JVET-R0173 AHG9: Cleanup of Constraint Flags [K. Naser, F. Le Léannec, M. Kerdranvat, P. de Lagrange (InterDigital)]
The draft VVC specification provides several constraint flags to profiles where certain coding tools are activated/deactivated. It is asserted that several redundant constraint flags are signalled when either monochrome coding or intra-only profiles are used. This contribution proposes cleaning up the constraint flags such that redundant coding of constraint flags is removed.
Proposals 1 and 2 are alternative ways of introducing various conditioning of the constraints on monochrome and intra. The same sort of conditioning is proposed in JVET-R0286 aspect 1. Currently the general constraint flags are never conditioned on anything and they are placed at a fixed position, so they can be easily extracted and carried at a system level in a fixed-length code. to stay consistent with that design philosophy, no action was taken on this.
Proposal 3 changes the semantics of the intra_only_constraint_flag to apply to ph_inter_slice_allowed_flag rather than slice_type. It was commented that this would impose a tighter constraint than currently specified and said that the current expression is more desirable, so no action was taken on this.