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Brightness control for HDMI monitor

ma flag

I cannot get the Ubuntu brightness slider to change the brightness of my (Dell) monitor which is attached by HDMI. I am using 21.10. This is a desktop system with no built in monitor. I can control the brightness via xrandr on the command line, but the gnome brightness slider does absolutely nothing. I can control the brightness slider either via the drop down in the top right corner or via keyboard function keys. Both work fine for moving the knob on the slider, but the brightness of the monitor is unaffected.

I have tried changing grub parameters but that seems to affect the mapping of keys to enable controlling the brightness slider, which isn't my problem.

I used to have video via my Vega enabled Ryzen CPU, and brightness didn't work. Now I have a dedicated Radeon card, and it still doesn't work.

I have searched extensively but all solutions that I find are focused on one of:

  1. making function keys work
  2. using xrandr or some other tool on the commandline
  3. installing alternative apps

The first two aren't my problem and the latter doesn't interest me.

Any pointers would be welcome.

us flag
The GNOME brightness slider is to control backlight of laptops, so are the function keys. You will need either need a software like https://github.com/ddccontrol/ddccontrol or https://github.com/lordamit/brightness/, or change the brightness by pressing the monitor's configuration keys.
Vegar Hatlevik avatar
ma flag
Thanks, I appreciate your answer, but it makes little sense that there's one way to do it for laptops and another for everyone else. Can't we control what happens when the slider moves? E.g. can we modify which command gets called?
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