JVET-E0075 AHG8: Spherical rotation orientation SEI for coding of 360° video [J. Boyce, Q. Xu (Intel)]

It was proposed to indicate spherical rotation orientation of 360 degree video, in an SEI message or in the PPS. An SEI message for HEVC and AVC is also proposed in JCTVC-Z0025. As proposed, an encoder may perform spherical rotation of the input video prior to encoding, using up to 3 parameters (yaw, pitch, roll), in order to improve coding efficiency. The decoder can use the SEI message or PPS contents to perform the recommended inverse spherical rotation after decoding, before display. Up to 17.8% bit-rate gain (using the WS-PSNR end-to-end metric) is reported for sequences for HM16.14 in the JVET 360° video test conditions, and up to 12.3% for JEM4.1. The average for the entire test set is reportedly 2.9% for HM16.14 and 2.3% for JEM4.1, and many of the sequences reportedly do not benefit from the spherical rotation. The proposed syntax is independent of the particular projection format used, but the recommended spherical rotation operation relies on having knowledge of the projection format.

In v2, some encoding preprocessing runtime data is provided.

Gains are smaller with JEM than with HEVC

No action was taken currently. It would be premature to modify JEM HL syntax on 360° video; an HEVC SEI message could be used when it is defined. Current 360° experiments can be run out-of-loop.

Software is included in the JCT-VC contribution.