Bela.io to trigger audio samples using Supercollider and sensors

internetplumber

Hello!
I am working on a project using bela.io to build a music instrument for an installation.
The performer will move on stage wearing an accelerometer (ADXL335), and I would like to use the reading of the x-axis acceleration (which I will get through the bela.io analogue input) to trigger an audio sample from a collection.
How I have a store and access a set of .wav audio samples on bela.io and then access them, through Supercollider?

On my local computer, this is the code I use to load samples and map them to MIDI keys.

~samples = Array.new;
~folder = PathName.new("/path/to/samples");

(
~folder.entries.do({
arg path;
~samples = ~samples.add(Buffer.read(s, path.fullPath));
});
)

(
SynthDef.new(\piano, {
arg buf, vel=64, gate=0, rate=1;
var sig, env, amp;
env = EnvGen.kr(Env.asr(), gate, doneAction:2);
sig = PlayBuf.ar(2, buf, rate*BufRateScale.ir( buf ));
amp = LinExp.kr(vel, 1, 127, 0.01, 1);
sig = sig * env * amp;
Out.ar(0, sig);
}).add;
)

~keys = Array.newClear(128);
MIDIClient.init;
MIDIIn.connectAll;

(
MIDIdef.noteOn(\noteOnDef, {
arg vel, note, ch, src;

~keys[note] = Synth.new(\piano, [
// MIDI note 23 corresponds to
    // the 0 index in the sample  array
\buf, ~samples[note-23].bufnum,
\vel, vel,
\gate, 1
]
);
});
)

(
MIDIdef.noteOff(\noteOffDef, {
arg vel, note, ch, src;
~keys[note].set(\gate, 0);
});
)

//Example
//a=Synth(\piano, [\buf, ~samples[37].bufnum,\vel, 63,\gate, 1]);

Many thanks!
Dom

giuliomoro

internetplumber How I have a store and access a set of .wav audio samples on bela.io and then access them, through Supercollider?

If you store the samples within the project folder, then you can just use a relative path instead of "/path/to/samples".

As to how to trigger them from the sensor reading, you should probably be using something like SendTrig

internetplumber

Dear Giulio,

thank you so much for your prompt response. I did a quick try by uploading 12 wave files (36.wav, 37.wav, ..., 48.wav) corresponding to 12 samples in the same directory where I have the .scd file.

I then wrote the following code:

  // starting server
  s = Server.default;
  //audio options
  s.options.numAnalogInChannels = 8;  
  s.options.numAnalogOutChannels = 8;
  s.options.numDigitalChannels = 16;
  s.options.blockSize = 16;
  s.options.numInputBusChannels = 2;
  s.options.numOutputBusChannels = 2;
  s.options.postln;

// main code
s.waitForBoot({
	~samples = Array.new;
	~folder = PathName.new("./");
       
        // load samples
	(
	~folder.entries.do({
	arg path;
	~samples = ~samples.add(Buffer.read(s, path.fullPath));
	});
	);

       // create basic instrument: play sample with a simple envelope
	(
	SynthDef.new("harp", {
	arg buf, vel=64, gate=0, rate=1;
	var sig, env, amp;
	env = EnvGen.kr(Env.asr(), gate, doneAction:2);
	sig = PlayBuf.ar(2, buf, rate*BufRateScale.ir( buf ));
	amp = LinExp.kr(vel, 1, 127, 0.01, 1);
	sig = sig * env * amp;
	Out.ar(0, sig);
	}).add;
	);

    // Read AnalogIn (channel 0) and map values to 36-48 (the notes available, through samples 36.wav ... 48.wav).
    (
    SynthDef("play_harp",{ arg out=0;
      Out.ar(out,
       Synth("harp", [\buf, ~samples[AnalogIn.ar( DC.ar( 0 ) ).range( 36, 48 )].bufnum,\vel, 63,\gate, 1]);
      )
    }).send(s);
    );
 
    s.sync;
    Synth.new("play_harp", target: s);
    
    });

Unfortunately the compiler fails with the following error:

....
  ^^ The preceding error dump is for ERROR: Primitive '_BasicAt' failed.
  Index not an Integer 
  RECEIVER: [ Buffer(0, nil, nil, nil, ./36.wav), Buffer(1, nil, nil, nil, ./37.wav), Buffer(2, nil, nil, nil, ./38.wav), Buffer(3, nil, 
  nil, nil, ./39.wav), Buffer(4, nil, nil, nil, ./_main.scd), Buffer(5, nil, nil, nil, ./settings.json) ]

So sorry to keep troubling you, do you think is there anything clearly wrong?
A huge thank-you!
Dom

giuliomoro

I am not sure what the error is (I don't know much at all about Supercollider). I would guess it has something to do with this line:

       Synth("harp", [\buf, ~samples[AnalogIn.ar( DC.ar( 0 ) ).range( 36, 48 )].bufnum,\vel, 63,\gate, 1]);

Are you perhaps supposed to convert the result of the expression
AnalogIn.ar( DC.ar( 0 ) ).range( 36, 48 )
to an integer before using it to index the array?

NOTE: please encode the code you paste in triple backticks (```) to ensure it is displayed properly. I already edited your post above and now it looks good.