Bitstream transmitter

Abstract

To improve coding efficiency in a transmitting bitstream.SOLUTION: A bitstream transmitter includes a circuit and a memory, the circuit derives a motion vector in a mode selected from a plurality of modes, and performs inter-prediction encoding of a target block using the motion vector, the plurality of modes including a plurality of first modes for predicting the motion vector without encoding information indicating a differential motion vector, in the skip mode, information indicating whether the second mode is used is not described in the bitstream, and information indicating whether a third mode is used is described in the bitstream, and in the non-skip mode, information indicating whether the second mode is used and information indicating whether the third mode is used are described in the bitstream, and when the second mode is used, the circuit encodes the target block in the non-skip mode and transmits a bitstream including the encoded target block.SELECTED DRAWING: Figure 16

Description

[Technical field]

[0001] The present disclosure relates to an encoding device and the like. [Background technology]

[0002] Conventionally, H.265 exists as a standard for encoding moving images. H.265 is also called High Efficiency Video Coding (HEVC). [Prior art documents] [Non-patent literature]

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

[0004] In such encoding and decoding methods, it is desirable to be able to improve the encoding efficiency.

[0005] An object of the present disclosure is to provide a coding device and the like that can improve coding efficiency. [Means for solving the problem]

[0006] A bitstream transmission device according to one embodiment of the present disclosure includes a circuit and a memory, the circuit using the memory to select one mode from a plurality of modes for deriving a motion vector, derive a motion vector for a target block in the selected mode, and use the derived motion vector to perform inter-prediction encoding of the target block in one of a skip mode and a non-skip mode different from the skip mode, the plurality of modes including a plurality of first modes for predicting the motion vector of the target block from encoded blocks surrounding the target block without encoding information indicating a differential motion vector into the bitstream, in the skip mode, information indicating whether a second mode included in the plurality of first modes is used is not described in the bitstream, and information indicating whether a third mode included in the plurality of first modes and different from the second mode is used is described in the bitstream, in the non-skip mode, information indicating whether the second mode is used and information indicating whether the third mode is used are described in the bitstream, and when the second mode is used, the target block is encoded in the non-skip mode regardless of the presence or absence of a residual coefficient, and the bitstream including the encoded target block is transmitted.

[0007] In addition, these comprehensive or specific aspects may be realized by a system, an apparatus, a method, an integrated circuit, a computer program, or a non-transitory recording medium such as a computer-readable CD-ROM, or may be realized by any combination of a system, an apparatus, a method, an integrated circuit, a computer program, and a recording medium. Effect of the Invention

[0008] The present disclosure can provide a coding device and the like that can improve coding efficiency. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a block diagram showing a functional configuration of a coding device according to the first embodiment. [Diagram 2] FIG. 2 is a diagram showing an example of block division according to the first embodiment. [Diagram 3] FIG. 3 is a table showing the transform basis functions corresponding to each transform type. [Figure 4A] FIG. 4A is a diagram showing an example of the shape of a filter used in ALF. [Figure 4B] FIG. 4B is a diagram showing another example of the shape of the filter used in the ALF. [Figure 4C] FIG. 4C is a diagram showing another example of the shape of the filter used in the ALF. [Figure 5A] FIG. 5A is a diagram showing 67 intra prediction modes in intra prediction. [Figure 5B] FIG. 5B is a flowchart for explaining an outline of the predicted image correction process by the OBMC process. [Figure 5C] FIG. 5C is a conceptual diagram for explaining an overview of the predicted image correction process by the OBMC process. [Figure 5D] FIG. 5D is a diagram showing an example of FRUC. [Figure 6] FIG. 6 is a diagram for explaining pattern matching (bilateral matching) between two blocks along a motion trajectory. [Figure 7] FIG. 7 is a diagram for explaining pattern matching (template matching) between a template in a current picture and a block in a reference picture. [Figure 8] FIG. 8 is a diagram for explaining a model assuming uniform linear motion. [Figure 9A] FIG. 9A is a diagram for explaining derivation of a motion vector for each sub-block based on motion vectors of a plurality of adjacent blocks. [Figure 9B] FIG. 9B is a diagram for explaining an overview of the motion vector derivation process in the merge mode. [Figure 9C] FIG. 9C is a conceptual diagram for explaining an overview of the DMVR process. [Figure 9D]FIG. 9D is a diagram for explaining an outline of a predicted image generating method using luminance correction processing by LIC processing. [Figure 10] FIG. 10 is a block diagram showing a functional configuration of a decoding device according to the first embodiment. As shown in FIG. [Figure 11] FIG. 11 is a flowchart of an inter prediction process performed by an encoding device according to a first example of the first embodiment. [Figure 12] FIG. 12 is a flowchart of an inter prediction process performed by a decoding device according to a first example of the first embodiment. [Figure 13] FIG. 13 is a diagram showing a syntax configuration according to a first example of the first embodiment. [Figure 14] FIG. 14 is a flowchart of an inter prediction process performed by an encoding device according to a second example of the first embodiment. [Figure 15] FIG. 15 is a flowchart of an inter prediction process performed by a decoding device according to a second example of the first embodiment. [Figure 16] FIG. 16 is a diagram showing a syntax configuration according to the second example of the first embodiment. [Figure 17] FIG. 17 is a flowchart of an inter prediction process performed by an encoding device according to a third example of the first embodiment. [Figure 18] FIG. 18 is a flowchart of an inter prediction process performed by a decoding device according to a third example of the first embodiment. [Figure 19] FIG. 19 is a diagram showing a syntax configuration according to the third example of the first embodiment. [Figure 20] FIG. 20 is a block diagram showing an example of implementation of the encoding device according to the first embodiment. [Figure 21] FIG. 21 is a block diagram showing an implementation example of the decoding device according to the first embodiment. As shown in FIG. [Figure 22] FIG. 22 is a diagram showing the overall configuration of a content supply system that realizes a content distribution service. [Figure 23] FIG. 23 is a diagram showing an example of a coding structure in scalable coding. [Figure 24]FIG. 24 is a diagram showing an example of a coding structure in scalable coding. [Diagram 25] FIG. 25 is a diagram showing an example of a display screen of a web page. [Figure 26] FIG. 26 is a diagram showing an example of a display screen of a web page. [Figure 27] FIG. 27 is a diagram illustrating an example of a smartphone. [Figure 28] FIG. 28 is a block diagram showing an example of the configuration of a smartphone. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] An encoding device according to one embodiment of the present disclosure includes a circuit and a memory, wherein the circuit uses the memory to select one mode from a plurality of modes for deriving a motion vector, derives a motion vector for a target block in the selected mode, and uses the derived motion vector to perform inter-predictive encoding of the target block in one of a skip mode and a non-skip mode different from the skip mode, wherein the plurality of modes include a plurality of first modes that predict the motion vector of the target block from already-encoded blocks surrounding the target block without encoding information indicating the motion vector into a stream, and when a second mode included in the plurality of first modes is selected, the target block is encoded in the non-skip mode regardless of whether or not there is a residual coefficient.

[0011] This allows the encoding device to improve the encoding efficiency, for example, because it is no longer necessary to transmit information indicating whether the second mode is used when the skip mode is used, thereby improving the encoding efficiency.

[0012] For example, when a third mode different from the second mode and included in the plurality of first modes is selected, the target block may be coded in the non-skip mode if there are residual coefficients, and may be coded in the skip mode if there are no residual coefficients.

[0013] For example, the second mode may be a mode in which a motion vector corresponding to an affine transformation is predicted from encoded blocks surrounding the current block.

[0014] According to this, when a mode in which the non-skip mode is likely to be selected due to the occurrence of a coefficient whose value is not zero is used, the non-skip mode is used regardless of the presence or absence of residual coefficients, and thus the influence of the skip mode not being selected can be suppressed.

[0015] For example, the third mode may be a FRUC mode or a merge mode.

[0016] For example, the circuitry may use the memory to further encode information indicating whether or not residual coefficients are present when the current block is encoded in the non-skip mode.

[0017] For example, the circuit may use the memory to further select whether or not to perform a luminance correction process on the target block, in which an average luminance value of a predicted image is corrected using a correction value predicted from luminance values ​​of encoded blocks surrounding the target block, and when performing the luminance correction process on the target block, may encode the target block in the non-skip mode regardless of whether or not the residual coefficients are present.

[0018] According to this, when a luminance correction process is performed in which the non-skip mode is likely to be selected due to the occurrence of a coefficient whose value is not zero, the non-skip mode is used regardless of the presence or absence of residual coefficients, and thus the influence of not selecting the skip mode can be suppressed.

[0019] For example, the circuit may use the memory to further encode information indicating whether or not there is a residual coefficient when performing the luminance correction process on the current block.

[0020] A decoding device according to one embodiment of the present disclosure includes a circuit and a memory, wherein the circuit uses the memory to select one mode from a plurality of modes for deriving a motion vector, derives a motion vector for a target block in the selected mode, and performs inter-prediction decoding of the target block using the derived motion vector in one of a skip mode and a non-skip mode different from the skip mode, wherein the plurality of modes include a plurality of first modes that predict the motion vector of the target block from decoded blocks surrounding the target block without decoding information indicating the motion vector from a stream, and when a second mode included in the plurality of first modes is selected, the target block is decoded in the non-skip mode regardless of whether or not there are residual coefficients.

[0021] This allows the decoding device to improve coding efficiency, for example, because it is no longer necessary to transmit information indicating whether the second mode is used when the skip mode is used, thereby improving coding efficiency.

[0022] For example, when a third mode different from the second mode and included in the plurality of first modes is selected, the target block may be decoded in the non-skip mode if there are residual coefficients, and the target block may be decoded in the skip mode if there are no residual coefficients.

[0023] For example, the second mode may be a mode in which a motion vector corresponding to an affine transformation is predicted from decoded blocks surrounding the current block.

[0024] According to this, when a mode in which the non-skip mode is likely to be selected due to the occurrence of a coefficient whose value is not zero is used, the non-skip mode is used regardless of the presence or absence of residual coefficients, and thus the influence of the skip mode not being selected can be suppressed.

[0025] For example, the third mode may be a FRUC mode or a merge mode.

[0026] For example, the circuitry may use the memory to further decode information indicating whether or not there are residual coefficients when the current block is decoded in the non-skip mode.

[0027] For example, the circuit may use the memory to further select whether or not to perform a luminance correction process on the target block, in which an average luminance value of a predicted image is corrected using a correction value predicted from luminance values ​​of decoded blocks surrounding the target block, and when performing the luminance correction process on the target block, decode the target block in the non-skip mode regardless of whether or not the residual coefficients are present.

[0028] According to this, when a luminance correction process is performed in which the non-skip mode is likely to be selected due to the occurrence of a coefficient whose value is not zero, the non-skip mode is used regardless of the presence or absence of residual coefficients, and thus the influence of not selecting the skip mode can be suppressed.

[0029] For example, the circuit may further use the memory to decode information indicating whether or not there are residual coefficients when performing the luminance correction process on the current block.

[0030] An encoding method according to one embodiment of the present disclosure includes selecting one mode from a plurality of modes for deriving a motion vector, deriving a motion vector for a target block in the selected mode, and using the derived motion vector to inter-predictively encode the target block in one of a skip mode and a non-skip mode different from the skip mode, wherein the plurality of modes include a plurality of first modes that predict the motion vector of the target block from already-encoded blocks surrounding the target block without encoding information indicating the motion vector into a stream, and when a second mode included in the plurality of first modes is selected, encoding the target block in the non-skip mode regardless of whether or not there are residual coefficients.

[0031] This makes it possible to improve the coding efficiency of the coding method, for example, because it is not necessary to transmit information indicating whether the second mode is used or not when the skip mode is used, thereby improving the coding efficiency.

[0032] A decoding method according to one embodiment of the present disclosure includes selecting one mode from a plurality of modes for deriving a motion vector, deriving a motion vector for a target block in the selected mode, and using the derived motion vector to perform inter-prediction decoding of the target block in one of a skip mode and a non-skip mode different from the skip mode, wherein the plurality of modes include a plurality of first modes that predict the motion vector of the target block from decoded blocks surrounding the target block without decoding information indicating the motion vector from a stream, and when a second mode included in the plurality of first modes is selected, the target block is decoded in the non-skip mode regardless of whether or not there are residual coefficients.

[0033] This makes it possible to improve the coding efficiency of the decoding method, for example, by eliminating the need to transmit information indicating whether the second mode is used or not when the skip mode is used, thereby improving the coding efficiency.

[0034] Furthermore, these comprehensive or specific aspects may be realized in a system, an apparatus, a method, an integrated circuit, a computer program, or a non-transitory recording medium such as a computer-readable CD-ROM, or may be realized in any combination of a system, an apparatus, a method, an integrated circuit, a computer program, and a recording medium.

[0035] Hereinafter, the embodiment will be described in detail with reference to the drawings.

[0036] The embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, component arrangement and connection forms, steps, and order of steps shown in the following embodiments are merely examples and are not intended to limit the scope of the claims. Furthermore, among the components in the following embodiments, components that are not described in an independent claim showing a top concept are described as optional components.

[0037] (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.

[0038] 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.

[0039] (1) For the encoding device or the decoding device of the first embodiment, among the multiple components constituting the encoding device or the decoding device, components corresponding to the components described in each aspect of the present disclosure are replaced with the components described in each aspect of the present disclosure. (2) In the encoding device or decoding device of the first embodiment, any modification such as addition, replacement, or deletion of functions or processes performed by some of the components constituting the encoding device or decoding device is made, and then the components corresponding to the components described in each aspect of the present disclosure are replaced with the components described in each aspect of the present disclosure. (3) Adding a process to the method implemented by the encoding device or decoding device of the first embodiment, and / or replacing or deleting some of the processes included in the method, and then replacing the process corresponding to the process described in each aspect of the present disclosure with the process described in each aspect of the present disclosure. (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) Implementing a component having some of the functions of some of the multiple components constituting the encoding device or decoding device of embodiment 1, or a component that performs some of the processing performed by some of the multiple components constituting the encoding device or decoding device of embodiment 1, in combination with a component described in each aspect of the present disclosure, a component having some of the functions of the component described in each aspect of the present disclosure, or a component that performs some of the processing performed by the component described in each aspect of the present disclosure. (6) In the method implemented by the encoding device or the decoding device of the first embodiment, among a plurality of processes included in the method, a process corresponding to a process described in each aspect of the present disclosure is replaced with a process described in each aspect of the present disclosure. (7) Some of the processes included in the method implemented by the encoding device or the decoding device of the first embodiment may be implemented in combination with the processes described in each aspect of the present disclosure.

