ROBUST WATERMARKING TECHNIQUES FOR SCALABLE CODED IMAGE AND VIDEO

In scalable image/video coding, high resolution content is encoded to the highest visual quality and the bit-streams are adapted to cater various communication channels, display devices and usage requirements. These content adaptations, which include quality, resolution and frame rate scaling may also affect the content protection data, such as, watermarks and are considered as a potential watermark attack. In this thesis, research on robust watermarking techniques for scalable coded image and video, are proposed and the improvements in robustness against various content adaptation attacks, such as, JPEG 2000 for image and Motion JPEG 2000, MC-EZBC and H.264/SVC for video, are reported. The spread spectrum domain, particularly wavelet-based image watermarking schemes often provides better robustness to compression attacks due to its multi-resolution decomposition and hence chosen for this work. A comprehensive and comparative analysis of the available wavelet-based watermarking schemes,is performed by developing a new modular framework, Watermark Evaluation Bench for Content Adaptation Modes (WEBCAM). This analysis is used to derive a watermark embedding distortion model, that establishes a directly proportional relationship between the sum of energy of the selected wavelet coefficients and the distortion performance, i.e., mean square error (MSE) in spatial domain. On the other hand, the improvements on robustness is achieved by modeling the bit plane discarding, which analyzes the effect of the quantization and de-quantization within the image coder and ranks the wavelet coefficients and other parameters according to their ability to retain the watermark data intact under quality scalable coding-based content adaptation. The work, then, extends these image watermarking models in video watermarking. But a direct extension of the image watermarking methods into frame by frame video watermarking without considering motion, results in flicker and other motion mismatch artifacts in the watermarked video. Motion compensated temporal filtering (MCTF) provides a good framework for accounting the motion. A generalized MCTF-based spatio-temporal decomposition domain (2D+t+2D) video watermarking framework is developed to address such issues. Improvements on imperceptibility and robustness are achieved by embedding the watermark in 2D+t compared to traditional t+2D MCTF based watermarking schemes. Finally, the research outcomes, discussed above, are combined to propose a novel concept of scalable watermarking scheme, that generates a distortion constrained robustness scalable watermarked media code stream which can be truncated at various points to generate the watermarked image or video with the desired distortion-robustness requirements.