Encoding device and decoding device

Abstract

To provide an encoder capable of properly handling an image to be encoded or decoded.SOLUTION: An encoder 1500 includes a processing circuit and memories 1505, 1506 connected to the processing circuit. By using the memories 1505, 1506, the processing circuit performs connection processing of connecting a plurality of images to each other to create a connected image, acquires a parameter for specifying a space area in the connected image generated in the connection processing, performs inter-screen prediction processing on the connected image, writes the parameter in a bit stream, and generates the bit stream by arithmetic coding. The inter-screen prediction processing includes padding processing of connecting the values of pixels in the space area and replacing the values with the value of another area that is not the space area. The value of another area is the value of a pixel closest from the space area. The inter-screen prediction processing is performed on an image block basis.SELECTED DRAWING: Figure 37

Description

[Technical Field]

[0001] The present disclosure relates to an apparatus and method for encoding an image, and an apparatus and method for decoding the encoded image. [Background technology]

[0002] Currently, HEVC is being developed as an image coding standard (see, for example, Non-Patent Document 1). However, the transmission and storage of next-generation video (e.g., 360-degree video) requires coding efficiency that exceeds current coding performance. Furthermore, several studies and experiments have been conducted on the compression of video captured with wide-angle lenses, such as non-rectilinear lenses. In these studies, image samples are manipulated to eliminate distortion aberrations, thereby linearizing the image to be processed before encoding. Image processing techniques are generally used for this purpose. [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] However, conventional encoding and decoding devices have a problem in that they are unable to appropriately handle images to be encoded or decoded.

[0005] Therefore, the present disclosure provides an encoding device and the like that can appropriately handle images to be encoded or decoded. [Means for solving the problem]

[0006] An encoding device according to one aspect of the present disclosure includes a processing circuit and a memory connected to the processing circuit, wherein the processing circuit uses the memory to perform a stitching process that stitches together a plurality of images to generate a stitched image, obtains parameters that identify free areas in the stitched image that will be generated by the stitching process, performs inter-frame prediction processing on the stitched image, writes the parameters to a bitstream, and generates the bitstream by arithmetic coding, wherein the inter-frame prediction processing includes a padding process that replaces pixel values ​​in the free areas with values ​​of other areas in the stitched image that are not the free areas, wherein the values ​​of the other areas are values ​​of pixels closest to the free areas, and the inter-frame prediction processing is performed in units of image blocks.

[0007] These comprehensive or specific aspects may be realized as 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 as any combination of a system, a method, an integrated circuit, a computer program, and a recording medium. [Effects of the Invention]

[0008] The encoding device of the present disclosure can appropriately handle images to be encoded or decoded. [Brief explanation 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. [Figure 2] FIG. 2 is a diagram showing an example of block division according to the first embodiment. [Figure 3] FIG. 3 is a table showing the transformation basis functions corresponding to each transformation type. [Figure 4A] FIG. 4A is a diagram showing an example of the shape of a filter used in ALF. [Figure 4B] FIG. 4B is a diagram showing another example of the shape of the filter used in ALF. [Figure 4C]FIG. 4C is a diagram showing another example of the shape of the filter used in ALF. [Figure 5] FIG. 5 is a diagram showing 67 intra prediction modes in intra prediction. [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 9] FIG. 9 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 10] FIG. 10 is a block diagram showing a functional configuration of a decoding device according to the first embodiment. [Figure 11] FIG. 11 is a flowchart showing an example of the video encoding process according to the second embodiment. [Figure 12] FIG. 12 is a diagram showing possible positions of a header in a bitstream in which parameters are written in the second embodiment. [Figure 13] FIG. 13 is a diagram showing a captured image and a processed image that has been subjected to image correction processing in the second embodiment. [Figure 14] FIG. 14 is a diagram showing a stitched image generated by stitching a plurality of images together using the stitching process according to the second embodiment. [Figure 15] FIG. 15 is a diagram showing the arrangement of a plurality of cameras and a stitched image including a blank area generated by stitching together images captured by the cameras in the second embodiment. [Figure 16] FIG. 16 is a flowchart showing the inter prediction process or motion compensation according to the second embodiment. [Figure 17]FIG. 17 is a diagram showing an example of barrel distortion caused by a non-rectilinear lens or a fisheye lens in the second embodiment. [Figure 18] FIG. 18 is a flowchart showing a modification of the inter prediction process or motion compensation process in the second embodiment. [Figure 19] FIG. 19 is a flowchart showing the image reconstruction process according to the second embodiment. [Figure 20] FIG. 20 is a flowchart showing a modified example of the image reconstruction process according to the second embodiment. [Figure 21] FIG. 21 is a diagram showing an example of partial encoding processing or partial decoding processing for a spliced ​​image according to the second embodiment. [Figure 22] FIG. 22 is a diagram showing another example of partial encoding processing or partial decoding processing for a spliced ​​image in the second embodiment. [Figure 23] FIG. 23 is a block diagram of an encoding device according to the second embodiment. [Figure 24] FIG. 24 is a flowchart showing an example of the video decoding process according to the second embodiment. [Figure 25] FIG. 25 is a block diagram of a decoding device according to the second embodiment. [Figure 26] FIG. 26 is a flowchart showing an example of a video encoding process according to the third embodiment. [Figure 27] FIG. 27 is a flowchart showing an example of the joining process according to the third embodiment. [Figure 28] FIG. 28 is a block diagram of an encoding device according to the third embodiment. [Figure 29] FIG. 29 is a flowchart showing an example of the video decoding process according to the third embodiment. [Figure 30] FIG. 30 is a block diagram of a decoding device according to the third embodiment. [Figure 31] FIG. 31 is a flowchart showing an example of a video encoding process according to the fourth embodiment. [Figure 32]FIG. 32 is a flowchart showing the intra-screen prediction process according to the fourth embodiment. [Figure 33] FIG. 33 is a flowchart showing the motion vector prediction process according to the fourth embodiment. [Figure 34] FIG. 34 is a block diagram of an encoding device according to the fourth embodiment. [Figure 35] FIG. 35 is a flowchart showing an example of the video decoding process according to the fourth embodiment. [Figure 36] FIG. 36 is a block diagram of a decoding device according to the fourth embodiment. [Figure 37] FIG. 37 is a block diagram of an encoding device according to one embodiment of the present disclosure. [Figure 38] FIG. 38 is a block diagram of a decoding device according to one embodiment of the present disclosure. [Figure 39] FIG. 39 is a diagram showing the overall configuration of a content supply system that realizes a content distribution service. [Figure 40] FIG. 40 is a diagram showing an example of a coding structure for scalable coding. [Figure 41] FIG. 41 is a diagram showing an example of a coding structure for scalable coding. [Figure 42] FIG. 42 is a diagram showing an example of a display screen of a web page. [Figure 43] FIG. 43 is a diagram showing an example of a display screen of a web page. [Figure 44] FIG. 44 is a diagram illustrating an example of a smartphone. [Figure 45] FIG. 45 is a block diagram showing an example of the configuration of a smartphone. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, the embodiments will be specifically described with reference to the drawings.

[0011] The embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, component placement and connection configurations, steps, and step order shown in the following embodiments are merely examples and are not intended to limit the scope of the claims. Furthermore, among the components in the following embodiments, components that are not described in the independent claims that represent the highest concepts are described as optional components.

[0012] (Embodiment 1) [Outline of the encoding device] First, an overview of a coding device according to Embodiment 1 will be described. Fig. 1 is a block diagram showing a functional configuration of a coding device 100 according to Embodiment 1. The coding device 100 is a video / image coding device that codes a video / image on a block-by-block basis.

[0013] 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.

[0014] The encoding device 100 is realized by, for example, a general-purpose processor and memory. In this case, when a software program stored in the memory is executed by the processor, the processor functions as the division unit 102, the subtraction unit 104, the transformation unit 106, the quantization unit 108, the entropy coding unit 110, the inverse quantization unit 112, the inverse transformation unit 114, the addition unit 116, the loop filter unit 120, the intra prediction unit 124, the inter prediction unit 126, and the prediction control unit 128. Alternatively, the encoding device 100 may be realized as one or more dedicated electronic circuits corresponding to the division unit 102, the subtraction unit 104, the transformation unit 106, the quantization unit 108, the entropy coding unit 110, the inverse quantization unit 112, the inverse transformation unit 114, the addition unit 116, the loop filter unit 120, the intra prediction unit 124, the inter prediction unit 126, and the prediction control unit 128.

[0015] Each component included in the encoding device 100 will be described below.

[0016] [Divided part] The division unit 102 divides each picture included in the input video into a plurality of blocks and outputs each block to the subtraction unit 104. For example, the division unit 102 first divides a picture into blocks of a fixed size (e.g., 128x128). These fixed-size blocks are sometimes called coding tree units (CTUs). The division unit 102 then divides each of the fixed-size blocks into blocks of a variable size (e.g., 64x64 or less) based on recursive quadtree and / or binary tree block division. These variable-size blocks are sometimes called coding units (CUs), prediction units (PUs), or transform units (TUs). Note that in this embodiment, there is no need to distinguish between CUs, PUs, and TUs, and some or all of the blocks in a picture may be the processing units of CUs, PUs, and TUs.

[0017] 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.

[0018] 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).

[0019] 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.

[0020] The top right 64x64 block is divided horizontally into two rectangular 64x32 blocks 14 and 15 (binary tree block division).

[0021] The lower-left 64x64 block is divided into four square 32x32 blocks (quadtree block decomposition). Of the four 32x32 blocks, the upper-left and lower-right blocks are further divided. The upper-left 32x32 block is divided vertically into two rectangular 16x32 blocks, and the right 16x32 block is further divided horizontally into two 16x16 blocks (binary tree block decomposition). The lower-right 32x32 block is divided horizontally into two 32x16 blocks (binary tree block decomposition). As a result, the lower-left 64x64 block is divided into 16x32 block 16, two 16x16 blocks 17 and 18, two 32x32 blocks 19 and 20, and two 32x16 blocks 21 and 22.

[0022] The bottom right 64x64 block 23 is not split.

[0023] 2, block 10 is divided into 13 variable-sized blocks 11 to 23 based on recursive quad-tree and binary tree block division. This type of division is sometimes called QTBT (quad-tree plus binary tree) division.

[0024] 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.

[0025] [Subtraction section] The subtraction unit 104 subtracts a prediction signal (prediction sample) from an original signal (original sample) for each block divided by the division unit 102. That is, the subtraction unit 104 calculates a prediction error (also referred to as a residual) of a block to be coded (hereinafter referred to as a current block). Then, the subtraction unit 104 outputs the calculated prediction error to the conversion unit 106.

[0026] The original signal is an input signal to the encoding device 100, and is a signal representing an image of each picture constituting a moving image (for example, a luminance (luma) signal and two color difference (chroma) signals). Hereinafter, the signal representing an image may also be referred to as a sample.

[0027] [Conversion section] The transform unit 106 transforms the spatial domain prediction errors into frequency domain transform coefficients and outputs the transform coefficients to the quantization unit 108. Specifically, the transform unit 106 performs, for example, a predetermined discrete cosine transform (DCT) or discrete sine transform (DST) on the spatial domain prediction errors.

[0028] The transform unit 106 may adaptively select a transform type from among a plurality of transform types and transform the prediction errors into transform coefficients using a transform basis function corresponding to the selected transform type. Such a transform is sometimes called an explicit multiple core transform (EMT) or an adaptive multiple transform (AMT).

[0029] The multiple transform types include, for example, DCT-II, DCT-V, DCT-VIII, DST-I, and DST-VII. Fig. 3 is a table showing transform basis functions corresponding to each transform type. In Fig. 3, N represents the number of input pixels. Selection of a transform type from among these multiple transform types may depend, for example, on the type of prediction (intra prediction or inter prediction) or the intra prediction mode.

[0030] Information indicating whether EMT or AMT is applied (e.g., referred to as an AMT flag) and information indicating the selected transformation type are signaled at the CU level. Note that signaling of this information does not need to be limited to the CU level, and may be at other levels (e.g., sequence level, picture level, slice level, tile level, or CTU level).

[0031] Furthermore, the transform unit 106 may retransform the transform coefficients (transform results). Such retransformation may be referred to as an adaptive secondary transform (AST) or a non-separable secondary transform (NSST). For example, the transform unit 106 performs retransformation for each sub-block (e.g., 4x4 sub-block) included in a block of transform coefficients corresponding to intra-prediction errors. Information indicating whether or not to apply NSST and information regarding the transform matrix used for NSST are signaled at the CU level. Note that signaling of this information does not need to be limited to the CU level, and may be at other levels (e.g., the sequence level, picture level, slice level, tile level, or CTU level).

[0032] [Quantization section] The quantization unit 108 quantizes the transform coefficients output from the transform unit 106. Specifically, the quantization unit 108 scans the transform coefficients of the current block in a predetermined scanning order and quantizes the transform coefficients based on quantization parameters (QP) corresponding to the scanned transform coefficients. The quantization unit 108 then outputs the quantized transform coefficients of the current block (hereinafter referred to as quantized coefficients) to the entropy coding unit 110 and the inverse quantization unit 112.

[0033] The predetermined order is an order for quantizing / dequantizing the transform coefficients. For example, the predetermined scanning order is defined as an ascending order (low frequency to high frequency) or a descending order (high frequency to low frequency).

[0034] The quantization parameter is a parameter that defines the quantization step (quantization width). For example, as the value of the quantization parameter increases, the quantization step also increases. In other words, as the value of the quantization parameter increases, the quantization error also increases.

[0035] [Entropy coding section] The entropy coding unit 110 generates a coded signal (coded bit stream) by variable-length coding the quantized coefficients input from the quantization unit 108. Specifically, the entropy coding unit 110, for example, binarizes the quantized coefficients and arithmetically codes the binary signal.

[0036] [Dequantization section] The inverse quantization unit 112 inverse quantizes the quantized coefficients input from the quantization unit 108. Specifically, the inverse quantization unit 112 inverse quantizes the quantized coefficients of the current block in a predetermined scanning order. The inverse quantization unit 112 then outputs the inverse quantized transform coefficients of the current block to the inverse transform unit 114.

[0037] [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.

[0038] 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.

[0039] [Adder] The adder 116 reconstructs the current block by adding the prediction error input from the inverse transformer 114 and the prediction signal 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.

[0040] [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.

[0041] [Loop filter section] The loop filter unit 120 applies a loop filter to the block reconstructed by the adder 116 and outputs the filtered reconstructed block to the frame memory 122. The loop filter is a filter (in-loop filter) used in the encoding loop, and includes, for example, a deblocking filter (DF), a sample adaptive offset (SAO), and an adaptive loop filter (ALF).

[0042] ALF applies a least squares error filter to remove coding artifacts, for example, for each 2x2 sub-block in the current block, one filter selected from multiple filters based on local gradient direction and activity.

