Encoding device, decoding device, encoding method, and decoding method

Abstract

To implement further improvement.SOLUTION: An encoder 100 is configured to: determine (S103) a first motion search range in a first reference picture of a block to be encoded, the first motion search range including a representative position indicated by a representative motion vector; calculate (S105) first evaluation values, which are evaluation values of a plurality of candidate regions included in the first motion search range, the first evaluation value being a difference between a corresponding candidate region in the candidate regions and a region in a second reference picture; determine (S107) a first peripheral region, which is a region included in the first motion search range and including a first candidate region and surroundings thereof, the first candidate region having a minimum first evaluation value, in the candidate regions included in the first motion search range; and determine (S112) a motion vector of the block to be encoded, using a minimum second evaluation value in the evaluation values of regions included in the first peripheral region.SELECTED DRAWING: Figure 13

Description

[Technical Field]

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

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

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

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

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

[0006] A coding device according to one aspect of the present disclosure includes a processor and a memory, wherein the processor uses the memory to derive a representative motion vector indicating a representative position based on motion vector candidates included in a candidate list having candidates derived based on motion vectors of blocks spatially or temporally adjacent to a current block to be coded, determine a first motion search range in a first reference picture of the current block to be coded that includes the representative position indicated by the representative motion vector, and calculate evaluation values ​​of a plurality of candidate areas included in the first motion search range, the evaluation values ​​being differences between the plurality of candidate areas and an area along a motion trajectory of the current block to be coded in a second reference picture different from the first reference picture. a first evaluation value for each of the plurality of candidate areas included in the first motion search range, a first surrounding area including the first candidate area having the smallest first evaluation value among the plurality of candidate areas included in the first motion search range and its surroundings, and a first surrounding area that is included in the first motion search range; a second evaluation value that is smallest among the evaluation values ​​of the areas included in the first surrounding area; a motion vector for the block to be coded is determined using a second evaluation value that is smallest among the evaluation values ​​of the areas included in the first surrounding area; and a bitstream including information indicating a mode for performing motion search is generated, wherein a first picture order count between a current picture including the block to be coded and the first reference picture and a second picture order count between the current picture and the second reference picture are equal.

[0007] A decoding device according to one aspect of the present disclosure is a decoding device comprising a processor and a memory, wherein the processor uses the memory to derive a representative motion vector indicating a representative position based on motion vector candidates included in a candidate list having candidates derived based on motion vectors of blocks spatially or temporally adjacent to a block to be decoded, determine a first motion search range in a first reference picture of the block to be decoded that includes the representative position indicated by the representative motion vector, and calculate evaluation values ​​of a plurality of candidate areas included in the first motion search range, the evaluation values ​​being a relationship between the plurality of candidate areas and the block to be decoded in a second reference picture different from the first reference picture. a first evaluation value, which is a difference between the first evaluation value and a region along the motion trajectory of the block; determining a first surrounding region, which is a region that includes the first candidate region having the smallest first evaluation value among the plurality of candidate regions included in the first motion search range and its surroundings and is included in the first motion search range; determining a motion vector of the block to be decoded using a second evaluation value, which is the smallest among the evaluation values ​​of the regions included in the first surrounding region; and determining a first picture order count between the current picture including the block to be decoded and the first reference picture and a second picture order count between the current picture and the second reference picture, which are equal to each other.

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

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

[0010] [Figure 1]FIG. 1 is a block diagram showing a functional configuration of a coding device according to the first embodiment. [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 block diagram showing an internal configuration of an inter prediction unit of the encoding device according to Embodiment 1. As shown in FIG. [Figure 12] FIG. 12 shows an example of the location of motion search range information in a bitstream according to the first embodiment. [Figure 13] FIG. 13 is a flowchart showing the process of the inter prediction unit of the encoding / decoding device according to Embodiment 1. [Figure 14] FIG. 14 is a diagram showing an example of a candidate list according to the first embodiment. [Figure 15] FIG. 15 is a diagram showing an example of a reference picture list according to the first embodiment. [Figure 16] FIG. 16 is a diagram showing an example of a motion search range according to the first embodiment. [Figure 17] FIG. 17 is a diagram showing an example of the surrounding area according to the first embodiment. [Figure 18] FIG. 18 is a block diagram showing an internal configuration of an inter prediction unit of a decoding device according to Embodiment 1. As shown in FIG. [Figure 19] FIG. 19 is a diagram showing an example of a motion search range in the second modification of the first embodiment. [Figure 20] FIG. 20 shows an example of a motion search range in the fourth modification of the first embodiment. [Figure 21] FIG. 21 is a diagram showing an example of a motion search range in the fifth modification of the first embodiment. [Figure 22] FIG. 22 is a diagram showing an example of a motion search range in Modification 6 of Embodiment 1. In FIG. [Figure 23]FIG. 23 is a block diagram showing a functional configuration of a coding / decoding system according to the seventh modification of the first embodiment. In FIG. [Figure 24] FIG. 24 shows a motion search range according to the ninth modification of the first embodiment. [Figure 25] FIG. 25 is a diagram showing the overall configuration of a content supply system that realizes a content distribution service. [Figure 26] FIG. 26 is a diagram showing an example of a coding structure for scalable coding. [Figure 27] FIG. 27 is a diagram showing an example of a coding structure for scalable coding. [Figure 28] FIG. 28 is a diagram showing an example of a display screen of a web page. [Figure 29] FIG. 29 is a diagram showing an example of a display screen of a web page. [Figure 30] FIG. 30 is a diagram illustrating an example of a smartphone. [Figure 31] FIG. 31 is a block diagram showing an example of the configuration of a smartphone. DETAILED DESCRIPTION OF THE INVENTION

[0011] (Findings that formed the basis of this disclosure) In the next generation of video compression standards, a mode in which motion estimation is performed on the decoder side is being considered to reduce the amount of motion information required for motion compensation. In such a mode, the decoder derives a motion vector for a block to be decoded by searching (motion estimation) an area in a reference picture that is similar to a previously decoded block that is different from the block to be decoded. In this case, the processing load of the decoder due to the motion estimation and the memory bandwidth required for the decoder due to the data transfer of the reference picture are expected to increase. Therefore, a technology to suppress the increase in processing load and memory bandwidth is required.

[0012] Therefore, a coding device according to one aspect of the present disclosure is a coding device that codes a block to be coded using a motion vector, and is equipped with a processor and a memory, wherein the processor uses the memory to derive multiple candidates, each having at least one motion vector, determines a motion search range in a reference picture, performs motion search within the motion search range of the reference picture based on the multiple candidates, and codes information regarding the determined motion search range.

[0013] This allows motion estimation to be performed within the determined motion estimation range. Therefore, since there is no need to perform motion estimation outside the motion estimation range, the processing load for motion estimation can be reduced. Furthermore, since there is no need to read reconstructed images outside the motion estimation range from the frame memory, the memory bandwidth required for motion estimation can be reduced.

[0014] Furthermore, in an encoding device according to one aspect of the present disclosure, for example, in the motion search, a candidate having a motion vector corresponding to a position outside the motion search range may be excluded from the plurality of candidates, a candidate may be selected from the remaining candidates of the plurality of candidates, and a motion vector for the block to be encoded may be determined based on the selected candidate.

[0015] This allows candidates to be selected after excluding candidates that have motion vectors corresponding to positions outside the motion search range, thereby reducing the processing load for candidate selection.

[0016] Furthermore, in the encoding device according to one aspect of the present disclosure, for example, the information relating to the motion search range may include information indicating the size of the motion search range.

[0017] This allows information indicating the size of the motion search range to be included in the bitstream. Therefore, a motion search range having the same size as the motion search range used in the encoding device can also be used in the decoding device. Furthermore, the processing load for determining the size of the motion search range in the decoding device can be reduced.

[0018] In addition, in the encoding device according to an aspect of the present disclosure, for example, the deriving of the plurality of candidates may include deriving the plurality of candidates from a plurality of already-encoded blocks that are spatially or temporally adjacent to the current block to be encoded, and the position of the motion search range may be determined based on an average motion vector of a plurality of motion vectors included in the plurality of candidates. Also, in the encoding device according to an aspect of the present disclosure, for example, the deriving of the plurality of candidates may include deriving the plurality of candidates from a plurality of blocks that are spatially or temporally adjacent to the current block to be encoded, and the position of the motion search range may be determined based on a median motion vector of a plurality of motion vectors included in the plurality of candidates.

