The functions described in this section compute the forward and
inverse discrete Fourier transform of real and complex signals. The DFT is less
efficient than the fast Fourier transform, however the length of the vector transformed
by the DFT can be arbitrary.
argument, passed to the initialization functions, suggests using special algorithm,
faster or more accurate. The
argument specifies the result normalization method. The complex
signal can be represented as a single array containing complex elements, or two separate
arrays containing real and imaginary parts. The output result of the FFT can be packed
in Pack, Perm, or CCS formats.
To use the DFT functions, you should initialize the specification
structure which contains such data as tables of twiddle factors. Use the
For more information about the fast computation of the discrete
Fourier transform, see [Mit93], section 8-2,
of the DFT
A special set of Intel IPP functions provides the so called
“out-of-order” DFT of the complex signal. In this case, the elements in frequency domain
for both forward and inverse transforms can be re-ordered to speed-up the computation of
the transforms. This re-ordering is hidden from the user and can be different in
different implementations of the functions. However, reversibility of each pair of
functions for forward/inverse transforms is ensured.