Modeling Bit Rate Variations in MPEG Sources
Modeling Bit Rate Variations in MPEG Sources
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Date
1998-10-15
Authors
Krunz, Marwan
Tripathi, Satish K.
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Abstract
In this paper, we propose a traffic model for the
characterization of VBR MPEG-coded video streams. This model provides the
means to generate synthetic MPEG streams that can be used in performance
studies of ATM networks. The model is appropriately fitted to three long
empirical video sequences taken from different movies. We use multiple
components to model bit rate variations in an MPEG stream. These
components have different time scales. Long-term variations in the bit
rate are captured at the scene level. Within a scene, the sizes of I
frames tend to slightly fluctuate around some average. Hence, we measure
the activity of the scene by the average size of I frames in that scene.
This average varies from one scene to another, and its randomness is
reasonably approximated by a lognormal distribution. For a given scene,
the fluctuations of the sizes of I frames about- their mean are modeled
as an AR(2) time series. Finally, we show that the sizes of P and B
frames can be appropriately fitted by lognormal distributions, with
corresponding parameters. Using the compression pattern, the complete
frame size sequence is formed by intermixing three subsequences, each of
which describes the frame size sequence for a particular frame type. The
validity of the model is demonstrated by the similarity between a
synthetic stream and an actual trace, in terms of the correlation
structure, the marginal distribution, the sample paths, and more
importantly, the queueing performance.
(Also cross-referenced as UMIACS-TR-95-120)