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Proceedings Paper

Synchronization of conference presentation sequence using delay equalization approach
Author(s): Rakesh K. Godavari; Mehmet Celenk
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Paper Abstract

In this paper, a delay equalization approach is proposed for cohesive conference presentation with minimal screen- freezing effect. The underlying screen-freezing effect is due to varying delays in the communication channels involved in broadcasting. In turn, this poses a threat to the goal of uniform delay distribution among data packets for synchronized presentation broadcast. We wish to achieve uniformity among packet arrival times to the recipients. This objective is achieved by transforming a given input delay distribution (D) to the desired output density through a delay equalization process. Considering a general case of between packet and frame delay distributions for a given input, the desired output is obtained through a delay equalization process. In case of a specific normal delay distribution, a memory-less system g(D) is determined as an approximation to the delay equalizer such that the equalizer output O(t)equalsg[D(t)] is uniformly distributed in the allowable delay limits of (a,b) assuring the specified quality of service (QoS) parameters. The corresponding delay is added at each recipient workstation, which acts as the wait period required before it begins its designated presentation.For a zero mean normal delay density case, the equalizer transfer function can be given in a closed from solution as O(t)equalsg[D(t)[equals(b-a)]0.5+eft(-D/$RO OTR(0)))[+a, where erf(x) is the standard error function. The histogram approximation is adopted as an asymptotically delay equalization means for general cases. This technique provides a means for modifying the dynamic range of data acquired by altering it into a desired distribution. In experimentation, equalizer characteristic functions are derived for a set of selected input delays to obtain the desired output. The delay equalizer system developed here is suited for deployment in a distributed hierarchical conferencing environment. To accommodate a broadcast continuity, the multimedia presentation is provided with a shared workspace among the web servers acting as administrators in the network. The arrival times and the presentation durations of the data packets at the recipient workstations are recorded in this shared workspace. For a case study, a Poisson distribution type delay density is selected to be the input for the delay equalizer with the desired output to be uniformly distributed. The transfer function input and output distributions are derived and depicted in a parametric form for different values of mean in the simulation results to illustrate the effectiveness of the equalization process. We have demonstrated that this method is appropriate for equalizing the lumped communication channel delays. Further work is in progress for developing the distributed channel delay equalization.

Paper Details

Date Published: 12 November 2001
PDF: 11 pages
Proc. SPIE 4518, Multimedia Systems and Applications IV, (12 November 2001); doi: 10.1117/12.448196
Show Author Affiliations
Rakesh K. Godavari, Ohio Univ. (United States)
Mehmet Celenk, Ohio Univ. (United States)

Published in SPIE Proceedings Vol. 4518:
Multimedia Systems and Applications IV
Andrew G. Tescher; Bhaskaran Vasudev; V. Michael Bove Jr., Editor(s)

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