Normalised Cross-correlation FFT
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From: dbd on 17 Mar 2010 19:35 On Mar 17, 3:09 pm, Dirk Bell <bellda2...(a)cox.net> wrote: .... > Right. As both of us have noted, the definitions can be used. The > question of interest, I believe, is how to implement the calculation > with maximal use of FFTs, which means how to calculate the shift > dependent normalization factor with FFTs assuming it is efficient to > do so. > > Dirk Will it help if I say "shift" the data through y instead of "slide"? There is no more to it than that. Calculate the FFT on time varying data in y at whatever strides (and thus, output sampling frequency) you wish to move through the data with. Dale B. Dalrymple
From: Dirk Bell on 18 Mar 2010 08:53 On Mar 17, 7:35 pm, dbd <d...(a)ieee.org> wrote: > On Mar 17, 3:09 pm, Dirk Bell <bellda2...(a)cox.net> wrote: > ... > > > Right. As both of us have noted, the definitions can be used. The > > question of interest, I believe, is how to implement the calculation > > with maximal use of FFTs, which means how to calculate the shift > > dependent normalization factor with FFTs assuming it is efficient to > > do so. > > > Dirk > > Will it help if I say "shift" the data through y instead of "slide"? > There is no more to it than that. Calculate the FFT on time varying > data in y at whatever strides (and thus, output sampling frequency) > you wish to move through the data with. > > Dale B. Dalrymple No really. Perhaps if you said what the data was you were talking about you would answer the OP's question. Dirk
From: Dirk Bell on 18 Mar 2010 11:13 On Mar 17, 7:35 pm, dbd <d...(a)ieee.org> wrote: > On Mar 17, 3:09 pm, Dirk Bell <bellda2...(a)cox.net> wrote: > ... > > > Right. As both of us have noted, the definitions can be used. The > > question of interest, I believe, is how to implement the calculation > > with maximal use of FFTs, which means how to calculate the shift > > dependent normalization factor with FFTs assuming it is efficient to > > do so. > > > Dirk > > Will it help if I say "shift" the data through y instead of "slide"? > There is no more to it than that. Calculate the FFT on time varying > data in y at whatever strides (and thus, output sampling frequency) > you wish to move through the data with. > > Dale B. Dalrymple Not really. Perhaps if you said what the data is you are talking about you would answer the OP's question. Dirk
From: dbd on 18 Mar 2010 12:22 On Mar 18, 8:13 am, Dirk Bell <bellda2...(a)cox.net> wrote: > ... > > Not really. Perhaps if you said what the data is you are talking > about you would answer the OP's question. > > Dirk The answer to the OP's question is "yes" and the description of the calculation is in the first reference. The OP is welcome to ask for any further clarification desired. My remarks are in terms of the reference I gave (and the notation in): The normalized correlation calculated by fft as described in section 3 on page 15 of: http://www.bksv.com/pdf/Bv0013.pdf Dual Channel FFT Analysis (Part I) Technical review No. 1 - 1984 Usenet text does not provide a convenient substitute for math formulas that are available in references. I've taken the time to provide a price free accessible reference for that reason. And pointed to a particular section in the reference. Your previous responses led me to assume you were capable of accessing and reading the reference. If not, what kind of assistance in accessing the internet do you need? Dale B. Dalrymple
From: Dirk Bell on 18 Mar 2010 13:58
On Mar 18, 12:22 pm, dbd <d...(a)ieee.org> wrote: > On Mar 18, 8:13 am, Dirk Bell <bellda2...(a)cox.net> wrote: > > > ... > > > Not really. Perhaps if you said what the data is you are talking > > about you would answer the OP's question. > > > Dirk > > The answer to the OP's question is "yes" and the description of the > calculation is in the first reference. The OP is welcome to ask for > any further clarification desired. > > My remarks are in terms of the reference I gave (and the notation in): > The normalized correlation calculated by fft as described in section 3 > on page 15 of:http://www.bksv.com/pdf/Bv0013.pdf > Dual Channel FFT Analysis (Part I) > Technical review No. 1 - 1984 > > Usenet text does not provide a convenient substitute for math formulas > that are available in references. I've taken the time to provide a > price free accessible reference for that reason. And pointed to a > particular section in the reference. Your previous responses led me to > assume you were capable of accessing and reading the reference. If > not, what kind of assistance in accessing the internet do you need? > > Dale B. Dalrymple Dale, I don't need any assistance, I am not the OP. I think the OP needs to know how to compute the one normalization factor function using FFTs. Dirk |