AudioBufferSourceNode.loopStart

The loopStart property's default value is 0.

Syntax

var source = audioCtx.createBufferSource();
source.loopStart = 3;

Value

A double.

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 slider controls are used to change the playbackRate, loopStart and loopEnd properties on the fly.

When the audio is played to the end, it loops, but you can control how long the loops last by altering loopStart and loopEnd. For example, if you set their values to 20 and 25, respectively, the audio will start to loop between 20 and 25 seconds in to the track.

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;
        songLength = buffer.duration;
        source.buffer = myBuffer;
        source.playbackRate.value = playbackControl.value;
        source.connect(audioCtx.destination);
        source.loop = true;

        loopstartControl.setAttribute('max', Math.floor(songLength));
        loopendControl.setAttribute('max', Math.floor(songLength));
      },

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

  }

  request.send();
}

  ...

loopstartControl.oninput = function() {
  source.loopStart = loopstartControl.value;
  loopstartValue.innerHTML = loopstartControl.value;
}

loopendControl.oninput = function() {
  source.loopEnd = loopendControl.value;
  loopendValue.innerHTML = loopendControl.value;
}

Specification

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

Browser compatibility

See also

• Using the Web Audio API