Re: [LAU] Questions about LV2

On 05/14/2013 12:26 PM, Julien Claassen wrote:
> Hello Florian!
> I had another look at the sampler and I can't fathom, how the GUI
> will communicate any extra info to the plugin. Perhaps via one of the
> sockets, that I saw with lsof. Unfortunately nothing like an OSC
> server or a direct UDP port as with LinuxSampler.
> What sort of a plugin did you write and how did you do your extra
> communications?
> Kind regards
> Julien
>

Well, I'm no expert on LV2 and especially not the patch extension. But
from my limited knowledge the message comes into the plugin the same way
midi messages come into it (via a "notification" port?). I ripped the
code for my plugin straight from the example sampler plugin from the LV2
distribution. So since it uses a gtk gui to offer the user a way to
select a patch file, that's what my plugin does. These are the involved
extensions afact:

http://lv2plug.in/ns/ext/patch/patch.html
http://lv2plug.in/ns/ext/state/

Only because you explicitly ask I will elaborate a little bit on my
plugin ladspa.m.lv2 (interest was pretty limited, so I actually kind of
accepted that it's a personal project interesting only to me ;D). It is
a simple little modular synthesis plugin which can run synthesis graphs
made up of LADSPA plugins. These synthesis graph definitions are in the
form of little files describing the graph. This is the protobuf
definition for the files:

https://github.com/fps/ladspa.m.proto/blob/master/ladspam.proto

You can use the generated python bindings to define instruments. This is
an example python program that builds up the instrument definition for a
simple 5-voice polyphonic instrument that has a sawtooth oscillator per
voice and modulation wheel controlled autopanning per voice (where each
voice uses a different panning rate):

https://github.com/fps/ladspa.m.proto/blob/master/examples.py/simple_sawtooth_autopanned.instrument.py

The plugin and the involved libraries/tools are still work in progress.
But since not a single other part of this chain depends on any graphical
toolkit and this is quite accessible it is a pity that the patch
selection part to actually make use of an instrument in an LV2 host has
this accessibility issue of requiring a custom GUI. And I would love for
that to change..

https://github.com/fps/ladspa.m.lv2

Regards,
Flo

-- 
Florian Paul Schmidt
http://fps.io
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