Video encoding device, image encoding method, image encoding program, video decoding device, image decoding method, image decoding program, transmission method and recording method for transmitting bit stream generated by image encoding device

Abstract

To provide a technique for improving coding efficiency by performing block division suitable for image coding and decoding.SOLUTION: An image encoding device includes a coding information storage unit that updates a candidate included in a history candidate list with inter prediction information used in inter-prediction, a spatial candidate derivation unit that derives a spatial candidate from the inter prediction information of a plurality of blocks adjacent to an encoding target block and adds the spatial candidate to a first candidate list, a history candidate derivation unit that adds one or more candidates included in the history candidate list to the first candidate list to form a second candidate list, a candidate selection unit that selects one selection candidate from candidates included in the second candidate list, and an inter prediction unit that performs inter prediction using the selection candidate as inter prediction information. The history candidate derivation unit switches whether to add a candidate that overlaps with a candidate included in the first candidate list according to an inter prediction mode.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an image encoding and decoding technique that divides an image into blocks and performs prediction. [Background technology]

[0002] In image encoding and decoding, the image to be processed is divided into blocks, which are collections of a certain number of pixels, and processed on a block-by-block basis. By dividing the image into appropriate blocks and appropriately setting intra-frame prediction (intra-prediction) and inter-frame prediction (inter-prediction), the encoding efficiency can be improved.

[0003] In video coding and decoding, coding efficiency is improved by inter-prediction, which predicts from pictures that have already been coded and decoded. Patent Document 1 describes a technique for applying affine transformation during inter-prediction. In video, it is not uncommon for objects to undergo transformations such as enlargement, reduction, and rotation, and applying the technique of Patent Document 1 enables efficient coding. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 9-172644 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the technique of Patent Document 1 involves image conversion, and therefore has the problem of a large processing load. In view of the above problem, the present invention provides an efficient encoding technique with a low load. [Means for solving the problem]

[0006] In order to solve the above problem, an image decoding device of one embodiment of the present invention includes an encoding information storage unit that updates candidates included in a history candidate list with inter prediction information used in inter prediction; a spatial candidate derivation unit that derives spatial candidates from inter prediction information of a plurality of blocks adjacent to a block to be decoded and adds the spatial candidates to a first candidate list; a history candidate derivation unit that adds one or more candidates included in the history candidate list to the first candidate list to create a second candidate list; a candidate selection unit that selects one selection candidate from the candidates included in the second candidate list; and an inter prediction unit that performs inter prediction using the selected candidate as inter prediction information, wherein the history candidate derivation unit switches whether or not to add candidates that overlap with candidates included in the first candidate list depending on the inter prediction mode. Effect of the Invention

[0007] According to the present invention, highly efficient image encoding / decoding processing can be realized with a low load. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a block diagram of an image encoding device according to a first embodiment. [Diagram 2] FIG. 1 is a block diagram of an image decoding device according to a first embodiment. [Diagram 3] 13 is a flowchart for explaining an operation of dividing a tree block. [Figure 4] FIG. 13 is a diagram showing how an input image is divided into tree blocks. [Diagram 5] FIG. 1 is a diagram illustrating a z-scan. [Figure 6] FIG. 13 is a diagram showing the divided shapes of blocks. [Figure 7] 13 is a flowchart for explaining an operation of dividing a block into four. [Figure 8] 13 is a flowchart for explaining an operation of dividing a block into two or three. [Figure 9] This is a syntax for expressing the shape of block division. [Figure 10] FIG. 1 is a diagram illustrating intra prediction. [Figure 11] FIG. 13 is a diagram for explaining reference blocks for inter prediction. [Figure 12] This is a syntax for expressing a coding block prediction mode. [Figure 13] FIG. 11 is a diagram showing the correspondence between syntax elements and modes relating to inter prediction. [Figure 14] FIG. 13 is a diagram for explaining affine transformation motion compensation of two control points. [Figure 15] FIG. 13 is a diagram for explaining affine transformation motion compensation of three control points. [Figure 16] FIG. 2 is a block diagram showing a detailed configuration of an inter prediction unit 201 in FIG. [Figure 17] 17 is a block diagram showing a detailed configuration of a normal predicted motion vector mode derivation unit 301 in FIG. 16. [Figure 18] 17 is a block diagram showing a detailed configuration of a normal merge mode derivation unit 302 in FIG. 16. [Figure 19] 17 is a flowchart for explaining a normal predicted motion vector mode derivation process of the normal predicted motion vector mode derivation unit 301 of FIG. 16. [Figure 20] 13 is a flowchart showing a processing procedure of a normal predictor motion vector mode derivation process having a function common to a normal predictor motion vector mode derivation unit 301 and a normal predictor motion vector mode derivation unit 401 according to the embodiment of the present invention. [Figure 21] 11 is a flowchart illustrating a procedure of a merge mode derivation process having a function common to a normal merge mode derivation unit 302 and a normal merge mode derivation unit 402 according to the embodiment of the present invention. [Figure 22] FIG. 3 is a block diagram showing a detailed configuration of an inter prediction unit 203 in FIG. 2. [Figure 23] 23 is a block diagram showing a detailed configuration of a normal predicted motion vector mode derivation unit 301 in FIG. 22. FIG. [Figure 24]17 is a block diagram showing a detailed configuration of a normal merge mode derivation unit 302 in FIG. 16. [Diagram 25] 23 is a flowchart for explaining a normal predicted motion vector mode derivation process of the normal predicted motion vector mode derivation unit 301 in FIG. 22. [Figure 26] 3 is a block diagram of a sub-block prediction motion vector mode derivation unit 303 in the encoding device of the present application. FIG. [Figure 27] 4 is a block diagram of a sub-block prediction motion vector mode derivation unit 403 in the decoding device of the present application. FIG. [Figure 28] FIG. 3 is a block diagram of a sub-block merge mode derivation unit 304 in the encoding device of the present application. [Figure 29] FIG. 4 is a block diagram of a sub-block merging mode derivation unit 404 in the decoding device of the present application. [Diagram 30] FIG. 13 is a diagram for explaining derivation of affine inheritance predicted motion vector candidates. [Diagram 31] FIG. 13 is a diagram for explaining derivation of affine constructed predicted motion vector candidates. [Diagram 32] FIG. 13 is a diagram for explaining affine inheritance merge candidate derivation. [Diagram 33] FIG. 13 is a diagram illustrating affine construction merge candidate derivation. [Diagram 34] 13 is a flowchart of deriving an affine inheritance predicted motion vector candidate. [Diagram 35] 13 is a flowchart of deriving an affine constructed predicted motion vector candidate. [Diagram 36] 13 is a flowchart of affine inheritance merge candidate derivation. [Figure 37] 13 is a flowchart of affine construct merge candidate derivation. [Figure 38] 38 is a flowchart for explaining a procedure for initializing and updating a history motion vector predictor candidate list. [Figure 39] 13 is a flowchart of a procedure of a same element confirmation process in the procedure of a process of deriving a history predicted motion vector candidate. [Diagram 40]13 is a flowchart of an element shifting process procedure in the history motion vector predictor candidate derivation process procedure. [Diagram 41] 13 is a flowchart illustrating a procedure of a process of deriving a history predicted motion vector candidate. [Diagram 42] 13 is a flowchart illustrating a history merging candidate derivation process procedure. [Diagram 43] FIG. 11 is a diagram for explaining a procedure of a history motion vector predictor candidate list update process. [Diagram 44] 13 is a flowchart for explaining the operation of the sub-block temporal merge candidate derivation unit 381. [Diagram 45] 13 is a flowchart illustrating a process of deriving adjacent motion information of a block. [Diagram 46] 13 is a flowchart illustrating a process of deriving a temporal motion vector. [Figure 47] 13 is a flowchart illustrating derivation of inter prediction information. [Figure 48] 13 is a flowchart illustrating a process of deriving sub-block motion information. [Figure 49] FIG. 2 is a diagram for explaining the temporal relationship between pictures. [Figure 50] 13 is a flowchart for explaining a process of deriving a temporal motion vector predictor candidate in a normal motion vector predictor mode derivation unit 301. [Figure 51] 13 is a flowchart for explaining the derivation process of ColPic in the derivation process of a temporal motion vector predictor candidate in the normal motion vector predictor mode derivation unit 301. [Figure 52] 13 is a flowchart for explaining a process of deriving coding information of ColPic in a process of derivation of a temporal motion vector predictor candidate in the normal motion vector predictor mode derivation unit 301. [Diagram 53] 13 is a flowchart illustrating a process of deriving inter prediction information. [Figure 54]13 is a flowchart showing the procedure of a process of deriving inter prediction information of a coding block when the inter prediction mode of the coding block colCb is bi-prediction (Pred_BI). [Figure 55] 13 is a flowchart illustrating a procedure of a motion vector scaling calculation process. [Figure 56] 13 is a flowchart illustrating a process of deriving a temporal merge candidate. [Figure 57] FIG. 13 is a diagram for explaining the prediction direction of motion compensation prediction in the case where uni-prediction is used and the L0 reference picture (RefL0Pic) is located at a time earlier than the current picture to be coded (CurPic). [Figure 58] FIG. 13 is a diagram for explaining the prediction direction of motion compensation prediction in a case where uni-prediction is performed and the reference picture for L0 prediction is at a later time than the current picture to be coded. [Figure 59] FIG. 1 is a diagram for explaining the prediction direction of motion compensation prediction in a bi-predictive case where a reference picture for L0 prediction is located at a time earlier than the picture to be coded and a reference picture for L1 prediction is located at a time later than the picture to be coded. [Figure 60] FIG. 13 is a diagram for explaining the prediction direction of motion compensation prediction in bi-prediction where a reference picture for L0 prediction and a reference picture for L1 prediction are located at a time earlier than the current picture to be coded. [Figure 61] FIG. 13 is a diagram for explaining the prediction direction of motion compensation prediction in bi-prediction where a reference picture for L0 prediction and a reference picture for L1 prediction are located at a time later than the current picture to be coded. [Figure 62] 13 is a table showing an example of a history motion vector predictor candidate added by initialization of a history motion vector predictor candidate list. [Figure 63] 13 is a table showing another example of a history motion vector predictor candidate added by initialization of the history motion vector predictor candidate list. [Figure 64] 13 is a table showing another example of a history motion vector predictor candidate added by initialization of the history motion vector predictor candidate list. [Figure 65]13 is a flowchart illustrating a procedure of a historical motion vector predictor candidate derivation process according to Modification 2 of the first embodiment. [Figure 66] FIG. 2 is a diagram illustrating an example of a hardware configuration of a coding / decoding device according to a first embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The technologies and technical terms used in this embodiment will be defined below.

[0010] <Tree Block> In the embodiment, the image to be encoded / decoded is divided equally into a predetermined size. This unit is defined as a tree block. As shown in FIG. 4, in the embodiment, the size of the tree block is set to 128x128 pixels, but the size of the tree block is not limited to this and may be set to any size. The tree blocks to be processed (corresponding to the encoding target in the encoding process and the decoding target in the decoding process) are switched in raster scan order, that is, from left to right and from top to bottom. The inside of each tree block can be further divided recursively. The block to be encoded / decoded after the tree block division is defined as an encoding block. In addition, the tree block and the encoding block are collectively defined as a block. Efficient encoding is possible by performing appropriate block division. The size of the tree block can be a fixed value previously determined by the encoding device and the decoding device, or the size of the tree block determined by the encoding device can be transmitted to the decoding device.

[0011] <Prediction mode> For each coding block to be processed, switching is performed between intra prediction (MODE_INTRA), which makes predictions from surrounding image signals of the processed image to be processed (in coding processing, signals for which coding has been completed are used for decoded images, image signals, etc., and in decoding processing, signals for images for which decoding has been completed, preview image signals, etc.), and inter prediction (MODE_INTER), which makes predictions from image signals of the processed image. The mode that distinguishes between this intra prediction (MODE_INTRA) and inter prediction (MODE_INTER) is defined as the prediction mode (PredMode). The prediction mode (PredMode) has values ​​of intra prediction (MODE_INTRA) or inter prediction (MODE_INTER), which can be selected for coding.

[0012] <Inter Prediction> In inter prediction, which performs prediction from an image signal of a processed image, multiple processed images can be used as reference pictures. In order to manage multiple reference pictures, two types of lists, L0 (reference list 0) and L1 (reference list L1), are defined, and reference pictures are identified using reference indexes for each. L0 prediction (Pred_L0) is available for P slices. L0 prediction (Pred_L0), L1 prediction (Pred_L1), and bi-prediction (Pred_BI) are available for B slices. L0 prediction (Pred_L0) is inter prediction that refers to a reference picture managed in L0, and L1 prediction (Pred_L1) is inter prediction that refers to a reference picture managed in L1. Bi-prediction (Pred_BI) is inter prediction in which both L0 prediction and L1 prediction are performed, and one reference picture managed in each of L0 and L1 is referenced. Information that identifies L0 prediction, L1 prediction, and bi-prediction is defined as a reference mode. In the subsequent processing, it is assumed that the constants and variables with the subscript LX in the output are processed for each L0 and L1.

[0013] <Predictive motion vector mode> The predicted motion vector mode is a mode in which an index for identifying a predicted motion vector, a differential motion vector, a reference mode, and a reference index are transmitted to determine inter prediction information for a block to be coded. The predicted motion vector is derived from a predicted motion vector candidate derived from a processed block adjacent to the block to be processed, or a block belonging to a processed image that is located at the same position as the block to be processed or in the vicinity (neighborhood), and an index for identifying the predicted motion vector.

[0014] <Merge mode> Merge mode is a mode in which inter-prediction information for the block to be processed is derived from inter-prediction information for a processed block adjacent to the block to be processed, or a block belonging to a processed image that is located at the same position as the block to be processed or in its vicinity (vicinity), without transmitting differential motion vectors or reference indexes. The spatial merge candidates are defined as processed blocks adjacent to the current block and the inter prediction information of the processed blocks. The temporal merge candidates are defined as blocks belonging to the processed image that are located at the same position as the current block or in the vicinity of the current block and the inter prediction information derived from the inter prediction information of the processed blocks. Each merge candidate is registered in a merge candidate list, and a merge index identifies the merge candidate to be used in predicting the current block.

[0015] <Proximity block> 11 is a diagram for explaining reference blocks to be referenced for deriving inter prediction information in the predicted motion vector mode and merge mode. A0, A1, A2, B0, B1, B2, and B3 are processed blocks adjacent to the block to be processed. T0 is a block belonging to an image that has already been coded / decoded and is located at the same position as the block to be coded / decoded in the image to be coded / decoded or in the vicinity (neighborhood).

[0016] A1 and A2 are blocks located to the left of the coding block to be processed and adjacent to the coding block to be processed. B1 and B3 are blocks located above the coding block to be processed and adjacent to the coding block to be processed. A0, B0, and B2 are blocks located at the bottom left, top right, and top left of the coding block to be processed, respectively.

[0017] How adjacent blocks are handled in the predicted motion vector mode and merge mode will be described in detail later.

[0018] <Affine transformation motion compensation> Affine transformation motion compensation is a method of dividing a block into subblocks of a predetermined unit, determining a motion vector for each subblock individually, and performing motion compensation. The motion vector of each subblock is derived based on one or more control points derived from inter prediction information of a processed block adjacent to the block to be processed, or a block belonging to a processed image that is located at the same position as the block to be processed or in the vicinity (neighborhood). In this embodiment, the size of the subblock is 4x4 pixels, but the size of the subblock is not limited to this, and the motion vector may be derived in units of pixels.

[0019] FIG. 14 shows an example of affine transformation motion compensation when there are two control points. In this case, the two control points have two parameters, a horizontal component and a vertical component, so the affine transformation when there are two control points is called a four-parameter affine transformation. CP1 and CP2 in FIG. 14 are the control points. FIG. 15 shows an example of affine transformation motion compensation when there are three control points. In this case, the three control points have two parameters, a horizontal component and a vertical component, so the affine transformation when there are three control points is called a six-parameter affine transformation. CP1, CP2, and CP3 in FIG. 15 are the control points.

[0020] Affine transform motion compensation can be used in both the predictive motion vector mode and the merge mode. A mode in which affine transform motion compensation is applied in the predictive motion vector mode is defined as a sub-block predictive motion vector mode, and a mode in which affine transform motion compensation is applied in the merge mode is defined as a sub-block merge mode.

[0021] <Inter prediction syntax> The syntax related to inter prediction will be described with reference to FIG. 12 and FIG. 13. merge_flag in FIG. 12 is a flag indicating whether the processing target coding block is to be in merge mode or predictive motion vector mode. merge_affine_flag is a flag indicating whether or not the sub-block merge mode is applied to the processing target coding block in merge mode. inter_affine_flag is a flag indicating whether or not the sub-block predictive motion vector mode is applied to the processing target coding block in predictive motion vector mode. cu_affine_type_flag is a flag for determining the number of control points in the sub-block predictive motion vector mode. FIG. 13 shows the values ​​of each syntax element and the corresponding prediction method. merge_flag=1, merge_affine_flag=0 correspond to the normal merge mode, which is a merge mode that is not a sub-block merge. merge_flag=1, merge_affine_flag=1 correspond to the sub-block merge mode. merge_flag=0, inter_affine_flag=0 correspond to the normal predictive motion vector mode, which is a predictive motion vector merge that is not a sub-block predictive motion vector mode. The sub-block predicted motion vector mode corresponds to merge_flag=0, inter_affine_flag=1. When merge_flag=0, inter_affine_flag=1, cu_affine_type_flag is further transmitted to determine the number of control points.

[0022] <poc> POC (Picture Order Count) is a variable associated with a picture to be coded, and is set to a value that increases by one in the picture output order. The POC value can be used to determine whether the pictures are the same, to determine the order of pictures in the output order, and to derive the distance between pictures. For example, if two pictures have the same POC value, they can be determined to be the same picture. If two pictures have different POC values, the picture with the smaller POC value can be determined to be the picture that will be output first, and the difference between the POCs of the two pictures indicates the distance between the pictures along the time axis.

[0023] (First embodiment) An image encoding device 100 and an image decoding device 200 according to a first embodiment of the present invention will be described.

[0024] 1 is a block diagram of an image coding device 100 according to a first embodiment. The video coding device according to the embodiment includes an image coding device 100, a block division unit 101, an inter prediction unit 102, an intra prediction unit 103, a decoded image memory 104, a prediction method determination unit 105, a residual signal generation unit 106, an orthogonal transform / quantization unit 107, a bit string coding unit 108, an inverse quantization / inverse orthogonal transform unit 109, a decoded image signal superimposition unit 110, and a coding information storage memory 111.

[0025] The block division unit 101 recursively divides an input image to generate coding blocks. The block division unit 101 includes a 4-division unit that divides a block to be divided horizontally and vertically, and a 2-3 division unit that divides a block to be divided either horizontally or vertically. The block division unit 101 supplies the generated image signal of the coding block to be processed to the inter prediction unit 102, the intra prediction unit 103, and the residual signal generation unit 106. The block division unit 101 also supplies information indicating the determined recursive division structure to the bit string coding unit 108. The detailed operation of the block division unit 101 will be described later.

[0026] The inter prediction unit 102 performs inter prediction of the coding block to be processed. A plurality of inter prediction information candidates are derived from the prediction mode stored in the coding information storage memory and the decoded image signal stored in the decoded image memory 104, an appropriate inter prediction mode is selected from the plurality of candidates, and the selected inter prediction mode and a predicted image signal according to the selected inter prediction mode are supplied to the prediction method determination unit 105. The detailed configuration and operation of the inter prediction unit 102 will be described later.

