Transmitting device and transmitting method

Abstract

To reduce the memory access amount in inter prediction processing.SOLUTION: A transmission device includes circuitry and memory. The circuitry is configured to: derive a base motion vector (S3001); derive a first motion vector (S3002); derive a differential motion vector (S3003); determine whether the differential motion vector is greater than a threshold (S3004); if it is determined that the differential motion vector is greater than the threshold, then set a second motion vector to a first value, and, if it is determined that the differential motion vector is not greater than the threshold, then set the second motion vector to a second value, and encode a processing target block using the second motion vector (S3007); and generate a bitstream including the processing target block encoded, and transmit the generated bitstream, where the threshold is different between a case where the processing target block is unidirectionally predicted and a case where the processing target block is bidirectionally predicted.SELECTED DRAWING: Figure 53

Description

Technical Field

[0001] The present disclosure relates to video coding, for example, systems, components, and methods in video encoding and decoding, etc.

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). Along with this progress, it is always necessary to provide improvements and optimizations to video coding technology in order to process the continuously increasing amount of digital video data in various applications.

[0003] Non-Patent Document 1 relates to an example of a conventional standard regarding the video coding technology described above.

Prior Art Documents

Non-Patent Documents

[0004]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Regarding the encoding method as described above, for the improvement of encoding efficiency, the improvement of image quality, the reduction of processing volume, the reduction of circuit scale, or the appropriate selection of elements or operations such as filters, blocks, sizes, motion vectors, reference pictures, or reference blocks, etc., the proposal of a new method is desired.

[0006] The present disclosure provides a configuration or method that can contribute to, for example, improvement of encoding efficiency, improvement of image quality, reduction of processing amount, reduction of circuit scale, improvement of processing speed, and appropriate selection of elements or operations. Note that the present disclosure may include a configuration or method that can contribute to benefits other than the above.

Means for Solving the Problems

[0007] For example, a transmission device according to one aspect of the present disclosure includes a circuit and a memory connected to the circuit. In operation, the circuit derives a reference motion vector that is a motion vector used for prediction of a processing target block and is a motion vector of a control point of an affine mode in the processing target block, the prediction mode of the processing target block being an affine mode. The circuit derives a first motion vector different from the reference motion vector, derives a differential motion vector based on a difference between the reference motion vector and the first motion vector, determines whether the differential motion vector is greater than a threshold value, and when it is determined that the differential motion vector is greater than the threshold value, sets a first value to a second motion vector different from the reference motion vector and the first motion vector. When it is determined that the differential motion vector is not greater than the threshold value, a second value different from the first value is set to the second motion vector. The circuit encodes the processing target block using the second motion vector, generates a bitstream including the encoded processing target block, transmits the generated bitstream, and the threshold value is different between the case where the processing target block is unidirectionally predicted and the case where the processing target block is bidirectionally predicted.

[0008] 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 appropriate filters, block sizes, motion vectors, reference pictures, reference blocks, and the like.

[0009] Further advantages and effects in one aspect of the present disclosure will become 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 it is not necessary to provide all of them in order to obtain one or more advantages and / or effects.

[0010] 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.

Effects of the Invention

[0011] The configuration or method according to one aspect of the present disclosure can contribute to, for example, one or more of improvement in coding efficiency, improvement in image quality, reduction in processing amount, reduction in circuit scale, improvement in processing speed, and appropriate selection of elements or operations. Note that the configuration or method according to one aspect of the present disclosure may contribute to benefits other than the above.

Brief Description of the Drawings

[0012]

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DETAILED DESCRIPTION OF THE INVENTION

[0013] An encoding device according to an aspect of the present disclosure includes a circuit and a memory connected to the circuit. In operation, the circuit derives a reference motion vector, which is a motion vector used for predicting a processing target block and is a motion vector of a control point of the processing target block, derives a first motion vector different from the reference motion vector, derives a differential motion vector based on a difference between the reference motion vector and the first motion vector, determines whether the differential motion vector is greater than a threshold value, changes the first motion vector when it is determined that the differential motion vector is greater than the threshold value, does not change the first motion vector when it is determined that the differential motion vector is not greater than the threshold value, and encodes the processing target block using the changed first motion vector or the first motion vector that has not been changed.

[0014] As a result, the encoding device can adjust the motion vectors so that the variations in the plurality of motion vectors within the processing target block divided into a plurality of sub-blocks fall within a predetermined range. Therefore, compared with the case where the variation in the motion vectors is larger than the predetermined range, the number of pixels to be referred to is reduced, so that the amount of data transferred from the memory can be suppressed within a predetermined range. Accordingly, the encoding device can reduce the memory access amount in the inter prediction process, and thus the encoding efficiency is improved.

[0015] For example, the reference motion vector may correspond to a first pixel set within the processing target block, and the first motion vector may correspond to a second pixel set different from the first pixel set within the processing target block.

[0016] As a result, the encoding device can appropriately control the variation in the plurality of motion vectors within the processing target block by using the reference motion vector determined based on the first pixel set and the first motion vector determined based on the second pixel set.

[0017] For example, when it is determined that the differential motion vector is larger than the threshold value, the circuit may change the first motion vector by using a value obtained by clipping the differential motion vector.

[0018] As a result, the encoding device can change the first motion vector so that the variation in the first motion vector falls within a predetermined range. Therefore, the encoding device can reduce the memory access amount in the inter prediction process, and thus the encoding efficiency is improved.

[0019] For example, the circuit may derive the control point of the processing target block based on the motion vector of an encoded block adjacent to the processing target block, and derive the reference motion vector of the processing target block, which is the motion vector of the control point.

[0020] As a result, the encoding device can derive the reference motion vector of the block to be processed based on the motion vectors of the encoded blocks adjacent to the block to be processed, so the prediction accuracy is improved.

[0021] For example, the control point may be a control point of the affine mode in the block to be processed, and the circuit may derive the reference motion vector, which is the motion vector of the control point.

[0022] As a result, the encoding device can predict the block to be processed in units of sub-blocks, so the prediction accuracy is improved.

[0023] For example, the control point may be located at at least one of the upper left corner, upper right corner, and lower left corner of the block to be processed.

[0024] As a result, since the motion vector of the control point located at the corner of the block to be processed is derived as the reference motion vector, the encoding device can adjust so that the variation of the first motion vectors in a plurality of sub-blocks within the block to be processed falls within a predetermined range. Therefore, the encoding device can reduce the amount of memory access in the inter-prediction process, so the encoding efficiency is improved.

[0025] For example, the circuit may derive the motion vector of at least one control point among the plurality of control points of the block to be processed as the reference motion vector.

[0026] As a result, the encoding device can derive the difference between the reference motion vector and the first motion vector, with the motion vector of at least one control point of the block to be processed as the reference motion vector.

[0027] For example, the reference motion vector may be derived as the average of the motion vectors of the plurality of control points.

[0028] As a result, the encoding device can derive the difference between the reference motion vector and the first motion vector, with the average of the motion vectors of a plurality of control points of the processing target block as the reference motion vector.

[0029] For example, the reference motion vector may be derived as a combination of the motion vectors of the plurality of control points. For example, in the combination, the maximum absolute value among the absolute values of the horizontal components of the motion vectors of the plurality of control points may be used as the horizontal component of the reference motion vector, and the maximum absolute value among the absolute values of the vertical components of the motion vectors of the plurality of control points may be used as the vertical component of the reference motion vector. Also, in the combination, the minimum absolute value among the absolute values of the horizontal components of the motion vectors of the plurality of control points may be used as the horizontal component of the reference motion vector, and the minimum absolute value among the absolute values of the vertical components of the motion vectors of the plurality of control points may be used as the vertical component of the reference motion vector.

[0030] As a result, the variation of the first motion vector within the processing target block is confined within a predetermined range. Therefore, the encoding efficiency is improved.

[0031] For example, the processing target block may be subjected to prediction processing using the affine mode.

[0032] As a result, the encoding device can predict the processing target block in units of sub-blocks, so the prediction accuracy is improved.

[0033] Also, a decoding apparatus according to one aspect of the present disclosure includes a circuit and a memory connected to the circuit. In operation, the circuit derives a reference motion vector, which is a motion vector used for predicting a processing target block and is a motion vector of a control point of the processing target block, derives a first motion vector different from the reference motion vector, derives a differential motion vector based on a difference between the reference motion vector and the first motion vector, determines whether the differential motion vector is greater than a threshold value, changes the first motion vector when it is determined that the differential motion vector is greater than the threshold value, does not change the first motion vector when it is determined that the differential motion vector is not greater than the threshold value, and decodes the processing target block using the changed first motion vector or the unchanged first motion vector.

[0034] Thereby, the decoding apparatus can adjust the motion vector so that the variation in the motion vectors within the processing target block divided into a plurality of sub-blocks falls within a predetermined range. Therefore, compared with the case where the variation in the motion vectors is greater than the predetermined range, the number of pixels to be referenced is reduced, so that the amount of data transferred from the memory can be suppressed within a predetermined range. Accordingly, the decoding apparatus can reduce the amount of memory access in the inter-prediction process, and thus the processing efficiency is improved.

[0035] For example, the reference motion vector may correspond to a first pixel set within the processing target block, and the first motion vector may correspond to a second pixel set different from the first pixel set within the processing target block.

[0036] Thereby, the decoding apparatus can appropriately control the variation in the motion vectors within the processing target block by using the reference motion vector determined based on the first pixel set and the first motion vector determined based on the second pixel set.

[0037] For example, when it is determined that the differential motion vector is greater than the threshold value, the circuit may change the first motion vector using a value obtained by clipping the differential motion vector.

[0038] Thereby, the decoding apparatus can change the first motion vector so that the variation of the first motion vector falls within a predetermined range. Therefore, the decoding apparatus can reduce the memory access amount in the inter prediction process, and thus the processing efficiency is improved.

[0039] For example, the circuit may derive the control point of the processing target block based on the motion vectors of the decoded blocks adjacent to the processing target block, and derive the reference motion vector of the processing target block, which is the motion vector of the control point.

[0040] Thereby, the decoding apparatus can derive the reference motion vector of the processing target block based on the motion vectors of the decoded blocks adjacent to the processing target block, and thus the prediction accuracy is improved.

[0041] For example, the control point is the control point of the affine mode in the processing target block, and the circuit may derive the reference motion vector, which is the motion vector of the control point.

[0042] Thereby, the decoding apparatus can predict the processing target block in units of sub-blocks, and thus the prediction accuracy is improved.

[0043] For example, the control point may be located at at least one of the upper left corner, upper right corner, and lower left corner of the processing target block.

[0044] As a result, since the motion vector of the control point located at the corner of the block to be processed is derived as the reference motion vector, the decoding device can adjust so that the variation of the first motion vectors in a plurality of sub-blocks within the block to be processed falls within a predetermined range. Therefore, the decoding device can reduce the memory access amount in the inter prediction process, and thus the processing efficiency is improved.

[0045] For example, the circuit may derive the motion vector of at least one control point among the plurality of control points of the block to be processed as the reference motion vector.

[0046] As a result, the decoding device can derive the difference between the reference motion vector and the first motion vector with the motion vector of at least one control point of the block to be processed as the reference motion vector.

[0047] For example, the reference motion vector may be derived as the average of the motion vectors of the plurality of control points.

[0048] As a result, the decoding device can derive the difference between the reference motion vector and the first motion vector with the average of the motion vectors of the plurality of control points of the block to be processed as the reference motion vector.

