Abstract: Several techniques for video encoding and video decoding are described. A method for video processing includes performing a conversion between a video block of a video and a bitstream of the video, wherein the video block uses a low frequency non-separable transform for the conversion, wherein the bitstream conforms to a format rule that specifies that a syntax element is included at a syntax level for the bitstream, wherein the syntax element is indicative of whether use of a scaling matrix which is derived from a reference scaling list is enabled for the video block, and wherein the syntax level is a sequence level, a picture level, or a slice level.

Abstract: Devices, systems, and methods for digital video coding, which includes matrix-based intra prediction methods for video coding, are described. In a representative aspect, a method for video processing includes performing a conversion between a current video block of a video and a bitstream representation of the current video block using a matrix based intra prediction (MIP) mode in which a prediction block of the current video block is determined by performing, on previously coded samples of the video, a boundary downsampling operation, followed by a matrix vector multiplication operation, and followed by an upsampling operation, where the upsampling operation is performed, in both a vertical direction and a horizontal direction in a fixed order, on samples obtained from the matrix vector multiplication operation.

Abstract: A method of video processing includes performing a conversion between a video and a bitstream of the video according to a rule, wherein the rule specifies that a sub-bitstream extraction process is implemented to generate a sub-bitstream for decoding, wherein the sub-bitstream extraction process is configured to extract, from the bitstream, a sub-bitstream with a target highest temporal identifier, and wherein, the rule specifies that, during the extracting, upon removing a video coding layer (VCL) network abstraction layer (NAL) unit, filler data units and filler supplemental enhancement information (SEI) messages in SEI NAL units that are associated with the VCL NAL unit are also removed.

Abstract: Methods, systems, and devices for picture header constraints for multi-layer coding are described. An example method of video processing includes performing a conversion between a video including one or more pictures and a bitstream of the video. The bitstream conforms to a format rule. The format rule specifies a constraint on a value of a first syntax element that specifies whether a second syntax element is present in a picture header syntax structure of a current picture. The second syntax element specifies a value of a picture order count (POC) most significant bit (MSB) cycle of the current picture.

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 including one or more layers and a bitstream of the video according to a rule, wherein the rule specifies, in a process of sub-bitstream extraction to output an output sub-bitstream, whether to generate non-scalable nested supplementary enhancement information (SEI) messages by extracting scalable-nested SEI messages from a scalable nesting SEI message based on a first flag indicating whether the SEI message applies to specific output layer sets (OLSs) and a second flag indicating whether the SEI message applies to all subpictures or only to specific subpictures.

Abstract: A messaging system may receive a plurality of messages in a conversation maintained by a messaging service. It may be determined that a first message sent from a first messaging application associated with a first user comprises information identifying a second user. The messaging system may receive information indicative of a date associated with the first message. At least one database may store an association among at least the first message, the second user, and the date. The messaging system may send information indicative of the date still being active in the at least one database to a second messaging application associated with the second user.

Abstract: A method of processing video data includes performing a conversion between a video and a bitstream of the video. The bitstream comprises one or more layers comprising one or more pictures comprising one or more subpictures according to a rule which specifies that, responsive to a condition, a selective processing of a first supplemental enhancement information network abstraction layer, SEI NAL, unit of a target output subpicture sub-bitstream that is extracted during a subpicture sub-bitstream extraction process.

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 video including one or more pictures and a bitstream of the video according to a format rule. The format rule specifies that a first syntax element that indicates whether motion vector difference for a particular reference picture list (RPL) is indicated is conditionally included in the bitstream based on (i) whether a second syntax element indicating whether an RPL information is included in a picture header and/or (ii) a number of reference pictures in the particular RPL in case that the RPL information is present in the picture header.

Abstract: Methods, systems and devices for implementing constraints used in video encoding and video decoding are described. An example method of video processing includes performing a conversion between a video including one or more pictures including one or more slices and a bitstream of the video, wherein the bitstream is organized into a plurality of access units (AUs), AU 0 to AU n, based on a format rule, where n is a positive integer, wherein the format rule specifies a relationship between removal times of each of the plurality of AUs from a coded picture buffer (CPB) during decoding and a number of slices in the each of the plurality of AUs.

