Abstract: Digital watermark is an important method to protect the copyright of video products.In this paper，a new robust watermarking algorithm is studied.While embedding，DCT is done to the luminance component of frames of the video.Then spread-spectrum sequence is added to the low-frequency coefficients.While detecting，inter prediction is done for the video.A frame is subtracted by its motion compensation image.The low-frequency DCT coefficient of the residual image is treated as the estimation of the watermark.The correlation of the original mark and its estimation version is used to decide whether the mark exists or not.The robustness is proved by some experiments.

Key words: digital watermark, video, Discrete Cosine Transform（DCT）, spread spectrum, motion estimation

摘要： 数字水印技术是视频版权保护的一种重要方法。研究了一种新的鲁棒型视频水印算法，水印嵌入时，对原始视频亮度分量的帧图像整体做DCT变换，将扩频序列叠加在其低频系数段上。水印检测时，首先基于运动估计对水印视频做帧间预测，把得到的运动补偿帧与当前帧相减，并对该残差图像整体做DCT变换，取相应低频系数段作为估计序列，将该序列与原始水印序列的相关性作为水印是否存在的判决依据。实验证明该算法具有良好的鲁棒性。

关键词: 数字水印, 视频, 离散余弦变换, 扩频通讯, 运动估计