Comment by meindnoch
10 months ago
It depends on the exact meaning of "YCbCr" and the meaning of "RGB". Is it BT.601? BT.709? BT.2020? Adobe RGB? Display P3?
Also extra fun is guaranteed if one end of the video cable is encoding with e.g. BT.601 primaries, while the other end is decoding as e.g. BT.709, or vice versa.
RGB to YCbCr conversion and back is well defined, and RGB->YCbCR->RGB should give you back the original RGB values, no matter what the colorspace was.
Lossless roundtrip conversion is only true for schemes like YCoCg-R [1]. It is not true for Rec.601, Rec.709, etc. because these standards require quantizing to 8bits (actually even less than 8bits due to the 16-235 thing).
[1] https://www.microsoft.com/en-us/research/wp-content/uploads/...
I'm not talking about mathematically exact reconstruction, I'm talking about not being able to see the difference.
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