JVET-S0211 AHG9: Extensibility for the number of virtual boundaries [M. Damghanian, M. Pettersson, R. Sjöberg, J. Enhorn, J. Ström, R. Yu, D. Liu (Ericsson)]
This contribution proposes to signal the number of virtual boundaries using ue(v) instead of the current signalling using u(2) for the four syntax elements sps_num_ver_virtual_boundaries, sps_num_hor_virtual_boundaries, ph_num_ver_virtual_boundaries and ph_num_hor_virtual_boundaries. The motivation for the proposed change was reported to be future extensibility. The value range of the four syntax elements are proposed to be kept as 0 to 3, inclusive, for version 1 of VVC.
The current “hard coding” of the constraint seemed only to try to prohibit violation, but forecloses future uses. It was commented that we generally do not use syntax solely to enforce constraints that could be violated in a reasonable future use.
AHG Recommendation (extensibility cleanup): Adopt (while retaining the current value range).