Bluetooth playback control on Gnome not working

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1

I have been using Gnome (v42) for a while now, and one problem I’ve had was trying to use my bluetooth headphone’s buttons to control playback and volume on my laptop. Instead, it shows a (\) kind of symbol when I press these buttons. The volume and brightness buttons on the laptop’s keyboard work fine.

I recently gave KDE (v5.26) a try, and that specific feature worked out of the box. Volume control works, and play/pause works (at least with mpv which I’m using often). The laptop’s volume and brightness buttons also work fine with KDE.

I kinda assume this is a Gnome vs KDE thing (at least the way their NixOS modules are set up), right?

Any tips where I should start investigating this?

For reference, this is my configuration.nix diff:

-    desktopManager.gnome.enable = true;
+    # desktopManager.gnome.enable = true;
+    desktopManager.plasma5.enable = true;

PS: all this on NixOS 22.05.

2

No idea, but have you tried pipewire instead of pulseaudio to see if it’s changing something? Pulseaudio is progressively getting replaced with pipewire (ubuntu made the change already I think) and pipewire is much better, at least in term of bluetooth. It may be a bug from gnome but it’s worse trying this first.

3

I have no idea if my KDE setup is using pipewire right now, but according to my running processes, I seem to be using pulseaudio:

~
❯ ps aux | grep pulse
kostas      2776  0.0  0.1 1924776 18264 ?       S<sl Nov21  11:00 /nix/store/41zya3v12yfrrql5fbfwn6m2cw4ffa87-pulseaudio-15.0/bin/pulseaudio --daemonize=no --log-target=journal
kostas      2874  0.0  0.0 237600  3912 ?        Sl   Nov21   0:00 /nix/store/41zya3v12yfrrql5fbfwn6m2cw4ffa87-pulseaudio-15.0/libexec/pulse/gsettings-helper
kostas    482422 11.1  1.0 2421340 172456 tty2   Sl+  22:00   0:03 /run/current-system/sw/bin/systemsettings kcm_pulseaudio
kostas    482664  0.0  0.0 223608  2628 pts/1    S+   22:00   0:00 /nix/store/qd9jxc0q00cr7fp30y6jbbww20gj33lg-gnugrep-3.7/bin/grep --color=auto pulse

~
❯ ps aux | grep pipe
kostas    482697  0.0  0.0 223608  2688 pts/1    S+   22:00   0:00 /nix/store/qd9jxc0q00cr7fp30y6jbbww20gj33lg-gnugrep-3.7/bin/grep --color=auto pipe
4

Yeah pulseaudio is certainly default for now. You need to enable it (see e.g. the wiki)