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 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 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: In coding and decoding of motion vectors of a B slice, in a case that a mode that causes a value of difference between motion vectors of L1 prediction defined in a picture header to be equal to zero is configured, a symmetric motion vector difference mode no longer operates regardless of a reference picture list structure. In a case that multiple slices are present in one picture, coding efficiency significantly decreases depending on a selected reference picture. A mode that causes a difference between motion vectors of L1 prediction of bi-directional prediction switchable per picture to be equal to zero is provided, and in a case that all of referable short-term reference pictures in two reference picture lists are preceding pictures or subsequent pictures, the mode is applicable.

Abstract: A video decoding apparatus is a video decoding apparatus for deriving a prediction image by using a reference picture included in a reference picture list.

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: A moving image decoding method for generating prediction images 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 horizontally neighboring samples and vertically neighboring samples in the first and second prediction images 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 third 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 derived based on a pixel bit length of eight.

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: 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: 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.

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: 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: 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 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.

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: 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: 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 the related art, in some cases the weighted prediction processing is performed even in a case that normal prediction processing is to be performed. A video decoding apparatus includes a weighted prediction processing unit configured to decode a weight coefficient and an offset value from coded data and to generate a prediction image by multiplying an interpolation image by the weight coefficient and adding the offset value to the interpolation image, and a normal prediction processing unit configured to generate a prediction image from the interpolation image. In a case that in the weighted prediction processing unit, a bi-prediction is performed and information of the weight coefficient and the offset value is absent for both a reference list 0 and a reference list 1, the normal prediction processing unit generates a bi-prediction image.

Abstract: An image coding apparatus includes a coded data generating unit configured to generate coded data including image data for a subpicture acquired by dividing a picture, where the coded data generating unit generates, on a per subpicture basis, a subpicture header including subpicture identification information used for identifying the subpicture, and causes the generated subpicture header to be included in the coded data.

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.