A MiniDisc (MD) is a magneto-optical disc-based data storage device initially intended for storage of up to 80 minutes of digitalized audio. Today, in the form of Hi-MD, it has developed into a general-purpose storage medium in addition to greatly expanding its audio roots.
MiniDisc was announced by Sony in 1991 and introduced January 12, 1992. The music format was originally based exclusively on ATRAC audio compression. Recently, the option of linear PCM recording was introduced to attain truly CD-quality recordings. MiniDiscs are popular in Japan as a digital upgrade to cassette tapes, but have not been as popular world-wide.
The Sony MZ-NHF800, a 2004 Hi-MD model.
In January 2004, Sony announced the Hi-MD media storage format. With its release in later 2004 came the ability to use newly-developed, high-capacity 1 gigabyte Hi-MD discs, sporting the same dimensions as regular MiniDiscs.