Real-Time Bitstream-Based Video Watermarking Technology And Its Application

The development of internet and digital multimedia technology makes video access control and copyright protection become an urgent problem, fortunately, video watermark provides an effective technology to solve this issue. Video watermaking can protect the copyright of digital video by embedding watermak signal into video data imperceptvively. Recently, video watermark is becoming a hot reseach topic of information security domain. Imperceptability, robustness and real-time are three major challenges for video watermarking, especially real-time is the key character for extensive application of video watermark. This dissertation mainly investigates real-time video watermark for MPEG video standard by considering imperceptibility and robustness. Considering the computation complexity and the imbalance of encoder and decoder, we propose a real-time video watermark scheme, in which watermark can be detected directly from watermarked bitstream. Moreover, this algorithm is also extended to video transcoding application. The main research contents are given as follows.(1) Summarize the research status, characteristics and applications of digital watermarking; especially focusing on unique characteristic of video watermarking. And then we introduce all categories of video watermarking and related algorithms. Several classical real-time video watermarking algorithms and theirs performances also studied in details, and the merits and defects of the algorithms are summarized.(2) Propose a real-time video watermarking scheme for MPEG. Firstly original video sequence are segmented into many scenes by fast scene segmentation scheme, and then watermark is embedded into only those appropriate scenes by adaptively selection. Moreover, visual model is utilized to adjust watermark strength to avoid causing perceptual distortion. Finally, watermarks are embedded by changing level of run-level pairs, hence adjusting the number of bit 1 in the bitstreams.. Extensive experimental results show that the proposed algorithm do not increase the bit rate of bitsstream while with good quality of watermarked video and excellent robustness to many attacks including temporal desynchronization, noise, reencoding et al.. Of course, the most outstanding property is the real-time. The watermark can be directly detected in bitstreams domain.(3) Consider the application of the proposed watermarking algorithm in video transcoding. Based on the analysis of characteristics of video transcoding technology, we propose a modified version of the above watermarking algorithm. First, we reinforce the reliability of watermark by only embedding watermark in I frames, second, block-based embedding is used to resist the time de-synchronization attack, and the maximum change of levels is embedded into EQSP pairs. Based on the properties of watermarking scheme and transcoder, we design the embedding module and detecting module in video transcoder. The video watermark scheme for video transcoding guarantees existence of watermark signal after video transcoding with slightly increasing the computation complexity.