Encoding device and encoding method

Abstract

To provide an encoder that can achieve processing load reduction while suppressing degradation of compression efficiency.SOLUTION: When an encoder 100 determines that intra-prediction is used for a block to be encoded, the encoder determines whether or not an intra-prediction mode of the block to be encoded is a predetermined mode, determines a first conversion base of the block to be encoded, generates a first conversion coefficient by performing first conversion using the first conversion base. Then, when the intra-prediction mode is not the predetermined mode or the first conversion base matches a predetermined conversion base, the encoder generates a second conversion coefficient by performing second conversion on the first conversion coefficient using a second conversion base, quantifies the second conversion coefficient, and when the intra-prediction mode is the predetermined mode and the first conversion base is different from the predetermined conversion base, the encoder quantifies the first conversion coefficient. When the encoder determines that the intra-prediction is not used for the block to be encoded, the encoder quantifies the first conversion coefficient.SELECTED DRAWING: Figure 11

Description

[Technical field]

[0001] This disclosure relates to block-based image / video encoding and decoding. [Background technology]

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

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

[0004] In such encoding and decoding techniques, there is a demand for reducing the processing load while preventing a decrease in compression efficiency.

[0005] Therefore, the present disclosure provides an encoding device, a decoding device, an encoding method, or a decoding method that can reduce the processing load while suppressing a decrease in compression efficiency. [Means for solving the problem]

[0006] An encoding device according to an aspect of the present disclosure includes a processor and a memory, and the processor, using the memory, determines whether or not intra prediction is to be used for a current block included in a picture, and when it is determined that intra prediction is to be used for the current block, determines whether or not an intra prediction mode of the current block is a predetermined mode, determines a first transform base for the current block, (i) generates first transform coefficients by performing a first transform on a residual signal of the current block using the first transform base, and (ii) generates first transform coefficients by performing a first transform on a residual signal of the current block using the first transform base. -1) When the intra prediction mode is not the specified mode or when the first transform base matches a specified transform base, a second transform coefficient is generated by performing a second transform on the first transform coefficient using a second transform base, and the second transform coefficient is quantized; (ii-2) when the intra prediction mode is the specified mode and the first transform base is different from the specified transform base, the first transform coefficient is quantized; and (ii-3) when it is determined that intra prediction is not to be used for the block to be coded, the first transform coefficient is quantized.

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

[0008] The present disclosure can provide an encoding device, a decoding device, an encoding method, or a decoding method that can reduce the processing load while suppressing a decrease in compression efficiency. [Brief description of the drawings]

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

[0010] Hereinafter, the embodiment will be described in detail with reference to the drawings.

[0011] The embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, component arrangement and connection forms, steps, and order of steps shown in the following embodiments are merely examples and are not intended to limit the scope of the claims. Furthermore, among the components in the following embodiments, components that are not described in an independent claim showing a top concept are described as optional components.

[0012] (Embodiment 1) First, an overview of the first embodiment will be described as an example of an encoding device and a decoding device to which the processes and / or configurations described in each aspect of the present disclosure can be applied. However, the first embodiment is merely an example of an encoding device and a decoding device to which the processes and / or configurations described in each aspect of the present disclosure can be applied, and the processes and / or configurations described in each aspect of the present disclosure can also be implemented in encoding devices and decoding devices different from the first embodiment.

[0013] When applying the processing and / or configurations described in each aspect of the present disclosure to the first embodiment, for example, any of the following may be performed.

[0014] (1) For the encoding device or the decoding device of the first embodiment, among the multiple components constituting the encoding device or the decoding device, components corresponding to the components described in each aspect of the present disclosure are replaced with the components described in each aspect of the present disclosure. (2) In the encoding device or decoding device of the first embodiment, any modification such as addition, replacement, or deletion of functions or processes performed by some of the components constituting the encoding device or decoding device is made, and then the components corresponding to the components described in each aspect of the present disclosure are replaced with the components described in each aspect of the present disclosure. (3) Adding a process to the method implemented by the encoding device or decoding device of the first embodiment, and / or replacing or deleting some of the processes included in the method, and then replacing the process corresponding to the process described in each aspect of the present disclosure with the process described in each aspect of the present disclosure. (4) Some of the components constituting the encoding device or decoding device of the first embodiment may be implemented in combination with components described in each aspect of the present disclosure, components having some of the functions of the components described in each aspect of the present disclosure, or components performing some of the processing performed by the components described in each aspect of the present disclosure. (5) Implementing a component having some of the functions of some of the multiple components constituting the encoding device or decoding device of embodiment 1, or a component that performs some of the processing performed by some of the multiple components constituting the encoding device or decoding device of embodiment 1, in combination with a component described in each aspect of the present disclosure, a component having some of the functions of the component described in each aspect of the present disclosure, or a component that performs some of the processing performed by the component described in each aspect of the present disclosure. (6) In the method implemented by the encoding device or the decoding device of the first embodiment, among a plurality of processes included in the method, a process corresponding to a process described in each aspect of the present disclosure is replaced with a process described in each aspect of the present disclosure. (7) Some of the processes included in the method implemented by the encoding device or the decoding device of the first embodiment may be implemented in combination with the processes described in each aspect of the present disclosure.

[0015] It should be noted that the manner of implementing the processes and / or configurations described in each aspect of the present disclosure is not limited to the above examples. For example, the processes and / or configurations may be implemented in a device used for a purpose other than the video / image encoding device or video / image decoding device disclosed in the first embodiment, or the processes and / or configurations described in each aspect may be implemented independently. Furthermore, the processes and / or configurations described in different aspects may be implemented in combination.

[0016] [Outline of the encoding device] First, a description will be given of an overview of a coding device according to embodiment 1. Fig. 1 is a block diagram showing a functional configuration of a coding device 100 according to embodiment 1. The coding device 100 is a video / image coding device that codes a video / image on a block-by-block basis.

[0017] As shown in FIG. 1, the encoding device 100 is a device that encodes an image on a block-by-block basis, and includes a division unit 102, a subtraction unit 104, a transformation unit 106, a quantization unit 108, an entropy encoding unit 110, an inverse quantization unit 112, an inverse transformation unit 114, an addition unit 116, a block memory 118, a loop filter unit 120, a frame memory 122, an intra prediction unit 124, an inter prediction unit 126, and a prediction control unit 128.

[0018] The encoding device 100 is realized by, for example, a general-purpose processor and a memory. In this case, when the software program stored in the memory is executed by the processor, the processor functions as the division unit 102, the subtraction unit 104, the transformation unit 106, the quantization unit 108, the entropy coding unit 110, the inverse quantization unit 112, the inverse transformation unit 114, the addition unit 116, the loop filter unit 120, the intra prediction unit 124, the inter prediction unit 126, and the prediction control unit 128. The encoding device 100 may also be realized as one or more dedicated electronic circuits corresponding to the division unit 102, the subtraction unit 104, the transformation unit 106, the quantization unit 108, the entropy coding unit 110, the inverse quantization unit 112, the inverse transformation unit 114, the addition unit 116, the loop filter unit 120, the intra prediction unit 124, the inter prediction unit 126, and the prediction control unit 128.

[0019] Each component included in the encoding device 100 will be described below.

[0020] [Divided part] The division unit 102 divides each picture included in the input video into a plurality of blocks, and outputs each block to the subtraction unit 104. For example, the division unit 102 first divides a picture into blocks of a fixed size (e.g., 128x128). These fixed-size blocks may be called coding tree units (CTUs). The division unit 102 then divides each of the fixed-size blocks into blocks of a variable size (e.g., 64x64 or less) based on recursive quadtree and / or binary tree block division. These variable-size blocks may be called coding units (CUs), prediction units (PUs), or transform units (TUs). Note that in this embodiment, it is not necessary to distinguish between CUs, PUs, and TUs, and some or all of the blocks in a picture may be the processing units of CUs, PUs, and TUs.

[0021] Fig. 2 is a diagram showing an example of block division according to embodiment 1. In Fig. 2, solid lines represent block boundaries based on quadtree block division, and dashed lines represent block boundaries based on binary tree block division.

[0022] Here, the block 10 is a square block of 128x128 pixels (128x128 block). This 128x128 block 10 is first divided into four square 64x64 blocks (quadtree block division).

[0023] The top-left 64x64 block is further divided vertically into two rectangular 32x64 blocks, and the left 32x64 block is further divided vertically into two rectangular 16x64 blocks (binary tree block division). As a result, the top-left 64x64 block is divided into two 16x64 blocks 11 and 12 and a 32x64 block 13.

[0024] The top right 64x64 block is divided horizontally into two rectangular 64x32 blocks 14, 15 (binary tree block division).

[0025] The bottom left 64x64 block is divided into four square 32x32 blocks (quadtree block division). Of the four 32x32 blocks, the top left and bottom right blocks are further divided. The top left 32x32 block is divided vertically into two rectangular 16x32 blocks, and the right 16x32 block is further divided horizontally into two 16x16 blocks (binary tree block division). The bottom right 32x32 block is divided horizontally into two 32x16 blocks (binary tree block division). As a result, the bottom left 64x64 block is divided into a 16x32 block 16, two 16x16 blocks 17, 18, two 32x32 blocks 19, 20, and two 32x16 blocks 21, 22.

[0026] The bottom right 64x64 block 23 is not split.

[0027] 2, the block 10 is divided into 13 variable-sized blocks 11 to 23 based on recursive quad-tree and binary tree block division. Such division is sometimes called QTBT (quad-tree plus binary tree) division.

[0028] In Fig. 2, one block is divided into four or two blocks (quadtree or binary tree block division), but the division is not limited to this. For example, one block may be divided into three blocks (ternary tree block division). Division including such ternary tree block division is sometimes called MBT (multi type tree) division.

[0029] [Subtraction section] The subtraction unit 104 subtracts a prediction signal (prediction sample) from an original signal (original sample) for each block divided by the division unit 102. That is, the subtraction unit 104 calculates a prediction error (also called a residual error) of a block to be coded (hereinafter, referred to as a current block). Then, the subtraction unit 104 outputs the calculated prediction error to the conversion unit 106.

[0030] The original signal is an input signal to the encoding device 100, and is a signal representing an image of each picture constituting a moving image (for example, a luminance (luma) signal and two color difference (chroma) signals). Hereinafter, the signal representing the image may also be referred to as a sample.

[0031] [Conversion section] The transform unit 106 transforms the prediction error in the spatial domain into transform coefficients in the frequency domain, and outputs the transform coefficients to the quantization unit 108. Specifically, the transform unit 106 performs, for example, a predetermined discrete cosine transform (DCT) or discrete sine transform (DST) on the prediction error in the spatial domain.

[0032] The transform unit 106 may adaptively select a transform type from among a plurality of transform types, and transform the prediction errors into transform coefficients using a transform basis function corresponding to the selected transform type. Such a transform may be called an explicit multiple core transform (EMT) or an adaptive multiple transform (AMT).

[0033] The multiple transform types include, for example, DCT-II, DCT-V, DCT-VIII, DST-I, and DST-VII. Figure 3 is a table showing the transform basis functions corresponding to each transform type. In Figure 3, N indicates the number of input pixels. The selection of the transform type from among the multiple transform types may depend on, for example, the type of prediction (intra prediction and inter prediction) or the intra prediction mode.

[0034] Such information indicating whether EMT or AMT is applied (e.g., called an AMT flag) and information indicating the selected transformation type are signaled at the CU level. Note that the signaling of such information does not need to be limited to the CU level, and may be at other levels (e.g., sequence level, picture level, slice level, tile level, or CTU level).

[0035] Furthermore, the transform unit 106 may retransform the transform coefficients (transformation results). Such retransformation may be called AST (adaptive secondary transform) or NSST (non-separable secondary transform). For example, the transform unit 106 performs retransformation for each subblock (e.g., 4x4 subblock) included in a block of transform coefficients corresponding to intra-prediction errors. Information indicating whether or not to apply NSST and information regarding a transform matrix used in NSST are signaled at a CU level. Note that signaling of these pieces of information does not need to be limited to the CU level, and may be at other levels (e.g., sequence level, picture level, slice level, tile level, or CTU level).

[0036] Here, a separable transformation is a method in which the transformation is performed multiple times by separating the input into directions equal to the number of dimensions, and a non-separable transformation is a method in which when the input is multidimensional, two or more dimensions are treated as one dimension and the transformation is performed together.

[0037] For example, one example of a non-separable transformation is when the input is a 4x4 block, it is treated as a single array with 16 elements, and the transformation process is performed on that array using a 16x16 transformation matrix.

[0038] Another example of a non-separable transformation is the Hypercube Givens Transform, which treats a 4x4 input block as a single array with 16 elements and then performs Givens rotations on that array multiple times.

[0039] [Quantization section] The quantization unit 108 quantizes the transform coefficients output from the transform unit 106. Specifically, the quantization unit 108 scans the transform coefficients of the current block in a predetermined scanning order, and quantizes the transform coefficients based on a quantization parameter (QP) corresponding to the scanned transform coefficients. Then, the quantization unit 108 outputs the quantized transform coefficients of the current block (hereinafter, referred to as quantized coefficients) to the entropy coding unit 110 and the inverse quantization unit 112.

[0040] The predetermined order is an order for quantization / dequantization of the transform coefficients. For example, the predetermined scanning order is defined as ascending (low to high) or descending (high to low) frequency order.

