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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
References in periodicals archive ?
The findings from this study indicated that practitioners believed AAC providers should possess unique skills and competencies, have a strong working relationship with the therapy animal, protect the welfare of the animal, interpret the animal's responses, and be able to work with the animal to be present with the client (Stewart et al.
The company's transaction provides AAC with capital to fund current and future growth opportunities.
Up to an additional GBP 200,000 of deferred consideration will be payable based upon AAC Cyroma achieving pre-tax profit targets for the years ending 31 December 2017 and 2018.
On August 4, 2015, Bleecker Street Research reported that AAC was aware of the investigation that led to the indictment and that the Company knew of at least 8 undisclosed patient deaths in AAC facilities.
Focused training of caregivers/spouses in AAC strategies has yielded some positive outcomes.
As Nicholas begins to use his AAC systems, his behavior improves, and Alicia engineers her entire home with AAC so that Nicholas is never without a way to use symbolic functional spontaneous communication.
Durante's vision and ours is to establish the AAC as a global benchmark for acquisition and combat support excellence through exceptional workforce development.
In short, it helps instructors teach, and students learn several AAC systems.
The MPEG-4 AAC licensing program has been fine-tuned, taking into account various market demands in radically different environments ranging from freely distributed PC-based software decoders to high-quality playback consumer electronics devices.
Although speech-language pathologists (SLPs) are typically responsible for the treatment of communication problems, the development of appropriate AAC interventions represents a formidable task that will require the expertise of SLPs and their collaboration with numerous school personnel.
In conjunction with the divestiture, AAC will lease the facilities from MedEquities pursuant to a 15-year triple-net lease at an initial lease rate of 8.