audible

Download the audiobook onto your phone.

Copy it to your computer (normally it's located in /storage/emulated/0/Android/data/com.audible.application/) but there's actually a setting in the app to migrate the data to an sd card if needed. The books will be named randomcharacters.aax

Now you need to find your amazon decryption key. If you already have this proceed to step 6. With a decent computer this should only take a minute or two. Clone this project https://github.com/inAudible-NG/tables and install ffmpeg 2.8.1+ then run ffprobe test.aax on your file. You want to copy the "file checksum == 999a6ab8...". That project can be found here if github removes it: http://project-rainbowcrack.com/

Now cd into that tables directory you cloned, and run ./rcrack . -h that_checksum_you_just_copied

You want to copy the hex value at the end of the results message once it finishes. It'll look something like 2054052c.

Since *.aax is simply encrypted m4b we can rip it byte for byte to a *.mp4 for archival. You could also then convert the resulting *.mp4 to opus for playback if you'd like.

ffmpeg -activation_bytes 2054052c -i test.aax -vn -c:a copy test.mp4
ffmpeg -i test.mp4 -acodec libopus -b 96 test.opus