Abstract: A video processing method includes determining, for a conversion between a block of a video and a bitstream representation of the video, that a secondary transform with a reduced dimension dimension (e.g., an inverse low frequency non-separable transform) is applicable to a single sub-block of the block in case a dimension of the block satisfies a condition. The secondary transform is performed between a forward primary transform and a quantization step or between a de-quantization step and an inverse primary transform. The reduced dimension is reduced from a dimension of the block. The method also includes performing the conversion based on the determining.

Abstract: A method of visual media processing includes determining a size of a buffer to store reference samples for prediction in an intra block copy mode; and performing a conversion between a current video block of visual media data and a bitstream of the current video block, using the reference samples stored in the buffer, wherein the conversion is performed in the intra block copy mode which is based on motion information related to a reconstructed block located in same video region with the current video block without referring to a reference picture.

Abstract: A method of video processing includes determining, for a conversion between a current block of a video and a bitstream representation of the video using a coding tool that accesses samples outside of the current block, that neighboring samples used for the conversion are unavailable. Samples that are located across a boundary of a video unit of the video are considered as unavailable samples. The method also includes performing, based on the determining, the conversion by padding samples in place of the neighboring samples that are unavailable. The padding samples are determined using samples that are restricted to be within a current processing unit associated with the current block.

Abstract: One example method of video processing includes implementing, by a processor, a decoder-side motion vector derivation (DMVD) scheme for motion vector refinement during a conversion between a current video block and a bitstream representation of the current video block by deriving parameters based on a deriving rule. The conversion may include compressing the current video block into the bitstream representation or uncompressing the bitstream representation into pixel values of the current video block.

Abstract: The disclosure relates to improvement on HMVP table. A method for processing video includes: maintaining, during a conversion between a current block of visual media data and a corresponding coded representation of the visual media data, a table storing history based motion vector prediction (HMVP) candidates which include motion information based on previously coded blocks; performing the conversion of the current block at least based on the table, wherein the table is of a HMVP table size which depends on one or more motion candidate lists, and the HMVP table size is a maximum number of candidates stored in the table.

Abstract: A method of video processing is provided. The method includes: determining, for a conversion between a current video unit of a video and a coded representation of the video, that applicability of a first coding tool and a second coding tool is mutually exclusive; and performing the conversion based on the determining, wherein the first coding tool corresponds to an adaptive color space transformation (ACT) tool; wherein use of the ACT tool comprises: converting, during encoding, a representation of a visual signal from a first color domain to a second color domain, or converting, during decoding, a representation of a visual signal from the second color domain to the first color domain.

Abstract: A method for visual media processing, including: computing, during a conversion between a current video block of visual media data and a bitstream representation of the current video block, a cross-component linear model (CCLM) and/or a chroma residual scaling (CRS) factor for the current video block based, at least in part, on neighboring samples of a corresponding luma block which covers a top-left sample of a collocated luma block associated with the current video block, wherein one or more characteristics of the current video block are used for identifying the corresponding luma block.

Abstract: A method for processing a video includes performing a conversion between a current block of visual media data and a corresponding coded representation of the visual media data. The conversion of the current block includes determining whether a use of one or both of a bi-directional optical flow (BIO) technique or a decoder-side motion vector refinement (DMVR) technique to the current block is enabled or disabled. Determining the use of the BIO technique or the DMVR technique is based on a cost criterion associated with the current block.

Abstract: A method of video processing includes performing a conversion between a video including a video region and a bitstream of the video according to a rule. The rule specifies a relationship between enablement of a palette mode and a coding type of the video region. The video region may represent a coding block of the video.

Abstract: Systems, methods and apparatus for video processing are described. The video processing may include video encoding, video decoding or video transcoding. One example method of video processing includes performing a conversion between a block of a video and a bitstream of the video according to a rule. The conversion is based on an adaptive motion vector difference resolution (AMVR) tool, and the rule specifies that selection of a context for a first bin within a bin string of a first syntax element that specifies the resolution of the motion vector difference associated with an AMVR shift is derived based on usage of a coding mode for the block.

