[pulseaudio-discuss] Multiple users (kde) on Debian

Colin Guthrie gmane at colin.guthr.ie
Tue Aug 24 01:39:17 PDT 2010

'Twas brillig, and Jeremy Nickurak at 23/08/10 15:40 did gyre and gimble:
>     No, that's not the right approach. This has been discussed many times on
>     this list. Just look at the archives, I'm not wasting hours of my life
>     reiterating what has already been discussed.
> A quick look around with google didn't indicate anything, except
> instructions on how to enable dmix instead of/in-addition-to pulseaudio.
> Dmix seems to be the solution that alot of the pulseaudio critics
> suggest as the silver bullet to audio problems... maybe the argument
> about dmix can be iterated once more in a wiki page, so there's a more
> permanent reference for that information?

DMIX is very clever in itself, and in the absence of PA on a given
system, I'd very much recommend it's usage.

Layering one software mixing system on top of another however is a very
silly idea, adding slowdowns and overhead to a pipeline that tries very
hard to minimise locking and copying to avoid such latencies.

Running two software mixers is not the solution to the architectural
differences of the PA model to any existing one. Our goal is to ensure
that only the the active user can access the sound hardware (and not
just sound hardware but USB ports etc. too). The people advocating PA on
top of dmix are those users who do not like that model and don't care
about the consequences of what they are suggesting from an
implementation perspective.

As we discussed previously the pseudo session started for the GDM login
prompt is the right approach here. There is always an "active" user,
whether it's a real user or a pseudo login user or an "idle" user.

It will then be up to the system administrator to configure various
agents for such sessions. These agents can connect to sources of audio
(e.g. mpd, a11y system etc.) and then be responsible for playing the
actual audio via the pseudo session's own PA daemon.

This requires a bit of a change to the various application stacks to
allow this, but the benefits are clear and defined and the end goal of
not allowing unauthorised access to sound hardware is maintained along
with graceful handover in a multi-user, single seat system.



Colin Guthrie

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Open Source:
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  PulseAudio Hacker [http://www.pulseaudio.org/]
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