Video decoding apparatus, video encoding apparatus, and computer-readable recording medium

Abstract

To provide a moving image decoding device for executing PROF prediction.SOLUTION: Derive an affine prediction parameter from the motion vectors of the plurality of control points, derive a first motion vector difference array from the affine prediction parameter, and clip the first motion vector difference array to derive a second motion vector difference array; An affine prediction unit configured to derive a first variable for calculating a gradient from a prediction array sample array, derive a second variable from a second motion vector difference array and the first variable for calculating the gradient, and derive a prediction sample value from the prediction array sample array and the second variable, wherein the first motion vector difference array is clipped in a range using a fixed value independent of a pixel bit depth, and the fixed value is equal to 32.SELECTED DRAWING: Figure 13

Description

[Technical Field]

[0001] FIELD Embodiments of the present invention relate to a predicted image generating device, a video decoding device, and a video encoding device. [Background technology]

[0002] In order to efficiently transmit or record moving images, a moving image encoding device is used that generates encoded data by encoding moving images, and a moving image decoding device is used that generates decoded images by decoding the encoded data.

[0003] Specific video encoding methods include, for example, H.264 / AVC and HEVC (High-Efficiency Video Coding) methods.

[0004] In such a video coding method, images (pictures) constituting a video are managed in a hierarchical structure consisting of slices obtained by dividing the images, coding tree units (CTUs) obtained by dividing the slices, coding units (sometimes called coding units (CUs)) obtained by dividing the coding tree units, and transform units (TUs) obtained by dividing the coding units, and are coded / decoded for each CU.

[0005] In such video coding methods, a predicted image is usually generated based on a locally decoded image obtained by encoding / decoding an input image, and the predicted image is subtracted from the input image (original image) to obtain a prediction error (sometimes called a "difference image" or "residual image"), which is then coded. Methods for generating predicted images include inter-frame prediction (inter-prediction) and intra-frame prediction (intra-prediction).

[0006] Non-Patent Document 1 is another recent example of a video encoding and decoding technique. Non-Patent Document 1 describes a number of merge predictions, one of which is triangle prediction, in which a current block is divided into triangular regions and a different inter prediction is performed for each region. Dividing the current block into shapes other than rectangular enables more accurate prediction even for complex textures, improving encoding efficiency. [Prior art documents] [Non-patent literature]

[0007] [Non-Patent Document 1] "Versatile Video Coding (Draft 6)", JVET-O2001-vE, Joint Video Exploration Team (JVET) of ITU-T SG 16 WP 3 and ISO / IEC JTC 1 / SC 29 / WG 11 Summary of the Invention [Problem to be solved by the invention]

[0008] Non-Patent Document 1 discloses the techniques of PROF (Prediction Refinement with Optical Flow), Triangle prediction, and Weighted prediction. However, the relationship between the two prediction methods, PROF and Weighted prediction, and Triangle prediction and Weighted prediction, is not clear, and there is a problem in that it is not clearly defined whether they can be executed simultaneously, or if not, how they should be distinguished when executed.

[0009] Therefore, the present invention has been made in consideration of the above-mentioned problems, and its object is to provide a video decoding device, an image coding device, and a predicted image generation method that realize a method of exclusively executing one of two prediction methods, or a method of simultaneously executing two prediction methods. [Means for solving the problem]

[0010] A video decoding device according to one embodiment of the present invention includes an affine prediction unit that derives affine prediction parameters from motion vectors of a plurality of control points, derives a first motion vector differential array from the affine prediction parameters, clips the first motion vector differential array to derive a second motion vector differential array, derives a first variable for calculating a gradient from a prediction array sample array, derives a second variable from the second motion vector differential array and the first variable for calculating the gradient, and derives predicted sample values ​​from the prediction array sample array and the second variable, wherein the first motion vector differential array is clipped within a range using a fixed value that is independent of pixel bit length, and the fixed value is equal to 32.

[0011] A video encoding device according to one embodiment of the present invention includes an affine prediction unit that derives affine prediction parameters from motion vectors of a plurality of control points, derives a first motion vector differential array from the affine prediction parameters, clips the first motion vector differential array to derive a second motion vector differential array, derives a first variable for calculating a gradient from a prediction array sample array, derives a second variable from the second motion vector differential array and the first variable for calculating the gradient, and derives predicted sample values ​​from the prediction array sample array and the second variable, wherein the first motion vector differential array is clipped within a range using a fixed value that is independent of pixel bit length, and the fixed value is equal to 32.

[0012] A computer-readable recording medium according to one embodiment of the present invention is a computer-readable recording medium having recorded thereon a program for causing a computer to decode a moving image, the program causing the computer to execute the steps of: deriving affine prediction parameters from motion vectors of a plurality of control points; deriving a first motion vector differential array from the affine prediction parameters; clipping the first motion vector differential array to derive a second motion vector differential array; deriving a first variable for calculating a gradient from a prediction array sample array; deriving a second variable from the second motion vector differential array and the first variable for calculating a gradient; and deriving a prediction sample value from the prediction array sample array and the second variable, wherein the first motion vector differential array is clipped within a range using a fixed value that is independent of the pixel bit length, and the fixed value is equal to 32. [Effects of the Invention]

[0013] According to one aspect of the present invention, it is possible to provide a video decoding device, or an image coding device and a predicted image generation method that realizes a method of exclusively executing one of two prediction methods, or a method of simultaneously executing two prediction methods, without reducing coding efficiency. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a schematic diagram showing the configuration of an image transmission system according to an embodiment of the present invention. [Figure 2] 1 is a diagram showing the configuration of a transmitting device equipped with a video encoding device according to this embodiment, and a receiving device equipped with a video decoding device, where (a) shows the transmitting device equipped with the video encoding device, and (b) shows the receiving device equipped with the video decoding device. [Figure 3] 1A and 1B are diagrams showing the configurations of a recording device equipped with a video encoding device according to an embodiment of the present invention, and a playback device equipped with a video decoding device, where (a) shows the configuration of a recording device equipped with a video encoding device, and (b) shows the configuration of a playback device equipped with a video decoding device. [Figure 4] FIG. 2 is a diagram showing a hierarchical structure of data in an encoded stream. [Figure 5] FIG. 10 is a diagram illustrating an example of division of a CTU. [Figure 6] FIG. 1 is a conceptual diagram illustrating an example of a reference picture and a reference picture list. [Figure 7] FIG. 1 is a schematic diagram illustrating a configuration of a video decoding device. [Figure 8] 10 is a flowchart illustrating a schematic operation of the video decoding device. [Figure 9] FIG. 10 is a schematic diagram showing the configuration of an inter-prediction parameter derivation unit. [Figure 10] 1 is a schematic diagram showing the configuration of a merge prediction parameter derivation unit and an AMVP prediction parameter derivation unit. [Figure 11] FIG. 10 is a diagram showing affine prediction motion vectors spMvLX[xi][yi]. [Figure 12] FIG. 2 is a schematic diagram showing the configuration of a PROF unit. [Figure 13] FIG. 10 is a diagram illustrating application conditions for PROF processing. [Figure 14] FIG. 10 is a schematic diagram showing the configuration of an inter-prediction image generation unit. [Figure 15] FIG. 1 is a block diagram showing a configuration of a video encoding device. [Figure 16] FIG. 10 is a schematic diagram showing the configuration of an inter-prediction parameter encoding unit. [Figure 17] FIG. 10 is a diagram illustrating a triangle prediction. [Figure 18] FIG. 2 is a diagram illustrating a configuration of a triangle synthesis unit according to the present embodiment. [Figure 19] FIG. 10 is a diagram illustrating the syntax of coding parameters for weighted prediction. [Figure 20] FIG. 10 is a diagram illustrating the syntax of coding parameters for weighted prediction. DETAILED DESCRIPTION OF THE INVENTION

[0015] (First embodiment) Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0016] FIG. 1 is a schematic diagram showing the configuration of an image transmission system 1 according to this embodiment.

[0017] The image transmission system 1 is a system that transmits an encoded stream obtained by encoding a target image, decodes the transmitted encoded stream, and displays the image. The image transmission system 1 includes a video encoding device (image encoding device) 11, a network 21, a video decoding device (image decoding device) 31, and a video display device (image display device) 41.

[0018] An image T is input to the video encoding device 11 .

[0019] The network 21 transmits the coded stream Te generated by the video coding device 11 to the video decoding device 31. The network 21 is the Internet, a wide area network (WAN), a local area network (LAN), or a combination of these. The network 21 is not necessarily limited to a bidirectional communication network, but may also be a unidirectional communication network that transmits broadcast waves such as terrestrial digital broadcasting and satellite broadcasting. Furthermore, the network 21 may be replaced by a storage medium on which the coded stream Te is recorded, such as a DVD (Digital Versatile Disc: registered trademark) or a BD (Blue-ray Disc: registered trademark).

[0020] The video decoding device 31 decodes each of the coded streams Te transmitted over the network 21, and generates one or more decoded images Td.

[0021] The moving image display device 41 displays all or part of one or more decoded images Td generated by the moving image decoding device 31. The moving image display device 41 includes, for example, a display device such as a liquid crystal display or an organic EL (Electro-luminescence) display. Examples of the form of the display include stationary, mobile, HMD, etc. Also, when the moving image decoding device 31 has high processing power, an image with high image quality is displayed, and when it has only lower processing power, an image that does not require high processing power and display ability is displayed.

[0022] <Operator> The operators used in this specification are described below.

[0023] >> is a right bit shift, << is a left bit shift, & is a bitwise AND, | is a bitwise OR, |= is an OR assignment operator, and || represents a logical OR.

[0024] x?y:z is a ternary operator that takes y when x is true (non-zero) and z when x is false (0).

[0025] Clip3(a, b, c) is a function that clips c to a value between a and b (inclusive). If c < a, it returns a; if c > b, it returns b; otherwise, it returns c (where a <= b).

[0026] abs(a) is a function that returns the absolute value of a.

[0027] Int(a) is a function that returns the integer value of a.

[0028] floor(a) is a function that returns the largest integer less than or equal to a.

[0029] ceil(a) is a function that returns the smallest integer greater than or equal to a.

[0030] a / d represents the division of a by d (truncating the decimal part).

[0031] <Structure of the coded stream Te> Before proceeding to a detailed description of the video encoding device 11 and video decoding device 31 according to this embodiment, the data structure of the encoded stream Te generated by the video encoding device 11 and decoded by the video decoding device 31 will be described.

[0032] 4 is a diagram showing a hierarchical structure of data in a coded stream Te. The coded stream Te illustratively includes a sequence and multiple pictures constituting the sequence. (a) to (f) of FIG. 4 show a coded video sequence that defines the sequence SEQ, a coded picture that defines the picture PICT, a coded slice that defines the slice S, coded slice data that defines the slice data, a coding tree unit included in the coded slice data, and a coding unit included in the coding tree unit, respectively.

[0033] (Coded Video Sequence) The coded video sequence defines a set of data that the video decoding device 31 refers to in order to decode the sequence SEQ to be processed. As shown in Fig. 4, the sequence SEQ includes a video parameter set (Video Parameter Set), a sequence parameter set SPS (Sequence Parameter Set), a picture parameter set PPS (Picture Parameter Set), an adaptation parameter set (APS), a picture PICT, and supplemental enhancement information SEI (Supplemental Enhancement Information).

[0034] The video parameter set VPS specifies a set of coding parameters common to multiple videos composed of multiple layers, as well as a set of coding parameters related to multiple layers included in the video and each individual layer.

[0035] The sequence parameter set SPS defines a set of coding parameters that the video decoding device 31 references to decode the target sequence. For example, the width and height of a picture are defined. Note that there may be multiple SPSs. In this case, one of the multiple SPSs is selected from the PPS.

[0036] The picture parameter set PPS defines a set of coding parameters that the video decoding device 31 references to decode each picture in the target sequence. For example, the picture parameter set PPS includes a reference value of the quantization width used in decoding the picture (pic_init_qp_minus26) and a flag indicating the application of weighted prediction (weighted_pred_flag). Note that there may be multiple PPSs. In this case, one of the multiple PPSs is selected for each picture in the target sequence.

[0037] (encoded picture) A coded picture defines a set of data that the video decoding device 31 refers to in order to decode a picture PICT to be processed. As shown in FIG. 4, the picture PICT includes slices 0 to NS-1 (NS is the total number of slices included in the picture PICT).

[0038] In the following description, when there is no need to distinguish between slices 0 to NS-1, the subscripts of the symbols may be omitted. The same applies to other data to which subscripts are added that are included in the coded stream Te described below.

[0039] (encoded slice) A coded slice defines a set of data that the video decoding device 31 refers to in order to decode a target slice S. As shown in Fig. 4, a slice includes a slice header and slice data.