[0041] The quantization parameter is a parameter that defines the quantization step (quantization width). For example, if the value of the quantization parameter increases, the quantization step also increases. In other words, if the value of the quantization parameter increases, the quantization error increases.

[0042] [Entropy coding part] The entropy coding unit 110 generates a coded signal (coded bit stream) by variable-length coding the quantized coefficients input from the quantization unit 108. Specifically, the entropy coding unit 110, for example, binarizes the quantized coefficients and arithmetically codes the binary signal.

[0043] [Dequantization section] The inverse quantization unit 112 inverse quantizes the quantized coefficients input from the quantization unit 108. Specifically, the inverse quantization unit 112 inverse quantizes the quantized coefficients of the current block in a predetermined scanning order. Then, the inverse quantization unit 112 outputs the inverse quantized transform coefficients of the current block to the inverse transform unit 114.

[0044] [Inverse conversion section] The inverse transform unit 114 restores the prediction error by inverse transforming the transform coefficients that are input from the inverse quantization unit 112. Specifically, the inverse transform unit 114 restores the prediction error of the current block by performing an inverse transform on the transform coefficients that corresponds to the transform performed by the transform unit 106. Then, the inverse transform unit 114 outputs the restored prediction error to the adder unit 116.

[0045] Note that the restored prediction error does not match the prediction error calculated by the subtraction unit 104 because information has been lost due to quantization. That is, the restored prediction error includes a quantization error.

[0046] [Addition section] The adder 116 reconstructs the current block by adding the prediction error input from the inverse transformer 114 and the prediction sample input from the prediction control unit 128. The adder 116 then outputs the reconstructed block to the block memory 118 and the loop filter unit 120. The reconstructed block is sometimes called a local decoded block.

[0047] [Block memory] The block memory 118 is a storage unit for storing blocks that are referenced in intra prediction and are in a picture to be coded (hereinafter, referred to as a current picture). Specifically, the block memory 118 stores the reconstructed blocks output from the adder 116.

[0048] [Loop filter section] The loop filter unit 120 applies a loop filter to the block reconstructed by the adder unit 116, and outputs the filtered reconstructed block to the frame memory 122. The loop filter is a filter (in-loop filter) used in the encoding loop, and includes, for example, a deblocking filter (DF), a sample adaptive offset (SAO), and an adaptive loop filter (ALF).

[0049] In ALF, a least squared error filter is applied to remove coding artifacts. For example, for each 2x2 sub-block in the current block, one filter is selected from among multiple filters based on local gradient direction and activity.

[0050] Specifically, first, sub-blocks (e.g., 2x2 sub-blocks) are classified into a plurality of classes (e.g., 15 or 25 classes). The classification of the sub-blocks is performed based on the gradient direction and activity. For example, a classification value C (e.g., C=5D+A) is calculated using a gradient direction value D (e.g., 0 to 2 or 0 to 4) and a gradient activity value A (e.g., 0 to 4). Then, based on the classification value C, the sub-blocks are classified into a plurality of classes (e.g., 15 or 25 classes).

[0051] The gradient direction value D is derived, for example, by comparing gradients in multiple directions (e.g., horizontal, vertical, and two diagonal directions), and the gradient activity value A is derived, for example, by adding gradients in multiple directions and quantizing the sum.

[0052] Based on the result of such classification, a filter for the sub-block is determined from among a plurality of filters.

[0053] The shape of the filter used in the ALF is, for example, a circularly symmetric shape. FIGS. 4A to 4C are diagrams showing a number of examples of the shape of the filter used in the ALF. FIG. 4A shows a 5×5 diamond-shaped filter, FIG. 4B shows a 7×7 diamond-shaped filter, and FIG. 4C shows a 9×9 diamond-shaped filter. Information indicating the shape of the filter is signaled at the picture level. Note that the signaling of the information indicating the shape of the filter does not need to be limited to the picture level, and may be at other levels (for example, the sequence level, slice level, tile level, CTU level, or CU level).

[0054] The on / off of ALF is determined, for example, at the picture level or the CU level. For example, whether or not to apply ALF is determined for luminance at the CU level, and whether or not to apply ALF is determined for chrominance at the picture level. Information indicating whether or not to apply ALF is signaled at the picture level or the CU level. Note that the signaling of information indicating whether or not to apply ALF is not limited to the picture level or the CU level, and may be at another level (for example, the sequence level, the slice level, the tile level, or the CTU level).

[0055] The coefficient sets of multiple selectable filters (e.g., up to 15 or 25 filters) are signaled at the picture level. Note that the signaling of the coefficient sets does not need to be limited to the picture level, but may be at other levels (e.g., sequence level, slice level, tile level, CTU level, CU level, or sub-block level).

[0056] [Frame memory] The frame memory 122 is a storage unit for storing reference pictures used in inter prediction, and may be called a frame buffer. Specifically, the frame memory 122 stores the reconstructed block filtered by the loop filter unit 120.

[0057] [Intra prediction section] The intra prediction unit 124 generates a prediction signal (intra prediction signal) by performing intra prediction (also called intra-screen prediction) of the current block with reference to a block in the current picture stored in the block memory 118. Specifically, the intra prediction unit 124 generates an intra prediction signal by performing intra prediction with reference to samples (e.g., luminance values, chrominance values) of blocks adjacent to the current block, and outputs the intra prediction signal to the prediction control unit 128.

[0058] For example, the intra prediction unit 124 performs intra prediction using one of a plurality of predefined intra prediction modes. The plurality of intra prediction modes includes one or more non-directional prediction modes and a plurality of directional prediction modes.

[0059] The one or more non-directional prediction modes include, for example, a planar prediction mode and a DC prediction mode defined in the H.265 / High-Efficiency Video Coding (HEVC) standard (Non-Patent Document 1).

[0060] The multiple directional prediction modes include, for example, 33 prediction modes defined in the H.265 / HEVC standard. The multiple directional prediction modes may include 32 prediction modes in addition to the 33 directions (a total of 65 directional prediction modes). FIG. 5A is a diagram showing 67 intra prediction modes (2 non-directional prediction modes and 65 directional prediction modes) in intra prediction. The solid arrows represent the 33 directions defined in the H.265 / HEVC standard, and the dashed arrows represent the additional 32 directions.

[0061] In addition, in the intra prediction of the chrominance block, the luminance block may be referenced. That is, the chrominance component of the current block may be predicted based on the luminance component of the current block. Such intra prediction may be called CCLM (cross-component linear model) prediction. An intra prediction mode of the chrominance block that refers to such a luminance block (for example, called a CCLM mode) may be added as one of the intra prediction modes of the chrominance block.

[0062] The intra prediction unit 124 may correct pixel values ​​after intra prediction based on the gradient of reference pixels in the horizontal / vertical directions. Intra prediction with such correction may be called position dependent intra prediction combination (PDPC). Information indicating whether or not PDPC is applied (e.g., called a PDPC flag) is signaled, for example, at a CU level. Note that the signaling of this information does not need to be limited to the CU level, and may be at other levels (e.g., sequence level, picture level, slice level, tile level, or CTU level).

[0063] [Inter prediction section] The inter prediction unit 126 generates a prediction signal (inter prediction signal) by performing inter prediction (also called inter prediction) of the current block with reference to a reference picture stored in the frame memory 122 and different from the current picture. The inter prediction is performed in units of the current block or a sub-block (e.g., 4x4 block) in the current block. For example, the inter prediction unit 126 performs motion estimation in the reference picture for the current block or the sub-block. Then, the inter prediction unit 126 generates an inter prediction signal of the current block or the sub-block by performing motion compensation using motion information (e.g., a motion vector) obtained by the motion estimation. Then, the inter prediction unit 126 outputs the generated inter prediction signal to the prediction control unit 128.

[0064] The motion information used for the motion compensation is signaled. For the signaling of the motion vector, a motion vector predictor may be used, i.e. the difference between the motion vector and the motion vector predictor may be signaled.

[0065] In addition, the inter prediction signal may be generated using not only the motion information of the current block obtained by motion search, but also the motion information of the adjacent block. Specifically, the inter prediction signal may be generated for each sub-block in the current block by performing weighted addition of the prediction signal based on the motion information obtained by motion search and the prediction signal based on the motion information of the adjacent block. Such inter prediction (motion compensation) may be called OBMC (overlapped block motion compensation).

[0066] In such an OBMC mode, information indicating the size of a sub-block for OBMC (e.g., called OBMC block size) is signaled at the sequence level. Also, information indicating whether or not to apply the OBMC mode (e.g., called OBMC flag) is signaled at the CU level. Note that the signaling level of these pieces of information does not need to be limited to the sequence level and CU level, and may be other levels (e.g., picture level, slice level, tile level, CTU level, or sub-block level).

[0067] The OBMC mode will now be described in more detail. Figures 5B and 5C are a flowchart and a conceptual diagram for explaining an overview of the predicted image correction process in the OBMC process.

[0068] First, a predicted image (Pred) is obtained by normal motion compensation using a motion vector (MV) assigned to a block to be coded.

[0069] Next, the motion vector (MV_L) of the already-encoded left adjacent block is applied to the block to be encoded to obtain a predicted image (Pred_L), and the predicted image is weighted and superimposed with Pred_L to perform a first correction of the predicted image.

[0070] Similarly, the motion vector (MV_U) of the already-encoded adjacent block above is applied to the block to be encoded to obtain a predicted image (Pred_U), and the predicted image that has been corrected the first time is weighted and overlaid with Pred_U to perform a second correction of the predicted image, which is used as the final predicted image.

[0071] Although a two-stage correction method using the left adjacent block and the upper adjacent block has been described here, it is also possible to configure a method in which more than two stages of correction are performed using the right adjacent block or the lower adjacent block.

[0072] The area in which overlapping is performed does not have to be the entire pixel area of ​​the block, but may be only a part of the area near the block boundary.

[0073] Note that although the above describes the process of correcting a predicted image from one reference picture, the process is similar when correcting a predicted image from multiple reference pictures. After obtaining corrected predicted images from each reference picture, the obtained predicted images are then overlaid to obtain the final predicted image.

[0074] The block to be processed may be a prediction block unit, or a sub-block unit obtained by further dividing the prediction block.

[0075] As a method of determining whether or not to apply OBMC processing, for example, there is a method of using obmc_flag, which is a signal indicating whether or not to apply OBMC processing. As a specific example, in an encoding device, it is determined whether or not the encoding target block belongs to an area with complex motion, and if it belongs to an area with complex motion, a value of 1 is set as obmc_flag and encoding is performed by applying OBMC processing, and if it does not belong to an area with complex motion, a value of 0 is set as obmc_flag and encoding is performed without applying OBMC processing. On the other hand, in a decoding device, by decoding obmc_flag described in a stream, whether or not to apply OBMC processing is switched according to the value, and decoding is performed.

[0076] In addition, the motion information may be derived on the decoding device side without being signaled. For example, a merge mode defined in the H.265 / HEVC standard may be used. Also, for example, the motion information may be derived by performing motion estimation on the decoding device side. In this case, the motion estimation is performed without using pixel values ​​of the current block.

[0077] Here, a mode in which motion estimation is performed on the decoding device side will be described. This mode in which motion estimation is performed on the decoding device side is sometimes called a pattern matched motion vector derivation (PMMVD) mode or a frame rate up-conversion (FRUC) mode.

[0078] An example of the FRUC process is shown in FIG. 5D. First, a list of multiple candidates (which may be the same as the merge list) each having a predicted motion vector is generated by referring to the motion vectors of encoded blocks spatially or temporally adjacent to the current block. Next, a best candidate MV is selected from multiple candidate MVs registered in the candidate list. For example, an evaluation value of each candidate included in the candidate list is calculated, and one candidate is selected based on the evaluation value.

[0079] Then, based on the motion vector of the selected candidate, a motion vector for the current block is derived. Specifically, for example, the motion vector of the selected candidate (best candidate MV) is derived as it is as the motion vector for the current block. Also, for example, the motion vector for the current block may be derived by performing pattern matching in the surrounding area of ​​the position in the reference picture corresponding to the motion vector of the selected candidate. That is, a search is performed in the surrounding area of ​​the best candidate MV in the same manner, and if there is an MV with a better evaluation value, the best candidate MV may be updated to the MV, and the MV may be set as the final MV of the current block. It is also possible to configure the system without performing this process.

[0080] The same processing may be performed when processing is performed in sub-block units.

[0081] The evaluation value is calculated by finding a difference value of the reconstructed image by pattern matching between an area in a reference picture corresponding to the motion vector and a predetermined area. The evaluation value may be calculated using information other than the difference value.

[0082] As the pattern matching, a first pattern matching or a second pattern matching is used. The first pattern matching and the second pattern matching are sometimes called bilateral matching and template matching, respectively.

[0083] In the first pattern matching, pattern matching is performed between two blocks in two different reference pictures that are along the motion trajectory of the current block. Therefore, in the first pattern matching, an area in another reference picture along the motion trajectory of the current block is used as a predetermined area for calculating the evaluation value of the above-mentioned candidate.

