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

learn more… | top users | synonyms

0
votes
0answers
7 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) - ...
0
votes
0answers
11 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: ...
1
vote
0answers
16 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 ...
0
votes
0answers
12 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?
0
votes
0answers
18 views

Speech analysis by using Linear predictive analysis or Discrete wavelet trasform

Could anyone explain the advantages and disadvantages of LPA over DWT for speech signal in term of time, memory, complexity and so on ? Actually my question is related to the field of communication, ...
0
votes
0answers
23 views

Amplitude and frequency plot for an input image.

This is my original image: First I have plotted scale vs frequency then transformed scale to frequency and got frequency-time plot: I have plotted highest power of coefficients (indicated by ...
0
votes
0answers
23 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 ...
0
votes
1answer
26 views

Intuition behind Wavelet Transform?

I was thinking sometime back about how to explain Wavelet Transform ELI5. So this is what I came across. The co-relation of two exact signals is 1. So if I have an input signal f(x) made up of an ...
4
votes
3answers
448 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 ...
0
votes
1answer
57 views

use wavelet for improving spectral resolution

let us consider following code ...
0
votes
2answers
81 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 ...
1
vote
2answers
68 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 ...
0
votes
0answers
27 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 ...
0
votes
0answers
46 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 ...
1
vote
1answer
57 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 ...
0
votes
1answer
56 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 ...
0
votes
1answer
114 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 ...
0
votes
1answer
28 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 ...
1
vote
1answer
70 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 ...
0
votes
0answers
94 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 ...
0
votes
0answers
20 views

get similar picture from wavelet transform

my today's question is related to previous question about wavelet, ...
1
vote
3answers
98 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) ...
1
vote
0answers
47 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 ...
0
votes
0answers
39 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 ...
0
votes
1answer
19 views

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 ...
1
vote
0answers
25 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 ...
0
votes
0answers
29 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 ...
0
votes
1answer
33 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 ...
1
vote
0answers
36 views

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 ...
1
vote
1answer
66 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. ...
0
votes
1answer
66 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 ...
2
votes
3answers
145 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 ...
5
votes
2answers
188 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 ...
0
votes
1answer
76 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 ...
4
votes
4answers
144 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 ...
4
votes
2answers
93 views

mean of wavelet for image processing

For many papers which talks about using wavelet transforms for feature detection in image processing, it is stated that it is advantageous for the wavelet to have zero mean? Why is this so? Thanks in ...
2
votes
0answers
32 views

How can I change the frequency band (Fb parameter) using cwtft?

The cwt matlab implementation uses the complex morlet wavelet as: psi(x) = (pi*Fb)^(-0.5)*exp(2*1j*pi*Fc*x)*exp(-(x^2)/Fb); However, it is possible to implement ...
-1
votes
2answers
57 views

how can i call the input data in wavelet transform and generate code for gabor wavelet manually? [closed]

I am an ECE student, and i am doing my project I want to generate a code for gabor wavelet transform. I have no idea could you help me with a sample program I have DNA as input sequences and how ...
-1
votes
2answers
85 views

Need to learn wavelet, suggest steps and resources [closed]

I am looking for a good introduction to wavelets and wavelet transforms. that covers the following: Vector Spaces – Properties– Dot Product – Basis – Dimension, Orthogonality and Orthonormality – ...
1
vote
0answers
55 views

Shifting of Shift-Invariant Wavelet Transforms

Main Question: Why would iterative wavelet/inverse-wavelet transforms cause a shift along the x-axis for undecimated (shift-invariant) wavelet transforms? I am attempting to remove backgrounds from ...
0
votes
1answer
58 views

Inverse of Wavelet Transforms - Background and Noise Removal

Main Problem: How can you inverse Wavelet Transforms (Using the data given by signal.scipy.cwt) I was wondering if anyone understands the ...
1
vote
1answer
32 views

Are all isotropic bandpass filter kernels, wavelets?

Are all isotropic bandpass filter kernels, wavelets? Are there any properties that the radial frequency profile has to meet to be considered a wavelet?
0
votes
0answers
24 views

How I calculate to system identification of shear building with wavelet?

I have a 3 story shear building and I excited with acceleration and then taken displacement of stories with SAP and then. I want to calculate the frequencies of system with wavelet. I attached my ...
0
votes
2answers
53 views

How do I implement the CDF wavelet inverse?

I understand and have implemented a 2D discrete wavelet transform that uses a Haar wavelet to process images. Now I would like to implement a 2D Cohen-Daubechies-Feauveau wavelet transform, but I am ...
3
votes
0answers
57 views

Error bounds in signal compression represented by truncated Moore-Penrose biorthogonal bases using von Neumann wavelets

I was reading and trying to reproduce the results in the arXiv preprint of Periodic Gabor Functions with Biorthogonal Exchange: A Highly Accurate and Efficient Method for Signal Compression by Asaf ...
0
votes
1answer
74 views

gabor wavelet and gabor transform

I was reading a paper 'A Flexible Framework for Local Phase Coherence Computation' (paper URL) on using wavelets for local phase coherence. I just want to be sure. Is the gabor wavelet the same as the ...
0
votes
3answers
100 views

Relationship between windowed fourier transform and wavelet transform

I was reading on windowed fourier transform and wavelet transform, and i was thinking that the windowed fourier transform is a subset of wavelet transform. Is that true?
1
vote
0answers
37 views

How to undecimate and make shift invariant a Dual-tree Complex Discrete Wavelet Transform in R

I have the following vector and wavelet transform (from R waveslim package) ...
0
votes
1answer
39 views

Two-dimensional wavelet analysis

Could you tell me why wavelets without scaling functions can't be used for two-dimensional analysis? What is the role of scaling function?
1
vote
1answer
73 views

Denoise EEG signal by using Daubechies function

I have an EEG signal and it contains eye blink artifacts. I read some references and know that it is possible to detect eye blinks and remove them by using wavelet transforms, but I don't know that ...