[0027] The intra prediction unit 103 performs intra prediction of the coding block to be processed. A predicted image signal is generated by intra prediction from a decoded image signal stored in the decoded image memory 104, an appropriate intra prediction mode is selected from a plurality of intra prediction modes, and the selected intra prediction mode and a predicted image signal according to the selected intra prediction mode are supplied to the prediction method determination unit 105. FIG. 10 shows an example of intra prediction. FIG. 10(a) shows the correspondence between the prediction direction of intra prediction and the prediction mode number. For example, prediction mode 50 generates an intra prediction image by copying pixels in the vertical direction. Prediction mode 1 is a DC mode, and is a mode in which all pixel values ​​of the block to be processed are the average value of the reference pixels. Prediction mode 0 is a Planar mode, and is a mode in which a two-dimensional intra prediction image is created from reference pixels in the vertical and horizontal directions. FIG. 10(b) is an example of generating an intra prediction image in the case of prediction mode 40. For each pixel of the block to be processed, the value of the reference pixel in the direction indicated by the prediction mode is copied. When the reference pixel in the prediction mode is not at an integer position, the reference pixel value is determined by interpolation from the reference pixel values ​​of neighboring integer positions.

[0028] The decoded image memory 104 stores the decoded image generated by the decoded image signal superimposing unit 110. The decoded image stored in the decoded image memory is supplied to the inter prediction unit 102 and the inter prediction unit 103.

[0029] The prediction method determination unit 105 determines the optimal prediction mode (inter prediction or intra prediction) by evaluating each prediction using the coding information and the coding amount of the residual signal, the distortion amount between the predicted image signal and the image signal, etc. In the case of the merge mode of the inter prediction, the coding information of the merge index and the information indicating whether or not it is a sub-block merge mode (sub-block merge flag) is supplied to the bit string coding unit 108, and in the case of the predicted motion vector mode of the inter prediction, the coding information of the inter prediction mode, the predicted motion vector index, the reference index of L0, L1, the difference motion vector, and the information indicating whether or not it is a sub-block mode (sub-block predicted motion vector flag) is supplied to the bit string coding unit 108. The determined coding information is supplied to the coding information storage memory 111.

[0030] The residual signal generation unit 106 generates a residual signal by subtracting the predicted image signal from the image signal to be processed, and supplies the residual signal to the orthogonal transformation and quantization unit 107 .

[0031] The orthogonal transform and quantization unit 107 performs orthogonal transform and quantization on the residual signal in accordance with the quantization parameter to generate an orthogonally transformed and quantized residual signal, and supplies the orthogonal transformed and quantized residual signal to a bit string coding unit 108 and an inverse quantization and inverse orthogonal transform unit 109 .

[0032] The bitstream coding unit 108 codes coding information according to the prediction method determined by the prediction method determining unit 104 for each coding block, in addition to information in units of sequences, pictures, slices, and coding blocks. Specifically, the coding information such as the prediction mode PredMode for each coding block, the division mode PartMode, a flag for determining whether or not it is a merge mode in the case of inter prediction (PRED_INTER), a sub-block merge flag, a merge index in the case of merge mode, an inter prediction mode in the case of not merge mode, a predicted motion vector index, information on a differential motion vector, and a sub-block predicted motion vector flag is coded according to a prescribed syntax rule described later, to generate a first coded bitstream. The bitstream coding unit 108 also entropy codes the orthogonally transformed and quantized residual signal according to a prescribed syntax rule to generate a second coded bitstream. The first coded bitstream and the second coded bitstream are multiplexed according to a prescribed syntax rule, and a bitstream is output.

[0033] The inverse quantization and inverse orthogonal transform unit 109 inverse quantizes and inverse orthogonal transforms the orthogonally transformed and quantized residual signal supplied from the orthogonal transform and quantization unit 107 to calculate a residual signal, and supplies it to a decoded image signal superimposition unit 110.

[0034] The decoded image signal superimposing unit 110 superimposes the predicted image signal according to the determination by the prediction method determining unit 105 and the residual signal that has been inverse quantized and inverse orthogonal transformed by the inverse quantization and inverse orthogonal transform unit 109 to generate a decoded image, and stores the decoded image in the decoded image memory 104. Note that the decoded image may be stored in the decoded image memory 104 after being subjected to a filtering process for reducing distortion such as block distortion caused by encoding.

[0035] The coding information storage memory 111 stores coding information such as a prediction mode (inter prediction or intra prediction) determined by the prediction method determination unit 105. In the case of inter prediction, the coding information stored in the coding information storage memory 111 includes a determined motion vector, a reference list, and a reference index, in the case of a merge mode of inter prediction, coding information of a merge index and information indicating whether or not a sub-block merge mode (sub-block merge flag), in the case of a predicted motion vector mode of inter prediction, an inter prediction mode, a predicted motion vector index of L0, L1, a reference index of L0, L1, a difference motion vector of L0, L1, information indicating whether or not a sub-block mode (sub-block predicted motion vector flag), and in the case of intra prediction, a determined intra prediction mode. The construction of a history candidate list managed by the coding information storage memory 111 will be described later.

[0036] Fig. 2 is a block diagram showing the configuration of a video decoding device according to an embodiment of the present invention, which corresponds to the video encoding device of Fig. 1. The video decoding device according to the embodiment includes a bitstream decoding unit 201, a block dividing unit 202, an inter prediction unit 203, an intra prediction unit 204, an encoded information storage memory 205, an inverse quantization and inverse orthogonal transform unit 206, a decoded image signal superimposition unit 207, and a decoded image memory 208.

[0037] 2 corresponds to the decoding process provided inside the video encoding device of FIG. 1, and therefore each of the components of the encoding information storage memory 205, the inverse quantization and inverse orthogonal transformation unit 206, the decoded image signal superimposition unit 207, and the decoded image memory 208 of FIG. 2 has a function corresponding to each of the components of the inverse quantization and inverse orthogonal transformation unit 109, the decoded image signal superimposition unit 110, the encoding information storage memory 111, and the decoded image memory 104 of the video encoding device of FIG. 1.

[0038] The bit stream supplied to the bit stream decoding unit 201 is separated according to a prescribed syntax rule. The separated first coded bit stream is decoded to obtain information on a sequence, a picture, a slice, and a coding block unit, and coding information on a coding block unit. Specifically, coding information related to a prediction mode PredMode for determining whether inter prediction (PRED_INTER) or intra prediction (PRED_INTRA) is performed on a coding block unit basis, a division mode PartMode, a flag for determining whether a merge mode is performed in the case of inter prediction (PRED_INTER), a merge index in the case of merge mode, a sub-block merge flag, an inter prediction mode in the case of a predicted motion vector mode, a predicted motion vector index of L0 and L1, a reference index of L0 and L1, a difference motion vector of L0 and L1, a sub-block predicted motion vector flag, and the like is decoded according to a prescribed syntax rule to be described later, and the coding information is supplied to the inter prediction unit 203 or the intra prediction unit 204, and the coding information storage memory 205. The dequantization unit 208 decodes the separated second coded bit string to calculate an orthogonally transformed and quantized residual signal, and supplies the orthogonally transformed and quantized residual signal to the inverse quantization and inverse orthogonal transformation unit 208 .

[0039] When the prediction mode PredMode of the coding block to be decoded is inter prediction (PRED_INTER) and a predicted motion vector mode, the inter prediction unit 203 derives multiple predicted motion vector candidates using the coding information of an already decoded image signal stored in the coding information storage memory 205, and registers them in a predicted motion vector candidate list described below. From the multiple predicted motion vector candidates registered in the predicted motion vector candidate list, the inter prediction unit 203 selects a predicted motion vector corresponding to the predicted motion vector index decoded and supplied by the first coding bitstream decoding unit 202, calculates a motion vector from the differential vector decoded by the bitstream decoding unit 201 and the selected predicted motion vector, and stores the motion vector in the coding information storage memory 205 together with other coding information. The coding information of the coding block supplied and stored here includes a prediction mode PredMode, a partition mode PartMode, flags predFlagL0[xP][yP] and predFlagL1[xP][yP] indicating whether to use L0 prediction and L1 prediction, reference indexes refIdxL0[xP][yP] and refIdxL1[xP][yP] of L0 and L1, motion vectors mvL0[xP][yP] and mvL1[xP][yP] of L0 and L1, etc. Here, xP and yP are indexes indicating the position of the upper left pixel of the coding block in a picture. When the prediction mode PredMode is inter prediction (MODE_INTER) and the inter prediction mode is L0 prediction (Pred_L0), the flag predFlagL0 indicating whether to use L0 prediction is 1, and the flag predFlagL1 indicating whether to use L1 prediction is 0. When the inter prediction mode is L1 prediction (Pred_L1), the flag predFlagL0 indicating whether or not to use L0 prediction is 0, and the flag predFlagL1 indicating whether or not to use L1 prediction is 1. When the inter prediction mode is bi-prediction (Pred_BI), the flag predFlagL0 indicating whether or not to use L0 prediction and the flag predFlagL1 indicating whether or not to use L1 prediction are both 1. Furthermore, when the prediction mode PredMode of the coding block to be decoded is inter prediction (PRED_INTER) and a merge mode, merge candidates are derived.Using the coding information of the already decoded coding block stored in the coding information storage memory 205, a plurality of merge candidates are derived and registered in a merge candidate list described later, a merge candidate corresponding to a merge index decoded and supplied by the bitstream decoding unit 201 is selected from the plurality of merge candidates registered in the merge candidate list, and inter prediction information such as flags predFlagL0[xP][yP], predFlagL1[xP][yP] indicating whether or not to use L0 prediction and L1 prediction of the selected merge candidate, reference indexes refIdxL0[xP][yP], refIdxL1[xP][yP] of L0 and L1, motion vectors mvL0[xP][yP], mvL1[xP][yP] of L0 and L1 are supplied to the motion compensation prediction unit 206 and stored in the coding information storage memory 205. Here, xP and yP are indexes indicating the position of the upper left pixel of the coding block in the picture. A detailed configuration and operation of the inter prediction unit will be described later.

[0040] The intra prediction unit 204 performs intra prediction when the prediction mode PredMode of the coding block to be decoded is intra prediction (PRED_INTRA). The coding information decoded by the bitstream decoding unit 201 includes an intra prediction mode, and generates a predicted image signal by intra prediction from a decoded image signal stored in the decoded image memory 210 according to the intra prediction mode, and supplies the predicted image signal to the decoded image signal superimposition unit 209. The intra prediction unit 204 corresponds to the intra prediction unit 103 of the image coding device 100, and therefore performs the same process as the intra prediction unit 103.

[0041] The inverse quantization and inverse orthogonal transform unit 208 performs inverse orthogonal transform and inverse quantization on the orthogonally transformed and quantized residual signal decoded by the first coded bitstream decoding unit 202, to obtain an inverse orthogonally transformed and inverse quantized residual signal.

[0042] The decoded image signal superimposition unit 209 superimposes the predicted image signal inter-predicted by the motion compensation prediction unit 206 or the predicted image signal intra-predicted by the intra prediction unit 204 on the residual signal inversely orthogonally transformed and inversely quantized by the inverse quantization and inverse orthogonal transformation unit 208, thereby decoding the decoded image signal and storing it in the decoded image memory 210. When storing the decoded image in the decoded image memory 210, the decoded image may be subjected to a filtering process for reducing block distortion and the like caused by encoding before being stored in the decoded image memory 210.

[0043] Next, the operation of the block division unit 101 in the image encoding device 100 will be described. Fig. 3 is a flowchart showing the operation of dividing an image into tree blocks and further dividing each tree block. First, an input image is divided into tree blocks of a predetermined size (step S1001). Each tree block is scanned in a predetermined order, i.e., in raster scan order (step S1002), and the inside of the tree block to be processed is divided (step S1003).

[0044] 7 is a flowchart showing the detailed operation of the division process in step S1003. First, it is determined whether or not the block to be processed is to be divided into four (step S1101).

[0045] If it is determined that the block to be processed should be divided into four, the block to be processed is divided into four (step S1102). Each block into which the block to be processed is divided is scanned in Z scan order, that is, in the order of upper left, upper right, lower left, and lower right (step S1103). FIG. 5 is an example of Z scan order, and 601 in FIG. 6 is an example in which the block to be processed is divided into four. Numbers 0 to 3 in 601 in FIG. 6 indicate the order of processing. Then, the flowchart in FIG. 7 is recursively called for each block divided in step S1101.

[0046] If it is determined that the processing target block should not be divided into four, it is divided into two and three (step S1105).

[0047] 8 is a flowchart showing the detailed operation of the 2-3 division process in step S1105. First, it is determined whether or not the block to be processed is to be divided into 2-3, that is, whether or not to divide into 2 or 3 (step S1201).

[0048] If it is not determined that the block to be processed should be divided into 2-3, that is, if it is determined that no division should be made, the division is terminated (S1211) and the process returns to the block in the upper hierarchy.

[0049] If it is determined that the block to be processed is to be divided into 2 or 3, it is then determined whether or not the block to be processed is to be further divided into 2 (step S1202).

[0050] If it is determined that the target block is to be divided into two, it is determined whether or not to divide the target block vertically (step S1203), and based on the result, the target block is divided vertically (step S1204) or horizontally (step S1205). As a result of step S1204, the target block is divided into two vertically as shown in FIG. 602, and as a result of step S1205, the target block is divided into two horizontally as shown in FIG. 604.

[0051] In step S1202, if it is not determined that the block to be processed should be divided into two, i.e., if it is determined that the block to be processed should be divided into three, it is determined whether to divide the block to be processed vertically (step S1206), and based on the result, the block to be processed is divided vertically (step S1207) or horizontally (step S1208). As a result of step S1207, the block to be processed is divided vertically into three as shown in FIG. 603, and as a result of step S1208, the block to be processed is divided horizontally into three as shown in FIG. 605.

[0052] After executing any one of steps S1204 to S1205, each block obtained by dividing the target block is scanned from left to right and from top to bottom (step S1209). Numbers 0 to 3 of 602 to 605 in Fig. 6 indicate the order of processing. The flowchart in Fig. 8 is recursively called for each divided block.

[0053] The recursive block division described here may limit the necessity of division depending on the number of divisions, the size of the block to be processed, etc. The information limiting the necessity of division may be realized in a configuration in which no information is transmitted by a prearrangement between the encoding device and the decoding device, or may be realized in a configuration in which the encoding device determines information limiting the necessity of division and transmits it to the decoding device by recording it in the encoded bit string.

[0054] Next, the operation of the block division unit 202 in the image decoding device 200 will be described. The block division unit 202 divides tree blocks in the same processing procedure as the block division unit 101 in the image encoding device 101. However, the difference is that the block division unit 101 in the image encoding device 101 determines the optimal block division shape by applying an optimization method such as optimal shape estimation by image recognition or distortion rate optimization, whereas the block division unit 202 in the image decoding device 200 determines the block division shape by decoding block division information recorded in the encoded bit string.

[0055] The syntax for block division in the first embodiment (syntax rules for coded bitstreams) is shown in Fig. 9. coding_quadtree() represents syntax for dividing a block into four, and multi_type_tree() represents syntax for dividing a block into two or three. qt_split is a flag indicating whether or not to divide a block into four. If the block is divided into four, qt_split=1 is set, and if not, qt_split=0 is set. If the block is divided into four (qt_split=1), each block is divided into four and divided into four recursively (coding_quadtree(0), coding_quadtree(1), coding_quadtree(2), coding_quadtree(3)). If the block is not divided into four (qt_split=0), the subsequent division is determined according to multi_type_tree(). mtt_split is a flag indicating whether or not to divide the block further. If further division is required (mtt_split=1), the mtt_split_vertical flag indicating whether to divide vertically or horizontally and the mtt_split_binary flag determining whether to divide into two or three are referenced. mtt_split_vertical=1 indicates vertical division, and mtt_split_vertical=0 indicates horizontal division. mtt_split_binary=1 indicates division into two, and mtt_split_binary=0 indicates division into three. Hierarchical block division is performed by recursively calling multi_type_tree until mtt_split=0 is reached.

[0056] <Inter Prediction> The inter prediction method according to the embodiment is implemented in the inter prediction unit 102 of the video encoding device in FIG. 1 and the inter prediction unit 203 of the video decoding device in FIG.

[0057] An inter prediction method according to an embodiment will be described with reference to the drawings. The inter prediction method is performed in both encoding and decoding processes on a coding block basis.

[0058] (Explanation of the inter prediction unit 102 on the encoding side) Fig. 16 is a diagram showing a detailed configuration of the inter prediction unit 102 of the video encoding device of Fig. 1. A normal predicted motion vector derivation unit 301 derives a plurality of normal predicted motion vector candidates, selects a predicted motion vector, and calculates a difference vector with respect to the detected motion vector. The detected inter prediction mode, reference index, motion vector, and calculated difference vector become inter prediction information for the normal predicted motion vector mode. This inter prediction information is supplied to an inter prediction mode determination unit 305. A detailed configuration and processing of the normal predicted motion vector derivation unit 301 will be described later.

[0059] The normal merge mode derivation unit 302 derives a plurality of normal merge candidates, selects a normal merge candidate, and obtains inter prediction information for the normal merge mode. This inter prediction information is supplied to the inter prediction mode determination unit 306. A detailed configuration and processing of the normal merge mode derivation unit 302 will be described later.

[0060] The sub-block predictive motion vector derivation unit 303 derives a plurality of sub-block predictive motion vector candidates, selects a sub-block predictive motion vector, and calculates a difference vector with the detected motion vector. The detected inter prediction mode, reference index, motion vector, and calculated difference vector become inter prediction information for the normal predictive motion vector mode. This inter prediction information is supplied to the inter prediction mode determination unit 306. The detailed configuration and processing of the sub-block predictive motion vector derivation unit 303 will be described later.

[0061] The subblock merging mode derivation unit 304 derives a plurality of subblock merging candidates, selects a subblock merging candidate, and obtains inter prediction information of the subblock merging mode. This inter prediction information is supplied to the inter prediction mode determination unit 306. The detailed configuration and processing of the subblock merging mode derivation unit 304 will be described later.

[0062] The inter prediction mode determination unit 305 determines the inter prediction mode based on the inter prediction information supplied from the normal prediction motion vector derivation unit 301, the normal merge mode derivation unit 302, the sub-block prediction motion vector derivation unit 303, and the sub-block merge mode derivation unit 304. The inter prediction mode determination unit 305 supplies the inter prediction information according to the determination result to a motion compensation prediction unit 306.

[0063] Based on the determined inter prediction information, the motion compensation prediction unit 306 performs inter prediction on the reference image signal stored in the decoded image memory 104. The detailed configuration and processing will be described later.

[0064] <Description of the Inter Prediction Unit 203 on the Decoding Side> FIG. 22 is a diagram showing a detailed configuration of the inter prediction unit 203 of the video decoding device of FIG.

[0065] The normal predicted motion vector derivation unit 401 derives a plurality of normal predicted motion vector candidates, selects a predicted motion vector, and calculates a difference vector with the detected motion vector. The detected inter prediction mode, reference index, motion vector, and difference vector become inter prediction information of the normal predicted motion vector mode. This inter prediction information is supplied to the motion compensation prediction unit 406 via a switch 408. The detailed configuration and processing of the normal predicted motion vector derivation unit 401 will be described later.

[0066] The normal merge mode derivation unit 402 derives a plurality of normal merge candidates, selects a normal merge candidate, and obtains inter prediction information for the normal merge mode. This inter prediction information is supplied to the motion compensation prediction unit 406 via a switch 408. The detailed configuration and processing of the normal merge mode derivation unit 402 will be described later.

[0067] The sub-block predictive motion vector derivation unit 403 derives a plurality of sub-block predictive motion vector candidates, selects a sub-block predictive motion vector, and calculates a difference vector with the detected motion vector. The detected inter prediction mode, reference index, motion vector, and calculated difference vector become inter prediction information for the normal predicted motion vector mode. This inter prediction information is supplied to the motion compensation prediction unit 406 via a switch 408. The detailed configuration and processing of the sub-block predictive motion vector derivation unit 403 will be described later.

[0068] The subblock merging mode derivation unit 404 derives a plurality of subblock merging candidates, selects a subblock merging candidate, and obtains inter-prediction information for the subblock merging mode. This inter-prediction information is supplied to the motion compensation prediction unit 406 via a switch 408. The detailed configuration and processing of the subblock merging mode derivation unit 404 will be described later.

