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JVET-D0071 AHG8: Truncated Square Pyramid Projection (TSP) For 360 Video [G. Van der Auwera, M. Coban, Hendry, M. Karczewicz (Qualcomm)]
This contribution presents a truncated square pyramid (TSP) projection scheme for VR/360 video. The implementation of the TSP projection, which has been integrated in the ‘360tools’ software, is described. Encoding results are reported comparing TSP projection, equirectangular (ERP) and downsampled cube map projection (DCP). The results reportedly suggest that: (1) TSP gives BD-rate savings over ERP for S-PSNR window sizes up to approx. 170°; (2) TSP provides coding gains of approximately 10% over the DCP projection.
An adaptive viewport streaming use case can be considered, with time aligned random access pictures (with 1 sec period). This can assume 30 viewports.
Coding efficiency depends upon the amount of head motion allowed until the next random access point period, for viewpoint switching.
A question was raised about the comparison with a scalable coding approach. An adaptive viewpoint puts a bigger burden on the server to store many viewpoint versions, but may save bitrate vs. scalable coding.