downdyad_sbs.sci

来自「小波分解源代码」· SCI 代码 · 共 40 行

function [beta, alpha] = DownDyad_SBS(x,qmf,dqmf)
// DownDyad_SBS -- Symmetric Downsampling operator
//  Usage
//    [beta,alpha] = DownDyad_SBS(x,qmf,dqmf)
//  Inputs
//    x     1-d signal at fine scale
//    qmf   quadrature mirror filter
//    dqmf  dual quadrature mirror filter
//  Outputs
//    beta  coarse coefficients
//    alpha fine coefficients
//  See Also
//    FWT_SBS
//  Copyright Aldo I Maalouf

 // oddf = (rem(length(qmf),2)==1);
	  oddf = ~(qmf(1)==0 & qmf(length(qmf))~=0);
    oddx = (rem(length(x),2)==1);
	
// symmetric extension of x
 	  if oddf then
 	      ex = extend(x,1,1);
 	  else
 	      ex = extend(x,2,2);
 	  end
 	
 	  // convolution
 	  ebeta = DownDyadLo_PBS(ex,qmf);
 	  ealpha = DownDyadHi_PBS(ex,dqmf);
 	       
 	  // project
 	  if oddx then
 	     beta = ebeta(1:(length(x)+1)/2);
 	     alpha = ealpha(1:(length(x)-1)/2);
 	  else
 	     beta = ebeta(1:length(x)/2);
 	     alpha = ealpha(1:length(x)/2);
 	  end      
endfunction