[mythtv-users] DVI v. Component

Cory Papenfuss papenfuss at juneau.me.vt.edu
Fri Aug 13 07:40:59 EDT 2004

> Hey, Cory: which make and model of funky transcoder box did you pick?
 	I built one using an AD724 chip that will modulate an appropriate VGA 
signal (15.7kHz/30Hz/interlaced) into NTSC composite or S-VID.  I didn't do 
much else than what the other homebrew designs on the 'net do.  Quality is 
outstanding... better than I've ever seen out of the mediocre-quality TVOUT 
cards I've tried.  The only problem is a slight "tearing" of mythtv ivtv 
records (probably from vsync beat frequencies).  Turning on kerneldeint greatly 
reduced it.

 	I was originally planning on making a "swiss-army-trancoder," that 
would take VGA in and output buffered VGA, composite, s-vid, and component. 
You would (of course) have to send out a modeline that's compatible with 
anything that you were going to use (no scanline conversion).  I just did a 
prototype with the hardest part (AD724), and I never got around to adding the 
few additional components.  Part of the reason is that from what I understand, 
component HDTV uses bi-level sync (at least for interlaced modes), rather than 
the more TTL-like on VGA and NTSC.  To build the VGA->component part of the 
transcoder would then require some more work.  The TV I'm using only supports 
480i on its component anyway.


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