an inter prediction image by performing motion compensation by BIO processing for each prediction block using the motion vector for each prediction block (S103A).

[0217] Furthermore, when the FRUC control information indicates 1 (1 in S101), the inter prediction unit 126 derives a motion vector for each prediction block according to the template FRUC method (S104), similar to the process shown in Fig. 13. Next, the inter prediction unit 126 obtains an inter prediction image by performing motion compensation by BIO processing for each prediction block using the motion vector for each prediction block (S103A).

[0218] On the other hand, when the FRUC control information indicates 2 (2 in S101), the inter predictor 126 derives a motion vector for each prediction block according to the bilateral FRUC method (S106). Thereafter, the inter predictor 126 derives a motion vector for each sub-block obtained by dividing the prediction block according to the bilateral FRUC method (S107).

[0219] Next, the inter prediction unit 126 performs motion compensation for each sub-block using the derived sub-block-based motion vector to obtain an inter prediction image (S108). Note that the motion compensation here is not BIO processing but normal motion compensation.

[0220] In this way, when the normal inter prediction method is used (0 in S101) and when the template FRUC method is used (1 in S101), the inter prediction unit 126 obtains an inter prediction image by performing motion compensation by BIO processing on a prediction block basis using the derived motion vector on a prediction block basis. On the other hand, when the bilateral FRUC method is used (2 in S101), the inter prediction unit 126 obtains an inter prediction image by performing normal motion compensation without applying BIO processing, using the motion vector on a sub-block basis.

[0221] The numbers used in the FRUC control information are merely examples, and other numbers may be used. The inter prediction unit 218 included in the decoder 200 also performs the same processing as the inter prediction unit 126 included in the encoding device 100.

[0222] Also, here, when the template FRUC method is used, the inter prediction unit 126 derives motion vectors on a prediction block basis and performs BIO processing on a prediction block basis, and when the bilateral FRUC method is used, it derives motion vectors on a sub-block basis and performs normal motion compensation processing on a sub-block basis; however, when the bilateral FRUC method is used, it may also derive motion vectors on a prediction block basis and perform BIO processing on a prediction block basis, and when the template FRUC method is used, it may also derive motion vectors on a sub-block basis and perform normal motion compensation processing on a sub-block basis.

[0223] In addition, the bilateral FRUC scheme has a greater effect of improving coding efficiency by deriving motion vectors on a sub-block basis than the template FRUC scheme. Therefore, it is preferable to derive motion vectors on a sub-block basis in the bilateral FRUC scheme, as shown in Figure 14.

[0224] 14, both the template FRUC method and the bilateral FRUC method are used, but only one of them may be used. In this case, when the FRUC method is used, the inter prediction unit 126 derives a motion vector for each sub-block and performs normal motion compensation processing.

[0225] Furthermore, the BIO processing in step S103A does not need to be completely identical for multiple motion vector derivation methods, i.e., the BIO processing used when the normal inter prediction method is used may be different from the BIO processing used when the template FRUC method is used.

[0226] Furthermore, for at least one of the multiple motion vector derivation methods, the BIO processing in step S103A may be replaced with another process (including a variant of the BIO processing) that generates a predicted image while correcting the predicted image in units of pixels or units smaller than the predicted block.

[0227] Furthermore, for at least one of the plurality of motion vector derivation methods, the BIO process in step S103A may be replaced with another process that generates a predicted image while correcting the predicted image using a motion vector in units of a prediction block as input.

[0228] The process shown in Figure 14 applies either the FRUC process for sub-blocks, which corrects motion vectors for each sub-block, or the BIO process for pixel-by-pixel correction of predicted images. This allows the process shown in Figure 14 to use a method with a significant synergistic effect for each FRUC method, while requiring roughly the same amount of processing as the process shown in Figure 13. This improves coding efficiency.

[0229] As described above, the encoding device 100 performs the processing shown in Fig. 15. The processing in the decoding device 200 is similar. In the first operation mode (first operation mode in S111), the encoding device 100 derives a first motion vector for each prediction block obtained by dividing an image included in a video using a first inter prediction method (S112), and performs a first motion compensation process using the derived first motion vector for each prediction block (S113). Here, the first motion compensation process is, for example, BIO processing, which is a motion compensation process that generates a prediction image by referring to a spatial gradient of luminance in an image generated by motion compensation using the derived first motion vector.

[0230] Furthermore, in the second operation mode (second operation mode at S111), the encoding device 100 derives a second motion vector for each sub-block obtained by dividing the prediction block using a second inter prediction method (S114), and performs a second motion compensation process using the second motion vector for each sub-block (S115). Here, the second motion compensation process is, for example, a motion compensation process that does not apply BIO processing, and generates a prediction image without referring to the spatial gradient of luminance in the image generated by motion compensation using the second motion vector.

[0231] According to this, in the first operating mode, the encoding device 100 performs the motion vector derivation process and the first motion compensation process on a prediction block basis, thereby reducing the amount of processing compared to performing these processes on a sub-block basis, for example. Furthermore, the first motion compensation process, which generates a prediction image by referring to the spatial gradient of luminance, can achieve correction on a unit smaller than the prediction block unit, thereby suppressing a decrease in encoding efficiency that occurs when processing is not performed on a sub-block basis. Furthermore, in the second operating mode, the encoding device 100 performs the motion vector derivation process and the second motion compensation process on a sub-block basis. Here, the second motion compensation process does not refer to the spatial gradient of luminance, and therefore requires less processing than the first motion compensation process. Furthermore, by having these two operating modes, the encoding device 100 can improve encoding efficiency. In this way, the encoding device 100 can reduce the amount of processing while suppressing a decrease in encoding efficiency.

[0232] For example, the first inter prediction method is different from the second inter prediction method, which is an inter prediction method, such as the FRUC method, that uses the degree of compatibility between two reconstructed images of two regions in two different pictures.

[0233] This allows inter-picture prediction to be performed on a sub-block basis, which is highly effective in improving coding efficiency by calculating motion vectors on a sub-block basis, thereby improving coding efficiency.

[0234] For example, the first inter-screen prediction method is one of (1) a third inter-screen prediction method (e.g., template FRUC method) that uses the degree of fit between a reconstructed image of an area in a target picture adjacent to a target prediction block and a reconstructed image of an area in a reference picture, and (2) a fourth inter-screen prediction method (e.g., bilateral FRUC method) that uses the degree of fit between two reconstructed images of two areas in two different reference pictures, and the second inter-screen prediction method is the other of the third inter-screen prediction method and the fourth inter-screen prediction method.

[0235] For example, the first inter prediction method is the third inter prediction method (for example, the template FRUC method), and the second inter prediction method is the fourth inter prediction method (for example, the bilateral FRUC method).

[0236] This allows inter-picture prediction to be performed on a sub-block basis, which is highly effective in improving coding efficiency by calculating motion vectors on a sub-block basis, thereby improving coding efficiency.

[0237] For example, the first inter prediction method is an inter prediction method (normal inter prediction method) that uses the degree of compatibility between a target prediction block and a reconstructed image of an area included in a reference picture, and the encoding device 100 generates an encoded bitstream including information for specifying the derived first motion vector. Furthermore, in the first inter prediction method, the decoding device 200 obtains information for specifying the first motion vector for each prediction block from the encoded bitstream and derives the first motion vector using the information.

[0238] [Template FRUC method and bilateral FRUC method] Below, we will explain how to derive motion vectors according to the template FRUC method or the bilateral FRUC method. The method for deriving a motion vector for each block and the method for deriving a motion vector for each sub-block are basically the same. In the following explanation, the method for deriving a motion vector for each block and the method for deriving a motion vector for each sub-block will be explained as methods for deriving a motion vector for a processing target area.

[0239] 16 is a conceptual diagram showing the template FRUC method used to derive motion vectors for a processing target region in the encoding device 100 and the decoding device 200. In the template FRUC method, motion vectors are derived using a method common to the encoding device 100 and the decoding device 200, without encoding and decoding information about the motion vectors for the processing target region.

[0240] Furthermore, in the template FRUC method, a motion vector is derived using a reconstructed image of an adjacent region, which is a region adjacent to the region to be processed, and a reconstructed image of a corresponding adjacent region, which is a region in a reference picture.

[0241] Here, the adjacent region is one or both of the region adjacent to the left and the region adjacent to the processing target region.

[0242] The corresponding adjacent region is a region specified using a candidate motion vector, which is a candidate for the motion vector of the processing target region. Specifically, the corresponding adjacent region is a region pointed to by the candidate motion vector from the adjacent region. The relative position of the corresponding adjacent region to the corresponding region pointed to by the candidate motion vector from the processing target region is equal to the relative position of the adjacent region to the processing target region.