[0069] Based on the determined inter prediction information, the motion compensation prediction unit 406 performs inter prediction on the reference image signal stored in the decoded image memory 108. The detailed configuration and processing are the same as those on the encoding side.

[0070] <Normal predicted motion vector mode derivation part (normal AMVP)> The normal prediction motion vector mode derivation unit 301 in Figure 16 includes a spatial prediction motion vector candidate derivation unit 321, a temporal prediction motion vector candidate derivation unit 322, a history prediction motion vector candidate derivation unit 323, a prediction motion vector candidate supplementation unit 325, a normal motion vector detection unit 326, a prediction motion vector candidate selection unit 327, and a motion vector subtraction unit 328.

[0071] The normal predictor motion vector mode derivation unit 402 in Figure 23 includes a spatial predictor motion vector candidate derivation unit 421, a temporal predictor motion vector candidate derivation unit 422, a history predictor motion vector candidate derivation unit 423, a predictor motion vector candidate supplementation unit 425, a predictor motion vector candidate selection unit 426, and a motion vector addition unit 428.

[0072] The processing procedures of the normal prediction motion vector mode derivation unit 301 on the encoding side and the normal prediction motion vector mode derivation unit 401 on the decoding side will be described with reference to the flowcharts of Fig. 19 and Fig. 25. Fig. 19 is a flowchart showing the normal prediction motion vector mode derivation processing procedure by the normal motion vector mode derivation unit 301 on the encoding side, and Fig. 25 is a flowchart showing the normal prediction motion vector mode derivation processing procedure by the normal motion vector mode derivation unit 401 on the decoding side.

[0073] <Normal prediction motion vector mode derivation part (normal AMVP): Explanation on the encoding side> The normal predictive motion vector mode derivation process procedure on the encoding side will be described with reference to FIG.

[0074] First, the normal motion vector detection unit 326 detects a normal motion vector for each inter prediction mode and reference index (step S100 in FIG. 19).

[0075] Next, the spatial prediction motion vector candidate derivation unit 321, the temporal prediction motion vector candidate derivation unit 322, the history prediction motion vector candidate derivation unit 323, the prediction motion vector candidate supplementation unit 325, the prediction motion vector candidate selection unit 327, and the motion vector subtraction unit 328 calculate the difference motion vector of the motion vector used in the inter prediction of the normal prediction motion vector mode for each of L0 and L1 (steps S101 to S106 in FIG. 19). Specifically, when the prediction mode PredMode of the encoding target block is inter prediction (MODE_INTER) and the inter prediction mode is L0 prediction (Pred_L0), the prediction motion vector candidate list mvpListL0 of L0 is calculated, the prediction motion vector mvpL0 is selected, and the difference motion vector mvdL0 of the motion vector mvL0 of L0 is calculated. When the inter prediction mode of the block to be coded is L1 prediction (Pred_L1), the L1 predicted motion vector candidate list mvpListL1 is calculated, the predicted motion vector mvpL1 is selected, and the differential motion vector mvdL1 of the motion vector mvL1 of L1 is calculated. When the inter prediction mode of the block to be coded is bi-prediction (Pred_BI), both L0 prediction and L1 prediction are performed, the L0 predicted motion vector candidate list mvpListL0 is calculated, the L0 predicted motion vector mvpL0 is selected, and the differential motion vector mvdL0 of the motion vector mvL0 of L0 is calculated, and the L1 predicted motion vector candidate list mvpListL1 is calculated, the L1 predicted motion vector mvpL1 is calculated, and the differential motion vector mvdL1 of the motion vector mvL1 of L1 is calculated.

[0076] A differential motion vector calculation process is performed for each of L0 and L1, but the process is common to both L0 and L1. Therefore, in the following description, L0 and L1 are represented as a common LX. In the process of calculating the differential motion vector of L0, X is 0, and in the process of calculating the differential motion vector of L1, X is 1. Furthermore, when referring to information of the other list instead of LX during the process of calculating the differential motion vector of LX, the other list is represented as LY.

[0077] When calculating the differential motion vector mvdLX of LX (YES in step S102 in FIG. 19), a candidate of the predicted motion vector of LX is calculated to construct a predicted motion vector candidate list mvpListLX of LX (step S103 in FIG. 19). A spatial predicted motion vector candidate derivation unit 321, a temporal predicted motion vector candidate derivation unit 322, a history predicted motion vector candidate derivation unit 323, and a predicted motion vector candidate supplementation unit 325 in the normal predicted motion vector mode derivation unit 301 derive multiple predicted motion vector candidates to construct the predicted motion vector candidate list mvpListLX. The detailed processing procedure of step S103 in FIG. 19 will be described later with reference to the flowchart in FIG. 20.

[0078] Next, the motion vector predictor candidate selection unit 327 selects the motion vector predictor mvpLX of LX from the motion vector predictor candidate list mvpListLX of LX (step S104 in FIG. 19). Each difference motion vector, which is the difference between the motion vector mvLX and each motion vector predictor candidate mvpListLX[i] stored in the motion vector predictor candidate list mvpListLX, is calculated, the amount of code when the difference motion vector is coded is calculated for each element of the motion vector predictor candidate list mvpListLX, and the motion vector predictor candidate mvpListLX[i] with the smallest amount of code for each motion vector predictor candidate among the elements registered in the motion vector predictor candidate list mvpListLX is selected as the motion vector predictor mvpLX. If there are multiple candidates for the predicted motion vector that result in the smallest amount of generated code in the predicted motion vector candidate list mvpListLX, the predicted motion vector candidate mvpListLX[i] represented by the smallest index i in the predicted motion vector candidate list mvpListLX is selected as the optimal predicted motion vector mvpLX.

[0079] Next, the motion vector subtraction unit 328 calculates a differential motion vector mvdLX of LX by subtracting the selected predicted motion vector mvpLX of LX from the motion vector mvLX of LX (step S105 in FIG. 19).

[0080] (Normal prediction motion vector mode derivation unit (normal AMVP): Decoding side explanation) Next, the normal predicted motion vector mode processing procedure on the decoding side will be described with reference to Fig. 25. On the decoding side, the spatial predicted motion vector candidate derivation unit 421, the temporal predicted motion vector candidate derivation unit 422, the history predicted motion vector candidate derivation unit 423, and the predicted motion vector candidate supplementation unit 425 calculate the motion vectors used in inter prediction of the normal predicted motion vector mode for each of L0 and L1 (steps S201 to S206 in Fig. 25). Specifically, when the prediction mode PredMode of the block to be decoded is inter prediction (MODE_INTER) and the inter prediction mode of the block to be decoded is L0 prediction (Pred_L0), the predicted motion vector candidate list mvpListL0 of L0 is calculated, the predicted motion vector mvpL0 is selected, and the motion vector mvL0 of L0 is calculated. When the inter prediction mode of the block to be decoded is L1 prediction (Pred_L1), the L1 predicted motion vector candidate list mvpListL1 is calculated, the predicted motion vector mvpL1 is selected, and the motion vector mvL1 of L1 is calculated. When the inter prediction mode of the block to be decoded is bi-prediction (Pred_BI), both L0 prediction and L1 prediction are performed, the L0 predicted motion vector candidate list mvpListL0 is calculated, the L0 predicted motion vector mvpL0 is selected, and the motion vector mvL0 of L0 is calculated, while the L1 predicted motion vector candidate list mvpListL1 is calculated, the L1 predicted motion vector mvpL1 is calculated, and the motion vector mvL1 of L1 is calculated.

[0081] As in the encoding side, the decoding side also performs motion vector calculation processing for each of L0 and L1, but the processing is common to both L0 and L1. Therefore, in the following description, L0 and L1 are represented as a common LX. In the processing for calculating the motion vector of L0, X is 0, and in the processing for calculating the motion vector of L1, X is 1. In addition, when referring to information of the other list instead of LX during the processing for calculating the motion vector of LX, the other list is represented as LY.

[0082] When calculating the motion vector mvLX of LX (YES in step S202 in FIG. 25), a candidate of the predicted motion vector of LX is calculated to construct a predicted motion vector candidate list mvpListLX of LX (step S203 in FIG. 25). A spatial predicted motion vector candidate derivation unit 421, a temporal predicted motion vector candidate derivation unit 422, a history predicted motion vector candidate derivation unit 423, and a predicted motion vector candidate supplementation unit 425 in the normal predicted motion vector mode derivation unit 401 calculate a plurality of predicted motion vector candidates to construct the predicted motion vector candidate list mvpListLX. The detailed processing procedure of step S203 in FIG. 25 will be described later with reference to the flowchart in FIG. 20.

[0083] Next, the predicted motion vector candidate selection unit 426 extracts the predicted motion vector candidate mvpListLX[mvpIdxLX] corresponding to the predicted motion vector index mvpIdxLX decoded and supplied by the bit string decoding unit 201 from the predicted motion vector candidate list mvpListLX as the selected predicted motion vector mvpLX (step S204 in Figure 25).

[0084] Next, the motion vector adder 427 calculates a motion vector mvLX of LX by adding the differential motion vector mvdLX of LX decoded and supplied by the bit stream decoder 201 and the predicted motion vector mvpLX of LX (step S205 in FIG. 25).

[0085] <Normal predicted motion vector mode derivation part (normal AMVP): Motion vector prediction method> Figure 20 is a flowchart showing the processing steps of a normal prediction motion vector mode derivation process having functions common to the normal prediction motion vector mode derivation unit 301 of a video encoding device and the normal prediction motion vector mode derivation unit 401 of a video decoding device according to an embodiment of the present invention.

[0086] The normal motion vector predictor mode derivation unit 301 and the normal motion vector predictor mode derivation unit 401 are provided with a motion vector predictor candidate list mvpListLXN (N is A or B, the same applies below). The motion vector predictor candidate list mvpListLXN has a list structure, and is provided with a storage area for storing a motion vector predictor index indicating a location in the motion vector predictor candidate list and a motion vector predictor candidate corresponding to the index as elements. The motion vector predictor index number starts from 0, and the motion vector predictor candidate is stored in the storage area of ​​the motion vector predictor candidate list mvpListLXN. In the following process, the coding block that is the motion vector predictor candidate of the motion vector predictor index i registered in the motion vector predictor candidate list mvpListLXN is represented by mvpListLXN[i], and is distinguished from the motion vector predictor candidate list mvpListLXN by using an array notation. In this embodiment, the motion vector predictor candidate list mvpListLXN can register up to two motion vector predictor candidates (inter prediction information). Furthermore, 0 is set to a variable numMvpCand indicating the number of motion vector predictor candidates registered in the motion vector predictor candidate list mvpListLXN.

[0087] The spatial motion vector predictor candidate derivation units 321 and 421 derive candidates for the motion vector predictor from the adjacent coding block on the left side, derive a flag availableFlagLXA indicating whether the motion vector predictor candidate of the coding block adjacent on the left side is available, a motion vector mvLXA, a reference index refIdxA, and a list ListA, and add mvLXA to the motion vector predictor candidate list mvpListLXA (step S301 in FIG. 20). Note that X is 0 when L0, and X is 1 when L1 (similar below). Next, the motion vector predictor candidate generation units 121 and 221 derive a motion vector predictor candidate from the coding block adjacent to the upper side, derive a flag availableFlagLXB indicating whether the motion vector predictor candidate of the coding block adjacent to the upper side is available, a motion vector mvLXB, a reference index refIdxB, and a list ListB, and if mvLXA and mvLXB are not equal, add mvLXB to the motion vector predictor candidate list mvpListLXB (step S302 in FIG. 20). The processes of steps S301 and S302 in FIG. 20 are common except for the positions and number of the adjacent blocks to be referenced, and derive a flag availableFlagLXN indicating whether the motion vector predictor candidate of the coding block is available, a motion vector mvLXN, a reference index refIdxN, and ListN (N is A or B, similarly below).

[0088] Next, the temporal motion vector predictor candidate derivation units 322 and 422 derive motion vector predictor candidates from coding blocks of pictures of different times, derive a flag availableFlagLXCol indicating whether the motion vector predictor candidate of the coding block of the picture of different time is available, a motion vector mvLXCol, a reference index refIdxCol, and a list ListCol, and add mvLXCol to the motion vector predictor candidate list mvpListLX (step S303 in FIG. 20). The derivation process procedure of step S303 will be described in detail later.

[0089] Here, it is assumed that the processing of the temporal motion vector predictor candidate derivation units 322 and 422 can be omitted in units of a sequence (SPS), a picture (PPS), or a slice.

[0090] Next, the history motion vector predictor candidate derivation units 323 and 423 add the history motion vector predictor candidates registered in the history motion vector predictor candidate list HmvpCandList to the motion vector predictor candidate list mvpListLX (step S304 in FIG. 20). The registration process procedure in step S304 will be described in detail later with reference to the flowchart in FIG. 41.

[0091] Next, the motion vector predictor candidate supplementation units 325 and 425 add motion vectors of a predetermined value, such as (0, 0), until the motion vector predictor candidate list mvpListLX is filled (S305 in FIG. 20).

[0092] <Normal merge mode derivation part (normal merge)> The normal merge mode derivation unit 302 in FIG. 18 includes a spatial merge candidate derivation unit 341, a temporal merge candidate derivation unit 342, an average merge candidate derivation unit 344, a history merge candidate derivation unit 345, a merge candidate supplementation unit 346, and a merge candidate selection unit 347.

[0093] The normal merge mode derivation unit 402 in FIG. 24 includes a spatial merge candidate derivation unit 441, a temporal merge candidate derivation unit 442, an average merge candidate derivation unit 444, a history merge candidate derivation unit 445, a merge candidate supplementation unit 446, and a merge candidate selection unit 447.

[0094] FIG. 21 is a flowchart illustrating the procedure of a merge mode derivation process having a function common to the normal merge mode derivation unit 302 of the video encoding device and the normal merge mode derivation unit 402 of the video decoding device according to an embodiment of the present invention.

[0095] The various processes will be described below in order. In the following description, unless otherwise specified, the slice type slice_type is a B slice, but can also be applied to the case of a P slice. However, when the slice type slice_type is a P slice, there is only L0 prediction (Pred_L0) as an inter prediction mode, and there is no L1 prediction (Pred_L1) or bi-prediction (Pred_BI), so that the process related to L1 can be omitted.

[0096] The normal merge mode derivation unit 302 and the normal merge mode derivation unit 402 include a merge candidate list mergeCandList. The merge candidate list mergeCandList has a list structure, and is provided with a merge index indicating a location in the merge candidate list and a storage area for storing merge candidates corresponding to the index as elements. The merge index number starts from 0, and merge candidates are stored in the storage area of ​​the merge candidate list mergeCandList. In the following process, the coding block that is a merge candidate of the merge index i registered in the merge candidate list mergeCandList is represented by mergeCandList[i], and is distinguished from the merge candidate list mergeCandList by using an array notation. In this embodiment, the merge candidate list mergeCandList can register up to six merge candidates (inter prediction information). Furthermore, 0 is set to a variable numMergeCand indicating the number of merge candidates registered in the merge candidate list mergeCandList.

[0097] The spatial merge candidate derivation unit 341 and the spatial merge candidate derivation unit 441 derive spatial merge candidates A, B, C, D, and E from the coding blocks A, B, C, D, and E adjacent to the coding / decoding target block from the coding information stored in the coding information storage memory 115 of the video coding device or the coding information storage memory 210 of the video decoding device, and register the derived spatial merge candidates in a merge candidate list mergeCandList (step S401 in FIG. 21). Here, N is defined to indicate either A, B, C, D, or E or the temporal merge candidate Col. A flag availableFlagN indicating whether inter prediction information of coding block N can be used as spatial merge candidate N, an L0 reference index refIdxL0N and an L1 reference index refIdxL1N of spatial merge candidate N, an L0 prediction flag predFlagL0N indicating whether L0 prediction is performed and an L1 prediction flag predFlagL1N indicating whether L1 prediction is performed, an L0 motion vector mvL0N, and an L1 motion vector mvL1N are derived. However, in this embodiment, a merge candidate is derived without referring to a coding block included in the same coding block as the coding block including the coding block to be processed, and therefore a spatial merge candidate included in the same coding block as the coding block including the coding block to be processed is not derived.

[0098] Next, the temporal merge candidate derivation unit 342 and the temporal merge candidate derivation unit 442 derive temporal merge candidates from pictures of different times, and register the derived temporal merge candidates in a merge candidate list mergeCandList (step S402 in FIG. 21). A flag availableFlagCol indicating whether the temporal merge candidate is available, an L0 prediction flag predFlagL0Col indicating whether L0 prediction of the temporal merge candidate is performed, an L1 prediction flag predFlagL1Col indicating whether L1 prediction is performed, and an L0 motion vector mvL0Col and an L1 motion vector mvL1Col are derived. The detailed processing procedure of step S402 will be described in detail later with reference to the flowcharts of FIGS. 44 to 47.

[0099] Here, it is assumed that the processing of the temporal merge candidate derivation unit 342 and the temporal merge candidate derivation unit 442 can be omitted in units of a sequence (SPS), a picture (PPS), or a slice.

[0100] Next, the average merge candidate derivation unit 344 and the average merge candidate derivation unit 444 derive average merge candidates from the merge candidate list mergeCandList, and register the derived average merge candidates in the merge candidate list mergeCandList (step S403 in FIG. 21). The average merge candidate is derived when the merge candidate list includes two or more candidates.

[0101] Next, the history merge candidate derivation unit 345 and the history merge candidate derivation unit 445 add the history prediction motion vector candidate registered in the history prediction motion vector candidate list HmvpCandList to the merge candidate list mergeCandList (step S404 in FIG. 21). The detailed processing procedure of step S404 will be described in detail later with reference to the flowchart in FIG.

[0102] Next, in the merge candidate supplementation unit 346 and the merge candidate supplementation unit 446, when the number of merge candidates registered in the merge candidate list mergeCandList, numMergeCand, is smaller than the maximum number of merge candidates, maxNumMergeCand, the number of merge candidates registered in the merge candidate list mergeCandList, numMergeCand, is set as an upper limit of the maximum number of merge candidates, maxNumMergeCand, and additional merge candidates are derived and registered in the merge candidate list mergeCandList (step S405 in FIG. 21). With the maximum number of merge candidates, maxNumMergeCand, a zero merge candidate with a motion vector of (0,0) value with a different reference index and a prediction mode of L0 prediction (Pred_L0) is added to the P slice. A zero merge candidate with a motion vector of (0,0) value with a different reference index and a prediction mode of bi-prediction (Pred_BI) is added to the B slice.

[0103] Next, the merge candidate selection unit 347 and the merge candidate supplementation unit 447 select a merge candidate from among the merge candidates registered in the merge candidate list mergeCandList. The merge candidate selection unit 347 on the encoding side selects a merge candidate by calculating the code amount and the distortion amount, and supplies a merge index indicating the selected merge candidate and inter prediction information of the merge candidate to the motion compensation prediction unit 406. On the other hand, the merge candidate supplementation unit 447 on the decoding side selects a merge candidate based on the decoded merge index, and supplies the selected merge candidate to the motion compensation prediction unit 406.

[0104] <average merge candidate> The average merge candidate will be described. The average merge candidate is derived using the first merge candidate and the second merge candidate, which are two merge candidates included in the merge candidate list. The average merge candidate is a merge candidate having an average motion vector of L0 prediction obtained by averaging the motion vector of L0 prediction of the first merge candidate and the motion vector of L0 prediction of the second merge candidate, and an average motion vector of L1 prediction obtained by averaging the motion vector of L1 prediction of the first merge candidate and the motion vector of L1 prediction of the second merge candidate. The reference index of the L0 prediction of the average merge candidate is the reference index of the L0 prediction of the first merge candidate, and the reference index of the L1 prediction of the average merge candidate is the reference index of the L1 prediction of the first merge candidate. In deriving the average motion vector, the horizontal component and the vertical component of the motion vector are independently averaged. That is, the horizontal component of the average motion vector of the L0 prediction of the average merge candidate is the average of the horizontal components of the motion vector of the L0 prediction of the first merge candidate and the motion vector of the L0 prediction of the second merge candidate, and the vertical component of the average motion vector of the L0 prediction of the average merge candidate is the average of the vertical components of the motion vector of the L0 prediction of the first merge candidate and the motion vector of the L0 prediction of the second merge candidate. The same is true for the average motion vector of the L1 prediction of the average merge candidate. By deriving the average merge candidate after deriving the history merge candidate, the history merge candidate becomes the target of the average merge candidate, and it becomes possible to derive the average merge candidate using the history merge candidate even if the total number of spatial merge candidates and / or temporal merge candidates is one or less, thereby improving coding efficiency. <Sub-block prediction motion vector mode derivation> Sub-block predicted motion vector mode derivation will now be described.

