G.729AB ITU-T compatible vocoder

ITU G.729 CS-ACELP (Conjugate Structure –Algebraic Code Excited Linear Predictive) is a speech coding and decoding standard that provides 4-kHz speech bandwidth at a bit rate of 8 kb/s. The standard specifies a code-excited linear predictive coder that uses an algebraic codebook to code the excitation signal. The coder operates on speech frames of 10 ms (80 samples at an 8-kHz sample rate). G.729 coder is well suited to a wide range of applications, including both voice storage and voice communications. It is ideally suited for telecommunications networks in which toll-quality speech is a requirement, and total communications link delay and the ability to operate in noisy environments (possibly through several tandem encode / decode (combinations) are important factors.

Annex A of G.729 (G.729A) is a low complexity version of G.729, which has lower speech quality. The G.729A+B comprises of G.729A with the additional option of Annex B. Annex B uses silence compression or discontinuous transmission to reduce the transmitted bit rate during the silent intervals of speech. Voice Activity Detection (VAD) and Comfort Noise Generation (CNG) algorithms are used to enable the transmission of Silence Descriptor (SID) frames during the periods of silence. G.729 Annex A offers the best complexity/quality ratio of the industry.


SoftRISC supports several processor platforms and maintains optimization efforts to improve performance specifications.