In this paper

a new trellis coded watermarking algorithm of trellis codes combine with constant robustness embedding is proposed. In the algorithm

both informed coding and informed embedding are used. The watermark is encoded by a dirty paper trellis encoder. Then the strength of the noise to be added to reduce the normalized correlation coefficient to a given threshold is computed

which is taken as a constant robustness parameter. The watermark signal is embedded into the cover work by Gram Schmidt orthogonal algorithm under the condition of the constant robustness parameter

and Viterbi algorithm is used to detect and extract the watermarked signal. Experimental results indicate that the proposed algorithm can improve the robustness to white Gaussian noise and amplitude scaling.