Coding of speech at 8 kbit/s using conjugate-structure algebraic-code-excited linear prediction (CS-ACELP) | |
Status | In force |
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Latest version | (10/17) October 2017 |
Organization | ITU-T |
Committee | ITU-T Study Group 16 |
Related standards | G.191, G.711, G.729.1 |
Domain | audio compression |
License | Freely available |
Website | https://www.itu.int/rec/T-REC-G.729 |
G.729 is a royalty-free[1] narrow-band vocoder-based audio data compression algorithm using a frame length of 10 milliseconds. It is officially described as Coding of speech at 8 kbit/s using code-excited linear prediction speech coding (CS-ACELP), and was introduced in 1996.[2] The wide-band extension of G.729 is called G.729.1, which equals G.729 Annex J.
Because of its low bandwidth requirements, G.729 is mostly used in voice over Internet Protocol (VoIP) applications when bandwidth must be conserved. Standard G.729 operates at a bit rate of 8 kbit/s, but extensions provide rates of 6.4 kbit/s (Annex D, F, H, I, C+) and 11.8 kbit/s (Annex E, G, H, I, C+) for worse and better speech quality, respectively.
G.729 has been extended with various features, commonly designated as G.729a and G.729b:
Dual-tone multi-frequency signaling (DTMF), fax transmissions, and high-quality audio cannot be transported reliably with this codec. DTMF requires the use of the named telephony events in the RTP payload for DTMF digits, telephony tones, and telephony signals as specified in RFC 4733.
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