JVET-O0159 Non-CE5: Deblocking tC table defined for 10-bit video [K. Andersson, J. Enhorn]
VTM-5.0 uses a tC table defined for 8-bit video which then is upscaled to the bit-depth a video is encoded at.
This contribution proposes to instead define the tC table for 10-bit video to get a better linear dependency between quantization step size and tC for 10-bit video and higher.
BDR results of 0.07%/-0.03%/-0.09%/-0.07% for AI/RA/LDB/LDP with ALF on and 0.06%/-0.03%/-0.04%/-0.04% for AI/RA/LDB/LDP with ALF off are reported.
Encoding time and decoding time unchanged
Currently, the 8-bit tc table is upscaled from 8 bit. The proposal suggests to define a new more granular tc table for 10 bit and downscale it for the case of 8 bit, and upscale for higher bit depth. However, with the current proposal the table for 8 bit becomes slightly different.
Generally agreed that the motivation of redefining the table for 10 bit is a resonable move, as 8 bit video has become less relevant.
The proponents are asked to modify the entries of the 10-bit table such that the downscaling operation would exactly reproduce the current 8 bit table.
Decision: Adopt JVET-O0159 with the modification in the entries of the 10-bit table such that the downscaling operation would exactly reproduce the current 8 bit table.