[0084] FIG. 6 is a diagram for explaining an example of pattern matching (bilateral matching) between two blocks along a motion trajectory. As shown in FIG. 6, in the first pattern matching, two motion vectors (MV0, MV1) are derived by searching for a pair of two blocks that are along the motion trajectory of a current block (Cur block) and are in two different reference pictures (Ref0, Ref1) that best match each other. Specifically, for the current block, a difference is derived between a reconstructed image at a designated position in a first coded reference picture (Ref0) designated by a candidate MV and a reconstructed image at a designated position in a second coded reference picture (Ref1) designated by a symmetric MV obtained by scaling the candidate MV by a display time interval, and an evaluation value is calculated using the obtained difference value. It is preferable to select the candidate MV with the best evaluation value among a plurality of candidate MVs as the final MV.

[0085] Under the assumption of continuous motion trajectories, the motion vectors (MV0, MV1) pointing to two reference blocks are proportional to the temporal distances (TD0, TD1) between the current picture (Cur Pic) and the two reference pictures (Ref0, Ref1). For example, if the current picture is located between two reference pictures in time and the temporal distances from the current picture to the two reference pictures are equal, the first pattern matching derives bidirectional motion vectors that are mirror-symmetric.

[0086] In the second pattern matching, pattern matching is performed between a template in the current picture (a block adjacent to the current block in the current picture (e.g., an upper and / or left adjacent block)) and a block in the reference picture. Therefore, in the second pattern matching, a block adjacent to the current block in the current picture is used as a predetermined area for calculating the evaluation value of the above-mentioned candidate.

[0087] Fig. 7 is a diagram for explaining an example of pattern matching (template matching) between a template in a current picture and a block in a reference picture. As shown in Fig. 7, in the second pattern matching, a motion vector of a current block is derived by searching in a reference picture (Ref0) for a block that best matches a block adjacent to a current block (Cur block) in a current picture (Cur Pic). Specifically, for the current block, a difference is derived between a reconstructed image of both or either of the left adjacent and / or upper adjacent coded areas and a reconstructed image at the same position in a coded reference picture (Ref0) specified by a candidate MV, an evaluation value is calculated using the obtained difference value, and a candidate MV with the best evaluation value among a plurality of candidate MVs is selected as a best candidate MV.

[0088] Information indicating whether such a FRUC mode is applied (e.g., when the FRUC flag is true) is signaled at the CU level. Also, when the FRUC mode is applied (e.g., when the FRUC flag is true), information indicating a pattern matching method (first pattern matching or second pattern matching) (e.g., when the FRUC mode flag is true) is signaled at the CU level. Note that the signaling of such information does not need to be limited to the CU level, and may be at other levels (e.g., sequence level, picture level, slice level, tile level, CTU level, or subblock level).

[0089] Here, a mode for deriving a motion vector based on a model assuming uniform linear motion will be described. This mode is based on BIO (bi-directional optical This is sometimes called "flow" mode.

[0090] Fig. 8 is a diagram for explaining a model assuming uniform linear motion. In Fig. 8, (vx, vy) indicates a velocity vector, and τ0 and τ1 indicate the temporal distance between the current picture (Cur Pic) and two reference pictures (Ref0, Ref1), respectively. (MVx0, MVy0) indicates a motion vector corresponding to the reference picture Ref0, and (MVx1, MVy1) indicates a motion vector corresponding to the reference picture Ref1.

[0091] In this case, under the assumption of uniform linear motion of the velocity vector (vx, vy), (MVx0, MVy0) and (MVx1, MVy1) are expressed as (vxτ0, vyτ0) and (-vxτ1, -vyτ1), respectively, and the following optical flow equation (1) holds.

[0092]

number

[0093] Here, I(k) denotes the luminance value of reference image k (k=0,1) after motion compensation. This optical flow equation indicates that the sum of (i) the time derivative of the luminance value, (ii) the product of the horizontal velocity and the horizontal component of the spatial gradient of the reference image, and (iii) the product of the vertical velocity and the vertical component of the spatial gradient of the reference image is equal to zero. Based on a combination of this optical flow equation and Hermite interpolation, block-wise motion vectors obtained from a merge list or the like are corrected pixel by pixel.

[0094] Note that the decoding device may derive a motion vector using a method other than the method based on a model assuming uniform linear motion. For example, a motion vector may be derived for each sub-block based on the motion vectors of multiple adjacent blocks.

[0095] Here, a mode in which a motion vector is derived for each sub-block based on the motion vectors of a plurality of adjacent blocks will be described. This mode is sometimes called an affine motion compensation prediction mode.

[0096] Fig. 9A is a diagram for explaining derivation of a motion vector for each subblock based on the motion vectors of multiple adjacent blocks. In Fig. 9A, the current block includes 16 4x4 subblocks. Here, the motion vector v0 of the upper left corner control point of the current block is derived based on the motion vectors of the adjacent blocks, and the motion vector v1 of the upper right corner control point of the current block is derived based on the motion vectors of the adjacent subblocks. Then, using the two motion vectors v0 and v1, the motion vector (vx, vy) of each subblock in the current block is derived by the following formula (2).

[0097]

number

[0098] Here, x and y respectively indicate the horizontal and vertical positions of the sub-block, and w indicates a predetermined weighting coefficient.

[0099] Such affine motion compensation prediction mode may include several modes with different methods of deriving the motion vectors of the upper left and upper right corner control points. Information indicating such affine motion compensation prediction mode (e.g., called affine flag) is signaled at the CU level. Note that the signaling of the information indicating this affine motion compensation prediction mode does not need to be limited to the CU level, and may be at other levels (e.g., sequence level, picture level, slice level, tile level, CTU level, or subblock level).

[0100] [Predictive control unit] The prediction control unit 128 selects either the intra-prediction signal or the inter-prediction signal, and outputs the selected signal to the subtraction unit 104 and the addition unit 116 as a prediction signal.

[0101] Here, an example of deriving a motion vector for a picture to be coded in the merge mode will be described. Fig. 9B is a diagram for explaining an overview of a motion vector derivation process in the merge mode.

[0102] First, a prediction MV list is generated in which prediction MV candidates are registered. The prediction MV candidates include spatially adjacent prediction MVs, which are MVs held by multiple coded blocks located spatially around the block to be coded, temporally adjacent prediction MVs, which are MVs held by nearby blocks projected onto the position of the block to be coded in the coded reference picture, joint prediction MVs, which are MVs generated by combining the MV values ​​of spatially adjacent prediction MVs and temporally adjacent prediction MVs, and zero prediction MVs, which are MVs with a value of zero.

[0103] Next, one prediction MV is selected from the multiple prediction MVs registered in the prediction MV list, and is determined as the MV for the block to be coded.

[0104] Furthermore, the variable length coding unit writes merge_idx, which is a signal indicating which predicted MV has been selected, into the stream and codes it.

[0105] Note that the predicted MVs registered in the predicted MV list described in Figure 9B are just an example, and the number may be different from the number shown in the figure, the configuration may not include some of the types of predicted MVs shown in the figure, or the configuration may include additional predicted MVs other than the types of predicted MVs shown in the figure.

[0106] Note that the final MV may be determined by performing DMVR processing, which will be described later, using the MV of the block to be coded derived in the merge mode.

[0107] Here, an example of determining the MV using the DMVR process will be described.

[0108] FIG. 9C is a conceptual diagram for explaining an overview of the DMVR process.

[0109] First, the optimal MVP set for the block to be processed is set as a candidate MV, and reference pixels are obtained from the first reference picture, which is a processed picture in the L0 direction, and the second reference picture, which is a processed picture in the L1 direction, according to the candidate MV, and a template is generated by taking the average of each reference pixel.

[0110] Next, the template is used to search the surrounding areas of the candidate MVs of the first and second reference pictures, and the MV with the smallest cost is determined as the final MV. The cost value is calculated using the difference value between each pixel value of the template and each pixel value of the search area, the MV value, etc.

[0111] The outline of the processing described here is basically the same for the encoding device and the decoding device.

[0112] Note that other processing may be used instead of the processing described here, as long as it is processing that can search the vicinity of the candidate MV and derive the final MV.

[0113] Here, a mode in which a predicted image is generated using LIC processing will be described.

[0114] FIG. 9D is a diagram for explaining an outline of a predicted image generating method using luminance correction processing by LIC processing.

[0115] First, a MV for obtaining a reference image corresponding to a block to be coded from a reference picture that is a coded picture is derived.

[0116] Next, for the block to be coded, the luminance pixel values ​​of the coded surrounding reference areas adjacent to the left and above and the luminance pixel values ​​at the equivalent positions in the reference picture specified by the MV are used to extract information indicating how the luminance values ​​have changed between the reference picture and the picture to be coded, and a luminance correction parameter is calculated.

[0117] A luminance correction process is performed on a reference image in a reference picture specified by the MV using the luminance correction parameter, thereby generating a predicted image for the block to be coded.

[0118] It should be noted that the shape of the peripheral reference region in FIG. 9D is just an example, and other shapes may be used.

[0119] Although the process of generating a predicted image from one reference picture has been described here, the process is similar when generating a predicted image from multiple reference pictures, and a luminance correction process is performed in a similar manner on the reference images obtained from each reference picture before generating a predicted image.

[0120] As a method of determining whether or not to apply LIC processing, for example, there is a method of using lic_flag, which is a signal indicating whether or not to apply LIC processing. As a specific example, in an encoding device, it is determined whether or not the encoding target block belongs to an area where a luminance change occurs, and if it belongs to an area where a luminance change occurs, a value of 1 is set as lic_flag and encoding is performed by applying LIC processing, and if it does not belong to an area where a luminance change occurs, a value of 0 is set as lic_flag and encoding is performed without applying LIC processing. On the other hand, a decoding device decodes lic_flag described in a stream, and switches whether or not to apply LIC processing depending on the value and performs decoding.

[0121] Another method of determining whether to apply LIC processing is, for example, a method of determining according to whether LIC processing is applied to surrounding blocks.As a specific example, when the block to be coded is in merge mode, determine whether the surrounding coded blocks selected when deriving MV in merge mode processing have been coded by applying LIC processing, and switch whether to apply LIC processing according to the result and perform coding.In addition, in this example, the process in decoding is exactly the same.

[0122] [Overview of the Decryption Device] Next, a description will be given of an overview of a decoding device capable of decoding the coded signal (coded bit stream) output from the above coding device 100. Fig. 10 is a block diagram showing a functional configuration of a decoding device 200 according to the first embodiment. The decoding device 200 is a video / image decoding device that decodes a video / image on a block-by-block basis.

[0123] As shown in FIG. 10, the decoding device 200 includes an entropy decoding unit 202, an inverse quantization unit 204, an inverse transform unit 206, an addition unit 208, a block memory 210, a loop filter unit 212, a frame memory 214, an intra prediction unit 216, an inter prediction unit 218, and a prediction control unit 220.

[0124] The decoding device 200 is realized by, for example, a general-purpose processor and a memory. In this case, when the software program stored in the memory is executed by the processor, the processor functions as the entropy decoding unit 202, the inverse quantization unit 204, the inverse transform unit 206, the addition unit 208, the loop filter unit 212, the intra prediction unit 216, the inter prediction unit 218, and the prediction control unit 220. The decoding device 200 may also be realized as one or more dedicated electronic circuits corresponding to the entropy decoding unit 202, the inverse quantization unit 204, the inverse transform unit 206, the addition unit 208, the loop filter unit 212, the intra prediction unit 216, the inter prediction unit 218, and the prediction control unit 220.

[0125] Each component included in the decoding device 200 will be described below.

[0126] [Entropy Decoding Part] The entropy decoding unit 202 entropy decodes the coded bit stream. Specifically, the entropy decoding unit 202 arithmetically decodes the coded bit stream into a binary signal, for example. The entropy decoding unit 202 then debinarizes the binary signal. As a result, the entropy decoding unit 202 outputs quantized coefficients to the inverse quantization unit 204 on a block-by-block basis.

[0127] [Dequantization section] The inverse quantization unit 204 inverse quantizes the quantized coefficients of a block to be decoded (hereinafter, referred to as a current block) that is input from the entropy decoding unit 202. Specifically, the inverse quantization unit 204 inverse quantizes each quantized coefficient of the current block based on a quantization parameter corresponding to the quantized coefficient. Then, the inverse quantization unit 204 outputs the inverse quantized quantized coefficients (i.e., transform coefficients) of the current block to the inverse transform unit 206.

[0128] [Inverse conversion section] The inverse transform unit 206 restores the prediction error by inverse transforming the transform coefficients input from the inverse quantization unit 204 .

[0129] For example, if the information interpreted from the encoded bitstream indicates that EMT or AMT is to be applied (e.g., the AMT flag is true), the inverse transform unit 206 inverse transforms the transform coefficients of the current block based on the interpreted information indicating the transform type.

[0130] Also for example, if the information interpreted from the coded bitstream indicates to apply NSST, then inverse transform unit 206 applies an inverse re-transform to the transform coefficients.

[0131] [Addition section] The adder 208 reconstructs the current block by adding the prediction error, which is an input from the inverse transformer 206, and the prediction sample, which is an input from the prediction control unit 220. The adder 208 then outputs the reconstructed block to the block memory 210 and the loop filter unit 212.

[0132] [Block memory] The block memory 210 is a storage unit for storing blocks that are referenced in intra prediction and are in a picture to be decoded (hereinafter, referred to as a current picture). Specifically, the block memory 210 stores the reconstructed block output from the adder 208.

[0133] [Loop filter section] The loop filter unit 212 applies a loop filter to the block reconstructed by the adder unit 208, and outputs the filtered reconstructed block to a frame memory 214, a display device, or the like.

