Lossless Predictive Audio Compression
LPAC - Lossless Predictive Audio Compression - is a lossless audio archiver created by the german engineer Tilman Liebchen.
It was a relatively popular format at one point because, even though not being open source, there were versions available for Linux and Solaris. A library also was available, making integration of LPAC encoding and decoding into other applications relatively easy. It was also much more efficient and featureful than the biggest competitor at the time, Shorten.
Recently, mr. Liebchen worked on what will be the standard lossless encoding scheme in MPEG-4 - MPEG-4 ALS (Audio Lossless coding). As of april 2005, the standardization process is in its final stages.