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Bede Liu

Technological advances have brought about a number of profound changes in our ways of handling information: how information is acquired, how it is distributed, and how it is used. Multimedia information, in particular, has already expanded its impact far beyond teaching, research, and entertainment. In the future, we can only expect that multimedia will have even stronger impact on the way we work, learn, socialize, do business, and so on.

With the increasing accessibility of digital media source material, the protection of ownership and the prevention of unauthorized alteration has become an important concern. Digital watermarking, a scheme to embed data or watermark into a multimedia data object, has been used for such purposes.

We have developed a simple scheme for image authentication by embedding a watermark that is not visible under normal viewing conditions but can be extracted to detect whether the host image has been modified, and if so, to detect where the modification took place.

Digital video are now being sent over a variety of communication links. When the channel deteriorates because of noise, interference, and so on, the picture quality can suffer abruptly. One strategy to guard against this "cliff" effect is to provide more protection for the bits that are more critical to the picture quality. When channel bit rate available for sending video over networks is changed because of traffic congestion and other factors, it is often desirable, nevertheless, to be able to send the video, but not at the full, original quality. In order to avoid real-time recoding the compressed video at a lower bit rate to suit the available bandwidth, we have investigated ways to encode the video in such a way so that this "transcoding" step can be done with greatly reduced effort.

In comparison with traditional text-based materials, the tools for the use of multimedia information are very primitive indeed. How to search, browse, and retrieve such information from a digital library represent a continuous challenge. We have developed tools to analyze the content and structure of multimedia information data and to extract a summary from these material for the above purposes.

Watermarking for detecting image modification