| Video surveillance system is an important application of television technology. The development of surveillance systems has experienced three stages on the whole: analog video surveillance systems, digital video surveillance systems and intelligent vision-based surveillance systems.The key technology of digital video surveillance systems is compression of digital video data. There are many international standards for compression of digital video data such as H.26x developed by ITU (International Telecommunications Union) and the well-known MPEG (Moving Picture Experts Group) standards and so on. H.261 and MPEG-1 are adopted in early digital video surveillance systems. The core of H.261 and MPEG-1 are discrete cosine transform and motion compensation which reduce the data capacity by exploiting the temporal and spatial redundancies due to similarity between neighbouring frames. The principle of MPEG-4 is object-based encoding, and its core is content-based scalability. Considering the fact of video surveillance systems, this paper has put forward a scheme for embedded digital video surveillance system based on MPEG-4.Digital video recoder (DVR) is the main body of the digital video surveillance system, and it consists of three modules: compression/decompression module, real-time monitoring module and system module. The hardware platform of DVR adopts 686CORE CPU board of Compulab Company, and its operating system is custom-built Linux.The compression/decompression subsystem takes charge of compression and saving of digital A/V data, and the chip adopted is VW2010 of VWEB. Hardware design of compression/decompression subsystem based-on VW2010 is discussed in chapter 3; Chaper 4 discusses three communication mechanisms between VW2010 and host: accessing internal registers, DMA and shared memory. Then, developing of the device driver of VW2010 under Linux is discussed. Specifically, this section discusses design of key data structures, outline of the device driver and algorithm of ioctl.
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