[0043] Specifically, first, sub-blocks (e.g., 2x2 sub-blocks) are classified into a plurality of classes (e.g., 15 or 25 classes). The sub-blocks are classified based on the gradient direction and activity. For example, a classification value C (e.g., C=5D+A) is calculated using a gradient direction value D (e.g., 0 to 2 or 0 to 4) and a gradient activity value A (e.g., 0 to 4). Then, based on the classification value C, the sub-blocks are classified into a plurality of classes (e.g., 15 or 25 classes).

[0044] The gradient direction value D is derived by, for example, comparing gradients in multiple directions (e.g., horizontal, vertical, and two diagonal directions), and the gradient activity value A is derived by, for example, adding gradients in multiple directions and quantizing the sum.

[0045] Based on the result of such classification, a filter for the sub-block is determined from among a plurality of filters.

[0046] The filter shape used in ALF is, for example, a circularly symmetric shape. FIGS. 4A to 4C are diagrams showing several examples of filter shapes used in ALF. FIG. 4A shows a 5x5 diamond-shaped filter, FIG. 4B shows a 7x7 diamond-shaped filter, and FIG. 4C shows a 9x9 diamond-shaped filter. Information indicating the filter shape is signaled at the picture level. Note that signaling of the information indicating the filter shape does not need to be limited to the picture level, and may be at other levels (e.g., sequence level, slice level, tile level, CTU level, or CU level).

[0047] Whether ALF is turned on or off is determined, for example, at the picture level or the CU level. For example, whether ALF is applied to luminance is determined at the CU level, and whether ALF is applied to chrominance is determined at the picture level. Information indicating whether ALF is turned on or off is signaled at the picture level or the CU level. Note that signaling of information indicating whether ALF is turned on or off does not need to be limited to the picture level or the CU level, and may be at another level (for example, the sequence level, the slice level, the tile level, or the CTU level).

[0048] The coefficient sets of multiple selectable filters (e.g., up to 15 or 25 filters) are signaled at the picture level. Note that the signaling of the coefficient sets does not need to be limited to the picture level, but may also be at other levels (e.g., sequence level, slice level, tile level, CTU level, CU level, or sub-block level).

[0049] [Frame memory] The frame memory 122 is a storage unit for storing reference pictures used in inter prediction, and is sometimes called a frame buffer. Specifically, the frame memory 122 stores the reconstructed blocks filtered by the loop filter unit 120.

[0050] [Intra prediction section] The intra prediction unit 124 generates a prediction signal (intra prediction signal) by performing intra prediction (also referred to as intra-picture prediction) of the current block with reference to blocks in the current picture stored in the block memory 118. Specifically, the intra prediction unit 124 generates the intra prediction signal by performing intra prediction with reference to samples (e.g., luminance values, chrominance values) of blocks adjacent to the current block, and outputs the intra prediction signal to the prediction control unit 128.

[0051] 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.

[0052] 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).

[0053] The multiple directional prediction modes include, for example, the 33 prediction modes defined in the H.265 / HEVC standard. Note that the multiple directional prediction modes may also include 32 prediction modes in addition to the 33 directions (a total of 65 directional prediction modes). Figure 5 is a diagram showing 67 intra prediction modes (2 non-directional prediction modes and 65 directional prediction modes) in intra prediction. Solid arrows represent the 33 directions defined in the H.265 / HEVC standard, and dashed arrows represent the additional 32 directions.

[0054] Note that a luminance block may be referenced in intra prediction of a chrominance block. That is, the chrominance component of the current block may be predicted based on the luminance component of the current block. This type of intra prediction is sometimes called CCLM (cross-component linear model) prediction. An intra prediction mode of a chrominance block that references such a luminance block (e.g., called a CCLM mode) may be added as one of the intra prediction modes for the chrominance block.

[0055] The intra prediction unit 124 may correct pixel values ​​after intra prediction based on gradients of reference pixels in the horizontal / vertical directions. Intra prediction involving such correction is sometimes called PDPC (position dependent intra prediction combination). Information indicating whether PDPC is applied (e.g., called a PDPC flag) is signaled, for example, at the CU level. Note that signaling of this information does not need to be limited to the CU level, and may be at other levels (e.g., sequence level, picture level, slice level, tile level, or CTU level).

[0056] [Inter prediction section] The inter prediction unit 126 generates a prediction signal (inter prediction signal) by performing inter prediction (also referred to as inter prediction) on the current block with reference to a reference picture stored in the frame memory 122 that is different from the current picture. The inter prediction is performed in units of the current block or sub-blocks (e.g., 4x4 blocks) within the current block. For example, the inter prediction unit 126 performs motion estimation on the current block or sub-block within the reference picture. The inter prediction unit 126 then generates an inter prediction signal for the current block or sub-block by performing motion compensation using motion information (e.g., a motion vector) obtained by the motion estimation. The inter prediction unit 126 then outputs the generated inter prediction signal to the prediction control unit 128.

[0057] The motion information used for motion compensation is signaled. For the signaling of the motion vector, a motion vector predictor may be used, i.e., the difference between the motion vector and the motion vector predictor may be signaled.

[0058] Note that an inter-prediction signal may be generated using not only the motion information of the current block obtained by motion estimation, but also the motion information of adjacent blocks. Specifically, an inter-prediction signal may be generated for each sub-block in the current block by weighting and adding a prediction signal based on the motion information obtained by motion estimation and a prediction signal based on the motion information of adjacent blocks. Such inter-prediction (motion compensation) may be called OBMC (overlapped block motion compensation).

[0059] In such an OBMC mode, information indicating the size of a sub-block for OBMC (e.g., called an OBMC block size) is signaled at the sequence level. Also, information indicating whether the OBMC mode is applied (e.g., called an OBMC flag) is signaled at the CU level. Note that the signaling level of this information is not limited to the sequence level and the CU level, and may be other levels (e.g., the picture level, slice level, tile level, CTU level, or sub-block level).

[0060] Alternatively, the motion information may be derived on the decoding device side without being signaled. For example, a merge mode defined in the H.265 / HEVC standard may be used. Alternatively, the motion information may be derived by performing motion estimation on the decoding device side. In this case, the motion estimation is performed without using pixel values ​​of the current block.

[0061] 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 flame rate up-conversion (FRUC) mode.

[0062] First, one of the candidates included in the merge list is selected as the starting position for the pattern matching search. As the pattern matching, first pattern matching or second pattern matching is used. The first pattern matching and second pattern matching are sometimes called bilateral matching and template matching, respectively.

[0063] 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.

[0064] 6 is a diagram for explaining 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 blocks that best matches one another among pairs of two blocks along the motion trajectory of a current block (Cur block) and in two different reference pictures (Ref0, Ref1).

[0065] Under the assumption of continuous motion trajectories, motion vectors (MV0, MV1) pointing to two reference blocks are proportional to the temporal distances (TD0, TD1) between a current picture (CurPic) and two reference pictures (Ref0, Ref1). For example, if the current picture is located between two reference pictures temporally and the temporal distances from the current picture to the two reference pictures are equal, the first pattern matching derives bidirectional motion vectors that are mirror-symmetric.

[0066] 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 (for example, an upper and / or left adjacent block)) and a block in the reference picture.

[0067] 7 is a diagram for explaining 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 the current block is derived by searching the reference picture (Ref0) for a block that best matches a block adjacent to the current block (Cur block) in the current picture (Cur Pic).

[0068] Information indicating whether such a FRUC mode is applied (e.g., called an FRUC flag) is signaled at the CU level. Furthermore, when the FRUC mode is applied (e.g., when the FRUC flag is true), information indicating a pattern matching method (first pattern matching or second pattern matching) (e.g., called an FRUC mode flag) is signaled at the CU level. Note that signaling of this information does not need to be limited to the CU level, and may be at other levels (e.g., the sequence level, the picture level, the slice level, the tile level, the CTU level, or the sub-block level).

[0069] Note that the motion information may be derived on the decoding device side using a method other than motion estimation. For example, based on a model assuming uniform linear motion, the correction amount of the motion vector may be calculated for each pixel using neighboring pixel values.

[0070] Here, we will explain a mode in which motion vectors are derived based on a model that assumes uniform linear motion. This mode is sometimes called BIO (bi-directional optical flow) mode.

[0071] FIG. 8 is a diagram for explaining a model assuming uniform linear motion. In FIG. 8, (v x ,v y) denotes a velocity vector, and τ0 and τ1 denote the temporal distance between the current picture (Cur Pic) and two reference pictures (Ref0 and Ref1), respectively. (MVx0,MVy0) denotes a motion vector corresponding to reference picture Ref0, and (MVx1,MVy1) denotes a motion vector corresponding to reference picture Ref1.

[0072] At this time, the velocity vector (v x ,v y ), (MVx0,MVy0) and (MVx1,MVy1) are respectively (v x τ0,v y τ0) and (-v x τ1,-v y τ1), and the following optical flow equation (1) holds:

[0073]

number

[0074] where I (k) denotes the luminance value of reference image k (k=0,1) after motion compensation. This optical flow equation indicates that the sum of (i) the time derivative of the luminance value, (ii) the product of the horizontal velocity and the horizontal component of the spatial gradient of the reference image, and (iii) the product of the vertical velocity and the vertical component of the spatial gradient of the reference image is equal to zero. Based on a combination of this optical flow equation and Hermite interpolation, block-wise motion vectors obtained from a merge list or the like are corrected pixel by pixel.

[0075] Note that the decoding device may derive motion vectors using a method other than that based on a model assuming constant-velocity linear motion. For example, a motion vector may be derived for each sub-block based on the motion vectors of multiple adjacent blocks.

[0076] Here, a mode in which a motion vector is derived for each sub-block based on the motion vectors of a plurality of neighboring blocks will be described. This mode is sometimes called an affine motion compensation prediction mode.

[0077] FIG. 9 is a diagram for explaining the derivation of motion vectors for each sub-block based on the motion vectors of multiple adjacent blocks. In FIG. 9, the current block includes 16 4x4 sub-blocks. Here, the motion vector v0 of the upper left corner control point of the current block is derived based on the motion vectors of the adjacent blocks, and the motion vector v1 of the upper right corner control point of the current block is derived based on the motion vectors of the adjacent sub-blocks. Then, using the two motion vectors v0 and v1, the motion vector (v x ,v y ) is derived.

[0078]

number

[0079] Here, x and y respectively indicate the horizontal and vertical positions of the sub-block, and w indicates a predetermined weighting coefficient.

[0080] Such an affine motion compensation prediction mode may include several modes in which the methods of deriving the motion vectors of the upper-left and upper-right corner control points are different. Information indicating such an affine motion compensation prediction mode (e.g., called an affine flag) is signaled at the CU level. Note that the signaling of the information indicating this affine motion compensation prediction mode does not need to be limited to the CU level, and may be at other levels (e.g., the sequence level, the picture level, the slice level, the tile level, the CTU level, or the sub-block level).

[0081] [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.

[0082] [Overview of the decoding device] Next, an overview will be given of a decoding device capable of decoding the coded signal (coded bitstream) output from the above coding device 100. Fig. 10 is a block diagram showing the functional configuration of a decoding device 200 according to Embodiment 1. The decoding device 200 is a video / image decoding device that decodes video / images on a block-by-block basis.

[0083] 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.

[0084] The decoding device 200 is realized by, for example, a general-purpose processor and memory. In this case, when a software program stored in the memory is executed by the processor, the processor functions as the entropy decoding unit 202, the inverse quantization unit 204, the inverse transform unit 206, the addition unit 208, the loop filter unit 212, the intra prediction unit 216, the inter prediction unit 218, and the prediction control unit 220. Alternatively, the decoding device 200 may be realized as one or more dedicated electronic circuits corresponding to the entropy decoding unit 202, the inverse quantization unit 204, the inverse transform unit 206, the addition unit 208, the loop filter unit 212, the intra prediction unit 216, the inter prediction unit 218, and the prediction control unit 220.

[0085] Each component included in the decoding device 200 will be described below.

[0086] [Entropy Decoding] The entropy decoding unit 202 entropy-decodes the coded bitstream. Specifically, the entropy decoding unit 202 arithmetically decodes the coded bitstream into a binary signal. The entropy decoding unit 202 then debinarizes the binary signal. As a result, the entropy decoding unit 202 outputs quantized coefficients to the inverse quantization unit 204 on a block-by-block basis.

[0087] [Dequantization section] The inverse quantization unit 204 inverse quantizes the quantized coefficients of a block to be decoded (hereinafter referred to as a current block) that is input from the entropy decoding unit 202. Specifically, the inverse quantization unit 204 inverse quantizes each quantized coefficient of the current block based on a quantization parameter corresponding to the quantized coefficient. The inverse quantization unit 204 then outputs the inverse quantized coefficients (i.e., transform coefficients) of the current block to the inverse transform unit 206.

[0088] [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 .

[0089] 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.

[0090] Also, for example, if the information decoded from the coded bitstream indicates that NSST is to be applied, the inverse transform unit 206 retransforms the transformed transform coefficients (transform results).

[0091] [Adder] The adder 208 reconstructs the current block by adding the prediction error input from the inverse transformer 206 and the prediction signal 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.

[0092] [Block Memory] The block memory 210 is a storage unit for storing blocks that are referenced in intra prediction and are in a picture to be decoded (hereinafter referred to as a current picture). Specifically, the block memory 210 stores the reconstructed blocks output from the adder 208.

[0093] [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.

[0094] If the information indicating ALF on / off read from the encoded bitstream indicates that ALF is on, one filter is selected from multiple filters based on the local gradient direction and activity, and the selected filter is applied to the reconstructed block.

[0095] [Frame memory] The frame memory 214 is a storage unit for storing reference pictures used in inter prediction, and is sometimes called a frame buffer. Specifically, the frame memory 214 stores the reconstructed blocks filtered by the loop filter unit 212.

[0096] [Intra prediction section] The intra prediction unit 216 generates a prediction signal (intra prediction signal) by performing intra prediction based on the intra prediction mode interpreted from the encoded bitstream, by referring to blocks in the current picture stored in the block memory 210. Specifically, the intra prediction unit 216 generates the intra prediction signal by performing intra prediction by referring to samples (e.g., luminance values, chrominance values) of blocks adjacent to the current block, and outputs the intra prediction signal to the prediction control unit 220.

[0097] 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.

[0098] Furthermore, when information interpreted from the coded bitstream indicates the application of PDPC, the intra prediction unit 216 corrects pixel values ​​after intra prediction based on the gradients of reference pixels in the horizontal and vertical directions.

[0099] [Inter prediction section] The inter prediction unit 218 predicts the current block by referring to a reference picture stored in the frame memory 214. The prediction is performed in units of the current block or sub-blocks (e.g., 4x4 blocks) within the current block. For example, the inter prediction unit 126 generates an inter prediction signal for the current block or sub-block by performing motion compensation using motion information (e.g., motion vectors) interpreted from the coded bitstream, and outputs the inter prediction signal to the prediction control unit 128.

[0100] In addition, if the information interpreted from the encoded bitstream indicates that the OBMC mode is to be applied, the inter prediction unit 218 generates an inter prediction signal using not only the motion information of the current block obtained by motion search, but also the motion information of adjacent blocks.

