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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Comparison between 2 images in Frequency domain

As you can see there are 2 images from the Tom and Jerry cartoon program. In the 1st image both Tom and Jerry are present. But in the 2nd one,only Tom is present.Now,we can clearly see this ...
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3answers
32 views

Removing periodic spike noise from ECG signal

The signal shown in the following figure is collected from a ECG sensor. The spike noise that is observed with a periodicity of 30 seconds was traced to the periodic blip of the LED as it draws ...
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41 views

Compare between JPEG and JPEG2000

JPEG image compression is Fourier based DCT while modern image compression technique like JPEG2000 is based on more multi-scale technique like Wavelets.I want to know how Fourier and Wavelets are ...
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6 views

how to choose a appropriate wavelet basis

everyone ,I'm not really undertand the theory of wavelet transform.I just want to use the tool to do some work about signal filtering .Now I have a set of signal ,I have tried in FFT ,but I haven't ...
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1answer
27 views

what is the delta parameter in scal2freq?

I am running complex morlet (cmor1-1.5) wavelet transform. I want to have the transformation for the range of [1,150] Hz whit step of 1 Hz. I want to use ...
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1answer
21 views

How does a wavelet help in image compression?

I understand how the discrete cosine transform is used in image compression in standards like JPEG. However, the concept of wavelets is a mystery to me. I do know that wavelets are functions that have ...
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23 views

Fractal Modulation Implementation

I would like to get help/assistance from whom could support me. I am trying to simulate the Fractal Modulation where the modulation and demodulation equations defined as: Modulation Equation ...
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0answers
10 views

What is the difference between Haar transform and Haar wavelet transform?

What is the difference between Haar transform and Haar wavelet transform? Haar transformation is a particular matrix multiplication. Haar wavelet transform is realised as filter banks. So is it ...
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1answer
27 views

How to cover all spectrum in wavelet when it which is behalved?

As I know , wavelet decomposition behave with halve. I mean that a way like this HH HL LH LL. But I wonder, how to corver the all spectrum when it was halved? I think if it want to all cover spectrum ...
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12 views

What is meant by “complete set” in the context of affine wavelets?

In the book by Sayood on compression, he says "if the set is complete, it is called affine wavelets". I want to know what is meant by completeness of wavelets.
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42 views

Why not stop with the first level decomposition in wavelet?

Typically, We do wavelet decomposition with the last one level. But I wonder, why do decomposition withh the last one level? In the other word, why not stop with the first decomposition level?
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32 views

What is the scaling function and wavelet function at wavelet analysis?

I'm trying to looking the meaning and functionality about scaling function and wavelet function at wavelet analysis. I have googling already. But I can't find and understand the meaning. What does ...
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24 views

Matrix expansion into bases

I have an image (that is a matrix), let's say of dimensions NxN. I then want to expand this matrix into M basis matrices (for the moment I'm still unsure how many M of these basis matrices I should ...
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1answer
103 views

How to find phase values on precise pixel locations of a given Image? [closed]

I have computed magnitude and phase spectrum of cameraman Gray scale image using fft function. Here, we get magnitude and phase spectrum of the whole image. .Please see the reconstruction of image ...
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1answer
52 views

Where is the “time and frequency” in a Discrete Wavelet Transform?

The DWT is motivated by the ability to see signal in time and frequency at the same time, if I understood that correctly. I am using the following Matlab commands for some signal x: ...
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32 views

Time frequency representation of DWT coefficients in Matlab

I am using discrete wavelet transform to analyze an audio file. I can calculate the dwt coefficients and the inverse dwt works fine. What I want to do now is to visualize how different coefficients ...
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0answers
16 views

Wavelets and filters?

I've tried using the search function to answer this question, but haven't found any explicit answers. I'm trying to study Gabor and log-Gabor filters. Most of the content I find is on Gabor wavelets ...
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0answers
50 views

Multilevel one-dimensional wavelet analysis-Downsampling

I'm a complete novice to digital signal processing and I am not completely sure about down sampling using wavedec and appcoef in 1D dwt. I am analyzing sound signal and I would to compere and see how ...
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1answer
27 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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41 views
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28 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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1answer
13 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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30 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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39 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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43 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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65 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
55 views

denosing using soft thresholding or hard thresholding in matlab

let us consider following code ...
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66 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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17 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
65 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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2answers
86 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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39 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
40 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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15 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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167 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
50 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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13 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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0answers
10 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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45 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
55 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
18 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
108 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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20 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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53 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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0answers
43 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
41 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
43 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?