Short answers, pulled from the story.
Karlheinz Brandenburg developed the MP3 format while working at Germany's University of Erlangen-Nuremberg in the early 1980s. He completed his doctoral work by 1989 and collaborated with James D. Johnston to refine compression algorithms before joining the Fraunhofer Institute for Integrated Circuits in 1993.
The core principle behind MP3 relies on auditory masking, a phenomenon where one sound makes another inaudible. This effect was first reported by American physicist Alfred M. Mayer in 1894 and later expanded by Richard Ehmer in 1959 to describe complete sets of auditory curves.
The Moving Picture Experts Group designed MP3 as part of its MPEG-1 standard suite which was approved in 1991. The algorithms were finalized in 1992 and published as international standard ISO/IEC 11172-3:1993 in 1993.
Nullsoft's audio player Winamp released in 1997 gained popularity rapidly with an estimated 80 million active users still present in 2023. Windows Media Player 5.2 added MP3 support in 1998 alongside portable solid-state digital audio players like MPMan developed by SaeHan Information Systems headquartered in Seoul South Korea.
Technicolor formerly called Thomson Consumer Electronics claimed control over MP3 licensing in many countries including United States Japan Canada and EU nations. They actively enforced these patents generating approximately €100 million for Fraunhofer Society in 2005 alone.