mglsp2sp

Functions

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

mglsp2sp [ option ] [ infile ]

  • -m int

    • order of line spectral pairs \((0 \le M)\)

  • -a double

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

  • -g double

    • gamma \((-1.0 \le \gamma < 0)\)

  • -c int

    • gamma \(\gamma = -1 / C\) \((1 \le C)\)

  • -l int

    • FFT length \((1 \le L)\)

  • -s double

    • sampling rate \((0 < F_s)\)

  • -k int

    • input gain type

      • 0 linear gain

      • 1 log gain

      • 2 without gain

  • -q int

    • input format

      • 0 frequency in rad

      • 1 frequency in \(\pi\) rad

      • 2 frequency in kHz

      • 3 frequency in Hz

  • -o int

    • output format

      • 0 \(20 \log_{10}|H(z)|\)

      • 1 \(\log|H(z)|\)

      • 2 \(|H(z)|\)

      • 3 \(|H(z)|^2\)

  • infile str

    • double-type mel-LSP

  • stdout

    • double-type spectrum

Parameters:

  • argc – [in] Number of arguments.

  • argv – [in] Argument vector.

Returns:

0 on success, 1 on failure.

See also

lpc2lsp

class MelGeneralizedLineSpectralPairsToSpectrum

Convert mel-LSP to spectrum.

The input is the \(M\)-th order line spectral paris:

\[ \begin{array}{cccc} K, & \omega(1), & \ldots, & \omega(M), \end{array} \]
where \(K\) is the gain. The output is the \((L/2+1)\)-length log amplitude spectrum:
\[ \begin{array}{cccc} \log|H(0)|, & \log|H(1)|, & \ldots, & \log|H(L/2)|, \end{array} \]
where \(L\) is the FFT length.

The transfer function of the all-pole filter is given by

\[ H(z) = K \cdot A^{1/\gamma}(z). \]
Thus,
\[ \log |H(z)| = \log K + \frac{1}{2\gamma} \log |A(z)|^2. \]
If \(M\) is even,
\[\begin{split}\begin{eqnarray} |A(\omega)|^2 &=& 2^{M} \left\{ \cos^2 \left( \frac{\tilde{\omega}}{2} \right) \prod_{m=1,3,\ldots}^{M} (\cos\tilde{\omega}-\cos\omega(m))^2 \right. \\ && \left. + \sin^2 \left( \frac{\tilde{\omega}}{2} \right) \prod_{m=2,4,\ldots}^{M} (\cos\tilde{\omega}-\cos\omega(m))^2 \right\}, \end{eqnarray}\end{split}\]
else
\[\begin{split}\begin{eqnarray} |A(\omega)|^2 &=& 2^{M-1} \left\{ \prod_{m=1,3,\ldots}^{M} (\cos\tilde{\omega}-\cos\omega(m))^2 \right. \\ && \left. + \sin^2 \tilde{\omega} \prod_{m=2,4,\ldots}^{M} (\cos\tilde{\omega}-\cos\omega(m))^2 \right\}, \end{eqnarray}\end{split}\]
where \(\tilde{\omega}\) is the angular frequency warped by the first-order all pass filter:
\[ \tilde{\omega} = \omega + 2\tan^{-1} \left( \frac{\alpha\sin\omega}{1 - \alpha\cos\omega} \right). \]

[1] A. V. Oppenheim and D. H. Johnson, “Discrete representation of signals,” Proc. of the IEEE, vol. 60, no. 6, pp. 681-691, 1972.

[2] N. Sugamura and F. Itakura, “Speech data compression by LSP speech analysis-synthesis technique,” Journal of IEICE, vol. J64-A, no. 8, pp. 599-606, 1981.

Public Functions

MelGeneralizedLineSpectralPairsToSpectrum(int num_order, double alpha, double gamma, int fft_length)
Parameters:

  • num_order – [in] Order of line spectral pairs, \(M\).

  • alpha – [in] Alpha, \(\alpha\).

  • gamma – [in] Gamma, \(\gamma\).

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

inline int GetNumOrder() const
Returns:

Order of coefficients.

inline double GetAlpha() const
Returns:

Alpha.

inline double GetGamma() const
Returns:

Gamma.

inline int GetFftLength() const
Returns:

FFT length.

inline bool IsValid() const
Returns:

True if this object is valid.

bool Run(const std::vector<double> &line_spectral_pairs, std::vector<double> *spectrum) const
Parameters:

  • line_spectral_pairs – [in] \(M\)-th order line spectral pairs. The first element is linear gain and the other elements are in normalized frequency \((0, \pi)\).

  • spectrum – [out] \((L/2+1)\)-length log amplitude spectrum.

Returns:

True on success, false on failure.