The Research On Digital Video Watermark Embedding And Extraction Algorithm

The technique of digital watermarking is to embed some marking information which claims the copyright in the digital multimedia data directly, the embedding process does not affect the effect and use value of the original content, also it can not be detected or noticed by human perception system. Furthermore, the embedded data can later be extracted or determined only through an appropriative watermark detector. Digital watermarking has first been extensively studied for still images, a lot of research results have been obtained, but the research of technique and applications for video watermarking is slower comparatively. Today, however, with the rapid development of multimedia technology, different kinds of video products are manufactured, as a consequence, the intellectual property protection problem of video products has become an urgent issue, and it is gaining increasingly recognition.In terms of the domain in which the watermark is inserted, video watermarking algorithms can be classified as spatial-temporal domain, transform domain or compressed domain watermarking algorithms. It is often claimed that embedding in the spatial-temporal domain is disadvantageous in terms of visibility and security, many of the spatial watermarking algorithms can't resist temporal synchronization attack, the traditional transform domain watermarking algorithms attempt to decompose frames in terms of a standard basis set,but this is not necessarily the optimal representation for a given frame,also it is difficult for most of the previous work on compressed-domain video watermarking algorithms to achieve unification of real-time and big capacity. Aiming at the problems, this thesis puts forward corresponding algorithms.As we know, Vector quantization(VQ) is a popular lossy compression scheme widely used in multimedia data compressions,however,VQ has been used for image compression for many years, we first propose a video compression scheme based on VQ, we then propose a multipurpose watermarking algorithm for this video compression scheme.The main innovative contributions of this dissertation are as follows:Refering to block classification watermarking algorithm and introducing the concept of active block, this dissertation proposes a video watermarking algorithm based on block classification. First, the luminance of every whole frame is first divided into a number of non-overlapping blocks,then,different blocks of the original video are separated into perceptually distinct categories according to motion information and region complexity,the blocks are classified into detailed blocks or non-detailed blocks according to the energy of the DCT AC coefficients,besides, blocks are also classified into active blocks or inactive blocks according to the difference between the corresponding DC coefficients in the neighboring frames,what's more,only blocks that lie in the intersection of detailed blocks and active blocks are selected for embedding. Meanwhile, the idea of bit-plane replacement is adopted in the embedding procedure. The simulation results verify the effectiveness of the algorithm.After analysing the image watermarking algorithm based on DCT and SVD, a watermarking method based on SVD in the DCT domain is proposed in this thesis. In our algorithm, the luminance of every whole frame is first divided into a number of non-overlapping blocks, then some blocks are randomly selected by a seed key according to watermark bit, besides, DCT is performed on the selected luminance block, the DC and low frequency components are selected to compose a coefficient matrix, what's more, SVD is applied to each coefficient block, last but not least, the obtained singular values are quantized and modified according to the corresponding watermark bit.The experiment is done to test the algorithm against malicious attack.According to the study of video watermarking algorithm based on motion vector,this thesis proposes to embed watermark by adjusting the angle between the integer and half pixel accuracy motion vectors. In the same time, on the basis of analysis of video watermarking algorithms in variable length coding (VLC) domain, we propose another watermarking algorithm which is performed by adjusting the relationship of the neighbouring quantized AC coefficients in succeeded variable length code.In order to increase the embedding capacity, the chroma components of the video are also selected to embed watermark bits. Simulation results show that the proposed algorithms can perform the real-time watermark embedding process without affecting visual quality of the video sequence and it is also standard-compliant,also, the proposed algorithm can achieve big capacity. On the basis of the study of VQ image watermarking algorithms,two multipurpose video watermarking algorithms are proposed in this thesis. According to the combination of VQ and H.263 standard, two video compression scheme based on spatial domain vector quantization and transform domain vector quantization are designed.Aiming at the hybrid video compression scheme based on spatial domain vector quantization, the proposed watermarking algorithm embeds robust watermark by exploiting the polarities of DC (Direct Current) coefficients, and the codebook expansion technique is adopted to embed fragile watermark in VQ indices of the predicted differential vector. Aiming at the hybrid video compression scheme based on transform domain vector quantization,the code-words labeling technique is adopted to embed digital fingerprint and robust watermark in low-frequency and mid-frequency vector indices. The I-frame fragile watermarking algorithm embeds the information of low-frequency and mid-frequency vector indices in high-frequency indices. The P-frame fragile watermarking algorithm embeds the feature of motion vector in quantized DCT coefficients.The experimental results show that the multipurpose watermarking algorithms are available.