common/alcomplex.h

   1 #ifndef ALCOMPLEX_H
   2 #define ALCOMPLEX_H
   3
   4 #include <complex>
   5 #include <type_traits>
   6
   7 #include "alspan.h"
   8
   9 /**
  10  * Iterative implementation of 2-radix FFT (In-place algorithm). Sign = -1 is
  11  * FFT and 1 is inverse FFT. Applies the Discrete Fourier Transform (DFT) to
  12  * the data supplied in the buffer, which MUST BE power of two.
  13  */
  14 template<typename Real>
  15 std::enable_if_t<std::is_floating_point<Real>::value>
  16 complex_fft(const al::span<std::complex<Real>> buffer, const al::type_identity_t<Real> sign);
  17
  18 /**
  19  * Calculate the frequency-domain response of the time-domain signal in the
  20  * provided buffer, which MUST BE power of two.
  21  */
  22 template<typename Real, size_t N>
  23 std::enable_if_t<std::is_floating_point<Real>::value>
  24 forward_fft(const al::span<std::complex<Real>,N> buffer)
  25 { complex_fft(buffer.subspan(0), -1); }
  26
  27 /**
  28  * Calculate the time-domain signal of the frequency-domain response in the
  29  * provided buffer, which MUST BE power of two.
  30  */
  31 template<typename Real, size_t N>
  32 std::enable_if_t<std::is_floating_point<Real>::value>
  33 inverse_fft(const al::span<std::complex<Real>,N> buffer)
  34 { complex_fft(buffer.subspan(0), 1); }
  35
  36 /**
  37  * Calculate the complex helical sequence (discrete-time analytical signal) of
  38  * the given input using the discrete Hilbert transform (In-place algorithm).
  39  * Fills the buffer with the discrete-time analytical signal stored in the
  40  * buffer. The buffer is an array of complex numbers and MUST BE power of two,
  41  * and the imaginary components should be cleared to 0.
  42  */
  43 void complex_hilbert(const al::span<std::complex<double>> buffer);
  44
  45 #endif /* ALCOMPLEX_H */