Come elaborare l’audio dal microfono dell’utente

François Beaufort
François Beaufort

È possibile accedere alla fotocamera e al microfono dell'utente sulla piattaforma web con l'API Media Capture and Streams. Il metodo getUserMedia() richiede all'utente di accedere a una fotocamera e/o a un microfono da acquisire come stream multimediale. Questo stream può quindi essere elaborato in un thread audio web separato con un AudioWorklet che fornisce un'elaborazione audio a bassissima latenza.

L'esempio seguente mostra come elaborare l'audio dal microfono dell'utente in modo efficiente.

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);

Supporto del browser

MediaDevices.getUserMedia()

Supporto dei browser

  • 53
  • 12
  • 36
  • 11

Fonte

Audio web

Supporto dei browser

  • 35
  • 12
  • 25
  • 14.1

Fonte

AudioWorklet

Supporto dei browser

  • 66
  • 79
  • 76
  • 14.1

Fonte

Per approfondire

Demo

<!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>

       
: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;
}
       

       
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.");
});