V_LPCAR2CC LPC: Convert AR filter to complex cepstrum [CC,C0]=(AR,NP)
Inputs: ar(nf,n+1) AR coefficients, one frame per row
np Number of cepstral coefficients to calculate [n]
Outputs: cc(nf,np) Complex cepstral coefficients, excluding c(0)
c0(nf,1) Coefficient c(0)
The "complex cepstral coefficients", cc(n), are the inverse discrete-time Fourier transform
of the log of the complex-valued spectrum. The cc(n) are real-valued and, for n<0, cc(n)=0.
The "real cepstral coeffcients", rc(n), are the inverse discrete-time Fourier transform
of the log of the magnitude spectrum; rc(0)=cc(0) and rc(n)=0.5*cc(n) for n~=0.0001 function [cc,c0]=v_lpcar2cc(ar,np) 0002 %V_LPCAR2CC LPC: Convert AR filter to complex cepstrum [CC,C0]=(AR,NP) 0003 % 0004 % Inputs: ar(nf,n+1) AR coefficients, one frame per row 0005 % np Number of cepstral coefficients to calculate [n] 0006 % 0007 % Outputs: cc(nf,np) Complex cepstral coefficients, excluding c(0) 0008 % c0(nf,1) Coefficient c(0) 0009 % 0010 % The "complex cepstral coefficients", cc(n), are the inverse discrete-time Fourier transform 0011 % of the log of the complex-valued spectrum. The cc(n) are real-valued and, for n<0, cc(n)=0. 0012 % The "real cepstral coeffcients", rc(n), are the inverse discrete-time Fourier transform 0013 % of the log of the magnitude spectrum; rc(0)=cc(0) and rc(n)=0.5*cc(n) for n~=0. 0014 0015 % Copyright (C) Mike Brookes 1998-2014 0016 % Version: $Id: v_lpcar2cc.m 10865 2018-09-21 17:22:45Z dmb $ 0017 % 0018 % VOICEBOX is a MATLAB toolbox for speech processing. 0019 % Home page: http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/voicebox.html 0020 % 0021 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 0022 % This program is free software; you can redistribute it and/or modify 0023 % it under the terms of the GNU General Public License as published by 0024 % the Free Software Foundation; either version 2 of the License, or 0025 % (at your option) any later version. 0026 % 0027 % This program is distributed in the hope that it will be useful, 0028 % but WITHOUT ANY WARRANTY; without even the implied warranty of 0029 % MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 0030 % GNU General Public License for more details. 0031 % 0032 % You can obtain a copy of the GNU General Public License from 0033 % http://www.gnu.org/copyleft/gpl.html or by writing to 0034 % Free Software Foundation, Inc.,675 Mass Ave, Cambridge, MA 02139, USA. 0035 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 0036 0037 [nf,p1]=size(ar); 0038 p=p1-1; 0039 if (nargin<2) np=p; end 0040 cc=zeros(nf,np); 0041 if any(ar(:,1)~=1) 0042 c0=-log(ar(:,1)); 0043 ar=ar./ar(:,ones(1,p1)); 0044 else 0045 c0=zeros(nf,1); 0046 end 0047 cm=(1:np).^(-1); 0048 if np>p 0049 xm=-(1:p); 0050 nz=np-p; 0051 for k=1:nf 0052 cc(k,:)=filter(1,ar(k,:),[ar(k,2:p1).*xm zeros(1,nz)]).*cm; 0053 end 0054 else 0055 p1=np+1; 0056 xm=-(1:np); 0057 for k=1:nf 0058 cc(k,:)=filter(1,ar(k,:),ar(k,2:p1).*xm).*cm; 0059 end 0060 end 0061 if ~nargout 0062 v_lpccc2pf(cc,[],[],c0); 0063 end