adding custom screen resolutions

[JonBondy]

My monitor's intrinsic size is 1366x768, but the only high-res screen resolutions I am offered are

1024x768
1152x864
1280x1024

Is there a way to enter a custom resolution into this list?

I've looked at LOTS of articles that talk about editing an X11 config file, but that file is not on my system. Also articles about installing various drivers, but I don't know if I need them.

I'm running a new ASUS MoBo with on-board video hardware (ATI Radeon HD 4200), latest Kubuntu

[oshunluvr]

Re: adding custom screen resolutions

No matter what you need to use the correct driver for your monitor to get the best performance. This alone may allow xorg to correctly configure it for you.

If not basically, there are two ways to do this manually:

1. If you want an xorg.conf file you can generate one and edit it. There are lots of posts here on how to do that. Alternately, download someone else's xorg.conf and put it in /etc/X11. It will be used if it is there.

2. xrandr can do it. You need to determine the correct modeline for your monitor. The command line tools for this will not generate a line for 1366x768 because 1366 is not divisible by 8. You may be able to find a correct modeline on the internet. There are a series of commands to get this done that can be put in your Xsession.d directory to happen automatically. If you want to try this method, post the output of xrandr -q

[JonBondy]

Re: adding custom screen resolutions

Thanks for your help!

You suggested getting the right driver for my monitor. Do you mean for my video hardware? In any event, is there a simple way to do this?

I'd be happy with 1360x768, if that is easier than 1366x768

Here is the xrandr output:

Screen 0: minimum 320 x 200, current 1152 x 864, maximum 8192 x 8192
VGA-0 disconnected (normal left inverted right x axis y axis)
DVI-0 connected 1152x864+0+0 (normal left inverted right x axis y axis) 628mm x 3433mm
1280x1024 75.0 60.0
1152x864 75.0*
1024x768 75.1 70.1 60.0
832x624 74.6
800x600 72.2 75.0 60.3 56.2
640x480 72.8 75.0 66.7 60.0
720x400 87.8 70.1

[oshunluvr]

Re: adding custom screen resolutions

Oops Of course I meant video card driver - there's no monitor drivers...

As far as your monitor - you DO need the manufacturers specs: native resolution and refresh rate (aka horz scan freq).

A small warning: try not to set your monitor at a resolution or scan freq. it cannot handle. I have heard it can cause damage, but I've never seen it happen. Most monitors have a range within which they can be used, but LCD monitors rarely look very good if you use other than maximum native resolution and scan freqs.

In my examples here I will assume your monitor is 1366x768 at 60hz. All commands are in a konsole terminal.

First you need a modeline. As I mentioned there are command line tools to generate one (but not at 1366). They are gtf and cvt. Here's an example of cvt output:

:~$ cvt 1366 768 60
# 1368x768 59.88 Hz (CVT) hsync: 47.79 kHz; pclk: 85.25 MHz
Modeline "1368x768_60.00" 85.25 1368 1440 1576 1784 768 771 781 798 -hsync +vsync

and heres gtf:

:~$ gtf 1360 768 60

# 1360x768 @ 60.00 Hz (GTF) hsync: 47.70 kHz; pclk: 84.72 MHz
Modeline "1360x768_60.00" 84.72 1360 1424 1568 1776 768 769 772 795 -HSync +Vsync

Notice the resolution changed from the requested 1366 to 1368 in both examples but the scan freq. is very slightly different..

I use this resolution on a 50" plasma tv. Since 1366 is the native resolution for a 1080i tv a good resource for correct modelines is mythtv databases because the mythtv users all use tv's. Here's a good place to start:modelines

Once you've settled on a modeline you want to try, here are the sequence of commands:

xrandr --newmode "1366x768" 84.75 1366 1440 1584 1776 768 769 772 800 -hsync +vsync
xrandr --addmode DVI-0 1366x768
xrandr --output DVI-0 --mode 1366x768

This will immediately change your display to the new mode. If it doesn't look right, switch back to the other mode and start over:

xrandr --output DVI-0 --mode 1152x864
xrandr --delmode DVI-0 1366x768
xrandr --rmmode 1366x768

If you want to attempt multiple modes in one sitting you can --newmode a dozen or so using different names and switch to them all one by one until you're happy. The names i.e. "1366x768" are meaningless to xrandr, it's the numbers after the name that it uses.

If you can't find a mode that's just right you can play with the numbers A LITTLE BIT! Here's a good resource to understand what's going on: ReadMe
The important part from that page is about 3/4 the way down and shows a nice table to help you.

Once you are satisfied with your resolution, add the three xrandr commands to something to get them executed. There are about a dozen places you can do this and I'm not sure which is the "proper" place. Try in /etc/X11/Xsession or /etc/rc.local and see if either works correctly for you.

[JonBondy]

Re: adding custom screen resolutions

Thanks for taking so much time to help me! In the end, I found, downloaded, and installed the appropriate ATI driver, and then ATI Catalyst, and was immediately able to use that to get to 1280x768, which is "close enough".

[oshunluvr]

Re: adding custom screen resolutions

As long as it looks OK to you that's all that matters.