Mumble increases "Microphone power" over time (Pipewire)

[adf-patrickha]

Description

Mumble raises the "Microphone power" to absurd levels over time (Observable via the Mumble audio statistics). It usually starts at 071%, and goes up to 400+%, which leads to constant loud noise, even when the hardware microphone is muted. This makes the input unusable, until Mumble is stopped. The output device remains
When I close mumble, wait a few seconds and restart it, the settings are back to normal.

This change affects other applications too that use the same input device. Interestingly no change is made on the input device settings. The input level of the device in alsamixer and pulsemixer stay the same. Also the services wireplumber, pipewire, pipewire-pulse do not log anything when Mumble increases the power.

Steps to reproduce

1. Open Mumble and connect to server
2. Open Audio Statistics (Self > Audio Statistics)
3. Wait over time and observe the Microphone power rising.

Mumble version

1.5.634

Mumble component

Client

OS

Linux

Reproducible?

Yes

Additional information

OS: Manjaro
Kernel: 6.6.40-1-MANJARO
Device: ThinkPad T14 Gen 5

Relevant log output

journalctl --user -u wireplumber -u pipewire -u pipewire-pulse -S today                                                                                                                           
-- No entries --

pulsemixer --list-sources
Source:		ID: source-344, Name: PRO Mono, Mute: 0, Channels: 1, Volumes: ['100%'], Default

Screenshots

Audio Statistics while unmuted, without talking:

Audio Statistics while muted:

[Krzmbrzl]

Have you tried disabling automatic gain control?

[adf-patrickha]

Have you tried disabling automatic gain control?

@Krzmbrzl do you mean the Max. Amplification settings in Settings > Audio Input > Audio Processing? I have that one on the lowest value 1.00. I don't think there is another setting, matching that description.
Here a screenshot from my input settings:

I also tried disabling the noise suppression, but it did not make a difference.

[Krzmbrzl]

Hm. I'm not aware of Mumble doing any input level adjustments that would be visible system wide... does this also happen with other audio backends?

@davidebeatrici do you have any idea about this?

[davidebeatrici]

Unfortunately not. I regularly use PipeWire with similar settings and have never encountered such an issue.

[Krzmbrzl]

@adf-patrickha does the behavior depend on what input mode (voice activation, PTT, continuous) you are using?

[adf-patrickha]

@adf-patrickha does the behavior depend on what input mode (voice activation, PTT, continuous) you are using?

No, I haven't used those modes, because they are not really an option for my use-case sadly. PTT does not work well with Wayland, as global hotkeys do not really work. I know RPC sub commands are a thing and I use them for togglemute/toggledeaf. But that does not really work with press/release keybindings from my experience.

And continuous does not work because of background noise and the need to togglemute all the time.
But I can give it a shot temporarily to see if behaves differently 👍

[adf-patrickha]

Same behavior with continuous:

Additional info btw.: I already tried another headset too. So it's not a hardware issue either.

[Krzmbrzl]

Hm okay - I have no idea what's going on. Can you reproduce the same issue on a different machine?

[adf-patrickha]

Hm okay - I have no idea what's going on. Can you reproduce the same issue on a different machine?

@Krzmbrzl No, it's not reproducable on another device. None of my colleagues are having this issue either. I only have this issue since switching to a new device (ThinkPad T14 Gen 5). But it's a Mumble specific issue that I'm not having with any other application using microphone input. So Mumble is the trigger causing the issue, but the root cause could also be the sound card or Pipewire for sure.