Co-projection-plane based 3-D padding for polyhedron projection for 360-degree video

TL;DR

This paper introduces a co-projection-plane based 3-D padding method for polyhedron projection in 360-degree video, effectively reducing texture discontinuities at face boundaries and improving coding performance.

Contribution

It proposes a novel 3-D padding technique that projects reference pixels onto the same plane to ensure texture continuity across face boundaries in polyhedron projections.

Findings

Significant improvement in rate-distortion performance.

Effective reduction of texture discontinuity at face boundaries.

Validated through implementation in HEVC reference software.

Abstract

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.