void FIfWinHCos (float win, double T1, double T2, double T3, double a)
Generate a Hamming/cosine window
A Hamming/cosine window is an asymmetric window, consisting of half of a
Hamming window and a quarter cycle of a cosine,
Consider the continuous-time variable t. The half Hamming window starts at
t=0, and reaches its peak value (unity) at t=T1. The window is constant at
unity from t=T1 to t=T2. The quarter cycle cosine window is unity at t=T2 and
decreases to zero at t=T3.
= 0 , t < 0
= (1-a) - a cos (----) , 0 <= t < T1
h(t) = 1 , T1 <= t < T2
= cos (---------) , T2 <= t < T3
= 0 , T3 <= t
A window of this form is used for the ITU-T G.729 8 kb/s coder and its
derivatives. The G.729 discrete-time window has 240 non-zero samples, and
is obtained by setting a = 0.46, T1 = 199.5, T2 = 200, T3 = 239.75. The
discrete-time window is sampled at t = i, with 0 <= i < 240. The G.729
window can be obtained with the following call
FIwinHCos (win, 199.5, 200.0, 239.75, 0.46)
<- float win
Array containing the window values
-> double T1
Length of the half Hamming window.
-> double T2
End point of the constant region, T2 >= T1.
-> double T3
End point of the quarter cycle cosine rollof, T3 >= T2. The number of
points in the window is floor (T3) + 1.
-> double a
Window parameter for the first part of the window; a=0.46 for a
conventional Hamming window, a=0.5 for a full raised-cosine window, a=0
for a rectangular window. The window is non-negative for 0 <= a <= 0.5.
Author / revision
/ Revision 1.7 2003/05/09
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