JVET-B0054 De-quantization and scaling for next generation containers [J. Zhao, A. Segall, S.-H. Kim, K. Misra (Sharp)] [late]
Chaired by J. Boyce.
This contribution proposes a change in the de-quantization and scaling process in JEM 1.0. For background, the change was said to be motivated by recent work in MPEG, where it has been shown that next generation "containers", such as ST-2084, re-shape quantization noise as a function of brightness. For current standards, this requires encoders to compensate by spatially varying the QP in an inverse manner. Here, it is proposed that a next-generation standards decoder could infer the needed compensation without significant QP signalling. This is accomplished by adapting the scaling of AC coefficients based on the DC coefficient and reconstructed prediction mean. Experiments performed using sequences under study in MPEG (and now JCT-VC) reportedly show a gain of 2.0% for both AI and RA configuration when the QP granularity is 16x16.
As proposed, the decoder infers a QP adjustment based on average luma values. Delta QP can also be signalled.
A LUT is signalled on a per-sequence basis. It was suggested that we would want to give encoder the ability to disable the feature.
Only AC coefficients are affected, and not the DC coefficients.
The proponent suggested that SDR content may also use the ST-2084 container, especially for services with a mix of SDR and HDR content.
Decision (SW): Make SW available in experimental SVN branch of JEM software. Include in the EE document for testing. Also include the luma QP adjustment encoder functionality.