Study On Multicast Of Audio And Video Based On Distance Education System

Nowadays, education has been rapidly developing, and the conflict between teaching and studying has become even more serious because of the relatively lack of education resources. Fortunately, the development of networking multimedia technology and the wide usage of Internet have the potential to resolve this problem, and the distant education system with multimedia has become applicable in real application.At present, there are many kinds of distance education systems, but each of them has some shortcomings. Some systems lack of interactive between teachers and students, meanwhile, other systems cannot support distance experiment. Even more, all the systems demand high band-width supporting. To design a perfect system, in the M.S. dissertation, the potential demand for distant education is analyzed from a few aspects, and some kinds of typical distant education system design are investigated, in which their advantages and shortcomings are illustrated, too. On the basis of comparison and synthesis, a new type of distant education system structure is then built up, and modules and their functions for the system are further introduced. This system solves above problems.In the front part of the paper, theories and technologies used by designing multimedia distant education system are introduced. Then theory and new method for capturing multimedia are studied, and graph quality captured by WDM device is better than that captured by previous VFW device.Furthermore, technology of data transmission through network is studied. The vast amount of data of multimedia messages adds heavily burden to Internet, and often causes the routing-jam with the even more increasing of Internet users, which has become the bottleneck in real application. In order to effectively solve this problem, the selection for communication protocols is of significant importance. System based on H.323 takes up broad band-width, and it needs support of broad-band network. So, it's not practicable . According to features of the system, the IP multicast technique is employed. Because Internet Group Management Protocol (IGMP) is used, same packet is transmitted at one time, this reduces greatly band-width. A new Socket communication protocol was proposed to realize transparent data exchange. Because of not using TCP/IP to transmit control message, it effectively economizes the band-width. In the receiving terminal , double buffers is used to decrease affect to quality of system caused by variable band-width. Finally, by using the technology of DirectShow and Winsock , two network transform filters are realized.