Programmer Guide/Command Reference/EVAL/cepstrum

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

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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.

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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.

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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.

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See also

fft, ifft, dft, dct, lpc, complex arithmetic

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