focuses on the application of Universal Multimedia Access (UMA) and
development of video adaptation methods in order to meet diverse requirements
of various terminals, networks and user interests. By video adaptation,
we refer to different possible schemes for changing the representation
and coding of the video streams such as resolution, temporal rate, bandwidth,
duration or others. We envision an architecture in which such adaptation
processes can be embedded in the intermediate proxy or at the server.
We also envision such adaptation processes can be done in real time
to support live video applications.
issues in realizing an efficient adaptation system involve the following:
of efficient algorithms and implementations of different adaptation
how different adaptation methods and their combinations affect the
video quality and required computation resources such as power and
- estimation and optimization
of the tradeoffs in the above relationships
In this project,
we propose a framework in which adaptation-resource-quality relations
are modeled by the utility function. We argue these exists
strong correlation between such utility functions and the content characteristics.
Video clips sharing similar characteristics (e.g., objects, scenes,
motions) also share similar utility functions.
we apply the above utility-fucntion framework and demonstrate a content-adpative
utility-based MPEG-4 transcoding system. Content features like complexity
and motion are extracted from each incoming video segment and used to
predict the utility function based on pre-trained classifiers. The optimal
adaptation operator among all possible options (such as frame dropping
and/or coefficient dropping from MPEG-4 sequences) is then automatically
selected based on the predicted utility function. Our extensive experiments
show very accurate prediction of the utility function as well as the
optimal operator. More importantly, the whole process of feature extraction,
classification, and prediction can be done in real time without needing
to use exhaustive comparison of different options.
architecture of the utility function prediction is shown in the figure
below is the screen shot of our live demo system, which simulates the
real time utility function prediction procedure. It also shows the extracted
features, dynamic network condition, comparison of the actual utility
function and predicted one, and comparison of the final transcoded video
description of the project can be found at the project
site. We are currently extending the research to incorporate subjective
quality modeling and power estimation.
Y. Wang, J.-G. Kim, and S.-F.
Chang, "Content-based utility function prediction for real-time
MPEG-4 transcoding," ICIP'2003, Barcelona, Spain, 14-17 Sep 2003.
J.-G. Kim, Yong Wang, and
S.-F. Chang, "Content-Adaptive Utility Based Video Adaptation",
ICME 2003 July 6-9, 2003, Baltimore, MD. [PDF]
J.-G. Kim, Y. Wang, S.-F.
Chang, K. Kang, J. Kim, "Description of utility function based
optimum transcoding," ISO/IEC JTC1/SC29/WG11 M8319 Fairfax May