[opendtv] Re: Overscanning on LCD TVs
- From: "Stessen, Jeroen" <jeroen.stessen@xxxxxxxxxxx>
- To: "opendtv@xxxxxxxxxxxxx" <opendtv@xxxxxxxxxxxxx>
- Date: Thu, 12 Nov 2009 20:13:46 +0100
Hi,
dan.grimes@xxxxxxxx<mailto:dan.grimes@xxxxxxxx> wrote:
> I was under the impression that HDMI and DVI use the same standard
> and are electronically equivalent. Of course, just because the
> signals mate doesn't mean the color space is the same.
Duh... no !
DVI is always R'G'B', 4:4:4, 8 bits, 0..255, and sRGB (Rec.709) color
primaries, no audio.
HDMI can be that, but it can also be Y'CbCr in both Rec.601 (up to 576p) and
Rec.709 (HD)
flavors, 4:2:2 or 4:2:2, 8 or 10 or 12 bits, 16..235(240) or 0.255 (times 4 or
16 dep. on # bits),
can be xvYCC extended color space, and in the future even other color primaries
(e.g.
AdobeRGB). Plus many flavors of digital audio, of course, and CEC command
channel.
Normally all these standards are published and negotiated over the EDID
channel. In the
absence of EDID, it should default to DVI. Which should mean 0.255, but for
video it is
actually better to stay with 16..235, so IMO a source could be forgiven for
leaving the
amplitudes as is. Only problem is: you don't know that it does. You could guess
it from
the resolution, i.e. 1280x720 and 1920x1080 are 16..235, and PC resolutions are
0..255.
Or you leave it to the viewer to adjust contrast and brightness until the
display is fully
driven. Which in the case of a digital cinema projector is not so easy. Duh...
> So any suggestions what one might use to analyze or discover the color spaces
> of > an HDMI and DVI-D signal? The same question might be had for HD-SDI.
The color space, if you mean the color primaries, is almost always Rec.709
a.k.a. sRGB.
If you mean which flavor of Y'CbCr (for HDMI): 601 for SD, 709 for HD,
irrelevant for
R'G'B' from a PC. The rest can be inferred from the EDID data, which is plain
I2C that
can be observed on the PC with the proper software. But it is never really easy.
OTOH, if you can just measure the 24 levels in a plain color bar, you would know
practically everything. It should be mandatory to send it during the VBI....
> We are converting between HDMI, DVI and HD-SDI to use different types and
> levels of equipment. It is impossible to use just one standard these days.
> But in the conversion, things get messed up and I am experiencing this.
> I would like to be able to straighten it out.
Can't the customer rep for the analyzer help you with some documentation ?
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
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