| The rich-media broadcasting system is a system providing webcam video, audio and screencast video in broadcasting. There are three drawbacks in Mainstream rich-media browsing systems. First, some use general video codecs to encode screen sequence which can not satisfy the demand of high visual quality and low bitrate delivered. Although some others use more efficient screencodecs, they ask users to install additional plug-ins which is inconvenient. Second, many systems still use unscalable C/S structure, while those who use scalable P2P structure also require users to install P2P plug-ins.Due to its wide installed base and cross-platform support, Adobe Flash is a suitable platform for rich-media client. For the first problem, this thesis leverages the FLV Data Tag to encapsulate screen sequence. Then it use Alchemy C/C++ to Actionscript compiling FLV based Remote Method Invocation to Flash Player with the decoding capability of a state-of-the-art screen codec format named SJSC. According to our evaluation tests, the solution is quite feasible in terms of decoder's CPU/memory usage. A visual quality test also shows the solution can achieve a better bit rate and quality trade-off than existing Flash-based screencast solutions.For the second drawback, this thesis makes use of the P2P technology introduced in Flash Player 10.1 and use"send"and"appendBytes"API to broadcast external rich-media stream indirectly supported by Adobe Flash. We conducted evaluation assessments in Planetlab nodes to test the fesibility of this mechanism. The results show the latency of 90% data is 8~11s, packet loss rate of 95% peers is 3%~10%, peers whose control overhead below 2% is 60%~90%, peers whose average download rate below data bit rate is 39.6%~100%, P2P bandwidth gain is 82%~98%, which prove the effect of P2P technology. According to these statistics, we succeeded in developing a P2P based rich-media live broadcasting system prototype. Its continuity index is at least 99%. |
PDF Full Text Request