User-space control elements in ext PCM plugin

User-space control elements in ext PCM plugin

[Marcus Weigelt]

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.

Marcus
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Re: User-space control elements in ext PCM plugin

[Colin Guthrie]

'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/

Day Job:
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Re: User-space control elements in ext PCM plugin

[Marcus Weigelt]

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: 

http://article.gmane.org/gmane.linux.alsa.devel/50181

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?

Marcus


-------- Original-Nachricht --------
> Datum: Wed, 07 Apr 2010 12:32:59 +0100
> Von: Colin Guthrie <gmane@colin.guthr.ie>
> An: alsa-devel@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/
> 
> Day Job:
>   Tribalogic Limited [http://www.tribalogic.net/]
> Open Source:
>   Mandriva Linux Contributor [http://www.mandriva.com/]
>   PulseAudio Hacker [http://www.pulseaudio.org/]
>   Trac Hacker [http://trac.edgewall.org/]
> 
> _______________________________________________
> Alsa-devel mailing list
> Alsa-devel@alsa-project.org
> http://mailman.alsa-project.org/mailman/listinfo/alsa-devel

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Re: User-space control elements in ext PCM plugin

[Jaroslav Kysela]

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On Wed, 7 Apr 2010, Marcus Weigelt wrote:

> 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?

The build-in softvol plugin uses this mechanism. But I'm not sure, if this 
way is supported in the external PCM plugins interface.

 						Jaroslav

-----
Jaroslav Kysela <perex@perex.cz>
Linux Kernel Sound Maintainer
ALSA Project, Red Hat, Inc.

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Re: User-space control elements in ext PCM plugin

[Marcus Weigelt]

Yes, I think the softvol plugin is the closest thing to what I want to do.
So I think I will just try it :) Thanks for your support!

Marcus

-------- Original-Nachricht --------
> Datum: Wed, 7 Apr 2010 13:58:40 +0200 (CEST)
> Von: Jaroslav Kysela <perex@perex.cz>
> An: Marcus Weigelt <noize007@gmx.de>
> CC: alsa-devel@alsa-project.org
> Betreff: Re: [alsa-devel] User-space control elements in ext PCM plugin

> On Wed, 7 Apr 2010, Marcus Weigelt wrote:
> 
> > 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?
> 
> The build-in softvol plugin uses this mechanism. But I'm not sure, if this
> way is supported in the external PCM plugins interface.
> 
>  						Jaroslav
> 
> -----
> Jaroslav Kysela <perex@perex.cz>
> Linux Kernel Sound Maintainer
> ALSA Project, Red Hat, Inc.

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