Detailed analysis of the technical points of large-scale video surveillance systems

With the popularity of broadband networks and the increasing demand for improved management levels by industry management departments, urban public security, transportation, finance, environmental protection, power, medical, education and other management departments have also demanded large-scale networked security and video surveillance platforms within the city. In the past two years, there has been a substantial increase, especially in the areas of urban public security and finance.

In the field of urban public security, the public security department is vigorously carrying out the construction of demonstration cities for strengthening the police with science and technology. The first 22 cities have started to implement urban security monitoring systems. Both cities and 1642 counties need network-based public safety and image monitoring systems.

In the financial field, in the past few years, major domestic state-owned banks and commercial banks have completed the construction of a large number of grassroots digital monitoring systems in accordance with the requirements of the People's Bank of China and the Ministry of Public Security for the digital reconstruction of bank image monitoring systems. Renovation work has also begun to carry out various network monitoring and management system transformation pilot work.

With the maturity of network transmission technology and image encoding and decoding technology, major breakthroughs have been made to meet the needs of customers in these emerging industries, and large-scale video surveillance systems are rapidly being built across the country.

1. Characteristics of large-scale monitoring system
With the construction of urban security system and industrial security system, we can see that these large-scale monitoring systems have some common characteristics:

1. Take the platform as the core, and the network as the link. The scale and planning of our current security system has already been a little daunting, or a bit daunting for users. How to monitor the images collected by a large number of cameras? How to manage a large number of codec devices? How to coordinate and manage a large number of back-end servers? Manpower cannot solve the management problems of large-scale monitoring systems, so the need to create a management platform is very urgent. A good management platform can put all cameras into management, all alarm points into management, all codec equipment into management, and all background servers into management, so that the entire system can run smoothly.

The premise of using the platform as the core to manage the entire monitoring system is to have a network with sufficient bandwidth (or enough bandwidth that can meet the requirements after management) to connect these devices and servers. Without a network, everything is empty talk.

2. Access to multiple different devices to achieve interconnection. Due to the historical situation of the security industry (independent small-scale applications mainly), there are many manufacturers of equipment, and each manufacturer has its own set of codecs and The practice of network transmission. This situation is very detrimental to the formation of large networks. But because of this status quo, we require our large-scale monitoring system platform to be able to access equipment from multiple manufacturers. One protects the user's original investment; the two provide a solution when the user reduces investment in the construction of the new system.

It now appears that the large monitoring systems that have been built and are under construction have made a lot of efforts in this regard, and have been connected to the video codec equipment of domestic mainstream manufacturers, and basically achieved the equipment manufacturers and models on the user side. Transparency.

3. The combination of security and business applications is getting closer and closer Security systems, as a specialized business of security (defense) systems, have always maintained a certain distance from other applications in the industry. However, with the deepening of network monitoring and the refinement of the management level, more and more requirements show that the security system needs to be more closely integrated with other business applications in the industry. Here are some simple examples: Internet cafe monitoring.

Internet cafes have typical industry characteristics. At the business level, the operators of Internet cafes pay attention to the operation status of Internet cafes, while public security departments and industrial and commercial administrations pay attention to whether the Internet cafes operate illegally. Therefore, for the video surveillance of Internet cafes, these two requirements are different. From a regulatory point of view, the general security monitoring system should meet certain requirements, and from the perspective of the operator, the ordinary security monitoring system obviously cannot meet his needs (and will increase his investment). Therefore, how to integrate the security system with the business system of Internet cafes to reduce investment and increase application efficiency is what our security system needs to consider. Only after solving such problems, our security system is welcomed by everyone. Thus helping customers succeed.

2. Technical points of large-scale monitoring system

In response to these characteristics, we can analyze the technical points of the large-scale video surveillance system:

1. The platform itself 1.1. Centralized management
Centralized management is reflected in a system managed by a central management and control server. Any system configuration changes and new unit additions are unifiedly authenticated, allocated, and scheduled by this central management server to ensure system consistency and availability. Security, and make each unit in the access system get timely and consistent information and instructions. The other servers in the system are unified by the central management server for load distribution. When the server changes, the central management server performs load transfer in time to achieve a reasonable distribution and balance of system resources. Centralized management is mainly reflected in that the system administrator can manage all the devices in the system as long as he is at his desk, and can also manage the servers and client units in the system without standing in front of any managed objects. Centralized management makes the system simple in architecture, reliable in system, easy to access client units, and convenient for authentication and authority management. Requests with control contention can be handled by a unified strategy and ensure the consistency of information.

