Adaptive Video Transmissions over the Internet: an Experimental Study

Several distributed multimedia applications, such as on-line games, video streaming and IF-telephony, require interactive operations between who provides the service (the sender) and who receives the service (the receiver). Considering video transmissions, interactive operations are well performed only if the receiver plays out video frames continuously and with short delay with respect to their transmission time. Unfortunately, this is not trivial especially over networks, as the Internet, whose traffic conditions greatly affect the packets transfer delay. This poses significant problems. For instance, it can happen that a frame f(i), supposed to be played out at time t(i), cannot be played out until time t(i)(double dagger). We denote as Video Time Difference, the difference t(i)(double dagger)-t(i) and in this paper we propose a mechanism that keeps tight and constant this video time difference. This is performed by slightly modifying the QoS of the delivered video. The proposed mechanism has been evaluated through simulations over real Internet traffic conditions and it is shown to be effective in supporting distributed multimedia interactive applications.