I bought an audio book from audible and want to convert it to mp3 from aa because my phone doesn't support the format. Is there any way to do that?

1 Answer 1



From their manual:

Audible AAX files are encrypted M4B files, and they can be decrypted by specifying a 4 byte activation secret.

ffmpeg -activation_bytes 1CEB00DA -i input.aax -vn -c:a copy output.mp3

Since the file is encrypted, you will need the activation secret in order to decrypt and convert.

  • Use audible-converter.ml to get the "activation bytes" from an Audible aax file.
    – mooie
    Mar 9, 2023 at 23:43
  • The manual states "output.mp4", not "output.mp3", as written above. Changing the output to mp3 gives an error and creates an empty file. The answer is to create an mp4 file and then convert that to an mp3 file. There may be a more elegant way, but I can attest that this two-step approach works. See superuser.com/q/332347/1340043 for mp4 to mp3 conversion
    – mooie
    Mar 9, 2023 at 23:46

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