User-oriented QoS in packet video delivery

We Focus on packet video delivery, with an emphasis on the quality of servi ce perceived by the end user. A video signal passes through several subsyst ems such as the source coder, the network, and the decoder. Each of these c an impair the information, either by data loss or by introducing delay. We describe how each of the subsystems can be tuned to optimize the quality of the delivered signal, for a given available bit rate in the network. The a ssessment of end-user quality is not trivial. We present recent research re sults, which rely on a model of the human visual system.