Technical Researches On Videoconference Based On H.323 Protocol

In this work the research on the videoconference was performed by developing a point-to-point videoconference system in LAN environment utilizing audio and video telecommunication and real-time data process technology. Firstly, the protocol standards and working principles of videoconference were investigated. Of the protocols, Protocol H.323 is mission-critical. Signaling H.225.0 was used in the communication module, and Protocol H.245 in the control module of audio and video stream. G.711 or G.723.1 Algorithm was employed to compress the audio data, meanwhile, H.261 or H.263 Algorithm was used to compress the video data. Secondly, the design resolutions of the modules of the videoconference system were described in detail together with the programming process. The system included the communication module, the record, compression, transmission and playing modules for audio, and the acquisition, compression, transmission and playing back modules for video and the image-regulating module for local video. In designing the communication module, we creatively applied the fast-start method and the tunneling mechanism to the calling process, so as to reduce the calling time and improve the efficiency. In the realization of audio transmission, the use of the RTP/RTCP protocols has ensured real-time and uninterrupted transmission of audio and video stream with no loss of packets. The developed software based on the above resolutions was tested in LAN environment of BJUT and the result show that the resolutions are practicable for the videoconference application. Lastly, we explored the technology of multi-endpoint videoconference, analyzed the basic problem of its developing and put forward my immature answer to this problem. However, in this work, we used the blending multi-endpoint mode to admit more participants in the videoconference.