Later, it was concluded that once the slot had been rendered inactive with port=0, it could subsequently be reused. And then it was recognized that if that was ok, then it might as well be possible for a new offer to totally change a "slot" in the SDP to an entirely different media type/transport, etc.
It still should be the case that the replacement media stream be somehow logically a replacement for the prior one.
Whay you suggest, switching from RTP/AVP to RTP/SAVP seem entirely reasonable. Of course, if you do this, you must be prepared for it to fail. This could fail in a couple of ways:
- the reinvite itself could fail. If so, the prior media streams must remain in effect
- the reinvite could succeed, but the media stream in the new offer could be rejected (port=0 in the answer). In that case you still have a call, but the old media stream is gone and there is nothing to replace it.
Paul
[EMAIL PROTECTED] wrote:
Chiatali,
My undertsanding of the section in 3264 you are querying is that if you offered two m= lines in the original request you need to offer at least that in the new request and that the ordering of them is preserved, new media offered should be appended to the previous SDP. So if you offered audio m= and video m= then you these should be in the new request. So you m line for audio is still there, you might just be adding another codec to it, or you may be setting one of them inactive. I hope I am right ! and I hope the above makes sense.
Regards - Wayne D.
Chiatali asked -->
*****************************
Hi Wayne,
But what does the below statement from RFC 3264 means " If an SDP is offered, which is different from the previous SDP, the
new SDP MUST have a matching media stream for each media stream in
the previous SDP. The i-th media stream in the previous SDP, counting from the top,matches the i-th media stream in the new SDP, counting from the top."
Is it not that if the 1st media stream in previous offer has RTP as the protocol then in the Subsequent offers sent the 1st stream must also use RTP as transport.
what does matching the media stream mean..?
Thanks,
Chaitali
[EMAIL PROTECTED] wrote:
Chaitali, If support for it has been indicated in the signalling from the UAS (UPDATE listed in the Allow header), the UAC can change the SDP by sending an UPDATE request (RFC3311), in early or comfirmed dialog - as in your example below. Or complete the initial INVITE request and then re-INVITE the UAS with the desired SDP.
Regards - Wayne D.
********************************************************** Chaitali asked ->
Hi All,
I need some clarifications regd Offer Answer Model.User A sends Invite to UserB with RTP as transport and B accepts the call with 200 User A SDP:
v=0
o=alice 2890844526 2890844526 IN IP4 host.atlanta.example.com
s=
c=IN IP4 host.atlanta.example.com
t=0 0
m=audio 49170 RTP/AVP 0 8
a=rtpmap:0 PCMU/8000
a=rtpmap:8 PCMA/8000
and B replies with v=0
o=bob 2808844564 2808844564 IN IP4 host.biloxi.example.com
s=
c=IN IP4 host.biloxi.example.com
t=0 0
m=audio 49172 RTP/AVP 0 8
a=rtpmap:0 PCMU/8000
a=rtpmap:8 PCMA/8000
Can B Send an Updated Offer changing the Transport Is this valid ? v=0 o=bob 2808844564 2808844565 IN IP4 host.biloxi.example.com s= c=IN IP4 host.biloxi.example.com t=0 0 m=audio 49172 RTP/SAVP 0 8 a=rtpmap:0 PCMU/8000 a=rtpmap:8 PCMA/8000
Thanks, Chaitali
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