[0243] 17 is a conceptual diagram showing the bilateral FRUC method used to derive motion vectors for a processing target region in the encoding device 100 and the decoding device 200. In the bilateral FRUC method, similar to the template FRUC method, motion vectors for a processing target region are not coded or decoded, and a motion vector is derived using a method common to both the encoding device 100 and the decoding device 200.

[0244] In addition, in the bilateral FRUC scheme, a motion vector is derived using two reconstructed images of two regions in two reference pictures. For example, as shown in Figure 17, a motion vector is derived using a reconstructed image of a corresponding region in a first reference picture and a reconstructed image of a symmetric region in a second reference picture.

[0245] Here, the corresponding region and the symmetric region are each specified using a candidate motion vector that is a candidate for the motion vector of the processing target region. Specifically, the corresponding region is a region pointed to by the candidate motion vector from the processing target region. The symmetric region is a region pointed to by the symmetric motion vector from the processing target region. The symmetric motion vector is a motion vector that constitutes a pair of candidate motion vectors for bidirectional prediction. The symmetric motion vector may be a motion vector derived by scaling the candidate motion vector.

[0246] 18 is a flowchart showing the operation of the inter prediction unit 126 of the encoding device 100 to derive a motion vector according to the template FRUC method or the bilateral FRUC method. The inter prediction unit 218 of the decoding device 200 operates in the same manner as the inter prediction unit 126 of the encoding device 100.

[0247] First, the inter prediction unit 126 derives candidate motion vectors by referring to the motion vectors of one or more processed regions that are temporally or spatially peripheral to the region to be processed.

[0248] In the bilateral FRUC scheme, the inter predictor 126 derives candidate motion vectors for bidirectional prediction. That is, the inter predictor 126 derives candidate motion vectors as a set of two motion vectors.

[0249] Specifically, in the bilateral FRUC method, if the motion vector of the processed region is a bidirectional prediction motion vector, the inter prediction unit 126 derives the bidirectional prediction motion vector as a bidirectional prediction candidate motion vector. If the motion vector of the processed region is a unidirectional prediction motion vector, the inter prediction unit 126 may derive a bidirectional prediction motion vector by scaling the unidirectional prediction motion vector, thereby deriving a bidirectional prediction candidate motion vector.

[0250] More specifically, in the bilateral FRUC scheme, the inter prediction unit 126 derives a motion vector that references a second reference picture by scaling a motion vector that references a first reference picture according to the display interval, thereby deriving a candidate motion vector that constitutes a pair of a motion vector for unidirectional prediction and a scaled motion vector as a candidate motion vector for bidirectional prediction.

[0251] Alternatively, in the bilateral FRUC scheme, when the motion vector of the processed region is a bidirectional prediction motion vector, the inter prediction unit 126 may derive the motion vector of the processed region as a candidate motion vector. And when the motion vector of the processed region is a unidirectional prediction motion vector, the inter prediction unit 126 may not derive the motion vector of the processed region as a candidate motion vector.

[0252] In the template FRUC method, the inter prediction unit 126 derives the motion vector of the processed area as a candidate motion vector, regardless of whether the motion vector of the processed area is a bidirectional prediction motion vector or a unidirectional prediction motion vector.

[0253] Then, the inter prediction unit 126 generates a candidate motion vector list composed of candidate motion vectors (S201). Here, when the processing target region is a sub-block, that is, when deriving a motion vector in units of sub-blocks, the inter prediction unit 126 may include a block-based motion vector as a candidate motion vector in the candidate motion vector list. In this case, the inter prediction unit 126 may include the block-based motion vector as a candidate motion vector with the highest priority in the candidate motion vector list.

[0254] Furthermore, in the bilateral FRUC method, when a block-based motion vector is a unidirectional prediction motion vector, the inter prediction unit 126 may derive a bidirectional prediction candidate motion vector from the unidirectional prediction motion vector by scaling, etc. For example, the inter prediction unit 126 may derive a bidirectional prediction candidate motion vector from the unidirectional prediction motion vector by scaling, etc., in the same way as when the surrounding motion vectors are unidirectional prediction motion vectors.

[0255] Then, the inter prediction unit 126 may include, in the candidate motion vector list, the candidate motion vector derived as the bidirectional prediction candidate motion vector from the unidirectional prediction motion vector.

[0256] Alternatively, in the bilateral FRUC scheme, when a block-based motion vector is a bidirectional prediction motion vector, the inter prediction unit 126 may include the block-based motion vector in the candidate motion vector list as a candidate motion vector. And when a block-based motion vector is a unidirectional prediction motion vector, the inter prediction unit 126 may not include the block-based motion vector in the candidate motion vector list as a candidate motion vector.

[0257] Then, the inter prediction unit 126 selects a best candidate motion vector from one or more candidate motion vectors included in the candidate motion vector list (S202). At this time, the inter prediction unit 126 calculates an evaluation value for each of the one or more candidate motion vectors according to the degree of compatibility between the two reconstructed images of the two evaluation target regions.

[0258] Specifically, in the template FRUC method, the two evaluation target regions are an adjacent region and a corresponding adjacent region as shown in Fig. 16, and in the bilateral FRUC method, the two evaluation target regions are a corresponding region and a symmetric region as shown in Fig. 17. As described above, the corresponding adjacent regions used in the template FRUC method and the corresponding region and symmetric region used in the bilateral FRUC method are determined according to the candidate motion vectors.

[0259] For example, the inter prediction unit 126 calculates a better evaluation value as the degree of conformance between two reconstructed images of two evaluation target regions increases. Specifically, the inter prediction unit 126 derives a difference value between two reconstructed images of two evaluation target regions. Then, the inter prediction unit 126 calculates an evaluation value using the difference value. For example, the inter prediction unit 126 calculates a better evaluation value as the difference value decreases.

[0260] Furthermore, the evaluation value may be calculated using not only the difference value but also other information. That is, the inter prediction unit 126 may calculate the evaluation value using the difference value and other information. For example, the priority of one or more candidate motion vectors, the amount of code based on the priority, etc. may affect the evaluation value.

[0261] Then, the inter prediction unit 126 selects the candidate motion vector with the best evaluation value from among the one or more candidate motion vectors as the best candidate motion vector.

[0262] Then, the inter prediction unit 126 derives a motion vector for the processing target area by searching the vicinity of the best candidate motion vector (S203).

[0263] That is, the inter prediction unit 126 similarly calculates evaluation values ​​for motion vectors indicating areas surrounding the area indicated by the best candidate motion vector. Then, if there is a motion vector with a better evaluation value than the best candidate motion vector, the inter prediction unit 126 updates the best candidate motion vector with the motion vector with the better evaluation value. Then, the inter prediction unit 126 derives the updated best candidate motion vector as the final motion vector for the processing target area.

[0264] The inter prediction unit 126 may derive the best candidate motion vector as the final motion vector for the processing target area without performing the process of searching the vicinity of the best candidate motion vector (S203). The best candidate motion vector is not limited to the candidate motion vector with the highest evaluation value. One of one or more candidate motion vectors with an evaluation value equal to or greater than a reference value may be selected as the best candidate motion vector according to a predetermined priority order.

[0265] Here, the processing related to the processing target region and the processed region may be, for example, encoding or decoding processing. More specifically, the processing related to the processing target region and the processed region may be processing for deriving a motion vector. Alternatively, the processing related to the processing target region and the processed region may be processing for reconstruction.

[0266] [BIO processing] 19 is a conceptual diagram showing the BIO processing in the encoding device 100 and the decoding device 200. In the BIO processing, a predicted image of a current block is generated by referring to the spatial gradient of luminance in an image obtained by performing motion compensation on the current block using the motion vector of the current block.

[0267] Before BIO processing, two motion vectors of the current block are derived: an L0 motion vector (MV_L0) and an L1 motion vector (MV_L1). The L0 motion vector (MV_L0) is a motion vector for referencing an L0 reference picture, which is a processed picture, and the L1 motion vector (MV_L1) is a motion vector for referencing an L1 reference picture, which is also a processed picture. The L0 reference picture and the L1 reference picture are two reference pictures that are simultaneously referenced in bi-prediction processing of the current block.

[0268] As a method for deriving the L0 motion vector (MV_L0) and the L1 motion vector (MV_L1), a normal inter prediction mode, a merge mode, a FRUC mode, or the like may be used. For example, in the normal inter prediction mode, the encoding device 100 derives a motion vector by performing motion estimation using an image of a current block, and encodes information about the motion vector. In addition, in the normal inter prediction mode, the decoding device 200 derives a motion vector by decoding information about the motion vector.

