Abstract: A decoder includes circuitry and memory. Using the memory, the circuitry, in a first operating mode, derives first motion vectors for a first block obtained by splitting a picture, using a first inter prediction scheme, and generates a prediction image corresponding to the first block, by referring to spatial gradients of luminance generated based on the first motion vectors. Using the memory, the circuitry, in a second operating mode, derives second motion vectors for a sub-block obtained by splitting a second block, using a second inter prediction scheme different from the first inter prediction scheme, the second block being obtained by splitting the picture, and generates a prediction image corresponding to the sub-block without referring to spatial gradients of luminance.

Abstract: A moving picture coding method includes: coding a coding target block using a motion vector; generating motion vector predictors; and coding the motion vector using one of the motion vector predictors generated in the generating of the motion vector predictors. In the generating of the motion vector predictors, a replacement vector which replaces a temporal motion vector predictor is added to the motion vector predictors when it is impossible to obtain the temporal motion vector predictor from a block which is included in a coded picture different from the coding target picture and corresponds to the coding target block.

Abstract: An encoder includes circuitry and memory coupled to the circuitry. The circuitry determines whether to split a current luma virtual pipeline decoding unit (VPDU) into smaller blocks. When it is determined not to split the current luma VPDU into smaller blocks, the circuitry predicts a block of chroma samples without using luma samples. When it is determined to split the luma VPDU into smaller blocks, the circuitry predicts the block of chroma samples using luma samples. The circuitry encodes the block using the predicted chroma samples.

Abstract: An encoder that; obtains two prediction images by performing motion compensation using two motion vectors; obtains a gradient value of each of pixels included in the two prediction images; derives a local motion estimation value for each of sub-blocks based on the pixel value and the gradient value of each of the pixels, the sub-blocks being obtained by partitioning the current block; and generates a final prediction image for the current block using the pixel value and the gradient value of each of the pixels, and the local motion estimation value derived for each of the sub-blocks. Each of the pixels in the two prediction images is interpolated with sub-pixel accuracy, and a reference range for the interpolation is included in a normal reference range that is referred to for motion compensation for the current block in normal inter prediction performed without using the local motion estimation value.

Abstract: Provided is an encoder which includes circuitry and memory. Using the memory, the circuitry splits an image block into a plurality of partitions, obtains a prediction image for a partition, and encodes the image block using the prediction image. When the partition is not a non-rectangular partition, the circuitry obtains (i) a first prediction image for the partition, (ii) a gradient image for the first prediction image, and (iii) a second prediction image as the prediction image using the first prediction image and the gradient image. When the partition is a non-rectangular partition, the circuitry obtains the first prediction image as the prediction image without using the gradient image.

Abstract: An encoder includes circuitry and memory. Using the memory, the circuitry, in operation, selects an encoding mode from among candidates including a decoder-side motion vector refinement (DMVR) encoding mode and a partition encoding mode. When the DMVR encoding mode is selected, the circuitry: obtains a first motion vector for a first image block; derives a second motion vector from the first motion vector using motion search; and generates a prediction image for the first image block using the second motion vector. When the partition encoding mode is selected, the circuitry: determines a plurality of partitions in a second image block; obtains a third motion vector for each partition; and generates a prediction image for the second image block using the third motion vector, without deriving a fourth motion vector from the third motion vector using motion search.

Abstract: A method of encoding video including: writing a plurality of predetermined buffer descriptions into a sequence parameter set of a coded video bitstream; writing a plurality of updating parameters into a slice header of the coded video bitstream for selecting and modifying one buffer description out of the plurality of buffer descriptions; and encoding a slice into the coded video bitstream using the slice header and the modified buffer description.

Abstract: An encoder that encodes a current block in a picture includes circuitry and memory. Using the memory, the circuitry: performs a first transform on a residual signal of the current block using a first transform basis to generate first transform coefficients; and performs a second transform on the first transform coefficients using a second transform basis to generate second transform coefficients and quantizes the second transform coefficients, when the first transform basis is the same as a predetermined transform basis; and quantizes the first transform coefficients without performing the second transform, when the first transform basis is different from the predetermined transform basis.

Abstract: An image coding method includes: generating a first flag indicating whether or not a motion vector predictor is to be selected from among one or more motion vector predictor candidates; generating a second flag indicating whether or not a motion vector predictor is to be selected from among the one or more motion vector predictor candidates in coding a current block to be coded in a predetermined coding mode, when the first flag indicates that a motion vector predictor is to be selected; and generating a coded signal in which the first flag and the second flag are included in header information, when the first flag indicates that a motion vector predictor is to be selected.

Abstract: An encoder includes circuitry and memory. Using the memory, the circuitry, in operation, selects an encoding mode from among candidates including a decoder-side motion vector refinement (DMVR) encoding mode and a partition encoding mode. When the DMVR encoding mode is selected, the circuitry: obtains a first motion vector for a first image block; derives a second motion vector from the first motion vector using motion search; and generates a prediction image for the first image block using the second motion vector. When the partition encoding mode is selected, the circuitry: determines a plurality of partitions in a second image block; obtains a third motion vector for each partition; and generates a prediction image for the second image block using the third motion vector, without deriving a fourth motion vector from the third motion vector using motion search.

