Technical field [0001] 　The present invention relates to a video coding device, a video coding method, a video coding program, a video decoding device, a video decoding method, and a video decoding program. Background technology [0002] 　As an international standard for compression coding of video data, H. 265 / HEVC (High Efficiency Video Coding) is known. In the following, H. 265 / HEVC may be referred to as HEVC. [0003] 　In HEVC, two prediction methods, intra prediction and inter prediction, are adopted, and three types of intra prediction modes are defined: planer prediction, DC prediction, and angle prediction. [0004] 　FIG. 1 shows the angles used in HEVC angle prediction. In the intra prediction, the locally decoded pixel value of the block encoded earlier in the raster scan order is used as the predicted pixel value, so that the reference direction is any direction from the lower left direction to the upper right direction clockwise. When the angle indicating the left horizontal direction is 0 degrees, the angle range in the reference direction is a range from −45 degrees to +135 degrees. [0005] 　Numbers 2 to 34 are sequentially assigned to each angle from −45 degrees to +135 degrees, and these numbers represent 33 intra-prediction modes for angle prediction. Note that 0 and 1 are assigned to the planner prediction and the DC prediction, respectively. These two intra-prediction modes correspond to non-directional spatial intra-prediction. In intra-predictive coding, the predicted pixel value of the block to be coded is generated by performing extrapolation that matches the designated reference direction out of the 33 reference directions. [0006] 　FIG. 2 shows an example of the extrapolation method in the case of the intra prediction mode “6” (-22.5 degrees). The upper adjacent block adjacent to the upper side of the coded target block and the left adjacent block adjacent to the left side of the coded target block are coded blocks. The upper adjacent block is adjacent to the upper side of the two horizontal sides of the coded block, and the left adjacent block is adjacent to the left side of the two vertical sides of the coded block. [0007] 　Adjacent pixel 201 (diagonal square) is a pixel in the upper adjacent block or left adjacent block, and pixel 202 (white square) is a pixel in the coded block. The line segment 203 with an arrow passing through each pixel 202 indicates the reference direction in the intra prediction mode “6”. [0008] 　The pixel value of the adjacent pixel 201 existing at the end of the line segment 203 with an arrow passing through each pixel 202 is used as the predicted pixel value of the pixel 202. When a plurality of line segments with arrows 203 pass through the pixel 202, the weighted addition of the pixel values ​​of the adjacent pixels 201 existing at the ends of the line segments 203 with arrows becomes the predicted pixel value. [0009] 　Currently, standardization work of VVC (Versatile Video Coding) is underway as the next international standard for compression coding of video data (see, for example, Non-Patent Document 1). The shape of the block in HEVC is only a square, but in VVC, a rectangular block is also used in order to further improve the coding efficiency. [0010] 　FIG. 3 shows an example of block division in VVC. FIG. 3A shows a quadrant. In this case, a block having a horizontal size (width) of W pixels and a vertical size (height) of H pixels is divided into four blocks having the same shape. The width of each block after division is W / 2 pixels, and the height is H / 2 pixels. In the following, the width of the W pixel may be described as "width W", and the height of the H pixel may be described as "height H". [0011] 　FIG. 3B shows a horizontal two division and a vertical two division. In the case of horizontal division, blocks having a width W and a height H are divided into two blocks having the same shape by a horizontal dividing line. The width of each block after division is W pixels, and the height is H / 2 pixels. On the other hand, in the case of vertical division, the blocks having the width W and the height H are divided into two blocks having the same shape by the division line in the vertical direction. The width of each block after division is W / 2 pixels, and the height is H pixels. [0012] 　FIG. 3C shows horizontal three divisions and vertical three divisions. In the case of the horizontal three division, the blocks having the width W and the height H are divided into three blocks by two horizontal dividing lines. The width of each block after division is W pixel, the height of the upper and lower two blocks is H / 4 pixel, and the height of the central block is H / 2 pixel. In the case of vertical division, the blocks having a width W and a height H are divided into three blocks by two vertical dividing lines. The height of each block after division is H pixel, the width of the two left and right blocks is W / 4 pixel, and the width of the central block is W / 2 pixel. [0013] 　FIG. 4 shows an example of dividing an image into blocks. As shown in FIG. 4, in VVC, not only square blocks but also rectangular blocks can be used. As the height and width ratio (aspect ratio) of the rectangular block, not only 1: 2 and 2: 1 but also other aspect ratios can be used. [0014] 　Further, in the processing of intra-prediction, a technique for improving subjective image quality and coding efficiency by using closer decoded pixels is known (see, for example, Patent Document 1). Prior art literature Patent documents [0015] Patent Document 1: Japanese Unexamined Patent Publication No. 2016-027756 Non-patent literature [0016] Non-Patent Document 1: “Versatile Video Coding (Draft 2)”, JVET-K1001, JVET of ITU-T SG 16 WP 3 and ISO / IEC JTC 1 / SC 29/WG 11, July 2018 Outline of the invention Problems to be solved by the invention [0017] 　In the method of encoding the parameter indicating the intra prediction mode of VVC, an MPM list including three most probable modes (Most Probable Mode, MPM) as an entry is used as in HEVC. MPM is used as a candidate value (prediction value) of the intra prediction mode in the coded block. [0018] 　However, when the shape of the adjacent block and the shape of the coded block are different, an appropriate MPM is not always set by the current method of generating the MPM list in VVC. [0019] 　It should be noted that such a problem occurs not only in video coding that employs VVC, but also in other video coding that employs intra-prediction for rectangular blocks. [0020] 　In one aspect, the present invention aims to set appropriate candidate values ​​in video coding using intra-prediction mode candidate values ​​for rectangular blocks. Means to solve problems [0021] 　In one proposal, the video coding apparatus includes a generation unit, a prediction unit, a first coding unit, and a second coding unit. [0022] 　The generation unit uses the first prediction mode information as the second prediction mode information based on the combination of the shape of the coded block in the image included in the video and the shape of the coded block adjacent to the coded block. Change to. The first prediction mode information is prediction mode information indicating