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AhG 9: On APS and GDR constraint Flags
Abstract
The VVC draft 8 specification provides several constraint flags that can be used to define profiles where certain coding tools are deactivated. Among these flags, no_aps_constraint_flag and no_gdr_constraint_flag are flags that restrict the usage of NAL unit types. It is asserted that the coding tools employing APS (ALF, LMCS and Scaling List) as well as GDR can be still be activated although there is no support for these NAL unit types. This creates inconsistency in the HLS of VVC, where a certain tool can be activated but never used. This contribution proposes disabling APS-related tools and GDR when their constraint flag is set to one.
JVET-R0178 AHG9: On APS and GDR constraint Flags [K. Naser, F. Le Léannec, T. Poirier, P. de Lagrange (InterDigital)]
See also 6.1.6.1 regarding GDR.
We currently have a flag no_aps_constraint_flag. It is proposed to add a constraint stating that when this flag is 1, sps_alf_enabled_flag, sps_lmcs_enabled_flag and sps_scaling_list_enabled_flag shall be equal to 0.
It was commented that ALF can be used without any APS, so it was agreed not to apply this part of the constraint.
Decision (sensibility constraint): Require that when no_aps_constraint_flag is equal to 1, sps_lmcs_enabled_flag and sps_scaling_list_enabled_flag shall be equal to 0.
References:
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Decisions
Decision (sensibility constraint): Require that when no_aps_constraint_flag is equal to 1, sps_lmcs_enabled_flag and sps_scaling_list_enabled_flag shall be equal to 0.
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