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1.
ATRAC (Adaptive TRansform Acoustic Coding), which was introduced with the MiniDisc in 1992 by Sony

ATRAC uses a variety of advanced technologies to analyze digital sound data, allowing it to reduce the size of that data while maintaining superb sound quality (ATRAC*1 compresses music data to approximately 1/5 the data rate of a CD; ATRAC3 and ATRAC3plus are able to compress music data to approximately 1/10 and 1/20 the data rate of a CD, respectively). This ability to reduce the size of data has enabled recording media to be made smaller and more tracks to be recorded on them
"Does your system play ATRAC?", "Hell no."
by Barticus May 10, 2006