DIGITAL WATERMARKING IN JOINT TIME-FREQUENCY DOMAIN

Filtering in time-frequency domain involves synthesis of signals with specific time-frequency signature. In this work we observe that watermarking of time-frequency distributions is a similar problem. The proposed domain is the joint time-frequency cells of the Wigner Distribution of the image. Watermarked cells are selected based on their impact on image quality as well as resilience to JPEG. Inversion of the watermarked Wigner is a signal synthesis problem and is inherently different from inverse DCT. Experimental results illustrate that timefrequency space has greater capacity and security advantage over spatial or spectral domains alone. 1