[0101] Furthermore, if the information interpreted from the coded bitstream indicates that the FRUC mode is to be applied, the inter prediction unit 218 derives motion information by performing motion search according to the pattern matching method (bilateral matching or template matching) interpreted from the coded bitstream. Then, the inter prediction unit 218 performs motion compensation using the derived motion information.

[0102] Furthermore, when the BIO mode is applied, the inter prediction unit 218 derives a motion vector based on a model assuming constant-velocity linear motion. Furthermore, when information interpreted from the coded bitstream indicates that the affine motion compensation prediction mode is to be applied, the inter prediction unit 218 derives a motion vector for each sub-block based on the motion vectors of multiple adjacent blocks.

[0103] [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.

[0104] (Embodiment 2) Next, some of the processes performed in the encoding device 100 and the decoding device 200 configured as described above will be specifically described with reference to the drawings. Note that it will be apparent to those skilled in the art that the embodiments described below may be combined to further enhance the benefits of the present disclosure.

[0105] The encoding device and decoding device in this embodiment can be used to encode and decode any multimedia data, and more specifically, can be used to encode and decode images captured by a non-rectilinear (e.g., fisheye) camera.

[0106] In the above-mentioned prior art, the same video encoding tools are used to compress the processed images and the images captured directly by the rectilinear lens. There are no video encoding tools in the prior art that are specifically customized to compress this type of processed images in a different way.

[0107] Typically, multiple cameras capture images first, and then stitch the images together to create a larger image, known as a 360-degree image. To make the image more comfortable to view on a flat screen display or to make objects in the image more easily detectable using machine learning techniques, image transformation processes, including "defishing" or straightening, may be performed before encoding the image. However, these image transformation processes typically involve interpolating image samples, resulting in overlapping information within the image. Furthermore, the stitching and image transformation processes can create empty spaces in the image, which are typically filled with default pixel values ​​(e.g., black pixels). These issues caused by the stitching and image transformation processes can reduce the coding efficiency of the encoding process.

[0108] To solve these problems, this embodiment uses adaptive video encoding and decoding tools as customized video encoding and decoding tools. To improve encoding efficiency, the adaptive video encoding tool can adapt to image transformation or image stitching processes used to process images prior to the encoder. By adapting the adaptive video encoding tool to such processes during the encoding process, the present disclosure can reduce any redundancy caused by these processes. The adaptive video decoding tool is similar to the adaptive video encoding tool.

[0109] In this embodiment, information on the image transformation process and / or image stitching process is used to adapt the video encoding and decoding tools, so that the video encoding and decoding tools can be applied to different types of processed images, thereby improving compression efficiency.

[0110] [Encoding process] A method for encoding moving images captured using a non-rectilinear lens according to the second embodiment of this disclosure will be described below, as shown in Fig. 11. The non-rectilinear lens is a wide-angle lens or an example thereof.

[0111] FIG. 11 is a flowchart showing an example of the video encoding process according to this embodiment.

[0112] In step S101, the encoding device writes a set of parameters into a header. Fig. 12 shows possible locations of the header in a compressed video bitstream. The written parameters (i.e., camera image parameters in Fig. 12) include one or more parameters related to image enhancement processing. For example, such parameters are written into a video parameter set, a sequence parameter set, a picture parameter set, a slice header, or a video system setup parameter set, as shown in Fig. 12. That is, the parameters written in this embodiment may be written into any header of the bitstream, or into SEI (Supplemental Enhancement Information). Note that the image enhancement processing corresponds to the above-mentioned image conversion processing.

[0113] <Example of image correction processing parameters> As shown in FIG. 13 , the captured image may be distorted due to the characteristics of the lens used during image capture. An image correction process was used to linearly correct the captured image. By linearly correcting the captured image, a rectangular image is generated. The written parameters include parameters for identifying or describing the image correction process used. The parameters used in the image correction process, for example, include parameters constituting a mapping table for mapping pixels of the input image to the intended output pixel values ​​of the image correction process. These parameters may include weight parameters for one or more interpolation processes and / or position parameters for specifying the locations of input and output pixels in the picture. In one possible implementation of the image correction process, the mapping table for the image correction process may be used for all pixels in the corrected image.

[0114] Other examples of parameters used to describe an image correction process include a selection parameter that selects one of multiple predefined correction algorithms, a direction parameter that selects one of multiple predetermined directions of the correction algorithm, and / or a calibration parameter that calibrates or fine-tunes the correction algorithm. For example, if there are multiple predefined correction algorithms (e.g., different algorithms are used for different types of lenses), the selection parameter is used to select one of these predefined algorithms. For example, if there are two or more directions in which the correction algorithm can be applied (e.g., if the image correction process can be performed horizontally, vertically, or in either direction), the direction parameter selects one of these predefined directions. If the image correction process can be calibrated, the calibration parameter allows the image correction process to be adjusted to suit different types of lenses.

[0115] <Example of parameters for splicing process> The written parameters may further include one or more parameters related to the stitching process. As shown in Figures 14 and 15, the image input to the encoding device may be the result of a stitching process that combines multiple images from different cameras. The written parameters include parameters that provide information about the stitching process, such as the number of cameras, the distortion center or principal axis of each camera, and the distortion level. Another example of parameters describing the stitching process includes parameters that identify the location of a stitched image created by overlapping pixels from multiple images. Each of these images may contain pixels that may appear in other images because there may be overlapping areas in the camera angles. In the stitching process, these overlapping pixels are processed and reduced to create the stitched image.

[0116] Another example of a parameter describing the stitching process includes a parameter specifying the layout of the stitched images. For example, the layout of images in the stitched image varies depending on the format of the 360-degree image, such as equirectangular projection, a cubic 3x2 layout, and a cubic 4x3 layout. Note that a 3x2 layout is a layout of six images arranged in three columns and two rows, and a 4x3 layout is a layout of twelve images arranged in four columns and three rows. The above parameter, the alignment parameter, is used to determine the continuity of images in a certain direction based on the alignment of the images. During motion compensation, pixels from other images or views can be used in inter-frame prediction, and these images or views are specified by the alignment parameter. Some images or pixels in images may also need to be rotated to ensure continuity.

[0117] Other examples of parameters include camera and lens parameters (e.g., focal length, principal point, scale factor, type of image sensor used in the camera, etc.) Yet another example of a parameter is physical information about the placement of the camera (e.g., camera position, camera angle, etc.).

[0118] Next, in step S102, the encoding device encodes the image using adaptive video encoding tools based on the written parameters. The adaptive video encoding tools include an inter-frame prediction process. The set of adaptive video encoding tools may also include an image reconstruction process.

[0119] <Distortion correction in inter-frame prediction> FIG. 16 is a flowchart illustrating an inter-frame prediction process that is applied when an image is identified as being captured using a non-rectilinear lens, when an image is identified as being linearly processed, or when an image is identified as being stitched together from one or more images. As shown in FIG. 16, in step S1901, the encoding device determines a certain location within the image as the distortion center or principal point based on parameters written in the header. FIG. 17 shows an example of distortion caused by a fisheye lens. Note that a fisheye lens is an example of a wide-angle lens. As the distance from the distortion center increases, the magnification decreases along the focal axis. Therefore, in step S1902, the encoding device can correct the distortion by wrapping pixels within the image to straighten the image based on the distortion center, or can undo the correction that was made. That is, the encoding device performs an image correction process (i.e., wrapping) on ​​the block of the distorted image to be encoded. Finally, in step S1903, the encoding device can perform block prediction to derive a block of predicted samples based on the pixels of the wrapped image. In this embodiment, the wrapping process or wrapping is a process of arranging or rearranging pixels, blocks, or images. The encoding device may also return the predicted block, which is a predicted block, to its original distorted state before the image correction process, and use the distorted predicted block as a predicted image of the distorted target block. The predicted image and the target block correspond to the predicted signal and current block in the first embodiment.

[0120] Another example of an adapted inter-frame prediction process includes an adapted motion vector process. The resolution of the motion vectors is lower for image blocks farther from the distortion center than for image blocks closer to the distortion center. For example, image blocks farther from the distortion center may have motion vector accuracy up to half-pixel accuracy, while image blocks closer to the distortion center may have higher motion vector accuracy up to one-eighth pixel accuracy. Because the adapted motion vector accuracy varies based on the image block position, the accuracy of the motion vectors coded in the bitstream may be adaptive depending on the end and / or start positions of the motion vectors. That is, the coding device may use parameters to vary the accuracy of the motion vectors depending on the block position.

[0121] Another example of an adaptive inter-prediction process includes an adaptive motion compensation process, in which pixels from different views may be used to predict image samples from a target view based on alignment parameters written in the header. For example, 360-degree image formats, such as equirectangular projection, a cubic 3x2 layout, or a cubic 4x3 layout, may have different image alignments within the stitched image. The alignment parameters are used to determine image continuity in a certain direction based on the image alignment. During the motion compensation process, pixels from other images or other views may be used in the inter-prediction process, and these images or views are specified by the alignment parameters. Some images or pixels within an image may also need to be rotated to ensure continuity.

[0122] That is, the encoding device may perform processing to ensure continuity. For example, when encoding the spliced ​​image shown in FIG. 15, the encoding device may perform wrapping processing based on the parameters. Specifically, of the five images included in the spliced ​​image (i.e., images A to D and a top view), the top view is a 180-degree image, and images A to D are 90-degree images. Therefore, the space displayed in the top view is continuous with the spaces displayed in each of images A to D, and the space displayed in image A is continuous with the space displayed in image B. However, in the spliced ​​image, the top view is not continuous with images A, C, and D, and image A is not continuous with image B. Therefore, the encoding device performs the wrapping processing described above to improve encoding efficiency. That is, the encoding device rearranges each image included in the spliced ​​image. For example, the encoding device rearranges each image so that image A and image B are continuous. This makes it possible to contiguous objects displayed separately in images A and B, thereby improving encoding efficiency. The wrapping process, which is a process of rearranging or arranging each image, is also called frame packing.

[0123] <Padding in inter-prediction> FIG. 18 is a flowchart illustrating a variation of the inter-frame prediction process that is applied when an image is identified as having been captured using a non-rectilinear lens, when an image is identified as having been linearly processed, or when an image is identified as having been stitched together from two or more images. As shown in FIG. 18, the encoding device identifies regions of the image as free regions in step S2001 based on parameters written in the header. These free regions are regions of the image that do not contain pixels from the captured image and are typically replaced with a predetermined pixel value (e.g., black pixels). FIG. 13 illustrates an example of such regions within an image. FIG. 15 illustrates another example of such regions when multiple images are stitched together. Next, in step S2002 of FIG. 18, the encoding device pads pixels in these identified regions with values ​​from other non-free regions of the image during motion compensation. The padded values ​​may be values ​​from the nearest pixel in the non-free region or values ​​from the nearest pixel, depending on the physical three-dimensional space. Finally, in step S2003, the encoding device performs block prediction to generate a block of predicted samples based on the padded values.

[0124] <Distortion correction during image reconstruction> FIG. 19 is a flowchart illustrating an image reconstruction process that is applied when an image is identified as having been captured using a non-rectilinear lens, when an image is identified as having been linearly processed, or when an image is identified as having been stitched together from two or more images. As shown in FIG. 19, the encoding device determines a position within the image as the distortion center or principal point based on parameters written in the header in step S1801. FIG. 17 shows an example of distortion caused by a fisheye lens. As the focal axis moves away from the distortion center, magnification decreases along the focal axis. Therefore, in step S1802, the encoding device may perform a wrapping process on reconstructed pixels within the image based on the distortion center to correct the distortion or undo the correction made to linearize the image. For example, the encoding device generates a reconstructed image by adding a prediction error image generated by inverse transform and a predicted image. At this time, the encoding device performs a wrapping process to linearize each of the prediction error image and the predicted image.

[0125] Finally, in step S1803, the encoding device stores in memory the blocks of the image reconstructed based on the pixels of the image that has undergone the wrapping process.

[0126] <Replacing pixel values ​​in image reconstruction> FIG. 20 shows a variation of the image reconstruction process that is applied when an image is identified as having been captured using a non-rectilinear lens, or when an image is identified as having been linearly processed, or when an image is identified as having been stitched together from one or more images. As shown in FIG. 20, based on the parameters written in the header, in step S2101, the encoding device identifies regions of the image as free regions. These free regions are regions of the image that do not contain pixels from the captured image and are typically replaced with a predetermined pixel value (e.g., black pixels). FIG. 13 shows an example of such regions in an image. FIG. 15 shows another example of such regions when multiple images are stitched together. Next, in step S2102, the encoding device reconstructs blocks of image samples.

[0127] Also, in step S2103, the encoding device replaces the reconstructed pixels in these identified regions with predetermined pixel values.

[0128] <Omission of encoding process> In step S102 of Fig. 11, another possible variation of the adaptive video coding tool is that the coding device may skip the coding process of an image, i.e., perform a partial coding process, based on the parameters written regarding the layout arrangement of the image and information about the active viewing area based on the user's eye gaze or head direction.

[0129] FIG. 21 illustrates an example of a user's viewing angle or head orientation with respect to different views captured by different cameras. As shown, the user's viewing angle is within the image captured by the camera from view 1 only. In this example, images from other views do not need to be encoded because they are outside the user's viewing angle. Therefore, to reduce the coding complexity or the transmission bit rate of the compressed images, the encoding or transmission process for these images can be omitted. In another possible example shown, because view 5 and view 2 are physically close to the active view 1, images from view 5 and view 2 are also encoded and transmitted. These images are not currently displayed to the viewer or user, but will be displayed to the viewer or user as the viewer changes his or her head orientation. These images are used to improve the user's viewing experience as the viewer changes his or her head orientation.

[0130] FIG. 22 shows another example of gaze angles or head orientations for different views captured by different cameras of a user. Here, the active gaze area is within the image from view 2. Therefore, the image from view 2 is coded and displayed to the user. Here, the encoding device predicts the estimated range of the viewer's head movement in the near future and defines a wider area as the possible gaze area for future frames. The encoding device also encodes images from views (other than view 2) that are not within the target's active gaze area but are within the wider future gaze area, and transmits them to enable the viewer to render the views faster. That is, not only the image from view 2, but also images from the top view and view 1, which at least partially overlap the possible gaze area shown in FIG. 22, are coded and transmitted. Images from the remaining views (view 3, view 4, and bottom view) are not coded, and the coding process for these images is omitted.

[0131] [Encoding device] FIG. 23 is a block diagram showing the configuration of a coding device that codes moving pictures according to this embodiment.

[0132] The encoding device 900 is a device for encoding an input video for each block in order to generate an output bitstream, and corresponds to the encoding device 100 in Embodiment 1. As shown in Fig. 23 , the encoding device 900 includes a transform unit 901, a quantization unit 902, an inverse quantization unit 903, an inverse transform unit 904, a block memory 905, a frame memory 906, an intra prediction unit 907, an inter prediction unit 908, a subtraction unit 921, an addition unit 922, an entropy encoding unit 909, and a parameter derivation unit 910.

