MPEG-4 AUDIO: AAC
Because of its exceptional performance and quality, Advanced Audio Coding (AAC) is at the core of the
MPEG-4 specification and is the new audio codec of choice for Internet, wireless, and digital broadcast arenas. AAC provides audio encoding that compresses much more efficiently than older formats such as MP3, yet delivers quality rivaling that of uncompressed CD audio.
AAC was developed by the MPEG group that includes Dolby, Fraunhofer (FhG), AT&T, Sony, and Nokiacompanies that have also been involved in the development of audio codecs such as MP3 and AC3 (also known as Dolby Digital). The AAC codec in QuickTime 6 builds upon new, state-of-the art signal processing technology from Dolby Laboratories and brings true variable bit rate (VBR) audio encoding to QuickTime.
Move Over MP3
Internet audio has become wildly popular in recent years, specifically in the MP3 format. But what most listeners dont realize is that MP3s compression technology is more than a decade old. In those ten years, many advances in perceptual audio coding and compression have been achieved. AAC takes full advantage of these advances, resulting in higher quality output at lower data rates, allowing even modem users to hear a difference.
When compared side-by-side, AAC proves itself worthy of replacing MP3 as the new Internet audio standard. Take a look at these AAC advantages over MP3:
Improved compression provides higher-quality results with smaller file sizes
Support for multichannel audio, providing up to 48 full frequency channels
Higher resolution audio, yielding sampling rates up to 96 kHz
Improved decoding efficiency, requiring less processing power for decode
The Data Speaks for Itself
In numerous comparison tests, AAC comes out on top. Check out these impressive results:
AAC compressed audio at 128 kbps (stereo) has been judged by expert listeners to be indistinguishable from the original uncompressed audio source.*
AAC compressed audio at 96 kbps generally exceeded the quality of MP3 compressed audio at 128 kbps. AAC at 128 kbps provides significantly superior performance than does MP3 at 128 kbps.*
AAC was the only Internet audio codec evaluated in the range Excellent at 64 kbps for all of the audio items tested in EBU listening tests.*
* See the
AAC website for reference.
Why Wait?
With the release of
QuickTime 6, the newest-generation technology for digital audio is now widely available AAC audio in MPEG-4. Hear the quality for yourself in our
MPEG-4 (AAC) Audio Gallery.
MP4 Players could bring the same audio quality that MP3 gave us, but at a much lower bit rate, boosting the overall number of songs we can store on our portable players. Or it could be used to maximize the sound quality of our music by giving us higher quality sound (than MP3), but at the same or higher bit rates resulting in true Dolby Digital/THX/Surround Sound!!! 
