Hi Experts,
Can anyone guide me on where to check the final negotiated codec in the trace on an SBC?
VoLTE to VoLTE Call
Thanks!
You can find it in the Session Description Protocol (SDP) messages within SIP signaling.
Typically, it appears between the INVITE and the SIP 200 OK messages.
In rare cases, it may be included in the ACK confirmation. After this exchange, you should see the codec selection.
1 Like
Additionally, the 183 Session Progress message is also commonly used to carry the SDP answer.
1 Like
Hi
This is a very complex question to answer since ultimate end to end codec depends on various things and I will summarise it in a way you can do more digging in the network you are working on.First it depends on the Handset A and B.Then the initial invite hits IMS it depends on the IMS config which decides which points IMS wants to anchor the call on.Usually there are few obvious once PCSCF,IBCF,MTAS(announcement platform),BGCF,MGCF etc.so once that is clear the respective MGW config decides the SDP offer answer codec list which needs to send back to UE.And also there are few concepts which are implimented in most IMS networks like TrFO(transcoder free operation)which will minise the transcoding within IMS network.And also there are CP features like SIP pre-condition implimentation which are directly related to QOS implimentation. In General lets say if you use updated handsets I will provide you with the standard codec which is the call is going to get set up end to end most of the time per technology.Volte:AMR-NB, Volte with HD voice:AMR-WB,VoNR:EVS etc.
Thank you.