# A Survey on Robust Video Watermarking Algorithms for Copyright Protection
## 4 Robust Watermarking Algorithms Based on Original Videos
### Video Watermarking in Transform Domain
#### 4.2.4 Hybrid Transform-Based Watermarking Algorithms  
To combine the advantages of different transformation methods to better improve the performance, many watermarking algorithms in the hybrid domain have emerged [62; 63; 64; 65; 66]. In a previous paper [62], scene identification and scene summarization were adopted to generate the video summary, and then the summary was used to detect the first type of feature regions by using the crowdsourcing technique. The second type of feature regions are detected by using the moving objects and the mosaic frame generated from the original video. After these two types of feature regions are merged, the final mosaic is generated, and the watermark is embedded into it by DCT, DWT, and SVD methods. To resist frame blending and projection attacks, [PERSON] et al. [63] combined DCT and 3D-DWT together to embed the watermark. Depending on the energy compression property of DCT and the multiresolution property of DWT, some hybrid DWT/DCT-based video watermarking algorithms have been proposed [64; 65]. In another past paper [66], a zero-video watermark algorithm based on 2D-DWT and pseudo-3D DCT was proposed. The introduction of the log-polar transform improves the robustness to rotation operations. The watermark is encoded into a code division multiple access watermark through spread spectrum technology and then SVD is combined to embed the watermark. The summary comparison of several watermarking algorithms in hybrid domain is shown in Table 6.  
In addition, to help readers know the performance of original video-based algorithms involved in the paper quickly, Table 7 gives the quantitative comparison of invisibility and robustness of several typical algorithms in spatial, DCT, and DWT domains, and Table 8 gives the quantitative comparison of invisibility and robustness of several typical algorithms in hybrid domain. In Tables 7 and 8, the numbers in \"()\" indicate the parameters of attacks and \"-\" shows that the attack is not mentioned in the reference. The reason may be that the algorithm cannot resist the attack, or the authors have not considered it. In addition, the full names of several typical attacks corresponding to the abbreviations mentioned in Tables 7 and 8 are given in Table 1. \begin{table}
\begin{tabular}{c c c c} \hline
**Ref.** & **Type** & **Watermark Preprocessing** & **Embedding Position** \\ \hline
[62] & Blind & Scrambling & Feature regions obtained by crowdsourcing and moving objects \\ \hline
[63] & Blind & - & Low-frequency DCT coefficients of regions around SIFT points in LLL sub-bands \\ \hline
[64] & Blind & Arnold transform & Middle-frequency components \\ \hline
[65] & Blind & Index mapping table & Three selected DCT coefficients of LL\({}_{2}\) sub-bands in suitable channel \\ \hline
[66] & Blind & Spread spectrum and Logistic map & Feature values generated by dual transform and log-polar in luminance component \\ \hline \end{tabular}
\end{table} 
Table 6: Summary comparison of several watermarking algorithms in hybrid domain. \begin{table}
\begin{tabular}{c c c c} \hline
**Ref.** & **Type** & **Watermark Preprocessing** & **Embedding Position** \\ \hline
[54] & Blind & Chaotic encryption & Singular value matrix of LL\({}_{1}\) sub-bands in Y component \\ \hline
[55] & Blind & Pseudorandom generator & Singular value matrix of diagonal detail coefficients of G component \\ \hline
[56] & Non-blind & SVD & Singular value matrix of LL\({}_{2}\) sub-bands in Y component \\ \hline
[57] & Blind & Fibonacci–Lucas transform & Singular value matrix of LH sub-bands of R component \\ \hline
[58] & Non-blind & Arnold transform & Singular value matrix of 2-level DWT LH and HL sub-bands in Y component \\ \hline
[59] & Blind & Chaotic map & Singular value matrix of LL sub-bands in Y component \\ \hline
[60] & Blind & 2-level DWT & Singular value matrix of HL\({}_{2}\) sub-bands of LH sub-bands in Y component \\ \hline \end{tabular}
\end{table} 
Table 5: Summary comparison of several SVD-based watermarking algorithms.