## Forums Search for: Wavelets

## 1D discrete wavelet synthesis

inHello The IDWT consists of upsampling and filtering mechanism. For instance if the signal is being reconstructed from its wavelet...

Hello The IDWT consists of upsampling and filtering mechanism. For instance if the signal is being reconstructed from its wavelet coefficients, does the reconstruction start from the first decomposition level or the last one? Moreover,if we upsample the signal (adding zeroes) does not this end up by producing more samples than the original signal had. For instance an original signal has...

## Regarding wavelets

inIs there a way to take a 1d wavelet trans to get 2 bands (lpf and hpf) over a fixed BW (say 4KHz) if the sampling freq is greater (eg 20KHz)

Is there a way to take a 1d wavelet trans to get 2 bands (lpf and hpf) over a fixed BW (say 4KHz) if the sampling freq is greater (eg 20KHz)

## Looking for a paper

Dear all, Right now I am writing a program of 9/7 wavelet.And I have been searching for a paper,i.e.,A. Cohen, I. Daubechies, and J. C....

Dear all, Right now I am writing a program of 9/7 wavelet.And I have been searching for a paper,i.e.,A. Cohen, I. Daubechies, and J. C. Feauveau, "Biorthogonal bases of compactly supported wavelets," Commun. Pure Appl. Math., vol. 45,pp. 485-560, 1992. I can't find it.Can anyone help? Thank you!

## Daubechie-4 Wavelet

inHi, i view in an article on the Daubechie-4 Wavelet that the level 1 Wavelets have an support of 4 time units. With this statement i agree but...

Hi, i view in an article on the Daubechie-4 Wavelet that the level 1 Wavelets have an support of 4 time units. With this statement i agree but further is written, that the level 2 wavelets have an support of 10 time units. But i hought it should have been 8. Can anybody explain why the support is ten time units? Thank you, Basti

## wavelet filterbank - filter construction? highpass/lowpass

Hello, I was wondering if somebody could help me and explain some details for me a little bit, help would be greatfully appreciated; I'm...

Hello, I was wondering if somebody could help me and explain some details for me a little bit, help would be greatfully appreciated; I'm studying this paper titled "Fast algorithms for Discrete and Continuous Wavelet Transform" by Olivier Rioul and Pierre Duhamel. I'm trying to implement a fast DWT/CWT algorithm based on this paper, it basically details a way of performing a fast DWT algori...

## Programing Daubechie Wavelet with 22 windows

inHi, I programed Daubechie Wavelet with 4 coefficients (4 windows) using Labview. However, due to my signal analysis, the result was...

Hi, I programed Daubechie Wavelet with 4 coefficients (4 windows) using Labview. However, due to my signal analysis, the result was not satisfactory, because it did not distinguishly show 2 signals at 2 different frequency after the iterations. Therefore, I need to try the one with 22 windows, but I don't know how to calculate the new coefficients, h1,h2,h3...h22, and other stuff needed to perform...

## Wavelet transformation of audio signals

inHallo, I am using .WAV files as audio signal input. For implementing D-4 Wavelet filter coefficients of both HPF and LPF, its said that I have...

Hallo, I am using .WAV files as audio signal input. For implementing D-4 Wavelet filter coefficients of both HPF and LPF, its said that I have to multiply with input array. How will you consider the input from WAV files as arrays, also what will be in the case of stereo, where it has left and right channel values? Also, I am in new in the world of wavelet. What is the purpose of scaling functio...

## Question from the book, Wavelet and filter banks by Nguy and Strang

inI have been spending some time analysis Daubechies 22, and I read the book. (Wavelet and Filter Bank by Nguy and Strang) There is one part that I...

I have been spending some time analysis Daubechies 22, and I read the book. (Wavelet and Filter Bank by Nguy and Strang) There is one part that I did not understand. On page 169, it did one example to find Daubechies coefficients at p = 2. I understood it till it said "Then the 2p-1 roots of C(z) are -1, -1, 2-squroots(3)" Then it went on to find the 4 coefficients of D4. I did not know how he go...

## Downsampling after wavelet denoising

inI am working on a time series which is sampled once every 10 minutes. I found by inspection of the auto correlation function that the...

I am working on a time series which is sampled once every 10 minutes. I found by inspection of the auto correlation function that the detail coefficients indicates pure noise for more than 7 levels of wavelet (db10) decomposition. So, I did 8 levels of wavelet decomposition and then set the 8 level detail coeff. to zero. I carried out the inverse transform, and now I wonder how much I can downsamp...

## Regarding Daubechies Wavelet with 22 vanishing points

inAs I studied, p equals the number of vanishing points of Daubeshies Wavelet in pi, which means p-1 degree order polynomial that can be put in...

As I studied, p equals the number of vanishing points of Daubeshies Wavelet in pi, which means p-1 degree order polynomial that can be put in scaling function. I am trying to find out what those h0, h1, h2...h22 are as I am trying to program Daubeshies with 22 vanishing points. Does anyone have any idea what are they? Thank you very much.

