[opendtv] Re: 1080P Question
- From: Tom Barry <trbarry@xxxxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Tue, 15 Sep 2009 19:13:52 -0400
Other times I've seen similar discussions I think it turns out most PC's
are set up for Rec 601 for viewing DVD's, etc. If so it would seem you
would have to first deal with that issue.
- Tom
Kilroy Hughes wrote:
> Thanks Jeroen.
> I reviewed the deck and am newly inspired to advocate allowing xvYCC
> (negative coefficient encoding in Y'CbCr).
>
> Any recommendation on how to correctly represent that in H.264 encoded
> content?
>
> It looks like Transfer Characteristics = 11 signals IEC 6966-2-4; and
> Primaries and Matrix Coefficients are the same as Rec 709 (VUI value = 1).
> Some inaccuracy there, but Transfer Characteristics different from Rec 709
> should encourage some guessing as to what real primaries were encoded.
>
> Kilroy Hughes
>
> From: opendtv-bounce@xxxxxxxxxxxxx [mailto:opendtv-bounce@xxxxxxxxxxxxx] On
> Behalf Of Stessen, Jeroen
> Sent: Wednesday, September 09, 2009 4:53 AM
> To: opendtv@xxxxxxxxxxxxx
> Subject: [opendtv] Re: 1080P Question
>
> Hello friends,
>
> Kilroy Hughes @ Microsoft wrote:
>
> Ø But, how bad does it look when content is encoded xvYCC and the display
> (or something else in the signal chain) clips negative RGB coefficients to
> Rec 709 gamut?
>
> I have given examples of that in my presentation at The Tech Retreat 2007.
> Don't I remember you being there ?? Maybe you can still download the ppt:
> http://data.memberclicks.com/site/hopa/2007_Presentation_Stessen.ppt .
>
> The short version is: the problem is only applicable to the out-of-gamut
> colors,
> so for the in-Rec.709-gamut colors it means nothing, they are fully
> compatible.
> Then, there are two kinds of out-of-gamut colors:
>
> - Wide-gamut, where MIN(R',G',B') goes < 0. Such colors are
> physically
> impossible on a standard gamut display, and must be gamut-mapped.
> Clipping to zero is one form of gamut mapping, and not even that bad.
>
> - Bright-gamut, where MAX(R',G',B') goes > 1. This is merely a
> problem of
> scale, the colors can be brought in-gamut by simple attenuation, which can
> also be done by the (xvYCC) source. However, failure to do so gives very
> visible and annoying clipping artefacts, so this must be properly dealt with.
>
>
> Ø I'm struggling with that chicken/egg problem for Internet delivered
> content. It might be possible to write new rules for a new channel and new
> devices, but if those files land on legacy devices or plug into legacy
> displays resulting in people have green faces ... I don't see a bridge to
> transition from a 709 to xvYCC world of content and devices.
>
> Duh, xvYCC was specifically designed with that transition in mind ! The
> artefacts
> of rendering on legacy displays can be kept minimal. Unfortunately, this
> makes the
> added value of an xvYCC display also rather minimal. The market is not taking
> it up. The Digital Cinema has its own wide-gamut standard of course, and it
> does
> not have to be compatible with anything else. However, Mark is using standard
> satellite equipment for his Opera broadcasts, and he has to use Rec.709 video.
> Given that the content may be fed to some real Digital Cinema projectors, it
> would
> seem that xvYCC is a nice compromise. But with the negligible amount of wide
> gamut colors in typical opera scenes, the benefit to the viewers would be
> zero.
>
>
> Ø Well, if all render devices recognized xvYCC content and displays, and
> could convert to 709 output if xvYCC isn't supported, then it would work ...
> but requiring that of all devices (which eliminates most existing devices)
> isn't likely.
>
> Avoiding clipping to 1, and defaulting to clipping to 0, already solves 90%
> of the
> issue. A better receiver would decode xvYCC and then apply a more accurate
> form of gamut mapping to a standard display gamut. As many displays are not
> really that standard, there would still be a small benefit of more accurate
> color
> rendering. But whether the customer would appreciate the difference ? Not
> likely.
>
> For xvYCC (x.v.Color) to become a success, we need wide-gamut sources,
> transmissions, and displays. Every camera is in principle suitable for
> wide-gamut,
> and some modern displays (new LCDs, DLP and laser projectors) can render
> a decently wide gamut, but there are no transmissions (or discs). End of
> story...
>
> Groeten,
> -- Jeroen
>
>
> Jeroen H. Stessen
> Specialist Picture Quality
>
> Philips Consumer Lifestyle
> Advanced Technology (Eindhoven)
> High Tech Campus 37 - room 8.042
> 5656 AE Eindhoven - Nederland
>
>
>
> Office mobex: (27) 99650
> VoipBuster: +31.85.785.3611 (VoIP-in to PC)
> Mobile 1: +31.6.1389.2492 (office gsm)
> Mobile 2: +31.6.4468.0021 (personal gsm)
> E-mail 1:
> Jeroen.Stessen@xxxxxxxxxxx<mailto:Jeroen.Stessen@xxxxxxxxxxx>
> E-mail 2:
> Jeroen.Stessen@xxxxxxxxxx<mailto:Jeroen.Stessen@xxxxxxxxxx>
> Website:
> www.consumer.philips.com<http://www.consumer.philips.com>
>
>
>
>
>
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