Protected 4ma/4mb file

[trianglejuice]

Ok, maybe this is a weird question, but I want to convert my mp3 audiobooks to protected m4a/m4b files.

I managed to convert them to simple m4a files (with iTunes), but those files are not protected.

The reason why I want to do this is because I want my iPod to recognize these files as an audiobook (so I can access them via the AudioBook folder and adjust the speed).

Thanks in advance,
Jasper.

[Las_Vegas]

From the looks of this document (http://docs.info.apple.com/article.html?artnum=61695) from Apple, you can identify an AAC file ('m4a') as an audio book by changing it's suffix to 'aa'. 'm4b' files are those encoded by apple for sale over iTunes as 'm4p' files are the protected form of 'm4a' files.