imdct.m

Matlab时频分析工具箱,希望能对大家有所帮助啊

function [f]=imdct(c,g,Ls)
%IMDCT  Inverse MDCT
%   Usage:  f=imdct(c,g);
%           f=imdct(c,g,Ls);
%
%   Input parameters:
%         c     : M*N array of coefficients.
%         g     : Window function.
%         Ls    : Final length of function (optional)
%   Output parameters:
%         f     : Input data
%
%   IMDCT(c,g) computes an inverse MDCT with window g. The number of
%   channels is deduced from the size of the coefficient array c.
%
%   The window g may be a text string decribing the window. The following
%   types are recognized
% 
%   'gauss'     - Gaussian window.
%
%   'dualgauss' - Canonical dual of Gaussian window.
%
%   'tight'     - Tight window generated from a Gaussian.
%
%   'sqrthann'  - Square root of Hanning window. This is a tight, FIR
%                 window.  
% 
%   IMDCT(f,g,Ls) does the same, but cuts or zero-extend the final
%   result to length Ls.
%
%   SEE ALSO:  MDCT, DGT, WILDUAL, WILORTH
%
%   REFERENCES:
%     H. Bölcskei and F. Hlawatsch. Oversampled Wilson-type cosine modulated
%     filter banks with linear phase. In Asilomar Conf. on Signals, Systems,
%     and Computers, pages 998-1002, nov 1996.
%     
%     H. S. Malvar. Signal Processing with Lapped Transforms. Artech House
%     Publishers, 1992.
%     
%     J. P. Princen and A. B. Bradley. Analysis/synthesis filter bank design
%     based on time domain aliasing cancellation. IEEE Transactions on
%     Acoustics, Speech, and Signal Processing, ASSP-34(5):1153-1161, 1986.
%     
%     J. P. Princen, A. W. Johnson, and A. B. Bradley. Subband/transform
%     coding using filter bank designs based on time domain aliasing
%     cancellation. Proceedings - ICASSP, IEEE International Conference on
%     Acoustics, Speech and Signal Processing, pages 2161-2164, 1987.

% This program is free software: you can redistribute it and/or modify
% it under the terms of the GNU General Public License as published by
% the Free Software Foundation, either version 3 of the License, or
% (at your option) any later version.
% 
% This program is distributed in the hope that it will be useful,
% but WITHOUT ANY WARRANTY; without even the implied warranty of
% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
% GNU General Public License for more details.
% 
% You should have received a copy of the GNU General Public License
% along with this program.  If not, see <http://www.gnu.org/licenses/>.

%   Author : Peter Soendergaard.

error(nargchk(2,3,nargin));


wasrow=0;
if isnumeric(g)
  if size(g,2)>1
    if size(g,1)>1
      error('g must be a vector');
    else
      % g was a row vector.
      g=g(:);
      
      % If the input window is a row vector, and the dimension of c is
      % equal to two, the output signal will also
      % be a row vector.
      if ndims(c)==2
        wasrow=1;
      end;
    end;
  end;
end;

M=size(c,1);
N=size(c,2);
W=size(c,3);

a=M;
L=M*N;

assert_L(L,size(g,1),L,a,2*M,'IMDCT');

g=comp_window(g,a,2*M,L,1,'IMDCT');

c=comp_idwiltiii(reshape(c,M*N,W),a,M);

f=comp_igdgt(c,g,a,2*M,L,0,.5,0,0);

% Check if Ls was specified.
if nargin==3
  f=postpad(f,Ls);
else
  Ls=L;
end;

f=comp_sigreshape_post(f,Ls,wasrow,[0; W]);

% Clean signal if it is known to be real
% If input is real, and window is real, output must be real as well.
if (isreal(g) && isreal(c));
  f=real(f);
end;