ATRAC
act adaptive transform coding
Adaptive Transform Acoustic Coding (ATRAC) is a family of proprietary audio compression algorithms developed by Sony. MiniDisc was the first commercial product to incorporate ATRAC, in 1992. ATRAC allowed a relatively small disc like MiniDisc to have the same running time as a CD while storing audio information with minimal perceptible loss in quality. Improvements to the codec in the form of ATRAC3, ATRAC3plus, and ATRAC Advanced Lossless followed in 1999, 2002, and 2006 respectively.
Files in ATRAC3 format originally had the .aa3 extension; however, in most cases, the files would be stored in an OpenMG Audio container using the extension .oma. Previously, files that were encrypted with OpenMG had the .omg extension, which was replaced by .oma starting in SonicStage v2.1. Encryption is no longer compulsory as of v3.2.
Other MiniDisc manufacturers such as Sharp and Panasonic also implemented their own versions of the ATRAC codec.
History
ATRAC was developed for Sony's MiniDisc format. ATRAC was updated with version 2, then version 3, version 4, version 4.5, and Type R and Type S.
The first major update was ATRAC3 (not to be confused with version 3 of original ATRAC) in 1999.
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This entry incorporates text from “ATRAC” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.