[mythtv-users] Hardware for Best TV-Out?

Cory Papenfuss papenfuss at juneau.me.vt.edu
Mon Oct 25 11:33:42 UTC 2004

> Keep in mind that a "real" (yet still not broadcast quality) RGB to NTSC
> encoder is going to cost ~$500--and that is for an encoder *only* with
> no rate conversion.  Not that I think a high quality encoder would really
> help from what I can see of nVidia's output.  A transcoding TBC might help.
> Unfortunately, mine has the component input option rather than RBG so I
> can't try it. :(
 	It cost me about $10 in parts to build one.  No rate conversion, 
just VGA->NTSC encoding (color subcarrier with UV modulation, etc).  Aside 
from having to set the VGA card up for 480i timings, (read: no console, 
only X), it works great.

> I'd love to get an answer on this as well.  As it stands I'm about ready to
> give up on the project on the theory that what I want cannot be done.  Because
> my source is ATSC the PVR-350 is not supported for output, and from what I've
> seen generic video card TV-Out technology has not advanced much since my last
> exposure.

 	I have gotten an email from a guy at NVIDIA who says that so long 
as you use a standard size for the TVOUT, the driver will try to bypass 
the scaler on the card.  It basically hard-codes the modeline for a 
standard mode (e.g. 720x480) to do this, and is probably why people have 
been unsuccessful tweaking modelines with nvidia cards.  I haven't played 
with it much myself, though.

The problem is that generating a reasonable quality NTSC signal is
> not trivial (TV Typewriter Cookbook to the contrary notwithstanding :).  You
> can't easily tack on cheap TV-Out functionality to a VGA card and get quality
> results.

 	Check out the AD724 chip.  A few passive components, one chip, and 
a crystal is all you need.


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