Can't adjust 3.5mm headphone audio volume in 3.6 beta

[austin-ek]

Your system information

• Steam client version: 1722380543
• SteamOS version: 3.6.9 (20240707.101)
• Opted into Steam client beta?: Yes
• Opted into SteamOS beta?: Yes
• Have you checked for updates in Settings > System?: Yes

Please describe your issue in as much detail as possible:

If I launch a game and then unplug/plug my 3.5mm headphones from the headphone jack on the Steam Deck, I can no longer adjust the audio volume for the headphones.

I tried using the physical volume buttons, the quick access menu volume slider, and the audio settings tab volume slider. All of the sliders work, but the volume doesn't actually change.

It seems that the slider is actually adjusting the speaker volume. If I turn the volume all the way up on the slider, the headphone volume doesn't change, but the speaker volume is at 100% when I unplug the headphones.

This is not present on the SteamOS 3.5 stable release. This is only an issue in 3.6 beta. Using Steam Deck LCD in game mode (was not able to reproduce in desktop mode).

This is not an issue for other audio output devices, only 3.5mm headphones (I've tried bluetooth headphones and USB-C headphones).

Steps for reproducing this issue:

1. Plug in 3.5mm headphones to the headphone jack on the Steam Deck (I have the LCD model).
2. Launch a game in game mode. It only happens when a game is open in game mode, and It happens with every game I've tried.
3. Unplug the headphones and plug them back in.
4. Try adjusting the volume using any method (volume buttons, quick access menu slider, or settings slider). You will see that the sliders work, but the output volume of the headphones doesn't actually change at all.

[austin-ek]

One workaround I could find is to add a dummy sink by adding this file in ~/.config/pipewire/pipewire-pulse.conf.d/dummy-sink.conf and restarting.

pulse.cmd = [
    { cmd = "load-module" args = "module-null-sink media.class=Audio/Sink sink_name=dummy channel_map=surround-51" flags = [ "nofail" ] }
]

And when I run into this issue, switching the audio to the dummy sink and back again makes the headphones volume adjustment work. It's not exactly a great workaround but it's something.

[Brooksiebear19]

Replying to https://github.com/ValveSoftware/SteamOS/issues/1593#issuecomment-2394758252

This does work! Switching to the dummy then to default again will not update the on-screen slider though, as that will show the speaker's volume. You have to press the physical volume buttons and then on-screen slider will work. I think switching to "external device" until default says "auto" might also work.