[0049] For example, the reference motion vector may be derived as a combination of the motion vectors of the plurality of control points. For example, in the combination, the maximum absolute value among the absolute values of the horizontal components of the motion vectors of the plurality of control points is used as the horizontal component of the reference motion vector, and the maximum absolute value among the absolute values of the vertical components of the motion vectors of the plurality of control points is used as the vertical component of the reference motion vector. Also, in the combination, the minimum absolute value among the absolute values of the horizontal components of the motion vectors of the plurality of control points may be used as the horizontal component of the reference motion vector, and the minimum absolute value among the absolute values of the vertical components of the motion vectors of the plurality of control points may be used as the vertical component of the reference motion vector.

[0050] As a result, the variation in the first motion vectors within the block to be processed is confined within a predetermined range. Therefore, the processing efficiency is improved.

[0051] For example, the block to be processed may be subjected to prediction processing using the affine mode.

[0052] As a result, the decoding apparatus can predict the block to be processed in units of sub-blocks, so that the prediction accuracy is improved.

[0053] Further, an encoding method according to an aspect of the present disclosure derives a reference motion vector that is a motion vector used for prediction of a block to be processed and is a motion vector of a control point of the block to be processed, derives a first motion vector different from the reference motion vector, derives a differential motion vector based on a difference between the reference motion vector and the first motion vector, determines whether the differential motion vector is greater than a threshold value, changes the first motion vector when it is determined that the differential motion vector is greater than the threshold value, does not change the first motion vector when it is determined that the differential motion vector is not greater than the threshold value, and encodes the block to be processed using the changed first motion vector or the first motion vector that has not been changed.

[0054] As a result, the encoding method can adjust the motion vectors so that the variation in the plurality of motion vectors within the block to be processed divided into a plurality of sub-blocks falls within a predetermined range. Therefore, compared with the case where the variation in the motion vectors is greater than a predetermined range, the number of pixels to be referenced is reduced, so that the amount of data transferred from the memory can be suppressed within a predetermined range. Therefore, the encoding method can reduce the amount of memory access in the inter prediction processing, so that the encoding efficiency is improved.

[0055] Also, a decoding method according to an aspect of the present disclosure derives a reference motion vector, which is a motion vector used for predicting a processing target block and is a motion vector of a control point of the processing target block, derives a first motion vector different from the reference motion vector, determines a differential motion vector based on a difference between the reference motion vector and the first motion vector, determines whether the differential motion vector is greater than a threshold value, changes the first motion vector when it is determined that the differential motion vector is greater than the threshold value, does not change the first motion vector when it is determined that the differential motion vector is not greater than the threshold value, and decodes the processing target block using the changed first motion vector or the first motion vector that has not been changed.

[0056] Thereby, the decoding method can adjust the motion vector so that the variation in the motion vectors within the processing target block divided into a plurality of sub-blocks falls within a predetermined range. Therefore, compared with the case where the variation in the motion vectors is greater than a predetermined range, the number of pixels to be referred to is reduced, and thus the amount of data transferred from the memory can be suppressed within a predetermined range. Accordingly, the decoding method can reduce the memory access amount in the inter-prediction process, and thus the processing efficiency is improved.

[0057] Furthermore, these general or specific aspects may be implemented by a system, an apparatus, a method, an integrated circuit, a computer program, or a non-transitory recording medium such as a computer-readable CD-ROM, or may be implemented by any combination of a system, an apparatus, a method, an integrated circuit, a computer program, and a recording medium.

[0058] Hereinafter, embodiments will be specifically described with reference to the drawings. Note that the embodiments described below are all examples showing general or specific aspects. 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.

[0059] 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, regarding the processes and / or configurations applied to the embodiments, any of the following may be implemented, for example.

[0060] (1) Any one of a plurality of components of the encoding device or the 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.

[0061] (2) In the encoding device or the decoding device of the embodiment, arbitrary changes such as addition, replacement, and deletion of functions or processes may be made to the functions or processes performed by some of the plurality of components of the encoding device or the 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.

[0062] (3) In the method implemented by the encoding device or the 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.

[0063] (4) Some of the plurality of components constituting the encoding device or the decoding device of the embodiment may be combined with the components described in any aspect of the present disclosure, or may be combined with components having a part of the functions described in any aspect of the present disclosure, or may be combined with components that implement a part of the processes performed by the components described in each aspect of the present disclosure.

[0064] (5) A component having a part of the functions of the encoding device or decoding device according to the embodiment, or a component that implements a part of the processing of the encoding device or decoding device according to the embodiment may be combined with or replaced by 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 implements a part of the processing described in any of the aspects of the present disclosure.

[0065] (6) In the method implemented by the encoding device or decoding device according to the embodiment, any of the plurality of processes included in the method may be replaced or combined with the process described in any of the aspects of the present disclosure or a similar process.

[0066] (7) Some of the plurality of processes included in the method implemented by the encoding device or decoding device according to the embodiment may be combined with the process described in any of the aspects of the present disclosure.

[0067] (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 according to 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.

[0068] [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 moving images in block units.

[0069] As shown in FIG. 1, the encoding device 100 is a device that encodes an image in block units, 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.

[0070] 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. Further, 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.

[0071] After explaining the overall processing flow of the encoding device 100 below, each component included in the encoding device 100 will be described.

[0072] [Overall Flow of Encoding Processing] FIG. 2 is a flowchart showing an example of the overall encoding processing by the encoding device 100.

[0073] 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).

[0074] 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).

[0075] 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).

[0076] 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.

[0077] 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.

[0078] 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).

[0079] 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.

[0080] When this reconstructed image is generated, the loop filter unit 120 performs filtering on the reconstructed image as necessary (step Sa_9).

[0081] 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.

[0082] 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 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 output encoded signal.

[0083] 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 those processes may be performed in parallel, and the order of those processes may be changed, etc.

[0084] [Splitting Unit] The splitting unit 102 splits each picture included in the input moving picture 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 (for example, 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 variable-size blocks (for example, 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 variable-size blocks are sometimes called Coding Units (CUs), Prediction Units (PUs), or Transformation 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 the processing units of CUs, PUs, and TUs.

[0085] FIG. 3 is a conceptual diagram showing an example of block splitting in the embodiment. In FIG. 3, the solid line represents the block boundary by quadtree block splitting, and the broken line represents the block boundary by binary tree block splitting.

[0086] 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).

[0087] 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.

[0088] The upper right 64x64 block is horizontally split into two rectangular 64x32 blocks 14, 15 (binary tree block splitting).

[0089] The bottom - 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 bottom - 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.

[0090] The bottom - right 64x64 block 23 is not divided.

[0091] As described above, in FIG. 3, block 10 is divided into 13 variable - size blocks 11 - 23 based on recursive quadtree and binary - tree block division. Such a division is sometimes called QTBT (quad - tree plus binary tree) division.

[0092] Note that 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). A division including such a ternary - tree block division is sometimes called MBT (multi - type tree) division.

[0093] [Picture Composition: Slice / Tile] To decode a picture in parallel, the picture may be composed in slice units or tile units. A picture composed of slice units or tile units may be formed by the dividing unit 102.

[0094] 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).

[0095] 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 four 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.

[0096] 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.

[0097] 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 four rectangular area tiles (Tile 1 - 4). When tiles are used, the processing order of the 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.

[0098] Note that one tile may contain one or more slices, and one slice may contain one or more tiles.

[0099] [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.

[0100] 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 (luma) signal and two color difference (chroma) signals). Hereinafter, the signal representing the image may also be referred to as a sample.

[0101] [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, for example, a predetermined discrete cosine transform (DCT) or discrete sine transform (DST) on the prediction error in the spatial domain. The predetermined DCT or DST may be determined in advance.

[0102] 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).

[0103] 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 transform basis functions corresponding to 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 on, for example, the type of prediction (intra prediction and inter prediction), or may depend on the intra prediction mode.

[0104] 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).

[0105] 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).

[0106] A separable transform and a non-separable transform may be applied to the transform unit 106. A separable transform is a method in which a plurality of 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.

[0107] 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 with 16 elements, and a 16×16 transformation matrix is used to perform a transformation process on the array.

[0108] In a further example of a non-separable transform, after regarding a 4×4 input block as an array with 16 elements, a transform (Hypercube Givens Transform) that performs a plurality of Givens rotations on the array may be performed.

[0109] 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 transformation 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 only dividing into two equal parts, but also into four equal parts, or information indicating the division can be separately encoded and signaled in the same way as CU division. Note that SVT is sometimes also called SBT (Sub-block Transform).

[0110] [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.

[0111] 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).

[0112] 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.

[0113] 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 values sampled at a predetermined interval by associating them with a predetermined level, and in this technical field, it may be referred to using other expressions such as rounding, rounding off, and scaling, or rounding, rounding off, and scaling may be adopted. The predetermined interval and level may be predetermined.

[0114] As methods of using the quantization matrix, there are a method of using a quantization matrix directly set on the encoder side and a method of using a default quantization matrix (default matrix). On the encoder 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 demerit that the amount of code increases due to the coding of the quantization matrix.

[0115] On the other hand, there is also a method of quantizing high-frequency components and low-frequency components in the same way without using a quantization matrix. Note that this method is equivalent to a method using a quantization matrix (flat matrix) in which all coefficients have the same value.

[0116] 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 sometimes be simply referred to as parameter sets.

[0117] [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, arithmetic-encodes the binary signal, and outputs a compressed bit stream or sequence.

[0118] [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 predefined.

[0119] [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.

[0120] 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.

[0121] [Addition Unit] The adder 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 adder 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.

[0122] [Block Memory] The block memory 118 is, for example, a storage unit for storing blocks within the 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 adder 116.

[0123] [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.

[0124] [Loop Filter Unit] The loop filter unit 120 applies a loop filter to the block reconstructed by the adder 116 and outputs the filtered reconstructed block to the frame memory 122. The loop filter is a filter (in-loop filter) used 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).

[0125] 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 is applied based on the direction and activity of the local gradient.

[0126] 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 direction and activity of gradients. For example, a classification value C (e.g., C = 5D+A) is calculated using a gradient direction value D (e.g., 0 to 2 or 0 to 4) and a gradient activity value A (e.g., 0 to 4). Then, based on the classification value C, the sub-blocks are classified into a plurality of classes.

[0127] 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.

[0128] Based on the results of such classification, a filter for the sub-blocks is determined from among a plurality of filters.

[0129] 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).

[0130] The on / off of ALF may be determined, for example, at the picture level or the CU level. For example, for luminance, it may be determined whether to apply ALF at the CU level, and for chrominance 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 the 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 the CU level, and it may be at other levels (for example, the sequence level, the slice level, the tile level, or the CTU level).

[0131] The coefficient sets of a plurality of selectable filters (for example, filters up to 15 or 25) are usually signaled at the picture level. Note that the signaling of the coefficient sets does not have to be limited to the picture level, and it may be at other levels (for example, the sequence level, the slice level, the tile level, the CTU level, the CU level, or the sub-block level).

[0132] [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.

[0133] FIG. 7 is a block diagram showing an example of the detailed configuration of the loop filter section 120 that functions as a deblocking filter.

[0134] 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.

[0135] The boundary determination section 1201 determines whether the pixel to be deblocking-filtered (i.e., the 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.

[0136] 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.

[0137] 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.

[0138] When the filter determination unit 1203 determines 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 the filter determination unit 1203 determines 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.

[0139] 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.

[0140] The switch 1206 selectively outputs the pixel that has not been deblocking filter processed and the pixel that has been deblocking filter processed by the filter processing unit 1205 according to the control by the process determination unit 1208.

