KEYWORDS: Video, Internet, Video processing, Local area networks, Sun, Visual communications, Image processing, Electronic imaging, Data communications, Multimedia
There are great challenges in streaming variable-bit-rate video over wide-area networks due to the significant variation
of network conditions. The utilization of the precious bandwidth of wide-area networks is often low in such streaming
systems. In this paper, we propose a novel framework to improve the bandwidth utilization from a new perspective.
Instead of focusing on the performance of each single media stream, we aim to improve the overall bandwidth utilization
for video streaming systems. We try to exploit the unoccupied bandwidth in ongoing streams and using it to deliver
some prefetched data which can be used to facilitate future streaming. Preliminary results show that our mechanism has
great potential to improve both the overall bandwidth utilization and the caching performance of the proxy servers in the
streaming systems.
Efficient delivery of streaming media content over the Internet becomes an important area of research as such content is rapidly gaining its popularity. Many research works studied this problem based on the client-proxy-server structure and proposed various mechanisms to address this problem such as proxy caching and prefetching. While the existing techniques can improve the performance of accesses to reused media objects, they are not so effective in reducing the startup delay for first-time accessed objects. In this paper, we try to address this issue by proposing a more aggressive prefetching scheme to reduce the startup delay of first-time accesses. In our proposed scheme, proxy servers aggressively prefetch media objects before they are requested. We make use of servers' knowledge about access patterns to ensure the accuracy of prefetching, and we try to minimize the prefetched data size by prefetching only the initial segments of media objects. Results of trace-driven simulations show that our proposed prefetching scheme can effectively reduce the ratio of delayed requests by up to 38% with very marginal increase in traffic.
KEYWORDS: Feature extraction, Distance measurement, Binary data, Detection and tracking algorithms, Image processing, Databases, Signal to noise ratio, Information security, Biometrics, Digital watermarking
This paper discusses one of the important issues in generating a robust media hash. Robustness of a media
hashing algorithm is primarily determined by three factors, (1) robustness-false alarm tradeoff achieved by the
chosen feature representation, (2) accuracy of the bit extraction step and (3) the distance measure used to measure
similarity (dissimilarity) between two hashes. The robustness-false alarm tradeoff in feature space is measured
by a similarity (dissimilarity) measure and it defines a limit on the performance of the hashing algorithm. The
distance measure used to compute the distance between the hashes determines how far this tradeoff in the
feature space is preserved through the bit extraction step. Hence the bit extraction step is crucial, in defining
the robustness of a hashing algorithm. Although this is recognized as an important requirement by all, to our
knowledge there is no work in the existing literature that elucidates the effcacy of their algorithm based on their
effectiveness in improving this tradeoff compared to other methods. This paper specifically demonstrates the
kind of robustness false alarm tradeoff achieved by existing methods and proposes a method for hashing that
clearly improves this tradeoff.
Delivering streaming media content over the Internet is a very challenging problem. Proxy servers has been introduced into the streaming media delivery systems over the Internet, and many mechanisms have been proposed based on this structure, such as proxy caching and prefetching. While the existing techniques can improve the performance of accesses to reused media objects, they are not effective in reducing the startup delay for first-time accesses. In this paper, we propose a more aggressive server-assisted prefetching mechanism to reduce the startup delay of first-time accesses. In this aggressive prefetching mechanism, proxy servers prefetch media objects before they are requested. To ensure the accuracy of this beforehand prefetching, we make use of server's knowledge about access patterns to locate the most popular media objects and provide such information to proxy servers as hint for prefetching. A proxy server makes decision based on the hint and its users' profile and prefetches suitable objects before they are accessed. Results of trace-driven simulations show that our proposed mechanism can effectively reduce the ratio of delayed requests by up to 38% with very marginal increase in traffic.
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