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:

$$\begin{array}{cccc}x(0),& x(1),& \dots ,& x(M).\end{array}$$

The outputs are

$$\begin{array}{r}\begin{array}{cccc}\mathrm{Re}(X(0)),& \mathrm{Re}(X(1)),& \dots ,& \mathrm{Re}(X(L-1)),\\ \mathrm{Im}(X(0)),& \mathrm{Im}(X(1)),& \dots ,& \mathrm{Im}(X(L-1)),\end{array}\end{array}$$

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.