PulseAudio

[David Zeuthen]

On Tue, 2007-02-27 at 13:04 -0500, xiphmont at xiph.org wrote:
> On 2/27/07, David Zeuthen <david at fubar.dk> wrote:
> > On Tue, 2007-02-27 at 17:06 +0000, Bastien Nocera wrote:
> > > I think this is still the best course of action for F7, given some
> > > work to 1) make PulseAudio work (as it doesn't right now for the
> > > above), 2) some integration with the GNOME sound properties so it
> > > spits out the sound events on the right device.
> >
> > This needs to work with fast-user-switching and that is *hard* given
> > that PA hogs the device (or at least used to) and most ALSA playback
> > devices can only have a single opener (no mixing).
> 
> Actually, it's easy.  Set up a system Pulse and everyone can use sound
> and emulation.  What needs to happen next is to implement session
> partitioning in Pulse, the emulation helpers and emulation daemons.
> 
> Pulse should always be running (even if it occasionally releases
> devices to save battery).

So it's like this. For *modern* Linux desktop we've been moving
functionality from system-wide daemons into per-session daemons *simply*
because system-wide daemons have a number of problems. 

One of those is  that you want to read user settings and enforce policy
depending on users session [1]. 

Another problem is that if you have system-wide daemons you need to
coordinate clients with different identities; e.g. you suddenly need to
label your objects and make sure that an object created by uid 500
cannot be manipulated by uid 501. Things like that. Does PA handle that
already?

For starters, how are all the exiting PA tools going to work with PA
running system-wide? How is it going to work with multiple sessions? I
don't think there's anything "easy" about this. If it was easy, wouldn't
you have RPM's for us already? ;-)

I think what you want is some system-wide private PA mixer service that
only per-session PA instances can connect to over a private protocol.

     David

[1] : see also Lennarts presentation about "Compiz for audio" plans
      which further marries that idea

   http://0pointer.de/blog/projects/freedom-lovers.html

     David