I use MusicBee to organize my mysic collection on pc and i have a lot of files with ratings.
MusicBee let's write rating in audio files and sync files with android.
I would like to see my 5 stars rating in my mobile also.
Poweramp has 5 stars rating system, but it doesn't read rating from files. It has its own independet database.
I sugget to let the app to read ratings from files to db the first time apppear files in scanning for examples.
I think it's very simple.