Peer-to-peer (P2P) swarm technologies have been shown to be very efficient for large scale content distribution systems, such as the well-known BitTorrent and eMule applications. However, these systems have been designed for generic file sharing with little consideration of media streaming support, and the user cannot start a movie playback before it is completely downloaded. The playing-as-downloading capability would be particularly useful for a downloading peer to evaluate if a movie is valuable to be downloaded, and it could also help the P2P content distribution system to locate and eliminate the polluted contents. In this paper we address this issue by introducing a new algorithm, wish driven chunk distribution (WDCD), which enables the P2P file sharing system to support the video-on-demand (VOD) function while keeping the P2P native downloading speed. A new parameter named next-play-frequency is added to the content chunk to strike a replication balance between downloading and streaming requests. We modify the eMule as the test bed by adding the WDCD algorithm and then verify the prototype implementation by experiments. The experimental results show that the proposed algorithm can keep the high downloading throughput performance of the eMule system with a good playing-as-downloading function.

关键词： Peer-to-peer (P2P),  Video-on-demand (VOD),  Playing-as-downloading,  eMule