Quote:
Originally Posted by FranceBB
specifying BT2020nc
Color primaries : BT.2020
Matrix coefficients : BT.2020 non-constant
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I see the WCG hype is dead but WCG still continue to decrease quality at user side at some (many) use cases. Users got one more way to make good visual content to look worse.
Unless your (typically unnatural synthetic) content is absolutely require WCG and only benefit from being produced from (typically unnatural) WCG scene it is really require to use BT.2020 colour gamut at 8bit system. It is only about lossless if you use float samples system with about unlimited precision and very low quantization noise.
In all other standard use cases typical natural scenes do not have out-of-standard (narrow/small) gamut colours so attempt to compress natural gamut into BT.2020 colour gamut in low-bits integer samples system only cause significant increase of quantization noise and loss of fine natural colours difference reproduction.
So correct 8bit HDR-legalized system must use standard (professional of 20 century, narrow/small) colour gamut of rec.709. So if your mezzanine source is bt.2020 colour gamut encoded - you need to extract natural (small) colour gamut from input bt.2020 content and encode it into bt.709 our lovely 8bit system.
So in AVS z_ConvertFormat it is something like:
=>709:std_b67:709:l
and simply put
ConvertBits(8) or better ConvertBits(8, dither=1) to better benefit with MPEG-friendly dithering.
And mark this any MPEG encoded 8bit content as having HLG HDR transfer. This will be our awaited 8bit MPEG HDR system with now legal and standartized to displaying HDR transfer. It also can be MPEG-1 encoded and put to VideoCD and make handwritten note on the CD surface about HLG transfer used. So user will not forgot to click HLG transfer decoder at the playback.