[0040] It should be noted that the manner of implementing the processes and / or configurations described in each aspect of the present disclosure is not limited to the above examples. For example, the processes and / or configurations may be implemented in a device used for a purpose other than the video / image encoding device or video / image decoding device disclosed in the first embodiment, or the processes and / or configurations described in each aspect may be implemented independently. Furthermore, the processes and / or configurations described in different aspects may be implemented in combination.

[0041] [Outline of the encoding device] First, a description will be given of an overview of a coding device according to embodiment 1. Fig. 1 is a block diagram showing a functional configuration of a coding device 100 according to embodiment 1. The coding device 100 is a video / image coding device that codes a video / image on a block-by-block basis.

[0042] 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.

[0043] The encoding device 100 is realized by, for example, a general-purpose processor and a memory. In this case, when the software program stored in the memory is executed by the processor, the processor functions as the division unit 102, the subtraction unit 104, the transformation unit 106, the quantization unit 108, the entropy coding unit 110, the inverse quantization unit 112, the inverse transformation unit 114, the addition unit 116, the loop filter unit 120, the intra prediction unit 124, the inter prediction unit 126, and the prediction control unit 128. The encoding device 100 may also be realized as one or more dedicated electronic circuits corresponding to the division unit 102, the subtraction unit 104, the transformation unit 106, the quantization unit 108, the entropy coding unit 110, the inverse quantization unit 112, the inverse transformation unit 114, the addition unit 116, the loop filter unit 120, the intra prediction unit 124, the inter prediction unit 126, and the prediction control unit 128.

[0044] Each component included in the encoding device 100 will be described below.

[0045] [Divided part] The division unit 102 divides each picture included in the input video into a plurality of blocks, and outputs each block to the subtraction unit 104. For example, the division unit 102 first divides a picture into blocks of a fixed size (e.g., 128x128). These fixed-size blocks may be called coding tree units (CTUs). The division unit 102 then divides each of the fixed-size blocks into blocks of a variable size (e.g., 64x64 or less) based on recursive quadtree and / or binary tree block division. These variable-size blocks may be called coding units (CUs), prediction units (PUs), or transform units (TUs). Note that in this embodiment, it is not necessary to distinguish between CUs, PUs, and TUs, and some or all of the blocks in a picture may be the processing units of CUs, PUs, and TUs.

[0046] 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.

[0047] 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).

[0048] 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.

[0049] The top right 64x64 block is divided horizontally into two rectangular 64x32 blocks 14, 15 (binary tree block division).

[0050] The bottom left 64x64 block is divided into four square 32x32 blocks (quadtree block division). Of the four 32x32 blocks, the top left and bottom right blocks are further divided. The top left 32x32 block is divided vertically into two rectangular 16x32 blocks, and the right 16x32 block is further divided horizontally into two 16x16 blocks (binary tree block division). The bottom right 32x32 block is divided horizontally into two 32x16 blocks (binary tree block division). As a result, the bottom left 64x64 block is divided into a 16x32 block 16, two 16x16 blocks 17, 18, two 32x32 blocks 19, 20, and two 32x16 blocks 21, 22.

[0051] The bottom right 64x64 block 23 is not split.

[0052] 2, the block 10 is divided into 13 variable-sized blocks 11 to 23 based on recursive quad-tree and binary tree block division. Such division is sometimes called QTBT (quad-tree plus binary tree) division.

[0053] 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.

[0054] [Subtraction section] The subtraction unit 104 subtracts a prediction signal (prediction sample) from an original signal (original sample) for each block divided by the division unit 102. That is, the subtraction unit 104 calculates a prediction error (also called a residual error) of a block to be coded (hereinafter, referred to as a current block). Then, the subtraction unit 104 outputs the calculated prediction error to the conversion unit 106.

[0055] The original signal is an input signal to the encoding device 100, and is a signal representing an image of each picture constituting a moving image (for example, a luminance (luma) signal and two color difference (chroma) signals). Hereinafter, the signal representing the image may also be referred to as a sample.

[0056] [Conversion section] The transform unit 106 transforms the prediction error in the spatial domain into transform coefficients in the frequency domain, and outputs the transform coefficients to the quantization unit 108. Specifically, the transform unit 106 performs, for example, a predetermined discrete cosine transform (DCT) or discrete sine transform (DST) on the prediction error in the spatial domain.

[0057] The transform unit 106 may adaptively select a transform type from among a plurality of transform types, and transform the prediction errors into transform coefficients using a transform basis function corresponding to the selected transform type. Such a transform may be called an explicit multiple core transform (EMT) or an adaptive multiple transform (AMT).

[0058] The multiple transform types include, for example, DCT-II, DCT-V, DCT-VIII, DST-I, and DST-VII. Figure 3 is a table showing the transform basis functions corresponding to each transform type. In Figure 3, N indicates the number of input pixels. The selection of the transform type from among the multiple transform types may depend on, for example, the type of prediction (intra prediction and inter prediction) or the intra prediction mode.

[0059] Such information indicating whether EMT or AMT is applied (e.g., called an AMT flag) and information indicating the selected transformation type are signaled at the CU level. Note that the signaling of such information does not need to be limited to the CU level, and may be at other levels (e.g., sequence level, picture level, slice level, tile level, or CTU level).

[0060] Furthermore, the transform unit 106 may retransform the transform coefficients (transformation results). Such retransformation may be called AST (adaptive secondary transform) or NSST (non-separable secondary transform). For example, the transform unit 106 performs retransformation for each subblock (e.g., 4x4 subblock) included in a block of transform coefficients corresponding to intra-prediction errors. Information indicating whether or not to apply NSST and information regarding a transform matrix used in NSST are signaled at a CU level. Note that signaling of these pieces of information does not need to be limited to the CU level, and may be at other levels (e.g., sequence level, picture level, slice level, tile level, or CTU level).

[0061] Here, a separable transformation is a method in which the transformation is performed multiple times by separating the input into directions equal to the number of dimensions, and a non-separable transformation is a method in which when the input is multidimensional, two or more dimensions are treated as one dimension and the transformation is performed together.

[0062] For example, one example of a non-separable transformation is when the input is a 4x4 block, it is treated as a single array with 16 elements, and a 16x16 transformation matrix is ​​used to transform the array.

[0063] Another example of a non-separable transformation is the Hypercube Givens Transform, which treats a 4x4 input block as a single array with 16 elements and then performs Givens rotations on that array multiple times.

[0064] [Quantization section] The quantization unit 108 quantizes the transform coefficients output from the transform unit 106. Specifically, the quantization unit 108 scans the transform coefficients of the current block in a predetermined scanning order, and quantizes the transform coefficients based on a quantization parameter (QP) corresponding to the scanned transform coefficients. Then, the quantization unit 108 outputs the quantized transform coefficients of the current block (hereinafter, referred to as quantized coefficients) to the entropy coding unit 110 and the inverse quantization unit 112.

[0065] The predetermined order is an order for quantization / dequantization of the transform coefficients. For example, the predetermined scanning order is defined as ascending (low to high) or descending (high to low) frequency order.

[0066] The quantization parameter is a parameter that defines the quantization step (quantization width). For example, if the value of the quantization parameter increases, the quantization step also increases. In other words, if the value of the quantization parameter increases, the quantization error increases.

[0067] [Entropy coding part] The entropy coding unit 110 generates a coded signal (coded bit stream) by variable-length coding the quantized coefficients input from the quantization unit 108. Specifically, the entropy coding unit 110, for example, binarizes the quantized coefficients and arithmetically codes the binary signal.

[0068] [Dequantization section] The inverse quantization unit 112 inverse quantizes the quantized coefficients input from the quantization unit 108. Specifically, the inverse quantization unit 112 inverse quantizes the quantized coefficients of the current block in a predetermined scanning order. Then, the inverse quantization unit 112 outputs the inverse quantized transform coefficients of the current block to the inverse transform unit 114.

[0069] [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.

[0070] Note that the restored prediction error does not match the prediction error calculated by the subtraction unit 104 because information has been lost due to quantization. That is, the restored prediction error includes a quantization error.

[0071] [Addition section] The adder 116 reconstructs the current block by adding the prediction error input from the inverse transformer 114 and the prediction sample input from the prediction control unit 128. The adder 116 then outputs the reconstructed block to the block memory 118 and the loop filter unit 120. The reconstructed block is sometimes called a local decoded block.

[0072] [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.

[0073] [Loop filter section] The loop filter unit 120 applies a loop filter to the block reconstructed by the adder unit 116, and outputs the filtered reconstructed block to the frame memory 122. The loop filter is a filter (in-loop filter) used in the encoding loop, and includes, for example, a deblocking filter (DF), a sample adaptive offset (SAO), and an adaptive loop filter (ALF).

[0074] In ALF, a least squared error filter is applied to remove coding artifacts. For example, for each 2x2 sub-block in the current block, one filter is selected from among multiple filters based on local gradient direction and activity.

[0075] Specifically, first, sub-blocks (e.g., 2x2 sub-blocks) are classified into a plurality of classes (e.g., 15 or 25 classes). The classification of the sub-blocks is performed based on the gradient direction and activity. For example, a classification value C (e.g., C=5D+A) is calculated using a gradient direction value D (e.g., 0 to 2 or 0 to 4) and a gradient activity value A (e.g., 0 to 4). Then, based on the classification value C, the sub-blocks are classified into a plurality of classes (e.g., 15 or 25 classes).

[0076] The gradient direction value D is derived, for example, by comparing gradients in multiple directions (e.g., horizontal, vertical, and two diagonal directions), and the gradient activity value A is derived, for example, by adding gradients in multiple directions and quantizing the sum.

[0077] Based on the result of such classification, a filter for the sub-block is determined from among a plurality of filters.

[0078] The shape of the filter used in the ALF is, for example, a circularly symmetric shape. FIGS. 4A to 4C are diagrams showing a number of examples of the shape of the filter used in the ALF. FIG. 4A shows a 5×5 diamond-shaped filter, FIG. 4B shows a 7×7 diamond-shaped filter, and FIG. 4C shows a 9×9 diamond-shaped filter. Information indicating the shape of the filter is signaled at the picture level. Note that the signaling of the information indicating the shape of the filter does not need to be limited to the picture level, and may be at other levels (for example, the sequence level, slice level, tile level, CTU level, or CU level).

[0079] The on / off of ALF is determined, for example, at the picture level or the CU level. For example, whether or not to apply ALF is determined for luminance at the CU level, and whether or not to apply ALF is determined for chrominance at the picture level. Information indicating whether or not to apply ALF is signaled at the picture level or the CU level. Note that the signaling of information indicating whether or not to apply ALF is not limited to the picture level or the CU level, and may be at another level (for example, the sequence level, the slice level, the tile level, or the CTU level).

[0080] The coefficient sets of multiple selectable filters (e.g., up to 15 or 25 filters) are signaled at the picture level. Note that the signaling of the coefficient sets does not need to be limited to the picture level, but may be at other levels (e.g., sequence level, slice level, tile level, CTU level, CU level, or sub-block level).

[0081] [Frame memory] The frame memory 122 is a storage unit for storing reference pictures used in inter prediction, and may be called a frame buffer. Specifically, the frame memory 122 stores the reconstructed block filtered by the loop filter unit 120.

[0082] [Intra prediction section] The intra prediction unit 124 generates a prediction signal (intra prediction signal) by performing intra prediction (also called intra-screen prediction) of the current block with reference to a block in the current picture stored in the block memory 118. Specifically, the intra prediction unit 124 generates an intra prediction signal by performing intra prediction with reference to samples (e.g., luminance values, chrominance values) of blocks adjacent to the current block, and outputs the intra prediction signal to the prediction control unit 128.

[0083] 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.

[0084] 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).

[0085] The multiple directional prediction modes include, for example, 33 prediction modes defined in the H.265 / HEVC standard. The multiple directional prediction modes may include 32 prediction modes in addition to the 33 directions (a total of 65 directional prediction modes). FIG. 5A is a diagram showing 67 intra prediction modes (2 non-directional prediction modes and 65 directional prediction modes) in intra prediction. The solid arrows represent the 33 directions defined in the H.265 / HEVC standard, and the dashed arrows represent the additional 32 directions.

[0086] In addition, in the intra prediction of the chrominance block, the luminance block may be referenced. That is, the chrominance component of the current block may be predicted based on the luminance component of the current block. Such intra prediction may be called CCLM (cross-component linear model) prediction. An intra prediction mode of the chrominance block that refers to such a luminance block (for example, called a CCLM mode) may be added as one of the intra prediction modes of the chrominance block.

[0087] The intra prediction unit 124 may correct pixel values ​​after intra prediction based on the gradient of reference pixels in the horizontal / vertical directions. Intra prediction with such correction may be called position dependent intra prediction combination (PDPC). Information indicating whether or not PDPC is applied (e.g., called a PDPC flag) is signaled, for example, at a CU level. Note that the signaling of this information does not need to be limited to the CU level, and may be at other levels (e.g., sequence level, picture level, slice level, tile level, or CTU level).

[0088] [Inter prediction section] The inter prediction unit 126 generates a prediction signal (inter prediction signal) by performing inter prediction (also called inter prediction) of the current block with reference to a reference picture stored in the frame memory 122 and different from the current picture. The inter prediction is performed in units of the current block or a sub-block (e.g., 4x4 block) in the current block. For example, the inter prediction unit 126 performs motion estimation in the reference picture for the current block or the sub-block. Then, the inter prediction unit 126 generates an inter prediction signal of the current block or the sub-block by performing motion compensation using motion information (e.g., a motion vector) obtained by the motion estimation. Then, the inter prediction unit 126 outputs the generated inter prediction signal to the prediction control unit 128.

[0089] The motion information used for the motion compensation is signaled. For the signaling of the motion vector, a motion vector predictor may be used, i.e. the difference between the motion vector and the motion vector predictor may be signaled.

