gusucode.com > 《MATLAB图像与视频处理实用案例详解》代码 > 《MATLAB图像与视频处理实用案例详解》代码/第 19 章 基于语音识别的信号灯图像模拟控制技术/voicebox/rdct.m
function y=rdct(x,n,a,b) %RDCT Discrete cosine transform of real data Y=(X,N,A,B) % Data is truncated/padded to length N. % % This routine is equivalent to multiplying by the matrix % % rdct(eye(n)) = diag([sqrt(2)*B/A repmat(2/A,1,n-1)]) * cos((0:n-1)'*(0.5:n)*pi/n) % % Default values of the scaling factors are A=sqrt(2N) and B=1 which % results in an orthogonal matrix. Other common values are A=1 or N and/or B=1 or sqrt(2). % If b~=1 then the columns are no longer orthogonal. % % see IRDCT for the inverse transform % BUG: in line 51 we should do chopping after transform and not before % Copyright (C) Mike Brookes 1998 % Version: $Id: rdct.m,v 1.6 2007/05/04 07:01:39 dmb Exp $ % % VOICEBOX is a MATLAB toolbox for speech processing. % Home page: http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/voicebox.html % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % 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 2 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 can obtain a copy of the GNU General Public License from % http://www.gnu.org/copyleft/gpl.html or by writing to % Free Software Foundation, Inc.,675 Mass Ave, Cambridge, MA 02139, USA. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% fl=size(x,1)==1; if fl x=x(:); end [m,k]=size(x); if nargin<2 n=m; end if nargin<4 b=1; if nargin<3 a=sqrt(2*n); end end if n>m x=[x; zeros(n-m,k)]; elseif n<m x(n+1:m,:)=[]; end x=[x(1:2:n,:); x(2*fix(n/2):-2:2,:)]; z=[sqrt(2) 2*exp((-0.5i*pi/n)*(1:n-1))].'; y=real(fft(x).*z(:,ones(1,k)))/a; y(1,:)=y(1,:)*b; if fl y=y.'; end