Hello,
Thanks for the reply. I have another clarification
to ask ...
In the second case that I had sent earlier.
> 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
What you have mentioned in your mail is that
the end-point is not allowed to break the "m="
line recd into multiple ones. In the scenario that
the end-point is willing to accept both media
formats 0 and 4; but on different ports (say, 5555
for the former and 6666 for the latter) how does it
convey this information to the other end without
breaking the media line?
Also is it not necessary/desirable to repond
definitively as to whether we are willing to accept
each codec that the other end-point sends in his
session description? Then the caller end-point
should be willing to discard a media format if it
does not figure in the response?
Thanks and regards,
Siddharth.
=================================
Siddharth Toshniwal
Software Engineer
Hughes Software Systems, Bangalore
http://www.hssworld.com
Jonathan Rosenberg <[EMAIL PROTECTED]> on 02/27/2001 02:02:08 PM
To: Siddharth J Toshniwal/HSSBLR, [EMAIL PROTECTED]
cc: [EMAIL PROTECTED], [EMAIL PROTECTED]
Subject: RE: [Sip-implementors] Clarifications on SDP usage
> -----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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