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Questions tagged [dwt]

DWT stands for Discrete Wavelet Transform. This transformation is commonly used in signal processing. Its main advantage over Fourier transform is its ability to preserve temporal information.

DWT stands for Discrete Wavelet Transform. This transformation is commonly used in signal processing.
Wavelets are considered as more advanced tool than Fourier transform for signal processing. DWT's main advantage is its ability to preserve temporal information of the signal while introducing frequency properties. This advantage is achieved due to the use of compact basis functions - the wavelets. The compact basis functions integrates spectral (frequency) information over compact domain thus preserving temporal information.

There are many types of DWT differes by their construction of their basis function. Very useful DWTs are Haar wavelets and Gabor wavelets.

For more information see wikipedia.

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Are Wavelet Coefficients simply the pixel values of decomposed image in 2D Discrete Wavelet Transform

I've been working with Discrete Wavelet Transform, I'm new to this theory. I want to access and modify the wavelet coefficients of the decomposed image, Are those wavelet coefficients simply the pixel values of the decomposed image in 2D DWT? This…
mfathirirhas
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How to find approximation and detail coefficient from a reconstructed signal?

I want to decompose a signal and by reconstructing this signal try to find approximation and detail coefficient from the reconstructed signal. For decomposition I used single level decomposition(Discrete Wavelet Transform-Db6) and for reconstruction…
Fahim Feroje Al Jami
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convfft() call in fftw causes crash. Is it about improper library linking?

In my study, i use 1-D DWT as a part of the algorithm and i write the application in 32-bit ubuntu linux with C++. As a novice linux user, i'm having some problems about compiling and linking my codes. To implement discrete wavelet transform in…
Sukru G
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Error in Singular Value Decomposition matlab code

I am getting error in the code below "matrix dimensions must agree" It occurs in the line of code (Shw=Sh+a*Sw;) The coverImage I am using is a grayscale image, tiff format as is the watermark. Any suggestions what my problem could be?? Thank…
Hitmanpaddy
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how to find out the exact threshold value for the correct recognition of person

hello I am novice here in matlab my task is to write a code for multimodal biometric system using discrete wavelet transform and pca (principle component analysis) for 100 people database containing 9 face, 2 ear and 2 thumbprint images. for same I…
user4045885
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Templates .dwt in Dreamweaver

I edited my site with FrontPage, there I created some template pages .dwt in the root of the each language /en/master.dwt /fr/master.dwt and so one. Now, when passed the site under Adobe Dreamweaver, it seems do not "recognize" them. I understood…
serhio
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Battle-Lemarié spline wavelet basis of any order in Python

I'm trying to analyse some data with the discrete wavelet transform (DWT) using Battle-Lemarié spline wavelets of any order. The analysis will be used in bi-dimensional images for de-noising, to calculate first and second derivatives and to extract…
regeirk
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DWT Implementation doesn't work, whats wrong?

I've implemented a 2D Discrete Wavelet-Transformation from a javacode (see here). When i execute the orginal code in java the result looks fine. But in my c++ implementation the result is distorted. I don't know why (see picture). Orginal…
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Appropriate choice of DWT Decomposition Level for watermark embedding

How can I determine that which level of DWT is suitable for embedding watermark? Like somewhere I read that if you use less than level-4 DWT, then it will decrease the capacity and similarly, if use more than level-4 DWT, it would affect the…
Alexandera
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How to convert an Upper case string to lower case string in DWT, Tridion

How to convert an Upper case string to lower case string in DWT, Tridion? I have a field in schema called ' title'. I got the value of title in DWT using "@@RenderComponentField(FieldPath+".title", 0)@@". I want to convert the returned value in to…
user1740212
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Looping component links in an Embedded field

We have a "component A" , which has a multivalue field of type 'embedded field'. The embedded field in turn has a multivalue field of type 'Component Link'. This looks like: Component A -> Embedded Shcema Fields -> Component Links How to iterate…
Huston Lopes
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Applying Discrete wavelet transformation (DWT) on a given data set using Matlab

I have a stock market data set with the following two fields: date closing_price I would like to apply DWT on this data set and plot a graph using Matlab. Can some one please guide me how to do it.. Thank you EDIT here is an example set of data…
rakesh kashyap
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CSS embeded within dwt vs external style sheet

I created a new website with 46 pages: http://www.lampshade111.com/ I use Microsoft Expression Web 4 employing a dynamic web template. All css was embedded within the heading of the dwt page and updated to every individual web page. Everything…
user1456314
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Wavelet: Linking Scale coefficients -> TimeStamp in DWT decomposition of time series

I'm using PyWavelets for singularity detection in a time series of measured values. The values were taken with a sample time of 10 ms and the length of each data set is 2048 values. Along with the data set, I have an array with the time stamps for…
babbyldockr
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implementation of discrete wavelet transform

I'm using wavelet transform to denoise a signal and I've implemented dwt in c trying to replicate the python library pywavelets but doing additional levels of wavelet transform doesn't seem to remove low frequency events compared to the python…
brian
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