ScriptProcessorNode: audioprocess event

{{APIRef("Web Audio API")}}{{Deprecated_Header}}

The audioprocess event of the {{domxref("ScriptProcessorNode")}} interface is fired when an input buffer of a script processor is ready to be processed.

[!NOTE] This feature was replaced by AudioWorklets and the {{domxref("AudioWorkletNode")}} interface.

This event is not cancelable and does not bubble.

Syntax

Use the event name in methods like {{domxref("EventTarget.addEventListener", "addEventListener()")}}, or set an event handler property.

addEventListener("audioprocess", (event) => { })

onaudioprocess = (event) => { }

Event type

An {{domxref("AudioProcessingEvent")}}. Inherits from {{domxref("Event")}}.

{{InheritanceDiagram("AudioProcessingEvent")}}

Event properties

Also implements the properties inherited from its parent, {{domxref("Event")}}.

• playbackTime {{ReadOnlyInline}}
  • : A double representing the time when the audio will be played, as defined by the time of {{domxref("BaseAudioContext/currentTime", "AudioContext.currentTime")}}.
• inputBuffer {{ReadOnlyInline}}
  • : An {{domxref("AudioBuffer")}} that is the buffer containing the input audio data to be processed. The number of channels is defined as a parameter numberOfInputChannels, of the factory method {{domxref("BaseAudioContext/createScriptProcessor", "AudioContext.createScriptProcessor()")}}. Note that the returned <code>AudioBuffer</code> is only valid in the scope of the event handler.
• outputBuffer {{ReadOnlyInline}}
  • : An {{domxref("AudioBuffer")}} that is the buffer where the output audio data should be written. The number of channels is defined as a parameter, <code>numberOfOutputChannels</code>, of the factory method {{domxref("BaseAudioContext/createScriptProcessor", "AudioContext.createScriptProcessor()")}}. Note that the returned <code>AudioBuffer</code> is only valid in the scope of the event handler.

Examples

scriptNode.addEventListener("audioprocess", (audioProcessingEvent) => {
  // The input buffer is a song we loaded earlier
  const inputBuffer = audioProcessingEvent.inputBuffer;

  // The output buffer contains the samples that will be modified and played
  const outputBuffer = audioProcessingEvent.outputBuffer;

  // Loop through the output channels (in this case there is only one)
  for (let channel = 0; channel < outputBuffer.numberOfChannels; channel++) {
    const inputData = inputBuffer.getChannelData(channel);
    const outputData = outputBuffer.getChannelData(channel);

    // Loop through the 4096 samples
    for (let 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;
    }
  }
});

You could also set up the event handler using the onaudioprocess property:

scriptNode.onaudioprocess = (audioProcessingEvent) => {
  // …
};

Specifications

{{Specifications}}

Browser compatibility

{{Compat}}

See also

• Web Audio API