Maxim Sobolev schrieb: > Klaus Darilion wrote: >> Hi! >> >> For a certain application where uplink is low bandwidth and downlink >> is high bandwidth I want to use the best available codec - ie. up >> G729, down G.711. >> >> How can I setup such an asymmetric session? >> >> eg. >> high down >> Alice ------------ Bob >> up low >> >> I think if Alice announces G711 and G729, and Bob answers with G.729, >> Alice must send with G729 and Bob can send with G711 too. Is this >> correct? > > As far as I know it's correct. In fact, Bob can even mix both 711 and > 729 frames within a stream as he sees fit. > >> Nevertheless, as this requires that Alice's SIP client support this. >> Is there also a method to explicitly define the asymmetric behavior? > > In one of product I worked on we relied on this functionality to inject > pre-encoded announcements into the RTP stream using the RTPproxy. All > popular SIP clients and carrier equipment we've tested to date handled > this correctly.
I think with softphones it is usually not a problem. But AFAIK there are embedded devices which load the codec code into the DSP once the codec is negotiated, or after reINVITE if the codec changes. Thus, with such devices tis would not work. Or if Alice sends a reINVITE containing only G729 to lock down on this codec. Then it also does not work. Thus I asked if there a method to explicitly negotiate asymmetric codecs. thanks klaus _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
