www.gusucode.com > 线性时频分析工具箱 - ltfat-1.0.1源码程序 > 线性时频分析工具箱 - LTFAT\demos\demo_nsdgt.m

    %DEMO_NSDGT  Nonsationary Gabor transform demo
%
%   This script sets up a nonstationary Gabor frame with the specified
%   parameters, computes windows and corresponding canonical dual windows
%   and a test signal, and plots the windows and the energy of the 
%   coefficients.
%
%   FIGURE 1 windows + dual windows
%
%    This figure shows the window functions used and the corresponding
%    canonical dual windows. 
%
%   FIGURE 2 spectrogram (absolute value of coefficients in dB)
%
%    This figure shows a (color coded) image of the nsdgt coefficient
%    modulus. 
%
%   SEE ALSO:  NSDGT, INSDGT, NSGABDUAL

% Copyright (C) 2005-2011 Peter L. Soendergaard.
% This file is part of LTFAT version 1.0.1
% 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/>.

disp(['Type "help demo_nsdgt" to see a description of how this example',...
  ' works.']);

% Setup parameters and length of signal.

Ls=1000; % Length of signal.

N=16; % Number of time positions

% Define a set of windows with length growing linearly. The step beetween
% to consecutive windows grows also linearly.

M=round(linspace(40,200,N)');
a=cumsum(round(M/2));
a=a-a(1);

a_new=round(M/2);

g={};
for ii=1:length(M)
    g{ii}=firwin('hann',M(ii));
end

% Compute corresponding dual windows
gd=nsgabdual(g,a_new,Ls);

% Plot them
figure(1);
color = ['b', 'r'];
for ii = 1:length(a)
    subplot(2,1,1);
    hold on;
    plot(a(ii)-1-floor(M(ii)/2)+(1:M(ii)), fftshift(g{ii}),...
      color(rem(ii,2)+1));
    subplot(2,1,2);
    hold on;
    plot(a(ii)-1-floor(M(ii)/2)+(1:M(ii)), fftshift(gd{ii}),...
      color(rem(ii,2)+1));
end

subplot(2,1,1);
title('Analysis windows');
xlabel('Time index');
subplot(2,1,2);
title('Dual synthesis windows');
xlabel('Time index');

% Define a sinus test signal.
f=sin(2*pi*0.3*(1:Ls)');

% Calculate coefficients.
c=nsdgt(f,g,a_new,M);

% Plot corresponding spectrogram
figure(2);
plotnsdgt(c,a,'dynrange',100);
title('Spectrogram of test signal')
xlabel('Time');
ylabel('Frequency');

% Test reconstruction
f_r=insdgt(c,gd,a_new,Ls);

% Print relative error of reconstruction.
rec_err = norm(f-f_r)/norm(f);

fprintf(['Relative error of reconstruction (should be close to zero.):'...
    '   %e \n'],rec_err);