[linux-audio-user] Common linux audio layer

Christoph Eckert mchristoph.eckert at t-online.de
Wed Jan 12 13:39:56 EST 2005

> Restarting JACK is not a very satisfactory recovery scheme.
>  All clients ports and their connections will be lost.

Well, running clients could remember the ports which they have 
been connected to and auto-reconnect as soon JACKd appears 
again (»active sensing« ;-). Clients could also do so 
persistentely by saving the last used ports to the config 
file. If the port isn't available any more, no auto 
connection gets made. Just an idea. Hydrogen already can do 
so, AFAIR. Very convenient.

> JACK does not work very well without RT privileges.

So, it'll still need some time until the security issues are 
addressed and prohibited.


> JACK is not designed for sharing between users.  Any
> shared-memory approach like JACK would be hopelessly
> insecure running as root while allowing arbitrary user
> connections.
> JACK does (recently and still only in CVS) support running
> multiple concurrent servers.  Each runs as a single user
> and connects to a single card.  So, multiple users could
> each have their own card, or one user could use several
> devices.

But I could not start two sessions for two different users and 
both having sound support on the same card? OK, thanks, I 

> One-at-a-time sequential use of a single card by multiple
> users works better now.  There were formerly a number of
> problems with it.

Perhaps, some day, jack will be able to run as root and allow 
different users with priviledges to do so to make connections 
to it :) .


> This is currently supported in JACK CVS, but not in any
> release version.

I already heard about it. I'm wondering how much the drift 
between the different cards would be, let's say, in a period 
of one hour. Perhaps I can try this out some day.


> Yes, we'll see.  Am I just hallucinating this or did
> someone say they run everything as root?  In that
> specialized environment, some of these problems might be
> more manageable.
> (System security would suck, of course.)

AFAIR I have heard the users always work as root. I really do 
not want to support this design.

> Steve is right that this is the hard part.  And, something
> like gstreamer is probably the best approach.  JACK is
> really not intended to be a general-purpose sound server. 
> Much of its success comes from Paul's clear focus on
> synchronous execution and low latency.

Well, I think a server between the common desktop applications 
and jack is absolutely the best thing. But I really like the 
idea that JACK is always present for the user, so if the user 
wants to run an audio application (like a guitar FX rack) he 
only needs to start it and it will connect to JACK directly 
instead of using the 'desktop' soundserver.

> If I had time, I'd play around with gstreamer and try to
> get it working really well with JACK.  Maybe someone here
> could do that and send progress reports to jackit-devel. 
> Give us a chance to be proactive about fixing problems.

I still didn't understand gstreamer completely (OK, I only 
spend some minutes on the website). But AFIR gstreamer is not 
a soundserver like arts or esound.

Thanks a lot for your wothy information.

 Best regards


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