Design For Virtual Data Gateway Of Network Video Surveillance System

Under the propulsion of safety city construction, network video surveillance systems have been an important technology in the maintenance of public order. However, multi-system integration has become an inevitable trend because of the coverage area and business functionality of early established systems cannot satisfy the cross-industry and transregional demands of security and protection any more. But due to historical reasons, the protocols and specifications of different vendors’ systems are non-uniform, which hinders the development of the industry seriously. Therefore, solving the system compatibility problem to achieve interoperability between devices from different vendors is significant for enhancing the depth and breadth of network video surveillance systems.In order to solve the above problem, a virtual data gateway software which is used to connect different systems has been researched and developed by this thesis. The software extracts a set of device call interfaces according to business requirement, and accesses dynamic link libraries which encapsulate the third party SDK or the general standard protocols to implement the conversion of communication protocols and video/audio streams with different format. Meanwhile, this thesis developed a message asynchronous processing mechanism based on scalable thread pools to deal with the great deal of interactive messages. The mechanism improves the efficiency of resource utilization and message processing through creating or destroying thread dynamically according to the quantity of associated devices and sharing message queues and semaphore to achieve interthread communications. Furthermore, in view of the problem that it is easy to make several gateways overload by associating gateways with devices in manual mode under large-scale real-time transcoding, this thesis designed an adaptive associating solution based on load balancing strategy. The solution reduces gateway’s load through putting overtime idle devices into sleeping state, and adopts device migration algorithm to realize load transfer indirectly, which releases the load unbalanced degree of the gateway cluster.Up to now, the virtual data gateway has accessed products from several vendors and general standard protocols successfully, which accomplishes the interconnection between different network video surveillance systems and reaches the design goal. The test results indicated that compared with manual mode, the adaptive associating solution shortens live start average response time significantly, which improves the overall performance of the system response effectively.