Design And Implementation, Based Wireless Mobile Technology, Interactive Multimedia E-leaning System

With the development of wireless mobile technology and E-learning technology, more and more people begin to study through the Internet with wireless mobile devices. Compared with PC, wireless mobile devices like mobile have such shortcomings like weak processing ability, tiny display screen, etc. Furthermore, compared with fixed networks, wireless networks have such characters like narrow bandwidth, instability, and high bit error rate.To solve above problems, domestic and overseas scholars do many research. Aiming at narrow bandwidth of wireless network and weak processing ability of mobile device, they develop video and audio codecs that consume less CPU ability and have higher efficiency. Aiming at instable network and high bit error rate, they develop network protocols that have better performance.Making use of these research achievements, we capture teacher's video and audio on PC, compress them and send to wireless mobile devices. At the same time, we capture student's audio on mobile, compress it and send back to teacher. In this way, we finish interaction procedure between teacher and student via multimedia way. In E-learning area, except video and audio, one more important information source is teacher's teaching material. Usually teacher gives a class with PC. Many ways are used to transmit teaching material on PC to student's wireless mobile devices. In order to support all kinds of teaching material, we process it as screen video stream. Reasearch about it is relatively little and not perfect.In order to compress screen video, we develop a screen video codec, which was based on MPEG-4 framework and named with SVMX. SVMX processes correspondingly according to screen's characters, therefore, we can get a high compression rate and low CPU utilization. In order to run on wireless mobile devices, we develop algorithm named with SVMX for mobile. Firstly, to display screen on PC (1024*768) clearer on mobile (320*240), we zoom out screen on PC with linear interpolation. Secondly, to overcome the bottleneck of narrow bandwidth and transmit power use, we improve the JPEG algorithm in SVMX, adjust parameters of QL and VBS. Therefore, we get a self-adaptive image encode way. Finally, we improve the motion prediction and compensation technology in SVMX, get better data compression rate.Aiming at the characters of instable wireless network and high bit error rate, we transmit video/audio via RTP protocol. Making use of statistical information with RTP, we solve such problems like delay and jitter, self-adaptive bandwidth and lip synchronization under the condition of narrow bandwidth, asymmetric channels.