Abstract: In this paper, we determine the watermark domain that maximizes data hiding capacity. We focus on the situation in which the watermarked signal undergoes lossy compression involving quantization in a specified compression domain. A novel linear model for the process of quantization is proposed which leads to analytical results estimating the data hiding capacity for various watermarking domains. Using this framework we predict appropriate transforms for robust spread spectrum data hiding in the face of JPEG compression. Simulation results verify our theoretical observations. We find that a repetition code used in conjunction with spread spectrum watermarking in a different domain than employed for compression improves data hiding capacity.