| Summary: | 博士 === 國立成功大學 === 電機工程學系碩博士班 === 91 === In recent years, we have entered the era of multimedia information due to the widespread development of important technique－digitalization. In this age, many service providers really hope that they can use networks, such as digital broadcasting system, to deliver the digital content (video, image, audio, etc.) to the viewers or listeners. However, the digital media is very easy to copy or resell illegally because of the digital content with the property of easy duplicating. This leads to intellectual property right’s (IPR) infringement of multimedia content and the serious obstruction of the development of digital broadcasting system. To solve these problems, we have developed new technologies, concentrating on the digital watermarking schemes, to support the development of digital broadcasting. Two major purposes of digital watermarking are to protect the intellectual property right of multimedia content from piracy for the service providers and to identify the authentication of multimedia content for users.
In this dissertation, we would propose some practical and effective methods for the protection of owner copyright and the user authentication of images and videos in digital broadcasting network. First, we focus on robust watermarking strategies using the schemes of visual cryptography to protect the intellectual property right of service provider. Then, a fragile watermarking, which can be applied to the interference detection in satellite communication network, is proposed for protecting the programs of digital broadcasting video.
In robust watermarking, a visual cryptography technique is proposed as a way of solving copyright protection problems for digital images. Our watermarking method employs a visual cryptography to separate the watermark into two parts, a public watermark and a secret watermark. For watermarking security, only the public watermark is inserted into the original image, while the owner holds the secret watermark. Without the secret watermark, it is almost impossible to extract the watermark even if the embedding algorithm is published.
In fragile watermarking, to provide the content authentication of video sequence, the watermark information is embedded into the video sequence of MPEG-2 streams by modifying the motion vector. In the monitoring end, the watermark can be extracted from the watermarked motion vector. Hence, the monitoring station can detect the authorized code from watermarked signals to authenticate the video contents. If the watermarked signal has no authorization information, the watermarking algorithm can easily detect the illegal use, and thus make a decision (such as detecting the location of interfered source) for prohibiting the illegal content to distribute in public broadcasting network.
Various experiments on the proposed robust watermarking method are presented to demonstrate the robustness to most common image processing operations such as JPEG compression, cropping, blurring and sharpening. The fragile watermarking method can detect the content modification and unauthorized use of multimedia. Consequently, our watermarking methods can provide both the protections of ownership copyright and consumer right in digital broadcasting system.
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