function f = idpwt(w,l,level)
% FUNCTION:     idpwt   Part of the DPWT Toolbox
%
% SYNOPSIS:     F = idpwt(W,L [,LEVEL])
%
% DESCRIPTION:  This is the inverse discrete periodic
%               wavelet transform using filter L. The 
%               wavelet coefficient vector is assumed
%               to be the product of a DPWT decomposition
%               down to level LEVEL. The output
%               vector F is the same size as W whose
%               size should be an integer power of 2. Wavelet
%               coefficient vector W should have structure,
%               W  = [flevel, wlevel, ...w(p-1), wp]
%               where flevel and wlevel are the row vectors
%               that are the level LEVEL decomposition 
%               products of the DPWT applied to a sequence fp.
% 
%               This routine does some argument testing and calculations
%               which are then passed on to the recursive function 
%               r_idpwt which actually implements the IDPWT.
%
%               The length of W must be an integer power of 2. 
%               Filter sequence L is not checked for satisfaction of 
%               perfect reconstruction criteria. It must be of even
%               length.
%
% SEE ALSO:     r_dpwt, idpwt, r_idpwt
% 
% REFERENCE:    N. Getz, "A Fast Discrete Periodic Wavelet Transform",
%               Electronics Research Laboratory, U.C. Berkeley, 1992.
%

% AUTHOR:       Neil Getz
%
% ORGANIZATION: University of California
%               Department of Electrical Engineering
%               and the Electronics Research Laboratory 
%               Cory Hall
%               Berkeley, CA 94720
%
% DATE: 12-11-92
% 

% Argument checking.
%
if(nargin < 2 | nargin > 3),
  help idpwt;
  return;
end;

p = log(length(w))/log(2);
N = length(l)/2;

if(round(N) ~= N),
  error('Length of arg 2 must be an even integer.')
elseif(p ~= round(p)),
  error('Length of arg 1 must be an integer power of 2.')
elseif(nargin == 3),
  if((level > p)|(level < 0))
    error('Level (arg 3) must not be greater than log2 of length of arg 1.')
  end
end
%

MATSHIFT = 1;	% Matlab indices start at 1, not 0.

% Conjugate filter calculation
%
h = l;	% For length.
for k = 0:2*N-1,
  h( MATSHIFT + k ) = (-1)^( MATSHIFT + k ) * l(MATSHIFT + 2*N - 1 - k);
end
%

% If level is not specified then go all the way.
if (nargin == 2),
  level = 0;
end
%

% The beef
f = r_idpwt(w, l, h, level);

% END idpwt().