An MPEG performance model and its application to adaptive forward error correction

We present a general analytical model for predicting the reconstructed frame rate of an MPEG stream. Our model captures the temporal relationships between I-, P, and B-frames but is independent of the channel and media characteristics. We derive an adaptive FEC scheme from the general model and verify it by comparing it to the results of a simulation. The prediction error of the model compared to the simulation for a wide array of parameter values is less than 5%. We then use the derived adaptive FEC scheme to study the optimal rate allocation (i.e., between generating a higher frame rate or increasing the protection for a lower frame rate) when equation-based TCP rate control is used to couple packet rates to channel characteristics such as round trip time and packet loss probabilities. Surprisingly, we find that optimal protection levels for I- and P-frames are relatively static as loss rates increase from 1% to 4% while changes in the frame type pattern are used to a meliorate the effects of the increased loss. The study demonstrates how our model can be used to reveal joint source/channel coding tradeoffs and how they relate to encoding and transmission parameters.