| Today, with the Development of communications technology, network video conferencing more and more people's extensive attention, at present with the continuous improvement of network bandwidth and processing power of PC, the continuous improvement for the video conferencing system provides the practical basis for the necessary hardware. Streaming media technology has emerged and has been a rapid development, and streaming media business has also been considered to be the future of the industry's high-speed broadband network, one of the mainstream business. We can expect video conferencing system will become the mainstream of the development of conferencing systems. This article is based on IP networks, multimedia communications standard for reference, video, audio, and data through real-time transport protocol RTP and multicast approach to the continuous flow mode in order from the source to the destination of transmission to achieve the LAN IP video multicast conferencing systems research, the main completed IP network video conferencing system software and part of the design. In this paper, video conferencing system at the same time the Ministry of Development and status at home and abroad made a brief introduction.The video conferencing system, the introduction of C / S architecture, the text of the principles of video conferencing systems and related technology standards, one detailed analysis and the systems involved in multicast and RTP communication technologies have also conducted in-depth analysis and research, and to achieve the local video / audio capture, RTP / multicast data transmission and reception, conference management and control of user activity such as functional blocks. The system is in the realization of the difference is that previous systems used in the transmission controlling transmission mode, the server IP will be based on the user categories of users, users will be within the same network segment broadcast another video / audio data, the server is only responsible for receiving the segment of users visual / audio stream instead of sending the paragraph of the video and audio data between users. As a result of effective mitigation of network bandwidth, video conferencing system to improve the fluency. In this system, also applied the audio and video compression technology, using H.263 and H.723.1 protocol development of the corresponding module, which is essential for the transmission process to reduce network congestion and network load, etc. have very good results.Partial implementation of communication system, the main use of technology and RTP Multicast transport protocol, RTP / RTCP multimedia network applications, one of the core protocols, this article focuses on the Internet, real-time video and audio synchronization in the design and implementation, video / audio encoded bit stream using RTP / RTCP protocol package to send to realize video conferencing audio and video synchronization. Experimental results show that the transmission of images of this proposal is the continuity of good, transmission delay is small, results would be ideal. At the same time, this article is a detailed description of the RTP protocol based on the basic content of the video conferencing system introduced the overall design and development process. After tests showed a high-bandwidth wide area system can guarantee good real-time online and media synchronization, but poor or network bandwidth, the case in poor condition could not find a more reasonable principles and synchronization packet loss, causing traffic delays accumulation and inter-media such as audio and video out of sync and other issues. This article also briefly described, and RTP / RTCP protocol elements, and has been achieved through the presentation for the LAN and WAN-based video conferencing system to illustrate the RTP / RTCP protocol in the application of video conferencing systems and implementation.The system based on the realization shown to enhance the coherence of the terminal made some optimization. The first is simply to receive up to a certain destination, the data cache immediately after the broadcast of multimedia application technology, which greatly improved the traditional way before, only after the files were all downloaded before they can watch the scenes. In the streaming media technology, data compression and caching technology in solving real-time transmission of multimedia files and playback, the play contributed role.Due to large-capacity audio and video files, plus the bandwidth restrictions of objective reasons, resulting in the transfer of these documents on the Internet speed is very slow. Streaming media data compression technology enables audio and video files has become very small, very suitable for longer published on the Web audio and video files. The second terminal will be judged as to send the camera to capture the current data on whether, and on a repeat, if the repetition is not sending data, so you can save a lot of bandwidth. Was the use of multicast technology enables high-performance IP network-to-multipoint data transfer. Because multicast can effectively save network bandwidth, reduce network load, thus greatly improves the data transfer rate, but also make use of the radio transmission is small, and so lack of spending to increase non-recipients. Therefore, in real-time data transmission, multimedia conferencing, data copy, and many other aspects of gaming and simulation, multicast technology has a wide range of applications. And designed based on an analysis of video streams to repeat the frame control method using the current frame and a frame of video data on a gray screen margin to analyze the participants whether there are changes in the terminal, if there is no change then suspended in the frame video data, As a result effective to reduce the burden of server and network load.Finally papers on the operation of the system test results and shortcomings. Mainly as follows: do not take into account multi-threaded processing, so that the user if the connection has been accounted for little more than the system CPU will be a very high rate, the system will become very slow; another file transfer is not designed to function. This system is used in the WindowsXP platform VC6 and DIRECTX, JRTPLIB database development to achieve, the system's hardware components are mainly USB serial digital camera, 100 MB Ethernet, PC machines and WINDOWS2003 server. With the continuous improvement in computer processing capabilities, streaming media pressure decoding technology, continuous improvement, Gigabit Ethernet, switches, and routers, the popularity of IP-based video conferencing system has reached the requirements of professional meeting rooms, the future will prove to be the use of One of the high incidence of network applications. |
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