FIfWinHCos
Routine

void FIfWinHCos (float win[], double T1, double T2, double T3, double a)
Purpose

Generate a Hamming/cosine window
Description
A Hamming/cosine window is an asymmetric window, consisting of half of a
Hamming window and a quarter cycle of a cosine,
Consider the continuoustime 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
pi t
= (1a)  a cos () , 0 <= t < T1
T1
h(t) = 1 , T1 <= t < T2
pi (tT2)
= cos () , T2 <= t < T3
2 (T3T2)
= 0 , T3 <= t
A window of this form is used for the ITUT G.729 8 kb/s coder and its
derivatives. The G.729 discretetime window has 240 nonzero samples, and
is obtained by setting a = 0.46, T1 = 199.5, T2 = 200, T3 = 239.75. The
discretetime 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)
Parameters

< 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 raisedcosine window, a=0
for a rectangular window. The window is nonnegative for 0 <= a <= 0.5.
Author / revision
P. Kabal
/ Revision 1.7 2003/05/09
See Also
FIfWinHamm,
FIfWinKaiser,
FIfWinRCos
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