Statistical characterization of MPEG VBR video at the Slice layer

In this paper, we statistically characterized four VBR encoded video sequences, containing I/B/P frames, at the Slice layer with the goal of developing an accurate source model to better understand the bit-rate behavior of these sources. We presented the cells/slice distributions and showed that it is “heavy tailed” and fits the Pareto distribution better than Gamma. We showed that an 8-state Markov Chain fits the cells/slice distribution well, reaching steady state after 37 to 80 transitions (2 to 5 frames). We also showed that the autocorrelation function is quasi-periodic which is mostly due to the frame sequence pattern rather than spatial content. We discussed the impact of I/B/P sequences on multiplexing and dynamic bandwidth allocation and proposed a multiplexing method called Time Shifted Multiplexing (TSM); whereby, the multiplexer attempts to overlap I and P frames of one video stream with B frames of an other. This tends to reduce both Peak-to-Mean-Ratio and Coefficient-of-Variation of the multiplexed output stream. We showed that coefficient-of-variation reduced in half and bandwidth requirements reduced by 41% using TSM.1