[0105] FIG. 26 is a block diagram of the sub-block prediction motion vector mode derivation unit 303 in the encoding device of the present application.

[0106] First, an affine inheritance predicted motion vector candidate is derived in the affine inheritance predicted motion vector candidate derivation unit 361. The derivation of the affine inheritance predicted motion vector candidate will be described later in detail.

[0107] Next, an affine construction motion vector predictor candidate derivation unit 362 derives an affine construction motion vector predictor candidate. The derivation of an affine construction motion vector predictor candidate will be described later in detail.

[0108] Next, an affine-common predictor motion vector candidate derivation unit 363 derives an affine-common predictor motion vector candidate. The derivation of an affine-common predictor motion vector candidate will be described later in detail.

[0109] The sub-block motion vector detection unit 366 detects a sub-block motion vector suitable for the sub-block prediction motion vector mode, and supplies the detected vector to a sub-block prediction motion vector candidate selection unit 367 and a difference calculation unit 368 .

[0110] The sub-block predictive motion vector candidate selection unit 367 selects a sub-block predictive motion vector candidate from among the sub-block predictive motion vector candidates derived in the affine inheritance predictive motion vector candidate derivation unit 361, the affine construction predictive motion vector candidate derivation unit 362, and the affine identical predictive motion vector candidate derivation unit 363 based on the motion vector supplied from the sub-block motion vector detection unit 366, and supplies information regarding the selected sub-block predictive motion vector candidate to the inter prediction mode determination unit 305 and the difference calculation unit 368.

[0111] The difference calculation unit 368 supplies the difference prediction motion vector obtained by subtracting the sub-block prediction motion vector selected by the sub-block prediction motion vector candidate selection unit 367 from the motion vector supplied from the sub-block motion vector detection unit 366 to the inter prediction mode determination unit 305.

[0112] FIG. 27 is a block diagram of the sub-block predicted motion vector mode derivation unit 403 in the decoding device of the present application.

[0113] First, an affine inheritance predictor motion vector candidate is derived in the affine inheritance predictor motion vector candidate derivation unit 461. The process of the affine inheritance predictor motion vector candidate derivation unit 461 is the same as the process of the affine inheritance predictor motion vector candidate derivation unit 361 in the encoding device of the present application.

[0114] Next, an affine construction predicted motion vector candidate is derived in the affine construction predicted motion vector candidate derivation unit 462. The process of the affine construction predicted motion vector candidate derivation unit 462 is the same as the process of the affine construction predicted motion vector candidate derivation unit 362 in the encoding device of the present application.

[0115] Next, an affine-common predictor motion vector candidate is derived in the affine-common predictor motion vector candidate derivation unit 463. The process of the affine-common predictor motion vector candidate derivation unit 463 is the same as the process of the affine-common predictor motion vector candidate derivation unit 363 in the encoding device of the present application.

[0116] The sub-block predictor motion vector candidate selection unit 467 selects a sub-block predictor motion vector candidate from among the sub-block predictor motion vector candidates derived in the affine inheritance predictor motion vector candidate derivation unit 461, the affine construction predictor motion vector candidate derivation unit 462, and the affine identical predictor motion vector candidate derivation unit 463, based on the predictor motion vector index transmitted from the encoding device and decoded, and supplies information about the selected sub-block predictor motion vector candidate to the motion compensation prediction unit 406 and the addition calculation unit 467.

[0117] The addition calculation unit 467 adds the differential motion vector transmitted from the encoding device and decoded to the sub-block predictive motion vector selected by the sub-block predictive motion vector candidate selection unit 466, and supplies the generated motion vector to the motion compensation prediction unit 406.

[0118] <Derivation of affine inheritance predicted motion vector candidates> A description will be given of the affine inheritance predictor motion vector candidate derivation unit 361. The affine inheritance predictor motion vector candidate derivation unit 461 is similar to the affine inheritance predictor motion vector candidate derivation unit 361.

[0119] The affine inherited motion vector predictor candidate inherits the motion vector information of the affine control point.

[0120] FIG. 30 is a diagram for explaining derivation of affine inheritance predicted motion vector candidates.

[0121] The affine inheritance motion vector predictor candidates are obtained by searching for motion vectors of affine control points of spatially adjacent encoded and decoded blocks.

[0122] Specifically, a maximum of one affine mode is searched for from each of the blocks (A0, A1) adjacent to the left side of the current block to be coded / decoded and the blocks (B0, B1, B2) adjacent to the top side of the current block to be coded / decoded, and these are used as the affine inheritance predicted motion vector.

[0123] FIG. 34 is a flowchart showing the derivation of affine inheritance predicted motion vector candidates.

[0124] First, the block (A0, A1) adjacent to the left side of the block to be coded / decoded is set as the left group (S3101), and it is determined whether the block including A0 is a block using affine guarantee (affine mode) (S3102). If A0 is in affine mode (S3102: YES), the affine model used by A0 is obtained (S3103), and processing moves to the adjacent block above. If A0 is not in affine mode (S3102: NO), the target for deriving affine inheritance predicted motion vector candidates is set to A0->A1, and an attempt is made to obtain the affine mode from the block including A1.

[0125] Next, the blocks (B0, B1, B2) adjacent to the upper side of the block to be coded / decoded are set as an upper group (S3104), and it is determined whether the block including B0 is in affine mode (S3105). If B0 is in affine mode (S3105: YES), the affine model used by B0 is obtained (S3106), and the process ends. If B0 is not in affine mode (S3105: NO), the target of affine inheritance predicted motion vector candidate derivation is set to B0->B1, and an attempt is made to obtain the affine mode from the block including B1. Furthermore, if B1 is not in affine mode (S3105: NO), the target of affine inheritance predicted motion vector candidate derivation is set to B1->B2, and an attempt is made to obtain the affine mode from the block including B2.

[0126] In this way, by dividing the blocks into left blocks and upper blocks, and searching for affine models for the left blocks from the bottom left to the top left blocks, and for the left blocks from the top right to the top left blocks, it is possible to obtain two affine models that are as different as possible, and to derive an affine prediction motion vector candidate in which one of the affine prediction motion vectors has a smaller differential motion vector.

[0127] <Derivation of affine-constructed motion vector candidates> The following describes the affine construction predicted motion vector candidate derivation unit 362. The affine construction predicted motion vector candidate derivation unit 462 is similar to the affine construction predicted motion vector candidate derivation unit 362.

[0128] The affine constructed motion vector predictor candidate constructs motion vector information of an affine control point from motion information of spatially adjacent blocks.

[0129] FIG. 31 is a diagram for explaining derivation of affine constructed predicted motion vector candidates.

[0130] The affine constructed motion vector predictor candidate is obtained by constructing a new affine model by combining motion vectors of spatially adjacent encoded and decoded blocks.

[0131] Specifically, the motion vector for the upper-left affine control point CP0 is derived from the block (B2, B3, A2) adjacent to the upper left of the current block to be coded / decoded, the motion vector for the upper-right affine control point CP1 is derived from the block (B1, B0) adjacent to the upper right of the current block to be coded / decoded, and the motion vector for the lower-left affine control point CP2 is derived from the block (A1, A0) adjacent to the lower left of the current block to be coded / decoded.

[0132] FIG. 35 is a flowchart showing the derivation of affine constructed motion vector predictor candidates.

[0133] First, the upper-left control point CP0, the upper-right control point CP1, and the lower-left affine control point CP2 are derived (S3201). The upper-left affine control point CP0 is calculated by searching for reference blocks having the same reference image as the block to be coded / decoded, in the priority order of B2, B3, A2 reference blocks. The upper-right affine control point CP1 is calculated by searching for reference blocks having the same reference image as the block to be coded / decoded, in the priority order of B1, B0 reference blocks. The lower-left affine control point CP2 is calculated by searching for reference blocks having the same reference image as the block to be coded / decoded, in the priority order of A1, A0 reference blocks.

[0134] When the three affine control points mode is selected as the affine construction predicted motion vector (S3202: YES), it is determined whether or not all three affine control points (CP0, CP1, CP2) have been derived (S3203). When all three affine control points (CP0, CP1, CP2) have been derived (S3203: YES), an affine model using the three affine control points (CP0, CP1, CP2) is set as the affine construction predicted motion vector (S3204). When the three affine control points mode is not selected and the two affine control points mode is selected (S3202: NO), it is determined whether or not all two affine control points (CP0, CP1) have been derived (S3205). When all two affine control points (CP0, CP1) have been derived (S3205: YES), an affine model using the two affine control points (CP0, CP1) is set as the affine construction predicted motion vector (S3206).

[0135] <Derivation of affine identical predictive motion vector candidates> The following describes the affine identical predictor motion vector candidate derivation unit 363. The affine identical predictor motion vector candidate derivation unit 463 is similar to the affine identical predictor motion vector candidate derivation unit 363.

[0136] The affine identical predictor motion vector candidates are obtained by deriving the same motion vector at each affine control point.

[0137] Specifically, similarly to the affine constructed motion vector candidate derivation units 362 and 462, each affine control point information is derived and all affine control points are set to the same value of CP0 to CP2, thereby obtaining the affine control vector. Alternatively, similarly to the normal motion vector predictor mode, the affine control vector can be obtained by setting all affine control points to the derived temporal motion vector.

[0138] <Sub-block merge mode derivation> Sub-block merge mode derivation will now be described.

[0139] 28 is a block diagram of the sub-block merge mode derivation unit 304 in the encoding device of the present application. The sub-block merge mode derivation unit 304 is provided with a sub-block merge candidate list subblockMergeCandList. This is similar to the merge candidate list mergeCandList in the normal merge mode derivation unit 302, and differs only in that the candidate list is different for each sub-block.

[0140] First, sub-block temporal merging candidates are derived in the sub-block temporal merging candidate derivation unit 381. The derivation of sub-block temporal merging candidates will be described later in detail.

[0141] Next, affine inheritance merge candidates are derived in affine inheritance merge candidate derivation unit 382. The derivation of affine inheritance merge candidates will be described later in detail.

[0142] Next, affine construct merge candidates are derived in the affine construct merge candidate derivation unit 383. The derivation of affine construct merge candidates will be described later in detail.

[0143] Next, affine-fixed merging candidates are derived in affine-fixed merging candidate derivation unit 384. The derivation of affine-fixed merging candidates will be described later in detail.

[0144] The sub-block merging candidate selection unit 386 selects a sub-block merging candidate from among the sub-block merging candidates derived in the sub-block temporal merging candidate derivation unit 381, the affine inheritance merging candidate derivation unit 382, ​​the affine construction merging candidate derivation unit 383, and the affine fixed merging candidate derivation unit 384, and supplies information about the selected sub-block merging candidate to the inter-prediction mode determination unit 305.

[0145] 29 is a block diagram of the sub-block merge mode derivation unit 404 in the decoding device of the present application. The sub-block merge mode derivation unit 404 includes a sub-block merge candidate list subblockMergeCandList. This is the same as the sub-block merge mode derivation unit 304.

[0146] First, sub-block temporal merging candidates are derived in the sub-block temporal merging candidate derivation unit 481. The process of the sub-block temporal merging candidate derivation unit 481 is the same as the process of the sub-block temporal merging candidate derivation unit 381.

[0147] Next, affine inheritance merge candidate derivation unit 482 derives affine inheritance merge candidates. The process of affine inheritance merge candidate derivation unit 482 is the same as the process of affine inheritance merge candidate derivation unit 382.

[0148] Next, affine construct merge candidates are derived in the affine construct merge candidate derivation unit 483. The process of the affine construct merge candidate derivation unit 483 is the same as the process of the affine construct merge candidate derivation unit 383.

[0149] Next, affine-fixed merge candidates are derived in affine-fixed merge candidate derivation unit 485. The process of affine-fixed merge candidate derivation unit 485 is the same as the process of affine-fixed merge candidate derivation unit 485.

[0150] The sub-block merging candidate selection unit 486 selects a sub-block merging candidate from among the sub-block merging candidates derived in the sub-block temporal merging candidate derivation unit 481, the affine inheritance merging candidate derivation unit 482, the affine construction merging candidate derivation unit 483, and the affine fixed merging candidate derivation unit 484, based on the index transmitted from the encoding device and decoded, and supplies information about the selected sub-block merging candidate to the motion compensation prediction unit 406.

[0151] <Sub-block time merge candidate derivation> The operation of the sub-block temporal merging candidate derivation unit 381 will be described later.

[0152] <Affine inheritance merge candidate derivation> A description will now be given of the affine inheritance merge candidate derivation unit 382. The affine inheritance merge candidate derivation unit 482 is similar to the affine inheritance merge candidate derivation unit 382.

[0153] An affine inheritance merge candidate inherits the affine model of the affine control points from the affine models of spatially adjacent blocks.

[0154] 32 is a diagram for explaining derivation of affine inheritance merge candidates. Similar to the derivation of affine inheritance prediction motion vectors, affine inheritance merge mode candidates are derived by searching for motion vectors of affine control points of spatially adjacent encoded and decoded blocks.

[0155] Specifically, a maximum of one affine mode is searched for from each of the blocks (A0, A1) adjacent to the left side of the block to be coded / decoded and the blocks (B0, B1, B2) adjacent to the top side of the block to be coded / decoded, and used for the affine merge mode.

[0156] FIG. 36 is a flowchart of affine inheritance merge candidate derivation.

[0157] First, the block (A0, A1) adjacent to the left side of the block to be coded / decoded is set as the left group (S3301), and it is determined whether the block including A0 is in affine mode (S3302). If A0 is in affine mode (S3102: YES), the affine model used by A0 is obtained (S3303), and processing moves to the adjacent block above. If A0 is not in affine mode (S3302: NO), the target for deriving affine inheritance merge candidates is set to A0->A1, and an attempt is made to obtain the affine mode from the block including A1.

[0158] Next, the blocks (B0, B1, B2) adjacent to the upper side of the block to be coded / decoded are set as an upper group (S3304), and it is determined whether the block including B0 is in affine mode (S3305). If B0 is in affine mode (S3305: YES), the affine model used by B0 is obtained (S3306), and the process ends. If B0 is not in affine mode (S3305: NO), the target for deriving affine inheritance merge candidates is set to B0->B1, and an attempt is made to obtain the affine mode from the block including B1. Furthermore, if B1 is not in affine mode (S3305: NO), the target for deriving affine inheritance merge candidates is set to B1->B2, and an attempt is made to obtain the affine mode from the block including B2.

[0159] <Affine construction merge candidate derivation> The following describes the affine construct merge candidate derivation unit 383. The affine construct merge candidate derivation unit 483 is similar to the affine construct merge candidate derivation unit 383.

[0160] 33 is a diagram for explaining derivation of affine construct merge candidates. The affine construct merge candidates construct an affine model of affine control points from motion information of spatially adjacent blocks and temporal coding blocks.

[0161] Specifically, the motion vector for the upper-left affine control point CP0 is derived from the block (B2, B3, A2) adjacent to the upper left of the block to be coded / decoded, the motion vector for the upper-right affine control point CP1 is derived from the block (B1, B0) adjacent to the upper right of the block to be coded / decoded, the motion vector for the lower-left affine control point CP2 is derived from the block (A1, A0) adjacent to the lower left of the block to be coded / decoded, and the motion vector for the lower-right affine control point CP3 is derived from the temporal coding block (T0) adjacent to the lower right of the block to be coded / decoded.

[0162] FIG. 37 is a flowchart of affine construct merge candidate derivation.

[0163] First, an upper left affine control point CP0, an upper right affine control point CP1, a lower left affine control point CP2, and a lower right affine control point CP3 are derived (S3401). The upper left control point CP0 is calculated by searching for blocks having motion information in the order of priority of B2, B3, and A2 blocks. The upper right control point CP1 is calculated by searching for blocks having motion information in the order of priority of B1 and B0 blocks. The lower left control point CP2 is calculated by searching for blocks having motion information in the order of priority of A1 and A0 blocks. The lower right control point CP3 is calculated by searching for motion information of a time block.

[0164] Next, it is determined whether an affine model can be constructed using three affine control points from the derived CP0, CP1, and CP2 (S3402), and if so (S3402: YES), the three affine control point affine model from CP0, CP1, and CP2 is designated as an affine merge candidate (S3403).

[0165] Next, it is determined whether an affine model can be constructed using three affine control points from the derived CP0, CP1, and CP3 (S3404), and if so (S3404: YES), the three affine control point affine model from CP0, CP1, and CP3 is designated as an affine merge candidate (S3405).

[0166] Next, it is determined whether an affine model can be constructed using three affine control points from the derived CP0, CP2, and CP3 (S3406), and if so (S3406: YES), the three affine control point affine model from CP0, CP2, and CP3 is designated as an affine merge candidate (S3407).

[0167] Next, it is determined whether an affine model can be constructed using three affine control points from the derived CP1, CP2, and CP3 (S3408), and if so (S3408: YES), the three affine control point affine model from CP1, CP2, and CP3 is designated as an affine merge candidate (S3409).

[0168] Next, it is determined whether an affine model can be constructed using two affine control points from the derived CP0 and CP1 (S3410), and if so (S3410: YES), the two affine control point affine model using CP0 and CP1 is designated as an affine merge candidate (S3411).

[0169] Next, it is determined whether an affine model can be constructed using two affine control points from the derived CP0 and CP2 (S3412), and if so (S3412: YES), the two-affine control point affine model using CP0 and CP2 is designated as an affine merge candidate (S3413).

[0170] Here, whether or not an affine model is constructed is determined based on the following conditions.

[0171] 1. The reference images for all affine control points are the same. (Affine transformation is possible) 2. At least one affine control point has a different motion vector (cannot be expressed by translation). In addition, for affine models other than the three-line affine control point affine model using CP0, CP1, CP2 and the two-line affine control point affine model using CP0 and CP1, the three-line control affine model is converted to a three-line affine control point affine model using CP0, CP1, CP2, and the two-line control affine model is converted to a two-line affine control point affine model using CP0 and CP1.

[0172] <Affine fixed merge candidate derivation> The following describes the affine-anchored merging candidate derivation unit 385. The affine-anchored merging candidate derivation unit 485 is similar to the affine-anchored merging candidate derivation unit 385.

[0173] The affine fixed merge candidate fixes the motion information of the affine control points with the fixed motion information.

[0174] Specifically, the motion vector of each affine control point is fixed to (0,0).

[0175] <Temporal motion vector prediction> Prior to the description of the temporal motion vector predictor, the temporal relationship of pictures will be described. Figure 49(a) shows the relationship between a coding block to be coded and a coded picture that is temporally different from the coding target picture. In the coding target picture, a specific coded picture to be referenced for coding is defined as ColPic. ColPic is specified by syntax.

[0176] 49(b) shows coded blocks in ColPic that are at the same position as the coding block to be coded and in the vicinity of the coding block. These coding blocks T0 and T1 are coding blocks at almost the same position in pictures that are different in time from the coding block to be coded.

[0177] The above description of the temporal relationship between pictures is for the encoding process, but the same applies to the decoding process. In other words, the above description of the decoding process can be applied in the same manner, with the encoding process replaced by the decoding process.

[0178] The operation of the temporal motion vector predictor candidate derivation unit 322 in the normal motion vector predictor mode derivation unit 301 in FIG. 17 will be described with reference to FIG.

[0179] First, ColPic is derived (step S4201). The derivation of ColPic will be described with reference to FIG.

