Abstract: A mechanism is provided that implements video coding and decoding such that only a specific partial image region on a screen can be independently decoded. A video decoding apparatus (31) according to an aspect of the present invention configures, in intra prediction, inter prediction, loop filter processing, or the like, a partial image region in a picture, handles a region outside the partial image region in a similar manner to a region outside the picture, and does not apply such restriction to a non-partial image region other than the partial image region in the picture.

Abstract: An image decoding device (31) includes a transform coefficient decoding unit (311) configured to decode a transform coefficient for a transform tree included in a coding unit. In the transform tree, the transform coefficient decoding unit splits a transform unit corresponding to luminance and then decodes the transform coefficient related to the luminance, and does not split the transform unit corresponding to chrominance and decodes the transform coefficient related to the chrominance.

Abstract: An image decoding apparatus is implemented that can suppress a decrease in coding efficiency in a case that a high compression rate is achieved. The image decoding apparatus includes a parameter decoder, and the parameter decoder decodes a skip flag indicating whether a skip mode is applied, and in a case that the skip flag does not indicate the skip mode, decodes a merge flag indicating whether a merge mode is applied, and in a case that the merge flag does not indicate the merge mode, decodes an MMVD flag indicating whether an MMVD mode is applied.

Abstract: An image decoding apparatus decodes a transform coefficient on a transform unit basis, decodes a flag scaling_matrix_for_lfnst_disabled_flag indicating whether to apply a quantization matrix during a non-separable transform, scales the transform coefficient by utilizing a scaling list, and performs a non-separable transform in accordance with a non-separable transform index lfnst_idx. In a case that scaling_matrix_for_lfnst_disabled_flag==1 and lfnst_idx !=0 and a size of a transform block is equal to or greater than a prescribed size, instead of scaling using the quantization matrix according to a position of the transform coefficient, uniform quantization not depending on the position of the transform coefficient is performed.

Abstract: In a case of referring to information between pictures by means of inter prediction, the entire picture needs to be decoded even in a case of decoding a small region. In a case of referring to information within a picture by means of intra prediction, referring to information across a tile boundary is not possible. In a case that a pixel pointed by a sub-block level motion vector of a target block that is calculated by scaling based on an available motion vector acquired from a spatial neighboring block or a temporal neighboring block is not present within a tile sequence, a process of replacing the pixel value with a pixel value within the tile sequence is performed. In a case of referring to a pixel outside of a tile by means of intra prediction, a process of replacing the pixel value with that of a pixel within the tile is performed.

Abstract: A video decoding apparatus includes: a matrix reference pixel derivation unit configured to derive, as a reference image, an image obtained by down-sampling an image adjacently above a target block and an image adjacently leftward of the target block; a weight matrix derivation unit configured to derive a matrix of weighting factors in accordance with an intra prediction mode and a target block size; a matrix prediction image derivation unit configured to derive a prediction image by using a product of elements of the reference image and elements of the matrix of the weighting factors; and a matrix prediction image interpolation unit deriving, as a prediction image, the prediction image or an image obtained by interpolating the prediction image, wherein the weight matrix derivation unit derives a matrix with a size of a width equal to or smaller than a width of the target block size and a height equal to or smaller than a height of the target block size.

Abstract: Complexity of coding/decoding of a video is reduced. An image decoding apparatus (31) includes a CN information decoder (10) configured to hierarchically split a coding node by at least any of binary tree split and ternary tree split. The CN information decoder refers to a method of splitting an immediately higher node, which is a node one generation higher than a target node, to restrict a method of splitting the target node.

Abstract: An apparatus includes an inter prediction unit configured to decode multiple reference picture list structures and to select one reference picture list structure from the multiple reference picture list structures on a per picture basis or on a per slice basis, wherein in the multiple reference picture list structures, the number of all reference pictures is one or more.

Abstract: An image decoding apparatus decodes a transform coefficient on a transform unit basis, decodes a flag scaling_matrix_for_lfnst_disabled_flag indicating whether to apply a quantization matrix during a non-separable transform, scales the transform coefficient by utilizing a scaling list, and performs a non-separable transform in accordance with a non-separable transform index lfnst_idx. In a case that scaling_matrix_for_lfnst_disabled_flag==1 and lfnst_idx !=0 and a size of a transform block is equal to or greater than a prescribed size, instead of scaling using the quantization matrix according to a position of the transform coefficient, uniform quantization not depending on the position of the transform coefficient is performed.

Abstract: A prediction image generation method is provided. The method derives a down-sampled luminance image and a down-sampled neighboring luminance image by down-sampling the luminance image of a target block and a neighboring luminance image based on information related to a down-sampling and indicating one of a plurality of position relationships between at least one luma pixel and a chroma pixel. The method derives a neighboring chrominance image, parameters derived from the down-sampled neighboring luminance image and the neighboring chrominance image, and the prediction image by using the down-sampled luminance image and the parameters. The position relationships include that a position of the chroma pixel is identical to a position of one of the at least one luma pixel and that the position of the chroma pixel is located in an intermediate of two of the at least one luma pixel on a left side of a 2×2 luma pixel block.

