Methods, systems, apparatuses for video processing are described. A method for processing video includes performing a conversion between a video and a bitstream of the video according to a format rule, and wherein the format rule specifies to include, in a general constraint syntax structure associated with the video, one or more general constraint flags indicating whether corresponding syntax elements are included in a sequence parameter set (SPS) and/or a picture parameter set (PPS) and/or a picture header (PH) and/or a slice header (SH) or to constrain values of the syntax elements in the SPS and/or the PPS and/or the PH and/or the SH.

Methods, systems, apparatuses for video processing are described. A method for processing video includes performing a conversion between a video and a bitstream of the video according to a format rule, and wherein the format rule specifies to include, in a general constraint syntax structure associated with the video, one or more general constraint flags indicating whether corresponding syntax elements are included in a sequence parameter set (SPS) and/or a picture parameter set (PPS) and/or a picture header (PH) and/or a slice header (SH) or to constrain values of the syntax elements in the SPS and/or the PPS and/or the PH and/or the SH.

Methods and apparatus for video processing, including coding and decoding, are described. One example video processing method includes performing a conversion between a video and a bitstream of the video according to a format rule, wherein the bitstream includes one or more output layer sets (OLSs), each OLS comprising one or more coded layer video sequences, and wherein the format rule specifies that a video parameter set indicates, for each of the one or more OLSs, a greatest allowed value of a chroma format indicator and/or a greatest allowed value of a bit depth used to represent pixels of the video.

Methods, apparatus, and computer readable storage medium for intra prediction mode coding in video decoding. The method includes receiving, by a device, a coded video bitstream for a block. The device includes a memory storing instructions and a processor in communication with the memory. The method also includes dividing, by the device, a list of intra modes into a plurality of intra mode sets for the block based on mode information of each intra mode in the list, the list of intra modes corresponding to an intra prediction mode of at least one neighboring block of the block; extracting, by the device from the coded video bitstream, a set index indicating an intra mode set from the plurality of intra mode sets; extracting, by the device from the coded video bitstream, a mode index indicating an intra prediction mode from the intra mode set; and determining, by the device, the intra prediction mode for the block based on the set index and the mode index.

Methods, apparatus, and computer readable storage medium for intra prediction mode coding in video decoding. The method includes receiving, by a device, a coded video bitstream for a block. The device includes a memory storing instructions and a processor in communication with the memory. The method also includes dividing, by the device, a list of intra modes into a plurality of intra mode sets for the block based on mode information of each intra mode in the list, the list of intra modes corresponding to an intra prediction mode of at least one neighboring block of the block; extracting, by the device from the coded video bitstream, a set index indicating an intra mode set from the plurality of intra mode sets; extracting, by the device from the coded video bitstream, a mode index indicating an intra prediction mode from the intra mode set; and determining, by the device, the intra prediction mode for the block based on the set index and the mode index.

An image encoding/decoding method and apparatus are provided. An image decoding method according to the present disclosure may include parsing, from a bitstream, first information specifying whether block difference pulse code modulation (BDPCM) applies to an intra-predicted current block, determining a prediction direction of BDPCM for the current block and generating a residual block of the current block based on the determined prediction direction of BDPCM, based on the first information specifying that BDPCM applies to the current block, generating a prediction block of the current block, by performing intra prediction based on an intra prediction mode of the current block, and reconstructing the current block based on the residual block and the prediction block.

An image encoding/decoding method and apparatus are provided. An image decoding method according to the present disclosure may include parsing, from a bitstream, first information specifying whether block difference pulse code modulation (BDPCM) applies to an intra-predicted current block, determining a prediction direction of BDPCM for the current block and generating a residual block of the current block based on the determined prediction direction of BDPCM, based on the first information specifying that BDPCM applies to the current block, generating a prediction block of the current block, by performing intra prediction based on an intra prediction mode of the current block, and reconstructing the current block based on the residual block and the prediction block.

According to an aspect, a video encoder selects a block of intermediate size from a set of block sizes for intra-prediction estimation for encoding a video signal. A set of neighboring blocks with the intermediate size are tested for combining. If the set of neighboring blocks are determined to be combinable, the video encoder selects a larger block size formed by the tested neighboring blocks for encoding. On the other hand, if the set of neighboring blocks are determined to be not combinable, the video encoder selects a smaller block size from the set of tested neighboring blocks for prediction. According to another aspect of the present disclosure, the best mode for intra-prediction is determined by first intra-predicting a block with intermediate modes in a set of modes. Then the intra-predictions are performed for the neighboring modes of at least one intermediate mode.

According to an aspect, a video encoder selects a block of intermediate size from a set of block sizes for intra-prediction estimation for encoding a video signal. A set of neighboring blocks with the intermediate size are tested for combining. If the set of neighboring blocks are determined to be combinable, the video encoder selects a larger block size formed by the tested neighboring blocks for encoding. On the other hand, if the set of neighboring blocks are determined to be not combinable, the video encoder selects a smaller block size from the set of tested neighboring blocks for prediction. According to another aspect of the present disclosure, the best mode for intra-prediction is determined by first intra-predicting a block with intermediate modes in a set of modes. Then the intra-predictions are performed for the neighboring modes of at least one intermediate mode.

The present invention relates to an image encoding/decoding method and apparatus. The image decoding method according to the present invention may comprise constructing N MPM lists for a current block, wherein N is equal to or greater than 1, deriving an intra prediction mode of the current block based on the N MPM lists, and performing intra prediction for the current block based on the intra prediction mode.