Co-projection-plane based 3-D padding for polyhedron projection for 360-degree video
This addresses quality degradation in 360-degree video compression for applications like VR, but it is incremental as it builds on existing polyhedron projection methods.
The paper tackled texture discontinuity near face boundaries in polyhedron projection for 360-degree video by proposing a co-projection-plane based 3-D padding method to ensure exact texture continuity during motion compensation, which significantly improved rate-distortion performance in High Efficiency Video Coding.
The polyhedron projection for 360-degree video is becoming more and more popular since it can lead to much less geometry distortion compared with the equirectangular projection. However, in the polyhedron projection, we can observe very obvious texture discontinuity in the area near the face boundary. Such a texture discontinuity may lead to serious quality degradation when motion compensation crosses the discontinuous face boundary. To solve this problem, in this paper, we first propose to fill the corresponding neighboring faces in the suitable positions as the extension of the current face to keep approximated texture continuity. Then a co-projection-plane based 3-D padding method is proposed to project the reference pixels in the neighboring face to the current face to guarantee exact texture continuity. Under the proposed scheme, the reference pixel is always projected to the same plane with the current pixel when performing motion compensation so that the texture discontinuity problem can be solved. The proposed scheme is implemented in the reference software of High Efficiency Video Coding. Compared with the existing method, the proposed algorithm can significantly improve the rate-distortion performance. The experimental results obviously demonstrate that the texture discontinuity in the face boundary can be well handled by the proposed algorithm.