[0134] If the information indicating ALF on / off read from the encoded bitstream indicates ALF on, one filter is selected from among multiple filters based on the local gradient direction and activity, and the selected filter is applied to the reconstructed block.

[0135] [Frame memory] The frame memory 214 is a storage unit for storing reference pictures used in inter prediction, and may be called a frame buffer. Specifically, the frame memory 214 stores the reconstructed blocks filtered by the loop filter unit 212.

[0136] [Intra prediction section] The intra prediction unit 216 generates a prediction signal (intra prediction signal) by performing intra prediction with reference to a block in the current picture stored in the block memory 210 based on an intra prediction mode interpreted from the encoded bit stream. Specifically, the intra prediction unit 216 generates an intra prediction signal by performing intra prediction with reference to samples (e.g., luminance values, chrominance values) of blocks adjacent to the current block, and outputs the intra prediction signal to the prediction control unit 220.

[0137] Note that, when an intra prediction mode that references a luminance block in intra prediction of a chrominance block is selected, the intra prediction unit 216 may predict the chrominance component of the current block based on the luminance component of the current block.

[0138] Furthermore, when information interpreted from the encoded bitstream indicates the application of PDPC, the intra prediction unit 216 corrects pixel values ​​after intra prediction based on the gradients of reference pixels in the horizontal / vertical directions.

[0139] [Inter prediction section] The inter prediction unit 218 predicts the current block by referring to a reference picture stored in the frame memory 214. The prediction is performed in units of the current block or sub-blocks (e.g., 4x4 blocks) in the current block. For example, the inter prediction unit 218 generates an inter prediction signal of the current block or sub-block by performing motion compensation using motion information (e.g., motion vectors) interpreted from the encoded bitstream, and outputs the inter prediction signal to the prediction control unit 220.

[0140] In addition, when the information interpreted from the encoded bitstream indicates that the OBMC mode is to be applied, the inter prediction unit 218 generates an inter prediction signal using not only the motion information of the current block obtained by motion search, but also the motion information of adjacent blocks.

[0141] Also, if the information interpreted from the encoded bitstream indicates that the FRUC mode is applied, the inter prediction unit 218 derives motion information by performing motion search according to the pattern matching method (bilateral matching or template matching) interpreted from the encoded bitstream. Then, the inter prediction unit 218 performs motion compensation using the derived motion information.

[0142] In addition, when the BIO mode is applied, the inter prediction unit 218 derives a motion vector based on a model assuming uniform linear motion. In addition, when information interpreted from the encoded bitstream indicates that an affine motion compensation prediction mode is applied, the inter prediction unit 218 derives a motion vector on a sub-block basis based on the motion vectors of multiple adjacent blocks.

[0143] [Predictive control unit] The prediction control unit 220 selects either the intra-prediction signal or the inter-prediction signal, and outputs the selected signal to the addition unit 208 as a prediction signal.

[0144] (Embodiment 2) Next, a second embodiment will be described. In this embodiment, the transform and the inverse transform will be described in detail. Note that the configurations of the encoding device and the decoding device according to this embodiment are substantially the same as those of the first embodiment, and therefore illustrations and descriptions thereof will be omitted.

[0145] [Processing of the conversion section and quantization section of the encoding device] First, the processing of the transform unit 106 and the quantization unit 108 of the encoding device 100 according to the present embodiment will be specifically described with reference to Fig. 11. Fig. 11 is a flowchart showing the transform and quantization processing in the encoding device 100 according to the second embodiment.

[0146] First, the conversion unit 106 determines whether to use intra prediction or inter prediction for a block to be coded (S101). For example, the conversion unit 106 determines whether to use intra prediction or inter prediction based on a cost based on a difference between an original image and a reconstructed image obtained by locally decoding a compressed image and / or a code amount. Alternatively, for example, the conversion unit 106 may determine whether to use intra prediction or inter prediction based on information (e.g., picture type) other than the cost based on the difference and / or the code amount.

[0147] Here, when it is determined that inter prediction is used for the coding target block (inter in S101), the transform unit 106 selects a first transform base for the coding target block from one or more candidates of the first transform base (S102). For example, the transform unit 106 fixedly selects a transform base of DCT-II as the first transform base for the coding target block. Also, for example, the transform unit 106 may select the first transform base from a plurality of candidates of the first transform base.

[0148] Then, the transform unit 106 performs a first transform on the residual of the block to be coded using the first transform base selected in step S102 to generate first transform coefficients (S103). The quantization unit 108 quantizes the generated first transform coefficients (S110), and the transform and quantization process ends.

[0149] On the other hand, when it is determined that intra prediction is used for the block to be coded (intra in S101), the conversion unit 106 selects a first conversion basis for the block to be coded from one or more candidates of the first conversion basis (S104). For example, the conversion unit 106 can select the first conversion basis using an adaptive basis selection mode. The adaptive basis selection mode is a mode in which a conversion basis is adaptively selected from a plurality of predetermined conversion basis candidates based on a cost based on a difference between an original image and a reconstructed image and / or a code amount. This adaptive basis selection mode is sometimes called an EMT mode or an AMT mode. As the candidates of the conversion basis, for example, the plurality of conversion bases shown in FIG. 6 can be used. Note that the candidates of the conversion basis are not limited to the plurality of conversion bases in FIG. 6. The candidates of the conversion basis may include, for example, a conversion basis equivalent to not performing conversion.

[0150] Also, for example, the transform unit 106 may select the first transform base using a non-adaptive basis selection mode (i.e., without using an adaptive basis selection mode). In the non-adaptive basis selection mode, for example, the transform unit 106 may select the first transform base based on coding parameters (e.g., block size, quantization parameter, intra prediction mode, etc.). The transform unit 106 may also select a fixed transform base (e.g., a transform base of DCT-II) predefined in a standard specification or the like. In this case, the selection of the transform base means that one predefined transform base is fixedly adopted. The transform unit 106 may also adaptively switch between the adaptive basis transform mode and the non-adaptive basis selection mode.

[0151] Next, the transform unit 106 performs a first transform on the residual of the encoding target block using the first transform base selected in step S104 to generate a first transform coefficient (S105). The transform unit 106 determines whether or not the intra prediction mode of the encoding target block is a predetermined mode (S106). For example, the transform unit 106 determines whether or not the intra prediction mode is a predetermined mode based on a cost based on a difference between an original image and a reconstructed image and / or an amount of code. Note that the determination of whether or not the intra prediction mode is a predetermined mode may be performed based on information other than the cost.

[0152] The predetermined mode may be defined in advance, for example, by a standard specification, etc. Also, for example, the predetermined mode may be determined based on encoding parameters, etc.

[0153] If the intra prediction mode is the predetermined mode (YES in S106), the transform unit 106 determines whether the first transform base selected in step S104 matches a predetermined transform base (S107). The predetermined transform base may be defined in advance, for example, by a standard specification or the like. Also, for example, the predetermined transform base may be determined based on an encoding parameter or the like.

[0154] If the intra prediction mode is not the predetermined mode (NO in S106), or if the first transform base is the same as the predetermined transform base (YES in S107), the transform unit 106 selects a second transform base for the encoding target block from one or more second transform base candidates (S108). The transform unit 106 generates second transform coefficients by performing a second transform on the first transform coefficients using the selected second transform base (S109). The quantization unit 108 quantizes the generated second transform coefficients (S110), and ends the transform and quantization process.

[0155] In the second transformation, a secondary transformation called NSST may be performed, or a transformation that selectively uses one of a plurality of candidates for the second transformation base may be performed. In this case, in the selection of the second transformation base, the selected transformation base may be fixed. In other words, a predetermined fixed transformation base may be selected as the second transformation base. In addition, a transformation base equivalent to not performing the second transformation may be used as the second transformation base.

[0156] If the intra prediction mode is a predetermined mode (YES in S106) and the first transformation base is different from the predetermined transformation base (NO in S107), the transformation unit 106 skips the second transformation base selection step (S108) and the second transformation step (S109). That is, the transformation unit 106 does not perform the second transformation. In this case, the first transformation coefficient generated in step S105 is quantized (S110), and the transformation and quantization process ends.

[0157] In this way, when the second transform step is skipped, information indicating that the second transform is not performed may be notified to the decoding device. Also, when the second transform step is skipped, the second transform may be performed using a second transform base equivalent to not performing the transform, and information indicating the second transform base may be notified to the decoding device.

[0158] The inverse quantization unit 112 and the inverse transformation unit 114 of the encoding device 100 perform processes inverse to those performed by the transformation unit 106 and the quantization unit 108, thereby reconstructing the current block to be encoded.

[0159] [Processing of the inverse quantization unit and inverse transform unit of the decoding device] Next, the processing of the inverse quantization unit 204 and the inverse transform unit 206 of the decoding device 200 according to the second embodiment will be specifically described with reference to Fig. 12. Fig. 12 is a flowchart showing the inverse quantization and inverse transform processing in the decoding device 200 according to the second embodiment.

[0160] First, the inverse quantization unit 204 inversely quantizes the quantized coefficients of the block to be decoded (S501). The inverse transform unit 206 determines whether to use intra prediction or inter prediction for the block to be decoded (S502). For example, the inverse transform unit 206 determines whether to use intra prediction or inter prediction based on information acquired from a bitstream.

[0161] When it is determined that inter prediction is used for the block to be decoded (inter in S502), the inverse transform unit 206 selects a first inverse transform base for the block to be decoded (S503). Selecting an inverse transform base (first inverse transform base or second inverse transform base) in the decoding device 200 means determining an inverse transform base based on predetermined information. For example, a base selection signal can be used as the predetermined information. In addition, an intra prediction mode, a block size, or the like can also be used as the predetermined information.

[0162] The inverse transform unit 206 performs a first inverse transform on the inverse quantized coefficients of the block to be decoded, using the first inverse transform basis selected in step S503 (S504), and ends the inverse quantization and inverse transform process.

[0163] When it is determined that intra prediction is to be used for the block to be decoded (intra in S502), the inverse transform unit 206 determines whether the intra prediction mode of the block to be decoded is a predetermined mode (S505). The predetermined mode used in the decoding device 200 is the same as the predetermined mode used in the encoding device 100.

[0164] If the intra prediction mode is the predetermined mode (YES in S505), the inverse transform unit 206 determines whether the first inverse transform base matches a predetermined inverse transform base (S506). As the predetermined inverse transform base, an inverse transform base corresponding to the predetermined transform base used in the encoding device 100 is used.

[0165] If the intra prediction mode is not the predetermined mode (NO in S505), or if the first inverse transform base matches the predetermined inverse transform base (YES in S506), the inverse transform unit 206 selects a second inverse transform base for the block to be decoded (S507). The inverse transform unit 206 performs a second inverse transform on the inverse quantized coefficients of the block to be decoded using the selected second inverse transform base (S508). The inverse transform unit 206 selects a first inverse transform base (S509). The inverse transform unit 206 performs a first inverse transform on the coefficients obtained by the second inverse transform in step S508 using the selected first inverse transform base (S510), and ends the inverse quantization and inverse transform process.

[0166] On the other hand, if the intra prediction mode is a predetermined mode (YES in S505) and the first inverse transform base is different from the predetermined inverse transform base (NO in S506), the inverse transform unit 206 skips the second inverse transform base selection step (S507) and the second inverse transform step (S508). That is, the inverse transform unit 206 selects the first inverse transform base (S509) without performing the second inverse transform. The inverse transform unit 206 performs the first inverse transform on the coefficients inversely quantized in step S501 using the selected first inverse transform base (S510), and ends the inverse quantization and inverse transform process.

[0167] [Effects, etc.] The inventors have found that in conventional coding, the amount of processing required to search for an optimal combination of a transform base and transform parameters (e.g., filter coefficients) in both the first transform and the second transform is enormous. In contrast, the coding device 100 and the decoding device 200 according to the present embodiment can skip the second transform according to the intra prediction mode and the first transform base. As a result, the amount of processing required to search for an optimal combination of a transform base and transform parameters in both the first transform and the second transform can be reduced, and a reduction in processing load can be achieved while suppressing a decrease in compression efficiency.

[0168] In this embodiment, when inter prediction is used for the coding target block, the second transform is not performed, but is not limited thereto. That is, when inter prediction is used for the coding target block, the first transform coefficient generated by the first transform may be subjected to the second transform. In this case, the second transform coefficient generated by the second transform is quantized.

[0169] Note that the order of steps in the flowcharts of Figures 11 and 12 is not limited to the order described in Figures 11 and 12. For example, in Figure 11, the step of determining whether or not the intra prediction mode is a predetermined mode (S106) and the step of determining whether or not the first transformation base matches the predetermined transformation base (S107) may be performed in the reverse order or simultaneously.

[0170] This aspect may be implemented in combination with at least a part of other aspects of the present disclosure. Also, some of the processes, some of the configurations of the device, and some of the syntax described in the flowcharts of this aspect may be implemented in combination with other aspects.

[0171] (Embodiment 3) Next, a third embodiment will be described. This embodiment differs from the second embodiment in that the predetermined mode used to determine the intra prediction mode is limited to the non-directional prediction mode. The present embodiment will be described below with reference to the drawings, focusing on the differences from the second embodiment. In the following drawings, steps that are substantially the same as those in the second embodiment are given the same reference numerals, and duplicated descriptions are omitted or simplified.

