Still I think there's a reasonable doubt about possible clipping when the source profile of the 3DLUT is BT.2020. This is from madshi 11-24-2017:
Quote:
Gamut:
madVR doesn't convert the gamut, unless the 3DLUT (SDR or HDR, doesn't matter) expects a different gamut than the source provides. E.g. if your 3DLUT is BT.2020 and the video is also BT.2020 then madVR doesn't do any gamut processing. However, if your 3DLUT was made for BT.709 videos, but the video is BT.2020, then madVR will convert gamut from BT.2020 to BT.709. Basically madVR makes sure that the 3DLUT receives the pixels in the format it expects.
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Pixel shader math is done in ICtCp and when the result is converted to RGB, some colors may fall out of gamut. When madVR converts the gamut, it maps those colors back in gamut, but in this case it could simply clip them, or let the 3DLUT clip them, which would make them look oversaturated.
I guess it maps them back in gamut anyway, but maybe using a source DCI-P3 3DLUT is safer.