Programmer Guide/Command Reference/EVAL/cepstrum: Difference between revisions
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;Usage 1:<code>cepstrum(<var>x</var>)</code> | ;Usage 1:<code>cepstrum(<var>x</var>)</code> | ||
:;<var>x</var>: a vector containing a log. amplitude spectrum | :;<var>x</var>: a vector containing a log. amplitude spectrum | ||
::*note: because | ::*note: because a radix-2 fft/ifft is used for the computation, the spectrum stored in ''x'' must be computed from a signal with <code>L=2^M</code> samples (<code>→ nrow(''x'')=L/2+1=2^M/2+1</code>). | ||
;Result 1:A vector with <code>L/2</code> values, containing the coefficients or the real cepstrum of ''x''. | ;Result 1:A vector with <code>L/2</code> values, containing the coefficients or the real cepstrum of ''x''. | ||
---- | ---- | ||
;Usage 2:<code>cepstrum(<var>x</var>, <var>m</var>)</code> | ;Usage 2:<code>cepstrum(<var>x</var>, <var>m</var>)</code> | ||
:;<var>x</var>: a vector containing a log. amplitude spectrum | :;<var>x</var>: a vector containing a log. amplitude spectrum | ||
:;<var>m</var>: the number of coefficients to be used for smoothing; 0 < ''m'' | :;<var>m</var>: the number of coefficients to be used for smoothing; 0 < ''m'' ≤ L/2 | ||
;Description: | ;Description: | ||
:# The real cepstrum ''c'' of ''x'' is computed. | :# The real cepstrum ''c'' of ''x'' is computed. | ||
| Line 19: | Line 19: | ||
:;<var>x</var>: a vector containing a log. amplitude spectrum | :;<var>x</var>: a vector containing a log. amplitude spectrum | ||
:;<var>o</var>: the first coefficient to be used for smoothing; 0 < ''o'' < L/2 | :;<var>o</var>: the first coefficient to be used for smoothing; 0 < ''o'' < L/2 | ||
:;<var>m</var>: the number of coefficients to be used for smoothing; 0 < ''m'' | :;<var>m</var>: the number of coefficients to be used for smoothing; 0 < ''m'' ≤ L/2-''o'' | ||
;Description: | ;Description: | ||
:# The real cepstrum ''c'' of ''x'' is computed. | :# The real cepstrum ''c'' of ''x'' is computed. | ||
| Line 26: | Line 26: | ||
;Result 2:A vector with same length as ''x'', containing the liftered spectrum. | ;Result 2:A vector with same length as ''x'', containing the liftered spectrum. | ||
---- | ---- | ||
;See also: [[ | ;See also: [[../fft|fft]], [[../ifft|ifft]], [[../dft|dft]], [[../dct|dct]], [[../lpc|lpc]], [[../ipeak|ipeak]], [[../formants|formants]] | ||
[[ | [[../#Functions|<function list>]] | ||
Latest revision as of 19:26, 21 April 2011
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^Msamples (→ nrow(x)=L/2+1=2^M/2+1).
- note: because a radix-2 fft/ifft is used for the computation, the spectrum stored in x must be computed from a signal with
- Result 1
- A vector with
L/2values, 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
-
- The real cepstrum c of x is computed.
- The coefficents m to
L/2-1of the cepstrum c are set to zero. - 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
-
- The real cepstrum c of x is computed.
- The coefficents 0 to o-1 and o+m to
L/2-1of the cepstrum c are set to zero. - The liftered spectrum is computed from the modified cepstrum c.
- Result 2
- A vector with same length as x, containing the liftered spectrum.
