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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19 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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11 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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52 views

Denoise images with wavelets

I try to understand what following algorythm from this gimp plugin does to denoise an image: ...
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1answer
26 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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8 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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15 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
28 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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0answers
15 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 ...
2
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1answer
64 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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0answers
10 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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19 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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22 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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0answers
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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0answers
36 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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0answers
28 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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0answers
22 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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0answers
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
63 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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0answers
12 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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0answers
28 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
34 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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0answers
34 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
37 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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73 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
66 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
58 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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26 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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0answers
22 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
62 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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24 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
23 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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0answers
35 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 ...
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0answers
26 views

Wavelet Transform library in Java

I'm wondering whether there is a good open-source wavelet transform library out there. Best I can find now is JWave, but it lacks documentation. Any alternative? Thanks.
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19 views

Stationary wavelet transfrom: diagonal detail response

I am using the PyWavelets library to take the stationary wavelet transform of some images. By looking at the documentation for the stationary wavelet transform, I notice that for each scale level it ...
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3answers
75 views

FIR / IIR and Wavelets

I am a self-learner of DSP by reading various books. I have accomplished basic understanding of Signals - CT and DT and a few transforms. I recently started to learn FIR / IIR Filters. The part that ...
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1answer
30 views

What are the settings of Daubechies and Complex Gaussian are called?

Hello What are the numbers of Daubechies and Complex Gaussian are called? I dont know what to call db4 or cgau8.
0
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1answer
73 views

time frequency localization using wavelet transform

I am currently doing analysis on Photoplethysmograph (PPG) data and I want to know the frequency (heart rate) at every time point so a windowed FFT might not be the best option. I am looking at ...
-1
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1answer
163 views

What are the advantages and disadvantages of the Ridgelet transform?

I used continuous wavelet transform (CWT) to analyze the behavior of a 1-D smooth signal(extracting its modal property, damping and frequency components)in my research. Now someone asked: Why the ...
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0answers
17 views

How to implement non-decimated inverse Wavelet transform?

Is it as simple reversing the forward non-decimated wavelet transform procedure with filter co-efficients altered to those for re-construction? Or is there something else that I need to take care of?
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1answer
79 views

Correct way to implement Discrete and Stationary Wavelet Transform?

Can someone please confirm if this is indeed the correct way to compute DWT: ...
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1answer
49 views

Wavelets: How does the admissibility condition imply this $\Psi(0)=0$

I'm reading through some material on wavelet and I'm finding it difficult to see why the following is true. Let $\Psi(\omega)$ is the Fourier transform of the mother wavelet $\psi(t)$ ...
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2answers
385 views

Denosing signal using soft and hard thresholding

Let us consider following code: fs=100; N=1000; t=0:1/fs:N-1; y=10*sin(2*pi*100*t)+0.5*randn(size(t)); plot(y) plot(t,y) I have applied following threshold ...
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1answer
58 views

Does modified Morlet wavelet function satisfy the admissibility condition?

Does modified Morlet wavelet function satisfy the admissibility condition ? Do you have any reference for the answer please. Thanks.
0
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1answer
58 views

What are some ways to detect the fundamental frequency in a signal using without using FFT?

I am trying to estimate the fundamental frequency in a signal to corroborate the result which I have got by FPGA implementation of an FFT algorithm. Hence, could someone give me some idea how to do ...
2
votes
1answer
162 views

How do you change pitch with wavelet transforms in MATLAB?

I'm trying to increase the pitch of a wav file using MATLAB. (I don't expect it to sound very good, but I'm trying to figure out how wavelets in MATLAB work.) Here's what I'm doing: ...
3
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0answers
74 views

Why does the Stationary Wavelet Transform shift this image?

I am running a stationary wavelet transformation on a brain image. I can't understand why it shifts with each level so that the image is no longer centered. You can see that the X component shifts to ...
3
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1answer
108 views

Normalized Wavelet power spectrum

I am analyzing the spectral components of a time series using the continuous wavelet transform following Torrence and Compo (1998). I would like to partition the signal variability or spectral power ...
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0answers
34 views

How can I get frequency information in wavelet?

I am working in image processing. I am confused while getting into wavelet. I applied the fft2() function on Lena image and I got frequency information for the same. But when I applied bior4.4, a ...
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0answers
120 views

How can I specify the scale parameter of the wavelet in PyWavelets (pywt)?

When computing wavelet transforms with PyWavelets (Discrete Wavelet Transform in Python), e.g. ...