audio-library-manager

If you have a directory with, e.g. /music with a library containing flac music tracks, this will resample the files to at most 48.000Hz (get rid of the 96Khz/192Khz files that one will never hear the difference to 48Khz). Also there's a flac -> opus conversion path (to e.g. /music-opus) to make a portable library. It will keep the information about the files in /music/.music-info.db.