Syntax reuse for affine mode with adaptive motion vector resolution

Abstract

A method for video processing is disclosed to include: determining, for a conversion between a coded representation of a current block of a video and the current block, a motion vector difference (MVD) precision to be used for the conversion from a set of allowed multiple MVD precisions applicable to a video region containing the current video block; and performing the conversion based on the MVD precision.

What is claimed is: 
     
         1 . A method of processing video data, the method comprising:
 determining that a coding mode for a first video block is an affine inter mode;
 determining, for motion information of the first video block, a motion precision from a motion precision set including multiple motion precisions; and 
 coding the first video block based on the determined coding mode and the determined motion precision; 
 wherein multiple syntax elements are selectively present in a video bitstream to indicate the motion precision in the motion precision set, 
 wherein the multiple syntax elements include a first syntax element and a second syntax element, 
 wherein the second syntax element is present in the video bitstream in case that the first syntax element is present in the video bitstream with a specific value, and 
 wherein the motion precision is related to one or more syntax elements of the multiple syntax elements being present in the video bitstream, 
 wherein semantics of at least one syntax element of the multiple syntax elements are different in a non-affine inter mode and in the affine inter mode, 
 wherein whether the first syntax element for the first video block is present in the video bitstream based on at least one of: 1) whether selection from multiple motion vector difference (MVD) precisions for affine inter coded blocks is enabled or disabled; or 2) MVDs of control point motion vectors of the first video block. 
   
     
     
         2 . The method of  claim 1 , wherein the coding includes encoding the first video block into the video bitstream. 
     
     
         3 . The method of  claim 1 , wherein the coding includes decoding the first video block from a video bitstream. 
     
     
         4 . The method of  claim 1 , wherein the first syntax element is not present in the video bitstream based on the at least one condition being satisfied:
 motion vector differences (MVDs) of all control point motion vectors of the first video block being zero;   multiple MVD precisions for affine inter coded blocks being disabled.   
     
     
         5 . The method of  claim 1 , wherein the first syntax element is present in the video bitstream based on the at least one condition being satisfied:
 multiple MVD precisions for affine inter coded blocks being enabled;
 the coding mode for the first block being determined as the affine inter mode; 
 at least one motion vector difference of at least one control point motion vectors of the first video block being non-zero. 
   
     
     
         6 . The method of  claim 1 , wherein the motion vector differences (MVDs) of control point motion vectors of the first video block comprises an MVD in each valid prediction direction for each control point motion vector, wherein when both the horizontal component and the vertical component of the MVD are zero, the MVD is a zero MVD. 
     
     
         7 . The method of  claim 1 , wherein the motion precision for the first block is a first motion precision which is a default precision, in respond to the first syntax element being not present in the video bitstream or the first syntax element being equal to zero. 
     
     
         8 . The method of  claim 7 , wherein the first motion precision is ¼ luma sample. 
     
     
         9 . The method of  claim 1 , wherein the second syntax element is present in the video bitstream based on the at least one condition being satisfied:
 the first syntax element being equal to non-zero;   the coding mode of the first video block being the affine inter mode.   
     
     
         10 . The method of  claim 1 , wherein the second syntax element is equal to zero corresponding to the motion precision being 1/16 luma sample, and is equal to non-zero corresponding to the motion precision being integer luma sample. 
     
     
         11 . The method of  claim 1 , wherein a same value of the second syntax element indicates different motion precisions for blocks coded with the affine inter mode and for blocks coded with a normal inter mode. 
     
     
         12 . The method of  claim 1 , wherein the second syntax element is selectively present in a video bitstream to indicate a motion precision in a motion precision set for a block coded with an intra block copy mode, wherein the first syntax element is skipped for the block coded with the intra block copy mode. 
     
     
         13 . The method of  claim 1 , wherein the first syntax element is coded using context-based coding that includes a use of at least one context model and at least one context, wherein at least one same context model is used for the first syntax element of both blocks coded with the affine inter mode and blocks coded with the normal inter mode, and selection of context is dependent on whether the coding mode of the block is the affine inter mode or normal inter mode. 
     