[0040] The slice header includes a group of coding parameters that the video decoding device 31 refers to in order to determine a decoding method for the current slice. Slice type designation information (slice_type) that designates the slice type is an example of a coding parameter included in the slice header.

[0041] Slice types that can be specified by the slice type specification information include (1) an I slice that uses only intra prediction during encoding, (2) a P slice that uses unidirectional prediction or intra prediction during encoding, and (3) a B slice that uses unidirectional prediction, bidirectional prediction, or intra prediction during encoding. Note that inter prediction is not limited to uni-prediction or bi-prediction, and a predicted image may be generated using more reference pictures. Hereinafter, P and B slices refer to slices that include blocks that can use inter prediction.

[0042] Note that the slice header may include a reference to a picture parameter set PPS (pic_parameter_set_id).

[0043] (encoded slice data) The coded slice data defines a set of data that the video decoding device 31 references in order to decode the slice data to be processed. As shown in Fig. 4(d), the slice data includes a CTU. A CTU is a block of a fixed size (e.g., 64x64) that constitutes a slice, and is also called a Largest Coding Unit (LCU).

[0044] (coding tree unit) 4 defines a set of data that the video decoding device 31 references in order to decode a CTU to be processed. The CTU is divided into coding units (CUs), which are basic units of encoding processing, by recursive quad tree (QT) division, binary tree (BT) division, or ternary tree (TT) division. BT division and TT division are collectively called multi-tree (MT) division. A node in a tree structure obtained by recursive quad tree division is called a coding node. Intermediate nodes in a quad tree, binary tree, or ternary tree are coding nodes, and the CTU itself is defined as the top-level coding node.

[0045] The CT includes, as CT information, a CU split flag (split_cu_flag) indicating whether CT splitting is performed, a QT split flag (qt_split_cu_flag) indicating whether QT splitting is performed, an MT split direction (mtt_split_cu_vertical_flag) indicating the split direction of MT splitting, and an MT split type (mtt_split_cu_binary_flag) indicating the split type of MT splitting. split_cu_flag, qt_split_cu_flag, mtt_split_cu_vertical_flag, and mtt_split_cu_binary_flag are transmitted for each encoding node.

[0046] If split_cu_flag is 1 and qt_split_cu_flag is 1, the coding node is split into four coding nodes (FIG. 5(b)).

[0047] When split_cu_flag is 0, the coding node is not split and has one CU as a node (Figure 5(a)). The CU is the terminal node of the coding node and is not split any further. The CU is the basic unit of the coding process.

[0048] When split_cu_flag is 1 and qt_split_cu_flag is 0, the coding node is MT-split as follows: When mtt_split_cu_binary_flag is 1, if mtt_split_cu_vertical_flag is 0, the coding node is split horizontally into two coding nodes (Figure 5(d)), and when mtt_split_cu_vertical_flag is 1, the coding node is split vertically into two coding nodes (Figure 5(c)). When mtt_split_cu_binary_flag is 0, if mtt_split_cu_vertical_flag is 0, the coding node is split horizontally into three coding nodes (Figure 5(f)), and when mtt_split_cu_vertical_flag is 1, the coding node is split vertically into three coding nodes (Figure 5(e)). These are shown in Figure 5(g).

[0049] Different trees may be used for luminance and chrominance. The tree type is indicated by treeType. For example, if a common tree is used for luminance (Y, cIdx=0) and chrominance (Cb / Cr, cIdx=1,2), the common single tree is indicated by treeType=SINGLE_TREE. If two different trees (DUAL trees) are used for luminance and chrominance, the luminance tree is indicated by treeType=DUAL_TREE_LUMA and the chrominance tree is indicated by treeType=DUAL_TREE_CHROMA.

[0050] (encoding unit) 4 defines a set of data that the video decoding device 31 references in order to decode a coding unit to be processed. Specifically, a CU is composed of a CU header CUH, prediction parameters, transformation parameters, quantization transformation coefficients, etc. The CU header defines a prediction mode, etc.

[0051] Prediction processing may be performed in units of CUs, or in units of sub-CUs obtained by further dividing a CU. If the sizes of a CU and a sub-CU are the same, there is one sub-CU in the CU. If the size of a CU is larger than the size of a sub-CU, the CU is divided into sub-CUs. For example, if the CU is 8x8 and the sub-CU is 4x4, the CU is divided into four sub-CUs, divided horizontally by two and vertically by two.

[0052] There are two types of prediction (prediction modes): intra prediction and inter prediction. Intra prediction is a prediction within the same picture, while inter prediction refers to a prediction process performed between different pictures (for example, between display times or between layer images).

[0053] The transform and quantization processes are performed in units of CU, but the quantized transform coefficients may be entropy coded in units of sub-blocks such as 4x4.

[0054] (Prediction parameters) The predicted image is derived from prediction parameters associated with the block, which include intra-prediction and inter-prediction parameters.

[0055] Hereinafter, prediction parameters of inter prediction will be described. The inter prediction parameters are composed of prediction list usage flags predFlagL0 and predFlagL1, reference picture indices refIdxL0 and refIdxL1, and motion vectors mvL0 and mvL1. predFlagL0 and predFlagL1 are flags indicating whether or not a reference picture list (L0 list, L1 list) is used, and when the value is 1, the corresponding reference picture list is used. Note that in this specification, when a "flag indicating whether XX is true" is used, a flag other than 0 (for example, 1) is considered to be XX, and 0 is considered to be not XX, and in logical negation, logical product, etc., 1 is treated as true and 0 is treated as false (the same applies below). However, in an actual device or method, other values ​​may be used as true and false values.

[0056] Syntax elements for deriving inter-prediction parameters include, for example, an affine flag affine_flag used in merge mode, a merge flag merge_flag, a merge index merge_idx, an MMVD flag mmvd_flag, an inter-prediction identifier inter_pred_idc for selecting a reference picture to be used in AMVP mode, a reference picture index refIdxLX, a prediction vector index mvp_LX_idx for deriving a motion vector, a difference vector mvdLX, and a motion vector precision mode amvr_mode.

[0057] (Reference Picture List) A reference picture list is a list of reference pictures stored in the reference picture memory 306. FIG. 6 is a conceptual diagram showing an example of reference pictures and reference picture lists. In FIG. 6(a), each rectangle represents a picture, each arrow represents the reference relationship between pictures, the horizontal axis represents time, I, P, and B in the rectangle represent intra-pictures, uni-predictive pictures, and bi-predictive pictures, respectively, and the numbers in the rectangle represent the decoding order. As shown in the figure, the decoding order of pictures is I0, P1, B2, B3, and B4, and the display order is I0, B3, B2, B4, and P1. FIG. 6(b) shows an example of a reference picture list for picture B3 (the target picture). A reference picture list is a list representing candidate reference pictures, and one picture (slice) may have one or more reference picture lists. In the example shown in the figure, the target picture B3 has two reference picture lists: an L0 list RefPicList0 and an L1 list RefPicList1. In each CU, refIdxLX specifies which picture in the reference picture list RefPicListX (X=0 or 1) to actually reference. The diagram shows an example where refIdxL0=2 and refIdxL1=0. Note that LX is a notation method used when there is no distinction between L0 prediction and L1 prediction; hereinafter, parameters for the L0 list and parameters for the L1 list will be distinguished by replacing LX with L0 or L1.

[0058] (Merge prediction and AMVP prediction) Prediction parameter decoding (encoding) methods include merge prediction mode and AMVP (Advanced Motion Vector Prediction) mode, and merge_flag is a flag for distinguishing between them. Merge prediction mode is a mode in which the prediction list usage flag predFlagLX, reference picture index refIdxLX, and motion vector mvLX are not included in the encoded data, but are derived from prediction parameters of already processed neighboring blocks, etc. AMVP mode is a mode in which inter_pred_idc, refIdxLX, and mvLX are included in the encoded data. Note that mvLX is encoded as mvp_LX_idx, which identifies the prediction vector mvpLX, and a difference vector mvdLX. In addition to merge prediction mode, affine prediction mode and MMVD prediction mode may also be used.

[0059] inter_pred_idc is a value indicating the type and number of reference pictures, and takes one of the values ​​PRED_L0, PRED_L1, or PRED_BI. PRED_L0 and PRED_L1 indicate uni-prediction using one reference picture managed in the L0 list and L1 list, respectively. PRED_BI indicates bi-prediction using two reference pictures managed in the L0 list and L1 list.

[0060] The merge_idx is an index indicating which prediction parameter is to be used as the prediction parameter for the current block from among prediction parameter candidates (merge candidates) derived from blocks for which processing has been completed.

[0061] (motion vector) mvLX indicates the amount of shift between blocks on two different pictures. The predicted vector and differential vector related to mvLX are called mvpLX and mvdLX, respectively.

[0062] (Inter prediction identifier inter_pred_idc and prediction list usage flag predFlagLX) The relationship between inter_pred_idc, predFlagL0, and predFlagL1 is as follows, and they can be converted to each other.

[0063] inter_pred_idc = (predFlagL1<<1)+predFlagL0 predFlagL0 = inter_pred_idc & 1 predFlagL1 = inter_pred_idc >> 1 Note that the inter prediction parameters may use a prediction list usage flag or an inter prediction identifier. Furthermore, the determination using the prediction list usage flag may be replaced with a determination using the inter prediction identifier. Conversely, the determination using the inter prediction identifier may be replaced with a determination using the prediction list usage flag.

[0064] (Bi-prediction biPred decision) The flag biPred indicating whether or not bi-prediction is performed can be derived based on whether two prediction list usage flags are both 1. For example, it can be derived using the following formula.

[0065] biPred = (predFlagL0==1 && predFlagL1==1) Alternatively, biPred can be derived based on whether the inter prediction identifier is a value indicating the use of two prediction lists (reference pictures). For example, it can be derived using the following formula:

[0066] biPred = (inter_pred_idc==PRED_BI) ? 1 : 0 (Configuration of video decoding device) The configuration of a video decoding device 31 (FIG. 7) according to this embodiment will be described.

[0067] The video decoding device 31 includes an entropy decoding unit 301, a parameter decoding unit (prediction image decoding device) 302, a loop filter 305, a reference picture memory 306, a prediction parameter memory 307, a prediction image generation unit (prediction image generation device) 308, an inverse quantization and inverse transform unit 311, an adder 312, and a prediction parameter derivation unit 320. Note that the video decoding device 31 may also be configured without including the loop filter 305, in accordance with the video coding device 11 described below.

[0068] The parameter decoding unit 302 further includes a header decoding unit 3020, a CT information decoding unit 3021, and a CU decoding unit 3022 (prediction mode decoding unit), and the CU decoding unit 3022 further includes a TU decoding unit 3024. These may be collectively referred to as a decoding module. The header decoding unit 3020 decodes parameter set information such as VPS, SPS, PPS, and APS, and slice headers (slice information) from the coded data. The CT information decoding unit 3021 decodes the CT from the coded data. The CU decoding unit 3022 decodes the CU from the coded data. When a prediction error is included in the TU, the TU decoding unit 3024 decodes QP update information (quantization correction value) and quantized prediction error (residual_coding) from the coded data.

[0069] The TU decoding unit 3024 decodes the QP update information and the quantized prediction error from the coded data when the mode is other than the skip mode (skip_mode==0). More specifically, when skip_mode==0, the TU decoding unit 3024 decodes the flag cu_cbp indicating whether or not the current block includes a quantized prediction error, and decodes the quantized prediction error when cu_cbp is 1. When cu_cbp does not exist in the coded data, it is derived as 0.

[0070] The TU decoding unit 3024 decodes an index mts_idx indicating a transform base from the coded data. The TU decoding unit 3024 also decodes an index stIdx indicating the use of a secondary transform and the transform base from the coded data. stIdx indicates no application of a secondary transform when it is 0, indicates one transform of a set (pair) of secondary transform bases when it is 1, and indicates the other transform of the pair when it is 2.

[0071] The TU decoding unit 3024 may also decode a sub-block transform flag cu_sbt_flag. When cu_sbt_flag is 1, the CU is divided into multiple sub-blocks and the residual of only one specific sub-block is decoded. The TU decoding unit 3024 may also decode a flag cu_sbt_quad_flag indicating whether the number of sub-blocks is 4 or 2, cu_sbt_horizontal_flag indicating the division direction, and cu_sbt_pos_flag indicating a sub-block that includes a non-zero transform coefficient.

[0072] The predicted image generating unit 308 includes an inter predicted image generating unit 309 and an intra predicted image generating unit 310 .

[0073] The prediction parameter derivation unit 320 includes an inter prediction parameter derivation unit 303 and an intra prediction parameter derivation unit 304 .

