[pulseaudio-discuss] Pulseaudio runs as mpd user after login

[Colin Guthrie]

'Twas brillig, and Maystar at web.de at 22/07/11 09:12 did gyre and gimble:
> Hey,
> 
> I'm running the latest kubuntu version on my machine with pulseaudio
> 0.9.22. For log-in I use the standard kdm. Since I've installed mpd,
> this daemon starts already while I'm booting the system. This is nice
> because I can listen music without log in. Unfortunately mpd starts
> pulseaudio as the user mpd and this instance is still running, if I'm
> logged in with my normal user account. Because this process blocks my
> sound card, all my user processes can't create any sound. So I have to
> stop mpd or kill the pulseaudio process of mpd to get my sound back.
> Both must be done as root after each boot. This is very inconvenient!
> Does anyone know a way to kill mpd's pulseaudio process on login?

You have probably already added the MPD user to the audio group. Unless
your card supports hardware mixing this will mean both MPD and your user
could try and access the card at the same time and block each other.
Most cards do not support hardware mixing.

MPD works in a way that is not really in line with standard desktop
systems in that it wants it's own access to the sound hardware when
there are not active users (as defined by console kit - see
ck-list-sessions). This means that there are no user specific ACLs
assigned to the audio hardware. This is why people add mpd user to the
audio group. It's a bit of a hack really.

There are various ways in which this _could_ be made to work nicely with
multi-user systems, but it'll take a bit of effort to do correctly.


But the simplest way to get things working for you is if this is
essentially a one user system, i.e. you are pretty much the only user
who logs in and you do not fast user switch to other users.

This method is simply:

 1. Add your user to the "audio" group.
 2. Configure MPD to run as your user.


Part 1 will break user switching as your user will always be able to
access the sound h/w. Normally this isn't nice as it can block other
users from accessing the h/w when they have specific rights to it (i.e.
their session is "active" acroding to ck-list-sessions and thus they
have a user-specific ACL on the devices)

But essentially, if this works for you, it's quite a simply setup. MPD
will spawn *your* pulseaudio daemon, and when you login, you'll connect
to it for all your desktop audio anyway.

HTHs

Col


-- 

Colin Guthrie
gmane(at)colin.guthr.ie
http://colin.guthr.ie/

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