Method and system using overlapped search space for bi-predictive motion vector refinement

A method for determination of a motion vector for an image block, using a processing circuit, comprising:

• determining a (k+1)-th motion vector in a first reference picture as a refinement of a k-th motion vector in the first reference picture for the image block by template matching in a k-th search space including a first plurality of candidate motion vector positions;
• determining a (k+1)-th motion vector in a second reference picture according to the (k+1)-th motion vector in the first reference picture,
• determining, according to the (k+1)-th motion vector in the second reference picture, a (k+1)-th search space including a second plurality of candidate motion vector positions;
• and
• determining (k+2)-th motion vector in the second reference picture as a refinement of the (k+1)-th motion vector in the second reference picture for the image block by template matching in the (k+1)-th search space,
• wherein the k-th search space in the first reference picture and the (k+1)-th search space in the second reference picture overlap in one or more candidate motion vector positions and k being a non-zero integer.

A non-transitory computer-readable medium storing program code, which when executed on a processor performs a method for determination of a motion vector for an image block, the method comprising:

• determining a (k+1)-th motion vector in a first reference picture as a refinement of a k-th motion vector in the first reference picture for the image block by template matching in a k-th search space including a first plurality of candidate motion vector positions;
• determining a (k+1)-th motion vector in a second reference picture according to the (k+1)-th motion vector in the first reference picture,
• determining, according to the (k+1)-th motion vector in the second reference picture, a (k+1)-th search space including a second plurality of candidate motion vector positions;
• and
• determining (k+2)-th motion vector in the second reference picture as a refinement of the (k+1)-th motion vector in the second reference picture for the image block by template matching in the (k+1)-th search space,
• wherein the k-th search space in the first reference picture and the (k+1)-th search space in the second reference picture overlap in one or more candidate motion vector positions and k being a non-zero integer.