Synchronization techniques to detect MPEG video frames for watermark retrieval

A main problem of I-frame based watermarking schemes is their lack of robustness regarding re-encoding attacks on MPEG material. After a normal post-processing modification the structure of the Groups of Pictures (GOPs) in the modified video should be the same as in the original one. An attack, which has the goal to destroy the watermark, could change this structure. The position of the marked intra coded frames will be shifted. Without detecting the correct frame position an incorrect watermark message could be retrieved. Our conceptual paper proposes a possible solution. A combined watermark, consisting of two watermark messages, is embedded into the video material to increase the robustness of the watermark. The first part of the message is the synchronization information to locate the previously marked frames. The second part contains the information watermark. Our approach is to design a template pattern based on the synchronization information. With the pattern th e original I-frame can be detected and the correct watermark information can be retrieved. After the recovery of the attacked video material the watermark can be correctly retrieved. We present the concept and the evaluation of the first test results.