[mythtv-users] Homebrew YPrPb/NTSC transcoder?

[papenfuss at juneau.me.vt.edu]

	Hello all... Now that I've got a mythtv-0.13 system set up, I'm trying 
to get the most out of it.  Sorry that this is off-topic a bit.

	 My new roomate has an HDTV-ready set with component in, and I like the
idea of using a real, honest-to-goodness modeline out of the VGA port to drive
the TV.  I've been scouring the 'net for some good plans to build a transcoder,
but figured I'd ask here too, in case anyone knows.

	I'm looking to build a "Swiss army knife" transcoder.  Takes VGA in, 
loops VGA back out, and provides component out (YPbPr), but also provides 
composite and S-Video out.  The second circuit (composite) is easy, since it's 
all done in the AD724 chip.  The first I've got issues with:

	Does anyone know why all the plans for transcoders on the 'net have H/V 
sync generators (one-shot timers, delayed logic gates, etc)?  Why can't it just 
use the sync pulse from a custom modeline off the VGA port?  Also, does anyone 
know where to find the specs for sync pulse length for HDTV modelines?

Thanks for any advice:
-Cory


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