Abstract: A method for video processing is provided. The method includes determining, for a conversion between a current video block of a video that is a chroma block and a coded representation of the video, a final prediction P(x, y) of a chroma sample at a position (x, y) in the current video block as a combination of prediction results of multiple cross-component linear models (MCCLMs), wherein the MCCLMs are selected based on the position (x, y) of the chroma sample; and performing the conversion based on the final prediction.

Abstract: A method for video processing includes determining, for a conversion between a current video block of a video and a coded representation of the video, whether an intra block copy (IBC) mode in which a prediction block for the current video block is calculated based on a block vector in a picture that includes current video block is enabled based on a rule on a block dimension; and performing the conversion based on the determining.

Abstract: Devices, systems and methods for video processing are described. An exemplary method for video processing includes determining, for a conversion between a current block of a video and a bitstream representation of the video, that a neighboring block of the current block that is coded in a palette mode is processed as an intra-coded block having a default mode during a construction of a list of most probable modes (MPM) candidates of the current block in case the neighboring block is located above or left of the current block. The method also includes performing the conversion based on the determining.

Abstract: A method of video processing includes determining a classification of samples of a block in a video picture of a video according to a rule, wherein the video picture is divided into multiple regions, and wherein the rule disallows use of neighboring samples of a current sample across one or more boundaries of the multiple regions for the classification. The one or more boundaries of the multiple regions comprises a virtual boundary for an adaptive loop filtering (ALF) process. The method also includes performing a conversion between the block and a bitstream representation of the video by selectively applying the ALF process according to the classification.

Abstract: Methods, systems, and devices related to sub-block based motion prediction in video coding are described. In one representative aspect, a video processing method includes partitioning a video block into a first set of sub-blocks according to a first pattern, partitioning the video block into a second set of sub-blocks according to a second pattern, in which at least one sub-block in the second set has a different size than a sub-block in the first set, and determining a prediction block corresponding to a combination of a first intermediate prediction block that is predictively generated from the first set of sub-blocks and a second intermediate prediction block that is predictively generated from the second set of sub-blocks.

Abstract: A method of visual media processing, includes: performing a conversion between a current video block of a visual media data and a bitstream representation of the visual media data according to a modification rule, wherein the current video block is coded using affine motion information; wherein the modification rule specifies to modify an affine motion information coded in the bitstream representation using motion vector differences and/or reference picture indices during decoding.

Abstract: A video processing method including inserting motion candidates in a first motion candidate list of a video region of a first video block using a list derivation rule, where the video region has a geometry shape that is a non-square and non-rectangular shape, and the first video block is coded with a geometry partition mode; and performing a conversion between the first video block and a bitstream of the first video block using the first motion candidate list.

Abstract: A video processing method is provided to include determining, for a conversion between a current video block of a current picture of a video and a coded representation of the video, that use of a coding tool is disabled for the current video block due to use of a reference picture having a dimension different from a dimension of the current picture for coding of the current video block into the coded representation; and performing the conversion based on the determining.

Abstract: A method for processing a video includes performing a conversion between a current block of visual media data and a corresponding coded representation of the visual media data, wherein the conversion of the current block includes determining whether a use of one or both of a bi-directional optical flow (BIO) technique or a decoder-side motion vector refinement (DMVR) technique to the current block is enabled or disabled, and wherein the determining the use of the BIO technique or the DMVR technique is based on a cost criterion associated with the current block.

Abstract: Combined intra and intra-block copy prediction for video coding is disclosed. A video processing method includes generating, for a conversion between a block of a video and a bitstream representation of the block, prediction for the block with a combined method which uses intra block copy (IBC) prediction and intra prediction in combination; and performing the conversion based on the prediction.