[fluid-dev] ladspa questions...

[Peter Billam]

Greetings :-)

I've been trying to work out how to use ladspa plugins.  I'd like
to implement cc71 and cc74 (filter Q and Freq), and also to do
The Great Missing Midi Controller namely whole-of-channel distortion,
for which I have previously used cc87 controlling foverdrive_1196

Most of the relevant stuff seems to be in bindings/fluid_ladspa.h eg:

  fluid_LADSPA_FxUnit_t* new_fluid_LADSPA_FxUnit(fluid_synth_t* synth);
  int fluid_LADSPA_handle_start(
    fluid_synth_t* synth, int ac, char** av, fluid_ostream_t out
  );
  void fluid_LADSPA_run(
    fluid_LADSPA_FxUnit_t* Fx_unit,
    fluid_real_t* left_buf[],    fluid_real_t* right_buf[],
    fluid_real_t* fx_left_buf[], fluid_real_t* fx_right_buf[]
  );
  fluid_LADSPA_Node_t* fluid_LADSPA_RetrieveNode(
    fluid_LADSPA_FxUnit_t* FxUnit, char * Name
  );
  fluid_LADSPA_Node_t* fluid_LADSPA_CreateNode(
    fluid_LADSPA_FxUnit_t* FxUnit, char * Name, int flags
  );
  void fluid_LADSPA_clear(fluid_LADSPA_FxUnit_t* FxUnit);

One, er, feature of new_fluid_LADSPA_FxUnit is that the plugin
will apply to all channels in the synth, which would make it
necessary to start a separate synth for every channel.
OTOH, I think I saw a comment somewhere about removing ladspa
dependencies from the synth object, so maybe this is changing ?

Is a 'Node' the plugin's control-parameter ? Eg: like the 3.0 in
  play chord.wav ladspa foverdrive_1196 3.0
or
  ecasound -i chord.wav -o alsa -el:foverdrive,3.0
?

There's doc/FluidSynth-LADSPA.pdf but that seems to be from 2002
and applies to the Iiwusynth...

Could someone give a newbie a tour of the state of ladspa ?
Is a hello-world example (at the C-API level) somewhere ?

Regards,  Peter Billam

http://www.pjb.com.au      address@hidden     (03) 6278 9410
"Follow the charge, not the particle."  --  Richard Feynman
 from The Theory of Positrons, Physical Review, 1949