Efficient LPC Quantization Methods - Digital Speech: Coding for Low Bit Rate Communication Systems - page 117

Table 5.8 Complexity of various
search strategies for a { 7 , 7 , 7 }

MSVQ codebook
Search type Complexity

SS 3840

TS: M = 2 6400

TS: M = 4 11 520

TS: M = 8 21 760

TS: M = 16 42 240

TS: M = 32 83 200

FS 20 971 520

1.6e04 1.25

codebook trained with SS
codebook retrained with TS

codebook trained with SS
codebook retrained with TS

1.5e04

1.20

1.4e04

1.3e04 1.15

1.2e04

1.10

1.1e04

1.0e04 1.05

SS TS2 TS4 TS8 TS16 TS32 SS TS2 TS4 TS8 TS16 TS32

Search strategy Search strategy

4.00

codebook trained with SS
codebook retrained with TS

3.00

2.00

1.00

SS TS2 TS4 TS8 TS16 TS32

Search strategy

Figure 5.13 Performance comparison with and without codebook reoptimization

use a 21-bit MSVQ codebook with three stages of 7 bits each which has been
trained using the weighting methods listed below:

• W1: no weighting (all weights are equal to 1 . 0)

• W2: EFR weighting method