Image encoder, image decoder and bit stream generation device

Abstract

To reduce a throughput.SOLUTION: An image encoder 100 comprises: circuitry; and a memory coupled to the circuitry. The circuitry defines a first partition and a second partition having a non-rectangular shape into a current image block so as to overlap them. When encoding the first partition and the second partition, a first uni-prediction motion vector is derived from a plurality of bi-prediction motion vector candidates, and a first prediction image of the first partition is generated using the first uni-prediction motion vector. A second uni-prediction motion vector is derived from a plurality of bi-prediction motion vector candidates, and a second prediction image of the second partition is generated using the second uni-prediction motion vector. The first prediction image and the second prediction image are combined, such that a prediction image of a current block is generated and the plurality of bi-prediction motion vector candidates is included in a marge list.SELECTED DRAWING: Figure 50

Description

Technical Field

[0001] The present disclosure relates to video coding, and more particularly to systems, components, and methods in the encoding and decoding of moving images for implementing an inter prediction function that constructs a prediction of a current frame based on reference frames.

Background Art

[0002] Video coding technology has advanced from H.261 and MPEG-1 to H.264 / AVC (Advanced Video Coding), MPEG-LA, H.265 / HEVC (High Efficiency Video Coding), and H.266 / VVC (Versatile Video Codec). With this advancement, there has always been a need to provide improvements and optimizations to video coding technology to handle the ever-increasing amount of digital video data in various applications. The present disclosure relates to further advancements, improvements, and optimizations in video coding, particularly in the inter prediction function that constructs a prediction of a current frame based on reference frames.

Summary of the Invention

[0003] In one aspect, an image encoding apparatus includes a circuit and a memory connected to the circuit. In operation, the circuit defines a first partition and a second partition having a non-rectangular shape in a current block of an image such that the first partition and the second partition overlap. When encoding the first partition and the second partition, the circuit uses only a single prediction motion vector. When encoding the first partition and the second partition, the circuit derives a first single prediction motion vector from a plurality of dual prediction motion vector candidates of the first partition and the second partition, generates a first predicted image of the first partition using the first single prediction motion vector, derives a second single prediction motion vector from the plurality of dual prediction motion vector candidates, generates a second predicted image of the second partition using the second single prediction motion vector, and generates a predicted image of the current block by combining the first predicted image and the second predicted image. The plurality of dual prediction motion vector candidates are included in a merge list.

[0004] Some implementations of the embodiments in the present disclosure may improve encoding efficiency, simplify encoding / decoding processing, increase the encoding / decoding processing speed, or efficiently select appropriate components / operations used for encoding and decoding, such as an appropriate filter, block size, motion vector, reference picture, reference block, etc.

[0005] Further advantages and effects in one aspect of the present disclosure will be apparent from the specification and the drawings. Such advantages and / or effects can be obtained by some embodiments and the features described in the specification and the drawings respectively, but not all of them are necessarily provided to obtain one or more advantages and / or effects.

[0006] Note that these general or specific aspects may be implemented by a system, a method, an integrated circuit, a computer program, a recording medium, or any arbitrary combination thereof.

Brief Description of the Drawings

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Best Mode for Carrying Out the Invention

[0008] Hereinafter, embodiments will be specifically described with reference to the drawings. Note that all of the embodiments described below show comprehensive or specific examples. The numerical values, shapes, materials, components, arrangement positions and connection forms of the components, steps, relationships and orders of the steps, etc. shown in the following embodiments are merely examples and are not intended to limit the scope of the claims.

[0009] Hereinafter, embodiments of an encoding device and a decoding device will be described. The embodiments are examples of an encoding device and a decoding device to which the processes and / or configurations described in each aspect of the present disclosure are applicable. The processes and / or configurations can also be implemented in encoding devices and decoding devices different from the embodiments. For example, with respect to the processes and / or configurations applied to the embodiments, any of the following may be implemented, for example.

[0010] (1) Any one of the plurality of components of the encoding device or decoding device of the embodiment described in each aspect of the present disclosure may be replaced or combined with any other component described in any aspect of the present disclosure.

[0011] (2) In the encoding device or decoding device of the embodiment, arbitrary changes such as addition, replacement, and deletion may be made to the functions or processes performed by some of the plurality of components of the encoding device or decoding device. For example, any function or process may be replaced or combined with any other function or process described in any aspect of the present disclosure.

[0012] (3) In the method implemented by the encoding device or decoding device of the embodiment, arbitrary changes such as addition, replacement, and deletion may be made to some of the plurality of processes included in the method. For example, any process in the method may be replaced or combined with any other process described in any aspect of the present disclosure.

[0013] (4) Among some of the components that make up the encoding device or decoding device of the embodiment, some components may be combined with the components described in any of the aspects of the present disclosure, or may be combined with components having a part of the functions described in any of the aspects of the present disclosure, or may be combined with components that perform a part of the processing performed by the components described in each aspect of the present disclosure.

[0014] (5) A component having a part of the functions of the encoding device or decoding device of the embodiment, or a component that performs a part of the processing of the encoding device or decoding device of the embodiment may be combined or replaced with a component described in any of the aspects of the present disclosure, a component having a part of the functions described in any of the aspects of the present disclosure, or a component that performs a part of the processing described in any of the aspects of the present disclosure.

[0015] (6) In the method performed by the encoding device or decoding device of the embodiment, any of the plurality of processes included in the method may be replaced or combined with the processes described in any of the aspects of the present disclosure, or with any similar processes.

[0016] (7) Some of the plurality of processes included in the method performed by the encoding device or decoding device of the embodiment may be combined with the processes described in any of the aspects of the present disclosure.

[0017] (8) The manner of implementing the processes and / or configurations described in each aspect of the present disclosure is not limited to the encoding device or decoding device of the embodiment. For example, the processes and / or configurations may be implemented in a device used for a purpose different from the moving image encoding or moving image decoding disclosed in the embodiment.

[0018] [Encoding Device] First, the encoding device according to the embodiment will be described. FIG. 1 is a block diagram showing the functional configuration of the encoding device 100 according to the embodiment. The encoding device 100 is a moving image encoding device that encodes a moving image in units of blocks.

[0019] As shown in FIG. 1, the encoding device 100 is a device that encodes an image in units of blocks, and includes a division unit 102, a subtraction unit 104, a conversion unit 106, a quantization unit 108, an entropy encoding unit 110, an inverse quantization unit 112, an inverse conversion 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.

[0020] The encoding device 100 is realized by, for example, a general-purpose processor and a memory. In this case, when a software program stored in the memory is executed by the processor, the processor functions as the division unit 102, the subtraction unit 104, the conversion unit 106, the quantization unit 108, the entropy encoding unit 110, the inverse quantization unit 112, the inverse conversion 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. Also, the encoding device 100 may be realized as one or more dedicated electronic circuits corresponding to the division unit 102, the subtraction unit 104, the conversion unit 106, the quantization unit 108, the entropy encoding unit 110, the inverse quantization unit 112, the inverse conversion 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.

[0021] After explaining the overall processing flow of the encoding device 100 below, each component included in the encoding device 100 will be described.

[0022] [Overall Flow of Encoding Process] FIG. 2 is a flowchart showing an example of the overall encoding process by the encoding device 100.

[0023] First, the splitting unit 102 of the encoding device 100 splits each picture included in the input picture, which is a moving picture, into a plurality of blocks of a fixed size (for example, 128×128 pixels) (step Sa_1). Then, the splitting unit 102 selects a splitting pattern (also referred to as a block shape) for the blocks of the fixed size (step Sa_2). That is, the splitting unit 102 further splits the blocks of the fixed size into a plurality of blocks that constitute the selected splitting pattern. Then, for each of the plurality of blocks, the encoding device 100 performs the processing of steps Sa_3 to Sa_9 on the block (that is, the block to be encoded).

[0024] That is, the prediction processing unit, which consists of all or part of the intra prediction unit 124, the inter prediction unit 126, and the prediction control unit 128, generates a prediction signal (also referred to as a prediction block) for the block to be encoded (current block) (step Sa_3).

[0025] Next, the subtraction unit 104 generates the difference between the block to be encoded and the prediction block as a prediction residual (also referred to as a difference block) (step Sa_4).

[0026] Next, the conversion unit 106 and the quantization unit 108 generate a plurality of quantization coefficients by performing conversion and quantization on the difference block (step Sa_5). Note that a block consisting of a plurality of quantization coefficients is also referred to as a coefficient block.

[0027] Next, the entropy encoding unit 110 generates an encoded signal by performing encoding (specifically, entropy encoding) on the coefficient block and the prediction parameters related to the generation of the prediction signal (step Sa_6). Note that the encoded signal is also referred to as an encoded bit stream, a compressed bit stream, or a stream.

[0028] Next, the inverse quantization unit 112 and the inverse conversion unit 114 restore a plurality of prediction residuals (that is, difference blocks) by performing inverse quantization and inverse conversion on the coefficient block (step Sa_7).

[0029] Next, the addition unit 116 reconstructs the current block into a reconstructed image (also referred to as a reconstructed block or a decoded image block) by adding the prediction block to the restored difference block (step Sa_8). Thereby, a reconstructed image is generated.

[0030] When this reconstructed image is generated, the loop filter unit 120 performs filtering on the reconstructed image as necessary (step Sa_9).

[0031] Then, the encoding device 100 determines whether the encoding of the entire picture is completed (step Sa_10). If it is determined that the encoding is not completed (No in step Sa_10), the processing from step Sa_2 is repeatedly executed.

[0032] Note that in the above example, the encoding device 100 selects one splitting pattern for a block of a fixed size and performs encoding of each block according to the selected splitting pattern. However, the encoding of each block may be performed according to each of a plurality of splitting patterns. In this case, the encoding device 100 may evaluate the cost for each of the plurality of splitting patterns, and select, for example, the encoded signal obtained by encoding according to the splitting pattern with the smallest cost as the encoded signal to be output.

[0033] As shown in the figure, the processing of these steps Sa_1 to Sa_10 is sequentially performed by the encoding device 100. Alternatively, a plurality of some of these processes may be performed in parallel, and the order of these processes may be changed, etc.

[0034] [Splitting Unit] The splitting unit 102 splits each picture included in the input moving image into a plurality of blocks and outputs each block to the subtraction unit 104. For example, the splitting unit 102 first splits the picture into blocks of a fixed size (e.g., 128x128). Other fixed block sizes may be adopted. These blocks of fixed size are sometimes called coding tree units (CTUs). Then, the splitting unit 102 splits each of the fixed-size blocks into blocks of variable size (e.g., 64x64 or less) based on, for example, recursive quadtree and / or binary tree block splitting. That is, the splitting unit 102 selects a splitting pattern. These blocks of variable size are sometimes called coding units (CUs), prediction units (PUs), or transform units (TUs). Note that in various processing examples, it is not necessary to distinguish between CUs, PUs, and TUs, and some or all of the blocks in the picture may be processing units for CUs, PUs, and TUs.

[0035] FIG. 3 is a conceptual diagram showing an example of block splitting in the embodiment. In FIG. 3, solid lines represent block boundaries by quadtree block splitting, and dashed lines represent block boundaries by binary tree block splitting.

[0036] Here, the block 10 is a square block of 128x128 pixels (128x128 block). This 128x128 block 10 is first split into four square 64x64 blocks (quadtree block splitting).

[0037] The upper-left 64x64 block is further vertically split into two rectangular 32x64 blocks, and the left 32x64 block is further vertically split into two rectangular 16x64 blocks (binary tree block splitting). As a result, the upper-left 64x64 block is split into two 16x64 blocks 11, 12 and a 32x64 block 13.

[0038] The upper-right 64x64 block is horizontally split into two rectangular 64x32 blocks 14, 15 (binary tree block splitting).

[0039] The lower left 64x64 block is divided into four square 32x32 blocks (quadtree block division). Among the four 32x32 blocks, the upper left block and the lower right block are further divided. The upper left 32x32 block is vertically divided into two rectangular 16x32 blocks, and the right 16x32 block is further horizontally divided into two 16x16 blocks (binary tree block division). The lower right 32x32 block is horizontally divided into two 32x16 blocks (binary tree block division). As a result, the lower left 64x64 block is divided into 16 16x32 blocks 16, two 16x16 blocks 17, 18, two 32x32 blocks 19, 20, and two 32x16 blocks 21, 22.

[0040] The lower right 64x64 block 23 is not divided.

[0041] As described above, in FIG. 3, block 10 is divided into 13 variable-size blocks 11 to 23 based on recursive quadtree and binary tree block division. Such division is sometimes called QTBT (quad-tree plus binary tree) division.

[0042] In addition, in FIG. 3, one block is divided into four or two blocks (quadtree or binary tree block division), but the division is not limited to these. For example, one block may be divided into three blocks (ternary tree block division). Such division including ternary tree block division is sometimes called MBT (multi type tree) division.

[0043] [Picture Composition Slice / Tile] To decode a picture in parallel, the picture may be composed in units of slices or tiles. A picture composed of units of slices or tiles may be composed by the dividing unit 102.

[0044] A slice is a basic encoding unit that constitutes a picture. A picture is composed of, for example, one or more slices. Also, a slice consists of one or more consecutive CTUs (Coding Tree Units).

[0045] Figure 4A is a conceptual diagram showing an example of the composition of a slice. For example, a picture contains 11×8 CTUs and is divided into 4 slices (Slice 1 - 4). Slice 1 consists of 16 CTUs, Slice 2 consists of 21 CTUs, Slice 3 consists of 29 CTUs, and Slice 4 consists of 22 CTUs. Here, each CTU in the picture belongs to one of the slices. The shape of the slice is in the form of dividing the picture horizontally. The boundary of the slice does not have to be at the edge of the screen and can be anywhere among the boundaries of the CTUs within the screen. The processing order (encoding order or decoding order) of the CTUs within a slice is, for example, in raster scan order. Also, a slice contains header information and encoded data. The header information may describe the characteristics of that slice, such as the CTU address at the start of the slice and the slice type.

[0046] A tile is a unit of a rectangular area that constitutes a picture. A number called TileId may be assigned to each tile in raster scan order.

[0047] Figure 4B is a conceptual diagram showing an example of the composition of a tile. For example, a picture contains 11×8 CTUs and is divided into 4 rectangular area tiles (Tile 1 - 4). When tiles are used, the processing order of CTUs is changed compared to when tiles are not used. When tiles are not used, multiple CTUs in the picture are processed in raster scan order. When tiles are used, in each of the multiple tiles, at least one CTU is processed in raster scan order. For example, as shown in Figure 4B, the processing order of the multiple CTUs included in Tile 1 is from the left end of the first row of Tile 1 to the right end of the first row of Tile 1, and then from the left end of the second row of Tile 1 to the right end of the second row of Tile 1.

[0048] Note that one tile may include one or more slices, and one slice may include one or more tiles.

[0049] [Subtraction unit] The subtraction unit 104 receives an input from the division unit 102 and subtracts a predicted signal (predicted sample input from the prediction control unit 128 shown below) from the original signal (original sample) in block units divided by the division unit 102. That is, the subtraction unit 104 calculates the prediction error (also referred to as the residual) of the block to be encoded (hereinafter referred to as the current block). Then, the subtraction unit 104 outputs the calculated prediction error (residual) to the conversion unit 106.

[0050] The original signal is the input signal of the encoding device 100 and is a signal representing the image of each picture constituting the moving image (for example, a luminance signal and two chroma signals). Hereinafter, the signal representing the image may also be referred to as a sample.

[0051] [Conversion unit] The conversion unit 106 converts the prediction error in the spatial domain into conversion coefficients in the frequency domain and outputs the conversion coefficients to the quantization unit 108. Specifically, the conversion unit 106 performs a predetermined discrete cosine transform (DCT) or discrete sine transform (DST) on the prediction error in the spatial domain, for example. The predetermined DCT or DST may be determined in advance.

[0052] Note that the conversion unit 106 may adaptively select a conversion type from a plurality of conversion types and convert the prediction error into conversion coefficients using a conversion basis function corresponding to the selected conversion type. Such a conversion is sometimes called an explicit multiple core transform (EMT) or an adaptive multiple transform (AMT).

[0053] The plurality of transform types include, for example, DCT-II, DCT-V, DCT-VIII, DST-I, and DST-VII. FIG. 5A is a table showing the transform basis functions corresponding to the example transform types. In FIG. 5A, N indicates the number of input pixels. The selection of a transform type from among these plurality of transform types may depend, for example, on the type of prediction (intra prediction and inter prediction), or may depend on the intra prediction mode.

[0054] Information indicating whether to apply such EMT or AMT (for example, called an EMT flag or an AMT flag) and information indicating the selected transform type are usually signaled at the CU level. Note that the signaling of this information does not necessarily have to be limited to the CU level, and may be at other levels (for example, bit sequence level, picture level, slice level, tile level, or CTU level).

[0055] Also, the transform unit 106 may re-transform the transform coefficients (transformation results). Such re-transformation may be called AST (adaptive secondary transform) or NSST (non-separable secondary transform). For example, the transform unit 106 performs re-transformation for each sub-block (for example, 4x4 sub-block) included in the block of transform coefficients corresponding to the intra prediction error. Information indicating whether to apply NSST and information regarding the transform matrix used for NSST are usually signaled at the CU level. Note that the signaling of this information does not necessarily have to be limited to the CU level, and may be at other levels (for example, sequence level, picture level, slice level, tile level, or CTU level).

[0056] A separable transform and a non-separable transform may be applied to the transform unit 106. A separable transform is a method in which multiple transformations are performed separately for each direction by the number of dimensions of the input, and a non-separable transform is a method in which when the input is multi-dimensional, two or more dimensions are regarded as one dimension and transformed together.

[0057] For example, as an example of a non-separable transform, when the input is a 4×4 block, it can be regarded as an array having 16 elements, and a transform process is performed on the array using a 16×16 transform matrix.

[0058] Also, in a further example of a non-separable transform, after regarding a 4×4 input block as an array having 16 elements, a transform (Hypercube Givens Transform) that performs a plurality of Givens rotations on the array may be performed.

