[mythtv-users] Correct nvidia tv-out pal-i config

Christopher Friend christopher_friend at hotmail.com
Tue May 8 11:02:50 UTC 2007

Hi, I've been trying to set up my xorg.conf file for nvidia's tv-out (with 
the official drivers & composite) but i'm progressing pretty slowly due to 
not really knowing which method i should be using.

Originally I had only a black and white signal after enabling the tv through 
nvidia-setitngs. adding

Option "TVStandard" "PAL-I"
Option "TVOutFormat" "COMPOSITE"
Option "SecondMonitorHorizSync"     "30 - 50"
Option "SecondMonitorVertRefresh"   "50.0"

the the device section of xorg.conf and restarting x fixes that, but it 
gives a pretty poor image (horizontal tearing, poor frame rate, only 800x600 
or 640xXXX available...).

Adding "720x576" in to the Modes gives me a 720x576 selectable res in 
nvidia-settings but still outputs in 60 Hz and with about 2cm space at top 
of tv screen.

I then tried various modelines, but i'm not sure if the thing even recognize 
custom modelines at all for the tv-out? I've seen a number of places say it 
doesn't but just as many saying it does.

I'm getting a near perfect signal out through windows by using the advanced 
timing window in the drivers, and chosing 720 x 576 @ 50.00 I from the mode 
and timing dropdown. this then lists the following info:

Horizontal pixels

Front porch: 16
Back porch: 71
Syn polarity: -
Front end active: 720
Sync width: 56 (presumably the sync pulse)
Scan rate: 15.60 kHz

Vertical lines

Front porch: 4
Back porch: 38
Syn polarity: -
Front end active: 576
Sync width: 6
Refresh rate: 25.002 Hz
Pixel clock: 13.48 MHz

Interlaced: Yes

Now adding all that lot to 
http://www.tkk.fi/Misc/Electronics/faq/vga2rgb/calc.html gives me the 
following modeline:

Modeline "720x576"   13.48   720 736 792 864   576 584 596 672 interlace 
-hsync -vsync

I've added that in various different places (seperate "modes" section, in 
with the tv monitor when it had its own section, in to device when not...) 
and it doesn't seem to change anything at all. well, it either continued 
outputting at 60 Hz and the same size regardless of how the pulse start/ends 
were numbered, and the one time i did get something different it was purely 
a blank screen and a number of things could have caused that.

I've also seen something in the wiki that suggests adding "Modes      
"720x576_50i"" in to the modes section should give me a correct 50 Hz 
interlaced signal, hopefully using the same kind of info that the window's 
driver uses when the same thing is selected through the windows driver gui, 
though it's the one thing i've not tried and i've no idea if it'll work.

Option "ModeValidation" "AllowNon60HzDFPModes" was also suggested, though i 
dunno if that has anything to do with tv's with the DFP bit in there.

So, does anyone know the correct way I should be going about trying to get a 
50 Hz interlaced 720x576 signal, preferably one that I can change both the 
overscan and horizontal / vertical alignment of? A modeline would do it but 
like i say, i'm not sure if they work at all and if they do, i'm not sure if 
i'm adding it in the right place.


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