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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27 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, ...
2
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0answers
16 views
wavelet transform boundary
I am doing 1D wavelet decomposition and I am particularly interested in parts at the border of the signal. These parts are affected by boundary effects.
I know that some of the methods to extend the ...
-1
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0answers
72 views
bandpass implementing with DWT in matlab
In matlab help in find the implementation of bandpass as following
...
0
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0answers
25 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 ...
2
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2answers
59 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 ...
2
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2answers
70 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 ...
2
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0answers
30 views
Wavelet filter coefficients
How can I obtain the wavelet filter coefficients ( i.e. lowpass decomposition filter, highpass decomposition filter, lowpass reconstruction filter, highpass reconstruction ...
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1answer
42 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)
...
3
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1answer
75 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
40 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 ...
0
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1answer
52 views
inner product with scaling function [closed]
I had asked following question on math.stackexchange and i redirected here.
$$
\int_0^1sin(x)ϕ(2^jx−k)dx
$$
Can matlab or pywavelet (or other softwares) compute the above integral where ϕ(x) is ...
2
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1answer
37 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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0answers
27 views
Steganography using Wavelet transform, not every wavelet recovering the hidden message efficiently
I'm working on a project to hide simple string inside a 255x255 Image using Wavelet transform, The problem is that,
When i used Haar Wavelet the result is ...
0
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1answer
27 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 ...
4
votes
1answer
53 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 ...
3
votes
0answers
65 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 ...
2
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1answer
33 views
Matlab stores all level of Wavelet's Approximation & Details in a single Row
I'd like to ask when we apply Wavelet transform on 1-D Signal in Matlab it simply stores both Approximations and Details into a single row which is quite annoying for me,
have a look,
Where,
X = ...
6
votes
1answer
171 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 ?
3
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2answers
71 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
98 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 ...
3
votes
2answers
126 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 ...
2
votes
1answer
171 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 ...
4
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3answers
234 views
Reading the Wavelet transform plot
I am having trouble understanding on how to read the plot plotted by a wavelet transform,
here is my simple Matlab code,
...
4
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1answer
51 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 ...
2
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1answer
116 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 ...
2
votes
1answer
51 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 ...
3
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0answers
49 views
What are the uses of those three types of wavelet transformations?
In my studies of wavelets, there appear to be 3 different families of them:
The Continuous wavelet transform
The Discrete wavelet transform
The Redundant wavelet transform
They are all based on ...
4
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0answers
114 views
Wavelets and cryptography
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 ...
2
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1answer
131 views
Scalogram (and related nomenclatures) for DWT?
My understanding of the scalogram is that, for a particular row, the scores of the projection of the input signal with the wavelet at a particular displacement is shown. Across rows, the same thing ...
4
votes
3answers
197 views
What's the difference between the Gabor-Morlet wavelet transform and the constant-Q transform?
At a glance, the constant-Q fourier transform and the complex Gabor-Morlet wavelet transform seem the same. Both are time-frequency representations, based on constant-Q filters, windowed sinusoids, ...
1
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1answer
184 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 ...
2
votes
2answers
335 views
Adding noise to an ECG signal
I am doing a project on ECG arrythmia analysis using matlab.
I have designed notch filter for removing 50 Hz noise but don't know how to add a 50 Hz powerline interference noise to a clean ECG ...
5
votes
0answers
165 views
Daubechies Wavelet and Matlab
I want to use waverec to evaluate a linear combination of the scaled and shifted wavelet of the form
$$ \sum_{i=1}^n\sum_{j=0}^{2^n-1}d_{nj} 2^{-n}\psi_{ij} ...
5
votes
2answers
103 views
Vanishing Moments
I am reading a book titled "Two Dimensional Wavelets and their relatives" by Antoine et al. and it talks about vanishing moments. I have trouble understanding the exact significance of it. Can anybody ...
1
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1answer
182 views
How to remove/reduce noise by using the Morlet wavelet?
Im trying to use morlet wavelet to reduce noise in my signal.
I found formula for morlet wavelet
$$\Psi(x) = \frac{1}{\sqrt{\pi\cdot bandwidth}} \cdot exp(i \cdot 2\pi \cdot centerFreq \cdot ...
10
votes
4answers
483 views
Bag of tricks for denoising signals while maintaining sharp transitions?
I know this is signal dependent, but when facing a new noisy signal what is your bag of tricks for trying to denoise a signal while maintaining sharp transitions (e.g. so any sort of simple averaging, ...
2
votes
1answer
165 views
Pitch detection algorithm for minsample size
I am looking for a pitch detection algorithm that uses the least number of samples.
I don't care about the processing time.
I hope to use this on audio signals.
I have tried using the one at the ...
2
votes
1answer
223 views
Signal matching: How to quantify the difference between two signals of varying frequency
I have two waves, and I would like to quantify the difference between them.
They are exponential sine waves where the frequency decreases with time.
I'm interested in the difference in decay ...
5
votes
1answer
651 views
Number of Daubechies coefficients
I am wondering about the correlation between input size and number of coefficients given by a discrete wavelet transform.
I am using Daubechies wavelets to describe a 1D function and I'm using ...
1
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1answer
85 views
wavelet analysis/ dimension reduction
How wavelet analysis works as a dimension reduction techniques?
The approximations coefficients at higher level of decomposition are the fewer retained coefficients from the originial ?Is it correct?
5
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0answers
504 views
Discrete (Inverse) Haar (2D) transform implementations
I am interested in implementations of the Haar transform, and its inverse, such that when composed always result in the identity operation. My inputs are discrete ordinals within a given range - and ...
7
votes
1answer
581 views
Tutorial on 2nd generation wavelets (with lifting)?
For some denoising and deconvolution experiments, I'd like to apply a 2nd generation wavelet transform (using lifting steps) to images.
I know that there are several implementations available, but ...
5
votes
2answers
702 views
Generating wavelet using amplitude spectra
Equation (4) of a recent paper (An improved peak-frequency-shift method for Q estimation) shows how to generate a wavelet using a zero-phase Ricker wavelet.
$|B_1(f)| = |B_0(f)|\exp(-\pi t f / Q)$
...
6
votes
0answers
85 views
What is the normalization factor for the quincunx lattice wavelet transform, and how do you find it?
On pages 57-60 (preview was available last I checked, images here in case), there is a quincunx lattice transform described.
Lattice:
...
8
votes
1answer
264 views
What does the normalization step of the Haar wavelet transform represent?
When you perform the Haar wavelet transform, you take the sums and differences, then at each stage, you multiply the entire signal by $\small\sqrt2$.
When taking the inverse transform, you multiply ...
6
votes
3answers
277 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 ...
7
votes
1answer
84 views
“Normalizing” my D4 wavelet transformation at each step reduces final image quality
Original image:
(Images included are .png images, so no additional distortion was added in save/upload for viewing)
I have used the D4 transform from page 20 of "Ripples in mathematics", which is ...
3
votes
1answer
147 views
T wave analyis and extraction using discrete wavelets
I'm doing a project in T-wave extraction from ECG signal. Initially I completed the preprocessing steps like noise removal and baseline drift cancellation. Then I need to extract T wave using discrete ...
8
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1answer
415 views
Apply wavelet transform to analyse EEG signal
I would like to apply The Morlet wavelet transform to analyse my EEG signals. I have many short signals each is only 1 min long. and they all recorded in 30Hz.
I have Two questions:
In the Morlet ...
8
votes
2answers
231 views
Explanation on Haarlets
Would someone be able to give me some info or a link etc ... regarding haarlets aka Haar wavelet-like features. I'm reading several papers for my master dissertation and several of these papers ...
