CODEWITHSUNDEEP
javascripthtmlaudiosignal-processingweb-audio-api
Philipp
Philipp

Reputation: 807

WebAudio - Oscillator setPeridiocWave

I create three different linear chirps using the code found here on SO. With some other code snippets I save those three sounds as separate .wav files. This works so far.

Now I want to play those three sounds at the exact same time. So I thought I could use the WebAudio API, feed three oscillator nodes with the float arrays I got from the code above. But I don't get at least one oscillator node to play its sound.

My code so far (shrinked for one oscillator)

var osc = audioCtx.createOscillator();
var sineData = linearChirp(freq, (freq + signalLength), signalLength, audioCtx.sampleRate); // linearChirp from link above
// sine values; add 0 at the front because the docs states that the first value is ignored
var imag = Float32Array.from(sineData.unshift(0));  
var real = new Float32Array(imag.length); // cos values
var customWave = audioCtx.createPeriodicWave(real, imag);
osc.setPeriodicWave(customWave);
osc.start();

At the moment I suppose that I do not quite understand the whole the math behind the peridioc wave.

The code that plays the three sounds at the same time works (with simple sin values in the oscillator nodes), so I assume that the problem is my peridioc wave.

Another question: is there a different way? Maybe like using three MediaElementAudioSourceNode that are linked to my three .wav files. I don't see a way to play them at the exact same time.

Upvotes: 4

Views: 190

Answers (1)

cwilso
cwilso

Reputation: 13908

The PeriodicWave isn't a "stick a waveform in here and it will be used as a single oscillation" feature - it builds a waveform through specifying the relative strengths of various harmonics. Note that in that code you pointed to, they create a BufferSource node and point its .buffer to the results of linearchirp(). You can do that, too - just use BufferSource nodes to play back the linearshirp() outputs, which (I think?) are just sine waves anyway? (If so, you could just use an oscillator and skip that whole messy "create a buffer" bit.)

If you just want to play back the buffers you've created, use BufferSource. If you want to create complex harmonics, use PeriodicWave. If you've created a single-cycle waveform and you want to play it back as a source waveform, use BufferSource and loop it.

Upvotes: 1

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