Looks like it was inspired by http://keyj.emphy.de/minimp3/ and https://keyj.emphy.de/kjmp2/ , always good to see more people trying to implement multimedia codecs. The theory behind it all is not easy to understand, but in practice it turns into a bunch of arithmetic and table lookups.
That said, this one being floating-point and requiring intrinsics makes it less portable.
That said, this one being floating-point and requiring intrinsics makes it less portable.