JVET-Q0342 AHG9: on signalling inter-layer dependency information in SPS [B. Wang, S. Esenlik, A. M. Kotra, H. Gao, E. Alshina (Huawei)]
This contribution was discussed Saturday 11 January at 2040 in Track A (chaired by GJS).
It is asserted that the current semantics of inter_layer_ref_pics_present_flag is not sufficient to address a situation when a sequence parameter set (SPS) is shared by multiple video coding layers wherein some of the shared layers are independent while the others have dependent layers. In such a case, the value of inter_layer_ref_pics_present_flag shall be 1 for the dependent shared layers but at the same time shall be 0 for independent shared layer. This contribution proposes two alternative solutions to this issue.
The current text prohibits sharing in some cases. An SPS cannot be shared by a dependent layer and an independent layer.
The proposed approach #1 seemed awkward, as it would add a multilayer loop in the SPS. The proposed approach #2 would disallow sharing. The current approach seems acceptable, so no action seemed necessary. Further study was encouraged.
Decision (Ed.): The name and phrasing of the semantics of inter_layer_ref_pics_present_flag should be editorially reviewed.