Re: Userspace ALSA Soundcard

[Takashi Iwai <tiwai@suse.de>]

At Thu, 14 Oct 2004 09:32:52 +0200,
Roger Villars wrote:
> 
> 
> Hello
> 
> I'm new to the ALSA Framework and I'm trying to program
> a "virtual" soundcard for a Bluetooth Headset that is running
> completely in userspace. No kernel modules or something.
> 
> You should only start a deamon program and then every ALSA beware
> program can "see" a new Soundcard.

Even the daemon wouldn't needed, I guess.
Well, the mixer might be problematic in some cases.

> First Question: Do you think this is possible?

Yes.

> Second Question: How?

A good question :)  There is no real documentation for this.
As you wrote below, jack_pcm.c is the best example to rerfer to.

> I heard that there is a file called pcm_jack.c in ALSA that is
> doing exactly what I need. But as I'm new to ALSA I don't know
> how and where in the code it is doing it.
> 
> Would be nice if somebody can give me some Know-how. 

Basically, you need to write dozen of callbacks for each pcm
operation.  The most cryptical part is the PCM configuration.
The PCM layer calls hw_params, hw_refine, and sw_params callbacks for
querying and setting up the proper configuration.


Takashi


-------------------------------------------------------
This SF.net email is sponsored by: IT Product Guide on ITManagersJournal
Use IT products in your business? Tell us what you think of them. Give us
Your Opinions, Get Free ThinkGeek Gift Certificates! Click to find out more
http://productguide.itmanagersjournal.com/guidepromo.tmpl