procedures for the study of multimedia call and associated system

摘要

The method comprises: 1) when an IP terminal initiates a video call to a 3G terminal, the video gateway previously initiates a video call to the 3G terminal; 2) if the video call failures, when the video gateway receives the failure code returned from the ISUP, the video gateway immediately and automatically reinitiates an audio call to the 3G terminal; if the video call failures and the ISUP is degraded to be only used by audio signals, it is unnecessary to initiate an audio call to the 3G terminal; 3) establishing an audio bearer between the 3G network and the IP terminal, namely the video gateway only establishes an audio media-stream connection with the IP terminal after the call mode is switched to an audio mode.