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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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How to gain hard and soft threshold in discrete wavelet transform by integer samples

I gained samples of audio signal that have integer representation. I want to take dwt from samples and destroy them, by selected threshold. My problem is threshold choice.
ali
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Normalization procedure behind haar transform in R

I run the haar transform for [9,7,3,5] (using wavelets package) and I'm not figuring out how to achieve the output coefficients. I believe that the unnormalized result would be: [6,2,1,-1]. From what I've read, the normalization is done by…
Printil
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How to modify the last 3 bits of signed numbers

When I apply the function dwt2() on an image, I get the four subband coefficients. By choosing any of the four subbands, I work with a 2D matrix of signed numbers. In each value of this matrix I want to embed 3 bits of information, i.e., the numbers…
mersana
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How do I apply changes to a template file?

I've uploaded the new file via FTP, but the changes didn't take effect: http://intrepidtraveler.com/Templates/press.dwt Why is this the case? http://intrepidtraveler.com/media/ (Trying to update the image links on the left hand side).
pmchrislee
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Discrete Wavelet Transform in Java creates white Spots in the Image

in my Java program, a image is loaded into the programm, then transformed using the discrete wavelet Transform and the resulting coefficients are used as picture data for the output image. The process works fine with natural images:…
darenkster
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Using DWT Haar transform method to hide text inside coefficients

I have written the code below which takes the Haar transform of an image and embeds a secret message, bit by bit on in the least significant bits of the coefficients. To use the bitset function I convert the double coefficients to uint64 and I…
NewUser
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horizontally place cA and cH subband's of DWT

I am new in MATLAB and interested in face recognition. I'm implementing the proposed method in this paper .It is said that after extracting cA and cH subbands , should horizontally place the two subbands and prepare it for taking DFT spectrum. I…
farzad
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add wavelet filters to discrete Haar wavelet transform (DWT)

I need help for 1-level 5/3 discrete Haar wavelet transform (DWT) source code with c# . I use this project, and the methods of forward wavelet transform is here : FWT(double[] data) { int h = data.Length >> 1; for (int i = 0; i <…
Elahe kh
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R: Comparing dissimilarity between metabolic models with Discrete Wavelet Transformation

I’m working on comparing bacteria metabolic models. Each model has a set of metabolites and their concentration for 200 time points. I’m in the process of comparing the models to cluster them based on their similarity. One method I followed is I…
SriniShine
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Image steganography based on DWT integer coefficients

I am trying to code DWT based steganography to hide an image inside another image. I am getting coefficients of subbands as float. How can I make them integers so that I can use lsb embedding?
raki ah
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FFMPEG wavelet transform

What library should I add to use DWT? j2k_dwt.h is too old and I can't find what library is using in FFMPEG API now. Thank you.
Vaigard
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how to denormalize the image in matlab

I am working on a project where i have to first normalize the image i.e convert the pixel range of my image from 16-235 (as it is only luminance component of the image , pixel values are always defined in the range 16-235) to 0 - 1 then i perform…
Kristen
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Expression Web: Frames vs. Dynamic Web Template

I am making a website that has a lot of links that do not change from page to page. I have made similar websites before using the DWT feature of Expression Web with good results, but I still see a lot of people using frames for this kind of thing. …
ubiquibacon
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Cant extract embedded stego message after compression is applied to image?

I am attempting to extract hidden data that has been hidden using DWT steganograpy.Then, when I apply compression, nothing happening! I have used the following code to compress my .bmp image, but no hidden message is being extracted after…
Hitmanpaddy
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Extraction of data from DWT subband

I am attempting to extract data from a DWT subband. I am able to embed data correctly (I have followed it in the debugger),cal PSNR etc. PSNR rate seem very high 76.2?? however,I am having lot of trouble extracting data back!It is sometimes…
Hitmanpaddy
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