Advanced Audio Coding
AAC is a codec designed to provide better compression than MP3s, and are improved versions of MPEG audio. AAC actually refers to two similar codecs - MPEG-2 AAC and MPEG-4 AAC.
AAC has many, many options avaliable and is heavily customisable depending on the desired output.
It has some advantages over MP3 - it has a greater range of sample frequencies, up to 48 channels and higher coding efficiency. It also has much better handling of frequencies above 16 kHz
Depending on the AAC profile and the MP3 encoder, 96 kbit/s AAC can give nearly the same or better perceptional quality as 128 kbit/s MP3.
MPEG-4 AAC is used by iTunes and iPod - and Apple Music Store sells a protected version of AAC, known as FairPlay (see also Apple website on AAC).
In addition, the Sony PSP (PlayStation Portable) has added AAC support with version 2.0 firmware update, which was released in August 2005 .
VideoLAN uses the FAAC (encoder) and FAAD (decoder) to provide support for AAC audio.
Some of the text on this page is originally from Wikipedia - see AAC (wikipedia)
