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author | pkienzle |
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date | Wed, 10 Oct 2001 19:54:49 +0000 |
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children | 2ac2777b30bc |
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## Copyright (C) 1994 Dept of Probability Theory and Statistics TU Wien ## ## This program is free software; you can redistribute it and/or modify ## it under the terms of the GNU General Public License as published by ## the Free Software Foundation; either version 2 of the License, or ## (at your option) any later version. ## ## This program is distributed in the hope that it will be useful, ## but WITHOUT ANY WARRANTY; without even the implied warranty of ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the ## GNU General Public License for more details. ## ## You should have received a copy of the GNU General Public License ## along with this program; if not, write to the Free Software ## Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA ## usage: cceps (x [, correct]) ## ## Returns the complex cepstrum of the vector x. ## If the optional argument correct has the value 1, a correction ## method is applied. The default is not to do this. ## Author: AW (Andreas.Weingessel@ci.tuwien.ac.at) on Apr 1, 1994 ## Last modifified by AW on Nov 8, 1994 function cep = cceps (x, c) if (nargin == 1) c = 0; elseif (nargin != 2) error ("usage: cceps (x [, correct])"); endif [nr, nc] = size (x); if (nc != 1) if (nr == 1) x = x'; nr = nc; else error ("cceps: x must be a vector"); endif endif bad_signal_message = ["cceps: bad signal x, ", ... "some Fourier coefficients are zero."]; F = fft (x); if (min (abs (F)) == 0) error (bad_signal_message); endif # determine if correction necessary half = fix (nr / 2); cor = 0; if (2 * half == nr) cor = (c && (real (F (half + 1)) < 0)); if (cor) F = fft (x(1:nr-1)) if (min (abs (F)) == 0) error (bad_signal_message); endif endif endif cep = fftshift (ifft (log (F))); # make result real if (c) cep = real (cep); if (cor) # make cepstrum of same length as input vector cep (nr) = 0; endif endif endfunction