| Summary: | 碩士 === 國立中興大學 === 通訊工程研究所 === 98 === Digital watermarking is application of Dirty-paper code. Watermarking that means we embed some information in host, and make distortion of host is unobservable, and we can get the embedded complete information even if the host is influenced by channel or attack. In this paper, we propose a modified digital watermarking system. This system is embedded the watermark with a modified trellis code. We use a 512 x 512 pixels image to embed 1585 bits. In stead of Gaussian distribution random code, we use linear block code to label each arcs in trellis structure, and then identify the desired watermark by the decoding algorithm of trellis code. In above condition, we can adjust the robustness of watermark and the fidelity of the embedded image.
In our simulation, we use the cooperation of trellis structure and linear block code. Furthermore, we partition the linear block code appropriately before we label codeword on each branch of trellis. Through different channel attacks, the modified trellis code still has better bit error rate performance.
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