How Do I Convert aax Files?

[aeridus]

I'm tinkering around with Nier in order to grab all the extra music since I liked the game so much. However, I've hit a roadblock. When I extracted files out of the cpk I found (and yet another cpk in the audio directory), I got a ton of aax files that I just don't know what to do with. The internet is not much help because all it says is "audiobook format". What the heck am I supposed to use to convert? Anything will do for the output format, such as aac, though flac is preferred.

Edit: Never mind, I managed to find vgmstream and it worked, thank goodness.