G.729 is a royalty-free 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. 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: G.729: This is the original codec using a high-complexity algorithm. G.729A or Annex A: This version has a medium complexity, and is compatible with G.729. It provides a slightly lower voice quality. G.729B or Annex B: This version extends G.729 with silence suppression, and is not compatible with the previous versions. G.729AB: This version extends G.729A with silence suppression, and is only compatible with G.729B. G.729.1 or Annex J: This version extends G.729A and B with scalable variable encoding using hierarchical enhancement layers. It provides support for wideband speech and audio, using modified discrete cosine transform (MDCT) coding. 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. G.729 annexes G.729 Annex A G.729a is a compatible extension of G.729, but requires less computational power. This lower complexity, however, bears the cost of marginally reduced speech quality. G.729a was developed by a consortium of organizations: France Télécom, Mitsubishi Electric Corporation, Nippon Telegraph and Telephone Corporation (NTT). The features of G.729a are: Sampling frequency 8 kHz/16-bit (80 samples for 10 ms frames) Fixed bit rate (8 kbit/s 10 ms frames) Fixed frame size (10 bytes (80 bits) for 10 ms frame) Algorithmic delay is 15 ms per frame, with 5 ms look-ahead delay G.729a is a hybrid speech coder which uses Algebraic Code Excited Linear Prediction (ACELP) The complexity of the algorithm is rated at 15, using a relative scale where G.711 is 1 and G.723.1 is 25. PSQM testing under ideal