Support converting *TO* AAX (Audible's proprietary format)

[C0rn3j]

Support was added at some point to convert from AAX to other formats. This works great.

https://ffmpeg.org/ffmpeg-all.html#Audible-AAX

However, ffmpeg does not appear to support converting TO this format.

Why is this needed? Some devices do not ship with a music player, and the only way to play audio is through Audible's app, which in turn does not seem to recognize any audio files besides their own proprietary ones. Example of this device would be Kindle Paperwhite 4 (10th gen), which let's you play audio through Bluetooth, but only through Audible.

Converting FROM AAX works great -

%  ffmpeg -activation_bytes aabbccdd -i Anomaly_B074TZ7Q5Q.aax -vn -c:a copy output.mp4
ffmpeg version n4.1 Copyright (c) 2000-2018 the FFmpeg developers
  built with gcc 8.2.1 (GCC) 20180831

Converting TO AAX however -

%  ffmpeg -activation_bytes aabbccdd -i output.mp4 -vn -c:a copy output.aax
...
[NULL @ 0x562448a9bac0] Unable to find a suitable output format for 'output.aax'
output.aax: Invalid argument

[Elon Musk]

No reason to write DRM files.

[C0rn3j]

What do you mean no reason? I explained a valid use case in the OP.

[Carl Eugen Hoyos]

I believe this ticket has similarities with a valid enhancement request.

[Ekevoo]

This limitation affects me, too. I didn't find a non-disruptive button to signal that, so I'm posting a comment.

[Balling]

​https://patchwork.ffmpeg.org/project/ffmpeg/patch/17559601585196510@sas2-2fa759678732.qloud-c.yandex.net/