> -----Original Message-----
> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]
> Sent: Thursday, February 22, 2001 4:13 AM
> To: [EMAIL PROTECTED]
> Cc: [EMAIL PROTECTED]; [EMAIL PROTECTED]
> Subject: [Sip-implementors] Clarifications on SDP usage
>
>
> Case 1:
> ----------
> Invite recd contained SDP message of the form:
>
> v=0
> o=mhandley 29739 7272939 IN IP4 126.5.4.3
> c=IN IP4 135.180.130.88
> m=audio 34567 RTP/AVP 0 4 12
> a=sendonly
>
> and the endpoint was willing to accept only media
> of format "0". In such a case, can it break the "m="
> line and reply with a SDP of the form:
>
> v=0
> o=abcd 456783 7272939 IN IP4 139.76.34.221
> c=IN IP4 139.76.34.221
> m=audio 36777 RTP/AVP 0
> a=sendonly
> m=audio 0 RTP/AVP 4
> m=audio 0 RTP/AVP 12
No. It cannot. From the spec:
B.1 Configuring Media Streams
The caller and callee align their media descriptions so that the n th media
stream ("m=" line) in the caller's
session description corresponds to the n th media stream in the callee's
description.
The proper response if it wants only format zero is:
v=0
o=mhandley 22739 7244939 IN IP4 1.2.3.4
c=IN IP4 1.2.3.4
m=audio 4564 RTP/AVP 0
a=recvonly
>
> Case 2:
> ----------
> Invite recd contained a SDP message of the form:
>
> v=0
> o=mhandley 29739 7272939 IN IP4 126.5.4.3
> c=IN IP4 135.180.130.88
> a=sendonly
> m=audio 34567 RTP/AVP 0 4 12
>
> and the endpoint can recv media format 0 and 4
> but can only send media format 12.
> In this case, is the following response valid?
> (What I basically mean to ask, is that whether a session-level
> attribute in the incoming INVITE can be replicated
> in the media-level attributes multiple times?)
>
> v=0
> o=abcd 456783 7272939 IN IP4 139.76.34.221
> c=IN IP4 139.76.34.221
> m=audio 36777 RTP/AVP 0
> a=sendonly
> m=audio 45321 RTP/AVP 4
> a=sendonly
> m=audio 0 RTP/AVP 12
You cannot split the m line. The proper response is to include only codecs 0
and 4 above. The spec is clear that if you are offered a stream as sendonly,
what is in the response is those from that set you wish to receive.
-Jonathan R.
---
Jonathan D. Rosenberg 72 Eagle Rock Ave.
Chief Scientist First Floor
dynamicsoft East Hanover, NJ 07936
[EMAIL PROTECTED] FAX: (973) 952-5050
http://www.cs.columbia.edu/~jdrosen PHONE: (973) 952-5000
http://www.dynamicsoft.com
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