Periodic broadcasting with VBR-encoded video

We consider designing near video on demand (NVOD) systems that minimize startup latency while maintaining high image quality. Recently nonuniform segmentation has been used to develop periodic broadcasting techniques for NVOD. These techniques give significant reductions in startup latency as compared with more conventional uniform segmentation. Essentially all of these schemes assume, however, that the videos are CBR-encoded. Since a CBR-encoded video has a larger average rate than an open-loop VBR encoding with the same image quality, there is potential to obtain further performance improvements by using VBR video. In this paper we develop a series of multiplexing schemes for the periodic broadcasting of VBR-encoded video that are based on smoothing, server buffering, and client prefetching. Two key but conflicting performance measures exist when using VBR video: latency and packet loss. By introducing small additional delays in our multiplexing schemes, our trace-based numerical work shows that the schemes can achieve nearly 100% link utilization with negligible packet loss. When the ratio of the CBR rate to the VBR average rate is a modest 1.8, startup latency can be reduced by a factor of four or more for common scenarios.