[0090] In addition, the inter prediction signal may be generated using not only the motion information of the current block obtained by motion search, but also the motion information of the adjacent block. Specifically, the inter prediction signal may be generated for each sub-block in the current block by performing weighted addition of the prediction signal based on the motion information obtained by motion search and the prediction signal based on the motion information of the adjacent block. Such inter prediction (motion compensation) may be called OBMC (overlapped block motion compensation).

[0091] In such an OBMC mode, information indicating the size of a sub-block for OBMC (e.g., called OBMC block size) is signaled at the sequence level. Also, information indicating whether or not to apply the OBMC mode (e.g., called OBMC flag) is signaled at the CU level. Note that the signaling level of these pieces of information does not need to be limited to the sequence level and CU level, and may be other levels (e.g., picture level, slice level, tile level, CTU level, or sub-block level).

[0092] The OBMC mode will now be described in more detail. Figures 5B and 5C are a flowchart and a conceptual diagram for explaining an overview of the predicted image correction process in the OBMC process.

[0093] First, a predicted image (Pred) is obtained by normal motion compensation using a motion vector (MV) assigned to a block to be coded.

[0094] Next, the motion vector (MV_L) of the already-encoded left adjacent block is applied to the block to be encoded to obtain a predicted image (Pred_L), and the predicted image is weighted and superimposed with Pred_L to perform a first correction of the predicted image.

[0095] Similarly, the motion vector (MV_U) of the already-encoded adjacent block above is applied to the block to be encoded to obtain a predicted image (Pred_U), and the predicted image that has been corrected the first time is weighted and overlaid with Pred_U to perform a second correction of the predicted image, which is then used as the final predicted image.

[0096] Although a two-stage correction method using the left adjacent block and the upper adjacent block has been described here, it is also possible to configure a method in which more than two stages of correction are performed using the right adjacent block or the lower adjacent block.

[0097] The area in which overlapping is performed does not have to be the entire pixel area of ​​the block, but may be only a part of the area near the block boundary.

[0098] Note that although the above describes the process of correcting a predicted image from one reference picture, the process is similar when correcting a predicted image from multiple reference pictures. After obtaining corrected predicted images from each reference picture, the obtained predicted images are then overlaid to obtain the final predicted image.

[0099] The block to be processed may be a prediction block unit, or a sub-block unit obtained by further dividing the prediction block.

[0100] As a method of determining whether or not to apply OBMC processing, for example, there is a method of using obmc_flag, which is a signal indicating whether or not to apply OBMC processing. As a specific example, in an encoding device, it is determined whether or not the encoding target block belongs to an area with complex motion, and if it belongs to an area with complex motion, a value of 1 is set as obmc_flag and encoding is performed by applying OBMC processing, and if it does not belong to an area with complex motion, a value of 0 is set as obmc_flag and encoding is performed without applying OBMC processing. On the other hand, in a decoding device, by decoding obmc_flag described in a stream, whether or not to apply OBMC processing is switched according to the value, and decoding is performed.

[0101] In addition, the motion information may be derived on the decoding device side without being signaled. For example, a merge mode defined in the H.265 / HEVC standard may be used. Also, for example, the motion information may be derived by performing motion estimation on the decoding device side. In this case, the motion estimation is performed without using pixel values ​​of the current block.

[0102] 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.

[0103] An example of the FRUC process is shown in FIG. 5D. First, a list of multiple candidates (which may be the same as the merge list) each having a predicted motion vector is generated by referring to the motion vectors of encoded blocks spatially or temporally adjacent to the current block. Next, a best candidate MV is selected from multiple candidate MVs registered in the candidate list. For example, an evaluation value of each candidate included in the candidate list is calculated, and one candidate is selected based on the evaluation value.

[0104] Then, based on the motion vector of the selected candidate, a motion vector for the current block is derived. Specifically, for example, the motion vector of the selected candidate (best candidate MV) is derived as it is as the motion vector for the current block. Also, for example, the motion vector for the current block may be derived by performing pattern matching in the surrounding area of ​​the position in the reference picture corresponding to the motion vector of the selected candidate. That is, a search is performed in the surrounding area of ​​the best candidate MV in the same manner, and if there is an MV with a better evaluation value, the best candidate MV may be updated to the MV, and the MV may be set as the final MV of the current block. It is also possible to configure the system without performing this process.

[0105] The same processing may be performed when processing is performed in sub-block units.

[0106] The evaluation value is calculated by finding a difference value of the reconstructed image by pattern matching between an area in a reference picture corresponding to the motion vector and a predetermined area. The evaluation value may be calculated using information other than the difference value.

[0107] As the pattern matching, a first pattern matching or a second pattern matching is used. The first pattern matching and the second pattern matching are sometimes called bilateral matching and template matching, respectively.

[0108] In the first pattern matching, pattern matching is performed between two blocks in two different reference pictures that are along the motion trajectory of the current block. Therefore, in the first pattern matching, an area in another reference picture along the motion trajectory of the current block is used as a predetermined area for calculating the evaluation value of the above-mentioned candidate.

[0109] FIG. 6 is a diagram for explaining an example of pattern matching (bilateral matching) between two blocks along a motion trajectory. As shown in FIG. 6, in the first pattern matching, two motion vectors (MV0, MV1) are derived by searching for a pair of two blocks that are along the motion trajectory of a current block (Cur block) and are in two different reference pictures (Ref0, Ref1) that best match each other. Specifically, for the current block, a difference is derived between a reconstructed image at a designated position in a first coded reference picture (Ref0) designated by a candidate MV and a reconstructed image at a designated position in a second coded reference picture (Ref1) designated by a symmetric MV obtained by scaling the candidate MV by a display time interval, and an evaluation value is calculated using the obtained difference value. It is preferable to select the candidate MV with the best evaluation value among a plurality of candidate MVs as the final MV.

[0110] Under the assumption of continuous motion trajectories, the motion vectors (MV0, MV1) pointing to two reference blocks are proportional to the temporal distances (TD0, TD1) between the current picture (Cur Pic) and the two reference pictures (Ref0, Ref1). For example, if the current picture is located between two reference pictures in time and the temporal distances from the current picture to the two reference pictures are equal, the first pattern matching derives bidirectional motion vectors that are mirror-symmetric.

[0111] In the second pattern matching, pattern matching is performed between a template in the current picture (a block adjacent to the current block in the current picture (e.g., an upper and / or left adjacent block)) and a block in the reference picture. Therefore, in the second pattern matching, a block adjacent to the current block in the current picture is used as a predetermined area for calculating the evaluation value of the above-mentioned candidate.

[0112] Fig. 7 is a diagram for explaining an example of pattern matching (template matching) between a template in a current picture and a block in a reference picture. As shown in Fig. 7, in the second pattern matching, a motion vector of a current block is derived by searching in a reference picture (Ref0) for a block that best matches a block adjacent to a current block (Cur block) in a current picture (Cur Pic). Specifically, for the current block, a difference is derived between a reconstructed image of both or either of the left adjacent and / or upper adjacent coded areas and a reconstructed image at the same position in a coded reference picture (Ref0) specified by a candidate MV, an evaluation value is calculated using the obtained difference value, and a candidate MV with the best evaluation value among a plurality of candidate MVs is selected as a best candidate MV.

[0113] Information indicating whether such a FRUC mode is applied (e.g., when the FRUC flag is true) is signaled at the CU level. Also, when the FRUC mode is applied (e.g., when the FRUC flag is true), information indicating a pattern matching method (first pattern matching or second pattern matching) (e.g., when the FRUC mode flag is true) is signaled at the CU level. Note that the signaling of such information does not need to be limited to the CU level, and may be at other levels (e.g., sequence level, picture level, slice level, tile level, CTU level, or subblock level).

[0114] Here, a mode in which a motion vector is derived based on a model assuming uniform linear motion will be described. This mode is sometimes called a BIO (bi-directional optical flow) mode.

[0115] FIG. 8 is a diagram for explaining a model assuming uniform linear motion. In FIG. x ,v y) denotes a velocity vector, and τ0 and τ1 denote the temporal distance between the current picture (CurPic) and two reference pictures (Ref0, Ref1), respectively. (MVx0,MVy0) denotes a motion vector corresponding to the reference picture Ref0, and (MVx1,MVy1) denotes a motion vector corresponding to the reference picture Ref1.

[0116] At this time, the velocity vector (v x ,v y Under the assumption of uniform linear motion of the object, (MVx0,MVy0) and (MVx1,MVy1) are respectively (v x τ0,v y τ0) and (-v x τ1,-v y τ1), and the following optical flow equation (1) holds:

[0117]

number

[0118] Here, I (k) denotes the luminance value of reference image k (k=0,1) after motion compensation. This optical flow equation indicates that the sum of (i) the time derivative of the luminance value, (ii) the product of the horizontal velocity and the horizontal component of the spatial gradient of the reference image, and (iii) the product of the vertical velocity and the vertical component of the spatial gradient of the reference image is equal to zero. Based on a combination of this optical flow equation and Hermite interpolation, block-wise motion vectors obtained from a merge list or the like are corrected pixel by pixel.

[0119] Note that the decoding device may derive a motion vector using a method other than the method based on a model assuming uniform linear motion. For example, a motion vector may be derived for each sub-block based on the motion vectors of multiple adjacent blocks.

[0120] Here, a mode in which a motion vector is derived for each sub-block based on the motion vectors of a plurality of adjacent blocks will be described. This mode is sometimes called an affine motion compensation prediction mode.

[0121] FIG. 9A is a diagram for explaining derivation of a motion vector for each sub-block based on the motion vectors of multiple adjacent blocks. In FIG. 9A, the current block includes 16 4x4 sub-blocks. Here, a motion vector v0 of the upper left corner control point of the current block is derived based on the motion vectors of the adjacent blocks, and a motion vector v1 of the upper right corner control point of the current block is derived based on the motion vectors of the adjacent sub-blocks. Then, using the two motion vectors v0 and v1, the motion vectors (v x ,v y ) is derived.

[0122]

number

[0123] Here, x and y respectively indicate the horizontal and vertical positions of the sub-block, and w indicates a predetermined weighting factor.

[0124] Such affine motion compensation prediction mode may include several modes with different methods of deriving the motion vectors of the upper left and upper right corner control points. Information indicating such affine motion compensation prediction mode (e.g., called affine flag) is signaled at the CU level. Note that the signaling of the information indicating this affine motion compensation prediction mode does not need to be limited to the CU level, and may be at other levels (e.g., sequence level, picture level, slice level, tile level, CTU level, or subblock level).

[0125] [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.

[0126] Here, an example of deriving a motion vector for a picture to be coded in the merge mode will be described. Fig. 9B is a diagram for explaining an overview of a motion vector derivation process in the merge mode.

[0127] First, a prediction MV list is generated in which prediction MV candidates are registered. The prediction MV candidates include spatially adjacent prediction MVs, which are MVs held by multiple coded blocks located spatially around the block to be coded, temporally adjacent prediction MVs, which are MVs held by nearby blocks projected onto the position of the block to be coded in the coded reference picture, joint prediction MVs, which are MVs generated by combining the MV values ​​of spatially adjacent prediction MVs and temporally adjacent prediction MVs, and zero prediction MVs, which are MVs with a value of zero.

[0128] Next, one prediction MV is selected from the multiple prediction MVs registered in the prediction MV list, and is determined as the MV for the block to be coded.

[0129] Furthermore, the variable length coding unit writes merge_idx, which is a signal indicating which predicted MV has been selected, into the stream and codes it.

[0130] Note that the predicted MVs registered in the predicted MV list described in Figure 9B are just an example, and the number may be different from the number shown in the figure, the configuration may not include some of the types of predicted MVs shown in the figure, or the configuration may include additional predicted MVs other than the types of predicted MVs shown in the figure.

[0131] Note that the final MV may be determined by performing DMVR processing, which will be described later, using the MV of the block to be coded derived in the merge mode.

[0132] Here, an example of determining the MV using the DMVR process will be described.

[0133] FIG. 9C is a conceptual diagram for explaining an overview of the DMVR process.

[0134] First, the optimal MVP set for the block to be processed is set as a candidate MV, and reference pixels are obtained from the first reference picture, which is a processed picture in the L0 direction, and the second reference picture, which is a processed picture in the L1 direction, according to the candidate MV, and a template is generated by taking the average of each reference pixel.

[0135] Next, the template is used to search the surrounding areas of the candidate MVs of the first and second reference pictures, and the MV with the smallest cost is determined as the final MV. The cost value is calculated using the difference value between each pixel value of the template and each pixel value of the search area, the MV value, etc.

[0136] The outline of the processing described here is basically the same for the encoding device and the decoding device.

[0137] 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.

[0138] Here, a mode in which a predicted image is generated using LIC processing will be described.

[0139] FIG. 9D is a diagram for explaining an outline of a predicted image generating method using luminance correction processing by LIC processing.

[0140] First, a MV for obtaining a reference image corresponding to a block to be coded from a reference picture that is a coded picture is derived.

[0141] 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.

[0142] A luminance correction process is performed on a reference image in a reference picture specified by the MV using the luminance correction parameter, thereby generating a predicted image for the block to be coded.

[0143] It should be noted that the shape of the peripheral reference region in FIG. 9D is just an example, and other shapes may be used.

[0144] 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.

[0145] As a method of determining whether or not to apply LIC processing, for example, there is a method of using lic_flag, which is a signal indicating whether or not to apply LIC processing. As a specific example, in an encoding device, it is determined whether or not the encoding target block belongs to an area where a luminance change occurs, and if it belongs to an area where a luminance change occurs, a value of 1 is set as lic_flag and encoding is performed by applying LIC processing, and if it does not belong to an area where a luminance change occurs, a value of 0 is set as lic_flag and encoding is performed without applying LIC processing. On the other hand, a decoding device decodes lic_flag described in a stream, and switches whether or not to apply LIC processing depending on the value and performs decoding.

[0146] Another method of determining whether to apply LIC processing is, for example, a method of determining according to whether LIC processing is applied to surrounding blocks.As a specific example, when the block to be coded is in merge mode, determine whether the surrounding coded blocks selected when deriving MV in merge mode processing have been coded by applying LIC processing, and switch whether to apply LIC processing according to the result and perform coding.In addition, in this example, the process in decoding is exactly the same.

[0147] [Overview of the Decryption Device] Next, a description will be given of an overview of a decoding device capable of decoding the coded signal (coded bit stream) output from the above coding device 100. Fig. 10 is a block diagram showing a functional configuration of a decoding device 200 according to the first embodiment. The decoding device 200 is a video / image decoding device that decodes a video / image on a block-by-block basis.

