Read there ...
http://en.wikipedia.org/wiki/ID3#ID3v2_rating_tag_issue
/t/11847/1
https://docs.mp3tag.de/mapping/#popularimeter
http://forum.gmusicbrowser.org/index.php?t...msg3458#msg3458
http://www.mediamonkey.com/forum/viewtopic.php?p=358691
... and search the forum, there might be some more references regarding rating or different schemes for granulating/granulation.
DD.20140508.1124.CEST