University of Konstanz
Graduiertenkolleg / PhD Program
Computer and Information Science

Colloquium of the Department and the PhD Program


Distributed scheduling and distortion memory for streaming packetized video


Dr. Jacob Chakareski, EPFL
Lausanne, Switzerland

date & place

Wednesday, 23.11.2005, 16:15 h
Room C252


In the first part of the talk, I will present an optimization framework for distributed packet selection for multiple video streams sharing a common communication resource. The framework enables the multiple senders to coordinate their packet transmission schedules, such that the average quality over all video clients is maximized. In particular, each of the senders allocates to its own video packets a share of the bandwidth available on the communication channel that is proportional to the relative importance of these packets. We will examine the performance of the distributed packet scheduling algorithm for two canonical problems in streaming media, namely adaptation to available bandwidth and adaptation to packet loss. Simulation results demonstrate that, for the difficult case of scheduling non-scalably encoded video streams, our framework is shown to be very efficient in terms of video quality, both over all streams jointly and also over the individual videos.

The source coding process and the packet loss process create certain dependencies between encoded video units in terms of the reconstruction distortion of the video signal at the receiver in case of transmission over packet erasure channels. In the second part of the talk, we will study the importance of this "distortion memory" via a specific class of memory-based models denoted Distortion Chains that can be used for predicting the distortion of the reconstructed video signal in case of missing multiple packets at the receiver. We show that taking into account even the smallest amount of memory that is possible can yield substantial gains in terms of packet selection (packet dropping) performance. An additional and rather surprising result of our study is the fact that in certain situations dropping an additional video packet (which could otherwise be delivered) can actually improve the quality of the reconstructed video.