El Tuesday 10 July 2007 20:03:53 Christian Schlatter escribió:
Iñaki Baz Castillo wrote:
Hi, I'm starting using OpenSer with Asterisk.
In calls passing through Asterisk the caller or callee get music on hold of Asterisk when is put on hold. But of course, direct calls between OpenSer users don't get this music.
I'm thinking in the posibility of detecting "on hold" reinvites (maybe reading the "a=sendonly" of SDP body) and rewriting the SDP IP contact to a music on hold server.
You would also have to tell the music server where to send the rtp stream. And you'd have to keep dialog state on the proxy in order to capture the off-hold INVITE and tell the music server to stop sending media.
This all leads to a sip proxy acting as a B2BUA/3PCC server which needs a lot of resources and is difficult to implement. I don't say it is impossible but adding this functionality to openser would be quite a task.
Unfortunately even the IETF has no clear message on music on hold, no wonder sip phones normally do not support it in a standards compliant way. There is a draft called "SIP Service Examples" that already has 12 revisions and that includes an example on how music on hold should be implemented.
http://www1.tools.ietf.org/html/draft-ietf-sipping-service-examples-12#sect ion-2.3
Previous revisions of this draft followed a 3PCC model for music on hold (http://tech-invite.com/Ti-sip-service-3.html), whereas revision 12 now implements music on hold with a call transfer.
One can only hope that we will see products implementing these procedures.
Pingtel seems to offer a music-on-hold server for the 3PCC model: http://interop.pingtel.com/#moh
And SNOM phones seem to work fine together with the pingtel/sipX solution: http://sipx-wiki.calivia.com/index.php/HowTo_configure_SNOM_SIP_phone_with_ sipX#Music_On_Hold_.28MoH.29
Thanks a lot. I see that it's not an easy task. I'll try it whena have some tiem and if I get something decent I''ll tell it here.
Regards.