[pulseaudio-discuss] How to do dynamic control?

Steven Wawryk stevenw at acres.com.au
Fri May 5 09:31:21 UTC 2017


I'm looking for some advice on how to go about a task I need to do.

Some time ago, I developed an ALSA driver (codec, I2S and soundcard) and 
a set of PulseAudio CLI
scripts for an in-house designed 24 channel audio card.  This worked 
well for a static setup that
didn't need any dynamic control.

Now, however, we have a requirement for some dynamic control.  In 
particular, PTT (push-to-talk) and
conditional filtering on some channels.  For PTT, some audio outputs 
need to be conditionally muted
according to the state of the PTT signals.  The conditional filtering is 
required for a channel that
is connected to a radio, which when in FM mode requires pre-emphasis on 
output and de-emphasis on
input.  Both the state of the PTT signals and the mode requiring 
filtering are detected in software.

How can I go about doing this?  My PulseAudio knowledge is limited to 
config and CLI.  The fact that
there are ALSA and PulseAudio utilities that allow dynamic muting says 
to me that it should be
possible to do it in software according to PTT, but it is a mystery to 
me how it's done.  Also, from
the PulseAudio module documentation I can see a "module-ladspa-sink" 
module that allows for
filtering, but I don't see how I can turn it on and off dynamically.


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