The recent large metropolitan area hot video monitoring system construction, some inter-city remote monitoring network is also in the pipeline. On the surface, the direct cause is video monitoring of successful application in the detection process of the bombings in London; In essence, is to social public safety monitoring surface (video surveillance system coverage) put forward more requirements. At the same time, also is the video surveillance technology matures, increasingly widely used. Camera technology to achieve a high level, sensitivity, resolution, reliability, can satisfy the most demand of security systems, optical fiber communication has realized the long-distance video baseband signal transmission, greatly expand the coverage of video surveillance system; Image compression technology and network environment and make it possible to remote monitoring. Therefore, when we build a new system of public security, large video surveillance network become the first, or even the only option.
Here's the "big" has two meanings: one is a large range of system monitoring, image signal transmission distance is long, the second is the camera is big enough system monitory point. Is now in the planning of some systems are covered the whole city, more than ten thousand cameras video system, its scale is far beyond the past some of the large video monitoring system is established. Quantitative change causes qualitative change, although the technology that make up the system link hasn't changed, such a system, its design goal, what is the main function, how to use, operation and management; In the face of such a large number of image information, how to get to the observation, analysis, storage and sharing, is something we never experience new concept. All things "is set, BuYuZeFei", security and technical personnel, managers in an optimistic for this good opportunity, first to answer these questions clearly. Here are some of the views of author and be discussed.
The system design goals
Planning any system, the first to clear requirements. In theory, safety requirement is to reduce risk and needs to take measures; Frankly speaking, is to set up a system to do, to achieve what purpose. Meet demand, realize the goal of security is the system design goal, it is managers (investors) will and desire, also is limited by the factors of technology, policy and capital. On large video monitoring system design goal is to adhere to is a clear problem, but it is not. People tend to London bombings or some through access to video data detection of the case example as the target of the construction of the monitoring system. Obviously, this is not a comprehensive, real demand, it does not produce a complete, reasonable system design targets. Construction of a security system, especially the large video monitoring system, the primary objective should be to prevent the occurrence of the event, reduce the loss caused by the incident, is by no means merely to forensics work after the event. Later analysis can only is a part of demand, one of the design goals.
Security is to set up a (relatively) predictable environment, to ensure (activities) against losses. Complete security system must have warning function, should have emergency response capability. Therefore, large safety video monitoring system of basic design goal should include:
The system of emergency response ability
Hereinafter referred to as "response" system, is the speed of the system of abnormal situation, to measure in time. City video surveillance system is mainly to emergencies (group, malignant, disasters, etc.) of the response, from the event or a clear precursor to make accurate judgment by the monitoring center of the image of the time. It involves the system coverage, the workings of a system and real-time monitoring, etc. In video monitoring system planning, shall be clearly put forward the system regional monitoring center of the response time and the response time of the monitoring center city.
The response capabilities of the system
Ability to respond is to reflect system ChuJing ability. Security system should be able to effectively prevent the occurrence of the event (inhibition in the bud), control the situation, avoid and reduce the loss and the occurrence of secondary disasters. System response time is used to measure, it said from the system response to the reaction force on the scene. To ensure the effectiveness of reaction, the system has ability to cope with personnel and equipment and the layout, configuration, make corresponding provisions.
The integrity of image information
Said the system of collection and storage of image information ability, including image quality, the monitoring area coverage, image recording and the content of the length of time, etc., can with specific technical indicators, space and time to measure. Video monitoring system as a kind of image, this is the most can reflect its technology level evaluation index. In the system planning must put forward reasonable design targets.
The integrity of the image information is not only the guarantee of system response ability and system on the basis of evidence collection work. The design goal was primarily determined by technology and equipment, and therefore subject to the conditions of equipment technical ability. In system planning, according to security requirements practically reasonable technology integration and the equipment selection, in order to achieve the best effect.
Large video monitoring system shall also have some other design goals, including integrated on an integrated platform of other technology systems (alarm, patrol, positioning, communication, etc.) should have corresponding design goal, here is not here.
Construction of large-scale video surveillance system from requirement analysis, puts forward reasonable design target, which can prevent the system can achieve the effect of countless unclear, heart, and can avoid the high expectations and unrealistic demands. Thereby, achieve system design target, the final effect evaluation is unfounded. Determine the system design goal is to implement target management system construction before problem. Security system (engineering) must implement target management, it can prevent the system from subjectivity and blindness of (engineering) design, but also ensure (project) quality management system and acceptance of the scientific, objective and impartiality.
The function of the system
In the clear after the basic needs of the system and the design goal, can the function of the planning system, or through the system Settings will function design goal. System can realize the function and system structure, technology integration, selection of key equipment, as well as the system's operation and management system have a close relationship. So say planning system function is the core of the system design. For large metropolitan area the size of the video monitoring system should have the following basic functions:
Dynamic monitoring
Any video real-time monitoring system should be the main function. But for a large system, will be a lot of images collected real-time monitoring is clearly wrong. System should spread this functionality to the front of the monitoring center. It is can get high quality image, 2 it is abnormal situation can be found on the fast response. System monitoring center has the function of the dynamic monitoring of the so-called "dynamic monitoring" is not found the abnormal situation by directly from the image for the purpose, but the global macro dynamic monitoring. Its demand for the real time and image quality than low real-time monitoring. System monitoring center of the functional requirement it has all the images of system resources, can the initiative to obtain any image. Can be used in a low rate of channel transmission format of image information.
