Files downloaded with the Audible Download Manager are stored with the .aax file extension, but the information I can find about this format seem to vary.
Regarding this source, the files are stored in the M4B container (MPEG-4 Part 14), also a quick look into the file header of the .aax files reveals
aax M4B mp42isom.
Furthermore, regarding this source, the audio is encoded with the ACELP codec.
If I would decrypt the .aax files DRM with my Audible authentication code without converting the audio, which format and codec would the audio be in?
(Also I'm not sure if this belongs here or in "Sound Design".)