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Not all displays are RGB. Mine is an LG OLED TV, and the sub-pixel structure is RGBW, not RGB, so there isn't necessarily a conversion to RGB before the signal hits the pixels. And the signal sent from the Lumagen to the screen pretty much has to be YCbCr 4:2:2 (because the TV can't fully resolve 4:4:4 - or at least it sort of can, but not without disabling some rather vital image processing).
Converting between component and RGB (or vice versa) should be more or less lossless, though I suppose there could be rounding errors - I'm slightly more inclined to trust the Lumagen to convert from RGB to component than the Pi - but I doubt it makes that much difference.
The things I want to avoid are A: doing more transformations than are necessary, and B: (particularly important) to avoid doing any unnecessary mapping between limited-range and full-range (or vice versa) - that's where the significant errors are going to creep in.
(I'm a bit dubious about BT.1886 gamma. How many things are really mastered with a gamma of 2.4? I think almost everything is actually mastered at 2.22.)
One thing that's still bothering me is: if the Pi is working internally with limited-range RGB, and also outputting that, why do below-black and above-white get clipped?
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Who said that the Pi is "working internally with limited-range RGB" ? I never saw that in the documentation...
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2017-11-15, 20:35
(This post was last modified: 2017-11-15, 20:58 by rascas.)
Well I just tested that file on a RPi 3 with a cheap ASUS vp228h monitor, without any color calibration, and I can see the diference in 14 to 25 (blacks) and from 230 to 236 (whites), more or less. This is with RGB Full, by default the Pi sets this monitor as RGB Limited. With RGB Limited I notice a little less blacks and whites (almost no difference), but RGB Full gives a better overall image quality in this case in my opinion.
I have to test it on another Pi connected to a better LG TV and also on my PC.