【 Weak current College 】 conferencing system application---Power By 【 China power house network 】

Abstract: this paper discusses meeting TV system, classification and application, and analyzes the video conference system problems of application. Keywords: video-conference system conferencing terminal equipment for digital transmission network multipoint control unit
Introduction as digital signal processing, coding and data transfer new technologies are emerging, video conference system (VideoconferencingSystem), video conference system is the use of television technology and equipment through the transport channel in two (or more locations) to convene a meeting of a means of communication. Videoconference system is put at more locations videoconference equipment connected together, the participants are being met, together with the Pro scene face-to-face dialogue.　　It has a real, efficient, real-time features, is a simple and effective for management, command, and the technical means of collaborative decision making.　　Therefore, it is widely used in various meetings of the Executive Council, science and technology, distance learning, and business negotiations, and other social activities. In government administration, videoconferencing systems in various meetings and document learning has an important role in making government work exchanges between leaders more convenient, and can quickly deal with unexpected events, such as emergency relief, flood of command, etc.　　In education, videoconference system can fully take advantage of the multimedia remote teaching network, achieving distance education network, covering urban and rural areas of open education system for all types of community members with multiple levels, a variety of education services. Implementation of basic education, vocational education, adult education and higher education between cohesion and communication, as learners offers numerous educational opportunities undoubtedly will play a bigger role. In business, application of video conference system can strengthen management, increase productivity and reduce costs. High-quality videoconferencing, in geographically dispersed organizations can address issues more quickly, save time, save money, but also the traditional meeting face-to-face exchanges of natural feeling to the participants, can quickly and accurately grasp the decision-making opportunities that enable more people to join the important decision, and a more open, more collaborative working environment. By video-conference system broadcast mode, you can easily, frequently organize remote training and distance learning, faster and improve the operations of various departments. Provide conferencing system, leadership can in some unexpected events on the issue of subordinate departments around; in key areas set up video conferencing system, you can truly become the leaders of clairvoyance, long ears, to facilitate timely and informed leadership, accurate, swift and forceful measures. Video conference system can meet the requirements of the general meeting of the TV, while providing data communication encryption interface. With the function number, communication is reliable, secure transmission, price low. Through the choice of communication encryption machine you can video conference and data communication provides secure communication to keep company secrets from leaking. 2. video conference system of classification and composition of videoconference system (VideoconferencingSystem) is a video-based interactive multimedia communications, it leverages existing image communication technology, computer, communication technology and microelectronics technology for this area or remote regions, point-to-point or multipoint video, between two-way duplex audio, and data, and other interactive information real-time communication, real time transmission of voice, images, and files. Video conference system by business, can be divided into public videoconference system, dedicated conferencing system and desktop video conferencing system. 2.1 public videoconference system public videoconference system is operated by China Telecom to reserve rental use of video-conference system, the system covers all provincial capitals and major cities. Need help with video conferencing units prior to appointment, videoconferencing Hall in China Telecom. For the newly established small companies and occasionally videoconferencing unit may consider this programme, its advantages are: to reduce the company's initial investment, capital pressure and does not require special maintenance; disadvantages: you need to use, you must make reservations in advance, cannot be TV anywhere, anytime, lost convenient, real-time. 2.2 dedicated conferencing system dedicated videoconference system is formed by an independent unit of its own dedicated conferencing system, including the formation of a dedicated transmission network, to purchase a dedicated conferencing system equipment. Its mainly in large companies, large enterprises, at present has built special-purpose system units with customs, police, railway, Bank, etc. Its advantages are: use, you do not have to make an appointment ahead of time, anytime, anywhere for videoconferencing; disadvantage: one-time investment is relatively large and also need special maintenance. 3 desktop video conference system
