Digital monitoring system is developed from the traditional closed-circuit television monitoring system (CCTV system for short) and is the product of the development of the information age. Today's digital monitoring system adopts 4C technology, namely computer technology, display technology, communication technology and control technology. The application of these high and new technologies has brought the technology of digital monitoring system to a new level. It can not only make managers sit in the control room to observe the work of all employees in the control area, but also provide on-site visual effects for the management and safety system. It can also record the activities of employees and outsiders in the business premises according to the system settings, providing strong evidence for resolving disputes. Therefore, the digital monitoring system has become an indispensable part of the modern management system of enterprises and institutions.
Advantages of digital monitoring
First, it is convenient for computer processing. Because the video image is digital, it can be compressed, analyzed, stored and displayed by making full use of the fast processing ability of the computer. Through video analysis, the abnormal situation can be found in time and the alarm can be linked to realize unattended operation.
Second, it is suitable for long-distance transmission. Digital information has strong anti-interference ability, is not easily affected by the attenuation of transmission line signals, and can be encrypted for transmission, so it can monitor the scene in real time thousands of kilometers away. Especially when the site environment is bad or it is inconvenient to go directly to the site, digital video monitoring can achieve the effect of visiting the site in person. Even if the scene is destroyed, the real record of the scene can still be obtained in the distance.
Third, it is easy to find. In the traditional analog monitoring system, when there is a problem, it takes a lot of time to watch the video tape and find the on-site records; In the digital video surveillance system, the corresponding on-site records can be found in a few minutes by using the index established by the computer.
Fourthly, the image quality and monitoring efficiency are improved. Computers can be used to denoise and sharpen unclear images. By adjusting the image size and with the help of the high resolution of the display, you can watch clear and high-quality images. In addition, you can watch 16 or even 32 video images on one monitor at the same time.
Fifth, the system is easy to manage and maintain. Digital video monitoring system is mainly composed of electronic equipment, which has high integration, and video transmission can use wired or wireless channels. In this way, the whole system is modular in structure, small in size and easy to install, use and maintain.
It is precisely because of the incomparable advantages of traditional analog monitoring and the development trend of digitalization, networking and intelligence in the current information society that digital video monitoring is gradually replacing analog monitoring and is widely used in all walks of life.
Historical Development of Video Surveillance System
With the rapid development of monitoring industry, the development of video monitoring system has gone through three stages.
Before the end of last century, the fully analog TV monitoring system, which mainly consisted of analog equipment, including cameras and tape recorders, was called the first generation analog monitoring system. At this stage, the monitoring system basically does not use video monitoring software.
2 1 century, with the rapid development of computer technology, the technology of computer processing video is becoming more and more mature. People use the high-speed data processing ability of computers to collect and compress videos, and use the high resolution of monitors to realize multi-screen display of images, thus greatly improving the image quality. Because the traditional analog video cable is still used for transmission, it is called the second generation semi-analog and semi-digital local video monitoring system. The monitoring software used in this stage is basically PC single DVR software.
Since 2004, with the increase of network bandwidth and the decrease of cost, the increase of hard disk capacity and the decrease of central storage cost, and the emergence of various practical video processing technologies, video surveillance has entered the era of all-digital network. Because it directly enters the network from the camera or the network video server, it is based on the compression, transmission, storage and playback of digital video, and is managed by powerful platform software, so it is called the third generation network-wide video monitoring management system. In the third generation video surveillance system, video surveillance software is essential. Ordinary users need to use video monitoring software for daily monitoring functions, and system administrators need to use video monitoring software to comprehensively manage and maintain all software and hardware resources in the monitoring system. It is no exaggeration to say that video surveillance software is the core of the third generation video surveillance system.
Composition of video monitoring system
Based on computing technology, a multifunctional and comprehensive modern digital monitoring system is formed by using network, database and multimedia technology, audio-visual technology, modern communication technology and automatic control technology. First of all, the design should ensure the advanced nature of digital monitoring system; However, the hardware and software of the system should be configured in the principle of economy, practicality, rationality and reliability. At the same time, the hardware and software of the system configuration must be modular and open structure, so that the monitoring system can expand and enhance the capacity and function of the whole system in the future. Effectively ensure the dynamic and advanced nature of the intelligent management system of the First Affiliated Hospital of Medical College, and keep the comprehensive level of the system first-class. This monitoring system is prepared to adopt the most advanced embedded network digital hard disk video recording system, video matrix and TV wall in China.
The schematic diagram of the video monitoring system is as follows:
system composition
The alarm system of monitoring system consists of camera (sometimes pickup and alarm detector), transmission, control, display and recording. Each part contains more specific equipment or components.
Camera component
The camera part is the front part of the monitoring system and the "eye" of the whole system. It is arranged in a certain position of the monitored place, so that its field of vision can cover all the monitored parts. Sometimes, the area under surveillance is very large. In order to save the number of cameras and simplify the transmission system and control display system, an electric (remote control) zoom lens is installed on the camera, so that the camera can observe farther and clearer. At the same time, the camera is installed on the electric pan/tilt, which can drive the camera to rotate horizontally and vertically through the control of the controller, so that the camera can cover the angle and area. In a word, the camera, like the eyes of the whole system, turns the content it monitors into an image signal and transmits it to the monitor in the control center.
