[mythtv-users] HDTV Modeline Help

Richard Shaw rshaw2 at midsouth.rr.com
Mon Dec 12 21:43:02 EST 2005

It looks like you're right. I tried a 1080i modeline and it did work. I 
would be happy with that but at 27" the text in Firefox was so I 
couldn't read it. Right now I'm messing with 540p which I have working 
but it doesn't look very good. It could be I'm trying to get it to work 
in 4:3 ratio instead of 16:9. I don't really want to have it in 
widescreen since it's not a widescreen television. I guess I shouldn't 
complain too much, the picture is otherwise good and I only paid $450 
for it.

Cory Papenfuss wrote:

>     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):
> http://www.plasmatvbuyingguide.com/dtv-hdtv-comparison19.html
> 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 though.
>     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.
> Cheers
> -Cory
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