Data payload optimality: A key issue for video watermarking applications

Watermarking aims at enforcing property right for digital video: a mark is imperceptibly - transparently - embedded into original data. The true owner is identified by detecting this mark. The robust watermarking techniques allow the mark detection even when the protected video is attacked. Transparency and robustness constraints restrict the mark size: the better transparency and robustness, the smaller the data payload. The paper presents a method to evaluate the maximum quantity of information which can be theoretically inserted into the 2D-DCT coefficient hierarchy, for prescribed transparency and robustness. This approach relies on the noisy channel model for watermarking. Within this mathematical framework, the maximal data payload is expressed by the channel capacity. As any capacity evaluation procedure requires an intimate knowledge of the noise sources, the paper first describes the developed statistical approach enabling: (1) to properly handle the inner dependency existing among successive frames in a video sequence, and (2) to accurately check-out the Gaussian behaviour for each noise source. The experiments were carried out in partnership with the SFR mobile service provider in France (Vodafone group).