## Forums Search for: Wavelets

## Maximum value of a spherical harmonic

inI have a function on a sphere represented in terms of a 3rd order spherical harmonic...

I have a function on a sphere represented in terms of a 3rd order spherical harmonic (http://www.research.scea.com/gdc2003/spherical- harmonic-lighting.pdf). This is somewhat similar to how wavelet compression, such as jpeg, represents a function over a 2d area in frequency space. I want to find the maximum value of this function analytically without converting from frequency space. An upp...

## approximate CWT(xd,scale,gaus3) from CWT(xdd,scale,gaus2) with matlab

inHi, all I am writing to have some difficulty in continuous wavelet transform(CWT) in matlab. The problem is : Given (1) two digital...

Hi, all I am writing to have some difficulty in continuous wavelet transform(CWT) in matlab. The problem is : Given (1) two digital signals (sampling frequency 1000 hz), xd( first derivative of x) and xdd (second derivative of x) from signal x. (2) two wavelets, gaus3 and gaus2. This means that derivative of gaus2 is gaus3. Having two conditions, I want to show the rel...

## encoding in compression using wavelet based method???

inHi all, I need to implement the following algorithm: decompose a signal length 2^L to an orthonormal basis (In this case is a wavelet...

Hi all, I need to implement the following algorithm: decompose a signal length 2^L to an orthonormal basis (In this case is a wavelet basis". Uniformly quantize the coefficients: 2^M+1 quant. levels, then use L bits to encode non zero quantized coefficients and M bits to encode its value. I am confused with "an orthonormal basis". Does it mean that I decompose the original signal onl...

## Visualizing DWT results

Hi! I'm using a standard dyadic discrete wavelet transform to analyze acoustical signals. The calculation itself works, but I'm looking for a...

Hi! I'm using a standard dyadic discrete wavelet transform to analyze acoustical signals. The calculation itself works, but I'm looking for a good way of displaying and quantifying the results. I have an array of transformation values w = [sn | dn | d(n-1) | d(n-2) | ... | d2 | d1 ] for each signal set I've analyzed. The toolkit I'm using (wavekit) supports bar graphs of the different...

## wavelet based method for removing Gaussian Noise

Dearl all: Hi all, I need to use wavelet based method to remove Gaussian white noise on an image. I have some confusion and would like to ask...

Dearl all: Hi all, I need to use wavelet based method to remove Gaussian white noise on an image. I have some confusion and would like to ask you: 1. What wavelet basis I should choose for decomposing the image? I intend to use Haar , DB2, db3, db4 to test the SNR to see what is the best. However I am considering for Gaussian Noise, if there are some best wavelet bases for this task, if...

## Formula to calculate the rate for a compression algorithm

inHi all, In the case I don't know the sampling frequency. Specifically, I only given a discrete function: f[n]= blah blah..... with length...

Hi all, In the case I don't know the sampling frequency. Specifically, I only given a discrete function: f[n]= blah blah..... with length N. I use wavelet based compression method: Decompose the signal into N wavelet coefficients, quantize and then encode these coefficients with M bits for each coefficient. Now to report the algorithm, I need to submit it's RATE. In the case, wh...

## Characterizing wavelet spectra

inHello! I'm trying to classify situations by their wavelet spectra, and I'm looking for a good way to characterize each spectrum. What ways...

Hello! I'm trying to classify situations by their wavelet spectra, and I'm looking for a good way to characterize each spectrum. What ways are there to extract a small number of characteristic values from a large multiscale analysis result that allow recognizing similar situations? Thanks Andreas Steffen

## How to plot a Wavelet transform in Matlab

Hi, I would like to plot a wavelet transform in 3-D, with scale, time and amplitude as 3 axes. First, to apply the WT, which function...

Hi, I would like to plot a wavelet transform in 3-D, with scale, time and amplitude as 3 axes. First, to apply the WT, which function would you use? Second, how would you plot the result? P.S. I have Signal Processing and Wavelet toolboxes. Thank you in advance. _____________________________________ Do you know a company who employs DSP engineers? Is it already listed at htt...

## HELP NEEDED: Understanding wavelet transform

inHi, I've been trying to learn about DWT for quite a while now. Still, I have some simple questions, which my searches on Google weren't able...

Hi, I've been trying to learn about DWT for quite a while now. Still, I have some simple questions, which my searches on Google weren't able to answer. Thank you in advance for your answers. 1. When decomposing a signal, using wavelet toolbox in matlab, what are the axis? Frequency over time? Or scale over time? 2. What does scale mean, if it's say 0.2, or 0.5. I don't see the relation...

## Describing a filter in a wavelet basis

inSuppose that I have used the same orthogonal (Dauberchies) wavelet basis to describe a filter I(t) and a set of signales x1(t), x2(t), x3(t)....