[0148] 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.

[0149] The decoding device 200 is realized by, for example, a general-purpose processor and a memory. In this case, when the software program stored in the memory is executed by the processor, the processor functions as the entropy decoding unit 202, the inverse quantization unit 204, the inverse transform unit 206, the addition unit 208, the loop filter unit 212, the intra prediction unit 216, the inter prediction unit 218, and the prediction control unit 220. The decoding device 200 may also be realized as one or more dedicated electronic circuits corresponding to the entropy decoding unit 202, the inverse quantization unit 204, the inverse transform unit 206, the addition unit 208, the loop filter unit 212, the intra prediction unit 216, the inter prediction unit 218, and the prediction control unit 220.

[0150] Each component included in the decoding device 200 will be described below.

[0151] [Entropy Decoding Part] The entropy decoding unit 202 entropy decodes the coded bit stream. Specifically, the entropy decoding unit 202 arithmetically decodes the coded bit stream into a binary signal, for example. The entropy decoding unit 202 then debinarizes the binary signal. As a result, the entropy decoding unit 202 outputs quantized coefficients to the inverse quantization unit 204 on a block-by-block basis.

[0152] [Dequantization section] The inverse quantization unit 204 inverse quantizes the quantized coefficients of a block to be decoded (hereinafter, referred to as a current block) that is input from the entropy decoding unit 202. Specifically, the inverse quantization unit 204 inverse quantizes each quantized coefficient of the current block based on a quantization parameter corresponding to the quantized coefficient. Then, the inverse quantization unit 204 outputs the inverse quantized quantized coefficients (i.e., transform coefficients) of the current block to the inverse transform unit 206.

[0153] [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 .

[0154] 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.

[0155] Also for example, if the information interpreted from the coded bitstream indicates to apply NSST, then inverse transform unit 206 applies an inverse re-transform to the transform coefficients.

[0156] [Addition section] The adder 208 reconstructs the current block by adding the prediction error, which is an input from the inverse transformer 206, and the prediction sample, which is an input from the prediction control unit 220. The adder 208 then outputs the reconstructed block to the block memory 210 and the loop filter unit 212.

[0157] [Block memory] The block memory 210 is a storage unit for storing blocks that are referenced in intra prediction and are in a picture to be decoded (hereinafter, referred to as a current picture). Specifically, the block memory 210 stores the reconstructed block output from the adder 208.

[0158] [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.

[0159] If the information indicating ALF on / off read from the encoded bitstream indicates ALF on, one filter is selected from among multiple filters based on the local gradient direction and activity, and the selected filter is applied to the reconstructed block.

[0160] [Frame memory] The frame memory 214 is a storage unit for storing reference pictures used in inter prediction, and may be called a frame buffer. Specifically, the frame memory 214 stores the reconstructed blocks filtered by the loop filter unit 212.

[0161] [Intra prediction section] The intra prediction unit 216 generates a prediction signal (intra prediction signal) by performing intra prediction with reference to a block in the current picture stored in the block memory 210 based on an intra prediction mode interpreted from the encoded bit stream. Specifically, the intra prediction unit 216 generates an intra prediction signal by performing intra prediction with reference to samples (e.g., luminance values, chrominance values) of blocks adjacent to the current block, and outputs the intra prediction signal to the prediction control unit 220.

[0162] 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.

[0163] Furthermore, when information interpreted from the encoded bitstream indicates the application of PDPC, the intra prediction unit 216 corrects pixel values ​​after intra prediction based on the gradients of reference pixels in the horizontal / vertical directions.

[0164] [Inter prediction section] The inter prediction unit 218 predicts the current block by referring to a reference picture stored in the frame memory 214. The prediction is performed in units of the current block or sub-blocks (e.g., 4x4 blocks) in the current block. For example, the inter prediction unit 218 generates an inter prediction signal of the current block or sub-block by performing motion compensation using motion information (e.g., motion vectors) interpreted from the encoded bitstream, and outputs the inter prediction signal to the prediction control unit 220.

[0165] In addition, when the information interpreted from the encoded bitstream indicates that the OBMC mode is to be applied, the inter prediction unit 218 generates an inter prediction signal using not only the motion information of the current block obtained by motion search, but also the motion information of adjacent blocks.

[0166] Also, if the information interpreted from the encoded bitstream indicates that the FRUC mode is applied, the inter prediction unit 218 derives motion information by performing motion search according to the pattern matching method (bilateral matching or template matching) interpreted from the encoded bitstream. Then, the inter prediction unit 218 performs motion compensation using the derived motion information.

[0167] In addition, when the BIO mode is applied, the inter prediction unit 218 derives a motion vector based on a model assuming uniform linear motion. In addition, when information interpreted from the encoded bitstream indicates that an affine motion compensation prediction mode is applied, the inter prediction unit 218 derives a motion vector on a sub-block basis based on the motion vectors of multiple adjacent blocks.

[0168] [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.

[0169] [First example of processing by the inter prediction unit of the encoding device] Fig. 11 is a flowchart showing a first example of the inter prediction process by the inter prediction unit 126 included in the encoding device 100. The process shown in Fig. 11 is repeatedly performed in units of prediction blocks, which are processing units of the inter prediction process.

[0170] The inter prediction mode information indicates the inter prediction mode used for inter prediction of a current block, which is a prediction block to be processed.

[0171] The inter prediction mode can be selected from a plurality of modes, which can be roughly divided into a method of encoding a differential motion vector (MV) and a method of not encoding a differential motion vector.

[0172] Methods that do not encode differential motion vectors include merge mode, in which a motion vector is selected and obtained from surrounding encoded blocks, FRUC mode, in which a motion vector is obtained by searching between encoded areas, and affine mode, in which a motion vector is obtained for each sub-block obtained by dividing the target block, assuming an affine transformation.

[0173] Specifically, when the inter prediction mode information indicates 0 (0 in S101), the inter prediction unit 126 derives a motion vector by merge mode (S102). When the inter prediction mode information indicates 1 (1 in S101), the inter prediction unit 126 derives a motion vector by FRUC mode (S103). When the inter prediction mode information indicates 2 (2 in S101), the inter prediction unit 126 derives a motion vector by affine mode (S104). When the inter prediction mode information indicates 3 (3 in S101), the inter prediction unit 126 derives a motion vector by a method of encoding a differential motion vector (S111).

[0174] In the method of not encoding the differential motion vector, after step S102, S103, or S104, the inter prediction unit 126 determines whether or not there is a residual coefficient whose value is not zero (S105). If there is no residual coefficient whose value is not zero (No in S105), the inter prediction unit 126 encodes the target block in skip mode (S106). On the other hand, if there is a residual coefficient whose value is not zero (Yes in S105), the inter prediction unit 126 encodes the target block in non-skip mode (S108).

[0175] In both the case where the skip mode is used and the case where the non-skip mode is used, the inter prediction unit 126 encodes a luminance correction processing signal indicating whether or not to apply a luminance correction process (LIC process) to a predicted image (S107 or S109). In addition, in the case of the non-skip mode, a residual coefficient always exists, so the inter prediction unit 126 does not encode a residual coefficient presence / absence signal indicating the presence or absence of a residual coefficient, but always encodes residual coefficient information indicating a residual coefficient (S110).

[0176] On the other hand, when a method of encoding a differential motion vector is used, after step S111, the inter prediction unit 126 always encodes the current block in non-skip mode (S112). Furthermore, the inter prediction unit 126 encodes a luminance correction processing signal indicating whether or not to apply luminance correction processing of a predicted image (S113). Furthermore, since there are cases where there are residual coefficients with non-zero values ​​and cases where there are no residual coefficients with non-zero values, the inter prediction unit 126 encodes a residual coefficient presence / absence signal (S114). Furthermore, when there are residual coefficients with non-zero values ​​(Yes in S115), the inter prediction unit 126 encodes residual coefficient information (S110), and when there are no residual coefficients with non-zero values ​​(No in S115), the inter prediction unit 126 does not encode the residual coefficient information.

[0177] The skip mode is, for example, a mode in which a signal related to a differential motion vector (for example, a signal indicating a differential motion vector) and a signal related to a residual coefficient (for example, a signal indicating a residual coefficient) are not coded. The non-skip mode is, for example, a mode in which at least one of a signal related to a differential motion vector and a signal related to a residual coefficient may be coded. Whether the skip mode or the non-skip mode is to be applied may be specified by a syntax such as "skip_flag".

[0178] [First example of processing by the inter prediction unit of the decoding device] Fig. 12 is a flowchart showing a first example of an inter prediction process by the inter prediction unit 218 included in the decoding device 200 that decodes the stream generated by the encoding device 100 described in Fig. 11. The process shown in Fig. 12 is repeatedly performed in prediction block units, which are processing units of the inter prediction process.

[0179] The inter prediction mode information indicates the inter prediction mode used for inter prediction of a current block, which is a prediction block to be processed.

[0180] The inter prediction mode can be selected from a plurality of modes, which can be roughly divided into a method in which the differential motion vector is decoded and a method in which the differential motion vector is not decoded.

[0181] Methods that do not decode differential motion vectors include merge mode, which selects and obtains motion vectors from surrounding decoded blocks, FRUC mode, which obtains motion vectors by searching between decoded areas, and affine mode, which assumes affine transformation and obtains motion vectors for each sub-block obtained by dividing the target block.

[0182] Specifically, when the inter prediction mode information indicates 0 (0 in S201), the inter prediction unit 218 derives a motion vector by merge mode (S202). When the inter prediction mode information indicates 1 (1 in S201), the inter prediction unit 218 derives a motion vector by FRUC mode (S203). When the inter prediction mode information indicates 2 (2 in S201), the inter prediction unit 218 derives a motion vector by affine mode (S204). When the inter prediction mode information indicates 3 (3 in S201), the inter prediction unit 218 derives a motion vector by a method of decoding a differential motion vector (S211).

[0183] In the method of not decoding the differential motion vector, after step S202, S203, or S204, the inter prediction unit 218 determines whether or not a signal indicating that the skip mode is used is decoded (S205). If the signal indicating that the skip mode is used is decoded (Yes in S205), the inter prediction unit 218 decodes the current block in the skip mode (S206). If not (No in S205), the inter prediction unit 218 decodes the current block in the non-skip mode (S208).

[0184] In both cases where the skip mode and the non-skip mode are used, the inter prediction unit 218 decodes a luminance correction processing signal indicating whether or not to apply luminance correction processing (LIC processing) to the predicted image (S207 or S209). In addition, in the case of the non-skip mode, a residual coefficient always exists, so the inter prediction unit 218 does not decode a residual coefficient presence / absence signal indicating the presence or absence of a residual coefficient, but always decodes residual coefficient information indicating the residual coefficient (S210).

[0185] On the other hand, when a method of encoding a differential motion vector is used, after step S211, the inter prediction unit 218 always decodes the current block in non-skip mode (S212). Furthermore, the inter prediction unit 218 decodes a luminance correction processing signal indicating whether or not to apply luminance correction processing of a predicted image (S213). Furthermore, since there are cases where residual coefficients with non-zero values ​​are present and not present, the inter prediction unit 218 decodes a residual coefficient presence / absence signal (S214). Furthermore, when there are residual coefficients with non-zero values ​​(Yes in S215), the inter prediction unit 218 decodes residual coefficient information (S210), and when there are no residual coefficients with non-zero values ​​(No in S215), the inter prediction unit 218 does not decode residual coefficient information.

[0186] [Syntax structure in the first example] FIG. 13 is a syntax table showing a first example of a syntax configuration of the stream generated by the encoding device 100 described with reference to FIG.

[0187] First, "skip_flag" specifies whether the skip mode or the non-skip mode is used.

[0188] When the skip mode is used, "fruc_mode" further specifies whether the FRUC mode is used. When the FRUC mode is not used, "affine_flag" further specifies whether the affine mode is used. When the affine mode is not used, "merge_idx" is described to specify the neighboring block to be referenced in the merge mode. Regardless of which mode is used, "lic_flag" is described to indicate whether or not to apply luminance correction processing to the predicted image.

[0189] When non-skip mode is used, "merge_flag" specifies whether a scheme that does not code a differential motion vector or a scheme that codes a differential motion vector is used.

[0190] If a method that does not code differential motion vectors is used, "fruc_mode" further specifies whether or not FRUC mode is used. If FRUC mode is not used, "affine_flag" further specifies whether or not affine mode is used. If affine mode is not used, "merge_idx" is written to specify the neighboring block to be referenced in merge mode.

[0191] When a method for encoding a differential motion vector is used, "MVD", which is information on the differential motion vector, is described.

[0192] Regardless of which mode is used, "lic_flag" is described to indicate whether or not to apply luminance correction processing to the predicted image. Furthermore, if a method that does not code differential motion vectors is not used, "root_cbf" is described to indicate whether or not there is a residual coefficient whose value is not zero. Furthermore, if it is indicated that there is a residual coefficient whose value is not zero, "residual" which is residual coefficient information is described.

[0193] However, when the process of the first example described with reference to Figs. 11 to 13 is used, when the skip mode is selected, it is necessary to describe "fruc_mode", "affine_flag", "merge_idx", and "lic_flag". As a result, when encoding using a large number of skip modes under low-rate encoding conditions, for example, the number of syntaxes described in the stream increases, which may result in a deterioration in encoding efficiency. In particular, in the affine mode and the luminance correction process for the predicted image, there is a high possibility that residual coefficients with non-zero values ​​are generated, so that the disadvantage of having to unnecessarily describe "affine_flag" and "lic_flag" in the skip mode is likely to become significant. In addition, there is also a possibility that the circuit for controlling the syntax becomes complicated.

[0194] [Second example of processing by the inter prediction unit of the encoding device] FIG. 14 is a flowchart showing a second example of the inter prediction process by the inter prediction unit 126 included in the encoding device 100.

[0195] When a merge mode other than the affine mode or a FRCU mode among the methods of not encoding a differential motion vector is used (0 or 1 in S101), similar to the process shown in FIG. 11, the inter prediction unit 126 determines whether or not there is a residual coefficient whose value is not zero (S105), and when there is no residual coefficient whose value is not zero (No in S105), it encodes the target block in skip mode (S106), and when there is a residual coefficient whose value is not zero (Yes in S105), it encodes the target block in non-skip mode (S108). In addition, in both cases where the skip mode is used and where the non-skip mode is used, the inter prediction unit 126 encodes the luminance correction processing signal (S107 and S109). In addition, in the case of the non-skip mode, the inter prediction unit 126 does not encode the residual coefficient presence / absence signal, but always encodes the residual coefficient information (S110).

