idwilt.m

linear time－frequency toolbox

function [f]=idwilt(c,g,Ls)
%IDWILT  Inverse discrete Wilson transform.
%   Usage:  f=idwilt(c,g);
%           f=idwilt(c,g,Ls);
%
%   Input parameters:
%         c     : M*N array of coefficients.
%         g     : Window function.
%         Ls    : Final length of function (optional)
%   Output parameters:
%         f     : Input data
%
%   IDWILT(c,g) computes an inverse discrete Wilson transform with window g.
%   The number of channels is deduced from the size of the coefficient array c.
%
%   g must be whole-point even.
%
%   IDWILT(f,g,Ls) does the same, but cuts of zero-extend the final
%   result to length Ls.
%
%   SEE ALSO:  DWILT, DGT, WILORTH
%
%   REFERENCES:
%     H. Bölcskei, H. Feichtinger, K. Gröchenig, and F. Hlawatsch. Discrete-time
%     Wilson expansions. In Proc. IEEE-SP 1996 Int. Sympos. Time-Frequency
%     Time-Scale Analysis, pages 525-528, jun 1996.
%     
%     Y.-P. Lin and P. Vaidyanathan. Linear phase cosine modulated maximally
%     decimated filter banks with perfect reconstruction. IEEE Trans. Signal
%     Process., 43(11):2525-2539, 1995.

%   Author : Peter Soendergaard.

error(nargchk(2,3,nargin));

if size(g,2)>1
  if size(g,1)>1
    error('g must be a vector');
  else
    % g was a row vector.
    g=g(:);
  end;
end;

%if ~iseven(g)
%  error('g must be whole point even.See help on pgauss.');
%end;

% If input is real, and window is real, output must be real as well.
inputwasreal = (isreal(g) && isreal(c));

Lwindow=size(g,1);
wasrow=0;

M=size(c,1)/2;
N=2*size(c,2);
W=size(c,3);

L=M*N;

Lwindow=size(g,1);

% Length of window must be dividable by M.
if rem(Lwindow,M)~=0
  error('Length of window must be dividable by M.')
end;

% Call computational subroutine.
a=M;

c=comp_idwilt(reshape(c,M*N,W),a,M);

f=comp_idgt(c,g,a,2*M,L);

% Check if Ls was specified.
if nargin==3
  f=postpad(f,Ls);
else
  Ls=L;
end;


f=comp_sigreshape_post(f,Ls,wasrow,[0; W]);

% Clean signal if it is known to be real
if inputwasreal
  f=real(f);
end;