@speechmatics/browser-audio-input-react

Browser audio input (React)

React bindings for the @speechmatics/browser-audio-input package, letting you manage audio input devices and permissions across browsers.

Installation

npm i @speechmatics/browser-audio-input-react

Usage

Microphone selection

Below is an example of a Microphone selection component.

import { useAudioDevices } from "@speechmatics/browser-audio-input-react";

function MicrophoneSelect({
  setDeviceId,
}: { setDeviceId: (deviceId: string) => void }) {
  const devices = useAudioDevices();

  switch (devices.permissionState) {
    case 'prompt':
      return (
        <label>
          Enable mic permissions
          <select
            onClick={devices.promptPermissions}
            onKeyDown={devices.promptPermissions}
          />
        </label>
      );
    case 'prompting':
      return (
        <label>
          Enable mic permissions
          <select aria-busy="true" />
        </label>
      );
    case 'granted': {
      const onChange = (e: ChangeEvent<HTMLSelectElement>) => {
        setDeviceId(e.target.value);
      };
      return (
        <label>
          Select audio device
          <select onChange={onChange}>
            {devices.deviceList.map((d) => (
              <option key={d.deviceId} value={d.deviceId}>
                {d.label}
              </option>
            ))}
          </select>
        </label>
      );
    }
    case 'denied':
      return (
        <label>
          Microphone permission disabled
          <select disabled />
        </label>
      );
    default:
      devices satisfies never;
      return null;
  }
}

PCM recording

This package exposes a context provider that can be used like so:

import { PcmAudioRecorderProvider } from '@speechmatics/browser-audio-input-react';

function App() {
  return (
    <PcmAudioRecorderProvider workletScriptURL="/path/to/pcm-audio-worklet.min.js">
      <Component>
    </PcmAudioRecorderProvider>
  );
}

// Now all child components can use the provided hooks

function Component() {
  const { startRecording, stopRecording, mediaStream, isRecording } =
    usePcmAudioRecorder();

  usePcmAudioListener((audio) => {
    // Handle Float32Array of audio however you like
  });
}

Note about AudioWorklet script URL

When recording audio in the browser, there are generally three approaches:

• ❌ createScriptProcessor(): Can capture PCM data on the main thread, but is deprecated and suffers from poor performance easily.
• ❌ MediaRecorder: Provides a simple API, but cannot capture PCM data (only MPEG/OGG)
• ✅ AudioWorklet: Captures/processes PCM on dedicated thread.

This library leverages AudioWorklet to capture PCM audio (specifically 32-bit Float PCM, which is the underlying representation in the browser).

Since AudioWorklets run outside the main thread, their code must be run from an external source (i.e. a URL).

Getting the AudioWorklet script

First make sure the base package (the one this package wraps) is installed:

npm i @speechmatics/browser-audio-input

The code for this PCM audio processor is provided by that library at /dist/pcm-audio-worklet.min.js. However, how this script is loaded depends on your bundler setup.

Webpack

At the moment, Webpack doesn't have a great story for AudioWorklet scripts (see Github issue). Instead, we recommend using the copy-webpack-plugin to copy our pcm-audio-worklet.min.js directly into your /public folder:

const CopyPlugin = require("copy-webpack-plugin");

module.exports = {
  // ... rest of your Webpack config
  plugins: [
    new CopyWebpackPlugin({
      patterns: [
        {
          from: path.resolve(
            __dirname,
            'node_modules/@speechmatics/browser-audio-input/dist/pcm-audio-worklet.min.js',
          ),
          to: path.resolve(__dirname, 'public/js/[name][ext]'),
        },
      ],
    }),
  ]
};

See Webpack documentation for more details.

Then use /js/pcm-audio-worklet.min.js (or whatever other path you define) as the path to the script:

// WEBPACK EXAMPLE
import { PcmAudioRecorderProvider } from '@speechmatics/browser-audio-input-react';

function App() {
  return (
    <PcmAudioRecorderProvider workletScriptURL="/js/pcm-audio-worklet.min.js">
      <Component>
    </PcmAudioRecorderProvider>
  );
}

Vite

Vite supports referencing bundled code by URL for use in Workers. This can be used like so:

// VITE EXAMPLE
import { PcmAudioRecorderProvider } from '@speechmatics/browser-audio-input-react';
import workletScriptURL from '@speechmatics/browser-audio-input/pcm-audio-worklet.min.js?url';

function App() {
  return (
    <PcmAudioRecorderProvider workletScriptURL={workletScriptURL}>
      <Component>
    </PcmAudioRecorderProvider>
  );
}