[0133] An image of the input video sequence (i.e., the current block) is input to the subtraction unit 921, and the subtracted value is output to the transformation unit 901. That is, the subtraction unit 921 calculates a prediction error by subtracting a prediction image from the current block. The transformation unit 901 transforms the subtracted value (i.e., the prediction error) into a frequency coefficient and outputs the obtained frequency coefficient to the quantization unit 902. The quantization unit 902 quantizes the input frequency coefficient and outputs the obtained quantized value to the inverse quantization unit 903 and the entropy coding unit 909.

[0134] The inverse quantization unit 903 inversely quantizes the sample values ​​(i.e., quantized values) output from the quantization unit 902, and outputs frequency coefficients to the inverse transform unit 904. The inverse transform unit 904 performs inverse frequency transform to convert the frequency coefficients into sample values ​​of the image, i.e., pixel values, and outputs the obtained sample values ​​to the adder 922.

[0135] The parameter derivation unit 910 derives parameters related to image correction processing, camera parameters, or splicing processing from images, and outputs the parameters to the inter prediction unit 908, the adder 922, and the entropy coding unit 909. For example, the input video may include these parameters, in which case the parameter derivation unit 910 extracts and outputs the parameters included in the video. Alternatively, the input video may include base parameters for deriving these parameters. In this case, the parameter derivation unit 910 extracts base parameters included in the video, converts the extracted base parameters into the above-mentioned parameters, and outputs them.

[0136] The adder 922 adds the sample values ​​output from the inverse transformer 904 to the pixel values ​​of the predicted image output from the intra predictor 907 or the inter predictor 908. That is, the adder 922 performs an image reconstruction process to generate a reconstructed image. The adder 922 outputs the resulting sum to the block memory 905 or the frame memory 906 for further prediction.

[0137] The intra prediction unit 907 performs intra-frame prediction. That is, the intra prediction unit 907 estimates the image of the current block using a reconstructed image included in the same picture as the current block, which is stored in the block memory 905. The inter prediction unit 908 performs inter-frame prediction. That is, the inter prediction unit 908 estimates the image of the current block using a reconstructed image included in a picture different from the picture of the current block, which is stored in the frame memory 906.

[0138] In this embodiment, the inter prediction unit 908 and the adder 922 adapt their processing based on the parameters derived by the parameter derivation unit 910. That is, the inter prediction unit 908 and the adder 922 perform processing according to the flowcharts shown in FIGS. 16, 18, 19, and 20 as processing by the adaptive video coding tool described above.

[0139] The entropy coding unit 909 codes the quantized value output from the quantization unit 902 and the parameters derived by the parameter derivation unit 910, and outputs a bitstream. That is, the entropy coding unit 909 writes the parameters into the header of the bitstream.

[0140] [Decryption process] FIG. 24 is a flowchart showing an example of the video decoding process according to this embodiment.

[0141] In step S201, the decoding device parses a set of parameters from a header. Figure 12 shows possible locations of the header in a compressed video bitstream. The parsed parameters include one or more parameters related to image enhancement processes.

[0142] <Example of image correction processing parameters> As shown in FIG. 13 , the captured image may be distorted due to the characteristics of the lens used during image capture. An image correction process may be used to linearly correct the captured image. The interpreted parameters include parameters that identify or describe the image correction process used. Examples of parameters used in the image correction process include parameters that configure a mapping table for mapping pixels of the input image to the intended output pixel values ​​of the image correction process. These parameters may include weight parameters for one or more interpolation processes or / and location parameters that specify the location of input and output pixels in the picture. In one possible implementation of the image correction process, the mapping table for the image correction process may be used for all pixels in the corrected image.

[0143] Other examples of parameters used to describe an image correction process include a selection parameter for selecting one of a plurality of predefined correction algorithms, a direction parameter for selecting one of a plurality of predetermined directions of the correction algorithm, and / or a calibration parameter for calibrating or fine-tuning the correction algorithm. For example, if there are multiple predefined correction algorithms (e.g., different algorithms are used for different types of lenses), the selection parameter is used to select one of these predefined algorithms. For example, if there are two or more directions in which the correction algorithm can be applied (e.g., if the image correction process can be performed horizontally, vertically, or in either direction), the direction parameter selects one of these predefined directions. For example, if the image correction process can be calibrated, the calibration parameter can adjust the image correction process to suit different types of lenses.

[0144] <Example of parameters for splicing process> The interpreted parameters may further include one or more parameters related to the stitching process. As shown in Figures 14 and 15, the encoded image input to the decoding device may be the result of a stitching process that combines multiple images from different cameras. The interpreted parameters include parameters that provide information about the stitching process, such as the number of cameras, the distortion center or principal axis of each camera, and the distortion level. Another example of a parameter describing the stitching process is a parameter that specifies the location of a stitched image created from overlapping pixels from multiple images. Each of these images may contain pixels that may appear in other images because there may be overlapping areas in the camera angles. During the stitching process, these overlapping pixels are processed and reduced to create the stitched image.

[0145] Another example of a parameter describing the stitching process includes a parameter specifying the layout of the stitched images. For example, the arrangement of images within the stitched image varies depending on the format of the 360-degree image, such as equirectangular projection, a cubic 3x2 layout, or a cubic 4x3 layout. The above parameter, the alignment parameter, is used to specify the continuity of images in a certain direction based on the image alignment. During motion compensation, pixels from other images or views can be used in inter-frame prediction, and these images or views are specified by the alignment parameter. Some images or pixels within an image may also need to be rotated to ensure continuity.

[0146] Other examples of parameters include camera and lens parameters (e.g., focal length, principal point, scale factor, type of image sensor used in the camera, etc.) Yet another example of a parameter is physical information about the placement of the camera (e.g., camera position, camera angle, etc.).

[0147] Next, in step S202, the decoding device decodes the image using an adaptive video decoding tool based on the interpreted parameters. The adaptive video decoding tool may include an inter-frame prediction process. The set of adaptive video decoding tools may also include an image reconstruction process. Note that the video decoding tool or adaptive video decoding tool may be the same as or correspond to the above-mentioned video encoding tool or adaptive video encoding tool.

[0148] <Distortion correction in inter-frame prediction> FIG. 16 is a flowchart illustrating an inter-frame prediction process that is applied when an image is identified as having been captured using a non-rectilinear lens, when an image is identified as having been linearly processed, or when an image is identified as having been stitched together from one or more images. As shown in FIG. 16, in step S1901, the decoding device determines a certain location within the image as the distortion center or principal point based on parameters written in the header. FIG. 17 shows an example of distortion caused by a fisheye lens. As the focal axis moves away from the distortion center, the magnification decreases along the focal axis. Therefore, in step S1902, the decoding device may perform a wrapping process on pixels within the image based on the distortion center to correct the distortion or undo the correction made to linearize the image. That is, the decoding device performs an image correction process (i.e., a wrapping process) on the block of the distorted image that is the target of the decoding process. Finally, in step S1903, the decoding device may perform block prediction to derive a block of predicted samples based on the pixels of the wrapped image. The decoding device may also restore the predicted block, which is the predicted block, to its original distorted state before the image correction process was performed, and use the distorted predicted block as a predicted image of the distorted block to be processed.

[0149] Another example of an adapted inter-frame prediction process includes an adapted motion vector process. The resolution of the motion vectors is lower for image blocks farther from the distortion center than for image blocks closer to the distortion center. For example, image blocks farther from the distortion center may have motion vector accuracy up to half-pixel precision, while image blocks closer to the distortion center may have higher motion vector accuracy up to one-eighth pixel precision. Since the adapted motion vector accuracy varies based on the image block position, the motion vector accuracy coded in the bitstream may be adaptive depending on the end and / or start positions of the motion vector. That is, the decoding device may use parameters to vary the accuracy of the motion vector depending on the block position.

[0150] Another example of an adaptive inter-prediction process includes an adaptive motion compensation process, in which pixels from different views may be used to predict image samples from a target view based on alignment parameters written in the header. For example, different 360-degree image formats, such as equirectangular projection, a cubic 3x2 layout, or a cubic 4x3 layout, may have different image alignments within the stitched image. The alignment parameters are used to determine image continuity in a certain direction based on the image alignment. During the motion compensation process, pixels from other images or other views may be used in the inter-prediction process, and these images or views are specified by the alignment parameters. Some images or pixels within an image may also need to be rotated to ensure continuity.

[0151] That is, the decoding device may perform a process to ensure continuity. For example, when encoding the spliced ​​image shown in Fig. 15, the decoding device may perform a wrapping process based on the parameters. Specifically, like the encoding device described above, the decoding device rearranges each image so that image A and image B are continuous. This makes it possible to make the objects displayed separately in image A and image B continuous, thereby improving encoding efficiency.

[0152] <Padding in inter-prediction> FIG. 18 is a flowchart illustrating a variation of the inter-frame prediction process that is applied when an image is identified as having been captured using a non-rectilinear lens, when an image is identified as having been linearly processed, or when an image is identified as having been stitched together from two or more images. As shown in FIG. 18, the decoding device identifies regions of the image as free regions in step S2001 based on parameters interpreted from the header. These free regions are regions of the image that do not contain pixels from the captured image and are generally replaced with a predetermined pixel value (e.g., black pixels). FIG. 13 shows examples of these regions within an image. FIG. 15 shows another example of these regions when multiple images are stitched together. Next, in step S2002 of FIG. 18, the decoding device pads pixels in these identified regions with values ​​from other non-free regions of the image during motion compensation. The padded values ​​may be values ​​from the nearest pixel in the non-free region, or the nearest pixel, depending on the physical three-dimensional space. Finally, in step S2003, the decoder performs block prediction to generate a block of predicted samples based on the padded values.

[0153] <Distortion correction during image reconstruction> FIG. 19 is a flowchart illustrating an image reconstruction process that is applied when an image is identified as having been captured using a non-rectilinear lens, when an image is identified as having been linearly processed, or when an image is identified as having been stitched together from two or more images. As shown in FIG. 19, the decoding device determines a position within the image as the distortion center or principal point in step S1801 based on parameters interpreted from the header. FIG. 17 shows an example of distortion caused by a fisheye lens. As the focal axis moves away from the distortion center, magnification decreases along the focal axis. Therefore, in step S1802, the decoding device may perform a wrapping process on reconstructed pixels within the image based on the distortion center to correct the distortion or undo the correction made to linearize the image. For example, the decoding device generates a reconstructed image by adding a prediction error image generated by an inverse transform and a predicted image. At this time, the decoding device performs a wrapping process to linearize each of the prediction error image and the predicted image.

[0154] Finally, in step S1803, the decoding device stores in memory the blocks of the image reconstructed based on the pixels of the image that has undergone the wrapping process.

[0155] <Replacing pixel values ​​in image reconstruction> FIG. 20 shows a variation of the image reconstruction process that is applied when an image is identified as having been captured using a non-rectilinear lens, or when an image is identified as having been linearly processed, or when an image is identified as having been stitched together from one or more images. As shown in FIG. 20, based on parameters decoded from the header, in step S2001, the decoder identifies regions of the image as free areas. These free areas are areas of the image that do not contain pixels from the captured image and are typically replaced with a predetermined pixel value (e.g., black pixels). FIG. 13 shows an example of such areas in an image. FIG. 15 shows another example of such areas when multiple images are stitched together. Next, in step S2102, the decoder reconstructs blocks of image samples.

[0156] Also, in step S2103, the decoding device replaces the reconstructed pixels in these identified regions with predetermined pixel values.

[0157] <Omission of decryption process> In step S202 of Fig. 24, another possible variation of the adaptive video decoding tool for an image may skip decoding processing of the image, i.e., based on the interpreted parameters for the layout arrangement of the image and information about the active viewing area based on the user's eye gaze or head direction, the decoding device may skip decoding processing of the image, i.e., perform partial decoding processing.

[0158] FIG. 21 illustrates an example of a user's viewing angle or head orientation with respect to different views captured by different cameras. As shown, the user's viewing angle is within the images captured by the camera from view 1 only. In this example, images from other views do not need to be decoded because they are outside the user's viewing angle. Therefore, to reduce the decoding complexity or the transmission bit rate of compressed images, the decoding or display process for these images can be omitted. In another possible example shown, because view 5 and view 2 are physically close to the active view 1, images from view 5 and view 2 are also decoded. These images are not currently displayed to the viewer or user, but will be displayed to the viewer or user as the viewer changes his or her head orientation. By reducing the time required to decode and display views in response to the user's head movement, these images are displayed as soon as possible to improve the user's viewing experience when the user changes his or her head orientation.

[0159] FIG. 22 shows another example of the gaze angle or head orientation for different views captured by different cameras of a user. Here, the active gaze area is within the image from view 2. Therefore, the image from view 2 is decoded and displayed to the user. Here, the decoding device predicts the estimated range of the viewer's head movement in the near future and defines a wider area as the possible gaze area for future frames. The decoding device also decodes images from views (other than view 2) that are not within the target's active gaze area but are within the wider future gaze area. That is, not only the image from view 2 but also images from the top view and view 1 that at least partially overlap the possible gaze area shown in FIG. 22 are decoded. This allows the viewer to display the images more quickly. Images from the remaining views (view 3, view 4, and below) are not decoded, and the decoding process for these images is omitted.

[0160] [Decryption device] FIG. 25 is a block diagram showing the configuration of a decoding device that decodes moving images according to this embodiment.

[0161] The decoding device 1000 is a device for decoding an input coded video (i.e., an input bitstream) for each block in order to generate a decoded video, and corresponds to the decoding device 200 of Embodiment 1. As shown in FIG. 25 , the decoding device 1000 includes an entropy decoding unit 1001, an inverse quantization unit 1002, an inverse transform unit 1003, a block memory 1004, a frame memory 1005, an adder 1022, an intra prediction unit 1006, and an inter prediction unit 1007.

[0162] An input bitstream is input to an entropy decoding unit 1001. Thereafter, the entropy decoding unit 1001 performs entropy decoding on the input bitstream and outputs values ​​obtained by the entropy decoding (i.e., quantized values) to an inverse quantization unit 1002. The entropy decoding unit 1001 further decodes parameters from the input bitstream and outputs the parameters to an inter prediction unit 1007 and an adder 1022.

[0163] The inverse quantization unit 1002 inverse quantizes the values ​​obtained by entropy decoding and outputs frequency coefficients to the inverse transform unit 1003. The inverse transform unit 1003 performs inverse frequency transform on the frequency coefficients to convert the frequency coefficients into sample values ​​(i.e., pixel values), and outputs the obtained pixel values ​​to the adder 1022. The adder 1022 adds the obtained pixel values ​​to pixel values ​​of a predicted image output from the intra prediction unit 1006 or the inter prediction unit 1007. In other words, the adder 1022 performs image reconstruction processing to generate a reconstructed image. The adder 1022 outputs the values ​​obtained by the addition (i.e., a decoded image) to a display, and outputs the obtained values ​​to the block memory 1004 or the frame memory 1005 for further prediction.

