Re: non-cypher related question on audio analysis

After you know something, remember this: The FIR filter is the same mathematically as a FFT, multiplication by a filter window function, and an inverse FFT. As I recall, you can process multiple FIR's in parallel.

you can do two FFT's by using the fact that: FFT( x(t) + j y(t) ) = Z(w) then X(l) = 1/2 ( Z(l) + Z*(N-l)) and Y(l) = 1/2j (Zl) - Z*(N-l)) Where x(t) <-> X(w) y(t) <-> Y(w) N is the length of both arrays j is sqrt(-1) Z* is the conjugate of Z (a+jb <-> a-jb )