[0059] In the transform in the transform unit 106, the type of basis for transformation into the frequency domain can also be switched according to the region within the CU. As an example, there is SVT (Spatially Varying Transform). In SVT, as shown in FIG. 5B, the CU is divided into two equal parts in the horizontal or vertical direction, and transformation into the frequency domain is performed only on one of the regions. The type of transform basis can be set for each region. For example, DST7 and DCT8 are used. In this example, only one of the two regions within the CU is transformed, and the other is not transformed, but both regions may be transformed. Also, the division method can be made more flexible, not limited to just dividing into two equal parts, but also dividing into four equal parts, or separately encoding information indicating the division and signaling it in the same way as CU division. Note that SVT is sometimes also called SBT (Sub-block Transform).

[0060] [Quantization Unit] 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 the quantization parameter (QP) corresponding to the scanned transform coefficients. Then, the quantization unit 108 outputs the quantized transform coefficients (hereinafter referred to as quantization coefficients) of the current block to the entropy encoding unit 110 and the inverse quantization unit 112. The predetermined scanning order may be predefined.

[0061] The predetermined scanning order is the order for quantization / inverse quantization of the conversion coefficients. For example, the predetermined scanning order may be defined in ascending order of frequency (from low frequency to high frequency) or descending order of frequency (from high frequency to low frequency).

[0062] The quantization parameter (QP) is a parameter that defines the quantization step (quantization width). For example, as the value of the quantization parameter increases, the quantization step also increases. That is, as the value of the quantization parameter increases, the quantization error increases.

[0063] Also, a quantization matrix may be used for quantization. For example, several types of quantization matrices may be used corresponding to frequency conversion sizes such as 4x4 and 8x8, prediction modes such as intra prediction and inter prediction, and pixel components such as luminance and chrominance. Note that quantization refers to digitizing the sampled values at predetermined intervals by associating them with predetermined levels, and in this technical field, it may be referred to using other expressions such as rounding, truncating, and scaling, or rounding, truncating, and scaling may be employed. The predetermined intervals and levels may be predefined.

[0064] As methods of using the quantization matrix, there are a method of using the quantization matrix directly set on the encoding device side and a method of using the default quantization matrix (default matrix). On the encoding device side, by directly setting the quantization matrix, a quantization matrix corresponding to the characteristics of the image can be set. However, in this case, there is a disadvantage that the amount of code increases due to the encoding of the quantization matrix.

[0065] On the other hand, there is also a method of quantizing the high-frequency component coefficients and the low-frequency component coefficients in the same way without using the quantization matrix. Note that this method is equivalent to a method of using a quantization matrix (flat matrix) in which all coefficients have the same value.

[0066] The quantization matrix may be specified, for example, by an SPS (Sequence Parameter Set) or a PPS (Picture Parameter Set). The SPS includes parameters used for a sequence, and the PPS includes parameters used for a picture. The SPS and the PPS may simply be called parameter sets.

[0067] [Entropy Encoding Unit] The entropy encoding unit 110 generates an encoded signal (encoded bit stream) based on the quantization coefficients input from the quantization unit 108. Specifically, the entropy encoding unit 110, for example, binarizes the quantization coefficients, arithmetically encodes the binary signal, and outputs a compressed bit stream or sequence.

[0068] [Inverse Quantization Unit] The inverse quantization unit 112 inverse quantizes the quantization coefficients input from the quantization unit 108. Specifically, the inverse quantization unit 112 inverse quantizes the quantization 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. The predetermined scanning order may be determined in advance.

[0069] [Inverse Transform Unit] The inverse transform unit 114 restores the prediction error (residual) by inverse-transforming the transform coefficients input from the inverse quantization unit 112. Specifically, the inverse transform unit 114 performs an inverse transform corresponding to the transform by the transform unit 106 on the transform coefficients to restore the prediction error of the current block. Then, the inverse transform unit 114 outputs the restored prediction error to the addition unit 116.

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

[0071] [Addition Unit] The addition unit 116 reconstructs the current block by adding the prediction error input from the inverse conversion unit 114 and the prediction sample input from the prediction control unit 128. Then, the addition unit 116 outputs the reconstructed block to the block memory 118 and the loop filter unit 120. The reconstructed block may also be called a local decoding block.

[0072] [Block Memory] The block memory 118 is, for example, a storage unit for storing blocks within an encoded target picture (referred to as the current picture) that are referenced in intra prediction. Specifically, the block memory 118 stores the reconstructed block output from the addition unit 116.

[0073] [Frame Memory] The frame memory 122 is, for example, a storage unit for storing reference pictures used in inter prediction, and may also be called a frame buffer. Specifically, the frame memory 122 stores the reconstructed block filtered by the loop filter unit 120.

[0074] [Loop Filter Unit] The loop filter unit 120 applies a loop filter to the block reconstructed by the addition unit 116 and outputs the filtered reconstructed block to the frame memory 122. The loop filter is a filter (in-loop filter) used within the encoding loop, and includes, for example, a deblocking filter (DF or DBF), a sample adaptive offset (SAO), and an adaptive loop filter (ALF).

[0075] In the case of the ALF, a least squares error filter for removing encoding distortion is applied, and for example, for each 2x2 sub-block within the current block, one filter selected from a plurality of filters based on the direction and activity of the local gradient is applied.

[0076] 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 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 the gradient direction value D (e.g., 0 to 2 or 0 to 4) and the 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.

[0077] The gradient direction value D is derived, for example, by comparing gradients in a plurality of directions (e.g., horizontal, vertical, and two diagonal directions). Also, the gradient activity value A is derived, for example, by adding gradients in a plurality of directions and quantizing the addition result.

[0078] Based on the results of such classification, a filter for the sub-block is determined from among a plurality of filters.

[0079] As the shape of the filter used in ALF, for example, a circularly symmetric shape is utilized. FIGS. 6A to 6C are diagrams showing a plurality of examples of the shape of the filter used in ALF. FIG. 6A shows a 5x5 diamond-shaped filter, FIG. 6B shows a 7x7 diamond-shaped filter, and FIG. 6C shows a 9x9 diamond-shaped filter. Information indicating the shape of the filter is usually signaled at the picture level. Note that the signaling of information indicating the shape of the filter is not necessarily limited to the picture level and may be at other levels (e.g., sequence level, slice level, tile level, CTU level, or CU level).

[0080] The on / off of ALF may be determined, for example, at the picture level or CU level. For example, for luminance, it may be determined whether to apply ALF at the CU level, and for color difference, it may be determined whether to apply ALF at the picture level. Information indicating the on / off of ALF is usually signaled at the picture level or CU level. Note that the signaling of information indicating the on / off of ALF does not have to be limited to the picture level or CU level, and it may be at other levels (for example, sequence level, slice level, tile level, or CTU level).

[0081] A set of coefficients for a plurality of selectable filters (for example, filters up to 15 or 25) is usually signaled at the picture level. Note that the signaling of the coefficient set does not have to be limited to the picture level, and it may be at other levels (for example, sequence level, slice level, tile level, CTU level, CU level, or sub-block level).

[0082] [Loop Filter Section > Deblocking Filter] In the deblocking filter, the loop filter section 120 reduces the distortion generated at the block boundary by performing filter processing on the block boundary of the reconstructed image.

[0083] FIG. 7 is a block diagram showing an example of a detailed configuration of the loop filter section 120 that functions as a deblocking filter.

[0084] The loop filter section 120 includes a boundary determination section 1201, a filter determination section 1203, a filter processing section 1205, a processing determination section 1208, a filter characteristic determination section 1207, and switches 1202, 1204, and 1206.

[0085] The boundary determination section 1201 determines whether a pixel to be deblocked filtered (i.e., a target pixel) exists near the block boundary. Then, the boundary determination section 1201 outputs the determination result to the switches 1202 and the processing determination section 1208.

[0086] When the boundary determination unit 1201 determines that the target pixel exists near the block boundary, the switch 1202 outputs the image before the filter process to the switch 1204. Conversely, when the boundary determination unit 1201 determines that the target pixel does not exist near the block boundary, the switch 1202 outputs the image before the filter process to the switch 1206.

[0087] The filter determination unit 1203 determines whether to perform deblocking filter processing on the target pixel based on the pixel values of at least one neighboring pixel around the target pixel. Then, the filter determination unit 1203 outputs the determination result to the switch 1204 and the process determination unit 1208.

[0088] When it is determined by the filter determination unit 1203 that deblocking filter processing is to be performed on the target pixel, the switch 1204 outputs the image before the filter process obtained via the switch 1202 to the filter processing unit 1205. Conversely, when it is determined by the filter determination unit 1203 that deblocking filter processing is not to be performed on the target pixel, the switch 1204 outputs the image before the filter process obtained via the switch 1202 to the switch 1206.

[0089] When the filter processing unit 1205 obtains the image before the filter process via the switches 1202 and 1204, it performs deblocking filter processing having the filter characteristics determined by the filter characteristic determination unit 1207 on the target pixel. Then, the filter processing unit 1205 outputs the pixel after the filter process to the switch 1206.

[0090] The switch 1206 selectively outputs the pixel that has not been subjected to deblocking filter processing and the pixel that has been subjected to deblocking filter processing by the filter processing unit 1205 according to the control by the process determination unit 1208.

[0091] The processing determination unit 1208 controls the switch 1206 based on the determination results of the boundary determination unit 1201 and the filter determination unit 1203 respectively. That is, when the processing determination unit 1208 determines that the target pixel exists near the block boundary by the boundary determination unit 1201 and determines that the target pixel is to be subjected to deblocking filter processing by the filter determination unit 1203, the processed pixel after the deblocking filter processing is output from the switch 1206. Further, in cases other than the above, the processing determination unit 1208 outputs the pixel that has not been subjected to deblocking filter processing from the switch 1206. By repeatedly outputting such pixels, the image after the filter processing is output from the switch 1206.

[0092] FIG. 8 is a conceptual diagram showing an example of a deblocking filter having filter characteristics symmetric with respect to a block boundary.

[0093] In the deblocking filter processing, for example, using the pixel value and the quantization parameter, one of two deblocking filters having different characteristics, that is, a strong filter and a weak filter, is selected. In the strong filter, as shown in FIG. 8, when there are pixels p0 to p2 and pixels q0 to q2 sandwiching the block boundary, the pixel values of the pixels q0 to q2 are changed to pixel values q'0 to q'2, for example, by performing the operations shown in the following equations.

[0094] q’0=(p1 + 2×p0 + 2×q0 + 2×q1 + q2 + 4) / 8 q’1=(p0 + q0 + q1 + q2 + 2) / 4 q’2=(p0 + q0 + q1 + 3×q2 + 2×q3 + 4) / 8

[0095] In the above formulas, p0 to p2 and q0 to q2 are the respective pixel values of pixels p0 to p2 and pixels q0 to q2. Also, q3 is the pixel value of pixel q3 adjacent to pixel q2 on the side opposite to the block boundary. Further, in the right side of each of the above formulas, the coefficient multiplied by the pixel value of each pixel used in the deblocking filter process is the filter coefficient.

[0096] Furthermore, in the deblocking filter process, clip processing may be performed so that the pixel value after the operation is not set to exceed the threshold value. In this clip processing, the pixel value after the operation by the above formula is clipped to "operation target pixel value ± 2 × threshold value" using the threshold value determined from the quantization parameter. Thereby, excessive smoothing can be prevented.

[0097] FIG. 9 is a conceptual diagram for explaining a block boundary where deblocking filter processing is performed. FIG. 10 is a conceptual diagram showing an example of the Bs value.

[0098] The block boundary where deblocking filter processing is performed is, for example, the boundary of a PU (Prediction Unit) or TU (Transform Unit) of an 8×8 pixel block as shown in FIG. 9. The deblocking filter processing can be performed in units of 4 rows or 4 columns. First, for blocks P and Q shown in FIG. 9, a Bs (Boundary Strength) value is determined as shown in FIG. 10.

[0099] According to the Bs value in FIG. 10, even for block boundaries belonging to the same image, it is determined whether to perform deblocking filter processing with different strengths. The deblocking filter processing for the chrominance signal is performed when the Bs value is 2. The deblocking filter processing for the luminance signal is performed when the Bs value is 1 or more and a predetermined condition is satisfied. The predetermined condition may be determined in advance. Note that the determination condition of the Bs value is not limited to that shown in FIG. 10, and may be determined based on other parameters.

[0100] [Prediction Processing Unit (Intra Prediction Unit, Inter Prediction Unit, Prediction Control Unit)] FIG. 11 is a flowchart showing an example of the processing performed by the prediction processing unit of the encoding apparatus 100. Note that the prediction processing unit includes all or some of the components of the intra prediction unit 124, the inter prediction unit 126, and the prediction control unit 128.

[0101] The prediction processing unit generates a predicted image of the current block (step Sb_1). This predicted image is also referred to as a prediction signal or a prediction block. Note that the prediction signal includes, for example, an intra prediction signal or an inter prediction signal. Specifically, the prediction processing unit generates a predicted image of the current block using the reconstructed image that has already been obtained by performing generation of a prediction block, generation of a difference block, generation of a coefficient block, restoration of the difference block, and generation of a decoded image block.

[0102] The reconstructed image may be, for example, an image of a reference picture, or an image of an encoded block in the current picture that is the picture including the current block. The encoded block in the current picture is, for example, an adjacent block of the current block.

[0103] FIG. 12 is a flowchart showing another example of the processing performed by the prediction processing unit of the encoding apparatus 100.

[0104] The prediction processing unit generates a predicted image in a first method (step Sc_1a), generates a predicted image in a second method (step Sc_1b), and generates a predicted image in a third method (step Sc_1c). The first method, the second method, and the third method are different methods for generating a predicted image, and may be, for example, an inter prediction method, an intra prediction method, and other prediction methods, respectively. In these prediction methods, the above-described reconstructed image may be used.

[0105] Next, the prediction processing unit selects any one of the plurality of predicted images generated in steps Sc_1a, Sc_1b, and Sc_1c (step Sc_2). The selection of this predicted image, that is, the selection of the method or mode for obtaining the final predicted image, may be performed based on calculating the cost for each generated predicted image and based on that cost. Alternatively, the selection of the predicted image may be performed based on the parameters used in the encoding process. The encoding device 100 may signal information for specifying the selected predicted image, method, or mode in an encoded signal (also referred to as an encoded bit stream). The information may be, for example, a flag. Thereby, the decoding device can generate a predicted image according to the method or mode selected in the encoding device 100 based on that information. In the example shown in FIG. 12, after the prediction processing unit generates predicted images for each method, it selects any one of the predicted images. However, the prediction processing unit may select a method or mode based on the parameters used in the above-described encoding process before generating those predicted images and generate a predicted image according to the method or mode.

[0106] For example, the first method and the second method are intra prediction and inter prediction, respectively, and the prediction processing unit may select the final predicted image for the current block from the predicted images generated according to these prediction methods.

[0107] FIG. 13 is a flowchart showing another example of the processing performed by the prediction processing unit of the encoding device 100.

[0108] First, the prediction processing unit generates a predicted image by intra prediction (step Sd_1a) and generates a predicted image by inter prediction (step Sd_1b). Note that the predicted image generated by intra prediction is also referred to as an intra predicted image, and the predicted image generated by inter prediction is also referred to as an inter predicted image.

[0109] Next, the prediction processing unit evaluates each of the intra-predicted image and the inter-predicted image (step Sd_2). A cost may be used for this evaluation. That is, the prediction processing unit calculates the cost C for each of the intra-predicted image and the inter-predicted image. This cost C can be calculated by an equation of an R-D optimization model, for example, C = D + λ × R. In this equation, D is the encoding distortion of the predicted image, which is represented by, for example, the sum of absolute differences between the pixel values of the current block and the pixel values of the predicted image. Also, R is the amount of generated code of the predicted image, specifically, the amount of code required for encoding motion information or the like for generating the predicted image. Also, λ is, for example, the Lagrange multiplier.

[0110] Then, the prediction processing unit selects, as the final predicted image of the current block, the predicted image for which the smallest cost C has been calculated from the intra-predicted image and the inter-predicted image (step Sd_3). That is, the prediction method or mode for generating the predicted image of the current block is selected.

[0111] [Intra Prediction Unit] The intra prediction unit 124 generates a prediction signal (intra prediction signal) by performing intra prediction (also referred to as in-picture prediction) of the current block with reference to the 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 (for example, luminance values, chrominance difference values) of blocks adjacent to the current block, and outputs the intra prediction signal to the prediction control unit 128.

[0112] For example, the intra prediction unit 124 performs intra prediction using one of a plurality of prescribed intra prediction modes. The plurality of intra prediction modes usually include one or more non-directional prediction modes and a plurality of directional prediction modes. The plurality of prescribed modes may be prescribed in advance.

[0113] The non-directional prediction modes of 1 or more include, for example, the Planar prediction mode and the DC prediction mode defined in the H.265 / HEVC standard.

[0114] The plurality of directional prediction modes include, for example, the 33-direction prediction mode defined in the H.265 / HEVC standard. Note that the plurality of directional prediction modes may further include a 32-direction prediction mode (a total of 65 directional prediction modes) in addition to the 33 directions. FIG. 14 is a conceptual diagram showing all 67 intra prediction modes (2 non-directional prediction modes and 65 directional prediction modes) that can be used 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 (the 2 non-directional prediction modes are not shown in FIG. 14).

[0115] In various processing examples, in the intra prediction of a chrominance block, a luminance block may be referred to. That is, based on the luminance component of the current block, the chrominance component of the current block may be predicted. Such intra prediction is sometimes called CCLM (cross-component linear model) prediction. An intra prediction mode of a chrominance block that refers to such a luminance block (for example, called the CCLM mode) may be added as one of the intra prediction modes of the chrominance block.

[0116] The intra prediction unit 124 may correct the pixel value after intra prediction based on the gradient of the reference pixels in the horizontal / vertical direction. Such intra prediction with such correction is sometimes called PDPC (position dependent intra prediction combination). Information indicating the presence or absence of application of PDPC (for example, called a PDPC flag) is usually signaled at the CU level. Note that the signaling of this information is not necessarily limited to the CU level and may be at other levels (for example, sequence level, picture level, slice level, tile level or CTU level).

