dstIV(s, int, window)

Perform an even-ordered DST-IV transform

This implementation has focus on speed rather than readability. It's optimized for projects performing many transform of the same length (images processing, or as in my case millions of 2^16 point DST-IV on frequency synthesis spectrum analysis).
Limitation: It only handles even-length inputs (it cannot compute for instance the 5-point DST).