Here are a few options for a write-up on a "script download Facebook video repack," depending on whether you need a technical description, a marketing blurb, or a user guide.
If you don’t want to maintain a fragile script, use yt-dlp – a command-line tool that already handles Facebook repacking perfectly: script download facebook video repack
If you want a deep write-up on any of the following lawful alternatives, pick one and I’ll provide it: Here are a few options for a write-up
Create a file named fb_repack.py and paste the following code: Use ffmpeg for remux/transcode