Getting and changing Volume

Getting and changing Volume

[Luca bedogni]

Hi all
	first message from me here.
I'm writing a simple application for interacting with alsa. All's ok,
except for the volume. 
I open the pcm devices correctly, but then can't find nothing to get
the current volume and setting the new one, such alsamixer does.

Any idea?

Bye
	Bedo
-- 
Debian Powered GNU/Linux User #373118
Bedogni Luca - 	Blog | http://blog.lucabedogni.it
		Site | http://www.lucabedogni.it
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Re: Getting and changing Volume

[Takashi Iwai]

At Wed, 30 Aug 2006 12:53:27 +0200,
Luca bedogni wrote:
> 
> Hi all
> 	first message from me here.
> I'm writing a simple application for interacting with alsa. All's ok,
> except for the volume. 
> I open the pcm devices correctly, but then can't find nothing to get
> the current volume and setting the new one, such alsamixer does.
> 
> Any idea?

Currently, there is no explicit API which mixer element corresponds to
a certain PCM stream.  So, most apps use simply the mixer interface
and access either "PCM" or "Master" mixer element for controlling the
total volume.

In theory, it's possible to build a softvol entry for each PCM
substream so that the volume can be controlled independently by each
app even if the hardware multi-stream PCM volume control isn't
possible.  But, it's still in dream as long as unimplemented...


Takashi

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Re: Getting and changing Volume

[Takashi Iwai]

At Wed, 30 Aug 2006 17:39:31 +0200,
Luca bedogni wrote:
> 
> On Wed, 30 Aug 2006 17:01:13 +0200
> Takashi Iwai <tiwai@suse.de> wrote:
> 
> > Currently, there is no explicit API which mixer element corresponds to
> > a certain PCM stream.  So, most apps use simply the mixer interface
> > and access either "PCM" or "Master" mixer element for controlling the
> > total volume.
> > 
> > In theory, it's possible to build a softvol entry for each PCM
> > substream so that the volume can be controlled independently by each
> > app even if the hardware multi-stream PCM volume control isn't
> > possible.  But, it's still in dream as long as unimplemented...
> 
> So it's not possible to control the volume? I've seen amixer and gamix
> codes for finding something helpful for me, but find nothing :(

It's of course possible to change the volume, but it will influence on
other streams, too.

The mixer interface is independent from the PCM interface.  You cannot
change the volume from snd_pcm_t handle.


Takashi

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