[0269] Then, in the BIO processing, an L0 predicted image is obtained by performing motion compensation on a current block using an L0 motion vector (MV_L0) with reference to an L0 reference picture. For example, the L0 predicted image may be obtained by applying a motion compensation filter to an image of an L0 reference pixel range including a block pointed to by the L0 motion vector (MV_L0) from the current block in the L0 reference picture and its surroundings.

[0270] Furthermore, an L0 gradient image indicating the spatial gradient of luminance at each pixel of the L0 predicted image is obtained. For example, the L0 gradient image is obtained by referring to the luminance of each pixel in an L0 reference pixel range including a block pointed to in the L0 reference picture by the L0 motion vector (MV_L0) from the current block and its surroundings.

[0271] Furthermore, an L1 predicted image is obtained by performing motion compensation on the current block using an L1 motion vector (MV_L1) with reference to the L1 reference picture. For example, the L1 predicted image may be obtained by applying a motion compensation filter to an image in an L1 reference pixel range including a block pointed to by the L1 motion vector (MV_L1) in the L1 reference picture from the current block and its surroundings.

[0272] In addition, an L1 gradient image indicating the spatial gradient of luminance at each pixel of the L1 predicted image is obtained. For example, the L1 gradient image is obtained by referring to the luminance of each pixel in an L1 reference pixel range including a block pointed to in the L1 reference picture by an L1 motion vector (MV_L1) from the current block and its surroundings.

[0273] Then, for each pixel of the current block, a local motion estimate is derived. Specifically, a pixel value at a corresponding pixel position in the L0 predicted image, a gradient value at a corresponding pixel position in the L0 gradient image, a pixel value at a corresponding pixel position in the L1 predicted image, and a gradient value at a corresponding pixel position in the L1 gradient image are used. The local motion estimate may also be referred to as a corrected motion vector (corrected MV).

[0274] Then, for each pixel of the target block, a pixel correction value is derived using the gradient value at the corresponding pixel position in the L0 gradient image, the gradient value at the corresponding pixel position in the L1 gradient image, and the local motion estimation value. Then, for each pixel of the target block, a predicted pixel value is derived using the pixel value at the corresponding pixel position in the L0 predicted image, the pixel value at the corresponding pixel position in the L1 predicted image, and the pixel correction value. In this way, a predicted image to which BIO processing has been applied is derived.

[0275] That is, a pixel value at a corresponding pixel position in the L0 predicted image and a predicted pixel value obtained from the pixel value at the corresponding pixel position in the L1 predicted image are corrected by the pixel correction value. In other words, a predicted image obtained from the L0 predicted image and the L1 predicted image is corrected using a spatial gradient of luminance in the L0 predicted image and the L1 predicted image.

[0276] 20 is a flowchart showing the operation performed as BIO processing by the inter prediction unit 126 of the encoding device 100. The inter prediction unit 218 of the decoding device 200 operates in the same manner as the inter prediction unit 126 of the encoding device 100.

[0277] First, the inter prediction unit 126 obtains an L0 predicted image by referring to the L0 reference picture using the L0 motion vector (MV_L0) (S401). Then, the inter prediction unit 126 obtains an L0 gradient image by referring to the L0 reference picture using the L0 motion vector (S402).

[0278] Similarly, the inter prediction unit 126 obtains an L1 predicted image by referring to the L1 reference picture using the L1 motion vector (MV_L1) (S401). Then, the inter prediction unit 126 obtains an L1 gradient image by referring to the L1 reference picture using the L1 motion vector (S402).

[0279] Next, the inter prediction unit 126 derives a local motion estimate for each pixel of the current block (S411) using the pixel value at the corresponding pixel position in the L0 predicted image, the gradient value at the corresponding pixel position in the L0 gradient image, the pixel value at the corresponding pixel position in the L1 predicted image, and the gradient value at the corresponding pixel position in the L1 gradient image.

[0280] The inter prediction unit 126 then derives a pixel correction value for each pixel of the current block using the gradient value at the corresponding pixel position in the L0 gradient image, the gradient value at the corresponding pixel position in the L1 gradient image, and the local motion estimation value. The inter prediction unit 126 then derives a predicted pixel value for each pixel of the current block using the pixel value at the corresponding pixel position in the L0 predicted image, the pixel value at the corresponding pixel position in the L1 predicted image, and the pixel correction value (S412).

[0281] Through the above operation, the inter prediction unit 126 generates a predicted image to which the BIO processing has been applied.

[0282] Specifically, the following equation (3) may be used to derive the local motion estimation value and the pixel correction value.

[0283]

number

[0284] In equation (3), I x 0 [x,y] is the horizontal gradient value at pixel location [x,y] in the L0 gradient image. x 1 [x,y] is the horizontal gradient value at pixel position [x,y] in the L1 gradient image. y 0 [x,y] is the vertical gradient value at pixel location [x,y] in the L0 gradient image. y 1 [x,y] is the vertical gradient value at pixel location [x,y] in the L1 gradient image.

[0285] In addition, in equation (3), I 0 [x, y] is the pixel value at pixel position [x, y] of the L0 predicted image. 1 [x, y] is the pixel value at pixel position [x, y] of the L1 predicted image. ΔI[x, y] is the difference between the pixel value at pixel position [x, y] of the L0 predicted image and the pixel value at pixel position [x, y] of the L1 predicted image.

[0286] In addition, in equation (3), Ω is, for example, a set of pixel positions included in an area having a pixel position [x, y] as its center. w[i, j] is a weighting coefficient for pixel position [i, j]. The same value may be used for w[i, j]. G x [x,y], G y [x,y], G x G y [x,y], sG x G y [x,y], sG x 2 [x,y], sG y 2 [x,y], sG x dI[x,y] and sG y dI[x,y] etc. are auxiliary calculated values.

[0287] In equation (3), u[x,y] is the horizontal value constituting the local motion estimate at pixel position [x,y], v[x,y] is the vertical value constituting the local motion estimate at pixel position [x,y], b[x,y] is the pixel correction value at pixel position [x,y], and p[x,y] is the predicted pixel value at pixel position [x,y].

[0288] Furthermore, in the above description, the inter prediction unit 126 derives a local motion estimation value for each pixel. However, the inter prediction unit 126 may derive a local motion estimation value for each sub-block, which is an image data unit that is coarser than a pixel and finer than the target block.

[0289] For example, in the above equation (3), Ω may be a set of pixel positions included in the sub-block. x G y [x,y], sG x 2 [x,y], sG y 2 [x,y], sG x dI[x,y], sG y dI[x,y], u[x,y] and v[x,y] may be calculated for each sub-block instead of for each pixel.

[0290] Furthermore, the encoding device 100 and the decoding device 200 can apply a common BIO process. That is, the encoding device 100 and the decoding device 200 can apply the BIO process in the same way.

[0291] [Example of an encoder implementation] 21 is a block diagram showing an example implementation of the encoding device 100 according to Embodiment 1. The encoding device 100 includes a circuit 160 and a memory 162. For example, multiple components of the encoding device 100 shown in FIGS. 1 and 11 are implemented by the circuit 160 and memory 162 shown in FIG. 21.

[0292] The circuit 160 is a circuit that performs information processing and is a circuit that can access the memory 162. For example, the circuit 160 is a dedicated or general-purpose electronic circuit that encodes moving images. The circuit 160 may be a processor such as a CPU. The circuit 160 may also be a collection of multiple electronic circuits. For example, the circuit 160 may fulfill the roles of multiple components of the encoding device 100 shown in FIG. 1 and the like, excluding components for storing information.

[0293] The memory 162 is a dedicated or general-purpose memory that stores information used by the circuit 160 to encode moving images. The memory 162 may be an electronic circuit and may be connected to the circuit 160. The memory 162 may also be included in the circuit 160. The memory 162 may also be a collection of multiple electronic circuits. The memory 162 may also be a magnetic disk, an optical disk, or the like, and may also be expressed as a storage, a recording medium, or the like. The memory 162 may also be a non-volatile memory or a volatile memory.

[0294] For example, the memory 162 may store a video to be encoded, or a bit string corresponding to the encoded video, or may store a program for the circuit 160 to encode the video.

[0295] Furthermore, for example, the memory 162 may serve as a component for storing information among the multiple components of the encoding device 100 shown in Fig. 1 etc. Specifically, the memory 162 may serve as the block memory 118 and the frame memory 122 shown in Fig. 1. More specifically, the memory 162 may store reconstructed blocks, reconstructed pictures, etc.

