Adaptive Motion Vector Resolutions in Raw Plenoptic Video Coding

This paper addresses the unique challenges of compressing raw plenoptic video, in which the inherent hexagonal micro-image layout and sparse distribution of motion vectors (MVs) often diminish the coding efficiency of conventional block-based motion compensation. To mitigate excessive overhead from motion vector difference (MVD) signaling, we use three specialized MV resolutions: a hexagonal-lattice (HL) alignment that matches the micro-image structure, an integer-pel resolution, and a quarter-pel resolution. We then develop a rate-distortion (RD)-optimized scheme that adaptively selects the most suitable MV resolution at the coding unit level. By integrating our approach into the Versatile Video Coding (VVC) framework, the proposed method reduces MVD bits significantly while preserving high prediction accuracy. Experiments using two comprehensive plenoptic camera datasets — lenslet 1.0 and lenslet 2.0 — demonstrate substantial gains over the VVC anchor, achieving average Bjontegaard–Delta rate savings of 5.90% and 1.80%, respectively. These results confirm that combining HL and conventional resolutions in an RD-optimized manner substantially enhances motion prediction efficiency for raw plenoptic video.