Subject: Re: [linux-audio-user] volume plugin
From: Oliver Gerlich (olig9_AT_gmx.de)
Date: Tue Apr 06 2004 - 00:11:44 EEST
Clemens Ladisch schrieb:
> olig9_AT_gmx.de wrote:
>
>>1.) Is it really possible to get inside a plugin the PCM & Master volume
>>settings that are set eg. with alsamixer?
>>2.) Would it be better to do all this in a new plugin,
>
>
> Yes. Yes.
>
> In ALSA, everything is a plugin. This is obvious with pcm plugins
> like dmix, but "hw" is a plugin, too (that just happens to access the
> hardware driver).
>
> For mixer controls and related stuff, there are ctl plugins. The only
> one so far is the "hw" plugin, which provides access to those controls
> implemented by the hardware driver.
>
> A volume scaling plugin would consist of a pcm plugin that would scale
> its input data before handing it off to a slave plugin, and of a
> related ctl plugin that would provide a virtual volume control and
> hand off requests for all other controls to a slave plugin.
>
>
> Regards,
> Clemens
>
>
>
Thanks for your help so far. I wonder that nobody has written such a
plugin yet...
Anyway, do you know if there's some documentation about writing an ALSA
plugin (apart from the existing sources)? Or is there a "simple plugin"
which just passes data along without changing anything (maybe
pcm_plugin.c is something like that)? That would be a good base for this.
Oh, and are there examples for the ctl plugins?
Oliver
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