JVET-O0803 Non-CE5: Unified design for longer tap deblocking line buffer reduction [A. M. Kotra, S. Esenlik, B. Wang, H. Gao, E. Alshina (Huawei)] [late]
In VTM-5.0, to reduce line buffer requirement for the longer tap filter at horizontal CTU boundaries, for the Luma component an asymmetric filter which only modifies 3 samples from the top CU, and 7 samples from the bottom CU is employed, whereas for the Chroma deblocking, the longer tap filter is completely switched off at the CTU boundaries. Since a potential “large block” blocking artefact could occur at the horizontal Chroma CTU boundary, the current proposal reportedly employs a longer tap asymmetric filter which modifies 1 sample from the top CTU but can still modify up to 3 samples from the bottom CTU to more effectively remove the blocking artefact.
The objective results, over VTM5.0 Anchor for CTC configuration are as follows
Config. | Y | U | V | EncT | DecT |
AI | 0.00% | 0.00% | 0.00% | 101% | 101% |
RA | 0.00% | -0.06% | -0.04% | 101% | 102% |
LDB | 0.02% | 0.00% | -0.10% | 101% | 102% |
LDP | 0.00% | 0.18% | -0.05% | 101% | 102% |
Subjective evaluation showed that the quality is slightly better when compared to the Anchor and reportedly the subjective benefits are better for 4:2:2 and 4:4:4 content.
Further study in CE. Unification is not necessary an argument, as there is a slight complexity increase, and should be justified by evidence that artefacts are avoided.