Abstract: Several techniques for video encoding and video decoding are described. One example method includes performing a conversion between a video unit of a current picture of a video and a bitstream of the video according to a rule. The rule specifies that, for a given picture to be available as a reference picture whose motion information is used for the conversion, the given picture has a same coding tree unit size or a same coding tree block size as the current picture.

Abstract: A method of video processing is described. The method includes determining, for a conversion between a current video block of a video unit of a video and a coded representation of the video, a default intra prediction mode for the video unit coded using a certain intra prediction mode such that a prediction block of the current video block is generated without extrapolating neighboring pixels of the current video block along a direction; and performing the conversion based on the determining.

Abstract: A method of visual media processing includes determining, for a conversion between a current video block of visual media data and a bitstream representation of the current video block, a buffer that stores reference samples for prediction in an intra block copy mode; for a sample spatially located at location of the current video block relative to an upper-left position of a coding tree unit including the current video block and having a block vector, computing a corresponding reference in the buffer at a reference location, wherein the reference location is determined using the block vector and the location; and upon determining that the reference location lies outside the buffer, re-computing the reference location based at least in part on a location of the current video block relative to the coding tree unit including the current video 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, multiple sets of parameters, wherein each set of parameters defines a cross-component linear model (CCLM) and is derived from a corresponding group of chroma samples at corresponding chroma sample positions; determining, based on the multiple sets of parameters, parameters for a final CCLM; and performing the conversion based on the final CCLM.

Abstract: The present application relates to signaling of combined intra-inter prediction. A method for processing video includes: coding, during a conversion between a current video block in a video data and a bitstream representation of the current video block, a combined inter-intra prediction (CIIP) flag for the current video block by a context model based coding without referring to a CIIP flag of one or more neighboring video blocks to the current video block, and performing, at least by applying the combined inter-intra prediction (CIIP) flag of the current video block, the conversion.

Abstract: Methods, systems and devices for defining and using constraints on picture types in video bitstream processing are disclosed. An example method of video processing includes performing a conversion between a video including one or more pictures and a bitstream of the video, wherein the bitstream conforms to a format rule. The format rule specifies that a picture timing (PT) supplemental enhancement information (SEI) message, when included in the bitstream, is access unit (AU) specific, and wherein each picture of the one or more pictures that is a random access skipped leading (RASL) picture includes only a RASL network abstraction layer unit type (NUT).

Abstract: A method of video processing includes performing a conversion between a video comprising one or more scalable video layers and a bitstream of the video. The video comprises one or more video pictures comprising one or more slices. The bitstream conforms to a format rule. The format rule specifies that a value of a field indicative of a slice type of a slice is set to indicate a type of intra slice in case that a corresponding network abstraction layer unit type is in a predetermined range and that a corresponding video layer flag indicates that a video layer containing the slice does not use inter-layer prediction.

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: A method of video processing is provided to include maintaining one or more tables, wherein each table includes one or more motion candidates and each motion candidate is associated with corresponding motion information; performing a conversion between a current block and a bitstream representation of a video including the current block by using motion information in a table; and updating, after performing of the conversion, one or more tables based on M sets of additional motion information associated with the current block, M being an integer.

Abstract: A video processing method includes determining, for a conversion between a block of a video and a bitstream representation of the video, a manner in which information for a Matrix-based Intra Prediction (MIP) coding technique is coded in the bitstream representation. A prediction block of the block is determined using the MIP coding technique based on performing a matrix vector multiplication operation on previously coded samples of the video. The method also includes performing the conversion based on the determining.

Abstract: An example method of video processing includes determining, for a conversion between a block of a first sub-picture of a video and a bitstream representation of the video, whether to apply a deblocking process across an edge between the block and a neighboring block of a second sub-picture based on whether a loop filtering process is allowed across subpicture boundaries. The method also includes performing the conversion based on the determining.

Abstract: Several techniques for video encoding and video decoding are described. One example method includes performing a conversion between a video including a video unit and a bitstream of the video according to a rule, wherein the rule specifies whether a transform skip residual coding operation is enabled for the video unit, and wherein one or more syntax elements are included in the bitstream at a video segment level indicative of whether the transform skip residual coding operation is enabled for the video unit.

Abstract: Examples of video encoding methods and apparatus and video decoding methods and apparatus are described. An example method of video processing includes performing a conversion between a video and a bitstream of the video, wherein the bitstream comprises one or more output layer sets comprising one or more video layers according to a rule, wherein the rule specifies a particular decoding order between a subpicture level information (SLI) supplemental enhancement information (SEI) message and a buffering period (BP) SEI message that apply to a particular output layer set, responsive to a condition that the SLI SEI message and the BP SEI message are included in an access unit.

Abstract: Devices, systems and methods for digital video coding, which includes using default motion candidates for video coding, are described. An exemplary method for video processing includes determining, for a conversion between a block of a video and a bitstream representation of the video, weights to use for a weighted average of prediction samples along an edge of two partitions of the block. The two partitions are generated according to a geometry partition mode, and the weights are selected from a first weighting factor group that at least one of the weights is equal to 0 or 1. The method also includes performing the conversion based on the determining.

Abstract: Devices, systems and methods for digital video coding, which includes inter prediction with refinement, are described. An exemplary method of video processing includes determining to use, for a conversion between a current block of a video and a bitstream representation of the video, a first linear optimization model for the conversion using a first coding mode, the first linear optimization model being derived from a second linear optimization model that is used for the conversion using a second coding mode, and performing, based on the determining, the conversion. Another exemplary method of video processing includes determining to use, for a conversion between a current block of a video and a bitstream representation of the video, a gradient value computation algorithm for a bi-directional optical flow tool, and performing, based on the determining, the conversion.

Abstract: A method, a video processing apparatus and computer-readable program medium for video process is disclosed. The method of video processing includes deriving, during a conversion between a current block of video and a bitstream representation of the current block, a new affine model using multiple original affine models with control point motion vectors; and performing the conversion by using the new affine model.

Abstract: Devices, systems and methods for digital video coding, which include sub-block based inter prediction methods, are described. An exemplary method for video processing includes determining, for a conversion between a current block of video and a bitstream representation of the video, a maximum number of candidates in a sub-block based merge candidate list and/or whether to add sub-block based temporal motion vector prediction (SbTMVP) candidates to the sub-block based merge candidate list based on whether temporal motion vector prediction (TMVP) is enabled for use during the conversion or whether a current picture referencing (CPR) coding mode is used for the conversion, and performing, based on the determining, the conversion.

Abstract: Devices, systems and methods for digital video processing, which includes selection of adjacent neighboring block for intra coding, are described. In a representative aspect, a method for video processing includes selecting, for a conversion between a current block of visual media data and a bitstream representation of the current block, an intra prediction mode based on at least one of spatial neighboring blocks to the current block, and performing the conversion based on the intra prediction mode. The at least one of the spatial neighboring blocks is different from a first block that is located to a left of a first row of the current block and a second block that is located above a first column of the current block.

Abstract: Methods, systems and devices for multi-motion model based video coding and decoding are described. An exemplary method for video processing includes determining, for a video block, a candidate for decoding using, for one or more target motion models from a number of motion models, one or more motion candidates from corresponding non-adjacent spatial or temporal blocks or motion information derived from previously coded blocks based on their associated motion models, and performing further processing of the video block using the candidate.

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, wherein 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.