| The information exchange based on networks makes the application and transmission for digital multimedia works more convenient.However the information safety and copyright protection for digital works are becoming the most urgent problem to be solved because of the easy illegal copy and tampering.Now digital watermarking technology supplies an effective method to protect digital works copyright.At present,the digital watermark research is focused on image,but video and audio are less.In recent years,digital video has turned into an indispensable entertainment way,but the development of its corresponding copyright protection technology is unadvanced yet.Thus the digital video copyright technology is cried for more deep application study.Therefore,in this dissertation,the digital video watermarking technology for copyright protection and content authentication are made a deep study.Firstly three different watermarking algorithms are presented, which are employed to protect digital video copyright and validate video content. Then a system for digital video copy protection and-real-time copyright tracking in network is proposed.The main researches in this dissertation are illustrated as follows:(1) A robust and blind video watermarking scheme is presented to protect video copyright,which is based on H.264 video compression standard.According to the adaptive judgment condition,the spread frequency watermarking sequence is embedded into some special DCT coefficients of each I frame 4~*4 luminance blocks in the interframe prediction stage of H.264.Consequently,watermarking method is adaptive.In the entropy decoding process,watermark is examined blindly.Moreover, coding controlling is adopted,which is based on Lagrangian optimization algorithm. Thus the video bits stream rate distortion is improved.Finally,watermark embedding and extracting scheme are simulated via the software reference model for H.264—JM9.2 and many kinds of experiments are utilized.Experimental results show that the amended watermarking algorithm is imperceptible,real time,robust and safe for video copyright protection.(2) A semi-fragile dual watermark approach is proposed to authenticate video content.The time and space domain characteristic values of video are extracted to be the dual watermarks.The time domain watermark is the serial numbers of I frames and the space one is the absolute average value of DCT AC(Alternating Current) coefficients in I frame luminance block.In order to improve the watermarking safety, the space domain watermark is encrypted by magic cube transformation.In the process of video content authentication,time domain attacks are inspected firstly and the juggled type is examined through a unilateralism linked list.Then the space domain tampering is located according to the extracted watermark and reconstructed examining watermark.Finally,several standard video sequences are tested by common attacks,such as PSNR value,inserting/removing/cutting frame serial number,deleting/removing space content etc.Experiment results are completed to reveal the imperceptibility and real time of presented algorithm.(3) Limitation of single watermark and predominance of multi-watermark are introduced.Then a video copyright protection multi-watermark algorithm is researched in virtue of the concept of zero watermarking.At first,watermark is preprocessed by m-sequence transformation.Then the semantic characteristic of video data is extracted as its characteristic matrix.Finally,the characteristic matrix and watermark are combined to be an ownership matrix.Copyright owner could take this ownership matrix as a key to register it via Trusted Third Party to protect his right. Once piracy happens,the copyright owner could use the ownership matrix and the suspected video to distill the watermark to reveal his copyright.Different watermark is applied to generated different ownership matrix in each different stage,such as copyright,release,distribution and application etc.These watermarks are independent. According to experimental results,the proposed multi-watermarking scheme is good at solving video multi-copyright problem.(4) The unresolved problems of digital video copyright management system are discussed,and then the application of digital watermark and Agent in digital right management system is presented.Based on the previous research,a digital video copyright management system based on watermarking and multi-agent is proposed.It is suitable for safe resource sharing in open networks.Finally,the main function modules are realized by software programming.The system running shows that the proposed system is reliable and applied.
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