The present disclosures relates generally to digital watermarking and data hiding. One claim recites an apparatus comprising: memory for storing data representing video; one or more electronic processors programmed for: embedding a first watermark signal in a first portion of the data, the first watermark signal comprising a first signal polarity and corresponding to first detection preconditioning; embedding a second watermark signal in a second portion of the data, the second watermark signal comprising a second signal polarity that is inversely related to the first signal polarity and corresponding to seconding detection preconditioning; controlling provision of the watermarked video for display in real time, in which temporal averaging of the first watermark signal and second watermark signal over time conceals the first watermark signal and the second watermark signal from a human observer of the video. Of course, other claims are provided too.