[0019] According to these methods, the position of the motion search range can be determined based on multiple candidates derived from multiple coded blocks adjacent to the current block to be coded, and therefore, an area suitable for searching a motion vector for the current block to be coded can be determined as the motion search range, thereby improving the accuracy of the motion vector.

[0020] Furthermore, in the encoding device according to one aspect of the present disclosure, for example, the position of the motion search range may be determined based on an average motion vector of multiple motion vectors used in encoding the encoded picture.

[0021] This allows the position of the motion search range to be determined based on the motion vector of the coded picture. Since the motion vector of the coded picture remains unchanged even if the current block in the current picture changes, it is no longer necessary to determine the motion search range from the motion vector of an adjacent block each time the current block changes. In other words, the processing load for determining the motion search range can be reduced.

[0022] In addition, in an encoding device according to one aspect of the present disclosure, for example, when determining a motion vector for the block to be encoded, pattern matching may be performed in a surrounding area of ​​a position in the reference picture corresponding to the selected candidate motion vector to find the area that best matches within the surrounding area, and the motion vector for the block to be encoded may be determined based on the best match.

[0023] This allows the motion vector for the current block to be coded to be determined based on pattern matching in the surrounding area in addition to the candidate motion vectors, thereby further improving the accuracy of the motion vector.

[0024] Furthermore, in an encoding device according to one aspect of the present disclosure, for example, when determining a motion vector for the block to be encoded, it may be determined whether the surrounding area is included in the motion search range, and if the surrounding area is included in the motion search range, the pattern matching may be performed in the surrounding area, and if the surrounding area is not included in the motion search range, the pattern matching may be performed in a partial area of ​​the surrounding area that is included in the motion search range.

[0025] This allows pattern matching to be performed on a partial area of ​​the surrounding area that is within the motion search range when the surrounding area is not included in the motion search range, thereby avoiding motion search outside the motion search range and reducing the processing load and memory bandwidth requirements.

[0026] Furthermore, in an encoding device according to one aspect of the present disclosure, for example, when determining a motion vector for the block to be encoded, it may be determined whether the surrounding area is included in the motion search range, and if the surrounding area is included in the motion search range, the pattern matching may be performed in the surrounding area, and if the surrounding area is not included in the motion search range, the motion vector included in the selected candidate may be determined as the motion vector for the block to be encoded.

[0027] This eliminates the need to perform pattern matching in the surrounding area if the surrounding area is not included in the motion search range, thereby avoiding motion search outside the motion search range and reducing the processing load and memory bandwidth requirements.

[0028] An encoding method according to one aspect of the present disclosure is an encoding method for encoding a block to be encoded using a motion vector, which derives multiple candidates, each having at least one motion vector, determines a motion search range in a reference picture, performs motion search within the motion search range of the reference picture based on the multiple candidates, and encodes information regarding the determined motion search range.

[0029] This makes it possible to achieve the same effects as the encoding device described above.

[0030] A decoding device according to one embodiment of the present disclosure is a decoding device that decodes a block to be decoded using a motion vector, and is equipped with a processor and a memory, wherein the processor uses the memory to decode information regarding a motion search range from a bitstream, derives multiple candidates each having at least one motion vector, determines a motion search range in a reference picture based on the information regarding the motion search range, and performs motion search within the motion search range of the reference picture based on the multiple candidates.

[0031] This allows motion estimation to be performed within the determined motion estimation range. Therefore, since there is no need to perform motion estimation outside the motion estimation range, the processing load for motion estimation can be reduced. Furthermore, since there is no need to read reconstructed images outside the motion estimation range from the frame memory, the memory bandwidth required for motion estimation can be reduced.

[0032] Furthermore, in a decoding device according to one aspect of the present disclosure, for example, in the motion search, a candidate having a motion vector corresponding to a position outside the motion search range may be excluded from the plurality of candidates, a candidate may be selected from the remaining candidates of the plurality of candidates, and a motion vector for the block to be decoded may be determined based on the selected candidate.

[0033] This allows candidates to be selected after excluding candidates that have motion vectors corresponding to positions outside the motion search range, thereby reducing the processing load for candidate selection.

[0034] Furthermore, in the decoding device according to one aspect of the present disclosure, for example, the information relating to the motion search range may include information indicating the size of the motion search range.

[0035] This allows information indicating the size of the motion search range to be included in the bitstream. Therefore, a motion search range having the same size as the motion search range used in the encoding device can also be used in the decoding device. Furthermore, the processing load for determining the size of the motion search range in the decoding device can be reduced.

[0036] In addition, in a decoding device according to an aspect of the present disclosure, for example, the derivation of the plurality of candidates may include deriving the plurality of candidates from a plurality of already-decoded blocks that are spatially or temporally adjacent to the block to be decoded, and the position of the motion search range may be determined based on an average motion vector of a plurality of motion vectors included in the plurality of candidates. In addition, in a decoding device according to an aspect of the present disclosure, for example, the derivation of the plurality of candidates may include deriving the plurality of candidates from a plurality of blocks that are spatially or temporally adjacent to the block to be decoded, and the position of the motion search range may be determined based on a median motion vector of a plurality of motion vectors included in the plurality of candidates.

[0037] According to these methods, the position of the motion search range can be determined based on multiple candidates derived from multiple decoded blocks adjacent to the block to be decoded. Therefore, an area suitable for searching a motion vector for the block to be decoded can be determined as the motion search range, thereby improving the accuracy of the motion vector.

[0038] Furthermore, in the decoding device according to one aspect of the present disclosure, for example, the position of the motion search range may be determined based on an average motion vector of a plurality of motion vectors used in decoding the already-decoded picture.

[0039] This allows the position of the motion search range to be determined based on a decoded picture. Since the motion vector of the decoded picture remains unchanged even if the block to be decoded in the picture to be decoded changes, it is no longer necessary to determine the motion search range from the motion vector of an adjacent block every time the block to be decoded changes. In other words, the processing load for determining the motion search range can be reduced.

[0040] In addition, in a decoding device according to one aspect of the present disclosure, for example, when determining a motion vector for the block to be decoded, pattern matching may be performed in a surrounding area of ​​a position in the reference picture corresponding to the selected candidate motion vector to find the area that best matches within the surrounding area, and the motion vector for the block to be decoded may be determined based on the area that best matches.

[0041] This allows the motion vector for the current block to be decoded to be determined based on pattern matching in the surrounding area in addition to the candidate motion vectors, thereby further improving the accuracy of the motion vector.

[0042] Furthermore, in a decoding device according to one aspect of the present disclosure, for example, when determining a motion vector for the block to be decoded, it may be determined whether the surrounding area is included in the motion search range, and if the surrounding area is included in the motion search range, the pattern matching may be performed in the surrounding area, and if the surrounding area is not included in the motion search range, the pattern matching may be performed in a partial area of ​​the surrounding area that is included in the motion search range.

[0043] This allows pattern matching to be performed on a partial area of ​​the surrounding area that is within the motion search range when the surrounding area is not included in the motion search range, thereby avoiding motion search outside the motion search range and reducing the processing load and memory bandwidth requirements.

[0044] Furthermore, in a decoding device according to one aspect of the present disclosure, for example, when determining a motion vector for the block to be decoded, it may be determined whether the surrounding area is included in the motion search range, and if the surrounding area is included in the motion search range, the pattern matching may be performed in the surrounding area, and if the surrounding area is not included in the motion search range, the motion vector included in the selected candidate may be determined to be the motion vector for the block to be decoded.

[0045] This eliminates the need to perform pattern matching in the surrounding area if the surrounding area is not included in the motion search range, thereby avoiding motion search outside the motion search range and reducing the processing load and memory bandwidth requirements.

[0046] A decoding method according to one embodiment of the present disclosure is a decoding method for decoding a block to be decoded using a motion vector, which reads information regarding a motion search range from a bitstream, derives multiple candidates each having at least one motion vector, determines a motion search range in a reference picture based on the information regarding the motion search range, and performs motion search within the motion search range of the reference picture based on the multiple candidates.

[0047] This makes it possible to achieve the same effects as the above-described decoding device.

[0048] These general or specific aspects may be realized as a system, an integrated circuit, a computer program, or a recording medium such as a computer-readable CD-ROM, or may be realized as any combination of a system, a method, an integrated circuit, a computer program, and a recording medium.

