Sony announced the MiniDisc in September 1992 and released it in November of that year for sale in Japan and in December in Europe, Canada, the US and other countries. The music format was originally based on ATRAC audio data compression, but the option of linear PCM digital recording was later introduced to meet audio quality comparable to that of a compact disc. MiniDiscs were very popular in Japan and found moderate success in Europe. Until March 2011 Sony had sold 22 million MD players.