Independently to generate enhanced security system
Based on the system of all image resources, according to the different security requirements to constitute a different size, different forms of enhanced security monitoring system. At a certain point such as cities or major activities of the region, but the image of the system about the resources together constitute a temporary private monitoring subsystem; Such as the system of image according to the specific area and route of special monitoring subnet. The subsystem of the monitoring center can also be a freedom of choice, it can be for front-end equipment for all of the functions of system control, and have the highest authority, even subsystem can be completely blocked up. Enhanced security system should be enhanced image quality (than the image quality of the dynamic monitoring system), and to get the support of other security technology system.
The diversity of store image information
Image information is the basic function of video monitoring system of storage, storage mode of diversity should be one of the characteristics of large video system. Will be a lot of image information after long distance transmission of centralized storage is obviously unreasonable, but completely scattered storage in the regional monitoring center, the image retrieval and management is not convenient, and poor safety. Recommended several number (depending on the system size) image storage center, and will they form network-attached storage (NAS) system. It can reduce the pressure of the system and can realize the unified management and sharing of resources. These storage center will become the basis of analysis of the image content.
The safety management
System monitoring center of the whole system must have a (regional center) and other systems are connected to the system (the system integration of social resources) on the function of the safety management. This is a very important function, can be through a visual interface to check system front-end equipment and regional centers equipment state (boot, do you have any image signal, etc.), and can make the diagnosis for the system fault. Networked with the system for video surveillance system in the society can also judge that whether it is in normal working condition. A good safety management system can also be through the inspection of the system working log, to the operation of the system, management personnel for examination and assessment. Safety management system will improve the level of the operation of the safety system, if the system and social security system can work normally, play their role, the safety level of urban nature is improved.
Open integrated management platform
For safety purpose to establish a large-scale video surveillance system must be an open platform for the integrated management, is a part of the city's public security system. It should be with emergency center city and other urban management system to achieve resource sharing, and provide them with the necessary technical support. Therefore, the system has both specificity, want to open again. It is important to note that in the system planning.
To sum up, city large video monitoring system with the above basic functions will be an information center, administrative center, emergency command center, is the city's public security comprehensive management platform.
Pay attention to the processing of a few technical problems
On television as the basic technology of video monitoring have reached a very high level, the traditional analog video system has been very mature, ancillary products, interface specification, there are a lot of successful cases. The development of digital video technology bring some new solutions for monitoring and control system, realized the function of many of the simulation system can not reach and applications, and some new concepts. But at the moment, the sex and maturity product is not high, has not been unified technical standards and evaluation methods. Digitalization is the only way for the development of video surveillance technology, but this is not a simple product, but the evolution process of mutual combination and mutual fusion. So, when making large video monitoring system planning must pay attention to the following questions:
The combination of analog and digital
Obviously, combine two basic modes, simulated way of real-time, high image quality (resolution and continuity), and in the local area within the scope of the characteristics of low cost, combined with the digital way in the image recording, remote transmission, and the advantage of network management is one of the best ideas. Should not be one-sided pursuit of "digital", more do not have a "digital is advanced" misconceptions.
The combination of analog and digital can be: of the simulation system through digital networks constitute a large system; Simulation of real-time monitoring and digital image recording; High image quality simulation system with the Numbers of the general monitoring system and so on a variety of ways. For the specific environmental conditions and to select the application purpose.
The compromise in the image quality and the system overhead
It must be pointed out: at present, the video monitoring system of the digital process is to cause a decline in image quality. Such as digital image formats display resolution than the analog video signal is low, it is the quality of images of sacrifice, for system resources (such as bandwidth, storage space) cost savings. This requests us in the system planning, to make a good compromise between the two. Different locations, different time, different methods of image processing, image quality will have different requirements, each link resources of the system is also different, to balance these factors comprehensively, make a reasonable choice.
Actively adopt image content analysis technique
Transition from visual interpretation to the automatic interpretation will be the inevitable process of video monitoring system, the current technology is not mature, also limited to the application environment. But, large-scale video surveillance system must actively adopt new technologies in this field, grope for experience, clear the direction of further improvement. Because they don't change the way to extract useful image information, image information is not to come out, the advantages of monitoring is still is the traditional pattern. Actually in the aspect of image automatic interpretation has some of the available technologies and products. Such as image content analysis technology, through it is found that the agglomeration phenomenon, car, can be in a timely manner to prevent mass incidents and congestion; Found that regional traffic density is too large, can prevent stampedes; Using the characteristics of simple identification can put the specific objects of image correlation, and so on. In the current, combine visual interpretation and automatic interpretation can be a choice.
Must consider a problem deeply
In addition to the above points, there are some technical issues need to be carefully considered. The author emphasizes to deeply consider problem. Security by the increasing demand on video monitoring to too fast, so we have some unprepared, appear soon. Technically not ready, the in the mind also not ready. Technology is not everything, never is not the final solution, it is limited to supplement by other aspects. And we also didn't go to consider these problems. Small system for the trouble we can afford, big system trouble can't afford, the resulting negative impact to the video monitoring technology development and application in the future could be disastrous. So I hope can fully detailed planning, seeking truth from facts, not to rush movement type. To cherish this opportunity, through the system construction to promote video monitoring technology to a new stage, and in the field of safety produce deep change values and methodology.
