| CPC H04N 19/137 (2014.11) [H04N 19/176 (2014.11); H04N 19/186 (2014.11); H04N 19/189 (2014.11)] | 12 Claims |

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1. A video decoder for decoding a picture of a video, wherein the video decoder comprises:
an input interface configured to receive the encoded video signal; and
a data decoder configured to:
decode chroma format information, the chroma format information indicating that luma subblocks and chroma subblocks are sampled in a 4:2:0 format or a 4:2:2 format;
determine, based on the chroma format information, a sub-height parameter and a sub-width parameter;
determine a motion vector for the chroma subblock based on a first luma motion vector and a second luma motion vector, the first luma motion vector corresponding to a first luma subblock of a plurality of luma subblocks at a first position and the second luma motion vector corresponding to a second luma subblock of the plurality of luma subblocks at a second position, wherein:
the first position is represented by [(xSbIdx>>SubWidthC<<SubWidthC)] [(ySbIdx>>SubHeightC<<SubHeightC)] and
the second position is represented by (xSbIdx>>SubWidthC<<SubWidthC)+SubWidthC] [(ySbIdx>>SubHeightC<<SubHeightC)+SubHeightC], where
xSbIdx is an x-index of one of the plurality of luma subblocks,
ySbIdx is an y-index of one of the plurality of luma subblocks
SubWidthC is the sub-width parameter, and
SubHeightC is the sub-height parameter; and
reconstruct a portion of the picture based on the first luma motion vector, the second luma motion vector, and the motion vector for the chroma subblock.
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