[SIPForum-discussion] Different types of G729 codec

Binan AL Halabi binanalhalabi at yahoo.com
Thu Aug 29 10:07:21 UTC 2013

Hi Waqas, 

G.729 is audio coding algorithm (high complexity algorithm).G.729 has two extensions G.729a and G.729b.

G.729a is compatible extension of G.729. G.729a requires less computations, less complexity and less voice quality accordingly.
Platforms that support G.729 should support G.729a. Some VOIP phones does not recognize G.729a as G.729. This can lead to fail in the call establishment.

G.729b and G.729ab are  silence compression scheme for G.729 and G.729a


annexX indicates that Annex X is used. It takes yes or no value.  "yes" is implied if annex-X parameter is omitted. so G.729 annexa=yes <--> G.729a 
and G.729 without annexa parameter <---> G.729a


Regarding  SDP offer/answer negotiation, it is expected to have something similar to this example:

Offer with G729 annexb=yes. answer with G729 annexb=no. Both sides proceed as if G729 is negotiated with annexb=no. 

Offer with G729 annexb=yes. answer with G729 and no annexb parameter.. Both sides proceed as if G729 is negotiated with annexb=yes. 

and so on.

These Offer/Answer negotiation considerations are done by Cisco systems and Nokia Siemens networks. They are going to be standard soon (December 2013).


 Från: Waqas Arshad <waqas.arshad000 at yahoo.com>
Till: "discussion at sipforum.org" <discussion at sipforum.org> 
Skickat: onsdag, 28 augusti 2013 17:06
Ämne: [SIPForum-discussion] Different types of G729 codec


Can someone please tell me the difference between following codecs in detail and their compatibility with each other?

g729 annexa=yes
g729 annexa=no
g729 annexb=yes
g729 annexb=no

I'll highly appreciate the responses.


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