[0296] Note that not all of the components shown in Figure 1 and the like need to be implemented in the encoding device 100, and not all of the above-described processes need to be performed. Some of the components shown in Figure 1 and the like may be included in another device, and some of the above-described processes may be executed by another device. Then, in the encoding device 100, some of the components shown in Figure 1 and the like are implemented, and some of the above-described processes are performed, thereby efficiently performing motion compensation.

[0297] Specifically, the encoding device 100 derives a first motion vector by a first inter prediction method using the degree of conformance between two reconstructed images of two regions in two different pictures for each prediction block obtained by dividing an image included in a moving image (S104 or S106 in FIG. 13). Here, the first inter prediction method is, for example, the above-mentioned FRUC method. Specifically, the first inter prediction method includes at least one of the template FRCU method and the bilateral FRUC method. That is, the two regions in the first inter prediction method are (1) a region in a current picture adjacent to a current prediction block and a region in a reference picture, or (2) two regions in two different reference pictures.

[0298] In other words, the first inter prediction method is a method in which a motion vector is derived by the same method on the encoding side and the decoding side. Also, in the first inter prediction method, information indicating the motion vector is not signaled in the encoded stream and is not transmitted from the encoding side to the decoding side. Also, in the first inter prediction method, the encoding device 100 derives a motion vector using pixel values ​​of an already-encoded prediction block and without using pixel values ​​of a target prediction block.

[0299] Next, the encoding device 100 performs a first motion compensation process to generate a predicted image by referring to the spatial gradient of luminance in an image generated by motion compensation using the derived first motion vector, for each prediction block (S103A in FIG. 13). Here, the first motion compensation process is, for example, the BIO process described above, and includes correction using a luminance gradient. Furthermore, in the first motion compensation process, the predicted image is corrected in units smaller than the prediction block (for example, pixel units or block units). Furthermore, in the first motion compensation process, a predicted image is generated using an area in the reference picture indicated by the motion vector and pixels surrounding the area.

[0300] According to this, the encoding device 100 performs the motion vector derivation process and the first motion compensation process by the first inter prediction method in units of prediction blocks, thereby reducing the amount of processing compared to when these processes are performed in units of sub-blocks. Furthermore, the first motion compensation process including correction using a luminance gradient can achieve correction in units smaller than the prediction block unit, thereby suppressing a decrease in encoding efficiency that occurs when processing is not performed in units of sub-blocks. Therefore, the encoding device 100 can reduce the amount of processing while suppressing a decrease in encoding efficiency.

[0301] Furthermore, the encoding device 100 derives a second motion vector for each prediction block by a second inter prediction method that uses a degree of compatibility between the current prediction block and a reconstructed image of an area included in the reference picture (S102 in FIG. 13).The encoding device 100 then generates an encoded bitstream including information for identifying the second motion vector.

[0302] Here, the second inter prediction method is, for example, the normal inter prediction method described above. In other words, the second inter prediction method is a method in which a motion vector is derived by a different method on the encoding side and a different method on the decoding side. Specifically, the encoding device 100 derives a motion vector using pixel values ​​of an already-encoded prediction block and pixel values ​​of a target prediction block. Then, the encoding device 100 signals information indicating the derived motion vector to the encoding stream. As a result, information indicating the motion vector derived by the encoding device 100 is transmitted from the encoding device 100 to the decoding device 200. The decoding device 200 derives a motion vector using the information included in the encoding stream.

[0303] Next, the encoding device 100 performs a second motion compensation process to generate a predicted image by referring to the spatial gradient of luminance in an image generated by motion compensation using the derived second motion vector, for each prediction block (S103A in FIG. 13). Here, the second motion compensation process is, for example, the BIO process described above, and includes correction using a luminance gradient. Furthermore, in the second motion compensation process, the predicted image is corrected in units smaller than the prediction block (for example, pixel units or block units). Furthermore, in the second motion compensation process, a predicted image is generated using an area in the reference picture indicated by the motion vector and pixels surrounding the area.

[0304] The second motion compensation process may be the same as the first motion compensation process, or may be partly different from the first motion compensation process.

[0305] This allows the processing unit of the motion compensation process to be the same when the first inter prediction method is used and when the second inter prediction method is used, thereby facilitating the implementation of the motion compensation process.

[0306] Furthermore, in the first operation mode (first operation mode at S111), the encoding device 100 derives a first motion vector for each prediction block obtained by dividing an image included in a video using a first inter prediction method (S112), and performs a first motion compensation process using the derived first motion vector for each prediction block (S113). Here, the first motion compensation process is, for example, a BIO process, which is a motion compensation process that generates a prediction image by referring to a spatial gradient of luminance in an image generated by motion compensation using the derived first motion vector.

[0307] Furthermore, in the second operation mode (second operation mode at S111), the encoding device 100 derives a second motion vector for each sub-block obtained by dividing the prediction block using a second inter prediction method (S114), and performs a second motion compensation process using the second motion vector for each sub-block (S115). Here, the second motion compensation process is, for example, a motion compensation process that does not apply BIO processing, and generates a prediction image without referring to the spatial gradient of luminance in the image generated by motion compensation using the second motion vector.

[0308] According to this, in the first operating mode, the encoding device 100 performs the motion vector derivation process and the first motion compensation process on a prediction block basis, thereby reducing the amount of processing compared to performing these processes on a sub-block basis, for example. Furthermore, the first motion compensation process, which generates a prediction image by referring to the spatial gradient of luminance, can achieve correction on a unit smaller than the prediction block unit, thereby suppressing a decrease in encoding efficiency that occurs when processing is not performed on a sub-block basis. Furthermore, in the second operating mode, the encoding device 100 performs the motion vector derivation process and the second motion compensation process on a sub-block basis. Here, the second motion compensation process does not refer to the spatial gradient of luminance, and therefore requires less processing than the first motion compensation process. Furthermore, by having these two operating modes, the encoding device 100 can improve encoding efficiency. In this way, the encoding device 100 can reduce the amount of processing while suppressing a decrease in encoding efficiency.

[0309] For example, the first inter prediction method is different from the second inter prediction method, which is an inter prediction method, such as the FRUC method, that uses the degree of compatibility between two reconstructed images of two regions in two different pictures.

[0310] This allows inter-picture prediction to be performed on a sub-block basis, which is highly effective in improving coding efficiency by calculating motion vectors on a sub-block basis, thereby improving coding efficiency.

[0311] For example, the first inter-screen prediction method is one of (1) a third inter-screen prediction method (e.g., template FRUC method) that uses the degree of fit between a reconstructed image of an area in a target picture adjacent to a target prediction block and a reconstructed image of an area in a reference picture, and (2) a fourth inter-screen prediction method (e.g., bilateral FRUC method) that uses the degree of fit between two reconstructed images of two areas in two different reference pictures, and the second inter-screen prediction method is the other of the third inter-screen prediction method and the fourth inter-screen prediction method.

[0312] For example, the first inter prediction method is the third inter prediction method (for example, the template FRUC method), and the second inter prediction method is the fourth inter prediction method (for example, the bilateral FRUC method).

[0313] This allows inter-picture prediction to be performed on a sub-block basis, which is highly effective in improving coding efficiency by calculating motion vectors on a sub-block basis, thereby improving coding efficiency.

[0314] For example, the first inter-frame prediction method is an inter-frame prediction method (normal inter-frame prediction method) that uses the degree of fit between a target prediction block and a reconstructed image of an area included in a reference picture, and the encoding device 100 generates an encoded bitstream that includes information for identifying the derived first motion vector.

[0315] [Example of implementation of a decryption device] 22 is a block diagram showing an implementation example of the decoding device 200 according to Embodiment 1. The decoding device 200 includes a circuit 260 and a memory 262. For example, the components of the decoding device 200 shown in FIGS. 10 and 12 are implemented by the circuit 260 and memory 262 shown in FIG.

[0316] The circuit 260 is a circuit that performs information processing and is a circuit that can access the memory 262. For example, the circuit 260 is a dedicated or general-purpose electronic circuit that decodes moving images. The circuit 260 may be a processor such as a CPU. The circuit 260 may also be a collection of multiple electronic circuits. For example, the circuit 260 may fulfill the roles of multiple components of the decoding device 200 shown in FIG. 10 and the like, excluding components for storing information.

[0317] The memory 262 is a dedicated or general-purpose memory that stores information for the circuit 260 to decode moving images. The memory 262 may be an electronic circuit and may be connected to the circuit 260. The memory 262 may also be included in the circuit 260. The memory 262 may also be a collection of multiple electronic circuits. The memory 262 may also be a magnetic disk, an optical disk, or the like, and may also be expressed as a storage, a recording medium, or the like. The memory 262 may also be a non-volatile memory or a volatile memory.

