[mythtv-users] NTSC ModeLine

Cory Papenfuss papenfuss at juneau.me.vt.edu
Thu Sep 2 18:21:15 EDT 2004

 	I wrote awhile back about modelines... check the archives and the wiki. 
In short, here's what I use, and it produces precisely NTSC spec (or at least 
the SDTV that I use thinks so)

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

 	I always hated that error message in X, because there's a big 
difference between a bad mode due to "clock" or "interlace" or "doublescan". 
You're using a Matrox card (MGA), and my experience has always been excellent 
with linux, custom modelines, interlaced, sync-on-green, and all sorts of 
nasties I could throw at it.

 	Check elsewhere in the logs for a "Dotclock range 12.0-250Mhz" to rule 
out that.  Try a standard VESA interlace modeline (e.g. 1024x768 at 43) to see if 
the card doesn't do interlace... some don't.

 	Of course, the obligatory question... why are you doing this?  Do you 
have a component tv that only does 480i or something?  VGA monitors don't do 
NTSC, but they will do double.  If you're using a standard tvout card, double 
the frequency, remove the interlace, and get on with life.  :)


* Cory Papenfuss							*
* Electrical Engineering Ph.D. Graduate Student                         *
* Virginia Polytechnic Institute and State University 			*

On Thu, 2 Sep 2004, Shaun Jackman wrote:

> I'm trying to find the best 640x480 interlaced NTSC ModeLine. This one
> looks good to me:
> 	ModeLine "ATSC-480-59.94i" 11.958  640 664 736 760  480 484 492 525 Interlace
> However, running X gives this error:
> (II) MGA(1): Not using mode "ATSC-480-59.94i" (bad mode
> clock/interlace/doublescan)
> What NTSC ModeLine works for you?
> Thanks,
> Shaun

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