## The Cascade Algorithm - Recursion, Wavelets

I'm trying to implement something called the "Cascade Algorithm" which is based upon the Dilation Equation, used when needed to approximate...

I'm trying to implement something called the "Cascade Algorithm" which is based upon the Dilation Equation, used when needed to approximate a Wavelet Scaling function or mother function. Everything is well apart from a small snag, I've been studying for a while now and still have no idea how to implement it?!! it goes something like this; f(t) = c(0)f(2t) + c(1)f(2t - 1) + c(2)f(2t - 2)...

## The Cascade Algorithm - Recursion, Wavelets

inI'm trying to implement something called the "Cascade Algorithm" which is based upon the Dilation Equation, used when needed to approximate...

I'm trying to implement something called the "Cascade Algorithm" which is based upon the Dilation Equation, used when needed to approximate a Wavelet Scaling function or mother function. Everything is well apart from a small snag, I've been studying for a while now and still have no idea how to implement it?!! it goes something like this; f(t) = c(0)f(2t) + c(1)f(2t - 1) + c(2)f(2t - 2)...

## DWT anti-causality

inHi, I have been playing around with the discrete wavelet transform (dwt) as a preprocessor for an adaptive system (for system identification...

Hi, I have been playing around with the discrete wavelet transform (dwt) as a preprocessor for an adaptive system (for system identification and time-series prediction). The problem is however that the DWT is anti-causal and suffers from boundary value problems (due to the signal extension). I've tried the first thing that I could think of - a dwt with an expanding window where I only k...

## Wavelets compression for circular data?

Is anyone aware of doing wavelet based compression of arrays of angular data (or phase data)? Instead of normal grau=yscale images, you have...

Is anyone aware of doing wavelet based compression of arrays of angular data (or phase data)? Instead of normal grau=yscale images, you have values from 0-360 degree (which you can quantize between 0-255), but if you have two neighboring pixzels with values of 255 an d0, dont treat it like a discontinuity.. hence this is tricky! Also, would the SAR imagery community (or any other community)...

## Wavelets for circular data?

Is anyone aware of doing wavelet based compression of arrays of angular data (or phase data)? Instead of normal grau=yscale images, you have...

Is anyone aware of doing wavelet based compression of arrays of angular data (or phase data)? Instead of normal grau=yscale images, you have values from 0-360 degree (which you can quantize between 0-255), but if you have two neighboring pixzels with values of 255 an d0, dont treat it like a discontinuity.. hence this is tricky! Also, would the SAR imagery community (or any other commu...

## FFT extrapolation on wavelet transform of weather data

inRecently i have been working on a problem regarding predicting weather conditions based on given collected data( of temp, humidity etc..)...

Recently i have been working on a problem regarding predicting weather conditions based on given collected data( of temp, humidity etc..) of past year or so. I decided to use FFT based extrapolation on the wavelet transform of the data of one weather identifier(say temperature). My reasons for doing so are: 1) I wanted to predict the future values of temperature based on past variation...

## Discrete wavelet transform implementation/existing algorithm

inHello. Is there anyone who has an experience of discrete wavelet transform implementation to achieve signal subband separation ? I'm working on...

Hello. Is there anyone who has an experience of discrete wavelet transform implementation to achieve signal subband separation ? I'm working on certain signal processing that is handled in subbands, the signal is separated into reasonably narrow frequency subbands and then each subband is processed separately. The subband separation is to be attained by means of discrete wavelet transform (dwt()...

## About sampling

inHi, I posted about "wavelet" sampling here http://tinyurl.com/efnh6 in a thread: "Nyquist didn't say that". Nothing of what I said does not...

Hi, I posted about "wavelet" sampling here http://tinyurl.com/efnh6 in a thread: "Nyquist didn't say that". Nothing of what I said does not have to be tied to wavelet terminology, thus I try not to use it in the following (to keep it general and perhaps more easily accessible). This is bit lengthy so if you're in a hurry then skip to the end of this post. Let there be a real function phi...

## how to normalize complex filter?

inHi! I'm trying to implement a wavelet transform via convolution and my "filter" is a complex wavelet. It works fine but the resulting...

Hi! I'm trying to implement a wavelet transform via convolution and my "filter" is a complex wavelet. It works fine but the resulting amplitude seems to be wrong... I think I have to normalize the wavelet somehow, but i can't figure out how. I understand that i can normalize a real filter (e.g. sinc) by summing up the samples and devide all samples by this number. I tried to do the s...

## need help regarding wavelet

inHi All, I am doing my thesis.I have to develope some algorithms for audio analysis. Actually,I have to record audio from mobile phone, and I...

Hi All, I am doing my thesis.I have to develope some algorithms for audio analysis. Actually,I have to record audio from mobile phone, and I have to test the audio for glitches,hiss, delay,distortion etc.We have selected wavelets for analysis because of resolution in time and frequency.I am using Matlab Wavelet toolbox for development. But,I am not sure ,how to use wavelets for this purpo...