JVET-P0565 CE8-related: Cross-component residual prediction for 4:4:4 format [K. Kawamura, S. Naito (KDDI)]

Residual modification process for transform blocks using cross-component prediction was adopted in the HEVC range extensions. This tool modifies the chrome residual signals by adding the scaled luma residual signals. In this contribution, a similar approach is proposed to improve the coding efficiency for 4:4:4 sequences. In VVC, luma and chroma coding trees is different in intra slice when chroma separate tree is enabled. An enabled condition of the modification is proposed to conform the VVC coding tree structure. Simulation results for 4:4:4 sequences show that -0.88% / -1.03% / -0.93% for AI/RA/LDB in single tree case and -0.51% / -0.74% for RA/LDB in chroma separate tree case.

For dual tree case, it is applied only in intra pictures

Gain is low for camera captured content compared to what it was in HEVC.

The benefit of the tool might be lower due to the fact that VVC has CCLM and JCC, which could be targeting the same properties.

For TGM1080, the gain is 2% for RA, 1.7% for AI, less for other SC classes.

Not worthwhile to include a new tool for SC for such small gain.

It is also noted that the VTM software still has some traces of this HEVC tool. Should be removed in a cleanup at some stage.