[mythtv-users] Excellent quality TVOUT from almost any video card

papenfuss at juneau.me.vt.edu papenfuss at juneau.me.vt.edu
Tue Jan 27 07:36:08 EST 2004


	Currently, I haven't done much different from these pages:
http://pwp.netcabo.pt/pscoelho/vgatv/ludovico/LC-AD724.html
http://www.hut.fi/Misc/Electronics/circuits/vga2tv/vga2palntsc.html

	I'm planning on adding the DIY transcoder circuits for progressive-scan
out to the same board for a "swiss-army knife" video converter.  Be warned,
however, that you need to ensure that your video card/driver combination
supports *INTERLACED* output if you ever hope to use something like the
circuits in the above link.  A notable problem seems to be NVIDIA cards.  I
don't know if it's hardware or driver, but whenver I try to use an interlaced
modeline on one I get something like this in my XFree86.0.log 

Not using default mode "1024x768i" (bad mode clock/interlace/doublescan)

	Matrox cards typically rock for everything (except ultimate 3D 
performance), but I've only got some older G100 and Milleniums.  Although 
they'll cook up the necessary modelines, they don't have XVideo.  So far I'm 
using a Rage128 which does both.

	Two other notes to mention.  First, there is *no* flicker reduction.  
TV-standard video sucks.  Period.  End-of-story.  Any "flicker reduction" is 
modifying the picture to throw away high-frequency information (read: 
makes picture fuzzy).  This is really only noticable on single horizontal lines 
in the GUI.

	The second note is VSYNC.  I played with it some more last night, and I 
believe the system really needs GENLOCK between the hauppauge card and the 
X-server.  There's some vertical "sync crawl" for lack of a better description.  
This (ironically) goes away when the "Deinterlaced playback" is turned on.  
Anyone know about potential quality reduction (read: fuzziness insertion) loss 
from this operation in mythtv?

	Hope that helps anyone looking into this.  It's certainly useable, and 
better than any other tvout cards I've tried.  I think you could get comparable 
results from a sufficiently good video card if it didn't try to do any flicker 
reduction.

-Cory

On Mon, 26 Jan 2004, Greg Estabrooks wrote:

> > signal on either composite or svid.  Results look as good or better than 
> > directly from a dvd player (on svid, anyway).
> > 
> > 	Once I get the bugs worked out, I'll post the info.
> 
>  Are you going to be releasing plans to it? I'm more than willing to be a 
> test subject :)
> 
> 

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