[0164] The intra prediction unit 1006 performs intra-frame prediction. That is, the intra prediction unit 1006 estimates the image of the block to be processed using a reconstructed image included in the same picture as the picture of the block to be processed, which is stored in the block memory 1004. The inter prediction unit 1007 performs inter-frame prediction. That is, the inter prediction unit 1007 estimates the image of the block to be processed using a reconstructed image included in a picture different from the picture of the block to be processed, which is stored in the frame memory 1005.

[0165] In this embodiment, the inter prediction unit 1007 and the adder 1022 perform processing based on the interpreted parameters. That is, the inter prediction unit 1007 and the adder 1022 perform processing according to the flowcharts shown in Figs. 16, 18, 19, and 20 as processing by the adaptive video decoding tool described above.

[0166] (Embodiment 3) [Encoding process] A method for performing video encoding processing on images captured using a non-rectilinear lens according to the third embodiment of this disclosure shown in FIG. 26 will be described.

[0167] FIG. 26 is a flowchart showing an example of the video encoding process according to this embodiment.

[0168] In step S301, the encoding device writes a set of parameters into a header. Figure 12 shows possible locations of such a header in a compressed video bitstream. The written parameters include one or more parameters related to the camera position. The written parameters may also include one or more parameters related to the camera angle or instructions on how to stitch multiple images together.

[0169] Other examples of parameters include camera and lens parameters (e.g., focal length, principal point, scale factor, type of image sensor used in the camera, etc.) Further examples of parameters include physical information regarding the placement of the camera (e.g., camera position, camera angle, etc.).

[0170] In this embodiment, the above parameters written in the header are also called camera parameters or splicing parameters.

[0171] Figure 15 shows an example of a method for stitching together images from two or more cameras. Figure 14 shows another example of a method for stitching together images from two or more cameras.

[0172] Next, in step S302, the encoding device encodes the image. In step S302, the encoding process may be adapted based on the spliced ​​image. For example, in the motion compensation process, the encoding device may refer to the larger spliced ​​image as a reference image instead of an image of the same size as the decoded image (i.e., an unspliced ​​image).

[0173] Finally, in step S303, the encoding device stitches the first image, which is the image coded and reconstructed in step S302, with the second image based on the written parameters to create a larger image, which may be used for predicting future frames (i.e., inter-frame prediction or motion compensation).

[0174] FIG. 27 is a flowchart showing a stitching process in which parameters written in a header are used. In step S2401, the encoding device determines camera parameters or stitching parameters from the parameters written for the target image. Similarly, in step S2402, the encoding device determines camera parameters or stitching parameters for another image from the parameters written for the other image. Finally, in step S2403, the encoding device stitches the images together using these determined parameters to create a larger image. These determined parameters are written to a header. Note that the encoding device may perform wrapping or frame packing, which arranges or rearranges multiple images to further improve coding efficiency.

[0175] [Encoding device] FIG. 28 is a block diagram showing the configuration of a coding device that codes moving pictures according to this embodiment.

[0176] The encoding device 1100 is a device for encoding an input video for each block in order to generate an output bitstream, and corresponds to the encoding device 100 in Embodiment 1. As shown in Fig. 28 , the encoding device 1100 includes a transform unit 1101, a quantization unit 1102, an inverse quantization unit 1103, an inverse transform unit 1104, a block memory 1105, a frame memory 1106, an intra prediction unit 1107, an inter prediction unit 1108, a subtraction unit 1121, an addition unit 1122, an entropy encoding unit 1109, a parameter derivation unit 1110, and an image splicing unit 1111.

[0177] An image of the input video sequence (i.e., the current block) is input to the subtraction unit 1121, and the subtracted value is output to the transformation unit 1101. That is, the subtraction unit 1121 calculates a prediction error by subtracting a prediction image from the current block. The transformation unit 1101 transforms the subtracted value (i.e., the prediction error) into a frequency coefficient and outputs the obtained frequency coefficient to the quantization unit 1102. The quantization unit 1102 quantizes the input frequency coefficient and outputs the obtained quantized value to the inverse quantization unit 1103 and the entropy coding unit 1109.

[0178] The inverse quantization unit 1103 inversely quantizes the sample values ​​(i.e., quantized values) output from the quantization unit 1102, and outputs frequency coefficients to the inverse transform unit 1104. The inverse transform unit 1104 performs an inverse frequency transform on the frequency coefficients to convert the frequency coefficients into sample values ​​of the image, i.e., pixel values, and outputs the resulting sample values ​​to the adder 1122.

[0179] The adder 1122 adds the sample values ​​output from the inverse transformer 1104 to the pixel values ​​of the predicted image output from the intra predictor 1107 or the inter predictor 1108. The adder 1122 outputs the resulting sum to the block memory 1105 or the frame memory 1106 for further prediction.

[0180] As in the first embodiment, the parameter derivation unit 1110 derives parameters related to the image splicing process or camera parameters from images, and outputs the parameters to the image splicing unit 1111 and the entropy coding unit 1109. That is, the parameter derivation unit 1110 performs the processes of steps S2401 and S2402 shown in FIG. 27 . For example, the input video may include these parameters, in which case the parameter derivation unit 1110 extracts and outputs the parameters included in the video. Alternatively, the input video may include base parameters for deriving these parameters. In this case, the parameter derivation unit 1110 extracts base parameters included in the video, converts the extracted base parameters into the above-mentioned parameters, and outputs them.

[0181] The image splicing unit 1111 splices the reconstructed target image to another image using the parameters, as shown in step S303 of Fig. 26 and step S2403 of Fig. 27. Thereafter, the image splicing unit 1111 outputs the spliced ​​image to the frame memory 1106.

[0182] The intra prediction unit 1107 performs intra prediction. That is, the intra prediction unit 1107 estimates the image of the block to be processed using a reconstructed image included in the same picture as the picture of the block to be processed, which is stored in the block memory 1105. The inter prediction unit 1108 performs inter prediction. That is, the inter prediction unit 1108 estimates the image of the block to be processed using a reconstructed image included in a picture different from the picture of the block to be processed, which is stored in the frame memory 1106. At this time, the inter prediction unit 1108 may refer to a larger image obtained by stitching multiple images together by the image stitching unit 1111, which is stored in the frame memory 1106, as a reference image.

[0183] The entropy coding unit 1109 codes the quantized values ​​output from the quantization unit 1102, obtains parameters from the parameter derivation unit 1110, and outputs a bitstream. That is, the entropy coding unit 1109 performs entropy coding on the quantized values ​​and parameters, and writes the parameters into the header of the bitstream.

[0184] [Decryption process] FIG. 29 is a flowchart showing an example of the video decoding process according to this embodiment.

[0185] In step S401, the decoding device parses a set of parameters from the header. Figure 12 shows possible locations of such a header in a compressed video bitstream. The parsed parameters include one or more parameters related to the camera position. The parsed parameters may also include one or more parameters related to the camera angle or instructions on how to stitch multiple images together. Other example parameters include camera and lens parameters (e.g., focal length, principal point, scale factor, type of image sensor used in the camera, etc.). Further example parameters include physical information related to the camera geometry (e.g., camera position, camera angle, etc.).

[0186] Figure 15 shows one example of how images from two or more cameras can be stitched together. Figure 14 shows another example of how images from two or more cameras can be stitched together.

[0187] Next, in step S402, the decoding device decodes the image. The decoding process in step S402 may also be adapted based on the stitched image. For example, the decoding device may refer to the stitched larger image as a reference image in the motion compensation process, instead of an image of the same size as the decoded image (i.e., an unstitched image).

[0188] Finally, in step S403, the decoding device stitches the first image, which is the image reconstructed in step S402, with the second image based on the interpreted parameters to create a larger image. The stitched image may be used for predicting future images (i.e., inter-frame prediction or motion compensation).

[0189] 27 is a flowchart showing the stitching process using the decoded parameters. In step S2401, the decoding device determines the camera parameters or stitching parameters by decode the header for the current image. Similarly, in step S2402, the decoding device determines the camera parameters or stitching parameters by decode the header for another image. Finally, in step S2403, the decoding device stitches the images together using these decoded parameters to create a larger image.

[0190] [Decryption device] FIG. 30 is a block diagram showing the configuration of a decoding device that decodes moving images according to this embodiment.

[0191] The decoding device 1200 is a device that decodes an input coded video (i.e., an input bitstream) for each block and outputs a decoded video, and corresponds to the decoding device 200 in Embodiment 1. As shown in Fig. 30 , the decoding device 1200 includes an entropy decoding unit 1201, an inverse quantization unit 1202, an inverse transform unit 1203, a block memory 1204, a frame memory 1205, an adder 1222, an intra prediction unit 1206, an inter prediction unit 1207, and an image splicing unit 1208.

[0192] An input bitstream is input to an entropy decoding unit 1201. Thereafter, the entropy decoding unit 1201 performs entropy decoding on the input bitstream, and outputs the values ​​obtained by the entropy decoding (i.e., quantized values) to an inverse quantization unit 1202. The entropy decoding unit 1201 further decodes parameters from the input bitstream, and outputs the parameters to an image splicing unit 1208.

[0193] The image splicing unit 1208 splices the reconstructed target image to another image using the parameters, and then outputs the image obtained by splicing to the frame memory 1205.

[0194] The inverse quantization unit 1202 inverse quantizes the values ​​obtained by entropy decoding and outputs frequency coefficients to the inverse transform unit 1203. The inverse transform unit 1203 performs an inverse frequency transform on the frequency coefficients, converting the frequency coefficients into sample values ​​(i.e., pixel values), and outputs the resulting pixel values ​​to the adder 1222. The adder 1222 adds the resulting pixel values ​​to pixel values ​​of a predicted image output from the intra prediction unit 1206 or the inter prediction unit 1207. The adder 1222 outputs the values ​​obtained by the addition (i.e., a decoded image) to a display, and also outputs the resulting values ​​to the block memory 1204 or the frame memory 1205 for further prediction.

[0195] The intra prediction unit 1206 performs intra-frame prediction. That is, the intra prediction unit 1206 estimates an image of the current block using a reconstructed image included in the same picture as the current block, which is stored in the block memory 1204. The inter prediction unit 1207 performs inter-frame prediction. That is, the inter prediction unit 1207 estimates an image of the current block using a reconstructed image included in a picture different from the picture of the current block, which is stored in the frame memory 1205.

[0196] (Fourth embodiment) [Encoding process] A method of performing video encoding processing on an image captured using a non-rectilinear lens according to the fourth embodiment of this disclosure shown in FIG. 31 will be described.

[0197] FIG. 31 is a flowchart showing an example of the video encoding process according to this embodiment.

[0198] In step S501, the encoding device writes a set of parameters into a header. Figure 12 shows possible locations of such a header in a compressed video bitstream. The written parameters include one or more parameters related to an identifier indicating whether the image was captured with a non-rectilinear lens. As shown in Figure 13, the captured image may be distorted due to the characteristics of the lens used during image capture. One example of a written parameter is a parameter indicating the location of the center or major axis of distortion.

[0199] Next, in step S502, the encoding device encodes the image using adaptive video encoding tools based on the written parameters. The adaptive video encoding tools include a motion vector prediction process. The set of adaptive video encoding tools may also include an intra-frame prediction process.

[0200] <In-screen prediction processing> 32 is a flowchart showing an intra-frame prediction process adapted based on the written parameters. As shown in FIG. 32, in step S2201, the encoding device determines a position in an image as a distortion center or principal point based on the written parameters. Next, in step S2202, the encoding device predicts one sample group using spatially neighboring pixel values. The sample group is, for example, a group of pixels such as a current block.

[0201] Finally, in step S2203, the encoding device performs a wrapping process on the predicted sample group using the determined distortion center or principal point to generate a block of predicted samples. For example, the encoding device may distort an image of the block of predicted samples and use the distorted image as the predicted image.

[0202] <Motion vector prediction> 33 is a flowchart showing a motion vector prediction process adapted based on the written parameters. As shown in FIG. 33, in step S2301, the encoding device determines a position in an image as the distortion center or principal point based on the written parameters. Next, in step S2302, the encoding device predicts a motion vector from spatially or temporally adjacent motion vectors.

[0203] Finally, in step S2303, the encoding device corrects the direction of the predicted motion vector using the determined distortion center or principal point.

[0204] [Encoding device] FIG. 34 is a block diagram showing the configuration of a coding device that codes moving pictures in this embodiment.

[0205] The encoding device 1300 is a device for encoding an input video for each block in order to generate an output bitstream, and corresponds to the encoding device 100 in Embodiment 1. As shown in Fig. 34 , the encoding device 1300 includes a transform unit 1301, a quantization unit 1302, an inverse quantization unit 1303, an inverse transform unit 1304, a block memory 1305, a frame memory 1306, an intra prediction unit 1307, an inter prediction unit 1308, a subtraction unit 1321, an addition unit 1322, an entropy encoding unit 1309, and a parameter derivation unit 1310.

[0206] An image of the input video sequence (i.e., the current block) is input to the subtraction unit 1321, and the subtracted value is output to the transformation unit 1301. That is, the subtraction unit 1321 calculates a prediction error by subtracting a prediction image from the current block. The transformation unit 1301 transforms the subtracted value (i.e., the prediction error) into a frequency coefficient and outputs the resulting frequency coefficient to the quantization unit 1302. The quantization unit 1302 quantizes the input frequency coefficient and outputs the resulting quantized value to the inverse quantization unit 1303 and the entropy coding unit 1309.

[0207] The inverse quantization unit 1303 inversely quantizes the sample values ​​(i.e., quantized values) output from the quantization unit 1302, and outputs frequency coefficients to the inverse transform unit 1304. The inverse transform unit 1304 performs an inverse frequency transform on the frequency coefficients, converts the frequency coefficients into sample values ​​of the image, i.e., pixel values, and outputs the resulting sample values ​​to the adder 1322.

[0208] As in the first embodiment, the parameter derivation unit 1310 derives, from an image, one or more parameters (specifically, parameters indicating the distortion center or principal point) related to an identifier indicating whether the image was captured using a non-rectilinear lens. The parameter derivation unit 1310 then outputs the derived parameters to the intra prediction unit 1307, the inter prediction unit 1308, and the entropy coding unit 1309. For example, the input video may include these parameters. In this case, the parameter derivation unit 1310 extracts and outputs the parameters included in the video. Alternatively, the input video may include base parameters for deriving these parameters. In this case, the parameter derivation unit 1310 extracts base parameters included in the video, converts the extracted base parameters into the above-mentioned parameters, and outputs them.

[0209] The adder 1322 adds the sample values ​​of the image output from the inverse transformer 1304 to the pixel values ​​of the predicted image output from the intra predictor 1307 or the inter predictor 1308. The adder 1322 outputs the resulting sum to the block memory 1305 or the frame memory 1306 for further prediction.