[0180] If the slice type slice_type is a B slice and the flag collocated_from_l0_flag is 0 (YES in step S4211, YES in step S4212), RefPicList1[0], i.e., the picture with the reference index of 0 in the reference list L1, becomes a picture colPic of a different time (step S4213). Otherwise, i.e., if the slice type slice_type is a B slice and the above-mentioned flag collocated_from_l0_flag is 1 (YES in step S4211, NO in step S4212), or if the slice type slice_type is a P slice (NO in step S4211, YES in step S4214), RefPicList0[0], i.e., the picture with the reference index of 0 in the reference list L0, becomes a picture colPic of a different time (step S4215). If slice_type is not a P slice (step S4214: NO), the process ends.

[0181] Again, refer to Fig. 50. After ColPic is derived, the coding block colCb is derived and coding information is obtained (step S4202). This process will be described with reference to Fig. 52.

[0182] First, a coding block located at the lower right (outside) of the same position as the coding block to be processed in a picture colPic of a different time is set as a coding block colCb of a different time (step S4221). This coding block corresponds to coding block T0 in FIG.

[0183] Next, the coding information of the coding block colCb of the different time is obtained (step S4222). If the PredMode of the coding block colCb of the different time is unavailable or the prediction mode PredMode of the coding block colCb of the different time is intra prediction (MODE_INTRA) (step S4223: NO, step S4224: YES), the coding block located at the lower right of the center in the same position as the coding block to be processed in the picture colPic of the different time is set as the coding block colCb of the different time (step S4225). This coding block corresponds to the coding block T1 in FIG. 49.

[0184] FIG. 50 will be referred to again. Next, inter prediction information is derived for each reference list (S4203, S4204). Here, for the coding block colCb, a motion vector mvLXCol for each reference list and a flag availableFlagLXCol indicating whether coding information is valid or not are derived. LX indicates a reference list, and LX is L0 when deriving reference list 0, and LX is L1 when deriving reference list 1. The derivation of inter prediction information will be described with reference to FIG. 53.

[0185] If the coding block colCb of a different time is not available (S4231S4231:NO), or if the prediction mode PredMode is intra prediction (MODE_INTRA) (S4232:NO), the flags availableFlagLXCol and predFlagLXCol are both set to 0 (step S4233), the motion vector mvLXCol is set to (0,0) (S4234), and the processing ends.

[0186] When the coding block colCb is available (S4231: Yes) and the prediction mode PredMode is not intra prediction (MODE_INTRA) (S4232: YES), mvCol, refIdxCol, and availableFlagCol are calculated in the following procedure.

[0187] When the flag PredFlagL0[xPCol][yPCol] indicating whether the L0 prediction of the coding block colCb is used is 0 (YES in S4235), the prediction mode of the coding block colCb is Pred_L1, so the motion vector mvCol is set to the same value as the L1 motion vector MvL1[xPCol][yPCol] of the coding block colCb (S4236), the reference index refIdxCol is set to the same value as the L1 reference index RefIdxL1[xPCol][yPCol] (S4237), and the list ListCol is set to L1 (S4238). Here, xPCol and yPCol are indexes indicating the position of the upper left pixel of the coding block colCb in the picture colPic of a different time.

[0188] On the other hand, if the L0 prediction flag PredFlagL0[xPCol][yPCol] of the coding block colCb is not 0 (NO in S4235), it is determined whether the L1 prediction flag PredFlagL1[xPCol][yPCol] of the coding block colCb is 0. If the L1 prediction flag PredFlagL1[xPCol][yPCol] of the coding block colCb is 0 (YES in S4239), the motion vector mvCol is set to the same value as MvL0[xPCol][yPCol] which is the L0 motion vector of the coding block colCb (S4240), the reference index refIdxCol is set to the same value as the L0 reference index RefIdxL0[xPCol][yPCol] (S4241), and the list ListCol is set to L0 (S4242).

[0189] If the L0 prediction flag PredFlagL0[xPCol][yPCol] of the coding block colCb and the L1 prediction flag PredFlagL1[xPCol][yPCol] of the coding block colCb are both not 0 (NO in S4235, NO in S4239), the inter prediction mode of the coding block colCb is bi-prediction (Pred_BI), so one of the two motion vectors L0 and L1 is selected (S4243).

[0190] FIG. 54 is a flowchart showing the procedure of a process for deriving inter prediction information of a coding block when the inter prediction mode of the coding block colCb is bi-prediction (Pred_BI).

[0191] First, it is determined whether the POC of all pictures registered in all reference lists is smaller than the POC of the current picture to be coded (S4251). If the POC of all pictures registered in all reference lists, L0 and L1, of the coding block colCb is smaller than the POC of the current picture to be coded (YES in S4251), and LX has derived a prediction vector candidate for the motion vector of L0, i.e., the L0 coding block to be coded (YES in S4252), the inter prediction information of the L0 side of the coding block colCb is selected. If LX has derived a prediction vector candidate for the motion vector of L1, i.e., the L1 coding block to be coded (NO in S4252), the inter prediction information of the L1 side of the coding block colCb is selected. On the other hand, if at least one of the POCs of pictures registered in all reference lists L0 and L1 of the coding block colCb is larger than the POC of the current picture to be coded (NO in S4251) and the flag collocated_from_l0_flag is 0 (YES in S4253), the inter-prediction information of L0 of the coding block colCb is selected, and if the flag collocated_from_l0_flag is 1 (NO in S4253), the inter-prediction information of L1 of the coding block colCb is selected.

[0192] When selecting inter-prediction information for L0 of the coding block colCb (YES in S4252, YES in S4253), the motion vector mvCol is set to the same value as MvL0[xPCol][yPCol] (S4254), the reference index refIdxCol is set to the same value as RefIdxL0[xPCol][yPCol] (S4255), and the list ListCol is set to L0 (S4256).

[0193] When selecting inter-prediction information for L1 of the coding block colCb (NO in S4252, NO in S4253), the motion vector mvCol is set to the same value as MvL1[xPCol][yPCol] (S4257), the reference index refIdxCol is set to the same value as RefIdxL1[xPCol][yPCol] (S4258), and the list ListCol is set to L1 (S4259).

[0194] Returning to FIG. 53, when inter prediction information is acquired from the coding block colCb, both the flag availableFlagLXCol and the flag predFlagLXCol are set to 1 (S4244).

[0195] Next, the motion vector mvCol is scaled to obtain a motion vector mvLXCol (S4245S4245). The procedure for the scaling calculation process of the motion vector mvLXCol will be described with reference to FIG.

[0196] An inter-picture distance td is calculated by subtracting the POC of the reference picture corresponding to the reference index refIdxCol referenced in the list ListCol of the coding block colCb from the POC of the picture colPic of the different time (S4261). Note that if the POC of the reference picture referenced in the list ListCol of the coding block colCb is earlier in display order than the picture colPic of the different time, the inter-picture distance td is a positive value, and if the POC of the reference picture referenced in the list ListCol of the coding block colCb is later in display order than the picture colPic of the different time, the inter-picture distance td is a negative value. td = POC of picture colPic at a different time - POC of reference pictures referenced in list ListCol of coding blocks colCb The inter-picture distance tb is calculated by subtracting the POC of the reference picture referred to by the list LX of the current picture to be coded from the POC of the current picture to be coded (S4262). Note that if the reference picture referred to by the list LX of the current picture to be coded is earlier in display order than the current picture to be coded, the inter-picture distance tb is a positive value, and if the reference picture referred to by the list LX of the current picture to be coded is later in display order, the inter-picture distance tb is a negative value. tb = POC of the current picture to be coded / decoded - POC of the reference picture corresponding to the reference index of the LX of the temporal merge candidate Next, the inter-picture distances td and tb are compared (S4263), and if the inter-picture distances td and tb are equal (YES in S4263), a motion vector mvLXCol is calculated by the following equation (S4264), and this scaling calculation process ends. mvLXCol = mvCol On the other hand, if the inter-picture distances td and tb are not equal (NO in S4263), the variable tx is calculated by the following formula (S4265). tx = ( 16384 + Abs( td ) >> 1 ) / td Next, the scaling coefficient distScaleFactor is calculated using the following equation (S4266). distScaleFactor = Clip3( -4096, 4095, ( tb * tx + 32 ) >> 6 ) Here, Clip3(x, y, z) is a function that limits the value z to a minimum value of x and a maximum value of y. Next, a motion vector mvLXCol is calculated by the following equation (S4267), and this scaling calculation process ends. mvLXCol = Clip3( -32768, 32767, Sign( distScaleFactor * mvLXCol ) * ((Abs( distScaleFactor * mvLXCol ) + 127 ) >> 8 ) ) Here, Sign(x) is a function that returns the sign of the value x, and Abs(x) is a function that returns the absolute value of the value x.

[0197] Referring again to FIG. 50, the motion vector mvL0Col of L0 is added as a candidate to the motion vector predictor candidate list mvpListLXN in the normal motion vector predictor mode derivation unit 301 described above (S4205). However, this addition is only made when the flag availableFlagL0Col=1 indicating whether the coding block colCb of the reference list 0 is valid or not. Also, the motion vector mvL1Col of L1 is added as a candidate to the motion vector predictor candidate list mvpListLXN in the normal motion vector predictor mode derivation unit 301 described above (S4205). However, this addition is only made when the flag availableFlagL1Col=1 indicating whether the coding block colCb of the reference list 1 is valid or not. With the above, the process of the temporal motion vector predictor candidate derivation unit 322 is terminated.

[0198] The above description of the normal prediction motion vector mode derivation unit 301 is for encoding, but the same applies to decoding. That is, the operation of the temporal prediction motion vector candidate derivation unit 422 in the normal prediction motion vector mode derivation unit 401 in Fig. 23 can be similarly described by replacing the encoding in the above description with decoding.

[0199] <Time Merge> The operation of the temporal merge candidate derivation unit 342 in the normal merge mode derivation unit 302 in FIG. 18 will be described with reference to FIG.

[0200] First, ColPic is derived (step S4301). Next, a coding block colCb is derived to obtain coding information (step S4302). Furthermore, inter prediction information is derived for each reference list (S4303, S4304). The above processes are the same as S4201 to S4204 in the temporal motion vector predictor candidate derivation unit 322, and therefore description thereof will be omitted.

[0201] Next, a flag availableFlagCol indicating whether the coding block colCb is valid or not is calculated (S4305). When the flag availableFlagL0Col or the flag availableFlagL1Col is 1, availableFlagCol is 1. In other cases, availableFlagCol is 0.

[0202] Then, the motion vector mvL0Col of L0 and the motion vector mvL1Col of L1 are added as candidates to the merge candidate list mergeCandList in the normal merge mode derivation unit 302 described above (S4306). However, this addition is only made when the flag indicating whether the coding block colCb is valid or not is availableFlagCol=1. With the above, the processing of the temporal merge candidate derivation unit 342 ends.

[0203] The above description of the temporal merge candidate derivation unit 342 is for encoding, but the same applies to decoding. That is, the operation of the temporal merge candidate derivation unit 442 in the normal merge mode derivation unit 402 in Fig. 24 can be similarly described by replacing encoding in the above description with decoding.

[0204] <Update of historical motion vector prediction candidate list> Next, a detailed description will be given of a method for updating the historical motion vector predictor candidate list HmvpCandList provided in the encoding information storage memory 111 on the encoding side and the decoding information storage memory 205. Fig. 38 is a flowchart illustrating the procedure of a historical motion vector predictor candidate derivation process.

[0205] In this embodiment, the history prediction motion vector candidate list HmvpCandList is updated in the coding information storage memory 111 and the coding information storage memory 205. A history candidate list update unit may be provided in the inter prediction unit 102 and the inter prediction unit 203 to update the history prediction motion vector candidate list HmvpCandList.

[0206] The historical prediction motion vector candidate list HmvpCandList is initially set at the beginning of the slice, and on the encoding side, the historical prediction motion vector candidate list HmvpCandList is updated when the prediction method determination unit 106 selects the normal prediction vector mode or the normal merge mode, and on the decoding side, the historical prediction motion vector candidate list HmvpCandList is updated when the inter prediction mode decoded by the bit string decoding unit 201 is the normal prediction vector mode or the normal merge mode. The inter prediction information used when performing inter prediction in normal prediction vector mode or normal merge mode is designated as the inter prediction information candidate hMvpCand to be registered, and if an inter prediction with the same value as the inter prediction information candidate hMvpCand to be registered exists among the inter prediction information registered in the historical prediction motion vector candidate list HmvpCandList provided in the encoding information storage memory 111 on the encoding side and the encoding information storage memory 205 on the decoding side, that element (inter prediction information) is deleted from the historical prediction motion vector candidate list HmvpCandList, and if an inter prediction with the same value as the inter prediction information candidate hMvpCand to be registered does not exist, the first element (inter prediction information) of the historical prediction motion vector candidate list HmvpCandList is deleted, and the inter prediction information candidate hMvpCand to be registered is added to the end of the historical prediction motion vector candidate list HmvpCandList.

[0207] The number of elements in the historical motion vector predictor candidate list HmvpCandList provided in the encoding information storage memory 111 on the encoding side and the encoding information storage memory 205 on the decoding side in the present invention is assumed to be six.

[0208] First, the historical motion vector predictor candidate list HmvpCandList is initialized in units of slices. Historical motion vector predictor candidates are added to all elements of the historical motion vector predictor candidate list HmvpCandList at the beginning of the slice, and the value of the number of historical motion vector predictor candidates NumHmvpCand registered in the historical motion vector predictor candidate list HmvpCandList is set to 6 (step S2101 in FIG. 38).

[0209] Here, the initialization of the historical motion vector predictor candidate list HmvpCandList is performed on a slice-by-slice basis (the first coding block of a slice), but it may also be performed on a picture-by-picture basis, a tile-by-tile basis, or a tree block row-by-tree block basis.

[0210] FIG. 62 is a table showing an example of a history prediction motion vector candidate added by initialization of the history prediction motion vector candidate list HmvpCandList. An example is shown in which the slice type is a B slice and the number of reference pictures is 4. Inter prediction information with a history prediction motion vector index ranging from (the number of history prediction motion vector candidates NumHmvpCand-1) to 0 and a motion vector value of (0, 0) according to the slice type is added as a history prediction motion vector candidate to the history prediction motion vector candidate list HmvpCandList, and the history prediction motion vector candidate list is filled with history candidates. At this time, the history prediction motion vector index starts from (the number of history prediction motion vector candidates NumHmvpCand-1), and a value incremented by 1 from 0 to (the number of reference pictures numRefIdx-1) is set to the reference index refIdxLX (X is 0 or 1). Thereafter, overlapping of history prediction motion vector candidates is permitted, and a value of 0 is set to refIdxLX. By setting all values ​​to the number of history motion vector predictor candidates NumHmvpCand and setting the value of the number of history motion vector predictor candidates NumHmvpCand to a fixed value, invalid history motion vector predictor candidates are eliminated. In this way, by assigning a small reference index value, which is generally highly selected, to candidates with a large history motion vector predictor index value that is likely to be added to the motion vector predictor candidate list or merge candidate list, it is possible to improve coding efficiency.

[0211] In addition, by filling the history prediction motion vector candidate list with history prediction motion vector candidates on a slice-by-slice basis, the number of history prediction motion vector candidates can be treated as a fixed value, thereby simplifying, for example, the history prediction motion vector candidate derivation process and the history merge candidate derivation process.

[0212] Here, the value of the motion vector is set to (0, 0), which is generally selected with a high probability, but any predetermined value may be used. For example, the coding efficiency of the differential motion vector may be improved by setting values ​​such as (4, 4), (0, 32), and (-128, 0), or by setting multiple predetermined values.

[0213] In addition, although the historical prediction motion vector index starts from (the number of historical prediction motion vector candidates NumHmvpCand-1) and the reference index refIdxLX (X is 0 or 1) is set to a value incremented by 1 from 0 to (the number of reference pictures numRefIdx-1), the historical prediction motion vector index may also start from 0.

[0214] FIG. 63 is a table showing another example of a history prediction motion vector candidate added by initialization of the history prediction motion vector candidate list HmvpCandList. An example is shown in which the slice type is a B slice and the number of reference pictures is two. In this example, inter prediction information with different reference indexes or motion vector values ​​is added as a history prediction motion vector candidate so that there is no overlap between the history prediction motion vector candidates in each element of the history prediction motion vector candidate list HmvpCandList, and the history prediction motion vector candidate list is filled. At this time, the history prediction motion vector index starts from (the number of history prediction motion vector candidates NumHmvpCand-1), and the reference index refIdxLX (X is 0 or 1) is set to a value incremented by 1 from 0 to (the number of reference pictures numRefIdx-1). After that, a motion vector with a different value, starting from 0, is added to refIdxLX as a history prediction motion vector candidate. All values ​​are set in the number of historical motion vector predictor candidates NumHmvpCand, and the value of the number of historical motion vector predictor candidates NumHmvpCand is set to a fixed value, thereby eliminating invalid historical motion vector predictor candidates.

[0215] In this way, by filling the history prediction motion vector candidate list with non-duplicate history prediction motion vector candidates on a slice-by-slice basis, it is possible to omit the processing of the merge candidate supplementation unit 346 subsequent to the history merge candidate derivation unit 345 in the normal merge mode derivation unit 302 described below, which is performed on an encoding block basis, thereby reducing the amount of processing.

[0216] Here, the values ​​of the motion vectors are set to small values ​​such as (0, 0) or (1, 0), but the values ​​of the motion vectors may be large as long as there is no overlap between the history motion vector predictor candidates.

[0217] In addition, although the historical prediction motion vector index starts from (the number of historical prediction motion vector candidates NumHmvpCand-1) and the reference index refIdxLX (X is 0 or 1) is set to a value incremented by 1 from 0 to (the number of reference pictures numRefIdx-1), the historical prediction motion vector index may also start from 0.

[0218] FIG. 64 is a table showing another example of historical motion vector predictor candidates added by initialization of the historical motion vector predictor candidate list HmvpCandList.

[0219] An example in which the slice type is a B slice is shown. In this example, inter prediction information with a reference index of 0 and different motion vector values ​​is added as a history prediction motion vector candidate to fill the history prediction motion vector candidate list so that there is no overlap between history prediction motion vector candidates in each element of the history prediction motion vector candidate list HmvpCandList. At this time, the history prediction motion vector index starts from (the number of history prediction motion vector candidates NumHmvpCand-1), and the reference index refIdxLX (X is 0 or 1) is set to 0. All values ​​are set in the number of history prediction motion vector candidates NumHmvpCand, and the value of the number of history prediction motion vector candidates NumHmvpCand is set to a fixed value, thereby eliminating invalid history prediction motion vector candidates.

[0220] In this way, by setting the reference index to 0, the initialization can be performed without taking the number of reference pictures into consideration, thereby further simplifying the processing.

[0221] Here, the value of the motion vector is a multiple of 2, but other values ​​may be used as long as the reference index is 0 and no overlap occurs between history motion vector predictor candidates.

[0222] In addition, although the historical prediction motion vector index starts from (the number of historical prediction motion vector candidates NumHmvpCand-1) and the reference index refIdxLX (X is 0 or 1) is set to a value incremented by 1 from 0 to (the number of reference pictures numRefIdx-1), the historical prediction motion vector index may also start from 0.

[0223] Next, the following update process of the historical motion vector predictor candidate list HmvpCandList is repeatedly performed for each coding block in the slice (steps S2102 to S2111 in FIG. 38).

[0224] First, initial settings are made for each coding block: A flag identicalCandExist indicating whether an identical candidate exists is set to FALSE, and a deletion target index removeIdx is set to 0 (step S2103 in FIG. 38).