[0049] Hereinafter, the embodiments will be specifically described with reference to the drawings.

[0050] 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.

[0051] (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.

[0052] 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.

[0053] (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.

[0054] 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.

[0055] [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.

[0056] 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.

[0057] 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.

[0058] Each component included in the encoding device 100 will be described below.

[0059] [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.

[0060] 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.

[0061] 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).

[0062] 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.

[0063] The top right 64x64 block is divided horizontally into two rectangular 64x32 blocks 14 and 15 (binary tree block division).

[0064] 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.

[0065] The bottom right 64x64 block 23 is not split.

[0066] 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.

[0067] 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.

[0068] [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.

[0069] 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.

[0070] [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.

[0071] 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).

[0072] 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.

[0073] 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).

[0074] 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).

[0075] 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.

[0076] 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.

[0077] 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).

[0078] [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.

[0079] 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).

[0080] 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.

[0081] [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.

[0082] [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.

[0083] [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.

[0084] 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. In other words, the restored prediction error includes a quantization error.

[0085] [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.

[0086] [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.

[0087] [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).

[0088] 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.

[0089] 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).

[0090] 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.

[0091] Based on the result of such classification, a filter for the sub-block is determined from among a plurality of filters.

[0092] 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).

[0093] 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).

[0094] 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).

[0095] [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.

[0096] [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.

[0097] 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.

[0098] 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).

[0099] 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.

[0100] 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.

[0101] 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).

[0102] [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.

[0103] 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.

[0104] 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).

[0105] 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).

[0106] 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.

[0107] First, a predicted image (Pred) is obtained by normal motion compensation using a motion vector (MV) assigned to the block to be coded.

[0108] 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.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] The target block to be processed may be a prediction block unit or a sub-block unit obtained by further dividing the prediction block.

[0114] 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.

[0115] 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.

[0116] 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.

[0117] 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.

[0118] 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.

[0119] The same processing may be performed when processing is performed in sub-block units.

[0120] 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.

[0121] 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.

[0122] 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.

[0123] 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.

[0124] 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.

[0125] 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.

[0126] 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.

[0127] 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).

[0128] 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.

[0129] 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.

[0130] 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:

[0131]

number

[0132] 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.

[0133] 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.

[0134] Here, a mode in which a motion vector is derived for each sub-block based on the motion vectors of a plurality of neighboring blocks will be described. This mode is sometimes called an affine motion compensation prediction mode.

[0135] 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.

[0136]

number

[0137] Here, x and y respectively indicate the horizontal and vertical positions of the sub-block, and w indicates a predetermined weighting coefficient.

[0138] 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).

[0139] [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.

[0140] 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.

[0141] 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.

[0142] 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.

[0143] Furthermore, the variable length coding unit encodes the stream by describing merge_idx, which is a signal indicating which predicted MV has been selected.

[0144] 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.

[0145] 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.

[0146] Here, an example of determining the MV using the DMVR process will be described.

[0147] FIG. 9C is a conceptual diagram for explaining an outline of the DMVR process.

[0148] 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.

[0149] 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.

[0150] The outline of the processing described here is basically the same for the encoding device and the decoding device.

[0151] 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.

[0152] Here, a mode for generating a predicted image using LIC processing will be described.

[0153] FIG. 9D is a diagram for explaining an outline of a predicted image generation method using luminance correction processing by LIC processing.

[0154] 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.

[0155] 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.

[0156] 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.

[0157] The shape of the peripheral reference region in FIG. 9D is an example, and other shapes may be used.

[0158] 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.

[0159] 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.

[0160] 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.

[0161] [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.

[0162] 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.

[0163] 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.

[0164] Each component included in the decoding device 200 will be described below.

[0165] [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.

[0166] [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.

[0167] [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 .

[0168] 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.

[0169] 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.

[0170] [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.

[0171] [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.

[0172] [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.

[0173] 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.

[0174] [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.

[0175] [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.

[0176] 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.

[0177] 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.

[0178] [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.

[0179] 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.

[0180] 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.

[0181] 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.

[0182] [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.

[0183] [Internal structure of the inter-prediction unit of the encoding device] Next, a description will be given of the internal configuration of the inter prediction unit 126 of the encoding device 100. Specifically, a description will be given of the functional configuration of the inter prediction unit 126 of the encoding device 100 for realizing a mode (FRUC mode) in which motion search is performed on the decoding device side.

[0184] 11 is a block diagram showing the internal configuration of the inter prediction unit 126 of the encoding device 100 according to Embodiment 1. The inter prediction unit 126 includes a candidate derivation unit 1261, a range determination unit 1262, a motion estimation unit 1263, and a motion compensation unit 1264.

[0185] The candidate derivation unit 1261 derives a plurality of candidates, each of which has at least one motion vector. These candidates may be called motion vector predictor candidates. Furthermore, a motion vector included in the candidates may be called a motion vector predictor.

[0186] Specifically, the candidate derivation unit 1261 derives multiple candidates based on motion vectors of coded blocks spatially or temporally adjacent to the current block (hereinafter referred to as adjacent blocks). The motion vectors of the adjacent blocks are motion vectors used in motion compensation of the adjacent blocks.

[0187] For example, when two reference pictures are referenced in the inter prediction of one neighboring block, the candidate derivation unit 1261 derives one candidate including two reference picture indexes and two motion vectors based on the two motion vectors corresponding to the two reference pictures. Also, when one reference picture is referenced in the inter prediction of one neighboring block, the candidate derivation unit 1261 derives one candidate including one reference picture index and one motion vector based on the one motion vector corresponding to the one reference picture.

[0188] A plurality of candidates derived from a plurality of adjacent blocks are registered in a candidate list. At this time, duplicate candidates may be deleted from the candidate list. If there is space in the candidate list, a candidate having a fixed motion vector (e.g., a zero motion vector) may be registered. Note that this candidate list may be the same as the merge list used in the merge mode.

[0189] A spatially adjacent block is a block included in the current picture and adjacent to the current block. For example, the spatially adjacent block is a block to the left, upper left, upper, or upper right of the current block. A motion vector derived from a spatially adjacent block is sometimes called a spatial motion vector.

[0190] A temporally adjacent block refers to a block included in a coded / decoded picture different from the current picture. The position of the temporally adjacent block in the coded / decoded picture corresponds to the position of the current block in the current picture. A temporally adjacent block may also be called a co-located block. A motion vector derived from a temporally adjacent block may also be called a temporal motion vector.

[0191] The range determination unit 1262 determines a motion search range in a reference picture. The motion search range refers to a partial area in a reference picture in which motion search is permitted.

[0192] The size of the motion search range is determined based on, for example, memory bandwidth and processing power. The memory bandwidth and processing power can be obtained from levels defined in a standard, for example. Alternatively, the memory bandwidth and processing power may be acquired from a decoding device. The size of the motion search range means the size of a partial region within a picture, and can be expressed, for example, by the number of horizontal pixels and the number of vertical pixels that indicate the distance from the center of the motion search range to the vertical and horizontal sides.

[0193] The position of the motion search range is determined based on, for example, a statistically representative vector of the motion vectors included in the candidates in the candidate list. In this embodiment, an average motion vector is used as the statistically representative vector. The average motion vector is a motion vector formed by averaging the horizontal and vertical values ​​of the multiple motion vectors.

[0194] Information about the determined motion search range (hereinafter referred to as motion search range information) is coded in the bitstream. The motion search range information includes at least one of information indicating the size of the motion search range and information indicating the position of the motion search range, and in this embodiment, it includes only information indicating the size of the motion search range. The position of the motion search range information in the bitstream is not particularly limited. For example, as shown in FIG. 12, the motion search range information may be written in (i) a video parameter set (VPS), (ii) a sequence parameter set (SPS), (iii) a picture parameter set (PPS), (iv) a slice header, or (v) a video system setting parameter. Note that the motion search range information may or may not be entropy coded.

[0195] The motion estimation unit 1263 performs motion estimation within a motion estimation range of the reference picture. That is, the motion estimation unit 1263 performs motion estimation within a motion estimation range of the reference picture. Specifically, the motion estimation unit 1263 performs motion estimation as follows.

[0196] First, the motion search unit 1263 reads a reconstructed image of the motion search range in the reference picture from the frame memory 122. For example, the motion search unit 1263 reads only the reconstructed image of the motion search range from the reference picture. Then, the motion search unit 1263 excludes candidates having motion vectors corresponding to positions outside the motion search range of the reference picture from the multiple candidates derived by the candidate derivation unit 1261. In other words, the motion search unit 1263 deletes candidates having motion vectors indicating positions outside the motion search range from the candidate list.

