Simplified entropy coding for sub-block based motion information list

Abstract

Devices, systems and methods for digital video coding, which include adaptive control point selection for affine coding, are described. An exemplary method for video processing includes selecting, for a conversion between a current block of a video and a bitstream representation of the video, a plurality of control points for the current block, the plurality of control points comprising at least one non-corner point of the current block, and each of the plurality of control points being representative of an affine motion of the current block; and performing, based on the plurality of control points, the conversion between the current block and the bitstream representation.

What is claimed is: 
     
         1 . A method of processing video data, comprising:
 determining, for a conversion between a current video block of a video and a bitstream of the video, that at least one of a plurality of bins used to code a merge index of a sub-block merge-based merge candidate list uses bypass coding, wherein the sub-block merge-based merge candidate list is constructed based on a sub-block temporal motion vector prediction (SbTMVP) candidate; and   performing the conversion based on the determining,   wherein the SbTMVP candidate is derived based on a temporal motion shift from a spatial neighboring block of the current video block, and wherein a reference picture related to the temporal motion shift is same as a collocated picture of the current video block;   wherein the sub-block merge-based merge candidate list is constructed further based on an inherited affine candidate, a constructed affine candidate, or a zero candidate;   wherein control point motion vectors of an inherited affine candidate is derived from control point motion vectors of a spatial neighboring block that is coded in affine mode;   wherein the temporal motion shift is used to locate at least one region in a picture different from a current picture comprising the current video block, and wherein a first bin of the plurality of bins is coded with at least one context, and wherein all other bins of the plurality of bins are bypass coded.   
     
     
         2 . The method of  claim 1 , wherein the at least one context consists of one context. 
     
     
         3 . The method of  claim 1 , wherein each of a first K bins of the plurality of bins is coded with at least one context, wherein all other bins of the plurality of bins are bypass coded, wherein K is a non-negative integer, wherein 0≤K≤maxSubMrgListLen−1, and wherein maxSubMrgListLen is a maximum length of the plurality of bins. 
     
     
         4 . The method of  claim 1 , wherein the control point motion vectors and motion vectors in inter perdition mode are all stored with 1/16-pel precision. 
     
     
         5 . The method of  claim 1 , wherein the conversion generates the current video block from the bitstream. 
     
     
         6 . The method of  claim 1 , wherein the conversion generates the bitstream from the current video block. 
     
     
         7 . 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 video block of a video and a bitstream of the video, that at least one of a plurality of bins used to code a merge index of a sub-block merge-based merge candidate list uses bypass coding, wherein the sub-block merge-based merge candidate list is constructed based on a sub-block temporal motion vector prediction (SbTMVP) candidate; and   perform the conversion based on the determination,   wherein the SbTMVP candidate is derived based on a temporal motion shift from a spatial neighboring block of the current video block, and wherein a reference picture related to the temporal motion shift is same as a collocated picture of the current video block;   wherein the sub-block merge-based merge candidate list is constructed further based on an inherited affine candidate, a constructed affine candidate, or a zero candidate;   wherein control point motion vectors of an inherited affine candidate is derived from control point motion vectors of a spatial neighboring block that is coded in affine mode;   wherein the temporal motion shift is used to locate at least one region in a picture different from a current picture comprising the current video block, and wherein a first bin of the plurality of bins is coded with at least one context, and wherein all other bins of the plurality of bins are bypass coded.   
     
     
         8 . The apparatus of  claim 7 , wherein the at least one context consists of one context. 
     
     
         9 . The apparatus of  claim 7 , wherein the control point motion vectors and motion vectors in inter perdition mode are all stored with 1/16-pel precision. 
     
     
         10 . The apparatus of  claim 7 , wherein the conversion generates the current video block from the bitstream. 
     
     
         11 . The apparatus of  claim 7 , wherein the conversion generates the bitstream from the current video block. 
     
     
         12 . A non-transitory computer-readable storage medium storing instruction that cause a processor to:
 determine, for a conversion between a current video block of a video and a bitstream of the video, that at least one of a plurality of bins used to code a merge index of a sub-block merge-based merge candidate list uses bypass coding, wherein the sub-block merge-based merge candidate list is constructed based on a sub-block temporal motion vector prediction (SbTMVP) candidate; and   perform the conversion based on the determination,   wherein the SbTMVP candidate is derived based on a temporal motion shift from a spatial neighboring block of the current video block, and wherein a reference picture related to the temporal motion shift is same as a collocated picture of the current video block;   wherein the sub-block merge-based merge candidate list is constructed further based on an inherited affine candidate, a constructed affine candidate, or a zero candidate;   wherein control point motion vectors of an inherited affine candidate is derived from control point motion vectors of a spatial neighboring block that is coded in affine mode;   wherein the temporal motion shift is used to locate at least one region in a picture different from a current picture comprising the current video block, and wherein a first bin of the plurality of bins is coded with at least one context, and wherein all other bins of the plurality of bins are bypass coded.   
     
     
         13 . The non-transitory computer-readable storage medium of  claim 12 , wherein the at least one context consists of one context. 
     
     
         14 . The non-transitory computer-readable storage medium of  claim 12 , wherein each of a first K bins of the plurality of bins is coded with at least one context, wherein all other bins of the plurality of bins are bypass coded, wherein K is a non-negative integer, wherein 0≤K≤maxSubMrgListLen−1, and wherein maxSubMrgListLen is a maximum length of the plurality of bins. 
     
     
         15 . The non-transitory computer-readable storage medium of  claim 12 , wherein the control point motion vectors and motion vectors in inter perdition mode are all stored with 1/16-pel precision. 
     
     
         16 . The non-transitory computer-readable storage medium of  claim 12 , wherein the conversion generates the current video block from the bitstream. 
     
     
         17 . The non-transitory computer-readable storage medium of  claim 12 , wherein the conversion generates the bitstream from the current video block. 
     
     
         18 . 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 at least one of a plurality of bins used to code a merge index of a sub-block merge-based merge candidate list uses bypass coding, wherein the sub-block merge-based merge candidate list is constructed based on a sub-block temporal motion vector prediction (SbTMVP) candidate; and   generating the bitstream based on the determining,   wherein the SbTMVP candidate is derived based on a temporal motion shift from a spatial neighboring block of a current video block of the video and wherein a reference picture related to the temporal motion shift is same as a collocated picture of the current video block;   wherein the sub-block merge-based merge candidate list is constructed further based on an inherited affine candidate, a constructed affine candidate, or a zero candidate;   wherein control point motion vectors of an inherited affine candidate is derived from control point motion vectors of a spatial neighboring block that is coded in affine mode;   wherein the temporal motion shift is used to locate at least one region in a picture different from a current picture comprising the current video block, and wherein a first bin of the plurality of bins is coded with at least one context, and wherein all other bins of the plurality of bins are bypass coded.   
     
     
         19 . The non-transitory computer-readable recording medium of  claim 18 , wherein the at least one context consists of one context. 
     
     
         20 . The non-transitory computer-readable recording medium of  claim 18 , wherein the control point motion vectors and motion vectors in inter perdition mode are all stored with 1/16-pel precision.