基于纹理特征的H.264/AVC顽健视频水印算法

在分析现有视频水印算法的基础上,结合H.264压缩编码标准的特性,提出了一种新的基于纹理特征的视频顽健水印算法。算法先对当前帧4×4块进行整数离散余弦变换,判断其是否是纹理块,再采用能量差的方式自适应选择系数嵌入水印。实验结果表明,该算法对视频质量和码率的影响较小,并且能有效抵抗高斯噪声、低通滤波、重编码等常见的视频水印攻击。     

A novel watermarking scheme for H.264/AVC video authentication

As the H.264/AVC-based video products become more and more popular, issues of copyright protection and authentication that are appropriate for this standard will be very important. In this paper, a content-based authentication watermarking scheme for H.264/AVC video is proposed. Considering the new feature of H.264/AVC, the content-based authentication code for spatial tampering is firstly generated using the reliable features extracted from video frame blocks. The authentication code, which can detect malicious manipulations but allow recompression, is embedded into the DCT coefficients in diagonal positions using a novel modulation method. Spatial tampering can be located by comparing the extracted and the original feature-based watermarks. In addition, combining ECC and interleaving coding, the frame index of each video frame is used as watermark information and embedded in the residual coefficients. Temporal tampering can be detected by the mismatch between the extracted and the observed frame index. Experimental results show that the proposed scheme can discriminate the malicious tampering from the mild signal processing. The tampered location can also be approximately determined according to the glide window and the predefined threshold.     

用于内容认证的VLC域的 H.264/AVC视频水印方案

A semi-fragile content authentication algorithm is proposed for low bit-rate H.264/AVC video in VLC domain. Utilizing the intra prediction mode and coded block pattern in VLC domain, the proposed algorithm chooses those macro-blocks from which the signature is extracted and constructs content signature at macro-block level according to the relationship among the energies of quantized low-frequency coefficients of sub-macroblocks. The signature is embedded by modifying the trailing coefficients. The experimental results show that the proposed algorithm performs well in visual quality impact and keep the bit-rate basically unchanged. In addition, the algorithm can embed signatures into I, P, B slices simultaneously and remarkably enhances the watermark capacity. By verifying the extracted signature, the algorithm can detect and locate video tampering efficiently.     

一种基于H.264半脆弱视频水印方案

这里提出一种基于H.264/AVC低比特率的半脆弱视频水印认证方案。将从I帧能量块中提取的特征码,以修改一对AC系数间的关系,完成水印在I帧的嵌入。在P帧中,引入参考水印位对运动分量的选择机制,并通过对所选运动分量奇偶性的调制完成水印嵌入。同时在I帧中采用Lagrangian优化算法和在P帧中采用拉格朗日代价函数式方案,有效地降低了水印嵌入带来的码率提升。实验证明了该算法的有效性。     

基于块差值的半脆弱可逆视频认证方法

针对半脆弱可逆视频认证问题,提出一种基于块差值直方图调整的半脆弱可逆视频认证方法.在H.264帧内预测后重构的I帧Y分量中,通过预测残差对图像块分类.根据人眼视觉模型,在纹理复杂的区域嵌入比纹理平滑区域更多的水印.在接收端使用K-means对各块的差值进行聚类,自适应判断块差值所属区间,实现高准确率的水印提取.通过空间和时间认证之后,通过嵌入算法的逆操作实现无损视频还原.实验结果表明:提出算法具有良好的视觉效果,能够抵抗常规图像处理和噪声攻击,并实现对恶意篡改区域定位功能.     

Robust Video Watermarking of H.264/AVC

A robust video watermarking scheme of the state-of-the-art video coding standard H.264/AVC is proposed in this brief. 2-D 8-bit watermarks such as detailed company trademarks or logos can be used as inconvertible watermark for copyright protection. A grayscale watermark pattern is first modified to accommodate the H.264/AVC computational constraints, and then embedded into video data in the compressed domain. With the proposed method, the video watermarking scheme can achieve high robustness and good visual quality without increasing the overall bit-rate. Experimental results show that our algorithm can robustly survive transcoding process and strong common signal processing attacks, such as bit-rate reduction, Gaussian filtering and contrast enhancement     

图像内容真实性认证的半易损水印方案研究

提出一种基于半易损的图像内容真实性认证方案。该算法既对不改变图像内容的一般性操作具有较好的顽健性，又能对改变图像内容的篡改操作具有较强的敏感性。在水印图像进行一般性处理后能够借助水印差别国和滑动窗检测并定位被篡改的区域。本文还从概率论的角度给出了精确的判决门限确定公式。仿真试验采用一般性操作和篡改操作相结合的方法，实验结果表明本文算法在保护数字图像内容真实性方面是可行的。     

融合宏块平坦度和时空相关性的预测模式选择算法

H.264/AVC以巨大编码复杂度为代价,在获得更高压缩率的同时,编码实时性也随之降低。针对视频编码中重要且耗时的帧间预测技术,分析了宏块平坦度和时空相关性,提出了一种快速的预测模式选择算法。仿真实验结果表明,本文提出算法与H.264/AVC(JM12.2)标准算法相比,在保持重建视频图像质量和输出码流结构的前提下,平均节省约70%的编码时间,并继承了H.264/AVC低码率的编码优势。     

Fast block mode decision algorithm in H.264/AVC video coding

The recent video coding standard H.264/AVC show extremely higher coding efficiency compare to any other previous standards. H.264/AVC can achieve over 50% of bit rate saving with same quality using the rate–distortion process, but it brings high computational complexity. In this paper, we propose an algorithm that can reduce the complexity of the codec by reducing the block mode decision process adaptively. Block mode decision process in H.264/AVC consists of inter mode decision process and intra mode decision process. We deal with reduction method for inter and intra mode decision. In this paper an efficient method is proposed to reduce the inter mode decision complexity using the direct prediction methods based on block correlation and adaptive rate distortion cost threshold for early stopping. The fast intra mode reduction algorithm based on inter mode information is also proposed to reduce the computational complexity. The experimental results show that the proposed algorithm can achieve up to 63.34–77.39% speed up ratio with a little PSNR loss. Increment in bit requirement is also not much noticeable.     

一种面向H.264/AVC的码率控制算法

码率控制是视频编码中非常重要的技术之一,任何标准离开码率控制其应用都会受到限制.H.264/AVC是目前最新的视频编码标准,本文根据H.264/AVC编码标准的特性及其HRD部分对码率控制的要求,提出了一种新的适合H.264/AVC的码率控制算法,该算法实现了率失真优化与码率控制的结合,使得在达到码率控制的同时也能保证较高的编码效率,同时在码率控制的过程中根据HRD缓冲区状态进行位分配调整,保证了编解码缓冲区既不上溢又不下溢.该算法作为技术提案已被H.264/AVC接受,并集成到H.264/AVC的校验模型软件中.