## Forums Search for: Wavelets

## Fast Fourier Transform with Wavelets - Anyone have any experience?

inI am trying to improve the speed of an FFT algorithm for processing a sonar bottom echo return signal. I implemented FFT for N = 8192 nodes. An...

I am trying to improve the speed of an FFT algorithm for processing a sonar bottom echo return signal. I implemented FFT for N = 8192 nodes. An FFT algorithm has NLogN performance however we're investigating improving the performance of the algorithm. There's a paper called Fast Approximate Fourier Transform via Wavelet Transform which proposes linear performance : http://citeseerx.ist.psu.edu/...

## Anyone know how to interpret Matlab Wavelet info?

inI am learning how to use the GUI Wavelet program in Matlab (newbie). I am working out an example and notice the following graphs labeled : S,...

I am learning how to use the GUI Wavelet program in Matlab (newbie). I am working out an example and notice the following graphs labeled : S, A1, A2, A3, A4, A5 and D1, D2, D3, D4, and D5. I am performing a level 5 decomposition. I am sure S = original signal but what does A1 to A5 and D1 to D5 mean? I assume its 1 to 5 because its a level 5 decomposition but I am not sure what A and D st...

## Wavelet Decomposition/ FFT

inI have managed to decompose a signal via wavelet transform. I have a signal with 256 points. The transform produced 256 wavelet coefficients....

I have managed to decompose a signal via wavelet transform. I have a signal with 256 points. The transform produced 256 wavelet coefficients. In FFT, we use the odd/even samples and combine them through a butterfly operation using the twiddle factor = e^-i*2PI*kn/N. The paper I am implementing says that we replace the odd/even samples with the wavelet coefficients and the twiddle factor wo...

## Matlab Wavelet (Haar Filter) Discrepancy

inThe 2x2 Haar wavelet transform is : 1/sqrt(2) * [1 1 1 -1] which equals [0.7071 ...

The 2x2 Haar wavelet transform is : 1/sqrt(2) * [1 1 1 -1] which equals [0.7071 0.7071

## Undecimated Wavelet Transform (a trous algorithm) - how to determine 'anchor'/'center' of convolution filter

i am currently implementing the 'Undecimated Wavelet Transform' with the 'a trous' algorithm. See...

i am currently implementing the 'Undecimated Wavelet Transform' with the 'a trous' algorithm. See e.g. http://www.znu.ac.ir/data/members/fazli_saeid/DIP/Paper/ISSUE2/04060954_2.pdf, section II-A. As far as I understand, the implementation (in 1D) for the 'decomposition' and 'reconstruction' phase is very simple, it boils down to the convolution with a low-pass and high-pass filter (where for le...

## Analog wavelet decomposition of wide BW RF signals

Hello friends, do you know any commercially available IC or measurement device implementing US patent no. US 6701297 B2: "Direct intermediate...

Hello friends, do you know any commercially available IC or measurement device implementing US patent no. US 6701297 B2: "Direct intermediate frequency sampling wavelet-based analog-to-digital and digital-to-analog converter" ? I am interested in recording RF signals with bandwidth starting from 1 up to 3 GHz. Kind regards Roman Rumian

## Spectrogram from Complex Morlet wavelet ( recreating article result from data)

inI am trying to recreate the following results: http://i.stack.imgur.com/muMxX.jpg from the following...

I am trying to recreate the following results: http://i.stack.imgur.com/muMxX.jpg from the following data: https://www.dropbox.com/s/mi3szqgzgku29rn/FS40.dat the time is in milliseconds (frequency is 40000 Hz) The article state that they used Complex Morlet wavelet to create the spectrogram: " Power estimates from the averaged LFPs were calculated from timeâfrequency sp

## Spectrogram from Complex Morlet wavelet ( recreating article result from data)

I am trying to recreate the following results: http://i.stack.imgur.com/muMxX.jpg from the following...

I am trying to recreate the following results: http://i.stack.imgur.com/muMxX.jpg from the following data: https://www.dropbox.com/s/mi3szqgzgku29rn/FS40.dat the time is in milliseconds (frequency is 40000 Hz) The article state that they used Complex Morlet wavelet to create the spectrogram: " Power estimates from the averaged LFPs were calculated from time?frequency spectrogram

## continuous wavelet transform with complex morlet wavelet as mother wavelet....

how to implement continuous wavelet transform with complex morlet wavelet as mother wavelet. i know fb and fc values also, but i dont know exact...

how to implement continuous wavelet transform with complex morlet wavelet as mother wavelet. i know fb and fc values also, but i dont know exact syntax(in matlab) so i am not able to implement....

## Correct way to implement Discrete and Stationary Wavelet Transform?

Can someone please confirm if this is indeed the correct way to compute DWT: load image load Haar wavelet for i = 1: Level periodize...

Can someone please confirm if this is indeed the correct way to compute DWT: load image load Haar wavelet for i = 1: Level periodize edges of image convolve image with Low pass Haar wavelet filter and store result in G convolve image with Low pass Haar wavelet filter and store result in H convolve G with low pass Haar to calculate approximation co-eff convolve G with high p...

