In this chapter we present some of our results concerning source models for coded VBR (variable bit rate) video. Video services have been forecasted to be a substantial portion of the traf®c on emerging broadband digital networks. Statistical source models of video traf®c are needed to design networks that delivery acceptable picture quality at minimum cost, and to control and shape the output rate of the coder. For example, one issue is deciding whether a new video connection can be admitted to a network, and the consequent determination of the bandwidth that must be allocated to the connection to. | Self-Similar Network Traffic and Performance Evaluation Edited by Kihong Park and Walter Wi 1 linger Copyright 2000 by John Wiley Sons Inc. Print ISBN 0-471-31974-0 Electronic ISBN 0-471-20644-X 12 LONG-RANGE DEPENDENCE AND QUEUEING EFFECTS FOR VBR VIDEO Daniel P. Heyman AT T Labs Middletown NJ 07748 T. V Lakshman Bell Laboratories Holmdel NJ 07733 INTRODUCTION In this chapter we present some of our results concerning source models for coded VBR variable bit rate video. Video services have been forecasted to be a substantial portion of the traffic on emerging broadband digital networks. Statistical source models of video traffic are needed to design networks that delivery acceptable picture quality at minimum cost and to control and shape the output rate of the coder. For example one issue is deciding whether a new video connection can be admitted to a network and the consequent determination of the bandwidth that must be allocated to the connection to ensure adequate quality of service. A model of the bandwidth that the connection will try to consume is required for this task. In addition to providing a good description of the bandwidth requirements the source model should be usable in the connection-acceptance decision model. Other chapters that contain related material are Chapters 9 13 16 and 17. Special Properties of Video There are some physical reasons why traces from video sources are special. Video is a succession of regularly spaced still pictures called frames. Each still picture is represented in digital form by a coding algorithm and then compressed to save 285 286 LONG-RANGE DEPENDENCE AND QUEUEING EFFECTS FOR VBR VIDEO bandwidth. See for example Netravili and Haskell 24 for full information about video coding. A common way to save bandwidth is to send a reference frame and then send the differences of successive frames. This is called interframe coding. Since the adjacent pictures cannot be too different from each other because most
