The video conference server refers to the use of video conferencing terminal equipment to build a complete remote video conferencing solution. The core equipment of the video conference server is the MCU multi-point control unit. The MCU is essentially a multimedia information exchange, which performs multi-point calling and connection, realizes functions of video broadcasting, video selection, audio mixing, data broadcasting, etc., and completes the connection and switching of each terminal signalm for video conferencing equipment. The MCU differs from the current switch in that the switch completes the point-to-point connection of the signal, while the MCU completes the multi-point-to-multipoint switching, tandem or broadcast. What is the core part of the video conferencing system and MCU: 1, MCU (MulTI-point Control Unit) video conferencing. Coordinate and control video transmission between multiple terminals.
The role of the MCU is to switch the input multi-way conference television signal, but since the conference television signal contains three different types of signals: image, voice and data, the switching effect of the MCU is not as simple as the telephone exchange. The signal is switched, and it has to deal with the three types of signals differently. The MCU adopts a multi-channel mixing mode (of course, can also adopt a switching mode) to transmit the voice signal, and directly transmits the video signal, and transmits the data signal in a broadcast mode or an MLP mode. In addition, the MCU also completes the processing of communication control signals and network interface signals.
There are two components: MC (MulTIpoint Controller) and MP (MulTIpoint Processor). The MC is mainly responsible for coordinating the sequence of transmission channels between terminals and using H.245 to define the specifications of the transmission content; MP is actually engaged in the reproduction and transfer of audio and video under the control rules of the MC in huddle room. And the processing of some video streams. In the MCU, the MC is a management function that must be provided, and the MP has a choice between the terminal's ability to handle the video and the overall environment architecture. 2. The composition of the video conference The composition of the conference system is very simple. Each conference site is equipped with a video conference terminal. The terminal is connected to the TV as an echo device and connected to the network as a transmission medium. A terminal usually has a core codec, a camera, an omnidirectional microphone, and a remote control. The core codec transmits the image and sound input from the camera and microphone through the network, and at the same time decodes the data transmitted from the network and restores the image and sound to the TV and the sound, realizing real-time interaction with the remote end. The terminal connects by calling the IP address or ISDN number (the line does not need to dial). However, in the case of three points, the MCU (Video Conferencing Multipoint Control Unit) must be used for management. Similar to the telephone exchange, the MCU (Multi-Point Control Unit) is used to determine which way (or which four channels are combined into one) to be broadcast as the main image for more than three points of the video conference. The sound of all venues is synchronized in real time. In the conference system with the MCU video conferencing system terminal, the audio and video data of all terminals are transmitted to the MCU for selective broadcast in real time. The MCU has a large data flow, and is usually connected to the central switch of the network. The controller uses the MCU management interface of the laptop to remotely manage the site. The calling mode may be called by the lifesize video conferencing by the MCU to each terminal, or the terminal may call the set conference number. If the network of the video conference system planned by the customer is relatively large, another video conference network can be established under the MCU, and the MCUs of the two networks implement video and audio exchange, and this method is called cascading of the MCU. For example, the bandwidth of the video conferencing network from the central to the provinces is 2M, and the province itself has its own video conferencing system. The central meeting uses its own MCU to save the meeting and use the provincial MCU. When it is necessary to upload and release, the MCU level can be connected. The advantage of cascading is that management will not be confusing; second, the bandwidth to the central area does not allow the data of dozens of points below to be squeezed into it. Industry definition of video conferencing MCU: The MCU is a physical entity. It is a rectangular parallelepiped and looks like a DVD player. MCUs cannot be used independently. Must be used in conjunction with a video conferencing terminal. The MCU is mainly divided into two parts, namely MC (MulTIpoint Controller) and MP (Multipoint Processor). MCU Chinese name is multi-point control unit, also known as single-chip microcomputer (SingleChipMicrocomputer), refers to the computer's CPU, RAM, ROM, timer and various I/ with the emergence and development of large-scale integrated circuits. The O interface is integrated on a chip to form a chip-level computer for different combinations of different applications. MCU is the key to multipoint video conferencing systems: MCUs act like a switch, but they are not the same as switches in a typical telephone network. The former switches the digital signal while the latter switches the analog signal. The MCU extracts the information and signaling of audio, video, data, etc. from the information flow of each conference site, and then sends the information and signaling of each conference site to the same processing module to complete the corresponding The process of audio mixing or switching, video mixing or switching, data broadcasting and routing, timing and conference control, and finally reassembling the various information required for each conference site and sending it to each corresponding terminal system device. The MCU also has the function of automatically unifying the transmission rate: all terminal systems of the same conference should work at the same rate. If the rate of the terminal connected to it is inconsistent in small conference room, it will automatically select the lowest rate of all terminal systems as the working rate. The MCU is used to support conferences of more than three node devices, and point-to-point communication does not require access. In the H.323 system, an MCU consists of a multipoint controller MC and several multipoint processors MP, but may also not contain the H.245 control information between the NP.MC processing terminals, thereby determining its video and The usual processing power of audio. If necessary, the MC can also control conference resources by determining which video streams and audio streams require multicast. The MC does not directly process any media stream and leaves it to the MP for processing. The MP mixes, switches, and processes audio, video, or data information in video conferencing hardware. MCs and MPs may exist in a dedicated device or as part of other H.323 components.
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