[mythtv-users] Component video adapters

Cory Papenfuss papenfuss at juneau.me.vt.edu
Thu Dec 9 19:13:28 UTC 2004

> I'm curious about these cheaper adapters though.  To do YPbPr video means
> an electrical conversion is required, which is what the 9A60 does.  But
> these adapters mentioned above may be different.  Is it that the Radeon
> 8500 (and related boards) already have the needed conversion circuits and
> that the adapter just provides the mechanical plug conversion?  That would
> explain why the adapter only is rated to work with specific ATI cards.
> And if that is the case, then I imagine there is some kind of driver
> aspect to this to get the card to generate YPbPr compatible signals -
> which I guess is why another poster here suggests that the adapters listed
> above currently don't work in Linux.
 	Strictly speaking, a video card output is nothing more than three 
DACs.  Whether the digital data that's sent to them is RGB or YPbPr 
doesn't matter, so it probably primarily a driver issue.  There are some 
slight hardware requirements on the video card (DAC max voltage, 
sync-on-[GY], etc), but the "circuitry" isn't really necessary as it is 
in the A960.  Remember that MPEG *is* YUV... the color transformation to 
RGB and back to YUV shouldn't even have to be done.

> modes are supported by the HDTV monitor (since there's no way for EDID
> data to be located in that case).  Anyone have any experience with this or
> a pointer to documentation about it (beyond the PDF listed on the svideo
> page)?

 	Why not?  IIRC the monitor ID info is sent as a serial bitstream 
on one of the pins.  Why can't the driver be "told" it's a HDTV with the 
adapter?  Seems reasonable.


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

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