Statistical Multiplexing Comparison of One-and Two-Layer Video Codecs for Teleconferencing

This paper deals with transmisssion of variabel-bit-rare (VBR) video over Asynchronous Transfer Mode (ATM) networks using statistical multiplexing. We compare the multiplexing behavior of a one layer encoder with the behavior of three two-layer encoders, using two 5-minute samples of a teleconferencing session. For the two-layer encoders, the enhancement layer is coded VBR, and the base layer is coded using 1) unrestricted variable-bit- rate, 2) various constant bit rates, or 3) various peak-bit-rate constraints. The per-channel bandwidth requirements associated with various assumed loss tolerances are computed, based both on gaussian approximations and on empirical frame-size distributions. We conclude that using a two-layer algorithm with a peak rate constraint almost equal to the mean bit rate of the single-layer VBR encoder combines the greatest efficiency with the greatest statistical reliability.