You know, the greatest reverse engineer I know is Derek B. He’s managed to RE such codecs as Canopus HQX and Cineform HD in the most efficient manner ever—saying he’ll do it and patiently waiting until somebody else does it.
So here are some words about his favourite lossless audio codec. The most interesting thing about it is that it was actively developed in 2001-2006 and then it was suddenly resurrected in 2015. Also it’s one of few non-standard codecs (i.e. not made into standard) that has several articles written about it.
The codec actually consists of two different formats, seemingly an old one and a newer one (that looks like it supports all range of sample type). The former is notable for having signal reconstruction stage using floating point math (a thing you don’t see in codecs every day), the latter seems to employ various parameter reading and reconstruction methods. Coding is done using low precision range coder (large values are decoded using chunks of 8 or 12 bits). So nothing really interesting there.
P.S. I’m definitely not going to write a decoder for it. There are too many lossless audio codecs already, let all proprietary ones (in custom containers too) die in peace.