| Summary: | 碩士 === 國立臺北科技大學 === 資訊工程系碩士班 === 92 === Digital watermarking techniques have been successfully applied to natural images and videos. On the other hand, the computer animation applied in virtual reality, cartoons, and movies may also need adequate copyright protection. In this thesis, we develop robust watermarking techniques for MPEG-4 2D mesh animation. We use several time-series transformation techniques, including discrete cosine transform (DCT), discrete wavelet transform (DWT), and singular spectrum analysis (SSA), to extract the spectral components of mesh movement. An invisible binary code watermark is added to the important components based on the spread-spectrum principle. At watermark extraction, a spatial-domain least-squares registration technique is used to restore the distorted mesh. A variety of attacks, including the affine transformation, smoothing, random noise, enhancement and attenuation, simplifying, and time warping, are used to verify the robustness of the proposed system. Experimental results show that our watermark system can withstand the aforementioned attacks. We also evaluate the time and storage complexity of the proposed watermarking system under different transformations.
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