Experiments with Digital Video Playback
Experiments with Digital Video Playback
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Date
1998-10-15
Authors
Gerber, Richard
Gharai, Ladan
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Abstract
In this paper we describe our experiments on digital video
applications, concentrating on the static and dynamic tradeoffs involved
in video playback. Our results were extracted from a controlled series 272
tests, which we ran in three stages.
In the first stage of 120 tests, we used a simple player-monitor
tool to evaluate the effects of various static parameters: compression
type, frame size, digitized rate, spatial quality and keyframe
distribution. The tests were carried out on two Apple Macintosh
platforms: at the lower end a Quadra 950, and at the higher end, a Power
PC 7100/80. Our quantitative metrics included average playback rate, as
well as the rate's variance over one-second intervals.
The first set of experiments unveiled several anomalous latencies.
To track them down we ran an additional 120 tests, whose analysis led us
to find the locus of the system's bottlenecks. They also let us conclude
that a software-only solution was sufficient for good video playback on
the systems under observation - provided that the operating system is
tuned accordingly.
In the next step we attempted to achieve this goal, by
implementing our own video playback software and accompanying device-level
handlers. Our emphasis was on achieving a controlled, deterministic
coordination between the various system components. An additional set of
32 experiments were carried out on our platforms, which showed significant
improvements in our quantitative performance measurements, as well as in
visual quality.
(Also cross-referenced as UMIACS-TR-95-103)