Dynamic adaptation in an image transcoding proxy for mobile WWW browsing |
| Richard Han, Pravin Bhagwat, Richard LaMaire, Todd Mummert, Veronique Perret, Jim Rubas |
| Transcoding proxies are used as intermediaries between generic World-Wide-Web
(WWW) servers and a variety of client devices in order to adapt to the
greatly varying bandwidths of different client communication links and
to handle the heterogeneity of possibly small-screened client devices.
Such transcoding proxies can adaptively adjust the amount by which a data
stream is reduced, using an aggressive lossy compression method (e.g.,
an image becomes less clear, text is summarized, etc.) We present an analytical
framework for determining whether to transcode and how much to transcode
an image for the two cases of store-and-forward transcoding as well as
streamed transcoding. These methods require prediction of transcoding delay,
prediction of transcoded image size (in bytes), and the estimation of network
bandwidth. We discuss methods of adaptation based on fixed quality as well
as fixed delay (automated/dynamic transcoding). We conclude with a description
of the practical adaptation policies that have been implemented in our
adaptive image transcoding proxy.
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| Paper (zipped postscript) |
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