## Haar Wavelet Coefficients(How to interpret)

Hi,I am a beginner in wavelet analysis.I understand the main idea of wavelet transform.It gives us time frequency representation of signals that...

Hi,I am a beginner in wavelet analysis.I understand the main idea of wavelet transform.It gives us time frequency representation of signals that helps us modify and extract useful features from a signal. I have implemented haar wavelet transform in matlab on images and on audio.In the case of images, I get a nice output whereby I can see the several different filtered outputs.However, such is not...

## How does wavelet decomposition extract frequency (Hz) information?

inHello, I'm trying to understand the basic concept behind wavelets. I can't see how recursive multiplication by arbitrary values (wavelet...

Hello, I'm trying to understand the basic concept behind wavelets. I can't see how recursive multiplication by arbitrary values (wavelet coefficients) produces frequency components within consecutive bands? Is wavelet output even comparable to real frequency components of input signal? I would appreciate it if someone could explain what's the relationship between wavelet output and

## should first coef of spiking decon Wiener filter be positive?

Spiking decon has been used in geophysics for over 50 years. An FIR Wiener filter is computed by Levinson recursion. The inputs are the...

Spiking decon has been used in geophysics for over 50 years. An FIR Wiener filter is computed by Levinson recursion. The inputs are the autocorrelation of the trace, and an impulse (1,0,0,0,...) as desired signal. It is based on certain assumptions, such as the wavelet being minimum phase and stationary (which are only approximations in reality). Now I have been looking at an open-source pac...

## "Pick you Wavelet" by Guo

Is that Java applet around any more? It had sliding pots for picking resnikoff parameters - = - Vasos Panagiotopoulos,...

Is that Java applet around any more? It had sliding pots for picking resnikoff parameters - = - Vasos Panagiotopoulos, Columbia'81+, Reagan, Mozart, Pindus, BioStrategist http://www.panix.com/~vjp2/vasos.htm ---{Nothing herein constitutes advice. Everything fully disclaimed.}--- [Homeland Security means private firearms not lazy obstructive guards] [Urb spraw...

## Mother or base wavelet by fitting

Has anyone done nonlin regression of Resnikoff parameters on basic wavelets - = - Vasos Panagiotopoulos, Columbia'81+, Reagan,...

Has anyone done nonlin regression of Resnikoff parameters on basic wavelets - = - Vasos Panagiotopoulos, Columbia'81+, Reagan, Mozart, Pindus, BioStrategist http://www.panix.com/~vjp2/vasos.htm ---{Nothing herein constitutes advice. Everything fully disclaimed.}--- [Homeland Security means private firearms not lazy obstructive guards] [Urb sprawl confounds terror] [...

## image in image search

inHello! I am trying to implement an algorithm which is supposed to find the best match of a given (small) image in a larger image. I have...

Hello! I am trying to implement an algorithm which is supposed to find the best match of a given (small) image in a larger image. I have thought about a few (naive) ways of implementation, and recently have been pointed at FT and wavelets, which - if applicable - sound rather interesting for my problem. So I was wondering whether you can give me any tips on whether using those transfo...

## Mr. Lyons...

inI'm happy to find out about your book, and just ordered the second edition. I discovered it during a quest to understand wavelets (I have...

I'm happy to find out about your book, and just ordered the second edition. I discovered it during a quest to understand wavelets (I have no experience with signal processing but need it now). From the 42 customer reviews at Amazon it's clear you've written something that may help me understand some foundations for wavelets such as Fourier Transforms. Since you apparently have a rapport...

## basic function, coefficient, wavey line explenations please

inhello, regarding this page http://www.hdbatik.co.uk/temp/waveletsbookpage.html from a book ('the world according to wavelets' by barbara...

hello, regarding this page http://www.hdbatik.co.uk/temp/waveletsbookpage.html from a book ('the world according to wavelets' by barbara hubbard) i've just started to read: first, why on earth is the temperature measurement graph in the top left graph wavey? if that was in a non-fourier/non-wavelets book that'd be a smooth curve, not wavey i'm sure. i can't help feel it's a case of init...

## apparent contradiction between coefficient graph and text

inon this page http://www.hdbatik.co.uk/temp/waveletsbookpage.html is a page from a book ('the world according to wavelets' hubbard)...

on this page http://www.hdbatik.co.uk/temp/waveletsbookpage.html is a page from a book ('the world according to wavelets' hubbard) i'm reading at the moment. in the text about the four graphs on the page it says: We will consider here the coefficients for times t = 1, 5, 10 and 50. For each such time, the coefficients are the same for the entire bar... in the bottom right graph of th...

## Time Support and vanishing moments

inHi everybody, I was going through the wavelets basics. How is Time support and vanishing moments relate to each other? I am trying to get hang...

Hi everybody, I was going through the wavelets basics. How is Time support and vanishing moments relate to each other? I am trying to get hang of it but there is too much mathematics involved and sometimes I feel lost ? Can someone help me understand the underlying concept? I will be grateful. Thanks Vijay Pal