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    AudioBufferSourceNode.playbackRate

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

    The default value is 1.0. When set to another value, the AudioBufferSourceNode applies pitch correction to the modified audio before sending it to the output.

    Syntax

    var source = audioCtx.createBufferSource();
    source.playbackRate.value = 1.25; // play 25% faster than normal speed (1)
    

    Note: Though the AudioParam returned is read-only, the value it represents is not.

    Value

    An AudioParam.

    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.

    Note: You can 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 API
    The definition of 'playbackRate' in that specification.
    Working Draft  

    Browser compatibility

    Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
    Basic support 14 webkit 23 Not supported 15 webkit
    22 (unprefixed)
    6 webkit
    Feature Android Chrome Firefox Mobile (Gecko) Firefox OS IE Phone Opera Mobile Safari Mobile
    Basic support Not supported 28 webkit 25 1.2 Not supported Not supported webkit

    See also

    Document Tags and Contributors

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