[0074] In the following, an example will be described in which CTUs and CUs are used as processing units, but this is not limiting and processing may be performed in sub-CU units. Alternatively, CTUs and CUs may be read as blocks, and sub-CUs as sub-blocks, and processing may be performed in block or sub-block units.

[0075] The entropy decoding unit 301 performs entropy decoding on the externally input coded stream Te to decode individual codes (syntax elements). Entropy coding can be divided into two types: variable-length coding of syntax elements using a context (probability model) adaptively selected according to the type of syntax element and surrounding circumstances, and variable-length coding of syntax elements using a predetermined table or formula. The former, CABAC (Context Adaptive Binary Arithmetic Coding), stores the CABAC state of the context (probability state index pStateIdx, which specifies the type (0 or 1) and probability of the most probable symbol) in memory. The entropy decoding unit 301 initializes all CABAC states at the beginning of a segment (tile, CTU row, slice). The entropy decoding unit 301 converts the syntax elements into a binary string (bin string) and decodes each bit of the bin string. When a context is used, a context index (ctxInc) is derived for each bit of the syntax element, the bit is decoded using the context, and the CABAC state of the used context is updated. Bits that do not use a context are decoded with equal probability (EP, bypass), and the ctxInc derivation and CABAC state are omitted. The decoded syntax elements include prediction information for generating a predicted image and a prediction error for generating a difference image.

[0076] The entropy decoding unit 301 outputs the decoded code to the parameter decoding unit 302. The decoded code includes, for example, a prediction mode predMode, merge_flag, merge_idx, inter_pred_idc, refIdxLX, mvp_LX_idx, mvdLX, etc. Control of which code to decode is performed based on an instruction from the parameter decoding unit 302.

[0077] (Basic flow) FIG. 8 is a flowchart illustrating the general operation of the video decoding device 31.

[0078] (S1100: Decode Parameter Set Information) The header decoder 3020 decodes parameter set information such as VPS, SPS, and PPS from the coded data.

[0079] (S1200: Decode slice information) The header decoding unit 3020 decodes the slice header (slice information) from the coded data.

[0080] Thereafter, the video decoding device 31 repeats the processes from S1300 to S5000 for each CTU included in the target picture, thereby deriving a decoded image of each CTU.

[0081] (S1300: Decode CTU Information) The CT information decoding unit 3021 decodes the CTU from the encoded data.

[0082] (S1400: Decode CT Information) The CT information decoding unit 3021 decodes the CT from the encoded data.

[0083] (S1500: CU Decoding) The CU decoding unit 3022 performs S1510 and S1520 to decode the CU from the encoded data.

[0084] (S1510: Decode CU Information) The CU decoding unit 3022 decodes CU information, prediction information, the TU split flag split_transform_flag, and CU residual flags cbf_cb, cbf_cr, and cbf_luma from the coded data.

[0085] (S1520: TU information decoding) When a prediction error is included in a TU, the TU decoding unit 3024 decodes the QP update information, the quantization prediction error, and the transform index mts_idx from the coded data. Note that the QP update information is a difference value from the quantization parameter predicted value qPpred, which is a predicted value of the quantization parameter QP.

[0086] (S2000: Generate predicted image) The predicted image generation unit 308 generates a predicted image for each block included in the current CU based on prediction information.

[0087] (S3000: Inverse Quantization and Inverse Transformation) The inverse quantization and inverse transform unit 311 executes inverse quantization and inverse transform processing on each TU included in the target CU.

[0088] (S4000: Generate decoded image) The addition unit 312 generates a decoded image of the current CU by adding the predicted image supplied from the predicted image generation unit 308 and the prediction error supplied from the inverse quantization and inverse transform unit 311.

[0089] (S5000: Loop filter) The loop filter 305 applies a loop filter such as a deblocking filter, SAO, or ALF to the decoded image to generate a decoded image.

[0090] (Configuration of the inter-prediction parameter derivation unit) The inter prediction parameter derivation unit 303 derives inter prediction parameters by referring to prediction parameters stored in the prediction parameter memory 307 based on the syntax elements input from the parameter decoding unit 302. The inter prediction parameter derivation unit 303 also outputs the inter prediction parameters to the inter prediction image generation unit 309 and the prediction parameter memory 307. The inter prediction parameter derivation unit 303 and its internal elements, namely, the AMVP prediction parameter derivation unit 3032, the merge prediction parameter derivation unit 3036, the affine prediction unit 30372, the MMVD prediction unit 30373, the triangle prediction unit 30377, the DMVR unit 30537, and the MV addition unit 3038, are means common to both the video encoding device and the video decoding device, and may therefore be collectively referred to as a motion vector derivation unit (motion vector derivation device). An example of the inter prediction parameter derivation unit 303 is shown in FIG. 9 .

[0091] When affine_flag is 1, that is, when affine prediction mode is indicated, the affine prediction unit 30372 derives inter prediction parameters in units of subblocks.

[0092] When mmvd_flag is 1, that is, when it indicates the MMVD prediction mode, the MMVD predictor 30373 derives inter prediction parameters from the merge candidates and difference vectors derived by the merge prediction parameter derivation unit 3036.

[0093] When triangleFlag is 1, that is, when it indicates triangle prediction mode, the triangle prediction unit 30377 derives triangle prediction parameters.

[0094] If merge_flag is 1, that is, if it indicates merge prediction mode, merge_idx is derived and output to the merge prediction parameter derivation unit 3036 .

[0095] When merge_flag is 0, that is, when it indicates the AMVP prediction mode, the AMVP prediction parameter derivation unit 3032 derives mvpLX from inter_pred_idc, refIdxLX, or mvp_LX_idx.

[0096] (MV addition section) The MV adder 3038 adds the derived mvpLX and mvdLX to derive mvLX.

[0097] (Affine prediction part) The affine prediction unit 30372 1) derives motion vectors for two control points CP0 and CP1 or three control points CP0, CP1, and CP2 of the target block, 2) derives affine prediction parameters for the target block, and 3) derives motion vectors for each sub-block from the affine prediction parameters.

[0098] In merge affine prediction, the motion vector cpMvLX[] of each control point CP0, CP1, CP2 is derived from the motion vectors of the blocks adjacent to the target block. In inter-affine prediction, the motion vector of each control point CP0, CP1, CP2 is derived from the motion vector of the adjacent block and the difference vector mvdCpLX[] derived from the encoded data.

[0099] 11 is a diagram showing an example of deriving the motion vector spMvLX of each sub-block that constitutes the target block (cbWidth*cbHeight) from the motion vector cpMvLX[0] of control point CP0, the motion vector cpMvLX[1] of CP1, and the motion vector cpMvLX[2] of CP2. As shown in the diagram, spMvLX is derived as the motion vector of the point (xPosCb, yPosCb) located at the center of each sub-block.

[0100] The affine prediction unit 30372 derives affine prediction parameters (mvScaleHor, mvScalerVer, dHorX, dHorY, dVerX, dVerY) of the current block from the motion vector of the control point.

[0101] mvScaleHor = cpMvLX[0][0] << 7 mvScaleVer = cpMvLX[0][1] << 7 dHorX = (cpMvLX[1][0] - cpMvLX[0][0]) << (7-log2CbW) dVerX = (cpMvLX[1][1] - cpMvLX[0][1]) << (7-log2CbW) If numCpMv==3, dHorY = (cpMvLX[2][0] - cpMvLX[0][0]) << (7 - log2CbH) dVerY = (cpMvLX[2][1] - cpMvLX[0][1]) << (7 - log2CbH) If numCpMv!=3, dHorY = - dVerX dVerY = dHorX Here, log2CbW and log2CbH are the logarithmic values ​​of the width cbWidth and height cbHeight of the target block.

[0102] The affine prediction unit 30372 derives spMvLX[i][j] (i=0, 1, 2, ..., (cbWidth / sbWidth)-1, j=0, 1, 2, ..., (cbHeight / sbHeight)-1) in the current block based on the affine prediction parameters of the current block using the following equation:

[0103] xPosCb = 2 + (i<<2) yPosCb = 2 + (j<<2) spMvLX[i][j][0] = mvScaleHor + dHorX * xPosCb + dHorY * yPosCb spMvLX[i][j][1] = mvScaleVer + dVerX * xPosCb + dVerY * yPosCb Further round shifting and clipping may be performed.

[0104] spMvLX[i][j][0] = Clip3(-2^17, 2^17, (spMvLX[i][j][0]+64)>>7 ) spMvLX[i][j][1] = Clip3(-2^17, 2^17, (spMvLX[i][j][1]+64)>>7 ) Here, sbWidth and sbHeight are the width and height of the target sub-block.

[0105] Furthermore, at the upper left coordinate (xSb, ySb) of the sub-block, spMvLX[i][j] is assigned to the corresponding mvLX in the screen, where x = 0..sbWidth-1, y = 0..sbHeight-1.

[0106] mvLX[xSb + x][yXb + y] = spMv[i][j] (PROF) PROF (Prediction Refinement with Optical Flow) is a method that calculates pixel-level optical flow based on pixel gradient information and corrects sub-block-level affine prediction.

[0107] 12, the specific contents of the processing performed by the BIO unit 30954 will be described. The BIO unit 30954 includes an L0,L1 predicted image generation unit 309541, a gradient image generation unit 309542, a correlation parameter calculation unit 309543, a motion compensation modified value derivation unit 309544, and a bidirectional predicted image generation unit 309545. The BIO unit 30954 generates a predicted image from the interpolated image received from the motion compensation unit 3091 and the inter prediction parameters received from the inter prediction parameter decoding unit 303, and outputs the predicted image to the addition unit 312. Note that the process of deriving the motion compensation modified value bdofOffset (motion compensation modified image) from the gradient image and modifying and deriving PredL0 and PredL1 is called bidirectional gradient change processing.

[0108] First, the variable cbProfFlagLX indicating the application condition of PROF is derived as follows.

[0109] cbProfFlagLX is set to FALSE if one or more of the following conditions are true:

[0110] numCpMv is equal to 2, cpMvLX[1][0] is equal to cpMvLX[0][0], and cpMvLX[1][1] is equal to cpMvLX[0][1].

[0111] ·numCpMv is equal to 3, cpMvLX[1][0] is equal to cpMvLX[0][0], cpMvLX[1][1] is equal to cpMvLX[0][1] and cpMvLX[2][0] is equal to cpMvLX[0][0], and cpMvLX[2][1] is equal to cpMvLX[0][1].

[0112] Generally, to obtain optical flow, it is assumed that the luminance is constant. However, in Non-Patent Document 1, this assumption is not taken into consideration in the application conditions of PROF. Therefore, in this embodiment, in addition to the above conditions, the following conditions are set for setting cbProfFlagLX to FALSE: bcwIdx[xCb][yCb] is not 0 (it is not the default weighting coefficient). luma_weight_lX_flag[refIdxLX] is 1. (The weighting coefficient for weighted prediction is applied.) (Note that X is 0 for L0 prediction and 1 for L1 prediction.) This solves the problem by adding a condition that PROF is not selected when a prediction method that handles brightness fluctuations (BCW prediction and weighted prediction) is adopted.

[0113] Otherwise, cbProfFlagLX is set to TRUE.

[0114] Fig. 13 is a flow chart illustrating the processing of this embodiment. Fig. 13(a) shows an example in which, after affine prediction processing (S2001), it is checked whether BcwIdx[xCb][yCb] is 0 (S2002), and if Yes, PROF processing is skipped, and if No, PROF processing (S2003) is executed. Fig. 13(b) shows an example in which, after affine prediction processing (S2004), it is checked whether luma_weight_lX_flag[refIdxLX] is 1 (S2005), and if Yes, PROF processing is skipped, and if No, PROF processing (S2006) is executed.

[0115] If cbProfFlagLX is TRUE, the motion vector difference array diffMv is derived as follows.

[0116] First, the variables sbWidth, sbHeight, dmvLimit, posOffsetX, and posOffsetY are derived as follows.

[0117] sbWidth = cbWidth / numSbX sbHeight = cbHeight / numSbY dmvLimit = 1 << Max(6, BitDepthY - 6) posOffsetX = 6 * dHorX + 6 * dVerX posOffsetY = 6 * dHorY + 6 * dVerY For x = 0..sbWidth - 1 and y = 0..sbHeight - 1, apply the following:

[0118] diffMv[x][y][0] = x *(dHorX << 2)+ y *(dVerX << 2)- posOffsetX diffMv[x][y][1] = x *(dHorY << 2)+ y *(dVerY << 2)- posOffsetY Furthermore, for i = 0..1, diffMv[x][y][0] =(diffMv[x][y][0] + 64 -(diffMv[x][y][0] >= 0))>> 7 diffMv[x][y][1] =(diffMv[x][y][1] + 64 -(diffMv[x][y][1] >= 0))>> 7 The values ​​of diffMv[x][y][i] are clipped as follows:

[0119] diffMv[x][y][i] = Clip3(-dmvLimit, dmvLimit-1, diffMv[x][y][i]) Using the diffMV thus obtained, the optical flow at the pixel level is calculated based on the gradient information of the affine prediction at the sub-block level, and the predicted sample value is corrected at the pixel level.

