The Wayback Machine - https://web.archive.org/web/20070715144709/http://eupat.ffii.org:80/patents/samples/ep287578/index.en.html
Acoustic Data Compression -- MP3 Base Patent
Iteratively perform certain calculations on acoustic data until a certain value is reached. The patent owner Karlheinz Brandenburg, core researcher of the MP3 project at Max Planck, received this patent in 1989. This patent and its owner were showcased by the European Commission's "IPR Helpdesk" project in 2001 as "inventor of the month". This is one of several dozen patents which cover the MP3 audio compression standard, and perhaps the most famous and basic one. It has always been treated as a model of how "technical" and "non-trivial" software patents can get.