[0318] For example, the memory 262 may store a bit string corresponding to an encoded video, or a video corresponding to a decoded bit string, or may store a program for the circuit 260 to decode the video.

[0319] Furthermore, for example, the memory 262 may serve as a component for storing information among the multiple components of the decoding device 200 shown in Fig. 10 etc. Specifically, the memory 262 may serve as the block memory 210 and the frame memory 214 shown in Fig. 10. More specifically, the memory 262 may store reconstructed blocks, reconstructed pictures, etc.

[0320] Note that the decoding device 200 does not necessarily have to implement all of the components shown in Figure 10 and the like, and does not necessarily have to perform all of the above-described processes. Some of the components shown in Figure 10 and the like may be included in another device, and some of the above-described processes may be executed by another device. Then, the decoding device 200 implements some of the components shown in Figure 10 and the like, and performs some of the above-described processes, thereby efficiently performing motion compensation.

[0321] Specifically, the decoding device 200 derives a first motion vector by a first inter prediction method using a degree of conformance between two reconstructed images of two regions in two different pictures for each prediction block obtained by dividing an image included in a moving image (S104 or S106 in FIG. 13). Here, the first inter prediction method is, for example, the above-mentioned FRUC method. Specifically, the first inter prediction method includes at least one of the template FRCU method and the bilateral FRUC method. That is, the two regions in the first inter prediction method are (1) a region in a current picture adjacent to a current prediction block and a region in a reference picture, or (2) two regions in two different reference pictures.

[0322] In other words, the first inter prediction method is a method in which a motion vector is derived by the same method on the encoding side and the decoding side. Also, in the first inter prediction method, information indicating the motion vector is not signaled in the encoded stream and is not transmitted from the encoding side to the decoding side. Also, in the first inter prediction method, the decoding device 200 derives a motion vector using pixel values ​​of a decoded prediction block and without using pixel values ​​of a target prediction block.

[0323] Next, the decoding device 200 performs a first motion compensation process to generate a predicted image by referring to the spatial gradient of luminance in an image generated by motion compensation using the derived first motion vector, for each prediction block (S103A in FIG. 13). Here, the first motion compensation process is, for example, the BIO process described above, and includes correction using a luminance gradient. In addition, in the first motion compensation process, the predicted image is corrected in units smaller than the prediction block (for example, in pixel units or block units). In addition, in the first motion compensation process, a predicted image is generated using an area in the reference picture indicated by the motion vector and pixels surrounding the area.

[0324] According to this, the decoding device 200 performs the motion vector derivation process and the first motion compensation process by the first inter prediction method in units of prediction blocks, thereby reducing the amount of processing compared to when these processes are performed in units of sub-blocks. Furthermore, the first motion compensation process including the correction using the luminance gradient can achieve correction in units smaller than the prediction block units, thereby suppressing a decrease in coding efficiency when processing is not performed in units of sub-blocks. Therefore, the decoding device 200 can reduce the amount of processing while suppressing a decrease in coding efficiency.

[0325] Furthermore, the decoding device 200 acquires information for specifying the second motion vector for each prediction block from the coded bitstream, and derives the second motion vector for each prediction block by the second inter prediction method using the information (S102 in FIG. 13).

[0326] Here, the second inter prediction method is, for example, the normal inter prediction method described above. In other words, the second inter prediction method is a method in which a motion vector is derived by a different method on the encoding side and a different method on the decoding side. Specifically, the encoding device 100 derives a motion vector using pixel values ​​of an already-encoded prediction block and pixel values ​​of a target prediction block. Then, the encoding device 100 signals information indicating the derived motion vector to the encoding stream. As a result, information indicating the motion vector derived by the encoding device 100 is transmitted from the encoding device 100 to the decoding device 200. The decoding device 200 derives a motion vector using the information included in the encoding stream.

[0327] Next, the decoding device 200 performs a second motion compensation process to generate a predicted image by referring to the spatial gradient of luminance in an image generated by motion compensation using the derived second motion vector, for each prediction block (S103A in FIG. 13). Here, the second motion compensation process is, for example, the BIO process described above, and includes correction using a luminance gradient. Furthermore, in the second motion compensation process, the predicted image is corrected in units smaller than the prediction block (for example, pixel units or block units). Furthermore, in the second motion compensation process, a predicted image is generated using an area in the reference picture indicated by the motion vector and pixels surrounding the area.

[0328] The second motion compensation process may be the same as the first motion compensation process, or may be partly different from the first motion compensation process.

[0329] This allows the processing unit of the motion compensation process to be the same when the first inter prediction method is used and when the second inter prediction method is used, thereby facilitating the implementation of the motion compensation process.

[0330] Furthermore, in the first operation mode (first operation mode at S111), the decoding device 200 derives a first motion vector for each prediction block obtained by dividing an image included in a video using a first inter prediction method (S112), and performs a first motion compensation process using the derived first motion vector for each prediction block (S113). Here, the first motion compensation process is, for example, a BIO process, which is a motion compensation process that generates a prediction image by referring to a spatial gradient of luminance in an image generated by motion compensation using the derived first motion vector.

[0331] Furthermore, in the second operation mode (second operation mode at S111), the decoding device 200 derives a second motion vector for each sub-block obtained by dividing the prediction block using a second inter prediction method (S114), and performs a second motion compensation process using the second motion vector for each sub-block (S115). Here, the second motion compensation process is, for example, a motion compensation process that does not apply BIO processing, and generates a prediction image without referring to the spatial gradient of luminance in the image generated by motion compensation using the second motion vector.

[0332] According to this, in the first operation mode, the decoding device 200 performs the motion vector derivation process and the first motion compensation process on a prediction block basis, thereby reducing the amount of processing compared to performing these processes on a sub-block basis, for example. Furthermore, the first motion compensation process, which generates a prediction image by referring to the spatial gradient of luminance, can achieve correction on a unit smaller than the prediction block unit, thereby suppressing a decrease in coding efficiency that occurs when processing is not performed on a sub-block basis. Furthermore, in the second operation mode, the decoding device 200 performs the motion vector derivation process and the second motion compensation process on a sub-block basis. Here, the second motion compensation process does not refer to the spatial gradient of luminance, and therefore requires less processing than the first motion compensation process. Furthermore, by having these two operation modes, the decoding device 200 can improve coding efficiency. In this way, the decoding device 200 can reduce the amount of processing while suppressing a decrease in coding efficiency.

[0333] For example, the first inter prediction method is different from the second inter prediction method, which is an inter prediction method, such as the FRUC method, that uses the degree of compatibility between two reconstructed images of two regions in two different pictures.

[0334] This allows inter-picture prediction to be performed on a sub-block basis, which is highly effective in improving coding efficiency by calculating motion vectors on a sub-block basis, thereby improving coding efficiency.

[0335] For example, the first inter-screen prediction method is one of (1) a third inter-screen prediction method (e.g., template FRUC method) that uses the degree of fit between a reconstructed image of an area in a target picture adjacent to a target prediction block and a reconstructed image of an area in a reference picture, and (2) a fourth inter-screen prediction method (e.g., bilateral FRUC method) that uses the degree of fit between two reconstructed images of two areas in two different reference pictures, and the second inter-screen prediction method is the other of the third inter-screen prediction method and the fourth inter-screen prediction method.

[0336] For example, the first inter prediction method is the third inter prediction method (for example, the template FRUC method), and the second inter prediction method is the fourth inter prediction method (for example, the bilateral FRUC method).

[0337] This allows inter-picture prediction to be performed on a sub-block basis, which is highly effective in improving coding efficiency by calculating motion vectors on a sub-block basis, thereby improving coding efficiency.

[0338] For example, in the first inter prediction method, the decoding device 200 obtains information for specifying the second motion vector in units of sub-blocks from the coded bitstream, and derives the second motion vector using the information.

[0339] [supplement] Furthermore, the encoding device 100 and the decoding device 200 in this embodiment may be used as an image encoding device and an image decoding device, or as a video encoding device and a video decoding device, respectively. Alternatively, the encoding device 100 and the decoding device 200 may be used as an inter prediction device (inter prediction device).

[0340] That is, the encoding device 100 and the decoding device 200 may correspond only to the inter prediction unit (inter prediction unit) 126 and the inter prediction unit (inter prediction unit) 218, respectively. Other components such as the transform unit 106 and the inverse transform unit 206 may be included in other devices.

