OscillatorNode: setPeriodicWave() method
The setPeriodicWave()
method of the OscillatorNode
interface is used to point to a PeriodicWave
defining a periodic waveform that can be used to shape the oscillator's output, when
type
is custom
.
Syntax
js
setPeriodicWave(wave)
Parameters
wave
-
A
PeriodicWave
object representing the waveform to use as the shape of the oscillator's output.
Return value
None (undefined
).
Examples
The following example illustrates simple usage of createPeriodicWave()
,
recreating a sine wave from a periodic wave.
js
const real = new Float32Array(2);
const imag = new Float32Array(2);
const ac = new AudioContext();
const osc = ac.createOscillator();
real[0] = 0;
imag[0] = 0;
real[1] = 1;
imag[1] = 0;
const wave = ac.createPeriodicWave(real, imag);
osc.setPeriodicWave(wave);
osc.connect(ac.destination);
osc.start();
osc.stop(2);
This works because a sound that contains only a fundamental tone is by definition a sine wave.
Here, we create a PeriodicWave
with two values. The first value is the DC
offset, which is the value at which the oscillator starts. 0 is good here, because we
want to start the curve at the middle of the [-1.0; 1.0] range.
The second and subsequent values are sine and cosine components. You can think of it as
the result of a Fourier transform, where you get frequency domain values from time
domain value. Here, with createPeriodicWave()
, you specify the frequencies,
and the browser performs an inverse Fourier transform to get a time domain buffer for
the frequency of the oscillator. Here, we only set one component at full volume (1.0) on
the fundamental tone, so we get a sine wave.
Specifications
Specification |
---|
Web Audio API # dom-oscillatornode-setperiodicwave |
Browser compatibility
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