Summary
This
Recommendation contains the description of an algorithm for the coding of
speech signals using conjugate-structure algebraic-code-excited linear
prediction (CS-ACELP).
In its
basic mode, the G.729 coder consists of a mono-rate speech coder at 8 kbits/s
using fixed-point arithmetic operations. Annexes A, B and D to J extend its
functionalities. Annex A provides a reduced-complexity version at the basic
coding rate of 8 kbit/s. Annex B defines source-controlled rate operation for
use with G.729 or Annex A. Annexes D, E and H provide multi-rate operation
and specify rate-switching mechanisms: Annex D provides lower bit-rate
extension at 6.4 kbit/s and Annex E provides higher bit-rate extension
at 11.8 kbit/s, whereas Annex H provides bit-rate 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 8-32 kbit/s scalable wideband
speech and audio coding algorithm in ITU-T 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
fixed-point 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
|
|
|
|
|
|
|
|
|
|
|
Fixed-point
|
X
|
X
|
X
|
|
X
|
X
|
X
|
X
|
X
|
X
|
|
X
|
|
Floating-point
|
|
|
|
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, fixed-point) and C (floating-point). Since the
voice activity detection (VAD) algorithm in Annex B was optimized for
transmission over connection-oriented 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.
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