the intra prediction mode used for coding the coded block. Then, the generation unit generates the candidate information including the candidate value of the prediction mode information by using the second prediction mode information. [0023] 　The prediction unit generates an intra prediction pixel value of the coded block in a predetermined intra prediction mode. The first coding unit encodes the coded target block using the intra prediction pixel value, and the second coding unit encodes the prediction mode information indicating a predetermined intra prediction mode using the candidate information. Effect of the invention [0024] 　According to the embodiment, an appropriate candidate value can be set in the video coding using the candidate value of the intra prediction mode for the rectangular block. A brief description of the drawing [0025] FIG. 1 is a diagram showing an angle used in angle prediction of HEVC. [Fig. 2] Fig. 2 is a diagram showing an extrapolation method. FIG. 3 is a diagram showing block division in VVC. [Fig. 4] Fig. 4 is a diagram showing block division of an image. FIG. 5 is a diagram showing an angle used in VVC angle prediction. [Fig. 6] Fig. 6 is a diagram showing an intra prediction mode assigned to angle prediction. [Fig. 7] Fig. 7 is a diagram showing an intra prediction mode added for a rectangular block. [Fig. 8] Fig. 8 is a diagram showing an angle prediction for a rectangular block. FIG. 9 is a functional configuration diagram of a video coding device. FIG. 10 is a functional configuration diagram of a video decoding device. FIG. 11 is a functional configuration diagram showing a specific example of a video coding device. FIG. 12 is a functional configuration diagram of an intra-prediction unit in a video coding device. FIG. 13 is a diagram showing a method of changing the first intra prediction mode. FIG. 14 is a flowchart of a video coding process. FIG. 15 is a flowchart of an intra-prediction process in a video coding device. FIG. 16 is a diagram showing a first method of determining adjacent blocks. FIG. 17 is a diagram showing a second adjacent block determination method. FIG. 18 is a diagram showing a third adjacent block determination method. FIG. 19 is a functional configuration diagram showing a specific example of a video decoding apparatus. FIG. 20 is a functional configuration diagram of an intra-prediction unit in a video decoding device. FIG. 21 is a flowchart of a video decoding process. FIG. 22 is a flowchart of an intra-prediction process in a video decoding device. [Fig. 23] Fig. 23 is a configuration diagram of an information processing device. Mode for carrying out the invention [0026] 　Hereinafter, embodiments will be described in detail with reference to the drawings. 　When performing intra-prediction for a rectangular block that is non-square, HEVC angle prediction (-45 degrees to +135 degrees) may not be sufficient. Therefore, VVC addresses this problem by expanding the angle range of angle prediction for rectangular blocks. [0027] 　FIG. 5 shows the angles used in VVC angle prediction. In VVC, the angle spacing used is reduced by half in order to double the accuracy of HEVC angle prediction. In addition, angles in the range of -73 degrees to -45 degrees and +135 degrees to +163 degrees have been added as reference directions for rectangular blocks. [0028] 　The angle range 501 represents an angle prediction of -45 degrees to +45 degrees (33 ways) for square and rectangular blocks, and an angle range 502 represents an angle prediction of +45 degrees to +135 degrees (32 ways) for square and rectangular blocks. Street). The angle range 503 represents the angle predictions (10 ways) of -73 degrees to -45 degrees added for the rectangular block, and the angle range 504 represents the angle of +135 degrees to +163 degrees added for the rectangular block. Represents predictions (10 ways). When the planner prediction and the DC prediction are added to the total of 85 angle predictions, the total number of intra prediction modes is 87. [0029] 　FIG. 6 shows the intra-prediction mode assigned to the angle prediction of the angle range 501 and the angle range 502 of FIG. Numbers from 2 to 66 are sequentially assigned to each angle from −45 degrees to +135 degrees, and these numbers represent 65 intra-prediction modes. 0 and 1 are assigned to the planner prediction and the DC prediction, respectively, as in the case of HEVC. [0030] 　FIG. 7 shows the intra prediction modes assigned to the angle predictions of the angle range 503 and the angle range 504 of FIG. Numbers 67 to 76 are assigned in order for each angle from immediately after +135 degrees to +163 degrees, and from -10 to-for each angle from -73 degrees to just before -45 degrees. Numbers up to 1 are assigned in order. Angle predictions 67-76 are used for oblong blocks whose width is greater than height, and angle predictions -10 to -1 are used for oblong blocks whose height is greater than width. [0031] 　By increasing the total number of intra-prediction modes, the prediction error in intra-prediction can be reduced, but the bit amount of the parameter indicating the intra-prediction mode increases. When improving the coding performance, it is desirable to strike a balance between reducing the prediction error and increasing the bit amount of the parameter. [0032] 　For VVC intra-prediction, the total number of intra-prediction modes is increased from 67 to 87 for rectangular blocks. However, by assigning an angle prediction number having a low prediction efficiency to a rectangular block to the added angle prediction, the total number of intra prediction modes that can be selected for each block is kept at 67. [0033] 　FIG. 8 shows an example of angle prediction for a rectangular block. The coded block 801 is a horizontally long block having an aspect ratio of 1: 2, and the pixel 802 is located in the lower right corner of the coded block 801. The upper adjacent block adjacent to the upper side of the coded target block and the left adjacent block adjacent to the left side of the coded target block are encoded blocks. The adjacent pixel 803 (diagonal line) is a pixel in the upper adjacent block or the left adjacent block, and is referred to in the intra prediction. [0034] 　Arrows 810, 811, 820, and 821 indicate reference directions of −45 degrees, -30 degrees, +135 degrees, and +150 degrees, respectively. Of these, arrows 811 and 821 indicate reference directions parallel to the diagonal line 831 connecting the lower left vertex and the upper right vertex of the coded block 801. When the pixel 802 is a prediction target pixel, the adjacent pixel 803 pointed to by each arrow is used as a reference pixel, and the pixel value of the adjacent pixel 803 is used as the predicted pixel value of the pixel 802. [0035] 　Here, the prediction efficiency of the angle prediction is inversely proportional to the distance between the prediction target pixel and the reference pixel. That is, the closer the distance between the prediction target pixel and the reference pixel is, the smaller the prediction error can be expected, so that the prediction efficiency is improved. As a result, the coding efficiency of the prediction target pixel