I extract subtitles from DVD using SubRip in Maestro format, and then import them in DVDMaestro for reauthoring.
SubRip also creates a palette (*.spf file) for colors which Maestro uses. This palette is in RGB.

I understand that DVD color space is YUV (YCrCb), and there are two transformations taking place in this process, i.e.,
DVD -> SubRip : YCrCb -> RGB
Import palette in Maestro, compile : RGB -> YCrCb

There are some clipping (scaling?) of numbers in these transformations, but one would expect the final result to be close
to the original.
And most of the time they are. But in some cases the results are noticeably different.

Recently I reauthored a DVD and the subs color in the reauthored DVD is greenish whereas on the original it is yellowish.
The text color on the original DVD was using IfoEdit:
Y = 179, Cr = 146, Cb = 53

I examined the sub palette in PcgEdit and the color used for text was correct, yellowish color with RGB values:
R = 218, G = 204, B = 38

In DVDSubEdit the color also shows correctly.

But in the SubRip produced palette (from original DVD) the text color is greenish with RGB values:
R = 215, G = 237, B = 57

And the values in the reauthored DVD using PcgEdit are:
R = 213, G = 236, B = 55
These are close to SubRip numbers, the differences being the result of clipping.
But they are completely different than the original DVD color.

I would like to know if this is a bug in SubRip, or that SubRip uses a different conversion formula.
After some googling there appear to be quite a few formulas for YUV to RGB conversion, and vice versa.
Isn't there a standard formula that everybody uses?


P.S. I also extracted subs from the DVD using VSRip in idx/sub format, and then used SubResync to save the subs
in Maestro format. It also had the same palette problem as SubRip.

P.S.S. After this experience I now change the subtitles colors manually. After I reauthor the DVD I then use IfoEdit to
copy the sub colors from the original IFO into the reauthored DVD IFO. This should copy the values directly in YUV
format and so there are no conversions taking place.