NIS07-6: Comparisons of Orthogonalisation and Writing-On-Dirty-Paper Schemes for High Capacity Watermarking

This paper investigates the application of high capacity watermarking in still images. The performance of two orthogonalisation schemes and one writing-on-dirty-paper scheme are discussed. Orthogonalisation is an embedding technique which uses sequences that are orthogonal to the cover image modulating the payload information. Writing-on-dirty- paper uses the codewords which have the maximum cross- correlation of the cover image to carry the message. Aspects of comparison are: 1) watermark fidelity, 2) payload capacity and 3) robustness. The watermark fidelity is measured using Watson´s perceptual model and mean squared error. Given fixed fidelity levels the payload capacity is measured in terms of bit error rate. Additive White Gaussian Noise (AWGN) with different variances is used to evaluate the robustness of the watermarks. Results are presented which categories the advantages and disadvantages of each scheme, under different situations. Certain trade-offs must be considered for specific requirement.