Performance comparison between VBR speech coders for adaptive VoIP applications

The recent introduction of new variable bit rate (VBR) speech coders has opened up new perspectives for the implementation of adaptive voice over IP (AVoIP) systems. The paper compares different VBR speech coding techniques in a scenario in which the rate of the single sources is dynamically adapted to the workload conditions. The coders compared are the AMR, the M³R and the G.729. Using source and rate control mechanism models, performance was evaluated in terms of loss probability, offered throughput and mean CMOS (comparison mean opinion score) with varying numbers of sources and different background noise conditions. The use of header compression mechanisms was also evaluated.