| Currently video surveillance technology has been in the developing period of digitalization.It has an explosive advancement since IP netcam arises, so research about IP camera has become one of the hottest technology of video surveillance. The key technology is how to compand audio and video data effectively and how to transmit in high quality.The research emphasis of the dissertation is about speech codec, network communication and camera control. So firstly a software system framework of server is constructed on the base of DSP/BIOS? ,which is a simple embedded real-time operation system ,and RF5(Reference Framework Version5), which both are free provided by Texas Instruments Incorporated .In the system, video and audio codec are encapsulated with eXpress XDAIS in order to reuse .Secondly implements the speech codec, which uses two type of speech standard: G711 and G723.1, thinking over network transmission and speech quality. The emphasis is implementation and optimization of G723.1 based on the C source code provided by ITU-T on DSP, while the implementation of G.711 is only in assemble language on DSP.In PC client, the speech codec implements through ActiveX control which is popular in Windows programming.Thirdly discusses about the network communication and system control which use NDK(Network Developer's Kit) provided by TI. Then puts forward a doable scheme about network control.Finally, present the research about PC client software in detail in the dissertation. The Client is developed in visual C++ 6.0 in Windows 2000/XP, and network communication takes use of Wonsock2.0. The DirectShow is used to play video,which used corresponding filter with different encoded video stream. Simultaneously DirectSound is used to play and control audio stream.The camera has passed the test in Windows2000/XP OS in LAN. It can realize digital audio/video communication over IP in variable frame rate and resolution and meet actual application need preferably. |
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