[0197] Next, the motion search unit 1263 selects a candidate from the remaining candidates. That is, the motion search unit 1263 selects a candidate from the candidate list from which candidates having motion vectors corresponding to positions outside the motion search range have been deleted.

[0198] The selection of the candidate is performed based on the evaluation value of each candidate. For example, when the above-mentioned first pattern matching (bilateral matching) is applied, the evaluation value of each candidate is calculated based on the difference value between the reconstructed image of an area in a reference picture corresponding to the motion vector of the candidate and the reconstructed image of an area in another reference picture along the motion trajectory of the current block. For example, when the second pattern matching (template matching) is applied, the evaluation value of each candidate is calculated based on the difference value between the reconstructed image of an area in a reference picture corresponding to the motion vector of the candidate and the reconstructed image of an encoded block adjacent to the current block in the current picture.

[0199] Finally, the motion search unit 1263 determines a motion vector for the current block based on the selected candidate. Specifically, the motion search unit 1263 performs pattern matching in a surrounding area of ​​a position in the reference picture corresponding to the motion vector included in the selected candidate, for example, to find the best-matching area within the surrounding area. Then, the motion search unit 1263 determines a motion vector for the current block based on the best-matching area within the surrounding area. Also, for example, the motion search unit 1263 may determine the motion vector included in the selected candidate as the motion vector for the current block.

[0200] The motion compensation unit 1264 performs motion compensation using the motion vector determined by the motion estimation unit 1263, thereby generating an inter prediction signal of the current block.

[0201] [Operation of the inter-prediction unit of the encoding device] Next, the operation of the inter prediction unit 126 configured as above will be described in detail with reference to Figures 13 to 17. Below, a case where inter prediction is performed with reference to a single reference picture will be described.

[0202] 13 is a flowchart showing the processing of the inter prediction unit of the encoding / decoding device according to Embodiment 1. In Fig. 13, the symbols in parentheses indicate the processing of the inter prediction unit of the decoding device.

[0203] First, the candidate derivation unit 1261 derives a plurality of candidates from neighboring blocks to generate a candidate list (S101). Figure 14 is a diagram showing an example of the candidate list in Embodiment 1. Here, each candidate has a candidate index, a reference picture index, and a motion vector.

[0204] Next, the range determining unit 1262 selects a reference picture from the reference picture list (S102). For example, the range determining unit 1262 selects the reference pictures in ascending order of reference picture index. For example, in the reference picture list of FIG. 15, the range determining unit 1262 first selects the reference picture with reference picture index "0".

[0205] The range determination unit 1262 determines a motion search range in the reference picture (S103). Here, the determination of the motion search range will be described with reference to FIG.

[0206] Fig. 16 is a diagram showing an example of the motion search range 1022 according to Embodiment 1. In Fig. 16, a current block 1000 and neighboring blocks 1001 to 1004 in the current picture are shown at corresponding positions in the reference picture.

[0207] First, the range determination unit 1262 obtains, from the candidate list, motion vectors 1011 to 1014 of the multiple adjacent blocks 1001 to 1004. Then, the range determination unit 1262 scales the motion vectors 1011 to 1014 as necessary, and calculates an average motion vector 1020 of the motion vectors 1011 to 1014.

[0208] For example, the range determination unit 1262 refers to the candidate list in FIG. 14 and calculates the average horizontal value of multiple motion vectors, "-25 (=((-48)+(-32)+0+(-20)) / 4)", and the average vertical value, "6 (=(0+9+12+3) / 4)", to calculate the average motion vector (-26,6).

[0209] Next, the range determination unit 1262 determines a representative position 1021 of the motion search range based on the average motion vector 1020. Here, the center position is used as the representative position 1021. Note that the representative position 1021 is not limited to the center position, and any of the vertex positions of the motion search range (for example, the upper left vertex position) may be used.

[0210] Furthermore, the range determination unit 1262 determines the size of the motion search range based on the memory bandwidth, processing power, etc. For example, the range determination unit 1262 determines the number of horizontal pixels and the number of vertical pixels that represent the size of the motion search range.

[0211] Based on the representative position 1021 and size of the motion search range determined in this manner, the range determination unit 1262 determines the motion search range 1022.

[0212] Returning now to the description of the flowchart in Fig. 13, the motion search unit 1263 excludes from the candidate list any candidate having a motion vector corresponding to a position outside the motion search range (S104). For example, in Fig. 16, the motion search unit 1263 excludes from the candidate list any candidate having motion vectors 1012 and 1013 that indicate positions outside the motion search range.

[0213] The motion search unit 1263 calculates evaluation values ​​for the candidates remaining in the candidate list (S105). For example, the motion search unit 1263 calculates, as the evaluation value, a difference value between a reconstructed image (template) of an adjacent block in the current picture and a reconstructed image of an area in the reference picture corresponding to the motion vector of the candidate (template matching). In this case, the area in the reference picture corresponding to the motion vector of the candidate is an area of ​​an adjacent block motion-compensated in the reference picture using the motion vector of the candidate. In the evaluation value calculated in this way, a decrease in the value indicates a higher evaluation. Note that the evaluation value may be the reciprocal of the difference value. In this case, a higher evaluation indicates a higher evaluation.

[0214] The motion search unit 1263 selects a candidate from the candidate list based on the evaluation value (S106). For example, the motion search unit 1263 selects the candidate with the smallest evaluation value.

[0215] The motion search unit 1263 determines a surrounding area of ​​the area corresponding to the motion vector of the selected candidate (S107). For example, when the motion vector 1014 in Fig. 16 is selected, the motion search unit 1263 determines a surrounding area 1023 of the area of ​​the current block motion-compensated using the motion vector 1014 in the reference picture, as shown in Fig. 17.

[0216] The size of the surrounding region 1023 may be predefined by a standard, for example. Specifically, a fixed size such as 8x8 pixels, 16x16 pixels, or 32x32 pixels may be predefined as the size of the surrounding region 1023. The size of the surrounding region 1023 may also be determined based on processing capabilities. In this case, information regarding the size of the surrounding region 1023 may be written to the bitstream. The number of horizontal pixels and the number of vertical pixels representing the size of the motion search range may be determined taking the size of the surrounding region 1023 into consideration, and written to the bitstream.

[0217] The motion search unit 1263 determines whether the determined surrounding area is included in the motion search range (S108). In other words, the motion search unit 1263 determines whether the entire surrounding area is included in the motion search range.

[0218] If the surrounding area is included in the motion search range (Yes in S108), the motion search unit 1263 performs pattern matching within the surrounding area (S109). As a result, the motion search unit 1263 obtains an evaluation value of the area in the reference picture that best matches the reconstructed image of the adjacent block within the surrounding area.

[0219] On the other hand, if the surrounding area is not included in the motion search range (No in S108), the motion search unit 1263 performs pattern matching on a partial area of ​​the surrounding area that is included in the motion search range (S110). In other words, the motion search unit 1263 does not perform pattern matching on a partial area of ​​the surrounding area that is not included in the motion search range.

[0220] The range determining unit 1262 determines whether or not there is an unselected reference picture within the reference pictures (S111). If there is an unselected reference picture (Yes in S111), the process returns to the selection of a reference picture (S102).

[0221] On the other hand, if there is no unselected reference picture (No in S111), the motion search unit 1263 determines a motion vector for the current picture based on the evaluation value (S112). That is, the motion search unit 1263 determines the candidate motion vector with the highest evaluation among multiple reference pictures as the motion vector for the current picture.

[0222] [Internal structure of the inter-prediction unit of the decoding device] Next, a description will be given of the internal configuration of the inter prediction unit 218 of the decoding device 200. Specifically, a description will be given of the functional configuration of the inter prediction unit 218 of the decoding device 200 for realizing a mode (FRUC mode) in which motion search is performed on the decoding device side.

[0223] 18 is a block diagram showing the internal configuration of the inter prediction unit 218 of the decoding device 200 according to Embodiment 1. The inter prediction unit 218 includes a candidate derivation unit 2181, a range determination unit 2182, a motion estimation unit 2183, and a motion compensation unit 2184.