[0117] [Inter Prediction Unit] The inter prediction unit 126 generates a prediction signal (inter prediction signal) by performing inter prediction (also referred to as inter - frame prediction) of a current block with reference to a reference picture stored in the frame memory 122 that is different from the current picture. The inter prediction is performed in units of a current block or a current sub - block (e.g., a 4x4 block) within the current block. For example, the inter prediction unit 126 performs motion estimation within the reference picture for the current block or the current sub - block, and finds the reference block or sub - block that most closely matches the current block or the current sub - block. Then, the inter prediction unit 126 acquires motion information (e.g., a motion vector) that compensates for the motion or change from the reference block or sub - block to the current block or sub - block. The inter prediction unit 126 performs motion compensation (or motion prediction) based on the motion information, and generates an inter prediction signal for the current block or sub - block. The inter prediction unit 126 outputs the generated inter prediction signal to the prediction control unit 128.

[0118] The motion information used for motion compensation may be signaled as an inter prediction signal in various forms. For example, a motion vector may be signaled. As another example, the difference between a motion vector and a motion vector predictor may be signaled.

[0119] [Basic Flow of Inter Prediction] FIG. 15 is a flowchart showing an example of the basic flow of inter prediction.

[0120] The inter prediction unit 126 first generates a predicted image (steps Se_1 to Se_3). Next, the subtraction unit 104 generates the difference between the current block and the predicted image as a prediction residual (step Se_4).

[0121] Here, in generating the prediction image, the inter prediction unit 126 generates the prediction image by determining the motion vector (MV) of the current block (steps Se_1 and Se_2) and performing motion compensation (step Se_3). Also, in determining the MV, the inter prediction unit 126 determines the MV by selecting candidate motion vectors (candidate MVs) (step Se_1) and deriving the MV (step Se_2). The selection of candidate MVs is performed, for example, by selecting at least one candidate MV from a candidate MV list. Also, in deriving the MV, the inter prediction unit 126 may determine the selected at least one candidate MV as the MV of the current block by further selecting at least one candidate MV from the at least one candidate MV. Alternatively, the inter prediction unit 126 may determine the MV of the current block by searching for the region of the reference picture indicated by the candidate MV for each of the selected at least one candidate MVs. Note that searching for the region of this reference picture may be referred to as motion estimation.

[0122] Also, in the above example, steps Se_1 to Se_3 are performed by the inter prediction unit 126, but processing such as step Se_1 or step Se_2 may be performed by other components included in the encoding device 100.

[0123] [Flow of Derivation of Motion Vector] FIG. 16 is a flowchart showing an example of motion vector derivation.

[0124] The inter prediction unit 126 derives the MV of the current block in a mode of encoding motion information (e.g., MV). In this case, for example, the motion information is encoded as a prediction parameter and signaled. That is, the encoded motion information is included in the encoded signal (also referred to as an encoded bitstream).

[0125] Alternatively, the inter prediction unit 126 derives an MV in a mode that does not encode motion information. In this case, the motion information is not included in the encoded signal.

[0126] Here, the modes of MV derivation may include, for example, the normal inter mode, merge mode, FRUC mode, and affine mode, which will be described later. Among these modes, the modes that encode motion information include the normal inter mode, merge mode, and affine mode (specifically, affine inter mode and affine merge mode). Note that the motion information may include not only the MV but also the predicted motion vector selection information, which will be described later. Also, the modes that do not encode motion information include the FRUC mode. The inter prediction unit 126 selects a mode for deriving the MV of the current block from these multiple modes and derives the MV of the current block using the selected mode.

[0127] FIG. 17 is a flowchart showing another example of motion vector derivation.

[0128] The inter prediction unit 126 derives the MV of the current block in a mode that encodes the differential MV. In this case, for example, the differential MV is encoded as a prediction parameter and signaled. That is, the encoded differential MV is included in the encoded signal. This differential MV is the difference between the MV of the current block and its predicted MV.

[0129] Alternatively, the inter prediction unit 126 derives an MV in a mode that does not encode the differential MV. In this case, the encoded differential MV is not included in the encoded signal.

[0130] Here, as described above, the modes for deriving the MV include the normal inter, merge mode, FRUC mode, and affine mode, etc., which will be described later. Among these modes, the modes for encoding the differential MV include the normal inter mode and the affine mode (specifically, the affine inter mode), etc. Also, the modes for not encoding the differential MV include the FRUC mode, the merge mode, and the affine mode (specifically, the affine merge mode), etc. The inter prediction unit 126 selects a mode for deriving the MV of the current block from these multiple modes, and derives the MV of the current block using the selected mode.

[0131] [Flow of Derivation of Motion Vector] FIG. 18 is a flowchart showing another example of the motion vector derivation. There are multiple modes for the MV derivation mode, that is, the inter prediction mode, which can be roughly divided into a mode for encoding the differential MV and a mode for not encoding the differential motion vector. The modes for not encoding the differential MV include the merge mode, the FRUC mode, and the affine mode (specifically, the affine merge mode). The details of these modes will be described later. Briefly, the merge mode is a mode for deriving the MV of the current block by selecting a motion vector from the surrounding encoded blocks, and the FRUC mode is a mode for deriving the MV of the current block by performing a search between the encoded regions. Also, the affine mode is a mode for deriving the motion vector of each of the multiple sub-blocks constituting the current block as the MV of the current block assuming an affine transformation.

[0132] Specifically, as shown in the figure, when the inter-prediction mode information indicates 0 (0 in Sf_1), the inter-prediction unit 126 derives a motion vector by the merge mode (Sf_2). Also, when the inter-prediction mode information indicates 1 (1 in Sf_1), the inter-prediction unit 126 derives a motion vector by the FRUC mode (Sf_3). Further, when the inter-prediction mode information indicates 2 (2 in Sf_1), the inter-prediction unit 126 derives a motion vector by the affine mode (specifically, the affine merge mode) (Sf_4). Also, when the inter-prediction mode information indicates 3 (3 in Sf_1), the inter-prediction unit 126 derives a motion vector by the mode that encodes the differential MV (for example, the normal inter mode) (Sf_5).

[0133] [MV Derivation > Normal Inter Mode] The normal inter mode is an inter-prediction mode that derives the MV of the current block based on a block similar to the image of the current block from the area of the reference picture indicated by the candidate MV. Also, in this normal inter mode, the differential MV is encoded.

[0134] FIG. 19 is a flowchart showing an example of inter-prediction by the normal inter mode.

[0135] The inter-prediction unit 126 first obtains a plurality of candidate MVs for the current block based on information such as the MVs of a plurality of encoded blocks temporally or spatially around the current block (step Sg_1). That is, the inter-prediction unit 126 creates a candidate MV list.

[0136] Next, the inter-prediction unit 126 extracts each of N (N is an integer of 2 or more) candidate MVs from the plurality of candidate MVs obtained in step Sg_1 as a prediction motion vector candidate (also referred to as a prediction MV candidate) according to a predetermined priority order (step Sg_2). Note that the priority order may be determined in advance for each of the N candidate MVs.

[0137] Next, the inter prediction unit 126 selects one candidate prediction motion vector from the N candidate prediction motion vectors as the prediction motion vector (also referred to as the prediction MV) of the current block (step Sg_3). At this time, the inter prediction unit 126 encodes prediction motion vector selection information for identifying the selected prediction motion vector into the stream. Note that the stream is the encoded signal or encoded bit stream described above.

[0138] Next, the inter prediction unit 126 refers to the encoded reference picture and derives the MV of the current block (step Sg_4). At this time, the inter prediction unit 126 further encodes the difference value between the derived MV and the prediction motion vector as the differential MV into the stream. Note that the encoded reference picture is a picture composed of a plurality of blocks reconstructed after encoding.

[0139] Finally, the inter prediction unit 126 generates a predicted image of the current block by performing motion compensation on the current block using the derived MV and the encoded reference picture (step Sg_5). Note that the predicted image is the inter prediction signal described above.

[0140] Also, information indicating the inter prediction mode (normal inter mode in the above example) used for generating the predicted image included in the encoded signal is encoded as, for example, prediction parameters.

[0141] Note that the candidate MV list may be used in common with lists used for other modes. Also, the processing related to the candidate MV list may be applied to the processing related to the lists used for other modes. The processing related to this candidate MV list is, for example, extraction or selection of candidate MVs from the candidate MV list, rearrangement of candidate MVs, or deletion of candidate MVs.

[0142] [MV Derivation > Merge Mode] The merge mode is an inter prediction mode that derives an MV by selecting a candidate MV from a candidate MV list as the MV of the current block.

[0143] FIG. 20 is a flowchart showing an example of inter prediction by the merge mode.

[0144] The inter prediction unit 126 first obtains a plurality of candidate MVs for the current block based on information such as the MVs of a plurality of encoded blocks temporally or spatially around the current block (step Sh_1). That is, the inter prediction unit 126 creates a candidate MV list.

[0145] Next, the inter prediction unit 126 derives the MV of the current block by selecting one candidate MV from the plurality of candidate MVs obtained in step Sh_1 (step Sh_2). At this time, the inter prediction unit 126 encodes the MV selection information for identifying the selected candidate MV into the stream.

[0146] Finally, the inter prediction unit 126 generates a predicted image of the current block by performing motion compensation on the current block using the derived MV and the encoded reference picture (step Sh_3).

[0147] Also, information indicating the inter prediction mode (merge mode in the above example) used for generating the predicted image, which is included in the encoded signal, is encoded as, for example, prediction parameters.

[0148] FIG. 21 is a conceptual diagram for explaining an example of the motion vector derivation process of the current picture by the merge mode.

[0149] First, a prediction MV list in which candidates for the predicted MV are registered is generated. As candidates for the predicted MV, there are a spatial adjacent prediction MV which is the MV of a plurality of encoded blocks spatially adjacent to the target block, a temporal adjacent prediction MV which is the MV of a neighboring block obtained by projecting the position of the target block in the encoded reference picture, a combined prediction MV which is an MV generated by combining the MV values of the spatial adjacent prediction MV and the temporal adjacent prediction MV, a zero prediction MV which is an MV with a value of zero, and the like.

[0150] Next, one predicted MV is selected from among the plurality of predicted MVs registered in the prediction MV list, and is determined as the MV of the target block.

[0151] Furthermore, in the variable length coding unit, a merge_idx which is a signal indicating which predicted MV is selected is described in the stream and coded.

[0152] Note that the predicted MVs registered in the prediction MV list described in FIG. 21 are merely examples, and may have a number different from the number in the figure, may have a configuration that does not include some of the types of predicted MVs in the figure, or may have a configuration in which predicted MVs other than the types of predicted MVs in the figure are added.

[0153] The final MV may be determined by performing a DMVR (decoder motion vector refinement) process described later using the MV of the target block derived in the merge mode.

[0154] Note that the candidates for the predicted MV are the above-described candidate MVs, the prediction MV list is the above-described candidate MV list. Also, the candidate MV list may be referred to as a candidate list. Also, merge_idx is MV selection information.

[0155] [MV Derivation > FRUC Mode] Motion information may be derived on the decoder side without being signaled from the encoder side. Note that, as described above, the merge mode defined in the H.265 / HEVC standard may be used. Also, for example, motion information may be derived by performing motion search on the decoder side. In the embodiment, on the decoder side, motion search is performed without using the pixel values of the current block.

[0156] Here, a mode for performing motion search on the decoder side will be described. This mode for performing motion search on the decoder side may be called the PMMVD (pattern matched motion vector derivation) mode or the FRUC (frame rate up-conversion) mode.

[0157] An example of the FRUC process is shown in Fig. 22 in the form of a flowchart. First, with reference to the motion vectors of the encoded blocks that are spatially or temporally adjacent to the current block, a list of a plurality of candidates each having a predicted motion vector (MV) (i.e., a candidate MV list, which may be common with the merge list) is generated (step Si_1). Next, the best candidate MV is selected from among the plurality of candidate MVs registered in the candidate MV list (step Si_2). For example, an evaluation value of each candidate MV included in the candidate MV list is calculated, and one candidate MV is selected based on the evaluation value. Then, based on the motion vector of the selected candidate, a motion vector for the current block is derived (step Si_4). Specifically, for example, the motion vector of the selected candidate (the best candidate MV) is directly derived as the motion vector for the current block. Also, for example, in the peripheral region of the position in the reference picture corresponding to the motion vector of the selected candidate, by performing pattern matching, a motion vector for the current block may be derived. That is, for the region around the best candidate MV, search using pattern matching and evaluation value in the reference picture is performed, and if there is an MV with a better evaluation value, the best candidate MV is updated to the MV, and it may be used as the final MV of the current block. It is also possible to adopt a configuration in which the process of updating to an MV having a better evaluation value is not performed.

[0158] Finally, the inter prediction unit 126 generates a predicted image of the current block by performing motion compensation on the current block using the derived MV and the encoded reference picture (step Si_5).

[0159] When processing is performed in units of sub-blocks, the same processing may be applied.

[0160] The evaluation value may be calculated by various methods. For example, the reconstructed image of the region in the reference picture corresponding to the motion vector is compared with the reconstructed image of a predetermined region (the region may be, for example, the region of another reference picture or the region of an adjacent block of the current picture as shown below). The predetermined region may be determined in advance.

[0161] Then, the difference between the pixel values of the two reconstructed images may be calculated and used as the evaluation value of the motion vector. Note that, in addition to the difference value, other information may be used to calculate the evaluation value.

[0162] Next, an example of pattern matching will be described in detail. First, one candidate MV included in the candidate MV list (for example, the merge list) is selected as the start point of the search by pattern matching. For example, as the pattern matching, the first pattern matching or the second pattern matching may be used. The first pattern matching and the second pattern matching may be called bilateral matching and template matching, respectively.

[0163] [MV Derivation > FRUC > Bilateral Matching] 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, as the predetermined region for calculating the evaluation value of the above-described candidate, the region in another reference picture along the motion trajectory of the current block is used. The predetermined region may be determined in advance.

[0164] FIG. 23 is a conceptual diagram for explaining an example of first pattern matching (bilateral matching) between two blocks in two reference pictures along a motion trajectory. As shown in FIG. 23, in the first pattern matching, two motion vectors (MV0, MV1) are derived by searching for the most matching pair among pairs of two blocks in two different reference pictures (Ref0, Ref1) that are two blocks along the motion trajectory of the current block (Cur block). Specifically, for the current block, the difference between the reconstructed image at the specified position in the first encoded reference picture (Ref0) specified by the candidate MV and the reconstructed image at the specified position in the second encoded reference picture (Ref1) specified by the symmetric MV obtained by scaling the candidate MV by the display time interval is derived, and an evaluation value is calculated using the obtained difference value. It is possible to select the candidate MV with the best evaluation value among a plurality of candidate MVs as the final MV, which can bring good results.

[0165] Under the assumption of a continuous motion trajectory, the motion vectors (MV0, MV1) indicating the 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, when the current picture is temporally located between the two reference pictures and the temporal distances from the current picture to the two reference pictures are equal, in the first pattern matching, mirror-symmetric bidirectional motion vectors are derived.

[0166] [MV Derivation > FRUC > Template Matching] In the second pattern matching (template 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., the 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 the predetermined region for calculating the evaluation value of the above-described candidate.

[0167] FIG. 24 is a conceptual 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. 24, in the second pattern matching, the motion vector of the current block is derived by searching for the block that most matches the block adjacent to the current block (Cur block) within the current picture (Cur Pic) in the reference picture (Ref0). Specifically, for the current block, the difference between the reconstructed image of the coded region of both or either of the left adjacent and upper adjacent blocks and the reconstructed image at the equivalent position in the coded reference picture (Ref0) specified by the candidate MV is derived, an evaluation value is calculated using the obtained difference value, and it is possible to select the candidate MV having the best evaluation value among a plurality of candidate MVs as the best candidate MV.

[0168] Information indicating whether or not to apply such a FRUC mode (for example, called a FRUC flag) may be signaled at the CU level. Also, when the FRUC mode is applied (for example, when the FRUC flag is true), information indicating the applicable pattern matching method (first pattern matching or second pattern matching) may be signaled at the CU level. Note that the signaling of this information does not have to be limited to the CU level and may be at other levels (for example, sequence level, picture level, slice level, tile level, CTU level, or sub-block level).

[0169] [MV Derivation > Affine Mode] Next, the affine mode for deriving a motion vector in sub-block units based on the motion vectors of a plurality of adjacent blocks will be described. This mode may be called an affine motion compensation prediction mode.

[0170] FIG. 25A is a conceptual diagram for explaining an example of deriving a motion vector for each sub-block based on motion vectors of a plurality of adjacent blocks. In FIG. 25A, a current block includes 16 4x4 sub-blocks. Here, based on the motion vectors of adjacent blocks, a motion vector v0 of the upper left control point of the current block is derived. Similarly, based on the motion vectors of adjacent sub-blocks, a motion vector v1 of the upper right control point of the current block is derived. Then, the two motion vectors v0 and v1 may be projected by the following equation (1A), and the motion vectors (v x , v y ) of each sub-block within the current block may be derived.

[0171] [Equation]

[0172] Here, x and y indicate the horizontal position and vertical position of the sub-block, respectively, and w indicates a predetermined weight coefficient. The predetermined weight coefficient may be determined in advance.

[0173] Information indicating such an affine mode (for example, called an affine flag) may be signaled at the CU level. Note that the signaling of the information indicating this affine mode is not necessarily limited to the CU level and may be at other levels (for example, sequence level, picture level, slice level, tile level, CTU level, or sub-block level).

[0174] Also, such an affine mode may include several modes in which the methods for deriving the motion vectors of the upper left and upper right control points are different. For example, the affine mode includes two modes: an affine inter (also called affine normal inter) mode and an affine merge mode.

[0175] [MV Derivation > Affine Mode] FIG. 25B is a conceptual diagram for explaining an example of deriving motion vectors of sub - blocks in affine mode having three control points. In FIG. 25B, the current block includes 16 4x4 sub - blocks. Here, based on the motion vectors of adjacent blocks, the motion vector v0 of the upper - left control point of the current block is derived, and similarly, based on the motion vectors of adjacent blocks, the motion vector v1 of the upper - right control point of the current block and the motion vector v2 of the lower - left control point of the current block are derived. Then, the three motion vectors v0, v1, and v2 may be projected by the following formula (1B), and the motion vectors (v x ,v y ) of each sub - block within the current block may be derived.

[0176] [Number]

[0177] Here, x and y indicate the horizontal position and the vertical position of the sub - block center, respectively, w indicates the width of the current block, and h indicates the height of the current block.

