LPCAR2PF Convert AR coefs to power spectrum PF=(AR,NP) Inputs: ar(nf,n) AR coefficients, one frame per row np Size of output spectrum is np+1 [n] Outputs: pf(nf,np+1) Power spectrum from DC to Nyquist f(1,np+1) Normalized frequencies (0 to 0.5) For high speed make np equal to a power of 2

- rfft RFFT Calculate the DFT of real data Y=(X,N,D)

0001 function [pf,f]=lpcar2pf(ar,np) 0002 %LPCAR2PF Convert AR coefs to power spectrum PF=(AR,NP) 0003 % 0004 % Inputs: ar(nf,n) AR coefficients, one frame per row 0005 % np Size of output spectrum is np+1 [n] 0006 % 0007 % Outputs: pf(nf,np+1) Power spectrum from DC to Nyquist 0008 % f(1,np+1) Normalized frequencies (0 to 0.5) 0009 % 0010 % For high speed make np equal to a power of 2 0011 0012 % Copyright (C) Mike Brookes 1998-2014 0013 % Version: $Id: lpcar2pf.m 5026 2014-08-22 17:47:43Z dmb $ 0014 % 0015 % VOICEBOX is a MATLAB toolbox for speech processing. 0016 % Home page: http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/voicebox.html 0017 % 0018 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 0019 % This program is free software; you can redistribute it and/or modify 0020 % it under the terms of the GNU General Public License as published by 0021 % the Free Software Foundation; either version 2 of the License, or 0022 % (at your option) any later version. 0023 % 0024 % This program is distributed in the hope that it will be useful, 0025 % but WITHOUT ANY WARRANTY; without even the implied warranty of 0026 % MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 0027 % GNU General Public License for more details. 0028 % 0029 % You can obtain a copy of the GNU General Public License from 0030 % http://www.gnu.org/copyleft/gpl.html or by writing to 0031 % Free Software Foundation, Inc.,675 Mass Ave, Cambridge, MA 02139, USA. 0032 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 0033 0034 [nf,p1]=size(ar); 0035 if nargin<2 0036 if nargout 0037 np=p1-1; 0038 else 0039 np=128; 0040 end 0041 end 0042 pf=abs(rfft(ar.',2*np).').^(-2); 0043 f=(0:np)/(2*np); 0044 if ~nargout 0045 plot(f,pf.'); 0046 xlabel('Normalized frequency f/f_s'); 0047 ylabel('LPC Power Spectrum'); 0048 end 0049

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