A system to provide a multipoint processing terminal and a multicast bridging terminal to provide mixing, switching, and other processing of media streams under the control of H.323 components. Application Programming Interfaces defined for the multipoint processing terminal provide a multipoint control unit with the capability to change the default behavior of the multipoint processing terminal by allowing the multipoint control unit to control the routing audio and video streams in the multipoint processing terminal and control the media formats in a multipoint conference. Multipoint processing acceleration functionality is provided by providing interfaces to allow hardware accelerated implementations of multipoint processing terminals. The multicast bridging terminals enables clients using one type of control signaling and media streaming to join other conferences using different types of control signaling and media streaming by receiving audio or video data from an incoming media stream and performing any processing necessary to transform the media stream from the incoming stream data format to the outgoing stream data format.