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Old 12-23-05, 12:03 PM   #1
korpenkraxar
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Join Date: Dec 2005
Posts: 7
Default Can we use virtual screen sizes to compensate for overscanning?

Hi! I'm using an MSI 6200 HDTV card, sending a 1920x1080i signal to my JVC TV-set using component output. The TV overscans the signal quite badly however - I can see something like 1700x1000 pixels. Is there any way in which I can compensate for this by configuring my xorg.conf file - can I set a smaller virtual screen by using a custom modeline or perhaps TwinView that also works for fullscreen video?

I have for instance tried these modified modeline below, but they and other variants does not work.

Original (working):
Modeline "1920x1080i" 74.52 1920 1952 2016 2208 1080 1084 1096 1126 -HSync -VSync Interlace

Modified (not working):
Modeline "1920x1080i_virt" 74.52 1712 1952 2016 2208 963 1084 1096 1126 -HSync -VSync Interlace

Modified (not working):
Modeline "1920x1080@65i" 85.12 1800 1952 2272 2304 1000 1104 1110 1135 interlace

Error message: Not using mode whatever (not a valid TV mode)

The only accepted ones are:

(**) NVIDIA(0): Validated modes for display device TV-0:
(**) NVIDIA(0): Mode "800x600PAL": 36.0 MHz, 37.5 kHz, 50.0 Hz
(**) NVIDIA(0): Mode "640x480PAL": 29.5 MHz, 31.2 kHz, 50.0 Hz
(**) NVIDIA(0): Default mode "1024x768": 65.0 MHz, 48.4 kHz, 60.0 Hz
(**) NVIDIA(0): Default mode "800x600": 40.0 MHz, 37.9 kHz, 60.3 Hz
(**) NVIDIA(0): Default mode "800x600": 81.0 MHz, 75.0 kHz, 60.0 Hz (D)
(**) NVIDIA(0): Default mode "800x600": 36.0 MHz, 35.2 kHz, 56.2 Hz
(**) NVIDIA(0): Default mode "640x480": 25.2 MHz, 31.5 kHz, 60.0 Hz
(**) NVIDIA(0): Default mode "640x480": 54.0 MHz, 60.0 kHz, 60.0 Hz (D)
(**) NVIDIA(0): Default mode "640x400": 41.7 MHz, 49.7 kHz, 60.0 Hz (D)
(**) NVIDIA(0): Default mode "400x300": 20.0 MHz, 37.9 kHz, 60.3 Hz (D)
(**) NVIDIA(0): Default mode "400x300": 18.0 MHz, 35.2 kHz, 56.3 Hz (D)
(**) NVIDIA(0): Default mode "320x240": 12.6 MHz, 31.5 kHz, 60.1 Hz (D)

Where my custom PAL ones look like this:

Modeline "800x600PAL" 36.00 800 816 820 960 600 653 655 750
Modeline "640x480PAL" 29.50 640 676 680 944 480 530 535 625

I am using the latest 8178 drivers. Can TwinView help me set a smaller virtual screen here? Or second best - which media players can play fullscreen centerd with a zoom factor like 0.85? VLC? Mplayer?
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Old 12-27-05, 10:59 AM   #2
korpenkraxar
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Posts: 7
Default Re: Can we use virtual screen sizes to compensate for overscanning?

No one?
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Old 12-27-05, 11:39 AM   #3
Thunderbird
 
Join Date: Jul 2002
Location: Netherlands, Europe
Posts: 2,105
Default Re: Can we use virtual screen sizes to compensate for overscanning?

You can allways launch a program in a window at specific coordinates.
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Old 12-27-05, 12:28 PM   #4
_john_i_
gtx260/8200M G/DIY Linux
 
Join Date: Aug 2004
Location: Austin, TX USA
Posts: 137
Default Re: Can we use virtual screen sizes to compensate for overscanning?

I've been battling the same thing here. I wish there was a way to make a subscreen. I tried running an Xnest window at the correct coordinates, but you lose nvidia glx and xv in the Xnest.

To compensate for this when watching movies with mplayer, through trial and error I have found a way set the "expand" video filter to shrink and position the movie properly so I don't lose anything to the overscan.

On my TV, I can multiply the width and hight by 0.097 to shrink the movie down to the right size. To shift it to the correct position I found I can multiply the width by 0.07 and the height by 0.04

So for a movie that is 680 x 382 pixels, I would derive the shrink parameters as: 680 * 0.097 = 65, 382 * 0.097 = 37, 680 * 0.07 = 47, 382 * 0.04 = 15

So on mplayer:

mplayer -vf expand=-65:-37:47:15 movie.avi

Note the first two numbers should be negative because we are shrinking it down by that many pixels. The third and fourth parameters shift it down and to the right.

I'm sure this formula will be different for your TV. If you are not using mplayer, I'm not sure how to accomplish this. It took a lot of trial and error to find the magic numbers.

I would really prefer a way to make X fit the proper position so I wouldn't have to do this.
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Old 01-18-06, 01:07 AM   #5
misterflibble
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Join Date: Jun 2004
Posts: 23
Thumbs up Re: Can we use virtual screen sizes to compensate for overscanning?

I tried what korpenkraxar suggested for modifying the modelines to shrink the picture for my 720p output and it worked perfectly! No more 91:47 aspect ratios, and finding ways of forcing mplayer, mythtv, and xine to use a portion of the screen!

I had to change the screen resolutions by increments of 8 pixels, or else the picture ended up tiny for some reason. I'm doing this with VGA output to a component convertor so I suspect that korpenkraxar's problem is that it's only set up to accept standard TV modes (ntsc, pal, 720p, 1080i, etc) on a "tv-out" device. There might be a way to modify this (remove the tvstandard line?) or force it to use a non-standard mode over component out. Anybody?

Haven't done any of this yet because its near-perfect, but [url="http://en.tldp.org/HOWTO/XFree86-Video-Timings-HOWTO/fixes.html#AEN437"]http://en.tldp.org/HOWTO/XFree86-Video-Timi has some methods for moving the picture around once you find the proper size. And btw, the methods for shrinking the screen listed there aren't sufficient for getting it much smaller horizontally without generating underscan vertically.

I'll try to find the old command-line options I had for mplayer and xine for video output sizes and aspect ratios that work if you can't modify X's resolution. Mplayer did have an option that didn't require messing with video filters.
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