Re:John Carmack on JPEG
by pdq on Friday June 04, 2021 @08:54PM
(#27400919)
This is correct, with one subtlety.
YUV to RGB conversion (and vice-versa) requires use of conversion coefficients (BT.470, BT.709, etc): https://en.wikipedia.org/wiki/YUV
Different apps/algorithms can choose their own coefficients, so you get a slightly different RGB colors. If you converted RGB back to YUV with a different set of coefficients, you would get a different result.
Re:John Carmack on JPEG
by astrange on Saturday June 05, 2021 @01:53AM
(#27402581)
JPEG specifies the matrix, I think it's the same as BT.470. It's fairly easy to guess the intent even if the metadata is missing (which, well, it usually is) - just have to know if the source is a video or not and then if it's HD or not.
YUV to RGB conversion (and vice-versa) requires use of conversion coefficients (BT.470, BT.709, etc): https://en.wikipedia.org/wiki/YUV
Different apps/algorithms can choose their own coefficients, so you get a slightly different RGB colors. If you converted RGB back to YUV with a different set of coefficients, you would get a different result.