JVET-K0318 CE2-2.1.1-related: HEVC luma filters and decisions for chroma deblocking [K. Andersson, Z. Zhang, R. Sjöberg (Ericsson)]
This contribution proposes to use HEVC luma filters and decisions for chroma deblocking with some minor adaptations in decisions. For BMS it also applies deblocking of implicit TU boundaries after deblocking of sub-block boundaries from motion prediction to ensure that implicit TU boundaries can be deblocked with more than 1 pixel even when it exist sub-block boundaries 4 samples from the implicit TU boundary. The modifications are implemented on top of CE2-2.1.1.
The proposed solution is claimed to improve subjective quality especially notable for Campfire at low bit rates. It also provides a luma,Cb,Cr BD rate impact of −0.19%, −0.18%, 0.17% / −0.18%, −2.20%, −2.22% / −0.12%,−1.89%, −1.69% for AI/RA/LD compared to VTM-1.0 and −0.12%, −1.08%, −0.93% / −0.12%, −2.08%, −2.28% / −0.20%, −2.46%, −2.40% for AI/RA/LD compared to BMS-1.0. Decoding time 105%/106%/107% for AI/RA/LD compared to VTM-1.0 and 103%/104%/103% for AI/RA/LD compared to BMS-1.0.
These are additional changes beyond the bug fix of enabling DBF on large TU boundaries.
It is suggested to use the luma type of decisions for chroma as well.
Samples close to large TU boundaries might be sampled twice (once over subblock and again with long filter at large TU). This would require two passes of DBF, and somewhat inhibit parallelism.
Further study in a CE was planned.