[0141] The processing determination unit 1208 controls the switch 1206 based on the respective determination results of the boundary determination unit 1201 and the filter determination unit 1203. That is, when the boundary determination unit 1201 determines that the target pixel exists near the block boundary and the filter determination unit 1203 determines that the target pixel is to be subjected to deblocking filter processing, the processing determination unit 1208 causes the deblocking filter-processed pixel to be output from the switch 1206. Further, in cases other than the above, the processing determination unit 1208 causes the pixel that has not been subjected to deblocking filter processing to be output from the switch 1206. By repeatedly outputting such pixels, the image after the filter processing is output from the switch 1206.

[0142] FIG. 8 is a conceptual diagram showing an example of a deblocking filter having filter characteristics symmetric with respect to a block boundary.

[0143] In the deblocking filter processing, for example, using the pixel value and the quantization parameter, one of two deblocking filters having different characteristics, namely, 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 respective 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.

[0144] 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

[0145] In the above equations, 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 equations, the coefficient multiplied by the pixel value of each pixel used in the deblocking filter process is the filter coefficient.

[0146] 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 equation 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.

[0147] 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.

[0148] 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.

[0149] According to the Bs value in FIG. 10, even for block boundaries belonging to the same image, it is determined whether or not 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.

[0150] [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. 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.

[0151] 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. 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.

[0152] 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.

[0153] FIG. 12 is a flowchart showing another example of the processing performed by the prediction processing unit of the encoding apparatus 100.

[0154] 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.

[0155] 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 by 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 that method or mode.

[0156] 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.

[0157] FIG. 13 is a flowchart showing another example of the processing performed by the prediction processing unit of the encoding device 100.

[0158] 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.

[0159] 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 coding 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 necessary for coding motion information or the like for generating the predicted image. Also, λ is, for example, the Lagrange multiplier.

[0160] 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, a prediction method or mode for generating the predicted image of the current block is selected.

[0161] [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.

[0162] For example, the intra prediction unit 124 performs intra prediction using one of a plurality of predefined intra prediction modes. The plurality of intra prediction modes usually include one or more non-directional prediction modes and a plurality of directional prediction modes. The plurality of predefined modes may be predefined in advance.

[0163] 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.

[0164] 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).

[0165] 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.

[0166] 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).

[0167] [Inter prediction unit] The inter prediction unit 126 generates a prediction signal (inter prediction signal) by performing inter prediction (also called inter - frame prediction) of the current block with reference to a reference picture stored in the frame memory 122 that is different from the current picture. The inter prediction is performed in units of the current block or a current sub - block (e.g., 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 current sub - block, and finds the reference block or sub - block that most matches the current block or 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.

[0168] 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.

[0169] [Basic Flow of Inter Prediction] FIG. 15 is a flowchart showing an example of the basic flow of inter prediction.

[0170] The inter prediction unit 126 first generates a prediction image (steps Se_1 to Se_3). Next, the subtraction unit 104 generates the difference between the current block and the prediction image as a prediction residual (step Se_4).

[0171] Here, in generating the prediction image, the inter prediction unit 126 generates the prediction image by performing determination of the motion vector (MV) of the current block (steps Se_1 and Se_2) and motion compensation (step Se_3). Also, in determining the MV, the inter prediction unit 126 determines the MV by performing selection of candidate motion vectors (candidate MVs) (step Se_1) and derivation of the MV (step Se_2). The selection of the 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 MVs. 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 the searching for the region of the reference picture may be referred to as motion estimation.

[0172] Also, in the above example, steps Se_1 to Se_3 are performed by the inter prediction unit 126, but the processing such as step Se_1 or step Se_2 may be performed by other components included in the encoding device 100.

[0173] [Flow of Derivation of Motion Vector] FIG. 16 is a flowchart showing an example of motion vector derivation.

[0174] 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 the encoded bitstream).

[0175] Alternatively, the inter prediction unit 126 derives the MV in a mode that does not encode the motion information. In this case, the motion information is not included in the encoded signal.

[0176] Here, the modes of MV derivation may include, for example, the normal inter mode, merge mode, FRUC mode, and affine mode described later. Among these modes, the modes that encode the 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 described later. Also, the mode that does not encode the motion information includes 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.

[0177] FIG. 17 is a flowchart showing another example of motion vector derivation.

[0178] 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.

[0179] Alternatively, the inter prediction unit 126 derives the 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.

[0180] 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, merge mode, and 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.

[0181] [Flow of Derivation of Motion Vector] FIG. 18 is a flowchart showing another example of motion vector derivation. There are multiple modes for the mode of MV derivation, that is, the inter prediction mode, and broadly speaking, there are 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, FRUC mode, and affine mode (specifically, the affine merge mode). Details of these modes will be described later, but briefly, the merge mode is a mode for deriving the MV of the current block by selecting a motion vector from surrounding encoded blocks, and the FRUC mode is a mode for deriving the MV of the current block by performing a search between encoded regions. Also, the affine mode is a mode for deriving the motion vector of each of a plurality of sub-blocks constituting the current block as the MV of the current block assuming an affine transformation.

[0182] Specifically, as shown in the figure, when the inter-prediction mode information indicates 0 (0 in Sf_1), the inter-prediction unit 126 derives the motion vector by the merge mode (Sf_2). Further, when the inter-prediction mode information indicates 1 (1 in Sf_1), the inter-prediction unit 126 derives the 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 the motion vector by the affine mode (specifically, the affine merge mode) (Sf_4). Further, when the inter-prediction mode information indicates 3 (3 in Sf_1), the inter-prediction unit 126 derives the motion vector by the mode that encodes the differential MV (for example, the normal inter mode) (Sf_5).

[0183] [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 region of the reference picture indicated by the candidate MV. Also, in this normal inter mode, the differential MV is encoded.

[0184] FIG. 19 is a flowchart showing an example of inter-prediction by the normal inter mode.

[0185] 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.

[0186] 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.

[0187] Next, the inter prediction unit 126 selects one candidate prediction motion vector from among 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.

[0188] 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.

[0189] 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.

[0190] 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.

[0191] Note that the candidate MV list may be used in common with lists used in other modes. Also, the processing related to the candidate MV list may be applied to the processing related to the lists used in 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.

[0192] [MV Derivation > Merge Mode] The merge mode is an inter prediction mode for deriving an MV by selecting a candidate MV from a candidate MV list as the MV of the current block.

[0193] FIG. 20 is a flowchart showing an example of inter prediction by the merge mode.

[0194] 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.

[0195] 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.

[0196] 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).

[0197] 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.

[0198] FIG. 21 is a conceptual diagram for explaining an example of the motion vector derivation process of the current picture by the merge mode.

[0199] First, a predicted MV list in which candidates for the predicted MV are registered is generated. As candidates for the predicted MV, there are a spatial adjacent predicted MV which is the MV of a plurality of encoded blocks spatially adjacent to the target block, a temporal adjacent predicted 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 predicted MV which is an MV generated by combining the MV values of the spatial adjacent predicted MV and the temporal adjacent predicted MV, a zero predicted MV which is an MV with a value of zero, and the like.

[0200] Next, one predicted MV is selected from among the plurality of predicted MVs registered in the predicted MV list, and thus determined as the MV of the target block.

[0201] Furthermore, in the variable length encoding unit, merge_idx, which is a signal indicating which predicted MV is selected, is described in the stream and encoded.

[0202] Note that the predicted MVs registered in the predicted 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.

[0203] The final MV may be determined by performing DMVR (decoder motion vector refinement) processing described later using the MV of the target block derived in the merge mode.

[0204] Note that the candidates for the predicted MV are the above-described candidate MVs, and the predicted 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.

[0205] [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.

[0206] Here, a mode of performing motion search on the decoder side will be described. This mode of performing motion search on the decoder side may be referred to as the PMMVD (pattern matched motion vector derivation) mode or the FRUC (frame rate up-conversion) mode.

[0207] An example of FRUC processing is shown in FIG. 22 in the form of a flowchart. First, by referring 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) (that is, a candidate MV list, which may be common to 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, the 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, a motion vector for the current block may be derived by performing pattern matching. That is, search using pattern matching and evaluation values in the reference picture is performed on the region around the best candidate MV, and if there is an MV with a better evaluation value, the best candidate MV may be 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 with a better evaluation value is not performed.

[0208] 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).

[0209] When processing is performed in units of sub-blocks, the same processing may be performed.

[0210] 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.

[0211] 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. In addition to the difference value, other information may be used to calculate the evaluation value.

[0212] 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.

[0213] [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.

[0214] 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.

[0215] 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.

[0216] [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.

[0217] FIG. 24 is a conceptual diagram for explaining an example of pattern matching (template matching) between a template in the current picture and a block in the reference picture. As shown in FIG. 24, in the second pattern matching, the motion vector of the current block is derived by searching in the reference picture (Ref0) for the block that best matches the block adjacent to the current block (Cur block) in the current picture (Cur Pic). Specifically, for the current block, the difference between the reconstructed image of the encoded region of both or either of the left adjacent and upper adjacent blocks and the reconstructed image at the equivalent position in the encoded 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, as the best candidate MV, the candidate MV having the best evaluation value among a plurality of candidate MVs.

[0218] 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 (the first pattern matching or the second pattern matching) may be 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, CTU level, or sub-block level).

[0219] [MV Derivation > Affine Mode] Next, an 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.

[0220] 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 formula (1A), and the motion vectors (v x ,v y ) of each sub - block within the current block may be derived.

[0221] [Number]

[0222] Here, x and y respectively indicate the horizontal position and vertical position of the sub - block, and w indicates a predetermined weight coefficient. The predetermined weight coefficient may be determined in advance.

[0223] 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).

[0224] Also, such an affine mode may include several modes in which the methods of 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.

[0225] [MV Derivation > Affine Mode] FIG. 25B is a conceptual diagram for explaining an example of deriving a motion vector of a sub-block unit in an affine mode having three control points. In FIG. 25B, a current block includes 16 4x4 sub-blocks. Here, a motion vector v0 of the upper left control point of the current block is derived based on the motion vectors of adjacent blocks. Similarly, a motion vector v1 of the upper right control point of the current block is derived based on the motion vectors of adjacent blocks, and a motion vector v2 of the lower left control point of the current block is derived based on the motion vectors of adjacent blocks. Then, the three motion vectors v0, v1, and v2 may be projected by the following equation (1B), and the motion vectors (v x , v y ) of each sub-block within the current block may be derived.

[0226]

Equation

[0227] 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.

[0228] 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 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).

[0229] Also, in such an affine mode having three control points, several modes with different methods of deriving the motion vectors of the upper left, upper right, and lower left control points may be included. For example, the affine mode includes two modes: an affine inter (also referred to as affine normal inter) mode and an affine merge mode.

[0230] [MV Derivation > Affine Merge Mode] FIG. 26A, FIG. 26B, and FIG. 26C are conceptual diagrams for explaining the affine merge mode.

[0231] In the affine merge mode, as shown in FIG. 26A, for example, among the encoded blocks A (left), block B (upper), block C (upper right), block D (lower left), and block 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 this identified block, the predicted motion vectors of the control points of the current block are calculated.

[0232] 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.

[0233] 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.

[0234] Note that this predicted motion vector derivation method may also 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.

[0235] FIG. 27 is a flowchart showing an example of the affine merge mode.

[0236] 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). The control points are, as shown in FIG. 25A, 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.

[0237] 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.

[0238] 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.

[0239] 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.

[0240] 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 on 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.

[0241] [MV Derivation > Affine Inter Mode] FIG. 28A is a conceptual diagram for explaining the affine inter mode having two control points.

[0242] In this affine inter 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.

[0243] FIG. 28B is a conceptual diagram for explaining the affine inter mode having three control points.

[0244] In this affine inter 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.

