The development of the Internet, together with the progress of multimedia processing techniques, has led to the problems of data piracy, data tampering and illegal dissemination. Digital watermarking is an effective approach to data authentication and copyright protection. This paper proposes a geometrically robust multi-bit video watermarking algorithm based on 2-D DFT (two-dimensional discrete Fourier transform). While most of the existing video watermarking schemes require synchronization to extract the watermark from rotated or scaled videos, which is time-consuming and affects the accuracy, the proposed method can do direct extraction without performing synchronization for videos attacked by rotation, scaling or cropping. For embedding the watermark, circular templates in DFT domain are transformed into spatial masks and added to the video frames in spatial domain. A perceptual model based on local contrast is applied to keep the fidelity of the watermarked video. We also propose an accurate and efficient extraction method which is based on the cross-correlation between the Wiener-filtered DFT magnitude and the stretched template sequence in polar coordinates. Experimental results show that the proposed algorithm is robust against various kinds of attacks, such as compression, filtering, rotation, scaling, cropping, frame averaging and frame rate changing.

互联网的发展以及多媒体处理技术的进步，导致了数据盗版，数据篡改和非法传播的问题。数字水印是一种有效的数据认证和版权保护方法。提出了一种基于二维DFT（二维离散傅里叶变换）的几何鲁棒多位视频水印算法。尽管大多数现有视频水印方案需要同步才能从旋转或缩放后的视频中提取水印，这既耗时又会影响准确性，但所提出的方法可以直接提取而无需对受到旋转，缩放或裁剪攻击的视频执行同步。要嵌入水印，DFT域中的圆形模板被转换为空间蒙版，并添加到空间域中的视频帧中。应用基于局部对比度的感知模型来保持水印视频的保真度。我们还提出了一种准确有效的提取方法，该方法基于维纳滤波后的DFT大小与极坐标中拉伸的模板序列之间的互相关。实验结果表明，该算法对压缩，滤波，旋转，缩放，裁剪，帧平均和帧频变化等多种攻击具有鲁棒性。我们还提出了一种准确有效的提取方法，该方法基于维纳滤波后的DFT大小与极坐标中拉伸的模板序列之间的互相关。实验结果表明，该算法对压缩，滤波，旋转，缩放，裁剪，帧平均和帧频变化等多种攻击具有鲁棒性。我们还提出了一种准确有效的提取方法，该方法基于维纳滤波后的DFT大小与极坐标中拉伸的模板序列之间的互相关。实验结果表明，该算法对压缩，滤波，旋转，缩放，裁剪，帧平均和帧频变化等多种攻击具有鲁棒性。