AudioProcessingEvent
Deprecated: This feature is no longer recommended. Though some browsers might still support it, it may have already been removed from the relevant web standards, may be in the process of being dropped, or may only be kept for compatibility purposes. Avoid using it, and update existing code if possible; see the compatibility table at the bottom of this page to guide your decision. Be aware that this feature may cease to work at any time.
The AudioProcessingEvent
interface of the Web Audio API represents events that occur when a ScriptProcessorNode
input buffer is ready to be processed.
An audioprocess
event with this interface is fired on a ScriptProcessorNode
when audio processing is required. During audio processing, the input buffer is read and processed to produce output audio data, which is then written to the output buffer.
Warning:
This feature has been deprecated and should be replaced by an AudioWorklet
.
Constructor
AudioProcessingEvent()
Deprecated-
Creates a new
AudioProcessingEvent
object.
Instance properties
Also implements the properties inherited from its parent, Event
.
playbackTime
Read only Deprecated-
A double representing the time when the audio will be played, as defined by the time of
AudioContext.currentTime
. inputBuffer
Read only Deprecated-
An
AudioBuffer
that is the buffer containing the input audio data to be processed. The number of channels is defined as a parameternumberOfInputChannels
, of the factory methodAudioContext.createScriptProcessor()
. Note that the returnedAudioBuffer
is only valid in the scope of the event handler. outputBuffer
Read only Deprecated-
An
AudioBuffer
that is the buffer where the output audio data should be written. The number of channels is defined as a parameter,numberOfOutputChannels
, of the factory methodAudioContext.createScriptProcessor()
. Note that the returnedAudioBuffer
is only valid in the scope of the event handler.
Examples
Adding white noise using a script processor
The following example shows how to use 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. (You can also access the source code.)
const myScript = document.querySelector("script");
const myPre = document.querySelector("pre");
const playButton = document.querySelector("button");
// Create AudioContext and buffer source
let audioCtx;
async function init() {
audioCtx = new AudioContext();
const source = audioCtx.createBufferSource();
// Create a ScriptProcessorNode with a bufferSize of 4096 and
// a single input and output channel
const scriptNode = audioCtx.createScriptProcessor(4096, 1, 1);
// Load in an audio track using fetch() and decodeAudioData()
try {
const response = await fetch("viper.ogg");
const arrayBuffer = await response.arrayBuffer();
source.buffer = await audioCtx.decodeAudioData(arrayBuffer);
} catch (err) {
console.error(
`Unable to fetch the audio file: ${name} Error: ${err.message}`,
);
}
// Give the node a function to process audio events
scriptNode.addEventListener("audioprocess", (audioProcessingEvent) => {
// The input buffer is the song we loaded earlier
let inputBuffer = audioProcessingEvent.inputBuffer;
// The output buffer contains the samples that will be modified
// and played
let outputBuffer = audioProcessingEvent.outputBuffer;
// Loop through the output channels (in this case there is only one)
for (let channel = 0; channel < outputBuffer.numberOfChannels; channel++) {
let inputData = inputBuffer.getChannelData(channel);
let 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) * 0.1;
}
}
});
source.connect(scriptNode);
scriptNode.connect(audioCtx.destination);
source.start();
// When the buffer source stops playing, disconnect everything
source.addEventListener("ended", () => {
source.disconnect(scriptNode);
scriptNode.disconnect(audioCtx.destination);
});
}
// wire up play button
playButton.addEventListener("click", () => {
if (!audioCtx) {
init();
}
});
Browser compatibility
BCD tables only load in the browser