[0245] FIG. 29 is a flowchart showing an example of the affine inter mode.

[0246] As shown in the figure, in the affine inter mode, first, the inter prediction unit 126 derives the predicted MV (v0, v1) or (v0, v1, v2) for 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.

[0247] 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.

[0248] 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 using cost evaluation or the like, and may describe a flag indicating which predicted motion vector is selected in the bit stream.

[0249] Next, the inter prediction unit 126 performs motion search (steps Sj_3 and Sj_4) while updating the predicted motion vectors selected or derived in step Sj_1 (step Sj_2). 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 using the above formula (1A) or formula (1B) (step Sj_3). Then, the inter prediction unit 126 performs motion compensation on each sub-block using those affine MVs and the encoded reference picture (step Sj_4). As a result, 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 in the motion search loop (step Sj_5). At this time, the inter prediction unit 126 further encodes the difference value between each of the determined MV and the predicted motion vector as a differential MV into the stream.

[0250] Finally, the inter prediction unit 126 generates a predicted image of the current block by performing motion compensation on the current block using the determined MV and the encoded reference picture (step Sj_6).

[0251] [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 coded block and the current block. FIGS. 30A and 30B are conceptual diagrams for explaining a method of deriving a prediction vector of control points when the number of control points is different between the coded block and the current block.

[0252] 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 coded 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 coded block including block A are derived. Then, from the derived motion vectors v3 and v4, a predicted motion vector v0 of the control point at the upper left corner of the current block and a predicted motion vector v1 of the control point at the upper right corner are calculated. Further, from the derived motion vectors v0 and v1, a predicted motion vector v2 of the control point at the lower left corner is calculated.

[0253] 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 coded 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 coded block including block A are derived. Then, from the derived motion vectors v3, v4, and v5, a predicted motion vector v0 of the control point at the upper left corner of the current block and a predicted motion vector v1 of the control point at the upper right corner are calculated.

[0254] This prediction 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.

[0255] [MV Derivation > DMVR] FIG. 31A is a flowchart showing the relationship between the merge mode and DMVR.

[0256] 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.

[0257] 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 region 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.

[0258] FIG. 31B is a conceptual diagram for explaining an example of the DMVR process for determining the MV.

[0259] 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.

[0260] Next, using the template, search for the peripheral regions 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 region, and the candidate MV value, etc.

[0261] 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.

[0262] Even if it is not the processing example itself described here, any processing may be used as long as it is a processing that can search the periphery of the candidate MV and derive the final MV.

[0263] [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.

[0264] FIG. 32 is a flowchart showing an example of generating a predicted image.

[0265] 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).

[0266] FIG. 33 is a flowchart showing another example of generating a predicted image.

[0267] The inter prediction unit 126 determines the motion vector of the current block (step Sn_1). Next, the inter prediction unit 126 generates a predicted 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 predicted image by correcting the predicted 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 predicted image as the final predicted image without correction (step Sn_5).

[0268] Also, in motion compensation, there is a mode of correcting luminance when generating a predicted image. That mode is, for example, LIC described later.

[0269] FIG. 34 is a flowchart showing another example of generating a predicted image.

[0270] 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 predicted image while performing luminance correction (step So_3). That is, the predicted 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 predicted image by normal motion compensation without performing luminance correction (step So_4).

[0271] [Motion Compensation > OBMC] An inter prediction signal may be generated using not only the motion information of the current block obtained by motion search but also the motion information of adjacent blocks. 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).

[0272] In the OBMC mode, information indicating the size of sub-blocks for OBMC (for example, called OBMC block size) may be signaled at the sequence level. Further, information indicating whether or not to apply the OBMC mode (for example, called OBMC flag) may be signaled at the CU level. Note that the signaling levels of these pieces of information do not have to be limited to the sequence level and the CU level, and may be other levels (for example, picture level, slice level, tile level, CTU level, or sub-block level).

[0273] 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 prediction image correction processing by OBMC processing.

[0274] 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 and indicates what the current block of the current picture refers to in order to obtain the prediction image.

[0275] 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 an 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.

[0276] 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 an 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).

[0277] 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.

[0278] 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.

[0279] 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 plurality of obtained corrected prediction images.

[0280] 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.

[0281] 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), decoding is performed by switching whether to apply the OBMC process according to the value.

[0282] 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.

[0283] FIG. 37 is a conceptual diagram for explaining generation of prediction images of two triangles.

[0284] 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.

[0285] In the example shown in FIG. 37, the first partition and the second partition are each a triangle, but they may be trapezoids, or they 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.

[0286] 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.

[0287] 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.

[0288] [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.

[0289] 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.

[0290] At this time, under the assumption of uniform linear motion of the velocity vector (vx, vy), (MVx0, MVy0) and (MVx1, MVy1) are represented by (vxτ0, vyτ0) and (-vxτ1, -vyτ1), respectively, and the following optical flow equation (2) may be adopted.

[0291]

Equation

[0292] 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.

[0293] 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.

[0294] [Motion Compensation > LIC] Next, an example of a mode for generating a predicted image (prediction) using LIC (local illumination compensation) processing will be described.

[0295] 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.

[0296] First, an MV is derived from the encoded reference picture to obtain a reference image corresponding to the current block.

[0297] 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 area (peripheral reference area) and the encoded upper adjacent reference area (peripheral reference area) in the current picture, and the luminance pixel values at the 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.

[0298] 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.

[0299] Note that the shape of the peripheral reference area in FIG. 39 is an example, and other shapes may be used.

[0300] 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 reference images obtained from each reference picture may be subjected to luminance correction processing in the same manner as described above, and then a predicted image may be generated.

[0301] As a method for determining whether to apply LIC processing, for example, there is a method that uses 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 encoding is performed by applying LIC processing. 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 thereof.

[0302] 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 neighboring blocks. As a specific example, when the current block is in merge mode, it is determined whether the encoded neighboring block selected during the derivation of the MV in the merge mode process has been encoded by applying LIC processing. Encoding is performed by switching whether to apply LIC processing according to the result. Note that even in this example, the same processing is applied to the processing on the decoder side.

[0303] Although the mode of LIC processing (luminance correction processing) has been described with reference to FIG. 39, the details will be described below.

[0304] First, the inter prediction unit 126 derives a motion vector for obtaining a reference image corresponding to the block to be encoded from the reference picture, which is an encoded picture.

[0305] Next, the inter prediction unit 126 extracts information indicating how the luminance values change between the reference picture and the picture to be coded for the block to be coded, using the luminance pixel values of the left and upper adjacent coded peripheral reference regions and the luminance pixel values at the equivalent positions in the reference picture specified by the motion vectors, and calculates the luminance correction parameters. For example, let the luminance pixel value of a certain pixel in the peripheral reference region within the picture to be coded 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 parameters, the coefficients A and B that optimize A×p1 + B = p0 for a plurality of pixels in the peripheral reference region.

[0306] 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 parameters, thereby generating a prediction image for the block to be coded. For example, let the luminance pixel value in the reference image be p2, and the luminance pixel value of the prediction image after the luminance correction processing be p3. The inter prediction unit 126 generates the prediction image after the luminance correction processing by calculating A×p2 + B = p3 for each pixel in the reference image.

[0307] 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 coded, and may be a region not adjacent to the block to be coded. The predetermined number regarding the pixels may be determined in advance.

[0308] 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 coded from the peripheral reference region within the picture to be coded, 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 within the picture to be coded.

[0309] Here, the operation of the encoding device 100 has been described. However, the operation of the decoding device 200 is typically the same.

[0310] 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.

[0311] Also, the LIC process may be applied in sub-block units. For example, correction parameters may be derived using the peripheral reference area of the current sub-block and the peripheral reference area of the reference sub-block in the reference picture specified by the MV of the current sub-block.

[0312] [Prediction control unit] The prediction control unit 128 selects either an intra prediction signal (a signal output from the intra prediction unit 124) or an inter prediction signal (a signal output from the inter prediction unit 126), and outputs the selected signal as a prediction signal to the subtraction unit 104 and the addition unit 116.

[0313] As shown in FIG. 1, in various examples of an encoding apparatus, 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 apparatus. The decoding apparatus 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.

[0314] [Implementation Example of Encoding Apparatus] FIG. 40 is a block diagram showing an implementation example of the encoding apparatus 100. The encoding apparatus 100 includes a processor a1 and a memory a2. For example, a plurality of components of the encoding apparatus 100 shown in FIG. 1 are implemented by the processor a1 and the memory a2 shown in FIG. 40.

[0315] 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 a moving image. 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 perform the roles of a plurality of components among the plurality of components of the encoding apparatus 100 shown in FIG. 1 and the like.

[0316] 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. Further, memory a2 may be included in processor a1. Also, memory a2 may be an aggregate of a plurality of electronic circuits. Further, 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.

[0317] 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, memory a2 may store a program for the processor a1 to encode a moving image.

[0318] Also, for example, memory a2 may serve as a component for storing information among a 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.

[0319] 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.

[0320] [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.

[0321] As shown in FIG. 41, the decoding apparatus 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.

[0322] The decoding apparatus 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 apparatus 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.

[0323] After explaining the overall processing flow of the decoding apparatus 200 below, each component included in the decoding apparatus 200 will be described.

[0324] [Overall Flow of Decoding Process] FIG. 42 is a flowchart showing an example of the overall decoding process by the decoding apparatus 200.

[0325] First, the entropy decoding unit 202 of the decoding apparatus 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 apparatus 100. Then, the decoding apparatus 200 performs the processing of steps Sp_2 to Sp_6 on each of the plurality of blocks constituting the division pattern.

[0326] 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).

[0327] 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).

[0328] Next, a prediction processing unit composed of 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).

[0329] 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).

[0330] When this reconstructed image is generated, the loop filter unit 212 performs filtering on the reconstructed image (step Sp_6).

[0331] 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.

[0332] 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 these processes may be performed in parallel, or the order may be changed, etc.

[0333] [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 processes as those performed by the intra prediction unit 124, the inter prediction unit 126, and the prediction control unit 128 on the encoding device side.

[0334] [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.

[0335] [Inverse Transform Unit] The inverse transform unit 206 restores the prediction error by inverse-transforming the transform coefficients that are the input from the inverse quantization unit 204.

[0336] For example, when the information decoded from the encoded bit stream indicates that EMT or AMT is to be applied (e.g., the AMT flag is true), the inverse transform unit 206 inverse-transforms the transform coefficients of the current block based on the information indicating the decoded transform type.

[0337] 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 an inverse reverse transform to the transform coefficients.

[0338] [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.

[0339] [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) that are referenced in intra prediction. Specifically, the block memory 210 stores the reconstructed block output from the addition unit 208.

[0340] [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, etc.

[0341] 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.

[0342] [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.

[0343] [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.

[0344] 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.

[0345] 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.

[0346] FIG. 44 is a flowchart showing another example of the processing performed by the prediction processing unit of the decoding apparatus 200.

[0347] 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.

[0348] 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).

[0349] 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.

[0350] [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 encoded bitstream. Specifically, the intra prediction unit 216 generates an intra prediction signal by performing intra prediction with reference to samples (e.g., luminance values, chrominance difference values) of blocks adjacent to the current block, and outputs the intra prediction signal to the prediction control unit 220.

[0351] In addition, when an intra prediction mode that refers to a luminance block is selected in the intra prediction of a chrominance difference block, the intra prediction unit 216 may predict the chrominance difference component of the current block based on the luminance component of the current block.

[0352] Also, when the information decoded from the encoded 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.

[0353] [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 bit stream (e.g., prediction parameters output from the entropy decoding unit 202), and outputs the inter prediction signal to the prediction control unit 220.

