| Along with the rapid development of network and multimedia, the transmission of multimedia stream has made great progress in recent years. Videoconference is a combination of network and multimedia, which can make people, who are in different area, free of communicating. Therefore, how to meet requirements of real-time quality, continuity, security, expansibility and maintainability is the focus of developing video conference system in the limited network resource condition.In this paper, a sort of distributed and loose-coupling videoconference based on embedded system is designed through the research of structure of video conference, multimedia stream code-decode technology, multimedia stream corresponding protocol, multicast technology. The multimedia is transported by multicast based on IP internet. Consequently, the multimedia stream is transmitted in one troop and sent once from the sender. In the following, it is sent to the members in this troop by the router.In this text, a sort of distributed and loose-coupling videoconference based on embedded system is designed. It has several functions, such as audio and video correspondence, chat, whiteboard, documentation transmission, application sharing and conference controlling and managing, which are realized through blocking program. The videoconference has four function blocks that are conference managing, au-video disposal, multimedia transfers and quality controlling of network. Conference managing block can launch a conference, start a conference, control the say-so and end a conference. Presides can control the whole process of a conference and manage other participants. Au-video disposal block implements au-video pick-up and play, au-video code and decode. Au-video disposal block is multitasking and realized based on multithreading mechanism. It gives the audio stream the upper priority to ensure fluent voice. Address to the different media streams, multimedia transfers block uses the different transmission modes. The text file and controlling information is transported by TCP protocol, however the audio and video stream is transported by RTCP/RTP/UDP protocol. This detached transmit manner can avoid the re-transmission of audio and video, alleviate the burden of network and guarantee the quality of videoconference.In this article, the design videoconference is the fusion of embedded system, communication and multimedia technology. In this way, the volume of videoconference is shortened, the running speed is quickened, the real-time disposal ability is toned up and the system expansibility is enhanced. |