is improved. [0036] 　The length of each arrow in FIG. 8 represents the distance between the prediction target pixel and the reference pixel. For example, the length of the arrow 810 is longer than the length of the arrow 820 existing on the extension line thereof. Assuming that the coded block 801 is a square, the lengths of both are the same. On the other hand, the length of the arrow 811 is the same as the length of the arrow 821 existing on the extension line thereof. [0037] 　From this, it can be seen that in the block having an aspect ratio of 1: 2, the angle prediction in the range of -30 degrees to −45 degrees has low prediction efficiency, and the probability of being selected in the intra prediction is low. For example, if there is a uniform texture around the coded block 801 and its edge direction is parallel to the arrow 810 and the arrow 820, the reference direction of the arrow 820 should be selected instead of the reference direction of the arrow 810. Therefore, improvement in prediction efficiency is expected. [0038] 　When extending angle prediction, it is possible to maintain the total number of available angle predictions without degrading prediction efficiency by reassigning numbers by taking advantage of these rectangular block-specific properties. it can. [0039] 　The method of reassigning the angle prediction numbers will be described with reference to FIGS. 5 to 7. In the number reassignment, among the angle predictions shown in FIG. 6, the angle prediction numbers having a lower prediction efficiency with respect to the rectangular block are assigned to the angle predictions shown in FIG. 7. [0040] 　For example, when the coded block is a horizontally long block, the angle obtained by reversing the 10 angles of the angle range 504 by about 180 ° is not used for the angle prediction. Specifically, the ten angles from bottom to top of the angle range 501 are not used, and the numbers 2 to 11 of these angles are assigned to the angles 67 to 76 of the angle range 504, respectively. [0041] 　On the other hand, when the block to be coded is a vertically long block, the angle obtained by reversing the 10 angles of the angle range 503 by about 180 ° is not used for the angle prediction. Specifically, the ten angles from right to left in the angle range 502 are not used, and the numbers 57-66 of these angles are assigned to the angles -10 to -1 in the angle range 503, respectively. Be done. [0042] 　Regarding the angle prediction of 12 to 56, the same number as the original number is assigned by reassignment regardless of the shape of the coded block. [0043] 　In the following, the numbers 0 to 66 after reassignment may be described as the first intra prediction mode, and the numbers -10 to 76 before reassignment may be described as the second intra prediction mode. The first intra prediction mode is an example of prediction mode information. The numbers of the second intra prediction modes represent the angles shown in FIGS. 6 and 7. [0044] 　When the parameter indicating the first intra prediction mode is encoded using the MPM list, the first intra prediction mode of the left adjacent block and the upper adjacent block, which has a high correlation with the first intra prediction mode of the coded block, is selected. , Used as an entry in the MPM list. In addition, Planar and DC predictions, which are likely to be selected in the coded block, are also used as entries in the MPM list. Different first intra prediction modes are set for each of the three entries in the MPM list. The 2-bit syntax element IntraLumaMPMIdx then specifies one of the three entries. [0045] 　If none of the entries in the MPM list match the first intra-prediction mode of the coded block, the syntax element IntraLumaMPMRemainder directly encodes the first intra-predicted mode of the coded block. [0046] 　At this time, if the total number of first intra prediction modes 3 that can be signaled by the MPM list is subtracted from the total number of first intra prediction modes 67 that can be selected in each block, the subtraction result is 64. Therefore, the total number of first intra prediction modes represented by IntraLumaMPMRemainder is 64. Since Log2 (64) = 6, the minimum number of bits of the IntraLumaMPM Remainder is 6 bits. [0047] 　In the VCS standard, the procedure for the video coding device to derive the IntraLumaMPMRemainder from the IntraDir indicating the first intra prediction mode is as follows. (P1) The video coding device sets the value of IntraDir to IntraLumaMPMRemainder. (P2) The video coding device sorts the entries in the MPM list in ascending order to generate mpm_sort [i] (i = 0.2, mpm_sort [0] For = 2) 　　CandModeList [0] = candIntraPredModeA 　　candModeList [1] = 2 + ((candIntraPredModeA + 61)% 64) 　　candModeList [2] = 2 + ((candIntraPredModeA -1)% 64) · (candIntraPredModeA! = CandIntraPredModeB) 　　candModeList [0] = candIntraPredModeA 　　candModeList [1] = candIntraPredModeB 　(candModeList [0]! = 0) and (candModeList [1]! = 0) 　　candModeList [2] = 0 　(candModeList [0]! = 1) and ( candModeList [1]! = 1) 　　candModeList [2] = 1 　Other than the above 　　candModeList [2] = 50 　However, “% 64” represents the remainder of division with 64 as the divisor. According to this generation method, candIntraPredModeA or candIntraPredModeB may be used as MPM. [0052] 　However, if the aspect ratio of the adjacent block (left adjacent block or upper adjacent block) is different from the aspect ratio of the coded block, the angle prediction that can be used in the adjacent block may not be available in the coded block. is there. [0053] 　For example, assume that the adjacent block is a vertically long block and the coded block is a square block. When the second intra prediction mode of the adjacent block is “-8”, the corresponding first intra prediction mode is “59”. [0054] 　However, from the viewpoint of continuity of the reference direction between blocks, as a candidate value for the first intra prediction mode of the block to be encoded, which is a square, among the angle predictions shown in FIG. "2", which is the number closest to the angle indicated by "8", is more suitable. Since it can be expected that the prediction error becomes smaller as the angle of the reference direction becomes closer, the probability that the reference direction is selected in the coded block increases. [0055] 　Therefore, when the aspect ratio of the adjacent block and the aspect ratio of the coded block are different, it is desirable to generate the MPM list in consideration of the continuity of the reference direction between the blocks. [0056] 　FIG. 9 shows an example of a functional configuration of the video coding apparatus of the embodiment. The video coding device 901 of FIG. 9 includes a generation unit 911, a prediction unit 912, a first coding unit 913, and a second coding unit 914. [0057] 　The generation unit 911 uses the first prediction mode information as the second prediction mode based on the combination of the shape of the coded block in the image included in the video and the shape of the coded block adjacent to the coded block. Change to information. The first prediction mode information is prediction mode information indicating the intra