Study On The Robustness Of Video Digital Watermarking Based On MPEG-4

Information exchange based on network supplies convenient approaches for the usage and spread of digital multimedia products. Digital products can be replicated and tampered illegitimately easily, so information security and copyright protection of the digital multimedia products become an urgent problem to be solved. As a new and effective approach to solve the problem of copyright protection, digital watermarking technology has emerged to be an active and flourishing research topic in the field of information security recently. Digital watermarking technology protects the digital products by embedding unperceivable and secret information into the digital products such as image, audio, video or software, which has no effect upon the using of the digital products. As MPEG-4 video standard is applied more and more widely, it must have the copyright protection technology such as digital watermarking to protect the copyright of MPEG-4 video data. Robustness is an important property of digital watermarking. How to improve the robustness of watermarking algorithm is one of the key problems of the digital watermarking technology.The research status, speciality, basic model and evaluation criterion of video watermarking technology are introduced in detail. And the basic principles about MPEG-4 video compression technique are also introduced. The measures about improving the robustness of watermarking algorithms are proposed based on researching on the robustness of image and video watermarking thoroughly. Finally, it proposes the measures about improving the security by analyzing the security of the watermarking algorithm based on quantization.The main research work of this thesis includes four aspects as follows:①The factors of influencing the robustness of digital watermarking are summarized in this thesis. The general strategies to improving the robustness of digital watermark are generalized by researching and analyzing many robust digital watermarking algorithms.②There are some inadequacies in the current digital watermarking algorithm based on convolution code and DCT coefficients quantization. The method which can judge the texture complexity of image blocks by calculating the quadratic sum of alternating current coefficients is proposed. Then the quantization step is adjusted adaptively to avoiding the block effect by enlarging the quantization step. And the quantization interval of the soft-decision decoding of convolution code is divided more rationally to improve the accuracy of Viterbi decoding. The experimental results show that the improved algorithm can improve the robustness of original watermarking algorithm and guarantee the invisibility of watermark.③One adaptive video watermarking algorithm based on convolution code and DCT coefficients quantization is proposed in this thesis. And the algorithm is suitable for MPEG-4 video standard. The experimental results show that the algorithm can improve the robustness of the watermark with invisibility and security. In addition, the real-time processing demand is also satisfied.④In this thesis, the loophole of security in the watermarking algorithm based on quantization is analyzed, and this security attack can be resisted by maintaining the mean intensity of the watermarked image. The experiment results show that the improved algorithm can enhance the security of the watermarking algorithm and affect the robustness little.