AAC

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AAC

AAC

(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.

Profiles
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
References in periodicals archive ?
She has plans to attract likeminded professionals to join the already talented ranks of ACC Construction.
The project was a complete success, and all three firms working so well together enabled ACC to complete the renovation ahead of schedule," added Medaglia.
The primates, during their meeting in February 2005, had requested that the Canadian and American churches "voluntarily withdraw" from the ACC meeting in Nottingham, England, last June as a step towards restoring unity within the Anglican Communion fractured by the issue of same-sex blessings in New Westminster and the ordination of a gay bishop in New Hampshire.
Despite attempts to rejuvenate Claremont Foundry, ACC has not yet built a sufficient volume of profitable casting business at this foundry," said Aiken.
ACC also specializes in construction of doctors' offices.
CoGS also urged the primate, Archbishop Andrew Hutchison, to convene an "ACC relationship steering committee" as recommended by the delegates and presenters to the ACC meeting.
Through increased content, participation and membership, enhanced by the handbook collaboration, Data Management is progressing, and the Defense Acquisition University ACC editors and support staff are striving to ensure its evolution from an SIA to a member Community within the ACC.
In June, responding to a recommendation in the 2004 Windsor Report, the ACC voted to invite the 38 primates, or heads of national churches, to join its 78 members.
Over the past two decades, ACC Construction has developed a reputation as a construction management and general contracting firm expert in private sector projects, including those in commercial office, educational, retail and healthcare fields.