[mythtv-users] HDTV Modeline Help

Cory Papenfuss papenfuss at juneau.me.vt.edu
Sun Dec 11 08:48:24 EST 2005

 	If you believe your EDID data, you cannot run 720p.  Indeed, the 
fact that you forced it to 45kHz and it was "jumpy" is an indicator that 
it will not sync there.  Look here (or lots of other places in the 
'net I'm too lazy to look up right now):
The bottom chart shows
480i:  31.5kHz/60Hz
720p:  45.0kHz/60Hz
1080i: 33.75kHz/60Hz

> I did a Xorg -probeonly and it did not find any compatible resolutions over 
> 848x480, however I was not supprised since I've read that many do not have 
> proper EDID info. It states that my hsync is 30-35kHz and my vsync is 
> 58-62Hz. Using modeline calculators it appears that if I specify 960x720p 
> that it is not possible to satisfy both sync requirements. I tried bumping 
> the max hsync up to 45 but was greeted with a "jumpy" screen so it appears is 
> that part may correct.
 	Here's the modeline that I use.  I believe it's pretty much 
frequency-spec compliant with the standard (or at least as close as can be 
made with NVidia's restrictions)

ModeLine "1080i" 74.175824 1920 1960 2008 2200 1080 1084 1094 1125 interlace -hsync -vsync

 	That puts out 33.72kHz HSYNC and 29.970 VSYNC.  It will be 
underwheliming to use as a desktop resolution because it will be huge and 
very flickery with the interlacing at 30Hz.  It should work with the TV 

 	One of the reasons your modeline generate probably didn't work is 
because they rarely offer the "interlace" option.  That effectively halves 
the horizontal scanrate required for a given resolution.  30-35kHz pretty 
much limits you to somewhere between 640x480-800x600 in computer-ese 
resolutions.  Not much more over EDTV.



* Cory Papenfuss                                                        *
* Electrical Engineering candidate Ph.D. graduate student               *
* Virginia Polytechnic Institute and State University                   *

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