[EMAIL PROTECTED] wrote:
> Hi Paul,
>
> now I have a problem in my understanding.
>
> A UAC sends out an INVITE with SDP for audio and video to a gateway. The
> gateway
> alters the SIP message to an Non-SIP signal. It sends a 183 with a SDP and
> confirms only audio to start early media. But now the caller accepts
> audio and video.
What do you mean by "the caller accepts audio and video"? It is the
callee that is doing the accepting, and it only accepted audio. So that
is all that will be used as a result of the offer/answer exchange in
this transaction.
> What should the gateway do? If it does not confirm video, video
> should
> be used. If it confirms video, video will maybe not used.
I am not familiar with a gateway that can handle video at all.
If the gateway may want to accept video, then it should decide before it
sends an answer, and the answer should reflect what it has decided to do.
OR, if it knows it can accept audio, and wants to accept and enable
early media on the audio while it decides if it will be accepting video
for the call, it can do that a couple of ways:
1) It can accept audio only in the invite. After the call is answered,
it can reinvite and add video.
2) If the UAC and UAS both support the 100rel option and the UPDATE
method, then the UAS can accept audio only using a reliable provisional
response. If it then later decides, before answering, that video can be
supported, it can send an UPDATE (before the 200 OK) with a new offer
that includes video.
Paul
> Could this scenario happen in pratice? If yes, what is the solution?
> Could the
> gateway have information about the endpoint?
>
> Regards,
> Markus
>
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