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 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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12 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
45 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
24 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.
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1answer
46 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 ...
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1answer
135 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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11 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
32 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
37 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
106 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
36 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.
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1answer
56 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 ...
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1answer
111 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: ...
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45 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 ...
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1answer
50 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
28 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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69 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. ...
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1answer
257 views

Feature extraction/reduction using DWT

For a given time series which is n timestamps in length, we can take Discrete Wavelet Transform (using 'Haar' wavelets), then we get (for an example, in Python) - ...
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41 views

Multilevel 2-D Wavelet Transform as a Matrix

I am trying to generate a single matrix $\Psi$ that will perform a multilevel 2-D wavelet decomposition. Such that for a 2-D image $X$, I can produce a coefficient "image" $\Theta$ as follows: ...
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20 views

Estimate the type of wavelet transform in receiver side

Suppose that a signal is decomposed by using discrete wavelet transform (DWT) and transmitted. Is it possible for receiver to find which type of wavelet is applied in transmitter side ? I mean, if ...
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383 views

Haar wavlet Transform in OpenCV

I am new to OpenCV. I am working on implementation of Haar wavelet transform of an image in OpenCV in C++. Please anyone suggest me how to implement?
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75 views

How to use pseudo frequencies with wavelet transforms

I'm slowly getting my head around the use of wavelet transforms (CWT & DWT) with my data, but I'm interested in how the wavelet transforms correspond to certain bands of frequencies. I'm using ...
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1answer
85 views

Intuition behind the Continuous Wavelet Transform?

I was thinking sometime back about how to explain the Continuous Wavelet Transform ELI5. So this is what I came across. The correlation of two exact signals is 1. So if I have an input signal $f(x)$ ...
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3answers
546 views

When can we write Heisenberg uncertainty Principle as a equality?

We know that Heisenberg uncertainty Principle states that $$\Delta f \Delta t \geq \frac{1}{4 \pi}.$$ But (in many case for Morlet wavelet) I have seen that they changed the inequality to an ...
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201 views

use wavelet for improving spectral resolution

let us consider following code ...
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2answers
101 views

does Increasing resolution lead to have a poor resolution?

As it has proven in some paper and books the time and frequency resolution of Morlet wavelet is : $\Delta t=\frac{f_c\sqrt{f_b}}{2f_i}$ $\Delta f=\frac{1}{2\pi f_c \sqrt{f_b}}$ I don't know how ...
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2answers
99 views

Morlet wavelet time and frequency resolution

I want to calculate Morlet time and frequency resolution. the Morlet wavelet function is define as : $\psi(t)=\frac{1}{\sqrt{\pi f_b}}e^{j2\pi f_c}e^{-t^2/f_b}$ Note: I know the answers, but I don't ...
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39 views

understanding 1D wavelet analysis

i would like to understand how should i use following code for code for detection of uknown frequencies?let us consider following signal ...
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111 views

CWT for filtering / feature extraction

I had asked a question last night in regards to how to process my data (Noise rejection / feature extraction) but I have a more specific question now that I hope someone can answer. As mentioned in ...
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1answer
121 views

Noise rejection / feature extraction

I'm hoping someone could point me in the direction of some signal processing methods to clean up my data. I'm collecting physiological data from human muscle (lower leg; gastrocnemius) during ...
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1answer
91 views

denosing given signal using wavelet

let us suppose that we have given following model $y(t)=A_1 \sin(\omega_1*t+\phi_1) + A_2 \sin(\omega_2*t+\phi_2) + A_3 \sin(\omega_3*t+\phi_3)+ \ldots +A_p \sin(\omega_p*t+\phi_p)+z(t)$ where ...
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1answer
195 views

Obtaining beat histogram using Tzanetakis algorithm

I am working to make a music player with automatic genre classification application in Java. On Google searches I mostly found the works of George Tzanetakis who describe an algorithm from Music Genre ...
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1answer
82 views

Wavelet thresholding

What is the difference between soft thresholding and hard thresholding. Where we use soft and hard thresholding in image for denoising. I understand that in hard thresholding, the coefficients below ...
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3answers
833 views

Continuous Wavelet Transform with Scipy.signal: what is parameter “widths” in cwt() function? How do time-frequency?

