Alignment of sps_independent_subpics_flag with the decision from the meeting notes

[mdamghanian]

The current semantics for sps_independent_subpics_flag is not seemingly aligned with the decision from the meeting notes. Current semantics (in Q2001-vD) and the meeting notes are shown in the following. For the alignment we suggest the following semantics:

sps_independent_subpics_flag equal to 1 specifies that all subpicture boundaries in the CLVS are treated as picture boundaries and there is no loop filtering across the subpicture boundaries. sps_independent_subpics_flag equal to 0 does not impose such a constraint. When not present, the value of sps_independent_subpics_flag is inferred to be equal to 0.

Current semantics:
sps_independent_subpics_flag equal to 1 specifies that no intra prediction, no inter prediction and no in-loop filtering operations may be performed across any subpicture boundary in the CLVS. sps_independent_subpics_flag equal to 0 specifies that inter prediction or in-loop filtering operations across the subpicture boundaries in the CLVS may be allowed. When not present, the value of sps_independent_subpics_flag is inferred to be equal to 0.

Meeting notes:
JVET-Q0271
To add a syntax element sps_independent_subpics_flag in the SPS. When equal to 1 it specifies that all subpicture boundaries in the CLVS are treated as picture boundaries and there is no loop filtering across the subpicture boundaries. subpic_treated_as_pic_flag[ i ] and loop_filter_across_subpic_enabled_flag[ i ] are signalled only when sps_independent_subpics_flag is equal to 0.

[yk]

Thanks! The suggested semantics is way better. I don't how the text in the draft ended as currently; probably the editing team overlook the exact meeting minutes but took what was in the proposal. Anyway, I will fix this when I take the token next time.

[yk]

Fixed in Q2001-vE.