Q: Before the latest revisions to iTunes, I think I used to be able to change the extension on a .mp3 file to .m4b and re-import it so that it holds its place when played like an audiobook. Now when I drag an .m4b file back into iTunes, iTunes does not respond – does not copy or import the file. Has the feature been stopped? If not, how can I convert long mp3s to book format?
A: iTunes doesn’t know how to handle .mp3 files renamed to .m4b, because MP3 and M4B aren’t the same formats.
The renaming trick only works when renaming existing AAC files (ending in .m4a) to a .m4b extension.
Second, this trick simply isn’t required anymore! The newest iTunes has an option to make any file – AAC or not – bookmarkable. To utilize this feature, select the song or songs you’d like to make bookmarkable, and choose “Get Info” from iTunes’ “File” menu.
Then, select the “Options” panel, check the “Remember playback position” box, and click OK. From now on, this file will behave as the .m4b files you’re used to, regardless of their filetype..