[0120] In Non-Patent Document 1, the variable dmvLimit, which indicates the range in which the value of diiffMV is clipped, is set to 1 << Max(6, BitDepthY - 6), but the range of motion vectors should not be a value that depends on the pixel bit length. Also, there is a problem that the precision of the calculation of predicted samples, which will be described later, exceeds 16 bits. Therefore, in this embodiment, dmvLimit = 32 Or, dmvLimit = 16 This will be implemented with a fixed value.

[0121] Next, two variables sbWidth and sbHeight that specify the width and height of the current sub-block, a predicted sample array predSamples of (sbWidth + borderExtension)*(sbHeight + borderExtension), and a motion vector difference array diffMv of (sbWidth * sbHeight) are input. The variable shift1 is set to 6.

[0122] For x = 0..sbWidth-1, for y = 0..sbHeight-1, the following ordered steps are applied: - The variables gradientH[x][y] and gradientV[x][y] used to calculate the gradient are derived as follows:

[0123] gradientH[x][y] =(predSamples[x + 2][y] >> shift1) -(predSamples[x][y] >> shift1) gradientV[x][y] =(predSamples[x][y + 2] >> shift1) -(predSamples[x][y] >> shift1) The variable dI is derived as follows.

[0124] dI = gradientH[x][y] * diffMv[x][y][0] + gradientV[x][y] * diffMv[x][y][1] The predicted sample value at the position (x, y) in the sub-block is derived as follows, and a (sbWidth) x (sbHeight) array pbSamples of the predicted sample values ​​is output.

[0125] pbSamples[x][y] = predSamples[x + 1][y + 1] +((dI + 1)>> 1) (Merge prediction) 10(a) is a schematic diagram showing the configuration of the merge prediction parameter derivation unit 3036 according to this embodiment. The merge prediction parameter derivation unit 3036 includes a merge candidate derivation unit 30361 and a merge candidate selection unit 30362. Note that a merge candidate includes prediction parameters (predFlagLX, mvLX, refIdxLX, bcwIdx) and is stored in a merge candidate list. An index is assigned to each merge candidate stored in the merge candidate list according to a predetermined rule.

[0126] The merge candidate derivation unit 30361 derives merge candidates by directly using the motion vectors and refIdxLX of decoded neighboring blocks. In addition, the merge candidate derivation unit 30361 may apply a spatial merge candidate derivation process, a temporal merge candidate derivation process, a pairwise merge candidate derivation process, and a zero merge candidate derivation process, which will be described later.

[0127] In the spatial merge candidate derivation process, the merge candidate derivation unit 30361 reads prediction parameters stored in the prediction parameter memory 307 according to a predetermined rule and sets them as merge candidates. The reference pictures are specified, for example, by prediction parameters for each of neighboring blocks within a predetermined range from the current block (e.g., all or part of the blocks adjacent to the left A1, right B1, upper right B0, lower left A0, and upper left B2 of the current block). The respective merge candidates are referred to as A1, B1, B0, A0, and B2. Here, A1, B1, B0, A0, and B2 are motion information derived from blocks containing the following coordinates: Figure 10(b) shows the positions of A1, B1, B0, A0, and B2.

[0128] A1: (xCb - 1, yCb + cbHeight - 1) B1: (xCb + cbWidth - 1, yCb - 1) B0: (xCb + cbWidth, yCb - 1) A0: (xCb - 1, yCb + cbHeight) B2: (xCb - 1, yCb - 1) The upper left coordinates of the target block are (xCb, yCb), the width is cbWidth, and the height is cbHeight.

[0129] As a temporal merge derivation process, the merge candidate derivation unit 30361 reads the prediction parameters of the lower right CBR of the target block or the block C in the reference image including the center coordinates from the prediction parameter memory 307, sets it as a merge candidate Col, and stores it in the merge candidate list mergeCandList[ ].

[0130] The pairwise candidate derivation unit derives a pairwise candidate avgK from the average of the two merge candidates (p0Cand, p1Cand) already stored in mergeCandList, and stores it in mergeCandList[].

[0131] mvLXavgK[0] = (mvLXp0Cand[0]+mvLXp1Cand[0]) / 2 mvLXavgK[1] = (mvLXp0Cand[1]+mvLXp1Cand[1]) / 2 The merge candidate derivation unit 30361 derives zero merge candidates Z0, ..., ZM, where refIdxLX is 0...M and both the X and Y components of mvLX are 0, and stores them in the merge candidate list.

[0132] The order in which the mergeCandList[] is stored is, for example, spatial merge candidates (A1, B1, B0, A0, B2), temporal merge candidates Col, pairwise merge candidates avgK, and zero merge candidates ZK. Note that reference blocks that are unavailable (e.g., blocks that are intra-predicted) are not stored in the merge candidate list. i = 0 if( availableFlagA1 ) mergeCandList[ i++ ] = A1 if( availableFlagB1 ) mergeCandList[ i++ ] = B1 if( availableFlagB0 ) mergeCandList[ i++ ] = B0 if( availableFlagA0 ) mergeCandList[ i++ ] = A0 if( availableFlagB2 ) mergeCandList[ i++ ] = B2 if( availableFlagCol ) mergeCandList[ i++ ] = Col if( availableFlagAvgK ) mergeCandList[ i++ ] = avgK if( i < MaxNumMergeCand ) mergeCandList[ i++ ] = ZK The merge candidate selection unit 30362 selects a merge candidate N indicated by merge_idx from among the merge candidates included in the merge candidate list using the following formula.

[0133] N = mergeCandList[merge_idx] Here, N is a label indicating a merge candidate, and can be A1, B1, B0, A0, B2, Col, avgK, ZK, etc. The motion information of the merge candidate indicated by label N is indicated by (mvLXN[0], mvLXN[0]), predFlagLXN, refIdxLXN, bcwIdxN.

[0134] The selected (mvLXN[0], mvLXN[0]), predFlagLXN, refIdxLXN, and bcwIdxN are selected as the inter prediction parameters for the current block. The merge candidate selection unit 30362 stores the inter prediction parameters of the selected merge candidate in the prediction parameter memory 307 and outputs them to the inter prediction image generation unit 309.

[0135] (MMVD Prediction Section 30373) The MMVD prediction unit 30373 obtains mvLX by adding mvdLX of a predetermined distance and a predetermined direction to the central vector mvpLX (motion vector mvLXN of merge candidate N) derived by the merge candidate derivation unit 30361. The MMVD prediction unit 30373 derives the central vector mvLX[] using the syntax element base_candidate_idx of the coded data, and derives the difference vector mMvdLX[] from direction_idx indicating an index in the direction table and distance_idx indicating an index in the distance table.

[0136] (Triangle forecast) In triangle prediction, a current block is divided into two triangular prediction units (PU0, PU1) using two types of diagonals, as shown in Figure 17. In the figure, (a) indicates the division direction triangleDir=0, and (b) indicates triangleDir=1. After generating predicted images for PU0 and PU1, weighting processing is performed on the diagonal edges.

[0137] Operations other than prediction (eg, transformation and quantization) are applied to the entire block.

[0138] (Syntax decoding) Triangle prediction on / off and parameters for on are notified in the encoded data as follows:

[0139] sps_triangle_enabled_flag is notified by SPS and indicates whether or not the Triangle prediction mode is used in the target sequence. When sps_triangle_enabled_flag is 0, it indicates that the Triangle prediction mode is not used in the target sequence, and when sps_triangle_enabled_flag is 1, it indicates that the Triangle prediction mode is used in the target sequence.

[0140] (Motion information derivation process) The triangle prediction unit 30377 derives merge indices m and n for PU0 and PU1, and a division direction triangleDir for triangle prediction.

[0141] m = merge_triangle_idx0 n = merge_triangle_idx1 + (merge_triangle_idx1 >= m) ? 1 : 0 triangleDir = merge_triangle_split_dir In the following, the merge candidate indicated by merge index m will be denoted as M, and the merge candidate indicated by merge index n will be denoted as N.

[0142] The merge prediction parameter derivation unit 3036 derives motion information (mvLXM, mvLXN, refIdxLXM, refIdxLXN, predFlagLXM, predFlagLXN, bcwIdxN, bcwIdxN, mergeCandList, etc.) of merge candidates M and N using the method described in (Merge Prediction). The triangle prediction unit 30377 uses this motion information to set motion vectors mvA and mvB, reference indices refIdxA and refIdxB, and prediction list flags predListFlagA and predListFlagB for PU0 and PU1.

[0143] mvA[0] = mvLXM[0] mvA[1] = mvLXM[1] refIdxA = refIdxLXM predListFlagA = X Here, the lowest 1 bit of m is set to X (m & 0x01). Note that if predFlagLXM is 0, X is set to (1-X). mvB[0] = mvLXN[0] mvB[1] = mvLXN[1] refIdxB = refIdxLXN predListFlagB = X Here, the lowest 1 bit of n is set to X (n & 0x01). If predFlagLXN is 0, X is set to (1-X).

[0144] These pieces of motion information are referenced to generate predicted images for PU0 and PU1.

[0145] (Deriving weighting coefficients for triangle mode) The triangle prediction unit 30377 derives the weighted prediction coefficients to be applied to the diagonal edge of the boundary between PU0 and PU1 in the following procedure: where nCbW=cbWidth and nCbH=cbHeight.

[0146] A variable nCbR representing the shape of the target block is derived.

[0147] nCbR = (nCbW > nCbH) ? (nCbW / nCbH) : (nCbH / nCbW) When triangleDir is 0, the weighting coefficient wValue of the predicted pixel is derived as follows:

[0148] wValue = (nCbW > nCbH) ? (Clip3(0, 8, (x / nCbR - y) + 4)) : (Clip3(0, 8, (x - y / nCbR) + 4)) If triangleDir is 1, derive wValue as follows:

[0149] wValue = (nCbW > nCbH) ? (Clip3(0, 8, (nCbH - 1 - x / nCbR - y) + 4)) : (Clip3(0, 8, (nCbW - 1 - x - y / nCbR) + 4)) An example of wValue is shown in FIG.

[0150] (Triangle mode motion vector storage processing) The triangle prediction unit 30377 stores the motion information of PU0 and PU1 in units of 4*4 sub-blocks in memory in the following procedure so that it can be referenced in subsequent processing.

[0151] numSbX and numSbY are the number of 4*4 sub-blocks in the horizontal and vertical directions of the target block, and set numSbX = cbWidth >> 2, numSbY = cbHeight >> 2. Set minSb = min(numSbX, numSbY).

[0152] Derive the block aspect ratio cbRatio.

[0153] cbRatio = (cbWidth > cbHeight) ? (cbWidth / cbHeight) : (cbHeight / cbWidth) For each position (xSbIdx, ySbIdx) of a 4*4 sub-block where xSbIdx = 0..numSbX - 1 and ySbIdx = 0..numSbY - 1, the following process is performed.

[0154] Derive xIdx and yIdx using (xSbIdx, ySbIdx).

[0155] xIdx = (cbWidth > cbHeight) ? (xSbIdx / cbRatio) : xSbIdx yIdx = (cbWidth > cbHeight) ? ySbIdx : (ySbIdx / cbRatio) When triangleDir==0, sType shown in FIG. 17(e) is derived as follows:

[0156] sType = (xIdx == yIdx) ? 2 : ((xIdx > yIdx) ? 0 : 1) When triangleDir==1, sType shown in FIG. 17(f) is derived as follows:

[0157] sType = (xIdx + yIdx == minSb) ? 2 : ((xIdx + yIdx < minSb) ? 0 : 1) sType is a parameter that indicates whether each 4*4 sub-block is located in PU0, PU1, or the boundary between PU0 and PU1. sType=0 indicates that the 4*4 sub-block is located in PU0. sType=1 indicates that the 4*4 sub-block is located in PU1. sType=2 indicates that the 4*4 sub-block is located on the boundary between PU0 and PU1.

[0158] If sType==0, do the following:

[0159] If the prediction list flag of PU0 is 0 (predListFlagA==0), PU0 is assumed to be unidirectionally predicted from L0, and if the prediction list flag of PU0 is not 0 (predListFlagA!=0), motion information is stored assuming that PU0 is unidirectionally predicted from L1.

[0160] predFlagL0 = (predListFlagA == 0) ? 1 : 0 predFlagL1 = (predListFlagA == 0) ? 0 : 1 refIdxL0 = (predListFlagA == 0) ? refIdxA : -1 refIdxL1 = (predListFlagA == 0) ? -1 : refIdxA mvL0[0] = (predListFlagA == 0) ? mvA[0] : 0 mvL0[1] = (predListFlagA == 0) ? mvA[1] : 0 mvL1[0] = (predListFlagA == 0) ? 0 : mvA[0] mvL1[1] = (predListFlagA == 0) ? 0 : mvA[1] Otherwise, if sType==1, or sType==2 and predListFlagA+predListFlagB!=1, then do the following: where predListFlagA+predListFlagB!=1 indicates that the reference picture lists of PU0 and PU1 are the same.

[0161] If the prediction list flag of PU1 is 0 (predListFlagB==0), PU1 is treated as L0 prediction (unidirectional prediction), and if the prediction list flag of PU1 is not 0 (predListFlagB!=0), PU1 is treated as L1 prediction (unidirectional prediction) and motion information is stored.

[0162] predFlagL0 = (predListFlagB == 0) ? 1 : 0 predFlagL1 = (predListFlagB == 0) ? 0 : 1 refIdxL0 = (predListFlagB == 0) ? refIdxB : -1 refIdxL1 = (predListFlagB == 0) ? -1 : refIdxB mvL0[0] = (predListFlagB == 0) ? mvB[0] : 0 mvL0[1] = (predListFlagB == 0) ? mvB[1] : 0 mvL1[0] = (predListFlagB == 0) ? 0 : mvB[0] mvL1[1] = (predListFlagB == 0) ? 0 : mvB[1] Otherwise (sType==2 and predListFlagA+predListFlagB==1), do the following: where predListFlagA+predListFlagB==1 indicates that the reference picture lists of PU0 and PU1 are different.

[0163] If the prediction list flag for PU0 is 0 (predListFlagA==0), bidirectional prediction is set with PU0 information stored in L0 and PU1 information stored in L1. If the prediction list flag for PU0 is not 0 (predListFlagA!=0), bidirectional prediction is set with PU1 information stored in L0 and PU0 information stored in L1.

[0164] predFlagL0 = 1 predFlagL1 = 1 refIdxL0 = (predListFlagA == 0) ? refIdxA : refIdxB refIdxL1 = (predListFlagA == 0) ? refIdxB : refIdxA mvL0[0] = (predListFlagA == 0) ? mvA[0] : mvB[0] mvL0[1] = (predListFlagA == 0) ? mvA[1] : mvB[1] mvL1[0] = (predListFlagA == 0) ? mvB[0] : mvA[0] mvL1[1] = (predListFlagA == 0) ? mvB[1] : mvA[1] (DMVR) Next, a DMVR (Decoder side Motion Vector Refinement) process performed by the DMVR unit 30375 will be described. When merge_flag is 1 for a target CU, or when the skip flag skip_flag is 1, the DMVR unit 30375 corrects the mvLX of the target CU derived by the merge prediction unit 30374 using a reference image. Specifically, when the prediction parameters derived by the merge prediction unit 30374 are bi-predictive, the DMVR unit 30375 corrects the motion vector using a predicted image derived from motion vectors corresponding to two reference pictures. The corrected mvLX is supplied to the inter-prediction image generation unit 309.

[0165] (AMVP forecast) 10(c) is a schematic diagram showing the configuration of the AMVP prediction parameter derivation unit 3032 according to this embodiment. The AMVP prediction parameter derivation unit 3032 includes a vector candidate derivation unit 3033 and a vector candidate selection unit 3034. The vector candidate derivation unit 3033 derives predictor vector candidates from the motion vectors of decoded adjacent blocks stored in the prediction parameter memory 307 based on refIdxLX, and stores the candidates in a predictor vector candidate list mvpListLX[].

[0166] The vector candidate selection unit 3034 selects, as mvpLX, the motion vector mvpListLX[mvp_LX_idx] indicated by mvp_LX_idx from among the predicted vector candidates in mvpListLX[ ]. The vector candidate selection unit 3034 outputs the selected mvpLX to the MV addition unit 3038.

[0167] (MV addition section) The MV addition unit 3038 calculates mvLX by adding the mvpLX input from the AMVP prediction parameter derivation unit 3032 and the decoded mvdLX. The addition unit 3038 outputs the calculated mvLX to the inter predicted image generation unit 309 and the prediction parameter memory 307.

[0168] mvLX[0] = mvpLX[0]+mvdLX[0] mvLX[1] = mvpLX[1] + mvdLX[1] (Motion Vector Scaling) A method for deriving motion vector scaling will now be described. Given a motion vector Mv (reference motion vector), a picture PicMv containing a block having Mv, a reference picture PicMvRef of Mv, a motion vector after scaling sMv, a picture CurPic containing a block having sMv, and a reference picture CurPicRef referenced by sMv, the derivation function MvScale(Mv, PicMv, PicMvRef, CurPic, CurPicRef) of sMv is expressed by the following equation:

[0169] sMv = MvScale(Mv,PicMv,PicMvRef,CurPic,CurPicRef) = Clip3(-R1,R1-1,sign(distScaleFactor*Mv)*((abs(distScaleFactor*Mv)+round1-1)>>shift1)) distScaleFactor = Clip3(-R2,R2-1,(tb*tx+round2)>>shift2) tx = (16384+abs(td)>>1) / td td = DiffPicOrderCnt(PicMv,PicMvRef) tb = DiffPicOrderCnt(CurPic,CurPicRef) Here, round1, round2, shift1, and shift2 are round and shift values ​​for division using reciprocals, for example, round1=1<<(shift1-1), round2=1<<(shift2-1), shift1=8, shift2=6. DiffPicOrderCnt(Pic1,Pic2) is a function that returns the difference in time information (e.g., POC) between Pic1 and Pic2. R1 and R2 limit the value range to perform processing with limited precision, for example, R1=32768, R2=4096.

[0170] Furthermore, the scaling function MvScale(Mv, PicMv, PicMvRef, CurPic, CurPicRef) may be expressed by the following formula:

[0171] MvScale(Mv,PicMv,PicMvRef,CurPic,CurPicRef) = Mv*DiffPicOrderCnt(CurPic,CurPicRef) / DiffPicOrderCnt(PicMv,PicMvRef) That is, Mv may be scaled according to the ratio between the difference in time information between CurPic and CurPicRef and the difference in time information between PicMv and PicMvRef.

[0172] (Configuration of the intra-prediction parameter derivation unit 304) The intra prediction parameter derivation unit 304 derives intra prediction parameters, for example, an intra prediction mode IntraPredMode, based on input from the parameter decoding unit 302, by referring to prediction parameters stored in the prediction parameter memory 307. The intra prediction parameter derivation unit 304 outputs the intra prediction parameters to the predicted image generation unit 308 and also stores them in the prediction parameter memory 307. The intra prediction parameter derivation unit 304 may derive different intra prediction modes for luma and chroma.

[0173] The loop filter 305 is a filter provided in the encoding loop that removes block distortion and ringing distortion to improve image quality. The loop filter 305 applies filters such as a deblocking filter, a sample adaptive offset (SAO), and an adaptive loop filter (ALF) to the decoded image of the CU generated by the adder 312.

[0174] The reference picture memory 306 stores the decoded image of the CU in a predetermined location for each current picture and current CU.

[0175] The prediction parameter memory 307 stores prediction parameters at a predetermined location for each CTU or CU. Specifically, the prediction parameter memory 307 stores parameters decoded by the parameter decoding unit 302, parameters derived by the prediction parameter derivation unit 320, and the like.

[0176] The predicted image generation unit 308 receives as input the parameters derived by the prediction parameter derivation unit 320. The predicted image generation unit 308 also reads a reference picture from the reference picture memory 306. The predicted image generation unit 308 generates a predicted image of a block or sub-block using the parameters and a reference picture (reference picture block) in the prediction mode indicated by predMode. Here, the reference picture block is a set of pixels on the reference picture (usually rectangular, and therefore called a block), and is an area referenced to generate a predicted image.

[0177] (Inter-prediction image generation unit 309) When predMode indicates inter prediction mode, the inter prediction image generation unit 309 generates a prediction image of a block or sub-block by inter prediction using the inter prediction parameters input from the inter prediction parameter derivation unit 303 and the reference picture.

[0178] 14 is a schematic diagram showing the configuration of an inter-prediction image generation unit 309 included in the prediction image generation unit 308 according to this embodiment. The inter-prediction image generation unit 309 includes a motion compensation unit (prediction image generation device) 3091 and a synthesis unit 3095. The synthesis unit 3095 includes an intra-inter synthesis unit 30951, a triangle synthesis unit 30952, a BDOF unit 30954, a weighted prediction unit 3094, and a PROF unit 30955.

[0179] (motion compensation) The motion compensation unit 3091 (interpolated image generation unit 3091) generates an interpolated image (motion-compensated image) by reading a reference block from the reference picture memory 306 based on the inter-prediction parameters (predFlagLX, refIdxLX, mvLX) input from the inter-prediction parameter derivation unit 303. The reference block is a block located at a position shifted by mvLX from the position of the current block on the reference picture RefPicLX specified by refIdxLX. Here, if mvLX does not have integer precision, an interpolated image is generated by applying a filter called a motion compensation filter for generating pixels at decimal positions.

[0180] The motion compensation unit 3091 first derives the integer position (xInt, yInt) and phase (xFrac, yFrac) corresponding to the coordinates (x, y) in the prediction block using the following equations.

[0181] xInt = xPb+(mvLX[0]>>(log2(MVPREC)))+x xFrac = mvLX[0]&(MVPREC-1) yInt = yPb+(mvLX[1]>>(log2(MVPREC)))+y yFrac = mvLX[1]&(MVPREC-1) Here, (xPb, yPb) are the upper left coordinates of a block of size cbWidth*cbHeight, where x=0...cbWidth-1, y=0...cbHeight-1, and MVPREC indicates the accuracy of mvLX (1 / MVPREC pixel accuracy). For example, MVPREC=16.

[0182] The motion compensation unit 3091 derives the temporary image temp[][] by performing horizontal interpolation on the reference picture refImg using an interpolation filter. In the following, Σ is the sum over k, where k=0..NTAP-1, shift1 is a normalization parameter that adjusts the value range, and offset1=1<<(shift1-1).

[0183] temp[x][y] = (ΣmcFilter[xFrac][k]*refImg[xInt+k-NTAP / 2+1][yInt]+offset1)>>shift1 Next, the motion compensation unit 3091 derives the interpolated image Pred[][] by vertically interpolating the temporary image temp[][]. In the following, Σ is the sum for k=0..NTAP-1, shift2 is a normalization parameter that adjusts the value range, and offset2=1<<(shift2-1).

[0184] Pred[x][y] = (ΣmcFilter[yFrac][k]*temp[x][y+k-NTAP / 2+1]+offset2)>>shift2 In the case of bi-prediction, the above Pred[][] is derived for each L0 list and L1 list (called interpolated images PredL0[][] and PredL1[][]), and the interpolated image Pred[][] is generated from PredL0[][] and PredL1[][].

[0185] The synthesis unit 3095 includes an IntraInter synthesis unit 30951 , a Triangle synthesis unit 30952 , a weighted prediction unit 3094 , and a BDOF unit 30954 .

[0186] (IntraInter synthesis processing) The IntraInter synthesis unit 30951 generates a predicted image by weighting the sum of the inter predicted image and the intra predicted image.

[0187] (Triangle synthesis processing) When MergeTriangleFlag is 1, the triangle synthesis unit 30952 generates the predicted image pbSamples.

[0188] In the following, pbSamples is a prediction block of size cbWidth*cbHeight. predSamplesLA and predSamplesLB are prediction images generated by the motion compensation unit 3091 using motion information of PU0 and PU1.

[0189] The triangle synthesis unit 30952 generates pbSamples according to triangleDir. In Non-Patent Document 1, weighted prediction processing is applied to the diagonal edge of the boundary between PU0 and PU1 using wValue using the following equation.

[0190] pbSamples[x][y] = Clip3(0, (1 << bitDepth) - 1, (predSamplesLA[x][y] * wValue + predSamplesLB[x][y] * (8 - wValue) + offset1) >> shift1) where shift1 = Max(5, 17 - bitDepth) and offset1 = 1 << (shift1 - 1).

[0191] The problem with the above formula is that the value of shift1 is incorrect as a prediction formula. In this embodiment, taking into consideration that the maximum value of wValue is 8, the above problem is solved by using shift1 = Max(6, 18 - bitDepth).

