Zero crossings are inexpensive to compute, and not very valuable (there's a lemma in here about the cost of getting information).FFT can certainly be done in realtime, even on a phone, but may require using GPU code or carefully tuned CPU code, depending on the platform.If you can make it work with ZCs, you will have people approaching you with business propositions.
Thank you Sean True. As they say, things are much easier to say than to do. I am going to take a step back and get out my scope and see if I can extract a sin wave from voice using analog low pass RC-CL components. If I can do it that way I will implement the filters with digital code. The frequency of a voice is much more complex that I originally envisioned. I have not given up, it still seems that there should be a way to extract the fundamental frequency with a simple block of code. Frank
