[mythtv-users] TV out card suggestions

[papenfuss at juneau.me.vt.edu]

	That's correct.  I built an equivalent board using the AD724 chip about
6 months ago.  The picture quality is excellent, *BUT* there are some serious
problems convincing video cards to output an appropriate signal.  The
intersection of video cards and/or drivers that support arbitrary (or at least
low) dot clocks, interlaced output, and non-buggy Xv acceleration is almost the
null set.  In my case, an ATI Rage 128 eventually worked.  Some nvidia cards
alegedly support interlacing with some version of the drivers, but non I have
tried.  You must use *exactly* NTSC (or PAL of you prefer) timings or the TV
won't sync.  If it's close, it might sync or might fry itself trying.

	Another issue appears to be beat frequency between the capture card 
(I've got both a PVR-250 and a BTTV one).  There's some "tearing" artifacts 
when watching interlaced video captures, even though the frequency is correct.  
I've turned on deinterlacing and it's happier.  Also, since you are doing no 
general deinterlacing (vid card only does what it's told), CG graphics might 
look flickery at 30/25 Hz.  That's no fault of the chip... just the guys at RCA 
70 years ago.

	In all, I like the fact that I *know* exactly what the video card is 
doing.  No unknown flicker "filters" etc to get in the way.  Colors are great.

	In case you're still interested, here's the modeline I use (720x480):

Modeline     "NTSCi"  14.318 720 760 824 910 480 484 492 525 interlace

-Cory

On Sat, 15 May 2004, Gert van der Knokke wrote:

> Michael T. Dean wrote:
> 
> > There's also the DIY approach.  Based on 
> > http://www.gossamer-threads.com/perl/mailarc/gforum.cgi?post=103525 , 
> > I'm building a converter using the design for the AD724-EB ( 
> > http://www.analog.com/UploadedFiles/Evaluation_Boards/Tools/452661188AD724eb.pdf 
> > ).  The AD724 chip is available from Newark ( http://www.newark.com/ ) 
> > and Arrow ( http://www.arrow.com/ )
> 
> With this chip you still need to program your VGA output to do PAL or 
> NTSC frequencies as the chip does not do scanrate conversions. AFAIK it 
> just combines the RGB and sync signals into a standard PAL or NTSC 
> composite/SVHS signal.
> 
> Gert
> 
> 
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