The traditional fixed-point car video surveillance only saves the video of the vehicle. In the 2G environment (GPRS/EDGE/CDMA), some manufacturers try to carry out instant transmission of pictures and videos. The image network transmission has a low occupancy rate of the network. Generally, the photo network can be transmitted back to the center in about 10 seconds; the video network transmission has higher requirements on the network, and the 2G network environment can only transmit video images with a low frame rate.
With the continuous popularization of 3G networks, in the 3G network environment, the network bandwidth is multiplied, which can meet the video data transmission requirements of high frame rate and high image quality. The original video-based surveillance solution based on video is gradually becoming more systematic, networked and platform-oriented. Due to the mobility of the vehicle, the user's need for remote video browsing of the vehicle, GPS positioning of the vehicle, and interaction of the vehicle terminal with the platform data is particularly urgent. The following is a brief discussion on the technical development direction of vehicle video surveillance system level solutions.
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First, the status quo and demand analysis of vehicle video surveillance system level solutions
1. Wireless network adaptability needs
There is a significant difference between the car wireless networked video surveillance system and the traditional fixed-point video surveillance:
1) The IP address of the terminal is not fixed and there is a firewall restriction; the IP address assigned by the operator to the wireless terminal may be replaced at any time, and the firewall is restricted, and some ports are closed;
2) The network bandwidth fluctuates greatly. The number of users in the wireless network, the geographical difference and the degree of network optimization affect the future quality. The network bandwidth changes in real time, and may even decrease to zero instantaneously. This requires the car video terminal to adapt to this network. Mode of bandwidth change;
3) Real-time motion of the vehicle terminal, the base station switches frequently, and the motion also causes the undeterminability of the video wireless network transmission. In order to improve the effect of car video wireless network transmission, it is necessary to improve the video encoding algorithm and network transmission protocol according to the above characteristics.
2. Data multi-level management requirements
The core requirement of a large-scale video surveillance system is that it can achieve multi-level management. The car video surveillance system should have the following functions:
1) Rights allocation management, for security reasons, it is necessary to classify users to have different rights and assign different tasks;
2) Video streaming media forwarding technology, the video transmitted from the wireless network to the center should be distributed to different users to meet the requirements of multiple users simultaneously browsing one channel of video;
3) System expansion performance, the system should consider the requirements for future capacity expansion after the number of users increases. On the basis of not changing the system topology, only the number of forwarding servers can be increased to perform system expansion.
3. Intelligent traffic management needs
Intelligent Transportation System (ITS) is a real-time, accurate and efficient integrated transportation that integrates a variety of advanced electronic technologies into the entire transportation management system. And management system.
As an organic component of intelligent transportation system, the vehicle video surveillance system can realize the following functions: 1) Vehicle GPS positioning information management, vehicle video monitoring terminal can transmit GPS satellite positioning information to the management center in real time; 2) Vehicle information real-time upload, vehicle video terminal The vehicle status (such as engine speed and other information) of the vehicle is transmitted to the management center in real time; 3) the data interaction function, in addition to the vehicle video network transmission, the 3G wireless network can also realize the sound, text, picture and other information. Interaction; 4) Other functions, intelligent traffic management has a strong demand for real-time vehicle passenger flow statistics, and the management center can have a general understanding of the number of people in the vehicle through real-time video browsing.
4. Advertising entertainment video delivery requirements
Advertising and entertainment can obtain certain benefits for car owners. In today's fierce competition in the domestic vehicle advertising industry, personalized car advertising services have become the general direction of car advertising development. The main needs of advertisers are: 1) Instantly update car advertising data, 3G network can meet the needs of advertisers to update car advertising in real time; 2) Advertising data feedback, advertisers need to conduct statistical analysis on the number of daily advertising, this is It is required that the vehicle terminal can accumulate the amount of advertisement play and interact with the center; 3) the data interaction function, while the advertisement is being served, the system should have the data interaction function of issuing announcement, weather forecast, road information and the like.
Second, system level solution analysis
1. Car video surveillance system structure
The vehicle video surveillance system consists of three parts: the vehicle terminal, the wireless network transmission subsystem, and the central management platform.
