function w = dpwt(f, l, level)
% FUNCTION:     dpwt  Part of DPWT Toolbox
%
% SYNOPSIS:	W = dpwt(F, L, [, LEVEL])
%
% DESCRIPTION:	This is the discrete periodic wavelet transform 
%               using the filter (usually low-p[ass) corresponding to L. 
%               The DPWT transform is performed down to level LEVEL. 
%               The resulting W has the same length as F. If LEVEL is 
%               not specified, or if LEVEL = 0 then the complete DPWT 
%               is calculated. Vector L is assumed to consist of
%               the low-pass half of a perfect reconstruction
%               filter pair.
%
%               The returned row vector W is W = [f0, w0, w1, ..., wp]
%               where f0 is length 1 and wp is a length 2^p row. These
%               are the wavelet coordinates of F.
%
%               This routine does some argument testing and calculations
%               which are then passed on to the recursive function 
%               R_DPWT which actually implements the DPWT.
%
%               The length of F must be an integer power of 2. PADWITHZEROS
%               may be uses to bring F to the necessary dimensions.
%               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, LH_TILDE, PADWITHZEROS
% 
% REFERENCE:    N. Getz, "A Fast Discrete Periodic Wavelet Transform",
%               Electronics Research Laboratory, U.C. Berkeley, 1992.
%

% AUTHOR:       Neil Getz
% DATE:         12-11-92
% 
p = log(length(f))/log(2);
N = length(l)/2;

% Argument checking.
%
if(nargin < 2 | nargin > 3),
  help dpwt;
  return;
elseif(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 log 2 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.
w = r_dpwt(f, l, h, level);

% END dpwt