Abstract not available in document
JVET-L0449 On Picture Order Count Signalling for VVC [S. Deshpande, B. Choi (Sharp)] [late]
This was discussed Wed 10 Oct. 1630 Track B
Picture order count signalling and decoding is proposed for VVC. In r1 of the proposal, some modifications are made to the signalling and constraints.
- It was proposed that the design should allow signalling of POC least-significant bit (LSB) values for all picture types. The lack of this was asserted to have caused problems for HEVC when it scalability extensions were created.
There was discussion of what the POC means (if anything) for an IDR picture in single-layer operation. The presence of an IDR picture would set the MSBs to zero and there would be no relationship between the POC values of different coded video sequences. The lack of MSBs had caused substantial difficulty in the layered coding (SHVC, MV-HEVC) design.
It was commented that this could also be helpful for alignment of multiple sub-bitstreams.
It was commented that various other work has used layering concepts even outside of ordinary scalability scenarios (3DOF+, 6DOF).
It was commented that the reference encoder relies on the POC of an IDR picture being zero. Software had not been provided.
It was commented that sending POC MSBs could make bitstream editing easier by allowing a picture to be converted from a non-IDR picture to an IDR picture without changing how the prediction of other pictures would operate.
See also JVET-L0064, which uses a definition of IRAP that needs POC on the the IRAP.
Decision: Adopted. The MSBs will still reset to zero at an IRAP and there will be no relation between POCs of different CVSs. (Currently the text does not have a non-IDR IRAP.) However, the software will need changes for this. For now, we can just have the encoder use 0 for the IDRs, but we need to put support for this into the software eventually. The contributor volunteered to work on that.
- It was proposed to have a variation in which there are no MSBs needed (due to a promise that there will be no wrapping).
- It was proposed to add syntax in the SPS to optionally enable a signalling of MSBs (and having a variable number of MSBs), and be able to signal the MSBs or not on a lower level basis.
No immediate action was taken on the 2nd and 3rd aspects; further study was encouraged.