[0225] It is determined whether or not there is an inter prediction information candidate hMvpCand to be registered in the history prediction motion vector candidate list HmvpCandList (step S2104 in FIG. 38). If the prediction method determination unit 105 on the encoding side determines that the mode is the normal prediction motion vector mode or the normal merge mode, or if the bitstream decoding unit on the decoding side decodes as the normal prediction motion vector mode or the normal merge mode, the inter prediction mode is set as hMvpCand. If the prediction method determination unit 105 on the encoding side determines that the mode is the intra prediction mode, the sub-block prediction motion vector mode, or the sub-block merge mode, or if the bitstream decoding unit on the decoding side decodes as the intra prediction mode, the sub-block prediction motion vector mode, or the sub-block merge mode, the update process of the history prediction motion vector candidate list HmvpCandList is not performed, and there is no inter prediction information candidate hMvpCand to be registered. If there is no inter prediction information candidate hMvpCand to be registered, steps S2105 to S2110 are skipped (NO in step S2104 in FIG. 38). When an inter-prediction information candidate hMvpCand to be registered exists, the processes in and after step S2105 are performed (YES in step S2104 in FIG. 38).

[0226] Next, it is determined whether or not an element identical to the inter-prediction information candidate hMvpCand to be registered exists among the elements of the history prediction motion vector candidate list HmvpCandList (step S2105 in FIG. 38). FIG. 39 is a flowchart of this identical element confirmation process procedure. If the value of the number of history prediction motion vector candidates NumHmvpCand is 0 (NO in step S2121 in FIG. 39), the history prediction motion vector candidate list HmvpCandList is empty and no identical candidate exists, so steps S2122 to S2125 in FIG. 39 are skipped and this identical element confirmation process procedure ends. If the value of the number of history prediction motion vector candidates NumHmvpCand is greater than 0 (YES in step S2121 in FIG. 39), the process of steps S2122 to S2125 is repeated for the history prediction motion vector index hMvpIdx from 0 to NumHmvpCand-1 (steps S2121 to S2125 in FIG. 39). First, the hMvpIdx-th element HmvpCandList[MvpIdx] counting from 0 in the history predicted motion vector candidate list is compared with the inter-prediction information candidate hMvpCand to see if they are the same (step S2123 in FIG. 39). If they are the same (YES in step S2123 in FIG. 39), a flag identicalCandExist indicating whether an identical candidate exists is set to TRUE, the value of hMVpIndex is set to the deletion target index removeIdx, and this identical element confirmation process ends. If they are not the same (NO in step S2123 in FIG. 39), hMvpIdx is incremented by 1 (steps S2121 and S2125 in FIG. 39), and the processes from step S2123 onwards are performed.

[0227] Here, by filling the history motion vector predictor candidate list with history motion vector predictor candidates, step S2121 in FIG. 39 can be omitted.

[0228] Returning to the flowchart of FIG. 38 again, a shift and addition process of elements of the historical motion vector predictor candidate list HmvpCandList is performed (step S2106 of FIG. 38). FIG. 40 is a flowchart of an element shift / addition process procedure of the historical motion vector predictor candidate list HmvpCandList in step S2106 of FIG. 38. First, it is determined whether to remove elements stored in the historical motion vector predictor candidate list HmvpCandList and then add a new element, or to add a new element without removing elements. Specifically, it is compared whether a flag identicalCandExist indicating whether an identical candidate exists is TRUE (true) or NumHmvpCand is 6 (step S2141 of FIG. 40). If either of the conditions that the flag identicalCandExist indicating whether an identical candidate exists is TRUE (true) or NumHmvpCand is 6 is satisfied (YES in step S2141 of FIG. 40), an element stored in the historical motion vector predictor candidate list HmvpCandList is removed and then a new element is added. The initial value of index i is set to the value of removeIdx + 1. The element shifting process of step S2143 is repeated from this initial value to NumHmvpCand (steps S2142 to S2144 in FIG. 40). The elements of HMVPCandList[i] are shifted forward by copying them to HMVPCandList[i - 1] (step S2143 in FIG. 40), and i is incremented by 1 (steps S2142 and S2145 in FIG. 40). Next, the inter prediction information candidate hMvpCand is added to the (NumHmvpCand-1)-th HMVPCandList[NumHmvpCand-1], counting from 0 which corresponds to the end of the historical motion vector predictor candidate list (step S2145 in FIG. 40), and the element shifting and adding process of this historical motion vector predictor candidate list HMVPCandList is terminated. On the other hand, if neither of the conditions is met (NO in step S2141 of Figure 40), in which the flag identicalCandExist indicating whether an identical candidate exists is TRUE, and NumHmvpCand is 6, a new element is added without removing any elements stored in the history predicted motion vector candidate list HmvpCandList.The inter prediction information candidate hMvpCand is added to the (NumHmvpCand-1)th HMVPCandList[NumHmvpCand], counting from 0, which corresponds to the end of the historical motion vector predictor candidate list, and NumHmvpCand is incremented by 1 (step S2145 in Figure 40), thereby completing the element shifting and addition process of this historical motion vector predictor candidate list HMVPCandList.

[0229] Here, the historical motion vector predictor candidate list is applied to both the motion vector predictor mode and the merge mode, but may be applied to only one of them.

[0230] As described above, when updating the history prediction motion vector candidate list, identical elements stored in the history prediction motion vector candidate list are removed before new elements are added, so that there are no duplicate elements in the history prediction motion vector candidate list, and the history prediction motion vector candidate list is composed of all different elements.

[0231] <Historical Prediction Motion Vector Candidate Derivation Process> Next, a detailed description will be given of a method for deriving a historical prediction motion vector candidate from the historical prediction motion vector candidate list HMVPCandList, which is a processing procedure in step S304 in Fig. 20 and is common to the historical prediction motion vector candidate derivation unit 323 of the normal prediction motion vector mode derivation unit 301 on the encoding side and the historical prediction motion vector candidate derivation unit 423 of the normal prediction motion vector mode derivation unit 401 on the decoding side. Fig. 41 is a flowchart illustrating the historical prediction motion vector candidate derivation processing procedure.

[0232] If the number of current motion vector predictor candidates numCurrMvpCand is equal to or greater than the maximum number of elements in the motion vector predictor candidate list (2 in this example) or the number of historical motion vector predictor candidates is equal to 0 (NO in step S2201 in FIG. 41), steps S2202 to S2208 in FIG. 41 are omitted and the historical motion vector predictor candidate derivation process procedure is terminated. If numCurrMvpCand is smaller than 2, which is the maximum number of elements in the motion vector predictor candidate list (YES in step S2201 in FIG. 41), steps S2202 to S2208 in FIG. 41 are performed.

[0233] Next, the processes of steps S2203 to S2207 in Fig. 41 are repeated from 1 to the smaller value of index i between 4 and NumHmvpCand (steps S2202 to S2208 in Fig. 41). If numCurrMvpCand is equal to or greater than 2, which is the maximum number of elements in the motion vector predictor candidate list (NO in step S2203 in Fig. 41), the processes of steps S2204 to S2208 in Fig. 41 are omitted, and the history motion vector predictor candidate derivation process procedure is terminated. If numCurrMvpCand is smaller than 2, which is the maximum number of elements in the motion vector predictor candidate list (YES in step S2203 in Fig. 41), the processes of step S2204 and subsequent steps in Fig. 41 are performed.

[0234] Next, the processes from step S2205 to S2206 are performed for variable Y being 0 and 1 (L0 and L1), respectively (steps S2204 to S2207 in FIG. 41). If numCurrMvpCand is equal to or greater than 2, which is the maximum number of elements in the motion vector predictor candidate list (NO in step S2205 in FIG. 41), the processes from step S2206 to S2208 in FIG. 41 are omitted, and the history motion vector predictor candidate derivation process procedure ends. If numCurrMvpCand is smaller than 2, which is the maximum number of elements in the motion vector predictor candidate list (YES in step S2205 in FIG. 41), the processes from step S2206 onward in FIG. 41 are performed.

[0235] Next, the LY motion vector of the historical motion vector predictor candidate HmvpCandList[NumHmvpCand - i] is added to the numCurrMvpCand-th element mvpListLY[numCurrMvpCand] counting from 0 in the LY prediction motion vector predictor candidate list, and numCurrMvpCand is incremented by 1 (step S2206 in FIG. 41).

[0236] The above-described processing from steps S2205 to S2206 in FIG. 41 is performed for both L0 and L1 (steps S2204 to S2207 in FIG. 41).

[0237] Index i is incremented by 1 (steps S2202 and S2208 in FIG. 41), and if index i is equal to or less than the smaller value of 4 or NumHmvpCand, the processes from step S2203 onwards are performed again (steps S2202 to S2208 in FIG. 41).

[0238] In this embodiment, as described above, in the history prediction motion vector candidate derivation process, the motion vector of an element of the history prediction motion vector candidate list is added to the prediction motion vector candidate list without comparing the motion vector of the element of the history prediction motion vector candidate list with the motion vector of an element of the prediction motion vector candidate list.

[0239] By adopting such a configuration, if the number of history motion vector predictor candidates is 2 or more, it can be guaranteed that the history motion vector predictor candidate list reaches the maximum number of elements after the history motion vector predictor candidate list candidate derivation process is completed. Also, it can reduce the processing amount and circuit scale for checking whether the motion vectors are the same or not.

[0240] The normal predictor motion vector mode is a mode in which motion information of the block to be processed is determined using the predictor motion vector candidates and differential vectors included in the predictor motion vector candidate list. Since there is room for determining an appropriate motion vector using the differential vector, even in cases where elements in the predictor motion vector candidate list inevitably overlap, the reduction in encoding efficiency due to a reduction in options can be kept to a minimum.

[0241] In addition, in the normal motion vector predictor mode, the motion vector predictor candidate list is processed separately for L0 prediction and L1 prediction. Therefore, even if elements are overlapped in the motion vector predictor candidate list for L0 prediction, the elements may not be overlapped in the motion vector predictor candidate list for L1 prediction.

[0242] In addition, the normal motion vector predictor mode processes motion vector predictor candidates and reference indexes separately, so that even if elements are duplicated in the motion vector predictor candidate list, the reference index is not affected.

[0243] Furthermore, since the motion vector predictor candidate list contains only two elements at most, even if elements in the motion vector predictor candidate list overlap, the number of options is reduced by only one.

[0244] In addition, since the history motion vector predictor candidate list does not include identical elements, a comparison between an element of the history motion vector predictor candidate list and an element of the predictor motion vector candidate list is practically meaningful only when only one element of the predictor motion vector candidate list is generated by the spatial motion vector predictor candidate derivation unit 421 and the temporal motion vector predictor candidate derivation unit 422, and therefore occurs very rarely. In addition, the normal motion vector predictor mode is generally selected when the motion with the adjacent block is not similar, and the element of the history motion vector predictor candidate list is unlikely to overlap with an element already added to the predictor motion vector candidate list.

[0245] For the reasons above, even if elements of the predicted motion vector candidate list overlap, it is possible to reduce the comparison process between the motion vectors of the historical predicted motion vector candidate and the motion vectors of the predicted motion vector candidate, while suppressing a decrease in encoding efficiency due to a reduction in options.

[0246] In addition, by filling the history prediction motion vector candidate list with non-duplicate history prediction motion vector candidates and adding elements of the history prediction motion vector candidate list to the prediction motion vector candidate list without comparing the elements of the history prediction motion vector candidate list with the elements of the prediction motion vector candidate list, it is possible to omit processing of the prediction motion vector supplementation unit 325 subsequent to the history prediction motion vector candidate derivation unit 323 in the normal prediction motion vector mode derivation unit 301.

[0247] <History merge candidate derivation process> Next, a detailed description will be given of a method for deriving history merge candidates from the history motion vector predictor candidate list HmvpCandList, which is a processing procedure in step S304 in Fig. 20 and is common to the history merge candidate derivation unit 345 of the normal merge mode derivation unit 302 on the encoding side and the history merge candidate derivation unit 423 of the normal merge mode derivation unit 401 on the decoding side. Fig. 42 is a flowchart illustrating the history merge candidate derivation processing procedure.

[0248] First, an initialization process is performed (step S2301 in FIG. 42). The value FALSE is set for each of the 0th to (numCurrMergeCand -1)th elements of isPruned[i], and the number of elements currently registered in the merge candidate list, numCurrMergeCand, is set to the variable numOrigMergeCand.

[0249] Next, elements in the history motion vector predictor candidate list that are not included in the merge candidate list are added to the merge candidate list. At this time, elements are checked and added in descending order from the end of the history motion vector predictor candidate list. The initial value of the index hMvpIdx is set to 1, and the addition process from step S2303 to step S2328 in FIG. 42 is repeated from this initial value to NumHmvpCand-1 (steps S2302 to S2329 in FIG. 42). If the number of elements registered in the current merge candidate list, numCurrMergeCand, is not equal to or less than (the maximum number of merge candidates, MaxNumMergeCand-1), merge candidates have been added to all elements in the merge candidate list, so this history merge candidate derivation process is terminated (NO in step S2303 in FIG. 42). If the number of elements registered in the current merge candidate list, numCurrMergeCand, is equal to or less than (the maximum number of merge candidates, MaxNumMergeCand-1), the process from step S2304 onward is performed. A value of FALSE is set to sameMotion (step S2304 in FIG. 42). Next, the initial value of index i is set to 0, and steps S2306 and S2307 in FIG. 42 are performed from this initial value to numOrigMergeCand-1 (S2305 to S2308 in FIG. 42). A comparison is made to see whether the (NumHmvpCand-hMvpIdx)-th element HmvpCandList[NumHmvpCand-hMvpIdx], counting from 0, of the history motion vector prediction candidate list is the same as the i-th element mergeCandList[i], counting from 0 of the merge candidate list (step S2306 in FIG. 42). Merge candidates have the same value when the values ​​of all the components (inter prediction mode, reference index, motion vector) that the merge candidates have are the same. If the values ​​are the same (YES in step S2306 in FIG. 39), sameMotion and isPruned[i] are both set to TRUE (step S2307 in FIG. 42). If the values ​​are not the same (NO in step S2306 in FIG. 39), the process in step S2307 is skipped.When the repeated processing from step S2305 to step S2308 in FIG. 42 is completed, a comparison is made to see whether sameMotion is FALSE (step S2309 in FIG. 42). If sameMotion is FALSE (YES in step S2309 in FIG. 42), that is, the (NumHmvpCand - hMvpIdx)-th element HmvpCandList[NumHmvpCand - hMvpIdx] counting from 0 in the history motion vector predictor candidate list does not exist in mergeCandList, so the (NumHmvpCand - hMvpIdx)-th element HmvpCandList[NumHmvpCand - hMvpIdx] is added, and numCurrMergeCand is incremented by 1 (step S2310 in FIG. 42). The index hMvpIdx is incremented by 1 (step S2302 in FIG. 42), and steps S2302 to S2311 in FIG. 42 are repeated.

[0250] When all elements in the history motion vector predictor candidate list have been checked, or when merge candidates have been added to all elements in the merge candidate list, this history merge candidate derivation process is completed. In this embodiment, as described above, in the history merge candidate derivation process, elements of the history prediction motion vector candidate list are compared with elements of the current merge candidate list, and only elements of the history prediction motion vector candidate list that are not present in the current merge candidate list are added to the merge candidate list. Unlike the normal predicted motion vector mode, the normal merge mode is a mode that directly determines the motion information of the block to be processed without using a difference vector, so that the coding efficiency can be improved by prohibiting the addition of elements of the history merge candidate list that overlap with elements of the current merge candidate list. Here, the elements of the history predicted motion vector candidate list are compared with all candidates of the current merge candidate list, but this is not limited to this as long as the coding efficiency can be improved by comparing at least the elements of the history predicted motion vector candidate list with the elements of the current merge candidate list. For example, the number of elements of the historical motion vector predictor candidate list to be compared may be limited to one or two, etc. Also, the number of elements of the current merge candidate list to be compared may be limited to one or two. In addition, in the normal merge mode, the merge candidate list includes both the motion vector of L0 prediction and the motion vector of L1 prediction. Therefore, unlike the normal prediction motion vector mode, the predicted motion vector of L0 prediction and the predicted motion vector of L1 prediction cannot be adjusted separately. In addition, in the normal merge mode, the merge candidate list includes both the reference indexes for L0 prediction and the reference indexes for L1 prediction. Therefore, unlike the normal prediction motion vector mode, the reference indexes for L0 prediction and the reference indexes for L1 prediction cannot be adjusted separately. In addition, since the merge candidate list contains up to six elements, which is more than the motion vector predictor candidate list, adding a duplicate element to the merge candidate list increases the number of duplicate elements in the merge candidate list, making it difficult to use the merge candidate list efficiently. In addition, the element of the history prediction motion vector candidate list that is added to the merge candidate list is the element that is added most recently among the elements of the history prediction motion vector candidate list.Therefore, the element of the history prediction motion vector candidate list that is added to the merge candidate list is the motion information that is spatially closest to the coding block to be processed.Generally, normal merge mode is selected when the motion of adjacent blocks is similar, and the element of the history prediction motion vector candidate list is likely to overlap with the element that has already been added to the merge candidate list. In order to address the above-mentioned issues, the addition of elements to the historical motion vector predictor candidate list that overlap with elements to the merge candidate list can be prohibited, thereby increasing the number of valid selection elements, thereby improving coding efficiency.

[0251] In addition, by making the maximum number of elements that can be included in a merge candidate list, which is 6, greater than the maximum number of elements that can be included in a predictor motion vector candidate list, which is 2, the probability of selecting the normal merge mode is increased, thereby reducing the comparison process between the motion vectors of the history predictor motion vector candidate and the motion vectors of the predictor motion vector candidate while suppressing a decrease in encoding efficiency due to overlapping elements in the predictor motion vector candidate list. In addition, by including a variety of merge candidates such as temporal merge candidates, history merge candidates, average merge candidates, and zero merge candidates in addition to spatial merge candidates, it is possible to increase the probability of selecting the normal merge mode, while suppressing a decrease in encoding efficiency due to overlapping elements in the predictor motion vector candidate list, while reducing the comparison process between the motion vector of the history predictor motion vector candidate and the motion vector of the predictor motion vector candidate.

[0252] <Sub-block time merge candidate derivation> The operation of the sub-block temporal merging candidate derivation unit 381 in the sub-block merging mode derivation unit 304 in FIG. 16 will be described with reference to FIG.

[0253] First, it is determined whether the coding block is smaller than 8x8 pixels (S4002).

[0254] If the coding block is smaller than 8x8 pixels (S4002: Yes), a flag indicating the presence of a sub-block temporal merge candidate is set to availableFlagSbCol=0 (S4003), and the processing of the sub-block temporal merge candidate derivation unit is terminated. Here, if temporal motion vector prediction is prohibited by the syntax, or if sub-block temporal merging is prohibited, the same processing as when the coding block is smaller than 8x8 pixels (S4002: Yes) is performed.

[0255] On the other hand, if the coding block is 8x8 pixels or more (S4002: No), adjacent motion information of the coding block in the coded picture is derived (S4004).

[0256] The process of deriving adjacent motion information of a coding block will be described with reference to FIG. 45. The process of deriving adjacent motion information is similar to the process of the spatial prediction motion vector candidate derivation unit 321 described above. However, the order of searching for adjacent blocks is A0, B0, B1, A1, and B2 is not searched. First, coding information is obtained for adjacent block n=A0 (S4052). The coding information indicates a flag availableFlagN indicating whether the adjacent block is available, a reference index refIdxLXN for each reference list, and a motion vector mvLXN.

[0257] Next, it is determined whether adjacent block n is valid or invalid (S4054). If a flag indicating whether the adjacent block is available or not is set to availableFlagN=1, the adjacent block is valid, otherwise it is invalid.

[0258] If adjacent block n is valid (S4054: Yes), the reference index refIdxLXN is set as the reference index refIdxLXn of adjacent block n (S4056), and the motion vector mvLXN is set as the motion vector mvLXn of adjacent block n (S4056), and the process of deriving adjacent motion information of blocks is terminated.

[0259] On the other hand, if adjacent block n is invalid (S4106: No), adjacent block n=B0 is set and coding information is obtained (S4104). Similar processing is then performed, looping in the order of B1, A1. The process of deriving adjacent motion information loops until the adjacent blocks become valid, and if all adjacent blocks A0, B0, B1, and A1 are invalid, the process of deriving adjacent motion information of blocks ends.

