[mythtv-users] VGA to Component adaptors

Cory Papenfuss papenfuss at juneau.me.vt.edu
Thu Apr 28 13:56:54 UTC 2005


> I just found this cable: 
> http://www.tigerdirect.ca/applications/SearchTools/item-details.asp?EdpNo=173735&CatId=0
>
> Do you think there is any chance it would work out of the box? I'm thinking 
> no, but it's almost worth trying. Could I hurt anything by using it?
>
> Thanks
> Tom

 	Look at the fine print on the bottom:
"Note: Your video source must provide a YPbPr component video signal from 
the HD15 port to use this cable."

 	That cable is no different from BNC breakout cables that provide 
RGBHV... just that it has RCA ends on it and relies on the Green signal to 
be the Y (and have composite sync on it).  I did a little 'net research 
this morning and concluded the following:

- EIA 770.1 and 770.2 define 480i and 480p analog component signals.  I'm 
pretty sure that they allow unipolar sync signals like standard video.
- EIA 770.3 (and SMPTE-274M) define HDTV analog component.  Colorspace is 
*slightly* different, and the sync is definately defined to be bipolar.

 	Basically, you could use one of those cables to get component out 
of RGB if it'll do sync on green.  Most vid cards that do sync on green 
are unipolar, I think, so it'd be abusing the spec.  It might work on some 
TV's and not others.

 	What you really want is a vid card that is smart enough to tell 
the computer it's doing Xv colorspace transformation, to get the YUV 
data... then not actually do it and barf out the YPbPr the three DACs. 
The sync should also be correct.

 	In other words... not likely.

*************************************************************************
* Cory Papenfuss                                                        *
* Electrical Engineering candidate Ph.D. graduate student               *
* Virginia Polytechnic Institute and State University                   *
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