Martin, Gaurav,
One important correction to what Martin wrote:
annexb=yes is assumed even if the annexb parameter is not present. This is the
default. So if you
don't support G.729B - you must declare annexb=no. Otherwise the other party is
expected to send you
SID frames that you wouldn't be able to decode.
See RFC3555:
annexb: indicates that Annex B, voice activity detection, is
used or preferred. Permissible values are "yes" and "no"
(without the quotes); "yes" is implied if this parameter is
omitted.
Thanks
Uzi
[EMAIL PROTECTED] wrote on 08/11/2005 08:13:06 AM:
> Hello Martin,
>
> Your understanding is correct.
> (http://www.iana.org/assignments/rtp-parameters)
>
> If you looked at the archives of this list, you would have found the
> answer to your query as this issue was discussed quiet recently. Anyway,
> a quick recap :
>
> G729B is different from G729 and G729A in the sense that it adds the use
> of SID frames. Since G729 and G729A are mutually compatible, so you
> don't need to explicitly negotiate G729A. Specifying G729 itself in the
> SDP will negotiate the A flavour. annexb = yes|no determines whether it
> will use G729B or not.
>
> However, I also read somewhere that you can actually negotiate G729AB by
> specifying "G729AB" in the SDP itself. Not too sure on that though.
>
> I hope this helps.
>
> regards,
>
> Gaurav
>
> -----Original Message-----
> From: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED] On Behalf Of Martin
> van den Berg
> Sent: Wednesday, August 10, 2005 2:29 PM
> To: sip-implementors@cs.columbia.edu
> Subject: [Sip-implementors] G729A and G729AB
>
> As I understand it, it is not possible to *explicitly* specify G729A and
> G729AB in an SDP offer/answer. Instead, if the payload type is 18, G729A
> is offered/answered, when "fmtp:18 annexb=yes" is present in the media
> attributes the sender is able to receive both G729A and G729AB.
>
> Is this statement correct?
>
> Martin.
>
> --
> Skype: MartinvdBerg
> http://sip.huisetalage.nl
>
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