floor 0 decode specification refers to undefined omega
Section 6.2.3 of the vorbis specification, step 2 of the LSP output synthesis, uses the value 'cos(w)' (omega), but never defines omega anywhere (I think). Difficult to search for omega in the document, as it probably only appears in images. (And difficult to google for it to see if it has a common LSP meaning, too.)
I can't check the source since I'm writing a clean-room implementation.