ScriptProcessorNode

输入和输出缓冲区大小在创建时定义, 当 AudioContext.createScriptProcessor() 方法被调用时 (都是由 AudioContext.createScriptProcessor()的 bufferSize 参数定义). 缓冲区大小必须是在 256 到 16384 之间的 2 的次幂, 为 256, 512, 1024, 2048, 4096, 8192 或者 16384. Small numbers lower the latency, but large number may be necessary to avoid audio breakup and glitches.

If the buffer size is not defined, which is recommended, the browser will pick one that its heuristic deems appropriate.

从上一级继承属性, AudioNode.

ScriptProcessorNode.bufferSize 只读

返回一个表示输入和输出缓冲区大小的整数. 它的值可以是在256–16384 之间的 2 的次幂.

ScriptProcessorNode.onaudioprocess

Represents the EventHandler to be called.

No specific methods; inherits methods from its parent, AudioNode.

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.

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);
}

• Using the Web Audio API