I'm hoping to find an Android app that can properly read and write MP3 ID3 tags for ratings (usually a popularity meter, called POPM in the tag). It's Matroska T=30 in the ID3v2.3 and IDv2.4 tags, and it's an 8-bit value in code (1-255), so it wouldn't be difficult to program the thresholds into a program for each full and half-star rating, e.g.:
Anyway, I have yet to find a program that supports multiple genre tags AND full star ratings on Android.
Poweramp is close with some third-party help. Poweramp does have a rating system, but it's not POPM in the MP3 ID3v2.3/ID3v2.4 tags and it doesn't support half-star ratings.
There is a third-party program that can synchronize in either direction though called Music Playlist Manager by flyingdutchman. I linked a Tasker script to automate that process on this forum post https://forum.powerampapp.com/topic/22162-poweramp-finally-needs-a-half-star-rating-system/ However, this sync process still loses your half-star ratings if you use those.
Any suggestions on other programs?