The ultimate goal when designing an application running on top of a communication network is the satisfaction of the final user. For a multimedia application, this can be instantiated into obtaining a high enough Quality of Experience (QoE). We think that the main component of QoE is the perceived quality, that is, the quality of the multimedia flow as seen by the human user, a clearly subjective concept.
This talk describes first the PSQA project. PSQA stands for Pseudo-Subjective Quality Assessment. It is a technology able to provide a numerical (that is, quantitative) and accurate estimation of the quality of a video, audio or multimedia flow, either one-way (for instance, video streaming) or interactive (for instance, IP telephony), as perceived by the end user, automatically and in real time if necessary. Then, we will show how PSQA can be coupled with classical modeling techniques, the main reason allowing this being the fact that the PSQA function has nice mathematical properties. Last, we will describe a project where we propose a new way of designing a P2P network for transmitting real-time video flows (IPTV). We will show how we use pseudo-random number generators to distribute the substreams composing the flow following a multisource approach, and how we use PSQA to modeling and designing the whole system.