[0224] The candidate derivation unit 2181 derives multiple candidates, each having at least one motion vector, similarly to the candidate derivation unit 1261 of the encoding device 100. Specifically, the candidate derivation unit 2181 derives multiple candidates based on the motion vectors of spatially and / or temporally neighboring blocks.

[0225] The range determination unit 2182 determines a motion search range in a reference picture. Specifically, the range determination unit 2182 first obtains motion search range information interpreted from the bitstream. Then, the range determination unit 2182 determines the size of the motion search range based on the motion search range information. Furthermore, the range determination unit 2182 determines the position of the motion search range, similar to the range determination unit 1262 of the encoding device 100. In this way, the motion search range in the reference picture is determined.

[0226] The motion search unit 2183 performs motion search within the motion search range of the reference picture. Specifically, the motion search unit 2183 first reads a reconstructed image of the motion search range in the reference picture from the frame memory 214. For example, the motion search unit 2183 reads only the reconstructed image of the motion search range from the reference picture. Then, similar to the motion search unit 1263 of the encoding device 100, the motion search unit 2183 performs motion search within the motion search range and determines a motion vector for the current block.

[0227] The motion compensation unit 2184 performs motion compensation using the motion vector determined by the motion estimation unit 2183, thereby generating an inter prediction signal of the current block.

[0228] [Operation of the inter-prediction unit of the decoder] Next, the operation of the inter prediction unit 218 configured as above will be described with reference to Fig. 13. The processing of the inter prediction unit 218 is the same as the processing of the inter prediction unit 126 of the encoding device 100, except that step S103 is replaced by step S203. Step S203 will be described below.

[0229] The range determining unit 2182 determines a motion search range in the reference picture (S203). At this time, the range determining unit 2182 determines the size of the motion search range based on motion search range information interpreted from the bitstream. Similarly to the range determining unit 1262 of the encoding device 100, the range determining unit 2182 determines the position of the motion search range based on multiple candidates included in the candidate list.

[0230] [Effects, etc.] As described above, the inter prediction unit 126 of the encoding device 100 and the inter prediction unit 218 of the decoding device 200 according to this embodiment can select a candidate after excluding candidates having motion vectors corresponding to positions outside the motion search range. This reduces the processing load for candidate selection. Furthermore, since it is not necessary to read reconstructed images outside the motion search range from the frame memory, it is possible to reduce the memory bandwidth required for motion search.

[0231] Furthermore, according to the encoding device 100 and the decoding device 200 of this embodiment, information about the motion search range can be written to a bitstream and the information about the motion search range can be read from the bitstream. Therefore, the same motion search range as that used in the encoding device 100 can also be used in the decoding device 200. Furthermore, the processing load for determining the motion search range in the decoding device 200 can be reduced.

[0232] Furthermore, according to the encoding device 100 and the decoding device 200 of this embodiment, it is possible to include information indicating the size of the motion search range in the bitstream. Therefore, it is possible to use a motion search range having the same size as the motion search range used in the encoding device 100 in the decoding device 200. Furthermore, it is possible to reduce the processing load for determining the size of the motion search range in the decoding device 200.

[0233] Furthermore, the inter prediction unit 126 of the encoding device 100 and the inter prediction unit 218 of the decoding device 200 according to this embodiment can determine the position of the motion search range based on the average motion vector obtained from multiple candidates derived from multiple blocks adjacent to the current block. Therefore, an area suitable for searching for a motion vector for the current block can be determined as the motion search range, thereby improving the accuracy of the motion vector.

[0234] Furthermore, the inter prediction unit 126 of the encoding device 100 and the inter prediction unit 218 of the decoding device 200 according to this embodiment can determine a motion vector for the current block based on pattern matching in the surrounding area in addition to candidate motion vectors, thereby further improving the accuracy of the motion vector.

[0235] Furthermore, according to the inter prediction unit 126 of the encoding device 100 and the inter prediction unit 218 of the decoding device 200 according to this embodiment, when a surrounding area is not included in the motion search range, pattern matching can be performed on a partial area of ​​the surrounding area that is within the motion search range. This makes it possible to avoid motion search outside the motion search range, thereby reducing the processing load and memory bandwidth requirements.

[0236] (First Modification of First Embodiment) In the above-mentioned first embodiment, the position of the motion search range was determined based on the average motion vector of the multiple motion vectors included in the multiple candidates in the candidate list, but in this modified example, it is determined based on the median motion vector of the multiple motion vectors included in the multiple candidates in the candidate list.

[0237] The range determination unit 1262, 2182 according to this modification references the candidate list and acquires multiple motion vectors included in the multiple candidates. The range determination unit 1262, 2182 then calculates a median motion vector of the acquired multiple motion vectors. The median motion vector is a motion vector that is the median of the horizontal and vertical values ​​of the multiple motion vectors.

[0238] The range determination unit 1262, 2182 calculates the median motion vector (-26, 6) by, for example, referring to the candidate list in Figure 14, calculating the median horizontal value of multiple motion vectors, "-26 (= ((-32) + (-20)) / 2)", and the median vertical value, "6 (= (9 + 3) / 2)".

[0239] Next, the range determination unit 1262, 2182 determines the representative position of the motion search range based on the calculated central motion vector.

[0240] As described above, the range determination units 1262 and 2182 according to this modification can determine the position of the motion search range based on the central motion vector obtained from multiple candidates derived from multiple blocks adjacent to the current block. Therefore, an area suitable for searching for a motion vector for the current block can be determined as the motion search range, thereby improving the accuracy of the motion vector.

[0241] 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.

[0242] (Modification 2 of Embodiment 1) Next, a second modification of the first embodiment will be described. In this modification, the position of the motion search range is determined based on the minimum motion vector instead of the average motion vector. The following describes this modification, focusing on the differences from the first embodiment.

[0243] The range determination units 1262 and 2182 according to this modification refer to the candidate list to acquire multiple motion vectors included in multiple candidates, and then select the motion vector with the smallest magnitude (i.e., the minimum motion vector) from the acquired multiple motion vectors.

[0244] The range determination units 1262 and 2182 refer to the candidate list in FIG. 14, for example, and select the motion vector (0, 8) with the smallest magnitude that is included in the candidates with candidate index "2" from among the multiple motion vectors.

[0245] Next, the range determination unit 1262, 2182 determines the representative position of the motion search range based on the selected minimum motion vector.

[0246] 19 is a diagram showing an example of a motion search range in Modification 2 of Embodiment 1. In Fig. 19, the range determination unit 1262, 2182 selects the motion vector 1013 having the smallest magnitude among the motion vectors 1011 to 1014 of adjacent blocks as the minimum motion vector 1030. Next, the range determination unit 1262, 2182 determines a representative position 1031 of the motion search range based on the determined representative position 1031. Then, the range determination unit 1262, 2182 determines the motion search range 1032 based on the determined representative position 1031.

[0247] As described above, the range determination units 1262 and 2182 according to this modification can determine the position of the motion search range based on the smallest motion vector obtained from multiple candidates derived from multiple blocks adjacent to the current block. Therefore, an area close to the current block can be determined as the motion search range, thereby improving the accuracy of the motion vector.

[0248] 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.

[0249] (Third Modification of First Embodiment) Next, a third modification of the first embodiment will be described. In this modification, the position of the motion search range is determined based on the motion vector of a coded / decoded picture other than the current picture, instead of the average motion vector. The following describes this modification, focusing on the differences from the first embodiment.

[0250] The range determination unit 1262, 2182 according to this modification refers to the reference picture list and selects a reference picture that is a coded / decoded picture other than the current picture. For example, the range determination unit 1262, 2182 selects the reference picture with the smallest reference picture index. Alternatively, for example, the range determination unit 1262, 2182 may select the reference picture that is closest to the current picture in output order.

[0251] Next, the range determination unit 1262, 2182 obtains multiple motion vectors used in encoding / decoding multiple blocks included in the selected reference picture, and then calculates an average motion vector of the obtained multiple motion vectors.

[0252] Then, the range determination units 1262 and 2182 determine the representative position of the motion search range based on the calculated average motion vector.

[0253] As described above, according to the range determination units 1262 and 2182 of this modification, since the motion vectors of the coded / decoded picture do not change even if the current block in the current picture changes, it is not necessary to determine the motion search range from the motion vectors of adjacent blocks every time the current block changes, which means that the processing load for determining the motion search range can be reduced.

