# A Survey on Robust Video Watermarking Algorithms for Copyright Protection
## 5 Robust Watermarking Algorithms Based on Compressed Videos
### H.264-Based Watermarking Algorithms  
H.264, which is also the 10 th part of MPEG-4, is a highly compressed digital video codec standard proposed by the joint video team (JVT) composed of the international telecommunication union-telecommunication (ITU-T), video coding expert group (VCEG), and ISO/IEC & MPEG. It has a higher data compression ratio and higher video picture quality [81]. Compared to the MPEG standard, H.264 adopts some different technologies, like prediction technology, so many conventional video watermarking algorithms are no longer applicable. Most robust video watermarking algorithms based on H.264/AVC choose to embed watermarks into DCT coefficients [82; 83; 84; 85; 86]. For the VOD service, [PERSON] et al. [82] proposed a real-time double watermarking algorithm. Through an effective error compensation mechanism and XOR mapping rules, copyright information and user information are embedded into I frame and P frame, respectively, as two watermarks. According to the characteristics of HVS, [PERSON] et al. [83] proposed a more accurate JND model to determine the watermark embedding strength by taking luminance masking, contrast masking, and spatial frequency sensitivity function all into account, and introduced it into video watermarking algorithm by the analysis of the energy distribution drift error. [PERSON] et al. [84] proposed a watermarking algorithm for spatial scalable video coding based on HVS, which embedded watermark information into high texture blocks of video streams. [PERSON] et al. [85] expanded the existing motion coherence region detection algorithm in the compression domain to detect moving objects in video shots, and embedded watermark information into them to resist geometric attacks. To achieve higher video visual quality and slight bit rate increase, [PERSON] et al. [86] embedded watermark information in the last nonzero level of quantized DCT (QDCT) blocks. In a past paper [87], the I_4 \(\times\) 4 type of macroblocks (MBs) based on energy content were used to selectively distribute watermark rows to greatly improve the robustness against the video transcoding attack. Based on the newly proposed bit stream syntax elements in H.264 standard,  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Ref.** & **Type** & **Standard** & **Embedding Position** \\ \hline
[71] & Blind & MPEG-2 & AC coefficients of luminance component of shadow frames \\
[72] & Blind & MPEG-2 & Last DC coefficient of the last macroblock of each slice in Y component \\
[73] & Blind & MPEG-2 & DCT coefficients of luminance blocks decomposed from bit streams \\
[74] & Blind & MPEG-2 & Spatial or frequency domain of Y-component \\
[75] & Blind & MPEG-2 & L. sub-bands of I frames \\
[76] & Blind & MPEG-4 & Luminance blocks of selected MBs \\
[78] & Blind & MPEG-4 & DCT coefficients of luminance blocks of VOPs \\
[79] & Blind & MPEG-4 & Local areas of I frames based on the extraction of feature points \\
[80] & Blind & MPEG-4 & Middle-frequency DCT coefficients of Y-component of I frames \\ \hline \hline \end{tabular}
\end{table}
Table 9: Summary comparison of several watermarking algorithms based on MPEG.  
[PERSON] et al. [88] embedded a watermark into the index of the reference frame during video encoding. A block modification technique based on optimization model is proposed, which can control robustness and video bit rate by manipulating two parameters. The summary comparison of several watermarking algorithms based on H.264 is shown in Table 10.