JVET-L0427 CE15-related: Separate Palette Coding for Luma and Chroma Components [R. Chernyak, S. Ikonin, J. Chen (Huawei)]
The contribution proposes a unification of Palette Coding tool for Single and Dual Trees. For screen content sequences it demonstrates 9.0% / 3.9% / 1.3% (AI / RA / LDB) on class TGM and 4.0% / 3.3% / 2.4% (AI / RA / LDB) on class F of Luma BD-rate saving on top of CE15.2, if Dual Tree is disabled.
In the current CTC, the palette is separated when the dual tree is enabled in SPS. The proposal proposed to use separate palette when the dual tree is disabled in SPS.
It was reported that coding performance benefit can be observed in non-CTC case by enabling separate palette for luma/chroma as compared to joint palette.
It was commented that joint palette requires sending one set of palette information, while separate palettes for luma/chroma maintain two sets of palette information. There is an increase of the complexity.
It was questioned by an expert that for CTC setting, if joint or separate palette should be used. It was requested that both should be evaluated.
This was further discussed in Track A. This should be included in the CE.
Non-CTC case (disabling separate tree) should also be investigated, as it allows using HEVC (joint) palette as is (joint palette). This would likely cause some loss compared to the anchor (which is CE15.2)
Tests:
- ST disabled + joint palette (inter+intra)
- ST enabled + separate palette (in intra slice) – anchor=CE15.2
- ST enabled + separate palette (inter+intra) = JVET-L0672
- ST disabled + separate palette (inter+intra) = JVET-L0427