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WaveShaperNode.oversample

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 Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support 10.0webkit 26.0 (26.0)  Not supported 15.0webkit
22 (unprefixed)
6.0webkit
Feature Android Firefox Mobile (Gecko) Firefox OS IE Mobile Opera Mobile Safari Mobile Chrome for Android
Basic support ? 26.0 1.2 ? ? ? 33.0

See also

Document Tags and Contributors

 Contributors to this page: fscholz, teoli, chrisdavidmills
 Last updated by: fscholz,