Harmonic Speech Coding - Digital Speech: Coding for Low Bit Rate Communication Systems - page 270

LSFs

LSF
Interpolation

LSF to LPC
Transform

Voicing frequency
marker

Unvoiced
Excitation

Synthetic
Speech

LPC
Synthesis
Filter

Amplitudes

Voiced
Excitation

Pitch

Figure 8.5 SB-LPC decoder

Table 8.1 Bit allocation of 4 kb/s
SB-LPC coder for a 20ms frame
Parameter Bits

LSFs 23

Pitch 5 + 7

Parity bit 1

Voicing 3 + 3

Gain 5 + 5

Harmonic amplitudes 14 + 14

(a)

(a)

(b)

(b)

0 50 100 150 200

0 50 100 150 200

samples samples

(a) (b)

Figure 8.6 Harmonic speech synthesis: (a) original speech, and (b) SB-LPC

A block diagram of the SB-LPC decoder is shown in Figure 8.5 and the bit
allocation is shown in Table 8.1. Figure 8.6 illustrates the same waveforms
shown in Figure 8.4, but synthesized using the SB-LPC coder. The time-
domain LPC filter adds its phase response to the coherent excitation signal