Template matching based motion vector refinement in video coding system

Abstract

A video encoder or a video decoder may perform operations to determine an initial motion vector (MV) such as a control point motion vector (CPMV) candidate according to an affine mode or an additional prediction signal representing an additional hypothesis motion vector, for a current sub-block in a current frame of a video stream; determine a current template associated with the current sub-block in the current frame; retrieve a reference template within a search area in a reference frame; and compute a difference between the reference template and the current template based on an optimization measurement. Additional operations performed may include iterating the retrieving and the computing the difference for a different reference template within the search area until a refinement MV, such as a refined CPMV or refined additional hypothesis motion vector, is found to minimize the difference according to the optimization measurement.

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