[0178] The affine modes with different numbers of control points (for example, two and three) may be switched and signaled at the CU level. Note that the information indicating the number of control points of the affine mode used at the CU level may be signaled at other levels (for example, sequence level, picture level, slice level, tile level, CTU level, or sub - block level).

[0179] Also, in such an affine mode having three control points, it may include several modes in which the methods of deriving the motion vectors of the upper - left, upper - right, and lower - left control points are different. For example, the affine mode includes two modes: the affine inter (also called affine normal inter) mode and the affine merge mode.

[0180] [MV Derivation > Affine Merge Mode] FIG. 26A, FIG. 26B, and FIG. 26C are conceptual diagrams for explaining the affine merge mode.

[0181] In the affine merge mode, as shown in FIG. 26A, for example, among the encoded blocks A (left), B (upper), C (upper right), D (lower left), and E (upper left) adjacent to the current block, a plurality of motion vectors corresponding to the blocks encoded in the affine mode are used. Based on these motion vectors, the predicted motion vectors of the respective control points of the current block are calculated. Specifically, these blocks are inspected in the order of encoded block A (left), block B (upper), block C (upper right), block D (lower left), and block E (upper left), and the first valid block encoded in the affine mode is identified. Based on the plurality of motion vectors corresponding to the identified block, the predicted motion vectors of the control points of the current block are calculated.

[0182] For example, as shown in FIG. 26B, when the block A adjacent to the left of the current block is encoded in the affine mode having two control points, the motion vectors v3 and v4 projected onto the upper left corner and upper right corner positions of the encoded block including block A are derived. Then, from the derived motion vectors v3 and v4, the predicted motion vector v0 of the control point at the upper left corner of the current block and the predicted motion vector v1 of the control point at the upper right corner are calculated.

[0183] For example, as shown in FIG. 26C, when the block A adjacent to the left of the current block is encoded in the affine mode having three control points, the motion vectors v3, v4, and v5 projected onto the upper left corner, upper right corner, and lower left corner positions of the encoded block including block A are derived. Then, from the derived motion vectors v3, v4, and v5, the predicted motion vector v0 of the control point at the upper left corner of the current block, the predicted motion vector v1 of the control point at the upper right corner, and the predicted motion vector v2 of the control point at the lower left corner are calculated.

[0184] Note that this predicted motion vector derivation method may be used to derive each predicted motion vector of the control points of the current block in step Sj_1 of FIG. 29 described later.

[0185] FIG. 27 is a flowchart showing an example of the affine merge mode.

[0186] In the affine merge mode, as shown in the figure, first, the inter prediction unit 126 derives each predicted MV of the control points of the current block (step Sk_1). As shown in FIG. 25A, the control points are the upper left and upper right points of the current block, or as shown in FIG. 25B, the upper left, upper right, and lower left points of the current block.

[0187] That is, as shown in FIG. 26A, the inter prediction unit 126 inspects these blocks in the order of the encoded block A (left), block B (upper), block C (upper right), block D (lower left), and block E (upper left), and identifies the first valid block encoded in the affine mode.

[0188] When block A is identified and block A has two control points, as shown in FIG. 26B, the inter prediction unit 126 calculates the motion vector v0 of the control point at the upper left corner of the current block and the motion vector v1 of the control point at the upper right corner from the motion vectors v3 and v4 at the upper left and upper right corners of the encoded block including block A. For example, the inter prediction unit 126 projects the motion vectors v3 and v4 at the upper left and upper right corners of the encoded block onto the current block to calculate the predicted motion vector v0 of the control point at the upper left corner of the current block and the predicted motion vector v1 of the control point at the upper right corner.

[0189] Alternatively, when block A is identified and block A has three control points, as shown in FIG. 26C, the inter prediction unit 126 calculates the motion vectors v0, v1, and v2 of the control points at the upper left corner, upper right corner, and lower left corner of the current block from the motion vectors v3, v4, and v5 at the upper left corner, upper right corner, and lower left corner of the encoded block including block A. For example, the inter prediction unit 126 projects the motion vectors v3, v4, and v5 at the upper left corner, upper right corner, and lower left corner of the encoded block onto the current block to calculate the predicted motion vector v0 of the control point at the upper left corner of the current block, the predicted motion vector v1 of the control point at the upper right corner, and the motion vector v2 of the control point at the lower left corner.

[0190] Next, the inter prediction unit 126 performs motion compensation for each of the plurality of sub-blocks included in the current block. That is, the inter prediction unit 126 calculates the motion vector of each of the plurality of sub-blocks as an affine MV using two prediction motion vectors v0 and v1 and the above formula (1A), or three prediction motion vectors v0, v1, and v2 and the above formula (1B) (step Sk_2). Then, the inter prediction unit 126 performs motion compensation for the sub-block using those affine MVs and the encoded reference picture (step Sk_3). As a result, motion compensation is performed on the current block, and a predicted image of the current block is generated.

[0191] [MV Derivation > Affine Inter Mode] FIG. 28A is a conceptual diagram for explaining the affine inter mode having two control points.

[0192] In this affine interpolation mode, as shown in FIG. 28A, a motion vector selected from the motion vectors of the encoded blocks A, B, and C adjacent to the current block is used as the predicted motion vector v0 of the control point at the upper left corner of the current block. Similarly, a motion vector selected from the motion vectors of the encoded blocks D and E adjacent to the current block is used as the predicted motion vector v1 of the control point at the upper right corner of the current block.

[0193] FIG. 28B is a conceptual diagram for explaining the affine interpolation mode having three control points.

[0194] In this affine interpolation mode, as shown in FIG. 28B, a motion vector selected from the motion vectors of the encoded blocks A, B, and C adjacent to the current block is used as the predicted motion vector v0 of the control point at the upper left corner of the current block. Similarly, a motion vector selected from the motion vectors of the encoded blocks D and E adjacent to the current block is used as the predicted motion vector v1 of the control point at the upper right corner of the current block. Further, a motion vector selected from the motion vectors of the encoded blocks F and G adjacent to the current block is used as the predicted motion vector v2 of the control point at the lower left corner of the current block.

[0195] FIG. 29 is a flowchart showing an example of the affine interpolation mode.

[0196] As shown, in the affine interpolation mode, first, the inter prediction unit 126 derives the predicted MVs (v0, v1) or (v0, v1, v2) of each of the two or three control points of the current block (step Sj_1). The control points are the points at the upper left corner, upper right corner, or lower left corner of the current block, as shown in FIG. 25A or FIG. 25B.

[0197] That is, the inter prediction unit 126 derives the predicted motion vectors (v0, v1) or (v0, v1, v2) of the control points of the current block by selecting the motion vector of any one of the encoded blocks near each control point of the current block shown in FIG. 28A or FIG. 28B. At this time, the inter prediction unit 126 encodes the prediction motion vector selection information for identifying the two selected motion vectors into the stream.

[0198] For example, the inter prediction unit 126 determines which block's motion vector to select as the predicted motion vector of the control point from the encoded blocks adjacent to the current block by using cost evaluation or the like, and may describe a flag indicating which predicted motion vector is selected in the bit stream.

[0199] Next, while updating the predicted motion vectors selected or derived in step Sj_1 respectively (step Sj_2), the inter prediction unit 126 performs motion search (steps Sj_3 and Sj_4). That is, the inter prediction unit 126 calculates the motion vectors of the respective sub-blocks corresponding to the updated predicted motion vectors as affine MVs by using the above formula (1A) or formula (1B) (step Sj_3). Then, the inter prediction unit 126 performs motion compensation on each sub-block by using those affine MVs and the encoded reference picture (step Sj_4). As a result, in the motion search loop, the inter prediction unit 126 determines, for example, the predicted motion vector that obtains the smallest cost as the motion vector of the control point (step Sj_5). At this time, the inter prediction unit 126 further encodes the difference value between the determined MV and each predicted motion vector into the stream as the differential MV.

[0200] [[ID=A]] Finally, the inter prediction unit 126 generates a predicted image of the current block by performing motion compensation on the current block by using the determined MV and the encoded reference picture (step Sj_6).

[0201] [MV Derivation > Affine Inter Mode] When switching and signaling affine modes with different numbers of control points (e.g., two and three) at the CU level, the number of control points may be different between the encoded block and the current block. FIGS. 30A and 30B are conceptual diagrams for explaining a method of deriving a predicted vector of control points when the number of control points is different between the encoded block and the current block.

[0202] For example, as shown in FIG. 30A, when the current block has three control points at the upper left corner, upper right corner, and lower left corner, and the block A adjacent to the left of the current block is encoded in an affine mode with two control points, motion vectors v3 and v4 projected onto the upper left corner and upper right corner positions of the encoded block including block A are derived. Then, from the derived motion vectors v3 and v4, a predicted motion vector v0 for the control point at the upper left corner of the current block and a predicted motion vector v1 for the control point at the upper right corner are calculated. Further, from the derived motion vectors v0 and v1, a predicted motion vector v2 for the control point at the lower left corner is calculated.

[0203] For example, as shown in FIG. 30B, when the current block has two control points at the upper left corner and upper right corner, and the block A adjacent to the left of the current block is encoded in an affine mode with three control points, motion vectors v3, v4, and v5 projected onto the upper left corner, upper right corner, and lower left corner positions of the encoded block including block A are derived. Then, from the derived motion vectors v3, v4, and v5, a predicted motion vector v0 for the control point at the upper left corner of the current block and a predicted motion vector v1 for the control point at the upper right corner are calculated.

[0204] This predicted motion vector derivation method may be used to derive each predicted motion vector of the control points of the current block in step Sj_1 of FIG. 29.

[0205] [MV Derivation > DMVR] FIG. 31A is a flowchart showing the relationship between the merge mode and DMVR.

[0206] The inter prediction unit 126 derives the motion vector of the current block in the merge mode (step Sl_1). Next, the inter prediction unit 126 determines whether to perform motion vector search, that is, motion search (step Sl_2). Here, if the inter prediction unit 126 determines not to perform motion search (No in step Sl_2), the motion vector derived in step Sl_1 is determined as the final motion vector for the current block (step Sl_4). That is, in this case, the motion vector of the current block is determined in the merge mode.

[0207] On the other hand, if it is determined to perform motion search in step Sl_1 (Yes in step Sl_2), the inter prediction unit 126 derives the final motion vector for the current block by searching the peripheral area of the reference picture indicated by the motion vector derived in step Sl_1 (step Sl_3). That is, in this case, the motion vector of the current block is determined by DMVR.

[0208] FIG. 31B is a conceptual diagram for explaining an example of the DMVR process for determining the MV.

[0209] First, the optimal MVP set for the current block (for example, in the merge mode) is used as the candidate MV. Then, according to the candidate MV (L0), reference pixels are specified from the first reference picture (L0) which is the encoded picture in the L0 direction. Similarly, according to the candidate MV (L1), reference pixels are specified from the second reference picture (L1) which is the encoded picture in the L1 direction. A template is generated by taking the average of these reference pixels.

[0210] Next, using the template, search the peripheral areas of the candidate MVs of the first reference picture (L0) and the second reference picture (L1) respectively, and determine the MV with the minimum cost as the final MV. Note that the cost value may be calculated using, for example, the difference value between each pixel value of the template and each pixel value of the search area, and the candidate MV value, etc.

[0211] Note that typically, in the encoding device and the decoding device described later, the configurations and operations of the processes described here are basically common.

[0212] Even if it is not the processing example itself described here, any processing may be used as long as it is a processing capable of searching the periphery of the candidate MV and deriving the final MV.

[0213] [Motion Compensation > BIO / OBMC] In motion compensation, there are modes for generating a predicted image and correcting the predicted image. Those modes are, for example, BIO and OBMC described later.

[0214] FIG. 32 is a flowchart showing an example of the generation of a predicted image.

[0215] The inter prediction unit 126 generates a predicted image (step Sm_1), and corrects the predicted image by, for example, any of the above-described modes (step Sm_2).

[0216] FIG. 33 is a flowchart showing another example of the generation of a predicted image.

[0217] The inter prediction unit 126 determines the motion vector of the current block (step Sn_1). Next, the inter prediction unit 126 generates a prediction image (step Sn_2) and determines whether to perform correction processing (step Sn_3). Here, when the inter prediction unit 126 determines to perform correction processing (Yes in step Sn_3), it generates a final prediction image by correcting the prediction image (step Sn_4). On the other hand, when the inter prediction unit 126 determines not to perform correction processing (No in step Sn_3), it outputs the prediction image as the final prediction image without correction (step Sn_5).

[0218] Also, in motion compensation, there is a mode for correcting luminance when generating a prediction image. That mode is, for example, LIC described later.

[0219] FIG. 34 is a flowchart showing another example of generating a prediction image.

[0220] The inter prediction unit 126 derives the motion vector of the current block (step So_1). Next, the inter prediction unit 126 determines whether to perform luminance correction processing (step So_2). Here, when the inter prediction unit 126 determines to perform luminance correction processing (Yes in step So_2), it generates a prediction image while performing luminance correction (step So_3). That is, a prediction image is generated by LIC. On the other hand, when the inter prediction unit 126 determines not to perform luminance correction processing (No in step So_2), it generates a prediction image by normal motion compensation without performing luminance correction (step So_4).

[0221] [Motion Compensation > OBMC] Not only the motion information of the current block obtained by motion search but also the motion information of adjacent blocks may be used to generate an inter prediction signal. Specifically, a prediction signal based on the motion information obtained by motion search (within the reference picture) and a prediction signal based on the motion information of adjacent blocks (within the current picture) may be weighted and added to generate an inter prediction signal for each sub-block within the current block. Such inter prediction (motion compensation) is sometimes called OBMC (overlapped block motion compensation).

[0222] In the OBMC mode, information indicating the size of sub-blocks for OBMC (e.g., called OBMC block size) may be signaled at the sequence level. Further, information indicating whether to apply the OBMC mode (e.g., called OBMC flag) may be signaled at the CU level. Note that the signaling levels of these pieces of information do not necessarily have to be limited to the sequence level and the CU level, and may be other levels (e.g., picture level, slice level, tile level, CTU level, or sub-block level).

[0223] An example of the OBMC mode will be described more specifically. FIGS. 35 and 36 are a flowchart and a conceptual diagram for explaining the outline of the prediction image correction process by OBMC processing.

[0224] First, as shown in FIG. 36, a prediction image (Pred) by normal motion compensation is obtained using the motion vector (MV) assigned to the processing target (current) block. In FIG. 36, the arrow “MV” points to the reference picture, indicating what the current block of the current picture refers to in order to obtain the prediction image.

[0225] Next, the motion vector (MV_L) already derived for the encoded left adjacent block is applied (reused) to the block to be encoded to obtain a predicted image (Pred_L). The motion vector (MV_L) is indicated by the arrow "MV_L" pointing from the current block to the reference picture. Then, the first correction of the predicted image is performed by superimposing the two predicted images Pred and Pred_L. This has the effect of blending the boundaries between adjacent blocks.

[0226] Similarly, the motion vector (MV_U) already derived for the encoded upper adjacent block is applied (reused) to the block to be encoded to obtain a predicted image (Pred_U). The motion vector (MV_U) is indicated by the arrow "MV_U" pointing from the current block to the reference picture. Then, the second correction of the predicted image is performed by superimposing the predicted image Pred_U on the predicted image (e.g., Pred and Pred_L) that has undergone the first correction. This has the effect of blending the boundaries between adjacent blocks. The predicted image obtained by the second correction is the final predicted image of the current block in which the boundary with the adjacent block is blended (smoothed).

[0227] Note that the above example is a two-pass correction method using left and upper adjacent blocks, but the correction method may also be a three-pass or more pass correction method using right and / or lower adjacent blocks.

[0228] Note that the area for superimposition may be only a partial area near the block boundary, rather than the pixel area of the entire block.

[0229] Here, the prediction image correction process of OBMC for obtaining one prediction image Pred by superimposing additional prediction images Pred_L and Pred_U from one reference picture has been described. However, when the prediction image is corrected based on a plurality of reference images, the same process may be applied to each of the plurality of reference pictures. In such a case, by performing the image correction of OBMC based on a plurality of reference pictures, after obtaining the corrected prediction images from each reference picture, the final prediction image is obtained by further superimposing the obtained plurality of corrected prediction images.

[0230] Note that in OBMC, the unit of the target block may be a prediction block unit or a sub-block unit obtained by further dividing the prediction block.

[0231] As a method for determining whether to apply the OBMC process, for example, there is a method using an obmc_flag which is a signal indicating whether to apply the OBMC process. As a specific example, the encoding device may determine whether the target block belongs to a region with complex motion. When the target block belongs to a region with complex motion, the encoding device sets the value 1 as the obmc_flag and applies the OBMC process for encoding. When the target block does not belong to a region with complex motion, the encoding device sets the value 0 as the obmc_flag and performs block encoding without applying the OBMC process. On the other hand, in the decoding device, by decoding the obmc_flag described in the stream (for example, the compressed sequence), the decoding is performed by switching whether to apply the OBMC process according to the value.

[0232] In the above example, the inter prediction unit 126 generates one rectangular prediction image for the rectangular current block. However, the inter prediction unit 126 may generate a plurality of prediction images with shapes different from the rectangle for the rectangular current block, and generate the final rectangular prediction image by combining the plurality of prediction images. The shape different from the rectangle may be, for example, a triangle.

[0233] FIG. 37 is a conceptual diagram for explaining the generation of two triangular prediction images.

[0234] The inter prediction unit 126 generates a prediction image of a triangle by performing motion compensation on the first partition of the triangle in the current block using the first MV of the first partition. Similarly, the inter prediction unit 126 generates a prediction image of a triangle by performing motion compensation on the second partition of the triangle in the current block using the second MV of the second partition. Then, the inter prediction unit 126 generates a prediction image of a rectangle same as the current block by combining these prediction images.

[0235] In the example shown in FIG. 37, the first partition and the second partition are each a triangle, but they may be trapezoids or may have different shapes from each other. Further, in the example shown in FIG. 37, the current block is composed of two partitions, but it may be composed of three or more partitions.

[0236] Also, the first partition and the second partition may overlap. That is, the first partition and the second partition may include the same pixel region. In this case, a prediction image of the current block may be generated using the prediction image in the first partition and the prediction image in the second partition.

[0237] Also, in this example, an example in which prediction images are generated by inter prediction for both two partitions is shown, but prediction images may be generated by intra prediction for at least one partition.

