MASTER THESIS Video Watermarking - Computer Graphics Group ...

The third and the fourth row sets contain the bit-rate growth ratio in
percent to the former bit-rate over either all slices or I slices only. Block method
increases bit-rate less in comparison with coefficient method because when 0 is
embedded, a half of transform coefficients are zeroed in block method while only
one coefficient is zeroed in coefficient method. Anyway, bit-rate is increased the
most when using noise method. This is mostly obvious in Renaissance because of
many uniform areas which are represented by small amount of data in the former
compressed video stream.
Each test iteration has been executed with five different copy IDs; values in
the table are average values of corresponding five results.
Figure 15 and Figure 16 show the difference between the original picture
and the watermarked one using noise method with weight factor of 20 for
demonstration.
Figure 15: Original picture Figure 16: Watermarked picture
Because of inter coded pictures may use watermarked pictures as reference
pictures in inter prediction, distortion caused by watermark embedding
propagates, as visible in Figure 17 and Figure 18. Therefore, the inter prediction
compensation is to be implemented in future work.
Figure 17: Original inter coded picture Figure 18: Distorted inter coded picture
In practice, weight factor of 2 is a good compromise between robustness and
perceptibility.
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