v_lpcar2db

V_LPCAR2DB LPC: Convert AR coefs to power spectrum in dB DB=(AR)

  Inputs: ar(nf,n)     AR coefficients, one frame per row
          np           Size of output spectrum is np+1 [n]

 Outputs: db(nf,np+1)  Power spectrum in dB 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

0001 function [db,f]=v_lpcar2db(ar,np)
0002 %V_LPCAR2DB LPC: Convert AR coefs to power spectrum in dB DB=(AR)
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: db(nf,np+1)  Power spectrum in dB 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 
0013 %      Copyright (C) Mike Brookes 1998
0014 %      Version: $Id: v_lpcar2db.m 10865 2018-09-21 17:22:45Z dmb $
0015 %
0016 %   VOICEBOX is a MATLAB toolbox for speech processing.
0017 %   Home page: http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/voicebox.html
0018 %
0019 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
0020 %   This program is free software; you can redistribute it and/or modify
0021 %   it under the terms of the GNU General Public License as published by
0022 %   the Free Software Foundation; either version 2 of the License, or
0023 %   (at your option) any later version.
0024 %
0025 %   This program is distributed in the hope that it will be useful,
0026 %   but WITHOUT ANY WARRANTY; without even the implied warranty of
0027 %   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
0028 %   GNU General Public License for more details.
0029 %
0030 %   You can obtain a copy of the GNU General Public License from
0031 %   http://www.gnu.org/copyleft/gpl.html or by writing to
0032 %   Free Software Foundation, Inc.,675 Mass Ave, Cambridge, MA 02139, USA.
0033 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
0034 
0035 [nf,p1]=size(ar);
0036 if nargin<2
0037     if nargout
0038         np=p1-1;
0039     else
0040         np=128;
0041     end
0042 end
0043 ff=v_rfft(ar.',2*np).';
0044 db=-10*log10(real(ff.*conj(ff)));
0045 f=(0:np)/(2*np);
0046 if ~nargout
0047         plot(f,db.');
0048         xlabel('Normalized frequency f/f_s');
0049         ylabel('LPC Power Spectrum (dB)');
0050 end
0051