[0354] When the information decoded from the encoded bit stream indicates that the OBMC mode is 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.

[0355] Also, when the information decoded from the encoded bit stream indicates that the FRUC mode is applied, the inter prediction unit 218 derives motion information by performing motion search according to the pattern matching method (bilateral matching or template matching) decoded from the encoded stream. Then, the inter prediction unit 218 performs motion compensation (prediction) using the derived motion information.

[0356] 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 bit stream indicates that the affine motion compensation prediction mode is 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.

[0357] [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.

[0358] FIG. 45 is a flowchart showing an example of inter prediction in the normal inter mode in the decoding apparatus 200.

[0359] The inter prediction unit 218 of the decoding apparatus 200 performs motion compensation for each block. The inter prediction unit 218 obtains 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.

[0360] Next, the inter prediction unit 218 extracts each of N (N is an integer of 2 or more) candidate MVs from the plurality of candidate MVs obtained 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.

[0361] 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 the N prediction MV candidates as the prediction motion vector (also referred to as a prediction MV) of the current block (step Ss_3).

[0362] 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).

[0363] 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).

[0364] [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.

[0365] [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.

[0366] 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.

[0367] 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 processor b1. Also, memory b2 may be included in 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.

[0368] 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.

[0369] 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, a reconstructed block, a reconstructed picture, etc. may be stored in memory b2.

[0370] 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.

[0371] [Definitions of Each Term] Each term may be defined as follows as an example.

[0372] A picture is an array of a plurality of luminance samples in a 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.

[0373] A frame is a composition of a top field in which a plurality of sample rows 0, 2, 4,... occur, and a bottom field in which a plurality of sample rows 1, 3, 5,... occur.

[0374] 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.

[0375] A tile is a rectangular area 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 area 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.

[0376] 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 area of a plurality of pixels consisting of a plurality of matrices of one luminance and two chrominances.

[0377] 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.

[0378] 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.

[0379] [First Aspect] Hereinafter, the encoding device 100, decoding device 200, encoding method, and decoding method according to the first aspect of the present disclosure will be described.

[0380] FIG. 47 is a flowchart showing an example of the inter prediction process in the first aspect. Hereinafter, an example of the inter prediction process in the decoding device 200 will be described.

[0381] The inter prediction unit 218 in the decoding device 200 derives a reference motion vector, which is a motion vector used for predicting the processing target block and is the motion vector of the control point of the processing target block, derives a first motion vector different from the reference motion vector, derives a differential motion vector based on the difference between the reference motion vector and the first motion vector, determines whether the differential motion vector is greater than a threshold value, changes the first motion vector when it is determined that the differential motion vector is greater than the threshold value, does not change the first motion vector when it is determined that the differential motion vector is not greater than the threshold value, and decodes the processing target block using the changed first motion vector or the unchanged first motion vector. For example, the reference motion vector corresponds to a first pixel set in the processing target block, and the first motion vector corresponds to a second pixel set different from the first pixel set in the processing target block.

[0382] Hereinafter, the inter prediction process will be described more specifically with reference to the drawings. Note that the reference motion vector and the first motion vector described below are examples and are not limited thereto.

[0383] First, in step S1001, the inter prediction unit 218 derives a reference motion vector for a first pixel set in the processing target block. Hereinafter, the process of step S1001 will be described more specifically with reference to FIG. 48.

[0384] FIG. 48 is a diagram showing an example of a block to be processed. As shown in FIG. 48, the block to be processed may be composed of a plurality of sub-blocks (sub-block 0 to sub-block 5). Also, each sub-block may have a different first motion vector (MV0 to MV5). An example of the first pixel set may be sub-block 0. At this time, the reference motion vector may be one of the plurality of first motion vectors within the block to be processed. In this example, the reference motion vector is MV0.

[0385] Another example of the first pixel set may be the entire block to be processed. In this example, the reference motion vector is the average of the first motion vectors of all the sub-blocks within the block to be processed, that is, the average from MV0 to MV5.

[0386] Next, in step S1002, the inter prediction unit 218 derives the first motion vector of the second pixel set within the block to be processed. The second pixel set is different from the first pixel set. An example of the second pixel set may be sub-block 2. In this example, the first motion vector of the second pixel set is MV2.

[0387] Also, another example of the second pixel set may be sub-block 1. In this example, the first motion vector is MV1.

[0388] Next, in step S1003, the inter prediction unit 218 derives a differential motion vector based on the difference between the reference motion vector of the first pixel set and the first motion vector of the second pixel set. An example of the value of the reference motion vector may be (-3, 4). An example of the first motion vector may be (16, 5). Therefore, the differential motion vector between the first motion vector and the reference motion vector is (-19, -1).

[0389] Next, in step S1004, the inter prediction unit 218 determines whether the differential motion vector derived in step S1003 is greater than a threshold value. The threshold value may be a set of a first value (hereinafter, the first threshold value) and a second value (hereinafter, the second threshold value). An example of the threshold value is (10, 20). Hereinafter, an example of the determination process will be described.

[0390] When the absolute value of the horizontal component of the differential motion vector derived in step S1003 by the inter prediction unit 218 is greater than the first threshold value, or the absolute value of the vertical component of the differential motion vector is greater than the second threshold value, the differential motion vector is determined to be greater than the threshold value (Yes in step S1004). In other words, if either the absolute value of the horizontal component or the absolute value of the vertical component of the differential motion vector is greater than the threshold value, the differential motion vector is determined to be greater than the threshold value. For example, when comparing the absolute value of the horizontal component of the differential motion vector (-19, -1) exemplified in step S1003 with the first threshold value, since |-19| > 10, the differential motion vector is determined to be greater than the threshold value. In this case, the inter prediction unit 218 changes the first motion vector. Details of the change will be described in step S1006.

[0391] On the other hand, when the absolute value of the horizontal component of the differential motion vector is not greater than the first value of the threshold value and the absolute value of the vertical component of the differential motion vector is not greater than the second threshold value, the inter prediction unit 218 determines that the differential motion vector is not greater than the threshold value (No in step S1004). In other words, when both the absolute value of the horizontal component and the absolute value of the vertical component of the differential motion vector are less than or equal to the threshold value, the differential motion vector is determined to be less than or equal to the threshold value. When the inter prediction unit 218 determines that the differential motion vector is not greater than the threshold value (No in step S1004), it does not change the first motion vector (step S1005).

[0392] Next, in step S1006, when the inter prediction unit 218 determines that the differential motion vector is greater than the threshold (Yes in step S1004), the inter prediction unit 218 changes the first motion vector using the clipped value of the differential motion vector. At this time, the differential motion vector (-19, -1) is clipped to (-10, -1). As described above, since the absolute value |-19| of the horizontal component of the differential motion vector is greater than 10 which is the first threshold of the threshold (10, 20), the absolute value of the horizontal component of the differential motion vector is clipped so as to match the first threshold. Therefore, the clipped differential motion vector becomes (-10, -1).

[0393] Subsequently, the inter prediction unit 218 changes the first motion vector using the clipped differential motion vector and the reference motion vector. For example, the changed first motion vector is (-3, 4) - (-10, -1) = (7, 5).

[0394] In step S1007, the inter prediction unit 218 decodes the second pixel set using the changed first motion vector or the unchanged first motion vector. In the example of S1001 to S1006, sub-block 2 is decoded using the changed motion vector (7, 5).

[0395] Note that the process 1000 shown in FIG. 47 may be a process of an encoding device.

[0396] The process 1000 can be applied to all sub-blocks within the processing target block. When the process 1000 is applied to all sub-blocks within the processing target block, the processing target block may be predicted using the affine mode. Also, when the process 1000 is applied to all sub-blocks within the processing target block, the processing target block may be predicted using the ATMVP (Alternative Temporal Motion Vector Prediction) mode.

[0397] Note that the ATMVP mode is an example of a sub - block mode classified into the merge mode. For example, in the encoded reference picture specified by the MV (MV0) of the block adjacent to the lower left of the current block, a temporal MV reference block associated with the current block is identified, and for each sub - block in the processing target block, the MV used at the time of encoding the area corresponding to the sub - block in the temporal MV reference block is identified. Note that the ATMVP mode in terms of sub - blocks will be described later with reference to FIG. 50.

[0398] Also, the first motion vector of other sub - blocks of the processing target block may be updated using the first motion vector changed in the sub - block for specifying the processing target block. Hereinafter, the processing example will be described with reference to FIGS. 47 and 48.

[0399] For example, the MV0 of sub - block 0 is identified as the reference motion vector, the MV2 of sub - block 2 is identified as the first motion vector, and the first motion vector after the change is determined using process 1000. The first motion vector after the change of sub - block 2 is MV2’=(V 2x ’,V 2y ’). Using the reference motion vector MV0 and the first motion vector MV2’ after the change, the first motion vector MV i ’=(V ix ’,V iy ’) of sub - blocks i (i = 1, 3, 4, 5) other than sub - block 2 in the processing target block is calculated by the following formula.

[0400] V ix ’=(V 2x ’―V 0x )*POS ix / W-(V 2y ’―V 0y )*POS iy / W+V 0x V iy ’=(V 2y ’-V 0y )*POS ix / W+(V 2x ’―V0x )*POS iy / W+V 0y

[0401] And, MV i ’ is not greater than the threshold value, MV i ’ is used as MV i to update MV i and decode sub-block i using MV. POS ix and POS iy are the horizontal position and vertical position of sub-block i.

[0402] In the example of FIG. 48, POS 1x =W / 2, POS 1y =0 POS 3x =0, POS 3y =H POS 4x =W / 2, POS 4y =H POS 5x =W, POS 5y =H

[0403] W and H are the horizontal position and vertical position of sub-block 2 in the block to be processed (e.g., the X coordinate and Y coordinate of the lower left corner).

[0404] The threshold value may correspond to the size of the block to be processed. For example, the larger the size of the block to be processed, the larger the threshold value.

[0405] Also, the threshold value may correspond to the number of reference pictures. For example, the larger the number of reference pictures, the smaller the threshold value.

[0406] The threshold value may be decoded from the header area. In addition, in encoding, the threshold value may be encoded in the header area such as the SPS header, PPS header, or slice header.

[0407] The threshold value is determined in advance and does not have to be decoded from the stream. In addition, in encoding, the threshold value is determined in advance and does not have to be encoded into the stream.

[0408] The threshold value may be determined so that the memory access amount in the worst case when the block to be processed is motion-compensated (predicted) in a predetermined prediction mode is equal to or less than the memory access amount when the block to be processed is bidirectionally motion-compensated (predicted) in units of 8×8 pixels in a prediction mode other than the predetermined prediction mode. The predetermined prediction mode is, for example, the affine mode. Hereinafter, examples of the limitation will be described.

[0409] "Mem_base" represents the memory access amount in the worst case with one 8×8 block as a unit when the block to be processed is bidirectionally predicted and motion-compensated (luminance value) in units of 8×8 sizes in a prediction mode other than the predetermined prediction mode.

[0410] The memory access amount in the worst case when the block to be processed (size: M×N) is motion-compensated (luminance value) in the predetermined prediction mode is represented by "Mem_CU", and the threshold value "Mem_th" for it is represented as follows using "Mem_base".

[0411] Mem_th = M×N / (8×8)*MC_base

[0412] "Mem_CU" is limited so as not to be greater than "Mem_th". Hereinafter, an example of the calculation process of the threshold value will be described.

[0413] Assuming that the size per pixel of the luminance signal is 1 byte and the number of taps of the filter for motion compensation processing is 8 taps, Mem_base = (8 + 7)×(8 + 7)×2 = 450 (in bytes).