[0260] Again, refer to Figure 44. Once the adjacent motion information has been derived (S4004), a temporal motion vector is derived (S4006).

[0261] The process of deriving a temporal motion vector will be described with reference to Fig. 46. First, the temporal motion vector tempMv is initialized to (0,0) (S4062).

[0262] Next, it is determined whether the adjacent motion information is valid or invalid (S4064). If the flag indicating whether the adjacent block is available or not is available, availableFlagN=1, the information is valid; otherwise, the information is invalid. If the adjacent motion information is invalid (S4064: No), the process of deriving the temporal motion vector is terminated.

[0263] On the other hand, if the adjacent motion information is valid (S4064: Yes), it is determined whether a flag predFlagL1N indicating whether L1 prediction is used in adjacent block N is 1 (S4066). If predFlagL1N=0 (S4066: No), proceed to the next process (S4078). If predFlagL1N=1 (S4066: Yes), it is determined whether the POC of all pictures registered in all reference lists is equal to or less than the POC of the current picture to be coded (S4068). If this determination is true (S4068: Yes), proceed to the next process (S4070).

[0264] If the slice type slice_type is a B slice and the flag collocated_from_l0_flag is 0 (S4070: Yes and S4072: Yes), it is determined whether ColPic is the same as the reference picture RefPicList1[refIdxL1N] (the picture with the reference index refIdxL1N in the reference list L1) (S4074). If this determination is true (S4074: Yes), the temporal motion vector tempMv=mvL1N is set (S4076). If this determination is false (S4074: No), the process proceeds to the next process (S4078). If the slice type slice_type is not a B slice and the flag collocated_from_l0_flag is not 0 (S4070: No or S4072: No), the process proceeds to the next process (S4078).

[0265] Then, it is determined whether a flag predFlagL0N indicating whether L0 prediction is used in adjacent block N is 1 (S4078). If predFlagL0N=1 (S4078: Yes), it is determined whether ColPic is the same as the reference picture RefPicList0[refIdxL0N] (the picture at the reference index refIdxL0N in the reference list L0) (S4080). If this determination is true (S4080: Yes), the temporal motion vector tempMv=mvL0N is set (S4082). If this determination is false (S4080: No), the process of deriving the temporal motion vector is terminated.

[0266] 44 will be referred to again. Next, ColPic is derived (S4016). This process is the same as S4201 in the temporal motion vector predictor candidate derivation unit 322, and therefore a description thereof will be omitted.

[0267] Then, a coding block colCb of a different time is set (S4017). This is to set a coding block located at the same position as the coding block to be processed in the lower right corner of the picture ColPic of the different time as colCb. This coding block corresponds to coding block T1 in FIG.

[0268] Next, the position obtained by adding the temporal motion vector tempMv to the coding block colCb is set as a new colCb (S4018). If the position of the upper left corner of the coding block colCb is (xColCb, yColCb) and the temporal motion vector tempMv is (tempMv[0], tempMv[1]) with 1 / 16 pixel accuracy, the position of the upper left corner of the new colCb is as follows: xColCb = Clip3( xCtb, xCtb + CtbSizeY + 3, xcolCb + ( tempMv[0] >> 4 ) ) yColCb = Clip3( yCtb, yCtb + CtbSizeY - 1, ycolCb + ( tempMv[1] >> 4 ) ) Here, the position of the top left corner of the tree block is (xCtb, yCtb), and the size of the tree block is CtbSizeY. As shown in the above formula, the position after adding tempMv is corrected to within the range of the size of the tree block so that it does not deviate significantly from the position before adding tempMv. If this position is outside the screen, it is corrected to within the screen.

[0269] Then, it is determined whether the prediction mode PredMode of this coding block colCb is inter prediction (MODE_INTER) (S4020). If the prediction mode of colCb is not inter prediction (S4020: No), a flag indicating the presence of a sub-block temporal merge candidate is set to availableFlagSbCol=0 (S4003), and the process of the sub-block temporal merge candidate derivation unit is terminated.

[0270] On the other hand, if the prediction mode of colCb is inter prediction (S4020: Yes), inter prediction information is derived for each reference list (S4022, S4023). Here, for colCb, a central motion vector ctrMvLX for each reference list and a flag ctrPredFlagLX indicating whether LX prediction is used or not are derived. LX indicates a reference list, and LX is L0 when deriving reference list 0, and LX is L1 when deriving reference list 1. The derivation of inter prediction information will be described with reference to FIG. 47.

[0271] If the coding block colCb of a different time is not available (S4112: NO), or if the prediction mode PredMode is intra prediction (MODE_INTRA) (S4114: NO), the flags availableFlagLXCol and predFlagLXCol are both set to 0 (step S4116), the motion vector mvCol is set to (0,0) (S4118), and the process of deriving the inter prediction information is terminated.

[0272] When the coded block colCb is available (S4112: Yes) and the prediction mode PredMode is not intra prediction (MODE_INTRA) (S4114: YES), mvCol, refIdxCol, and availableFlagCol are calculated in the following procedure.

[0273] When the flag PredFlagLX[xPCol][yPCol] indicating whether the LX prediction of the coding block colCb is used is 1 (YES in S4120), the motion vector mvCol is set to the same value as the motion vector MvLX[xPCol][yPCol] of the LX of the coding block colCb (S4122), the reference index refIdxCol is set to the same value as the reference index RefIdxLX[xPCol][yPCol] of LX (S4124), and the list listCol is set to LX (S4126). Here, xPCol and yPCol are indexes indicating the position of the upper left pixel of the coding block colCb in the picture colPic of a different time.

[0274] On the other hand, if the flag PredFlagLX[xPCol][yPCol] indicating whether or not LX prediction of the coding block colCb is used is 0 (NO in S4120), the following process is performed. First, it is determined whether the POC of all pictures registered in all reference lists is equal to or less than the POC of the current picture to be coded (S4128). It is also determined whether the flag PredFlagLY[xPCol][yPCol] indicating whether or not LY prediction of colCb is used is 1 (S4128). Here, LY prediction is defined as a reference list different from LX prediction. That is, when LX=L0, LY=L1, and when LX=L1, LY=L0.

[0275] If this judgment is true (S4128: Yes), the motion vector mvCol is set to the same value as the LY motion vector MvLY[xPCol][yPCol] of the coding block colCb (S4130), the reference index refIdxCol is set to the same value as the LY reference index RefIdxLY[xPCol][yPCol] (S4132), and the list listCol is set to LX (S4134).

[0276] On the other hand, if this determination is false (S4128: No), the flags availableFlagLXCol and predFlagLXCol are both set to 0 (step S4116), the motion vector mvCol is set to (0,0) (S4118), and the process of deriving inter prediction information ends.

[0277] When inter prediction information is acquired from the coding block colCb, both the flag availableFlagLXCol and the flag predFlagLXCol are set to 1 (S4136).

[0278] Next, the motion vector mvCol is scaled to obtain a motion vector mvLXCol (S4138). This process is the same as S4245 in the temporal motion vector predictor candidate derivation unit 322, and therefore a description thereof will be omitted.

[0279] Again, refer to Figure 44. Once inter prediction information is derived for each reference list, the calculated motion vector mvLXCol is set as the central motion vector ctrMvLX, and the calculated flag predFlagLXCol is set as the flag ctrPredFlagLX (S4022, S4023).

[0280] Then, it is determined whether the central motion vector is valid or invalid (S4024). If ctrPredFlagL0=0 and ctrPredFlagL1=0, it is invalid; otherwise, it is invalid. If the central motion vector is invalid (S4024: No), a flag indicating the presence of a sub-block temporal merge candidate is set to availableFlagSbCol=0 (S4003), and the processing of the sub-block temporal merge candidate derivation unit is terminated.

[0281] On the other hand, if the central motion vector is valid (S4024: Yes), a flag indicating the presence of a sub-block temporal merge candidate is set to availableFlagSbCol=1 (S4025), and sub-block motion information is derived (S4026). This process will be described with reference to FIG.

[0282] First, the number of sub-blocks in the width direction, numSbX, and the number of sub-blocks in the height direction, numSbY, are calculated from the width cbWidth and height cBheight of the coding block colCb (S4152). Also, refIdxLXSbCol=0 is set (S4152). After this process, the process is repeated in units of the predicted sub-block colSb. This repetition is performed while changing the height direction index ySbIdx from 0 to numSbY and the width direction index xSbIdx from 0 to numSbX.

[0283] If the top left position of the coding block colCb is (xCb, yCb), the top left position (xSb, ySb) of the prediction sub-block colSb is calculated as follows. xSb = xCb + xSbIdx * sbWidth ySb = yCb + ySbIdx * sbHeight Next, the position obtained by adding the temporal motion vector tempMv to the prediction sub-block colSb is set as new colSb (S4154). If the position of the upper left corner of the prediction sub-block colSb is (xColSb, yColSb) and the temporal motion vector tempMv is (tempMv[0], tempMv[1]) with 1 / 16 pixel accuracy, the position of the upper left corner of the new colSb is as follows: xColSb = Clip3( xCtb, xCtb + CtbSizeY + 3, xSb + ( tempMv[0] >> 4 ) ) yColSb = Clip3( yCtb, yCtb + CtbSizeY - 1, ySb + ( tempMv[1] >> 4 ) ) Here, the position of the top left corner of the tree block is (xCtb, yCtb), and the size of the tree block is CtbSizeY. As shown in the above formula, the position after adding tempMv is corrected to within the range of the size of the tree block so that it does not deviate significantly from the position before adding tempMv. If this position is outside the screen, it is corrected to within the screen.

[0284] Then, inter prediction information is derived for each reference list (S4156, S4158). Here, for the prediction sub-block colSb, a motion vector mvLXSbCol for each reference list in sub-block units and a flag availableFlagLXSbCol indicating whether the prediction sub-block is valid or not are derived. LX indicates a reference list, and LX is L0 when deriving reference list 0, and LX is L1 when deriving reference list 1. The derivation of the inter prediction information is the same as S4022 and S4023 in FIG. 47, and therefore description will be omitted.

[0285] After deriving the inter prediction information (S4156, S4158), it is determined whether or not the prediction sub-block colSb is valid (S4160). If availableFlagL0SbCol=0 and availableFlagL1SbCol=0, colSb is invalid; otherwise, it is determined to be valid. If colSb is invalid (S4160: No), the motion vector mvLXSbCol is set as the central motion vector ctrMvLX (S4162). Furthermore, the flag predFlagLXSbCol indicating whether or not LX prediction is being used is set as the flag ctrPredFlagLX in the central motion vector (S4162). This completes the derivation of the sub-block motion information.

[0286] Refer again to Figure 44. Then, the L0 motion vector mvL0SbCol and the L1 motion vector mvL1SbCol are added as candidates to the subblock merge candidate list subblockMergeCandList in the subblock merge mode derivation unit 304 described above (S4028). However, this addition is only made when the flag availableSbCol = 1 indicating the presence of a subblock temporal merge candidate. With this, the processing of the temporal merge candidate derivation unit 342 ends.

[0287] The above description of the sub-block temporal merging candidate derivation unit 381 is for encoding, but the same is true for decoding. That is, the operation of the sub-block temporal merging candidate derivation unit 481 in the sub-block merging mode derivation unit 404 in Fig. 22 can be similarly described by replacing encoding in the above description with decoding.

[0288] <Motion compensation prediction processing> The motion compensation prediction unit 306 acquires the position and size of a block currently being subjected to prediction processing in encoding. The motion compensation prediction unit 306 also acquires inter prediction information from the inter prediction mode determination unit 305. A reference index and a motion vector are derived from the acquired inter prediction information, and a reference picture specified by the reference index in the decoded image memory is acquired at a position where the reference picture is moved by the amount of the motion vector from the same position as the image signal of the prediction block, and then a prediction signal is generated.

[0289] In the case where the reference mode in inter prediction is prediction from a single reference picture, such as L0 prediction or L1 prediction, the prediction signal obtained from one reference picture is used as a motion compensation prediction signal, and in the case where the reference mode is prediction from two reference pictures, such as BI prediction, the weighted average of the prediction signals obtained from the two reference pictures is used as a motion compensation prediction signal, and the motion compensation prediction signal is supplied to the prediction method determination unit. Here, the ratio of the weighted average of bi-prediction is set to 1:1, but the weighted average may be performed using other ratios. For example, the weighting ratio may be set to be larger as the picture interval between the picture to be predicted and the reference picture becomes closer. In addition, the weighting ratio may be calculated using a correspondence table of combinations of picture intervals and weighting ratios.

[0290] The motion compensation prediction unit 406 has the same function as the motion compensation prediction unit 306 on the encoding side. The motion compensation prediction unit 406 obtains inter prediction information from a normal prediction motion vector mode derivation unit 401, a normal merge mode derivation unit 402, a sub-block prediction motion vector mode derivation unit 403, and a sub-block merge mode derivation unit 404 via a switch 408.

[0291] The motion compensation prediction unit 406 supplies the obtained motion compensation prediction signal to the decoded image signal superimposition unit 207 .

[0292] <About prediction direction> 57 to 61 are diagrams for explaining the prediction direction of motion compensation prediction. A process of performing prediction from a single reference picture is defined as uni-prediction, and in the case of uni-prediction, prediction is performed using one of two reference pictures registered in a reference list, called L0 prediction or L1 prediction.

[0293] Figure 57 shows a case where the L0 reference picture (RefL0Pic) is located before the current picture (CurPic) in uni-prediction. Figure 58 shows a case where the L0 prediction reference picture is located after the current picture in uni-prediction. Similarly, uni-prediction can be performed by replacing the L0 prediction reference picture in Figures 57 and 58 with the L1 prediction reference picture (RefL1Pic).

[0294] A process of making predictions from two reference pictures is defined as bi-prediction, and in the case of bi-prediction, both L0 prediction and L1 prediction are used and expressed as BI prediction. FIG. 59 shows a case of bi-prediction where the reference picture of L0 prediction is at a time before the picture to be coded, and the reference picture of L1 prediction is at a time after the picture to be coded. FIG. 60 shows a case of bi-prediction where the reference picture of L0 prediction and the reference picture of L1 prediction are at a time before the picture to be coded. FIG. 61 shows a case of bi-prediction where the reference picture of L0 prediction and the reference picture of L1 prediction are at a time after the picture to be coded. In this way, the relationship between the prediction type and time of L0 / L1 can be used without being limited to L0 being the past direction and L1 being the future direction. In addition, in the case of bi-prediction, each of L0 prediction and L1 prediction may be performed using the same reference picture. Note that the determination of whether to perform motion compensation prediction in a uni-predictive or bi-predictive manner is made based on information (eg, a flag) indicating whether or not to use L0 prediction and whether or not to use L1 prediction, for example.

[0295] <About reference indexes> In an embodiment of the present invention, in order to improve the accuracy of motion compensation prediction, it is possible to select an optimal reference picture from among multiple reference pictures in motion compensation prediction. To this end, the reference picture used in the motion compensation prediction is used as a reference index, and the reference index is coded into the coding stream together with a coding vector.

[0296] <Motion compensation process based on normal predicted motion vector mode> 16 , when inter prediction information by the normal prediction motion vector mode derivation unit 301 is selected in the inter prediction mode determination unit 305, the motion compensation unit 306 acquires this inter prediction information from the inter prediction mode determination unit 305, derives a reference mode, a reference index, and a motion vector of the block currently being processed, and generates a motion compensation prediction signal. The generated motion compensation prediction signal is supplied to the prediction method determination unit 105.

[0297] 22, when a switch 408 is connected to the normal prediction motion vector mode derivation unit 401 during the decoding process, the motion compensation unit 406 obtains inter prediction information from the normal prediction motion vector mode derivation unit 401, derives a reference mode, a reference index, and a motion vector of the block currently being processed, and generates a motion compensation prediction signal. The generated motion compensation prediction signal is supplied to the decoded image signal superimposition unit 207.

[0298] <Motion compensation processing based on normal merge mode> 16 , when the inter prediction information by the normal merge mode derivation unit 302 is selected in the inter prediction mode determination unit 305, the motion compensation unit 306 acquires the inter prediction information from the inter prediction mode determination unit 305, derives the reference mode, reference index, and motion vector of the block currently being processed, and generates a motion compensation prediction signal. The generated motion compensation prediction signal is supplied to the prediction method determination unit 105.

[0299] 22, when a switch 408 is connected to the normal merge mode derivation unit 402 during the decoding process, the motion compensation unit 406 obtains inter prediction information from the normal merge mode derivation unit 402, derives a reference mode, a reference index, and a motion vector for the block currently being processed, and generates a motion compensation prediction signal. The generated motion compensation prediction signal is supplied to the decoded image signal superimposition unit 207.

[0300] <Motion compensation process based on sub-block predicted motion vector mode> 16 , when inter prediction information is selected by the sub-block prediction motion vector mode derivation unit 303 in the inter prediction mode determination unit 305, the motion compensation unit 306 acquires the inter prediction information from the inter prediction mode determination unit 305, derives a reference mode, a reference index, and a motion vector of the block currently being processed, and generates a motion compensation prediction signal. The generated motion compensation prediction signal is supplied to the prediction method determination unit 105.

[0301] 22, when a switch 408 is connected to the sub-block prediction motion vector mode derivation unit 403 during the decoding process, the motion compensation unit 406 obtains inter prediction information from the sub-block prediction motion vector mode derivation unit 403, derives a reference mode, a reference index, and a motion vector for the block currently being processed, and generates a motion compensation prediction signal. The generated motion compensation prediction signal is supplied to the decoded image signal superimposition unit 207.

[0302] <Motion compensation processing based on sub-block merge mode> 16 , when inter prediction information is selected by the sub-block merge mode derivation unit 304 in the inter prediction mode determination unit 305, the motion compensation unit 306 acquires the inter prediction information from the inter prediction mode determination unit 305, derives a reference mode, a reference index, and a motion vector for the block currently being processed, and generates a motion compensation prediction signal. The generated motion compensation prediction signal is supplied to the prediction method determination unit 105.

[0303] 22, when a switch 408 is connected to the sub-block merging mode derivation unit 404 during the decoding process, the motion compensation unit 406 obtains inter prediction information from the sub-block merging mode derivation unit 404, derives a reference mode, a reference index, and a motion vector for the block currently being processed, and generates a motion compensation prediction signal. The generated motion compensation prediction signal is supplied to the decoded image signal superimposition unit 207.

[0304] <Motion compensation processing based on affine transformation prediction> In the normal prediction motion vector mode and normal merge mode, motion compensation using an affine model can be used based on the following flags. The following flags are reflected in the following flags based on the inter prediction conditions determined by the inter prediction mode determination unit 305 in the encoding process, and are encoded in the encoded stream. In the decoding process, whether or not to perform motion compensation using an affine model is specified based on the following flags in the encoded stream.

[0305] sps_affine_enabled_flag indicates whether or not motion compensation based on an affine model can be used in inter prediction. If sps_affine_enabled_flag is 0, motion compensation based on an affine model is suppressed on a sequence-by-sequence basis. In addition, inter_affine_flag and cu_affine_type_flag are not transmitted in the CU syntax of the coded video sequence. If sps_affine_enabled_flag is 1, motion compensation based on an affine model can be used in the coded video sequence.

[0306] sps_affine_type_flag indicates whether motion compensation using a six-parameter affine model can be used in inter prediction.

[0307] If sps_affine_type_flag is 0, motion compensation based on the six-parameter affine model is suppressed. Also, cu_affine_type_flag is not transmitted in the CU syntax of the coded video sequence. If sps_affine_type_flag is 1, motion compensation based on the six-parameter affine model can be used in the coded video sequence.

[0308] If sps_affine_type_flag is not present, it shall be set to 0.

[0309] When decoding a P or B slice, if inter_affine_flag is 1 in the currently processed CU, motion compensation using an affine model is used to generate a motion compensation prediction signal for the currently processed CU.

[0310] If inter_affine_flag is 0, no affine model is used for the currently processed CU.

