Advanced Audio Coding

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Advanced Audio Coding

(AAC) A successor to MP3, allowing lower bit rates and more stable quality.

See MPEG-2 AAC Low Profile and MPEG-4 AAC Main Profile.
This article is provided by FOLDOC - Free Online Dictionary of Computing (


(Advanced Audio Coding) An audio compression technology that is part of the MPEG-2 and MPEG-4 standards. AAC, especially MPEG-4 AAC, provides greater compression and better sound quality than MP3, which also came out of the MPEG standard.

Popularized by the iPod
AAC is the default format for Apple's iPod. It was chosen because it improved sound quality and also supported copy protection, which was administered through Apple's iTunes software. AAC song files purchased from the iTunes online store were sold with copy protection, but Apple dropped it in 2009 (see FairPlay). With iTunes, users may also choose to rip their CDs to AAC instead of MP3.

AAC is available in profiles, which determine how the algorithms work to encode the audio data. Main offers the highest quality. Low Complexity (LC) is lower quality, but uses less CPU processing. Scalable Sampling Rate (SSR) is a variation of LC. Long Term Prediction was added in MPEG-4 to improve the Main profile. See aacPlus, Apple Lossless, MP3 and iPod. Following are the file extensions used for AAC:

AAC File Extension   Type of AAC File

     MP4   Standard MPEG-4 video & audio

     M4A   Unprotected AAC
     M4A   Apple Lossless

     M4P   Protected AAC
     M4B   Protected AAC audiobook
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References in periodicals archive ?
High-Efficiency Advanced Audio Coding (HE AAC) is an international standard for audio encoding authorized for use by Dolby Laboratories to hundreds of companies around the world.
The industry's alternative has been to make compressed audio formats available for sale that consumers cannot easily copy, such as the Advanced Audio Coding (AAC) format.
When copy-restriction routines no longer lock songs to certain players or programs, a few other things will change.Apple's iPod -- which dominated the market before the arrival of the iTunes Store -- should still do well, as should the Advanced Audio Coding format Apple uses for iTunes downloads.
According to the company, the platform consists of semiconductor chips, as well as a set of multimedia software and protocol stack software, including multimedia features such as H.263 and H.264 video capability, as well as support for MPEG-1 Audio Layer 3 (MP3), Windows Media Audio (WMA), Advanced Audio Coding (AAC), aacPlus and Enhanced aacPlus audio formats.
of Southern California) present a senior undergraduate or graduate level textbook on advanced audio coding techniques.
- The AVIC-VH009MD, AVIC-VH009, and AVIC-ZH009 are equipped with a 5.1 multi-channel processor for playback of multi-channel programs such as DVD-Videos and the MPEG-2 AAC (MPEG-2 Advanced Audio Coding) sources from terrestrial TV broadcasts.

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