Abstract: Focusing on the issue that the video watermarking information is vulnerable to geometric attacks and the balance between robustness and adaptability of the watermarking algorithm, a dual watermarking scheme based on human visual characteristics and Scale Invariant Feature Transform (SIFT) was proposed. Firstly, the human visual threshold in the video sequence was taken as the maximum embedding strength of the watermark; secondly, the video frame was processed by Discrete Wavelet Transform (DWT). An adaptive watermarking algorithm based on video motion information was proposed for medium-high frequency subband coefficients; based on statistical properties of wavelet coefficients, an anti-geometric attack video watermarking scheme was proposed for low-frequency ones. Finally, SIFT was acted as the trigger to judge whether the video frame was subjected to geometric attacks. The video frames were corrected by using the SIFT scale and orientation invariance when it was under geometric attack, and the watermark signal of the video frame was extracted after correction. For video frame under non-geometric attack, the medium-high frequency extraction scheme was used directly. In comparison with the real-time robust video watermarking algorithm, called VW-HDWT (Video Watermarking based on Histogram in DWT domain) algorithm, the Peak Signal-to-Noise Ratio (PSNR) value was improved by 7.5%. Compared with the watermarking algorithm based on feature area, the capacity of watermark embedding could be increased by about 10 times. The experimental results show that the proposed scheme is robust to common geometric attacks in the condition of fine watermarking transparency.

Key words: anti-geometric attack, Human Visual System (HVS), Scale Invariant Feature Transform (SIFT), dual watermarking, Discrete Wavelet Transform (DWT)

摘要： 针对视频水印容易遭受几何攻击以及水印的鲁棒性与透明性的平衡问题，提出一种基于人眼视觉特性与尺度不变特征变换（SIFT）相结合的抗几何攻击视频双水印算法。首先获取视频序列中人眼视觉掩蔽阈值作为水印的最大嵌入强度。其次，将视频帧进行离散小波变换（DWT），对中高频子带系数提出基于视频运动信息的自适应水印算法；针对低频子带，提出基于小波低频系数统计特性的抗几何攻击视频水印算法。最后，以SIFT作为触发器判断视频帧是否遭受几何攻击，对遭受几何攻击的视频帧利用SIFT的尺度与方向不变性进行校正，并对校正后的视频帧提取水印信号；针对非几何攻击的视频帧，直接利用中高频提取算法。所提算法与实时性视频水印算法——基于小波域直方图的视频水印（VW-HDWT）算法比较，峰值性噪比值（PSNR）提高了7.5%；与基于特征区域的水印算法相比，水印嵌入容量提高约10倍。实验结果表明，在保证水印透明度较好的情况下，所提算法对常规几何攻击具有较强的鲁棒性。

关键词: 抗几何攻击, 人类视觉系统, 尺度不变特征变换, 双水印, 离散小波变换