no, annexb and annexa are different things: annexa is a codec efficiency improvement annexb is silence suppression
In practice, I have seen usage of "rtpmap:18 G729a/8000" but it has no RFC-based meaning. There is no way to indicate g729A. You just have to use g729. The reason for lack of g729a in RFC 3550 is that g729 and g729a should interoperate seemlessly - as it says... "The speech coding algorithms in the main body of G.729 and in G.729 Annex A are fully interoperable with each other, so there is no need to further distinguish between them. " (It is strange how strong the text is - I would say that the "there is no need to further distinguish between them" is a matter of opinion. Some people will claim they prefer G729 (non-annexA) but anyway, there is no RFC-standard way to indicate this in SDP as far as I know). Regards, Attila -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Somesh S. Shanbhag Sent: 03 November 2008 12:48 To: [EMAIL PROTECTED]; sip-implementors@lists.cs.columbia.edu Subject: Re: [Sip-implementors] rtpmap:18 G729a/8000 ? I think you need to represent in two lines a=rtpmap:18 G729/8000 a=fmtp:18 annexb=no Somesh S Shanbhag M G L Bangalore -----Original Message----- From: [EMAIL PROTECTED] on behalf of [EMAIL PROTECTED] Sent: Mon 11/3/2008 6:08 PM To: sip-implementors@lists.cs.columbia.edu Subject: [Sip-implementors] rtpmap:18 G729a/8000 ? Hi, Please let me know if "rtpmap:18 G729a/8000" is a wrong format. I guess RFC3551 says it should work (page 19, as pasted below) and I am not able to find anything so specific in RFC3550. ------------------------------------------------------------------------ -------------------- 4.5.6 G729 G729 is specified in ITU-T Recommendation G.729, "Coding of speech at 8 kbit/s using conjugate structure-algebraic code excited linear prediction (CS-ACELP)". A reduced-complexity version of the G.729 algorithm is specified in Annex A to Rec. G.729. The speech coding algorithms in the main body of G.729 and in G.729 Annex A are fully interoperable with each other, so there is no need to further distinguish between them. An implementation that signals or accepts use of G729 payload format may implement either G.729 or G.729A unless restricted by additional signaling specified elsewhere related specifically to the encoding rather than the payload format. The G.729 and G.729 Annex A codecs were optimized to represent speech with high quality, where G.729 Annex A trades some speech quality for an approximate 50% complexity reduction [10]. See the next Section (4.5.7) for other data rates added in later G.729 Annexes. For all data rates, the sampling frequency (and RTP timestamp clock rate) is 8,000 Hz. ------------------------------------------------------------------------ ---------------------- Thanks & Regards Viresh Gupta Manager - International Network Planning Enterprise Services, Bharti Airtel Limited, 234, Okhla Industrial Area, Phase- III, New Delhi - 110020, India D (91) 1141711283 M (91) 9871008236 E [EMAIL PROTECTED] Airtel for Business On your side. By your side. This e-mail and any files transmitted with it are for the sole use of the intended recipient(s) and may contain confidential and privileged information. If you are not the intended recipient, please contact the sender by reply e-mail and destroy all copies and the original message. Any unauthorized review, use, disclosure,dissemination, forwarding, printing or copying of this email or any action taken in reliance on this e-mail is strictly prohibited and may be unlawful. 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