introduction
The i.Mx27 multimedia application processor is the newest member of the Freescale Semiconductor DragONBall family.
A mobile video surveillance terminal based on i.MX27 is designed, which is used in the bus video surveillance system. The video data and GPS location information collected by the terminal can be transmitted to the bus dispatching and monitoring center in real time. In the case of poor network, the video data and GPS location information can also be saved locally, and the high-speed transmission through the WIFI wireless network after the bus arrives at the station To the monitoring center.
1 The composition and function description of the bus video surveillance system
1.1 System composition
The whole system is divided into front-end vehicle monitoring system, communication line, and monitoring platform. The front-end vehicle monitoring system includes vehicle-mounted hard disk recorder, surveillance camera, monitoring head, alarm button, alarm flashing light, LCD screen, intercom headset, GPS and other communication lines. The front-end mobile transmission (EDGE / CDMA 1X) and the back-end command center Ethernet network monitoring platform include monitoring software and a series of service groups such as GIS, streaming media, database, application server, etc., and can be used in public transport branches, municipal public security bureaus, police stations, etc. as needed. The unit builds a multi-polar monitoring platform, the logical relationship of levels can be flexibly configured according to the needs, and the system has good scalability.
The structure diagram of the system composition is shown in Figure 1.
1.2 System function description
(1) Video surveillance function. The vehicle-mounted equipment supports up to 4 cameras, which can monitor the front and rear doors and the front and rear of the car respectively;
(2) GPS positioning function. The video monitoring device should obtain the current time, latitude and longitude information from the GPS device, and embed it in the recorded video file or video stream in the form of a time label (that is, subtitle mode); GPS information (1 per second) is simultaneously written to the log file, use Value-added processing in the later stage: the video files saved inside the video device correspond to this GPS log file one by one;
(3) Mass communication function. When the vehicle is located in a parking lot, station, etc. where there is a high-speed wireless network such as WIFI / WinMax, it can enter the background data transmission working mode at any time. The transmitted content includes video files and GPS logs;
(4) Real-time communication function. When the terminal is installed with GPRS / CDMA network communication module function, it can transmit real-time video data and GPS location information.
2 Mobile video surveillance terminal hardware design
The mobile video surveillance transmission terminal uses i.MX27 as the core device, and the GPS module and WIFI module are expanded to realize the collection, storage and wireless transmission functions of mobile video. At the same time, the GPS device can accurately locate the real-time location of the mobile device.
The system hardware structure diagram is shown in Figure 2.
3. Mobile video monitoring terminal software design
The terminal system uses an embedded Linux operating system to improve service reliability and system efficiency. The main flow chart of the software is shown in Figure 3.
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