[SIPForum-discussion] Codecs in 200 OK response

[pradeep gali]

If the INVITE is sending "m=audio 39838 RTP/AVP 0 8 18 101" , the 200 OK
SDP is expected to be with any one Codec like "m=audio 39838 RTP/AVP 0 101.


On Mon, Oct 7, 2013 at 2:39 AM, Waqas Arshad <waqas.arshad000 at yahoo.com>wrote:

> Hi,
>
> Can someone please confirm if the SDP of 200 OK (in response to an INVITE)
> can contain multiple codecs in m-line or it should have only one codec at
> which B party has responded to establish the connection. e.g.
>
> INVITE SDP:
> m=audio 39838 RTP/AVP 0 8 18 101
> a=rtpmap:0 pcmu/8000
> a=rtpmap:8 pcma/8000
> a=rtpmap:18 G729/8000
> a=fmtp:18 annexb=no
> a=rtpmap:101 telephone-event/8000
> a=fmtp:101 0-15
> a=sendrecv
>
> 200 OK SDP:
> m=audio 18238 RTP/AVP 0 101
> a=rtpmap:101 telephone-event/8000
> a=fmtp:101 0-15
> a=X-sqn: 0
> a=X-cap: 1 audio RTP/AVP 100
> a=X-cpar: a=rtpmap:100 X-NSE/8000
> a=X-cpar: a=fmtp:100 200-202
> a=X-cap: 2 image udptl t38
>
> So can 200 OK SDP contain m-line as below too or just one codec at which
> call is going to be established???
>
> m=audio 18238 RTP/AVP 0 8 18 101
>
> Secondly, can someone please suggest the meaning of a=X-sqn in above 200OK?
>
> Thanks in advance.
> Waqas
>
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-- 
Pradeep Gali
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