[0311] If inter_affine_flag is not present, it shall be set to 0.

[0312] When decoding a P or B slice, if cu_affine_type_flag is 1 for the currently processed CU, motion compensation using a 6-parameter affine model is used to generate a motion compensation prediction signal for the currently processed CU.

[0313] If cu_affine_type_flag is 0, motion compensation based on a four-parameter affine model is used to generate a motion compensated prediction signal for the currently processed CU.

[0314] In motion compensation based on the affine model, reference indexes and motion vectors are derived for each subblock, and therefore a motion compensation prediction signal is generated using the reference indexes and motion vectors to be processed for each subblock.

[0315] <Variation 1> A first modified example of the present embodiment will be described. This modified example differs from the present embodiment in that a merge differential motion vector mode is added, and only the differences from the present embodiment will be described. If umve_flag in FIG. 12 is 1, the merge differential motion vector mode is selected, and if umve_flag is 0, the normal merge mode is selected.

[0316] Next, the operation of the merge motion vector difference mode will be described. This mode can add one merge motion vector difference to each of the L0 prediction motion vector and the L1 prediction motion vector of one of the top two merge candidates (merge candidates with merge indexes 0 and 1 in the merge candidate list).

[0317] In the case of the merge motion vector difference mode, the merge motion vector difference is coded by the bitstream coding unit 108 and decoded by the bitstream decoding unit 201 .

[0318] As described above, since the merge candidate list is also used in the merge differential motion vector mode, the addition of elements to the historical predicted motion vector candidate list that overlap with elements of the merge candidate list can be prohibited, thereby increasing the number of valid selection elements and improving coding efficiency.

[0319] In addition, by adding the merge differential motion vector mode and reducing the probability of selecting the normal predicted motion vector mode, it is possible to reduce the comparison process between the motion vectors of the history predicted motion vector candidate and the motion vector of the predicted motion vector candidate while suppressing a decrease in encoding efficiency due to overlapping elements in the predicted motion vector candidate list. <Variation 2> Modification 2 of the present embodiment will be described. This modification differs from the present embodiment in the operations of the history motion vector predictor candidate derivation units 323 and 423 shown in FIG. 41, and only the differences from the present embodiment will be described. FIG. 65 is a flowchart illustrating the history motion vector predictor candidate derivation process procedure of modification 2. FIG. 65 differs from FIG. 41 in that step S2209 is added. FIG. 65 has the same operations as FIG. 41 except for step S2209.

[0320] The process to be performed when numCurrMvpCand is smaller than 2, which is the maximum number of elements in the motion vector predictor candidate list (YES in step S2205 in FIG. 65) will be described.

[0321] It is checked whether the LY reference index of the history motion vector predictor candidate HmvpCandList[NumHmvpCand-i] is the same as the LY reference index of the coding block to be processed (step S2209 in FIG. 65), and if the LY reference index of the history motion vector predictor candidate HmvpCandList[NumHmvpCand-i] is the same as the LY reference index of the coding block to be processed (YES in step S2209 in FIG. 65), proceed to S2206. If the LY reference index of the history motion vector predictor candidate HmvpCandList[NumHmvpCand-i] is not the same as the LY reference index of the coding block to be processed (NO in step S2209 in FIG. 65), proceed to S2207.

[0322] As described above, when the LY reference index of the history prediction motion vector candidate is the same as the LY reference index of the coding block to be processed, the motion vector of the history prediction motion vector candidate is added to the predicted motion vector candidate list for LY prediction, so that a highly accurate history prediction motion vector candidate can be added to the predicted motion vector candidate list without comparing the motion vector of the history prediction motion vector candidate with the motion vector of the predicted motion vector candidate.

[0323] In this embodiment, in the history prediction motion vector candidate derivation process, elements of the history prediction motion vector candidate list are added to the prediction motion vector candidate list without comparing the elements of the history prediction motion vector candidate list with the elements of the prediction motion vector candidate list, while in the history merge candidate derivation process, elements of the history merge candidate list are compared with elements of the merge list, and only history merge candidate lists that do not exist in the merge list are added to the merge list. By adopting the above configuration, the following effects can be obtained.

[0324] 1. In the process of deriving candidates for the history predictor motion vector candidate list, there is no need to perform additional candidate derivation processing, which reduces the amount of processing and the circuit size. Furthermore, even in cases where elements in the predictor motion vector candidate list are inevitably duplicated, the decrease in coding efficiency due to a reduction in options can be kept to a minimum.

[0325] 2. In the history merge candidate derivation process, by prohibiting the addition of elements to the history merge candidate list that overlap with elements of the merge list, an appropriate merge candidate list can be constructed in the normal merge mode, which determines motion information for the block to be processed without using a difference vector, thereby improving coding efficiency.

[0326] 3. By filling the history prediction motion vector candidate list with non-duplicate history prediction motion vector candidates, the processing of the merge candidate supplementation unit 346 subsequent to the history merge candidate derivation unit 345 in the normal merge mode derivation unit 302 can be omitted, thereby reducing the amount of processing.

[0327] 4. By filling the history prediction motion vector candidate list with non-duplicate history prediction motion vector candidates and adding elements of the history prediction motion vector candidate list to the prediction motion vector candidate list without comparing the elements of the history prediction motion vector candidate list with the elements of the prediction motion vector candidate list, it is possible to omit processing of the prediction motion vector supplementation unit 325 subsequent to the history prediction motion vector candidate derivation unit 323 in the normal prediction motion vector mode derivation unit 301.

[0328] All of the above-described embodiments may be combined in multiple forms.

[0329] In all the embodiments described above, the coded bit stream output by the image coding device has a specific data format so that it can be decoded according to the coding method used in the embodiment, and the image decoding device corresponding to the image coding device can decode the coded bit stream in the specific data format.

[0330] When a wired or wireless network is used to exchange coded bitstreams between an image coding device and an image decoding device, the coded bitstream may be converted into a data format suitable for the transmission mode of the communication channel before being transmitted. In this case, a transmitting device is provided that converts the coded bitstream output by the image coding device into coded data in a data format suitable for the transmission mode of the communication channel and transmits the coded bitstream to the network, and a receiving device is provided that receives the coded data from the network, restores it to a coded bitstream, and supplies it to the image decoding device.

[0331] The transmitting device includes a memory that buffers the coded bit stream output by the image coding device, a packet processing unit that packetizes the coded bit stream, and a transmitting unit that transmits the packetized coded data via a network. The receiving device includes a receiving unit that receives the packetized coded data via the network, a memory that buffers the received coded data, and a packet processing unit that packetizes the coded data to generate a coded bit stream and provides it to the image decoding device.

[0332] Also, a display unit for displaying an image decoded by the image decoding device may be added to the configuration to form a display device. In this case, the display unit reads out the decoded image signal generated by the decoded image signal superimposition unit 205 and stored in the decoded image memory 206, and displays it on a screen.

[0333] Moreover, an imaging unit may be added to the configuration and the captured image may be input to the image coding device to form an imaging device. In this case, the imaging unit inputs a captured image signal to the block division unit 101.

[0334] 66 shows an example of a hardware configuration of a coding / decoding device of the present application. The coding / decoding device includes the configurations of an image coding device and an image decoding device according to an embodiment of the present invention. The coding / decoding device 9000 includes a CPU 9001, a codec IC 9002, an I / O interface 9003, a memory 9004, an optical disk drive 9005, a network interface 9006, and a video interface 9009, and each unit is connected by a bus 9010.

[0335] The image encoding unit 9007 and the image decoding unit 9008 are typically implemented as a codec IC 9002. The image encoding process of the image encoding device according to the embodiment of the present invention is executed by the image encoding unit 9007, and the image decoding process of the image decoding device according to the embodiment of the present invention is executed by the image encoding unit 9007. The I / O interface 9003 is realized by, for example, a USB interface, and is connected to an external keyboard 9104, mouse 9105, etc. The CPU 9001 controls the encoding / decoding device 9000 so as to execute an operation desired by the user based on a user operation input via the I / O interface 9003. The user operation by the keyboard 9104, mouse 9105, etc. includes a selection of whether to execute an encoding or decoding function, a setting of encoding quality, an input / output destination of the encoded stream, an input / output destination of an image, etc.

[0336] When a user desires to play back an image recorded on the disc recording medium 9100, the optical disc drive 9005 reads out an encoded bit stream from the inserted disc recording medium 9100, and sends the read encoded stream to an image decoding unit 9008 of the codec IC 9002 via a bus 9010. The image decoding unit 9008 executes image decoding processing in the image decoding device according to the embodiment of the present invention on the input encoded bit stream, and sends the decoded image to an external monitor 9103 via a video interface 9009. The encoding / decoding device 9000 also has a network interface 9006, and can be connected to an external distribution server 9106 or a mobile terminal 9107 via a network 9101. When a user desires to play back an image recorded on the distribution server 9106 or the mobile terminal 9107 instead of the image recorded on the disc recording medium 9100, the network interface 9006 acquires an encoded stream from the network 9101, instead of reading out the encoded bit stream from the input disc recording medium 9100. Furthermore, when a user wishes to play back the image recorded in memory 9004, image decoding processing is performed on the encoded stream recorded in memory 9004 in an image decoding device according to an embodiment of the present invention.

[0337] When a user desires to encode an image captured by an external camera 9102 and record the encoded stream in memory 9004, the video interface 9009 inputs the image from the camera 9102 and sends the image to an image encoding unit 9007 of the codec IC 9002 via a bus 9010. The image encoding unit 9007 executes image encoding processing in the image encoding device according to the embodiment of the present invention on the image input via the video interface 9009 to generate an encoded bit stream. The encoded bit stream is then sent to the memory 9004 via the bus 9010. When a user desires to record the encoded stream in the disc recording medium 9100 instead of the memory 9004, the optical disc drive 9005 writes the encoded stream to the inserted disc recording medium 9100.

[0338] It is also possible to realize a hardware configuration having an image encoding device but not an image decoding device, or a hardware configuration having an image decoding device but not an image encoding device. Such a hardware configuration can be realized, for example, by replacing the codec IC 9002 with an image encoding unit 9007 or an image decoding unit 9008, respectively.

[0339] The above-mentioned encoding and decoding processes may be realized not only as a transmission, storage, and receiving device using hardware, but also as firmware stored in a ROM (read-only memory) or flash memory, or as software for a computer, etc. The firmware program or software program may be provided by recording it on a recording medium readable by a computer, etc., or may be provided from a server via a wired or wireless network, or may be provided as data broadcasting of terrestrial or satellite digital broadcasting.

[0340] The present invention has been described above based on the embodiments. The embodiments are merely examples, and it will be understood by those skilled in the art that various modifications are possible in the combination of each component and each treatment process, and that such modifications are also within the scope of the present invention. [Explanation of symbols]

[0341] 100 image encoding device, 101 block division unit, 102 inter prediction unit, 103 intra prediction unit, 104 decoded image memory, 105 prediction method determination unit, 106 residual signal generation unit, 107 orthogonal transform / quantization unit, 108 bit string encoding unit, 109 inverse quantization / inverse orthogonal transform unit, 110 decoded image signal superposition unit, 111 encoded information storage memory, 200 image decoding device, 201 bit string decoding unit, 202 block division unit, 203 inter prediction unit, 204 intra prediction unit, 205 encoded information storage memory, 205 inverse quantization / inverse orthogonal transform unit, 207 decoded image signal superposition unit, 208 decoded image memory.< / poc>

Claims

1. a spatial candidate derivation unit that derives spatial candidates from inter prediction information of a plurality of blocks adjacent to a current block to be coded, and registers the spatial candidates in a first candidate list; a history candidate derivation unit that adds history candidates included in the history candidate list as candidates to the first candidate list to generate a second candidate list; a candidate selection unit that selects a selection candidate from the candidates included in the second candidate list; an inter prediction unit that performs inter prediction using the selection candidates; Equipped with the history candidate derivation unit, when a prediction mode of the encoding target block is a first prediction mode, determines whether or not to add the history candidate to the first candidate list based on whether a motion vector and a reference index included in the history candidate are identical to a motion vector and a reference index included in a candidate included in the first candidate list; and, when the prediction mode is a second prediction mode, adds the history candidate to the first candidate list regardless of whether a motion vector of the history candidate is identical to a motion vector of a candidate included in the first candidate list; a maximum number of candidates included in the second candidate list when the prediction mode is a first prediction mode is greater than a maximum number of candidates included in the second candidate list when the prediction mode is a second mode. A video encoding device.

2. a spatial candidate derivation step of deriving spatial candidates from inter prediction information of a plurality of blocks adjacent to the encoding target block, and registering the spatial candidates in a first candidate list as candidates; a history candidate derivation step of adding history candidates included in the history candidate list as candidates to the first candidate list to generate a second candidate list; a candidate selection step of selecting a selection candidate from the candidates included in the second candidate list; an inter prediction step of performing inter prediction using the selection candidates; having the history candidate derivation step, when a prediction mode of the encoding target block is a first prediction mode, determines whether or not to add the history candidate to the first candidate list based on whether a motion vector and a reference index included in the history candidate are identical to a motion vector and a reference index included in a candidate included in the first candidate list; and, when the prediction mode is a second prediction mode, adds the history candidate to the first candidate list regardless of whether a motion vector of the history candidate is identical to a motion vector of a candidate included in the first candidate list; a maximum number of candidates included in the second candidate list when the prediction mode is a first prediction mode is greater than a maximum number of candidates included in the second candidate list when the prediction mode is a second mode. Image encoding method.

3. On the computer, a spatial candidate derivation step of deriving spatial candidates from inter prediction information of a plurality of blocks adjacent to the encoding target block, and registering the spatial candidates in a first candidate list as candidates; a history candidate derivation step of adding history candidates included in the history candidate list as candidates to the first candidate list to generate a second candidate list; a candidate selection step of selecting a selection candidate from the candidates included in the second candidate list; an inter prediction step of performing inter prediction using the selected candidates; Run the command, the history candidate derivation step, when a prediction mode of the encoding target block is a first prediction mode, determines whether or not to add the history candidate to the first candidate list based on whether a motion vector and a reference index included in the history candidate are identical to a motion vector and a reference index included in a candidate included in the first candidate list; and, when the prediction mode is a second prediction mode, adds the history candidate to the first candidate list regardless of whether a motion vector of the history candidate is identical to a motion vector of a candidate included in the first candidate list; a maximum number of candidates included in the second candidate list when the prediction mode is a first prediction mode is greater than a maximum number of candidates included in the second candidate list when the prediction mode is a second mode. Image encoding program.

4. a spatial candidate derivation unit that derives spatial candidates from inter prediction information of a plurality of blocks adjacent to a decoding target block, and registers the spatial candidates in a first candidate list as candidates; a history candidate derivation unit that adds history candidates included in the history candidate list as candidates to the first candidate list to generate a second candidate list; a candidate selection unit that selects a selection candidate from the candidates included in the second candidate list; an inter prediction unit that performs inter prediction using the selection candidates; Equipped with the history candidate derivation unit, when a prediction mode of the decoding target block is a first prediction mode, determines whether or not to add the history candidate to the first candidate list based on whether a motion vector and a reference index included in the history candidate are identical to a motion vector and a reference index included in a candidate included in the first candidate list; and, when the prediction mode is a second prediction mode, adds the history candidate to the first candidate list regardless of whether a motion vector of the history candidate is identical to a motion vector of a candidate included in the first candidate list; a maximum number of candidates included in the second candidate list when the prediction mode is a first prediction mode is greater than a maximum number of candidates included in the second candidate list when the prediction mode is a second mode. Video decoding device.

5. a spatial candidate derivation step of deriving spatial candidates from inter prediction information of a plurality of blocks adjacent to the block to be decoded, and registering the spatial candidates in a first candidate list as candidates; a history candidate derivation step of adding history candidates included in the history candidate list as candidates to the first candidate list to generate a second candidate list; a candidate selection step of selecting a selection candidate from the candidates included in the second candidate list; an inter prediction step of performing inter prediction using the selection candidates; having the history candidate derivation step, when a prediction mode of the decoding target block is a first prediction mode, determines whether or not to add the history candidate to the first candidate list based on whether a motion vector and a reference index included in the history candidate are identical to a motion vector and a reference index included in a candidate included in the first candidate list; and, when the prediction mode is a second prediction mode, adds the history candidate to the first candidate list regardless of whether a motion vector of the history candidate is identical to a motion vector of a candidate included in the first candidate list; a maximum number of candidates included in the second candidate list when the prediction mode is a first prediction mode is greater than a maximum number of candidates included in the second candidate list when the prediction mode is a second mode. Image decoding method.

6. On the computer, a spatial candidate derivation step of deriving spatial candidates from inter prediction information of a plurality of blocks adjacent to the decoding target block, and registering the spatial candidates in a first candidate list as candidates; a history candidate derivation step of adding history candidates included in the history candidate list as candidates to the first candidate list to generate a second candidate list; a candidate selection step of selecting a selection candidate from the candidates included in the second candidate list; an inter prediction step of performing inter prediction using the selected candidates; Run the command, the history candidate derivation step, when a prediction mode of the decoding target block is a first prediction mode, determines whether or not to add the history candidate to the first candidate list based on whether a motion vector and a reference index included in the history candidate are identical to a motion vector and a reference index included in a candidate included in the first candidate list; and, when the prediction mode is a second prediction mode, adds the history candidate to the first candidate list regardless of whether a motion vector of the history candidate is identical to a motion vector of a candidate included in the first candidate list; a maximum number of candidates included in the second candidate list when the prediction mode is a first prediction mode is greater than a maximum number of candidates included in the second candidate list when the prediction mode is a second mode. Image decoding program.

7. A transmission method for transmitting a bitstream generated by an image encoding device, comprising: a spatial candidate derivation step of deriving spatial candidates from inter prediction information of a plurality of blocks adjacent to the encoding target block, and registering the spatial candidates in a first candidate list as candidates; a history candidate derivation step of adding history candidates included in the history candidate list as candidates to the first candidate list to generate a second candidate list; a candidate selection step of selecting a selection candidate from the candidates included in the second candidate list; an inter prediction step of performing inter prediction using the selection candidates; a bitstream generating step of encoding the encoding information to generate a bitstream; a bitstream transmitting step of transmitting the bitstream; having the history candidate derivation step, when a prediction mode of the encoding target block is a first prediction mode, determines whether or not to add the history candidate to the first candidate list based on whether a motion vector and a reference index included in the history candidate are identical to a motion vector and a reference index included in a candidate included in the first candidate list; and, when the prediction mode is a second prediction mode, adds the history candidate to the first candidate list regardless of whether a motion vector of the history candidate is identical to a motion vector of a candidate included in the first candidate list; a maximum number of candidates included in the second candidate list when the prediction mode is a first prediction mode is greater than a maximum number of candidates included in the second candidate list when the prediction mode is a second mode. Transmission method.

8. A recording method for recording a bit stream generated by an image encoding device onto a recording medium, comprising: a spatial candidate derivation step of deriving spatial candidates from inter prediction information of a plurality of blocks adjacent to the encoding target block, and registering the spatial candidates in a first candidate list as candidates; a history candidate derivation step of adding history candidates included in the history candidate list as candidates to the first candidate list to generate a second candidate list; a candidate selection step of selecting a selection candidate from the candidates included in the second candidate list; an inter prediction step of performing inter prediction using the selection candidates; a bitstream generating step of encoding the encoding information to generate a bitstream; a bitstream recording step of recording the bitstream on the recording medium; having the history candidate derivation step, when a prediction mode of the encoding target block is a first prediction mode, determines whether or not to add the history candidate to the first candidate list based on whether a motion vector and a reference index included in the history candidate are identical to a motion vector and a reference index included in a candidate included in the first candidate list; and, when the prediction mode is a second prediction mode, adds the history candidate to the first candidate list regardless of whether a motion vector of the history candidate is identical to a motion vector of a candidate included in the first candidate list; a maximum number of candidates included in the second candidate list when the prediction mode is a first prediction mode is greater than a maximum number of candidates included in the second candidate list when the prediction mode is a second mode. Recording method.

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