SungWoo Lee wrote:
> Thanks for the comment.
>
> It is straight forward to answer whichever I want. However, there is still
> one issue remaind. Let's say I am to send fax. After establishing voice
> session, the receiver side sends re-INVITE whose SDP contains both
> audio and image in order to switch over to T.38 mode. Obviously, from
> the context, I am supposed to take image in this case.
>
> My question is how I can decide to take image in this case or decide
> to take audio in other case. I guess I have to check the context to decide
> which one to take, which is still confusing.
I think the simple answer here is that if both are present you can't
really tell from the signaling which is to be used. On the receiving
side you must look at the media to understand.
There is nothing preventing the other party from sending both
concurrently, though that might not be common. When you are sending, you
can use whichever one you want, or you can use both concurrently if you
are able.
If you don't want to use both concurrently, but are capable of either,
then you may answer the offer supporting both but specify a=inactive for
the one you don't want to use initially. Then you will guarantee that
you only get one. Whether that will work with your caller is TBD.
Paul
> What do you think?
>
>
> Lee, Sungwoo
>
> Mobile: 82-10-3015-4329
> Telecommunication System Div.
> Samsung Electronics Co., LTD.
>
> IMPOSSIBLE itself says I M POSSIBLE
>
>
> ------- Original Message -------
> Sender : Paul Kyzivat<[EMAIL PROTECTED]>
> Date : 2008-07-02 21:02 (GMT+09:00)
> Title : Re: [Sip-implementors] Initial INVITE with both audio and image
> mediadescriptor in SDP
>
> You are being offered two media streams. You may accept both, accept
> audio and reject image, accept image and reject audio, or even answer
> the call while rejecting both streams. (The latter is not common and
> probably not very friendly - better to reject with 488 in that case.)
>
> If you are capable of both audio and image, you should probably accept
> both. Then you can wait to see what arrives. If you are sending, send
> whichever you have to send, or even both.
>
> Paul
>
> SungWoo Lee wrote:
>> Dear all,
>>
>> I have a question regarding receiving INVITE which has both audio and image
>> mediadescriptor in its SDP. In this case, I don't know which mediadescriptor
>> I should take, and I am not even sure whether this is legal format or not.
>> Following is the sample incoming INVITE message that I received. If this is
>> the initial INVITE, am I supposed to ignore FAX thing and take audio only?
>> What if I receive this when I am trying to send FAX and the receiver side
>> sends this re-INVITE to switch over to T.38 mode? Is there any RFCs
>> regarding this issue? Looking forward to your answers.
>>
>> INVITE sip:[EMAIL PROTECTED]:5060 SIP/2.0
>> FROM: <sip:[EMAIL
>> PROTECTED]:5060;transport=tcp>;epid=765FF3B2D3;tag=9e148ff751
>> TO: <sip:[EMAIL
>> PROTECTED]:5060;transport=tcp>;tag=5614b60-afea878-13c4-50022-d4-47032be0-d4
>> CSEQ: 1 INVITE
>> CALL-ID: 55fde78-afea878-13c4-50022-d4-35449e22-d4
>> MAX-FORWARDS: 70
>> VIA: SIP/2.0/TCP 10.254.168.129:1593;branch=z9hG4bKfc5951b3
>> CONTACT:
>> <sip:exum.xxx.local:5065;transport=Tcp;maddr=10.254.168.129;ms-opaque=15a74095d736a37f>
>> CONTENT-LENGTH: 282
>> USER-AGENT: XXXX
>> CONTENT-TYPE: application/sdp
>>
>> v=0
>> o=- 0 1 IN IP4 10.254.168.129
>> s=session
>> c=IN IP4 10.254.168.129
>> t=0 0
>> m=audio 6353 RTP/AVP 0 8 101 13
>> a=rtpmap:0 PCMU/8000/1
>> a=rtpmap:8 PCMA/8000/1
>> a=rtpmap:101 telephone-event/8000
>> m=image 1592 udptl t38
>> a=T38FaxRateManagement:transferredTCF
>> a=T38FaxUdpEC:t38UDPFEC
>>
>>
>> Sungwoo
>>
>> _______________________________________________
>> Sip-implementors mailing list
>> [email protected]
>> https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
>>
>
>
_______________________________________________
Sip-implementors mailing list
[email protected]
https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
