29.1633GPPInterworking between the IP Multimedia (IM) Core Network (CN) subsystem and Circuit Switched (CS) networksTS
E.3.1 Functionalities required in the IM-MGW for multimedia calls support
To enable a multimedia Interworking, the IM-MGW needs to support the reframing of the H.263 video codec and the AMR audio codec between CS transport and PS transport as a minimum. The IM-MGW may also support the reframing of other codecs and the transcoding of audio and/or video codecs.
At the CS side, the IM-MGW needs to terminate the H.223 protocol and multiplex / de-multiplex audio, video and H.245 signalling. How H.245 related information (e.g. H.245 messages or extracted information) is communicated between the MGCF and the IM-MGW is described in clause E.4.