Method and Apparatus of Motion Refinement for Video Coding

An apparatus of video coding using Pattern-based MV derivation (PMVD), Bi-directional optical flow (BIO) or Decoder-side MV refinement (DMVR) to refine motion for a bi-direction predicted block, the apparatus of video coding comprising one or more electronic circuits or processors arranged to:

• receive input data associated with a current block in a current picture, wherein the current block is coded using bi-direction prediction;
• determine a first motion-compensated reference block associated with the current block in a first reference picture from reference picture list 0, wherein the first motion-compensated reference block includes additional surrounding first pixels around a corresponding block of the current block in the first reference picture for performing interpolation filter required for any fractional motion vector of the current block;
• determine a second motion-compensated reference block associated with the current block in a second reference picture from reference picture list 1, wherein the second motion-compensated reference block includes additional surrounding second pixels around the corresponding block of the current block in the second reference picture for performing interpolation filter required for any fractional motion vector of the current block;
• apply PMVD process, BIO process or DMVR process to generate motion refinement for the current block using reference data corresponding to the first motion-compensated reference block and the second motion-compensated reference block without other reference data outside the first motion-compensated reference block and the second motion-compensated reference block;
• and
• encode or decode the current block based on motion-compensated prediction according to the motion refinement.

A non-transitory computer readable medium storing program instructions causing a processing circuit of an apparatus to perform a video coding method, and the method comprising:

• receiving input data associated with a current block in a current picture, wherein the current block is coded using bi-direction prediction;
• determining a first motion-compensated reference block associated with the current block in a first reference picture from reference picture list 0, wherein the first motion-compensated reference block includes additional surrounding first pixels around a corresponding block of the current block in the first reference picture for performing interpolation filter required for any fractional motion vector of the current block;
• determining a second motion-compensated reference block associated with the current block in a second reference picture from reference picture list 1, wherein the second motion-compensated reference block includes additional surrounding second pixels around the corresponding block of the current block in the second reference picture for performing interpolation filter required for any fractional motion vector of the current block;
• applying PMVD process, BIO process or DMVR process to generate motion refinement for the current block using reference data corresponding to the first motion-compensated reference block and the second motion-compensated reference block without other reference data outside the first motion-compensated reference block and the second motion-compensated reference block;
• and
• encoding or decoding the current block based on motion-compensated prediction according to the motion refinement.