Tech spike routing sound to system input

GPT guideline
Routing an audio file to the system's input (microphone) on macOS is a multi-step process involving virtual audio devices and custom scripting. Here’s a step-by-step guide:

Step 1: Install Virtual Audio Device Software
Download and Install BlackHole: BlackHole is a popular virtual audio driver for macOS that can route audio between applications. [Download BlackHole](https://github.com/ExistentialAudio/BlackHole).
Install BlackHole: Follow the installation instructions provided on the download page or GitHub repository.
Step 2: Configure macOS Audio Settings
Open 'Audio MIDI Setup': You can find this in Applications > Utilities.
Create a Multi-Output Device:
Click the '+' button at the bottom left and choose 'Create Multi-Output Device'.
In the right panel, check the boxes for 'BlackHole 16ch' and your built-in output (e.g., Internal Speakers).
Right-click on the 'Multi-Output Device' and select 'Use This Device For Sound Output'. This step is crucial for routing the audio.
Create an Aggregate Device (if you want to hear the audio yourself):
Similarly, create an 'Aggregate Device' that includes both 'BlackHole 16ch' and your built-in input (e.g., Internal Microphone).
This device can be used to both route audio to BlackHole and capture input from your microphone.
Step 3: Configure Node.js Environment
Install Node.js: If not already installed, [download and install Node.js](https://nodejs.org/).
Create a Node.js Project: Make a new directory for your project and initialize it with npm init.
Install Required Packages: You might need packages like node-speaker to play audio. However, note that node-speaker and similar packages might not support routing audio directly to a virtual device.
Step 4: Write Node.js Script
The following is a conceptual script. It plays an audio file using Node.js, but due to limitations of Node.js packages, it might not route the audio to BlackHole directly. You may need to use other methods or software to play the audio file through BlackHole.

javascript
Copy code
const Speaker = require('speaker');
const fs = require('fs');
const path = require('path');

const audioFilePath = path.join(__dirname, 'your_audio_file.mp3'); // Replace with your audio file path

const speaker = new Speaker({
  channels: 2,
  bitDepth: 16,
  sampleRate: 44100
});

const audioStream = fs.createReadStream(audioFilePath);
audioStream.pipe(speaker);
Usage
Run your Node.js script. It will play the audio file.
In any application where you want this audio file to be the input (like Zoom, Skype, or Google Meet), select 'BlackHole 16ch' as your microphone input.
Important Notes
API Limitation: Node.js APIs and the node-speaker package may not directly support output routing to virtual devices. You might need additional software or scripting.
Testing: This setup can be complex and may require testing and tweaking to work as expected.
Audio Playback: There are limitations to how audio playback works in Node.js, and the above script may not fulfill all the requirements for routing audio to a virtual device.
Conclusion
While Node.js can play audio files, routing this audio to a virtual microphone input on macOS using Node.js alone is challenging. It typically involves a combination of system-level audio configuration, virtual audio devices, and possibly additional software or scripting outside of Node.js to achieve the desired audio routing.
luni-ai / public-roadmap

Tech spike routing sound to system input #50
