Hat tip to https://github.com/KrumpetPirate/AAXtoMP3, it allowed me to see what i needed to do to allow ffmpeg to work.
** Work in Progress **
When finished this should create a private RSS podcast feed for each AAX file added.
Should allow for you to used a podcast client to listen to your audible books
Note that this project does NOT ‘crack’ the DRM. It simply allows the user to use their own encryption key (fetched from Audible servers) to decrypt the audiobook in the same manner that the official audiobook playing software does.
Please only use this application for gaining full access to your own audiobooks for archiving/conversion/convenience. DeDRMed audiobooks should not be uploaded to open servers, torrents, or other methods of mass distribution. No help will be given to people doing such things. Authors, retailers, and publishers all need to make a living, so that they can continue to produce audiobooks for us to hear, and enjoy. Don’t be a parasite.
This blurb is borrowed from (https://github.com/KrumpetPirate/AAXtoMP3)[AAXtoMP3] who got it from the https://apprenticealf.wordpress.com/ page.