| Compared with traditional analog video devices, digital video devices have a lot of advantages, such as higher picture quality, superior data storage, and more convenient records searches. With the development of video compression technologies and disk storage technologies, digital technology is becoming the mainstream in the surveillance field. There are two kinds of digital video recorders, PC based DVRs and embedded DVRs. Embedded DVRs use embedded CPUs and embedded operating systems. Thus they have many advantages, such as shorter response time, higher reliability, and better usability. This thesis analyzed the requirement and background of DVRs, and designed a DVR that based on VxWorks operating system. The 686CORE embedded PC module is hardware platform of this DVR, and VW2010 CODEC chips which processing audio and video streaming are the key components of this DVR. Firstly, the design of the DVR's software was given, such as the layered software architecture, task decomposition and inter-task communication. And some key technologies of the software design were discussed, such as event-driven model, finite state machine model and memory pool allocation. Then the implementation of the DVR's software layers was discussed in detail, such as VxWorks BSP, the device driver of VW2010 chips. In the next chapter, the implementation of the tasks was discussed. And a systematic testing process was introduced in detail, followed by some testing cases and the testing results. Finally, the functional reliability of the system was evaluated and analyzed. With the constant progress of technology, various kinds of new demands have been brought forward. This thesis proposed some weak points and some improvement methods of the existing scheme at the end. |
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