A wavelet is a wave-like oscillation with an amplitude that starts out at zero, increases, and then decreases back to zero.

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Wavelet transform on vibrations

I am working on wavelet transformation on vibration signals. I have data with displacement values, I had performed 'wavedec' function on my signal. I obtained the corresponding aprox. coefs and det. ...
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1answer
24 views

How matching pusuit algorithm works

I could infer from books and wiki that a matching pursuit finds signal approximations from a redundant dictionary. Let f be the signal, ai be the basis and Ri be the residue.. here we choose the inner ...
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26 views
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10 views

Image denoising algorithm in matlab

I'm trying to denoise a grayscale image using the two level denoising algorithm as shown in the following block diagram. I used wiener filtering for denoising.Code is given below. ...
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8 views

Wavelet packet transform (WPT) features dimensionality

Just a question that could be trivial for someone but I'm doubtful. Let's say that I have a signal, e.g. electromyography signal, of length $300$. If I apply a WPT, how can I define the dimensionality ...
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11 views

DIrectional data in image

What is mean by directional content as perceived in Contourlet transform of image/signal processing? Wavelet transform cannot capture directional information.
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19 views

Phase of damped sines

There is a interest about determination of phases relative to each other. I measured one signal in time domain. It consists of three damped sines plus noise. One component is present all the time, so ...
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27 views

Unable to obtain accurate amplitude using Continuous Wavelet Transform

I'm doing an analysis of pre-known signal (example in Mathworks), consisting of two sinusoids, one at 100Hz and the other at 50Hz. I applied CWT to the combined signal and the amplitude (~7 for 50Hz ...
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35 views

Complex Morlet Wavelet piano sound analysis

my project is monophonic music transcription I am using complex Morlet wavelet but over the 1000 Hz complex Morlet does not give all results right, my code is like that ; ...
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37 views

How can I get the inverse of complex continuous wavelet transform in matlab?

There is a function in matlab, namely "CWT" that yields the complex coefficients of the wavelet transform for a certain complex mother wavelet. However, it seems the inversion is not a straightforward ...
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60 views

Resolution problem of high frequency components in wavelet domain

I am trying to exploit the sparsity of Chirp signal in wavelet domain. But I have trouble working with continuous wavelet transform. For lower frequencies everything is OK, however as frequency ...
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1answer
40 views

denosing using soft thresholding or hard thresholding in matlab

let us consider following code ...
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28 views

Help for programming CWT using complex morlet wavelet?

Here is my code for continuous wavelet transform using complex morlet wavelet. But it's not giving accurate result..Please anybody help to rectify my mistakes..thanks in advance :) ...
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11 views

Is there any wavelet similar to coif2 but with rounder trough at the bottom?

Is there a standard wavelet funtion which is similar to coiflet 2 but with a more blunt or round trough at the bottom? It is like mexican hat wavelet but inverted.
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2answers
52 views

why wavelet coefficients are zeros after decomposition

I am learning wavelet theory for image processing. To understand the theory, I write one Matlab program to decompose one black-white image. The program is as follows ...
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83 views

Can wavelets be used for complex texture discrimination?

I've recently been studying wavelet analysis with a view to differentiating certain areas of texture images where the texture differs from the background pattern (which is quite random); for example a ...
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34 views

Clarification about wavelet thresholds

I am trying to wrap my head around the original wavelet shrinkage papers of Donoho and others from the mid-90s. There are a couple of curious things that confuse me, and I'd appreciate some input: ...
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1answer
34 views

How convert scal to frequency when use cwt in matlab

I am new in DSP.I have the flowing code t = linspace(0,1,1000); x = cos(2*pi*60*t); CWTcoeffs = cwt(x,1:64,'sym8','plot'); colormap jet; and my output is: ...
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14 views

EZW parent-child relation

I’m trying to learn the EZW principle. I’m having trouble understanding the parent-child relationship. In my case, I want to use it on a 1 dimensional signal. So, let’s say for example a signal of 4 ...
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1answer
153 views

Denoise images with wavelets

I try to understand what following algorithm from this gimp plugin does to denoise an image: ...
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1answer
38 views

How to narrow the frequency band of a wavelet

I have a ricker wavelet with a dominant frequency of 15 Hz. The fourier transform shows its frequency band is almost to 50 Hz. How can I narrow the frequency band of this 15 Hz ricker wavelet? I ...
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11 views

Translation Step For wavelet

For the DWT the discretized translation steps are chosen depending on the scale of the wavelet. Usually this is done by subsampling the wavelet by a factor of 2 (for dyadic grid) prior to correlation ...
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9 views

Can you use a Symlet wavelet for CWT?

Can you use a discrete wavelet such as Symlet wavelet for CWT? If yes, what would you call the wavelet, the scaling function or the wavelet function?
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31 views

Calculating coefficients of 2D Daubechies Wavelet

I want to implement a 2D Discrete Daubechies Wavelet for image denoise. I can use MATLAB to calculate 1D DB Wavelet coefficient. [LoD, HiD] = wfilters('db4'); ...
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1answer
46 views

Critically sampled Laplacian Pyramid from 2nd generation Wavelet

I'd like to know if a technique I have in mind is already used and has a name I can look up, and whether it is likely to work and be useful! My aim is to produce a discrete wavelet transform that is ...
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16 views

Are there condition numbers associated with the STFT, DWT?

