[pulseaudio-discuss] multiseat and PulseAudio?

Tomasz Chmielewski mangoo at wpkg.org
Mon May 16 02:49:01 PDT 2011

On 16.05.2011 11:37, Colin Guthrie wrote:

> Well in this evironment, I'd say that if you only have one card to be
> shared between the seats, then system wide mode is likely the right option.
> It's not nice generally because:
>   2. One user can spy on the other user monitor their VOIP streams etc.

Since all users hear the same audio from loudspeakers, it's not a concern :)

> And we don't test it particularly heavily, but all in all it should work
> fine (assuming you write your own init script and/or your distro does
> that for you).

Unfortunately, it does not work fine, and was a reason why I'm 
investigating running PulseAudio per-user.

When I run it in system mode, it crashes (or exits? not sure). It's not 
something what happens very often - once every 3 days perhaps. But 
annoying (no music anymore, normal user can't start PA in system mode etc.).
Since the documentation said I'm not likely to get any help when asking 
for system mode issues, I though I'm really doing something wrong and I 
should use it per-user.

>> If I start PulseAudio in the user mode, only one user gets a sound card;
>> the second one gets "Dummy Output".
> Yeah, that's either because the second user does not have permission to
> access the device (due to ConsoleKit ACLs only the "active"
> (ck-list-sessions) user should get the ACL, but this could actually
> cover both users in your setup) or due to the fact that the card can
> only be opened once.
> Normally what you'd due is define some kind of udev magic that defines
> "seats" and thus contextually assigns certain USB ports and/or h/w to a
> given seat. Then when a user (any user - it's not tied to the seat) logs
> in, console-kit and udev both apply the right ACLs and PA can start and
> only show the relevant sound cards to the relevant seats. This is how it
> should work in an ideal world - everyone getting their own stuff. But in
> a situation where you accept all the problems listed above (things like
> security likely don't apply when people know each other :)) then system
> wide is fine.
> Hope that helps :)

Well, the theory is nice :) but from user's perspective, sound with 
multiseat became unreliable when distributions migrated to PulseAudio 
(not that the life of a multiseat user was ever easy, but still, it's 
yet one thing which discourages multiseat).

Perhaps I'll try to see why PA crashes/exits when used by multiple users 
in the system mode, report it to the mailing list, and hope won't get 
too many "system mode is unsupported, go away" replies ;)

Tomasz Chmielewski

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