[linux-audio-user] Jack + Alsa routing?

Florian Schmidt mista.tapas at gmx.net
Tue Oct 19 05:38:51 EDT 2004


On Tue, 19 Oct 2004 10:09:14 +0300
Juhana Sadeharju <kouhia at nic.funet.fi> wrote:

> Hello.

Hi

> 
> I'm developing a jack application. The test files are played to
> the application with aplay and mpg123.
> 
> How do I route the played audio to my application and
> then the output to Alsa?

Hmm, this doesn't really make sense to me.. What do you mean by "routing".
You cannot feed the output of an alsa application into the jack graph w/o
capturing the mix on the soundcard. Well it _might_ be possible by using the
"file" pcm plugin, using a pipe and having the jack app read from that
pipe.

> 
> Note that aplay plays to the "wave" control in alsamixer.

aplay plays to the pcm device specified by the -D switch. If none is given
it plays to the "default" device which is usually equivalent to plughw:0,0
iirc.

The "wave" control on your soundcard happens to control the playback volume of
the default pcm.

> Now my application connects to
>  alsa_pcm:in_1
>  alsa_pcm:in_2
>  alsa_pcm:out_1
>  alsa_pcm:out_2
> and it is the same "wave" control.

sure, as jackd is an alsa application that uses hw:0,0 per default, its
volume is, of course, controlled by the "wave" slider in alsamixer.

> 
> Puzzle: To prevent aplay from going to speakers, I have to turn
> the "wave" to zero. But then how do I route anything to speakers
> if my application outputs to the same "wave"?
> 
> You may freely assume the aplay and mpg123 are not changed in
> any way.

Did i mention already that this doesn't quite make sense to me? Please
explain in more clear words (since you still seem to be somewhat confused by
the technicalities) what exactly you are trying to do.

flo


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