关键词: 数字水印, 视频, 离散余弦变换, 扩频通讯, 运动估计

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