     
         14 . The method of  claim 1 , wherein the second syntax element is coded using context-based coding that includes a use of at least one context model and at least one context, wherein at least one same context model and at least one same context are used for the second syntax element of both blocks coded with the affine inter mode and blocks coded with the normal inter mode. 
     
     
         15 . The method of  claim 1 , wherein the motion information comprises at least one of a motion vector difference (MVD), motion vector predictor (MVP) and motion vector (MV). 
     
     
         16 . A video processing apparatus comprising a processor and a non-transitory memory with instructions thereon, wherein the instructions upon execution by the processor, cause the processor to:
 determine that a coding mode for a first video block is an affine inter mode;
 determine, for motion information of the first video block, a motion precision from a motion precision set including multiple motion precisions; and 
 code the first video block based on the determined coding mode and the determined motion precision; 
 wherein multiple syntax elements are selectively present in a video bitstream to indicate the motion precision in the motion precision set, 
 wherein the multiple syntax elements include a first syntax element and a second syntax element, 
 wherein the second syntax element is present in the video bitstream in case that the first syntax element is present in the video bitstream with a specific value, and 
 wherein the motion precision is related to one or more syntax elements of the multiple syntax elements being present in the video bitstream, 
 wherein semantics of at least one syntax element of the multiple syntax elements are different in a non-affine inter mode and in the affine inter mode, 
 wherein whether the first syntax element for the first video block is present in the video bitstream based on at least one of: 1) whether selection from multiple motion vector difference (MVD) precisions for affine inter coded blocks is enabled or disabled; or 2) MVDs of control point motion vectors of the first video block. 
   
     
     
         17 . A non-transitory computer-readable storage medium storing instructions that cause a processor to:
 determine that a coding mode for a first video block is an affine inter mode;
 determine, for motion information of the first video block, a motion precision from a motion precision set including multiple motion precisions; and 
 code the first video block based on the determined coding mode and the determined motion precision; 
 wherein multiple syntax elements are selectively present in a video bitstream to indicate the motion precision in the motion precision set, 
 wherein the multiple syntax elements include a first syntax element and a second syntax element, 
 wherein the second syntax element is present in the video bitstream in case that the first syntax element is present in the video bitstream with a specific value, and 
 wherein the motion precision is related to one or more syntax elements of the multiple syntax elements being present in the video bitstream, 
 wherein semantics of at least one syntax element of the multiple syntax elements are different in a non-affine inter mode and in the affine inter mode, 
 wherein whether the first syntax element for the first video block is present in the video bitstream based on at least one of: 1) whether selection from multiple MVD precisions for affine inter coded blocks is enabled or disabled; 2) motion vector differences (MVDs) of control point motion vectors of the first video block. 
   
     
     
         18 . A non-transitory computer-readable recording medium storing a video bitstream which is generated by a method performed by a video processing apparatus, wherein the method comprises:
 determining that a coding mode for a first video block is an affine inter mode;
 determining, for motion information of the first video block, a motion precision from a motion precision set including multiple motion precisions; and 
 encoding the first video block into the video bitstream based on the determined coding mode and the determined motion precision; 
 wherein multiple syntax elements are selectively present in the video bitstream to indicate the motion precision in the motion precision set, 
 wherein the multiple syntax elements include a first syntax element and a second syntax element, 
 wherein the second syntax element is present in the video bitstream in case that the first syntax element is present in the video bitstream with a specific value, and 
 wherein the motion precision is related to one or more syntax elements of the multiple syntax elements being present in the video bitstream, 
 wherein semantics of at least one syntax element of the multiple syntax elements are different in a non-affine inter mode and in the affine inter mode, 
 wherein whether the first syntax element for the first video block is present in the video bitstream based on at least one of: 1) whether selection from multiple motion vector difference (MVD) precisions for affine inter coded blocks is enabled or disabled; or 2) MVDs of control point motion vectors of the first video block.