Robust Bandlimited Watermarking With Trellis Coded Modulation

Digital watermarking is equivalent to bandlimited, powerlimited digital communication. The power limit is due to the requirement of imperceptible watermarks, and has long been recognized. The bandwidth limit is due to the lowpass spectrum of images and possible lowpass attacks (malicious or unintentional). This is related to the concept of channel capacity, and has only recently been addressed in the context of watermarking. To achieve high reliability without loss of watermark data rates, we propose an adaptation of trellis coded modulation (TCM). Our method is applicable to a wide class of watermarking algorithms. The objective is to maintain the data rate while improving reliability of watermark detection, in terms of bit error rates (BER). Alternatively, higher data rates can be achieved while maintaining watermark BER. We conduct experiments for blind as well as informed detection. Simulation results show significant improvement compared to conventional methods over a wide range of channel (attack) signal-to-noise ratios