3.5 Experimental Results
3.5.2 Performance Against WER and FTF Attacks
The next set of experiments is to evaluate the performance of the proposed watermarking schemes against the WER and the FTF attacks. The performance is compared with that of two frame-by-frame additive watermarking schemes: the SS-1 and the SS embedding. In all the schemes, the embedding strength was chosen in such a way that the PSNR of the watermarked sequence is around38dB. The PSNR of the attacked sequence with respect to the host sequence is used as the measure of the visual quality of the attacked video.
For the WER attack, the watermarked video frames are spatially low-pass filtered using an adaptive Wiener filter with a 5×5window [VPH+00]. The Wiener filter is implemented using the MATLAB function. The resulting low-pass frames are subtracted from the watermarked frames and the differ- ences are averaged to get an estimate of the watermark. Finally, the attacked frames are obtained by remodulating the watermarked frames with the estimated watermark [DD04b]. The performance of the watermarking schemes against the WER attack is presented in Table 3.5. As expected, the attack is effective against the SS-1 watermarking scheme while the other schemes survive it. In the case of the SS-1 watermarking, the PSNR of the attacked videos is higher than that of the watermarked sequences (38dB) and the increase in the PSNR is at the cost of the decrease in the NC values. As explained in the previous Section, the robustness of the proposed watermarking schemes against the WER attack owes to the embedding of dynamic watermarks in the dynamic frames.
In the experiments to evaluate the performance against the FTF attack, we consider two sequences:
News and Akiyo, in addition to the sequences used in the previous experiments. These sequences are selected due to their near-static nature, for which the FTF attack is known to be effective. A temporal window width of 9frames is used in the experiments. From the results presented in Table 3.6 it can be observed that the SS-1 watermarking scheme survives the FTF attack in both the static and dynamic sequences whereas the detectability of the SS watermark is considerably degraded. On the other hand, the watermark embedded using the proposed schemes survives the FTF attack in the static sequences and becomes undetectable in the dynamic sequences. Note that the poor detectability of the watermark in the dynamic sequences is not critical since the quality of the attacked videos is significantly degraded as indicated by the low PSNR values. The poor visual quality of the attacked sequences is evident from the sample frames shown in Figure 3.6.
3.5. EXPERIMENTAL RESULTS 61
integer-pixel half-pixel quarter-pixel
Sequence Level 1 Level 2 Level 3 Level 1 Level 2 Level 3 Level 1 Level 2 Level 3
Antibes 0.98 0.96 0.95 0.98 0.97 0.96 0.98 0.97 0.96
Foreman 0.86 0.72 0.56 0.9 0.8 0.68 0.9 0.82 0.7
Coastguard 0.92 0.83 0.69 0.94 0.87 0.78 0.95 0.9 0.81
Mobile 0.84 0.77 0.63 0.91 0.85 0.76 0.91 0.86 0.77
Stefan 0.87 0.74 0.57 0.9 0.8 0.68 0.91 0.83 0.71
(a)
integer-pixel half-pixel quarter-pixel
Sequence Level 1 Level 2 Level 3 Level 1 Level 2 Level 3 Level 1 Level 2 Level 3
Antibes 0.98 0.97 0.95 0.98 0.97 0.96 0.99 0.98 0.97
Foreman 0.89 0.77 0.63 0.92 0.84 0.74 0.94 0.87 0.78
Coastguard 0.93 0.85 0.74 0.95 0.9 0.82 0.96 0.92 0.86
Mobile 0.84 0.78 0.64 0.92 0.86 0.77 0.92 0.88 0.79
Stefan 0.88 0.77 0.61 0.92 0.83 0.72 0.93 0.86 0.75
(b)
Table 3.1: Detector performance of the proposed MPEG-2 watermarking scheme against the MC-FTF attack with varying levels of MC-RTWT decomposition and varying precision of motion-estimation.
The motion vectors for the attack are estimated using the FSBM from (a) the host sequence and (b) the watermarked sequence.
integer-pixel half-pixel quarter-pixel
Sequence Level 1 Level 2 Level 3 Level 1 Level 2 Level 3 Level 1 Level 2 Level 3
Antibes 0.97 0.96 0.95 0.98 0.97 0.96 0.98 0.97 0.96
Foreman 0.8 0.64 0.48 0.86 0.74 0.61 0.87 0.75 0.63
Coastguard 0.9 0.79 0.66 0.92 0.85 0.75 0.93 0.87 0.77
Mobile 0.83 0.75 0.61 0.91 0.84 0.74 0.91 0.86 0.76
Stefan 0.83 0.69 0.53 0.88 0.76 0.64 0.88 0.78 0.66
(a)
integer-pixel half-pixel quarter-pixel
Sequence Level 1 Level 2 Level 3 Level 1 Level 2 Level 3 Level 1 Level 2 Level 3
Antibes 0.98 0.97 0.96 0.99 0.98 0.97 0.99 0.98 0.97
Foreman 0.85 0.71 0.57 0.9 0.81 0.7 0.91 0.83 0.73
Coastguard 0.92 0.83 0.71 0.94 0.88 0.79 0.95 0.9 0.82
Mobile 0.85 0.77 0.63 0.92 0.86 0.77 0.92 0.88 0.79
Stefan 0.86 0.73 0.58 0.91 0.81 0.7 0.92 0.83 0.72
(b)
Table 3.2: Detector performance of the proposed MPEG-2 watermarking scheme against the MC-FTF attack with varying levels of MC-RTWT decomposition and varying precision of motion-estimation.
