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IPTV delivers television content over an IP infrastructure with the potential to enrich the viewing experience of users by integrating data applications with video delivery. From an engineering perspective, IPTV places both significant steady state and transient demands on network bandwidth. Typical IPTV streaming techniques incur delays to fill the play-out buffer. But, when viewers switch or surf channels, it is important to minimize this user-perceived latency. Traditional Instant Channel Change (ICC) techniques reduce this latency by having a separate unicast assist channel for every user changing channels. Instead, we propose a multicast-based approach using a secondary ldquochannel change streamrdquo in association with the multicast of the regular quality stream for the channel requested. During channel change events, the user does a multicast join to this new stream and experiences smaller display latency. In the background, the play-out buffer of the new full-quality multicast stream is filled. Then, the transition to the new channel is complete. We show that this approach has several performance benefits including lower bandwidth consumption even during flash crowds of channel changes, lower display latency (50% lower), and lower variability of network & server load. The tradeoff is a lower quality video during the play-out buffering period of a few seconds. Our results are based upon both synthetic channel change arrival patterns as well as traces collected from an operational IPTV environment.
Date of Conference: 6-10 Jan. 2008