Monday, December 31, 2012

Fix for TV Overscan in Ubuntu with Nvidia Drivers

Ok, this problem has been a consistent thorn in my side for as long as I've been running Ubuntu on my TV (a number of years). On a lot of HDTVs, setting your computer to display 1080p or 720p or whatever will often cut off the edges of the screen. This cutoff is known as overscan and it used to be necessary because all sorts of garbage data would be displayed in the edges of broadcast signals and video games. Nowadays, that doesn't happen and we want to see every bit of the picture but many TVs still do it.

The easiest fix on TVs of any reasonable quality is to set the TV to "just scan" or "pixel perfect" mode (it goes by many different names depending on manufacturer). However, if your TV is cheap/crappy, you won't have such an option and the only way to deal with it is via software. This works just dandy in Windows, where the Nvidia driver has a handy little "overscan compensation" option where you can adjust a slider until your entire desktop is visible.

Sometimes, depending on driver revision and apparently some other unknown (to me) factors, a similar slider is available in the nvidia-settings applications in Ubuntu. This is undependable, though, and it will sometimes be grayed out or even disappear after you've used it in the past! :O

If you run into any of this, the way to fix it is to add a line to your /etc/X11/xorg.conf files that invokes the ViewPortIn/ViewPortOut options in the driver. So, open a terminal and type:
sudo nano /etc/X11/xorg.conf
You should see:
Section "Device"        Identifier    "Default Device"        Option        "NoLogo"       "True"EndSection
Or something similar. If you don't see any of that (e.g., if your file is totally empty), then just add it in manually.

Next, add a new line under the "NoLogo" line that looks like this (all one line, btw):
Option    "metamodes" "DFP-0: idealxresolution { ViewPortIn=idealxresolution,ViewPortOut=desiredxresolution+excessX+excessY }"
So, if, like me, you want it to run in 720p with 24 pixels of horizontal overscan compensation added to left/right sides and 14 pixels of vertical overscan compensation added to top/bottom, your line will look like this:
Option "metamodes" "DFP-1: 1280x720 { ViewPortIn=1280x720,ViewPortOut=1232x692+24+14 }"
Now, you'll notice that the buffers I've added to the end are exactly half of the total amount of resolution I'm chopping off. That's because the specified amount is added to both sides.

You'll also notice that my line uses DFP-1 instead of DFP-0. I'm not sure why that is, but that's what it identifies as in my nvidia-settings application, so be sure to check there first to find out what yours should be labeled as.

Log out and back in and it should use the new resolution. If not, try rebooting.

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