File format signaling of error mitigation in sub-picture bitstream based viewport dependent video coding
A video coding mechanism for viewpoint dependent video coding is disclosed. The mechanism includes mapping a spherical video signal, stitched from multiple directional video signals, into a plurality of sub-picture video signals each containing a sequence of sub-pictures. The plurality of sub-picture video signals are encoded as a plurality of sub-picture bitstreams. The plurality of sub-picture bitstreams are composed into a plurality of sub-picture tracks to be compatible with a multi-bitstream merge function for reconstruction of the spherical video signal. A track level mergable indication is encoded within a track level box for the sub-picture tracks, which indicates the sub-picture tracks are compatible with the multi-bitstream merge function for reconstruction of the spherical video signal.
1. A method comprising:
encoding pictures in sub-picture bitstreams in tracks by:
ensuring no sample values outside a sub-picture are referenced for inter-prediction,
restricting motion vectors to point to full-sample locations inside the sub-picture and to fractional-sample locations that employ only full-sample locations inside the sub-picture for interpolation, and
restricting inter-prediction so motion vector candidates for temporal motion vector prediction are not derived from blocks outside the sub-picture; and
encoding a track level mergable indication to indicate that a sub-picture bitstream carried in a current sub-picture track cannot be merged with a sub-picture bitstream carried in another track belonging to a same track group to generate a single video bitstream without decoding mismatches caused by rewriting only header data of the sub-picture bitstreams.
2. The method of claim 1 , wherein the track level mergable indication is included in a Sub-Picture Region Box.
3. The method of claim 1 , wherein the track level mergable indication, when set, further indicates that wavefront parallel processing is disabled.
4. The method of claim 1 , wherein the track level mergable indication is encoded in a track header box in a track box for each track containing one of the sub-picture bitstreams.
5. The method of claim 1 , wherein the track level mergable indication is encoded in a track group box describing associations between sub-picture tracks including the sub-picture bitstreams.
6. The method of claim 1 , wherein the track level mergable indication is encoded in a media box describing track media information.
7. A video coding device comprising:
a processor configured to:
encode pictures in sub-picture bitstreams in tracks by:
ensuring no sample values outside a sub-picture are referenced for inter-prediction,
restricting motion vectors to point to full-sample locations inside the sub-picture and to fractional-sample locations that employ only full-sample locations inside the sub-picture for interpolation, and
restricting inter-prediction so motion vector candidates for temporal motion vector prediction are not derived from blocks outside the sub-picture; and
encode a track level mergable indication to indicate that a sub-picture bitstream carried in a current sub-picture track cannot be merged with a sub-picture bitstream carried in another track belonging to a same track group to generate a single video bitstream without decoding mismatches caused by rewriting only header data of the sub-picture bitstreams.
8. The video coding device of claim 7 , wherein the track level mergable indication is included in a Sub-Picture Region Box.
9. The video coding device of claim 7 , wherein the track level mergable indication, when set, further indicates that wavefront parallel processing is disabled.
10. The video coding device of claim 7 , wherein the track level mergable indication is encoded in a track header box in a track box for each track containing one of the sub-picture bitstreams.
11. The video coding device of claim 7 , wherein the track level mergable indication is encoded in a track group box describing associations between sub-picture tracks including the sub-picture bitstreams.
12. A non-transitory computer readable medium comprising a computer program product for use by a video coding device, the computer program product comprising computer executable instructions stored on the non-transitory computer readable medium such that when executed by a processor cause the video coding device to:
encode pictures in sub-picture bitstreams in tracks by:
ensuring no sample values outside a sub-picture are referenced for inter-prediction,
restricting motion vectors to point to full-sample locations inside the sub-picture and to fractional-sample locations that employ only full-sample locations inside the sub-picture for interpolation, and
restricting inter-prediction so motion vector candidates for temporal motion vector prediction are not derived from blocks outside the sub-picture; and
encode a track level mergable indication to indicate that a sub-picture bitstream carried in a current sub-picture track cannot be merged with a sub-picture bitstream carried in another track belonging to a same track group to generate a single video bitstream without decoding mismatches caused by rewriting only header data of the sub-picture bitstreams.
13. The non-transitory computer readable medium of claim 12 , wherein the track level mergable indication is included in a Sub-Picture Region Box.
14. The non-transitory computer readable medium of claim 12 , wherein the track level mergable indication, when set, further indicates that wavefront parallel processing is disabled.
15. The non-transitory computer readable medium of claim 12 , wherein the track level mergable indication is encoded in a track header box in a track box for each track containing one of the sub-picture bitstreams.
16. The non-transitory computer readable medium of claim 12 , wherein the track level mergable indication is encoded in a track group box describing associations between sub-picture tracks including the sub-picture bitstreams.