Constraints for video coding and decoding

Abstract

A method of video processing is provided that includes performing a conversion between a block of a video and a bitstream of the video. The bitstream conforms to a formatting rule specifying that a size of a merge estimation region (MER) is indicated in the bitstream and the size of the MER is based on a dimension of a video unit. The MER comprises a region used for deriving a motion candidate for the conversion.

What is claimed is: 
     
         1 . A method of processing video data, comprising:
 determining, for a conversion between a current block of a video and a bitstream of the video, that a first prediction mode is applied to the current block;   maintaining a predictor palette table;   constructing, in the first prediction mode, a current palette comprising one or more palette predictors for the current block based on the predictor palette table; and   performing the conversion based on the first prediction mode,   wherein in the first prediction mode, reconstructed samples of the current block are represented by a set of representative color values, and the set of representative color values comprises at least one of 1) palette predictors derived from the current palette, 2) escaped samples, or 3) palette information included in the bitstream, and   wherein a maximum number of entries in the current palette is restricted to m×8, and a maximum number of entries in the predictor palette table are restricted to n×8, and wherein m and n are positive integers.   
     
     
         2 . The method of  claim 1 , wherein m or n is equal to 4 or 8. 
     
     
         3 . The method of  claim 1 , wherein a syntax element indicating a parallel merge estimation level is included in the bitstream, and wherein the maximum value of the syntax element depends on a size of a coding tree unit (CTU). 
     
     
         4 . The method of  claim 3 , wherein the maximum value of the syntax element is constrained to be smaller than the size of the CTU. 
     
     
         5 . The method of  claim 3 , wherein the syntax element is coded by an exponential Golomb code. 
     
     
         6 . The method of  claim 1 , wherein the conversion includes encoding the current block into the bitstream. 
     
     
         7 . The method of  claim 1 , wherein the conversion includes decoding the current block from the bitstream. 
     
     
         8 . An apparatus for processing video data comprising a processor and a non-transitory memory with instructions thereon, wherein the instructions upon execution by the processor, cause the processor to:
 determine, for a conversion between a current block of a video and a bitstream of the video, that a first prediction mode is applied to the current block;   maintain a predictor palette table;   construct, in the first prediction mode, a current palette comprising one or more palette predictors for the current block based on the predictor palette table; and   perform the conversion based on the first prediction mode,   wherein in the first prediction mode, reconstructed samples of the current block are represented by a set of representative color values, and the set of representative color values comprises at least one of 1) palette predictors derived from the current palette, 2) escaped samples, or 3) palette information included in the bitstream, and   wherein a maximum number of entries in the current palette is restricted to m×8, and a maximum number of entries in the predictor palette table are restricted to n×8, and wherein m and n are positive integers.   
     
     
         9 . The apparatus of  claim 8 , wherein m or n is equal to 4 or 8. 
     
     
         10 . The apparatus of  claim 8 , wherein a syntax element indicating a parallel merge estimation level is included in the bitstream, and wherein the maximum value of the syntax element depends on a size of a coding tree unit (CTU). 
     
     
         11 . The apparatus of  claim 10 , wherein the maximum value of the syntax element is constrained to be smaller than the size of the CTU. 
     
     
         12 . The apparatus of  claim 10 , wherein the syntax element is coded by an exponential Golomb code. 
     
     
         13 . The apparatus of  claim 8 , wherein the conversion includes encoding the current block into the bitstream. 
     
     
         14 . The apparatus of  claim 8 , wherein the conversion includes decoding the current block from the bitstream. 
     
     
         15 . A non-transitory computer-readable storage medium storing instructions that cause a processor to:
 determine, for a conversion between a current block of a video and a bitstream of the video, that a first prediction mode is applied to the current block;   maintain a predictor palette table;   construct, in the first prediction mode, a current palette comprising one or more palette predictors for the current block based on the predictor palette table; and   perform the conversion based on the first prediction mode,   wherein in the first prediction mode, reconstructed samples of the current block are represented by a set of representative color values, and the set of representative color values comprises at least one of 1) palette predictors derived from the current palette, 2) escaped samples, or 3) palette information included in the bitstream, and   wherein a maximum number of entries in the current palette is restricted to m×8, and a maximum number of entries in the predictor palette table are restricted to n×8, and wherein m and n are positive integers.   
     
     
         16 . The non-transitory computer-readable storage medium of  claim 15 , wherein a syntax element indicating a parallel merge estimation level is included in the bitstream, and wherein the maximum value of the syntax element depends on a size of a coding tree unit (CTU). 
     
     
         17 . The non-transitory computer-readable storage medium of  claim 16 , wherein the maximum value of the syntax element is constrained to be smaller than the size of the CTU. 
     
     
         18 . The non-transitory computer-readable storage medium of  claim 16 , wherein the syntax element is coded by an exponential Golomb code. 
     
     
         19 . A non-transitory computer-readable recording medium storing a bitstream of a video which is generated by a method performed by a video processing apparatus, wherein the method comprises:
 determining that a first prediction mode is applied to a current block of a video;   maintaining a predictor palette table;   constructing, in the first prediction mode, a current palette comprising one or more palette predictors for the current block based on the predictor palette table; and   generating the bitstream based on the first prediction mode,   wherein in the first prediction mode, reconstructed samples of the current block are represented by a set of representative color values, and the set of representative color values comprises at least one of 1) palette predictors derived from the current palette, 2) escaped samples, or 3) palette information included in the bitstream, and   wherein a maximum number of entries in the current palette is restricted to m×8, and a maximum number of entries in the predictor palette table are restricted to n×8, and wherein m and n are positive integers.   
     
     
         20 . The non-transitory computer-readable recording medium of  claim 19 , wherein a syntax element indicating a parallel merge estimation level is included in the bitstream, and wherein the maximum value of the syntax element depends on a size of a coding tree unit (CTU),
 wherein the maximum value of the syntax element is constrained to be smaller than the size of the CTU.