cepstrum

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Compute the real cepstrum or the cepstrum smoothed/liftered spectrum of the logarithmic spectrum x.


Usage 1
cepstrum(x)
x
a vector containing a log. amplitude spectrum
  • note: because a radix-2 fft/ifft is used for the computation, the spectrum stored in x must be computed from a signal with L=2^M samples (-> nrow(x)=L/2+1=2^M/2+1).
Result 1
A vector with L/2 values, containing the coefficients or the real cepstrum of x.

Usage 2
cepstrum(x, m)
x
a vector containing a log. amplitude spectrum
m
the number of coefficients to be used for smoothing; 0 < m <= L/2
Description
  1. The real cepstrum c of x is computed.
  2. The coefficents m to L/2-1 of the cepstrum c are set to zero.
  3. The smoothed spectrum is computed from the modified cepstrum c.
Result 2
A vector with same length as x, containing the smoothed spectrum.

Usage 2
cepstrum(x, o, m)
x
a vector containing a log. amplitude spectrum
o
the first coefficient to be used for smoothing; 0 < o < L/2
m
the number of coefficients to be used for smoothing; 0 < m <= L/2-o
Description
  1. The real cepstrum c of x is computed.
  2. The coefficents 0 to o-1 and o+m to L/2-1 of the cepstrum c are set to zero.
  3. The liftered spectrum is computed from the modified cepstrum c.
Result 2
A vector with same length as x, containing the liftered spectrum.

See also
ifft, dft, dct, cepstrum, lpc, complex arithmetic

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