MFCC.zip_梅尔频率_音频特征提取_频率特征提取

function [x,mn,mx]=melbankm(p,n,fs,fl,fh,w) %MELBANKM determine matrix for a mel-spaced filterbank [X,MN,MX]=(P,N,FS,FL,FH,W) % % Inputs: p number of filters in filterbank % n length of fft % fs sample rate in Hz % 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: % 't' triangular shaped filters in mel domain (default) % 'n' hanning shaped filters in mel domain % 'm' hamming shaped filters in mel domain % % '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: x a sparse matrix containing the filterbank amplitudes % If x is the only output argument then size(x)=[p,1+floor(n/2)] % otherwise size(x)=[p,mx-mn+1] % mn the lowest fft bin with a non-zero coefficient % mx the highest fft bin with a non-zero coefficient % % Usage: f=fft(s); f=fft(s); % x=melbankm(p,n,fs); [x,na,nb]=melbankm(p,n,fs); % n2=1+floor(n/2); z=log(x*(f(na:nb)).*conj(f(na:nb))); % z=log(x*abs(f(1:n2)).^2); % c=dct(z); c(1)=[]; % % To plot filterbanks e.g. plot(melbankm(20,256,8000)') % % Copyright (C) Mike Brookes 1997 % % Last modified Tue May 12 16:15:28 1998 % % VOICEBOX home page: http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/voicebox.html % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % This program is free software; you can redistribute it and/or modify % it under the terms of the GNU General Public License as published by % the Free Software Foundation; either version 2 of the License, or % (at your option) any later version. % % This program is distributed in the hope that it will be useful, % but WITHOUT ANY WARRANTY; without even the implied warranty of % MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the % GNU General Public License for more details. % % You can obtain a copy of the GNU General Public License from % ftp://prep.ai.mit.edu/pub/gnu/COPYING-2.0 or by writing to % Free Software Foundation, Inc.,675 Mass Ave, Cambridge, MA 02139, USA. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% if nargin < 6 w='tz'; if nargin < 5 fh=0.5; if nargin < 4 fl=0; end end end f0=700/fs; fn2=floor(n/2); lr=log((f0+fh)/(f0+fl))/(p+1); % convert to fft bin numbers with 0 for DC term bl=n*((f0+fl)*exp([0 1 p p+1]*lr)-f0); b2=ceil(bl(2)); b3=floor(bl(3)); if any(w=='y') pf=log((f0+(b2:b3)/n)/(f0+fl))/lr; fp=floor(pf); r=[ones(1,b2) fp fp+1 p*ones(1,fn2-b3)]; c=[1:b3+1 b2+1:fn2+1]; v=2*[0.5 ones(1,b2-1) 1-pf+fp pf-fp ones(1,fn2-b3-1) 0.5]; mn=1; mx=fn2+1; else b1=floor(bl(1))+1; b4=min(fn2,ceil(bl(4)))-1; pf=log((f0+(b1:b4)/n)/(f0+fl))/lr; fp=floor(pf); pm=pf-fp; k2=b2-b1+1; k3=b3-b1+1; k4=b4-b1+1; r=[fp(k2:k4) 1+fp(1:k3)]; c=[k2:k4 1:k3]; v=2*[1-pm(k2:k4) pm(1:k3)]; mn=b1+1; mx=b4+1; end if any(w=='n') v=1-cos(v*pi/2); elseif any(w=='m') v=1-0.92/1.08*cos(v*pi/2); end if nargout > 1 x=sparse(r,c,v); else x=sparse(r,c+mn-1,v,p,1+fn2); end