[linux-audio-dev] Project: modular synth editor

[Mike Rawes]

 --- Alfons Adriaensen <fons.adriaensen at alcatel.be> wrote: > On Wed, Jan 14,
2004 at 03:14:59PM +0000, Mike Rawes wrote:
> 
> > The key here would be to develop an API (I suppose more accurately an ACI -
> > application Control interface) to cover all intended functionality, which
> would
> > include:
> > 
> > * Querying installed LADSPA plugins
> >     Including RDF categorisation
> >      http://plugin.org.uk/lrdf
> > * Instantiating (adding) plugins and removing them
> > * Connecting / disconnecting ports
> >     including 'translation' between different port types, e.g.
> >       Control rate <->Audio rate
> >       Range hint scaling (e.g. mapping a +/- 1.0 audio 
> >        signal to a logarithmic 5 octave frequency 
> >        range) - AlsaModularSynth has a wise approach 
> >        of standardising the scales - 1 'Volt' per 
> >        octave for frequency etc. much like the old
> >        hardware modulars.
> > * Managing inputs/outputs 
> >     JACK for audio (be it actual audio, or control 
> >      values at audio rate)
> >     OSC 'ports' for control-rate connections
> >     MIDI connections
> >     OSS / ALSA audio I/O ?
> >     LADCCA, iirc, is designed for controlling 
> >      LADSPA plugins remotely - worth checking out anyway
> >      http://pkl.net/~node/ladcca.html
> > * Creation and management of subpatches 
> >     A nice feature would be any subpatches automatically 
> >      become available as plugins as they are created, 
> >      presented alongside vanilla LADSPA ones.
> >     Maybe have a 'publish subpatch' function that lets
> >      you slot in a subpatch into the RDF heirarchy as well.
> > * Setting up polyphony 
> >     Either for the whole graph or just portions of 
> >      it - think multiple synths and an effects unit 
> >      in a single graph.
> > * Querying state (e.g. for presentation in a GUI)
> >     Pretty much everything:
> >       Connection state
> >       Names of plugins / ports / subpatches
> >       Inputs and Outputs
> >       Subpatches
> 
> This corresponds quite closely to the long term aims for a second generation
> AMS (see my message of a few weeks ago).
> 
> As for using LADSPA as the native module format, my first idea when I started
> analysing the requirements for a new AMS was exactly that. But there's a lot
> of functionality that's hard to implement using the defined LADSPA
> interfaces.
> Some of this could could maybe be added in a backwards compatible way, but
> the end result wouldn't be very clean, so I've now all but abandoned this
> idea. 
> The problem is not with the lack of a GUI - that would be separate process
> anyway, but quite basic things such a checking the number of voices

I see higher level 'instrument' type stuff as being a wrapper outside the
plugin - or more likely, a small graph of plugins - such as a pair of ADSRs, a
DCO and a DCA. 

I've 'manually' got polyphony in SSM with a distributor which routes a signal
to successive destinations when triggered, and multiple sets of the same graph
(there's also an example patch with SSM that does this). AMS 1.x does this per
plugin I think, though I haven't studied the code. 

> (I
> proposed
> a backwards compatible solution some time ago, but that thread went of into
> another direction :-), or just finding out if a port is connected or not.

My plans had all ports connected by default (so they take on the value given
from the hints) - just attach a dummy buffer to the unconnected ports. 

> So any new design will either have only 'static' built-in modules, or define
> its own plugin format. I'll probably go for the second option, and will take
> the resulting flames with it. LAPSPA support will remain, of course.

With the exception of samples or other 'blob' data (e.g. IR impulses), I'm
fairly confident that a good modular could be constructed with LADSPA as it is.
I'm prepared to be proved wrong though!

- 
Myk


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