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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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Using steganography to embed data in DWT subband coefficients

I have been doing more research on the topic of DWT Steganography. I have came across the code below on the web. This is the first time I have came across subbands coefficients being specified. I have an idea what the code does but I would like…
Hitmanpaddy
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Embedding data from a text file into DWT subband using steganography

I am attempting to embed data from a text file(which contains only numeric data) into LL subband of an image using a steganography. I am getting an error "Error using bitset ASSUMEDTYPE must be an integer type name" in the line of code:…
Hitmanpaddy
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DWT Steganography

I am studying in the field of steganography/watermarking. I am fairly new to this, so please bear with me! I found an excellent post on here How do I encapsulate some text information in an image and extract it using MATLAB? using LSB method, which…
Hitmanpaddy
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Hiding data from a text file in a image file using dwt steganography

The code below hides the text "helloworld" in the two specified DWT coefficients using steganography. I have been trying to adapt the code to hide data contained in a .txt file. I have been working on this for a while but cant seem to get anything…
Hitmanpaddy
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Applying Haar to bitmap image using matlab

I using the following code in matlab to attempt to apply haar dwt to bitmap image im = imread('image.bmp'); [LL,LH,HL,HH] = dwt2(im,'haar'); figure; imshow(im); I am getting the following error: Undefined function 'dwt2' for input arguments of…
user1877082
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apply wavelet with haar filter and reconstruction image with approximation coefficients

I want apply wavelet with haar filter on an image and then reconstruction the image with approximation coefficients. I run this code in matlab: f = imread('pic.tif'); sX = size(f); [cA,cH,cV,cD] = dwt2(f,'haar'); x =…
mgh
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Image Steganography in matlab

i am new in matlab, and i got final project to make digital image steganography using combination DWT and DCT. in this project i use 2-L DWT and then 8x8 block DCT and embed the image by using DCT. here are my questions : how to choose LH sub-band…
Maulana Wahid
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Discrete Wavelet Transform C++ Implementation - Run time error

I am looking for some help using the Discrete Wavelet Transform (DWT) Library found here: wavelet2d.sourceforge.net/ The trouble is a run time error, which occurs at the DWT function call. It seems to be associated with the length vector in the…
user3158334
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Compute DWT coefficients to denoise eeg signal

Now, i want to denoise EEG signal, i have an EEG signal(2048 coefficients) and after run Daubechies4, i also obtain 2048 coefficients, i want to know how to determine details and approximate coefficients on that, and daubechies4 is 4-level…
Ankal
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using dwt2 and idwt2 in matlab

I just had my theory of wavelets complete and decided to test using matlab. However, I am not able to interpret the result of dwt2 and idwt2. When I used imshow to display my results, I did not get any image. [ca,ch,cv,cd] =…
Lakshmi Narayanan
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Discrete Wavelet Transform in MATLAB

I am working with audio signal processing and need to perform a 3-Band DWT. I am trying to use the dwt function in MATLAB to do this. However, after reading about this function I realized it only allows you to input two filters, a Hi and Low Band,…
Math244
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C/C++ wavelet library that return also the NxN wavelet matrix

I am looking for a C++ library for Discrete Wavelet Transform (DWT) which can also return the NxN DWT matrix of the transform. There was a similar question opened here Looking for a good C/C++ wavelet library for signal processing but I am looking…
user3100
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Matlab DWT H-level

I'm trying to implement some watermarking algorithm found in a paper1. This is a line of the paper: Do the H-level DWT for all the renumbered segments. Then in simulation section the author explains the wavelet used for experiments. DWT transform…
Jorge Zapata
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multidimensional discrete wavelet transform

can anyone tell me the correct method to use the getOutputValue function in the following link? Also, how does the author get the 2nd and 3rd image from the code. http://www.codeproject.com/Articles/385658/Multidimensional-Discrete-Wavelet-Transform…
Abhishek Thakur
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Dealing with a site that uses a DWT file and its indicies

I am having a slight issue with a site I am in charge of updating. The creator of the site used a Dreamweaver template as its base, and has about 10 of its html files with the DWT code inside of it. I'm not big on Dreamweaver anymore, and could…
Sapp
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