Research On Multimedia Digital Watermarking Algorithms For Copyright Protection And Assessment For Imperceptibility

As an important branch of information hiding, digital watermarking is an effective method for copyright protection. Watermarking is defined as the process of embedding special identification information directly into digital multimedia, such as digital image, audio, video, document, software and so on. And the watermark information can not affect the value in use of the digital media. Moreover, it is difficult to detect, distort or remove the digital watermarking. So, the watermark is used for verifying the copyright of the digital media content, authenticating the truth of the digital contents, confirming the tracking infringement of the digital contents. The main research contents are based on the watermarking methods of copyright protection for digital image and digital video. Main achievements in this thesis are summarized as follows:1. A practical watermarking algorithm for the copyright protection of JPEG image is proposed in this paper. By operating the pixel matrix of depressed the JPEG image, we can use the DCT coefficients to embed the watermark. The strength of watermark can be controlled by visual masking and analysis of the quantization condition during the embedding of watermark No original image is needed when extracting the watermark. The proposed scheme can achieve excellent robustness to common image processing methods and some attacks in favor of protecting the copyright of JPEG image.2. Digital video watermarking technology has attracted a great deal of research interest in the past few years for the copyright protection. An innovative practical video watermarking algorithm based on MPEG-2is proposed in this paper. By operating the compressed video data-stream directly, we embed watermarking information in DC coefficients of block image which is in the IDR picture, in DPCM process of MPEG-2coder. Watermark can be extracted blindly without original images and complete decoding is unnecessary. The algorithm designs one kind of synchronization code in order to resolve the synchronization problem. Watermark information is embedded periodically for random testing. The proposed scheme can achieve good excellent robustness to common video processing methods such as low bit rate MPEG-2compression and synchronization attacks.3. Along with rapid development of HDTV, copyright protection of digital contents has been more and more concerned. H.264, the latest video compression standard, is widely used in many video standards and technologies, such as digital video broadcasting handheld, blue-ray disk and HD-DVD. An innovative watermarking algorithm based on H.264compressed domain is proposed. The embedding and extracting are performed using the syntactic elements of the compressed bit stream. In this way, complete decoding is unnecessary in both embedding and extracting processes. Through the analyses of the time and space, some appropriate sub-blocks are selected for embedding watermarks, increasing watermark robustness while reducing the declination of the visual quality. In order to avoid bit-rate increasing and strengthen the security of this video watermarking scheme, only a set of nonzero coefficients quantized in different parts of macroblocks is chosen for inserting watermark. The experiment results show the proposed scheme can achieve excellent robustness against some common attacks.4. Considering the importance of the assessment for imperceptibility in digital watermarking technology, a new objective method WVWPSNR (Wavelet and Vision_Weighted Peak Signal Noise Ratio) is presented in this paper. In which the method is based on DWT, and the sensitivity of HVS (Human Visual System) is weighted using sub-band division. In this method, the assessment values of the new method accord with MOS (Mean Opinion Score). In order to demonstrate the effectiveness and to verify the reliability of WVWPSNR method, a series of experiment for JPEG、JPEG2000、White Noise、Gaussian Blur and FastFading images are made and tested. The results suggest that the proposed method can provide accurate measures of image quality under JPEG compression.5. In order to put the watermarking technology in practice much more widely, we design and carry out a practical multimedia watermark system. The main functional modules include watermark management, watermark domain management, watermark algorithm server management and system management (system monitoring and log management). The technologies are consisted of watermark generating, watermark embedding, watermark extraction, especially the plan design of blind watermarking. In order to enhance the practicability, watermark detection and extraction module can be used as an independent tool. Digital watermarking comparison method includes subjective assessment and objective assessment. In objective method, PSNR and BER are used.