[pulseaudio-discuss] system-wide daemon

[Lennart Poettering]

On Tue, 09.02.10 12:24, Jeremy Nickurak (jeremy at nickurak.ca) wrote:

> On Tue, Feb 9, 2010 at 09:41, Tanu Kaskinen <tanuk at iki.fi> wrote:
> 
> > That's easier said than done. Only one process can have direct access to
> > the sound card at a time. Each user has his own pulseaudio instance
> > running. How do you implement constant access in such scenario? I fear
> > it would require a major redesign effort in pulseaudio. I haven't seen
> > any concrete design proposals enabling simultaneous access for multiple
> > users while at the same time retaining all the desirable properties that
> > the current system has.
> 
> 
> Off the top of my head....
> 
> "root" or other system-level pulseaudio instance opens and owns the physical
> hardware for the entire time a computer is up.
> 
> All the user pulseaudio instances connect through that.
> 
> What's the downside here?

You don't want to stack audio stacks (hey, a pun!), for latency,
memory consumption reasons.

Also, you don't want to get into this permission mess, which you will
doubtlessly enter if you want to make this fast, i.e. continue to
support SHM and so on.

> Alternatively, rely on the underlying layer to do multiplexing. If the
> hardware supports it, awesome. If it doesn't, let dmix handle it.

Modern hw doesn't support it. And dmix doesn't do any of the
timer-based scheduling stuff we want.

It's not that easy.

Lennart

-- 
Lennart Poettering                        Red Hat, Inc.
lennart [at] poettering [dot] net
http://0pointer.net/lennart/           GnuPG 0x1A015CC4