v_lpcpf2ff

V_LPCPF2FF Convert power spectrum to complex spectrum [FF,FO]=(PF,NP,FI)

  Inputs: pf(nf,n)     Power spectrum at n discrete frequencies, one frame per row
          np           Number of complex cepstral coefficients to use (excluding c0) [n-1]
                          should be greater than the sum of the numerator
                          and denominator filter orders but less than n
          fi(1,n)      Vector of frequencies [linspace(0,0.5,n)]
                         including this argument slows down the routine

 Outputs: ff(nf,n)     Complex spectrum (pf = abs(ff).^2
          fo(1,n)      Vector of frequencies

 This routine converts a power spectrum into the corresponding complex
 spectrum. It determines the phase spectrum under the assumption that it
 is minimum phase. The routine works by converting first to the compex
 cepstrum.

0001 function [ff,fo]=v_lpcpf2ff(pf,np,fi)
0002 %V_LPCPF2FF Convert power spectrum to complex spectrum [FF,FO]=(PF,NP,FI)
0003 %
0004 %  Inputs: pf(nf,n)     Power spectrum at n discrete frequencies, one frame per row
0005 %          np           Number of complex cepstral coefficients to use (excluding c0) [n-1]
0006 %                          should be greater than the sum of the numerator
0007 %                          and denominator filter orders but less than n
0008 %          fi(1,n)      Vector of frequencies [linspace(0,0.5,n)]
0009 %                         including this argument slows down the routine
0010 %
0011 % Outputs: ff(nf,n)     Complex spectrum (pf = abs(ff).^2
0012 %          fo(1,n)      Vector of frequencies
0013 %
0014 % This routine converts a power spectrum into the corresponding complex
0015 % spectrum. It determines the phase spectrum under the assumption that it
0016 % is minimum phase. The routine works by converting first to the compex
0017 % cepstrum.
0018 
0019 %      Copyright (C) Mike Brookes 2014
0020 %      Version: $Id: v_lpcpf2ff.m 10865 2018-09-21 17:22:45Z dmb $
0021 %
0022 %   VOICEBOX is a MATLAB toolbox for speech processing.
0023 %   Home page: http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/voicebox.html
0024 %
0025 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
0026 %   This program is free software; you can redistribute it and/or modify
0027 %   it under the terms of the GNU General Public License as published by
0028 %   the Free Software Foundation; either version 2 of the License, or
0029 %   (at your option) any later version.
0030 %
0031 %   This program is distributed in the hope that it will be useful,
0032 %   but WITHOUT ANY WARRANTY; without even the implied warranty of
0033 %   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
0034 %   GNU General Public License for more details.
0035 %
0036 %   You can obtain a copy of the GNU General Public License from
0037 %   http://www.gnu.org/copyleft/gpl.html or by writing to
0038 %   Free Software Foundation, Inc.,675 Mass Ave, Cambridge, MA 02139, USA.
0039 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
0040 [nf,nq]=size(pf);
0041 if nargin<3 fi=[];
0042     if nargin<2
0043         np=nq-1; % number of cepstal coefficients (excl c(0))
0044     end
0045 end
0046 [cc,c0]=v_lpcpf2cc(pf,np,fi);
0047 if ~numel(fi)
0048     fi=nq-1;
0049 end
0050 [fx,fo]=v_lpccc2ff(cc,fi,-1,c0);
0051 ff=sqrt(pf).*exp(1i*angle(fx));
0052 if ~nargout
0053     subplot(2,1,2);
0054     plot(fo,unwrap(angle(ff.')));
0055     xlabel('Normalized frequency f/f_s');
0056     ylabel('Phase (rad)');
0057     subplot(2,1,1);
0058     plot(fo,db(abs(ff.')),'-b',fo,db(pf.')/2,':k');
0059     xlabel('Normalized frequency f/f_s');
0060     ylabel('Gain (dB)');
0061 end
0062 
0063