[LAD] [Jack-Devel] New proposal for the jackd/jackdbus mess

Paul Davis paul at linuxaudiosystems.com
Tue May 26 13:11:49 UTC 2009

On Mon, May 25, 2009 at 7:27 PM, Fernando Lopez-Lezcano
<nando at ccrma.stanford.edu> wrote:
> On Wed, 2009-05-20 at 11:20 +0100, Krzysztof Foltman wrote:
>> Stéphane Letz wrote:
>> > This scheme seems to hopefully solve most of the problems we had, and
>> > requires only a bit of change for the "jackdbus" front-end to continue
>> > working, but not much.
>> One obvious problem is that it will be necessary to create yet another
>> IPC protocol for control communication between libjack.so and
>> libjackserver.so. Why not use something already proven and with existing
>> tools like call monitor, command line interface etc. - that's why D-Bus
>> was used in first place.

Even though for the last couple of years (at least), Stephane has been
doing a lot more work and taking on much more responsibility for JACK
than myself, I still seem to be wearing the hat of JACK's "benign
dictator", so I'm going to cast a couple of things in stone that I
don't think have been made clear enough in the email discussion (not
true on IRC, but this email exchange has also attracted a lot of
written words).

1) JACK is intentionally a multi-platform technology, and still
attempts to use only POSIX-defined system interfaces unless the
required components are not available or so poorly functioning that an
alternative is required.

2) Because of this, JACK itself is not going to use platform-specific
technologies for any kind of public interfaces. JACK on OS X and
Windows uses non-POSIX technologies but not in any way that is visible
to a typical user or to JACK clients. This observation rules out the
use of *any* platform-specific IPC system, whether its D-Bus,
Microsoft's COM or various parts of the Cocoa API on OS X. The fact
that D-Bus can be run on Windows or OS X doesn't change this - no
developer on those platforms would consider it to be a part of those
platforms or consider it viable to require users to install and use

3) The discussions about the control API have managed to gloss over
the specific problems that were outlined at LAC2008 (Koln) in a way
that is probably not helpful. So I will restate my recollection of
them here. This is why we wanted to extend the JACK API (in no
particular order):

     * better desktop integration when desired
     * provide the ability to stop/start/reconfigure the server,
including adding/removing/changing backends and/or devices in use
     * enable to use of "profiles" to define startup parameters for
the server, thus allowing any JACK client to correctly start
           the server without a hack like ~/.jackdrc (but
back-compatibility with ~/.jackdrc was considered important)
     * provide an easier way to load internal clients
     * provide a better way to present messages to the user, probably
but not necessarily via a control application

So, these are the things that need to be considered "cast in stone".
Nothing should prevent anyone from integrating the JACK "control" and
"configuration" APIs with D-Bus, OSC, Freedesktop.org/XDG, Cocoa, COM,
or any other "broader" system. But such integration should not and
will not be a part of the "JACK" implementation(s) "core". It is
possible that we may even distribute some code  that performs this
integration for specific protocols as part of JACK. But it should not
be thought of as a core part of the system, merely a bridge to other
things to make JACK a bit more useful and a bit easier to use, similar
to the way JACK currently uses libsndfile.

I will write separately on some specifics of the proposal that Stephane posted.

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