comp_gdgt.m

linear time－frequency toolbox

function [c,Ls]=comp_gdgt(f,g,a,M,L,c_t,c_f,c_w,timeinv)
%COMP_GDGT  Compute generalized DGT
%   Usage:  c=comp_gdgt(f,g,a,M,L,c_t,c_f,c_w,timeinv);
%
%   Input parameters:
%         f       : Input data
%         g       : Window function.
%         a       : Length of time shift.
%         M       : Number of modulations.
%         L       : Length of transform to do.
%         c_t     : Centering in time of modulation.
%         c_f     : Centering in frequency of modulation.
%         c_w     : Centering in time of window.
%         timeinv : Should we compute a time invariant Gabor system.
%   Output parameters:
%         c       : M*N array of coefficients.
%         Ls      : Length of input signal.
%

%   AUTHOR : Peter Soendergaard.

Lwindow=size(g,1);

W=size(f,2);
N=L/a;

% Preprocess to handle c_f different from 0.
if (c_f~=0)
  halfmod=exp(-2*pi*i*c_f*(0:L-1).'/M);
  f=f.*repmat(halfmod,1,W);
end;

if Lwindow<L
  % Do the filter bank algorithm

  c=comp_dgt_fb(f,g,a,M);

else
  % Do the factorization algorithm
  
  b=L/M;
  N=L/a;
  W=size(f,2);

  % Get the factorization of the window.
  gf=comp_wfac(g,a,M);
  
  % Compute the window application and the DFT modulation.
  c=fft(comp_dgt_fw(f,gf,a,M))/sqrt(M);
  
end;

if timeinv
  c=reshape(c,M,N,W);
  c=phaselock(c,a);
  c=reshape(c,M,N*W);
end;

% Post-process if c_t is different from 0.
if (c_t~=0)

  % The following is necessary because REPMAT does not work for
  % 3D arrays.
  halfmod=repmat(exp(-2*pi*i*c_t*((0:M-1)+c_f).'/M),1,N*W);
  
  c=c.*halfmod;
end;

c=reshape(c,M,N,W);