JVET-Q0400 AHG9: On extra picture header bits in VVC [K. Sühring, R. Skupin, Y. Sanchez, T. Schierl (HHI)]
This contribution proposes to add reserved extra bits to the picture header similar to extra slice header bits in HEVC. The proposal, however, differs from the HEVC design in that the presence of the flags in the picture header is controlled by the sequence parameter set.
Revision 1 of this document reflects track review of this contribution by adding syntax for slice header integration of the proposed extra bits mechanism. The number of flags to be added to the picture header is also reduced. It is also proposed to make signalling of non_reference_picture_flag in picture headers optional.
This was further discussed on Thursday 16 January in Track A at 1120 (chaired by GJS).
We also have an ability to put extension data at the end of SHs and PHs. The proposal would add a way to put such data earlier, so that they are more accessible to system-level scanning. There is something roughly like this for SHs in HEVC (num_extra_slice_header_bits sent in the PPS).
Decision (extensibility cleanup): Adopt. Code the number of “extra_bits_bytes” as u(2) and constrain it to 0..2. In the PH, these go right after the POC recovery point count. In the SH, these go right after the slice address. Encoders are required to set the count to zero; decoders are required to ignore the extra bits.
No action was taken on the proposal aspect of making the non-ref pic flag use this mechanism.