[0172] [Processing of the conversion section and quantization section of the encoding device] First, the processing of the transform unit 106 and the quantization unit 108 of the coding device 100 according to the present embodiment will be specifically described with reference to Fig. 13. Fig. 13 is a flowchart showing the transform and quantization processing in the coding device 100 according to the third embodiment.

[0173] First, the transform unit 106 determines whether intra prediction or inter prediction is used for the encoding target block (S101). Here, when it is determined that inter prediction is used for the encoding target block (inter in S101), the transform unit 106 selects a first transform base (S102), and performs a first transform on the residual of the encoding target block using the selected first transform base to generate a first transform coefficient (S103). The quantization unit 108 quantizes the generated first transform coefficient (S110), and ends the transform and quantization process.

[0174] On the other hand, when it is determined that intra prediction is used for the block to be coded (intra in S101), the conversion unit 106 determines whether the intra prediction mode of the block to be coded is a non-directional prediction mode (S201). The non-directional prediction mode is a mode that does not use a specific direction for predicting the block to be decoded. Specifically, the non-directional prediction mode is, for example, a DC prediction mode and / or a planar prediction mode. In the non-directional prediction mode, for example, a pixel value is predicted using an average value of reference pixels or an interpolated value of reference pixels. Conversely, a mode that uses a specific direction for predicting the block to be decoded is called a directional prediction mode. In the directional prediction mode, a pixel value is predicted by stretching the value of the reference pixel in a specific direction. Note that the pixel value is a value of a pixel unit that constitutes a picture, for example, a luminance value or a chrominance value.

[0175] Here, if the intra prediction mode is different from the non-directional prediction mode (NO in S201), the transform unit 106 selects a first transform base for the encoding target block (S202). The transform unit 106 generates first transform coefficients by performing a first transform on the residual of the encoding target block using the first transform base selected in step S202 (S203). Furthermore, the transform unit 106 selects a second transform base for the encoding target block (S204). The transform unit 106 generates second transform coefficients by performing a second transform on the first transform coefficients generated in step S203 using the second transform base selected in step S204 (S205). The processes in steps S202 to S205 are substantially the same as the processes in steps S104 to S109 in the case where step S106 is NO in FIG. 11. Thereafter, the quantization unit 108 quantizes the second transform coefficients generated in step S205 (S110), and ends the transform and quantization process.

[0176] On the other hand, if the intra prediction mode matches the non-directional prediction mode (YES in S201), the transform unit 106 selects a first transform base for the encoding target block (S206). The transform unit 106 performs a first transform on the residual of the encoding target block using the first transform base selected in step S206 to generate a first transform coefficient (S207). The transform unit 106 determines whether the first transform base selected in step S206 matches a predetermined transform base (S208). As the predetermined transform base, for example, a transform base of DCT-II and / or a transform base similar thereto can be used.

[0177] Here, if the first transform base matches the predetermined transform base (YES in S208), the transform unit 106 selects a second transform base for the encoding target block (S209). Then, the transform unit 106 generates second transform coefficients by performing a second transform on the first transform coefficients generated in step S207 using the second transform base selected in step S209 (S210). After that, the quantization unit 108 quantizes the second transform coefficients generated in step S210 (S110), and ends the transform and quantization process.

[0178] On the other hand, if the first transformation base is different from the predetermined transformation base (NO in S208), the transformation unit 106 skips the step of selecting the second transformation base (S209) and the second transformation step (S210). That is, the transformation unit 106 does not perform the second transformation. In this case, the first transformation coefficient generated in step S207 is quantized (S110), and the transformation and quantization process ends.

[0179] The process of steps S206 to S209 is substantially the same as the process of steps S104 to S109 in the case where step S106 in FIG. 11 is YES.

[0180] [Processing of the inverse quantization unit and inverse transform unit of the decoding device] Next, the processing of the inverse quantization unit 204 and the inverse transform unit 206 of the decoding device 200 according to the present embodiment will be specifically described with reference to Fig. 14. Fig. 14 is a flowchart showing the inverse quantization and inverse transform processing in the decoding device 200 according to the third embodiment.

[0181] First, the inverse quantization unit 204 inversely quantizes the quantized coefficients of the block to be decoded (S501). The inverse transform unit 206 determines whether intra prediction or inter prediction is to be used for the block to be decoded (S502).

[0182] When it is determined that inter prediction is used for the block to be decoded (inter in S502), the inverse transform unit 206 selects a first inverse transform basis for the block to be decoded (S503). The inverse transform unit 206 performs a first inverse transform on the inverse quantized coefficients of the block to be decoded using the first inverse transform basis selected in step S503 (S504), and ends the inverse quantization and inverse transform process.

[0183] On the other hand, when it is determined that intra prediction is used for the block to be decoded (intra in S502), the inverse transform unit 206 determines whether or not the intra prediction mode of the block to be decoded is a non-directional prediction mode (S601).

[0184] Here, if the intra prediction mode is not a non-directional prediction mode (NO in S601), the inverse transform unit 206 selects a second inverse transform base for the block to be decoded (S602). The inverse transform unit 206 performs a second inverse transform on the inverse quantized coefficients of the block to be decoded using the selected second inverse transform base (S603). The inverse transform unit 206 selects a first inverse transform base (S604). The inverse transform unit 206 performs a first inverse transform on the coefficients obtained by the second inverse transform in step S603 using the selected first inverse transform base (S605), and ends the inverse quantization and inverse transform process.

[0185] On the other hand, if the intra prediction mode is a non-directional prediction mode (YES in S601), the inverse transform unit 206 determines whether the first inverse transform base matches a predetermined inverse transform base (S606). The predetermined inverse transform base used in the decoding device 200 is an inverse transform base corresponding to the predetermined transform base used in the encoding device 100.

[0186] Here, if the first inverse transform base matches the predetermined inverse transform base (YES in S606), the inverse transform unit 206 selects a second inverse transform base for the block to be decoded (S607). The inverse transform unit 206 performs a second inverse transform on the inverse quantized coefficients of the block to be decoded using the selected second inverse transform base (S608). The inverse transform unit 206 selects a first inverse transform base (S609). The inverse transform unit 206 performs a first inverse transform on the coefficients obtained by the second inverse transform in step S608 using the selected first inverse transform base (S610), and ends the inverse quantization and inverse transform process.

[0187] On the other hand, if the first inverse transform base is different from the predetermined inverse transform base (NO in S606), the inverse transform unit 206 skips the step of selecting the second inverse transform base (S607) and the step of performing the second inverse transform (S608). That is, the inverse transform unit 206 selects the first inverse transform base (S609) without performing the second inverse transform. The inverse transform unit 206 performs the first inverse transform on the coefficients inversely quantized in step S501 using the selected first inverse transform base (S610), and ends the inverse quantization and inverse transform process.

[0188] [Effects, etc.] As described above, according to the encoding device 100 and the decoding device 200 of this embodiment, the second transform can be skipped when the intra prediction mode is a non-directional prediction mode. In the non-directional prediction mode, the residual error is often flattened within a block. Therefore, if a transform base other than the transform base of DCT-II and a transform base similar thereto is used, high-frequency components tend to remain, and the distribution of transform coefficients tends to be random. In this case, the effect of improving compression efficiency by the second transform is reduced, so that the second transform can be skipped to suppress the decrease in compression efficiency and realize a reduction in processing load.

[0189] In this embodiment, when inter prediction is used for the coding target block, the second transform is not performed, but is not limited thereto. That is, when inter prediction is used for the coding target block, the first transform coefficient generated by the first transform may be subjected to the second transform. In this case, the second transform coefficient generated by the second transform is quantized.

[0190] It should be noted that the order of steps in the flowcharts of FIGS. 13 and 14 is not limited to the order described in FIGS.

[0191] This aspect may be implemented in combination with at least a part of other aspects of the present disclosure. Also, some of the processes, some of the configurations of the device, and some of the syntax described in the flowcharts of this aspect may be implemented in combination with other aspects.

[0192] (Embodiment 4) Next, the fourth embodiment will be described. This embodiment differs from the second embodiment in that the first transformation base is fixed according to the block size in the adaptive basis selection mode. This embodiment will be described below with reference to the drawings, focusing on the differences from the second and third embodiments. In the following drawings, steps that are substantially the same as those in the second and third embodiments are given the same reference numerals, and duplicated descriptions are omitted or simplified.

[0193] [Processing of the conversion section and quantization section of the encoding device] First, the processing of the transform unit 106 and the quantization unit 108 of the coding device 100 according to the fourth embodiment will be specifically described with reference to Fig. 15. Fig. 15 is a flowchart showing the transform and quantization processing in the coding device 100 according to the fourth embodiment.

[0194] First, the transform unit 106 determines whether intra prediction or inter prediction is used for the encoding target block (S101). Here, when it is determined that inter prediction is used for the encoding target block (inter in S101), the transform unit 106 selects a first transform base (S102), and performs a first transform on the residual of the encoding target block using the selected first transform base to generate a first transform coefficient (S103). The quantization unit 108 quantizes the generated first transform coefficient (S110), and ends the transform and quantization process.

[0195] On the other hand, when it is determined that intra prediction is to be used for the encoding target block (intra in S101), the conversion unit 106 determines whether or not the size of the encoding target block matches a predetermined size, and whether or not an adaptive basis selection mode is to be used for the encoding target block (S301). Whether or not to use the adaptive basis selection mode can be determined based on, for example, a difference between an original image and a reconstructed image and / or a cost based on the amount of code.

[0196] The predetermined size may be, for example, a specific block size predefined by a standard specification or the like. Specifically, the predetermined size may be, for example, 4x4 pixels. A plurality of block sizes may be used as the predetermined size. Specifically, the predetermined size may be, for example, 4x4 pixels, 8x4 pixels, and 4x8 pixels. It may also be determined whether the size of the block to be coded matches the predetermined size by determining whether the size of the block to be coded satisfies a predetermined condition. In this case, the predetermined condition may be, for example, a condition that both the horizontal size and the vertical size are equal to or smaller than a predetermined number of pixels, or at least one of the horizontal size and the vertical size is equal to or smaller than a predetermined number of pixels.

[0197] If the size of the block to be coded is different from a predetermined size, or if the adaptive basis selection mode is not used (NO in S301), the conversion unit 106 determines whether the intra prediction mode of the block to be coded is a non-directional prediction mode (S201).

[0198] Here, if the intra prediction mode is different from the non-directional prediction mode (NO in S201), the transform unit 106 selects a first transform base for the block to be coded (S202). For example, if it is determined that the adaptive basis selection mode is to be used, the transform unit 106 adaptively selects the first transform base from among a plurality of first transform base candidates. Also, for example, if it is determined that the adaptive basis selection mode is not to be used, the transform unit 106 fixedly selects a predefined transform base (for example, a transform base of DCT-II).

[0199] The transform unit 106 performs a first transform on the residual of the block to be coded using the first transform base selected in step S202, thereby generating first transform coefficients (S203). Furthermore, the transform unit 106 selects a second transform base for the block to be coded (S204). The transform unit 106 performs a second transform on the first transform coefficients generated in step S203 using the second transform base selected in step S204, thereby generating second transform coefficients (S205). Thereafter, the quantization unit 108 quantizes the second transform coefficients generated in step S205 (S110), thereby completing the transform and quantization process.

[0200] On the other hand, if the intra prediction mode matches the non-directional prediction mode (YES in S201), the transform unit 106 selects a first transform base for the block to be coded (S206). For example, if it is determined that the adaptive basis selection mode is to be used, the transform unit 106 adaptively selects the first transform base from among a plurality of first transform base candidates. Also, for example, if it is determined that the adaptive basis selection mode is not to be used, the transform unit 106 fixedly selects a predefined transform base (for example, a transform base of DCT-II).

[0201] The transform unit 106 performs a first transform on the residual of the block to be coded using the first transform base selected in step S206 to generate first transform coefficients (S207). The transform unit 106 determines whether the first transform base selected in step S206 matches a second predetermined transform base (S208). As the second predetermined transform base, for example, a transform base of DCT-II and / or a transform base similar thereto can be used.

[0202] Here, if the first transformation base coincides with the second predetermined transformation base (YES in S208), the transformation unit 106 selects a second transformation base for the encoding target block (S209). Then, the transformation unit 106 generates second transformation coefficients by performing a second transformation on the first transformation coefficients generated in step S207 using the second transformation base selected in step S209 (S210). After that, the quantization unit 108 quantizes the second transformation coefficients generated in step S210 (S110), and ends the transformation and quantization process.

[0203] On the other hand, if the first transformation base is different from the second predetermined transformation base (NO in S208), the transformation unit 106 skips the step of selecting the second transformation base (S209) and the second transformation step (S210). That is, the transformation unit 106 does not perform the second transformation. In this case, the first transformation coefficient generated in step S207 is quantized (S110), and the transformation and quantization process ends.

[0204] When the size of the block to be coded matches the predetermined size and the adaptive basis selection mode is used (YES in S301), the transform unit 106 fixes the first transform base to the first predetermined transform base (S302). As the first predetermined transform base, for example, the transform base of DST-VII can be used. Note that the first predetermined transform base is not limited to the transform base of DST-VII. For example, the transform base of DCT-V may be used as the first predetermined transform base.

[0205] The transform unit 106 performs a first transform on the residual of the current block to be coded using the first transform base fixed in step S302 to generate a first variation coefficient (S303). The transform unit 106 determines whether the intra prediction mode of the current block to be coded is a non-directional prediction mode (S304).

