Abstract:

Aiming at insufficient robustness of depth map in multi-view 3D video with depth format, a 3D robust video watermarking algorithm based on depth map was proposed. Firstly, a depth map was divided into 4×4 nonoverlapped blocks, the mean square error of each block of pixels was calculated, and a threshold was set to distinguish the texture block and the flat block. Secondly, the block energy value of the texture block was calculated, and a threshold was set according to the calculated result to selectively embed the watermark bits. Finally, the transformed and quantized DC coefficients of each block were obtained and used to construct a 3×3 invertible matrix, then QR decomposition was performed on the invertible matrix and the watermark was embedded in the decomposed Q matrix. The proposed algorithm guarantees that the average Peak Signal to Noise Ratio (PSNR) is a constant, and the average Bit Error Rate (BER) under re-encoding attack with different Quantization Parameter (QP) values (25, 30, 35, 40) is 14.9%. Experimental results show that the algorithm has good robustness and embedding capacity, and has little impact on the quality of video.

Key words: depth map, video watermarking, mean square error, QR decomposition, DC coefficient

摘要：

针对多视点加深度格式的3D视频中深度图鲁棒性不足的问题，提出了一种基于深度图的3D鲁棒视频水印算法。首先，将深度图不重叠的划分为4×4大小的块，计算每一块像素域的均方差，并设置一个阈值来区分纹理块和平坦块；其次，对纹理块计算区域块的能量值，根据计算的能量值设置一个阈值来选择性嵌入水印比特位；最后，获取每个块变换量化后的DC系数，根据获取的DC系数值构造3×3的可逆矩阵，对可逆矩阵进行QR分解，将水印嵌入在分解后的Q矩阵中。所提算法保证了平均峰值信噪比不变，且不同量化参数（QP）值（25、30、35、40）的重编码攻击下的平均误码率为14.9%。从测试的结果来看，该算法具有较好鲁棒性和嵌入容量，同时对视频的质量影响很小。

关键词: 深度图, 视频水印, 均方差, QR分解, DC系数