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Re: [WM]: human visual system in video
Hi,
The watermark strength factor of a video watermarking system has a
spatial and a temporal part. There exist good publications which
describe the spatial factor*.
Some video watermarking papers describe a temporal shape factor as they
claim that a benefit can be gained by exploiting the decrease of
spatial acuity (sharpness) of a moving object. I argue against the
watermark strength factor adaptation to the motion content as prior
knowledge of the ability of the viewers visual system to track an
object is not available. The spatial acuity is a function of the
ability of the visual system to track an object with smooth-pursuit eye
movements and does not depend directly on the image velocity. Assuming
the availability of this prior knowledge does not solve the
perceptibility of the watermark when the sequence is viewed at a slower
frame rate or even is stopped, as the moving object will accelerate at
a slower pace and makes it easier to track. Therefore a stronger
watermark will become perceptible. The only case where a stronger
watermark can be embedded imperceptibly is immediately following
drastic scene changes. As these frames will be coarser quantized and
the visual system needs time to adapt to the new scene. There is only
one case where one can embed a stronger watermark into a moving object
that is when the acceleration is random and difficult to track.
Hope that helps,
Dominique
* S.Voloshynovskiy, A.Herrigel, N.Baumgärtner, T.Pun, A stochastic
approach to content adaptive digital image watermarking, In
International Workshop on Information Hiding, Notes in Computer
Science, Ed. Andreas Pfitzmann, Dresden, Germany, September (1999), pp.
211-236.
On Mon, 22 Sep 2003 10:42:41 +0800 jd_sun <jd_sun@sina.com> wrote:
> Hi,every watermarker:
> Would you like to tell me whether there are some papers on human
visual masking model
> for video? And how to get them? I think there must be some papers on
video perceptual
> measure or the masking model for video, just like there are so many
human visual system
> for images.Thanks for any help in advance!
>
> Yours Sincerely,
Ph.D. student in Image Communications
Dominique Albert Winne, Electrical & Electronic Engineering
Room 2.19 MVB, tel: (0044) 0117/9545126
D.Winne@bristol.ac.uk (private: winnje@hotmail.com)
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