JVET-O0290 CE5-related: Modified syntax design of ALF clipping parameters signalling [O. Chubach, C.-Y. Chen, T.-D. Chuang, C.-W. Hsu, Y.-W. Huang, S.-M. Lei (MediaTek)]
This contribution is related to adaptive loop filter (ALF) clipping parameters signalling in VVC. In this contribution, it is proposed to replace Kth order Exponential-Golomb code used for coding clipping parameters with either fixed length code or truncated unary code. It is also proposed to remove the filter coefficient dependency when signalling clipping parameters and signal clipping parameters no matter if the coefficients are equal to zero or not. In addition, it is proposed not to signal the flag, alf_luma_use_fixed_filter_flag, used to indicate the fixed filter sets are used for predicting ALF coefficients and infer its value to be equal to zero, when clipping operation is enabled in luma ALF (alf_luma_clip_idx=1). It is reported that all the above proposed changes result in tiny BD-rate changes in the range of -0.02% to +0.02%. It is claimed that these changes avoid unnecessary signalling of flags and remove parsing dependency.
An aspect that is different from the other proposals (see under JVET-O0047, JVET-O0064) is shown in italic font above.
It is noted that there were other contribution (JVET-O0669, JVET-O0425) which completely disable the prediction such that this additional modification would not be necessary