[0238] [Motion Compensation > BIO] Next, a method for deriving a motion vector will be described. First, a mode for deriving a motion vector based on a model assuming uniform linear motion will be described. This mode is sometimes called the BIO (bi-directional optical flow) mode.

[0239] Figure 38 is a conceptual diagram for explaining a model assuming uniform linear motion. In Figure 38, (vx, vy) represents the velocity vector, and τ0 and τ1 represent the temporal distances between the current picture (Cur Pic) and two reference pictures (Ref0, Ref1), respectively. (MVx0, MVy0) represents the motion vector corresponding to the reference picture Ref0, and (MVx1, MVy1) represents the motion vector corresponding to the reference picture Ref1.

[0240] At this time, under the assumption of uniform linear motion of the velocity vector (vx, vy), (MVx0, MVy0) and (MVx1, MVy1) are represented as (vxτ0, vyτ0) and (-vxτ1, -vyτ1), respectively, and the following optical flow equation (2) may be adopted.

[0241] [Equation]

[0242] Here, I(k) represents the luminance value of the reference image k (k = 0, 1) after motion compensation. This optical flow equation indicates that the sum of (i) the temporal 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 the combination of this optical flow equation and Hermite interpolation, the motion vector in block units obtained from the merge list or the like may be corrected in pixel units.

[0243] Note that the motion vector may be derived on the decoder side by a method different from the derivation of the motion vector based on the model assuming uniform linear motion. For example, the motion vector may be derived in sub-block units based on the motion vectors of a plurality of adjacent blocks.

[0244] [Motion Compensation > LIC] Next, an example of a mode for generating a predicted image (prediction) using LIC (local illumination compensation) processing will be described.

[0245] FIG. 39 is a conceptual diagram for explaining an example of a method for generating a predicted image using luminance correction processing by LIC processing.

[0246] First, an MV is derived from the encoded reference picture to obtain a reference image corresponding to the current block.

[0247] Next, for the current block, information indicating how the luminance value has changed between the reference picture and the current picture is extracted. This extraction is performed based on the luminance pixel values in the encoded left adjacent reference region (peripheral reference region) and the encoded upper adjacent reference region (peripheral reference region) in the current picture, and the luminance pixel values at equivalent positions in the reference picture specified by the derived MV. Then, a luminance correction parameter is calculated using the information indicating how the luminance value has changed.

[0248] A predicted image for the current block is generated by performing a luminance correction process of applying the luminance correction parameter to the reference image in the reference picture specified by the MV.

[0249] Note that the shape of the peripheral reference region in FIG. 39 is an example, and other shapes may be used.

[0250] Also, although the process of generating a predicted image from one reference picture has been described here, the same applies when generating a predicted image from a plurality of reference pictures. The luminance correction process may be performed on the reference images obtained from each reference picture in the same manner as described above, and then the predicted image may be generated.

[0251] As a method for determining whether to apply LIC processing, for example, there is a method of using lic_flag, which is a signal indicating whether to apply LIC processing. As a specific example, in an encoding device, it is determined whether the current block belongs to an area where a luminance change has occurred. If it belongs to an area where a luminance change has occurred, a value of 1 is set as lic_flag, and LIC processing is applied for encoding. If it does not belong to an area where a luminance change has occurred, a value of 0 is set as lic_flag, and encoding is performed without applying LIC processing. On the other hand, in a decoding device, by decoding the lic_flag described in the stream, decoding may be performed by switching whether to apply LIC processing according to the value.

[0252] As another method for determining whether to apply LIC processing, for example, there is also a method of determining according to whether LIC processing has been applied to surrounding blocks. As a specific example, when the current block is in merge mode, it is determined whether the encoded block in the surrounding area selected when deriving the MV in the merge mode processing has been encoded by applying LIC processing. Encoding is performed by switching whether to apply LIC processing according to the result. Note that also in this example, the same processing is applied to the processing on the decoder side.

[0253] Although the mode of LIC processing (luminance correction processing) has been described with reference to FIG. 39, the details will be described below.

[0254] First, the inter prediction unit 126 derives a motion vector for obtaining a reference image corresponding to the encoding target block from a reference picture that is an encoded picture

[0255] Next, the inter prediction unit 126 extracts information indicating how the luminance values change between the reference picture and the picture to be encoded for the block to be encoded, using the luminance pixel values in the left and upper adjacent encoded peripheral reference regions and the luminance pixel values at the equivalent positions in the reference picture specified by the motion vector, and calculates the luminance correction parameter. For example, let the luminance pixel value of a certain pixel in the peripheral reference region within the picture to be encoded be p0, and the luminance pixel value of the pixel in the peripheral reference region within the reference picture at the equivalent position to this pixel be p1. The inter prediction unit 126 calculates, as the luminance correction parameter, the coefficients A and B that optimize A×p1 + B = p0 for a plurality of pixels in the peripheral reference region.

[0256] Next, the inter prediction unit 126 performs luminance correction processing on the reference image in the reference picture specified by the motion vector using the luminance correction parameter, thereby generating a predicted image for the block to be encoded. For example, let the luminance pixel value in the reference image be p2, and the luminance pixel value of the predicted image after the luminance correction processing be p3. The inter prediction unit 126 generates the predicted image after the luminance correction processing by calculating A×p2 + B = p3 for each pixel in the reference image.

[0257] Note that the shape of the peripheral reference region in FIG. 39 is an example, and other shapes may be used. Also, a part of the peripheral reference region shown in FIG. 39 may be used. For example, a region including a predetermined number of pixels decimated from each of the upper adjacent pixel and the left adjacent pixel may be used as the peripheral reference region. Also, the peripheral reference region is not limited to the region adjacent to the block to be encoded, and may be a region not adjacent to the block to be encoded. The predetermined number regarding the pixels may be determined in advance.

[0258] Also, in the example shown in FIG. 39, the peripheral reference region in the reference picture is the region specified by the motion vector of the picture to be encoded from the peripheral reference region in the picture to be encoded, but it may be the region specified by another motion vector. For example, the other motion vector may be the motion vector of the peripheral reference region in the picture to be encoded.

[0259] Here, the operation of the encoding device 100 has been described. However, the operation of the decoding device 200 is typically the same.

[0260] Note that the LIC process may be applied not only to luminance but also to color difference. At this time, correction parameters may be derived individually for each of Y, Cb, and Cr, or a common correction parameter may be used for any of them.

[0261] Also, the LIC process may be applied in sub-block units. For example, correction parameters may be derived using the peripheral reference region of the current sub-block and the peripheral reference region of the reference sub-block in the reference picture specified by the MV of the current sub-block.

[0262] [Prediction control unit] The prediction control unit 128 selects either the intra-prediction signal (the signal output from the intra-prediction unit 124) or the inter-prediction signal (the signal output from the inter-prediction unit 126), and outputs the selected signal as the prediction signal to the subtraction unit 104 and the addition unit 116.

[0263] As shown in FIG. 1, in various examples of an encoding device, the prediction control unit 128 may output prediction parameters input to the entropy encoding unit 110. The entropy encoding unit 110 may generate an encoded bit stream (or sequence) based on the prediction parameters input from the prediction control unit 128 and the quantization coefficients input from the quantization unit 108. The prediction parameters may be used in a decoding device. The decoding device may receive and decode the encoded bit stream and perform the same processing as the prediction processing performed in the intra prediction unit 124, the inter prediction unit 126, and the prediction control unit 128. The prediction parameters may include a selection prediction signal (e.g., a motion vector, a prediction type, or a prediction mode used in the intra prediction unit 124 or the inter prediction unit 126), or any index, flag, or value based on or indicating the prediction processing performed in the intra prediction unit 124, the inter prediction unit 126, and the prediction control unit 128.

[0264] [Implementation Example of Encoding Device] FIG. 40 is a block diagram showing an implementation example of the encoding device 100. The encoding device 100 includes a processor a1 and a memory a2. For example, a plurality of components of the encoding device 100 shown in FIG. 1 are implemented by the processor a1 and the memory a2 shown in FIG. 40.

[0265] The processor a1 is a circuit that performs information processing and is a circuit that can access the memory a2. For example, the processor a1 is a dedicated or general-purpose electronic circuit that encodes moving images. The processor a1 may be a processor such as a CPU. Also, the processor a1 may be an aggregate of a plurality of electronic circuits. Also, for example, the processor a1 may play the roles of a plurality of components among the plurality of components of the encoding device 100 shown in FIG. 1 and the like.

[0266] Memory a2 is a dedicated or general-purpose memory in which information for the processor a1 to encode a moving image is stored. Memory a2 may be an electronic circuit and may be connected to processor a1. Also, memory a2 may be included in processor a1. Further, memory a2 may be an aggregate of a plurality of electronic circuits. Also, memory a2 may be a magnetic disk, an optical disk, etc., or may be expressed as a storage or a recording medium, etc. Also, memory a2 may be a non-volatile memory or a volatile memory.

[0267] For example, memory a2 may store the moving image to be encoded, or may store the bit string corresponding to the encoded moving image. Also, a program for the processor a1 to encode a moving image may be stored in memory a2.

[0268] Also, for example, memory a2 may serve as a component for storing information among the plurality of components of the encoding device 100 shown in FIG. 1 etc. For example, memory a2 may serve as the block memory 118 and the frame memory 122 shown in FIG. 1. More specifically, memory a2 may store the reconstructed blocks, the reconstructed pictures, etc.

[0269] Note that in the encoding device 100, not all of the plurality of components shown in FIG. 1 etc. need to be implemented, and not all of the plurality of processes described above need to be performed. A part of the plurality of components shown in FIG. 1 etc. may be included in another device, and a part of the plurality of processes described above may be executed by another device.

[0270] [Decoder device] Next, for example, a decoder device capable of decoding the encoded signal (encoded bit stream) output from the above encoding device 100 will be described. FIG. 41 is a block diagram showing the functional configuration of the decoder device 200 according to the embodiment. The decoder device 200 is a moving image decoder device that decodes a moving image in block units.

[0271] As shown in FIG. 41, the decoding device 200 includes an entropy decoding unit 202, an inverse quantization unit 204, an inverse transformation 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.

[0272] The decoding device 200 is realized by, for example, a general-purpose processor and a memory. In this case, when a software program stored in the memory is executed by the processor, the processor functions as the entropy decoding unit 202, the inverse quantization unit 204, the inverse transformation 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. Further, the decoding device 200 may be realized as one or more dedicated electronic circuits corresponding to the entropy decoding unit 202, the inverse quantization unit 204, the inverse transformation 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.

[0273] After explaining the overall processing flow of the decoding device 200 below, each component included in the decoding device 200 will be described.

[0274] [Overall Flow of Decoding Process] FIG. 42 is a flowchart showing an example of the overall decoding process by the decoding device 200.

[0275] First, the entropy decoding unit 202 of the decoding device 200 specifies a division pattern of a block of a fixed size (for example, 128×128 pixels) (step Sp_1). This division pattern is the division pattern selected by the encoding device 100. Then, the decoding device 200 performs the processing of steps Sp_2 to Sp_6 for each of the plurality of blocks constituting the division pattern.

[0276] That is, the entropy decoding unit 202 decodes (specifically, entropy decodes) the encoded quantization coefficients and prediction parameters of the block to be decoded (also referred to as the current block) (step Sp_2).

[0277] Next, the inverse quantization unit 204 and the inverse transform unit 206 restore a plurality of prediction residuals (i.e., difference blocks) by performing inverse quantization and inverse transform on the plurality of quantization coefficients (step Sp_3).

[0278] Next, a prediction processing unit including all or part of the intra prediction unit 216, the inter prediction unit 218, and the prediction control unit 220 generates a prediction signal (also referred to as a prediction block) of the current block (step Sp_4).

[0279] Next, the addition unit 208 reconstructs the current block into a reconstructed image (also referred to as a decoded image block) by adding the prediction block to the difference block (step Sp_5).

[0280] Then, when this reconstructed image is generated, the loop filter unit 212 performs filtering on the reconstructed image (step Sp_6).

[0281] Then, the decoding device 200 determines whether the decoding of the entire picture is completed (step Sp_7). If it is determined that the decoding is not completed (No in step Sp_7), the processing from step Sp_1 is repeatedly executed.

[0282] As shown in the figure, the processing of steps Sp_1 to Sp_7 is sequentially performed by the decoding device 200. Alternatively, a plurality of some of those processes may be performed in parallel, or the order may be changed, etc.

[0283] [Entropy Decoding Unit] The entropy decoding unit 202 entropy-decodes the encoded bit stream. Specifically, the entropy decoding unit 202, for example, arithmetically decodes the encoded bit stream into a binary signal. Then, the entropy decoding unit 202 de-binarizes the binary signal. The entropy decoding unit 202 outputs quantization coefficients to the inverse quantization unit 204 in block units. The entropy decoding unit 202 may output prediction parameters included in the encoded bit stream (see FIG. 1) to the intra prediction unit 216, the inter prediction unit 218, and the prediction control unit 220 in the embodiment. The intra prediction unit 216, the inter prediction unit 218, and the prediction control unit 220 can execute the same prediction processing as that performed by the intra prediction unit 124, the inter prediction unit 126, and the prediction control unit 128 on the encoder side.

[0284] [Inverse Quantization Unit] The inverse quantization unit 204 inverse-quantizes the quantization coefficients of the block to be decoded (hereinafter referred to as the current block), which is the input from the entropy decoding unit 202. Specifically, for each of the quantization coefficients of the current block, the inverse quantization unit 204 inverse-quantizes the quantization coefficient based on the quantization parameter corresponding to the quantization coefficient. Then, the inverse quantization unit 204 outputs the inverse-quantized quantization coefficients (i.e., transform coefficients) of the current block to the inverse transform unit 206.

[0285] [Inverse Transform Unit] The inverse transform unit 206 restores the prediction error by inverse-transforming the transform coefficients, which is the input from the inverse quantization unit 204.

[0286] For example, when the information decoded from the encoded bit stream indicates that EMT or AMT is to be applied (for example, the AMT flag is true), the inverse transform unit 206 inverse-transforms the transform coefficients of the current block based on the information indicating the decoded transform type.

[0287] Also, for example, when the information decoded from the encoded bit stream indicates that NSST is to be applied, the inverse transform unit 206 applies inverse reverse transformation to the transform coefficients.

[0288] [Addition unit] The addition unit 208 reconstructs the current block by adding the prediction error which is the input from the inverse conversion unit 206 and the prediction sample which is the input from the prediction control unit 220. Then, the addition unit 208 outputs the reconstructed block to the block memory 210 and the loop filter unit 212.

[0289] [Block memory] The block memory 210 is a storage unit for storing blocks within the decoded target picture (hereinafter referred to as the current picture) which are blocks referenced in intra prediction. Specifically, the block memory 210 stores the reconstructed block output from the addition unit 208.

[0290] [Loop filter unit] The loop filter unit 212 applies a loop filter to the block reconstructed by the addition unit 208, and outputs the filtered reconstructed block to the frame memory 214 and a display device or the like.

[0291] When the information indicating the on / off of the ALF read from the encoded bitstream indicates that the ALF is on, one filter is selected from a plurality of filters based on the local gradient direction and activity, and the selected filter is applied to the reconstructed block.

[0292] [Frame memory] The frame memory 214 is a storage unit for storing reference pictures used in inter prediction, and is sometimes called a frame buffer. Specifically, the frame memory 214 stores the reconstructed block filtered by the loop filter unit 212.

[0293] [Prediction processing unit (intra prediction unit, inter prediction unit, prediction control unit)] FIG. 43 is a flowchart showing an example of the processing performed by the prediction processing unit of the decoding apparatus 200. The prediction processing unit includes all or some of the components of the intra prediction unit 216, the inter prediction unit 218, and the prediction control unit 220.

[0294] The prediction processing unit generates a predicted image of the current block (step Sq_1). This predicted image is also referred to as a prediction signal or a prediction block. Note that the prediction signal includes, for example, an intra prediction signal or an inter prediction signal. Specifically, the prediction processing unit generates a predicted image of the current block using the reconstructed image already obtained by performing generation of a prediction block, generation of a difference block, generation of a coefficient block, restoration of the difference block, and generation of a decoded image block.

[0295] The reconstructed image may be, for example, an image of a reference picture, or may be an image of a decoded block in the current picture that is a picture including the current block. The decoded block in the current picture is, for example, an adjacent block of the current block.

[0296] FIG. 44 is a flowchart showing another example of the processing performed by the prediction processing unit of the decoding apparatus 200.

[0297] The prediction processing unit determines a method or mode for generating a predicted image (step Sr_1). For example, this method or mode may be determined based on, for example, prediction parameters.

[0298] When the prediction processing unit determines the first method as the mode for generating the predicted image, it generates the predicted image according to the first method (step Sr_2a). When the prediction processing unit determines the second method as the mode for generating the predicted image, it generates the predicted image according to the second method (step Sr_2b). When the prediction processing unit determines the third method as the mode for generating the predicted image, it generates the predicted image according to the third method (step Sr_2c).

[0299] The first method, the second method, and the third method are different methods for generating a predicted image, and may be, for example, an inter prediction method, an intra prediction method, and other prediction methods, respectively. In these prediction methods, the above-described reconstructed image may be used.

[0300] [Intra Prediction Unit] 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 the intra prediction mode decoded from the coded bitstream. Specifically, the intra prediction unit 216 generates an intra prediction signal by performing intra prediction with reference to samples (for example, luminance values, chrominance difference values) of blocks adjacent to the current block, and outputs the intra prediction signal to the prediction control unit 220.

[0301] In addition, when an intra prediction mode that refers to a luminance block in the intra prediction of a chrominance difference block is selected, the intra prediction unit 216 may predict the chrominance difference component of the current block based on the luminance component of the current block.

[0302] Also, when the information decoded from the coded bitstream indicates the application of PDPC, the intra prediction unit 216 corrects the pixel value after intra prediction based on the gradient of the reference pixels in the horizontal / vertical direction.

[0303] [Inter Prediction Unit] The inter prediction unit 218 predicts the current block by referring to the reference picture stored in the frame memory 214. The prediction is performed in units of the current block or sub-blocks (e.g., 4x4 blocks) within the current block. For example, the inter prediction unit 218 generates an inter prediction signal for the current block or sub-block by performing motion compensation using motion information (e.g., motion vectors) decoded from the encoded bitstream (e.g., prediction parameters output from the entropy decoding unit 202), and outputs the inter prediction signal to the prediction control unit 220.

