[opendtv] Re: negative RGB (was: "we'll forever be stuck with by going ATSC")
- From: jeroen.stessen@xxxxxxxxxxx
- To: opendtv@xxxxxxxxxxxxx
- Date: Thu, 13 Jan 2005 15:26:26 +0100
Hello,
Alan Roberts wrote:
> the idea of allowing negative (and super white) values for RGB is
> entertaining and interesting. ITU1361 introduced it in about 1990
What a coincidence... Hans had my Gamma Sutra (Poynton's latest book)
open on page 266, where the gamma curve of ITU-1361 is illustrated !
Were you also involved in its creation ?
> The problem is that although it increases the analysis gamut,
> it isn't enough to cover the more saturated cyan/greens we are
> seeing now,
Kees Jaspers was concluding the same thing about e-sRGB, in preparation
of the paper that he was supposed to present next to yours on my seminar.
He wrote that e-sRGB still does not cover the entire visible gamut.
> and it grossly codes a huge gamut of non-existent colours.
Which according to Tom might not be a problem in combination with
compression. But it still seems to be a waste: to extend a gamma
function, which is intended only to compress luminance levels, in
order to increase a colour gamut. It also codes a huge gamut of
non-existent luminance levels... It just doesn't seem right to me !
> In fact, it's a far less efficient gamut extension system that
> simply using XYZ as the aiming primaries in the camera.
Prin should be happy to read this. But even XYZ is considered
inefficient (before compression)... Why not use LMS instead ?
> I have a wonderful demonstration of this, and showed it at the
> recent RTS HDTV colloquium in Reading.
You make me jealous...
> It really isn't a sensible way to extend the gamut.
Another coincidence: I have been asked to look at the "xvYCC"
proposal, which is based on bipolar gamma curves similar to 1361
or e-sRGB, but then converted (in the gamma domain) from R'G'B' to
Y'CbCr. The aim is to remain maximally compatible with ITU R.709.
Are you suggesting then that this is an equally bad idea ?
Then what do you think of my proposal in the last paragraph of
my first message in this thread ? Could that be the better way ?
Best regards,
-- Jeroen
+-------------------------------+----------------------------------------+
| From: Jeroen H. Stessen | E-mail: Jeroen.Stessen@xxxxxxxxxxx |
| Building: SFJ-5.22 Eindhoven | Philips Digital Systems Laboratories |
| Phone: ++31.40.2732739 | Visiting & mail address: Glaslaan 2 |
| Mobile: ++31.6.44680021 | NL 5616 LW Eindhoven, the Netherlands |
| Pager: ++31.6.65133818 | Website: http://www.pdsl.philips.com/ |
+-------------------------------+----------------------------------------+
----------------------------------------------------------------------
You can UNSUBSCRIBE from the OpenDTV list in two ways:
- Using the UNSUBSCRIBE command in your user configuration settings at
FreeLists.org
- By sending a message to: opendtv-request@xxxxxxxxxxxxx with the word
unsubscribe in the subject line.
Other related posts:
