This is the code that powers the new Loops Duet camera.
It shows the original video on the left or top of the screen, and your camera preview (front or back) and plays the og video while your recording. You can stop recording and it pauses, and resumes when you continue.
It supports both side-by-side and vertical layouts.
https://github.com/joinloops/loops-expo/blob/main/src/app/private/video/duet/
Edit: Apparently mastodon is breaking the url, its the [id].tsx file