[SIPForum-discussion] Codecs in 200 OK response

[Lokesh Reddy]

Hi Waqas,

Yes there should be a only one codec in calle response(200OK) . it looks
like below example :

[INVITE]


v=0

o=alice 2311817675 2311817675 IN IP4 172.16.58.221

s=SIP session

c=IN IP4 172.16.58.221

t=0 0

m=audio 37000 RTP/AVP 120 121 101 8 0 106 105

a=rtpmap:120 AMR-WB/16000/1

a=rtpmap:121 AMR-WB/16000/1

a=rtpmap:101 EVRC/8000/1

a=rtpmap:8 PCMA/8000/1

a=rtpmap:0 PCMU/8000/1

a=rtpmap:106 telephone-event/16000/1

a=rtpmap:105 telephone-event/8000/1

a=fmtp:120 octet-align=0

a=fmtp:121 octet-align=1

a=fmtp:101 maxinterleave=2

a=fmtp:106 0-15

a=fmtp:105 0-15

a=rtcp:37001

a=ptime:20

a=maxptime


200OK response:
v=0

o=bob 2334362403 2334362403 IN IP4 172.16.58.221

s=SIP session

c=IN IP4 172.16.58.221

t=0 0

m=audio 37200 RTP/AVP 101 105

a=rtpmap:101 EVRC/8000/1

a=rtpmap:105 telephone-event/8000/1

a=fmtp:101 maxinterleave=2

a=fmtp:105 0-15

a=rtcp:37201

a=ptime:20

a=maxptime:400

a=sendrecv

Regards,
Lokesh Reddy Bandi



On Mon, Oct 7, 2013 at 1:09 PM, 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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