A fast Fourier transform (FFT) is an efficient algorithm to compute the discrete Fourier transform (DFT) and its inverse

delphi fft souce plus example (fast Fourier transform Direct and Inverse)

DSPLab is a library of delphi components for digital signal processing. The library contains two components: IIR Filter and FFT. IIR Filter is Butterworth, Bessel and Chebyshev infinite-impulse-response (IIR) filters, with lowpass, highpass, bandpass