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AudioProcessingEvent

この翻訳は不完全です。英語から この記事を翻訳 してください。

The Web Audio API AudioProcessingEvent represents events that occur when a ScriptProcessorNode input buffer is ready to be processed.

Note: As of the August 29 2014 Web Audio API spec publication, this feature has been marked as deprecated, and is soon to be replaced by Audio Workers.

プロパティ

The list below includes the properties inherited from its parent, Event.

プロパティ 説明
target 読取専用 EventTarget The event target (the topmost target in the DOM tree).
type 読取専用 DOMString The type of event.
bubbles 読取専用 boolean Does the event normally bubble?
cancelable 読取専用 boolean Is it possible to cancel the event?
playbackTime 読取専用 double The time when the audio will be played, as defined by the time of AudioContext.currentTime
inputBuffer 読取専用 AudioBuffer The buffer containing the input audio data to be processed. The number of channels is defined as a parameter, numberOfInputChannels, of the factory method AudioContext.createScriptProcessor(). Note the the returned AudioBuffer is only valid in the scope of the onaudioprocess function.
outputBuffer 読取専用 AudioBuffer The buffer where the output audio data should be written. The number of channels is defined as a parameter, numberOfOutputChannels, of the factory method AudioContext.createScriptProcessor(). Note the the returned AudioBuffer is only valid in the scope of the onaudioprocess function.

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 'AudioProcessingEvent' in that specification.
草案  

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support 10.0webkit 25.0 (25.0)  未サポート 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

ドキュメントのタグと貢献者

 このページの貢献者: Tomoyuki.Shirakawa
 最終更新者: Tomoyuki.Shirakawa,