(1) Vehicle-mounted terminals (ie, vehicle-mounted DVRs), in addition to traditional video functions, should also have: GPS satellite positioning, 3G wireless network transmission, multimedia advertising entertainment video broadcasting and other functions.
(2) The wireless network transmission subsystem, the system can perform real-time wireless network transmission of data by means of the operator's 3G network system.
(3) The central management platform manages the system in a unified manner, assigns the rights of users and terminals, manages the streaming media forwarding of video data, and interactive functions of data information.
2. Introduction to the function of car video surveillance system
(1) Video live browsing
Real-time browsing of video images uploaded by the vehicle terminal, and adjustment and management of parameters such as resolution, code stream, frame rate, and image quality of the video image.
(II) Alarm processing The emergency alarm in the vehicle video surveillance system is a major point. After the vehicle terminal issues an alarm signal, the client software should immediately pop up the video image inside and outside the vehicle and make an audible alarm prompt. In addition, the system should also have alarm functions such as equipment failure alarm, overspeed alarm, blocking alarm, and cross-border alarm.
(3) Interactive management of data
The vehicle terminal and the central management platform can exchange information such as sound, video, picture, text, etc., to meet the user's demand for advertising and entertainment data interaction.
(4) Vehicle dispatch management
The monitoring center performs positioning and dispatch management on the vehicle, displays the geographical location information of the vehicle on the large screen of the monitoring center, and performs reasonable scheduling management according to the road condition of the vehicle location.
(5), data retrieval and analysis
The system can trace and analyze historical data, such as historical video recording retrieval and playback, GPS positioning track playback, and alarm data retrieval analysis.
3. Key technical features of vehicle video surveillance system
(1) Wireless video firewall penetration technology
In order to break through the restrictions on the wireless network of operators, the system should support the firewall penetration function. The firewall penetration technology is similar to the VPN technology. The vehicle terminal adopts the active connection mode for network connection, that is, establish a constant connection between the vehicle terminal and the central server. The path, usually transmits the heartbeat packet and GPS positioning information; when the video needs to be transmitted, the client extracts the video stream to the vehicle terminal through the forwarding server.
(2) Video streaming low bandwidth wireless network transmission technology
Video wireless low bandwidth wireless transmission technologies include the following:
(1) Adopting a coding algorithm with high compression efficiency, the H.264 compression algorithm is mainly used at present;
(2) The video stream transmission can adapt to the change of the wireless network bandwidth, and timely adjust the video transmission frame rate and the code stream;
(3) In order to ensure the security of video information, the operator's private network can be used for data transmission, such as China Telecom's VPDN network, China Mobile and China Unicom's APN network.
(3) Streaming media forwarding technology
Streaming media forwarding technology diagram
Due to the limitation of the uplink bandwidth of the wireless network, in order to meet the monitoring center or other remote customers for video access to the vehicle terminal at the same time, the monitoring center should configure the streaming media forwarding server. The video access to the vehicle terminal is all forwarded through the streaming media forwarding server, so that the video service of the vehicle terminal only occupies one channel. Streaming media forwarding technology can alleviate network bandwidth tension, improve the efficiency of responding to access, and exchange for higher bandwidth utilization with minimal time.
(4) Multi-server load balancing technology
There is a large amount of data interaction between the monitoring center and the vehicle terminal. GPS positioning information needs to occupy a large amount of database storage space. When the vehicle exceeds a certain number, one server cannot meet the system management requirements, and the system should support multiple servers to balance the load. System load balancing means that multiple servers are processed in parallel in a symmetric manner. Each server has an equivalent status and can provide services independently without the assistance of other servers. Multi-server load balancing technology also provides complete system seamless expansion. s solution.
(5) Choice of 3G video wireless network transmission system
The video network transmission mainly uses the 3G network uplink, and the following describes the uplink rates of the three different 3G network standards.
In addition, the local network coverage should be fully considered when using the wireless network standard.
Today, with the rapid development of electronic technology, we can foresee that in the near future, the vehicle video surveillance system will be an important component of intelligent transportation, providing a strong guarantee for vehicle dispatch management, driving safety, and improving vehicle utilization.
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