JVET-R0140 AHG14: Max BT/TT size restriction for lossless coding encoder configuration [T. Zhou, E. Sasaki, T. Ikai (Sharp)]
This contribution proposes a max BT/TT size restriction for lossless coding encoder configuration, which set MAX_BT_SIZE and MAX_TT_SIZE being equal to 8 Comparing to the current VTM-8.0 lossless anchor, the proposed modification provides average bitsaving difference of 0.32 %, 0.22 % and 0.24 % with 44 %, 22 % and 44 % encoding runtime on AI, RA and LB configuration respectively.
It is asked whether it was also considered to reduce the CTU size.
Generally, global lossless coding is not a very relevant application case of VVC, and not competitive in terms of runtime/compression benefit compared to HEVC.
The runtime advantage would mainly support easier executing of experimentation, but this does not appear a big problem currently.
In mixed lossy/lossless, which is a more relevant application case, such a restriction would not be done, and this should be kept consistent.
The information of how to design a faster lossless encoder is beneficial and very welcome.
No action was taken on this.