[alsa-devel] User-space control elements in ext PCM plugin

Marcus Weigelt noize007 at gmx.de
Wed Apr 7 13:54:33 CEST 2010

Hi Colin, 

thanks for your answer. In general the pulse plugin does more or less what I want - present controls in userspace, right.
But the PulsePlugin actually consists of two plugins, a PCM plugin (pcm_pulse.c) and control plugin (ctl_pulse.c). 
As far as I understand, the control events/messages from the user space sliders are directed to the pulse audio server via the ctl_plugin. My question is actually, how to make use of them directly in the pcm plugin?

As I told, a similiar request was done three years ago: 


That´s where I got the idea of creating the user-space control elements directly inside of the PCM plugin, or did I get it wrong?


-------- Original-Nachricht --------
> Datum: Wed, 07 Apr 2010 12:32:59 +0100
> Von: Colin Guthrie <gmane at colin.guthr.ie>
> An: alsa-devel at alsa-project.org
> Betreff: Re: [alsa-devel] User-space control elements in ext PCM plugin

> 'Twas brillig, and Marcus Weigelt at 07/04/10 11:01 did gyre and gimble:
> > Hi,
> > 
> > I´m having an external PCM plugin that should do some processing on
> > the audio. That part works fine. Now I´d like to have some way to
> > modify the way to give some parameters to the plugin to tell it how
> > the processing is done (eg. set delay time, pan, attack time, ...). 
> > I´ve searched the web for days and hours, but could not really find
> > something. On the alsa mailing list there was a similiar question
> > three years ago, and the answer was, that one could create user-space
> > control elements in the plugin. How is that done? I could not find
> > examples or good documentation about it. Did I miss something out?
> > Can anyone give me a hint, maybe a link to some docs about it or
> > source of a PCM plugin creating/using user space control elements?
> > Thanks a lot.
> Try looking at the PulseAudio plugin. It presents userspace sliders to
> control the volume. If I've not misunderstood your request this should
> do what you need.
> Col
> -- 
> Colin Guthrie
> gmane(at)colin.guthr.ie
> http://colin.guthr.ie/
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