How the reconstruction biorthogonal filters are calculated?
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Hello,
do anybody know, how the reconstruction biorthogonal filters (LoR and HiR) are calculated? I use function [LoD,HiD,LoR,HiR] = wfilters(wname) to obtain decomposition and reconstruction filters for WT. I know that LoR is created from HiD and HiR from LoD by changing the sign of even or odd indexes of impulse response. It is done according to the equations (which I found to be equivalent):
LoR(z)=HiD(-z) and HiR(z)=-LoD(-z)
or
LoR(z)=-HiD(-z) and HiR(z)=LoD(-z)
I found that bior2.2, bior2.4,... (even Nr and Nd) corresponds with the first equation, while bior1.5, bior3.3,...(odd Nr and Nd) corresponds with the second equation. So, are the equations equivalent or is there any rule which one to use for particular wavelet?
Thank you!
Andrea
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