prediction mode used for coding the coded block. Then, the generation unit 911 uses the second prediction mode information to generate candidate information including the candidate value of the prediction mode information. [0058] 　The prediction unit 912 generates the intra prediction pixel value of the coded block in the predetermined intra prediction mode. The first coding unit 913 encodes the coded target block using the intra prediction pixel value, and the second coding unit 914 encodes the prediction mode information indicating a predetermined intra prediction mode using the candidate information. To do. [0059] 　FIG. 10 shows an example of a functional configuration of the video decoding device of the embodiment. The video decoding device 1001 of FIG. 10 includes a decoding unit 1011, a generation unit 1012, a prediction unit 1013, and a restoration unit 1014. [0060] 　The decoding unit 1011 decodes the coded video and extracts the predicted residual information of the decoding target block in the coded image included in the coded video. Further, the decoding unit 1011 extracts the prediction mode information indicating the intra prediction mode of the decoding target block and the first prediction mode information indicating the intra prediction mode of the decoded block adjacent to the decoding target block. [0061] 　The generation unit 1012 changes the first prediction mode information to the second prediction mode information based on the combination of the shape of the decoding target block and the shape of the decoded block, and uses the second prediction mode information to obtain the prediction mode information. Generate candidate information including candidate values ​​for. [0062] 　The prediction unit 1013 uses the candidate information to generate the intra prediction pixel value of the decoding target block in the intra prediction mode indicated by the prediction mode information of the decoding target block. The restoration unit 1014 generates the pixel value of the decoding target block by using the intra-predicted pixel value and the predicted residual information. [0063] 　According to the video coding device 901 of FIG. 9 and the video decoding device 1001 of FIG. 10, an appropriate candidate value can be set in the video coding using the candidate value of the intra prediction mode for the rectangular block. [0064] 　FIG. 11 shows a specific example of the video coding device 901 of FIG. The video coding device 1101 of FIG. 11 includes a subtraction unit 1111, a conversion / quantization unit 1112, an entropy coding unit 1113, a mode determination unit 1114, an intra prediction unit 1115, and an inter prediction unit 1116. The video coding device 1101 further includes an inverse quantization / inverse conversion unit 1117, an addition unit 1118, a post filter unit 1119, and a frame memory 1120. The subtraction unit 1111 and the conversion / quantization unit 1112 correspond to the first coding unit 913 in FIG. [0065] 　The video coding device 1101 can be implemented as, for example, a hardware circuit. In this case, each component of the video coding device 1101 may be mounted as an individual circuit, or may be mounted as one integrated circuit. [0066] 　The video coding device 1101 encodes the input video and outputs the coded video as a coded stream. The video coding device 1101 can transmit the coded stream to the video decoding device 1001 of FIG. 10 via the communication network. [0067] 　For example, the video coding device 1101 may be incorporated in a video camera, a video transmitting device, a videophone system, a computer, or a mobile terminal device. [0068] 　The input video includes a plurality of images corresponding to each of the plurality of times. The image at each time is sometimes called a picture or frame. Each image may be a color image or a monochrome image. In the case of a color image, the pixel value may be in RGB format or YUV format. [0069] 　By implementing the same local decoding process as the decoding process in the video decoding device in the video coding device, the same predicted image is obtained from the parameters indicating the prediction mode and the predicted residual information in the video coding device and the video decoding device. Can be generated. In this case, since only the difference information needs to be transmitted as a coded stream, video coding with high compression efficiency is realized. The inverse quantization / inverse conversion unit 1117, the addition unit 1118, the post filter unit 1119, and the frame memory 1120 are used for the local decoding process in the video coding apparatus 901. [0070] 　Each image is divided into unit blocks of a predetermined size, and each image is encoded in the unit block in the order of raster scan. The unit block may be used as it is as the coded block, or a block obtained by further dividing the unit block into smaller blocks may be used as the coded block. Then, intra-prediction or inter-prediction is performed on the coded block. [0071] 　In the case of intra prediction, a prediction image of the coded block in each intra prediction mode is generated using the adjacent pixels in the upper adjacent block or the left adjacent block, and the intra prediction mode having the highest prediction efficiency is selected. As the intra prediction mode, planer prediction, DC prediction, and angle prediction shown in FIG. 5 are used, and parameters and prediction residual information indicating the intra prediction mode with the highest prediction efficiency are transmitted as a coded stream. [0072] 　In the case of inter-prediction, the image that has been encoded in the past is set as the reference image, and block matching processing is performed between the coded target block and the reference block in the reference image by motion vector search, so that the most prediction efficiency is achieved. High reference blocks are detected. Then, the information of the reference image and the information of the motion vector indicating the position of the detected reference block are transmitted as parameters indicating the inter-prediction mode, and the difference between the reference block and the coded target block is used as the prediction residual information. Be transmitted. [0073] 　The intra prediction unit 1115 calculates the intra prediction pixel value of the coded block using the decoded pixel value before applying the post filter output from the addition unit 1118, and outputs the intra prediction pixel value to the mode determination unit 1114. The inter-prediction unit 1116 calculates the inter-prediction pixel value of the coded block using the pixel value of the reference image output from the frame memory 1120, and outputs the inter-prediction pixel value to the mode determination unit 1114. [0074] 　Since one type of coding process is applied to one coded block, the mode determination unit 1114 determines whether intra-prediction or inter-prediction has higher prediction efficiency, and the prediction efficiency is higher. Select the higher prediction result. Then, the mode determination unit 1114 outputs the predicted pixel value of the selected prediction result among the intra-predicted pixel value or the