Re: [iiwusynth-devel] What I'm planning to do with iiwusynth

[Peter Hanappe]

Bob Ham wrote:
> Hi all,
>
> I thought I'd write down some ideas I've been having for a frontend to
> iiwusynth in order to get reactions, suggestions, etc, so here goes.  

I knew you were working on something but I was wondering on what. I
happy to hear about it.

> I
> want to have a tabbed window where each tab represents one instance of
> iiwusynth.  In each you can edit all the settings for the instance; the
> soundfont stack, reverb, ladspa, etc.  Each instance would be running in
> the same program; ie I'm intending to do this via libiiwusynth rather
> than the command line or anything.  One thing that concerns me is the
> interface to synths' controls once they've been created.  There seems to
> be quite a few methods for telling the synth to do something; I've seen
> tcp server stuff, "shell" stuff and whatnot around in the includes and
> I'm not sure what's going on at a high level.  If someone could explain
> what these things are about I'd appreciate it.

For what you're doing, it seems to me the best way to go is to create a
synth with new_iiwu_synth and then control it through the synth's API
defined in iiwusynth/synth.h. The shell and the tcp server are all just
wrappers around the synth's interface. Too high level to be efficient
for what you want to do.

> Another thing that could be a problem is each synth's jack client.  I'm
> not sure, but I suspect there might be Issues with more than one
> jack_client_t in a single address space.  It could mean having to make
> synths share the same jack client and have them do their jack processing
> via libiiwusynth.  That's not too big an issue tho and could dealt with
> quite cleanly I reckon.

You might have a problem if you create a jack driver for each synth.
Since the Jack driver creates a real-time thread for every client,
you'll end up with as many threads as synths which is a waste of
resources.

You can create one jack driver and share it between several synths. I
started to make the interface to the drivers slightly more generic.
It's been done rather quickly so there surely still are some problems.
The new interface just requires a callback function, and is independent
of the iiwusynth object. In code, you could done something like this:

iiwu_synth* synth[8];

void audio_init()
{
  int i;
  iiwu_settings_t* settings;
  iiwu_audio_driver_t* adriver;

  settings = new_iiwu_settings();

  for (i = 0; i < 8; i++) {
    synth[i] = new_iiwu_synth(settings);
  }

  iiwu_settings_setstr(settings, "audio.driver", "jack");
  adriver = new_iiwu_audio_driver2(settings, audio_callback, NULL);
}


int audio_callback(void* data, int len,
                   int nin, float** in,
                   int nout, float** out)
{
  int i;
  for (i = 0; i < 8; i++) {
    iiwu_synth_process(synth[i], len, 0, NULL, nout, out);
  }
}


However, I had the same question as Josh: why several synths?
I don't mean this in a negative sense. I'm just curious to know what
kind of setup you have in mind that needs many synths.
Do you have anything running, yet?


> Anyway, that's what I'm thinking about.

Hope this helped.

Cheers,
P


> Bob