Waveform Quantization and Compression - Digital Signal Processing: Fundamentals and Applications - page 545

end
if y < 3
ap ¼ ap þ 1/8.0;
end
if td ¼¼ 1
ap ¼ ap þ 1/8.0;
end
if tr

¼¼ 1

ap ¼ 1.0;

end
y

¼ al*yu þ (1.0-al)*yl;

end
end
iiout ¼ out;
Program 11.14. W-MDCT function.

function [ tdac_coef ] ¼ wmdct(ipsig)
%
% This function transforms the signal vector using the W-MDCT.
% Usage:
% ipsig: input signal block of N samples (N ¼ even number)
% tdac_coe: W-MDCT coefficents (N/2 coefficients)
%
N ¼ length(ipsig);
NN ¼ N;
for i ¼ 1:NN
h(i) ¼ sin((pi/NN)*(i-1 þ 0.5));
end
for k ¼ 1:N/2
tdac_coef(k) ¼ 0.0;
for n ¼ 1:N
tdac_coef(k)

þ .
h(n)*ipsig(n)*cos((2*pi/N)*(k-1

¼ tdac_coef(k)

þ 0.5)*(n-1 þ 0.5 þ N/4));

end
end
tdac_coef 2*tdac_coef;

Program 11.15. Inverse W-IMDCT function.

¼

function [ opsig ] ¼ wimdct(tdac_coef)
%
% This function transforms the W-MDCT coefficients back to the signal.
% Usage:
% tdac_coeff: N/2 W-MDCT coeffcients
% opsig: output signal black with N samples
%
N ¼ length(tdac_coef);
tmp_coef ¼ ((-1)^(N þ 1))*tdac_coef(N:-1:1);
tdac_coef ¼ [ tdac_coef tmp_coef];