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melcepst

PURPOSE ^

MELCEPST Calculate the mel cepstrum of a signal C=(S,FS,W,NC,P,N,INC,FL,FH)

SYNOPSIS ^

function [c,tc]=melcepst(s,fs,w,nc,p,n,inc,fl,fh)

DESCRIPTION ^

MELCEPST Calculate the mel cepstrum of a signal C=(S,FS,W,NC,P,N,INC,FL,FH)


 Simple use: (1) c=melcepst(s,fs)          % calculate mel cepstrum with 12 coefs, 256 sample frames
              (2) c=melcepst(s,fs,'E0dD')   % include log energy, 0th cepstral coef, delta and delta-delta coefs

 Inputs:
     s      speech signal
     fs  sample rate in Hz (default 11025)
     w   mode string (see below)
     nc  number of cepstral coefficients excluding 0'th coefficient [default 12]
     p   number of filters in filterbank [default: floor(3*log(fs)) =  approx 2.1 per ocatave]
     n   length of frame in samples [default power of 2 < (0.03*fs)]
     inc frame increment [default n/2]
     fl  low end of the lowest filter as a fraction of fs [default = 0]
     fh  high end of highest filter as a fraction of fs [default = 0.5]

        w   any sensible combination of the following:

               'R'  rectangular window in time domain
                'N'     Hanning window in time domain
                'M'     Hamming window in time domain (default)

               't'  triangular shaped filters in mel domain (default)
               'n'  hanning shaped filters in mel domain
               'm'  hamming shaped filters in mel domain

                'p'     filters act in the power domain
                'a'     filters act in the absolute magnitude domain (default)

               '0'  include 0'th order cepstral coefficient
                'E'  include log energy
                'd'     include delta coefficients (dc/dt)
                'D'     include delta-delta coefficients (d^2c/dt^2)

               'z'  highest and lowest filters taper down to zero (default)
               'y'  lowest filter remains at 1 down to 0 frequency and
                        highest filter remains at 1 up to nyquist freqency

               If 'ty' or 'ny' is specified, the total power in the fft is preserved.

 Outputs:    c     mel cepstrum output: one frame per row. Log energy, if requested, is the
                 first element of each row followed by the delta and then the delta-delta
                 coefficients.
           tc    fractional time in samples at the centre of each frame
                 with the first sample being 1.

CROSS-REFERENCE INFORMATION ^

This function calls: This function is called by:

