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What is AAC in Mac OS: coding scheme, originally a component of the MPEG-2 standard as MPEG-2 AAC.

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AAC definition

Explanation: Advanced Audio Coding. A compressed, lossy, perceptual coding scheme, originally a component of the MPEG-2 standard as MPEG-2 AAC. Defined in 1997 as part of ISO/IEC 13818-7. Enhanced for the MPEG-4 standard as MPEG-4 AAC. MPEG-2 AAC provides better perceived audio quality at the same bit rate compared to MPEG-1, layer 3 ( MP3 ), according to results published in ISO/IEC JTC1/SC29/WG11, N2006 (February 1998). MPEG-4 AAC extends MPEG-2 AAC with additional coding tools. See also lossy compression

More definitions for Mac OS users such as AAC in Dictionary A.