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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490 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
990 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
632 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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560 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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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
1k 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
951 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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bandpass implementing with DWT in matlab

In matlab help in find the implementation of bandpass as following ...
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164 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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162 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
518 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
540 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
339 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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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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109 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
406 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
512 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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96 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 ...
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1answer
389 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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297 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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3k 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
805 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 ...
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1answer
927 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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408 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
268 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
951 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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1answer
410 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 ...
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1answer
1k 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 ...
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1answer
152 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?
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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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2answers
3k 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. $|B_1(f)| = |B_0(f)|\exp(-\pi t f / Q)$ ...
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1answer
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) ...
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154 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 ...
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1answer
297 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 ...
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1answer
2k 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 ...