2013-12-09 15:18

Fixing HDMI overscan on Ubuntu again

A while ago, I wrote about using a cheap 1080p TV as external monitor on Ubuntu. That happens to cause some weird problems because the TV is trying to be smart about clipping things, etc (just read it if you want.)

In it I outlined a bunch of approaches that succeed in fixing overscan with different levels of success. Here's some extra detail for one of those, setting up a custom mode which doesn't trigger overscan:

First, go to http://www.arachnoid.com/modelines/ and create a modeline for some mode that is close to 1080p but not quite there. How close to 1080p you can get before your TV decides "this is 1080p I am doing overscan" will vary.

For example, I can do 1800x1012 with this modeline and can probably do a bit more:

Modeline "1800x1012_60.00" 151.42 1800 1912 2104 2408 1012 1013 1016 1048 -HSync +Vsync

Then, to experiment, we can add this mode to X using xrandr. Here HDMI1 is the output I have connected to my TV:

xrandr --newmode "1800x1012_60.00" 151.42 1800 1912 2104 2408 1012 1013 1016 1048 -HSync +Vsync
xrandr --addmode HDMI1 "1800x1012_60.00"
xrandr --output HDMI1 --mode "1800x1012_60.00"

I don't think it works as well as the force-dvi hack from the last time, but hey, I do get HDMI audio, and I have not seen this described elsewhere using xrandr.


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