Evaluation of Video Communication over Packet Switching Networks

  • Authors:
  • Klaus D. Heidtmann

  • Affiliations:
  • -

  • Venue:
  • EDCC-3 Proceedings of the Third European Dependable Computing Conference on Dependable Computing
  • Year:
  • 1999

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Abstract

Real-time video communication as a component of distributed multimedia systems for new evolving applications like video telefony and video-conferencing is strongly dependent on the quality of service provided by its communication support. Dependability attributes of the undelying communication system playing a predominant role with regard to the quality achievable from applications and users point of view. Especially video compression reduces data rates by removing the original redundancy of video sequencies but creates dependencies between data of different images enabling extensive error propagation. So real-time video communication becomes extremely sensitive to faulty transmitted, lost or too late arriving data. This dependability inherent for instance in most packet switching networks results in low video quality. In this paper we study video communication via best-effort networks, which present the actual communication infrastructure. First we illustrate the effect of transmission deficiencies on the visual quality of the received video. Then an analytical model of dependability is developed, which reflects the transmission of MPEG and H.261 coded video streams. We apply our model to compute appropriate or even optimal parameters for video encoders. Forward error control using error correcting codes provides the communication process with fault tolerance, which may improve the quality of video transmission by systematic redundancy. So we extend our model to determine the required level of redundancy. Finally we discuss further mechanisms of fault tolerance to achieve high video quality even in case of modest or even low quality of service delivered by communication systems.