Recently I learned that the DFT has good numerical stability since it can be represented as an orthogonal matrix, which has a condition number of 1. Is it possible to represent the STFT and DWT as ...
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1answer
90 views

How can we calculate the frequency response of each filter of a Discrete Wavelet Decomposition filter bank?

I am using the Multilevel Wavelet decomposition. The decomposition results in a filter bank such as the following: Specifically, I am using one of the Daubechies wavelets, ...
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17 views

choosing how many DWT Decomposition levels for 1D

I am building application decomposition of 1D signal sampling frequency $f_s=256$, number of samples $N=512$ - how many levels if the above signal passed through LPF of $70 Hz$ $f_s=256$, number ...
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34 views

What causes edge effects in wavelet transform?

Can someone explain why wavelet transform of a sequence of number will show higher energy at the edges of that time-frequency energy plot? Thanks
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29 views

Wavelets: Conceptually are filter banks, Mallat's pyramidal algorithm and Quadrature mirror filters are one and the same?

I am reading up again on wavelet theory, one thing that is not clear to me is the difference between filter banks, the pyramidal algorithm and quadrature mirror filter. For example, quadrature ...
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18 views

Larger image after wavelet reconstruction

Depending on the size of the original image and depending on the kind of padding used during 2D discrete wavelet transform and reconstruction, the reconstructed image has a larger size. Is there a ...
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38 views

Windowed FFT vs Morlet

I wonder if there is a difference between taking a Wavelet Transform on a signal s using a Morlet Wavelet w (i.e. correlation between s and w) and taking the Fourier Transform on subsequent parts of s ...
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38 views

Feature extraction - DWT

I am new to DSP, I know a quite bit about Python. I have started to code to classify audio (wav files) ...
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24 views

Continuous wavelet function spanning piecewise functions

Is there a continuous wavelet function that spans the space of piecewise: linear functions (as Haar wavelet spans the space of piecewise constant functions). polynomial functions?
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15 views

Definition of Cohen's class

The Cohen's class is defined as a class of time-frequency quadratic energy distributions which are covariant by translations in time and in frequency. Can please someone explain why the invariance by ...
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1answer
81 views

what method for thresholding?

I want to do one threshold method on high pass components of a wavelet frame decomposition approch,for edge detection in image. I have 14 high pass components. for thresholding, I need keep the ...
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17 views

What is the absolute value of the wavelet coefficient?

A wavelet coefficient is usually a complex number. I'm curious whether the absolute value of the wavelet coefficient represents the energy in the signal.
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33 views

High error due to resample function in MATLAB

I am working on training the output of the wavelet transform of a signal using a neural network in MATLAB. So I decided to use 3 layer ...
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1answer
44 views

Orthornormal Wavelet scaling function coefficient calculation (filter design)

I stumbled upon an equation system as shown in the image below while designing an orthonormal wavelet filter. I tried solving the equation (5.63,5.64,5.65 => 5.66) but no avail. I'm not sure if ...
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41 views

Wavelet Denoising: Which thresholding method is considered good in this case?

I performed a routine MATLAB 1-D wavelet denoising using Daubechies 16 Wavelet at level 32 Example Code: ...
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2answers
39 views

Why is successive decomposition of a signal performed only on low pass component?

The question says it all. In typical (wavelet-like) decomposition of a signal, why is only the low pass component chosen for successive decomposition ?
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81 views

Are discrete wavelet transform based statistical features invariant to rotation/translation/scale?

I'm reading a paper where image classification is done. Their approach is to use the discrete wavelet transform with bi-orthogonal wavelets of degree 3.5 and decomposition of level 3 on images. Based ...
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1answer
74 views

What does “real time” signal processing mean?

I thought this was supposed to be an obvious question, until I finally set up my real time system. So basically I have a transmitter that sends 128 samples/second to a receiver. The transmitted ...
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1answer
72 views

Why use Wavelet Denosing instead of Band pass Filtering

What is the important advantage of adopting a wavelet based denosing scheme such as SURE, SUREshrink, etc. than using approaches involving low pass, high pass, band pass, band reject filter for signal ...
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32 views

Selecting the number of cycles for wavelet transform

I'm trying some wavelet analysis of EEG signals, using the phase lock measures from [1], specifically the S-PLV measure. In order to calculate that we perform a wavelet transform on the signals and ...
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26 views

What is the difference between Time-Frequency Represenation and TF Decomposition

I'm asking as I'm looking at Wavelet transforms, and I see that it is possible to have a TF decomposition or a representation of the signal. Looking for example at the code here we can see that the ...
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1answer
87 views

Similarity between two Signals: cycle by cycle

I need to find the similarity between two signals, i.e., measured signal and the reference signal(e.g. a simple sinusoidal signal). What I mean by similarity is, if there is any decentralized glitch ...
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28 views

watermark embedding using 2d arrays

I have LL2 in a 2D array.(extracted after a 2-level DWT). And watermark W1 also in a 2D array.(a binary image, which only contains 0s and 255s). I need help regarding embedding the W1 in LL2 according ...
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1answer
28 views

Can a wavelet transform give time dependent phase of sinusoids in signal

I have a signal which contains sinusoidal components that oscillate at different frequencies. I think the phase of the sinusoids is changing with time. I could do a Fourier transform on small chunks ...
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42 views

Wavelet Transform: Terms and Definitions

I have some doubts in respect to terms and definitions in the domain of wavelet transform/analysis. I analyse a signal by correlating each time my original time samples with different scaled and ...