[0206] Here, if the intra prediction mode is different from the non-directional prediction mode (NO in S304), the transform unit 106 selects a second transform base (S305). Then, the transform unit 106 generates a second transform coefficient by performing a second transform on the first transform coefficient generated in step S303 using the second transform base selected in step S305 (S306). After that, the quantization unit 108 quantizes the second transform coefficient generated in step S306 (S110), and ends the transform and quantization process.

[0207] On the other hand, if the intra prediction mode matches the non-directional prediction mode (YES in S304), the transform unit 106 skips the second transform base selection step (S305) and the second transform step (S306). That is, the transform unit 106 does not perform the second transform. In this case, the first transform coefficient generated in step S303 is quantized (S110), and the transform and quantization process ends.

[0208] [Entropy coding process of the coding device] Next, the encoding process related to the transform in the entropy encoding unit 110 of the encoding device 100 according to the fourth embodiment will be specifically described with reference to Fig. 16. Fig. 16 is a flowchart showing the encoding process in the encoding device 100 according to the fourth embodiment.

[0209] When inter prediction is used for the block to be coded (inter in S401), the entropy coding unit 110 codes a first basis selection signal into a bit stream (S402). Here, the first basis selection signal is information or data indicating the first transformation basis selected in step S102.

[0210] Encoding a signal in a bitstream means arranging a code representing information in the bitstream. The code is generated, for example, by context-adaptive binary arithmetic coding (CABAC). It is not necessary to use CABAC or entropy coding to generate the code. For example, the code may be the information itself (e.g., a flag of 0 or 1).

[0211] Next, the entropy coding unit 110 codes the coefficients quantized in step S110 (S403), and ends the coding process.

[0212] When intra prediction is used for the block to be coded (intra in S401), the entropy coding unit 110 codes an intra prediction mode signal indicating the intra prediction mode of the block to be coded into the bitstream (S404). Furthermore, the entropy coding unit 110 codes an adaptive selection mode signal indicating whether or not an adaptive basis selection mode is used for the block to be coded into the bitstream (S405).

[0213] Here, if the adaptive basis selection mode is used and the size of the encoding target block is different from the predetermined size (YES in S406), the entropy coding unit 110 codes the first basis selection signal in the bit stream (S407). Here, the first basis selection signal is information or data indicating the first transformation basis selected in step S202 or S206. On the other hand, if the adaptive basis selection mode is not used, or if the adaptive basis selection mode is used and the size of the encoding target block matches the predetermined size (NO in S406), the entropy coding unit 110 skips the coding step of the first basis selection signal (S407). That is, the entropy coding unit 110 does not code the first basis selection signal.

[0214] Here, if the second transformation has been performed (YES in S408), the entropy coding unit 110 codes the second base selection signal into the bitstream (S409). Here, the second base selection signal is information or data indicating the second transformation base selected in step S204, S209, or S305. On the other hand, if the second transformation has not been performed (NO in S408), the entropy coding unit 110 skips the coding step (S409) of the second base selection signal. That is, the entropy coding unit 110 does not code the second base selection signal.

[0215] Finally, the entropy coding unit 110 codes the coefficients quantized in step S110 (S410), and the coding process ends.

[0216] [Entropy decoding process of the decoding device] Next, the process of the entropy decoding unit 202 of the decoding device 200 according to the fourth embodiment will be specifically described with reference to Fig. 17. Fig. 17 is a flowchart showing the decoding process in the decoding device 200 according to the fourth embodiment.

[0217] When inter prediction is used for the current block to be decoded (inter in S701), the entropy decoding unit 202 decodes a first basis selection signal from the bitstream (S702).

[0218] Decoding a signal from a bit stream means deciphering a code indicating information from the bit stream and restoring the information from the deciphered code. For example, context-adaptive binary arithmetic decoding (CABAD) is used to restore information from a code. Note that, for example, CABAD and entropy decoding do not necessarily have to be used to restore information from a code. For example, when the deciphered code itself indicates information (e.g., a flag of 0 or 1), it is sufficient to simply decipher the code.

[0219] Next, the entropy decoding unit 202 decodes the quantized coefficients from the bit stream (S703), and ends the decoding process.

[0220] When intra prediction is used for the block to be decoded (intra in S701), the entropy decoding unit 202 decodes an intra prediction mode signal from the bit stream (S704). Furthermore, the entropy decoding unit 202 decodes an adaptive selection mode signal (S705).

[0221] Here, if the adaptive basis selection mode is used and the size of the block to be decoded is different from the predetermined size (YES in S706), the entropy decoding unit 202 decodes the first basis selection signal from the bit stream (S707). On the other hand, if the adaptive basis selection mode is not used, or if the adaptive basis selection mode is used and the size of the block to be decoded is the same as the predetermined size (NO in S706), the entropy decoding unit 202 skips the step of decoding the first basis selection signal (S707). In other words, the entropy decoding unit 202 does not decode the first basis selection signal.

[0222] Here, if the second inverse transform is to be performed (YES in S708), the entropy decoding unit 202 decodes the second basis selection signal from the bit stream (S709). On the other hand, if the second inverse transform is not to be performed (NO in S708), the entropy decoding unit 202 skips the step of decoding the second basis selection signal (S709). In other words, the entropy decoding unit 202 does not decode the second basis selection signal.

[0223] Finally, the entropy decoding unit 202 decodes the quantized coefficients from the bitstream (S710), and the decoding process ends.

[0224] [Processing of the inverse quantization unit and inverse transform unit of the decoding device] Next, the processing of the inverse quantization unit 204 and the inverse transform unit 206 of the decoding device 200 according to the fourth embodiment will be specifically described with reference to Fig. 18. Fig. 18 is a flowchart showing the inverse quantization and inverse transform processing in the decoding device 200 according to the fourth embodiment.

[0225] First, the inverse quantization unit 204 inversely quantizes the quantized coefficients of the block to be decoded (S501). The inverse transform unit 206 determines whether intra prediction or inter prediction is to be used for the block to be decoded (S502). When it is determined that inter prediction is to be used for the block to be decoded (inter in S502), the inverse transform unit 206 selects a first inverse transform basis for the block to be decoded (S503). The inverse transform unit 206 performs a first inverse transform on the inverse quantized coefficients of the block to be decoded using the first inverse transform basis selected in step S503 (S504), and ends the inverse quantization and inverse transform process.

[0226] When it is determined that intra prediction is used for the block to be decoded (intra in S502), the inverse transform unit 206 determines whether the size of the block to be decoded matches a predetermined size and whether an adaptive basis selection mode is used for the block to be decoded (S801). For example, the inverse transform unit 206 determines whether an adaptive basis selection mode is used based on the adaptive selection mode signal decoded in step S705 of FIG. 17.

[0227] If the size of the block to be decoded is different from a predetermined size, or if the adaptive basis selection mode is not used (NO in S801), the inverse transform unit 206 determines whether the intra prediction mode of the block to be decoded is a non-directional prediction mode (S601).

[0228] Here, if the intra prediction mode is not a non-directional prediction mode (NO in S601), the inverse transform unit 206 selects a second inverse transform base for the block to be decoded (S602). For example, the inverse transform unit 206 selects the second inverse transform base based on the second base selection signal decoded in step S709 of FIG. 17. The inverse transform unit 206 performs a second inverse transform on the dequantized coefficients of the block to be decoded using the selected second inverse transform base (S603). The inverse transform unit 206 selects a first inverse transform base (S604). For example, if the adaptive base selection mode is used, the inverse transform unit 206 selects the first inverse transform base based on the first base selection signal decoded in step S707 of FIG. 17. The inverse transform unit 206 performs a first inverse transform on the coefficients obtained by the second inverse transform in step S603 using the selected first inverse transform basis (S605), and ends the inverse quantization and inverse transform processing.

[0229] On the other hand, if the intra prediction mode is a non-directional prediction mode (YES in S601), the inverse transform unit 206 determines whether the first inverse transform base matches the second predetermined inverse transform base (S606). For example, if the adaptive basis selection mode is used, the inverse transform unit 206 determines whether the first inverse transform base matches the second predetermined inverse transform base based on the first basis selection signal decoded in step S707 of FIG. 17. As the second predetermined inverse transform base, an inverse transform base corresponding to the second predetermined transform base used in the encoding device 100 is used.

[0230] Here, if the first inverse transform base matches the second predetermined inverse transform base (YES in S606), the inverse transform unit 206 selects a second inverse transform base for the block to be decoded (S607). For example, the inverse transform unit 206 selects the second inverse transform base based on the second base selection signal decoded in step S709 of FIG. 17. The inverse transform unit 206 performs a second inverse transform on the dequantized coefficients of the block to be decoded using the selected second inverse transform base (S608). The inverse transform unit 206 selects a first inverse transform base (S609). For example, when the adaptive base selection mode is used, the inverse transform unit 206 selects the first inverse transform base based on the first base selection signal decoded in step S707 of FIG. 17. The inverse transform unit 206 performs a first inverse transform on the coefficients obtained by the second inverse transform in step S608 using the selected first inverse transform basis (S610), and ends the inverse quantization and inverse transform processing.

[0231] If the size of the block to be decoded matches the predetermined size and the adaptive basis selection mode is used (YES in S801), the inverse transform unit 206 determines whether the intra prediction mode of the block to be decoded is a non-directional prediction mode (S802).

[0232] Here, if the intra prediction mode is not a non-directional prediction mode (NO in S802), the inverse transform unit 206 selects a second inverse transform base for the block to be decoded (S803). For example, the inverse transform unit 206 selects the second inverse transform base based on the second base selection signal decoded in step S709 of FIG. 17. The inverse transform unit 206 performs a second inverse transform on the dequantized coefficients of the block to be decoded using the selected second inverse transform base (S804). The inverse transform unit 206 fixes the first inverse transform base to a first predetermined inverse transform base (S805). As the first predetermined inverse transform base, an inverse transform base corresponding to the first predetermined transform base used in the encoding device 100 is used. The inverse transform unit 206 performs a first inverse transform on the coefficients obtained by the second inverse transform in step S804 using the fixed first inverse transform basis (S806), and ends the inverse quantization and inverse transform processing.

[0233] On the other hand, if the intra prediction mode is a non-directional prediction mode (YES in S802), the inverse transform unit 206 skips the step of selecting the second inverse transform base (S803) and the step of performing the second inverse transform (S804). That is, the inverse transform unit 206 fixes the first inverse transform base to the first predetermined inverse transform base (S805) without performing the second inverse transform. The inverse transform unit 206 performs the first inverse transform on the coefficients inversely quantized in step S501 using the fixed first inverse transform base (S806), and ends the inverse quantization and inverse transform process.

[0234] [Effects, etc.] As described above, according to the encoding device 100 and the decoding device 200 according to the present embodiment, when the adaptive basis selection mode is used, the first transform base can be fixed according to the block size. Therefore, the load of the first transform in the adaptive basis selection mode can be reduced.

[0235] In this embodiment, when inter prediction is used for the coding target block, the second transform is not performed, but is not limited thereto. That is, when inter prediction is used for the coding target block, the first transform coefficient generated by the first transform may be subjected to the second transform. In this case, the second transform coefficient generated by the second transform is quantized.

[0236] It should be noted that the order of steps in the flowcharts of Figures 15 to 18 is not limited to the order shown in Figures 15 to 18. For example, in Figure 16, the order of signal coding may be another order predefined by standards or the like.

[0237] In this embodiment, a plurality of signals (intra prediction mode signal, adaptive selection mode signal, first base selection signal, and second base selection signal) are coded in a bitstream, but these signals may not be coded in a bitstream. For example, these signals may be notified from the coding device 100 to the decoding device 200 separately from the bitstream.

[0238] In this embodiment, the positions of the multiple signals (intra prediction mode signal, adaptive selection mode signal, first base selection signal, and second base selection signal) in the bitstream are not particularly limited. The multiple signals are, for example, encoded into at least one of multiple headers. As the multiple headers, for example, a video parameter set, a sequence parameter set, a picture parameter set, and a slice header can be used. In addition, when a signal is in multiple layers (for example, a picture parameter set and a slice header), a signal in a lower layer (for example, a slice header) overwrites a signal in a higher layer (for example, a picture parameter set).

[0239] This aspect may be implemented in combination with at least a part of other aspects of the present disclosure. Also, some of the processes, some of the configurations of the device, and some of the syntax described in the flowcharts of this aspect may be implemented in combination with other aspects.

[0240] (Embodiment 5) In the above embodiments and modifications, each of the functional blocks can usually be realized by an MPU, a memory, etc. Furthermore, the processing by each of the functional blocks is usually realized by a program execution unit such as a processor reading and executing software (programs) recorded on a recording medium such as a ROM. The software may be distributed by downloading, etc., or may be recorded on a recording medium such as a semiconductor memory and distributed. Of course, each functional block can also be realized by hardware (dedicated circuitry).

[0241] Furthermore, the processes described in the embodiments and the modifications may be realized by centralized processing using a single device (system), or may be realized by distributed processing using multiple devices. The processor that executes the above programs may be either single or multiple. That is, centralized processing or distributed processing may be performed.

[0242] The present invention is not limited to the above-mentioned embodiments, and various modifications are possible, which are also included within the scope of the present invention.