[0192] Another problem with Non-Patent Document 1 is that it does not explicitly state how to perform triangle synthesis processing when weighted prediction is applied. Because triangle prediction is a merge mode, it can only be switched on and off on a slice-by-slice basis. Therefore, it is possible to consider a method in which triangle prediction is not performed if pps_weighted_pred_flag or pps_weighted_bipred_flag is 1 in PPS, or a method in which weighted prediction is not applied during triangle prediction even if a weighting factor is present. However, both methods have problems in terms of coding efficiency.

[0193] Therefore, in this embodiment, the following weighted prediction process is performed on the predicted images predSamplesLA and predSamplesLB, and then triangle synthesis process is performed.

[0194] predSamplesLA[x][y] = Clip3(0,(1< <Max(14, bitDepth+2)-1, ((PredsampleLA[x][y]*w0+(1<<(log2WD-1))>>log2WD)+o0) predSamplesLB[x][y] = Clip3(0,(1< <Max(14, bitDepth+2)-1, ((PredsampleLB[x][y]*w1+(1<<(log2WD-1))>>log2WD)+o1) pbSamples[x][y] = Clip3(0, (1 << bitDepth) - 1, (predSamplesLA[x][y] * wValue + predSamplesLB[x][y] * (8 - wValue) + offset1) >> shift1) where shift1 = Max(6, 18 - bitDepth) and offset1 = 1 << (shift1 - 1).

[0195] In this way, by generating an interpolated image that has been subjected to weighted prediction processing in advance and then performing triangle synthesis processing, triangle prediction can be performed efficiently even when the brightness fluctuates, such as in a faded image.

[0196] In another embodiment, a weighted prediction process, described below, is performed on two predicted images predSamplesLA and predSamplesLB according to refIdxA and refIdxB to generate a predicted image with a pixel bit length of bitDepth, and then triangular synthesis processing is performed as follows.

[0197] pbSamples[x][y] = (predSamplesLA[x][y] * wValue + predSamplesLB[x][y] * (8 - wValue) + 4) >> 3 In this way, by generating a predicted image that has been subjected to weighted prediction processing in advance and then performing triangle synthesis processing, triangle prediction can be performed efficiently even when brightness fluctuates, such as in faded images. While the above-mentioned method required the special generation of an interpolated image that has been subjected to weighted prediction processing, this embodiment allows triangle synthesis processing to be performed after normal weighted prediction processing.

[0198] 18 is a diagram illustrating the triangle synthesis unit 30952 of this embodiment, which receives motion compensation information from the motion compensation unit 3091 as input and outputs a predicted image to the adder 312. The triangle synthesis unit 30952 is made up of an L0 default predicted image generation unit 309521, an L0 weighted predicted image generation unit 309522, an L1 default predicted image generation unit 309523, an L1 weighted predicted image generation unit 309524, and a triangle predicted image generation unit 309525. The predicted images predSamplesLA and predSamplesLB are associated with L0 prediction and L1 prediction, and default prediction or weighted prediction is selected depending on whether a weighting coefficient is present. After processing, the triangle predicted image generation unit 309525 performs synthesis processing of the triangle prediction.

[0199] (BDOF prediction) In bi-prediction mode, the BDOF unit 30954 generates a predicted image by referring to two predicted images (a first predicted image and a second predicted image) and a gradient correction term.

[0200] If the inter prediction parameter decoding unit 303 determines that L0 unidirectional prediction is being performed, the motion compensation unit 3091 generates PredL0[x][y]. If the inter prediction parameter decoding unit 303 determines that L1 unidirectional prediction is being performed, the motion compensation unit 3091 generates PredL1[x][y]. On the other hand, if the inter prediction parameter decoding unit 303 determines that the mode is bi-prediction, the following processing continues. The synthesis unit 3095 references bdofAvailableFlag, which indicates whether or not to perform BDOF processing, and determines whether or not BDOF processing is required. If bdofAvailableFlag indicates TRUE, the BDOF unit 30954 performs BDOF processing to generate a bi-directional predicted image, and if it indicates FALSE, the synthesis unit 3095 generates a predicted image using normal bi-directional predicted image generation.

[0201] (Weight prediction) The weighted prediction unit 3094 generates a predicted image pbSamples of the block from the interpolated image PredLX. First, the syntax related to the weighted prediction unit 3094 will be described.

[0202] FIG. 19(a) shows an example of the syntax of sps_weighted_pred_flag and sps_weighted_bipred_flag in a Sequence Parameter Set (SPS).

[0203] sps_weighted_pred_flag equal to 1 indicates that weighted prediction may be applied to P slices that reference an SPS. sps_weighted_pred_flag equal to 0 indicates that weighted prediction is not applied to P slices that reference an SPS. sps_weighted_bipred_flag equal to 1 indicates that weighted prediction may be applied to B slices that reference an SPS. sps_weighted_bipred_flag equal to 0 indicates that weighted prediction is not applied to B slices that reference an SPS.

[0204] FIG. 19(b) shows an example of the syntax of pps_weighted_pred_flag and pps_weighted_bipred_flag in the Picture Parameter Set (PPS).

[0205] pps_weighted_pred_flag equal to 0 indicates that weighted prediction is not applied to the P slice that references the PPS. pps_weighted_pred_flag equal to 1 indicates that weighted prediction is applied to the P slice that references the PPS. When sps_weighted_pred_flag equals 0, the weighted predictor 3094 sets the value of pps_weighted_pred_flag to 0. If pps_weighted_pred_flag is not present, the value is set to 0.

[0206] When pps_weighted_bipred_flag is equal to 0, it indicates that weighted prediction is not applied to B slices that reference a PPS. When pps_weighted_bipred_flag is equal to 1, it indicates that weighted prediction is applied to B slices that reference a PPS. When sps_weighted_bipred_flag is equal to 0, the weighted prediction unit 3094 sets the value of pps_weighted_bipred_flag to 0. If pps_weighted_bipred_flag is not present, it sets the value to 0.

[0207] FIG. 20 shows the Weighted prediction parameters syntax() of Non-Patent Document 1, which is called in the slice header. Here, luma_weight_l0_flag[i] = 1 indicates that a weighting factor for the luma component of L0 prediction is present. luma_weight_l0_flag[i] = 0 indicates that a weighting factor for the luma component of L0 prediction is not present. If luma_weight_l0_flag[i] is not present, the weight predictor 3094 infers that it is equal to 0. chroma_weight_l0_flag[i] = 1 indicates that a weighting factor for the chrominance predicted value of L0 prediction is present. chroma_weight_l0_flag[i] = 0 indicates that a weighting factor for the chrominance predicted value of L0 prediction is not present. If chroma_weight_l0_flag[i] is not present, the weight predictor 3094 infers that it is equal to 0. Similarly, luma_weight_l1_flag[i] = 1 indicates that a weighting factor for the luma component of L1 prediction is present. When luma_weight_l1_flag[i] is 0, it indicates that a weighting factor for the luma component of L1 prediction is not present. When luma_weight_l1_flag[i] is not present, the weight predictor 3094 infers it to be equal to 0. When chroma_weight_l1_flag[i] is 1, it indicates that a weighting factor for the chrominance predicted value of L1 prediction is present. When chroma_weight_l1_flag[i] is 0, it indicates that a weighting factor for the chrominance predicted value of L1 prediction is not present. When chroma_weight_l1_flag[i] is not present, the weight predictor 3094 infers it to be equal to 0.

[0208] In Non-Patent Document 1, the variable weightedPredFlag is derived as follows. If slice_type is equal to P, weightedPredFlag is set equal to pps_weighted_pred_flag defined in PPS. Otherwise, if slice_type is equal to B, weightedPredFlag is set equal to pps_weighted_bipred_flag defined in PPS.

[0209] However, the above setting has a problem in that it is not possible to fully express the relationship between the combination of the prediction methods (DMVR, BDOF, PROF, BCW) defined in Non-Patent Document 1 and weighted prediction.

[0210] Therefore, in this embodiment, the weighted prediction unit 3094 derives the variable weightedPredFlag as follows. ·If slice_type is equal to P, set weightedPredFlag to (pps_weighted_pred_flag &&((cIdx == 0)? luma_weight_l0_flag [refIdxL0]:chroma_weight_l0_flag[refIdxL0])). Otherwise (slice_type equals B), set weightedPredFlag to (pps_weighted_bipred_flag && ((cIdx == 0) ? (luma_weight_l0_flag[refIdxL0] || luma_weight_l1_flag[refIdxL1]) : (chroma_weight_l0_flag[refIdxL0] || chroma_weight_l1_flag[refIdxL1])). By deriving the weighting coefficients as described above, it becomes possible to specify separately for the luminance and color difference signals that weighted prediction is not performed when no weighting coefficient exists, thereby solving the above problem.

[0211] When one of the prediction list usage flags (predFlagL0 or predFlagL1) is 1 (uni-prediction) and weightedPredFlag is 0 (weighted prediction is not used), the following equation is processed to adjust PredLX (LX is L0 or L1) to the pixel bit depth bitDepth.

[0212] pbSamples[x][y] = Clip3(0,(1<<bitDepth)-1,(PredLX[x][y]+offset1)> >shift1) Here, shift1=14-bitDepth, offset1=1<<(shift1-1).

[0213] Furthermore, when both prediction list usage flags (predFlagL0 and predFlagL1) are 1 (bi-prediction PRED_BI) and weighted prediction is not used, the following equation is processed to average PredL0 and PredL1 and adjust them to the pixel bit rate.

[0214] pbSamples[x][y] = Clip3(0,(1<<bitDepth)-1,(PredL0[x][y]+PredL1[x][y]+offset2)> >shift2) Here, shift2=15-bitDepth, offset2=1<<(shift2-1).

[0215] Furthermore, when uni-prediction and weighted prediction are performed, the weighted prediction unit 3094 derives a weighted prediction coefficient w0 and an offset o0 from the coded data, and performs processing according to the following equations.

[0216] pbSamples[x][y] = Clip3(0,(1< <bitDepth)-1, ((PredLX[x][y]*w0+(1<<(log2WD-1)))>>log2WD)+o0) Here, log2WD is a variable indicating a predetermined shift amount.

[0217] Furthermore, when bi-prediction PRED_BI and weighted prediction are performed, the weighted prediction unit 3094 derives weighted prediction coefficients w0, w1, o0, and o1 from the coded data and performs the processing of the following equations.

[0218] pbSamples[x][y] = Clip3(0,(1< <bitDepth)-1,(PredL0[x][y]*w0+PredL1[x][y]*w1+((o0+o1+1)<<log2WD))> >(log2WD+1)) In Non-Patent Document 1, the value of the variable AbsDeltaPocSt[listIdx][rplsIdx][i] is changed depending on the values ​​of sps_weighted_pred_flag and sps_weighted_bipred_flag in the semantics of abs_delta_poc_st[listIdx][rplsIdx][i] in the syntax of Reference picture list structure syntax. However, because the Reference picture list structure syntax (ref_pic_list_struct) is called before sps_weighted_pred_flag and sps_weighted_bipred_flag are decoded in SPS, a problem occurs in which decoding cannot be performed correctly.

[0219] As an embodiment to solve the above problem and enable correct decoding, -Inside ref_pic_list_struct, prohibit the use of flags that turn tools on and off. ref_pic_list_struct is decoded using PPS and slice headers, not SPS. ref_pic_list_struct is decoded after the flag that turns the SPS tools on and off is decoded. The above problems can be solved by using any of the above methods.

[0220] (BCW forecast) Bi-prediction with CU-level Weights (BCW) prediction is a prediction method that allows switching of weighting factors determined in advance at the CU level. Two variables nCbW and nCbH that specify the width and height of the current coding block, two (nCbW) x (nCbH) arrays predSamplesL0 and predSamplesL1, flags predFlagL0 and predFlagL1 indicating whether to use a prediction list, reference indices refIdxL0 and refIdxL1, a BCW prediction index bcw_idx, and a variable cIdx that specifies the indexes of the luminance and chrominance components are input, BCW prediction processing is performed, and the predicted sample values ​​of the (nCbW) x (nCbH) array pbSamples are output.

[0221] If the sps_bcw_enabled_flag, which indicates whether or not this prediction is used at the SPS level, is set to TRUE, and the reference pictures indicated by the two reference indexes refIdxL0 and refIdxL1 do not have weighted prediction coefficients, and the number of coding blocks is equal to or less than a certain number, the syntax explicitly encodes and decodes bcw_idx at the CU level, and assigns that value to the variable bcwIdx. If bcw_idx does not exist, the variable bcwIdx is assigned 0.

