| Security Industry in China has made considerable progress since the new century. The emergence of intelligent building, intelligent community, High-tech electronic and digital network products make security industry a great boom。Network monitoring system has been widely used in every field, including government institutions, airports, railway, bank and other important units. While more and more high quality security program need clear, lifelike video synchronous monitoring system, audio monitoring field has now became a new trend of the Security Industry.Since audio join into network monitoring system, audio and video synchronization has became the key project in monitoring system. Because of the network transmission, audio and video data are not synchronous when they are transferred to customers, which dramatically decrease the performance of the system. Therefore, we are in urgent need of developing a kind of audio and video synchronization solution in the monitoring system. At present, there are many domestic and international scholars researching audio and video synchronization, and they have proposed lots of synchronization algorithm. Among them, the RTP synchronization algorithm based on the real-time transfer protocol is more suitable for this system synchronization solution. The system is composed of media server, network servicer and the client-side. According to the features of the audio and video streaming data in the transmission process, this system can be divided into several models such as acquisition, compression, sending, transmitting, receiving, decompression, synchronous playback etc. We do software and hardware designing for these modules, then make full use of RTP protocol timestamp to design a kind of audio and video synchronization algorithm referring to audio stream. This paper firstly introduces the research background and significance, and then states the development of monitoring system and situation of the synchronization technology. The paper pays more attention to the key technologies related to the topic, including audio and video compression coding technology, streaming media real-time transmission RTP protocol, and Directshow development platform, mainly analyzing their technical features. Then the paper presents the overall structure of the system and its hardware and software, then determine the best MTU value sent by audio and video data through actual test. Finally, this system will recover the original time relationship of audio and video data by secondary cache, and the introduction of synchronous control algorithm will realize the synchronization of audio and video playback. |
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