smcep

Functions

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

smcep [ option ] [ infile ]

• -m int

  • order of coefficients \((0 \le M)\)

• -a double

  • all-pass constant \((|\alpha| < 1)\)

• -t double

  • emphasized frequency in \(\pi\) rad \((0 \le \theta \le 1.0)\)

• -l int

  • FFT length \((2 \le N)\)

• -q int

  • input format

    • 0 amplitude spectrum in dB

    • 1 log amplitude spectrum

    • 2 amplitude spectrum

    • 3 power spectrum

    • 4 windowed waveform

• -f int

  • accuracy factor \((1 \le F)\)

• -i int

  • number of iterations \((0 \le J)\)

• -d double

  • convergence threshold \((0 \le \epsilon)\)

• -e double

  • small value added to power spectrum

• -E double

  • relative floor in decibels

• infile str

  • double-type windowed sequence or spectrum

• stdout

  • double-type mel-cepstral coefficients

In the example below, mel-cepstral coefficients are extracted from data.d.

frame < data.d | window | smcep -t 0.12 > data.mcep

Parameters:

• argc – [in] Number of arguments.

• argv – [in] Argument vector.

Returns:

0 on success, 1 on failure.

See also

mgcep

class SecondOrderAllPassMelCepstralAnalysis

Calculate mel-cepstrum from periodogram.

The input is the half of periodogram:

\[ \begin{array}{cccc} |X(0)|^2, & |X(1)|^2, & \ldots, & |X(N/2)|^2, \end{array} \]

where \(N\) is the FFT length. The output is the \(M\)-th order mel-cepstral coefficients:

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

In the mel-cepstral analysis based on the second order all-pass function, the spectrum of speech signal is modeled by \(M\)-th order mel-cepstral coefficients as follows:

\[ H(z) = \exp \sum_{m=0}^M \tilde{c}(m) \displaystyle\frac{A^m(z) + A^m(z^{-1})}{2}, \]

where

\[ A(z) = \left( \frac{z^{-2} - 2\alpha\cos\theta z^{-1} + \alpha^2} {1 - 2\alpha \cos\theta z^{-1} + \alpha^2 z^{-2}} \right)^{1/2}. \]

The phase characteristic of the all-pass function is controlled by the two parameters: \(\alpha\) and \(\theta\).

Note that the implemenation is based on an unpublished paper.

Public Functions

SecondOrderAllPassMelCepstralAnalysis(int fft_length, int num_order, int accuracy_factor, double alpha, double theta, int num_iteration, double convergence_threshold)

Parameters:

• fft_length – [in] Number of FFT bins, \(N\).

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

• accuracy_factor – [in] Accuracy of frequency transform. This must be a power of two.

• alpha – [in] Frequency warping factor, \(\alpha\).

• theta – [in] Frequency emphasis factor, \(\theta\).

• num_iteration – [in] Number of iterations of Newton method, \(J\).

• convergence_threshold – [in] Convergence threshold, \(\epsilon\).

inline int GetFftLength() const

Returns:

FFT length.

inline int GetNumOrder() const

Returns:

Order of coefficients.

inline double GetAlpha() const

Returns:

All-pass constant.

inline double GetTheta() const

Returns:

Frequency emphasis factor.

inline int AccuracyFactor() const

Returns:

A factor for making a conversion matrix of frequency transform.

inline int GetNumIteration() const

Returns:

Number of iterations.

inline double GetConvergenceThreshold() const

Returns:

Convergence threshold.

inline bool IsValid() const

Returns:

True if this object is valid.

bool Run(const std::vector<double> &periodogram, std::vector<double> *mel_cepstrum, SecondOrderAllPassMelCepstralAnalysis::Buffer *buffer) const

Parameters:

• periodogram – [in] \((N/2+1)\)-length periodogram.

• mel_cepstrum – [out] \(M\)-th order mel-cepstral coefficients.

• buffer – [out] Buffer.

Returns:

True on success, false on failure.

class Buffer

Buffer for SecondOrderAllPassMelCepstralAnalysis class.

class SecondOrderAllPassFrequencyTransform

Transform a minimum phase sequence into a frequency-warped sequence.

Public Functions

SecondOrderAllPassFrequencyTransform(int num_input_order, int num_output_order, int fft_length, double alpha, double theta)

Parameters:

• num_input_order – [in] Order of input, \(M_1\).

• num_output_order – [in] Order of output, \(M_2\).

• fft_length – [in] FFT length used to make conversion matrix.

• alpha – [in] Frequency warping factor, \(\alpha\).

• theta – [in] Frequency emphasis factor, \(\theta\).

inline int GetNumInputOrder() const

Returns:

Order of input.

inline int GetNumOutputOrder() const

Returns:

Order of output.

inline double GetAlpha() const

Returns:

Frequency warping factor.

inline double GetTheta() const

Returns:

Frequency emphasis factor.

inline bool IsValid() const

Returns:

True if this object is valid.

bool Run(const std::vector<double> &minimum_phase_sequence, std::vector<double> *warped_sequence) const

Parameters:

• minimum_phase_sequence – [in] \(M_1\)-th order input sequence.

• warped_sequence – [out] \(M_2\)-th order output sequence.

Returns:

True on success, false on failure.

class SecondOrderAllPassInverseFrequencyTransform

Transform a frequency-warped sequence into a minimum phase sequence.

Public Functions

SecondOrderAllPassInverseFrequencyTransform(int num_input_order, int num_output_order, int fft_length, double alpha, double theta)

Parameters:

• num_input_order – [in] Order of input, \(M_1\).

• num_output_order – [in] Order of output, \(M_2\).

• fft_length – [in] FFT length used to make conversion matrix.

• alpha – [in] Frequency warping factor, \(\alpha\).

• theta – [in] Frequency emphasis factor, \(\theta\).

inline int GetNumInputOrder() const

Returns:

Order of input.

inline int GetNumOutputOrder() const

Returns:

Order of output.

inline double GetAlpha() const

Returns:

Frequency warping factor.

inline double GetTheta() const

Returns:

Frequency emphasis factor.

inline bool IsValid() const

Returns:

True if this object is valid.

bool Run(const std::vector<double> &warped_sequence, std::vector<double> *minimum_phase_sequence) const

Parameters:

• warped_sequence – [in] \(M_1\)-th order input sequence.

• minimum_phase_sequence – [out] \(M_2\)-th order output sequence.

Returns:

True on success, false on failure.