US 11,924,457 B2
Method and apparatus for affine based inter prediction of chroma subblocks
Vasily Alexeevich Rufitskiy, Moscow (RU); Timofey Mikhailovich Solovyev, Moscow (RU); Alexey Konstantinovich Filippov, Moscow (RU); and Jianle Chen, San Diego, CA (US)
Assigned to HUAWEI TECHNOLOGIES CO., LTD., Shenzhen (CN)
Filed by HUAWEI TECHNOLOGIES CO., LTD., Guangdong (CN)
Filed on Aug. 20, 2021, as Appl. No. 17/407,548.
Application 17/407,548 is a continuation of application No. PCT/CN2020/076493, filed on Feb. 24, 2020.
Claims priority of provisional application 62/824,302, filed on Mar. 26, 2019.
Claims priority of provisional application 62/823,653, filed on Mar. 25, 2019.
Claims priority of provisional application 62/809,551, filed on Feb. 22, 2019.
Prior Publication US 2021/0409753 A1, Dec. 30, 2021
Int. Cl. H04N 19/513 (2014.01); H04N 19/159 (2014.01); H04N 19/176 (2014.01); H04N 19/186 (2014.01); H04N 19/30 (2014.01)
CPC H04N 19/513 (2014.11) [H04N 19/159 (2014.11); H04N 19/176 (2014.11); H04N 19/186 (2014.11); H04N 19/30 (2014.11)] 24 Claims
OG exemplary drawing
 
1. A method of chroma motion vector derivation used in an affine based inter prediction of a current image block including a luma block and a co-located chroma block, comprising:
determining chroma scaling factors in horizontal and vertical directions respectively based on chroma format information, wherein the chroma format information indicates a chroma format of a current picture which the current image block belongs to;
determining a set (S) of luma subblocks of the luma block based on values of the chroma scaling factors; and
determining a chroma motion vector for a respective chroma subblock of chroma subblocks in the chroma block based on motion vectors of one or more luma subblocks in the set (S) of luma subblocks,
wherein, when both SubWidthC and SubHeightC are equal to 1, the set (S) of luma subblocks comprises a luma subblock indexed by
S0=(xSbIdx,ySbIdx);
when at least one of SubWidthC and SubHeightC is not equal to 1, the set (S) of luma subblocks comprises: a first luma subblock indexed by
S0=((xSbIdx>>(SubWidthC−1)<<(SubWidthC−1)),(ySbIdx>>(SubHeightC−1)<<(SubHeightC−1))), and a second luma subblock indexed by
S1=((xSbIdx>>(SubWidthC−1)<<(SubWidthC−1))+(SubWidthC−1),(ySbIdx>>(SubHeightC−1)<<(SubHeightC−1))+(SubHeightC−1))
wherein SubWidthC and SubHeightC represent the chroma scaling factors in the horizontal and vertical directions, respectively;
xSbIdx and ySbIdx represent a subblock index in the horizontal direction and a subblock index in the vertical direction, respectively, for a luma subblock in the set (S);
“<<” represents a left arithmetic shift;
“>>” represents a right arithmetic shift;
xSbIdx is an integer number ranging from 0 to numSbX−1 and ySbIdx is an integer ranging from 0 to numSbY−1;
numSbX indicates the number of luma subblocks in the luma block along the horizontal direction; and
numSbY indicates the number of luma subblocks in the luma block along the vertical direction.