I search to display a time-frequency signal with an original discrete temporal signal (sampling step = 0.001sec). I use Python and the library Scipy.signal. I use the function ...
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121 views

Fast Fourier Transform and Clustering of Time Series

I'm making a project connected with identifying dynamic of sales. That's how the piece of my database looks like: There are free columns: Product - present the group of product Week - time since ...
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24 views

get similar picture from wavelet transform

my today's question is related to previous question about wavelet, ...
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3answers
144 views

use wavelet transform to extract frequencies from given signal

let us suppose that we have following signal values,which consists by deterministic components and random noise(white noise) ...
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55 views

Algorithms for removing oscillations?

I am interested in removing oscillations from a signal to capture the lower-frequency variations, similar to the objective of this problem. The oscillations vary in frequency in the time domain, so ...
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46 views

Disadvantageous of wavelet transform

i have question related to wavelet transform:we know that while Fourier transform is good for spectral analysis or which frequency components occurred in signal,it will not give information about at ...
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2answers
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Is there any difference between the 2D continuous and discrete Gabor filter when it comes to MATLAB implementation

I want to know the difference between the 2D continuous and discrete Gabor filter when it comes to Matlab implementation. I found many files related to 2D Gabor filter on Mathworks File Exchange but I ...
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0answers
51 views

Causal Wavelet Decomposition

I've seen the use of a Causal wavelet mentioned a few times but have never seen any examples of them in use with Matlab. Is it possible to to perform a Wavelet Decomposition using a causal wavelet ...
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66 views

determining number of levels in discrete wavelet transform

I want to determine number of levels of decomposition of discrete wavelet transform when number of samples is not a power of 2 .I tried to decompose a signal of length 14 by using wavemenu of matlab ...
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1answer
66 views

Convolve a minimum phase wavelet with delta peak

let's assume I have two time series: one with a delta peak at position $x$ and another time series with a minimum phase wavelet that starts at time $y$ with a maximum peak at position $z$. Now, when ...
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Derive Maximum of zero phase rotated wavelet from rotated wavelet

I have one question concerning phase rotation of signals and I am not sure wether it works or not: Let's assume we have a zero-phase wavelet x(t) i.e. Ricker wavelet. Unfortunately, in our ...
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2answers
196 views

convolution of signal with wavelet

I know that the complex wavelet transform is given by $$\int_{-\infty}^{\infty}f(x)\psi^*_{s,u}(x)\,dx$$ where $f$ is the signal, $\psi_{s,u}(x)=\frac{1}{\sqrt{s}}\psi(\frac{x-u}{s})$ is the wavelet. ...
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1answer
81 views

Suggestions for FFT based tools to analyze music - Preferably MATLAB/free software packages [closed]

I am interested in analyzing full length songs for general features of the track which are not otherwise apparent. For e.g., I want to look at various parts of the song with time-frequency ...
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3answers
273 views

Why does a narrower window in a Fourier transform or STFT give poor frequency resolution?

In theory of FT(Fourier transform) and STFT(Short Time Fourier Transform) it is said that "A wide window gives better frequency resolution but poor time resolution. A narrower window gives good time ...
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2answers
253 views

Combining two images

I am working with speckle noise reduction in ultrasound images. I have used wavelet transform for removing the noise by eliminating certain frequencies in order to eliminate any existing noise. Since ...
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1answer
115 views

Fourier Transform of Morlet wavelet Fucntion?

as you know the Morlet Fucntion is given by: $\frac{1}{\sqrt{\pi f_b}}e^{\frac{-t^2}{f_b}}e^{j2\pi f_c}$ The Fourier transform of this equation is: $e^{-\pi^2 f_b(f-f_c)^2}$ (is it right)? First I ...
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205 views

Why does the high frequency component of an image contain more noise?

I am working with wavelet transforms. When we apply a discrete wavelet transform to an image, it decomposes into four components named the approximation component, thevertical component, the ...