Merge Mode With Motion Vector Difference

This paper proposes a new motion vector expression method named merge mode with motion vector difference (MMVD) for future video coding standards. In the previous standards, two approaches arc typically used for motion vector representation. In the first one, the motion vector is derived from neighboring blocks and is directly used for motion compensation (merge mode in IIEVC), and in the other one, the motion vector is represented with motion vector predictor and a difference (adaptive motion vector prediction; AMVP in HEVC). The merge mode benefits by saving bits for representing motion information. The AMVP represents more accurate motion information but it needs to signal the motion difference information, which consumes additional bits. MMVD provides a compromised solution for the trade-off between motion vector accuracy and its overhead. MMVD can improve motion vector accuracy by introducing a simplified motion vector representation. The results show that the proposed method improves coding efficiency of VVC with an average of 0.51% in BD-rate saving.