Projection based advanced motion model for cubic mapping for 360-degree video
This addresses motion handling for 360-degree video compression, but it is incremental as it builds on existing projection methods.
The paper tackled irregular motion in 360-degree video by projecting pixels from cube maps back to a sphere to exploit uniform motion, resulting in performance improvements for sequences with obvious motions as implemented in High Efficiency Video Coding.
This paper proposes a novel advanced motion model to handle the irregular motion for the cubic map projection of 360-degree video. Since the irregular motion is mainly caused by the projection from the sphere to the cube map, we first try to project the pixels in both the current picture and reference picture from unfolding cube back to the sphere. Then through utilizing the characteristic that most of the motions in the sphere are uniform, we can derive the relationship between the motion vectors of various pixels in the unfold cube. The proposed advanced motion model is implemented in the High Efficiency Video Coding reference software. Experimental results demonstrate that quite obvious performance improvement can be achieved for the sequences with obvious motions.