## Forums Search for: Wavelets

## Filters design for Discrete Wavelet Transform

Dear all, I have a question about how can I design filters for DWT using a given mother wavelet? I have found that if we have the filters we...

Dear all, I have a question about how can I design filters for DWT using a given mother wavelet? I have found that if we have the filters we can use dilation equation to build scaling function and then using scaling function and wavelet equation it is possible to construct the mother wavelet, but I am looking for opposite direction which means that with the given new mother wavelet pattern, I ...

## WAVELET PACKET DIVISION MULTIPLEXING

Dear All; kindly i make my Thesis in WAVELET PACKET DIVISION MULTIPLEXING and i need help from my colleage to start to discover this new...

Dear All; kindly i make my Thesis in WAVELET PACKET DIVISION MULTIPLEXING and i need help from my colleage to start to discover this new topic in the DSP and use it in fourth Gereration , i just starting to make my researchs and i need the help from any one know any information about WPDM and how i can use it in multicarrier to apply that in fourth generation in mobile communication ...

## help needed to implement multiple wavelet denoising

The function for denoising in my code is function output = SureDenoise(input,wtype,sigma) here only one orthonormal wavelet called sym8 is...

The function for denoising in my code is function output = SureDenoise(input,wtype,sigma) here only one orthonormal wavelet called sym8 is used and the function for decomposition is WT = WaveDecompo(input,wtype,J) here input is the noisy image and J is the number of scales.While decomposing the image is decomposed into lowpass and highpass subbands.The denoising is done only the highpas...

## Channel response

Please can anybody help me with this: Is there any matlab program that can approximately compute the time-varying channel response h(tau,t)...

Please can anybody help me with this: Is there any matlab program that can approximately compute the time-varying channel response h(tau,t) directly from the equation h(tau,t)=sigma(An(t)delta(tau-tau n(t)) A direct approximation will help me in an ongoing research in wavelet applications to signal transmission Thanks

## Choosing an appropriate wavelet basis

inI have been spending some time learning about and implementing wavelets, but there is still one lingering question that I have: How do you go...

I have been spending some time learning about and implementing wavelets, but there is still one lingering question that I have: How do you go about choosing the best wavelet basis given a priori knowledge of the exact signal you are applying it to? In my particular case, I have what looks like a single Gaussian enveloped sinusoid of a particular bandwidth and center frequency. This "puls...

## Inverse Discrete Wavelet transform

Below is a reply by Jani Huhtanen in another old thread... > Below is a diagram of the synthesis part of the wavelet transform (one >...

Below is a reply by Jani Huhtanen in another old thread... > Below is a diagram of the synthesis part of the wavelet transform (one > level): > > y0[n]--UpSample--x0[n]--G0(z)--z0[n]-- > + ---> z[n] > y1[n]--UpSample--x1[n]--G1(z)--z1[n]-- > > Say that y0[n] and y1[n] are defined for n=1..8 (i.e. 8 samples). After > UpSample x0[n] and x1[n] are defined for

## 2D wavelets for image recognition

Does anyone know of a good reference for 2D wavelet pattern recognition? I am trying to match similar shapes using a clustering technique like...

Does anyone know of a good reference for 2D wavelet pattern recognition? I am trying to match similar shapes using a clustering technique like k-means. My images are of mechanical drawings so the outside boundary alone may not be sufficient for my purpose. Thanks in advance for your help, caveman

## Plot local maxima of a scalogram

Hello every body, I am asking your kindness to help me to plot the local maxima of a scalogram (computed with the Discrete wavelet Transform)....

Hello every body, I am asking your kindness to help me to plot the local maxima of a scalogram (computed with the Discrete wavelet Transform). Indeed, I find the local maxima of the scalogram by considering the localmax matlab function but I can't plot the obtained result as a significant figure that allows me to interpret the signal singularities. Best regards.

## Image Denoising and Wavelet Thresholding

inHello, I am currently doing a research on the above subject. I am not sure about the level of decomposition during wavelet transform. What is...

Hello, I am currently doing a research on the above subject. I am not sure about the level of decomposition during wavelet transform. What is the reasonable number of levels to decompose for image denoising? Thanks.

## Trying to follow the math behind wavelets

inHi. I'm trying to understand wavelet theory, and the CWT in particular, and I'm running into some rough spots. If anyone has a few minutes to...

Hi. I'm trying to understand wavelet theory, and the CWT in particular, and I'm running into some rough spots. If anyone has a few minutes to comment, or point me at a better place to ask these questions, it would be greatly appreciated. After scanning a few 'web pages and online articles, it appeared that wavelets would be a good way of decomposing a complex, coded data stream like the ...