[0304] When the information decoded 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.

[0305] Also, when the information decoded from the encoded bitstream indicates that the FRUC mode is to be applied, the inter prediction unit 218 derives motion information by performing motion search according to the pattern matching method (bilateral matching or template matching) decoded from the encoded stream. Then, the inter prediction unit 218 performs motion compensation (prediction) using the derived motion information.

[0306] In addition, the inter prediction unit 218 derives a motion vector based on a model assuming uniform linear motion when the BIO mode is applied. Also, when the information decoded from the encoded bitstream indicates that the affine motion compensation prediction mode is to be applied, the inter prediction unit 218 derives a motion vector in units of sub-blocks based on the motion vectors of a plurality of adjacent blocks.

[0307] [MV Derivation > Normal Inter Mode] When the information decoded from the symbolized bitstream indicates that the normal inter mode is to be applied, the inter prediction unit 218 derives an MV based on the information decoded from the encoded stream and performs motion compensation (prediction) using the MV.

[0308] Figure 45 is a flowchart showing an example of inter prediction in the normal inter mode in the decoding apparatus 200.

[0309] The inter prediction unit 218 of the decoding apparatus 200 performs motion compensation for each block. The inter prediction unit 218 acquires a plurality of candidate MVs for the current block based on information such as the MVs of a plurality of decoded blocks temporally or spatially around the current block (step Ss_1). That is, the inter prediction unit 218 creates a candidate MV list.

[0310] Next, the inter prediction unit 218 extracts each of N (N is an integer of 2 or more) candidate MVs from among the plurality of candidate MVs acquired in step Ss_1 as a prediction motion vector candidate (also referred to as a prediction MV candidate) according to a predetermined priority order (step Ss_2). Note that the priority order may be determined in advance for each of the N prediction MV candidates.

[0311] Next, the inter prediction unit 218 decodes prediction motion vector selection information from the input stream (i.e., the symbolized bitstream), and uses the decoded prediction motion vector selection information to select one prediction MV candidate from among the N prediction MV candidates as the prediction motion vector (also referred to as the prediction MV) of the current block (step Ss_3).

[0312] Next, the inter prediction unit 218 decodes the differential MV from the input stream, and derives the MV of the current block by adding the difference value, which is the decoded differential MV, to the selected prediction motion vector (step Ss_4).

[0313] Finally, the inter prediction unit 218 generates a predicted image of the current block by performing motion compensation on the current block using the derived MV and the decoded reference picture (step Ss_5).

[0314] [Prediction control unit] The prediction control unit 220 selects either the intra prediction signal or the inter prediction signal, and outputs the selected signal as a prediction signal to the adder 208. Overall, the configuration, function, and processing of the prediction control unit 220, the intra prediction unit 216, and the inter prediction unit 218 on the decoder side may correspond to the configuration, function, and processing of the prediction control unit 128, the intra prediction unit 124, and the inter prediction unit 126 on the encoder side.

[0315] [Implementation example of decoder] FIG. 46 is a block diagram showing an implementation example of the decoder 200. The decoder 200 includes a processor b1 and a memory b2. For example, a plurality of components of the decoder 200 shown in FIG. 41 are implemented by the processor b1 and the memory b2 shown in FIG. 46.

[0316] The processor b1 is a circuit that performs information processing and is a circuit that can access the memory b2. For example, the processor b1 is a dedicated or general-purpose electronic circuit that decodes an encoded moving image (i.e., an encoded bitstream). The processor b1 may be a processor such as a CPU. Also, the processor b1 may be an aggregate of a plurality of electronic circuits. Also, for example, the processor b1 may play the roles of a plurality of components among the plurality of components of the decoder 200 shown in FIG. 41 and the like.

[0317] Memory b2 is a dedicated or general-purpose memory in which information for the processor b1 to decode the encoded bitstream is stored. Memory b2 may be an electronic circuit and may be connected to the processor b1. Also, memory b2 may be included in the processor b1. Further, memory b2 may be an aggregate of a plurality of electronic circuits. Also, memory b2 may be a magnetic disk, an optical disk, etc., or may be expressed as a storage or recording medium, etc. Also, memory b2 may be a non-volatile memory or a volatile memory.

[0318] For example, a moving image or an encoded bitstream may be stored in memory b2. Also, a program for the processor b1 to decode the encoded bitstream may be stored in memory b2.

[0319] Also, for example, memory b2 may serve as a component for storing information among a plurality of components of the decoding device 200 shown in FIG. 41 etc. Specifically, memory b2 may serve as the block memory 210 and the frame memory 214 shown in FIG. 41. More specifically, reconstructed blocks, reconstructed pictures, etc. may be stored in memory b2.

[0320] Note that in the decoding device 200, not all of the plurality of components shown in FIG. 41 etc. need to be implemented, and not all of the plurality of processes described above need to be performed. A part of the plurality of components shown in FIG. 41 etc. may be included in another device, and a part of the plurality of processes described above may be executed by another device.

[0321] [Definitions of Terms] Each term may be defined as follows as an example.

[0322] A picture is an array of a plurality of luminance samples in monochrome format, or an array of a plurality of luminance samples and two corresponding arrays of a plurality of chrominance samples in color formats of 4:2:0, 4:2:2, and 4:4:4. The picture may be a frame or a field.

[0323] A frame is a composition of a top field where a plurality of sample rows 0, 2, 4, ··· occur, and a bottom field where a plurality of sample rows 1, 3, 5, ··· occur.

[0324] A slice is an integer number of coded tree units included in one independent slice segment and all subsequent dependent slice segments (if any) preceding the next independent slice segment (if any) in the same access unit.

[0325] A tile is a rectangular region of a plurality of coded tree blocks in a specific tile column and a specific tile row in a picture. The tile may be a rectangular region of a frame that is still intended to be independently decoded and encoded, although a loop filter spanning the edges of the tile may still be applied.

[0326] A block is an MxN (N rows and M columns) array of a plurality of samples, or an MxN array of a plurality of transform coefficients. The block may be a square or rectangular region of a plurality of pixels consisting of a plurality of matrices of one luminance and two chrominances.

[0327] A CTU (Coded Tree Unit) may be a coded tree block of a plurality of luminance samples of a picture having three sample arrays, or two corresponding coded tree blocks of a plurality of chrominance samples. Alternatively, a CTU may be a coded tree block of a plurality of samples of either a monochrome picture or a picture encoded using a syntax structure used for encoding three separate color planes and a plurality of samples.

[0328] The super block may constitute one or two mode information blocks, or may be a square block of 64×64 pixels that is recursively divided into four 32×32 blocks and can be further divided.

[0329] FIG. 47A is a flowchart showing an example of a processing flow 1000 that divides an image block into a plurality of partitions including at least a first partition and a second partition, predicts a motion vector from a set of motion vector candidates of at least the first partition, and performs further processing according to an embodiment. The processing flow 1000 may be performed by, for example, the encoding device 100 in FIG. 1, the decoding device 200 in FIG. 41, or the like.

[0330] In step S1001, the image block is divided into a plurality of partitions including at least a first partition. Each partition may or may not have a non-rectangular shape. FIG. 48 is a conceptual diagram showing an example of a method of dividing an image block into a first partition and a second partition. For example, as shown in FIG. 48, the image block may be divided into two or more partitions of various shapes. The illustrated examples in FIG. 48 include an image block divided from the upper left corner to the lower right corner of the image block to generate a first partition and a second partition both having a non-rectangular shape (e.g., a triangle), an image block divided into an L-shaped partition and a rectangular partition, an image block divided into a pentagonal partition and a triangular partition, an image block divided into a hexagonal partition and a pentagonal partition, and an image block divided into two polygonal partitions. The various partition shapes shown may be formed by dividing the image block in another way. For example, two triangular partitions may be formed by dividing the image block from the upper right corner to the lower left corner of the image block to generate a first partition and a second partition both having a triangular shape. In some embodiments, two or more partitions of the image block may have overlapping portions.

[0331] In step S1002, the process predicts a first motion vector from at least a set of motion vector candidates of a first partition. The motion vector candidates of the motion vector candidate list may include motion vector candidates derived from at least spatial adjacent partitions or temporal adjacent partitions of the first partition. In step S1003, at least the first partition is encoded or decoded using the first motion vector.

[0332] FIG. 49 is a conceptual diagram showing spatial adjacent partitions and non - adjacent spatial adjacent partitions in the vicinity of a first partition of a current picture. The adjacent spatial adjacent partition is a partition adjacent to the first partition of the current picture. The non - adjacent spatial adjacent partition is a partition away from the first partition of the current picture. In some embodiments, the set of motion vector candidates in S1002 of FIG. 47A may be derived from at least spatial adjacent partitions of the first partition of the current picture.

[0333] In some embodiments, the set of motion vector candidates may be derived from a motion vector candidate list such as a motion vector candidate list used in an inter - prediction mode (e.g., merge mode, skip mode, or inter mode). Such a list may include both single - prediction motion vector candidates and dual - prediction motion vector candidates.

[0334] FIG. 50 is a conceptual diagram showing single - prediction motion vector candidates and dual - prediction motion vector candidates for an image block of a current picture. The single - prediction motion vector candidate is a single motion vector of a current block in the current picture with respect to a single reference picture. As shown in the upper part of FIG. 50, the single - prediction motion vector candidate is a motion vector from a block of the current picture to a block of a reference picture before the current picture in display order. In some embodiments, the reference picture may be after the current picture in display order.

[0335] The dual-prediction motion vector candidate consists of two motion vectors, namely, the first motion vector of the current block with respect to the first reference picture and the second motion vector of the current block with respect to the second reference picture. As shown in FIG. 50, the lower-left dual-prediction motion vector candidate has the first motion vector from the block of the current picture to the block of the first reference picture and the second motion vector from the block of the current picture to the block of the second reference picture. As illustrated, the first reference picture and the second reference picture are before the current picture in the display order. The lower-right dual-prediction motion vector candidate in FIG. 50 has the first motion vector from the block of the current picture to the block of the first reference picture and the second motion vector from the block of the current picture to the block of the second reference picture. The first reference picture is before the current picture in the display order, and the second reference picture is after the current picture in the display order.

[0336] In some embodiments, the set of motion vector candidates for predicting the motion vectors of at least one partition may be a single-prediction motion vector candidate set. FIG. 47B is a flowchart showing an example of a processing flow 1000' that divides an image block into a plurality of partitions including at least a first partition and a second partition, predicts motion vectors from a single-prediction motion vector candidate set of at least the first partition, and performs further processing according to the embodiment. The processing flow 1000' may be performed by, for example, the encoding device 100 in FIG. 1, the decoding device 200 in FIG. 41, or the like. The processing flow 1000' in FIG. 47B is different from the processing flow 1000 in FIG. 47A in that motion vectors are predicted from a single-prediction motion vector candidate set in step 1002' in FIG. 47B. The single-prediction motion vector candidate set may be used to reduce the number of arithmetic operations and the memory bandwidth required for partitioning encoding.

[0337] The single-prediction motion vector candidate set may be derived from the list of motion vector candidates by including, for example, only the single-prediction motion vectors of the list within the motion vector candidate set. However, the single-prediction motion vectors may also be derived from the bi-prediction motion vectors in various ways, or from the single-prediction motion vector candidates in various ways.

[0338] For example, an index may be used to derive single-prediction motion vector candidates to be included in the single-prediction motion vector candidate set from the bi-prediction motion vector candidates of the list of motion vector candidates. For example, the bidirectional motion vector candidates may have associated indexes that identify a first reference picture within a first list (e.g., reference picture list L0) and a second reference picture within a second list (e.g., reference picture list L1). Table 1 below shows an example mapping of indexes of bi-prediction motion vector candidates to the first reference picture in the first reference picture list and the second reference picture in the second reference picture list.

[0339] [Table 1] Table 1: Example mapping of indexes of bi-prediction motion vector candidates to reference pictures in reference picture lists

[0340] Regarding Table 1, the dual-prediction motion vector candidate with an index of 1 points to reference picture 0 in reference picture list L0 and reference picture 8 in reference picture list L1. Two single-prediction motion vector candidates may be derived from the dual-prediction motion vector candidate with an index of 1, the single-prediction motion vector candidate for the block of reference picture 0 and the current block based on reference picture list L0, and the single-prediction motion vector for the block of reference picture 8 and the current block based on reference picture list L1. One or both of the single-prediction motion vector candidates may be included in the set of single-prediction motion vector candidates that predict the motion vector for the current partition of the block of the target image (e.g., the single-prediction motion vector based on the reference picture in list L0, the single-prediction motion vector based on reference picture list L1, or both). Note that for the current picture, reference picture 8 in list L0 is the same as reference picture 8 in list L1.

[0341] Similarly, the dual-prediction motion vector candidate with an index of 2 points to reference picture 8 in reference picture list L0 and reference picture 16 in reference picture list L1. Two single-prediction motion vector candidates may be derived from the dual-prediction motion vector candidate with an index of 2, the single-prediction motion vector candidate for the block of reference picture 8 and the current block, and the single-prediction motion vector for the block of reference picture 16 and the current block. One or both of the single-prediction motion vector candidates may be included in the set of single-prediction motion vector candidates that predict the motion vector for the current partition of the block of the target image (e.g., the single-prediction motion vector candidate based on the reference picture in list L0, the single-prediction motion vector candidate based on reference picture list L1, or both).

[0342] In some embodiments, only the single-prediction motion vector candidates based on the reference picture of list L0 are included in the set of single-prediction motion vector candidates derived from the bi-prediction motion vector candidates of the candidate list. In some embodiments, only the single-prediction motion vector candidates based on the reference picture list L1 are included in the set of single-prediction motion vector candidates. In some embodiments, the set of single-prediction motion vector candidates is, for example, an ordered set in which the single-prediction motion vector candidates based on the reference picture of list L0 are followed by the single-prediction motion vector candidates based on the reference picture list L1 within the set of single-prediction motion vector candidates.

[0343] In some embodiments, the motion vectors of the bi-prediction motion vector candidates included in the set of single-prediction motion vector candidates may be determined based on the encoding order or display order of the pictures. The principle may also be to include the motion vectors of the bi-prediction motion vector candidates pointing to the closest reference picture or the earliest reference picture in time. FIGS. 51 to 53 are conceptual diagrams showing the steps of determining a single-prediction motion vector from the bi-prediction motion vector candidates included in the set of single-prediction motion vector candidates based on the encoding order or display order of the pictures.

[0344] In some embodiments, the motion vector of the reference picture of the bi-prediction motion vector closest to the current picture in the display order is included in the set of single-prediction motion vector candidates. As illustrated in FIG. 51, the bi-prediction motion vector candidates include Mv0 pointing to reference picture 0 and Mv1 pointing to reference picture 1. Since reference picture 1 is closer to the current picture in the display order than reference picture 0, Mv1 is selected as the single-prediction motion vector to be included in the set of single-prediction motion vectors.

[0345] In some embodiments, the motion vectors of the reference pictures of the bi-prediction motion vectors closest to the current picture in the encoding order are included in the single-prediction motion vector candidate set. As shown in FIG. 52, the bi-prediction motion vector candidates include Mv0 pointing to reference picture 1 and Mv1 pointing to reference picture 2. Since reference picture 1 is closer to the current picture in the encoding order than reference picture 2, Mv0 is selected as the single-prediction motion vector to be included in the single-prediction motion vector set.

[0346] In some embodiments, the motion vectors of the reference pictures of the bi-prediction motion vectors that are reference pictures before the current picture in the display order are included in the single-prediction motion vector candidate set. As shown in FIG. 52, the bi-prediction motion vector candidates include Mv0 pointing to reference picture 1 and Mv1 pointing to reference picture 2. Since reference picture 1 is a reference picture before the current picture in the display order, Mv0 is selected as the single-prediction motion vector to be included in the single-prediction motion vector set.

[0347] In some embodiments, the motion vectors of the reference pictures of the bi-prediction motion vectors that are reference pictures after the current picture in the display order are included in the single-prediction motion vector candidate set. As shown in FIG. 52, the bi-prediction motion vector candidates include Mv0 pointing to reference picture 1 and Mv1 pointing to reference picture 2. Since reference picture 2 is a reference picture after the current picture in the display order, Mv1 is selected as the single-prediction motion vector to be included in the single-prediction motion vector set.

[0348] The above method examples for deriving a single prediction motion vector from a dual prediction motion vector may be combined in some embodiments. For example, in some embodiments, the motion vector of the reference picture that is closest to the current picture in display order and before the current picture among the dual prediction motion vectors may be included in the set of single prediction motion vector candidates. As illustrated in FIG. 53, the dual prediction motion vector candidates include Mv0 pointing to reference picture 1 and Mv1 pointing to reference picture 2. Since reference picture 1 is a reference picture before the current picture in display order, even if reference picture 2 is closer to the current picture in display order or at the same distance from the current picture, Mv0 is selected as the single prediction motion vector to be included in the single prediction motion vector set.

[0349] In another example, in some embodiments, the motion vector of the reference picture that is closest to the current picture in display order and after the current picture among the dual prediction motion vectors may be included in the set of single prediction motion vector candidates. As illustrated in FIG. 53, the dual prediction motion vector candidates include Mv0 pointing to reference picture 1 and Mv1 pointing to reference picture 2. Since reference picture 2 is after the current picture in display order, even if reference picture 1 is closer to the current picture in display order or at the same distance from the current picture, Mv1 is selected as the single prediction motion vector to be included in the single prediction motion vector set.

[0350] In another example, in some embodiments, the motion vector that is the motion vector of the reference picture of the dual prediction motion vector closest to the current picture in display order and points to reference picture list 0 may be included in the set of single prediction motion vector candidates. Other combinations of methods for deriving single prediction motion vector candidates from a list of motion vector candidates may also be used (e.g., single prediction motion vector candidates from the list and single prediction motion vector candidates derived from the dual prediction motion vector candidates in the list, etc.).

[0351] Also, as described above, the single prediction motion vectors of the single prediction motion vector set may also be derived from the single prediction motion vectors. FIGS. 54 to 56 are conceptual diagrams showing steps of generating one or more single prediction motion vectors from the single prediction motion vectors.

