Questions tagged [wavelet]

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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1answer
583 views

Reconstruct DWT for each cD1,cD2,cD3 and cA3 signals

This question must be basic for this forum, but I'm only start working with DWT recently, and I was working with CWT before. I ...
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2answers
711 views

Examples of Causal and Complex Wavelets?

I'm looking for wavelets that are both: causal (a wavelet coefficient $W(j,k)$, where $j$ is scale and $k$ is translation, does not use data from $t > k$ to be estimated). complex (such as the ...
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1answer
1k views

discrete Haar wavelet transform, fast and efficient method?

I'm working on my own implementation of the discrete Haar wavelet transform, I understand the wavelet theory and how to construct the Haar matrix of size N to perform the transform, but obviously ...
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0answers
267 views

Hints and helps to implement an accurate wavelet packet transfrom

I want to implement a Time-Freqency analysis by wavelet packets. I don't know what level and sampling rate should I use. I've tried different value for level(3,4,5,6,). but I couldn't get an accurate ...
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1answer
895 views

Spectrogram from Complex Morlet wavelet ( recreating article result from data)

I am trying to recreate the following results: ...from the following data: Dropbox Link (FS40.dat) The time is in milliseconds (frequency is 40000 Hz) The article state that they used Complex ...
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0answers
247 views

What's the similarities and differences between Wigner transform and wavelet transform?

Wigner transform and continuous wavelet transform are both some kind of time-frequency representation of a signal. What are the similarities and differences between them? Could you give some ...
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1answer
364 views

Creating a matrix of Gaussian wavelets at dyadic scales

I need to create a diagonal matrix containing the Fourier coefficients of the Gaussian wavelet function, but I'm unsure of what to do. Currently, I'm using function ...
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1answer
2k views

What is the definition of a noiselet?

I am reading about different integral transforms. Fourier transform being a subject I will soon take a class on. Looking at the wavelet transform there is one term that I do not understand, that is ...
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1answer
857 views

Heisenberg Uncertainly Principle and wavelet transform

I am using CMOR(complex morlet) wavelet in Fourier space in order to reconstruct my signal and also estimate damping and frequencies of the embedded modes. there are two main parameters in cmor. the ...
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1answer
937 views

Wavelet time extraction

I am trying to understand one simple thing in wavelets and I searched a lot, but did not get any idea. I need to perform Multilevel 1-D wavelet decomposition on my signal. I have arrays ...
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0answers
161 views

understanding discrete wavelets

I was reading section 4.3.3 from chapter 4 of "A Wavelet Tour of Signal Processing", "...Let $\bar{f}(t)$ be a continuous time signal defined over $[0,1]$. Let $f[n]$ be the discrete signal obtained ...
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1answer
94 views

Plotting wavelet co-efficients

I need to take the wavelet transform of an image (for reference, I will be using Debauchies wavelets, and the test image will either be Lenna or matlabs default woman image),and plot the coefficients ...
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1k views

inverse continuous wavelet transform and [Parm] in cwtft

what is 'parm' means when you set the name of wavelet function in cwtft or icwtft. ...
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1answer
182 views

What's the physical meanning and principle of applying anisotropic diffusion in transform domain?

I am reading several papers applying anisotropic diffusion in the transform domain like Shearlet, curvelet. All of them have got excellent results. The physical meaning and principle of applying ...
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1answer
190 views

Can I run a GA to optimize wavelet transform?

I am running a wavelet transform (cmor) to estimate damping and frequencies that exists in a signal.cmor has 2 parameters that I can change them to get more accurate results. center frequency(Fc) and ...
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0answers
108 views

How to optimize a wavelet transform?

I am using complex morlet wavelet to estimate frequencies and damping ratios in a 1-D signal. I have done it so far, and the results are accurate enough. Now my question is how can I modify or ...
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76 views

Reconstructing a partially deleted image through wavelets

I am trying to form an approximation of the wavelet transform from a partially sampled image. Reconstruction in the 1D case is easy. We have $w = h x$, with $w$ as the wavelet coefficients, $h$ as ...
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2answers
12k views

Using continuous verses discrete wavelet transform in digital applications

I am familiar with much of the mathematical background behind wavelets. However when implementing algorithms on a computer with wavelets I am less certain about whether I should be using continuous or ...
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1answer
3k views

Understanding this Haar Wavelet Example

I'm trying to understand Wavelet Transform , I've done well enough to understand Continuous Wavelet Transform which was easy enough, where we simply stretch the wavelet and match it with the original ...
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1answer
406 views

Impossible to make a scalogram of a signal with 262144 samples

I have a signal with 262144 samples and "sampled" with 200Msps. I want to use the cwt (Continuous Wavelet Transform), for making a time-frequency scalogram. Also, I worked in some scripts in python ...
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0answers
612 views

why wavelet (CWT) doesn't show accurate results always?

hmm any one can help please? I have a signal that contains some modes in it. I've run a CWT transform but I haven't got my desired results. so I implement a test signal that contains freqs [0.1,0.3,0....
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1answer
636 views

Data fusion using 2d discrete wavelet transform (DWT)

I am working on a project that employs a linear array sensor that provides data from the same object at two different energies. Collected in time, I end up with two images (16-bit sensor values, MxM ...
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1answer
493 views

Complex Cepstral Transform on Audio in MATLAB

Hello I am trying to computer the Complex Cepstral Transform of an audio signal. I am using wavread to get an array of data type double precision. However, when I ...
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2answers
999 views

Are there any good texts on EEG analysis geared towards programmers

I just have a quick question. I'm a second year computer science major with a background in C# and C++. I'm interested in studying neuroscience after graduation, and I've been researching some ...
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1answer
635 views

Audio Watermarking - What is typically embedded?