[0341] In addition, in this embodiment, each component may be configured with dedicated hardware, or may be realized by executing a software program suitable for each component. Each component may be realized by a program execution unit such as a CPU or processor reading and executing a software program recorded on a recording medium such as a hard disk or semiconductor memory.

[0342] Specifically, each of the encoding device 100 and the decoding device 200 may include a processing circuitry and a storage device electrically connected to and accessible from the processing circuitry. For example, the processing circuitry corresponds to the circuit 160 or 260, and the storage device corresponds to the memory 162 or 262.

[0343] The processing circuit includes at least one of dedicated hardware and a program execution unit, and executes processing using a storage device. If the processing circuit includes a program execution unit, the storage device stores the software program executed by the program execution unit.

[0344] Here, the software for realizing the encoding device 100 or the decoding device 200 according to the present embodiment is the following program.

[0345] Furthermore, each component may be a circuit, as described above. These circuits may form a single circuit as a whole, or may each be a separate circuit. Furthermore, each component may be realized by a general-purpose processor or a dedicated processor.

[0346] Furthermore, a process performed by a specific component may be performed by another component. The order in which the processes are performed may be changed, or multiple processes may be performed in parallel. Furthermore, the encoding / decoding device may include the encoding device 100 and the decoding device 200.

[0347] Although aspects of the encoding device 100 and the decoding device 200 have been described above based on the embodiments, the aspects of the encoding device 100 and the decoding device 200 are not limited to these embodiments. As long as they do not deviate from the spirit of this disclosure, various modifications conceivable by those skilled in the art to the present embodiments and configurations constructed by combining components of different embodiments may also be included within the scope of the aspects of the encoding device 100 and the decoding device 200.

[0348] 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 device configurations, and some of the syntax described in the flowcharts of this aspect may be implemented in combination with other aspects.

[0349] (Embodiment 2) In each of the above embodiments, each of the functional blocks can typically be realized by an MPU, memory, etc. Furthermore, the processing by each of the functional blocks is typically 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 circuits).

[0350] Furthermore, the processing 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 program may be a single processor or multiple processors. That is, centralized processing or distributed processing may be performed.

[0351] The aspects of the present disclosure are not limited to the above examples, and various modifications are possible, and these modifications are also included within the scope of the aspects of the present disclosure.

[0352] Furthermore, here, we will explain 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. 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 that includes both. Other components of the system can be appropriately changed depending on the situation.

[0353] [Usage example] 23 is a diagram showing the overall configuration of a content supply system ex100 that provides 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.

[0354] In this content supply system ex100, devices such as a computer ex111, a game console 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 a combination of any of the above elements. The devices may be connected to each other directly or indirectly via a telephone network or short-range wireless communication, without using the base stations ex106 to ex110, which are fixed wireless stations. Furthermore, a streaming server ex103 is connected to devices such as the computer ex111, the game console ex112, the camera ex113, the home appliance ex114, and the smartphone ex115 via the Internet ex101, etc. Furthermore, the streaming server ex103 is connected to a terminal in a hotspot on an airplane ex117, etc., via a satellite ex116.

[0355] Note that wireless access points, hotspots, etc. may be used instead of the base stations ex106 to ex110. Furthermore, 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.

[0356] The camera ex113 is a device capable of taking still images and videos, such as a digital camera. The smartphone ex115 is a smartphone, mobile phone, or PHS (Personal Handyphone System) that is compatible with mobile communication systems generally known as 2G, 3G, 3.9G, 4G, and 5G.

[0357] The home appliance ex118 is a refrigerator or an appliance included in a home fuel cell cogeneration system.

[0358] 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 streaming and the like. In live streaming, a terminal (such as a computer ex111, a game console ex112, a camera ex113, a home appliance ex114, a smartphone ex115, or a terminal on an airplane ex117) performs the encoding process described in each of the above embodiments on still images or video content captured by a user using the terminal, multiplexes the video data obtained by 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.

[0359] Meanwhile, the streaming server ex103 streams the transmitted content data to the requesting client. The client is a computer ex111, a game console ex112, a camera ex113, a home appliance ex114, a smartphone ex115, a terminal on an airplane ex117, or the like, which is 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.

[0360] [Distributed processing] The streaming server ex103 may also be multiple servers or multiple computers that process, record, and distribute data in a distributed manner. For example, the streaming server ex103 may be implemented as a CDN (Content Delivery Network), where content distribution is achieved through a network connecting numerous edge servers distributed around the world. In a CDN, a physically nearby edge server is dynamically assigned depending on the client. Content is then cached and distributed to that edge server, thereby reducing delays. Furthermore, if an error occurs or communication conditions change due to increased traffic, 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 affected network portion, thereby achieving high-speed and stable distribution.

[0361] In addition to the distributed processing of the distribution itself, the encoding of captured data can be performed on each device, on the server side, or shared among devices. For example, encoding generally involves two processing loops. The first loop detects the image complexity or code size for each frame or scene. The second loop maintains image quality while improving encoding efficiency. For example, a device can perform the first encoding process, and the server that receives the content can perform the second encoding process, thereby improving content quality and efficiency while reducing the processing load on each device. In this case, if there is a request for near-real-time reception and decoding, the data encoded by a device can be received and played back on another device, enabling more flexible real-time distribution.

[0362] As another example, the camera ex113 or the like extracts features from an image, compresses the data related to the features as metadata, and transmits the 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 accordingly. The feature data is particularly effective in improving the accuracy and efficiency of motion vector prediction when the server recompresses the image. Alternatively, the terminal may perform simple encoding such as VLC (variable length coding), and the server may perform encoding with a heavy processing load such as CABAC (context-adaptive binary arithmetic coding).

[0363] As another example, in a stadium, shopping mall, factory, etc., there may be multiple pieces of video data that have been shot by multiple terminals of almost the same scene. In this case, using the multiple terminals that shot the video and, as necessary, other terminals and servers that did not shoot the video, encoding processes are assigned to each of them, for example, in units of GOPs (Group of Pictures), pictures, or tiles obtained by dividing a picture, for distributed processing. This reduces delays and achieves better real-time performance.

[0364] Furthermore, since multiple pieces of video data are of nearly 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 encoded data from each terminal and change the reference relationships between multiple pieces of data, or correct or replace the pictures themselves and re-encode them. This allows for the generation of streams with improved quality and efficiency for each piece of data.

[0365] The server may also perform transcoding to change the encoding format of the video data before distributing it. For example, the server may convert MPEG-based encoding to VP-based encoding, or convert H.264 to H.265.

[0366] In this way, the encoding process can be performed by a terminal or one or more servers. Therefore, although the following uses terms such as "server" or "terminal" to refer to the entity performing the process, 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.

[0367] [3D, multi-angle] In recent years, there has been an increasing trend 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 nearly synchronized with each other. The videos taken by each device are integrated based on the relative positional relationship between the devices obtained separately, or on areas where feature points included in the videos match.

[0368] 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. Furthermore, if the server can acquire the relative positional relationship between the capturing terminals, it can generate a 3D shape of the scene based on not only the 2D video but also images of the same scene captured from different angles. The server may also separately encode 3D data generated by point clouds, or may select or reconstruct images to be transmitted to the receiving terminal from images captured by multiple terminals based on the results of recognizing or tracking people or objects using the 3D data.

[0369] In this way, users can enjoy scenes by selecting any video corresponding to each camera device, or can enjoy content in which video from any viewpoint is extracted from 3D data reconstructed using multiple images or videos. Furthermore, like the video, sound may also be collected from multiple different angles, and the server may multiplex and transmit sound from a specific angle or space in accordance with the video.

[0370] 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 left eye, and may perform encoding that allows reference between the viewpoint images 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.

[0371] In the case of AR images, the server superimposes virtual object information in virtual space onto camera information in real space based on the 3D position or the user's viewpoint movement. The decoding device may acquire or store virtual object information and 3D data, generate a 2D image according to the user's viewpoint movement, and smoothly connect the images to create superimposed data. Alternatively, the decoding device may send the user's viewpoint movement to the server in addition to a request for virtual object information, and the server may create superimposed data based on the viewpoint movement received from the 3D data stored on the server, encode the superimposed data, and distribute it to the decoding device. Note that the superimposed data may also have an α value indicating transparency in addition to RGB, and the server may set the α value of parts other than the object created from the 3D data to 0, etc., to encode the parts in a transparent state. Alternatively, the server may generate data by setting a predetermined RGB value as the background, like a chromakey, and using the background color for parts other than the object.