[0414] Assume that the prediction mode of the block to be processed is the affine mode, the size of the block to be processed is 64×64 pixels, the number of reference pictures is 2, and Mem_th = 64 / 8 * 64 / 8 * 450 = 28800.

[0415] Assume that “H” and “V” respectively represent the thresholds of the first and second components of the threshold.

[0416] The worst-case condition for prediction processing in the normal inter mode other than the affine mode is when the block to be processed is divided into 8×8 pixel blocks and all 8×8 pixel blocks are motion-compensated by bidirectional prediction. Determine the range of memory that can be referenced when performing prediction processing in the affine mode so as not to exceed the memory access amount in this worst-case condition. Assume that the range of memory that can be referenced in the affine mode is calculated by the following formula [1]. Calculate H and V so that the range of memory access in the affine mode is equal to or less than Mem_th (for example, 28800). Here, an example in the case where the affine mode performs bidirectional prediction is described.

[0417] Mem_CU = (64 + 7 + 2*H)(64 + 7 + 2*V)*2 ≤ 28800 [1]

[0418] Assume H = V and solve formula [1], then H = V = 24.

[0419] Note that the above calculation process of the threshold is also applicable to blocks to be processed with different sizes and different numbers of reference pictures. FIG. 49 is a diagram showing an example of the calculated threshold. Note that in FIG. 49, an example where H = V is shown, but H > V or H < V may also be possible.

[0420] As shown in FIG. 49, the threshold value is different between the case of unidirectional prediction of the processing target block (number of reference frames = 1) and the case of bidirectional prediction (number of reference frames = 2). In the example of the above formula [1], the size of the processing target block predicted in the affine mode is 64×64. When performing bidirectional prediction, that is, when referring to two reference pictures, both the first threshold value H and the second threshold value V are 24. For example, when unidirectionally predicting a 64×64-sized processing target block predicted in the affine mode, that is, when referring to only one reference picture, both the first threshold value H and the second threshold value V are 49. In FIG. 49, using the above formula [1], the threshold values for all block sizes that can be predicted in the affine mode are calculated and tabulated.

[0421] [Explanation of ATMVP Mode in Sub-Block Unit] FIG. 50 is a diagram for explaining the ATMVP mode in sub-block units.

[0422] In the merge mode, one candidate MV is selected from the MV (motion vector) candidate list generated by referring to the processed blocks to determine the MV of the processing target block. One candidate registered in this MV candidate list is the candidate MV of the ATMVP mode.

[0423] In the ATMVP mode in sub-block units, first, the MV (MV0) of the block adjacent to the lower left of the processing target block is referred to, and the temporal MV reference block associated with the processing target block in the encoded reference picture specified by MV0 is identified.

[0424] Next, for each sub-block within the processing target block, the MV used when encoding the corresponding region in the temporal MV reference block is identified. Then, by referring to the MV and scaling it according to the time interval, the MV of each sub-block is obtained.

[0425] Then, motion compensation is performed for each sub-block using the MV to generate a predicted image, and a difference image between the predicted image and the input image is generated. For the difference image within the processing target block, orthogonal transformation and quantization processing are applied in units of the processing target block.

[0426] In FIG. 50, a block adjacent to the lower left is used as the block that refers to MV0, but other blocks may be used.

[0427] Also, the size of the sub-block may be configured as 4×4, may be configured as 8×8, or may be configured with other sizes. Further, the size of the sub-block may be configured to be switchable in units such as slices or pictures.

[0428] Here, the processing in encoding has been described, but the same processing is performed in decoding.

[0429] [Technical Advantages of the First Aspect] In the first aspect of the present disclosure, a process for deriving a first motion vector is introduced into the inter prediction process. As described above, the process of selecting an appropriate first motion vector so that the variation of the plurality of first motion vectors within the processing target block falls within a predetermined range can reduce the memory bandwidth of the inter prediction process.

[0430] [Second Aspect] Hereinafter, an encoding device 100, a decoding device 200, an encoding method, and a decoding method according to the second aspect of the present disclosure will be described. Here, the description will focus on the differences from the first aspect, and the description of the content overlapping with the first aspect will be omitted.

[0431] FIG. 51 is a flowchart showing an example of the inter prediction process in the second aspect. Hereinafter, an example of the inter prediction process in the decoding device 200 will be described.

[0432] In the decoder 200, the inter prediction unit 218 derives a reference motion vector which is a motion vector used for predicting a processing target block and is the motion vector of the control point of the processing target block, derives a first motion vector different from the reference motion vector, derives a differential motion vector based on the difference between the reference motion vector and the first motion vector, determines whether the differential motion vector is greater than a threshold value, changes the first motion vector when it is determined that the differential motion vector is greater than the threshold value, does not change the first motion vector when it is determined that the differential motion vector is not greater than the threshold value, and decodes the processing target block using the changed first motion vector or the unchanged first motion vector. For example, the control point is the control point of the affine mode in the processing target block, and the inter prediction unit 218 derives the motion vector of the control point as the reference motion vector.

[0433] Hereinafter, the inter prediction process will be described more specifically with reference to the drawings. Note that the reference motion vector and the first motion vector described below are examples and are not limited thereto.

[0434] First, in step S2001, the inter prediction unit 218 derives a reference motion vector for the first pixel set in the processing target block. The reference motion vector is the motion vector of the control point of the processing target block. Hereinafter, the process of step S2001 will be described more specifically with reference to FIG. 52. Note that the processes of steps S2002 to S2007 are the same as the processes of steps S1002 to S1007 in FIG. 47 described in the first aspect. Note that the process 2000 shown in FIG. 51 may be the process of the encoding device.

[0435] FIG. 52 is a diagram showing an example of motion vectors at control points of a block to be processed. (a) of FIG. 52 is a diagram for explaining an example of derivation of motion vectors in units of sub-blocks in an affine mode having two control points. (b) of FIG. 52 is a diagram for explaining an example of derivation of motion vectors in units of sub-blocks in an affine mode having three control points. In (a) and (b) of FIG. 52, illustration of sub-blocks within the block to be processed is omitted. For example, as shown in FIG. 48, the block to be processed may be composed of a plurality of sub-blocks (sub-block 0 to sub-block 5). Also, each sub-block may have different first motion vectors (MV0 to MV5). Further, for example, the first pixel set may be sub-block 0 or the entire block to be processed.

[0436] In (a) and (b) of FIG. 52, the control points in the block to be processed are derived based on the motion vectors of adjacent decoded sub-blocks. For example, based on the motion vectors of adjacent blocks, the motion vector (hereinafter, the upper left control vector) mv0 of the upper left control point of the block to be processed is derived, and similarly, based on the motion vectors of adjacent blocks, the motion vector (hereinafter, the upper right control vector) mv1 of the upper right control point of the block to be processed is derived. Also, for example, based on the motion vectors of adjacent blocks, the motion vector (hereinafter, the lower left control vector) mv2 of the lower left control point of the block to be processed is derived.

[0437] The inter prediction unit 218 may derive the motion vector of at least one of these plurality of control points as a reference motion vector. For example, in the case of a 4-parameter affine motion model, the reference motion vector may be derived based on at least the upper left control vector mv0 or the upper right control vector mv1, and in the case of a 6-parameter affine motion model, the reference motion vector may be derived based on at least the upper left control vector mv0, the upper right control vector mv1, or the lower left control vector mv2.

[0438] Note that the reference motion vector may be the motion vector of one predetermined control point. For example, the reference motion vector may be the upper left corner control vector mv0. At this time, the reference motion vector may be set as mv0 in both the four-parameter affine motion model and the six-parameter affine motion model.

[0439] Also, the reference motion vector may be derived as the average of the motion vectors of a plurality of control points. For example, the reference motion vector may be derived as the average of the upper left corner control vector mv0 and the upper right corner control vector mv1, the average of the upper left corner control vector mv0, the upper right corner control vector mv1, and the lower left corner control vector mv2, the average of the upper left corner control vector mv0 and the lower left corner control vector mv2, or the average of the upper right corner control vector mv1 and the lower left corner control vector mv2.

[0440] Also, the reference motion vector may be derived as a combination of the motion vectors of a plurality of control points. For example, in this combination, the maximum absolute value among the absolute values of the horizontal components of the motion vectors of a plurality of control points may be used as the horizontal component of the reference motion vector, and the maximum absolute value among the absolute values of the vertical components of the motion vectors of a plurality of control points may be used as the vertical component of the reference motion vector. For example, when the upper left corner control vector mv0 is (-3, 8), the upper right corner control vector mv1 is (-5, 4), and the lower left corner control vector mv2 is (10, -6), the reference motion vector is (10, 8).

[0441] Also, for example, in this combination, the minimum absolute value among the absolute values of the horizontal components of the motion vectors of a plurality of control points may be used as the horizontal component of the reference motion vector, and the minimum absolute value among the absolute values of the vertical components of the motion vectors of a plurality of control points may be used as the vertical component of the reference motion vector. For example, when the upper left corner control vector mv0 is (-3, 8), the upper right corner control vector mv1 is (-5, 4), and the lower left corner control vector mv2 is (10, -6), the reference motion vector is (3, 4).

[0442] Next, a method for deriving the motion vector of each sub-block within the processing target block using the motion vectors of a plurality of control points will be described. In the example of Fig. 52(a), the motion vectors mv0 and mv1 of two control points are projected according to the following equation (3) to obtain the motion vectors (mv x , mv y ) of each sub-block within the processing target block.

[0443]

Equation

[0444] Here, x and y respectively indicate the horizontal position and vertical position of the center of the sub-block, W indicates the width of the processing target block (CU), and H indicates the height of the processing target block (CU).

[0445] Also, in the example of Fig. 52(b), the motion vectors mv0, mv1, and mv2 of three control points are projected according to the following equation (4) to obtain the motion vectors (mv x , mv y ) of each sub-block within the processing target block.

[0446]

Equation

[0447] Affine modes with different numbers of control points (e.g., two and three) may be switched and signaled at the CU level. Note that information indicating the number of control points of the affine mode used at the CU level may be signaled at other levels (e.g., sequence level, picture level, slice level, tile level, CTU level, or sub-block level).

[0448] In addition, in the affine mode having such three control points, several modes in which the methods for deriving the motion vectors of the upper left, upper right, and lower left corner control points are different may be included. For example, the affine mode includes two modes: the affine normal intermediate mode and the affine merge mode.

[0449] [Technical advantages of the second aspect] In the second aspect of the present disclosure, a process for deriving a reference motion vector is introduced based on the inter prediction process. As described above, the process of deriving an appropriate reference motion vector so that the variation of the plurality of first motion vectors within the processing target block falls within a predetermined range can reduce the memory bandwidth of the inter prediction process more than the first aspect.

[0450] [Typical example of processing] Typical examples of the processing of the encoding device 100 and the decoding device 200 shown above are shown below.

[0451] FIG. 53 is a flowchart showing the operations performed by the encoding device 100. The encoding device 100 includes a circuit and a memory connected to the circuit. The circuit and memory included in the encoding device 100 may correspond to the processor a1 and the memory a2 shown in FIG. 40. The circuit of the encoding device 100 performs the following in operation.

[0452] For example, the circuit of the encoding device 100 derives a reference motion vector that is a motion vector used for predicting a processing target block and is a motion vector of a control point of the processing target block (S3001), derives a first motion vector different from the reference motion vector (S3002), derives a differential motion vector based on the difference between the reference motion vector and the first motion vector (S3003), determines whether the differential motion vector is greater than a threshold value (S3004), and if it is determined that the differential motion vector is greater than the threshold value (Yes in S3004), changes the first motion vector (S3006), and if it is determined that the differential motion vector is not greater than the threshold value (No in S3004), does not change the first motion vector (S3005), and encodes the processing target block using the changed first motion vector or the unchanged first motion vector (S3007).

