Artist and cover not recognized on my smartphone with aac files

change the mp3 format by acc of my music collection, edit the tags and put covers but in the player of my smartphone I can not see the covers and in the artist field I see "(unknown)". mp3tag can work with aac files or I must return to the mp3 format? . I want to optimize the size of my music collection because it is more than 80 GB. It is important for me that my collection is organized and available on my smartphone

see e.g. this thread:

this one:

or this one: