JCTVC-M0377 Non-RCE1: Crosscheck of JCTVC-M0116 proposed by MediaTek [J. Kim (LG)] [late]
JCTVC-M0412 AHG5: CU based chroma intra prediction with reduced reference [K. Kawamura, T. Yoshino, S. Naito (KDDI)] [late] [miss]
The proposal is a reduced-complexity LM chroma scheme for non-4:2:0 operation.
This contribution proposes a CU-based chroma prediction by reduced references which predicts chroma samples using linear combination of luma samples (known as "LM chroma") for non 4:2:0 format. When a block size is large, the processing load of the parameter derivation process for each coding unit is reduced by using a limited set of reference samples in the worst case. Compared with the top of CU-based chroma prediction in JCTVC-M0097, the Y/G BD-rate loss is 0.0% for whole AI conditions while the number of reference samples are limited.
It was remarked to consider whether this solves the "division by 3" problem. It seems to partially do so, but (as proposed) the modification only applies to large block sizes.
The basic pipeline issue remains, that this introduces a cross-component dependency that is not otherwise present.
It was agreed to study this in the CE that will include LM chroma and the other reduced-support region simplification.
JCTVC-M0451 AHG5: Cross-check report of CU based chroma intra prediction with reduced reference (JCTVC-M0412) [S. Matsuo, M. Matsumura, S. Takamura, H. Fujii, A. Shimizu (NTT)]
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