Franz Edler wrote:
From: Paul Kyzivat Sent: Wednesday, March 30, 2005 9:42 PM
If you only want early media in the backwards direction then you can wait for the 200 to send SDP.
I have to better clarify the situation: In our case we have to get announcements via a PSTN gateway before answer. There is a regulatory requirement in Austria to render announcements in certain cases (value added numbers) explaining the expected charges before the caller answers. Therefore we cannot wait for 200 OK, because 200 OK comes only after the announcement.
Without any 183 session progress we either hear nothing or a local generated ringing tone. I understand, that to trigger the rendering of the RTP-stream in the User Agent an 183 is a good response.
But why should I nee any SDP inside this 183?
Devices use a bunch of schemes in practice to decide when to start rendering received media. But the only robust scheme that I have seen discussed requires the UAC to start rendering media as soon as it begins receiving media.
OTOH, in practice you will have to do what works with the devices you have. But that isn't a standards issue.
Paul _______________________________________________ Sip-implementors mailing list [email protected] http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
