# 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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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 ...
77 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 ...
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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### 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 ...
408 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 ...
613 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....
641 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 ...
494 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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### 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 ...
636 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 ...
563 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 ...
63 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 ? ...
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 ...
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 ...
1k views

### bandpass implementing with DWT in matlab

In matlab help in find the implementation of bandpass as following ...
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, ...
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 ...
554 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 ...
565 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 ...
360 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) ...
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 ...
114 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 ...
441 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 "...
540 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 ...
399 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 ...
311 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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### 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 ...
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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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 ?
837 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 ...
988 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 ...
420 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 ...
313 views

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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### 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 ...
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 ...
416 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 ...
2k 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 ...
161 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?
3k 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 ...
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### 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. $|B_1(f)| = |B_0(f)|\exp(-\pi t f / Q)$ ...
5k views

### What's the difference between the Gabor and Morlet wavelets?

The Gabor wavelet is a kind of the Gaussian modulated sinusoidal wave (source)   Gabor wavelets are formed from two components, a complex sinusoidal carrier and a Gaussian envelope. (source) ...
162 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", ...
304 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 ...