How to process audio from the user's microphone

François Beaufort

Accessing the user's camera and microphone is possible on the web platform with the Media Capture and Streams API. The getUserMedia() method prompts the user to access a camera and/or microphone to capture as a media stream. This stream can then be processed in a separate Web Audio thread with an AudioWorklet that provides very low latency audio processing.

The example below shows how you can process audio from the user's microphone in a performant way.

let stream;

startMicrophoneButton.addEventListener("click", async () => {
  // Prompt the user to use their microphone.
  stream = await navigator.mediaDevices.getUserMedia({
    audio: true,
  });
  const context = new AudioContext();
  const source = context.createMediaStreamSource(stream);

  // Load and execute the module script.
  await context.audioWorklet.addModule("processor.js");
  // Create an AudioWorkletNode. The name of the processor is the
  // one passed to registerProcessor() in the module script.
  const processor = new AudioWorkletNode(context, "processor");

  source.connect(processor).connect(context.destination);
  log("Your microphone audio is being used.");
});

stopMicrophoneButton.addEventListener("click", () => {
  // Stop the stream.
  stream.getTracks().forEach(track => track.stop());

  log("Your microphone audio is not used anymore.");
});

// processor.js
// This file is evaluated in the audio rendering thread
// upon context.audioWorklet.addModule() call.

class Processor extends AudioWorkletProcessor {
  process([input], [output]) {
    // Copy inputs to outputs.
    output[0].set(input[0]);
    return true;
  }
}

registerProcessor("processor", Processor);

Browser support

MediaDevices.getUserMedia()

Browser Support

Source

Web Audio

Browser Support

Source

AudioWorklet

Browser Support

Source

Demo

HTML

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1" />
    <link
      rel="icon"
      href="data:image/svg+xml,<svg xmlns=%22http://www.w3.org/2000/svg%22 viewBox=%220 0 100 100%22><text y=%22.9em%22 font-size=%2290%22>🎙️</text></svg>"
    />
    <title>How to process audio from the user's microphone</title>
  </head>
  <body>
    <h1>How to process audio from the user's microphone</h1>
    <button id="startMicrophoneButton">Start using microphone</button>
    <button id="stopMicrophoneButton" disabled>Stop using microphone</button>
    <pre id="logs"></pre>
  </body>
</html>

CSS


        :root {
  color-scheme: dark light;
}
html {
  box-sizing: border-box;
}
*,
*:before,
*:after {
  box-sizing: inherit;
}
body {
  margin: 1rem;
  font-family: system-ui, sans-serif;
}
button {
  display: block;
  margin-bottom: 4px;
}
pre {
  color: red;
  white-space: pre-line;
}

JS


        const startMicrophoneButton = document.querySelector('#startMicrophoneButton');
const stopMicrophoneButton = document.querySelector('#stopMicrophoneButton');

let stream;

startMicrophoneButton.addEventListener("click", async () => {
  // Prompt the user to use their microphone.
  stream = await navigator.mediaDevices.getUserMedia({
    audio: true,
  });
  const context = new AudioContext();
  const source = context.createMediaStreamSource(stream);

  // Load and execute the module script.
  await context.audioWorklet.addModule("processor.js");
  // Create an AudioWorkletNode. The name of the processor is the
  // one passed to registerProcessor() in the module script.
  const processor = new AudioWorkletNode(context, "processor");

  source.connect(processor).connect(context.destination);

  stopMicrophoneButton.disabled = false;
  log("Your microphone audio is being used.");
});

stopMicrophoneButton.addEventListener("click", () => {
  // Stop the stream.
  stream.getTracks().forEach(track => track.stop());

  log("Your microphone audio is not used anymore.");
});

How to process audio from the user's microphone

Browser support

MediaDevices.getUserMedia()

Web Audio

AudioWorklet

Further reading

Demo

HTML

CSS

JS