I have my media library from 20 years ago: it is embedded in my music files using standardised tagging formats. Any in-software 'media-library' I have used in that time has simply been a cache of and search interface for this metadata. Similarly some video files support tags and there are some standards for external metadata storage that can live next to the files I believe.

I highly doubt the music file metadata shown in the video only exists in an opaque internal representation within VLC.