Summary
This
Recommendation contains the description of an algorithm for the coding of
speech signals using conjugatestructure algebraiccodeexcited linear
prediction (CSACELP).
In its
basic mode, the G.729 coder consists of a monorate speech coder at 8 kbits/s
using fixedpoint arithmetic operations. Annexes A, B and D to J extend its
functionalities. Annex A provides a reducedcomplexity version at the basic
coding rate of 8 kbit/s. Annex B defines sourcecontrolled rate operation for
use with G.729 or Annex A. Annexes D, E and H provide multirate operation
and specify rateswitching mechanisms: Annex D provides lower bitrate
extension at 6.4 kbit/s and Annex E provides higher bitrate extension
at 11.8 kbit/s, whereas Annex H provides bitrate extensions at both 6.4
kbit/s and 11.8 kbit/s. Therefore, Annexes D, E and H do not implement the
discontinuous transmission mode of Annex B. For this functionality, further
annexes were developed. Annexes F and G use the basic algorithms in Annex B
to provide discontinuous transmission (DTX) functionality for, respectively, Annexes
D and E. Annex I provides DTX functionality for Annex H and describes
the integration of G.729 main body with Annexes B, D and E. Annex J
makes reference to the G.729 extension for the 832 kbit/s scalable wideband
speech and audio coding algorithm in ITUT RecommendationG.729.1, which is interoperable with G.729 and its
Annexes A and B. As G.729 main body, its Annexes A, B and D to J use
fixedpoint arithmetic. Alternative implementations based on floating‑point
arithmetic operations are provided in Annex C for G.729 and Annex A, and
in Annex C+ for Annex I.
This
information is summarized in the Table below.

Annexes

Functionality



A

B

C

D

E

F

G

H

I

C+

J

Low complexity


X

X










Fixedpoint

X

X

X


X

X

X

X

X

X


X

Floatingpoint




X







X


8 kbit/s

X

X

X

X

X

X

X

X

X

X

X

X

6.4 kbit/s





X


X


X

X

X


11.8 kbit/s






X


X

X

X

X


DTX



X




X

X


X

X


Embedded variable bit rate, wideband












X

Appendix I deals with external synchronous reset
capability in systems using external silence
compression in conjunction
with the speech coding algorithm in the main body of G.729 (fixed‑point) or in
its Annexes A (low complexity, fixedpoint) and C (floatingpoint). Since the
voice activity detection (VAD) algorithm in Annex B was optimized for
transmission over connectionoriented circuits, Appendices II and III deal
with optimization of the VAD in Annex B when it is used for packet circuits
such as VoIP applications.