[0222] If the variable bcwIdx is 0, the predicted sample values ​​are derived as follows:

[0223] pbSamples[x][y] = Clip3(0, (1 << bitDepth)- 1, (predSamplesL0[x][y] + predSamplesL1[x][y] + offset2)>> shift2) Otherwise, if bcwIdx is not equal to 0, the following applies:

[0224] The variable w1 is set equal to bcwWLut[bcwIdx], where bcwWLut[k] = {4, 5, 3, 10, -2}.

[0225] The variable w0 is set to (8-w1), and the predicted sample values ​​are derived as follows:

[0226] pbSamples[x][y] = Clip3(0, (1 << bitDepth)- 1, (w0 * predSamplesL0[x][y] + w1 * predSamplesL1[x][y] + offset3)>>(shift2 + 3)) When BCW prediction is used in AMVP prediction mode, the inter prediction parameter decoding unit 303 decodes bcw_idx and sends it to the BCW unit 30955. When BCW prediction is used in merge prediction mode, the inter prediction parameter decoding unit 303 decodes the merge index merge_idx, and the merge candidate derivation unit 30361 derives bcwIdx for each merge candidate. Specifically, the merge candidate derivation unit 30361 uses the weighting coefficients of the neighboring blocks used to derive the merge candidates as the weighting coefficients of the merge candidates to be used for the current block. In other words, in merge mode, the weighting coefficients used in the past are inherited as the weighting coefficients of the current block.

[0227] (Intra-predicted image generation unit 310) When predMode indicates an intra prediction mode, the intra prediction image generation unit 310 performs intra prediction using the intra prediction parameters input from the intra prediction parameter derivation unit 304 and reference pixels read from the reference picture memory 306 .

[0228] The inverse quantization and inverse transform unit 311 inverse quantizes the quantized transform coefficients input from the parameter decoding unit 302 to obtain transform coefficients.

[0229] The adder 312 generates a decoded image for the block by adding, for each pixel, the predicted image for the block input from the predicted image generation unit 308 and the prediction error input from the inverse quantization and inverse transform unit 311. The adder 312 stores the decoded image for the block in the reference picture memory 306 and also outputs it to the loop filter 305.

[0230] (Configuration of a video encoding device) Next, the configuration of the video encoding device 11 according to this embodiment will be described. Fig. 15 is a block diagram showing the configuration of the video encoding device 11 according to this embodiment. The video encoding device 11 includes a prediction image generation unit 101, a subtraction unit 102, a transformation and quantization unit 103, an inverse quantization and inverse transformation unit 105, an addition unit 106, a loop filter 107, a prediction parameter memory (prediction parameter storage unit, frame memory) 108, a reference picture memory (reference image storage unit, frame memory) 109, a coding parameter determination unit 110, a parameter coding unit 111, a prediction parameter derivation unit 120, and an entropy coding unit 104.

[0231] The predicted image generation unit 101 generates a predicted image for each CU. The predicted image generation unit 101 includes the inter predicted image generation unit 309 and the intra predicted image generation unit 310, which have already been described, and therefore further description thereof will be omitted.

[0232] The subtraction unit 102 generates a prediction error by subtracting pixel values ​​of the predicted image of the block input from the predicted image generation unit 101 from pixel values ​​of the image T. The subtraction unit 102 outputs the prediction error to the transformation and quantization unit 103.

[0233] The transform / quantization unit 103 calculates transform coefficients by frequency transforming the prediction errors input from the subtraction unit 102, and derives quantized transform coefficients by quantizing them. The transform / quantization unit 103 outputs the quantized transform coefficients to the parameter coding unit 111 and the inverse quantization / inverse transform unit 105.

[0234] The inverse quantization and inverse transform unit 105 is the same as the inverse quantization and inverse transform unit 311 (FIG. 7) in the video decoding device 31, and a description thereof will be omitted. The calculated prediction error is output to the adder .

[0235] The parameter coding unit 111 includes a header coding unit 1110, a CT information coding unit 1111, and a CU coding unit 1112 (prediction mode coding unit). The CU coding unit 1112 further includes a TU coding unit 1114. The following describes an outline of the operation of each module.

[0236] The header encoding unit 1110 performs encoding processing of parameters such as header information, division information, prediction information, and quantized transform coefficients.

[0237] The CT information encoding unit 1111 encodes QT, MT (BT, TT) division information and the like.

[0238] The CU encoding unit 1112 encodes CU information, prediction information, division information, and the like.

[0239] When a prediction error is included in a TU, the TU encoding unit 1114 encodes the QP update information and the quantized prediction error.

[0240] The CT information encoding unit 1111 and the CU encoding unit 1112 supply syntax elements such as inter prediction parameters (predMode, merge_flag, merge_idx, inter_pred_idc, refIdxLX, mvp_LX_idx, mvdLX), intra prediction parameters, and quantized transform coefficients to the parameter encoding unit 111.

[0241] The entropy coding unit 104 receives the quantized transform coefficients and coding parameters (division information, prediction parameters) from the parameter coding unit 111. The entropy coding unit 104 entropy codes these to generate and output a coded stream Te.

[0242] The prediction parameter derivation unit 120 is a means including an inter-prediction parameter coding unit 112 and an intra-prediction parameter coding unit 113, and derives intra-prediction parameters and intra-prediction parameters from the parameters input from the coding parameter determination unit 110. The derived intra-prediction parameters and intra-prediction parameters are output to the parameter coding unit 111.

[0243] (Configuration of Inter-Prediction Parameter Encoding Unit) 16 , the inter prediction parameter coding unit 112 includes a parameter coding control unit 1121 and an inter prediction parameter derivation unit 303. The inter prediction parameter derivation unit 303 has the same configuration as the video decoding device. The parameter coding control unit 1121 includes a merge index derivation unit 11211 and a vector candidate index derivation unit 11212.

[0244] The merge index derivation unit 11211 derives merge candidates and the like, and outputs them to the inter prediction parameter derivation unit 303. The vector candidate index derivation unit 11212 derives predicted vector candidates and the like, and outputs them to the inter prediction parameter derivation unit 303 and the parameter coding unit 111.

[0245] (Configuration of the intra-prediction parameter encoding unit 113) The intra prediction parameter encoding unit 113 includes a parameter encoding control unit 1131 and an intra prediction parameter derivation unit 304. The intra prediction parameter derivation unit 304 has the same configuration as the video decoding device.

[0246] However, unlike the video decoding device, the inputs to the inter prediction parameter derivation unit 303 and the intra prediction parameter derivation unit 304 are the coding parameter determination unit 110 and the prediction parameter memory 108 , and they are output to the parameter coding unit 111 .

[0247] The adder 106 generates a decoded image by adding, for each pixel, the pixel values ​​of the predicted block input from the predicted image generation unit 101 and the prediction errors input from the inverse quantization and inverse transform unit 105. The adder 106 stores the generated decoded image in a reference picture memory 109.

[0248] The loop filter 107 performs deblocking filtering, SAO, and ALF on the decoded image generated by the adder 106. Note that the loop filter 107 does not necessarily have to include the above three types of filters, and may be configured with only a deblocking filter, for example.

[0249] The prediction parameter memory 108 stores the prediction parameters generated by the coding parameter determination unit 110 in a predetermined location for each current picture and CU.

[0250] The reference picture memory 109 stores the decoded image generated by the loop filter 107 at a predetermined location for each current picture and CU.

[0251] The coding parameter determination unit 110 selects one set of coding parameters from among a plurality of sets of coding parameters. The coding parameters are the above-mentioned QT, BT, or TT division information, prediction parameters, or parameters to be coded that are generated in relation to these. The predicted image generation unit 101 generates a predicted image using these coding parameters.

[0252] The coding parameter determination unit 110 calculates an RD cost value indicating the magnitude of the information amount and the coding error for each of the multiple sets. The RD cost value is, for example, the sum of the code amount and the value obtained by multiplying the squared error by a coefficient λ. The code amount is the information amount of the coded stream Te obtained by entropy coding the quantization error and the coding parameters. The squared error is the sum of the squares of the prediction errors calculated by the subtraction unit 102. The coefficient λ is a preset real number greater than zero. The coding parameter determination unit 110 selects the set of coding parameters that minimizes the calculated cost value. The coding parameter determination unit 110 outputs the determined coding parameters to the parameter coding unit 111 and the prediction parameter derivation unit 120.

[0253] Note that parts of the video encoding device 11 and the video decoding device 31 in the above-described embodiments, such as the entropy decoding unit 301, the parameter decoding unit 302, the loop filter 305, the predicted image generating unit 308, the inverse quantization and inverse transform unit 311, the adder 312, the prediction parameter derivation unit 320, the predicted image generating unit 101, the subtractor 102, the transform and quantization unit 103, the entropy encoding unit 104, the inverse quantization and inverse transform unit 105, the loop filter 107, the encoding parameter determining unit 110, the parameter encoding unit 111, and the prediction parameter derivation unit 120, may be implemented by a computer. In this case, a program for implementing these control functions may be recorded on a computer-readable recording medium, and the program may be read into and executed by a computer system. Note that the term "computer system" used here refers to a computer system built into either the video encoding device 11 or the video decoding device 31, and includes hardware such as an OS and peripheral devices. Furthermore, "computer-readable recording media" refers to portable media such as flexible disks, optical magnetic disks, ROMs, and CD-ROMs, as well as storage devices such as hard disks built into computer systems. Furthermore, "computer-readable recording media" may also include devices that dynamically store programs for a short period of time, such as communication lines used when transmitting programs over networks like the Internet or communication lines like telephone lines, or devices that store programs for a fixed period of time, such as volatile memory within computer systems that serve as servers or clients in such cases. Furthermore, the programs may be programs that realize some of the aforementioned functions, or may be programs that can realize the aforementioned functions in combination with programs already stored in the computer system.

[0254] Furthermore, part or all of the video encoding device 11 and video decoding device 31 in the above-described embodiments may be realized as an integrated circuit such as an LSI (Large Scale Integration). Each functional block of the video encoding device 11 and video decoding device 31 may be individually implemented as a processor, or part or all of them may be integrated into a processor. Furthermore, the integrated circuit implementation method is not limited to LSI, and may be implemented using a dedicated circuit or a general-purpose processor. Furthermore, if an integrated circuit implementation technology that can replace LSI emerges due to advances in semiconductor technology, an integrated circuit based on that technology may be used.

[0255] One embodiment of the present invention has been described in detail above with reference to the drawings, but the specific configuration is not limited to that described above, and various design changes and the like are possible within the scope that does not deviate from the gist of the present invention.

[0256] [Application example] The above-described video encoding device 11 and video decoding device 31 can be mounted on various devices that transmit, receive, record, and play back video. The video may be a natural video captured by a camera or the like, or an artificial video (including CG and GUI) generated by a computer or the like.

[0257] First, it will be explained with reference to FIG. 2 that the above-described video encoding device 11 and video decoding device 31 can be used for transmitting and receiving video.

[0258] 2(a) is a block diagram showing the configuration of a transmitting device PROD_A equipped with a video encoding device 11. As shown in the figure, the transmitting device PROD_A includes an encoding unit PROD_A1 that encodes video to obtain encoded data, a modulation unit PROD_A2 that modulates a carrier wave with the encoded data obtained by the encoding unit PROD_A1 to obtain a modulated signal, and a transmitting unit PROD_A3 that transmits the modulated signal obtained by the modulation unit PROD_A2. The above-described video encoding device 11 is used as this encoding unit PROD_A1.

[0259] The transmitting device PROD_A may further include, as a source of moving images to be input to the encoding unit PROD_A1, a camera PROD_A4 that captures moving images, a recording medium PROD_A5 on which moving images are recorded, an input terminal PROD_A6 for inputting moving images from the outside, and an image processing unit A7 that generates or processes images. In the figure, the transmitting device PROD_A is shown as having all of these components, but some of them may be omitted.

[0260] The recording medium PROD_A5 may record unencoded video, or may record video encoded using a recording encoding method that is different from the transmission encoding method. In the latter case, a decoding unit (not shown) that decodes the encoded data read from the recording medium PROD_A5 according to the recording encoding method may be interposed between the recording medium PROD_A5 and the encoding unit PROD_A1.

[0261] 2(b) is a block diagram showing the configuration of a receiving device PROD_B equipped with a video decoding device 31. As shown in the figure, the receiving device PROD_B includes a receiving unit PROD_B1 that receives a modulated signal, a demodulating unit PROD_B2 that obtains coded data by demodulating the modulated signal received by the receiving unit PROD_B1, and a decoding unit PROD_B3 that obtains video by decoding the coded data obtained by the demodulating unit PROD_B2. The above-mentioned video decoding device 31 is used as this decoding unit PROD_B3.

