MASTER THESIS Video Watermarking - Computer Graphics Group ...

5.4.2 Scaling
The scaling test scales down the watermarked video sequences to the
specified resolution using MPlayer bicubic “scale” filter. The resolution is given by
scaling factor (column in Table 5 named SF) which determines how much the
images of the output raw stream are scaled down – e.g. scaling factor of 1/4
means that the image area size is reduced 4-times, i.e. both width and height are
halved.
The raw stream is compressed at the scaling factor fragment of the former
bit-rate, i.e. for example scaling factor of 1/4 means 1/4 of the former bit-rate.
Then, the compressed stream is scaled up back to the former resolution and
recompressed at the former bit-rate because the synchronization of the pure
watermark with the tested video sequence in the detection process is out of scope
of this thesis. Moreover, the human operator which would convert the sequence to
the former stadium is better than any artificial intelligence automaton.
Table 5: Scaling test results
Looking at the results, we can say that noise method is more robust than the
other two methods, especially for lower scaling factors. Anyway, the higher
resolution the sequence has the less impaired the watermark is.
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