AAC
A KDE/Qt application for Linux/Unix called easytag will edit metadata about AAC-encoded files as long as they end with the .m4a extension. Typically, renaming files to .m4a and back to the original extension after editing is sufficient. This method can be used to configure typical ID3v2 metadata including cover art. This cover art is used by Apple's iTunes and their media players. Note that easytag does not have the ability to add chapter points into Audiobooks (.m4b).