[0352] For example, in some embodiments, only the single prediction motion vectors of the list of motion vector candidates may be included in the single prediction motion vector candidate set, and additional single prediction motion vectors may be derived from the single prediction motion vectors of the list of motion vector candidates and included in the single prediction motion vector set. FIG. 54 shows the single prediction motion vector Mv0 of the list of motion vector candidates included in the single prediction motion vector candidate set. Mv0 points to the reference picture in list L0 related to the index of the single prediction motion vector. In addition to Mv0, the mirror vector Mv0' of Mv0 that points to the reference picture in list L1 related to the index of the single prediction motion vector may also be included in the single prediction motion vector set.

[0353] In another example, FIG. 55 shows the single prediction motion vector Mv0 of the list of motion vector candidates included in the single prediction motion vector candidate set. Mv0 points to the first reference picture in list L0 related to the index of the single prediction motion vector. In addition to Mv0, the scaled motion vector of Mv0 may be included in the single prediction motion vector candidate set. As shown in FIG. 55, the scaled version Mv0' of Mv0 that points to the second reference picture in list L0, and the scaled version Mv0'' of Mv0 that points to the third reference picture in list L0 may also be included in the single prediction motion vector set.

[0354] In some embodiments, each motion vector of the single-prediction motion vector candidates of the list and the dual-prediction motion vector candidates of the list may be included in the single-prediction motion vector candidate set. For FIGS. 51 to 53, in addition to any single-prediction motion vector candidate included in the list, both Mv0 and Mv1 will be included in the single-prediction motion vector candidate set. The single-prediction motion vector candidate set may usually include five or six single-prediction motion vector candidates (for example, five for one pattern, six for one block).

[0355] In some embodiments, the single-prediction motion vectors included in the single-prediction motion vector set may be derived from both motion vectors of the dual-prediction motion vector candidates. FIG. 56 shows an example of deriving the single-prediction motion vectors to be included in the set from both motion vectors of the dual-prediction motion vector candidates. As illustrated in FIG. 56, the dual-prediction motion vector candidates include Mv0 pointing to reference picture 0 and Mv1 pointing to reference picture 1. A mirror vector Mv1' of Mv1 pointing to reference picture 0 (the reference picture pointed to by Mv0) is generated. The average of Mv0 and Mv1' may be taken, and the resulting vector may be included in the single-prediction motion vector candidate set (for example, together with any single-prediction motion vector candidate in the list).

[0356] In some embodiments, the average motion vector of two motion vectors of adjacent partitions of at least one partition and the single-prediction motion vectors of the list are included in the set. In some embodiments, the motion vectors derived from multiple motion vectors of adjacent partitions and the single-prediction motion vectors of the list are included in the set. The adjacent partitions may be encoded using a motion vector derivation model such as the affine mode. In some embodiments, a weighted combination of multiple motion vectors of multiple adjacent partitions and the single-prediction motion vectors of the list are included in the set. The weights applied to the multiple motion vectors among the multiple motion vectors may be based on, for example, the position, size, coding mode, etc. of the adjacent partitions.

[0357] In one embodiment, the prediction step of the first motion vector (see S1002 in FIG. 47A and S1002' in FIG. 47B) includes a step of selecting a motion vector from a set of first motion vector candidates and a step of comparing the selected motion vector with the motion vectors of adjacent partitions. FIG. 57 is a conceptual diagram showing the unidirectional motion vectors of the first partition and the second partition of an image block. As shown in FIG. 57, Mv0 is selected from at least the set of motion vector candidates of the first partition (the white triangle shown), and Mv1 may be selected from the set of motion vector candidates of the adjacent partition (the shaded triangle shown). Note that the two triangular-shaped partitions of the block do not have the same single prediction motion vector candidates.

[0358] In one embodiment, Mv0 is a single prediction motion vector and is used to predict the motion vector of the first partition.

[0359] In one embodiment, Mv0 is a bi-prediction motion vector candidate and Mv1 is a single prediction motion vector candidate. A motion vector of Mv0 that points in the same prediction direction as the prediction direction pointed to by Mv1 (e.g., list L0 or list L1) may be selected as the motion vector used for predicting at least the first motion vector of the first partition. In another example, a motion vector of Mv0 that points in the prediction direction opposite to the prediction direction pointed to by Mv1 (e.g., list L0 or list L1) may be selected as the motion vector used for predicting at least the first motion vector of the first partition.

[0360] In one embodiment, both Mv0 and Mv1 are dual-prediction motion vector candidates. The difference between Mv0 and Mv1 may be determined. For example, if the difference in the L0 direction is greater than or equal to the difference in the L1 direction, the motion vector of Mv0 in the L0 direction may be used to predict the first motion vector. Otherwise, the motion vector of Mv0 in the L1 direction may be used. In another example, if the difference in the L0 direction is greater than or equal to the difference in the L1 direction, the motion vector of Mv0 in the L1 direction may be used to predict the first motion vector. Otherwise, the motion vector of Mv0 in the L0 direction may be used.

[0361] In another example, the step of predicting the first motion vector may include the step of selecting a motion vector from a single-prediction motion vector set based on the position or size of the single-prediction motion vector candidate.

[0362] The single-prediction motion vector candidate set of adjacent partitions may include, for example, five single-prediction motion vector candidates (e.g., {Mv1, Mv2, Mv3, Mv4, Mv5}). If Mv2 is selected as the single-prediction motion vector for predicting the motion vector for an adjacent partition, Mv2 is not included (or may be excluded) in the single-prediction motion vector candidate set for predicting the first motion vector for at least the first partition. When removing Mv2 from the single-prediction motion vector candidate set, Mv2 may be replaced with another single-prediction motion vector (e.g., Mv6).

[0363] In one embodiment, whether to use a first motion vector candidate set (which may include both single-prediction motion vector candidates and dual-prediction motion vector candidates) or a second single-prediction motion vector candidate set to predict the motion vector of a partition of an image block may be based on various criteria.

[0364] For example, FIG. 58 is a flowchart showing an example of a processing flow 2000 that predicts a motion vector of a partition of an image block from a first single-prediction motion vector candidate set or a second motion vector candidate set including a bi-prediction motion vector candidate and a single-prediction motion vector candidate according to the shape of the partition, and performs further processing according to the embodiment.

[0365] In step S2001, an image block is divided into a plurality of partitions including at least a first partition. Each partition may or may not be a non-rectangular shape. For an example of dividing an image block into a plurality of partitions, refer to FIG. 48.

[0366] In step S2002, the processing flow 2000 determines or decides whether the current partition (for example, at least the first partition as shown) is a rectangular partition. In step S2002, if it is determined that the current partition is a rectangular partition, the processing flow 2000 proceeds to S2004. In step S2002, if it is not determined that the current partition is a rectangular partition, the processing flow 2000 proceeds to S2003.

[0367] In step S2004, a first motion vector is predicted from the first single-prediction motion vector candidate set. The first set may be generated as described above, for example. In step S2003, a first motion vector is predicted from the second motion vector candidate set. The second set may include both single-prediction motion vector candidates and bi-prediction motion vector candidates. In step S2005, the current partition is encoded or decoded using the first motion vector.

[0368] In another example, FIG. 59 shows a process flow for predicting a motion vector of a partition of an image block from a first single-prediction motion vector candidate set or a second motion vector candidate set including dual-prediction motion vector candidates and single-prediction motion vector candidates according to the size of the block or the partition, and performing further processing according to the embodiment. It is a flowchart showing an example of the process flow.

[0369] In step S3001, the image block is divided into a plurality of partitions including at least a first partition. Each partition may or may not be a non-rectangular shape. For an example of dividing an image block into a plurality of partitions, refer to FIG. 48.

[0370] In step S3002, the process flow 3000 determines or decides whether the size of the current block or the current partition is larger than a threshold size. In step S3002, if it is determined that the size of the current block or the current partition is not larger than the threshold size, the process flow 3000 proceeds to S3004. In step S3002, if it is determined that the size of the current block or the current partition is larger than the threshold size, the process flow 3000 proceeds to S3003.

[0371] In step S3004, a first motion vector is predicted from the first single-prediction motion vector candidate set. The first set may be generated as described above, for example. In step S3003, a first motion vector is predicted from the second motion vector candidate set. The second set may include both single-prediction motion vector candidates and dual-prediction motion vector candidates. In step S3005, the current partition is encoded or decoded using the first motion vector.

[0372] Various threshold sizes may be adopted. For example, a 16×16 pixel threshold size may be adopted, or a block or partition smaller than 16×16 pixels may be processed using a single prediction motion vector candidate set, while a larger size may be processed using dual prediction. Also, the size of an image block or partition may be the width of the image block or partition, the height of the image block or partition, the ratio of the width of the image block or partition to its height, the ratio of the height of the image block or partition to its width, the number of luminance samples of the image block or partition, the number of samples of the image block or partition, and various combinations thereof, etc.

[0373] FIG. 60 is a flowchart showing an example of a processing flow 4000 that derives the motion vectors of the first partition and the second partition from the motion vector candidate sets of the first partition and the second partition and performs further processing according to the embodiment.

[0374] In step S4001, an image block is divided into a plurality of partitions including at least a first partition and a second partition. Each partition may or may not be a non-rectangular shape. For example, the first partition and the second partition may be triangular partitions. Refer to FIG. 48 for an example of dividing an image block into a plurality of partitions.

[0375] In step S4002, the processing flow 4000 creates a first motion vector candidate set for the first partition and the second partition. The first motion vector candidate set may be a motion vector candidate list of the image block. The motion vector candidates in the motion vector candidate list may include dual prediction motion vector candidates and single prediction motion vector candidates. In one embodiment, the first motion vector candidate set may be a dual prediction motion vector candidate set.

[0376] In step S4003, at least two motion vectors are selected from the first set of motion vector candidates. The selected motion vector candidates may include dual-prediction motion vector candidates and single-prediction motion vector candidates. In one embodiment, the selected motion vector candidates are dual-prediction motion vector candidates.

[0377] In step S4004, processing flow 4000 derives a first motion vector of a first partition and a second motion vector of a second partition based on a comparison result based on the at least two selected motion vector candidates. This may be done in various ways.

[0378] For example, the at least two selected motion vector candidates may both be dual-prediction motion vector candidates each having two motion vectors for a total of four motion vectors. The derived first motion vector and second motion vector may be two of the four motion vectors having the largest difference in magnitude among the four motion vectors of the at least two selected motion vector candidates. The derived first motion vector and second motion vector are single-prediction motion vectors.

[0379] In another example, the at least two selected motion vector candidates may both be dual-prediction motion vector candidates each having two motion vectors for a total of four motion vectors. The derived first motion vector and second motion vector may be two of the four motion vectors having the smallest difference in magnitude among the four motion vectors of the at least two selected motion vector candidates. The derived first motion vector and second motion vector are single-prediction motion vectors.

[0380] In another example, at least one of the at least two selected motion vector candidates may be a bi-predicted motion vector candidate having two motion vectors (a total of three or four motion vectors). The derived first motion vector and second motion vector may be the two motion vectors among the plurality of motion vectors of the at least two selected motion vector candidates that are the largest or the smallest. The derived first motion vector and second motion vector are single-predicted motion vectors. In step S4005, the first partition and the second partition are encoded or decoded using the derived first motion vector and second motion vector.

[0381] One or more of the aspects disclosed herein may be implemented in combination with at least a part of other aspects in the present disclosure. Also, some of the processes described in the flowchart of one or more of the aspects disclosed herein, some of the configurations of the apparatus, some of the syntax, etc. may be implemented in combination with other aspects.

[0382] [Implementation and Application] In each of the above embodiments, each of the functional or operational blocks can usually be realized by an MPU (micro processing unit), a memory, etc. Also, the processing by each of the functional blocks may be realized as a program execution unit such as a processor that reads and executes software (program) recorded on a recording medium such as a ROM. The software may be distributed. The software may be recorded on various recording media such as a semiconductor memory. Note that it is also possible to realize each functional block by hardware (a dedicated circuit). Various combinations of hardware and software can be adopted.

[0383] 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 a plurality of devices. Also, the processor that executes the above program may be singular or plural. That is, centralized processing may be performed, or distributed processing may be performed.

[0384] Aspects of the present disclosure are not limited to the above embodiments, and various modifications are possible, and these are also included within the scope of the aspects of the present disclosure.

[0385] Furthermore, here, application examples of the moving image encoding method (image encoding method) or moving image decoding method (image decoding method) shown in each of the above embodiments, and various systems for implementing the application examples will be described. Such a system may be characterized by having an image encoding device using an image encoding method, an image decoding device using an image decoding method, or an image encoding / decoding device having both. Other configurations of such a system can be appropriately changed as the case may be.

[0386] [Usage Example] FIG. 61 is a diagram showing the overall configuration of a suitable content supply system ex100 for realizing a content distribution service. The communication service providing area is divided into a desired size, and base stations ex106, ex107, ex108, ex109, ex110, which are fixed radio stations in the illustrated example, are installed in each cell.

[0387] In this content supply system ex100, devices such as computer ex111, game console ex112, camera ex113, home appliance ex114, and smartphone ex115 are connected to the Internet ex101 via Internet service provider ex102 or communication network ex104, and base stations ex106 to ex110. The content supply system ex100 may be connected by combining any of the above devices. In various implementations, the devices may be directly or indirectly connected to each other via a telephone network or short-range wireless, etc., without passing through base stations ex106 to ex110. Further, the streaming server ex103 may be connected to devices such as computer ex111, game console ex112, camera ex113, home appliance ex114, and smartphone ex115 via the Internet ex101 or the like. Also, the streaming server ex103 may be connected to terminals within a hotspot in an airplane ex117 via a satellite ex116.

[0388] Note that a wireless access point or hotspot, etc. may be used instead of base stations ex106 to ex110. Also, the streaming server ex103 may be directly connected to the communication network ex104 without passing through the Internet ex101 or the Internet service provider ex102, or may be directly connected to the airplane ex117 without passing through the satellite ex116.

[0389] The camera ex113 is a device capable of taking still images and video, such as a digital camera. Also, the smartphone ex115 is a smartphone device, mobile phone, or PHS (Personal Handy-phone System), etc. that supports the mobile communication system standards called 2G, 3G, 3.9G, 4G, and in the future, 5G.

[0390] The home appliance ex114 is a refrigerator or a device included in a household fuel cell cogeneration system, etc.

[0391] In the content supply system ex100, a terminal having a photographing function is connected to a streaming server ex103 through a base station ex106 or the like, enabling live distribution and the like. In live distribution, the 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) may perform the encoding process described in each of the above embodiments on the still image or moving image content photographed by the user using the terminal, may multiplex the video data obtained by encoding and the audio data obtained by encoding the sound corresponding to the video, and may transmit 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.

[0392] On the other hand, the streaming server ex103 stream-distributes the content data transmitted to the requested client. The client is a computer ex111, a game machine ex112, a camera ex113, a home appliance ex114, a smartphone ex115, or a terminal in an airplane ex117 that can decode the encoded data. Each device that has received the distributed data may decode and reproduce the received data. That is, each device may function as an image decoding device according to one aspect of the present disclosure.

[0393] [Distributed processing] Also, the streaming server ex103 may be a plurality of servers or a plurality of computers that distribute, process, and record data. For example, the streaming server ex103 may be implemented by a CDN (Content Delivery Network), and content delivery may be realized by a network connecting a large number of edge servers distributed around the world and between the edge servers. In a CDN, a physically closer edge server can be dynamically assigned according to the client. Then, by caching and delivering the content to the edge server, the delay can be reduced. Also, when several types of errors occur or the communication state changes due to an increase in traffic, etc., the processing can be distributed among multiple edge servers, the delivery entity can be switched to another edge server, or the part of the network with a failure can be bypassed to continue the delivery, so high-speed and stable delivery can be realized.

[0394] Moreover, not only the distributed processing of the delivery itself, but also the encoding process of the captured data may be performed on each terminal, on the server side, or shared between them. As an example, generally in the encoding process, the processing loop is performed twice. In the first loop, the complexity of the image in units of frames or scenes, or the amount of codes is detected. Also, in the second loop, a process to improve the encoding efficiency while maintaining the image quality is performed. For example, by having the terminal perform the first encoding process and the server side that receives the content perform the second encoding process, it is possible to improve the quality and efficiency of the content while reducing the processing load on each terminal. In this case, if there is a requirement to receive and decode in almost real time, the first encoded data performed by the terminal can also be received and played back by other terminals, so more flexible real-time delivery becomes possible.

[0395] As another example, cameras such as camera ex113 extract feature amounts (amounts of features or characteristics) from images, compress data related to the feature amounts as metadata, and transmit the compressed data to a server. The server performs compression according to the meaning (or importance of content) of the image, for example, by determining the importance of an object from the feature amounts and switching the quantization accuracy. The feature amount data is particularly effective in improving the accuracy and efficiency of motion vector prediction during re-compression at the server. Also, simple encoding such as VLC (Variable Length Coding) may be performed at the terminal, and encoding with a large processing load such as CABAC (Context Adaptive Binary Arithmetic Coding) may be performed at the server.

[0396] As yet another example, in a stadium, a shopping mall, a factory, etc., there may be a plurality of video data in which substantially the same scene is captured by a plurality of terminals. In this case, using the plurality of terminals that performed the shooting, and other terminals and a server that did not perform shooting as necessary, encoding processing is respectively assigned and distributed processing is performed, for example, in units of GOP (Group of Picture), picture units, or tile units obtained by dividing a picture. Thereby, the delay can be reduced and more real-time performance can be realized.

[0397] Since the plurality of video data are of substantially the same scene, the server may manage and / or give instructions so that the video data captured by each terminal can be referred to each other. Also, the server may receive the encoded data from each terminal and change the reference relationship between the plurality of data, or correct or replace the picture itself and re-encode it. Thereby, a stream with improved quality and efficiency of each piece of data can be generated.

[0398] Furthermore, the server may perform transcoding to change the encoding method of the video data and then distribute the video data. For example, the server may convert an MPEG-based encoding method to a VP-based (e.g., VP9) method, or convert H.264 to H.265, etc.

