Bootstrap a fully isolated computer, then transfer files in either direction with the same optical channel.
1. Install the receiver optically
On the isolated computer, manually type and run bootstrap.py. Then show it this stream. It writes optical_receiver.py but never executes it.
Requires Python 3, OpenCV (cv2), and a camera already installed.
2. Send a file to Python
3. Receive a file from Python
Run python optical_receiver.py on the isolated computer, choose 2. Send, then open the normal receiver here and point its camera at the computer screen.
128 bytes at 2 QR/s is the reliable starting point for a weak webcam. Use 96 bytes at 1 QR/s if it still struggles; raise speed only after a clean test.