US Patent 11343529 Calculation of predication refinement based on optical flow

A method of video processing includes determining a first motion displacement Vx(x,y) at a position (x,y) and a second motion displacement Vy(x,y) at the position (x,y) in a video block coded using an optical flow based method, wherein x and y are fractional numbers, where Vx(x,y) and Vy(x,y) are determined based at least on the position (x,y) and a center position of a basic video block of the video block, and performing a conversion between the video block and a bitstream representation of the current video block using the first motion displacement and the second motion displacement.