[0196] In the process shown in FIG. 14, unlike the process shown in FIG. 11, when the affine mode is used, the same operation as when the method of encoding the differential motion vector is used is performed.

[0197] That is, when a method for encoding a differential motion vector is used, or when an affine mode among methods for not encoding a differential motion vector is used (2 or 3 in S101), the inter prediction unit 126 always encodes the current block in non-skip mode (S112) and encodes a luminance correction processing signal (S113). In addition, the inter prediction unit 126 encodes a residual coefficient presence / absence signal (S114), and when there is a residual coefficient whose value is not zero (Yes in S115), encodes residual coefficient information (S110).

[0198] [Second example of processing by the inter prediction unit of the decoding device] FIG. 15 is a flowchart showing a second example of the inter prediction process performed by the inter prediction unit 218 included in the decoding device 200 that decodes the stream generated by the encoding device 100 described with reference to FIG.

[0199] When a merge mode other than the affine mode or a FRCU mode is used among the methods that do not code a differential motion vector (0 or 1 in S201), similar to the process shown in FIG. 12, if a signal indicating that the skip mode is used is decoded (Yes in S205), the inter prediction unit 218 decodes the target block in the skip mode (S206), otherwise (No in S205), the inter prediction unit 218 decodes the target block in the non-skip mode (S208). In addition, in both cases where the skip mode is used and where the non-skip mode is used, the inter prediction unit 218 decodes the luminance correction processing signal (S207 and S209). In addition, in the case of the non-skip mode, the inter prediction unit 218 always decodes the residual coefficient information without decoding the residual coefficient presence / absence signal (S210).

[0200] In the process shown in FIG. 15, unlike the process shown in FIG. 12, when the affine mode is used, the same operation as when the method of decoding a differential motion vector is used is performed.

[0201] That is, when the method of decoding the differential motion vector is used, or when the affine mode of the method of not decoding the differential motion vector is used (2 or 3 in S201), the inter prediction unit 218 always decodes the target block in non-skip mode (S212) and decodes the luminance correction processing signal (S213). In addition, the inter prediction unit 218 decodes the residual coefficient presence / absence signal (S214), and when there is a residual coefficient (Yes in S215), decodes the residual coefficient information (S210).

[0202] [Syntax configuration in the second example] FIG. 16 is a syntax table showing a second example of the syntax configuration of the stream generated by the encoding device 100 described with reference to FIG.

[0203] First, "skip_flag" specifies whether the skip mode or the non-skip mode is used.

[0204] When the skip mode is used, "fruc_mode" further specifies whether or not the FRUC mode is used. When the FRUC mode is not used, "merge_idx" is described to specify the neighboring block to be referenced in the merge mode. In addition, when either mode is used, "lic_flag" is described to indicate whether or not to apply the luminance correction process of the predicted image.

[0205] When non-skip mode is used, "merge_flag" specifies whether a scheme that does not code a differential motion vector or a scheme that codes a differential motion vector is used.

[0206] If a method that does not code differential motion vectors is used, "fruc_mode" further specifies whether or not FRUC mode is used. If FRUC mode is not used, "affine_flag" further specifies whether or not affine mode is used. If affine mode is not used, "merge_idx" is written to specify the neighboring block to be referenced in merge mode.

[0207] When a method for encoding a differential motion vector is used, "MVD", which is information on the differential motion vector, is described.

[0208] Regardless of which mode is used, "lic_flag" is described to indicate whether or not to apply luminance correction processing to the predicted image. Furthermore, when a method that does not code a differential motion vector is not used, or when an affine mode among methods that do not code a differential motion vector is used, "root_cbf" is described to indicate whether or not there is a residual coefficient whose value is not zero. When it is indicated that there is a residual coefficient whose value is not zero, "residual" which is residual coefficient information is described.

[0209] [Effect of the second example] According to the second example, when the skip mode is selected, it is necessary to describe "fruc_mode", "merge_idx", and "lic_flag". Therefore, for example, when encoding using multiple skip modes under low-rate encoding conditions, the number of syntaxes described in the stream is less than that of the first example described with reference to Figs. 11 to 13. This may improve the encoding efficiency. In particular, in the affine mode, since there is a high possibility that residual coefficients with non-zero values ​​are generated, the effect of reducing the amount of code by not describing "affine_flag" in the skip mode is likely to be large. In addition, it may be possible to further simplify the circuit for controlling the syntax.

[0210] Note that not all of the components described in the second example are always necessary, and the encoding device 100 or the decoding device 200 may include only some of the components described in the second example.

[0211] For example, in FIG. 14 and FIG. 15, an example is described in which four modes corresponding to 0 to 3 are used as inter prediction mode information, but the numbers and modes are only examples, and other numbers and modes may be used. In particular, in a method in which a differential motion vector is not coded, an example is described in which three modes, merge mode, FRUC mode, and affine mode, are used, but it is sufficient that two or more of these modes are used. In addition, modes other than these modes may be used. In addition, a process similar to the process described for the affine mode may be applied to another mode other than the affine mode.

[0212] Furthermore, the syntax configuration described in FIG. 16 is just an example, and part of the syntax in FIG. 16 may be replaced with another syntax, deleted, or added.

[0213] [Third example of processing by the inter prediction unit of the encoding device] FIG. 17 is a flowchart showing a third example of the inter prediction process by the inter prediction unit 126 included in the encoding device 100.

[0214] In the process shown in Fig. 17, step S116 is added and step S107 is deleted from the process shown in Fig. 14. Also, step S109 is changed to step S109A.

[0215] When a merge mode other than the affine mode or a FRCU mode among the methods of not encoding a differential motion vector is used (0 or 1 in S101), after step S102 or S103, the inter prediction unit 126 determines whether or not to apply a luminance correction process to a predicted image (S116). When it is determined that the luminance correction process of a predicted image is not applied (No in S116), the inter prediction unit 126 determines whether or not there is a residual coefficient whose value is not zero (S105), and if there is no residual coefficient whose value is not zero (No in S105), it encodes the target block in skip mode (S106), and if there is a residual coefficient (Yes in S105), it encodes the target block in non-skip mode (S108).

[0216] In addition, the inter prediction unit 126 does not code the luminance correction processing signal in the skip mode, and in the non-skip mode, sets the luminance correction processing signal to a value indicating no application and codes it (S109A). In addition, in the non-skip mode, the inter prediction unit 126 always codes the residual coefficient information without coding the residual coefficient presence / absence signal (S110).

[0217] In addition, in the process shown in Figure 17, when applying brightness correction processing of a predicted image in merge mode or FRUC mode (Yes in S116), processing similar to that when affine mode and a method for encoding a differential motion vector are used is performed.

[0218] When the method of encoding the differential motion vector is used (3 in S101), when the affine mode of the method of not encoding the differential motion vector is used (2 in S101), and when the method of not encoding the differential motion vector is used and the luminance correction process of the predicted image is applied (Yes in S116), the inter prediction unit 126 always encodes the target block in non-skip mode (S112) and encodes the luminance correction process signal (S113). In addition, the inter prediction unit 126 encodes the residual coefficient presence / absence signal (S114), and when there is a residual coefficient whose value is not zero (Yes in S115), encodes the residual coefficient information (S110).

[0219] [Third example of processing by the inter prediction unit of the decoding device] FIG. 18 is a flowchart showing a third example of the inter prediction process performed by the inter prediction unit 218 included in the decoding device 200 that decodes the stream generated by the encoding device 100 described in FIG.

[0220] The process shown in FIG. 18 is similar to the process shown in FIG. 15 in that step S216 is added and step S207 is deleted.

[0221] When a merge mode or FRCU mode other than affine mode among the methods that do not code differential motion vectors is used (0 or 1 in S201), if a signal indicating that skip mode is used is decoded (Yes in S205), the inter prediction unit 218 decodes the current block in skip mode (S206), and otherwise (No in S205), it decodes the current block in non-skip mode (S208).

[0222] In addition, the inter prediction unit 218 does not decode the luminance correction processing signal in the skip mode, and decodes the luminance correction processing signal in the non-skip mode (S209). If the decoded luminance correction processing signal indicates that the luminance correction processing of the predicted image is to be applied (Yes in S216), the inter prediction unit 218 decodes the residual coefficient presence / absence signal (S214), and if there is a residual coefficient (Yes in S215), decodes the residual coefficient information (S210). Note that in the non-skip mode and if the luminance correction processing signal indicates that the luminance correction processing of the predicted image is not to be applied (No in S216), a residual coefficient is always present, so the inter prediction unit 218 always decodes the residual coefficient information without decoding the residual coefficient presence / absence signal (S210).

[0223] The operations when a method for decoding a differential motion vector is used and when an affine mode among methods for not encoding a differential motion vector is used (2 or 3 in S201) are the same as those in FIG.

[0224] [Syntax structure in the third example] FIG. 19 is a syntax table showing a third example of the syntax configuration of the stream generated by the encoding device 100 described with reference to FIG.

[0225] First, "skip_flag" specifies whether the skip mode or the non-skip mode is used.

[0226] When the skip mode is used, "fruc_mode" further specifies whether or not the FRUC mode is used. When the FRUC mode is not used, "merge_idx" is described to specify a neighboring block to be referenced in the merge mode.

[0227] When the non-skip mode is used, "merge_flag" specifies whether a method is used that does not encode the differential motion vector or a method is used that encodes the differential motion vector.

[0228] If a method that does not code differential motion vectors is used, "fruc_mode" further specifies whether or not FRUC mode is used. If FRUC mode is not used, "affine_flag" further specifies whether or not affine mode is used. If affine mode is not used, "merge_idx" is written to specify the neighboring block to be referenced in merge mode.

[0229] When a method for encoding a differential motion vector is used, "MVD", which is information on the differential motion vector, is described.

[0230] Regardless of which mode is used, "lic_flag" is described, which indicates whether or not luminance correction processing of the predicted image is applied. Furthermore, when a method that does not code a differential motion vector is not used, when an affine mode among methods that do not code a differential motion vector is used, or when it is indicated that luminance correction processing of the predicted image is to be applied, "root_cbf" is described, which indicates whether or not there is a residual coefficient whose value is not zero. When it is indicated that there is a residual coefficient whose value is not zero, "residual" which is residual coefficient information is described.

[0231] [Effect of the third example] According to the third example, when the skip mode is selected, only the description of "fruc_mode" and "merge_idx" is required. Therefore, for example, when encoding using a large number of skip modes under low-rate encoding conditions, the number of syntaxes described in the stream is further reduced compared to the second example described with reference to Figs. 14 to 16. This may further improve the encoding efficiency. In particular, in the affine mode and the luminance correction process of the predicted image, there is a high possibility that residual coefficients with non-zero values ​​will occur, so that the effect of reducing the amount of code by not describing "affine_flag" and "lic_flag" in the skip mode is likely to be large. In addition, there is a possibility that the circuit for controlling the syntax can be further simplified.

[0232] Note that not all of the components described in the third example are always necessary, and the encoding device 100 or the decoding device 200 may include only some of the components described in the third example.

[0233] For example, in FIG. 17 and FIG. 18, an example is described in which four modes corresponding to 0 to 3 are used as inter prediction mode information, but the numbers and modes are only examples, and other numbers and modes may be used. In particular, in a method in which a differential motion vector is not coded, an example is described in which three modes, merge mode, FRUC mode, and affine mode, are used, but it is sufficient that two or more of these modes are used. In addition, modes other than these modes may be used. In addition, a process similar to the process described for the affine mode may be applied to another mode other than the affine mode.

[0234] Furthermore, the syntax configuration described in FIG. 19 is just an example, and part of the syntax in FIG. 19 may be replaced with another syntax, deleted, or added.

[0235] In the third example, a process related to luminance correction of a predicted image is added to the process described in the second example, but a process related to luminance correction of a predicted image may be added to the process of the first example described in Figures 11 to 13. In that case, even if the skip mode is selected, "affine_flag" is described, but it is not necessary to describe "lic_flag", so that it is possible to improve the coding efficiency more than the configuration of the first example described using Figures 11 to 13.

[0236] [LIC processing] The LIC process (luminance correction process) has been described with reference to FIG. 9D, and will be described in detail below.

[0237] First, the inter prediction unit 126 derives a motion vector for obtaining a reference image corresponding to the current block to be coded from a reference picture that is a coded picture.

[0238] Next, the inter prediction unit 126 uses the luminance pixel values ​​of the coded surrounding reference areas adjacent to the left and above and the luminance pixel value at the same position in the reference picture specified by the motion vector to extract information indicating how the luminance values ​​have changed between the reference picture and the coding target picture, and calculates a luminance correction parameter. For example, the luminance pixel value of a pixel in the surrounding reference area in the coding target picture is set to p0, and the luminance pixel value of a pixel in the surrounding reference area in the reference picture at the same position as the pixel is set to p1. The inter prediction unit 126 calculates coefficients A and B that optimize A×p1+B=p0 for multiple pixels in the surrounding reference area as the luminance correction parameter.

[0239] Next, the inter prediction unit 126 performs luminance correction processing on a reference image in a reference picture specified by the motion vector using the luminance correction parameter to generate a predicted image for the block to be coded. For example, the luminance pixel value in the reference image is p2, and the luminance pixel value of the predicted image after the luminance correction processing is p3. The inter prediction unit 126 calculates A×p2+B=p3 for each pixel in the reference image to generate a predicted image after the luminance correction processing.

[0240] Note that the shape of the surrounding reference area in FIG. 9D is an example, and other shapes may be used. Also, a part of the surrounding reference area shown in FIG. 9D may be used. Also, the surrounding reference area is not limited to an area adjacent to the target block to be coded, and may be an area not adjacent to the target block to be coded. Also, in the example shown in FIG. 9D, the surrounding reference area in the reference picture is an area specified by the motion vector of the target block to be coded from the surrounding reference area in the target block to be coded, but may be an area specified by another motion vector. For example, the other motion vector may be the motion vector of the surrounding reference area in the target block to be coded.

