Subject: Re: LADPA (was Re: [linux-audio-dev] emagic (logic) drops VST support under OS X)
From: Steve Harris (S.W.Harris_AT_ecs.soton.ac.uk)
Date: Thu Sep 05 2002 - 00:47:45 EEST
OK, heres a graph of how I think a simple plugins via jack session could
look: http://www.ecs.soton.ac.uk/~swh/jack-plugin-graph.png
Control data is in red, audio data in black, and I know you can't have
bidirectional jack connections, but it makes the diagram simpler ;)
The apps are App A+B the DSP plugin clients are P1-4 and the gui clients
are just labeled GUI. The subgraphs are SG X+Y, whether they are explicitly
marked as such in jackd or not. The distinction between plguins and apps
is purely subjective of course.
Neither of the apps are capable of automation, as they dont have control
lines going to the dsp components.
The subgraphs make it more obvious how the state (re)store could work:
* The user instructs jackd that they want to store the session
* Jackd writes out /tmp/$$/jackd.state describing the connections between
apps.
* Jackd creates /tmp/$$/app_a/ and instructs App A to store its state there
* App A writes out .../app_a/my.state, creates .../app_a/P1/ and instructs
P1 to write its state there, rpt. for P2 etc.
* Jackd creates /tmp/$$/app_b/ and instructs App B to store its state there
* App B writes out .../app_b/my.state, creates .../app_a/P4/ ...
* Jackd tars up /tmp/$$ and there you go.
To restore, you just unstar to the state tarball, jackd launches the apps,
passing in thier state directory, and they each launch thier subgraphs.
Obviously this recurses, if for eg you have P5 that has a subgraph of its
own. And the same mechanism can be used to save the state of a single apps
plugin graph.
- Steve
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