AA, Audible Audio Book File (.aa)
The AA Audio file format
The AA file extension is used by the Audible audio book service to store audio books in a digital format. Audible is part of the Amazon company. Various devices can play AA files, like the Apple iPod or Amazon Kindle. The format is, however, not supported by most digital audio players. A conversion to a more compatible audio format like MP3 is needed to, for example, listen to the audio book in Windows Media Player. The AA file format has, since its introduction, been improved, creating the AAX file extension.
Technical details of AA files
AA files belong to the audio files category, however they differ from audio files like MP3 or WAV in some aspects. Next to the actual auditory data, AA files can also contain further information like chapter markers and bookmarks. AA files can be saved in three different formats, ranging from 8 kbit/s to 32 kbit/s. The audio quality is thus dependent on the bitrate, ranging from AM radio-like to MP3 quality. AA files can be DRM protected which makes it impossible to convert to a more widely used audio format.