[linux-audio-dev] Re: Modular Jack patch bay

Dave Robillard drobilla at connect.carleton.ca
Fri Feb 6 01:16:34 UTC 2004


On Thu, 2004-02-05 at 15:42, Juhana Sadeharju wrote:
> >From: Dave Robillard <drobilla at connect.carleton.ca>
> >
> >This is what LADCCA is for really.. session management is well out of
> >the domain of a patch bay, IMO
> 
> So what is the purpose of Patchbay?
> Users launch applications from a shell and then uses Patchbay for
> connecting the applications?

The patchbay will also be LADCCA supported, so you can save your
connections and module placement and all that in the session as well.

> That would mean a lot of manual connection work each time.
> A few weeks ago I tested a midi keyboard with Fluidsynth.
> Each time I changed the sample file in the shell, I had to
> reconnect the thing. Very annoying.

That's just a FluidSynth braindead-ism.  It annoys the heck out of me
too, if I get the time I'd like to look into it (can't be that hard).  

> I could not see a screenshot of the LADCCA? Does it provide
> what I suggested? Is the case that either we should add the requested
> features to Patchbay or add GUI to LADCCA? If both are out of question,
> we need yet another application.

LADCCA is a session management 'system', not really an application.. it
does come with a gtk frontend.. I'm afraid you're just going to have to
read about it to understand it. :)

> Yes, but how user would know what connections to make?
> The reverb was just one example figured out in frustation,
> but maybe people would like to provide such connections
> for other applications? A synth application followed by effect
> applications.

Synth --(jack)--> jack-rack

> LADSPA requires a host. If one places multiple effects to the
> path, then the host must support multiple effects and their easy
> control. Too complicated. Jack + multiple simple LADSPA hosts would
> work better -- if there would be some way to easily control the Jack
> system.

No, it would work a LOT worse.  The overhead of an application for every
plugin?  BAD idea.  Besides, effects rack programs do exist that do 
what you're talking about (and they're not that complicated ;) ).  Some
are even modular (see SSM, AMS).

I don't mean this in a negative way at all, but you need to learn about
(what I call) the 'linux audio architechture' - alsa sequencer, jack,
LADSPA, and LADCCA before recommending features to apps like this one. 
With a better understanding of the architechture you'll be able to
express your ideas in ways that make sense to the developers.  The
linux-audio-user archives would be a good place to start.
 
> Now I would like to have a completely graphical control application,
> such as Patchbay.

I think perhaps what you're thinking is a patch bay combined (somewhat
seamlessley) with a LADSPA host?  So you could, say, run fluidsynth into
freeverb into alsa audio out?

I've certainly thought of this before, and it is possible, but
definately not trivial.  It would be marginally cool, but a
synth/effects rack and a patch bay are fundamentally different things,
and I'm a big proponent of the 'unix philosophy'.. tools that do one
thing and do them right.

Now on the other hand, the idea of a nice simple little modular LADSPA
host (usable as both a synth and/or an effects rack) is a good one
indeed...

-Dave




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