[0372] Similarly, the decoding of distributed data may be performed by each client terminal, by the server, or by multiple terminals. For example, one terminal may first send a reception request to the server, and then other terminals may receive and decode content according to the request, after which the decoded signal is transmitted to a device with a display. By distributing the processing and selecting appropriate content regardless of the capabilities of the communication terminals themselves, high-quality data can be reproduced. As another example, large-sized image data may be received on a TV or other device, and only a portion of the picture, such as a tile into which the picture is divided, may be decoded and displayed on the viewer's personal device. This allows the viewer to share the overall picture while checking their own area of ​​responsibility or an area of ​​interest in more detail.

[0373] In the future, it is expected that content will be seamlessly received by switching the appropriate data for the current connection using delivery system standards such as MPEG-DASH in situations where multiple short-, medium-, or long-distance wireless communications are available, both indoors and outdoors. This will allow users to freely select and switch between decoding and display devices, such as their own devices, indoors and outdoors, in real time. Decoding can also be performed by switching between decoding and display devices based on user location information. This will enable users to display map information on the wall or ground of a neighboring building with an embedded display device while traveling to their destination. It is also possible to switch the bit rate of received data based on the accessibility of the encoded data on the network, such as if the encoded data is cached on a server that can be quickly accessed from the receiving device or copied to an edge server in a content delivery service.

[0374] [Scalable Coding] Regarding content switching, we will explain it using a scalable stream, as shown in Figure 24, compressed and encoded using the video encoding method described in each of the above embodiments. The server may have multiple streams with the same content but different qualities, but may also switch content by taking advantage of the characteristics of a temporally / spatially scalable stream achieved by encoding the content separately into layers, as shown in the figure. In other words, the decoding side determines up to which layer to decode based on internal factors such as performance and external factors such as communication bandwidth, allowing the decoding side to freely switch between low-resolution and high-resolution content. For example, if a user wants to continue watching a video they were watching on their smartphone ex115 while on the go on a device such as an Internet TV after returning home, the device can simply decode the same stream up to different layers, thereby reducing the burden on the server.

[0375] Furthermore, in addition to the above-described scalability configuration 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 in the base layer based on the meta-information. Super-resolution may mean either improving the signal-to-noise ratio at the same resolution or increasing the resolution. The meta-information may include 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.

[0376] Alternatively, a picture may be divided into tiles or the like according to the meaning of objects in the image, and the decoding side may select tiles to decode and decode only a portion of the area. Furthermore, by storing the object's attributes (such as a person, a car, or a ball) and its position in the video (such as a coordinate position in the same image) 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. 25, the meta information is stored using a data storage structure different from that of pixel data, such as an SEI message in HEVC. This meta information indicates, for example, the position, size, or color of the main object.

[0377] Furthermore, meta information may be stored in units consisting of multiple pictures, such as streams, sequences, or random access units, which allows the decoding side to obtain the time when a specific person appears in the video, and by combining this with information in units of pictures, it is possible to identify the picture in which the object exists and the position of the object within the picture.

[0378] [Webpage optimization] FIG. 26 is a diagram showing an example of a web page display screen on a computer ex111 or the like. FIG. 27 is a diagram showing an example of a web page display screen on a smartphone ex115 or the like. As shown in FIGS. 26 and 27, a web page may include multiple link images that are links to image content, and the appearance of the web page may differ depending on the device used to view the page. When multiple link images are visible on the screen, the display device (decoding device) may display a still image or I-picture contained in each content as a link image, display a video such as a GIF animation using multiple still images or I-pictures, or receive only the base layer and decode and display the video until the user explicitly selects a link image, or until the link image approaches the center of the screen or until the entire link image is within the screen.

[0379] When a link image is selected by a user, the display device decodes the base layer with the highest priority. 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. To ensure real-time performance, before a selection is made or when the communication bandwidth is very limited, the display device decodes and displays only forward-referenced pictures (I-pictures, P-pictures, and forward-reference-only B-pictures), thereby reducing the delay between the decoding time of the first picture and the display time (the delay from the start of content decoding to the start of display). Alternatively, the display device may intentionally ignore the picture reference relationships and roughly decode all B-pictures and P-pictures using forward reference, and then perform normal decoding as the number of received pictures increases over time.

[0380] [Autonomous 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.

[0381] In this case, since a vehicle, drone, airplane, etc. 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 depending on the user's selection, user situation, or communication bandwidth status.

[0382] In this way, in the content supply system ex100, the client can receive, decode, and play back the encoded information sent by the user in real time.

[0383] [Distribution of personal content] Furthermore, the content supply system ex100 allows not only high-quality, long-duration content from video distribution companies, but also unicast or multicast distribution of low-quality, short-duration content from individuals. 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 before encoding. This can be achieved, for example, with the following configuration.

[0384] During shooting, either in real time or after accumulating the footage, the server performs recognition processing such as detecting shooting errors, scene search, semantic analysis, and object detection from the original image or encoded data. Based on the recognition results, the server manually or automatically corrects out-of-focus or camera shake, deletes less important scenes (e.g., scenes with lower brightness or out-of-focus compared to other pictures), emphasizes object edges, changes color, and performs other editing. The server then encodes the edited data based on the editing results. It is also known that viewing rates decrease if the shooting time is too long. Therefore, the server may automatically clip not only less important scenes as described above but also scenes with little movement, based on the image processing results, so that the content falls within a specific time range depending on the shooting time. Alternatively, the server may generate and encode a digest based on the results of the semantic analysis of the scene.

[0385] In some cases, personal content may contain content that infringes copyright, moral rights, or portrait rights, or may cause the scope of sharing to exceed the intended scope, resulting in inconvenience to individuals. Therefore, for example, the server may intentionally defocus images of people's faces on the periphery of the screen or the interior of a house before encoding. The server may also recognize whether the image to be encoded contains the face of a person other than a pre-registered person, and if so, perform processing such as blurring the face. Alternatively, as pre- or post-processing before encoding, the user may specify a person or background area they wish to modify in the image for copyright or other reasons, and the server may replace the specified area with another image or blur the focus. For a person, the server may track the person in the video and replace the image of the face.

[0386] Furthermore, because viewing personal content with small data volumes requires real-time performance, the decoding device first receives the base layer as a top priority, and then decodes and plays it back, depending on the bandwidth. The decoding device may also receive an enhancement layer during this time, and if the content is played back more than twice, such as when playback is looped, it may play back high-quality video, including the enhancement layer. A stream that has undergone scalable encoding in this way can provide an experience in which the video appears rough when not selected or when viewing begins, but gradually becomes smoother and the image quality improves. In addition to scalable encoding, a similar experience can also be provided by configuring a single stream consisting of a rough stream played the first time and a second stream that is encoded with reference to the first video.

[0387] [Other use cases] Furthermore, these encoding or decoding processes are generally performed by the LSIex500 possessed by each terminal. The LSIex500 may be a single chip or may be configured with multiple chips. It is also possible to incorporate video encoding or decoding software into some kind of recording medium (such as a CD-ROM, flexible disk, or hard disk) that can be read by the computer ex111, and perform the encoding or decoding process using that software. Furthermore, if the smartphone ex115 is equipped with a camera, video data captured by the camera may be transmitted. This video data is data that has been encoded by the LSIex500 possessed by the smartphone ex115.

[0388] The LSIex500 may be configured to download and activate application software. In this case, the terminal first determines whether it supports the content encoding method or has the capability to execute a specific service. If the terminal does not support the content encoding method or does not have the capability to execute a specific service, the terminal downloads the codec or application software and then acquires and plays the content.

[0389] 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 transmitted and received over broadcast radio waves using a satellite or the like, the content supply system ex100 is more suited to multicast than the content supply system ex100, which is more suited to unicast, but similar applications are possible with regard to encoding and decoding processes.

[0390] [Hardware configuration] FIG. 28 is a diagram illustrating a smartphone ex115. FIG. 29 is a diagram illustrating an example configuration 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 capturing video and still images, and a display unit ex458 for displaying video captured by the camera unit ex465 and decoded data of the video and other data 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 voice or sound, an audio input unit ex456 such as a microphone for inputting voice, a memory unit ex467 capable of storing encoded data or decoded data such as captured video or still images, recorded voice, received video or still images, and email, and a slot unit ex464 that serves as an interface with a SIM ex468 for identifying users and authenticating access to various data, including networks. In addition, an external memory may be used instead of the memory unit ex467.

[0391] In addition, a main control unit ex460 that comprehensively controls the display unit ex458 and 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.

[0392] When the power key is turned on by a user, the power supply circuit unit ex461 supplies power from the battery pack to each unit, thereby starting up the smartphone ex115 into an operational state.

