Variable-Sized Tiling and Rate Allocation for 360° Video Streaming

In recent years, the quality of 360° video over bandwidth-constrained networks has received a lot of attention. To reduce the bandwidth cost, some tile-based 360° video streaming systems split video spatially into variable-sized coarse-grained tiles by grouping areas with the similar quality levels. However, these approaches do not minimize the number of tiles, resulting in considerable overhead in re-encoding the boundaries between small tiles. To improve the coding efficiency of 360° video, we propose a new video tiling scheme called TRAS, by using the convex decomposition of concave polygon. Meanwhile, to maximize user's quality of experience (QoE), we propose a greedy bitrate selection algorithm by considering the tile size and coding efficiency. The experiment results demonstrate that, compared with the state-of-the-art approaches, TRAS reduces the coding overhead by about 18% and significantly improves the video quality by about 5 dB.