Video Watermarking by Using Geometric Warping Without Visible Artifacts

Our paper proposes an enhanced video watermarking approach. The fundamental idea is to use geometric warping for watermarks with high predictable robustness to lossy compression. We explain the basic watermarking approach which uses a block based statistic (Normed Centre of Gravity NCG) to describe the geometric structure of blocks. The NCG also is used to choose robust blocks. To embed the watermark information the chosen blocks are changed by geometric warping. To extract the watermark, the original video is not necessary. The NCG is used to detect the watermarked blocks and compute the embedded watermark bit. In some cases, the independent geometric warping of blocks which contain the same object results in visible artifacts. We propose to link blocks in space and time to block groups. In contrast to the basic approach, the blocks of one block group can be warped in dependence on each other. Thus, the visible artifacts are prevented.