[pulseaudio-discuss] Config option to disable auto microphone boost?

[Arun Raghavan]

On Wed, 11 May 2016, at 06:22 PM, Laszlo KERTESZ wrote:
> Back with more data.
> I used this option since then, but it turns out that even if Pulseaudio
> doesnt do it,some other apps will still abuse the gain adjustments.
> 
> For example i just finished a Google Hangout session (working from my
> home
> desktop) and with "aec_args="analog_gain_control=0\
> digital_gain_control=0"" - the mic boost (element "Rear Mic Boost") was
> going back to 53 (mid level) causing loud noise when there was silence on
> my side (used headphones with microphone).
> After i set "volume = zero"
> in /usr/share/pulseaudio/alsa-mixer/paths/analog-input-rear-mic.conf,
> "[Element Rear Mic Boost]" section and restarted Pulseaudio, AGC
> adjustments were still made by Chrome, but only within the "Capture"
> control and nobody complained anymore.

Indeed, it might be interesting to explore an option to disable using
boost controls via UI. At least for me, that's not something I see
myself immediately having the time for. 

> So Hangouts does this, and it seems Chrome has AGC built in for "plain"
> Webrtc too with no option to disable (i at least couldnt find one). I
> tested Jitsi Meet (Webrtc MUC server, locally deployed) and Chrome uses
> AGC
> boost adjustments with the same Pulseaudio setup.

FWIW, with the upcoming PA 9.0, things may get better with built-in AGC.

On Firefox, I see a config option to disable AGC, haven't tested if it
does.

> Skype on the other hand always worked just fine with echo-cancel - either
> doesn't do AGC on its own or does it better (this point isnt that
> important
> now since it will likely stop working for audio/video in the immediate
> future and the browser version will replace it with Webrtc sometimes,
> hopefully before it, returning us to the previous point). Thinking about
> it, desktop apps in general are echo-cancel-friendly, even the
> java-powered
> Jitsi desktop client.
> 
> It seems that in cases like this the "aec_args" are insufficient and some
> option should be provided to disable the gain adjustments server-wide
> since
> the editing of the config files are overwritten on Pulseaudio update.
> 
> Also note the fact that some sound cards (like most? USB headsets) that
> don't have variable mic boost options are immune to this issue. I have
> one
> USB headset wit mic (actually tried multiple models, all with the same
> results) at work and they work just fine with echo-cancel regardless of
> Pulseaudio's settings.

We currently don't have the ability to do that. We might get this at
some point as part of ongoing efforts to enable sandboxing.

-- Arun