Layer thickness in congestion-controlled scalable video
Jean-Paul Wagner, Pascal Frossard · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 2009
We address the problem of the proper choice of the thickness of pre-encoded video layers in congestion-controlled streaming applications. While congestion control permits to distribute the network resources in a fair manner among the different video sessions, it generally imposes an adaptation of the streaming rate when the playback delay is constrained. This can be achieved by adding or dropping layers in scalable video along with efficient smoothing of the video streams. The size of the video layers directly drives the convergence of the congestion control to the stable state. In this paper, we derive bounds on both the encoding rates of the video layers that depend on the prefetch delay that can be used for stream smoothing. We then discuss the practical scheduling aspects related to the transmission of layered video when delays are constrained. We finally describe an implementation of the proposed scheduler and we analyze its performance in NS-2 simulations. We show that it is possible to derive a media-friendly rate allocation for layered video in different transmission scenarios, and that the proper choice of the layer thickness improves the average video quality when the prefetch delay is constrained.