Abstract: A decoder that decodes a current block using a motion vector includes: a processor; and memory. Using the memory, the processor: derives a first candidate vector from one or more candidate vectors of one or more neighboring blocks that neighbor the current block; determines, in a first reference picture for the current block, a first adjacent region that includes a position indicated by the first candidate vector; calculates evaluation values of a plurality of candidate regions included in the first adjacent region; and determines a first motion vector of the current block, based on a first candidate region having a smallest evaluation value among the evaluation values. The first adjacent region is included in a first motion estimation region determined based on the position indicated by the first candidate vector.

Abstract: A transmitting method for transmitting a bitstream to a terminal is provided. The bit stream is generated by coding a current block of a picture and has an index for identifying a motion vector candidate from a motion vector candidate list. The motion vector candidate list is generated and includes motion vector candidates and a value for each motion vector candidate. A second candidate is arranged before a first candidate in the motion vector candidate list. The first candidate is sorted before the second candidate in the motion vector candidate list based on the values of the first and second candidates. The value of the first candidate is higher than the value of the second candidate. For each motion vector candidate, the value is based on a number of times the motion vector candidate is selected as a motion vector predictor for neighboring blocks.

Abstract: A decoder includes memory and a processor coupled to the memory and configured to: generate a first coefficient value by applying a CCALF (cross component adaptive loop filtering) process to a first reconstructed image sample of a luma component; clip the first coefficient value such that the clipped first coefficient value is within a first range from ?27 to 27?1; generate a second coefficient value by applying an ALF (adaptive loop filtering) process to a second reconstructed image sample of a chroma component; clip the second coefficient value such that the clipped second coefficient value is within a second range different from the first range; generate a third coefficient value by adding the clipped first coefficient value to the clipped second coefficient value; and generate a third reconstructed image sample of the chroma component using the third coefficient value.

Abstract: A three-dimensional data encoding method includes: calculating a predicted value of a position of a three-dimensional point according to one of inter prediction and intra prediction; calculating a residual between the predicted value and the position; arithmetic-encoding the residual using a first context when the predicted value is calculated according to the inter prediction; and arithmetic-encoding the residual using a second context different from the first context when the predicted value is calculated according to the intra prediction. The residual is expressed by third residual information indicating a bit count of the residual.

Abstract: An image encoder/decoder includes circuitry and a memory coupled to the circuitry. When a geometry of a block of a picture satisfies a first condition, the circuitry splits the block of the picture into sub blocks having a first set of geometries. When the geometry of the block does not satisfy the first condition, the circuitry splits the block of the picture into sub blocks having a second set of geometries, the second set of geometries being different from the first set of geometries. The circuitry encodes/decodes the sub blocks of the block.

Abstract: An encoder includes circuitry and memory. Using the memory, the circuitry, in operation, selects an encoding mode from among candidates including a decoder-side motion vector refinement (DMVR) encoding mode and a partition encoding mode. When the DMVR encoding mode is selected, the circuitry: obtains a first motion vector for a first image block; derives a second motion vector from the first motion vector using motion search; and generates a prediction image for the first image block using the second motion vector. When the partition encoding mode is selected, the circuitry: determines a plurality of partitions in a second image block; obtains a third motion vector for each partition; and generates a prediction image for the second image block using the third motion vector, without deriving a fourth motion vector from the third motion vector using motion search.

Abstract: An encoder includes circuitry and memory connected to the circuitry. The circuitry: derives an absolute value of a sum of horizontal gradient values; derives, as a first parameter, the total sum of the absolute values of horizontal gradient values; derives, as a second parameter, the total sum of the absolute values of vertical gradient values; derives a horizontal-related pixel difference value; derives, as a third parameter, the total sum of the absolute values of horizontal-related pixel difference values; derives a vertical-related pixel difference value; derives, as a fourth parameter, the total sum of the absolute values of vertical-related pixel difference values; and generates a prediction image using the first to fourth parameters.

Abstract: An encoder includes circuitry and memory. Using the memory, the circuitry, in operation, selects an encoding mode from among candidates including a decoder-side motion vector refinement (DMVR) encoding mode and a partition encoding mode. When the DMVR encoding mode is selected, the circuitry: obtains a first motion vector for a first image block; derives a second motion vector from the first motion vector using motion search; and generates a prediction image for the first image block using the second motion vector. When the partition encoding mode is selected, the circuitry: determines a plurality of partitions in a second image block; obtains a third motion vector for each partition; and generates a prediction image for the second image block using the third motion vector, without deriving a fourth motion vector from the third motion vector using motion search.

Abstract: Provided is an encoder which includes circuitry and memory. The circuitry encodes an image block using the memory. In encoding the image block, the circuitry: obtains one or more size parameters related to a size of the image block; determines whether the one or more size parameters and one or more thresholds satisfy a determined relationship; encodes a split parameter when the one or more size parameters and the one or more thresholds are determined to satisfy the determined relationship, the split parameter indicating whether the image block is to be split into a plurality of partitions including a non-rectangular partition; and encodes the image block after splitting the image block into the plurality of partitions when the split parameter indicates that the image block is to be split into the plurality of partitions.

Abstract: An encoder includes circuitry and memory. Using the memory, the circuitry performs prediction on an image. A motion vector predictor list used in the prediction includes a spatially neighboring motion vector predictor obtained from a block spatially neighboring a current block, and a spatially broad motion vector predictor obtained from a block positioned at any of a plurality of predetermined positions in a second range that is broader than a first range that spatially neighbors the current block. The plurality of predetermined positions are defined by a regular interval using the top-left of a current picture as a reference point.