Desktop videoconferencing systems (Desktop Video Conferring System, DVCS) is an intelligent building internal adoption of multimedia communication video conference system, the system is based on computer communication means, less investment, quick and easy to use, quick to meet Office Automation data communications and video multimedia communication requirements. Desktop video conferencing system is installed on the computer image multimedia interface card, card, multimedia software and input/output device, the text to the image displayed on the screen, the parties concerned can modify text on the screen together with the chart, fax machines, phones and other means of communication, writing, and timely information on the files transferred to the other party. Desktop videoconferencing system not only with General computer (network) communication features, and a dynamic color video images, sound, text, data, information on real-time duplex bi-directional Synchronous transfers and interactive communication. It also has: point-point or multi-point video conferencing between, real-time online file transfer, synchronization, transfer files and there is a belt fax video image and sound of e-mail, remote control other camera features such as screen locations. 2.4 conferencing system consisting of a videoconference system is mainly composed of conferencing terminal equipment, digital transmission network and multipoint control unit (MCU) made up of three parts. 2.4.1 conferencing terminal equipment meeting TV terminal equipment mainly includes videoInput/output devices, audio input/output device, video codec, audio codec, information and communication equipment and multiplexing/signal line equipment.　　Its basic function is to make local cameras of image signal, microphone picks up sound signal compression, encoding, and synthesis for 64Kbps digital signal to 1920Kbps, passes through the transport network, are transmitted to the remote site. At the same time, receive the distance from the venue, the digital signal decoding, restored into a simulation of image and sound signals.　　Video input device: it includes cameras, recorders, cameras are the main camera, video camera and video camera, graphics and input should be not less than four. Main camera is easy to use conferencing camera automatically tracking system, automatic camera system can automatically track speakers (camera and floor unit for synchronization), automatic lens angle changes, change in focal length and other functions, and the speaker's personal image to video signal forms sent to the video and projector, projected on the big screen. Video output device: it includes monitors, projectors, video walls, split screen processor, etc. Meeting room screen display is divided into single-screen, and dual-screen two, single-screen display mode: only one monitor displays the received on end scenes or characters;　　dual-screen display mode: one data terminal equipment of the two monitors appear on the end of the two images, one monitor display to end spokesman image, another monitor is available for display on the client sent to illustrations or documents. Audio input/output device: it includes a microphone, speakers, tuning equipment and echo suppressor, etc. Video decoder: on the one hand it to the video signal format conversion process to adapt to different systems through; on the other hand on the video signal to digital compression processing to meet the narrowband digital channel transmission, also supports multipoint videoconference system multipoint control unit multi point switch control.　　Video codec suitable for all common intermediate format (CIF) or 1/4 common intermediate format (QCIF) approach to image. Under specific conditions, or CTX or CTX PLUS other codec, but must be compatible with the CIF, QCIF, facilitate the user's selection of different demands the appropriate codec.　　Audio codec: mainly on analog audio signal processing in digital encoding, and has delivered. Audio codec should have audio signals to PCM, ADPCM or LD-CELP decoding capabilities. The multiplexer/signal line equipment: its video, audio, data signal into transmission rate is 64-1920Kbps data stream, a user/network interface compatible signal format. 2.4.2 digital transmission network is used by video-conference system in two ways: first, is the earliest launch ITU-T H.320 protocol based dedicated system; second, the recent launch of H.323 protocol based on open systems. 2.4.2.1 support H.320 agreement in principle, as long as the network is to provide circuit-switched networks are in the form of support H.320 Protocol. Of these, DDN circuit, satellite circuit features: private network;
Network delay small (usually less than 10ms), and to determine the delay;
Usually use 384bit/s bandwidth can consist of good-quality videoconference system;
Use Star or tree-like structure support conferencing system.
ISDN circuits features: using the public switched telephone network for communication over a dial-up mode;
Communication speed 128384bit/s (2B channel);
You can use multiple 2B channel to support high-speed communications, channel high quality requirements;
Typically used to support point-to-point or small-scale videoconferencing.
2.4.2.2 support H.323 protocol H.323 protocol based network video conferencing system is usually through the local network by IP (router) network to communicate, so in addition to the above support agreement network H.320 can use, you can use the frame relay and ATM networks. DDN circuit features: a. communication bandwidth is usually selected videoconference equipment rate, plus the necessary IP overhead (typically 20%); the system will need to use the net for system call establishment and demolition, network bandwidth control, etc.;
Apart from the frame relay network with DDN circuit features, plus: network delay, generally within 10ms-100ms, and uncertain;
Communication is the basic bandwidth videoconferencing system terminal equipment rate plus 20% of the cost of IP, should also be taken into account by the IP packet into a frame relay Group increased by a small amount of overhead.