Suppose that I have used the same orthogonal (Dauberchies) wavelet basis to describe a filter I(t) and a set of signales x1(t), x2(t), x3(t). Now I want to calculate the convolutions (I*x1)(t), (I*x2)(t), (I*x3)(t).. and express them in the same wavelet basis as the signals and the filter. Is there a smart way to do this within the wavelet formalism? Is it better to do inverse wavelet tran...

## Re: Describing a filter in a wavelet basis

Corrected a bad typo below... Rune On 23 May, 21:13, Rune Allnor wrote: > On 23 May, 09:23, Palle Uldenborg wrote: > > > ...

Corrected a bad typo below... Rune On 23 May, 21:13, Rune Allnor wrote: > On 23 May, 09:23, Palle Uldenborg wrote: > > > Suppose that I have used the same orthogonal (Dauberchies) wavelet > > basis to describe a filter I(t) and a set of signales x1(t), x2(t), > > x3(t). Now I want to calculate the convolutions (I*x1)(t), (I*x2)(t), >

## Re: Describing a filter in a wavelet basis

Corrected a bad typo below... Rune On 23 May, 21:13, Rune Allnor wrote: > On 23 May, 09:23, Palle Uldenborg wrote: > > > ...

Corrected a bad typo below... Rune On 23 May, 21:13, Rune Allnor wrote: > On 23 May, 09:23, Palle Uldenborg wrote: > > > Suppose that I have used the same orthogonal (Dauberchies) wavelet > > basis to describe a filter I(t) and a set of signales x1(t), x2(t), > > x3(t). Now I want to calculate the convolutions (I*x1)(t), (I*x2)(t), >

## Re: Describing a filter in a wavelet basis

Corrected a bad typo below... Rune On 23 May, 21:13, Rune Allnor wrote: > On 23 May, 09:23, Palle Uldenborg wrote: > > > ...

Corrected a bad typo below... Rune On 23 May, 21:13, Rune Allnor wrote: > On 23 May, 09:23, Palle Uldenborg wrote: > > > Suppose that I have used the same orthogonal (Dauberchies) wavelet > > basis to describe a filter I(t) and a set of signales x1(t), x2(t), > > x3(t). Now I want to calculate the convolutions (I*x1)(t), (I*x2)(t), >

## Re: Describing a filter in a wavelet basis

## Articles searching

Dear ALL!!! If sombody can, please, help me to get e-copies of such articles. I am from Russia, and have no an access to it. I will be very...

Dear ALL!!! If sombody can, please, help me to get e-copies of such articles. I am from Russia, and have no an access to it. I will be very grateful for you help!!! 1. Rational resolution decompositions for signal processing Anderson, B.P.; Warhola, G.T. 2. Pascal Auscher "Wavelet bases for L2(R) with rational dilation factor" 3. Anderson, B.P. The Rational Resolution Analysis: A Gen...

## Power System Oscillation analysis

inWhat other methods can be used to analyse power system oscillations from phasor measurements besides FFT and Wavelet?

What other methods can be used to analyse power system oscillations from phasor measurements besides FFT and Wavelet?

## Wavelets

inDear ALL!! Suppose, I have image (256x256): img = im2double(imread('lena.bmp')); Then I perform discrete wavelet transform and get 4...

Dear ALL!! Suppose, I have image (256x256): img = im2double(imread('lena.bmp')); Then I perform discrete wavelet transform and get 4 components of source image: [a, h, v, d] = dwt2(img, 'db1'); Then I reconstruct signal using only detail components: det = idwt2([], h, v, d, 'db1'); Next I downsample det with 3/4, i.e. get det2 with size 192x192: det2 = downsample(det, 3/4); - n...

## Re: ANNOUNCEMENT: New image format

He's Late schrieb: > I seem to have left out some important punctuation. Vista sucks, this is true, > but the HDR Photo(? I was in error in...

He's Late schrieb: > I seem to have left out some important punctuation. Vista sucks, this is true, > but the HDR Photo(? I was in error in typing earlier) , HDPhoto format (*.hdp > and *.wdp filename extensions) has some very strong advantages, which got its > start through Vista. Full EXIF and IPTC support, wavelet compression, Pardon me, HDPhoto is not wavelet based. It uses an overlap

## Real-time wavelet denoising

inDoes anyone have experience developing real-time wavelet denoising software without using any DSP chip? I have a problem with delay time caused...

Does anyone have experience developing real-time wavelet denoising software without using any DSP chip? I have a problem with delay time caused by buffering data and want to reduce the delay time as much as possible. The data I am dealing with is 1-D with sampling rate lower than 1kHz. I have developed the application in C++. The program reads data into a buffer sample by sample until the buffer h...

## Feature Extraction

inHi All, I have a question about the feature extraction. I used the continuous wavelet transform(CWT)for my 1D signal and will select the mean...

Hi All, I have a question about the feature extraction. I used the continuous wavelet transform(CWT)for my 1D signal and will select the mean and median frequency as features from that CWT. My question is how to select these frequencies from the CWT by using MATLAB. Thanks in advance