563489578934

Sec. 3–3 Pulse Code Modulation 153
1.0
0.8
Output |w 2 (t)|
0.6
0.4
0.2
Compression
quantizer
characteristic
Uniform quantizer
characteristic
0
0
0.2 0.4 0.6
Input |w 1 (t)|
(a) M = 8 Quantizer Characteristic
0.8
1.0
V = 1.0
1.0
0.8
m = 255
m = 100
1.0
0.8
A = 100
Output |w 2 (t)|
0.6
0.4
m = 1
m = 5
Output |w 2 (t)|
0.6
0.4
A = 87.6
A = 5
A = 2
0.2
m = 0
0.2
A = 1
0
0
(b) m-law Characteristic
0.2 0.4 0.6 0.8
Input |w 1 (t)|
Figure 3–9
1.0
V = 1.0
0
0
(c) A-law Characteristic
0.2 0.4 0.6 0.8
Input |w 1 (t)|
Compression characteristics (first quadrant shown).
1.0
V = 1.0
Example 3–5 µ-LAW COMPRESSION CHARACTERISTIC
Plot the µ-law compression characteristic as illustrated in Figure 3–9b. See Example3_05.m for
the solution.
In practice, the smooth nonlinear characteristics of Fig 3–9b are approximated by
piecewise linear chords as shown in Fig. 3–9d for the µ 255 characteristic [Dammann,
McDaniel, and Maddox, 1972]. Each chord is approximated by a uniform quantizer with
16 steps and an input step size that is set by the particular segment number. That is, 16 steps