2.4.3 multipoint control unit (MCU)
Multipoint control unit (MCU) settings in network contacts for multiple locations of the meetings at the mutual communication, work at 64Kbps-2Mbps, chart below. Multipoint control unit is a multipoint videoconference of necessary equipment, the main function is to complete the multi-channel video/audio data stream processing and Exchange, select a source stream broadcasting; at the same time provide a wide range of session control functions. Now, many manufacturers developed a multipoint control unit (MCU) has been able to achieve the H.320 and all two protocol H.323 compatible, easy to upgrade and when video conferencing in a network problem, you can convert between direct network, greatly improving the videoconferencing system reliability and security. 3. video conference system problems to establish the "stable, full-featured" teleconferencing system, mainly reflected in the system data transmission quality and purchase equipment. In addition, the video conference system for conference rooms also have certain requirements, mainly reflected in the Conference Room of the environment and the power supply system. 3.1 videoconference system of transmission quality construction Conference TV system, depending on the purpose and importance to select transmission quality, it can be divided into three levels, high quality: circuit based on DDN, E1 leased lines, in line with the International Telecommunication Union (ITU), H.320 network protocol standard that channel rate should be 2M, equipment isFull hardware Codec (codec), 30fps FCIF format video, rich circuit interface and many features such as intelligent voice; medium quality: circuit generally is based on private IP network, meet (ITU) h.323 network protocol standard that channel rate should be above the device also 768k is full hardware Codec, 20 ~ 30fps FCIF format video; low quality: provides software-only format video Codec, 10fpsFCIF, circuit based on IP, consistent with (ITU) h.323 network protocol standard desktop video conferencing requirements, channel rate in 384k following. Building a stable and reliable conferencing system network, not only requires good data transmission channel for security, you must also have excellent performance of the video conference system equipment. 3.2 videoconferencing system on the meeting room request complete conferencing system planning and design in addition to the meeting room provides meeting staff and comfortable meeting environment, it is more important to realistically reflect the scene (venue) of the characters and scenes and so on, so that participants have a tele-presence, in order to achieve the vision and language exchange of good results from the transmission of images in the room include figures, scenes, charts, text, and so it should be clear to the defence. 3.2.1 meeting room environment requires a temperature of 18-22 ° c;
Humidity is 60%-80%;
Rate per person per hour ≥ 18 cubic meters;
Environmental noise is 40dB;
The tone is light-colored, white and black is prohibited;
Site lighting using artificial light sources, to design, with 3500K color temperature cold light source, monitor and projector illuminance ≤ 80lx;
Acoustics: Interior should have carpet, ceiling, walls should be equipped with soundproofed Windows, double glazing, should be adopted into out noise insulation should be adopted;
3.2.2 Conference Room conference room of power supply system in order to guarantee safe and reliable power supply, to reduce the power of the electrical crosstalk channels, three sets of power supply system should be used. A power supply system as room lighting; second power supply system as a whole terminal equipment, control room equipment and power supply, uninterrupted power supply systems (UPS); the third set of power supply system for air conditioning equipment of power supply. Grounding of the power supply system of the more important issues.　　Control room or machinery room, meeting room of the ground required, preferably in the control room or room set of ground bus on the wire. If you are an individual setting for grounding, grounding resistance should not be greater than 4 Ohms; set up separate grounding has difficulty, can also be combined with other Earth system grounding, grounding resistance should not be greater than 0.3 ohm. Necessary to emphasize that the use of joint grounding, protect the ground wire must be in three-phase five wires in the fifthline, and the AC power line of zero; otherwise, it must be strictly separated from the zero line unbalanced power will have serious interference with the image. 4. video conference system cost construction cost of conferencing system mainly includes two aspects: first, is the one-time investment of the device, its costs and the use of equipment; second, a video conference system for running costs, the costs and the renting of a circuit, circuit number and lease time. 4.1 equipment from the main video conference system manufacturers provide, meeting room-meeting at TV terminal equipment is usually 10-30 million; the venue of meeting TV terminal equipment prices usually 20-50 million; tabletop Conference TV terminal equipment prices typically 5-10 million. Multipoint control unit (MCU) price and its control points, control points, the higher the price. 4.2 system running cost for domestic enterprise conferencing system, the main cost of leased circuits. If using DDN circuit, rate 384bit/s, monthly fee for each circuit 2 million; frame relay rates slightly lower, a PVC logic circuits of costs for the same rate of 40% of the DDN circuit. 5. concluding remarks with the development of information times, videoconference system is among the industries play an important role, it will be an essential part of the industry. Construction of the "stable, full-featured" teleconferencing system, can be summarized as: positioning accurately-positioning system of the transmission quality; equipment is the key-choosing high quality, and provide the openness of the equipment; stability is required-select performance stable reliable transmission circuits, terminal equipment and the MCU devices. Only build the "stable, full-featured" teleconferencing system before they can fully play its real advantage, we can achieve the desired results. Reference 1. The intelligent building infrastructure, the Chief Editor 2. wangna intelligent building practical technology "Yang Shao-features editor