[0241] Although the operation of encoding device 100 has been described above, the operation of decoding device 200 is also similar.

[0242] [others] In the present disclosure, the mode referred to as the skip mode may be called by other names. The skip mode in the present disclosure is, for example, a mode designated by a skip flag ("skip_flag" in the syntax).

[0243] Below, some examples of conditions for applying the skip mode will be given based on the explanations in each aspect of the present disclosure.

[0244] In a first example of inter processing by the inter prediction unit 126 included in the encoding device 100 according to the present disclosure, in a method in which a signal related to a differential motion vector is not encoded, a mode in which a stream having a syntax configuration in which a signal related to a residual coefficient is not encoded is called a skip mode, and the other modes are called non-skip modes.

[0245] In a first example of inter prediction processing by the inter prediction unit 218 included in the decoding device 200 according to the present disclosure, in a method in which a signal related to a differential motion vector is not coded, a mode for decoding a stream having a syntax configuration in which a signal related to a residual coefficient is not coded is called a skip mode, and the other modes are called non-skip modes.

[0246] In a second example of inter prediction processing by the inter prediction unit 126 included in the encoding device 100 according to the present disclosure, in a method of deriving motion vectors using merge mode or FRUC mode, a mode that generates a stream with a syntax configuration that does not code signals related to residual coefficients is called skip mode, and other modes are called non-skip modes.

[0247] In a second example of inter prediction processing by the inter prediction unit 218 included in the decoding device 200 according to the present disclosure, in a method of deriving motion vectors using merge mode or FRUC mode, a mode for decoding a stream having a syntax configuration in which signals related to residual coefficients are not coded is called a skip mode, and other modes are called non-skip modes.

[0248] In a third example of inter prediction processing by the inter prediction unit 126 included in the encoding device 100 of the present disclosure, in a method of deriving motion vectors using merge mode or FRUC mode, a mode that generates a stream with a syntax configuration that does not apply brightness correction processing to the predicted image and does not code signals related to residual coefficients is called skip mode, and other modes are called non-skip modes.

[0249] In a third example of inter prediction processing by the inter prediction unit 218 included in the decoding device 200 according to the present disclosure, in a method of deriving a motion vector using merge mode or FRUC mode, a mode in which a luminance correction process is not applied to the predicted image and a stream of a syntax configuration in which a signal related to residual coefficients is not coded is decoded is called a skip mode, and the other modes are called non-skip modes.

[0250] Moreover, the signal related to the residual coefficient is, for example, a signal indicating the residual coefficient.

[0251] The above conditions for encoding in skip mode are merely examples, and encoding device 100 or decoding device 200 may determine whether or not to apply skip mode based on conditions other than those above, and may then perform encoding or decoding.

[0252] For example, the method of deriving a motion vector, which is one of the criteria for determining whether to encode in skip mode, may be limited to only one method such as merge mode, or may be a combination of merge mode and affine mode. In addition, methods of deriving a motion vector without encoding a signal related to a differential motion vector other than the merge mode, FURC mode, and affine mode exemplified in this disclosure may be targets for applying the skip mode.

[0253] In some aspects of the multiple examples of the inter prediction process by the inter prediction unit in the encoding device 100 or the decoding device 200 described in the present disclosure, the encoding device 100 or the decoding device 200 performs encoding without applying the mode specified by the skip flag, even if the signal related to the residual coefficient is not encoded in some modes among the multiple modes in which a motion vector is derived without encoding a signal related to a differential motion vector. According to this configuration, encoding can be performed without including information or a flag indicating whether or not a mode for deriving a motion vector that is not subject to application of the mode specified by the skip flag is used in the syntax of the mode specified by the skip flag. As a result, for example, in cases where the encoding efficiency is reduced by including information or a flag indicating whether or not a condition with a low probability of occurrence is satisfied in the syntax of the mode specified by the skip flag, it is possible to improve the encoding efficiency.

[0254] In some aspects of the multiple examples of inter prediction processing by the inter prediction unit in the encoding device 100 or the decoding device 200 described in the present disclosure, the encoding device 100 or the decoding device 200 performs encoding without applying the mode specified by the skip flag when a specific condition is satisfied even if a signal related to a residual coefficient is not encoded in a method in which a signal related to a differential motion vector is not encoded. The specific condition is, for example, when a luminance correction process of a predicted image is applied. According to this configuration, encoding can be performed without including information or a flag indicating whether or not a condition that is not applicable to the mode specified by the skip flag is satisfied in the syntax of the mode specified by the skip flag. As a result, for example, in a case where the encoding efficiency is reduced by including information or a flag indicating whether or not a condition that is unlikely to occur is satisfied in the syntax of the mode specified by the skip flag, it is possible to improve the encoding efficiency.

[0255] [Example of an implementation of an encoding device] Fig. 20 is a block diagram showing an implementation example of the encoding device 100 according to embodiment 1. The encoding device 100 includes a circuit 160 and a memory 162. For example, a number of components of the encoding device 100 shown in Fig. 1 are implemented by the circuit 160 and the memory 162 shown in Fig. 20.

[0256] The circuit 160 is a circuit that performs information processing and is a circuit that can access the memory 162. For example, the circuit 160 is a dedicated or general-purpose electronic circuit that encodes moving images. The circuit 160 may be a processor such as a CPU. The circuit 160 may also be a collection of multiple electronic circuits. For example, the circuit 160 may play the roles of multiple components of the encoding device 100 shown in FIG. 1 and the like, excluding components for storing information.

[0257] The memory 162 is a dedicated or general-purpose memory in which information for the circuit 160 to encode a moving image is stored. The memory 162 may be an electronic circuit and may be connected to the circuit 160. The memory 162 may be included in the circuit 160. The memory 162 may be a collection of multiple electronic circuits. The memory 162 may be a magnetic disk, an optical disk, or the like, and may be expressed as a storage or a recording medium, or the like. The memory 162 may be a non-volatile memory or a volatile memory.

[0258] For example, the memory 162 may store a video to be encoded, or a bit string corresponding to the encoded video, or may store a program for the circuit 160 to encode the video.

[0259] Also, for example, the memory 162 may play the role of a component for storing information among the multiple components of the encoding device 100 shown in Fig. 1 etc. Specifically, the memory 162 may play the role of the block memory 118 and the frame memory 122 shown in Fig. 1. More specifically, the memory 162 may store reconstructed blocks, reconstructed pictures, etc.

[0260] In addition, in the encoding device 100, all of the components shown in Fig. 1 and the like may not be implemented, and all of the above-described processes may not be performed. Some of the components shown in Fig. 1 and the like may be included in another device, and some of the above-described processes may be executed by another device. Then, in the encoding device 100, some of the components shown in Fig. 1 and the like are implemented, and some of the above-described processes are performed, so that motion compensation is efficiently performed.

[0261] Specifically, the encoding device 100 selects one mode from a plurality of modes for deriving a motion vector, and derives a motion vector for a target block in the selected mode (S102, S103, S104, and S111 in FIG. 14). Next, the encoding device 100 performs inter-prediction encoding of the target block by one of the skip mode and a non-skip mode different from the skip mode, using the derived motion vector (S106, S108, or S112 in FIG. 14). The plurality of modes include a plurality of first modes (e.g., merge mode, FRUC mode, and affine mode) that predict the motion vector of the target block from encoded blocks surrounding the target block, without encoding information indicating the motion vector into a stream. When a second mode included in the plurality of first modes is selected, the encoding device 100 encodes the target block in the non-skip mode regardless of the presence or absence of residual coefficients (S112 in FIG. 14).

[0262] This enables the encoding efficiency of the encoding device 100 to be improved. For example, when the skip mode is used, there is no need to transmit information indicating whether the second mode is used or not, and therefore the encoding efficiency can be improved.

[0263] For example, when a third mode (e.g., merge mode or FRUC mode) that is included in the multiple first modes and is different from the second mode is selected, encoding device 100 encodes the target block in non-skip mode (S108 in FIG. 14) if there are residual coefficients (Yes in S105 in FIG. 14), and encodes the target block in skip mode (S106 in FIG. 14) if there are no residual coefficients (No in S105 in FIG. 14).

[0264] For example, the second mode is a mode (affine mode) in which a motion vector corresponding to an affine transformation is predicted from encoded blocks surrounding the current block.

[0265] According to this, when a mode in which the non-skip mode is likely to be selected due to the occurrence of a coefficient whose value is not zero is used, the non-skip mode is used regardless of the presence or absence of residual coefficients, and thus the influence of the skip mode not being selected can be suppressed.

[0266] For example, the third mode is a FRUC mode or a merge mode.

[0267] For example, when the current block is coded in the non-skip mode, the coding apparatus 100 further codes information indicating whether or not there is a residual coefficient (S114 in FIG. 14).

[0268] For example, the encoding device 100 further selects whether or not to perform a luminance correction process on the current block, which corrects an average luminance value of a predicted image using a correction value predicted from luminance values ​​of coded blocks surrounding the current block (S116 in FIG. 17). When performing a luminance correction process on the current block (Yes in S116 in FIG. 17), the encoding device 100 codes the current block in non-skip mode regardless of the presence or absence of residual coefficients (S112 in FIG. 17).

[0269] According to this, when a luminance correction process is performed in which the non-skip mode is likely to be selected due to the occurrence of a coefficient whose value is not zero, the non-skip mode is used regardless of the presence or absence of residual coefficients, and thus the influence of not selecting the skip mode can be suppressed.

[0270] For example, when the encoding device 100 further performs luminance correction processing on the current block (Yes in S116 in FIG. 17), the encoding device 100 encodes information indicating whether or not there is a residual coefficient (S114 in FIG. 17).

[0271] [Example of implementation of a decryption device] Fig. 21 is a block diagram showing an implementation example of the decoding device 200 according to embodiment 1. The decoding device 200 includes a circuit 260 and a memory 262. For example, a plurality of components of the decoding device 200 shown in Fig. 10 are implemented by the circuit 260 and the memory 262 shown in Fig. 21.

[0272] The circuit 260 is a circuit that performs information processing and is a circuit that can access the memory 262. For example, the circuit 260 is a dedicated or general-purpose electronic circuit that decodes moving images. The circuit 260 may be a processor such as a CPU. The circuit 260 may also be a collection of multiple electronic circuits. For example, the circuit 260 may play the role of multiple components of the decoding device 200 shown in FIG. 10 and the like, excluding components for storing information.

[0273] The memory 262 is a dedicated or general-purpose memory in which information for the circuit 260 to decode a moving image is stored. The memory 262 may be an electronic circuit and may be connected to the circuit 260. The memory 262 may be included in the circuit 260. The memory 262 may be a collection of multiple electronic circuits. The memory 262 may be a magnetic disk, an optical disk, or the like, and may be expressed as a storage or a recording medium, or the like. The memory 262 may be a non-volatile memory or a volatile memory.

[0274] For example, the memory 262 may store a bit string corresponding to an encoded video, or a video corresponding to a decoded bit string, or may store a program for the circuit 260 to decode the video.

[0275] Also, for example, the memory 262 may play the role of a component for storing information among the multiple components of the decoding device 200 shown in Fig. 10 etc. Specifically, the memory 262 may play the role of the block memory 210 and the frame memory 214 shown in Fig. 10. More specifically, the memory 262 may store reconstructed blocks, reconstructed pictures, etc.

[0276] In addition, in the decoding device 200, all of the components shown in Fig. 10 and the like may not be implemented, and all of the above-described processes may not be performed. Some of the components shown in Fig. 10 and the like may be included in another device, and some of the above-described processes may be executed by another device. Then, in the decoding device 200, some of the components shown in Fig. 10 and the like are implemented, and some of the above-described processes are performed, so that motion compensation is efficiently performed.

[0277] Specifically, the decoding device 200 selects one mode from a plurality of modes for deriving a motion vector, and derives a motion vector for a target block in the selected mode (S202, S203, S204, and S211 in FIG. 15). Next, the decoding device 200 performs inter-prediction decoding of the target block by one of the skip mode and a non-skip mode different from the skip mode, using the derived motion vector (S206, S208, or S212 in FIG. 15). The plurality of modes include a plurality of first modes (e.g., merge mode, FRUC mode, and affine mode) in which the motion vector of the target block is predicted from decoded blocks surrounding the target block, without decoding information indicating the motion vector from a stream. When a second mode included in the plurality of first modes is selected, the decoding device 200 decodes the target block in the non-skip mode regardless of the presence or absence of residual coefficients (S212 in FIG. 15).

[0278] This enables the decoding device 200 to improve the coding efficiency. For example, when the skip mode is used, there is no need to transmit information indicating whether the second mode is used or not, and therefore the coding efficiency can be improved.

[0279] For example, when a third mode (e.g., merge mode or FRUC mode) that is included in the multiple first modes and is different from the second mode is selected, decoding device 200 decodes the target block in non-skip mode (S208 in FIG. 15) if there are residual coefficients (No in S205 in FIG. 15), and decodes the target block in skip mode (S206 in FIG. 15) if there are no residual coefficients (Yes in S205 in FIG. 15).

[0280] For example, the second mode is a mode (affine mode) in which a motion vector corresponding to an affine transformation is predicted from decoded blocks surrounding the current block.

[0281] According to this, when a mode in which the non-skip mode is likely to be selected due to the occurrence of a coefficient whose value is not zero is used, the non-skip mode is used regardless of the presence or absence of residual coefficients, and thus the influence of the skip mode not being selected can be suppressed.

[0282] For example, the third mode is a FRUC mode or a merge mode.

[0283] For example, when the current block is decoded in the non-skip mode, the decoding device 200 further decodes information indicating whether or not there is a residual coefficient (S214 in FIG. 18).

[0284] For example, the decoding device 200 further selects whether or not to perform a luminance correction process on the current block, which corrects an average luminance value of a predicted image using a correction value predicted from luminance values ​​of decoded blocks surrounding the current block (S216 in FIG. 18). When performing the luminance correction process on the current block (Yes in S216 in FIG. 18), the decoding device 200 decodes the current block in non-skip mode regardless of the presence or absence of residual coefficients (S208 in FIG. 18).

[0285] According to this, when a luminance correction process is performed in which the non-skip mode is likely to be selected due to the occurrence of a coefficient whose value is not zero, the non-skip mode is used regardless of the presence or absence of residual coefficients, and thus the influence of not selecting the skip mode can be suppressed.

