In head mounted display(HMD),in order to cancel pincushion distortion,the images displayed on the mobile should be prewarped with barrel distortion.The copyright of the mobile video should be verified on both the orig...In head mounted display(HMD),in order to cancel pincushion distortion,the images displayed on the mobile should be prewarped 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.展开更多
Riemann problems for the compressible Euler system in two space dimensions are complicated and difficult,but a viable alternative remains missing.The author lists merits of one-dimensional Riemann problems and compare...Riemann problems for the compressible Euler system in two space dimensions are complicated and difficult,but a viable alternative remains missing.The author lists merits of one-dimensional Riemann problems and compares them with those for the current two-dimensional Riemann problems,to illustrate their worthiness.Two-dimensional Riemann problems are approached via the methodology promoted by Andy Majda in the spirits of modern applied mathematics;that is,simplified model is built via asymptotic analysis,numerical simulation and theoretical analysis.A simplified model called the pressure gradient system is derived from the full Euler system via an asymptotic process.State-of-the-art numerical methods in numerical simulations are used to discern small-scale structures of the solutions,e.g.,semi-hyperbolic patches.Analytical methods are used to establish the validity of the structure revealed in the numerical simulation.The entire process,used in many of Majda's programs,is shown here for the two-dimensional Riemann problems for the compressible Euler systems of conservation laws.展开更多
基金partially supported by Fundamental Research Funds for the Central Universities of China(2016JKF01203)National Natural Science Foundation of China(61401408,61402484,and 61502160)
文摘In head mounted display(HMD),in order to cancel pincushion distortion,the images displayed on the mobile should be prewarped 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.
基金supported partially by the National Science Foundation (No.DMS-0603859)
文摘Riemann problems for the compressible Euler system in two space dimensions are complicated and difficult,but a viable alternative remains missing.The author lists merits of one-dimensional Riemann problems and compares them with those for the current two-dimensional Riemann problems,to illustrate their worthiness.Two-dimensional Riemann problems are approached via the methodology promoted by Andy Majda in the spirits of modern applied mathematics;that is,simplified model is built via asymptotic analysis,numerical simulation and theoretical analysis.A simplified model called the pressure gradient system is derived from the full Euler system via an asymptotic process.State-of-the-art numerical methods in numerical simulations are used to discern small-scale structures of the solutions,e.g.,semi-hyperbolic patches.Analytical methods are used to establish the validity of the structure revealed in the numerical simulation.The entire process,used in many of Majda's programs,is shown here for the two-dimensional Riemann problems for the compressible Euler systems of conservation laws.
