20 mar 2010 kl. 13.43 skrev Iñaki Baz Castillo: > 2010/3/20 Olle E. Johansson <o...@edvina.net>: >> >> 18 mar 2010 kl. 12.34 skrev Iñaki Baz Castillo: >>> Nothing special, the UAC should b able to receive such RTP (real >>> audio) and render it to the human via the phone speaker. >>> It's really common and 200% valid. >> >> As a best current practise, I would recommend first sending a 180 Ringing, >> so that all involved applications can change state. The 183 could very well >> mean an error message, so you can not assume that it means ringing. Not >> sending 180 makes life very hard for gateways. You are also allowed to >> include sdp in an 180 message and both send your preferred ring tone and >> change state in the same message. > > > Who should send such 180 prior to the 183? This is, if Alice calls Bob > (who after so many calls already hates Alice) and Bob's phone is down, > then provider would reply an early-media message "the person you are > calling hates you and has switched off the phone". This audio would > come into a 183. Why should be a 180 required before? > > > Also, there are cases in which the PSTN gateways reply a 183 followed > by a 180. This makes crazy some phones which don't know what to render > (real audio of 183 or artificial ringing requested by the 180). > In the case of using early media just to send a ring tone, I would prefer sending 180 with SDP, or 180 first, then 183 with SDP. I don't like devices that only send 183 with SDP for ring tone.
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