[0453] Thereby, the encoding device 100 can adjust the motion vector so that the variation of the motion vectors in the processing target block divided into a plurality of sub-blocks falls within a predetermined range. Therefore, compared with the case where the variation of the motion vector is larger than the predetermined range, the number of pixels to be referenced is reduced, so that the amount of data transferred from the memory can be suppressed within a predetermined range. Therefore, the encoding device 100 can reduce the memory access amount in the inter prediction process, and thus the encoding efficiency is improved.

[0454] For example, the reference motion vector may correspond to a first pixel set in the processing target block, and the first motion vector may correspond to a second pixel set different from the first pixel set in the processing target block.

[0455] Thereby, the encoding device 100 can appropriately control the variation of the motion vectors in the processing target block by using the reference motion vector determined based on the first pixel set and the first motion vector determined based on the second pixel set.

[0456] For example, when it is determined that the differential motion vector is larger than the threshold value, the circuit of the encoding device 100 may change the first motion vector using the value obtained by clipping the differential motion vector.

[0457] Thereby, the encoding device 100 can change the first motion vector so that the variation of the first motion vector falls within a predetermined range. Therefore, since the encoding device 100 can reduce the memory access amount in the inter prediction process, the encoding efficiency is improved.

[0458] For example, the circuit of the encoding device 100 may derive a control point of the processing target block based on the motion vector of the encoded block adjacent to the processing target block, and derive a reference motion vector of the processing target block, which is the motion vector of the control point.

[0459] Thereby, since the encoding device 100 can derive the reference motion vector of the processing target block based on the motion vector of the encoded block adjacent to the processing target block, the prediction accuracy is improved.

[0460] For example, the control point is a control point of the affine mode in the processing target block, and the circuit of the encoding device 100 may derive a reference motion vector, which is the motion vector of the control point.

[0461] Thereby, since the encoding device 100 can predict the processing target block in units of sub-blocks, the prediction accuracy is improved.

[0462] For example, the control point may be located at at least one of the upper left corner, the upper right corner, and the lower left corner of the processing target block.

[0463] As a result, since the motion vector of the control point located at the corner of the processing target block is derived as the reference motion vector, the encoding device 100 can adjust so that the variation of the first motion vectors in a plurality of sub-blocks within the processing target block falls within a predetermined range. Therefore, since the encoding device 100 can reduce the memory access amount in the inter prediction process, the encoding efficiency is improved.

[0464] For example, the circuit of the encoding device 100 may derive the motion vector of at least one control point among the plurality of control points of the processing target block as the reference motion vector.

[0465] As a result, the encoding device 100 can derive the difference between the reference motion vector and the first motion vector, using the motion vector of at least one control point of the processing target block as the reference motion vector.

[0466] For example, the reference motion vector may be derived as the average of the motion vectors of the plurality of control points.

[0467] As a result, the encoding device 100 can derive the difference between the reference motion vector and the first motion vector, using the average of the motion vectors of the plurality of control points of the processing target block as the reference motion vector.

[0468] For example, the reference motion vector may be derived as a combination of the motion vectors of the plurality of control points. For example, in the combination, the maximum absolute value among the absolute values of the horizontal components of the motion vectors of the plurality of control points is used as the horizontal component of the reference motion vector, and the maximum absolute value among the absolute values of the vertical components of the motion vectors of the plurality of control points is used as the vertical component of the reference motion vector. Also, for example, in the combination, the minimum absolute value among the absolute values of the horizontal components of the motion vectors of the plurality of control points is used as the horizontal component of the reference motion vector, and the minimum absolute value among the absolute values of the vertical components of the motion vectors of the plurality of control points is used as the vertical component of the reference motion vector.

[0469] As a result, the variation in the first motion vector within the processing target block is confined within a predetermined range. Therefore, the encoding efficiency is improved.

[0470] For example, the processing target block may be subjected to prediction processing using the affine mode.

[0471] As a result, the encoding apparatus 100 can predict the processing target block in units of sub-blocks, so that the prediction accuracy is improved.

[0472] FIG. 54 is a flowchart showing the operations performed by the decoding apparatus 200. For example, the decoding apparatus 200 includes a circuit and a memory connected to the circuit. The circuit and the memory included in the decoding apparatus 200 may correspond to the processor b1 and the memory b2 shown in FIG. 46. The circuit of the decoding apparatus 200 performs the following in operation.

[0473] Also, the circuit of the decoding apparatus 200 derives a reference motion vector that is a motion vector used for predicting the processing target block and is the motion vector of the control point of the processing target block (S4001), derives a first motion vector different from the reference motion vector (S4002), derives a differential motion vector based on the difference between the reference motion vector and the first motion vector (S4003), determines whether the differential motion vector is greater than a threshold value (S4004), and if it is determined that the differential motion vector is greater than the threshold value (Yes in S4004), changes the first motion vector (S4006), and if it is determined that the differential motion vector is not greater than the threshold value (No in S4004), does not change the first motion vector (S4005), and decodes the processing target block using the changed first motion vector or the first motion vector that has not been changed (S4007).

[0474] As a result, the decoding device 200 can adjust the motion vectors so that the variations in the plurality of motion vectors within the processing target block divided into a plurality of sub-blocks fall within a predetermined range. Therefore, compared with the case where the variation in the motion vectors is larger than the predetermined range, the number of pixels to be referred to is reduced, so that the amount of data transferred from the memory can be suppressed within a predetermined range. Accordingly, the decoding device 200 can reduce the memory access amount in the inter prediction process, and thus the processing efficiency is improved.

[0475] For example, the reference motion vector may correspond to the first pixel set within the processing target block, and the first motion vector may correspond to a second pixel set different from the first pixel set within the processing target block.

[0476] As a result, the decoding device 200 can appropriately control the variation in the plurality of motion vectors within the processing target block by using the reference motion vector determined based on the first pixel set and the first motion vector determined based on the second pixel set.

[0477] For example, when it is determined that the differential motion vector is larger than the threshold value, the circuit of the decoding device 200 may change the first motion vector by using a value obtained by clipping the differential motion vector.

[0478] As a result, the decoding device 200 can change the first motion vector so that the variation in the first motion vector falls within a predetermined range. Therefore, the decoding device 200 can reduce the memory access amount in the inter prediction process, and thus the processing efficiency is improved.

[0479] For example, the circuit of the decoding device 200 may derive a control point of the processing target block based on the motion vector of the decoded block adjacent to the processing target block, and derive the reference motion vector of the processing target block, which is the motion vector of the control point.

[0480] As a result, the decoding device 200 can derive the reference motion vector of the processing target block based on the motion vectors of the decoded blocks adjacent to the processing target block, so the prediction accuracy is improved.

[0481] For example, the control point may be a control point of the affine mode in the processing target block, and the circuit of the decoding device 200 may derive the reference motion vector, which is the motion vector of the control point.

[0482] As a result, the decoding device 200 can predict the processing target block in units of sub-blocks, so the prediction accuracy is improved.

[0483] For example, the control point may be located at at least one of the upper left corner, upper right corner, and lower left corner of the processing target block.

[0484] As a result, since the motion vector of the control point located at the corner of the processing target block is derived as the reference motion vector, the decoding device 200 can adjust so that the variation of the first motion vectors in a plurality of sub-blocks within the processing target block falls within a predetermined range. Therefore, the decoding device 200 can reduce the memory access amount in the inter prediction process, so the processing efficiency is improved.

[0485] For example, the circuit of the decoding device 200 may derive the motion vector of at least one control point among the plurality of control points of the processing target block as the reference motion vector.

[0486] As a result, the decoding device 200 can derive the difference between the reference motion vector and the first motion vector, using the motion vector of at least one control point of the processing target block as the reference motion vector.

[0487] For example, the reference motion vector may be the average of the motion vectors of the plurality of control points.

[0488] As a result, the decoding device 200 can derive the difference between the reference motion vector and the first motion vector, using the average of the motion vectors of a plurality of control points of the processing target block as the reference motion vector.

[0489] For example, the reference motion vector may be derived as a combination of the motion vectors of a plurality of control points. For example, in this combination, the maximum absolute value among the absolute values of the horizontal components of the motion vectors of the plurality of control points may be used as the horizontal component of the reference motion vector, and the maximum absolute value among the absolute values of the vertical components of the motion vectors of the plurality of control points may be used as the vertical component of the reference motion vector. Also, for example, in this combination, the minimum absolute value among the absolute values of the horizontal components of the motion vectors of the plurality of control points may be used as the horizontal component of the reference motion vector, and the minimum absolute value among the absolute values of the vertical components of the motion vectors of the plurality of control points may be used as the vertical component of the reference motion vector.

[0490] As a result, the variation of the first motion vector within the processing target block is confined within a predetermined range. Therefore, the processing efficiency is improved.

[0491] For example, the processing target block may be subjected to prediction processing using the affine mode.

[0492] As a result, since the decoding device 200 can predict the processing target block in units of sub-blocks, the prediction accuracy is improved.

[0493] Also, as described above, each component may be a circuit. These circuits may form one circuit as a whole, or may be separate circuits respectively. Also, each component may be realized by a general-purpose processor or a dedicated processor.

[0494] Also, the processing executed by a specific component may be executed by another component. Also, the order in which the processing is executed may be changed, or a plurality of processes may be executed in parallel. Also, the encoding / decoding device may include the encoding device 100 and the decoding device 200.

[0495] The above-described aspects of the encoding device 100 and the decoding device 200 have been described based on a plurality of examples. However, the aspects of the encoding device 100 and the decoding device 200 are not limited to these examples. As long as the gist of the present disclosure is not deviated from, various modifications conceived by those skilled in the art applied to each example, and forms constructed by combining components in different examples may also be included within the scope of the aspects of the encoding device 100 and the decoding device 200.

[0496] [Combination with Other Aspects] One or more aspects disclosed herein may be implemented in combination with at least a part of other aspects in the present disclosure. Also, a part of the processing described in the flowchart of one or more aspects disclosed herein, a part of the configuration of the device, a part of the syntax, etc. may be implemented in combination with other aspects.

[0497] For example, the reference motion vector may be a combination of the MV of the first sub-block and the MV of the control point. Also, the reference motion vector may be a plurality of motion vectors, and the MV of the first sub-block and the MV of the control point may be compared with their respective threshold values.

[0498] Also, by comparing the MV of the first sub-block and the MV of the control point, either one of them may be used as the reference motion vector. Using the MV of the first sub-block and the MV of the control point (for example, by averaging, etc.), one reference motion vector may be obtained.

[0499] Note that not all of the above-described processes / elements are necessarily required. The device / method may include a part of the processes / elements. Also, the above-described processes may be executed by the decoding device as well as the encoding device.

[0500] [Implementation and Application] In each of the above embodiments, each of the functional or operative blocks can generally be realized by an MPU (micro processing unit), a memory, and the like. Further, 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 each functional block can also be realized by hardware (a dedicated circuit). Various combinations of hardware and software can be adopted.

[0501] The processing described in each embodiment may be realized by centralized processing using a single device (system), or may be realized by distributed processing using a plurality of devices. Further, the processor that executes the above program may be singular or plural. That is, centralized processing or distributed processing may be performed.

[0502] 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.

[0503] Furthermore, here, application examples of the moving image encoding method (image encoding method) or the 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 including both. Other configurations of such a system can be appropriately changed as the case may be.

[0504] [Usage Example] FIG. 55 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, and ex110, which are fixed radio stations in the illustrated example, are installed in each cell.