[0399] In this way, the encoding process can be performed by the terminal or one or more servers. Therefore, hereinafter, descriptions such as "server" or "terminal" will be used as the entity performing the process. However, part or all of the processes performed by the server may be performed by the terminal, or part or all of the processes performed by the terminal may be performed by the server. Also, regarding these, the same applies to the decoding process.

[0400] [3D, Multi-angle] There is an increasing trend to integrate and utilize different scenes captured by a plurality of cameras ex113 and / or terminals such as smartphones ex115 that are substantially synchronized with each other, or images or videos of the same scene captured from different angles. The videos captured by each terminal can be integrated based on the relative positional relationship between the terminals obtained separately or the regions where the feature points included in the videos match.

[0401] The server may not only encode a two-dimensional moving image, but also automatically encode a still image based on scene analysis of the moving image or at a time specified by the user, and transmit it to the receiving terminal. If the server can further obtain the relative positional relationship between the shooting terminals, it can generate the three-dimensional shape of the scene based on not only the two-dimensional moving image but also the videos of the same scene captured from different angles. The server may separately encode the three-dimensional data generated by a point cloud or the like, or select or reconstruct the video to be transmitted to the receiving terminal from the videos captured by a plurality of terminals based on the results of recognizing or tracking a person or an object using the three-dimensional data.

[0402] In this way, the user can arbitrarily select each video corresponding to each shooting terminal to enjoy the scene, or can enjoy the content obtained by cutting out the video from the selected viewpoint from the three-dimensional data reconstructed using a plurality of images or videos. Furthermore, sounds are also collected from a plurality of different angles together with the video, and the server may multiplex the sound from a specific angle or space with the corresponding video and transmit the multiplexed video and sound.

[0403] In recent years, content that associates the real world with the virtual world, such as Virtual Reality (VR) and Augmented Reality (AR), has also become popular. In the case of VR images, the server may create viewpoint images for the right eye and the left eye respectively, and perform encoding that allows references between each viewpoint video by means of Multi-View Coding (MVC) or the like, or may perform encoding as separate streams without referring to each other. At the time of decoding the separate streams, it is preferable to synchronize and play them so that a virtual three-dimensional space is reproduced according to the user's viewpoint.

[0404] In the case of AR images, the server may superimpose virtual object information in the virtual space on the camera information of the real space based on the three-dimensional position or the movement of the user's viewpoint. The decoding device may acquire or hold the virtual object information and the three-dimensional data, generate a two-dimensional image according to the movement of the user's viewpoint, and create superimposed data by smoothly connecting them. Alternatively, the decoding device may transmit the movement of the user's viewpoint to the server in addition to the request for the virtual object information. 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 distribute it to the decoding device. Note that the superimposed data typically has an α value indicating transparency in addition to RGB, and the server may encode it with the α value of the portion other than the object created from the three-dimensional data set to 0 or the like so that the portion is in a transparent state. Alternatively, the server may generate data in which an RGB value of a predetermined value is set as the background like chroma key, and the portion other than the object is the background color. The RGB value of the predetermined value may be predetermined.

[0405] The decoding process of the data delivered in the same manner may be performed on the client side (e.g., a terminal), on the server side, or may be shared between 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 another terminal and decoded, and the decoded signal may be transmitted to a device having a display. By dispersing the processing regardless of the performance of the communicable terminals themselves and selecting appropriate content, it is possible to reproduce data with good image quality. As another example, while receiving large-size image data on a TV or the like, a part of the area such as a tile in which a picture is divided may be decoded and displayed on the personal terminal of the viewer. Thereby, while sharing the overall image, it is possible to check at hand the area of one's own field of responsibility or the area that one wants to check in more detail.

[0406] In a situation where multiple short-range, medium-range, or long-range wireless communications inside and outside the house can be used, it may be possible to receive content seamlessly using a delivery system standard such as MPEG-DASH. The user may freely select a decoding device or a display device such as the user's terminal and a display arranged inside and outside the house and switch them in real time. Also, using the user's own location information or the like, decoding can be performed while switching the terminal to be decoded and the terminal to be displayed. Thereby, while the user is moving to the destination, it becomes possible to map and display information on a part of the wall surface or the ground of the adjacent building in which the displayable device is embedded. Also, based on the ease of access to the encoded data on the network, such as the encoded data being cached in a server that can be accessed from the receiving terminal in a short time or being copied to an edge server in a content delivery service, it is also possible to switch the bit rate of the received data.

[0407] [Scalable Encoding] Regarding content switching, an explanation will be given using a scalable stream compressed and encoded by applying the moving image encoding method shown in each of the above embodiments, as shown in FIG. 62. The server may have a plurality of streams with the same content but different qualities as individual streams. However, by taking advantage of the characteristics of a temporally / spatially scalable stream realized by encoding in layers as shown in the figure, a configuration for switching content may be adopted. That is, by determining which layer to decode according to internal factors such as performance and external factors such as the state of the communication bandwidth on the decoding side, the decoding side can freely switch between low-resolution content and high-resolution content for decoding. For example, when a user wants to watch the continuation of a video that was being viewed on a smartphone ex115 while moving on a device such as an Internet TV after returning home, the device only needs to decode the same stream to a different layer, thus reducing the burden on the server side.

[0408] Furthermore, as described above, pictures are encoded for each layer. In addition to the configuration that realizes scalability in the enhancement layer above the base layer, the enhancement layer may include meta information based on statistical information of the image or the like. The decoding side may generate high-quality content by super-resolving the picture of the base layer based on the meta information. The super-resolution may improve the signal-to-noise ratio while maintaining and / or expanding the resolution. The meta information includes information for specifying linear or non-linear filter coefficients for use in super-resolution processing, or information for specifying parameter values in filter processing, machine learning, or least squares operation used in super-resolution processing.

[0409] Alternatively, a configuration may be provided in which a picture is divided into tiles or the like according to the meaning of an object or the like in the image. The decoding side decodes only a part of the area by selecting the tile to be decoded. Further, by storing the attributes of the object (such as a person, a car, a ball, etc.) and the position in the video (such as the coordinate position in the same image) as meta information, the decoding side can specify the position of a desired object based on the meta information and determine the tile including the object. For example, as shown in FIG. 63, the meta information may be stored using a data storage structure different from the pixel data, such as an SEI (supplemental enhancement information) message in HEVC. This meta information indicates, for example, the position, size, or color of the main object.

[0410] The meta information may be stored in a unit composed of a plurality of pictures, such as a stream, a sequence, or a random access unit. The decoding side can obtain the time when a specific person appears in the video, etc., and by combining the information per picture and the time information, can specify the picture in which the object exists and determine the position of the object in the picture.

[0411] [Optimization of Web Page] FIG. 64 is a diagram showing an example of a display screen of a web page on a computer ex111 or the like. FIG. 65 is a diagram showing an example of a display screen of a web page on a smartphone ex115 or the like. As shown in FIGS. 64 and 65, the web page may include a plurality of link images that are links to image contents, and the appearance thereof may be different depending on the device for viewing. When a plurality of link images are visible on the screen, until the user explicitly selects a link image, or until the link image approaches the vicinity of the center of the screen or the entire link image enters the screen, the display device (decoding device) may display a still image or an I picture that each content has as a link image, or may display a video like a gif animation using a plurality of still images or I pictures, etc., or may receive only the base layer and decode and display the video.

[0412] When a user selects a linked image, the display device performs decoding, for example, with the base layer having the highest priority. If there is information indicating that the HTML constituting the web page is scalable content, the display device may decode up to the enhancement layer. Furthermore, in order to ensure real-time performance, before selection or when the communication bandwidth is extremely strict, the display device can reduce the delay (the delay from the start of content decoding to the start of display) between the decoding time and the display time of the leading picture by decoding and displaying only forward-referenced pictures (I pictures, P pictures, B pictures with only forward references). Additionally, the display device may deliberately ignore the reference relationship of pictures, coarsely decode all B pictures and P pictures with forward references, and perform normal decoding as the received pictures increase over time.

[0413] [Autonomous Driving] Also, when transmitting and receiving still image or video data such as two-dimensional or three-dimensional map information for the autonomous driving or driving assistance of a vehicle, in addition to the image data belonging to one or more layers, the receiving terminal may also receive weather or construction information, etc. as meta information and decode them in association. Note that the meta information may belong to a layer or may simply be multiplexed with the image data.

[0414] In this case, since vehicles, drones, airplanes, etc. including the receiving terminal move, the receiving terminal can realize seamless reception and decoding by transmitting the position information of the receiving terminal while switching between base stations ex106 to ex110. Also, the receiving terminal can dynamically switch how much meta information to receive or how much to update the map information according to the user's selection, the user's situation, and / or the state of the communication bandwidth.

[0415] In the content supply system ex100, the client can receive, decode, and play back the encoded information transmitted by the user in real time.

[0416] [Delivery of Personal Content] In addition, in the content supply system ex100, not only high-quality and long-duration content by video distributors but also unicast or multicast distribution of low-quality and short-duration content by individuals is possible. It is considered that such individual content will increase in the future. In order to make individual content into better content, the server may perform encoding processing after performing editing processing. This can be realized, for example, using the following configuration.

[0417] During shooting in real time or after accumulating and shooting, the server performs recognition processing such as shooting error, scene search, semantic analysis, and object detection from the original image data 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 with lower brightness or out-of-focus compared to other pictures, emphasizes the edges of objects, or changes the color tone. The server encodes the edited data based on the editing result. It is also known that if the shooting time is too long, the viewing rate will decrease. The server may automatically clip not only less important scenes but also scenes with little movement within a specific time range according to the shooting time so as to become content within the specific time range, based on the image processing result. Alternatively, the server may generate a digest based on the result of semantic analysis of the scene and encode it.

[0418] Personal content may sometimes contain elements that, as they are, would infringe copyright, moral rights, or portrait rights, etc., and there may be inconvenient situations for individuals, such as the sharing scope exceeding the intended scope. Therefore, for example, the server may deliberately change an image so that the face of a person in the peripheral part of the screen or the inside of a house is out of focus and then encode it. Furthermore, the server may recognize whether a face of a person different from a pre-registered person appears in the image to be encoded, and if it does, perform processing such as applying a mosaic to the face part. Or, as pre-processing or post-processing of encoding, a user may specify a person or a background area that the user wants to process the image from the perspective of copyright, etc. The server may perform processing such as replacing the specified area with another video or blurring the focus. In the case of a person, in a moving image, the person can be tracked and the video of the face part of the person can be replaced.

[0419] Since the viewing of personal content with a small data volume has a strong requirement for real-time performance, depending on the bandwidth, the decoding device may first receive the base layer with the highest priority and perform decoding and playback. During this period, the decoding device may receive the enhancement layer and, when the playback is looped or played back two or more times, play back a high-quality video including the enhancement layer. For a stream with scalable encoding like this, the video is rough when not selected or at the beginning of viewing, but it can provide an experience where 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 back for the first time and a second stream encoded with reference to the first video are configured as one stream.

[0420] [Other implementation and application examples] Also, these encoding or decoding processes are generally processed in the LSIex500 possessed by each terminal. The LSI (large scale integration circuitry) ex500 (see FIG. 61) may be a one-chip configuration or a configuration consisting of multiple chips. Note that software for moving image encoding or decoding may be incorporated into some recording medium (such as a CD-ROM, flexible disk, or hard disk) readable by a computer ex111 or the like, and encoding or decoding processing may be performed using the software. Further, when the smartphone ex115 has a camera, video data acquired by the camera may be transmitted. The video data at this time may be data encoded by the LSIex500 possessed by the smartphone ex115.

[0421] Note that 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 may download a codec or application software and then acquire and play the content.

[0422] Also, not limited to the content supply system ex100 via the Internet ex101, at least one of the moving image encoding device (image encoding device) or the moving image decoding device (image decoding device) of the above embodiments can be incorporated into a digital broadcast system. Since multiplexed data in which video and audio are multiplexed is carried on a broadcast radio wave using a satellite or the like for transmission and reception, there is a difference in that it is more suitable for multicast compared to the unicast-friendly configuration of the content supply system ex100, but similar applications are possible for encoding and decoding processes.

[0423] [Hardware Configuration] FIG. 66 is a diagram showing further details of the smartphone ex115 shown in FIG. 61. Further, FIG. 67 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 capturing video and still images, and a display unit ex458 for displaying data obtained by decoding video images captured by the camera unit ex465 and video images 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 captured video or still images, recorded audio, received video or still images, encoded data such as emails, or decoded data, and a slot unit ex464 which is an interface unit for the SIM ex468 for identifying the user and authenticating access to various data including the network. Note that an external memory may be used instead of the memory unit ex467.

[0424] A main control unit ex460 capable of comprehensively controlling the display unit ex458, the operation unit ex466, etc., 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 / demultiplexing unit ex453, an audio signal processing unit ex454, a slot unit ex464, and a memory unit ex467 are connected via a synchronization bus ex470.

[0425] When the power key is turned on by the user's operation, the power supply circuit unit ex461 activates the smartphone ex115 to an operable state and supplies power to each unit from the battery pack.

[0426] The smartphone ex115 performs processes such as calls and data communication based on the control of the main control unit ex460 having a CPU, ROM, RAM, etc. During a call, the voice signal picked up by the voice input unit ex456 is converted into a digital voice signal by the voice signal processing unit ex454, subjected to spread spectrum processing by the modulation / demodulation unit ex452, and subjected to digital-to-analog conversion processing and frequency conversion processing by the transmission / reception unit ex451, and the resulting signal is transmitted via the antenna ex450. Also, the received data is amplified and subjected to frequency conversion processing and analog-to-digital conversion processing, subjected to inverse spread spectrum processing by the modulation / demodulation unit ex452, converted into an analog voice signal by the voice signal processing unit ex454, and then output from the voice output unit ex457. In the data communication mode, text, still images, or video data can be sent under the control of the main control unit ex460 via the operation input control unit ex462 based on operations of the operation unit ex466 of the main body unit or the like. Similar transmission and reception processes are performed. 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 / demultiplexing unit ex453. The voice signal processing unit ex454 encodes the voice signal picked up by the voice input unit ex456 while the camera unit ex465 is capturing video or still images, and sends the encoded voice data to the multiplexing / demultiplexing unit ex453. The multiplexing / demultiplexing unit ex453 multiplexes the encoded video data and the encoded voice data in a predetermined manner, performs modulation processing and conversion processing by the modulation / demodulation unit (modulation / demodulation circuit unit) ex452 and the transmission / reception unit ex451, and transmits it via the antenna ex450. The predetermined manner may be determined in advance.

[0427] When receiving a video attached to an email 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 / demultiplexing 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, 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 moving image encoding method shown in each of the above embodiments, and a video or a still image included in the linked moving image file is displayed from the display unit ex458 via the display control unit ex459. The audio signal processing unit ex454 decodes the audio signal, and audio is output from the audio output unit ex457. Since real-time streaming is becoming increasingly popular, depending on the user's situation, it may not be socially appropriate to play audio. Therefore, as an initial value, it is desirable to have a configuration that plays only video data without playing the audio signal, and the audio may be played synchronously only when the user performs an operation such as clicking on the video data.

[0428] Also, here, the smartphone ex115 has been described as an example. However, as the terminal, in addition to the transceiver type terminal having both an encoder and a decoder, other implementation forms such as a transmitting terminal having only an encoder and a receiving terminal having only a decoder are conceivable. In the digital broadcast system, it has been described as receiving or transmitting multiplexed data in which audio data is multiplexed with video data. However, in the multiplexed data, character data related to the video, etc. may be multiplexed in addition to the audio data. Also, instead of the multiplexed data, the video data itself may be received or transmitted.

[0429] Although the main control unit ex460 including the CPU has been described as controlling the encoding or decoding process, many types of terminals often have a GPU. Therefore, a configuration may be adopted in which a wide area is processed in a batch by taking advantage of the performance of the GPU using a memory shared by the CPU and the 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 processes of motion search, deblocking filter, SAO (Sample Adaptive Offset), and transform / quantization in units such as pictures using the GPU instead of the CPU.

Claims

1. A circuit, a memory connected to the circuit, and in operation, the circuit defines a first partition and a second partition having non-rectangular shapes in a current block of an image such that the first partition and the second partition overlap each other, uses only a single prediction motion vector when encoding the first partition and the second partition, when encoding the first partition and the second partition, the circuit derives a first single prediction motion vector from a plurality of dual prediction motion vector candidates of the first partition and the second partition, generates a first predicted image of the first partition using the first single prediction motion vector, derives a second single prediction motion vector from the plurality of dual prediction motion vector candidates, generates a second predicted image of the second partition using the second single prediction motion vector, generates a predicted image of the current block by combining the first predicted image and the second predicted image, wherein the plurality of dual prediction motion vector candidates are included in a merge list, An image encoding apparatus.

2. A circuit, a memory connected to the circuit, and in operation, the circuit defines a first partition and a second partition having non-rectangular shapes in a current block of an image such that the first partition and the second partition overlap each other, uses only a single prediction motion vector when decoding the first partition and the second partition, when decoding the first partition and the second partition, the circuit derives a first single prediction motion vector from a plurality of dual prediction motion vector candidates of the first partition and the second partition, generates a first predicted image of the first partition using the first single prediction motion vector, derives a second single prediction motion vector from the plurality of dual prediction motion vector candidates, generates a second predicted image of the second partition using the second single prediction motion vector, generates a predicted image of the current block by combining the first predicted image and the second predicted image, wherein the plurality of dual prediction motion vector candidates are included in a merge list, An image decoding apparatus.

3. A circuit, a memory connected to the circuit, and in operation, the circuit Generate prediction parameters for causing a decoding device to execute prediction processing on an image block, Include the prediction parameters and the image block in a bitstream, In the prediction processing, A first partition and a second partition having non-rectangular shapes are defined in the image block such that the first partition and the second partition overlap each other, Only a single prediction motion vector is used to decode the first partition and the second partition, Upon decoding the first partition and the second partition, A first single prediction motion vector is derived from a plurality of dual prediction motion vector candidates of the first partition and the second partition, A first predicted image of the first partition is generated using the first single prediction motion vector, A second single prediction motion vector is derived from the plurality of dual prediction motion vector candidates, A second predicted image of the second partition is generated using the second single prediction motion vector, A predicted image of the image block is generated by combining the first predicted image and the second predicted image, The plurality of dual prediction motion vector candidates are included in a merge list, A bitstream generation device.

Images