Wavelet Packet Decomposition filter specification
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Hi, I am looking to perform Wavelet Packet Decomposition on a 2 dimensional image using my own filter coefficients.
I have noticed that when performing standard 2-D Wavelet Decomposition there is a function 'dwt2' which takes high and low pass filters as parameters, however when performing Wavelet Packet Decomposition only a wavelet name can be specified and not the actual filters.
Just wondering is anyone aware of a function which will enable me to specify my own high and low pass filters for use with Wavelet Packet Decomposition? Or, if anyone has any ideas these would also be greatly appreciated.
thanks, John
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Accepted Answer
Wayne King
on 14 Dec 2011
Hi John, yes the filter I gave you above matches exactly. What you have to realize is that Wavelet Toolbox multiplies the orthogonal lowpass filter by sqrt(2) so that it satisfies the properties of a conjugate quadrature filter. This is built into the way Daubechies describes her filters. She describes them divided by sqrt(2).
If you do this:
[LoD,HiD] = wfilters('db10');
h = fliplr(LoD/sqrt(2))
You will see exactly the filter you are looking for. So you can just use wpdec2() with 'db10'.
Hope that helps
More Answers (2)
Wayne King
on 14 Dec 2011
Hi, John, you have your own orthogonal or biorthogonal filters? Then, yes, you can add them to the toolbox with wavemngr() and then use them in wpdec2
You should ensure that these are orthogonal or biorthogonal filters, or you will not have a wavelet packet transform.
Wayne King
on 14 Dec 2011
In what sense do you say they're different? You may be confusing the way the Wavelet Toolbox refers to db#. The Wavelet Toolbox uses the number of vanishing moments and not the length of the filter. The length is twice the number of vanishing moments.
[LoD,HiD] = wfilters('db10');
length(LoD)
Does the above filter give you what you need?
Is this paper somewhere I can see?
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