bianal3.m

来自「这是伯克里wavelet transforms一书中的例子的代码」· M 代码 · 共 38 行

function biodd = bianal3(data,lpf,hpf)
%bianal3(data,lpf,hpf) effects a one level decomposition of 
%of the input signal, data, using the biorthogonal filter bank
%defined by filters lpf and hpf. The filters are assumed to be 
%WSS and the extension is WSS symetric extension. The length of 
%data is odd.
%
%This routine is used by analw for biorthogonal wavelet decomposition.
%
%Author: Ajit S. Bopardikar
%Copyright (c) 1998 by Addison Wesley Longman, Inc.
%

   l  = length(data);
   ll = length(lpf);
   lh = length(hpf);

   le = (ll-1)/2; %extension length
   he = (lh-1)/2; %extension length

   if (ll>lh) %if the lpf has even group delay
    d0 = 0;
    d1 = 1;
   elseif (lh>ll) %if the hpf has even group delay
     d0 = 1;
     d1 = 0;
   end; %endif

   ext = [data(le+1:-1:2) data data(l-1:-1:l-le-1)]; %extension
   lp = conv(ext,lpf);
   biodd = lp(ll+d0:2:l+ll-1); %lowpass subband

   ext = [data(he+1:-1:2) data data(l-1:-1:l-he-1)]; %extension
   lp = conv(ext,hpf);
   biodd = [biodd lp(lh+d1:2:l+lh-1)]; %the subband decomposed signal