[0243] Further, here, application examples of the video coding method (image coding method) or video decoding method (image decoding method) shown in the above embodiment and each modification example and a system using the same will be described. The system is characterized by having an image coding device using the image coding method, an image decoding device using the image decoding method, and an image coding / decoding device equipped with both. Other configurations in the system can be appropriately changed depending on the case.

[0244] [Usage example] 19 is a diagram showing the overall configuration of a content supply system ex100 that realizes a content distribution service. The area where communication services are provided is divided into cells of a desired size, and base stations ex106, ex107, ex108, ex109, and ex110, which are fixed wireless stations, are installed in each cell.

[0245] In this content supply system ex100, devices such as a computer ex111, a game machine ex112, a camera ex113, a home appliance ex114, and a smartphone ex115 are connected to the Internet ex101 via an Internet service provider ex102 or a communication network ex104, and base stations ex106 to ex110. The content supply system ex100 may be configured to connect any of the above elements in combination. Each device may be directly or indirectly connected to each other via a telephone network or short-distance wireless communication, without going through the base stations ex106 to ex110, which are fixed wireless stations. In addition, the streaming server ex103 is connected to each device such as a computer ex111, a game machine ex112, a camera ex113, a home appliance ex114, and a smartphone ex115 via the Internet ex101, etc. In addition, the streaming server ex103 is connected to a terminal in a hot spot in an airplane ex117, etc., via a satellite ex116.

[0246] Instead of the base stations ex106 to ex110, wireless access points or hot spots may be used. The streaming server ex103 may be directly connected to the communication network ex104 without going through the Internet ex101 or the Internet service provider ex102, or may be directly connected to an airplane ex117 without going through a satellite ex116.

[0247] The camera ex113 is a device capable of taking still images and videos, such as a digital camera. The smartphone ex115 is a smartphone, a mobile phone, or a PHS (Personal Handyphone System) that is compatible with a mobile communication system generally called 2G, 3G, 3.9G, 4G, and 5G in the future.

[0248] The home appliance ex118 is a refrigerator or an appliance included in a home fuel cell cogeneration system.

[0249] In the content supply system ex100, a terminal having a photographing function is connected to a streaming server ex103 via a base station ex106 or the like, thereby enabling live distribution and the like. In live distribution, a terminal (such as a computer ex111, a game machine ex112, a camera ex113, a home appliance ex114, a smartphone ex115, and a terminal in an airplane ex117) performs the encoding process described in the above embodiment and each modification on still image or video content photographed by a user using the terminal, multiplexes the video data obtained by encoding with sound data obtained by encoding sound corresponding to the video, and transmits the obtained data to the streaming server ex103. That is, each terminal functions as an image encoding device according to one aspect of the present invention.

[0250] On the other hand, the streaming server ex103 streams the transmitted content data to the requesting client. The client is a computer ex111, a game machine ex112, a camera ex113, a home appliance ex114, a smartphone ex115, a terminal in an airplane ex117, or the like, capable of decoding the encoded data. Each device that receives the distributed data decodes and plays back the received data. That is, each device functions as an image decoding device according to one aspect of the present invention.

[0251] [Distributed processing] The streaming server ex103 may be a plurality of servers or computers that process, record, and distribute data in a distributed manner. For example, the streaming server ex103 may be realized by a CDN (Contents Delivery Network), and content distribution may be realized by a network that connects a large number of edge servers distributed around the world. In a CDN, an edge server that is physically close to the client is dynamically assigned according to the client. The content is cached and distributed to the edge server, thereby reducing delays. In addition, when an error occurs or the communication state changes due to an increase in traffic, the processing can be distributed among multiple edge servers, the distribution entity can be switched to another edge server, or distribution can be continued by bypassing the part of the network where a failure has occurred, thereby realizing high-speed and stable distribution.

[0252] In addition to the distributed processing of the distribution itself, the encoding processing of the captured data may be performed by each terminal, may be performed by the server side, or may be shared among the terminals. As an example, in the encoding processing, a processing loop is generally performed twice. In the first loop, the complexity of the image or the amount of code is detected for each frame or scene. In the second loop, processing is performed to maintain the image quality and improve the encoding efficiency. For example, the terminal performs the first encoding processing, and the server side that receives the content performs the second encoding processing, thereby improving the quality and efficiency of the content while reducing the processing load on each terminal. In this case, if there is a request to receive and decode almost in real time, the data encoded once by the terminal can be received and played back by other terminals, making it possible to perform more flexible real-time distribution.

[0253] As another example, the camera ex113 etc. extracts features from an image, compresses data related to the features as metadata, and transmits the compressed data to the server. The server performs compression according to the meaning of the image, for example, by determining the importance of an object from the features and switching the quantization precision. The feature data is particularly effective in improving the precision and efficiency of motion vector prediction when the server performs recompression. Alternatively, the terminal may perform simple encoding such as VLC (variable length coding), and the server may perform encoding with a large processing load such as CABAC (context-adaptive binary arithmetic coding).

[0254] As another example, in a stadium, a shopping mall, a factory, etc., there may be a plurality of video data in which almost the same scene has been shot by a plurality of terminals. In this case, using the plurality of terminals that shot the video and, as necessary, other terminals and servers that did not shoot the video, coding processing is assigned to each of them, for example, in units of GOPs (Group of Pictures), in units of pictures, or in units of tiles obtained by dividing a picture, for distributed processing. This reduces delays and realizes better real-time performance.

[0255] In addition, since the multiple video data are of almost the same scene, the server may manage and / or instruct the video data shot by each terminal to be mutually referenced. Alternatively, the server may receive the encoded data from each terminal and change the reference relationship between the multiple data, or correct or replace the pictures themselves and re-encode them. This makes it possible to generate a stream with improved quality and efficiency for each piece of data.

[0256] The server may also perform transcoding to change the encoding format of the video data before distributing it. For example, the server may convert an MPEG-based encoding format into a VP-based encoding format, or convert H.264 into H.265.

[0257] In this way, the encoding process can be performed by a terminal or one or more servers. Therefore, in the following, descriptions such as "server" or "terminal" are used to indicate the entity performing the processing, but some or all of the processing performed by the server may be performed by the terminal, and some or all of the processing performed by the terminal may be performed by the server. The same applies to the decoding process.

[0258] [3D, multi-angle] In recent years, it has become common to integrate and use images or videos of different scenes or the same scene taken from different angles by multiple devices such as cameras ex113 and / or smartphones ex115 that are almost synchronized with each other. The videos taken by the devices are integrated based on the relative positional relationship between the devices that is obtained separately, or on areas where feature points included in the videos match.

[0259] The server may not only encode 2D video, but also encode still images automatically or at a time specified by the user based on scene analysis of the video and transmit them to the receiving terminal. If the server can obtain the relative positional relationship between the shooting terminals, the server may generate a 3D shape of the scene based on not only 2D video but also images of the same scene captured from different angles. The server may separately encode 3D data generated by point clouds, etc., or may generate images to be transmitted to the receiving terminal by selecting or reconstructing images from images captured by multiple terminals based on the results of recognizing or tracking people or objects using the 3D data.

[0260] In this way, the user can enjoy a scene by selecting any video corresponding to each shooting terminal, or can enjoy content in which a video from any viewpoint is cut out from 3D data reconstructed using multiple images or videos. Furthermore, sound may be collected from multiple different angles, just like the video, and the server may multiplex the sound from a specific angle or space with the video and transmit it in accordance with the video.

[0261] In recent years, content that associates the real world with a virtual world, such as Virtual Reality (VR) and Augmented Reality (AR), has also become popular. In the case of VR images, the server creates viewpoint images for the right eye and the left eye, respectively, and may perform encoding that allows reference between each viewpoint video using Multi-View Coding (MVC) or the like, or may encode them as separate streams without mutual reference. When decoding the separate streams, it is preferable to play them in synchronization with each other so that a virtual three-dimensional space is reproduced according to the user's viewpoint.

[0262] In the case of an AR image, the server superimposes virtual object information in the virtual space on camera information in the real space based on the three-dimensional position or the movement of the user's viewpoint. The decoding device may obtain or hold virtual object information and three-dimensional data, generate a two-dimensional image according to the movement of the user's viewpoint, and smoothly connect them to create superimposed data. Alternatively, the decoding device may transmit the movement of the user's viewpoint to the server in addition to a request for virtual object information, and the server may create superimposed data according to the movement of the viewpoint received from the three-dimensional data held by the server, encode the superimposed data, and deliver it to the decoding device. Note that the superimposed data may have an α value indicating the transparency in addition to RGB, and the server may set the α value of the part other than the object created from the three-dimensional data to 0, etc., and encode the data in a state in which the part is transparent. Alternatively, the server may generate data in which a predetermined value of RGB value is set to the background like a chromakey, and the part other than the object is the background color.

[0263] Similarly, the decoding process of the distributed data may be performed by each client terminal, or may be performed by the server side, or may be shared among them. As an example, a certain terminal may once send a reception request to the server, and the content corresponding to the request may be received by other terminals, decoded, and the decoded signal may be transmitted to a device having a display. By distributing the processing and selecting appropriate content regardless of the performance of the communication-enabled terminals themselves, data with good image quality can be reproduced. In another example, while large-sized image data is received by a TV or the like, a part of the area, such as tiles into which the picture is divided, may be decoded and displayed on the viewer's personal terminal. This allows the viewer to share the overall picture while checking his / her own area of ​​responsibility or the area he / she wants to check in more detail at hand.

[0264] In the future, it is expected that content will be seamlessly received by switching appropriate data for the currently connected communication using delivery system standards such as MPEG-DASH under circumstances where multiple short-distance, medium-distance, or long-distance wireless communication is available, regardless of whether indoors or outdoors. This allows users to freely select and switch in real time not only their own terminals but also decoding devices or display devices such as displays installed indoors and outdoors. In addition, decoding can be performed while switching the decoding device and the display device based on the user's location information, etc. This makes it possible to move while displaying map information on the wall or part of the ground of a neighboring building where a displayable device is embedded while moving to a destination. It is also possible to switch the bit rate of the received data based on the accessibility of the encoded data on the network, such as when the encoded data is cached on a server that can be accessed from the receiving terminal in a short time, or when it is copied to an edge server in a content delivery service.

[0265] [Scalable Coding] The switching of contents will be described using a scalable stream compressed and coded by applying the video coding method shown in the above embodiment and each modification shown in FIG. 20. The server may have multiple streams with the same content but different qualities as individual streams, but may be configured to switch contents by taking advantage of the characteristics of a temporal / spatial scalable stream realized by coding in layers as shown in the figure. In other words, the decoding side can freely switch between low-resolution content and high-resolution content by determining which layer to decode according to an internal factor such as performance and an external factor such as the state of the communication band. For example, if a user wants to continue watching a video that was viewed on a smartphone ex115 while on the move on a device such as an Internet TV after returning home, the device can decode the same stream up to a different layer, thereby reducing the burden on the server side.

[0266] Furthermore, as described above, in addition to the configuration that realizes scalability in which pictures are coded for each layer and an enhancement layer exists above a base layer, the enhancement layer may include meta-information based on image statistics, etc., and the decoding side may generate high-quality content by super-resolving pictures of the base layer based on the meta-information. Super-resolution may be either an improvement in the signal-to-noise ratio at the same resolution or an increase in resolution. The meta-information includes information for specifying linear or nonlinear filter coefficients used in the super-resolution process, or information for specifying parameter values ​​in the filter process, machine learning, or least squares calculation used in the super-resolution process.

[0267] Alternatively, a picture may be divided into tiles or the like according to the meaning of an object in an image, and the decoding side may select a tile to decode to decode only a part of the area. Also, by storing the attribute of an object (person, car, ball, etc.) and its position in a video (coordinate position in the same image, etc.) as meta information, the decoding side can identify the position of a desired object based on the meta information and determine the tile containing the object. For example, as shown in FIG. 21, the meta information is stored using a data storage structure different from pixel data such as an SEI message in HEVC. This meta information indicates, for example, the position, size, or color of a main object.

[0268] Meta information may also be stored in units consisting of multiple pictures, such as streams, sequences, or random access units, etc. This allows the decoding side to obtain the time when a specific person appears in the video, and by combining this with picture-by-picture information, it is possible to identify the picture in which an object exists and the position of the object within the picture.

[0269] [Web page optimization] FIG. 22 is a diagram showing an example of a display screen of a web page in a computer ex111 or the like. FIG. 23 is a diagram showing an example of a display screen of a web page in a smartphone ex115 or the like. As shown in FIG. 22 and FIG. 23, a web page may include multiple link images that are links to image content, and the appearance of the web page differs depending on the device used to view the page. When multiple link images are visible on the screen, the display device (decoding device) displays a still image or I-picture that each content has as a link image, displays an image such as a gif animation using multiple still images or I-pictures, or receives only the base layer to decode and display the image until the user explicitly selects the link image, or until the link image approaches the center of the screen or the entire link image enters the screen.

[0270] When a link image is selected by a user, the display device gives top priority to decoding the base layer. If the HTML constituting the web page contains information indicating that the content is scalable, the display device may decode up to the enhancement layer. In order to ensure real-time performance, before selection or when the communication bandwidth is very tight, the display device decodes and displays only forward-reference pictures (I-pictures, P-pictures, and B-pictures with forward reference only), thereby reducing the delay between the decoding time of the first picture and the display time (the delay from the start of decoding the content to the start of display). The display device may also ignore the reference relationship between pictures and roughly decode all B-pictures and P-pictures with forward reference, and perform normal decoding as the number of received pictures increases over time.