Abstract: A video decoding apparatus (31) for splitting an image into tiles, splits a tile of the tiles into coding tree units (CTUs), and decodes a video on a per-CTU basis, the video decoding apparatus including a header decoder (3020) configured to decode tile unit information indicating a unit for a size of a tile from header information of a coding stream, and a coding tree (CT) decoder (3021) configured to split the tile into CTUs, wherein the header decoder derives a tile upper left position and a tile size by using the tile unit information.

Abstract: An image decoding apparatus including a header decoder configured to decode, from coded data, a flag indicating whether dependent quantization is enabled and a flag prohibiting transform skip residual quantization, and a TU decoder configured to decode a transform coefficient in a TU block in an RRC mode in which a LAST position is coded, the LAST position corresponding to a decoding start position for the transform coefficient, or a TSRC mode in which the LAST position is not coded. The TU decoder performs dependent quantization in the RRC mode in a case that the transform coefficient for transform skip is decoded in the TSRC mode, and does not perform dependent quantization in the RRC mode in a case that the transform coefficient for transform skip is decoded in the RRC mode.

Abstract: In a scheme in which only a part of one picture is intra-predicted and the rest of the region is inter-predicted, generation of a significant code amount and generation of a delay can be avoided in a specific picture. However, because only a part of the picture is coded by means of the intra prediction, coding efficiency is deteriorated as compared to an I picture in which the entire picture is coded by means of the intra prediction. A picture is split into a restricted region and a non-restricted region. Prediction is performed by using an intra prediction in which only a pixel of the restricted region is referred to or an inter prediction in which a restricted reference region of a reference picture is referred to for a block of the restricted region. Prediction is performed by using the intra prediction in which a decoded pixel in the picture is referred to or the inter prediction in which the reference picture is referred to for the block of the non-restricted region.

Abstract: Complexity of coding/decoding of a video is reduced. An image decoding apparatus (31) includes a CN information decoder (10) configured to hierarchically split a coding node by at least any of binary tree split and ternary tree split. The CN information decoder refers to a method of splitting an immediately higher node, which is a node one generation higher than a target node, to restrict a method of splitting the target node.

Abstract: The coding efficiency and the amount of processing can be further improved in methods that use the correlation between spatial and temporal directions to estimate parameters that are required for predictions. In LM prediction that predicts pixel values of chrominance, based on pixel values of luminance, an index for a filter that downsamples a luminance image is adaptively signalled.

Abstract: An adaptive motion vector prediction unit configured to adaptively perform spatial prediction that performs prediction using a motion vector around a target block and temporal prediction that performs prediction using a motion vector of a collocated picture is included, and in the temporal prediction performed by the adaptive motion vector prediction unit, the collocated picture to be referred to is designated on a per picture basis, and a reference list is designated on a per slice basis.

Abstract: An image decoding apparatus is provided with a CT information decoding unit that decodes division information indicating a division method for binary tree division with respect to a coding node of a coding tree unit, and performs the binary tree division with respect to the coding node by referring to the division information of another decoded coding node.

Abstract: An image decoding device (31) includes a transform coefficient decoding unit (311) configured to decode a transform coefficient for a transform tree included in a coding unit. In the transform tree, the transform coefficient decoding unit splits a transform unit corresponding to luminance and then decodes the transform coefficient related to the luminance, and does not split the transform unit corresponding to chrominance and decodes the transform coefficient related to the chrominance.

Abstract: A slice or a tile can be decoded in a single picture, without reference to information outside of a target slice or outside of a target tile. However, there are problems in that in order to decode some regions of a video in a sequence, the entire video needs to be reconstructed, and in that the slice and the tile coexist in the single picture, and the slices include an independent slice and dependent slice, causing the coding structure to be complex. In the present invention, a flag indicating whether a shape of a slice is rectangular or not is decoded, and in a case that the flag indicates that the shape of the slice is rectangular, a position and a size of the slice that is rectangular are not changed in a period of time of referring to a same SPS. The slice that is rectangular is decoded independently without reference to information of another slice. As described above, introducing the slice that is rectangular instead of the tile can simplify the coding structure that is complex.

Abstract: An image decoding apparatus decodes a transform coefficient on a transform unit basis, decodes a flag scaling_matrix_for_lfnst_disabled_flag indicating whether to apply a quantization matrix during a non-separable transform, scales the transform coefficient by utilizing a scaling list, and performs a non-separable transform in accordance with a non-separable transform index lfnst_idx. In a case that scaling_matrix_for_lfnst_disabled_flag==1 and lfnst_idx !=0 and a size of a transform block is equal to or greater than a prescribed size, instead of scaling using the quantization matrix according to a position of the transform coefficient, uniform quantization not depending on the position of the transform coefficient is performed.