wildual.m

linear time－frequency toolbox

function [gamma]=wildual(g,M,L)
%WILDUAL  Canonical dual window.
%   Usage:  gamma=wildual(g,M);
%           gamma=wildual(g,M,L);
%
%   Input parameters:
%         g     : Gabor window.
%         M     : Number of modulations.
%         L     : Length of window. (optional)
%   Output parameters:
%         gamma : Canonical dual window.
%
%   WILDUAL(g,M) returns the dual window of the Wilson or MDCT basis with
%   window g, parameter M and length equal to the length of the window g.
%
%   WILDUAL(g,M,L) does the same, but now L is used as the length of the
%   Wilson basis. g will be cut or zero-extended to length L.
%
%   The input window g must be whole-point even.
%
%   SEE ALSO:  WILORTH, ISWPEVEN

%   Author : Peter Soendergaard.

if prod(size(M))~=1
  error('M must be a scalar');
end;

wasrow=0;

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

%if ~iseven(g)
%  error('g must be whole point even.See help on pgauss.');
%end;
  
if nargin==3
  % firextend is now safe.
  g=firextend(g,L);
else
  L=length(g);
end;

if rem(L,M)~=0
  error('The length of the transform must be dividable by M.');
end;

if mod(L/M,2)~=0
  error('L/M must be even.');
end;

a=M;
  
gf=comp_wfac(g,a,2*M);
gammaf=2*comp_candual_fac(gf,L,a,2*M);
gamma=comp_iwfac(gammaf,L,a,2*M);

if wasrow
  gamma=gamma.';
end;