US Patent 11310526 Hardware friendly constrained motion vector refinement

A video codec that encodes or decodes video sequences using decoder-side motion vector refinement is provided. The video codec identifies a first motion vector and a second motion vector for coding a current block of pixels of a current video frame in the video sequence. The video codec determines whether to perform motion vector refinement for the current block of pixels based on a comparison between a linear dimension of the current block of pixels and a threshold. When motion vector refinement is performed, the video codec refines the first and second motion vectors to minimize a distortion cost and codes the current block of pixels by using the refined first and second motion vectors. When motion vector refinement is not performed, the video codec codes the current block of pixels by using the identified first and second motion vectors.