[pulseaudio-discuss] Simulating Mic Boost in Pulseaudio

[T. H.]

Hello all,

For some reason, after moving from ALSA 1.0.15 to 1.0.16, my alsamixer does
not display anymore the Mic Boost (+20dB) option for my digital microphone
(of an Intel HDA ICH8), which is quite useful to enhance its capture volume
in Ekiga, Skype etc.

This annoying bug started me wondering if it is possible to simulate this
mic boost using pulseaudio, which I use on top of ALSA.

I was thinking about two possible solutions:

1) instructing pulseaudio to feed the output of the microphone capture
source to some sort of amplitude multiplier module, which would become the
default source. However, I don't know if there is such a module and how to
plug it to the correct location.

2) forcing pulseaudio to accept a default source volume  >100%. I noticed
that some channels allow me to choose up to 400% (e.g., the sink
alsa_output.pci_8086_284b_sound_card_0_alsa_playback_0), but the one I
assume the microphone uses
(alsa_input.pci_8086_284b_sound_card_0_alsa_capture_0), for some reason,
resumes its 100% position immediately after I choose something >100%. I
don't know if this is the expected behavior, but it would be nice if I could
force it to accept larger values in order to boost the volume of my digital
mic, for instance, by changing some config file.

Since I'm just starting using pulseaudio, I'm not sure if any of these
solutions would be straighforward to configure, though they seem sensible to
me. If someone in this list has been successful trying to do something
similar, I'd would be very interested to hear! If not, the details on how to
implement this idea might be an interesting topic to discuss here, since it
could be used as a generic solution, using pulseaudio, to improve the
volume deficiencies in microphones of many people.

Thanks in advance,
HatX
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