Abstract: An encoder capable of properly handling an image to be encoded or decoded includes processing circuitry and memory connected to the processing circuitry. Using the memory, the processing circuitry: obtains parameters including at least one of (i) one or more parameters related to a first process for correcting distortion in an image captured with a wide angle lens and (ii) one or more parameters related to a second process for stitching a plurality of images; generates an encoded image by encoding a current image to be processed that is based on the image or the plurality of images; and writes the parameters into a bitstream including the encoded image.

Abstract: An encoder capable of properly handling an image to be encoded or decoded includes processing circuitry and memory connected to the processing circuitry. Using the memory, the processing circuitry: obtains parameters including at least one of (i) one or more parameters related to a first process for correcting distortion in an image captured with a wide angle lens and (ii) one or more parameters related to a second process for stitching a plurality of images; generates an encoded image by encoding a current image to be processed that is based on the image or the plurality of images; and writes the parameters into a bitstream including the encoded 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: An encoder capable of properly handling an image to be encoded or decoded includes processing circuitry and memory connected to the processing circuitry. Using the memory, the processing circuitry: obtains parameters including at least one of (i) one or more parameters related to a first process for correcting distortion in an image captured with a wide angle lens and (ii) one or more parameters related to a second process for stitching a plurality of images; generates an encoded image by encoding a current image to be processed that is based on the image or the plurality of images; and writes the parameters into a bitstream including the encoded image.

Abstract: An encoder, when sub-block encoding is to be performed, determines a plurality of sub-blocks in a first image block, the plurality of sub-blocks including a first sub-block, determines a first motion vector for the first sub-block by referring to a first candidate list, performs first inter prediction processing on the first sub-block using the first motion vector, and encodes the first image block using a result of the first inter prediction processing. When partition encoding is to be performed, the encoder, in operation, determines a plurality of partitions in a second image block, the plurality of partitions including a first partition, determines a second motion vector for the first partition by referring to a second candidate list, performs second inter prediction processing on the first partition using the second motion vector, and encodes the second image block using a result of the second inter prediction processing.

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 image decoder includes circuitry and a memory, wherein the circuitry, in operation, calculates first values of a first partition in a current block, using a first motion vector for the first partition; calculates second values of a second partition in the current block, using a second motion vector for the second partition; calculates third values of a set of pixels between the first partition and the second partition, using the first motion vector; calculates fourth values of the set of pixels, using the second motion vector; and weights the third values and the fourth values. A number of pixels in a row in the set of pixels is two or more, and two or more weights applied to the third values increase along the row.

Abstract: An encoder includes circuitry and a memory coupled to the circuitry. The circuitry, in operation, determines whether or not a ternary split process of splitting a block into three sub blocks in a first direction parallel to a first longer side of the block is allowed by comparing a size of a second shorter side of the block to a minimum threshold value. The circuitry, responsive to the ternary split process being allowed, writes, into a bitstream, a split direction parameter indicative of a splitting direction. The circuitry, in operation, splits the block into a plurality of sub blocks in a direction indicated by the split direction parameter; and encodes the plurality of sub blocks. The minimum threshold value corresponds to a minimum size supported in a transform process.

Abstract: An encoder encodes a video, and includes: circuitry; and memory coupled to the circuitry. Using the memory, the circuitry: obtains at least two items of prediction information for a first partition included in the video; derives at least one template from neighboring samples which neighbor the first partition; calculates at least two costs, using the at least one template and the at least two items of prediction information; using the at least two costs, (i) determines at least one splitting direction for the first partition or (ii) assigns one of the at least two items of prediction information to a second partition split from the first partition according to the splitting direction, and another thereof to a third partition split from the first partition according to the splitting direction; and encodes the first partition according to the splitting direction and the at least two items of prediction information.

Abstract: An image encoder writes a first parameter and a second parameter to a bitstream, and derives a partition mode based on the first and second parameters. Responsive to the derived partition mode being a first partition mode, the image encoder executes the first partition mode including: splitting a block of a picture into a plurality of first blocks including a N×2N block sized N pixels by 2N pixels; splitting the N×2N block, wherein a ternary split is allowed to split the N×2N block in a vertical direction, which is a direction along the 2N pixels, into a plurality of sub blocks including at least one sub block sized N/4×2N, while a binary split is not allowed to split the N×2N block in the vertical direction into two sub blocks that are equally sized N/2×2N; and encoding the plurality of sub blocks.

Abstract: An encoder which includes circuitry and memory. Using the memory, the circuitry generates a list which includes candidates for a first motion vector for a first partition. The list has a maximum list size and an order of the candidates, and at least one of the maximum list size or the order of the candidates is dependent on at least one of a partition size or a partition shape of the first partition. The circuitry selects the first motion vector from the candidates included in the list; encodes an index indicating the first motion vector among the candidates in the list into the bitstream based on the maximum list size; and generates the predicted image for the first partition using the first motion vector.

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 a memory coupled to the circuitry, wherein the circuitry, in operation, performs a partition process. The partition process includes calculating first values of a set of pixels between a first partition and a second partition in a current block, using a first motion vector for the first partition; calculating second values of the set of pixels, using a second motion vector for the second partition; and calculating third values of the set of pixels by weighting the first values and the second values. When a ratio of a width to a height of the current block is larger than 4 or a ratio of the height to the width of the current block is larger than 4, the circuitry disables the partition process.

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: 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: 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: 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.