What is a AAC file?
High-quality compressed audio, Apple's preferred format
Advanced Audio Coding (AAC) is the default encoding used by Apple iTunes and the iTunes Music Store. It is a compressed audio file similar to an .MP3 file, but offers several performance improvements; examples include a higher coding efficiency for both stationary and transient signals, a simpler filterbank, and better handling of frequencies above 16 kHz; maintains quality nearly indistinguishable from the original audio source.
