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Analysis of Packet Loss for Compressed Video: Effect of Burst Losses and Correlation Between Error Frames

Video communication is often afflicted by various forms of losses, such as packet loss over the Internet. This paper examines the question of whether the packet loss pattern, and in particular, the burst length, is important for accurately estimating the expected mean-squared error distortion resulting from packet loss of compressed video. We focus on the challenging case of low-bit-rate video where each P-frame typically fits within a single packet. Specifically, we: 1) verify that the loss pattern does have a significant effect on the resulting distortion; 2) explain why a loss pattern, for example a burst loss, generally produces a larger distortion than an equal number of isolated losses; and 3) propose a model that accurately estimates the expected distortion by explicitly accounting for the loss pattern, inter-frame error propagation, and the correlation between error frames. The accuracy of the proposed model is validated with H.264/AVC coded video and previous frame concealment, where for most sequences the total distortion is predicted to within plusmn0.3 dB for burst loss of length two packets, as compared to prior models which underestimate the distortion by about 1.5 dB. Furthermore, as the burst length increases, our prediction is within plusmn0.7 dB, while prior models degrade and underestimate the distortion by over 3 dB. The proposed model works well for video-telephony-type of sequences with low to medium motion. We also present a simple illustrative example, of how knowledge of the effect of burst loss can be used to adapt the schedule of video streaming to provide improved performance for a burst loss channel, without requiring an increase in bit rate.