Cinnamon: Add option to prevent pulseaudio from adjusting microphone input gain

[bgemmill]

```

• Cinnamon version: 4.6.7
• Distribution: Linux Mint 20 Ulyana
• 64 bit
  ```

Issue
Users should have the option to fix the input gain of an audio device and prevent automatic adjustment.

At the moment, applications can change input gain, and in some cases can lead to unwanted outcomes.

WebRTC in Chrome has an automatic gain adjustment that defaults to on, and will sometimes trend to 0% or 100% even if that ends up silencing the participant or just sending noise over the line. For reference:
https://askubuntu.com/questions/279407/how-to-disable-microphone-from-auto-adjusting-its-input-volume
https://askubuntu.com/questions/689209/how-to-disable-microphone-volume-auto-adjustment-in-cisco-webex

There is no global option to disable this automatic gain control when it leads to bad outcomes, and the Chrome team does not seem to want to make such an option:
https://bugs.chromium.org/p/chromium/issues/detail?id=435112#c3

Steps to reproduce
1) Set input gain of a micrpohone to 50% in the sound settings, and leave the sound settings window open to observe.
2) Attend a meet.google.com video call with a number of participants.
3) Talk for a while at varying volume. Get in a spirited discussion or attempt to speak up a few times.
4) Observe the microphone volume drifting in the sound control panel window.
5) If you become too soft to hear or unintelligible, you must manually set the slider back to 50% during the meeting.

Expected behaviour
There should be a button to fix the input gain in the input sound control panel.

It looks like this could be done by setting that pulseaudio input device's mic boost parameter to a fixed value from merge in pulseaudio settings for that device:
https://nzeid.net/pulseaudio-disable-auto-volume
https://askubuntu.com/a/736655
https://askubuntu.com/a/761103

[token47]

+1 on this, please please please implement this. This auto gain is terrible most of the time. I have an external mixing table where I carefully set levels for mic and monitor clipping and the auto gain is always ruining my setup.

[artdimaio]

+1 please!

I have the same issue, I work remotely on discord, and even with a pretty good mic, the boost level auto adjusting makes the gains extremely high and my voice gets ultra loud...

[cnvx]

+1
I'm experiencing this problem when using Jitsi Meet (another WebRTC solution) using the internal mic.

[bgemmill]

I've submitted the issue to the pulseaudio project in case this is a double counting problem with microphone gain versus microphone boost:
https://gitlab.freedesktop.org/pulseaudio/pulseaudio/-/issues/999