fwt_sbs.sci

小波分解源代码

function wcoef = FWT_SBS(x,L,qmf,dqmf)
// FWT_SBS -- Forward Wavelet Transform (symmetric extension, biorthogonal, symmetric)
//  Usage
//    wc = FWT_SBS(x,L,qmf,dqmf)
//  Inputs
//    x    1-d signal; arbitrary length
//    L    Coarsest Level of V_0;  L << J
//    qmf    quadrature mirror filter (symmetric)
//    dqmf   quadrature mirror filter (symmetric, dual of qmf)
//  Outputs
//    wc    1-d wavelet transform of x.
// 
//  Description
//    1. qmf filter may be obtained from MakePBSFilter
//    2. usually, length(qmf) < 2^(L+1)
//    3. To reconstruct use IWT_SBS
// 
//  See Also
//    IWT_SBS, MakePBSFilter
// 
//  References
//   Based on the algorithm developed by Christopher Brislawn.
//   See "Classification of Symmetric Wavelet Transforms"
// 
//  Copyright Aldo I Maalouf

  [n,J] = dyadlength(x);
	
	wcoef = zeros(1,n);
	beta = ShapeAsRow(x);  // take samples at finest scale as beta-coeffts

	dp = dyadpartition(n);
	
	for j=J-1:-1:L
	  [beta, alfa] = DownDyad_SBS(beta,qmf,dqmf);
	  //dyadj = (dp(j+1)+1):dp(j+2);
    dyadj = (dp(j+1)):dp(j+2);
	  wcoef(dyadj) = alfa;
	end
	wcoef(1:length(beta)) = beta;
	wcoef = ShapeLike(wcoef,x);
	endfunction