Security system is to maintain social public safety, for the purpose of using security products and other related products of intrusion alarm system, video security monitoring system, access control system, explosion-proof safety inspection system, etc.; By these systems for the subsystem or integrated electronic system or network. According to the China security industry "twelfth five-year" development plan "shows that by the end of 2010, China's security industry output value of more than 2300 one hundred million yuan, including security product output value is about 100 billion yuan. And according to the planning for the requirement of the "twelfth five-year" period doubling industry estimates, security industry output will reach 500 billion yuan in 2015. Video monitoring system as an important part of security system, because of its expanding application fields, and the industry scale expands unceasingly, occupy the market share of more than half of the domestic security industry. This paper mainly discusses the video monitor the course of evolution.

Video monitoring of the development of the four stages
Along with the computer multimedia technology, coding compression technology, network transmission technology, storage technology and video monitoring constantly fusion, such as the development of video surveillance has experienced analog video surveillance, digital video monitoring, network video monitoring, the evolution of the hd video monitoring, product function, morphology and composition of video monitoring architecture, etc. There have been great changes in all aspects.
Analog video monitoring stage
Analog video monitoring began in the 1970 s, the stage is mainly use analog cameras for video signal acquisition, through matrix host or coaxial cable to transmit video signals to display and recording equipment. In the analog video monitoring system, mainly simulation, simulated keyboard matrix switching control equipment is the core of the whole system, and display and video equipment were used more monitor and tape video recorder (VCR, VideoCassetteRecorder).
Analog video monitoring system is also known as CCTV (China central television (CCTV), ClosedCircuitTelevision), it is composed of analog camera, video distributor, analog matrix, control the keyboard and video tape recorder (VCR) and so on, can realize the basic function such as surveillance, video recording, playback, mainly adopts coaxial cable (75 Ω, 1.0 the Vp - p) composite video broadcast signal (CVBS, CompositeVideoBroadcastSignal,) transmission.
Digital video monitoring stage
Digital video monitoring began in the late 1990 s, the stage is mainly using video compression card analog camera module with the analog signals of conversion, encoding, compression, at the same time using the PC to the local store. This stage of the hard disk video recorder adopts PC architecture, mainly realizes the analog signals and digital video coding, compression, storage function, the network transmission, software applications, matrix control function is not very perfect, so in actual project application, usually used with analog matrix.
PC hard disk video recorder (PC - DigitalVideoRecoder, PC - DVR) was born in the early stage of the era of digital video monitoring, for digital video surveillance would be able to complete the analog signal digital provides a reliable guarantee, effectively solve the analog video surveillance video storage medium and the limitation of the storage period. Digital video surveillance system is mainly composed of analog camera, PC hard disk video recorders, monitors, etc, can realize monitoring (listen), video recording, playback, alarm linkage, voice intercom, the basic function such as real time control.
PC hard disk video recorder can realize front-end analog signal digital-to-analog conversion, encoding, compression, can also achieve compression data stored locally, signal transmission medium is still a coaxial cable (75 Ω, 1.0 the Vp - p).
Network video monitoring stage
Network video monitoring began in 2005, the early stage of the main use of embedded network hard disk video (E - DVR, EmbeddedDigitalVideoRecoder) or embedded video server (DVS, DigitalVideoServer) will be digital, analog signal encoding, compression after access networks, network video monitoring. With the deepening of the peace of city construction, financial and other industries the continuous expansion of video monitoring, video surveillance network demand increasingly obvious, the development of video surveillance network has a positive influence. At present, the video surveillance industry has been basically realize network video monitoring.
1, the simulation of the access network video monitoring
Daily applications, the small monitoring scenario if requirements for video resolution is not high, may choose plan of simulation, using the simulation camera + DVR + + PC monitor (client) "architecture. Under this framework, the front-end usually adopt standard definition analog camera to realize the collection of video signal, through coaxial cable transmission to the DVR is encoded and stored, DVR can display the real-time preview, playback operation. The scenario in general by the DVR realize networking, the client can be accessed by remote DVR, realize remote operation.
2, modulus of hybrid access network video monitoring
Front-end analog camera signal can be directly transmitted to the monitoring center, also can be placed near the front-end equipment video coding equipment, number of analog video signals to digital compression and coding, can convert transmission of packets on the Internet (or directly use the network camera), through the IP network (wired/wireless) transmitted to the monitoring center. In the monitoring center, analog signal through a video distributor access analog matrix, while digital signal through a video decoding devices convert analog video signal into analog matrix, all the audio data stored on the hard disk video recorder (H - DVR) blend.
Hd video monitoring stage
Network monitoring, as a basic application after being satisfied, eager to see the face, the demand of the details, such as the license plate characteristics the user's attention to video resolution on the promotion of high-definition video monitor emergence.
To achieve real hd video monitoring, collection, transmission, storage, decoding, display, control each link has strict requirements, be short of one cannot. Video surveillance industry in our country is still in its infancy, hd video monitoring hd this trend will continue for a long time.
1, all IP access way of hd video monitoring
All IP access hd monitor is one of the most typical application pattern. The architecture, the audio data in the form of IP packet transmission in IP network.
Front end: using network coding compression after high-definition cameras for video image acquisition comes back through the network, and access to the alarm and voice signal back camera.
Transfer: layers of data transmission through Ethernet connection.
Storage: because of video streams for encoding digital signal after all, can do it through the NVR, NAS or IPSAN storage.
Shows: by decoder to decode front-end video source on the wall, according to complete the round tour of image display, switching, and so on.
Control: through the keyboard control decoder or front-end ball machine, yuntai equipment to complete the corresponding operation.
Management: can be unified by the client for all the equipment management, and linkage with alarm, voice signal.
2, full digital access way of hd video monitoring
Generally, digital access high-definition monitor model application is relatively less.
Front end: the camera on the transmission of signals from the image sensor, bare uncompressed data collected in the image detail, color reduction, the respect such as control delay than the network cameras have an advantage, but the cost is higher.
Transfer: general data transmission through hd-sdi or light transmission, for maximum distance of 100 meters, hd-sdi transmission for long distance transmission is using optical transceiver.
Storage: because the video stream is uncompressed data transmitted back to the center, the capacity is very big, need after compression hd encoder to through the NVR, NAS or IPSAN storage.
Display: video can be transmitted back to the center through the video distributor to isolate all the way on digital video matrix, digital matrix of hd-sdi signal and the signal directly to switch on the light, according to the wall can also complete the round tour of image display, switching operation, such as high cost but digital matrix.
Control: through the keyboard control digital matrix or the front ball machine, yuntai equipment to complete the corresponding operation.
Management: can be unified by the client for all the equipment management, and linkage with alarm, voice signal.
conclusion
The first year of 2010 is regarded as the hd monitor, major manufacturers have launched products and solutions is given priority to with high-definition cameras, in each big BBS communication "hd" calls for more and more.

These two years, the enterprise gradually increased spending on hd product, and lead the other small and medium-sized enterprises accelerate towards to the hd era, "hd" and "hd monitor" concept is gradually accepted by people cognition and. But hd monitor came on the heels of the massive information storage and retrieval problem. In the face of such a large information, how to effectively liberation of human, improve the beforehand prevention ability; How to integrate the social from all walks of life video resources, saving storage space, realize information interconnection has become an important problem we need to think about the next step.

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