Re: [xine-devel] YUV conversions

[Billy B. <ve...@du...>]

Michael Roitzsch (mr...@us...):

> Hi James,
> 
> > MPEG2 is Y'CbCr, not YCbCr.
> >
> > > * Decoders (and post plugins like goom) outputting RGB should use
> > > the second (unclamped RGB to clamped YCbCr) conversion.
> >
> > Do you mean RGB or R'G'B' here ?
> > I think that we will only gain the correct conversions if we all use
> > the correct terms when talking about them.
> 
> What's the difference?

  When specifying the colourspace it is good to say Y'CbCr since it
makes it more clear that Y' is different from the Y in the XYZ
colourspace, since luma, Y', is calculated from gamma corrected RGB and
luminance, Y, is calculated from linear intensity RGB.

  http://www.poynton.com/PDFs/YUV_and_luminance_harmful.pdf

  To distinguish gamma corrected RGB from linear intensity RGB, Poynton
uses the notation R'G'B' for gamma corrected, RGB for linear intensity.
I think this covers it:

  http://www.inforamp.net/%7Epoynton/PDFs/TIDV/Gamma.pdf

  Pretty much everything you deal with in xine would be gamma corrected
RGB and Y'CbCr.

  -Billy