ATRAC3

(Adaptive TRansform Acoustic Coding3) An audio compression technology from Sony that provides multiple compression ratios depending on desired sound quality. At 132 Kbps, the music can be compressed to approximately 10% of the space used by a CD. Introduced on the MiniDisc in 1993, the original ATRAC format provided near CD quality sound, but ATRAC3, introduced in 1999, rivals the CD. ATRAC compression is 5:1; ATRAC3 is 10:1.

ATRAC3plus
In 2002, Sony introduced ATRAC3plus, which provides a 20:1 compression ratio, bringing the data down to 5% of the original CD. It can achieve very high quality sound at 48 and 64 Kbps or be practically indistinguishable from the original at 256 Kbps. The CD data rate is 1,411 Kbps. See Sony Memory Stick and OpenMG.