Just starting research in audio watermarking and have read many papers regarding audio watermarking but I am still a little confused on what exactly gets embedded into the signal. For example, one ...
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0answers
561 views

3 Band Wavelet Transform In MATLAB

I am currently working on an audio watermarking project in MATLAB. I currently have a code I am using to construct a nxn 3 Band Wavelet Transform matrix. However, when I try to construct a matrix that ...
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1answer
62 views

fliter doesn't filter

In this code I try to decompose music from singer sound with wfilters but when I hear it it is still mixed where Iam I wrong ? ...
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1answer
2k views

Interpreting Coefficients from wavelet

The wavelet transform informs what all derived wavelets (from mother wavelets) with different scales at different point of time , are present (along with the associated strength) in my original ...
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3answers
1k views

How do I get started with Wavelets

Our current project requires us to do some analysis using Wavelet Transform. Can anybody suggest me a practical book, preferably with MATLAB or C examples. I am currently reading some tutorials, but ...
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0answers
1k views

bandpass implementing with DWT in matlab

In matlab help in find the implementation of bandpass as following ...
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0answers
166 views

Multiresolution discrete wavelet transforms: First steps

I have been looking at trying to use wavelets for multichannel audio dynamic range processor. I am in the very early stages of trying to get decomposition and reconstruction working. In this thesis, ...
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0answers
164 views

Are there any lossless embedding algorithm to support Haar(DWT) in audio watermarking?

I've been trying to do some research on audio watermarking and what i wanted is to insert string into audio file in the transform domain (DWT), i've read some literature of DWT especially HAAR ...
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2answers
538 views

Scalogram (Wavelet)

Using a signal of three joined sinus of equal length at different frequencies (40 Hz, 50 Hz, 80 Hz) I calculate a scalogram of it (scale vertical, time horizontal, The steps of variing the scale ...
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2answers
555 views

Implementing Wavelet Transform using Equations

I want to implement Wavelet Transform from the scratch, that mean breaking the wavelet transform into its equations to implement in any Programming language. Matlab Comes with built-in functions to ...
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1answer
358 views

Question about the Haar Wavelet transform

I'm trying to detect the presence of a sinusoid in 1/f noise conditions using the STFT and the DWT with Haar wavelets. I find this interesting phenomenon that I'm not able to explain (see plot at 1) ...
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1answer
2k views

Matlab DWT H-level

I'm trying to implement some watermarking algorithm found in a paper*. This is a line of the paper: Do the H-level DWT for all the renumbered segments. Then in simulation section the author ...
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0answers
113 views

Reconstruction from Convolution

I am trying to implement Wavelet transform in an embedded environment. The problem I face goes like this: Two vectors, A and B. A is input samples. B is vector co-efficients. I take convolution of A ...
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1answer
429 views

Is Entropy Coding in Wavelet equivalent to Huffman Coding in DCT

How exactly we should describe the process of Entropy Coding in wavelets ? can't it be simply called Coding ? Here is the block Diagram of Image compression using wavelet, I am confused about the "...
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1answer
523 views

How to turn Morlet wavelet into second generation wavelet?

I have a very specific application which requires to use the complex Morlet wavelet (or Gabor wavelet, if that's the name you use). I currently use the convolution theorem to compute wavelets ...
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1answer
397 views

2-D Wavelet output changing when using 'figure' command in Matlab

I am having trouble understanding what is causing the problem to my Wavelet output when i am trying to display the image with the figure command. I want to display both the Original image and its ...
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0answers
308 views

Wavelet computation with filter bank - differing results

I'm trying to get a grip on Wavelets. I've read "Wavelets, Their Friends, and What They Can Do for You" which lead me to an implementation of the discrete DWT with filter banks. Basically, I'm using ...
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1answer
2k views

wavelet denoising routine for environmental data series

I have a time series of water temperature, e.g. y = 1+(30-10).*rand(1,365); I have previously used the wavelet denoising routine in the wavelet toolbox by matlab ...
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2answers
1k views

Why Low Frequency called Approximation and High Frequency Detail?

While we are decomposing a signal using Wavelets into levels why do we call our high frequency components as Detail and Low Frequency Components as Approximation ?
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1answer
4k views

Why Wavelet developed when we already had Short-time Fourier transform

If we already had Short-time Fourier transform for better analysis of a signal than Discrete Fourier Transform, then what was the need that leads to development of Wavelet Transform ?
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1answer
823 views

1-D Wavelet Toolbox in Matlab

I'm so happy that i managed to come at this level to understand Wavelet transform to some extent with the help of Stackexchange fellows, Initially i had so many difficulties as i had no concept of ...
5
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1answer
973 views

wavelet analysis normalized to have unit energy

I am analyzing some time series of sea surface water temperature and am using wavelet analysis to do so. I am computing the continuous wavelet transform and then removing some specific frequencies and ...
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0answers
419 views

Wavelets and cryptography [closed]

What papers/articles/books are considered good for getting started with wavelets' application to cryptography? I'm primarily interested in irregular grid wavelets, but regular grid will do for ...
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1answer
293 views

Multidimensionnal wavelet admissibility criteria

I've read there are two admissibility criteria for wavelets, both of which are designed to preserve total power of the signal (source: http://en.wikipedia.org/wiki/Wavelet#Mother_wavelet, as well as ...
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1answer
1k views

Using Discrete Wavelet Transform in the time-frequency domain

I am creating an application that works like the Shazam service. In short, my goal is to create an audio pattern matching service. However, I would like to use DWT and not the short time Fourier ...
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3answers
1k views

Which mother wavelet for a scalogram?

I'm attempting to create a real-time scalogram (from a 1 dimensional signal) in the style of a spectrogram; Looking through various papers+books; the Gabor wavelet, or complex Morlet seems to be ...

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