A Perceptual Quality Model Intended Adaptive VoIP Applications

Quality models predict the perceptual quality of services as they calculate subjective ratings from measured parameters. In this paper, we present a new quality model that evaluates VoIP telephone calls. In addition to packet loss rate, coding mode and delay, it takes into account the impairments due to changes in the transmission configuration (e.g. switching the coding mode or re-scheduling the playout time). Moreover, this model can be used at run time to control the transmission of such calls. It is also computationally efficient and open-source. To demonstrate the potential of our model, we apply it to select the ideal coding and packet rate in bandwidth-limited environments. Furthermore, we decide, based on model predictions, whether to delay the playout of speech frames after delay spikes. Delay spikes often occur after congestion and cause packets to arrive too late. We show a considerable improvement in perceptual speech quality if our model is applied to control VoIP transmissions