The AudioBuffer interface represents a short audio asset residing in memory, created from an audio file using the AudioContext.decodeAudioData() method, or from raw data using AudioContext.createBuffer(). Once put into an AudioBuffer, the audio can then be played by being passed into an AudioBufferSourceNode.

Objects of these types are designed to hold small audio snippets, typically less than 45 s. For longer sounds, objects implementing the MediaElementAudioSourceNode are more suitable. The buffer contains data in the following format:  non-interleaved IEEE754 32-bit linear PCM with a nominal range between -1 and +1, that is, 32bits floating point buffer, with each samples between -1.0 and 1.0. If the AudioBuffer has multiple channels, they are stored in separate buffer.

Properties

AudioBuffer.sampleRate Read only
Returns a float representing the sample rate, in samples per second, of the PCM data stored in the buffer.
AudioBuffer.length Read only
Returns an integer representing the length, in sample-frames, of the PCM data stored in the buffer.
AudioBuffer.duration Read only
Returns a double representing the duration, in seconds, of the PCM data stored in the buffer.
AudioBuffer.numberOfChannels Read only
Returns an integer representing the number of discrete audio channels described by the PCM data stored in the buffer.

Methods

AudioBuffer.getChannelData()
Returns a Float32Array containing the PCM data associated with the channel, defined by the channel parameter (with 0 representing the first channel).
AudioBuffer.copyFromChannel()
Copies the samples from the specified channel of the AudioBuffer to the destination array.
AudioBuffer.copyToChannel()
Copies the samples to the specified channel of the AudioBuffer, from the source array.

Example

The following simple example shows how to create an AudioBuffer and fill it with random white noise. You can find the full source code at our audio-buffer demo repository; a running live version is also available.

// Stereo
var channels = 2;

// Create an empty two second stereo buffer at the
// sample rate of the AudioContext
var frameCount = audioCtx.sampleRate * 2.0;
var myArrayBuffer = audioCtx.createBuffer(channels, frameCount, audioCtx.sampleRate);

button.onclick = function() {
  // Fill the buffer with white noise;
  // just random values between -1.0 and 1.0
  for (var channel = 0; channel < channels; channel++) {
    // This gives us the actual array that contains the data
    var nowBuffering = myArrayBuffer.getChannelData(channel);
    for (var i = 0; i < frameCount; i++) {
      // Math.random() is in [0; 1.0]
      // audio needs to be in [-1.0; 1.0]
      nowBuffering[i] = Math.random() * 2 - 1;
    }
  }

  // Get an AudioBufferSourceNode.
  // This is the AudioNode to use when we want to play an AudioBuffer
  var source = audioCtx.createBufferSource();

  // set the buffer in the AudioBufferSourceNode
  source.buffer = myArrayBuffer;

  // connect the AudioBufferSourceNode to the
  // destination so we can hear the sound
  source.connect(audioCtx.destination);

  // start the source playing
  source.start();

}

Specifications

Specification Status Comment
Web Audio API
The definition of 'AudioBuffer' in that specification.
Working Draft Initial definition.

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support 14 webkit 25 (25) Not supported 15 webkit
22
6 webkit
copyFromChannel() and copyToChannel() ? 27 (27) Not supported ? ?
Feature Android Chrome Firefox Mobile (Gecko) Firefox OS IE Phone Opera Mobile Safari Mobile
Basic support Not supported 28 webkit 25.0 (25) 1.2 Not supported Not supported webkit
copyFromChannel() and copyToChannel() Not supported ? 27.0 (27)   Not supported Not supported ?

See also

Document Tags and Contributors

Last updated by: Jeremie,