Robust watermarking of mobile video resistant against barrel distortion

In head mounted display (HMD), in order to cancel pincushion distortion, the images displayed on the mobile should be pre-warped with barrel distortion. The copyright of the mobile video should be verified on both the original view and the pre-warped virtual view. A robust watermarking resistant against barrel distortion for HMDs is proposed in this paper. Watermark mask is embedded into image in consideration of imperceptibility and robustness of watermarking. In order to detect watermark from the pre-warped image with barrel distortion, an estimation method of the barrel distortion is proposed for HMDs. Then, the same warp is enforced on the embedded watermark mask with the estimated parameters of barrel distortion. The correlation between the warped watermark and the pre-warped image is computed to predicate the existence of watermark. As shown in experimental results, watermark of mobile video can be detected not only from the original views, but also from the pre-warped virtual view. It also shows that the proposed scheme is resistant against combined barrel distortion and common post-processing, such as JPEG compression.