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(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 ?
Aberdeen AAC's Jane davidson is a medal contender in the women's 100m hurdles and long jump.
Michael Ferguson (Aberdeen AAC) was third in the men's 3000m in 8:27.87 with Morpeth's Rory Leonard winning in 8:24.91.
Alongside the AAC blocks, Starken's main products are panels and lintels with density of 450kg/cubic meter up to 700kg/cub meter.
Furthermore, AAC Qaiser Khan Kundi carried out checking on University Road areas and arrested 6 persons for erecting encroachments and overcharging of consumers.
AAC can work with almost any theoretical counseling modality, but most importantly, it is a practice that strengthens the core conditions between the counselor and the client.
Through this acquisition, AAC accelerates its longstanding plan to diversify into government pay, leverage an existing outpatient and business development presence in New England and continue the expansion of its hospital strategy.
'AAC block entrains air or gas in the concrete and produces a much lighter block.
Aiming at giving the reader a view about some essential aspects for understanding the theme, it is deemed important to explain how AAC is conceived in this study.
"Our participation, as the only non-federal vertical launch complex on the panel, was confirmation that the current transition to a lower cost commercial launch site has attracted the attention of the government and has increased our potential for expanded operations in future years," said Craig Campbell, AAC President and CEO.
The main aim of this paper is to utilise available local AAC waste as a lightweight aggregate in concrete production which could allow converting industrial wastes into value-added products.
A: According to Robert Silvers, who developed the .300 AAC Blackout for Advanced Armament Corp.
AAC has also agreed to withdraw its objections to JPMorgan's global RMBS settlement with RMBS trustees.