[pulseaudio-discuss] Dynamic range compression

[Tanu Kaskinen]

On Mon, 2015-09-28 at 15:30 +0200, Mikhail Morfikov wrote:
> A few days ago I found a module called module-ladspa-sink ,
> and it can be enabled by adding the following code to the
> /etc/pulse/default.pa file:
> 
> .ifexists module-ladspa-sink.so
> .nofail
> load-module module-ladspa-sink sink_name=compressor plugin=sc4m_1916
> label=sc4m control=1,1.5,401,-30,20,5,12
> .fail
> .endif
> 
> It works, but I was trying to figure out what exactly
> control=1,1.5,401,-30,20,5,12 means. There's a link
> (http://plugin.org.uk/ladspa-swh/docs/ladspa-swh.html#tth_sEc2.92),
> where you can find some documentation on the sc4m_1916 plugin,
> but actually I don't really know which of the values corresponds
> to the specific options. In the link, there's 9 parameters,
> and in the code above, there's 7 I think.
> 
> Is there someone who could cast a little light on the control
> numbers?

module-ladspa-sink fails to load if you don't provide all parameters,
so if it works, the plugin really has only 7 control parameters. I
don't know how you then should map them to the documentation. There
very likely is some handy little program somewhere that you could use
to inspect the plugin, but the only one that I can mention off the top
of my head is JACK Rack, but that obviously depends on JACK, and if you
don't already use JACK, it can be a bit of a hassle to set it up. I'd
expect there to be some simple command line ladspa plugin inspector
program too that doesn't need any audio access.

[1] https://wiki.freedesktop.org/www/Software/PulseAudio/Documentation/User/Modules/#index47h3

-- 
Tanu