[0254] Here, the representative position of the motion search range is determined based on the average motion vector of the selected reference picture, but this is not limiting. For example, a central motion vector may be used instead of the average motion vector. Also, for example, a motion vector of a co-located block may be used instead of the average motion vector.

[0255] 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.

[0256] (Fourth Modification of First Embodiment) Next, a fourth modification of the first embodiment will be described. In this modification, a reference picture is divided into a plurality of regions, and motion vectors included in a plurality of candidates are grouped based on the divided regions. At this time, the position of the motion search range is determined based on the group that includes the largest number of motion vectors.

[0257] The following describes this modification, focusing on the differences from the first embodiment, with reference to Fig. 20. Fig. 20 is a diagram showing an example of a motion search range in the fourth modification of the first embodiment.

[0258] The range determination units 1262 and 2182 according to this modification divide the reference picture into regions. For example, as shown in Fig. 20, the range determination units 1262 and 2182 divide the reference picture into four regions (first to fourth regions) based on the position of the current picture.

[0259] The range determination units 1262, 2182 group the motion vectors of adjacent blocks based on the regions. For example, in Fig. 20, the range determination units 1262, 2182 group the motion vectors 1011 to 1014 into a first group including the motion vector 1013 corresponding to the first region and a second group including the motion vectors 1011, 1012, and 1014 corresponding to the second region.

[0260] The range determination unit 1262, 2182 determines the position of the motion search range based on the group that includes the largest number of motion vectors. For example, in Fig. 20, the range determination unit 1262, 2182 determines the representative position 1041 of the motion search range based on the average motion vector 1040 of the motion vectors 1011, 1012, and 1014 included in the second group. Note that instead of the average motion vector, a median motion vector or a minimum motion vector may be used.

[0261] As described above, the range determination units 1262 and 2182 according to this modification can determine an area suitable for searching for a motion vector for the current block as the motion search range, thereby improving the accuracy of the motion vector.

[0262] 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.

[0263] (Fifth Modification of First Embodiment) Next, a fifth variation of the first embodiment will be described. This variation differs from the first embodiment in that the position of the motion search range is corrected. This variation will be described below, focusing on the differences from the first embodiment, with reference to Fig. 21. Fig. 21 is a diagram showing an example of a motion search range in the fifth variation of the first embodiment.

[0264] The range determination unit 1262, 2182 according to this modification corrects the position of the motion search range determined based on, for example, an average motion vector. Specifically, the range determination unit 1262, 2182 first tentatively determines the motion search range based on the average motion vector of multiple motion vectors included in multiple candidates. For example, the range determination unit 1262, 2182 tentatively determines the motion search range 1050 as shown in FIG. 21 .

[0265] Here, the range determination unit 1262, 2182 determines whether a position corresponding to a zero motion vector is included in the tentatively determined motion search range. That is, the range determination unit 1262, 2182 determines whether a reference position (e.g., the upper left corner) of the current block in the reference picture is included in the tentatively determined motion search range 1050. For example, in FIG. 21 , the range determination unit 1262, 2182 determines whether the tentatively determined motion search range 1050 includes a position 1051 corresponding to a zero motion vector.

[0266] Here, if the position corresponding to the zero motion vector is not included in the tentatively determined motion search range, the range determination unit 1262, 2182 corrects the position of the tentatively determined motion search range so that the motion search range includes the position corresponding to the zero motion vector. For example, in Figure 21, the tentatively determined motion search range 1050 does not include the position 1051 corresponding to the zero motion vector, so the range determination unit 1262, 2182 corrects the motion search range 1050 to the motion search range 1052. As a result, the corrected motion search range 1052 includes the position 1051 corresponding to the zero motion vector.

[0267] On the other hand, if the position corresponding to the zero motion vector is included in the tentatively determined motion search range, the range determination unit 1262, 2182 determines the tentatively determined motion search range as is, that is, the range determination unit 1262, 2182 does not correct the position of the motion search range.

[0268] As described above, the range determination units 1262 and 2182 according to this modification can determine an area suitable for searching for a motion vector for the current block as the motion search range, thereby improving the accuracy of the motion vector.

[0269] 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.

[0270] (Sixth Modification of First Embodiment) Next, we will explain Variation 6 of Embodiment 1. In Variation 5 above, the position of the motion search range is corrected to include a position corresponding to a zero motion vector, but in this Variation, the position of the motion search range is corrected to include a position corresponding to the motion vector of one of multiple adjacent blocks.

[0271] This modification will be described below with reference to Fig. 22. Fig. 22 is a diagram showing an example of a motion search range in Modification 6 of the first embodiment.

[0272] First, the range determination units 1262, 2182 tentatively determine a motion search range based on, for example, an average motion vector, as in Modification 5. For example, the range determination units 1262, 2182 tentatively determine a motion search range 1050 as shown in FIG.

[0273] Here, the range determination units 1262, 2182 determine whether a position corresponding to the motion vector of one of the multiple adjacent blocks is included in the provisionally determined motion search range. For example, in FIG. 22, the range determination units 1262, 2182 determine whether the provisionally determined motion search range 1050 includes a position 1053 corresponding to the motion vector 1011 of the adjacent block 1001. A predetermined adjacent block may be used as the one of the multiple adjacent blocks, such as the left adjacent block or the above adjacent block.

[0274] Here, if the position corresponding to the motion vector of one of the multiple adjacent blocks is not included in the tentatively determined motion search range, the range determination unit 1262, 2182 corrects the position of the tentatively determined motion search range so that the motion search range includes the position corresponding to the motion vector. For example, in Figure 22, the tentatively determined motion search range 1050 does not include position 1053 corresponding to motion vector 1011 of adjacent block 1001, so the range determination unit 1262, 2182 corrects the motion search range 1050 to motion search range 1054. As a result, the corrected motion search range 1054 includes position 1053.

[0275] On the other hand, if the position corresponding to the motion vector of one of the adjacent blocks is included in the tentatively determined motion search range, the range determination unit 1262, 2182 determines the tentatively determined motion search range as is, that is, the range determination unit 1262, 2182 does not correct the position of the motion search range.

[0276] As described above, the range determination units 1262 and 2182 according to this modification can determine an area suitable for searching for a motion vector for the current block as the motion search range, thereby improving the accuracy of the motion vector.

[0277] 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.

[0278] (Seventh Modification of the First Embodiment) Next, Variation 7 of Embodiment 1 will be described. This variation differs from Embodiment 1 above in that information regarding the motion search range is not included in the bitstream. This variation will be described below with reference to FIG. 23, focusing on the differences from Embodiment 1 above.

[0279] 23 is a block diagram showing a functional configuration of a coding / decoding system 300 according to Variation 7 of Embodiment 1. As shown in FIG. 23, the coding / decoding system 300 includes a coding system 310 and a decoding system 320.

[0280] The encoding system 310 encodes an input video image and outputs a bitstream. The encoding system 310 includes a communication device 311, an encoding device 312, and an output buffer 313.

[0281] The communication device 311 exchanges capability information with the decoding system 320 via a communication network (not shown) or the like, and generates motion search range information based on the capability information. Specifically, the communication device 311 transmits coding capability information to the decoding system 320 and receives decoding capability information from the decoding system 320. The coding capability information includes information such as the processing capability and memory bandwidth for motion search in the coding system 310. The decoding capability information includes information such as the processing capability and memory bandwidth for motion search in the decoding system 320.

[0282] The encoding device 312 encodes the input video image and outputs the bitstream to the output buffer 313. At this time, the encoding device 312 performs substantially the same processing as the encoding device 100 according to the first embodiment, except that the encoding device 312 determines the size of the motion search range based on the motion search range information acquired from the communication device 311.

[0283] The output buffer 313 is a so-called buffer memory, which temporarily stores the bit stream input from the encoding device 312 and outputs the stored bit stream to the decoding system 320 via a communication network or the like.

[0284] The decoding system 320 decodes the bitstream input from the encoding system 310 and outputs an output video to a display (not shown) or the like. The decoding system 320 includes a communication device 321, a decoding device 322, and an input buffer 323.

[0285] Like the communication device 311 of the encoding system 310, the communication device 321 exchanges capability information with the encoding system 310 via a communication network or the like, and generates motion search range information based on the capability information. Specifically, the communication device 311 transmits decoding capability information to the encoding system 310 and receives encoding capability information from the encoding system 310.