inter-predicted pixel value to the subtraction unit 1111 and the addition unit 1118. [0075] 　The subtraction unit 1111 outputs the difference between the pixel value of the coded block and the predicted pixel value output from the mode determination unit 1114 to the conversion / quantization unit 1112 as a prediction residual. The conversion / quantization unit 1112 performs orthogonal conversion and quantization of the predicted residual, and outputs the quantization coefficient as the predicted residual information to the entropy coding unit 1113 and the inverse quantization / inverse conversion unit 1117. [0076] 　The entropy coding unit 1113 converts the quantization coefficient and the parameter indicating the selected intra prediction mode or inter prediction mode into a binary string by entropy coding (variable length coding), and outputs a coded image. .. [0077] 　The inverse quantization / inverse conversion unit 1117 restores the predicted residual by performing inverse quantization and inverse orthogonal transformation of the quantization coefficient, and outputs the restored predicted residual to the addition unit 1118. The addition unit 1118 adds the predicted pixel values ​​output from the mode determination unit 1114 and the predicted residuals output from the inverse quantization / inverse conversion unit 1117 to generate a decoded pixel value before applying the post filter. .. Then, the addition unit 1118 outputs the generated decoded pixel value to the post filter unit 1119 and the intra prediction unit 1115. [0078] 　In order to reduce the quantization error, the post-filter unit 1119 applies the post-filter to the decoded pixel value before applying the post-filter, and generates the decoded pixel value after applying the post-filter. Then, the post-filter unit 1119 outputs the generated decoded pixel value to the frame memory 1120. [0079] 　The frame memory 1120 stores the decoded pixel value after applying the post filter as a locally decoded pixel value. The locally decoded pixel value stored in the frame memory 1120 is output to the inter-prediction unit 1116 as a pixel value of the reference image. [0080] 　FIG. 12 shows an example of the functional configuration of the intra prediction unit 1115 of FIG. The intra prediction unit 1115 of FIG. 12 includes an MPM generation unit 1211, a prediction mode calculation unit 1212, a coding unit 1213, a prediction mode calculation unit 1214, and a filter unit 1215. The MPM generation unit 1211, the coding unit 1213, and the filter unit 1215 correspond to the generation unit 911, the second coding unit 914, and the prediction unit 912 in FIG. 9, respectively. [0081] 　Shape parameters indicating the shapes of the coded block, the left adjacent block, and the upper adjacent block are input to the MPM generation unit 1211 and the prediction mode calculation unit 1214 from a coding control unit (not shown). As the shape parameters, the width W and the height H of each block are used. [0082] 　The MPM generation unit 1211 is input from the prediction mode calculation unit 1212 with the first intra prediction mode of the coded block, the left adjacent block, and the upper adjacent block. The MPM generation unit 1211 changes the first intra prediction mode of the adjacent block based on the combination of the shape of the coded block and the shape of each adjacent block. The first intra prediction mode of the adjacent block for which the inter prediction mode is selected is regarded as DC prediction. [0083] 　Then, the MPM generation unit 1211 generates an MPM list by using the changed first intra prediction mode of the left adjacent block and the upper adjacent block, and sets the generated MPM list and the first intra prediction mode of the coded target block. Is output to the coding unit 1213. The MPM list is an example of candidate information including candidate values ​​of prediction mode information. [0084] 　The prediction mode calculation unit 1214 determines the second intra prediction mode having the highest prediction efficiency for the coded target block by performing a search process for calculating the prediction efficiencies of all the second intra prediction modes. Then, the prediction mode calculation unit 1214 outputs the determined second intra prediction mode to the prediction mode calculation unit 1212 and the filter unit 1215. [0085] 　The prediction mode calculation unit 1212 converts the second intra prediction mode output from the prediction mode calculation unit 1214 into the first intra prediction mode, and outputs the second intra prediction mode to the MPM generation unit 1211. As a result, the number of the second intra prediction mode indicating each angle shown in FIGS. 6 and 7 is converted into the number of the first intra prediction mode. [0086] 　The filter unit 1215 applies a filter corresponding to the second intra prediction mode output from the prediction mode calculation unit 1214 to the decoded pixel value before applying the post filter, and generates an intra prediction pixel value of the coded block. To do. Then, the filter unit 1215 outputs the generated intra-predicted pixel value to the mode determination unit 1114. The filter corresponding to the second intra prediction mode is defined by the VVC standard. [0087] 　The coding unit 1213 encodes the first intra prediction mode of the coded block using the MPM list, and generates an intra prediction parameter indicating the first intra prediction mode. Then, the coding unit 1213 outputs the generated intra prediction parameter to the mode determination unit 1114. IntraLumaMPMFlag, IntraLumaMPMIdx, and IntraLumaMPMRemainder are used as intra prediction parameters. [0088] 　The IntraLumaMPMFlag is a flag indicating whether or not to use the MPM list. When the IntraLumaMPMFlag is logical "1", the MPM list is used, and when the IntraLumaMPMFlag is logical "0", the MPM list is not used. IntraLumaMPMIdx is a parameter that specifies an entry in the MPM list, and IntraLumaMPMRemainder is a parameter that specifies the remaining first intra-prediction mode that is not registered in the MPM list. [0089] 　When the first intra prediction mode of the coded block corresponds to any entry in the MPM list, IntraLumaMPMFlag is set to logical “1” and IntraLumaMPMIdx specifying that entry is generated. On the other hand, if the first intra prediction mode of the coded block does not correspond to any entry in the MPM list, the IntraLumaMPMFlag is set to logical “0”. Then, the first intra prediction mode is converted to the IntraLumaMPM Remainder by the above-mentioned procedures (P1) to (P3). [0090] 　Next, a method of generating an MPM list will be described. First, the MPM generation unit 1211 is adjacent to each other based on a combination of the ratio H / W of the height H to the width W of the coded block and the ratio Hn / Wn of the height Hn to the width Wn of each adjacent block. Change the first intra prediction mode of the block. This change is made independently for each of the left adjacent block and the upper adjacent block. [0091] 　Here, it is assumed that the angle A1 indicated by the first intra prediction mode of the adjacent block is an angle that is not used for intra prediction