Web/API/AudioBufferSourceNode/playbackRate

The playbackRate property of the AudioBufferSourceNode interface Is a k-rate AudioParam that defines the speed at which the audio asset will be played.

A value of 1.0 indicates it should play at the same speed as its sampling rate, values less than 1.0 cause the sound to play more slowly, while values greater than 1.0 result in audio playing faster than normal. The default value is 1.0. When set to another value, the AudioBufferSourceNode resamples the audio before sending it to the output.

Syntax

AudioBufferSourceNode.playbackRate.value = playbackRateProportion;

Value

An AudioParam whose value is a floating-point value indicating the playback rate of the audio as a decimal proportion of the original sampling rate.

Consider a sound buffer containing audio sampled at 44.1 kHz (44,100 samples per second). Let's see what a few values of playbackRate do:

A playbackRate of 1.0 plays the audio at full speed, or 44,100 Hz.
A playbackRate of 0.5 plays the audio at half speed, or 22,050 Hz.
A playbackRate of 2.0 doubles the audio's playback rate to 88,200 Hz.

Example

In this example, the AudioContext.decodeAudioData() function is used to decode an audio track, and put it into an AudioBufferSourceNode. Buttons are provided to play and stop the audio playback, and a slider control is used to change the playbackRate property value on the fly.

You can [[../../../../../../../mdn.github.io/webaudio-examples/decode-audio-data/index|run the example live]] (or view the source.) Play the song and alter the playback rate for some fun results.

<input class="playback-rate-control" type="range" min="0.25" max="3" step="0.05" value="1">
<span class="playback-rate-value">1.0</span>

function getData() {
  source = audioCtx.createBufferSource();
  request = new XMLHttpRequest();

  request.open('GET', 'viper.ogg', true);

  request.responseType = 'arraybuffer';

  request.onload = function() {
    var audioData = request.response;

    audioCtx.decodeAudioData(audioData, function(buffer) {
        myBuffer = buffer;
        source.buffer = myBuffer;
        source.playbackRate.value = playbackControl.value;
        source.connect(audioCtx.destination);
        source.loop = true;
      },

      function(e){"Error with decoding audio data" + e.err});

  }

  request.send();
}

// wire up buttons to stop and play audio, and range slider control

play.onclick = function() {
  getData();
  source.start(0);
  play.setAttribute('disabled', 'disabled');
  playbackControl.removeAttribute('disabled');
}

stop.onclick = function() {
  source.stop(0);
  play.removeAttribute('disabled');
  playbackControl.setAttribute('disabled', 'disabled');
}

playbackControl.oninput = function() {
  source.playbackRate.value = playbackControl.value;
  playbackValue.innerHTML = playbackControl.value;
}

Specification

Specification	Status	Comment
Web Audio APIThe definition of 'playbackRate' in that specification.	Working Draft

Browser compatibility

Update compatibility data on GitHub

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`playbackRate`	Chrome Full support 14	Edge Full support 12	Firefox Full support 25	IE No support No	Opera Full support 15	Safari Full support 6	WebView Android Full support Yes	Chrome Android Full support 18	Firefox Android Full support 26	Opera Android Full support 14	Safari iOS Full support 6	Samsung Internet Android Full support 1.0

Legend

Full support: Full support
No support: No support