The oversample
property of the WaveShaperNode
interface is an enumerated value indicating if oversampling must be used. Oversampling is a technique for creating more samples (up-sampling) before applying a distortion effect to the audio signal.
Once applied, the number of samples is reduced to its initial numbers. This leads to better results by avoiding some aliasing, but comes at the expense of a lower precision shaping curve.
The possible oversample
values are:
Value | Effect |
---|---|
'none' |
Do not perform any oversampling. |
'2x' |
Double the amount of samples before applying the shaping curve. |
'4x' |
Multiply by 4 the amount of samples before applying the shaping curve. |
Syntax
distortion.oversample = enumeratedValue;
Values
- distortion is a
WaveShaperNode
. - enumeratedValue is one of
'none'
,'2x'
, or'4x'
.
Example
The following example shows basic usage of an AudioContext to create a wave shaper node. For applied examples/information, check out our Voice-change-O-matic demo (see app.js for relevant code).
Note: Distortion curves are not the easiest thing to work out, and you will probably need to look around to find such algorithms. We found the below distortion curve code on Stack Overflow.
var audioCtx = new (window.AudioContext || window.webkitAudioContext)(); var distortion = audioCtx.createWaveShaper(); ... function makeDistortionCurve(amount) { var k = typeof amount === 'number' ? amount : 50, n_samples = 44100, curve = new Float32Array(n_samples), deg = Math.PI / 180, i = 0, x; for ( ; i < n_samples; ++i ) { x = i * 2 / n_samples - 1; curve[i] = ( 3 + k ) * x * 20 * deg / ( Math.PI + k * Math.abs(x) ); } return curve; }; ... distortion.curve = makeDistortionCurve(400); distortion.oversample = '4x';
Specifications
Specification | Status | Comment |
---|---|---|
Web Audio API The definition of 'oversample' in that specification. |
Working Draft |
Browser compatibility
Feature | Chrome | Edge | Firefox (Gecko) | Internet Explorer | Opera | Safari (WebKit) |
---|---|---|---|---|---|---|
Basic support | 10.0webkit | (Yes) | 26.0 (26.0) | No support | 15.0webkit 22 (unprefixed) |
6.0webkit |
Feature | Android | Edge | Firefox Mobile (Gecko) | Firefox OS | IE Mobile | Opera Mobile | Safari Mobile | Chrome for Android |
---|---|---|---|---|---|---|---|---|
Basic support | ? | (Yes) | 26.0 | 1.2 | ? | ? | ? | 33.0 |