The motion vectors for the attack are estimated using the HVSBM from (a) the host sequence and (b) the watermarked sequence.
3.5. EXPERIMENTAL RESULTS 62
SS-1 SS MPEG-2
Sequence FSBM HVSBM FSBM HVSBM FSBM HSVM
Antibes 0.39 0.25 0.14 0.14 0.95 0.96
Foreman 0.38 0.41 0.17 0.18 0.63 0.57
Coastguard 0.29 0.25 0.16 0.16 0.74 0.71
Mobile 0.19 0.21 0.14 0.14 0.64 0.63
Stefan 0.42 0.4 0.18 0.18 0.61 0.58
Table 3.3: Comparative performance of the proposed MPEG-2 watermarking scheme against the MC- FTF attack with 3 level MC-RTWT decomposition. The motion vectors for the attack are estimated from the watermarked sequence by using the FSBM and the HSVBM with an integer-pixel accuracy.
integer-pixel half-pixel quarter-pixel
Sequence Level 1 Level 2 Level 3 Level 1 Level 2 Level 3 Level 1 Level 2 Level 3
Antibes 0.97 0.95 0.93 0.98 0.96 0.94 0.98 0.96 0.94
Foreman 0.86 0.68 0.53 0.89 0.77 0.65 0.9 0.79 0.68
Coastguard 0.9 0.75 0.6 0.92 0.8 0.69 0.93 0.83 0.72
Mobile 0.84 0.71 0.59 0.9 0.81 0.71 0.91 0.82 0.73
Stefan 0.85 0.68 0.52 0.89 0.77 0.65 0.9 0.79 0.67
Table 3.4: Detector performance of the proposed MC-TWT domain watermarking scheme against the MC-FTF attack with varying levels of MC-RTWT decomposition and varying precision of motion- estimation. The motion vectors for the attack is estimated from the watermarked sequence by using the HVSBM.
SS-1 SS MPEG-2 MC-TWT
Sequence PSNR NC PSNR NC PSNR NC PSNR NC
Antibes 43.13 0.18 35.67 0.98 35.77 0.97 35.69 0.97 Foreman 43.91 0.14 35.68 0.97 36.17 0.94 35.73 0.96 Coastguard 39.08 0.45 35.62 0.99 35.89 0.98 35.66 0.98 Mobile 38.2 0.55 35.61 0.99 35.85 0.98 35.62 0.99 Stefan 38.71 0.49 35.62 0.99 36.1 0.97 35.7 0.97
Table 3.5: Comparative performance of the proposed watermarking schemes against the WER attack.
3.5. EXPERIMENTAL RESULTS 63
SS-1 SS MPEG-2 MC-TWT
Sequence PSNR NC PSNR NC PSNR NC PSNR NC
Antibes 26.11 1.00 26.33 0.11 26.33 0.14 26.33 0.13 Foreman 26.43 1.00 26.67 0.11 26.65 0.19 26.65 0.19 Coastguard 25.3 1.00 25.48 0.11 25.47 0.21 25.47 0.16 Mobile 20.26 1.00 20.32 0.11 20.32 0.24 20.32 0.17 Stefan 20.72 1.00 20.79 0.11 20.78 0.28 20.78 0.26 News 35.79 1.00 38.54 0.11 35.96 0.95 36.00 0.93 Akiyo 31.86 1.00 32.77 0.11 32.04 0.86 32.05 0.82
Table 3.6: Comparative performance of the proposed watermarking schemes against the FTF attack.
3.5. EXPERIMENTAL RESULTS 64
Figure 3.4: A sample frame from the Foreman sequence marked using the MPEG-2 watermarking scheme (top) and the corresponding watermark (bottom).
3.5. EXPERIMENTAL RESULTS 65
Figure 3.5: A sample frame from the Antibes sequence marked using the MPEG-2 watermarking scheme (top) and the corresponding watermark (bottom).
3.5. EXPERIMENTAL RESULTS 66
Figure 3.6: A sample frame from the Coastguard (top) and Foreman (bottom) sequences after the FTF attack.