[0286] The decoding device 322 decodes the bitstream input from the input buffer 323 and outputs the output video to a display or the like. At this time, the decoding device 322 performs substantially the same processing as the decoding device 200 according to the first embodiment, except that the decoding device 322 determines the motion search range based on the motion search range information acquired from the communication device 321. Note that if the motion search range determined based on the motion search range information acquired from the communication device 321 exceeds the motion search range that the decoding device 322 can process, the decoding device 322 may transmit a message to the communication device 321 indicating that decoding is impossible.

[0287] The input buffer 323 is a so-called buffer memory, which temporarily stores the bit stream input from the encoding system 310 and outputs the stored bit stream to the decoding device 322 .

[0288] As described above, according to the encoding / decoding system 300 of this modification, even if information about the motion search range is not included in the bitstream, the encoding device 312 and the decoding device 322 can perform motion search using the same motion search range. This makes it possible to reduce the amount of code required for the motion search range. Furthermore, since there is no need for the range determination unit 1262 to perform processing to determine the number of horizontal pixels and the number of vertical pixels that represent the size of the motion search range, the amount of processing can be reduced.

[0289] (Eighth Modification of First Embodiment) In the first embodiment, all of the reference pictures included in the reference picture list are selected in order, but it is not necessary to select all of the reference pictures. In this modification, an example will be described in which the number of selected reference pictures is limited.

[0290] The range determination unit 1262 of the encoding device 100 according to this modification determines the number of reference pictures permitted to be used in motion estimation in FRUC mode (hereinafter referred to as "allowed reference picture number") based on the memory bandwidth, processing power, etc., as well as the size of the motion estimation range. Information related to the determined allowed reference picture number (hereinafter referred to as "allowed reference picture number information") is written to the bitstream.

[0291] Furthermore, the range determining unit 2182 of the decoding device 200 according to this modification determines the allowed number of reference pictures based on the information about the allowed number of reference pictures decoded from the bitstream.

[0292] Note that the position in the bitstream where the information on the allowed number of reference pictures is written is not particularly limited. For example, the information on the allowed number of reference pictures may be written in the VPS, SPS, PPS, slice header, or video system setting parameters, similar to the motion search range information shown in Fig. 12 .

[0293] The number of reference pictures used in FRUC mode is limited based on the thus determined number of allowed reference pictures. Specifically, the range determination unit 1262, 2182 determines whether there are unselected reference pictures and the number of selected reference pictures is less than the number of allowed reference pictures, for example, in step S111 of Fig. 13. Here, if there are no unselected reference pictures or if the number of selected reference pictures is equal to or greater than the number of allowed reference pictures (Yes in S111), the process proceeds to step S112. This prohibits the selection of reference pictures in a number exceeding the number of allowed reference pictures from the reference picture list.

[0294] In this case, in step S111 of Fig. 13, the range determination unit 1262, 2182 may select reference pictures, for example, in ascending order of reference picture index values ​​or in order of temporal proximity to the current picture. In this case, a reference picture with a smaller reference picture index value or a reference picture temporally close to the current picture is preferentially selected from the reference picture list. Note that the temporal distance between the current picture and a reference picture may be determined based on a POC (Picture Order Count).

[0295] As described above, the range determining units 1262 and 2182 according to this modification can limit the number of reference pictures used in motion estimation to the permissible number of reference pictures or less, thereby reducing the processing load for motion estimation.

[0296] For example, when temporal scalable encoding / decoding is performed, the range determination unit 1262, 2182 may limit the number of reference pictures included in a layer lower than the layer of the current picture indicated by the time identifier based on the allowed number of reference pictures.

[0297] (Ninth Modification of First Embodiment) Next, a description will be given of a ninth modification of the first embodiment. In this modification, a method for determining the size of a motion search range when multiple reference pictures are referred to in inter prediction will be described.

[0298] When multiple reference pictures are referenced in inter prediction, the size of the motion search range may depend on the number of reference pictures referenced in inter prediction in addition to the memory bandwidth and processing capability. Specifically, the range determination unit 1262, 2182 first determines the total size of multiple motion search ranges in the multiple reference pictures referenced in inter prediction based on the memory bandwidth and processing capability. Then, the range determination unit 1262, 2182 determines the size of the motion search range for each reference picture based on the number of multiple reference pictures and the determined total size. In other words, the range determination unit 1262 determines the size of the motion search range in each reference picture so that the sum of the sizes of the multiple motion search ranges in the multiple reference pictures matches the total size of the multiple motion search ranges determined based on the memory bandwidth and processing capability.

[0299] The motion search range for each reference picture determined in this manner will be specifically described with reference to Figure 24. Figure 24 is a diagram showing the motion search range in Variation 9 of Embodiment 1. (a) of Figure 24 shows an example of the motion search range in prediction where two reference pictures are referenced (bi-prediction), and (b) of Figure 24 shows an example of the motion search range in prediction where four reference pictures are referenced.

[0300] 24(a), motion search ranges F20 and B20 are determined for forward reference picture 0 and backward reference picture 0, respectively. Pattern matching (template matching or bilateral matching) is performed within motion search ranges F20 and B20.

[0301] 24(b), motion search ranges F40, F41, B40, and B41 are determined for forward reference picture 0, forward reference picture 1, backward reference picture 0, and backward reference picture 1, respectively. Therefore, pattern matching is performed within these motion search ranges F40, F41, B40, and B41.

[0302] Here, the total size of motion search ranges F20 and B20 is approximately equal to the total size of motion search ranges F40, F41, B40, and B41. In other words, the size of the motion search range for each reference picture is determined based on the number of reference pictures referenced in inter prediction.

[0303] As described above, the range determination units 1262 and 2182 according to this modification can determine the size of the motion search range for each reference picture based on the number of reference pictures used in inter prediction. This makes it possible to control the total size of the area in which motion search is performed, thereby more efficiently reducing the processing load and memory bandwidth requirements.

[0304] (Another variation of the first embodiment) While the encoding device and the decoding device according to one or more aspects of the present disclosure have been described above based on embodiments and modifications, the present disclosure is not limited to these embodiments and modifications. As long as they do not deviate from the spirit of the present disclosure, various modifications conceivable by those skilled in the art to the present embodiment or modifications, or configurations constructed by combining components of different modifications, may also be included within the scope of one or more aspects of the present disclosure.

[0305] For example, in the above-described embodiment and modifications, motion estimation in FRUC mode is performed in units of variable-sized blocks called coding units (CUs), prediction units (PUs), or transform units (TUs). However, this is not limiting. Motion estimation in FRUC mode may also be performed in units of sub-blocks obtained by further dividing variable-sized blocks. In this case, vectors (e.g., mean vectors, median vectors, etc.) for determining the position of the motion estimation range may be calculated in units of pictures, blocks, or sub-blocks.

[0306] Furthermore, for example, in the above-described embodiment and each modification, the size of the motion search range is determined based on the processing power, memory bandwidth, etc. However, this is not limiting. For example, the size of the motion search range may be determined based on the type of reference picture. For example, the range determination unit 1262 may determine the size of the motion search range to be a first size when the reference picture is a B picture, and may determine the size of the motion search range to be a second size larger than the first size when the reference picture is a P picture.

[0307] Furthermore, for example, in the above-described embodiment and each modification, if a position corresponding to a motion vector included in a candidate is not included in the motion search range, the candidate is excluded from the candidate list, but this is not limited to this. For example, if a part or all of the surrounding area of ​​a position corresponding to a motion vector included in a candidate is not included in the motion search range, the candidate may be excluded from the candidate list.

[0308] Furthermore, for example, in the above-described embodiment and each modification, pattern matching is performed in the surrounding area of ​​the position corresponding to the motion vector included in the selected candidate, but this is not limited to this. For example, pattern matching of the surrounding area may not be performed. In this case, the motion vector included in the candidate may be determined as the motion vector for the current block.

[0309] For example, in the above-described embodiment and each modification, the candidate excluded from the candidate list has a motion vector corresponding to a position outside the motion search range. However, this is not limited to this. For example, if a pixel used for interpolation is not included in the motion search range when motion compensation is performed with fractional pixel accuracy using a motion vector included in the candidate, the candidate may be excluded from the candidate list. In other words, whether a candidate is excluded may be determined based on the position of a pixel used for fractional pixel interpolation. For example, when BIO or OBMC is applied, a candidate that uses a pixel outside the motion search range in BIO or OBMC may be excluded from the candidate list. For example, the candidate with the smallest reference picture index among the multiple candidates may be left, and the other candidates may be excluded.

