Hi, On Pk, 2015-04-17 at 16:21 -0400, Paul Heitkemper wrote: > Can I send SDP to a phone to request it to send audio to a multicast > Group, as opposed to the UAC in the Contact URL?
In theory, yes, multicast streams are allowed in SIP offer / answer model. Note that if the stream is unidirectional, the meanings of sendonly and recvonly attributes are "reversed" for multicast. That is, if you want the other end only to send audio to a multicast group address 239.193.0.123, you would use m=audio 5000 RTP/AVP 0 c=IN IP4 239.193.0.123/1 a=sendonly while for unicast you would use m=audio 5000 RTP/AVP 0 c=IN IP4 192.168.0.123 a=recvonly (Strictly speaking, the meaning is reversed for unicast streams when using SIP offer / answer model, which baffles me; if I understand correctly, the semantics of sendonly for unicast in plain SDP are the same as for multicast.) > Does anyone have any idea of how widely-implemented this is in the > industry? Probably very rare. I don't know of any UA that would support multicast, but then I haven't looked very hard, either. Best, Jānis _______________________________________________ Sip-implementors mailing list Sip-implementors@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