[0393] The smartphone ex115 processes calls, data communications, and other communications under the control of a main control unit ex460, which includes a CPU, ROM, RAM, and the like. During calls, the audio signal collected by the audio input unit ex456 is converted into a digital audio signal by the audio signal processing unit ex454, which then undergoes spectrum spread processing by the modulation / demodulation unit ex452, digital-to-analog conversion processing and frequency conversion processing by the transmission / reception unit ex451, and then transmitted via the antenna ex450. The received data is amplified, frequency-converted, and analog-to-digital converted, then subjected to spectrum despreading processing by the modulation / demodulation unit ex452, and converted into an analog audio signal by the audio signal processing unit ex454, which then outputs the amplified data from the audio output unit ex457. During data communications mode, text, still images, or video data is sent to the main control unit ex460 via the operation input control unit ex462 by operating the operation unit ex466, etc., of the main unit, and similar transmission and reception processing is performed. When transmitting video, still images, or video and audio in the data communication mode, the video signal processing unit ex455 compression-encodes the video signal stored in the memory unit ex467 or the video signal input from the camera unit ex465 using the video encoding method described in each of the above embodiments, and sends the encoded video data to the multiplexing / demultiplexing unit ex453. The audio signal processing unit ex454 also encodes the audio signal picked up by the audio input unit ex456 while the camera unit ex465 is capturing video, still images, etc., and sends the encoded audio data to the multiplexing / demultiplexing unit ex453. The multiplexing / demultiplexing unit ex453 multiplexes the encoded video data and encoded audio data using a predetermined method, and modulates and converts the data in the modulation / demodulation unit (modulation / demodulation circuit unit) ex452 and the transmission / reception unit ex451 before transmitting the data via the antenna ex450.

[0394] When receiving video attached to an email or chat, or video linked to a web page, etc., the multiplexed data received via the antenna ex450 is decoded by the multiplexing / separation unit ex453, which separates the multiplexed data into a video data bitstream and an audio data bitstream. The multiplexing / separation unit ex453 then 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 using a video decoding method corresponding to the video encoding method described in each of the above embodiments, and displays the video or still image included in the linked video file on the display unit ex458 via the display control unit ex459. The audio signal processing unit ex454 decodes the audio signal, and the audio is output from the audio output unit ex457. Note that with the widespread use of real-time streaming, audio playback may be socially inappropriate depending on the user's circumstances. Therefore, a configuration that initially plays only the video data without playing the audio signal is desirable. The audio may be played in synchronization only when the user performs an operation such as clicking on the video data.

[0395] Although the smartphone ex115 has been used as an example, three types of implementation 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 onto video data is received or transmitted, but the multiplexed data may also 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.

[0396] While the main control unit ex460, which includes a CPU, controls the encoding and decoding processes, devices often also include a GPU. Therefore, a configuration is possible in which a memory shared by the CPU and GPU, or a memory with addresses managed for common use, is used to take advantage of the GPU's performance and process a large area at once. This shortens encoding time, ensures real-time performance, and achieves low latency. It is particularly efficient to perform motion estimation, deblocking filtering, SAO (Sample Adaptive Offset), and transformation and quantization processes at a picture level or other unit in the GPU rather than the CPU.

[0397] 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 device configurations, and some of the syntax described in the flowcharts of this aspect may be implemented in combination with other aspects. [Industrial Applicability]

[0398] The present disclosure is applicable to, for example, television receivers, digital video recorders, car navigation systems, mobile phones, digital cameras, digital video cameras, video conference systems, electronic mirrors, and the like. [Explanation of symbols]

[0399] 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 160, 260 circuits 162, 262 memory 200 Decryption Device 202 Entropy Decoding Unit

Claims

1. The circuit and a memory; the circuit performs a motion compensation process using the memory, the motion compensation process including a first operation mode and a second operation mode; In the first mode of operation, deriving a first motion vector in a merge mode for each prediction block obtained by dividing an image included in a moving image; performing a first motion compensation process for generating a predicted image by referring to a spatial gradient of luminance in an image generated by motion compensation using the first motion vector; In the second mode of operation, deriving motion vectors of a plurality of control points of the prediction block based on motion vectors of blocks spatially adjacent to the prediction block; deriving a second motion vector for bidirectional prediction on a sub-block basis for each of a plurality of sub-blocks obtained by dividing the prediction block using the motion vectors of the plurality of control points; performing a second motion compensation process to generate a predicted image without referring to a spatial gradient of luminance in an image generated by motion compensation using the second motion vector; Encoding device.

2. The circuit and a memory; the circuit performs a motion compensation process using the memory, the motion compensation process including a first operation mode and a second operation mode; In the first mode of operation, deriving a first motion vector in a merge mode for each prediction block obtained by dividing an image included in a moving image; performing a first motion compensation process for generating a predicted image by referring to a spatial gradient of luminance in an image generated by motion compensation using the first motion vector; In the second mode of operation, deriving motion vectors of a plurality of control points of the prediction block based on motion vectors of blocks spatially adjacent to the prediction block; deriving a second motion vector for bidirectional prediction on a sub-block basis for each of a plurality of sub-blocks obtained by dividing the prediction block using the motion vectors of the plurality of control points; performing a second motion compensation process to generate a predicted image without referring to a spatial gradient of luminance in an image generated by motion compensation using the second motion vector; Decryption device.

3. An encoding method for performing a motion compensation process, the motion compensation process including a first operation mode and a second operation mode, In the first mode of operation, deriving a first motion vector in a merge mode for each prediction block obtained by dividing an image included in a moving image; performing a first motion compensation process for generating a predicted image by referring to a spatial gradient of luminance in an image generated by motion compensation using the first motion vector; In the second mode of operation, deriving motion vectors of a plurality of control points of the prediction block based on motion vectors of blocks spatially adjacent to the prediction block; deriving a second motion vector for bidirectional prediction on a sub-block basis for each of a plurality of sub-blocks obtained by dividing the prediction block using the motion vectors of the plurality of control points; performing a second motion compensation process to generate a predicted image without referring to a spatial gradient of luminance in an image generated by motion compensation using the second motion vector; Encoding method.

4. A decoding method for performing a motion compensation process, the motion compensation process including a first operation mode and a second operation mode, In the first mode of operation, deriving a first motion vector in a merge mode for each prediction block obtained by dividing an image included in a moving image; performing a first motion compensation process for generating a predicted image by referring to a spatial gradient of luminance in an image generated by motion compensation using the first motion vector; In the second mode of operation, deriving motion vectors of a plurality of control points of the prediction block based on motion vectors of blocks spatially adjacent to the prediction block; deriving a second motion vector for bidirectional prediction on a sub-block basis for each of a plurality of sub-blocks obtained by dividing the prediction block using the motion vectors of the plurality of control points; performing a second motion compensation process to generate a predicted image without referring to a spatial gradient of luminance in an image generated by motion compensation using the second motion vector; Decryption method.

5. The circuit and a memory; the circuit performs a motion compensation process using the memory, the motion compensation process including a first operation mode and a second operation mode; In the first mode of operation, deriving a first motion vector in a merge mode for each prediction block obtained by dividing an image included in a moving image; performing a first motion compensation process for generating a predicted image by referring to a spatial gradient of luminance in an image generated by motion compensation using the first motion vector; In the second mode of operation, deriving motion vectors of a plurality of control points of the prediction block based on motion vectors of blocks spatially adjacent to the prediction block; deriving a second motion vector for bidirectional prediction on a sub-block basis for each of a plurality of sub-blocks obtained by dividing the prediction block using the motion vectors of the plurality of control points; performing a second motion compensation process for generating a predicted image without reference to a spatial gradient of luminance in an image generated by motion compensation using the second motion vector; generating a bitstream including information for deriving the first motion vector or the second motion vector; Bitstream generator.

6. A method for transmitting a bitstream that performs motion compensation processing, the motion compensation processing including a first operation mode and a second operation mode, In the first mode of operation, deriving a first motion vector in a merge mode for each prediction block obtained by dividing an image included in a moving image; performing a first motion compensation process for generating a predicted image by referring to a spatial gradient of luminance in an image generated by motion compensation using the first motion vector; In the second mode of operation, deriving motion vectors of a plurality of control points of the prediction block based on motion vectors of blocks spatially adjacent to the prediction block; deriving a second motion vector for bidirectional prediction on a sub-block basis for each of a plurality of sub-blocks obtained by dividing the prediction block using the motion vectors of the plurality of control points; performing a second motion compensation process for generating a predicted image without reference to a spatial gradient of luminance in an image generated by motion compensation using the second motion vector; generating a bitstream including information for deriving the first motion vector or the second motion vector; transmitting the generated bitstream; Sending method.

Images