[0286] For example, when the decoding device 200 further performs luminance correction processing on the current block (Yes in S216 in FIG. 18), the decoding device 200 decodes information indicating whether or not there is a residual coefficient (S214).

[0287] [supplement] Furthermore, the encoding device 100 and the decoding device 200 in this embodiment may be used as an image encoding device and an image decoding device, or as a video encoding device and a video decoding device, respectively. Alternatively, the encoding device 100 and the decoding device 200 may be used as an inter prediction device (inter prediction device).

[0288] That is, the encoding device 100 and the decoding device 200 may correspond only to the inter prediction unit (inter prediction unit) 126 and the inter prediction unit (inter prediction unit) 218, respectively. Other components such as the transform unit 106 and the inverse transform unit 206 may be included in other devices.

[0289] In the present embodiment, each component may be implemented by dedicated hardware or by executing a software program suitable for each component. Each component may be implemented by a program execution unit such as a CPU or processor reading and executing a software program recorded on a recording medium such as a hard disk or semiconductor memory.

[0290] Specifically, each of the encoding device 100 and the decoding device 200 may include a processing circuitry and a storage device electrically connected to and accessible from the processing circuitry. For example, the processing circuitry corresponds to the circuit 160 or 260, and the storage device corresponds to the memory 162 or 262.

[0291] The processing circuit includes at least one of dedicated hardware and a program execution unit, and executes processing using a storage device. In addition, when the processing circuit includes a program execution unit, the storage device stores a software program to be executed by the program execution unit.

[0292] Here, the software for realizing the encoding device 100 or the decoding device 200 according to the present embodiment is a program as follows.

[0293] Also, each component may be a circuit, as described above. These circuits may form one circuit as a whole, or each may be a separate circuit. Also, each component may be realized by a general-purpose processor, or a dedicated processor.

[0294] Furthermore, a process executed by a specific component may be executed by another component. The order in which the processes are executed may be changed, or multiple processes may be executed in parallel. Furthermore, the encoding / decoding device may include the encoding device 100 and the decoding device 200.

[0295] Although the aspects of the encoding device 100 and the decoding device 200 have been described above based on the embodiment, the aspects of the encoding device 100 and the decoding device 200 are not limited to this embodiment. As long as it does not deviate from the spirit of this disclosure, various modifications conceived by a person skilled in the art to this embodiment and forms constructed by combining components in different embodiments may also be included within the scope of the aspects of the encoding device 100 and the decoding device 200.

[0296] This aspect may be implemented in combination with at least a part of other aspects of the present disclosure. Also, some of the processes, some of the configurations of the device, and some of the syntax described in the flowcharts of this aspect may be implemented in combination with other aspects.

[0297] (Embodiment 2) In each of the above embodiments, each of the functional blocks can usually be realized by an MPU, a memory, etc. Furthermore, the processing by each of the functional blocks is usually realized by a program execution unit such as a processor reading and executing software (programs) recorded on a recording medium such as a ROM. The software may be distributed by downloading, etc., or may be recorded on a recording medium such as a semiconductor memory and distributed. Of course, each functional block can also be realized by hardware (dedicated circuitry).

[0298] Furthermore, the processes described in each embodiment may be realized by centralized processing using a single device (system), or may be realized by distributed processing using multiple devices. The processor that executes the above program may be either single or multiple. That is, centralized processing or distributed processing may be performed.

[0299] The aspects of the present disclosure are not limited to the above examples, and various modifications are possible, which are also included within the scope of the aspects of the present disclosure.

[0300] Further, here, application examples of the video coding method (image coding method) or video decoding method (image decoding method) shown in each of the above embodiments and a system using the same will be described. The system is characterized by having an image coding device using the image coding method, an image decoding device using the image decoding method, and an image coding / decoding device equipped with both. Other configurations in the system can be appropriately changed depending on the case.

[0301] [Usage example] 22 is a diagram showing the overall configuration of a content supply system ex100 that realizes a content distribution service. The area where communication services are provided is divided into cells of a desired size, and base stations ex106, ex107, ex108, ex109, and ex110, which are fixed wireless stations, are installed in each cell.

[0302] In this content supply system ex100, devices such as a computer ex111, a game machine ex112, a camera ex113, a home appliance ex114, and a smartphone ex115 are connected to the Internet ex101 via an Internet service provider ex102 or a communication network ex104, and base stations ex106 to ex110. The content supply system ex100 may be configured to connect any of the above elements in combination. Each device may be directly or indirectly connected to each other via a telephone network or short-distance wireless communication, without going through the base stations ex106 to ex110, which are fixed wireless stations. In addition, the streaming server ex103 is connected to each device such as a computer ex111, a game machine ex112, a camera ex113, a home appliance ex114, and a smartphone ex115 via the Internet ex101, etc. In addition, the streaming server ex103 is connected to a terminal in a hot spot in an airplane ex117, etc., via a satellite ex116.

[0303] Instead of the base stations ex106 to ex110, wireless access points or hot spots may be used. The streaming server ex103 may be directly connected to the communication network ex104 without going through the Internet ex101 or the Internet service provider ex102, or may be directly connected to an airplane ex117 without going through a satellite ex116.

[0304] The camera ex113 is a device capable of taking still images and videos, such as a digital camera. The smartphone ex115 is a smartphone, a mobile phone, or a PHS (Personal Handyphone System) that is compatible with a mobile communication system generally called 2G, 3G, 3.9G, 4G, and 5G in the future.

[0305] The home appliance ex118 is a refrigerator or an appliance included in a home fuel cell cogeneration system.

[0306] In the content supply system ex100, a terminal having a photographing function is connected to a streaming server ex103 via a base station ex106 or the like, thereby enabling live distribution and the like. In live distribution, a terminal (such as a computer ex111, a game machine ex112, a camera ex113, a home appliance ex114, a smartphone ex115, and a terminal in an airplane ex117) performs the encoding process described in each of the above embodiments on still image or video content photographed by a user using the terminal, multiplexes the video data obtained by the encoding with audio data obtained by encoding audio corresponding to the video, and transmits the obtained data to the streaming server ex103. That is, each terminal functions as an image encoding device according to one aspect of the present disclosure.

[0307] Meanwhile, the streaming server ex103 streams the transmitted content data to the requesting client. The client is a computer ex111, a game machine ex112, a camera ex113, a home appliance ex114, a smartphone ex115, a terminal in an airplane ex117, or the like, capable of decoding the encoded data. Each device that receives the distributed data decodes and plays back the received data. That is, each device functions as an image decoding device according to one aspect of the present disclosure.

[0308] [Distributed processing] The streaming server ex103 may be a plurality of servers or computers that process, record, and distribute data in a distributed manner. For example, the streaming server ex103 may be realized by a CDN (Contents Delivery Network), and content distribution may be realized by a network that connects a large number of edge servers distributed around the world. In a CDN, an edge server that is physically close to the client is dynamically assigned according to the client. The content is cached and distributed to the edge server, thereby reducing delays. In addition, when an error occurs or the communication state changes due to an increase in traffic, the processing can be distributed among multiple edge servers, the distribution entity can be switched to another edge server, or distribution can be continued by bypassing the part of the network where a failure has occurred, thereby realizing high-speed and stable distribution.

[0309] In addition to the distributed processing of the distribution itself, the encoding processing of the captured data may be performed by each terminal, may be performed by the server side, or may be shared among the terminals. As an example, in the encoding processing, a processing loop is generally performed twice. In the first loop, the complexity of the image or the amount of code is detected for each frame or scene. In the second loop, processing is performed to maintain the image quality and improve the encoding efficiency. For example, the terminal performs the first encoding processing, and the server side that receives the content performs the second encoding processing, thereby improving the quality and efficiency of the content while reducing the processing load on each terminal. In this case, if there is a request to receive and decode almost in real time, the data encoded once by the terminal can be received and played back by other terminals, making it possible to perform more flexible real-time distribution.

[0310] As another example, the camera ex113 etc. extracts features from an image, compresses data related to the features as metadata, and transmits the compressed data to the server. The server performs compression according to the meaning of the image, for example, by determining the importance of an object from the features and switching the quantization precision. The feature data is particularly effective in improving the precision and efficiency of motion vector prediction when the server performs recompression. Alternatively, the terminal may perform simple encoding such as VLC (variable length coding), and the server may perform encoding with a large processing load such as CABAC (context-adaptive binary arithmetic coding).

[0311] As another example, in a stadium, a shopping mall, a factory, etc., there may be a plurality of video data in which almost the same scene has been shot by a plurality of terminals. In this case, using the plurality of terminals that shot the video and, as necessary, other terminals and servers that did not shoot the video, coding processing is assigned to each of them, for example, in units of GOPs (Group of Pictures), in units of pictures, or in units of tiles obtained by dividing a picture, for distributed processing. This reduces delays and realizes better real-time performance.

[0312] In addition, since the multiple video data are of almost the same scene, the server may manage and / or instruct the video data shot by each terminal to be mutually referenced. Alternatively, the server may receive the encoded data from each terminal and change the reference relationship between the multiple data, or correct or replace the pictures themselves and re-encode them. This makes it possible to generate a stream with improved quality and efficiency for each piece of data.

[0313] The server may also perform transcoding to change the encoding format of the video data before distributing it. For example, the server may convert an MPEG-based encoding format into a VP-based encoding format, or convert H.264 into H.265.

[0314] In this way, the encoding process can be performed by a terminal or one or more servers. Therefore, in the following, descriptions such as "server" or "terminal" are used to indicate the entity performing the processing, but some or all of the processing performed by the server may be performed by the terminal, and some or all of the processing performed by the terminal may be performed by the server. The same applies to the decoding process.

[0315] [3D, multi-angle] In recent years, it has become common to integrate and use images or videos of different scenes or the same scene taken from different angles by multiple devices such as cameras ex113 and / or smartphones ex115 that are almost synchronized with each other. The videos taken by the devices are integrated based on the relative positional relationship between the devices that is obtained separately, or on areas where feature points included in the videos match.

[0316] The server may not only encode 2D video, but also encode still images automatically or at a time specified by the user based on scene analysis of the video and transmit them to the receiving terminal. If the server can obtain the relative positional relationship between the shooting terminals, the server may generate a 3D shape of the scene based on not only 2D video but also images of the same scene captured from different angles. The server may separately encode 3D data generated by point clouds, etc., or may generate images to be transmitted to the receiving terminal by selecting or reconstructing images from images captured by multiple terminals based on the results of recognizing or tracking people or objects using the 3D data.

[0317] In this way, the user can enjoy a scene by selecting any video corresponding to each shooting terminal, or can enjoy content in which a video from any viewpoint is cut out from 3D data reconstructed using multiple images or videos. Furthermore, sound may be collected from multiple different angles, just like the video, and the server may multiplex the sound from a specific angle or space with the video and transmit it in accordance with the video.

[0318] In recent years, content that associates the real world with a virtual world, such as Virtual Reality (VR) and Augmented Reality (AR), has also become popular. In the case of VR images, the server creates viewpoint images for the right eye and the left eye, respectively, and may perform encoding that allows reference between each viewpoint video using Multi-View Coding (MVC) or the like, or may encode them as separate streams without mutual reference. When decoding the separate streams, it is preferable to play them in synchronization with each other so that a virtual three-dimensional space is reproduced according to the user's viewpoint.

[0319] In the case of an AR image, the server superimposes virtual object information in the virtual space on camera information in the real space based on the three-dimensional position or the movement of the user's viewpoint. The decoding device may obtain or hold virtual object information and three-dimensional data, generate a two-dimensional image according to the movement of the user's viewpoint, and smoothly connect them to create superimposed data. Alternatively, the decoding device may transmit the movement of the user's viewpoint to the server in addition to a request for virtual object information, and the server may create superimposed data according to the movement of the viewpoint received from the three-dimensional data held by the server, encode the superimposed data, and deliver it to the decoding device. Note that the superimposed data has an α value indicating the transparency in addition to RGB, and the server may set the α value of the part other than the object created from the three-dimensional data to 0, etc., and encode the data in a state in which the part is transparent. Alternatively, the server may generate data in which a predetermined value of RGB value is set to the background like a chromakey, and the part other than the object is the background color.

[0320] Similarly, the decoding process of the distributed data may be performed by each client terminal, or may be performed by the server side, or may be shared among them. As an example, a certain terminal may once send a reception request to the server, and the content corresponding to the request may be received by other terminals, decoded, and the decoded signal may be transmitted to a device having a display. By distributing the processing and selecting appropriate content regardless of the performance of the communication-enabled terminals themselves, data with good image quality can be reproduced. In another example, while large-sized image data is received by a TV or the like, a part of the area, such as tiles into which the picture is divided, may be decoded and displayed on the viewer's personal terminal. This allows the viewer to share the overall picture while checking his / her own area of ​​responsibility or the area he / she wants to check in more detail at hand.

[0321] In the future, it is expected that content will be seamlessly received by switching appropriate data for the currently connected communication using delivery system standards such as MPEG-DASH under circumstances where multiple short-distance, medium-distance, or long-distance wireless communication is available, whether indoors or outdoors. This allows users to freely select and switch in real time not only their own terminals but also decoding devices or display devices such as displays installed indoors or outdoors. In addition, decoding can be performed while switching the decoding device and the display device based on the user's location information, etc. This makes it possible to move while displaying map information on the wall or part of the ground of a neighboring building where a displayable device is embedded while moving to a destination. It is also possible to switch the bit rate of the received data based on the accessibility of the encoded data on the network, such as when the encoded data is cached on a server that can be accessed in a short time from the receiving terminal, or copied to an edge server in a content delivery service.

[0322] [Scalable Coding] The switching of contents will be described using a scalable stream compressed and coded by applying the video coding method shown in each of the above embodiments, as shown in FIG. 23. The server may have multiple streams with the same content but different qualities as individual streams, but may be configured to switch contents by taking advantage of the characteristics of a temporal / spatial scalable stream realized by coding in layers as shown in the figure. In other words, the decoding side can freely switch between low-resolution content and high-resolution content by determining which layer to decode according to an internal factor such as performance and an external factor such as the state of the communication band. For example, if you want to continue watching a video you were watching on your smartphone ex115 while on the move on a device such as an Internet TV after you get home, the device can decode the same stream up to a different layer, reducing the burden on the server side.