[0210] The intra prediction unit 1307 performs intra-frame prediction. That is, the intra prediction unit 1307 estimates the image of the current block using a reconstructed image included in the same picture as the current block, which is stored in the block memory 1305. The inter prediction unit 1308 performs inter-frame prediction. That is, the inter prediction unit 1308 estimates the image of the current block using a reconstructed image included in a picture in the frame memory 1306 that is different from the picture of the current block.

[0211] In this embodiment, the intra prediction unit 1307 and the inter prediction unit 1308 perform processing based on parameters derived by the parameter derivation unit 1310. That is, the intra prediction unit 1307 and the inter prediction unit 1308 perform processing according to the flowcharts shown in Figs. 32 and 33, respectively.

[0212] The entropy coding unit 1309 codes the quantized value output from the quantization unit 1302 and the parameters derived by the parameter derivation unit 1310, and outputs a bitstream. That is, the entropy coding unit 1309 writes the parameters into the header of the bitstream.

[0213] [Decryption process] FIG. 35 is a flowchart showing an example of the video decoding process according to this embodiment.

[0214] In step S601, the decoding device decodes a set of parameters from a header. Figure 12 shows possible locations of such a header in a compressed video bitstream. The decoded parameters include one or more parameters related to an identifier indicating whether the image was captured with a non-rectilinear lens. As shown in Figure 13, the captured image may be distorted due to the characteristics of the lens used during image capture. One example of a decoded parameter is a parameter indicating the location of the center or major axis of distortion.

[0215] Next, in step S602, the decoding device decodes the image using an adaptive video decoding tool based on these interpreted parameters. The adaptive video decoding tool includes a motion vector prediction process. The adaptive video decoding tool may also include an intra-frame prediction process. Note that the video decoding tool or adaptive video decoding tool is the same as or corresponds to the above-mentioned video encoding tool or adaptive video encoding tool.

[0216] <In-screen prediction processing> FIG. 32 is a flowchart showing an intra-frame prediction process adapted based on the interpreted parameters. As shown in FIG. 32, in step S2201, the decoding device determines a position within an image as a distortion center or principal point based on the interpreted parameters. Next, in step S2202, the decoding device predicts a group of samples using spatially neighboring pixel values. Finally, in step S2203, the decoding device performs a wrapping process on the predicted group of samples using the determined distortion center or principal point to generate a block of predicted samples. For example, the decoding device may distort an image of the block of predicted samples and use the distorted image as the predicted image.

[0217] <Motion vector prediction> 33 is a flowchart showing a motion vector prediction process adapted based on the interpreted parameters. As shown in FIG. 33, in step S2301, the decoding device determines a position in an image as a distortion center or principal point based on the interpreted parameters. Next, in step S2302, the decoding device predicts a motion vector from spatially or temporally adjacent motion vectors. Finally, in step S2303, the decoding device corrects the direction of the motion vector using the determined distortion center or principal point.

[0218] [Decryption device] FIG. 36 is a block diagram showing the configuration of a decoding device that decodes moving images in this embodiment.

[0219] The decoding device 1400 is a device for decoding an input coded video (i.e., an input bitstream) for each block and outputting a decoded video, and corresponds to the decoding device 200 in Embodiment 1. As shown in FIG. 36 , the decoding device 1400 includes an entropy decoding unit 1401, an inverse quantization unit 1402, an inverse transform unit 1403, a block memory 1404, a frame memory 1405, an adder 1422, an intra prediction unit 1406, and an inter prediction unit 1407.

[0220] An input bitstream is input to an entropy decoding unit 1401. Thereafter, the entropy decoding unit 1401 performs entropy decoding on the input bitstream, and outputs values ​​obtained by the entropy decoding (i.e., quantized values) to an inverse quantization unit 1402. The entropy decoding unit 1401 further decodes parameters from the input bitstream, and outputs the parameters to an inter prediction unit 1407 and an intra prediction unit 1406.

[0221] The inverse quantization unit 1402 inverse quantizes the values ​​obtained by entropy decoding and outputs frequency coefficients to the inverse transform unit 1403. The inverse transform unit 1403 performs an inverse frequency transform on the frequency coefficients to convert the frequency coefficients into sample values ​​(i.e., pixel values), and outputs the resulting pixel values ​​to the adder 1422. The adder 1422 adds the resulting pixel values ​​to pixel values ​​of a predicted image output from the intra prediction unit 1406 or the inter prediction unit 1407. The adder 1422 outputs the values ​​obtained by the addition (i.e., a decoded image) to a display, and outputs the resulting values ​​to the block memory 1404 or the frame memory 1405 for further prediction.

[0222] The intra prediction unit 1406 performs intra-frame prediction. That is, the intra prediction unit 1406 predicts the image of the current block using a reconstructed image included in the same picture as the current block, which is stored in the block memory 1404. The inter prediction unit 1407 performs inter-frame prediction. That is, the inter prediction unit 1407 estimates the image of the current block using a reconstructed image included in a picture different from the picture of the current block, which is stored in the frame memory 1405.

[0223] In this embodiment, the inter prediction unit 1407 and the intra prediction unit 1406 adapt their processing based on the interpreted parameters. That is, the inter prediction unit 1407 and the intra prediction unit 1406 perform processing according to the flowcharts shown in Figs. 32 and 33 as processing by an adaptive video decoding tool.

[0224] (summary) The above describes examples of the encoding device and decoding device of the present disclosure using each embodiment, but the encoding device and decoding device according to one aspect of the present disclosure are not limited to these embodiments.

[0225] For example, in each of the above embodiments, the encoding device encodes video using parameters related to image distortion or parameters related to image splicing, and the decoding device decodes the encoded video using these parameters. However, the encoding device and decoding device according to one aspect of the present disclosure do not need to perform encoding or decoding using these parameters. In other words, they do not need to perform processing using the adaptive video encoding tool and adaptive video decoding tool in the above embodiments.

[0226] FIG. 37 is a block diagram of an encoding device according to one embodiment of the present disclosure.

[0227] 37 , the encoding device 1500 according to one aspect of the present disclosure is a device corresponding to the encoding device 100 of Embodiment 1, and includes a transform unit 1501, a quantization unit 1502, an inverse quantization unit 1503, an inverse transform unit 1504, a block memory 1505, a frame memory 1506, an intra prediction unit 1507, an inter prediction unit 1508, a subtraction unit 1521, an addition unit 1522, and an entropy encoding unit 1509. Note that the encoding device 1500 does not include the parameter derivation units 910, 1110, and 1310.

[0228] The above-described components included in the encoding device 1500 perform the same processes as those in the first to fourth embodiments, but do not perform processes using an adaptive video encoding tool. That is, the adder 1522, the intra prediction unit 1507, and the inter prediction unit 1508 perform encoding processes without using parameters derived by the parameter derivation units 910, 1110, and 1310 in the second to fourth embodiments, respectively.

[0229] Furthermore, the encoding device 1500 acquires a video and parameters related to the video, generates a bitstream by encoding the video without using the parameters, and writes the above-mentioned parameters into the bitstream. Specifically, the entropy encoding unit 1509 writes the parameters into the bitstream. Note that the parameters may be written into the bitstream at any position.

[0230] Furthermore, each image (i.e., picture) included in the above-described video input to the encoding device 1500 may be a distortion-corrected image or a stitched image obtained by stitching together images from multiple views. A distortion-corrected image is a rectangular image obtained by correcting distortion in an image captured by a wide-angle lens such as a non-rectilinear lens. Such an encoding device 1500 encodes a video including the distortion-corrected image or stitched image.

[0231] Here, the quantization unit 1502, the inverse quantization unit 1503, the inverse transform unit 1504, the intra prediction unit 1507, the inter prediction unit 1508, the subtraction unit 1521, the addition unit 1522, and the entropy coding unit 1509 are configured as, for example, a processing circuit. Furthermore, the block memory 1505 and the frame memory 1506 are configured as memories.

[0232] That is, the encoding device 1500 includes a processing circuit and a memory connected to the processing circuit. The processing circuit uses the memory to acquire parameters related to at least one of a first process for correcting distortion in an image captured by a wide-angle lens and a second process for stitching together multiple images, generates an encoded image by encoding the first image or an image to be processed that is based on the multiple images, and writes the parameters into a bitstream that includes the encoded image.

[0233] As a result, since the above-mentioned parameters are written in the bitstream, the image to be coded or decoded can be handled appropriately by using the parameters.

[0234] Here, the parameter writing may include writing the parameter to a header in a bitstream. Furthermore, the encoding of the image to be processed may include, for each block included in the image to be processed, encoding the block by applying an encoding process based on the parameter to the block. Here, the encoding process may include at least one of an inter-frame prediction process and an image reconstruction process.

[0235] As a result, for example, as in embodiment 2, by using inter prediction processing and image reconstruction processing as adaptive video coding tools, it is possible to appropriately code a target image, such as a distorted image or a spliced ​​image, and as a result, it is possible to improve the coding efficiency for the target image.

[0236] In addition, when writing the parameters, the parameters related to the second process described above may be written into a header in the bitstream, and when encoding the image to be processed, the encoding process for each block included in the image to be processed obtained by the second process may be omitted based on the parameters.

[0237] 21 and 22 in Embodiment 2, it is possible to omit coding of blocks included in images that will not be looked at by the user in the near future, among multiple images included in a spliced ​​image, thereby reducing the processing load and the amount of code.

[0238] In addition, in writing the parameters, at least one of the position and the camera angle of each of the plurality of cameras may be written to a header in the bitstream as a parameter related to the second process. In encoding the image to be processed, the image to be processed, which is one of the plurality of images, may be encoded, and the image to be processed may be spliced ​​with other images of the plurality of images using the parameters written to the header.

[0239] This allows a large image obtained by splicing to be used for inter prediction or motion compensation, as in the third embodiment, for example, thereby improving coding efficiency.

[0240] In addition, when writing the parameters, at least one of a parameter indicating whether the image is captured using a wide-angle lens and a parameter related to distortion caused by the wide-angle lens may be written to a header in the bitstream as a parameter related to the above-mentioned first process.In addition, when encoding the image to be processed, for each block included in the image to be processed, which is an image captured using a wide-angle lens, the block may be encoded by applying an encoding process based on the parameters written to the header to the block.Here, the encoding process may include at least one of a motion vector prediction process and an intra-frame prediction process.

[0241] As a result, by using the motion vector prediction process and the intra-frame prediction process as adaptive video coding tools, as in the fourth embodiment, it is possible to appropriately code a distorted image to be processed, thereby improving the coding efficiency of distorted images.

[0242] The encoding process may also include one of an inter-frame prediction process and an intra-frame prediction process, and the prediction process may include a wrapping process that arranges or rearranges multiple pixels included in an image.

[0243] This allows for correcting distortion of a target image and appropriately performing inter prediction processing based on the corrected image, as in, for example, embodiment 2. Also, as in, for example, embodiment 4, intra prediction processing is performed on a distorted image, and the predicted image obtained by this processing can be appropriately distorted to match the distorted target image. As a result, it is possible to improve the coding efficiency of distorted images.

[0244] The encoding process may also include an inter-prediction process for curved, diagonal or angular image boundaries, including padding of the image using parameters written in the header as described above.

[0245] This allows inter-picture prediction processing to be performed appropriately, as in the second embodiment, for example, and coding efficiency to be improved.

[0246] In addition, the encoding process may include an inter-frame prediction process and an image reconstruction process, and each of the inter-frame prediction process and the image reconstruction process may include a process for replacing pixel values ​​with predetermined values ​​based on parameters written in the above-mentioned header.

[0247] This allows inter-picture prediction processing and image reconstruction processing to be performed appropriately, as in the second embodiment, for example, and allows coding efficiency to be improved.

[0248] Furthermore, in encoding the image to be processed, the encoded image to be processed may be reconstructed, and the image obtained by splicing the reconstructed image to be processed with the other image described above may be stored in memory as a reference frame to be used in the inter-frame prediction process.

[0249] This allows a large image obtained by splicing to be used for inter prediction or motion compensation, as in the third embodiment, for example, thereby improving coding efficiency.

[0250] Note that the encoding devices of the above-described second to fourth embodiments encode videos including distorted images, videos including spliced ​​images, or videos including non-spliced ​​images from multiple views. However, the encoding device of the present disclosure may correct distortion of images included in the video to encode the video, or may not correct distortion. If distortion correction is not performed, the encoding device acquires videos including images whose distortion has been corrected in advance by another device and encodes the video. Similarly, the encoding device of the present disclosure may splice images from multiple views included in the video to encode the video, or may not splice images. If splicing is not performed, the encoding device acquires videos including images in which images from multiple views have been spliced ​​in advance by another device and encodes the video. Furthermore, the encoding device of the present disclosure may perform all or only part of the distortion correction. Furthermore, the encoding device of the present disclosure may perform all or only part of the splicing of images from multiple views.

[0251] FIG. 38 is a block diagram of a decoding device according to one embodiment of the present disclosure.

[0252] A decoding device 1600 according to one embodiment of the present disclosure is a device equivalent to the decoding device 200 of embodiment 1, and as shown in FIG. 38, includes an entropy decoding unit 1601, an inverse quantization unit 1602, an inverse transform unit 1603, a block memory 1604, a frame memory 1605, an intra prediction unit 1606, an inter prediction unit 1607, and an addition unit 1622.

[0253] The above-described components included in the decoding device 1600 perform the same processing as those in the above-described Embodiments 1 to 4, but do not perform processing using an adaptive video decoding tool. That is, the adder 1622, the intra predictor 1606, and the inter predictor 1607 perform decoding processing without using the above-described parameters included in the bitstream.

[0254] Furthermore, the decoding device 1600 acquires a bitstream, extracts coded video and parameters from the bitstream, and decodes the coded video without using the parameters. Specifically, the entropy decoding unit 1601 decodes the parameters from the bitstream. Note that the parameters may be written at any position in the bitstream.

[0255] Furthermore, each image (i.e., coded picture) included in the bitstream input to the decoding device 1600 may be a distortion-corrected image or a stitched image obtained by stitching together images from multiple views. A distortion-corrected image is a rectangular image obtained by correcting distortion in an image captured by a wide-angle lens such as a non-rectilinear lens. Such a decoding device 1600 decodes video including the distortion-corrected image or stitched image.

[0256] Here, the entropy decoding unit 1601, the inverse quantization unit 1602, the inverse transform unit 1603, the intra prediction unit 1606, the inter prediction unit 1607, and the addition unit 1622 are configured as, for example, a processing circuit. Furthermore, the block memory 1604 and the frame memory 1605 are configured as memories.

[0257] That is, the decoding device 1600 includes a processing circuit and a memory connected to the processing circuit. The processing circuit uses the memory to obtain a bitstream including an encoded image, decodes from the bitstream parameters related to at least one of a first process for correcting distortion of an image captured by a wide-angle lens and a second process for stitching together multiple images, and decodes the encoded image.

[0258] This allows the image being coded or decoded to be handled appropriately using the above parameters interpreted from the bitstream.