[0310] Furthermore, for example, in the above-described embodiment and each modification, a case where a mode limiting a motion search range is always applied in a reference picture has been described, but this is not limiting. For example, application / non-application of the mode may be selected in units of video, sequence, picture, slice, or block. In this case, flag information indicating whether or not the mode is applied may be included in the bitstream. The position of this flag information in the bitstream does not need to be particularly limited. For example, the flag information may be included in the same position as the motion search range information shown in FIG. 12.

[0311] Furthermore, for example, although the above-described embodiment and modifications do not provide a detailed description of motion vector scaling, the motion vector of each candidate may be scaled based on a reference picture as a base. Specifically, the motion vector of each candidate may be scaled based on a reference picture that is different from the reference picture index of the encoding and decoding results. As the reference picture as a base, for example, a reference picture with a reference picture index of "0" may be used. Also, for example, the reference picture as a base may be the reference picture that is closest to the current picture in output order.

[0312] Unlike the case of inter-frame prediction as in the above-described embodiment and each modified example, even when an area located above or to the left of the current block in the current picture is referenced to search for a block identical to the current block (for example, in the case of intra block copy), the motion search range may be limited as in the above-described embodiment and each modified example.

[0313] In the above-described embodiment and each modification, information defining a correspondence relationship between a feature or type of the current block or current picture and a plurality of motion search range sizes may be determined in advance, and the size of the motion search range corresponding to the feature or type of the current block or current picture may be determined by referring to the information. As the feature, for example, a size (number of pixels) or the like may be used, and as the type, for example, a prediction mode (for example, uni-prediction, bi-prediction, etc.) may be used.

[0314] (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).

[0315] 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.

[0316] 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.

[0317] 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.

[0318] [Usage example] 25 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.

[0319] 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.

[0320] 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.

[0321] 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.

[0322] The home appliance ex118 is a refrigerator or an appliance included in a home fuel cell cogeneration system.

[0323] 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.

[0324] 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.

[0325] [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.

[0326] 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.

[0327] 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).

[0328] 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.

[0329] 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.

[0330] 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.

[0331] 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.

[0332] [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.

[0333] 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.

[0334] 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.

[0335] 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.

[0336] 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.

[0337] 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.

[0338] 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.

[0339] [Scalable Coding] Content switching will be described using a scalable stream, shown in FIG. 26, 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 temporal / spatial scalability achieved by encoding the stream in layers, as shown. In other words, the decoder determines which layer to decode based on internal factors such as performance and external factors such as communication bandwidth, allowing the decoder 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.

[0340] 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.

[0341] 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. 27, 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.

[0342] 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.

[0343] [Webpage optimization] FIG. 28 is a diagram showing an example of a web page display screen on a computer ex111 or the like. FIG. 29 is a diagram showing an example of a web page display screen on a smartphone ex115 or the like. As shown in FIGS. 28 and 29, 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.

[0344] 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.

[0345] [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.

[0346] 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.

[0347] 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.

[0348] [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.

[0349] 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.

[0350] 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.

[0351] 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.

[0352] [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.

[0353] 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.

[0354] 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.

[0355] [Hardware configuration] FIG. 30 is a diagram illustrating a smartphone ex115. FIG. 31 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.

[0356] 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.

[0357] 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.

[0358] 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.

[0359] 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.

[0360] 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.

[0361] 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. [Industrial Applicability]

[0362] The present disclosure is applicable to, for example, television receivers, digital video recorders, car navigation systems, mobile phones, digital cameras, digital video cameras, and the like. [Explanation of symbols]

[0363] 100, 312 encoding device 102 Division 104 Subtraction section 106 Conversion unit 108 Quantization section 110 Entropy coding unit 112, 204 Inverse quantization section 114, 206 Inverse conversion unit 116, 208 Addition section 118, 210 block memory 120, 212 Loop filter section 122, 214 frame memory 124, 216 Intra prediction section 126, 218 Inter prediction section 128, 220 Predictive control unit 200, 322 Decoding device 202 Entropy Decoding Unit 300 Encoding and Decoding System 310 Coding System 311, 321 Communication equipment 313 Output Buffer 320 Decoding System 323 Input Buffer 1261, 2181 Candidate derivation part 1262, 2182 Range determination section 1263, 2183 Motion Search Unit 1264, 2184 Motion compensation unit

Claims

1. 1. An encoding device, comprising: a processor; a memory; The processor uses the memory to: deriving a representative motion vector indicating a representative position based on motion vector candidates included in a candidate list having candidates derived based on motion vectors of blocks spatially or temporally adjacent to the encoding target block; determining a first motion search range including the representative position indicated by the representative motion vector in a first reference picture of the current block to be coded; calculating first evaluation values ​​for each of a plurality of candidate areas included in the first motion search range, the first evaluation values ​​being differences between the plurality of candidate areas and an area along the motion trajectory of the current block in a second reference picture different from the first reference picture; determining a first surrounding area, which is an area including a first candidate area having a smallest first evaluation value among the plurality of candidate areas included in the first motion search range and its surroundings, and which is an area included in the first motion search range; determining a motion vector of the current block to be coded using a second evaluation value that is the smallest among evaluation values ​​of areas included in the first surrounding area; generating a bitstream including information indicating that a mode for performing motion estimation is to be applied; a first picture order count between the current picture including the current block and the first reference picture is equal to a second picture order count between the current picture and the second reference picture; Encoding device.

2. A decoding device, comprising: a processor; a memory; The processor uses the memory to: deriving a representative motion vector indicating a representative position based on motion vector candidates included in a candidate list having candidates derived based on motion vectors of blocks spatially or temporally adjacent to the block to be decoded; determining a first motion search range including the representative position indicated by the representative motion vector in a first reference picture of the block to be decoded; calculating first evaluation values ​​for each of a plurality of candidate areas included in the first motion search range, the first evaluation values ​​being differences between the plurality of candidate areas and an area along the motion trajectory of the block to be decoded in a second reference picture different from the first reference picture; determining a first surrounding area, which is an area including a first candidate area having a smallest first evaluation value among the plurality of candidate areas included in the first motion search range and its surroundings, and which is an area included in the first motion search range; determining a motion vector of the current block using a second evaluation value that is the smallest among evaluation values ​​of areas included in the first surrounding area; a first picture order count between the current picture including the current block and the first reference picture is equal to a second picture order count between the current picture and the second reference picture; Decryption device.

3. 1. An encoding method comprising: deriving a representative motion vector indicating a representative position based on motion vector candidates included in a candidate list having candidates derived based on motion vectors of blocks spatially or temporally adjacent to the encoding target block; determining a first motion search range including the representative position indicated by the representative motion vector in a first reference picture of the current block to be coded; calculating first evaluation values ​​for each of a plurality of candidate areas included in the first motion search range, the first evaluation values ​​being differences between the plurality of candidate areas and an area along the motion trajectory of the current block in a second reference picture different from the first reference picture; determining a first surrounding area, which is an area including a first candidate area having a smallest first evaluation value among the plurality of candidate areas included in the first motion search range and its surroundings, and which is an area included in the first motion search range; determining a motion vector of the current block to be coded using a second evaluation value that is the smallest among evaluation values ​​of areas included in the first surrounding area; generating a bitstream including information indicating that a mode for performing motion estimation is to be applied; a first picture order count between the current picture including the current block and the first reference picture is equal to a second picture order count between the current picture and the second reference picture; Encoding method.

4. 1. A decoding method comprising: deriving a representative motion vector indicating a representative position based on motion vector candidates included in a candidate list having candidates derived based on motion vectors of blocks spatially or temporally adjacent to the block to be decoded; determining a first motion search range including the representative position indicated by the representative motion vector in a first reference picture of the block to be decoded; calculating first evaluation values ​​for each of a plurality of candidate areas included in the first motion search range, the first evaluation values ​​being differences between the plurality of candidate areas and an area along the motion trajectory of the block to be decoded in a second reference picture different from the first reference picture; determining a first surrounding area, which is an area including a first candidate area having a smallest first evaluation value among the plurality of candidate areas included in the first motion search range and its surroundings, and which is an area included in the first motion search range; determining a motion vector of the current block using a second evaluation value that is the smallest among evaluation values ​​of areas included in the first surrounding area; a first picture order count between the current picture including the current block and the first reference picture is equal to a second picture order count between the current picture and the second reference picture; Decryption method.

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