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   -> Volume 6, Issue 3

Question: Denoising: How does N affect the threshold ?
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Author Message (Andrew Dorrell)

PostPosted: Fri Feb 28, 1997 1:34 am    
Subject: Question: Denoising: How does N affect the threshold ?
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#22 Question: Denoising: How does N affect the threshold ?

Dear waveleteers,

I have been trying to apply the wavelet shrinkage techniques of Donoho
and Johnson to some practical image processing problems but keep
hitting a problem: the factor 'n' in the threshold calculation. It
seems that the threshold at any level is dependent on the number of
coefficients (samples) you have! This just doesn't make sense to me
(especially as I am considering the use of different sized "windows"
over a large image). Surely the optimal threshold will be a function
of the noise variance only? The distributions of the noise and signal
are assumed to be stationary aren't they? Am I missing some
fundamental point in a big way?

Please help! :-/

Mr Andrew Dorrell School of Electrical Engineering University of
Technology, Sydney PO Box 123 Broadway NSW 2007 AUSTRALIA Phone: 61 2
330 2395 Fax: 61 2 330 2435 email:
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