Once objects are identified, their watermarks may be retrieved from the object database and used to determine ownership rights. Rather than watermarking true objects with irregular boundaries, we watermark blocks using a modified form of MPEG motion tracking. Given a block in the current frame, an affine transformation vector is obtained by minimizing a cost function measuring the mismatch between the block and each predictor candidate. The range of predictor candidates are limited by scale, rotation, and translation. The error corresponding to the best matching candidate is compared to a similarity threshold.
Candidate blocks with mismatches less than the threshold are signed with identical watermarks.
The author representation, visual masking, and motion compensation are combined to form our video watermarking algorithm shown in Figure 1. Diagram of video watermarking technique. Each of the following steps is repeated for each frame. M masking values for the current frame are computed. Segmenting the frame into blocks ensures that the frequency masking estimates are localized.