In H.323-compliant multimedia networks, a device that supports conferencing among three or more participating terminals.The MCU comprises a Multipoint Controller (MC) and optional Multipoint Processors (MPs). The MC is responsible for call control negotiation to achieve common levels of communication.The MP may process either a single media stream or multiple media streams, depending on the nature of the conference. See also H.323 and multimedia.
(1) (MicroController Unit) A computer on a single chip. See microcontroller.
(2) (Multipoint Control Unit) A device that is used to moderate a videoconference of three or more end points, an end point being one or more users in a single location. In "continuous presence" mode, the most common method, the screen is split into one large and several smaller surrounding windows. The MCU sends the video of the dominant speaker to the large window. "Voice switch" mode has only one window, and the MCU switches the dominant speaker to that window. In "chair mode," a human moderator manually controls who is on screen at any given time. An MCU also provides an audio bridge that mixes the audio from all end points. An MCU may include a built-in H.323 gatekeeper for translating user names into IP addresses, a video PBX for call switching, forwarding and transfer as well as video network management for quality of service (QoS), bandwidth management and accounting. See videoconferencing.