Glossary

AA (Audible Audio)
The proprietary file format used by the Audible.com service for delivering audio versions of books and articles.

AAC (Advanced Audio Coding)
Also called MPEG-4 AAC, this audio codec is the continuation of the MP3 codec created by Fraunhofer-Gesellschaft. Due to advances in the technology, AAC files encoded at a 96 kbps bit rate sound slightly better than MP3s encoded at 128 kbps.

AIFF
An uncompressed Macintosh audio format, functionally identical to Windows' WAV. Uncompressed, sound files occupy a huge amount of disk space, thus the need for compressed formats, such as MP3.

ATRAC
Sony's audio codec used by MiniDisc players. It involves dropping all frequencies below and above the human hearing range (20Hz to 20KHz).

ATRAC3
Sony’s audio codec used by MDLP MiniDisc players and Sony portable players. It allows twice the data compression of ATRAC.

codec
An algorithm for compressing and decompressing the data that makes up audio and video files. Once a file has been compressed by a codec like MP3 or RealAudio, it is smaller and easier to transmit across the Web, and, in most cases, still sounds fairly true to the original.