[SIPForum-discussion] Offer-Answer SDP

[Arunachala]

Hi,

It just means that both parties agree that they have the capability to
send-recv packets in either G729 or G723 in the media stream at the same
time. This means that there is no need for a reINVITE/UPDATE to zero-in on a
single codec.

So, if you are either of the parties, and you can not handle multiple codecs
in the same stream, then you should offer/answer with a single preferred
codec.

-Arun

On Fri, Aug 19, 2011 at 2:46 PM, call foreign <callf4rgn at gmail.com> wrote:

> Hi
>
> I need ideas and explanation on this call scenario;
>
> Origination UA sent multiple codecs;
>
>    v=0
>    o=alice 2890844526 2890844526 IN IP4 host.anywhere.com
>    s=
>    c=IN IP4 host.anywhere.com
>    t=0 0
>    m=audio 62986 RTP/AVP 18 4
>    a=rtpmap:18 G729/8000
>    a=rtpmap:4 G723/8000
>
>
> Termination UA respond with multiple codecs;
>
>    v=0
>    o=bob 2890844730 2890844731 IN IP4 host.example.com
>    s=
>    c=IN IP4 host.example.com
>    t=0 0
>    m=audio 54344 RTP/AVP 18 4
>     a=rtpmap:18 G729/8000
>    a=rtpmap:4 G723/8000
>    a=sendrecv
>
>
> Question:
>
> What would be the actual media on the session considering that the
> OFFER-ANSWER has been completed on the signaling with an INVITE-200OK-ACK
> messages.  Please note the origination has never included attribute
> "a=inactive" on the initial offer.  In addition, termination side responded
> with attribute "a=sendrecv" immediately without an update offer from the
> origination on which codec it choose for the final media stream.
>
> Does this imply that the actual media stream been used on the session is
> G729 if codec preference is considered?
>
> Please share if you have encountered this scenario.
>
> Regards
>
>
>
>
>
>
>
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