Adaptive bilateral matching for decoder side motion vector refinement

An apparatus for processing video data, comprising:

• at least one memory;
• and
• at least one processor coupled to the at least one memory, the at least one processor configured to:
• obtain one or more reference pictures for a current picture;
• identify a first motion vector and a second motion vector for a merge mode candidate;
• determine a selected motion vector search strategy for the merge mode candidate from a plurality of motion vector search strategies, wherein the selected motion vector search strategy is associated with one or more constraints based on at least one of the first motion vector or the second motion vector, wherein the one or more constraints are associated with at least one of a first motion vector difference associated with the first motion vector or a second motion vector difference associated with the second motion vector, and wherein the one or more constraints include a zero value constraint for at least one of the first motion vector difference or the second motion vector difference;
• determine, using the selected motion vector search strategy, one or more refined motion vectors based on at least one of the first motion vector or the second motion vector and the one or more reference pictures wherein, to determine the one or more refined motion vectors and based on the zero value constraint, the at least one processor is further configured to maintain a first one of the first motion vector difference or the second motion vector difference as a fixed value and search relative to a second one of the first motion vector difference or the second motion vector difference;
• and
• process the merge mode candidate using the one or more refined motion vectors.