in the shape of the coded block. In this case, among the angles used for intra prediction in the shape of the coded block, the first intra prediction mode corresponding to the angle A2 closest to the angle A1 is used as the changed first intra prediction mode. [0092] 　This makes it possible to generate an MPM list containing the first intra prediction mode available in the coded block as an entry. Further, among the angle predictions that can be used in the coded block, the angle prediction that is closest to the angle prediction adopted in the adjacent block is included as an entry, so that the prediction efficiency of the first intra prediction mode based on the MPM list is improved. .. [0093] 　FIG. 13 shows an example of such a method of changing the first intra prediction mode. Each row of the table in FIG. 13 corresponds to a predetermined value of Hn / Wn, and each column corresponds to a predetermined value of H / W. Therefore, each cell of the table corresponds to a predetermined combination of Hn / Wn and H / W. [0094] 　The first line represents Hn / Wn ≧ 4, the second line represents Hn / Wn = 2, the third line represents Hn / Wn = 1, and the fourth line represents Hn / Wn = 1/2. The fifth line represents Hn / Wn ≦ 1/4. The first column represents H / W ≧ 4, the second column represents H / W = 2, the third column represents H / W = 1, and the fourth column represents H / W = 1/2. The fifth column represents H / W ≦ 1/4. [0095] 　In each cell, a change instruction in the format of "Same" or "ModeBefore-> ModeAfter" is described as a method of changing the first intra prediction mode. “Same” indicates an instruction not to change the first intra prediction mode, and a change instruction in the format of “ModeBefore → ModeAfter” indicates the first intra prediction mode indicated by the ModeBefore number and the first intraprediction indicated by the ModeAfter number. Indicates an instruction to change to the mode. [0096] 　For example, when Hn / Wn = W / H, the first intra prediction mode is not changed. When Hn / Wn ≠ W / H, only the first intra prediction mode indicated by the ModeBefore number is changed, and the other first intra prediction modes are not changed. [0097] 　For example, in the case of Hn / Wn ≧ 4 and H / W = 1, if the first intra prediction mode is any of “57” to “66”, the first intra prediction mode is changed to “2”. .. On the other hand, if the first intra prediction mode is any of "0" to "56", the first intra prediction mode is not changed. [0098] 　Further, in the case of Hn / Wn = 2 and H / W = 1/2, if the first intra prediction mode is any of "2" to "7" or "61" to "66", the first intra prediction mode is used. The prediction mode is changed to "8". On the other hand, if the first intra prediction mode is any of "0", "1", or "8" to "60", the first intra prediction mode is not changed. [0099] 　The MPM generation unit 1211 uses the first intra prediction mode changed by the change method of FIG. 13 as the candIntraPredModeA and the candIntraPredModeB, and determines the candModeList [0] to the candModeList [2] according to the above-mentioned VVC standard generation method. [0100] 　According to the video coding device 1101 of FIG. 11, the first intra prediction mode of the adjacent block is changed based on the combination of the shape of the coded block and the shape of the adjacent block. As a result, even when the aspect ratio of the adjacent block and the aspect ratio of the coded block are different, an appropriate MPM list can be generated in consideration of the continuity of the reference direction between the blocks. [0101] 　By encoding the first intra prediction mode of the coded block using an appropriate MPM list, the probability that the MPM list is used is increased, and the compression efficiency of the intra prediction parameters is improved. Therefore, it becomes possible to efficiently encode the video. [0102] 　FIG. 14 is a flowchart showing an example of the video coding process performed by the video coding device 1101 of FIG. In this video coding process, the coding process is performed for each CU (Coding Unit) which is an example of a block. [0103] 　First, the intra prediction unit 1115 makes an intra prediction for each block (CU) of each block size (step 1401). Then, the intra prediction unit 1115 determines the intra prediction mode and selects the intra prediction mode having the highest prediction efficiency (step 1402). [0104] 　On the other hand, the inter-prediction unit 1116 performs inter-prediction for blocks of each block size (step 1403). Inter-prediction is performed for each PU (Prediction Unit) in which the CU is further divided. Then, the inter-prediction unit 1116 determines the inter-prediction mode and selects the inter-prediction mode having the highest prediction efficiency (step 1404). [0105] 　Next, the mode determination unit 1114 makes a mode determination and determines whether to apply the intra prediction mode or the inter prediction mode in block (CU) units (step 1405). Then, the subtraction unit 1111 and the conversion / quantization unit 1112 encode the coded target block according to the prediction mode determined by the mode determination unit 1114 to generate a quantization coefficient (step 1406). [0106] 　Next, the video coding device 1101 determines whether or not the coding of the image is completed (step 1407). When the unprocessed block remains (step 1407, NO), the video coding apparatus 1101 repeats the processing after step 1401 for the next block. [0107] 　On the other hand, when the coding of the image is completed (step 1407, YES), the entropy coding unit 1113 performs variable length coding for the parameter indicating the quantization coefficient and the determined prediction mode (step 1408). [0108] 　Next, the video coding device 1101 determines whether or not the coding of the video is completed (step 1409). When the unprocessed image remains (step 1409, NO), the video coding apparatus 1101 repeats the processing after step 1401 for the next image. Then, when the video coding is completed (step 1409, YES), the video coding device 1101 ends the process. [0109] 　FIG. 15 is a flowchart showing an example of the intra prediction process in step 1401 of FIG. First, the MPM generation unit 1211 changes the first intra prediction mode of the left adjacent block and the upper adjacent block, and generates an MPM list using the changed first intra prediction mode (step 1501). [0110] 　Next, the prediction mode calculation unit 1214 determines the second intra prediction mode of the coded block (step 1502), and the prediction mode calculation unit 1212 changes the determined second intra prediction mode to the first intra prediction mode. Convert (step 1503). [0111] 　Next, the coding unit 1213 generates an IntraLumaMPMFlag indicating whether or not to use the MPM list (step 1504), and checks the value of the generated IntraLumaMPMFlag (step 1505). [0112] 　When the IntraLumaMPMFlag is logical “1” (step 1505, YES), the coding unit 1213 generates an IntraLumaMPMIdx indicating an entry in the MPM list, which corresponds to the first intra prediction mode of the coded block (step 1506). .. On the other hand, when the IntraLumaMPMFlag is logic "0" (step 1505, NO), the coding unit 1213 generates an IntraLumaMPMRemainder corresponding to the first intra prediction mode of the coded block (step 1507). [0113] 　The filter unit 1215 generates an intra-predicted pixel value of the coded block to be encoded in the determined second intra-predicted mode (step 1508). [0114] 　Next, with reference to FIGS. 16 to 18, a method of determining the adjacent block to be used for generating the MPM list when a plurality of blocks are adjacent to the coded block in step 1501 of FIG. 15 will be described. .. [0115] 　FIG. 16 shows an example of the first adjacent block determination method. Of the plurality of left-adjacent blocks adjacent to the left side of the coded block 1601, the left-adjacent block 1602 located at the top is selected as the left-adjacent block used for generating the MPM list. Further, among the plurality of upper adjacent blocks adjacent to the upper side of the coded block 1601, the leftmost upper adjacent block 1603 is selected as the upper adjacent block used for generating the MPM list. [0116] 　FIG. 17 shows an example of the second adjacent block determination method. When the coded block 1701 is a horizontally long rectangle, the left adjacent block 1702 located at the top of the plurality of left adjacent blocks adjacent to the left side of the coded block 1701 is the left adjacent block used to generate the MPM list. Selected as a block. Further, among the plurality of upper adjacent blocks adjacent to the upper side of the coded block 1701, the uppermost adjacent block 1703 located on the rightmost side is selected as the upper adjacent block used for generating the MPM list. [0117] 　On the other hand, when the coded block 1711 is a vertically long rectangle, the left adjacent block 1712 located at the bottom of the plurality of left adjacent blocks adjacent to the left side of the coded block 1711 is used to generate the MPM list. Selected as the left adjacent block. Further, among the plurality of upper adjacent blocks adjacent to the upper side of the coded block 1711, the upper adjacent block 1713 located on the leftmost side is selected as the upper adjacent block used for generating the MPM list. [0118] 　FIG. 18 shows an example of a third adjacent block determination method. In the third adjacent block determination method, among the plurality of left adjacent blocks adjacent to the left side of the coded block, the left adjacent block having the most frequent first intra prediction mode is the left adjacent block used to generate the MPM list. Selected as a block. Further, among the plurality of upper adjacent blocks adjacent to the upper side of the coded block, the upper adjacent block having the most frequent first intra prediction mode is selected as the upper adjacent block used for generating the MPM list. [0119] 　By generating the MPM list using the adjacent block having the most frequent first intra prediction mode among the plurality of adjacent blocks, the prediction efficiency of the first intra prediction mode based on the MPM list is improved. [0120] 　For example, it is assumed that the first intra prediction mode M1 of the upper adjacent block 1811 to the upper adjacent block 1814 adjacent to the upper side of the horizontally long coded target block 1801 is determined as follows. [0121] 　Upper adjacent block 1811 M1 = I1 　Upper adjacent block 1812 M1 = I2 　Upper adjacent block 1813 M1 = I2 　Upper adjacent block 1814 M1 = I3 　I1 to I3 have different numbers. In this case, the frequency of I1 is once, the frequency of I2 is two, and the frequency of I3 is one. Therefore, the upper adjacent block 1812 and the upper adjacent block 1813 having the highest frequency I2 are selected, and the first intra prediction mode of these blocks is adopted as the first intra prediction mode of the upper adjacent block. [0122] 　When the upper adjacent block 1811 to the upper adjacent block 1814 have different first intra prediction modes, the upper adjacent block is selected according to the first adjacent block determination method or the second adjacent block determination method. If any of the upper adjacent blocks is encoded in the inter-prediction mode, the upper adjacent block is excluded from the frequency count target. [0123] 　For the left adjacent block 1821 and the left adjacent block 1822 adjacent to the left side of the coded block 1801, the left adjacent block used for generating the MPM list is selected in the same manner as in the case of the upper adjacent block 1811 to the upper adjacent block 1814. To. [0124] 　Further, the same adjacent block determination method is applied to the upper adjacent block 1841 and the upper adjacent block 1842 adjacent to the upper side of the vertically long coded target block 1831. The same adjacent block determination method is applied to the left adjacent block 1851 to the left adjacent block 1853 adjacent to the left side of the coded block 1831. [0125] 　For example, it is assumed that the first intra prediction mode M1 of the left adjacent block 1851 to the left adjacent block 1853 is determined as follows. [0126] 　Left adjacent block 1851 M1 = I4 　Left adjacent block 1852 M1 = I5 　Left adjacent block 1853 M1 = I6 　I4 to I6 are different numbers. In this case, the frequency of I4 to I6 is once. [0127] 　However, the length of the side of the left adjacent block 1852 in contact with the coded block 1831 is twice the length of the side of the left adjacent block 1851 or the left adjacent block 1853 in contact with the coded block 1831. .. Therefore, the left adjacent block 1852 having the longest side in contact with the coded block 1831 may be selected as the left adjacent block used for generating the MPM list. [0128] 　FIG. 19 shows a specific example of the video decoding apparatus 1001 of FIG. The video decoding device 1901 of FIG. 19 includes an entropy decoding unit 1911, an inverse quantization / inverse conversion unit 1912, an intra prediction unit 1913, an inter prediction unit 1914, an addition unit 1915, a post filter unit 1916, and a frame memory 1917. The entropy decoding unit 1911 corresponds to the decoding unit 1011 in FIG. 10, and the inverse quantization / inverse conversion unit 1912 and the addition unit 1915 correspond to the restoration unit 1014. [0129] 　The video decoding device 1901 can be implemented as, for example, a hardware circuit. In this case, each component of the video decoding device 1901 may be mounted as an individual circuit, or may be mounted as one integrated circuit. [0130] 　The video decoding device 1901 decodes the coded stream of the input coded video and outputs the decoded video. The video decoding device 1901 can receive the coded stream from the video coding device 1101 of FIG. 11 via the communication network. [0131] 　For example, the video decoding device 1901 may be incorporated in a video camera, a video receiving device, a videophone system, a computer, or a mobile terminal device. [0132] 　The entropy decoding unit 1911 decodes the encoded video by entropy decoding (variable length decoding), extracts the quantization coefficient of each block in the image to be decoded as prediction residual information, and a parameter indicating the