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G.729 is an audio data compression algorithm for voice that compresses digital voice in packets of 10 milliseconds duration. It is officially described as ''Coding of speech at 8 kbit/s using code-excited linear prediction'' speech coding (CS-ACELP).〔International Telecommunications Union, Standardization Sector (ITU-T), Study Group 15 (1993-1996), ''Recommendation G.729'', March 1996.〕 Because of its low bandwidth requirements, G.729 is mostly used in Voice over Internet Protocol (VoIP) applications where bandwidth must be conserved, such as conference calls. Standard G.729 operates at a bit rate of 8 kbit/s, but there are extensions, which 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. The differences between these versions are noteworthy because they each have additional properties and thus different use-cases: * G729: original codec. Uses high-complexity algorithm * G729A or A annex: medium complexity variant of G.729 and it is compatible with G729. It is less complex but has slightly lower voice quality * G729B or B annex: G729 with silence suppression and not compatible with the previous ones. * G729AB: G729A with silence suppression and only compatible with G729B. 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 RTP Payload for DTMF Digits, Telephony Tones, and Telephony Signals as specified in RFC 2833. ==G.729 Annexes== 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「G.729」の詳細全文を読む スポンサード リンク
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