/trunk/Level 1/mdctv.m

function y = mdctv(x)

% MDCTV Calculates the Modified Discrete Cosine Transform in a vectorized way

%   y = mdctv(x)

%

%   Use either a Sine or a Kaiser-Bessel Derived window (KBDWin)with 

%   50% overlap for perfect TDAC reconstruction.

%   Remember that MDCT coefs are symmetric: y(k)=-y(N-k-1) so the full

%   matrix (N) of coefs is: yf = [y;-flipud(y)];

%

%   x: input signal (can be either a column or frame per column)

%   y: MDCT of x

%

%   Fast ! ! !



% ------- mdctv.m ------------------------------------------

% Marios Athineos, marios@ee.columbia.edu

% http://www.ee.columbia.edu/~marios/

% Copyright (c) 2002 by Columbia University.

% All rights reserved.

% ----------------------------------------------------------



[flen,fnum] = size(x);

% Make column if it's a single row

if (flen==1)

    x = x(:);

    flen = fnum;

    fnum = 1;

end

% Make sure length is even

if (rem(flen,2)~=0)

    error('MDCT is defined only for even lengths.');

end



% We need these for furmulas below

N  = flen;    % Length of window

M  = N/2;     % Number of coefficients

N0 = (M+1)/2;



% Create the transformation matrix

[n,k] = meshgrid(0:(N-1),0:(M-1));

T = cos(pi*(n+N0).*(k+0.5)/M);

clear k n;



% So the MDCT is simply !!!

y = T*x;

end