Transmission part
The transmission part is the channel of system image signal, sound signal and control signal. At present, most video surveillance systems adopt video baseband transmission mode. If the camera is far away from the control center, RF transmission or optical fiber transmission is also used. Generally, the transmission distance is relatively short, so baseband transmission mode can be adopted, that is, 75 ohm video coaxial cable. The key requirement of image signal transmission is that after the image signal passes through the transmission system, there will be no obvious noise and distortion (neither chromaticity signal nor brightness signal will produce obvious distortion), and the clarity and gray level of the original image signal (the image signal output by the camera) will not be significantly reduced.
control section
The control part is the "heart" and "brain" of the whole system, and it is the command center to realize the functions of the whole system. The control part is mainly composed of the main console (some systems have auxiliary consoles). The main functions in the main console include: video signal amplification and distribution, image signal correction and compensation, image signal switching, image signal recording, etc. Remote control camera, electric zoom lens, tripod head, etc. Conduct comprehensive and meticulous monitoring or tracking monitoring of monitoring sites; Deploy and disarm the system defense zone. When there is illegal intrusion in the front-end defense zone, the alarm signal is transmitted to the main console, which can display the alarm defense zone, linkage alarm, flashing lights, front-end lights, video recorders and other equipment. Select the number of hard disk video recorders according to the risk level of the system and the number of key places in the region.
Video recording part
The video recording system adopts Hikvar DVR hard disk recorder, and adopts advanced digital multimedia technology, computer image processing technology and high-speed network technology to fully realize the security function of digital monitoring in the hospital. The specific functions are as follows:
Advanced digital compression technology: adopting the most advanced compression technology in the industry at present, the adaptive recording mode with adjustable video frame rate and variable bit rate in MPEG mode greatly improves the compression rate on the premise of ensuring image quality.
Multi-screen display: 1, 4, 9, 16, 32 screen segmentation monitoring modes can be selected at will, and the full screen can be enlarged, and the segmentation mode can be identified by the system intelligently.
Cycle video recording function: remind when the hard disk is full, and then automatically replace the earliest video file to realize cycle video recording.
Character superposition function: the information of monitoring points can be superimposed on each video, and the characters can be automatically adjusted to facilitate query and control.
Alarm pre-recording function: When the video alarm is triggered, you can pre-record the content 5 seconds before the trigger to make the video content complete.
Video alarm function: dynamically monitor the alarm video, and each video picture can be set with two alarm partitions with the same sensitivity, which can accurately trigger the alarm and adjust the sensitivity. Alarm triggers the start of video recording, which can set the duration of video recording and make rational use of hard disk space. It also has the functions of alarm linkage camera power supply, lighting and so on.
System self-check function: When the video source is lost, the system will automatically give an alarm.
System locking function: in the case of no operation, the system will automatically lock after a set time, and all operations will be invalid. The operation cannot continue until the password is re-entered.
Hard disk space prompt: indicates the occupation of all hard disk resources.
Video management function: it has the functions of continuous video recording, manual video recording, dynamic alarm video recording and sensor alarm video recording at any control point. You can preset a week's video template, which is convenient and accurate.
Automatic locking function: automatic locking of alarm files. When the hard disk is full, the unlocked files are deleted by time, and if they are all locked files, they are deleted by time.
Timing video recording function: you can set the video and audio code stream and video quality of each video, automatically record the video in a specified time period, start and close the video at a fixed time, and realize the function of automatically starting the surveillance video unattended.
Alarm linkage function: it can configure the same number of alarm input/output as video input, and link camera power supply, lighting and so on. And can make voice call alarm or GSM mobile phone short message alarm through telephone line.
Automatic alarm switching: the system will automatically switch the screen after the alarm. If an alarm switches to a single screen, if multiple alarms switch to multiple screens, the alarm information will be superimposed.
Image capture and printing: You can save a single frame image as a BMP file, and you can print the captured image for backup at any time.
Remote image transmission: the image can be transmitted to the superior supervision unit remotely through telephone line, DDN, E 1, LAN and other networking methods.
Network control function: applicable to any existing network (LAN, DDN, E 1, PSTN telephone network, etc.). ) transmit the audio and video signals of the monitoring place to ensure the transmission speed and quality. If necessary, it can authorize the control of the pan-tilt lens. Extensible multi-level control, supporting multi-server and multi-client. You can set the access rights of network clients, and each client can connect to 16 servers at the same time, which supports simultaneous transmission of four screens.
Video playback function: 25 frames per second per channel, which can be extended to full screen, supports four-picture playback, and adopts forward/reverse playback, fast playback/slow playback, fast forward/reverse playback, single-frame playback and multi-file continuous playback.
Local amplification function: a local image of the playback screen can be dynamically or statically amplified to facilitate evidence collection.
Playback processing function: Playback video can be softened, sharpened and reversed, which is convenient for evidence collection.
Video retrieval function: search by file, date, time, monitoring point and storage letter.
Video segmentation and merging: a long video file can be divided into useful parts as needed, which is convenient for effectively using video backup space and burning CDs; Or combine several short and effective video files into one video file, which is convenient for forensic management and CD burning.
Password protection function: protect system settings through password authorization to prevent unauthorized people from modifying the system.
Video backup function: Support multiple backup methods (hot-swappable hard disk, CD-RW burning disk, server, U disk, etc. ).
Multi-task work at the same time: monitoring, video recording, playback and remote network transmission can be carried out at the same time without affecting each other.
China security industry network www.21CSP.com.cn.