| （英） |
We propose a method for extracting watermarks additively
embedded in video frames by using blind source separation (BSS).
Conventional additive embedding methods require the original
signal during decoding.
A video consists of a sequence of multiple still images, and
similarity between successive frames is high.
By using the similarity between frames and the BSS technique,
we show that the proposed method can perform blind decoding.
After separating the original signal and the watermark
from the stego-frames by BSS,
it is necessary to identify the frame containing
the watermark from the separated signals.
We propose a method to identify watermarked frames based on
correlation.
We embedded a binary image, or logo, into frames as a watermark.
Since the embedding strength $¥beta$ affects the quality of video
and the bit error rate (BER) of the estimated image, the PSNR for
stego-frames and BER for the image were evaluated.
In the case that the strength was weak, the PSNR was over
$47~¥mathrm{dB}$, but the BER was $0.3$ at maximum.
In the case of strong strength,
the PSNR was $30$ to $42~¥mathrm{dB}$ and the BER was less than $0.1$.
As a result, the embedding strength of $¥beta=0.02$ was recommended,
which achieved $¥mathrm{PSNR}>42~¥mathrm{dB}$ and $¥mathrm{BER}<0.1$. |