| With rapid developments of Internet and multimedia technology, the research of video and audio real-time transfer attracts lots of attentions. At the same time, video transfer rate and quality of image were highly demanded by users. Due to its high compress rate, high quality and low transfer rate, MPEG-4 becomes the main standard for multimedia compressing. Real time protocol (RTP) implemented an Synchronous control mechanism of end-to-end media streaming, which provides real-time data transfer based on the unicast or broadcast networks. Embedded system has the attributes of quick-react, multiple-task, high-stability, portable, power-save and low-cost, so it becomes more competitive in the market.After analyzing RTP protocol and Mpeg-4 standard, we studied embedded network video transfer system's architecture and its implementation, and proposed a hardware design based on double cores: embedded processor+ video codec IC, which guarantees the attribute of real-time multitask and has powerful abilities of video or audio handling and computing. At the same time, in order to make our system implement real time transfer, we studied how to apply RTP in stream multimedia transfer and how to implement a light-weight TCP/IP protocol stack that can be applied to embedded system firstly, then we finished the software design that comprise following works: transplanting LWIP ontoμC/OS-Ⅱ, transplanting livemedia library, modifying Mplayer's source code in order to match video and audio coding format.At last, by debugging and compiling, we implemented our real-time embedded network video transfer system based on RTP protocol on the platform which has a core of video coding IC NW901 and embedded processor ARM L7210. The experiments shows that our system has lower initial delay and real time stable streaming session. Even when bandwitdh becomes lower, the video plays smoothly. Moreover, the products is protable and low-cost. |
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