fft

Functions

int main(int argc, char *argv[])

fft [ option ] [ infile ]

  • -l int

    • FFT length \((1 \le L)\)

  • -m int

    • order of sequence \((0 \le M < L)\)

  • -o int

    • output format

      • 0 real and imaginary parts

      • 1 real part

      • 2 imaginary part

      • 3 amplitude spectrum

      • 4 power spectrum

  • infile str

    • double-type data sequence

  • stdout

    • double-type FFT sequence

The below example analyzes a sine wave using Blackman window by padding imaginary part with zeros.

sin -p 30 -l 256 | window -L 512 | fft -o 3 > sine.spec

Parameters

  • argc – [in] Number of arguments.

  • argv – [in] Argument vector.

Returns

0 on success, 1 on failure.

See also

fftr ifft phase grpdelay

class sptk::FastFourierTransform

Calculate DFT of complex-valued input data.

The inputs are \(M\)-th order complex-valued data:

\[\begin{split} \begin{array}{cccc} \mathrm{Re}(x(0)), & \mathrm{Re}(x(1)), & \ldots, & \mathrm{Re}(x(M)), \\ \mathrm{Im}(x(0)), & \mathrm{Im}(x(1)), & \ldots, & \mathrm{Im}(x(M)). \end{array} \end{split}\]
The outputs are
\[\begin{split} \begin{array}{cccc} \mathrm{Re}(X(0)), & \mathrm{Re}(X(1)), & \ldots, & \mathrm{Re}(X(L-1)), \\ \mathrm{Im}(X(0)), & \mathrm{Im}(X(1)), & \ldots, & \mathrm{Im}(X(L-1)), \end{array} \end{split}\]
where \(L\) is the FFT length and must be a power of two.

Public Functions

explicit FastFourierTransform(int fft_length)
Parameters

fft_length – [in] FFT length, \(L\).

FastFourierTransform(int num_order, int fft_length)
Parameters

  • num_order – [in] Order of input, \(M\).

  • fft_length – [in] FFT length, \(L\).

inline int GetNumOrder() const
Returns

Order of input.

inline int GetFftLength() const
Returns

FFT length.

inline bool IsValid() const
Returns

True if this object is valid.

bool Run(const std::vector<double> &real_part_input, const std::vector<double> &imag_part_input, std::vector<double> *real_part_output, std::vector<double> *imag_part_output) const
Parameters

  • real_part_input – [in] \(M\)-th order real part of input.

  • imag_part_input – [in] \(M\)-th order imaginary part of input.

  • real_part_output – [out] \(L\)-length real part of output.

  • imag_part_output – [out] \(L\)-length imaginary part of output.

Returns

True on success, false on failure.

bool Run(std::vector<double> *real_part, std::vector<double> *imag_part) const
Parameters

  • real_part – [inout] Real part.

  • imag_part – [inout] Imaginary part.

Returns

True on success, false on failure.