[0259] Here, the parameter may be interpreted from a header in a bitstream. Furthermore, the coded image may be decoded by applying a decoding process based on the parameter to each block included in the coded image. Here, the decoding process may include at least one of an inter-frame prediction process and an image reconstruction process.

[0260] As a result, for example, as in embodiment 2, by using inter-frame prediction processing and image reconstruction processing as adaptive video decoding tools, it is possible to appropriately decode coded images that are, for example, distorted images or spliced ​​images.

[0261] In addition, when interpreting the parameters, the parameters related to the above-mentioned second process are read from the header in the bitstream, and when decoding the coded image, for each block included in the coded image generated by coding the image obtained by the second process, the decoding process for that block may be omitted based on the parameters.

[0262] 21 and 22 in Embodiment 2, it is possible to omit decoding of blocks included in images that will not be looked at by the user in the near future, among a plurality of images included in a spliced ​​image that is an encoded image, thereby reducing the processing load.

[0263] In the parameter interpretation, at least one of the position and the camera angle of each of the plurality of cameras may be interpreted from a header in the bitstream as a parameter related to the second process. In the coded image decoding, a coded image generated by coding one of the plurality of images may be decoded, and the decoded coded image may be spliced ​​with other images of the plurality of images using the parameter interpreted from the header.

[0264] This allows a large image obtained by splicing to be used for inter prediction or motion compensation, as in the third embodiment, for example, and allows a bitstream with improved coding efficiency to be appropriately decoded.

[0265] In addition, in the parameter interpretation, at least one of a parameter indicating whether the image is captured with a wide-angle lens and a parameter related to distortion caused by the wide-angle lens may be interpreted from a header in the bitstream as a parameter related to the above-mentioned first process.In addition, in the decoding of the coded image, for each block included in the coded image generated by coding the image captured with the wide-angle lens, the block may be decoded by applying a decoding process based on the parameters interpreted from the header to the block.Here, the decoding process may include at least one of a motion vector prediction process and an intra-frame prediction process.

[0266] As a result, for example, as in the fourth embodiment, by using the motion vector prediction process and the intra-frame prediction process as adaptive video decoding tools, it is possible to appropriately decode a coded image that is, for example, a distorted image.

[0267] The decoding process may also include one of an inter-frame prediction process and an intra-frame prediction process, and the prediction process may include a wrapping process that arranges or rearranges multiple pixels included in an image.

[0268] This allows for correcting distortion in an encoded image and appropriately performing inter prediction processing based on the corrected image, as in, for example, embodiment 2. Also, as in, for example, embodiment 4, it is possible to perform intra prediction processing on a distorted encoded image and appropriately distort the resulting predicted image in accordance with the distorted encoded image. As a result, it is possible to appropriately predict an encoded image that is a distorted image.

[0269] The decoding process may also include inter-prediction processing, which may involve padding of the image over curved, diagonal or angular image boundaries using parameters interpreted from the header.

[0270] This allows inter-picture prediction processing to be performed appropriately, for example, as in the second embodiment.

[0271] In addition, the decoding process may include an inter-frame prediction process and an image reconstruction process, and each of the inter-frame prediction process and the image reconstruction process may include a process for replacing pixel values ​​with predetermined values ​​based on parameters read from the above-mentioned header.

[0272] This makes it possible to appropriately perform inter-picture prediction processing and image reconstruction processing, for example, as in the second embodiment.

[0273] In addition, when decoding an encoded image, the encoded image may be decoded, and an image obtained by splicing the decoded encoded image with the other image described above may be stored in memory as a reference frame to be used in inter-frame prediction processing.

[0274] This makes it possible to use a large image obtained by splicing together for inter-picture prediction or motion compensation, as in the third embodiment, for example.

[0275] Note that the decoding devices of the above-described second to fourth embodiments decode a bitstream including distorted images, a bitstream including spliced ​​images, or a bitstream including non-spliced ​​images from multiple views. However, the decoding device of the present disclosure may correct distortion of images included in the bitstream in order to decode the bitstream, or may not correct distortion. If distortion correction is not performed, the decoding device obtains a bitstream including images whose distortion has been corrected in advance by another device and decodes the bitstream. Similarly, the decoding device of the present disclosure may splice images from multiple views included in the bitstream in order to decode the bitstream, or may not splice images. If splicing is not performed, the decoding device obtains a bitstream including a large image generated in advance by splicing images from multiple views by another device and decodes the bitstream. Furthermore, the decoding device of the present disclosure may perform all or only part of the distortion correction. Furthermore, the decoding device of the present disclosure may perform all or only part of the splicing of images from multiple views.

[0276] (Other embodiments) In each of the above embodiments, each of the functional blocks can typically be realized by an MPU, memory, etc. Furthermore, the processing by each of the functional blocks is typically realized by a program execution unit such as a processor reading and executing software (programs) recorded on a recording medium such as a ROM. The software may be distributed by downloading, etc., or may be recorded on a recording medium such as a semiconductor memory and distributed. Of course, each functional block can also be realized by hardware (dedicated circuits).

[0277] Furthermore, the processing described in each embodiment may be realized by centralized processing using a single device (system), or may be realized by distributed processing using multiple devices. The processor that executes the program may be a single processor or multiple processors. That is, centralized processing or distributed processing may be performed.

[0278] The present invention is not limited to the above-described embodiments, and various modifications are possible, and these modifications are also included within the scope of the present invention.

[0279] Furthermore, here, we will explain application examples of the video coding method (image coding method) or video decoding method (image decoding method) shown in each of the above embodiments and a system using the same. The system is characterized by having an image coding device using the image coding method, an image decoding device using the image decoding method, and an image coding / decoding device that includes both. Other components of the system can be appropriately changed depending on the situation.

[0280] [Usage example] 39 is a diagram showing the overall configuration of a content supply system ex100 that provides a content distribution service. The area where communication services are provided is divided into cells of a desired size, and base stations ex106, ex107, ex108, ex109, and ex110, which are fixed wireless stations, are installed in each cell.

[0281] In this content supply system ex100, devices such as a computer ex111, a game console ex112, a camera ex113, a home appliance ex114, and a smartphone ex115 are connected to the Internet ex101 via an Internet service provider ex102 or a communication network ex104 and base stations ex106 to ex110. The content supply system ex100 may be configured to connect a combination of any of the above elements. The devices may be connected to each other directly or indirectly via a telephone network or short-range wireless communication, without using the base stations ex106 to ex110, which are fixed wireless stations. Furthermore, a streaming server ex103 is connected to devices such as the computer ex111, the game console ex112, the camera ex113, the home appliance ex114, and the smartphone ex115 via the Internet ex101, etc. Furthermore, the streaming server ex103 is connected to a terminal in a hotspot on an airplane ex117, etc., via a satellite ex116.

[0282] Note that wireless access points, hotspots, etc. may be used instead of the base stations ex106 to ex110. Furthermore, the streaming server ex103 may be directly connected to the communication network ex104 without going through the Internet ex101 or the Internet service provider ex102, or may be directly connected to an airplane ex117 without going through a satellite ex116.

[0283] The camera ex113 is a device capable of taking still images and videos, such as a digital camera. The smartphone ex115 is a smartphone, mobile phone, or PHS (Personal Handyphone System) that is compatible with mobile communication systems generally known as 2G, 3G, 3.9G, 4G, and 5G.

[0284] The home appliance ex118 is a refrigerator or an appliance included in a home fuel cell cogeneration system.

[0285] In the content supply system ex100, a terminal having a photographing function is connected to a streaming server ex103 via a base station ex106 or the like, thereby enabling live streaming and the like. In live streaming, a terminal (such as a computer ex111, a game console ex112, a camera ex113, a home appliance ex114, a smartphone ex115, or a terminal on an airplane ex117) performs the encoding process described in each of the above embodiments on still images or video content captured by a user using the terminal, multiplexes the video data obtained by encoding with audio data obtained by encoding audio corresponding to the video, and transmits the obtained data to the streaming server ex103. That is, each terminal functions as an image encoding device according to one aspect of the present invention.

[0286] Meanwhile, the streaming server ex103 streams the transmitted content data to the requesting client. The client is a computer ex111, a game console ex112, a camera ex113, a home appliance ex114, a smartphone ex115, a terminal on an airplane ex117, or the like, which is capable of decoding the encoded data. Each device that receives the distributed data decodes and plays back the received data. That is, each device functions as an image decoding device according to one aspect of the present invention.

[0287] [Distributed processing] The streaming server ex103 may also be multiple servers or multiple computers that process, record, and distribute data in a distributed manner. For example, the streaming server ex103 may be implemented as a CDN (Content Delivery Network), where content distribution is achieved through a network connecting numerous edge servers distributed around the world. In a CDN, a physically nearby edge server is dynamically assigned depending on the client. Content is then cached and distributed to that edge server, thereby reducing latency. Furthermore, if an error occurs or communication conditions change due to increased traffic, processing can be distributed among multiple edge servers, the distribution entity can be switched to another edge server, or distribution can be continued by bypassing the affected network portion, thereby achieving high-speed and stable distribution.

[0288] In addition to the distributed processing of the distribution itself, the encoding of captured data can be performed on each device, on the server side, or shared among devices. For example, encoding generally involves two processing loops. The first loop detects the image complexity or code size for each frame or scene. The second loop maintains image quality while improving encoding efficiency. For example, a device can perform the first encoding process, and the server that receives the content can perform the second encoding process, thereby improving content quality and efficiency while reducing the processing load on each device. In this case, if there is a request for near-real-time reception and decoding, the data encoded by a device can be received and played back on another device, enabling more flexible real-time distribution.

[0289] As another example, the camera ex113 or the like extracts features from an image, compresses the data related to the features as metadata, and transmits the data to the server. The server performs compression according to the meaning of the image, for example, by determining the importance of an object from the features and switching the quantization precision accordingly. The feature data is particularly effective in improving the accuracy and efficiency of motion vector prediction when the server recompresses the image. Alternatively, the terminal may perform simple encoding such as VLC (variable length coding), and the server may perform encoding with a heavy processing load such as CABAC (context-adaptive binary arithmetic coding).

[0290] As another example, in a stadium, shopping mall, factory, etc., there may be multiple pieces of video data that have been shot by multiple terminals of almost the same scene. In this case, using the multiple terminals that shot the video and, as necessary, other terminals and servers that did not shoot the video, encoding processes are assigned to each of them, for example, in units of GOPs (Group of Pictures), pictures, or tiles obtained by dividing a picture, for distributed processing. This reduces delays and achieves better real-time performance.

[0291] Furthermore, since multiple pieces of video data are of nearly the same scene, the server may manage and / or instruct the video data shot by each terminal to be mutually referenced. Alternatively, the server may receive encoded data from each terminal and change the reference relationships between multiple pieces of data, or correct or replace the pictures themselves and re-encode them. This allows for the generation of streams with improved quality and efficiency for each piece of data.

[0292] The server may also perform transcoding to change the encoding format of the video data before distributing it. For example, the server may convert MPEG-based encoding to VP-based encoding, or convert H.264 to H.265.

[0293] In this way, the encoding process can be performed by a terminal or one or more servers. Therefore, although the following uses terms such as "server" or "terminal" to refer to the entity performing the process, some or all of the processing performed by the server may be performed by the terminal, and some or all of the processing performed by the terminal may be performed by the server. The same applies to the decoding process.

[0294] [3D, multi-angle] In recent years, there has been an increasing trend to integrate and use images or videos of different scenes or the same scene taken from different angles by multiple devices such as cameras ex113 and / or smartphones ex115 that are nearly synchronized with each other. The videos taken by each device are integrated based on the relative positional relationship between the devices obtained separately, or on areas where feature points included in the videos match.

[0295] The server may not only encode 2D video, but also encode still images automatically or at a time specified by the user based on scene analysis of the video and transmit them to the receiving terminal. Furthermore, if the server can acquire the relative positional relationship between the capturing terminals, it can generate a 3D shape of the scene based on not only the 2D video but also images of the same scene captured from different angles. The server may also separately encode 3D data generated by point clouds, or may select or reconstruct images to be transmitted to the receiving terminal from images captured by multiple terminals based on the results of recognizing or tracking people or objects using the 3D data.

[0296] In this way, users can enjoy scenes by selecting any video corresponding to each camera device, or can enjoy content in which video from any viewpoint is extracted from 3D data reconstructed using multiple images or videos. Furthermore, like the video, sound may also be collected from multiple different angles, and the server may multiplex and transmit sound from a specific angle or space in accordance with the video.

[0297] In recent years, content that associates the real world with a virtual world, such as Virtual Reality (VR) and Augmented Reality (AR), has also become popular. In the case of VR images, the server creates viewpoint images for the right eye and left eye, and may perform encoding that allows reference between the viewpoint images using Multi-View Coding (MVC) or the like, or may encode them as separate streams without mutual reference. When decoding the separate streams, it is preferable to play them in synchronization with each other so that a virtual three-dimensional space is reproduced according to the user's viewpoint.

[0298] In the case of AR images, the server superimposes virtual object information in virtual space onto camera information in real space based on the 3D position or the user's viewpoint movement. The decoding device may acquire or store virtual object information and 3D data, generate a 2D image according to the user's viewpoint movement, and smoothly connect the images to create superimposed data. Alternatively, the decoding device may send the user's viewpoint movement to the server in addition to a request for virtual object information, and the server may create superimposed data based on the viewpoint movement received from the 3D data stored on the server, encode the superimposed data, and distribute it to the decoding device. Note that the superimposed data may also have an α value indicating transparency in addition to RGB, and the server may set the α value of parts other than the object created from the 3D data to 0, etc., to encode the parts in a transparent state. Alternatively, the server may generate data by setting a predetermined RGB value as the background, like a chromakey, and using the background color for parts other than the object.

[0299] Similarly, the decoding of distributed data may be performed by each client terminal, by the server, or by multiple terminals. For example, one terminal may first send a reception request to the server, and then other terminals may receive and decode content according to the request, after which the decoded signal is transmitted to a device with a display. By distributing the processing and selecting appropriate content regardless of the capabilities of the communication terminals themselves, high-quality data can be reproduced. As another example, large-sized image data may be received on a TV or other device, and only a portion of the picture, such as a tile into which the picture is divided, may be decoded and displayed on the viewer's personal device. This allows the viewer to share the overall picture while checking their own area of ​​responsibility or an area of ​​interest in more detail.

[0300] In the future, it is expected that content will be seamlessly received by switching the appropriate data for the current connection using delivery system standards such as MPEG-DASH in situations where multiple short-, medium-, or long-distance wireless communications are available, both indoors and outdoors. This will allow users to freely select and switch between decoding and display devices, such as their own devices, indoors and outdoors, in real time. Decoding can also be performed by switching between decoding and display devices based on user location information. This will enable users to display map information on the wall or ground of a neighboring building with an embedded display device while traveling to their destination. It is also possible to switch the bit rate of received data based on the accessibility of the encoded data on the network, such as if the encoded data is cached on a server that can be quickly accessed from the receiving device or copied to an edge server in a content delivery service.

