中文摘要：

为解决P2P流媒体系统在异构环境下传输和共享视频数据的问题，对广泛应用于基于可扩展视频编码（SVC）的P2P流媒体系统中的等时长分片算法进行了研究，研究结果表明，该算法对SVC数据特性考虑不够充分，当网络丢包率高时可能导致视频质量严重下降。为了解决这一问题，提出了不等时长分片算法。该算法通过调整分片播放时长控制各层数据成功传输概率，优先保证重要性高的分层的正确传输。实验和仿真结果表明，与等时长分片算法相比，不等时长分片算法令分片传输时间更加稳定，且大大提高了重要性高的分层的成功传输概率，能够提升多种网络中客户端的视频质量，更加适合于府用存鼻桕网络中．

英文摘要：

The equal playback length segmentation algorithm, widely used in P2P streaming systems based on scalable video coding （SVC） , was studied to find an approach for P2P streaming systems to transmit and share video data in a helerogeneous environment. The results show that this algorithm does not consider the data characteristics of SVC adequately, and it may decrease video qualities on clients seriously when packet loss rate is high. To deal with this problem, the study proposed an unequal playback length segmentation algorithm. It adjusts the transmission success possibility of layers by changing the playback length of chunks, and guarantees the successful transmission of layers with high importance levels firstly. The proposed algorithm was evaluated by experiments and simulations and the results show that, compared with the equal playback length segmentation algorithm, the new proposed algorithm will smooth the transmission time of chunks, and increase the transmission success possibility of layers with high impor tance levels. Moreover, it performances better in different network environments and it is suitable to heterogeneous networks.