### 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 Recommendation G.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.