SOURCE CODE ^

0001 function [c,tc]=melcepst(s,fs,w,nc,p,n,inc,fl,fh)
0002 %MELCEPST Calculate the mel cepstrum of a signal C=(S,FS,W,NC,P,N,INC,FL,FH)
0003 %
0004 %
0005 % Simple use: (1) c=melcepst(s,fs)          % calculate mel cepstrum with 12 coefs, 256 sample frames
0006 %              (2) c=melcepst(s,fs,'E0dD')   % include log energy, 0th cepstral coef, delta and delta-delta coefs
0007 %
0008 % Inputs:
0009 %     s      speech signal
0010 %     fs  sample rate in Hz (default 11025)
0011 %     w   mode string (see below)
0012 %     nc  number of cepstral coefficients excluding 0'th coefficient [default 12]
0013 %     p   number of filters in filterbank [default: floor(3*log(fs)) =  approx 2.1 per ocatave]
0014 %     n   length of frame in samples [default power of 2 < (0.03*fs)]
0015 %     inc frame increment [default n/2]
0016 %     fl  low end of the lowest filter as a fraction of fs [default = 0]
0017 %     fh  high end of highest filter as a fraction of fs [default = 0.5]
0018 %
0019 %        w   any sensible combination of the following:
0020 %
0021 %               'R'  rectangular window in time domain
0022 %                'N'     Hanning window in time domain
0023 %                'M'     Hamming window in time domain (default)
0024 %
0025 %               't'  triangular shaped filters in mel domain (default)
0026 %               'n'  hanning shaped filters in mel domain
0027 %               'm'  hamming shaped filters in mel domain
0028 %
0029 %                'p'     filters act in the power domain
0030 %                'a'     filters act in the absolute magnitude domain (default)
0031 %
0032 %               '0'  include 0'th order cepstral coefficient
0033 %                'E'  include log energy
0034 %                'd'     include delta coefficients (dc/dt)
0035 %                'D'     include delta-delta coefficients (d^2c/dt^2)
0036 %
0037 %               'z'  highest and lowest filters taper down to zero (default)
0038 %               'y'  lowest filter remains at 1 down to 0 frequency and
0039 %                        highest filter remains at 1 up to nyquist freqency
0040 %
0041 %               If 'ty' or 'ny' is specified, the total power in the fft is preserved.
0042 %
0043 % Outputs:    c     mel cepstrum output: one frame per row. Log energy, if requested, is the
0044 %                 first element of each row followed by the delta and then the delta-delta
0045 %                 coefficients.
0046 %           tc    fractional time in samples at the centre of each frame
0047 %                 with the first sample being 1.
0048 %
0049 
0050 % BUGS: (1) should have power limit as 1e-16 rather than 1e-6 (or possibly a better way of choosing this)
0051 %           and put into VOICEBOX
0052 %       (2) get rdct to change the data length (properly) instead of doing it explicitly (wrongly)
0053 
0054 %      Copyright (C) Mike Brookes 1997
0055 %      Version: $Id: melcepst.m 4914 2014-07-24 08:44:26Z dmb $
0056 %
0057 %   VOICEBOX is a MATLAB toolbox for speech processing.
0058 %   Home page: http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/voicebox.html
0059 %
0060 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
0061 %   This program is free software; you can redistribute it and/or modify
0062 %   it under the terms of the GNU General Public License as published by
0063 %   the Free Software Foundation; either version 2 of the License, or
0064 %   (at your option) any later version.
0065 %
0066 %   This program is distributed in the hope that it will be useful,
0067 %   but WITHOUT ANY WARRANTY; without even the implied warranty of
0068 %   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
0069 %   GNU General Public License for more details.
0070 %
0071 %   You can obtain a copy of the GNU General Public License from
0072 %   http://www.gnu.org/copyleft/gpl.html or by writing to
0073 %   Free Software Foundation, Inc.,675 Mass Ave, Cambridge, MA 02139, USA.
0074 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
0075 
0076 if nargin<2 fs=11025; end
0077 if nargin<3 w='M'; end
0078 if nargin<4 nc=12; end
0079 if nargin<5 p=floor(3*log(fs)); end
0080 if nargin<6 n=pow2(floor(log2(0.03*fs))); end
0081 if nargin<9
0082    fh=0.5;   
0083    if nargin<8
0084      fl=0;
0085      if nargin<7
0086         inc=floor(n/2);
0087      end
0088   end
0089 end
0090 
0091 if isempty(w)
0092    w='M';
0093 end
0094 if any(w=='R')
0095    [z,tc]=enframe(s,n,inc);
0096 elseif any (w=='N')
0097    [z,tc]=enframe(s,hanning(n),inc);
0098 else
0099    [z,tc]=enframe(s,hamming(n),inc);
0100 end
0101 f=rfft(z.');
0102 [m,a,b]=melbankm(p,n,fs,fl,fh,w);
0103 pw=f(a:b,:).*conj(f(a:b,:));
0104 pth=max(pw(:))*1E-20;
0105 if any(w=='p')
0106    y=log(max(m*pw,pth));
0107 else
0108    ath=sqrt(pth);
0109    y=log(max(m*abs(f(a:b,:)),ath));
0110 end
0111 c=rdct(y).';
0112 nf=size(c,1);
0113 nc=nc+1;
0114 if p>nc
0115    c(:,nc+1:end)=[];
0116 elseif p<nc
0117    c=[c zeros(nf,nc-p)];
0118 end
0119 if ~any(w=='0')
0120    c(:,1)=[];
0121    nc=nc-1;
0122 end
0123 if any(w=='E')
0124    c=[log(max(sum(pw),pth)).' c];
0125    nc=nc+1;
0126 end
0127 
0128 % calculate derivative
0129 
0130 if any(w=='D')
0131   vf=(4:-1:-4)/60;
0132   af=(1:-1:-1)/2;
0133   ww=ones(5,1);
0134   cx=[c(ww,:); c; c(nf*ww,:)];
0135   vx=reshape(filter(vf,1,cx(:)),nf+10,nc);
0136   vx(1:8,:)=[];
0137   ax=reshape(filter(af,1,vx(:)),nf+2,nc);
0138   ax(1:2,:)=[];
0139   vx([1 nf+2],:)=[];
0140   if any(w=='d')
0141      c=[c vx ax];
0142   else
0143      c=[c ax];
0144   end
0145 elseif any(w=='d')
0146   vf=(4:-1:-4)/60;
0147   ww=ones(4,1);
0148   cx=[c(ww,:); c; c(nf*ww,:)];
0149   vx=reshape(filter(vf,1,cx(:)),nf+8,nc);
0150   vx(1:8,:)=[];
0151   c=[c vx];
0152 end
0153  
0154 if nargout<1
0155    [nf,nc]=size(c);
0156 %    t=((0:nf-1)*inc+(n-1)/2)/fs;
0157    ci=(1:nc)-any(w=='0')-any(w=='E');
0158    imh = imagesc(tc/fs,ci,c.');
0159    axis('xy');
0160    xlabel('Time (s)');
0161    ylabel('Mel-cepstrum coefficient');
0162     map = (0:63)'/63;
0163     colormap([map map map]);
0164     colorbar;
0165 end
0166

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