fftr

Functions

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

fftr [ option ] [ infile ]

-l int
- FFT length \((2 \le L)\)
-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
-H bool
- output only half part
infile str
- double-type data sequence
stdout
- double-type FFT sequence

The below example analyzes a sine wave using Blackman window.

sin -p 30 -l 256 | window | fftr -o 3 > sine.spec

Parameters

argc – [in] Number of arguments.
argv – [in] Argument vector.

Returns

0 on success, 1 on failure.

See also

fft ifft spec phase grpdelay

class sptk::RealValuedFastFourierTransform

Calculate DFT of real-valued input data.

The input is \(M\)-th order real-valued data:

\[ \begin{array}{cccc} x(0), & x(1), & \ldots, & x(M). \end{array} \]

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 RealValuedFastFourierTransform(int fft_length)

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

RealValuedFastFourierTransform(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, std::vector<double> *real_part_output, std::vector<double> *imag_part_output, RealValuedFastFourierTransform::Buffer *buffer) const

Parameters

real_part_input – [in] \(M\)-th order real part of input.
real_part_output – [out] \(L\)-length real part of output.
imag_part_output – [out] \(L\)-length imaginary part of output.
buffer – [out] Buffer.

Returns

True on success, false on failure.

bool Run(std::vector<double> *real_part, std::vector<double> *imag_part, RealValuedFastFourierTransform::Buffer *buffer) const

Parameters

real_part – [inout] Real part.
imag_part – [out] Imaginary part.
buffer – [out] Buffer.

Returns

True on success, false on failure.

class Buffer: Buffer for RealValuedFastFourierTransform class.

class sptk::RealValuedInverseFastFourierTransform

Calculate inverse DFT of real-valued input data.

This is almost similar to RealValuedFastFourierTransform. The DFT results are divided by the FFT length \(L\).

Public Functions

explicit RealValuedInverseFastFourierTransform(int fft_length)

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

RealValuedInverseFastFourierTransform(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, std::vector<double> *real_part_output, std::vector<double> *imag_part_output, RealValuedInverseFastFourierTransform::Buffer *buffer) const

Parameters

real_part_input – [in] \(M\)-th order real part of input.
real_part_output – [out] \(L\)-length real part of output.
imag_part_output – [out] \(L\)-length imaginary part of output.
buffer – [out] Buffer.

Returns

True on success, false on failure.

bool Run(std::vector<double> *real_part, std::vector<double> *imag_part, RealValuedInverseFastFourierTransform::Buffer *buffer) const

Parameters

real_part – [inout] Real part.
imag_part – [out] Imaginary part.
buffer – [out] Buffer.

Returns

True on success, false on failure.

class Buffer: Buffer for RealValuedInverseFastFourierTransform class.