prediction mode of each block. Is extracted. Further, the entropy decoding unit 1911 also extracts a shape parameter indicating the shape of each block. The parameter indicating the prediction mode includes an intra prediction parameter indicating an intra prediction mode or an inter prediction parameter indicating an inter prediction mode. [0133] 　Then, the entropy decoding unit 1911 outputs the quantization coefficient to the inverse quantization / inverse conversion unit 1912, outputs the shape parameter and the intra prediction parameter to the intra prediction unit 1913, and outputs the inter prediction parameter to the inter prediction unit 1914. .. [0134] 　The inverse quantization / inverse conversion unit 1912 restores the predicted residual by performing inverse quantization and inverse orthogonal transformation of the quantization coefficient, and outputs the restored predicted residual to the addition unit 1915. [0135] 　The intra prediction unit 1913 uses the shape parameter and the intra prediction parameter output from the entropy decoding unit 1911 to obtain the intra prediction pixel value of the block to be decoded from the decoding pixel value before applying the post filter output from the addition unit 1915. calculate. Then, the intra prediction unit 1913 outputs the calculated intra prediction pixel value to the addition unit 1915. [0136] 　The inter-prediction unit 1914 performs motion compensation processing using the inter-prediction parameter output from the entropy decoding unit 1911 and the pixel value of the reference image output from the frame memory 1917, and performs the inter-prediction pixel value of the decoding target block. To calculate. Then, the inter-prediction unit 1914 outputs the calculated inter-prediction pixel value to the addition unit 1915. [0137] 　The addition unit 1915 adds the predicted pixel values ​​output from the intra prediction unit 1913 or the inter prediction unit 1914 and the prediction residuals output from the inverse quantization / inverse conversion unit 1912, and decodes before applying the post filter. Generate pixel values. Then, the addition unit 1915 outputs the generated decoded pixel value to the post filter unit 1916 and the intra prediction unit 1913. [0138] 　In order to reduce the quantization error, the post-filter unit 1916 applies the post-filter to the decoded pixel value before applying the post-filter, and generates the decoded pixel value after applying the post-filter. Then, the post-filter unit 1916 outputs the generated decoded pixel value to the frame memory 1917. [0139] 　The frame memory 1917 stores the decoded pixel value after applying the post filter, and outputs the decoded video including the decoded pixel value. The decoded pixel value stored in the frame memory 1917 is output to the inter-prediction unit 1914 as the pixel value of the reference image. [0140] 　FIG. 20 shows an example of a functional configuration of the intra prediction unit 1913 of FIG. The intra prediction unit 1913 of FIG. 20 includes an MPM generation unit 2011, a storage unit 2012, a prediction mode calculation unit 2013, a prediction mode calculation unit 2014, and a filter unit 2015. The MPM generation unit 2011 and the filter unit 2015 correspond to the generation unit 1012 and the prediction unit 1013 of FIG. 10, respectively. [0141] 　Shape parameters are input from the entropy decoding unit 1911 to the MPM generation unit 2011 and the prediction mode calculation unit 2014. In addition, intra-prediction parameters are input to the prediction mode calculation unit 2013 from the entropy decoding unit 1911. The input intra prediction parameters include IntraLumaMPMFlag and IntraLumaMPMIdx or IntraLumaMPMRemainder. [0142] 　The storage unit 2012 stores the width, height, and first intra prediction mode of each block. DC prediction is stored as the first intra prediction mode of the block for which the inter prediction mode is selected. Then, the storage unit 2012 outputs the width Wn and height Hn of the left adjacent block and the upper adjacent block, and the first intra prediction mode of each of the left adjacent block and the upper adjacent block to the MPM generation unit 2011. [0143] 　The MPM generation unit 2011 changes the first intra prediction mode of the adjacent block by the same change method as that of the video coding apparatus 1101 of FIG. 11 based on the combination of the shape of the block to be decoded and the shape of each adjacent block. To do. At this time, the MPM generation unit 2011 is adjacent to the MPM generation unit 2011 based on the combination of the ratio H / W of the height H to the width W of the decoding target block and the ratio Hn / Wn of the height Hn to the width Wn of each adjacent block. Change the first intra prediction mode of the block. This change is made independently for each of the left adjacent block and the upper adjacent block. [0144] 　Here, it is assumed that the angle A1 indicated by the first intra prediction mode of the adjacent block is an angle that is not used for intra prediction in the shape of the decoding target block. In this case, among the angles used for intra prediction in the shape of the block to be decoded, the first intra prediction mode corresponding to the angle A2 closest to the angle A1 is used as the changed first intra prediction mode. For example, the MPM generation unit 2011 can change the first intra prediction mode of the adjacent block according to the change method shown in FIG. [0145] 　By changing the first intra prediction mode by the same change method as that of the video coding apparatus 1101, the MPM list used for coding the intra prediction parameters can be restored from the coded video. [0146] 　The MPM generation unit 2011 generates an MPM list by the above-mentioned VVC standard generation method using the changed first intra prediction mode of the left adjacent block and the upper adjacent block, and generates the generated MPM list in the prediction mode calculation unit 2013. Output to. [0147] 　The prediction mode calculation unit 2013 obtains the first intra prediction mode of the decoding target block from the input intra prediction parameters using the MPM list, and outputs the first intra prediction mode to the storage unit 2012 and the prediction mode calculation unit 2014. When the IntraLumaMPMFlag is logical "1", the MPM list entry specified by IntraLumaMPMIdx is output as the first intra prediction mode of the decryption target block. [0148] 　On the other hand, when the IntraLumaMPMFlag is the logic "0", the IntraDir is obtained from the IntraLumaMPMRemainder by the above-mentioned procedures (P11) to (P13), and the IntraDir is output as the first intra prediction mode of the decoding target block. [0149] 　The prediction mode calculation unit 2014 converts the first intra prediction mode of the decoding target block into the second intra prediction mode based on the width W and the height H of the decoding target block. The procedure for converting the first intra prediction mode M1 to the second intra prediction mode M2 ​​is as follows. ・ When W = H 　　M2 = M1 ・ When W> H 　　・ When 2 ≦ M1 2H), mL = When 　　other than 12.2 ≦ M1 In the case of 2W), if mH = 56 　　· mH