Weighted Pairwise MV Candidate Addition with Zero Motion Vector Reduction for Merge Candidate

In the Versatile Video Coding (VVC), the merge mode lets a decoder to derive a motion vector (MV) autonomously using the motion information of a selected previously inter-coded block. For this purpose, a merge candidate list is maintained by encoder and decoder by filling it up with various candidates. In this process, if the merge candidate list is not sufficiently full, zero motion vector is repetitively added as required, thus, the redundant zero MVs in the merge candidate list may limit diversity of the list, resulting in low coding efficiency. In this paper we propose a new method of adding up additional merge candidates based on pairwise average of merge candidates. The additional MVs replacing the redundant zero MVs are obtained by linearly combining the MVs of the first and second candidate in the merge candidate list. The proposed method attains coding gain of 0.01%, 0.04%, and 0.05% respectively of Y, Cb, and Cr channels against VTM-22.0. The result also shows that the candidate list is diversified more by the proposed method, which consequently increases the coding efficiency.