AAC file extension

This is a compressed audio file that is similar to an MP3 file, but provides some performance improvements, for example a higher coding efficiency for stationary and transient signals, a simpler filterbank and better handling of frequencies above 16 kHz. This format maintains quality nearly indistinguishable from the original audio source. Apple iTunes and the iTunes Music Store use Advanced Audio Coding (AAC) as the standard encoding. AAC-encoded files are usually stored with M4A extension.