A trellis-enhanced secure spread watermarking scheme and its performance analysis

Digital watermarking is a technique that aims at hiding a message signal in a multimedia signal for copyright claim, authentication, device control, or broadcast monitoring, etc. We focus on embedding watermarks into still images. We propose to scramble the watermark with pseudo-noise (PN) or orthogonal codes before it is embedded into an image. We also try to incorporate error correction coding (ECC) into the watermarking scheme, anticipating reduction of the watermark bit error rate (WBER). We consider to adopt trellis-based schemes (including trellis-code modulation (TCM) and turbo codes) to improve the WBER. Due to the similarity between the PN/orthogonal coded watermarking and the spread spectrum communication, it is natural that, following similar derivations regarding data BER, we derive certain explicit quantitative relationship regarding the trade-off between the WBER and the distortion suffered by the original image, which is measured in terms of the embedded image's signal-to-noise ratio (abbreviated as ISNR).