Transcoding is accomplished using codec policies and those configurations are applied in sip-interface or realm-config elements. Oracle SBC based the decision to transcode based in the following diagram:

Transcoding decision is taken based on:

• SDP offer (O₀, offer is also modified by codec policy removing and re-ordering the allowed ones, or adding codecs not originally in the offer when egressing)
• SDP answer (A₀) is subject to only egress policy (acts as ingress for the answer)
• Depending on codecs removed from offer, codecs added and codecs in the SDP answer
• If the two top a= lines in O₁ and A₁ don’t match, transcoding will occur.
• The add-on-egress parameter must be configured for transcoding to occur.
• Codecs listed in the add-on-egress will only be added if O₁ contains at least one transcodable codec

In our lab environment:

Lets test configure this in our lab environment in the next entry.