[0271] [Automatic driving] Furthermore, when transmitting and receiving still image or video data such as 2D or 3D map information for automatic driving or driving assistance of a vehicle, the receiving terminal may receive weather or construction information as meta information in addition to image data belonging to one or more layers, and may associate and decode these. Note that the meta information may belong to a layer, or may simply be multiplexed with the image data.

[0272] In this case, since a car, drone, or airplane including a receiving terminal moves, the receiving terminal can realize seamless reception and decoding while switching between base stations ex106 to ex110 by transmitting the location information of the receiving terminal at the time of a reception request. Also, the receiving terminal can dynamically switch how much meta information to receive or how much to update map information according to the user's selection, the user's situation, or the state of the communication band.

[0273] In this manner, in the content supply system ex100, the client can receive, decode, and play back encoded information transmitted by the user in real time.

[0274] [Distribution of personal content] Furthermore, the content supply system ex100 allows not only high-quality, long-duration content from video distributors, but also low-quality, short-duration content from individuals via unicast or multicast distribution. It is expected that such personal content will continue to increase in the future. To improve the quality of personal content, the server may perform editing processing before encoding processing. This can be achieved, for example, by the following configuration.

[0275] During shooting, in real time or after accumulating, the server performs recognition processing such as shooting errors, scene search, semantic analysis, and object detection from the original image or encoded data. Then, based on the recognition result, the server manually or automatically corrects out-of-focus or camera shake, deletes less important scenes such as scenes that are less bright than other pictures or are out of focus, emphasizes object edges, changes color, and performs other editing. The server encodes the edited data based on the editing result. It is also known that if the shooting time is too long, the viewer rating will decrease, and the server may automatically clip not only scenes of less importance as described above but also scenes with little movement based on the image processing result so that the content will be within a specific time range depending on the shooting time. Alternatively, the server may generate a digest based on the result of the semantic analysis of the scene and encode it.

[0276] In addition, there are cases where personal contents contain images that infringe copyrights, moral rights, portrait rights, etc., and the scope of sharing may exceed the intended scope, which may be inconvenient for individuals. Therefore, for example, the server may change the image to an unfocused image of a person's face on the periphery of the screen, or the inside of a house, and encode it. The server may also recognize whether the image to be encoded contains a face of a person other than a person registered in advance, and if so, may perform processing such as blurring the face. Alternatively, as pre-processing or post-processing of encoding, the user may specify a person or background area that he or she wishes to process in the image from the viewpoint of copyright, etc., and the server may replace the specified area with another image or blur the focus. If it is a person, the image of the face part can be replaced while tracking the person in the video.

[0277] In addition, since viewing of personal content with a small amount of data requires real-time performance, the decoding device first receives the base layer as a top priority, and performs decoding and playback, although this depends on the bandwidth. The decoding device may receive an enhancement layer during this time, and when playback is looped or otherwise played two or more times, play high-quality video including the enhancement layer. In this way, if the stream is scalably encoded, it is possible to provide an experience in which the video is rough when not selected or when viewing begins, but the stream gradually becomes smarter and the image quality improves. In addition to scalable encoding, a similar experience can be provided even if a rough stream played the first time and a second stream encoded with reference to the first video are configured as one stream.

[0278] [Other use cases] Moreover, these encoding or decoding processes are generally processed in an LSIex500 possessed by each terminal. The LSIex500 may be a single chip or may be configured with multiple chips. Note that software for encoding or decoding moving images may be incorporated into some kind of recording medium (such as a CD-ROM, a flexible disk, or a hard disk) that can be read by the computer ex111 or the like, and the encoding or decoding process may be performed using the software. Furthermore, if the smartphone ex115 has a camera, video data captured by the camera may be transmitted. The video data in this case is data that has been encoded by the LSIex500 possessed by the smartphone ex115.

[0279] The LSIex500 may be configured to download and activate application software. In this case, the terminal first determines whether the terminal supports the encoding method of the content or has the ability to execute a specific service. If the terminal does not support the encoding method of the content or does not have the ability to execute a specific service, the terminal downloads a codec or application software, and then acquires and plays the content.

[0280] Furthermore, at least one of the video encoding devices (image encoding devices) or video decoding devices (image decoding devices) of the above-mentioned embodiments and modifications can be incorporated into a digital broadcasting system, not limited to the content supply system ex100 via the Internet ex101. Since multiplexed data in which video and audio are multiplexed is carried and transmitted over broadcasting radio waves using a satellite or the like, there is a difference in that it is more suitable for multicast compared to the content supply system ex100, which has a configuration that is easy to use for unicast, but similar applications are possible with regard to the encoding process and decoding process.

[0281] [Hardware configuration] FIG. 24 is a diagram showing a smartphone ex115. FIG. 25 is a diagram showing a configuration example of the smartphone ex115. The smartphone ex115 includes an antenna ex450 for transmitting and receiving radio waves to and from the base station ex110, a camera unit ex465 capable of taking videos and still images, and a display unit ex458 for displaying data obtained by decrypting the video captured by the camera unit ex465 and the video received by the antenna ex450. The smartphone ex115 further includes an operation unit ex466 such as a touch panel, an audio output unit ex457 such as a speaker for outputting audio or sound, an audio input unit ex456 such as a microphone for inputting audio, a memory unit ex467 capable of storing encoded data such as captured video or still images, recorded audio, received video or still images, and e-mail, or decoded data, and a slot unit ex464 which is an interface unit with a SIMex468 for identifying a user and authenticating access to various data including a network. In addition, an external memory may be used instead of the memory unit ex467.

[0282] In addition, a main control unit ex460, which comprehensively controls the display unit ex458 and operation unit ex466, etc., is connected to a power supply circuit unit ex461, an operation input control unit ex462, a video signal processing unit ex455, a camera interface unit ex463, a display control unit ex459, a modulation / demodulation unit ex452, a multiplexing / separation unit ex453, an audio signal processing unit ex454, a slot unit ex464, and a memory unit ex467 via a bus ex470.

[0283] When the power key is turned on by a user's operation, the power supply circuit unit ex461 starts up the smartphone ex115 into an operational state by supplying power to each unit from the battery pack.

[0284] The smartphone ex115 performs processes such as telephone calls and data communications under the control of a main control unit ex460 having a CPU, a ROM, and a RAM. During a telephone call, a voice signal collected by a voice input unit ex456 is converted into a digital voice signal by a voice signal processing unit ex454, which is then subjected to spectrum spreading processing by a modulation / demodulation unit ex452, and the digital-to-analog conversion processing and frequency conversion processing by a transmission / reception unit ex451 is then transmitted via an antenna ex450. In addition, the received data is amplified, and subjected to frequency conversion processing and analog-to-digital conversion processing, and the spectrum inverse spreading processing by a modulation / demodulation unit ex452 is then performed, and the analog voice signal is converted into an analog voice signal by a voice signal processing unit ex454, which is then output from a voice output unit ex457. During a data communication mode, text, still images, or video data is sent to the main control unit ex460 via an operation input control unit ex462 by operating an operation unit ex466 or the like of the main unit, and transmission and reception processing is performed in the same manner. When transmitting video, still images, or video and audio in the data communication mode, the video signal processing unit ex455 compresses and encodes the video signal stored in the memory unit ex467 or the video signal input from the camera unit ex465 by the moving image encoding method shown in the above embodiment and each modification, and sends the encoded video data to the multiplexing / separation unit ex453. The audio signal processing unit ex454 also encodes the audio signal collected by the audio input unit ex456 while the camera unit ex465 is capturing the video or still image, and sends the encoded audio data to the multiplexing / separation unit ex453. The multiplexing / separation unit ex453 multiplexes the encoded video data and the encoded audio data by a predetermined method, and performs modulation and conversion processing in the modulation / demodulation unit (modulation / demodulation circuit unit) ex452 and the transmission / reception unit ex451, and transmits the data via the antenna ex450.

[0285] When receiving a video attached to an e-mail or chat, or a video linked to a web page, etc., in order to decode the multiplexed data received via the antenna ex450, the multiplexing / separation unit ex453 separates the multiplexed data into a bit stream of video data and a bit stream of audio data by separating the multiplexed data, and supplies the encoded video data to the video signal processing unit ex455 via the synchronization bus ex470, and supplies the encoded audio data to the audio signal processing unit ex454. The video signal processing unit ex455 decodes the video signal by a video decoding method corresponding to the video encoding method shown in the above embodiment and each modification, and displays the video or still image included in the linked video file on the display unit ex458 via the display control unit ex459. The audio signal processing unit ex454 also decodes the audio signal, and audio is output from the audio output unit ex457. Note that since real-time streaming is widespread, there may be cases where audio playback is socially inappropriate depending on the user's situation. Therefore, as an initial value, a configuration in which only video data is played without playing audio signals is preferable. The audio may be played in sync only when the user performs an operation such as clicking on the video data.

[0286] In addition, although the smartphone ex115 has been described as an example here, three types of implementation formats are possible for the terminal: a transmitting / receiving terminal having both an encoder and a decoder, a transmitting terminal having only an encoder, and a receiving terminal having only a decoder. Furthermore, in the digital broadcasting system, multiplexed data in which audio data and the like are multiplexed with video data is received or transmitted, but the multiplexed data may include text data related to the video in addition to audio data, or the video data itself may be received or transmitted instead of the multiplexed data.

[0287] Although the main control unit ex460 including the CPU controls the encoding or decoding process, terminals often have a GPU. Therefore, a configuration may be used in which a wide area is processed collectively by utilizing the performance of the GPU using a memory shared by the CPU and GPU, or a memory whose addresses are managed so that they can be used in common. This can shorten the encoding time, ensure real-time performance, and achieve low latency. In particular, it is efficient to perform the processing of motion search, deblocking filter, SAO (Sample Adaptive Offset), and transformation and quantization collectively in units such as pictures by the GPU, rather than by the CPU. [Industrial Applicability]

[0288] The present disclosure is applicable to, for example, television receivers, digital video recorders, car navigation systems, mobile phones, digital cameras, digital video cameras, and the like. [Explanation of symbols]

[0289] 100 Encoding device 102 Division 104 Subtraction section 106 Conversion unit 108 Quantization section 110 Entropy coding unit 112, 204 Inverse quantization section 114, 206 Inverse conversion unit 116, 208 Addition section 118, 210 Block Memory 120, 212 Loop filter section 122, 214 frame memory 124, 216 Intra prediction section 126, 218 Inter prediction section 128, 220 Predictive control unit 200 Decryption device 202 Entropy Decoding Unit

Claims

1. 1. An encoding device, comprising: A processor and a memory, the processor using the memory: determining whether intra prediction is to be used for a coding target block included in a picture; When it is determined that intra prediction is to be used for the encoding target block, it is determined whether or not an intra prediction mode of the encoding target block is a predetermined mode; determining a first transformation basis for the encoding target block; (i) generating first transform coefficients by performing a first transform on a residual signal of the current block to be coded using the first transform base; (ii-1) when the intra prediction mode is not the predetermined mode or when the first transform base is equal to a predetermined transform base, generating second transform coefficients by performing a second transform on the first transform coefficients using a second transform base, and quantizing the second transform coefficients; (ii-2) quantizing the first transform coefficient when the intra prediction mode is the predetermined mode and the first transform base is different from the predetermined transform base; (ii-3) quantizing the first transform coefficient when it is determined that intra prediction is not used for the encoding target block; Encoding device.

2. 1. A method of encoding, comprising: determining whether intra prediction is to be used for a coding target block included in a picture; When it is determined that intra prediction is to be used for the encoding target block, it is determined whether or not an intra prediction mode of the encoding target block is a predetermined mode; determining a first transformation basis for the encoding target block; (i) generating first transform coefficients by performing a first transform on a residual signal of the current block to be coded using the first transform base; (ii-1) when the intra prediction mode is not the predetermined mode or when the first transform base is equal to a predetermined transform base, generating second transform coefficients by performing a second transform on the first transform coefficients using a second transform base, and quantizing the second transform coefficients; (ii-2) quantizing the first transform coefficient when the intra prediction mode is the predetermined mode and the first transform base is different from the predetermined transform base; (ii-3) quantizing the first transform coefficient when it is determined that intra prediction is not used for the encoding target block; Encoding method.

3. 1. An encoding device, comprising: A processor and a memory, the processor using the memory: determining whether or not to use intra prediction for a first encoding target block, a second encoding target block, and a third encoding target block included in a picture; When it is determined that intra prediction is used for the first encoding target block and the second encoding target block, it is determined whether or not an intra prediction mode of the first encoding target block and the second encoding target block is a predetermined mode; determining a first transformation basis for the first block to be coded, the second block to be coded, and the third block to be coded; performing a first transform using the first transform base on a residual signal of the first encoding target block in which the intra prediction mode is not the predetermined mode or the first transform base coincides with a predetermined transform base, and further performing a second transform using a second transform base to generate transform coefficients, and quantizing the transform coefficients; generating transform coefficients by performing a first transform using the first transform base on a residual signal of the second block to be coded, the residual signal being in the predetermined mode and the first transform base being different from the predetermined transform base, and quantizing the transform coefficients while skipping a second transform; performing a first transform on a residual signal of the third block to be coded, for which it has been determined that intra prediction is not to be used, using the first transform base to generate transform coefficients, and quantizing the transform coefficients while skipping the second transform; Encoding device.

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