Sampling and Quantization - Digital Speech: Coding for Low Bit Rate Communication Systems - page 34

Quantizer

^

x n (n)

x(n)

.

Quantizer

Estimate

σ x

De-quantizer

^

x n (n)

^

x(n)

De-quantizer

Estimate

σ x

Figure 3.5 Block diagram of a backward adaptive quantizer

Quantizer

x n (n)

x(n)

.

Fixed

Quantizer

Select

M i

De-quantizer

^

x n (n)

^

x(n)

Fixed

De-quantizer

Select

M i

Figure 3.6 Block diagram of one word memory (Jayant) quantizer

For large quantized previous samples, multiplier values are greater than
one and for small previously quantized samples multiplier values are less
than one. A typical set of step sizemultiplier values for 2, 3 and 4 bit quantizers
are shown in Table 3.2.