JVET-R0154 AHG9/16: On sign data hiding for BDPCM blocks [S. Yoo, J. Choi, J. Lim, S. Kim (LGE)]
The current VVC draft specification could allow both the sign data hiding (SDH) and BDPCM to be enabled. However, the levels of the coefficients can be modified by BDPCM, and it can affect the SDH decision in the residual coding. This document proposes two control mechanisms to prevent the unintended usage of sign data hiding (SDH) when BDPCM is enabled and transform skip residual coding is disabled. Firstly, a flag to enable sign data hiding (sps_sign_data_hiding_enabled_flag) is not signalled when BDPCM is enabled. Secondly, sign data hiding is disabled in each residual coding block when corresponding block is BDPCM coded. Thirdly, sign data hiding is disabled in each residual coding block when corresponding block is transform skipped.
“Method 1” is a high-level change that does not allow enabling SDH in SPS when BDPCM is enabled. Alternatively, this could be done by bitstream constraint.
“Method 2” and “Method 3” are identical with M1 and M2 in JVET-R0116.
It is agreed that the combination of BDPCM and SDH is a somewhat useless combination. A block level change would be undesirable at this point of VVC development, and restricting it at a high level would be sufficient, also simplifying conformance testing.
The issue was resolved – see further notes under JVET-R0271.