Electron Audio Loopback

An Electron plugin for capturing system audio loopback on macOS 12.3+, Windows 10+ and Linux without any third-party loopback drivers or dependencies.

To play around with a full example, check out the mic-speaker-streamer repo. It's a simple app that allows you to simultaneously stream your microphone and system audio to a third-party transcription API while also recording both streams into a WAV file. Alternatively, check out the bundled example in this repo.

Real-World Usage

If your app is using Electron Audio Loopback, make a PR to add it to the list below! Both open and closed source apps are welcome.

• mic-speaker-streamer: An example microphone/system audio transcription app using OpenAI's Realtime API.

Installation

npm install electron-audio-loopback

Usage

Main Process Setup

const { app } = require('electron');
const { initMain } = require('electron-audio-loopback');

// Initialize this plugin in your main process
// before the app is ready. Simple!
initMain();

app.whenReady().then(() => {
  // Your app initialization...
});

Renderer Process Usage

Manual Mode (Recommended)

If you do not have nodeIntegration enabled in your renderer process, then you'll need to manually initialize the plugin via IPC. See the example below:

// preload.js
const { contextBridge, ipcRenderer } = require('electron');

contextBridge.exposeInMainWorld('electronAPI', {
  enableLoopbackAudio: () => ipcRenderer.invoke('enable-loopback-audio'),
  disableLoopbackAudio: () => ipcRenderer.invoke('disable-loopback-audio')
});

// renderer.js
async function getLoopbackAudioMediaStream() {
    // Tell the main process to enable system audio loopback.
    // This will override the default `getDisplayMedia` behavior.
    await window.electronAPI.enableLoopbackAudio();

    // Get a MediaStream with system audio loopback.
    // `getDisplayMedia` will fail if you don't request `video: true`.
    const stream = await navigator.mediaDevices.getDisplayMedia({ 
      video: true,
      audio: true,
    });
    
    // Remove video tracks that we don't need.
    // Note: You may find bugs if you don't remove video tracks.
    const videoTracks = stream.getVideoTracks();

    videoTracks.forEach(track => {
        track.stop();
        stream.removeTrack(track);
    });

    // Tell the main process to disable system audio loopback.
    // This will restore full `getDisplayMedia` functionality.
    // Do this if you need to use `getDisplayMedia` for other
    // purposes elsewhere in your app.
    await window.electronAPI.disableLoopbackAudio();
    
    // Boom! You've got a MediaStream with system audio loopback.
    // Use it with an audio element or Web Audio API.
    return stream;
}

Automatic Mode

If nodeIntegration is enabled in your renderer process, then you can import the renderer helper function directly. This will take care of everything for you in one line of code.

const { getLoopbackAudioMediaStream } = require('electron-audio-loopback');

// Get a MediaStream with system audio loopback
const stream = await getLoopbackAudioMediaStream();

// The stream contains only audio tracks
const audioTracks = stream.getAudioTracks();
console.log('Audio tracks:', audioTracks);

// Use the stream with an audio element or Web Audio API
const audioElement = document.getElementById('audio');
audioElement.srcObject = stream;
audioElement.play();

If you don't want to remove the video tracks, you can pass removeVideo: false to the getLoopbackAudioMediaStream function.

API Reference

Main Process Functions

• initMain(options?: InitMainOptions): Initialize the plugin in the main process. Must be called before the app is ready.
  • sourcesOptions: The options to pass to the desktopCapturer.getSources method.
  • forceCoreAudioTap: Whether to force the use of the Core Audio API on macOS (can be used to bypass bugs for certain macOS versions).
  • loopbackWithMute: Whether to use the loopback audio with mute. Defaults to false.
  • sessionOverride: The session to override. Defaults to session.defaultSession.
  • onAfterGetSources: A function that is called after the sources are retrieved. Useful for advanced & unique scenarios. Defaults to undefined.

Renderer Process Functions

• getLoopbackAudioMediaStream(options?: GetLoopbackAudioMediaStreamOptions): Helper function that returns a Promise, resolves to a MediaStream containing system audio loopback. Video tracks are automatically removed from the stream.
  • removeVideo: Whether to remove the video tracks from the stream. Defaults to true.

IPC Handlers

The plugin registers these IPC handlers automatically, ensure you don't override them!

• enable-loopback-audio: Enables system audio loopback capture
• disable-loopback-audio: Disables system audio loopback capture

Requirements

• Electron >= 31.0.1 (this is cruicial, older Electron versions will not work!)
• macOS 12.3+
• Windows 10+
• Most Linux distros with PulseAudio as a sound server

Development

Prerequisites

• Node.js 18+
• npm or yarn

Setup

# Install dependencies
npm install

# Build the project
npm run build

# Development mode with watch
npm run dev

# Lint code
npm run lint

# Run example
npm test

PR's welcome!

Project Structure

src/
├── index.ts          # Main entry point with conditional exports
├── main.ts           # Main process initialization
├── config.ts         # Configuration
├── types.d.ts        # Type definitions
└── renderer.ts       # Renderer process helper function

License

MIT © Alec Armbruster @alectrocute