Centralized management is also reflected in a management system such as a multi-level management of the center of the organization. The center establishes the main control center domain, with a central control server, and the subordinate establishes a sub-center domain, with a sub-center control server, and the instructions of the superior center. It can be sent to the subordinate center, and the information and requests of the subordinate center can also be submitted to the superordinate center for centralized release, and the users are managed according to a unified organization to realize the management of multiple subordinate areas. The system arbitrates and grants the interconnection of the two domains.

1.2. Distributed Services
Since a server cannot afford too many device accesses, to ensure a large number of concurrent accesses, multiple servers can be used to provide distributed services, and different access types must also be processed by separate servers. There are multiple application servers in a domain, allowing application servers to be dynamically increased or decreased. When the corresponding server is connected to the central control server, the server becomes available. The central control server coordinates the load between the servers (DVR access distribution) according to a certain strategy. The system allows dynamic increase or decrease of servers. If a server is disconnected, its load is automatically distributed to other active servers.

When the central control server fails, the application server keeps working. After the failure is resolved, the application server reports the current status of the DVR device and the client's access status to the control server when it is connected to the control server.

When the client requests system access, it will get the connection information of the central control server, automatically connect to the management server of the device to be accessed, and submit the access request to be made.

1.3. Hierarchical storage
It consists of multi-domain storage and front-end storage. Each domain manages its own equipment. There are multiple storage servers in a domain to balance the load of the equipment and store data resources under a unified path. The unified directory access protocol is used here. Therefore, different storage servers have the same path when accessing the same resource, thereby achieving the purpose of central storage. Secondly, local storage is also provided on the front-end device. The video is stored locally, mainly to achieve the purpose of continuous storage when the network is disconnected, and different strategies can be used to store the necessary and long-term data in the center. Store short-term comprehensive video data.

1.4. Media data forwarding
Due to the large amount of repetitiveness of video surveillance, for client access, the system uses a forwarding server-based transmission method to distribute real-time video, and isolates the device from the client network segment through multiple network cards, and the device network segment uses a secure TCP Connection, which can avoid the conflict between the two types of network segments, ensure the integrity of the data source, and increase the actual bandwidth of the server network.

For historical video viewing on the DVR, the video data is transferred to the user's request through the streaming media on-demand server. The system transmits based on TCP to ensure the integrity of the video data. In response to a large number of video viewing requests, the server has also made a cache storage and hit strategy, which greatly reduces the repeated requests to the DVR for the request to view the same video, and also ensures the timeliness of the data obtained by the client.

1.5. System scalability
Adopt the distributed service of the system, and realize the processing of dynamic service increase and decrease, and realize the dynamic extension of the system;

Second, the use of different types of service separation and service registration / deregistration mechanisms have enabled the system to achieve dynamic scalability.

2. Device access 2.1. Unified access protocol
To connect the equipment of different manufacturers to a large-scale monitoring system, the equipment must communicate in accordance with the system's equipment access protocol. Only when all the equipment in the entire system speak the same language can the entire system be interconnected. The purpose of interworking.

Therefore, defining a universal and extensible device access protocol is an important technical task for large-scale monitoring systems.

2.2. Provide video development kit
Our unified communication protocol does not mean that all the problems of system interconnection are solved. Due to various reasons, there are many differences in the audio and video data encoding formats of various manufacturers, and each manufacturer is required to follow a unified encoding Format, unified data encapsulation format to output audio and video data is obviously a bit too demanding. Therefore, it is better to decode the data encoded by the devices of different manufacturers with the decoding library (decoding device) provided by the manufacturer.

Therefore, if you want to connect the device to a large-scale monitoring system, the device manufacturer needs to provide a video development kit.

3. Middleware technology The characteristics of the industry are various, and the requirements of customers are very different. It will be a trend in the future to integrate the security system into other business application systems. Therefore, the management platform based on our large-scale monitoring system needs to be a very open platform that can provide various development interfaces: input, output, intermediate control, etc. ,

Therefore, building the basic platform of the security system into a middleware platform is a better solution.

Provide centralized management, device access, media forwarding, centralized storage, electronic map service, alarm access, etc. on this middleware platform.