[0505] In this content supply system ex100, various devices such as a computer ex111, a game machine ex112, a camera ex113, home appliances ex114, and a smartphone ex115 are connected to the Internet ex101 via an Internet service provider ex102 or a communication network ex104 and base stations ex106 to ex110. The content supply system ex100 may be 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 communication without passing through base stations ex106 to ex110. Further, the streaming server ex103 may be connected to various devices such as a computer ex111, a game machine ex112, a camera ex113, home appliances ex114, and a 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.

[0506] Note that a wireless access point, a hotspot, or the like 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.

[0507] The camera ex113 is a device capable of still image shooting and video shooting such as a digital camera. The smartphone ex115 is a smartphone device, a mobile phone, or a PHS (Personal Handy-phone System) etc. corresponding to the mobile communication system methods called 2G, 3G, 3.9G, 4G, and in the future 5G.

[0508] The home appliance ex114 is a device included in a refrigerator or a home fuel cell cogeneration system etc.

[0509] In the content supply system ex100, a terminal having a shooting function is connected to the streaming server ex103 through a base station ex106 etc., enabling live distribution etc. In live distribution, the terminal (computer ex111, game machine ex112, camera ex113, home appliance ex114, smartphone ex115, and the terminal etc. in the airplane ex117) may perform the encoding process described in each of the above embodiments on the still image or video content shot 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 an aspect of the present disclosure.

[0510] 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 etc. in the airplane ex117 capable of decoding the encoded data. Each device that has received the distributed data may perform a decoding process on the received data and play it back. That is, each device may function as an image decoding device according to an aspect of the present disclosure.

[0511] [Distributed processing] In addition, the streaming server ex103 may be a plurality of servers or a plurality of computers that distribute, process, record, and deliver 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. 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.

[0512] Furthermore, 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 code is detected. Also, in the second loop, a process is performed to improve the encoding efficiency while maintaining the image quality. 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 reduce the processing load on each terminal while improving the quality and efficiency of the content. 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.

[0513] As another example, cameras such as ex113 extract feature amounts (amounts of features or characteristics) from images, compress data regarding the feature amounts as metadata, and transmit the data to a server. The server performs compression according to the meaning (or importance of content) of the image, for example, determines the importance of an object from the feature amounts and switches the quantization accuracy. Feature amount data is particularly effective for 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.

[0514] 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 have performed shooting, and other terminals and a server that have not performed shooting as necessary, encoding processing is respectively assigned in units such as GOP (Group of Picture), picture unit, or tile unit obtained by dividing a picture, and distributed processing is performed. Thereby, delay can be reduced and more real-time performance can be realized.

[0515] 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 among 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.

[0516] 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.

[0517] Thus, the encoding process can be performed by a terminal or one or more servers. Therefore, hereinafter, descriptions such as "server" or "terminal" are 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.

[0518] [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 smartphone 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 area where the feature points included in the videos match.

[0519] The server may not only encode a two-dimensional moving image, but also automatically or at a time specified by the user encode a still image based on scene analysis of the moving image and transmit it to the receiving terminal. When the server can obtain the relative positional relationship between the shooting terminals, the server 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 based on the result of recognizing or tracking a person or an object using the three-dimensional data, select or reconstruct the video to be transmitted to the receiving terminal from the videos captured by a plurality of terminals.

[0520] 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. Further, 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.

[0521] 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 right-eye and left-eye viewpoint images respectively and perform encoding that allows reference 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, they may be played back in synchronization with each other so that a virtual three-dimensional space is reproduced according to the user's viewpoint.

[0522] In the case of AR images, the server may superimpose virtual object information on the virtual space based on the camera information of the real space according to 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 the 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.

[0523] The decoding process of the data delivered in the same way 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 an 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 in one's own field of responsibility or the area that one wants to check in more detail.

[0524] 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 or a display arranged inside and outside the house and switch 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.

[0525] [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. 56. 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, for example, the device only needs to decode the same stream to a different layer, thus reducing the burden on the server side.

[0526] Furthermore, as described above, pictures are encoded for each layer. In addition to the configuration where scalability is realized 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. Super-resolution may improve the signal-to-noise ratio while maintaining and / or enlarging 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 operations used in super-resolution processing.

[0527] Alternatively, a configuration may be provided in which a picture is divided into tiles or the like according to the meaning such as an object 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 identify the position of the desired object based on the meta information and determine the tile including the object. For example, as shown in FIG. 57, 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.

[0528] 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, and by combining the picture unit information and the time information, can identify the picture in which the object exists and determine the position of the object in the picture.

[0529] [Optimization of Web Page] FIG. 58 is a diagram showing an example of a display screen of a web page on a computer ex111 or the like. FIG. 59 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. 58 and 59, a 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 to be browsed. 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 with a plurality of still images or I pictures, etc., or may receive only the base layer, decode and display the video.

[0530] 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. Further, in order to ensure real-time performance, before selection or when the communication bandwidth is very strict, the display device can reduce the delay (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-reference pictures (I pictures, P pictures, B pictures with only forward reference). Additionally, the display device may deliberately ignore the reference relationship of pictures, perform rough decoding with all B pictures and P pictures as forward references, and perform normal decoding as the received pictures increase over time.

[0531] [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 support 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.

[0532] 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~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.

[0533] In the content supply system ex100, the client can receive, decode, and play back the encoded information transmitted by the user in real time.

[0534] [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. Such individual content is considered to increase in the future. In order to make individual content better, the server may perform encoding processing after performing editing processing. This can be realized, for example, using the following configuration.

[0535] At the time of shooting in real time or accumulating and after 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 a scene with lower brightness or out-of-focus compared to other pictures, emphasizes the edges of the object, or changes the color tone, etc. The server encodes the edited data based on the editing result. Also, it is known that the viewing rate decreases if the shooting time is too long. The server may automatically clip not only less important scenes but also scenes with little movement, etc., within a specific time range according to the shooting time, based on the image processing result, so that the content is within a specific time range. Or, the server may generate a digest based on the result of semantic analysis of the scene and encode it.

[0536] Personal content may sometimes contain elements that, as they are, would infringe copyright, moral rights of the author, or the right of portrait, etc., and may be inconvenient for individuals, such as when the scope of sharing exceeds the intended scope. Therefore, for example, the server may deliberately change the image to be out of focus, such as the face of a person in the peripheral part of the screen or the inside of a house, and then encode it. Furthermore, the server may recognize whether a face of a person different from the 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. Alternatively, as pre-processing or post-processing of encoding, the 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, the person can be tracked in the moving image, and the video of the face part of the person can be replaced.

[0537] 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, it may 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 for the first time and a second stream encoded with reference to the first video are configured as one stream.

[0538] [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. 55) 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 processes may be performed using such software. Further, when the smartphone ex115 has a camera, the 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.

[0539] 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.

[0540] 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 broadcast radio waves 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.

[0541] [Hardware Configuration] FIG. 60 is a diagram showing further details of the smartphone ex115 shown in FIG. 55. Also, FIG. 61 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 identifying the user and authenticating access to various data including the network with a SIM ex468. Note that an external memory may be used instead of the memory unit ex467.

[0542] 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.

[0543] 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.

[0544] 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 imaging 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.

[0545] When receiving video attached to an email or chat, or 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 the audio. Therefore, as an initial value, it is desirable to have a configuration that plays only the 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.

[0546] Also, although the smartphone ex115 has been described as an example here, as the terminal, in addition to the transceiver type terminal having both an encoder and a decoder, other implementation forms such as a transmission terminal having only an encoder and a reception 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.

[0547] Although the main control unit ex460 including a CPU has been described as controlling the encoding or decoding process, many types of terminals are often equipped with a GPU. Therefore, a configuration 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 address is managed so as to be commonly used may be adopted. This can shorten the encoding time, ensure real-time performance, and achieve low latency. In particular, it is efficient to perform motion search, deblocking filter, SAO (Sample Adaptive Offset), and transform / quantization processes in units such as pictures using the GPU instead of the CPU.

Industrial Applicability

[0548] The present disclosure can be applied to, for example, a television receiver, a digital video recorder, a car navigation system, a mobile phone, a digital camera, a digital video camera, a video conferencing system, or an electronic mirror.

Explanation of Signs

[0549] 100 Encoding device 102 Splitting unit 104 Subtraction unit 106 Transformation unit 108 Quantization unit 110 Entropy encoding unit 112, 204 Inverse quantization unit 114, 206 Inverse transformation unit 116, 208 Addition unit 118, 210 Block memory 120, 212 Loop filter unit 122, 214 Frame memory 124, 216 Intra prediction unit 126, 218 Inter prediction unit 128, 220 Prediction control unit 200 Decoding device 202 Entropy decoding unit 1201 Boundary determination unit 1202, 1204, 1206 Switch 1203 Filter Judgment Unit 1205 Filter Processing Unit 1207 Filter Characteristic Determination Unit 1208 Processing Judgment Unit a1, b1 Processors a2, b2 Memories

Claims

1. The circuit, a memory connected to the circuit, The circuit, in operation, The prediction mode of the processing target block is an affine mode, deriving a reference motion vector, which is a motion vector for use in predicting the current block, and which is a motion vector of an affine mode control point in the current block; deriving a first motion vector different from the reference motion vector; deriving a differential motion vector based on a difference between the reference motion vector and the first motion vector; determining whether the differential motion vector is greater than a threshold; if it is determined that the differential motion vector is greater than the threshold, a first value is set to a second motion vector different from the reference motion vector and the first motion vector; if it is determined that the differential motion vector is not greater than the threshold, a second value different from the first value is set to the second motion vector; encoding the current block using the second motion vector; generating a bitstream including the encoded current block; Transmitting the generated bitstream; The threshold value differs depending on whether the current block is unidirectionally predicted or bidirectionally predicted. Transmitting device.

2. The prediction mode of the processing target block is an affine mode, deriving a reference motion vector, which is a motion vector for use in predicting the current block, and which is a motion vector of an affine mode control point in the current block; deriving a first motion vector different from the reference motion vector; deriving a differential motion vector based on a difference between the reference motion vector and the first motion vector; determining whether the differential motion vector is greater than a threshold; if it is determined that the differential motion vector is greater than the threshold, a first value is set to a second motion vector different from the reference motion vector and the first motion vector; if it is determined that the differential motion vector is not greater than the threshold, a second value different from the first value is set to the second motion vector; encoding the current block using the second motion vector; generating a bitstream including the encoded current block; Transmitting the generated bitstream; The threshold value differs depending on whether the current block is unidirectionally predicted or bidirectionally predicted. Transmission method.

3. A computer-readable non-transitory storage medium for storing a bitstream and a program, the bit stream includes an encoded signal that has been encoded and compressed with respect to a prediction parameter related to generation of a prediction block of a current block of a video; When the program is read by a processor, The prediction mode of the processing target block is an affine mode, deriving a reference motion vector, which is a motion vector for use in predicting the current block, and which is a motion vector of an affine mode control point in the current block; deriving a first motion vector different from the reference motion vector; deriving a differential motion vector based on a difference between the reference motion vector and the first motion vector; determining whether the differential motion vector is greater than a threshold; if it is determined that the differential motion vector is greater than the threshold, a first value is set to a second motion vector different from the reference motion vector and the first motion vector; if it is determined that the differential motion vector is not greater than the threshold, a second value different from the first value is set to the second motion vector; encoding the current block using the second motion vector; generating the bitstream including the encoded current block; Transmitting the generated bitstream; The threshold value differs depending on whether the current block is unidirectionally predicted or bidirectionally predicted. Non-transitory storage medium.

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