Abstract: An image decoding apparatus is provided that selectively uses a merge mode in a case that an MMVD mode is not available, thus achieving high coding efficiency. The image decoding apparatus includes a parameter decoder, and in a case that a regular merge flag indicates a regular merge mode, checks a flag indicating whether an MMVD prediction signalled in a sequence parameter set or the like is available, and in a case that the MMVD prediction is not available, decodes motion vector information obtained from a merge candidate.

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 (31) includes a CT information decoding unit (10) configured, in each coding tree, to decode a constraint flag indicating whether or not to constrain decoding a prediction unit, and a CU decoding unit (20) configured, in the coding tree, to decode a prediction unit in a coding node to be decoded first and to not decode a prediction unit in another coding node, in a case that the constraint flag indicates constraint of decoding the prediction unit. According to the present invention, it is possible to reduce a coding amount of PU and complexity of coding/decoding an image while maintaining a split with a high degree of freedom by CT split (QT split and BT split).

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: Provided is a video decoding apparatus for decoding coded data of a tile group in which a picture is split into rectangular regions, the tile group being composed of segments, the video decoding apparatus including: a header decoder configured to decode the number of tiles, a WPP enabled flag, and a slice enabled flag indicating whether segments in a target tile group are rectangular tiles, CTU rows, or slices from a tile group header, wherein the header decoder is configured to decode only one of the number of tiles being two or more, the WPP enabled flag being 1, and the slice enabled flag being 1 in one tile group.

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 and an image coding apparatus that reduce complexity of high image quality processing are implemented. The image decoding apparatus includes an inter prediction parameter decoding processing unit that includes processing of, regarding two motion vectors, modifying the two motion vectors from an error of two prediction images. In a case that neither of the two prediction images is a case of weighted prediction, the processing of modifying the two motion vectors is performed.

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: 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: A prediction image generation method using two prediction images to generate a prediction image by a device is provided. First and second prediction image are generated. Bidirectional prediction gradient change prediction processing is performed by using a first shift value and difference values of the first and second prediction images respectively in horizontal and vertical directions to generate a first, second, third and fourth gradient images. Motion information is derived by using the first and second prediction images, the first, second, third and fourth gradient images, a second shift value, and a third shift value. Motion compensation correction value is derived by using the motion information and the first, second, third and the fourth gradient images. The prediction image is generated by using the first and second prediction images and the motion compensation correction value. The first, second and third shift values are respectively equal to 6, 4 and 1.

Abstract: A load in processing of searching for a motion vector is reduced. In order to solve the problem described above, a motion vector derivation apparatus according to one aspect of the present invention that derives a motion vector to be referred to for generating a prediction image to be used for coding or decoding of a video includes a motion vector search unit configured to search for a motion vector on a prediction unit basis through matching processing. The motion vector search unit is configured to stop search of the motion vector, depending on whether or not a conditional expression according to a pixel bit-depth is satisfied.

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: NPL 2 describes prediction (BIO prediction) using BIO processing in which in a case that a prediction image is derived, a gradient image is utilized to achieve high image quality, and this prediction involves an assumption that pixel values are temporally constant. Thus, there is a problem in that a fade image in which a pixel value has a temporal variation or the like is not successfully processed. A bi-directional optical flow sample prediction process unit that generates a prediction image using a gradient image derived from two interpolation images derives interpolation images for determining an optical flow by using a weight coefficient and an offset coefficient decoded from coded data for weighted bi-prediction, and generates a prediction image.

Abstract: The amount of memory required for CCLM prediction is reduced. The CCLM prediction parameter derivation unit (310442) derives a scale shift value corresponding to a luma difference value, and derives a CCLM prediction parameter, by shifting, by using the scale shift value, a value obtained by multiplying a value of a table referred to with a value obtained by performing right shift of the luma difference value by the scale shift value as an index and a chroma difference value. In addition, in a case of deriving a prediction image, a bit width is reduced by adaptively deriving a shift amount of a linear prediction parameter from the chroma difference value.

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: In a moving image decoding device for decoding encoded data of a tile group splitting a picture into one or more rectangular regions and consisting of one or more segments, a WPP enabled flag for indicating whether a segment in an object tile group is a CTU row having a height of one CTU is decoded, and when the WPP enabled flag is 1, after a CTU at a right end of the CTU row is decoded, an end bit of a first segment having a fixed value is decoded.

Abstract: A device is provided with: a first transformer which transforms an coding unit (CU); and a second transformer which transforms a part of first transform coefficients output from the first transformer, wherein the second transformer transforms at least any of the first transform coefficients for a region (first region) having different sizes in a horizontal direction and a vertical direction or the first transform coefficients for a non-rectangular region (second region).

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: A video decoding apparatus includes matrix reference pixel derivation circuitry that derives reference samples by using top neighboring samples and left neighboring samples of a current block, weight matrix derivation circuitry that derives a weight matrix, matrix prediction image derivation circuitry that derives a prediction image, and matrix prediction image interpolation circuitry that derives a predicted image by using the prediction image. A size index is derived according to a value of a target block width and a value of a target block height. A prediction size is derived using the size index. In a case that a first condition, that both the value of the transform block width and the value of the transform block height are equal to 4, is true, the size index is set equal to 0 and the prediction size is set equal to 4.

Abstract: In a case that luminance information is used for a chrominance prediction in a separate coding tree structure, there is a problem that chrominance blocks cannot be decoded before all luminance blocks constituting a tree are decoded. An image decoding apparatus that splits an image into coding tree units (CTUs) that are rectangular for processing includes a CT information decoding unit configured to split a CTU of the CTUs into coding trees CTs and to process one or more color components as a single coding tree using one coding tree CT of the coding trees CTs or process two or more color components as a separate coding tree using two or more coding trees CTs of the coding trees CTs depending on a tree mode, a CU decoding unit configured to decode a split flag indicating whether to further split a CT of the CTs and to recursively perform block splitting, and an intra predictor configured to use a decoded image of one color component to generate a prediction image of another color component.