The Standard

G.729 Annex A with Annex B (G.729AB) is a low bit rate speech coder standard from International Telecommunication Union–Telecommunication standardization sector (ITU-T), for compressing toll quality speech (8000 samples/second). G.729AB is algorithmically simpler to G.729. The coders G.729 and G.729A are inter-operable, i.e., G.729 packet can be decoded by G.729A decoder and vice versa. The typical applications of this speech coder are in telephony over packet networks, like Voice-over-Internet-Protocol (VoIP). This is a very robust speech coder, with very good speech quality comparable to 32 Kbps ADPCM coder.

This coder works at bit rate of 8000 bits/second. Like G.729 Codec, G.729AB is also based on the principle of Complementary Symmetry - Algebraic Code Excited Linear Prediction (CS-ACELP). The coder works on a frame of 80 speech samples (10 msec). Besides, there is a look ahead of 40 samples (5 msec). So the total algorithmic delay for the coder is 15 msec.

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