[Freeswitch-users] Portaudio Improvements

Mitch Capper mitch.capper at gmail.com
Sat Jan 22 21:52:13 MSK 2011

It is true PA lacks volume control, it had been something I was debating.
Adding gain is pretty simple as you are for the most part just multiplying
up the samples I believe so would not be a major item to add to portaudio, I
however decided not to go this route for two reasons.  1) In Windows each
application has its own volume setting (Vista and higher),  and apps are
starting to tie into this than internal volume controls.  The downside is it
doesn't distort audio/have a gain option.   This is when I thought about
allowing for a fixed gain amount added to portaudio.  2) Freeswitch actually
has its own built in volume control settings with set_audio_level.
set_audio_level allows for 9 settings (4 lower 4 higher) and seems to do a
good job at digital volume control.
Avoiding modifying the audio stream itself could also result in less
distortion when using actual volume controls (headsets, etc).

So if you want volume control I would say take a look at set_audio_level as
it may be the simplest method.   Adding it to portaudio would work but one
of the nice advantages of set_audio_level is the fact you can also do it per
channel rather than globally:)


On Fri, Jan 21, 2011 at 5:44 PM, Seven Du <dujinfang at gmail.com> wrote:

> In addition to AEC. I also found PA lacks the ability to change the
> sound device volume. I tried to control sound devices in QT but
> haven't find a way. Ideas on this?
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