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    AudioContext.createScriptProcessor()

    The createScriptProcessor() method of the AudioContext interface creates a ScriptProcessorNode used for direct audio processing.

    Syntax

    var audioCtx = new AudioContext();
    myScriptProcessor = audioCtx.createScriptProcessor(1024, 1, 1);

    Parameters

    bufferSize
    The buffer size in units of sample-frames. If specified, the bufferSize must be one of the following values: 256, 512, 1024, 2048, 4096, 8192, 16384. If it's not passed in, or if the value is 0, then the implementation will choose the best buffer size for the given environment, which will be a constant power of 2 throughout the lifetime of the node.
    This value controls how frequently the audioprocess event is dispatched and how many sample-frames need to be processed each call. Lower values for bufferSize will result in a lower (better) latency. Higher values will be necessary to avoid audio breakup and glitches. It is recommended for authors to not specify this buffer size and allow the implementation to pick a good buffer size to balance between latency and audio quality.
    numberOfInputChannels
    Integer specifying the number of channels for this node's input, defaults to 2. Values of up to 32 are supported.
    numberOfOutputChannels
    Integer specifying the number of channels for this node's output, defaults to 2. Values of up to 32 are supported.

    Important: Webkit currently (version 31) requires that a valid bufferSize be passed when calling this method.

    Note: It is invalid for both numberOfInputChannels and numberOfOutputChannels to be zero.

    Returns

    A ScriptProcessorNode.

    Example

    The following example shows basic usage of a ScriptProcessorNode to take a track loaded via AudioContext.decodeAudioData, process it, adding a bit of white noise to each audio sample of the input track (buffer) and play it through the AudioDestinationNode. For each channel and each sample frame, the scriptNode.onaudioprocess function takes the associated audioProcessingEvent and uses it to loop through each channel of the input buffer, and each sample in each channel, and add a small amount of white noise, before setting that result to be the output sample in each case.

    Note: For a full working example, see our script-processor-node github repo (also view the source code.)

    var myScript = document.querySelector('script');
    var myPre = document.querySelector('pre');
    var playButton = document.querySelector('button');
          
    // Create AudioContext and buffer source
    var audioCtx = new AudioContext();
    source = audioCtx.createBufferSource();
    
    // Create a ScriptProcessorNode with a bufferSize of 4096 and a single input and output channel
    var scriptNode = audioCtx.createScriptProcessor(4096, 1, 1);
    console.log(scriptNode.bufferSize);
    
    // load in an audio track via XHR and decodeAudioData
    
    function getData() {
      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;
      },
        function(e){"Error with decoding audio data" + e.err});
      }
      request.send();
    }
    
    // Give the node a function to process audio events
    scriptNode.onaudioprocess = function(audioProcessingEvent) {
      // The input buffer is the song we loaded earlier
      var inputBuffer = audioProcessingEvent.inputBuffer;
    
      // The output buffer contains the samples that will be modified and played
      var outputBuffer = audioProcessingEvent.outputBuffer;
    
      // Loop through the output channels (in this case there is only one)
      for (var channel = 0; channel < outputBuffer.numberOfChannels; channel++) {
        var inputData = inputBuffer.getChannelData(channel);
        var outputData = outputBuffer.getChannelData(channel);
    
        // Loop through the 4096 samples
        for (var sample = 0; sample < inputBuffer.length; sample++) {
          // make output equal to the same as the input
          outputData[sample] = inputData[sample];
    
          // add noise to each output sample
          outputData[sample] += ((Math.random() * 2) - 1) * 0.2;         
        }
      }
    }
    
    getData();
    
    // wire up play button
    playButton.onclick = function() {
      source.connect(scriptNode);
      scriptNode.connect(audioCtx.destination);
      source.start();
    }
          
    // When the buffer source stops playing, disconnect everything
    source.onended = function() {
      source.disconnect(scriptNode);
      scriptNode.disconnect(audioCtx.destination);
    }
    

    Specifications

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

    Browser compatibility

    Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
    Basic support 10.0webkit 25.0 (25.0)  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: ingk, Thormme, kscarfone, teoli, chrisdavidmills
    Last updated by: teoli,