[0323] Furthermore, as described above, in addition to the configuration that realizes scalability in which pictures are coded for each layer and an enhancement layer exists above a base layer, the enhancement layer may include meta-information based on image statistics, etc., and the decoding side may generate high-quality content by super-resolving pictures of the base layer based on the meta-information. Super-resolution may be either an improvement in the signal-to-noise ratio at the same resolution or an increase in resolution. The meta-information includes information for specifying linear or nonlinear filter coefficients used in the super-resolution process, or information for specifying parameter values ​​in the filter process, machine learning, or least squares calculation used in the super-resolution process.

[0324] Alternatively, a picture may be divided into tiles or the like according to the meaning of an object in an image, and the decoding side may select a tile to decode to decode only a part of the area. Also, by storing the attribute of an object (person, car, ball, etc.) and its position in a video (coordinate position in the same image, etc.) as meta information, the decoding side can identify the position of a desired object based on the meta information and determine the tile containing the object. For example, as shown in FIG. 24, the meta information is stored using a data storage structure different from pixel data such as an SEI message in HEVC. This meta information indicates, for example, the position, size, or color of a main object.

[0325] Meta information may also be stored in units consisting of multiple pictures, such as streams, sequences, or random access units, etc. This allows the decoding side to obtain the time when a specific person appears in the video, and by combining this with picture-by-picture information, it is possible to identify the picture in which an object exists and the position of the object within the picture.

[0326] [Web page optimization] FIG. 25 is a diagram showing an example of a display screen of a web page in a computer ex111 or the like. FIG. 26 is a diagram showing an example of a display screen of a web page in a smartphone ex115 or the like. As shown in FIG. 25 and FIG. 26, a web page may include multiple link images that are links to image content, and the appearance of the web page differs depending on the device used to view the page. When multiple link images are visible on the screen, the display device (decoding device) displays a still image or I-picture that each content has as a link image, displays an image such as a gif animation using multiple still images or I-pictures, or receives only the base layer to decode and display the image until the user explicitly selects the link image, or until the link image approaches the center of the screen or the entire link image enters the screen.

[0327] When a link image is selected by a user, the display device gives top priority to decoding the base layer. If the HTML constituting the web page contains information indicating that the content is scalable, the display device may decode up to the enhancement layer. In order to ensure real-time performance, before selection or when the communication bandwidth is very tight, the display device decodes and displays only forward-reference pictures (I-pictures, P-pictures, and B-pictures with forward reference only), thereby reducing the delay between the decoding time of the first picture and the display time (the delay from the start of decoding the content to the start of display). The display device may also ignore the reference relationship between pictures and roughly decode all B-pictures and P-pictures with forward reference, and perform normal decoding as the number of received pictures increases over time.

[0328] [Automatic driving] Furthermore, when transmitting and receiving still image or video data such as 2D or 3D map information for automatic driving or driving assistance of a vehicle, the receiving terminal may receive weather or construction information as meta information in addition to image data belonging to one or more layers, and may associate and decode these. Note that the meta information may belong to a layer, or may simply be multiplexed with the image data.

[0329] In this case, since a car, drone, or airplane including a receiving terminal moves, the receiving terminal can realize seamless reception and decoding while switching between base stations ex106 to ex110 by transmitting the location information of the receiving terminal at the time of a reception request. Also, the receiving terminal can dynamically switch how much meta information to receive or how much to update map information according to the user's selection, the user's situation, or the state of the communication band.

[0330] In this manner, in the content supply system ex100, the client can receive, decode, and play back encoded information transmitted by the user in real time.

[0331] [Distribution of personal content] Furthermore, the content supply system ex100 allows not only high-quality, long-duration content from video distributors, but also low-quality, short-duration content from individuals via unicast or multicast distribution. It is expected that such personal content will continue to increase in the future. To improve the quality of personal content, the server may perform editing processing before encoding processing. This can be achieved, for example, by the following configuration.

[0332] During shooting, in real time or after accumulating, the server performs recognition processing such as shooting errors, scene search, semantic analysis, and object detection from the original image or encoded data. Then, based on the recognition result, the server manually or automatically corrects out-of-focus or camera shake, deletes less important scenes such as scenes that are less bright than other pictures or are out of focus, emphasizes object edges, changes color, and performs other editing. The server encodes the edited data based on the editing result. It is also known that if the shooting time is too long, the viewer rating will decrease, and the server may automatically clip not only scenes of less importance as described above but also scenes with little movement based on the image processing result so that the content will be within a specific time range depending on the shooting time. Alternatively, the server may generate a digest based on the result of the semantic analysis of the scene and encode it.

[0333] In addition, there are cases where personal contents contain images that infringe copyrights, moral rights, portrait rights, etc., and the scope of sharing may exceed the intended scope, which may be inconvenient for individuals. Therefore, for example, the server may change the image to an unfocused image of a person's face on the periphery of the screen, or the inside of a house, and encode it. The server may also recognize whether the image to be encoded contains a face of a person other than a person registered in advance, and if so, may perform processing such as blurring the face. Alternatively, as pre-processing or post-processing of encoding, the user may specify a person or background area that he or she wishes to process in the image from the viewpoint of copyright, etc., and the server may replace the specified area with another image or blur the focus. If it is a person, the image of the face part can be replaced while tracking the person in the video.

[0334] In addition, since viewing of personal content with a small amount of data requires real-time performance, the decoding device first receives the base layer as a top priority, and performs decoding and playback, although this depends on the bandwidth. The decoding device may receive an enhancement layer during this time, and when playback is looped or otherwise played two or more times, play high-quality video including the enhancement layer. In this way, if the stream is scalably encoded, it is possible to provide an experience in which the video is rough when not selected or when viewing begins, but the stream gradually becomes smarter and the image quality improves. In addition to scalable encoding, a similar experience can be provided even if a rough stream played the first time and a second stream encoded with reference to the first video are configured as one stream.

[0335] [Other use cases] Moreover, these encoding or decoding processes are generally processed in an LSIex500 possessed by each terminal. The LSIex500 may be a single chip or may be configured with multiple chips. Note that software for encoding or decoding moving images may be incorporated into some kind of recording medium (such as a CD-ROM, a flexible disk, or a hard disk) that can be read by the computer ex111 or the like, and the encoding or decoding process may be performed using the software. Furthermore, if the smartphone ex115 has a camera, video data captured by the camera may be transmitted. The video data in this case is data that has been encoded by the LSIex500 possessed by the smartphone ex115.

[0336] The LSIex500 may be configured to download and activate application software. In this case, the terminal first determines whether the terminal supports the encoding method of the content or has the ability to execute a specific service. If the terminal does not support the encoding method of the content or does not have the ability to execute a specific service, the terminal downloads a codec or application software, and then acquires and plays the content.

[0337] Furthermore, at least one of the video encoding device (image encoding device) or video decoding device (image decoding device) of each of the above embodiments can be incorporated into a digital broadcasting system, not limited to the content supply system ex100 via the Internet ex101. Since multiplexed data in which video and audio are multiplexed is carried and transmitted over broadcasting radio waves using a satellite or the like, there is a difference in that it is more suitable for multicast compared to the content supply system ex100, which has a configuration that is easy to use for unicast, but similar applications are possible with regard to the encoding process and decoding process.

[0338] [Hardware configuration] FIG. 27 is a diagram showing a smartphone ex115. FIG. 28 is a diagram showing a configuration example of the smartphone ex115. The smartphone ex115 includes an antenna ex450 for transmitting and receiving radio waves to and from the base station ex110, a camera unit ex465 capable of taking videos and still images, and a display unit ex458 for displaying the video captured by the camera unit ex465 and the decoded data of the video received by the antenna ex450. The smartphone ex115 further includes an operation unit ex466 such as a touch panel, an audio output unit ex457 such as a speaker for outputting audio or sound, an audio input unit ex456 such as a microphone for inputting audio, a memory unit ex467 capable of storing encoded data such as captured video or still images, recorded audio, received video or still images, and e-mail, or decoded data, and a slot unit ex464 which is an interface unit with a SIMex468 for identifying a user and authenticating access to various data including a network. In addition, an external memory may be used instead of the memory unit ex467.

[0339] In addition, a main control unit ex460, which comprehensively controls the display unit ex458 and the operation unit ex466, etc., is connected to a power supply circuit unit ex461, an operation input control unit ex462, a video signal processing unit ex455, a camera interface unit ex463, a display control unit ex459, a modulation / demodulation unit ex452, a multiplexing / separation unit ex453, an audio signal processing unit ex454, a slot unit ex464, and a memory unit ex467 via a bus ex470.

[0340] When the power key is turned on by a user's operation, the power supply circuit unit ex461 starts up the smartphone ex115 into an operational state by supplying power to each unit from the battery pack.

[0341] The smartphone ex115 performs processes such as telephone calls and data communications under the control of a main control unit ex460 having a CPU, a ROM, and a RAM. During a telephone call, a voice signal collected by a voice input unit ex456 is converted into a digital voice signal by a voice signal processing unit ex454, which is then subjected to spectrum spreading processing by a modulation / demodulation unit ex452, and the digital-to-analog conversion processing and frequency conversion processing by a transmission / reception unit ex451 is then transmitted via an antenna ex450. In addition, the received data is amplified, and subjected to frequency conversion processing and analog-to-digital conversion processing, and the spectrum inverse spreading processing by a modulation / demodulation unit ex452 is then performed, and the analog voice signal is converted into an analog voice signal by a voice signal processing unit ex454, which is then output from a voice output unit ex457. During a data communication mode, text, still images, or video data is sent to the main control unit ex460 via an operation input control unit ex462 by operating an operation unit ex466 or the like of the main unit, and transmission and reception processing is performed in the same manner. When transmitting video, still images, or video and audio in the data communication mode, the video signal processing unit ex455 compresses and encodes the video signal stored in the memory unit ex467 or the video signal input from the camera unit ex465 by the moving image encoding method shown in each of the above embodiments, and sends the encoded video data to the multiplexing / separation unit ex453. The audio signal processing unit ex454 also encodes the audio signal collected by the audio input unit ex456 while the camera unit ex465 is capturing the video or still images, and sends the encoded audio data to the multiplexing / separation unit ex453. The multiplexing / separation unit ex453 multiplexes the encoded video data and the encoded audio data by a predetermined method, and performs modulation and conversion processing in the modulation / demodulation unit (modulation / demodulation circuit unit) ex452 and the transmission / reception unit ex451, and transmits the data via the antenna ex450.

[0342] When receiving a video attached to an e-mail or chat, or a video linked to a web page, etc., in order to decode the multiplexed data received via the antenna ex450, the multiplexing / separation unit ex453 separates the multiplexed data into a bit stream of video data and a bit stream of audio data by separating the multiplexed data, and supplies the encoded video data to the video signal processing unit ex455 via the synchronization bus ex470, and supplies the encoded audio data to the audio signal processing unit ex454. The video signal processing unit ex455 decodes the video signal by a video decoding method corresponding to the video encoding method shown in each of the above embodiments, and displays the video or still image contained in the linked video file on the display unit ex458 via the display control unit ex459. The audio signal processing unit ex454 also decodes the audio signal, and audio is output from the audio output unit ex457. Note that since real-time streaming is widespread, there may be cases where audio playback is socially inappropriate depending on the user's situation. Therefore, as an initial value, a configuration in which only video data is played without playing audio signals is preferable. The audio may be played in sync only when the user performs an operation such as clicking on the video data.

[0343] In addition, although the smartphone ex115 has been described as an example here, three types of implementation formats are possible for the terminal: a transmitting / receiving terminal having both an encoder and a decoder, a transmitting terminal having only an encoder, and a receiving terminal having only a decoder. Furthermore, in the digital broadcasting system, multiplexed data in which audio data and the like are multiplexed with video data is received or transmitted, but the multiplexed data may include text data related to the video in addition to audio data, or the video data itself may be received or transmitted instead of the multiplexed data.

[0344] Although the main control unit ex460 including the CPU controls the encoding or decoding process, terminals often have a GPU. Therefore, a configuration may be used in which a wide area is processed collectively by utilizing the performance of the GPU using a memory shared by the CPU and GPU, or a memory whose addresses are managed so that they can be used in common. This can shorten the encoding time, ensure real-time performance, and achieve low latency. In particular, it is efficient to perform the processing of motion search, deblocking filter, SAO (Sample Adaptive Offset), and transformation and quantization collectively in units such as pictures by the GPU, rather than by the CPU.

[0345] This aspect may be implemented in combination with at least a part of other aspects of the present disclosure. Also, some of the processes, some of the configurations of the device, and some of the syntax described in the flowcharts of this aspect may be implemented in combination with other aspects. [Industrial Applicability]

[0346] The present disclosure is applicable to, for example, television receivers, digital video recorders, car navigation systems, mobile phones, digital cameras, digital video cameras, video conference systems, electronic mirrors, and the like. [Explanation of symbols]

[0347] 100 Encoding device 102 Division 104 Subtraction section 106 Conversion unit 108 Quantization section 110 Entropy coding unit 112, 204 Inverse quantization section 114, 206 Inverse conversion unit 116, 208 Addition section 118, 210 Block Memory 120, 212 Loop filter section 122, 214 frame memory 124, 216 Intra prediction section 126, 218 Inter prediction section 128, 220 Predictive control unit 160, 260 circuits 162, 262 memory 200 Decryption device 202 Entropy Decoding Unit

Claims

[Claim 1] The circuit, A memory. The circuit uses the memory to: selecting one mode from a plurality of modes for deriving a motion vector, and deriving a motion vector for the target block in the selected mode; using the derived motion vector, inter-predictively encoding the current block in one of a skip mode and a non-skip mode different from the skip mode; the plurality of modes include a plurality of first modes for predicting a motion vector of the current block from previously coded blocks surrounding the current block without coding information indicating a differential motion vector into a bitstream; In the skip mode, information indicating whether a second mode included in the plurality of first modes is used is not described in the bit stream, and information indicating whether a third mode, which is included in the plurality of first modes and is different from the second mode, is used is described in the bit stream; In the non-skip mode, information indicating whether the second mode is used and information indicating whether the third mode is used are described in the bitstream; If the second mode is used, encoding the current block in the non-skip mode regardless of the presence or absence of residual coefficients; transmitting the bitstream including the encoded current block; Bitstream transmitter.

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