What is AAC?

Advanced Audio Coding (AAC) is a standard compression and encoding format for digital audio. AAC is part of the MPEG-4 standard, which was established by the Moving Pictures Experts Group (MPEG), the committee that developed the MPEG-1 and MPEG-2 standards that are used all over the world in CD-ROM and DVD discs and other technologies.

AAC is similar in many ways to the popular MP3 format. The encoding and compression techniques are designed in such a way that some information is discarded because of limitations of the human ear. This allows for smaller files than recordings that faithfully reproduce all sounds.

Audio transparency is the concept that the quality of the audio is such that you can hear every detail; the encoding process is able to accurately represent the original audio without sacrificing details. Supposedly, AAC audio requires a bit rate of 128 kilobits per second (kbps) to achieve transparency, while MP3 audio requires a bit rate of 256 kbps to achieve the same transparency.

What this means is that AAC files require approximately half of the file space as an MP3 to achieve the same quality; this means your portable audio player can store twice as many AAC-format songs as MP3 songs, assuming your player supports AAC.

The Apple iPod and iPhone, the Sony Playstation 3, the Nintendo Wii, and many other devices can use AAC files, or utilize the AAC standard internally.

The AAC standard was developed as a joint effort of many different companies, including AT&T Bell Laboratories, Dolby, Nokia, and Fraunhofer IIS.

Advantages of AAC over MP3

AAC was designed as a deliberate improvement to the MP3 format. Here are just a few of the upgrades made:

The AAC standard contains more sample frequencies than MP3; AAC uses 8 kHz to 96 kHz versus the 16 kHz to 48 kHz of MP3.
AAC uses up to 48 channels, while MP3 uses up to 5.1 channels maximum.
AAC also has a higher efficiency for coding stationary signals and transient signals.
AAC has more tools to increase compression efficiency than the MP3 standard.
AAC handles audio frequencies above 16 kHz better than the MP3 format.