Abstract: Several techniques for video encoding and video decoding are described. An example method of processing video data includes performing a conversion between a video including one or more subpictures and a bitstream of the video according to a format rule, wherein the format rule specifies that a first syntax element in a scalable nesting supplemental enhancement information message in the bitstream is set to a particular value in response to the scalable nesting supplemental enhancement information message including one or more subpicture level information supplemental enhancement information messages, and wherein the particular value of the first syntax element indicates that the scalable nesting supplemental enhancement information message includes one or more scalable-nested supplemental enhancement information messages that apply to a specific output video layer set.

Abstract: A video processing method includes performing a conversion between a video having one or more video layers comprising a current picture comprising a current slice and a bitstream of the video according to a rule. The rule specifies a condition under which a reference picture list for the current slice is disallowed to have an active entry that refers to a picture that precedes, in a decoding order or an output order, an intra random access point picture associated with the current picture.

Abstract: A method includes performing a conversion, according to a rule, between a current slice of a current picture of a video and a bitstream of the video, wherein the rule specifies that a first syntax element of a picture parameter set (PPS) and a second syntax element of the PPS control whether a third syntax element is included in the bitstream, and wherein the first syntax element indicates whether a weighted prediction is enabled for bi-directional slices of coded pictures referring to the PPS, the second syntax element indicates whether information related to the weighted prediction is present in picture headers or slice headers of coded pictures referring to the PPS, and the third syntax element indicates a number of weights associated with a reference picture list 1 of the current slice.

Abstract: A method for processing video data is provided to include: determining whether a sharing of merge list information is enabled for a merge sharing node that corresponds to an ancestor node in a coding unit split tree to allow leaf coding units of the ancestor node in the coding unit split tree to use the merge list information; and performing a conversion between a current video block of a video and a bitstream of the video based on the determining.

Abstract: A method of video processing comprises determining, for a conversion between a first block of video and a bitstream representation of the first block, a range of motion vector difference (MVD) component associated with the first block, wherein the range of MVD component is [?2M, 2M?1], where M=17; constraining value of the MVD component to be in the range of MVD component; and performing the conversion based on the constrained MVD component.

Abstract: A method of video processing is provided. The method includes determining, for a conversion between a video comprising a video unit and a bitstream of the video, whether a first coding tool is enabled for the video unit according to a rule. The rule specifies that the first coding tool and a second coding tool are mutually exclusively enabled. The first coding tool or the second coding tool comprises a sign data hiding tool. The method also includes performing the conversion according to the determining.

Abstract: Methods and apparatus for video processing, including coding and decoding, are described. One example video processing method includes performing a conversion between a video having one or more video layers and a bitstream of the video according to a format rule, and wherein the format rule specifies that a value of a flag that indicates whether to remove pictures previously decoded and stored in a decoded picture buffer from the decoded picture buffer when decoding an access unit of a certain type is included in the bitstream.

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. The bitstream includes one or more layers including one or more network abstraction layer (NAL) units according to a format rule that specifies that a first layer identifier in a header of an end of sequence network abstraction layer (EOS NAL) unit is required to be equal to a second layer identifier of one of the one or more layers in the bitstream.

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. The bitstream conforms to a format rule. The bitstream includes one or more layers including one or more picture units (PUs). The format rule specifies that, responsive to a first PU in a layer of the bitstream following an end of sequence network abstraction layer (EOS NAL) unit in the layer in a decoding order, a variable of the first PU is set to a particular value, wherein the variable indicates whether the first PU is a coded layer video sequence start (CLVSS) PU.

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: Devices, systems and methods for encoding and decoding digital video using a table containing coding candidates are described. In a representative aspect, a video processing method is provided to include maintaining a set of tables, wherein each table includes motion candidates and each motion candidate is associated with corresponding motion information; and performing a conversion between a bitstream representation of a video including a current block and the current block, and wherein the performing of the conversion includes checking at most N motion candidates in a table based on a rule.