Cryptography Reference
In-Depth Information
Table 12.1.
Comparisons of image quality and watermark robustness with single
watermarking in Sec. 12.4.1 under different channel erasure probabilities with a
codebook length of L = 512.
Watermarked image
Extracted BCR
Channel erasure probability
p
1
p
2
quality (in dB)
(in %)
0
0
32.53
100
0.05
0.05
30.69
97.56
0.1
0.1
28.90
95.14
0.25
0.25
24.59
88.18
0.3
0.3
23.14
86.04
0.4
0.4
21.52
81.46
0.5
0.5
19.98
76.25
0
1
26.18
73.34
1
0
26.09
80.55
12.9.2 Results with Multiple Watermarking
For the multiple watermarking algorithm in Sec. 12.4.1, simulations with dif-
ferent channel erasure probabilities are presented in Fig. 12.11 and Fig. 12.12
with a codebook of length L = 512, and in Fig. 12.13 and Fig. 12.14 for
the codebook of length L = 1024. We also use tables to make comparisons
with the results obtained from other existing algorithms. In Table 12.2 and
Table 12.3, we present the watermarked PSNR values and the BCR values
of the extracted watermarks with a codebook with length of L = 512. Ta-
ble 12.4 and Table 12.5 are their counterparts with the codebook with length
of L = 1024.
In Fig. 12.11, p
1
and p
2
denote the erasure probabilities with Channel
1 and Channel 2. Fig. 12.11(a) shows that the extracted watermarks under
error-free transmission. These are identical to those embedded in Fig. 12.8. In
Fig. 12.11(b)(d), they represent the results when transmitting over lightly
to heavily erased channels. The BCR values are high and the extracted wa-
termarks are recognizable even when p
1
= p
2
=0.5. In Fig. 12.12, we demon-
strate the case when one of the channels experiences a total breakdown.
When Channel 2 breaks down, as shown in Fig. 12.12(a), the first watermark
is recognizable, while the second cannot be distinguished. When Channel 1
breaks down, as shown in Fig. 12.12(b), we obtain similar results to those in
Fig. 12.12(a).
In Table 12.2 and Table 12.3, the PSNR and the BCR values under differ-
ent erasure probabilities are indicated. Comparisons with the results in [10]
and [11] are also made. The PSNR values in Table 12.2 show error-resilient
capabilities with MDVQ under severely erased channels. The PSNR values
with our algorithm outperform others in most cases. Under the error free con-
dition, the watermarked PSNR using our algorithm has the best performance.
