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[solved] Emulate non-existent display-resolution
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musv
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PostPosted: Thu Aug 14, 2014 7:12 pm    Post subject: [solved] Emulate non-existent display-resolution Reply with quote

Good evening (or morning),

I've bought me a nice, very cheap monitor some weeks ago. That thing can do 2560x1600 and 1280x800 (which looks quite ugly), but for some strange reason there's no other screen resolution possible.

less /var/log/Xorg.0.log:
[  2125.202] (**) NVIDIA(0): Using HorizSync/VertRefresh ranges from the EDID for display
[  2125.202] (**) NVIDIA(0):     device KJT DVI (DFP-0) (Using EDID frequencies has been
[  2125.202] (**) NVIDIA(0):     enabled on all display devices.)
[  2125.202] (WW) NVIDIA(0): No valid modes for "DFP-0:1920x1200"; removing.
[  2125.202] (WW) NVIDIA(0): No valid modes for "DFP-0:1440x900"; removing.
[  2125.203] (WW) NVIDIA(0): No valid modes for "DFP-0:1024x640"; removing.
[  2125.203] (II) NVIDIA(0): Validated MetaModes:
[  2125.203] (II) NVIDIA(0):     "DFP-0:2560x1600"
[  2125.203] (II) NVIDIA(0):     "DFP-0:1280x800"
[  2125.203] (II) NVIDIA(0): Virtual screen size determined to be 2560 x 1600
[  2125.238] (--) NVIDIA(0): DPI set to (101, 101); computed from "UseEdidDpi" X config
[  2125.238] (--) NVIDIA(0):     option


And so of course xrandr fails, when I try to set a different resolution:
Code:
xrandr --output DVI-I-1 --mode "1920x1200"
xrandr: cannot find mode 1920x1200


Unfortunately a lot of games don't provide 2560x1600. Currently I'm playing Ufo AI. Version-2.4 provided a 2560x1600 setting, Version 2.5 doesn't.

Is there a chance to provide a resolution of 1920x1200 (or any other resolution) to the program / X-Server / Desktop, which will be scaled by the graphics card to the native monitor resolution of 2560x1600? The goal is to have any possible resolution in the programs without the need to switch the monitor mode.


Last edited by musv on Fri Aug 15, 2014 8:54 am; edited 1 time in total
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NeddySeagoon
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PostPosted: Thu Aug 14, 2014 9:04 pm    Post subject: Reply with quote

musv,

I had a Samsung monitor like that.

The native panel resolution is 2560x1600. 1280x800 is achieved by making each pixel in the 1280x800 into four on screen pixels.
The display lacks a rescale feature.

However all is not lost. Some graphics cards can do rescaling but the feature is not normally used as a 1:1 mapping between the pixel buffer in the video card and th pixels on the screen is a very good thing.

You need to try to set your Xorg to drive the display at 2560x1200 and at the same time allow the game to draw at whatever resolution it wants.
This is graphics card and driver dependent. I suspect it will need a lot of CPU/GPU resource too so it may impact the frame rate you can get it a game.

There is also an ugly hack. Write a mode line to display the game image centred on the screen with black borders.
Top left is easiest but you can do any random position you like.

Lastly, just because the EDID does not advertise a mode does not mean it won't work.
Try the emergency manual override with a mode line.
Providing the display is a flat panel, it won't harm the display if it doesn't work.

Hmm not even 640x480, that is rare. How does the grub splash screen look?
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Computer users fall into two groups:-
those that do backups
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musv
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PostPosted: Fri Aug 15, 2014 8:47 am    Post subject: Reply with quote

NeddySeagoon wrote:
You need to try to set your Xorg to drive the display at 2560x1200 and at the same time allow the game to draw at whatever resolution it wants.
This is graphics card and driver dependent. I suspect it will need a lot of CPU/GPU resource too so it may impact the frame rate you can get it a game.

That's what I did. In Civ5 it works "reliable". But there's nothing scaled. The 1920x1200 view port is centered with big black borders on the big screen.

In Ufo AI I had some strange variations:
  • The game starts with 1920x1200 in the lower-left side of the monitor. The upper and right part remains black.
  • The X-Server switched "somehow" automatically to 1280x800. Sometimes it works, sometimes the virtual screen size of 2560x1600 remains. In this case the mouse pointer is vanished. Moving the mouse scrolls the virtual screen.
  • In one case I got a full screen with the 1920x1200 resolution. I'm not sure, how I achieved that. Maybe you're right, and the monitor can switch to that resolution even if it's not a supported resolution mode. Unfortunately there occurred a problem after the next reboot. The monitor remained in standby mode and didn't show anything, neither in Grub/Framebuffer nor in X. I had to turn off the computer and the monitor completely (plug off the power).


NeddySeagoon wrote:
Hmm not even 640x480, that is rare. How does the grub splash screen look?

Works without problems. Don't know why. I configured there a resolution of 1440x900, but it works with the standard vga resolution too.

I found a solution. I doesn't look very good, the picture lost a lot of sharpness, but it works with Civ5 and with Ufo AI:
Code:
xrandr --output DVI-I-1 --mode 2560x1600 --scale 0.75x0.75 --fb 1920x1200 --panning 1920x1200

  • mode: real screen size
  • fb: virtual screen size
  • panning: didn't understand exactly, what it means. But in my case it should be the same value as fb.

Xvidtune shows me a resolution of 1920x1200. Both games give me a full screen.

To switch back:
Code:
xrandr --output DVI-I-1 --mode 2560x1600 --scale 1x1


With that solution I can live for the needed cases. But better solutions are still welcome.
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NeddySeagoon
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PostPosted: Fri Aug 15, 2014 10:14 pm    Post subject: Reply with quote

musv,

In the video world, pan means to move the view so that things appear at one side of the screen' move across the screen an vanish at the other side.
Panning can be carried out in either direction to keep something important from vanishing from view.

When a wide screen film was shown on a standard (not HD) TV, broadcasters, could choose 'letterbox' mode which shomeh the whole image but with black bars at the top and bottom of the screen, or pan and scan, which filled the screen but cropped the edges. For some sceans, the action would have been cropped, so the telecine device was panned to show a part of the image that would otherwise have been cropped.

Since your display works correctly at 640x480, its worth testing with modelines.
You can switch resolutions using the keyboard, its Ctl-Alt-+ and Ctrl-Alt-- (thats plus and minus) on the numeric pad.
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NeddySeagoon

Computer users fall into two groups:-
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