## Wavelets calculation

Suppose I have an input sequence like : x[n] = { x0,x1,x2,x3 }. I have to calculate the DWT level 2: W2 = { S(2,0) ,...

Suppose I have an input sequence like : x[n] = { x0,x1,x2,x3 }. I have to calculate the DWT level 2: W2 = { S(2,0) , T(2,0) , T(1,0) , T(1,1) } Where S(m,n) is an approximation coefficient and T(m,n) is a wavelet coefficient; m is related to the scale and n is related to the localization. Can anyone suggest me a link or tell what exactly are the equations that I ...

## related to the wavelet theory

inHi, I am new to everything related to the wavelet theory, but i find it very interesting and would like to know more about it. I have...

Hi, I am new to everything related to the wavelet theory, but i find it very interesting and would like to know more about it. I have some questions and was hoping someone could help me. 1. What is the number of zero moments of a Haar mother wavelet? Is the answer related to the fact that the Haar function is not continiously diferentiable? 2. Why a RI spline wavelet is superiour to...

## 2D wavelet followed by 2D FFT?

inI am having trouble understanding the meaning of an operation that a customer finds useful. They have a 2D block of data that is part of a...

I am having trouble understanding the meaning of an operation that a customer finds useful. They have a 2D block of data that is part of a medical image. They do a 2D wavelet transform on this, followed by a 2D FFT of the wavelet coefficient set. I find it hard to visualize what the result of this means. Any sugestions would be welcome. Thanks, Chris ==========================...

## Interesting application of Wavelet based filtering

Hello all, Here is an interesting paper analyzing trends in alcohol sales and the economic cycle using wavelet based filtering. The paper is to...

Hello all, Here is an interesting paper analyzing trends in alcohol sales and the economic cycle using wavelet based filtering. The paper is to appear in Applied Economic Letters. http://swopec.hhs.se/oruesi/abs/oruesi2008_002.htm Best regards. Ravi.

## Frequency warping

inHello, I've been reading about frequency warping, but I'm not sure what's the best route to take. It seems that using all-pass filters can't be...

Hello, I've been reading about frequency warping, but I'm not sure what's the best route to take. It seems that using all-pass filters can't be reconstructed, and WFIR's are expensive, and there's warped wavelet techniques but I haven't bought the papers on this. Googling around gave me some mixed reports that CELP uses WPLC, which turns out to be an all-pass system that others said would...

## Discrete Wavelet Transform

inI have heard the DWT requires only N calculations. The documents I have read say it uses FIR filters so wouldn't this mean at each stage...

I have heard the DWT requires only N calculations. The documents I have read say it uses FIR filters so wouldn't this mean at each stage N*N calculations are required? Even if the signal is decimated at each stage how can you be using FIR filters (convolution) and not end up with a large number of calculations? The only thing that would reduce the calculations would be to use FFT convolution bu...

## Noise variance estimate

inI'm trying to implement a simple denoising module based on wavelet filter-banks (DWT) with VAD. Noise is white, but I'm going to use other noises...

I'm trying to implement a simple denoising module based on wavelet filter-banks (DWT) with VAD. Noise is white, but I'm going to use other noises as well (car, babble, pink,..) 1) How can one estimate the noise variance on each subband? 2) Would it be better to build VAD on the base of decomposition or as stand-alone module (energy feature)? The main problem that I'm not sure how to use stan...

## Wavelet filters

inHello, Does anyone know the relation between the signal and mother wavelet function? In other words, what wavelet (db2, db6, sym,...) would...

Hello, Does anyone know the relation between the signal and mother wavelet function? In other words, what wavelet (db2, db6, sym,...) would better decompose the signal into subbands. Thanks

## Subband Spectral Entropy

inHello, Could you please advice on how to find the spectral entropy on each subband of discrete wavelet trasform decomposition? Thanks

Hello, Could you please advice on how to find the spectral entropy on each subband of discrete wavelet trasform decomposition? Thanks

## about implementing redundant discrete wavelet transform

Hi can anybody guide me about implementation of redundant discrete wavelet transform in matlab. It is simply the undecimated DWT. I have...

Hi can anybody guide me about implementation of redundant discrete wavelet transform in matlab. It is simply the undecimated DWT. I have written my own code for DWT and idwt. As in RDWT there is no down sampling , I have removed that block in DWT and similarly upsampling in idwt.But the reconstructed image comes very whitish.please guide me. vandana