comp_idgt_fb.m

linear time－frequency toolbox

function [f]=comp_idgt_fb(coef,g,a,M)
%COMP_IDGT_FB  Filter bank IDGT.
%   Usage:  f=comp_idgt_fb(c,g,a,M);
%       
%   This is a computational routine. Do not call it directly.
%
%   SEE ALSO: IDGT

%   Author : Peter Soenderagaard.

% Compute the real length of the transform.
N=size(coef,2);
W=size(coef,3);

L=N*a;
b=L/M;

gl=length(g);

coef=ifft(coef);

coef=reshape(coef,M*N,W);

gl=length(g);

% The fftshift actually makes some things easier.
g=fftshift(g);

f=zeros(L,W);

% Values used to calculate correct splitting.
no_split_s=ceil((gl/2/a));
no_split_e=floor((L-gl/2)/a);

nrange=(0:N-1)';
spr=rem(nrange*a-gl/2+L,L)+1;       % Starting point
epr=rem(nrange*a-gl/2+gl-1+L,L)+1;  % ending point.
nsplitr=L+1-spr;

% Make multicolumn g by replication.
gw=repmat(g,1,W);

% This covers the the cases when splitting is necessary:
Nsplit=[0:no_split_s-1,no_split_e+1:N-1];
% This n is one-indexed, to avoid to many +1
for n=Nsplit+1
  
  % Rotate the coefficients, duplicate them until they have same
  % length as g, and multiply by g.
  ff=repmat(circshift(coef((n-1)*M+1:n*M,:),-(n-1)*a+gl/2),gl/M,1).*gw;
  
  % Add the ff vector to f at position sp.
  f(spr(n):L,:)=f(spr(n):L,:)+ff(1:nsplitr(n),:);
  f(1:epr(n),:)=f(1:epr(n),:)+ff(nsplitr(n)+1:gl,:);
    
end;

% This cover the cases when splitting is not necessary:
% This n is one-indexed, to avoid to many +1
for n=no_split_s+1:no_split_e+1
    
  % Rotate the coefficients, duplicate them until they have same
  % length as g, and multiply by g.
  ff=repmat(circshift(coef((n-1)*M+1:n*M,:),-(n-1)*a+gl/2),gl/M,1).*gw;
  
  % Add the ff vector to f at position sp.
  f(spr(n):epr(n),:)=f(spr(n):epr(n),:)+ff;
  
end;

% Scale correctly.
f=M*f;