The Research And Realization Of Net Teaching System Based On P2P Technology

Multimedia Network teaching now begins becoming a most important teaching way besides the traditional teaching way. This new teaching way aims at that anyone can learn anything at anytime and from anywhere. Facing with the very large amount of multimedia data, many technologies should be involved in and variety of computer resources should be utilized if you want to transmit multimedia data efficiently on the internet.This thesis first analyzed the characteristic of network, and brings up a proposal based on the P2P transmission for data crossing network middleboxes. Proceed from a safety demand and the shortage of IPV4 addresses, now existed on the internet everywhere a great deal of middleboxes which including firewall equipments and network address translate equipments etc. Generally these equipments will discard all unknown packages, therefore, if introduceed no special techniques, a PC can't directly visit another which was ruled over by a middlebox. Based on the existed crossing techniques, This proposal put forward a new algorithm to process the course of P2P corssing a middlebox which may not support self loop-back mappings, thus further expanded the sphere of the P2P application.P2P is a kind of peer to peer communication technology which can utilize the computer capabilities of all the participants on the internet. This utilization accompanied with IP group cast technology used to dispatch multimedia data on the internet largely lightened the data supplier or the server's burden.This thesis secondly deeply analyzed the P2P transmission model. In this model, every PC machine may logout at any time and thus may result in pintable, so the model must be adjusted by itself instantly to adapter itself to the changes. On the other way, set another transmission path redundantly also can improve the system's robust feature.Video and audio data must be coded and compressed before they are transmitted on the internet. With the perfect performance of high compression ratio and network adaptation, H.264 proposal's issue followed with a great of interest from variety of fields especially communication field. The H.264 proposal still adopts the former hybrid code mode which include DPCM and the transformation code model, Its code way can be divided into 2 layers on the concept. VCL (Video Coding Layer) is efficiently responsible for the video contents presentation. NAL (Network Abstraction Layer) is responsible for the packaging and transmission of the data using the fitting way according to the network.As to the audio code proposal, G729 proposal, bringing about high quality of speech sounds and low algorithm delay, was widely used in a variety of fields in data communication sphere.This thesis also analyzed the functions and modules construction of a network teaching system which was satisfied by a 3 layers model designed by author. Remote control, which is one of the key functions in a network teaching system was implemented in this thesis by using the hook function provided by the windows software development kit APIs.