Additional SDP re-negotiation on PS->CS SRVCC

Hello,

Have you met a problem of SRVCC procedure fail due to codecs mismatch on PS and CS legs?

I am looking for possibility to force SBC to re-negotiate codecs / update SDP during the ATGW configure process (step 3. in diagram). Is this configurable at all?

In my case two terminals, which are registered on the same SBC, make a local VoLTE call. They negotiate to use codec AMR-WB. Once the call is established, one of terminals looses VoLTE bearer and performs CS fallback. The problem is that on MSC this terminal uses AMR, so, MSC sends AMR in its SDP offer to SBC. SBC sends in SDP Answer only AMR-WB, so I assume that it just copies the codec information from PS leg (port 23050) to CS leg (port 23052).