[0262] The receiving device PROD_B may further include, as destinations of the moving images output by the decoding unit PROD_B3, a display PROD_B4 for displaying the moving images, a recording medium PROD_B5 for recording the moving images, and an output terminal PROD_B6 for outputting the moving images to the outside. In the figure, the receiving device PROD_B is shown as having all of these components, but some of them may be omitted.

[0263] The recording medium PROD_B5 may be for recording unencoded video, or may be encoded using an encoding method for recording that is different from the encoding method for transmission. In the latter case, it is preferable to interpose an encoding unit (not shown) between the decoding unit PROD_B3 and the recording medium PROD_B5, which encodes the video acquired from the decoding unit PROD_B3 according to the encoding method for recording.

[0264] The transmission medium for transmitting the modulated signal may be wireless or wired. The transmission mode for transmitting the modulated signal may be broadcast (here, this refers to a transmission mode in which the destination is not specified in advance) or communication (here, this refers to a transmission mode in which the destination is specified in advance). In other words, the transmission of the modulated signal may be realized by any of wireless broadcasting, wired broadcasting, wireless communication, and wired communication.

[0265] For example, a broadcasting station (such as a broadcasting facility) / receiving station (such as a television receiver) for terrestrial digital broadcasting is an example of a transmitting device PROD_A / receiving device PROD_B that transmits and receives modulated signals via wireless broadcasting. Also, a broadcasting station (such as a broadcasting facility) / receiving station (such as a television receiver) for cable television broadcasting is an example of a transmitting device PROD_A / receiving device PROD_B that transmits and receives modulated signals via cable broadcasting.

[0266] Furthermore, a server (such as a workstation) / client (such as a television receiver, personal computer, or smartphone) of an Internet-based VOD (Video On Demand) service or video sharing service is an example of a transmitter PROD_A / receiver PROD_B that transmits and receives modulated signals via communication (usually, a LAN uses either a wireless or wired transmission medium, while a WAN uses a wired transmission medium). Here, personal computers include desktop PCs, laptop PCs, and tablet PCs. Smartphones also include multi-function mobile phone terminals.

[0267] The client of the video hosting service has the function of decoding the encoded data downloaded from the server and displaying it on a display, as well as the function of encoding the video images captured by a camera and uploading them to the server. In other words, the client of the video hosting service functions as both the transmitting device PROD_A and the receiving device PROD_B.

[0268] Next, it will be explained with reference to FIG. 3 that the above-described video encoding device 11 and video decoding device 31 can be used for recording and reproducing video.

[0269] 3(a) is a block diagram showing the configuration of a recording device PROD_C equipped with the above-mentioned video encoding device 11. As shown in the figure, the recording device PROD_C includes an encoding unit PROD_C1 that obtains encoded data by encoding video, and a writing unit PROD_C2 that writes the encoded data obtained by the encoding unit PROD_C1 onto a recording medium PROD_M. The above-mentioned video encoding device 11 is used as this encoding unit PROD_C1.

[0270] The recording medium PROD_M may be (1) a type that is built into the recording device PROD_C, such as an HDD (Hard Disk Drive) or SSD (Solid State Drive), (2) a type that is connected to the recording device PROD_C, such as an SD memory card or USB (Universal Serial Bus) flash memory, or (3) a type that is loaded into a drive device (not shown) built into the recording device PROD_C, such as a DVD (Digital Versatile Disc: registered trademark) or BD (Blu-ray Disc: registered trademark).

[0271] The recording device PROD_C may further include a camera PROD_C3 that captures moving images, an input terminal PROD_C4 for inputting moving images from an external device, a receiving unit PROD_C5 for receiving moving images, and an image processing unit PROD_C6 that generates or processes images, as sources of moving images to be input to the encoding unit PROD_C1. Although the figure illustrates a configuration in which the recording device PROD_C includes all of these components, some of them may be omitted.

[0272] The receiving unit PROD_C5 may receive unencoded video, or may receive encoded data encoded by a transmission encoding method different from the recording encoding method. In the latter case, a transmission decoding unit (not shown) that decodes the encoded data encoded by the transmission encoding method may be interposed between the receiving unit PROD_C5 and the encoding unit PROD_C1.

[0273] Examples of such a recording device PROD_C include a DVD recorder, a BD recorder, and an HDD (Hard Disk Drive) recorder (in this case, the input terminal PROD_C4 or the receiving unit PROD_C5 is the main source of moving images).Other examples of such a recording device PROD_C include a camcorder (in this case, the camera PROD_C3 is the main source of moving images), a personal computer (in this case, the receiving unit PROD_C5 or the image processing unit C6 is the main source of moving images), and a smartphone (in this case, the camera PROD_C3 or the receiving unit PROD_C5 is the main source of moving images).

[0274] 3(b) is a block diagram showing the configuration of a playback device PROD_D equipped with the above-mentioned video decoding device 31. As shown in the figure, the playback device PROD_D includes a reading unit PROD_D1 that reads coded data written on a recording medium PROD_M, and a decoding unit PROD_D2 that obtains video by decoding the coded data read by the reading unit PROD_D1. The above-mentioned video decoding device 31 is used as this decoding unit PROD_D2.

[0275] The recording medium PROD_M may be (1) a type that is built into the playback device PROD_D, such as an HDD or SSD, (2) a type that is connected to the playback device PROD_D, such as an SD memory card or USB flash memory, or (3) a type that is loaded into a drive device (not shown) built into the playback device PROD_D, such as a DVD or BD.

[0276] The playback device PROD_D may further include, as destinations of the video output by the decoding unit PROD_D2, a display PROD_D3 that displays the video, an output terminal PROD_D4 that outputs the video to the outside, and a transmission unit PROD_D5 that transmits the video. Although the figure shows an example of a configuration in which the playback device PROD_D includes all of these, some of them may be omitted.

[0277] The transmitting unit PROD_D5 may transmit unencoded video, or may transmit encoded data encoded by a transmission encoding method different from the recording encoding method. In the latter case, it is preferable to interpose an encoding unit (not shown) between the decoding unit PROD_D2 and the transmitting unit PROD_D5, which encodes the video by the transmission encoding method.

[0278] Examples of such a playback device PROD_D include a DVD player, a BD player, and an HDD player (in this case, the output terminal PROD_D4 to which a television receiver or the like is connected is the main destination of the moving images). Other examples of such a playback device PROD_D include a television receiver (in this case, the display PROD_D3 is the main destination of the moving images), a digital signage (also called an electronic billboard or electronic bulletin board, and the display PROD_D3 or the transmitter PROD_D5 is the main destination of the moving images), a desktop PC (in this case, the output terminal PROD_D4 or the transmitter PROD_D5 is the main destination of the moving images), a laptop or tablet PC (in this case, the display PROD_D3 or the transmitter PROD_D5 is the main destination of the moving images), and a smartphone (in this case, the display PROD_D3 or the transmitter PROD_D5 is the main destination of the moving images).

[0279] (hardware and software implementations) Furthermore, each block of the above-mentioned video decoding device 31 and video encoding device 11 may be realized in hardware by a logic circuit formed on an integrated circuit (IC chip), or may be realized in software using a CPU (Central Processing Unit).

[0280] In the latter case, each of the above devices includes a CPU that executes instructions of a program that realizes each function, a ROM (Read Only Memory) that stores the program, a RAM (Random Access Memory) that expands the program, and a storage device (recording medium) such as a memory that stores the program and various data.The object of the embodiment of the present invention can also be achieved by supplying each of the above devices with a recording medium on which program code (executable program, intermediate code program, source program) of a control program for each of the above devices, which is software that realizes the above-mentioned functions, is recorded in a computer-readable manner, and having the computer (or CPU or MPU) read and execute the program code recorded on the recording medium.

[0281] Examples of the recording medium that can be used include tapes such as magnetic tape and cassette tape, magnetic disks such as floppy disks (registered trademark) and hard disks, disks including optical disks such as CD-ROMs (Compact Disc Read-Only Memory), MO disks (Magneto-Optical discs), MDs (Mini Discs), DVDs (Digital Versatile Discs: registered trademark), CD-Rs (CD Recordable), and Blu-ray Discs (registered trademark), cards such as IC cards (including memory cards) and optical cards, semiconductor memories such as mask ROMs, EPROMs (Erasable Programmable Read-Only Memory), EEPROMs (Electrically Erasable and Programmable Read-Only Memory: registered trademark), and flash ROMs, and logic circuits such as PLDs (Programmable logic devices) and FPGAs (Field Programmable Gate Arrays).

[0282] Furthermore, each of the above devices may be configured to be connectable to a communications network, and the program code may be supplied via the communications network. This communications network may be any network capable of transmitting the program code. For example, the Internet, an intranet, an extranet, a local area network (LAN), an integrated services digital network (ISDN), a value-added network (VAN), a community antenna television / cable television (CATV) communications network, a virtual private network, a telephone line network, a mobile communications network, a satellite communications network, etc. Furthermore, the transmission media constituting this communications network may be any medium capable of transmitting the program code, and are not limited to any particular configuration or type. For example, the present invention can be used in wired communication such as IEEE (Institute of Electrical and Electronic Engineers) 1394, USB, power line carrier, cable TV line, telephone line, or ADSL (Asymmetric Digital Subscriber Line) line, or in wireless communication such as IrDA (Infrared Data Association), infrared such as that used in remote controls, Bluetooth (registered trademark), IEEE 802.11 wireless, HDR (High Data Rate), NFC (Near Field Communication), DLNA (Digital Living Network Alliance: registered trademark), mobile phone networks, satellite lines, or terrestrial digital broadcasting networks. Note that the present invention can also be realized in the form of a computer data signal embedded in a carrier wave in which the program code is embodied by electronic transmission.

[0283] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. In other words, embodiments obtained by combining technical means modified appropriately within the scope of the claims are also included in the technical scope of the present invention. [Industrial Applicability]

[0284] The embodiments of the present invention can be suitably applied to a video decoding device that decodes coded data obtained by coding image data, and a video coding device that generates coded data obtained by coding image data, and can also be suitably applied to the data structure of coded data generated by a video coding device and referenced by the video decoding device. [Explanation of symbols]

[0285] 31 Image decoding device 301 Entropy Decoding Unit 302 Parameter Decoding Unit 303 Inter-prediction parameter derivation unit 304 Intra prediction parameter derivation unit 305, 107 Loop filter 306, 109 Reference Picture Memory 307, 108 Prediction parameter memory 308, 101 Prediction image generation unit 309 Inter-prediction image generation unit 310 Intra-prediction image generation unit 311, 105 Inverse quantization and inverse transform unit 312, 106 Addition section 320 Prediction parameter derivation part 11 Image encoding device 102 Subtraction section 103 Transformation and Quantization Unit 104 Entropy coding unit 110 Encoding parameter determination unit 111 Parameter Encoding Unit 112 Inter-prediction parameter coding unit 113 Intra prediction parameter coding unit 120 Prediction parameter derivation part

Claims

1. A video decoding device, deriving affine prediction parameters from the motion vectors of the plurality of control points; deriving a first motion vector difference array from the affine prediction parameters; clipping the first motion vector difference array to derive a second motion vector difference array; Deriving a first variable for calculating a gradient from the predicted array sample array; deriving a second variable from the second motion vector difference array and the first variable from which the gradient is calculated; an affine prediction unit that derives predicted sample values ​​from the predicted sample array and the second variable; Here, the first motion vector difference array is clipped to a range using a fixed value that does not depend on a pixel bit length, and the fixed value is equal to 32.

2. A video encoding device, comprising: deriving affine prediction parameters from the motion vectors of the plurality of control points; deriving a first motion vector difference array from the affine prediction parameters; clipping the first motion vector difference array to derive a second motion vector difference array; Deriving a first variable for calculating a gradient from the predicted array sample array; deriving a second variable from the second motion vector difference array and the first variable from which the gradient is calculated; an affine prediction unit that derives predicted sample values ​​from the predicted sample array and the second variable; Here, the first motion vector difference array is clipped to a range using a fixed value that does not depend on a pixel bit length, and the fixed value is equal to 32.

3. A computer-readable recording medium having a program recorded thereon for causing a computer to decode a moving image, The program is executed on the computer. deriving affine prediction parameters from motion vectors of a plurality of control points; deriving a first motion vector difference array from the affine prediction parameters; clipping the first motion vector difference array to derive a second motion vector difference array; deriving a first variable for calculating a gradient from the predicted array sample array; deriving a second variable from the second motion vector difference array and the first variable from which the gradient is calculated; deriving predicted sample values ​​from the predicted sample array and the second variable; wherein the first motion vector difference array is clipped to a range using a fixed value that is independent of pixel bit length, and the fixed value is equal to 32.

Images