[0301] [Scalable Coding] Regarding content switching, we will explain it using a scalable stream, as shown in Figure 40, compressed and encoded using the video encoding method described in each of the above embodiments. The server may have multiple streams with the same content but different qualities, but may also switch content by taking advantage of the characteristics of a temporally / spatially scalable stream, which is achieved by encoding the content separately into layers, as shown in the figure. In other words, the decoding side determines which layer to decode based on internal factors such as performance and external factors such as communication bandwidth, allowing the decoding side to freely switch between low-resolution and high-resolution content. For example, if a user wants to continue watching a video they were watching on their smartphone ex115 while on the go on a device such as an Internet TV after returning home, the device can simply decode the same stream up to different layers, thereby reducing the burden on the server.

[0302] Furthermore, in addition to the above-described scalability configuration in which pictures are coded for each layer and an enhancement layer exists above a base layer, the enhancement layer may include meta-information based on image statistics, etc., and the decoding side may generate high-quality content by super-resolving pictures in the base layer based on the meta-information. Super-resolution may mean either improving the signal-to-noise ratio at the same resolution or increasing the resolution. The meta-information may include information for specifying linear or nonlinear filter coefficients used in the super-resolution process, or information for specifying parameter values ​​in the filter process, machine learning, or least-squares calculation used in the super-resolution process.

[0303] Alternatively, a picture may be divided into tiles or the like according to the meaning of objects in the image, and the decoding side may select tiles to decode and decode only a portion of the area. Furthermore, by storing the object's attributes (such as a person, a car, or a ball) and its position in the video (such as a coordinate position in the same image) as meta information, the decoding side can identify the position of a desired object based on the meta information and determine the tile containing the object. For example, as shown in Figure 41, the meta information is stored using a data storage structure different from that of pixel data, such as an SEI message in HEVC. This meta information indicates, for example, the position, size, or color of the main object.

[0304] Furthermore, meta information may be stored in units consisting of multiple pictures, such as streams, sequences, or random access units, which allows the decoding side to obtain the time when a specific person appears in the video, and by combining this with information in units of pictures, it is possible to identify the picture in which the object exists and the position of the object within the picture.

[0305] [Webpage optimization] FIG. 42 is a diagram showing an example of a web page display screen on a computer ex111 or the like. FIG. 43 is a diagram showing an example of a web page display screen on a smartphone ex115 or the like. As shown in FIGS. 42 and 43, a web page may include multiple link images that are links to image content, and the appearance of the web page may differ depending on the device used to view the page. When multiple link images are visible on the screen, the display device (decoding device) may display a still image or I-picture contained in each content as a link image, display a video such as a GIF animation using multiple still images or I-pictures, or receive only the base layer to decode and display the video, until the user explicitly selects a link image, or until the link image approaches the center of the screen or until the entire link image is within the screen.

[0306] When a link image is selected by a user, the display device decodes the base layer with the highest priority. If the HTML constituting the web page contains information indicating that the content is scalable, the display device may decode up to the enhancement layer. To ensure real-time performance, before a selection is made or when the communication bandwidth is very limited, the display device decodes and displays only forward-referenced pictures (I-pictures, P-pictures, and forward-reference-only B-pictures), thereby reducing the delay between the decoding time of the first picture and the display time (the delay from the start of content decoding to the start of display). Alternatively, the display device may intentionally ignore the picture reference relationships and roughly decode all B-pictures and P-pictures using forward reference, and then perform normal decoding as the number of received pictures increases over time.

[0307] [Autonomous driving] Furthermore, when transmitting and receiving still image or video data such as 2D or 3D map information for automatic driving or driving assistance of a vehicle, the receiving terminal may receive weather or construction information as meta information in addition to image data belonging to one or more layers, and may associate and decode these. Note that the meta information may belong to a layer, or may simply be multiplexed with the image data.

[0308] In this case, since a vehicle, drone, airplane, etc. including a receiving terminal moves, the receiving terminal can realize seamless reception and decoding while switching between base stations ex106 to ex110 by transmitting the location information of the receiving terminal at the time of a reception request. Also, the receiving terminal can dynamically switch how much meta information to receive or how much to update map information depending on the user's selection, user situation, or communication bandwidth status.

[0309] In this way, in the content supply system ex100, the client can receive, decode, and play back the encoded information sent by the user in real time.

[0310] [Distribution of personal content] Furthermore, the content supply system ex100 allows not only high-quality, long-duration content from video distribution companies, but also unicast or multicast distribution of low-quality, short-duration content from individuals. It is expected that such personal content will continue to increase in the future. To improve the quality of personal content, the server may perform editing before encoding. This can be achieved, for example, with the following configuration.

[0311] During shooting, either in real time or after accumulating the footage, the server performs recognition processing such as detecting shooting errors, scene search, semantic analysis, and object detection from the original image or encoded data. Based on the recognition results, the server manually or automatically corrects out-of-focus or camera shake, deletes less important scenes (e.g., scenes with lower brightness or out-of-focus compared to other pictures), emphasizes object edges, changes color, and performs other editing. The server then encodes the edited data based on the editing results. It is also known that viewing rates decrease if the shooting time is too long. Therefore, the server may automatically clip not only less important scenes as described above but also scenes with little movement, based on the image processing results, so that the content falls within a specific time range depending on the shooting time. Alternatively, the server may generate and encode a digest based on the results of the semantic analysis of the scene.

[0312] In some cases, personal content may contain content that infringes copyright, moral rights, or portrait rights, or may cause the scope of sharing to exceed the intended scope, resulting in inconvenience to individuals. Therefore, for example, the server may intentionally defocus images of people's faces on the periphery of the screen or the interior of a house before encoding. The server may also recognize whether the image to be encoded contains the face of a person other than a pre-registered person, and if so, perform processing such as blurring the face. Alternatively, as pre- or post-processing before encoding, the user may specify a person or background area they wish to modify in the image for copyright or other reasons, and the server may replace the specified area with another image or blur the focus. For a person, the server may track the person in the video and replace the image of the face.

[0313] Furthermore, because viewing personal content with small data volumes requires real-time performance, the decoding device first receives the base layer as a top priority, and then decodes and plays it back, depending on the bandwidth. The decoding device may also receive an enhancement layer during this time, and if the content is played back more than twice, such as when playback is looped, it may play back high-quality video, including the enhancement layer. A stream that has undergone scalable encoding in this way can provide an experience in which the video appears rough when not selected or when viewing begins, but gradually becomes smoother and the image quality improves. In addition to scalable encoding, a similar experience can also be provided by configuring a single stream consisting of a rough stream played the first time and a second stream that is encoded with reference to the first video.

[0314] [Other use cases] Furthermore, these encoding or decoding processes are generally performed by the LSIex500 possessed by each terminal. The LSIex500 may be a single chip or may be configured with multiple chips. It is also possible to incorporate video encoding or decoding software into some kind of recording medium (such as a CD-ROM, flexible disk, or hard disk) that can be read by the computer ex111, and perform the encoding or decoding process using that software. Furthermore, if the smartphone ex115 is equipped with a camera, video data captured by the camera may be transmitted. This video data is data that has been encoded by the LSIex500 possessed by the smartphone ex115.

[0315] The LSIex500 may be configured to download and activate application software. In this case, the terminal first determines whether it supports the content encoding method or has the capability to execute a specific service. If the terminal does not support the content encoding method or does not have the capability to execute a specific service, the terminal downloads the codec or application software and then acquires and plays the content.

[0316] Furthermore, at least one of the video encoding device (image encoding device) or video decoding device (image decoding device) of each of the above embodiments can be incorporated into a digital broadcasting system, not limited to the content supply system ex100 via the Internet ex101. Since multiplexed data in which video and audio are multiplexed is transmitted and received over broadcast radio waves using a satellite or the like, the content supply system ex100 is more suited to multicast than the content supply system ex100, which is more suited to unicast, but similar applications are possible with regard to encoding and decoding processes.

[0317] [Hardware configuration] FIG. 44 is a diagram illustrating a smartphone ex115. FIG. 45 is a diagram illustrating an example configuration of the smartphone ex115. The smartphone ex115 includes an antenna ex450 for transmitting and receiving radio waves to and from the base station ex110, a camera unit ex465 capable of capturing video and still images, and a display unit ex458 for displaying video captured by the camera unit ex465 and decoded data of the video and other images received by the antenna ex450. The smartphone ex115 further includes an operation unit ex466 such as a touch panel, an audio output unit ex457 such as a speaker for outputting voice or sound, an audio input unit ex456 such as a microphone for inputting voice, a memory unit ex467 capable of storing encoded data or decoded data such as captured video or still images, recorded voice, received video or still images, and email, and a slot unit ex464 that serves as an interface with a SIM ex468 for identifying users and authenticating access to various data, including networks. In addition, an external memory may be used instead of the memory unit ex467.

[0318] In addition, a main control unit ex460 that comprehensively controls the display unit ex458 and operation unit ex466, etc., is connected to a power supply circuit unit ex461, an operation input control unit ex462, a video signal processing unit ex455, a camera interface unit ex463, a display control unit ex459, a modulation / demodulation unit ex452, a multiplexing / separation unit ex453, an audio signal processing unit ex454, a slot unit ex464, and a memory unit ex467 via a bus ex470.

[0319] When the power key is turned on by a user, the power supply circuit unit ex461 supplies power from the battery pack to each unit, thereby starting up the smartphone ex115 into an operational state.

[0320] The smartphone ex115 processes calls, data communications, and other communications under the control of a main control unit ex460, which includes a CPU, ROM, RAM, and the like. During calls, the audio signal collected by the audio input unit ex456 is converted into a digital audio signal by the audio signal processing unit ex454, which then undergoes spectrum spread processing by the modulation / demodulation unit ex452, digital-to-analog conversion processing and frequency conversion processing by the transmission / reception unit ex451, and then transmitted via the antenna ex450. The received data is amplified, frequency-converted, and analog-to-digital converted, then subjected to spectrum despreading processing by the modulation / demodulation unit ex452, and converted into an analog audio signal by the audio signal processing unit ex454, which then outputs the amplified data from the audio output unit ex457. During data communications mode, text, still images, or video data is sent to the main control unit ex460 via the operation input control unit ex462 by operating the operation unit ex466, etc., of the main unit, and similar transmission and reception processing is performed. When transmitting video, still images, or video and audio in the data communication mode, the video signal processing unit ex455 compression-encodes the video signal stored in the memory unit ex467 or the video signal input from the camera unit ex465 using the video encoding method described in each of the above embodiments, and sends the encoded video data to the multiplexing / demultiplexing unit ex453. The audio signal processing unit ex454 also encodes the audio signal picked up by the audio input unit ex456 while the camera unit ex465 is capturing video, still images, etc., and sends the encoded audio data to the multiplexing / demultiplexing unit ex453. The multiplexing / demultiplexing unit ex453 multiplexes the encoded video data and encoded audio data using a predetermined method, and modulates and converts the data in the modulation / demodulation unit (modulation / demodulation circuit unit) ex452 and the transmission / reception unit ex451 before transmitting the data via the antenna ex450.

[0321] When receiving video attached to an email or chat, or video linked to a web page, etc., the multiplexed data received via the antenna ex450 is decoded by the multiplexing / separation unit ex453, which separates the multiplexed data into a video data bitstream and an audio data bitstream. The multiplexing / separation unit ex453 then supplies the encoded video data to the video signal processing unit ex455 via the synchronization bus ex470, and supplies the encoded audio data to the audio signal processing unit ex454. The video signal processing unit ex455 decodes the video signal using a video decoding method corresponding to the video encoding method described in each of the above embodiments, and displays the video or still image included in the linked video file on the display unit ex458 via the display control unit ex459. The audio signal processing unit ex454 decodes the audio signal, and the audio is output from the audio output unit ex457. Note that with the widespread use of real-time streaming, audio playback may be socially inappropriate depending on the user's circumstances. Therefore, a configuration that initially plays only the video data without playing the audio signal is desirable. The audio may be played in synchronization only when the user performs an operation such as clicking on the video data.

[0322] Although the smartphone ex115 has been used as an example, three types of implementation are possible for the terminal: a transmitting / receiving terminal having both an encoder and a decoder, a transmitting terminal having only an encoder, and a receiving terminal having only a decoder. Furthermore, in the digital broadcasting system, multiplexed data in which music data and the like are multiplexed onto video data is received or transmitted, but the multiplexed data may also include text data related to the video in addition to audio data, or the video data itself may be received or transmitted instead of the multiplexed data.

[0323] While the main control unit ex460, which includes a CPU, controls the encoding and decoding processes, devices often also include a GPU. Therefore, a configuration is possible in which a memory shared by the CPU and GPU, or a memory with addresses managed for common use, is used to take advantage of the GPU's performance and process a large area at once. This shortens encoding time, ensures real-time performance, and achieves low latency. It is particularly efficient to perform motion estimation, deblocking filtering, SAO (Sample Adaptive Offset), and transformation and quantization processes at a picture level or other unit in the GPU rather than the CPU. [Industrial Applicability]

[0324] The present disclosure can be applied to devices such as televisions, digital video recorders, car navigation systems, mobile phones, digital cameras, or digital video cameras, which serve as encoding devices that encode images or decoding devices that decode encoded images. [Explanation of symbols]

[0325] 1500 encoding device 1501 Conversion Unit 1502 Quantization section 1503 Inverse quantization section 1504 Inverse conversion unit 1505 Block Memory 1506 Frame Memory 1507 Intra prediction unit 1508 Inter Prediction Unit 1509 Entropy coding unit 1521 Subtraction section 1522 Addition section 1600 Decoding Device 1601 Entropy Decoding Unit 1602 Inverse quantization section 1603 Inverse conversion unit 1604 Block Memory 1605 frame memory 1606 Intra prediction unit 1607 Inter Prediction Unit 1622 Addition section

Claims

1. a processing circuit; a memory connected to the processing circuitry; The processing circuitry uses the memory to: A stitched image is generated by stitching multiple images together. obtaining a parameter that identifies an empty area in the stitched image that is generated by the stitching process; performing inter-picture prediction processing on the stitched image; writing said parameters into a bitstream; generating the bitstream by arithmetic coding; the inter-picture prediction process includes a padding process of replacing pixel values ​​in the empty area with values ​​in another area in the spliced ​​image that is not the empty area, the value of the other region is the value of the pixel closest to the empty region, The inter-picture prediction process is performed in units of image blocks. Encoding device.

2. a processing circuit; a memory connected to the processing circuitry; The processing circuitry uses the memory to: Arithmetically decoding multiple images from the bitstream; obtaining, from the bitstream, a parameter specifying a free area generated by a joining process that joins the plurality of images; By performing the joining process, a joined image is generated; performing inter-picture prediction processing on the stitched image; the inter-picture prediction process includes a padding process of replacing pixel values ​​in the empty area with values ​​in another area in the spliced ​​image that is not the empty area, the value of the other region is the value of the pixel closest to the empty region, The inter-picture prediction process is performed in units of image blocks. Decryption device.

Images