## "definition" of CONVOLUTION

Started by in comp.dsp15 years ago 9 replies

I think I'm missing something basic. http://mathworld.wolfram.com/Convolution.html defines convolution as "A convolution is an integral that...

I think I'm missing something basic. http://mathworld.wolfram.com/Convolution.html defines convolution as "A convolution is an integral that expresses the amount of overlap of one function g as it is shifted over another function f. ..." So what is difference between convolution and correlation?

## Convolution

Started by in comp.dsp14 years ago 15 replies

Hi Im currently in a bit of muddle. Im currently doing an assignment (in c on TMS320C6713 DSK) and we have been told clearly that we cannot...

Hi Im currently in a bit of muddle. Im currently doing an assignment (in c on TMS320C6713 DSK) and we have been told clearly that we cannot use FFT and we must use Convolution. At this point im reading lots of web sites (TI.Com) etc and i have found a convolution.c example program. However when i read this example they are implementing convolution whilst using FFT functions?? I have...

Started by in comp.dsp11 years ago 35 replies

Hi everyone, I'm currently a student studying electrical engineering at University so I'm new to both these forums and the subject of DSP in...

Hi everyone, I'm currently a student studying electrical engineering at University so I'm new to both these forums and the subject of DSP in general. I would just like to ask how can I compute the circular convolution of the two sequences: {x(n)} = {4,3,2,1} and {h(n)} = {5,6,7} I know how to compute the linear convolution, but I am stuck as to how to do the circular convolution.. Co...

## Constant in convolution intergal

Started by in comp.dsp14 years ago 3 replies

Convolution between A(t) and S (t) is defined as integral (-infinity to +infinity) with inside integral we have A(T)S(t-T)dT, now suppose...

Convolution between A(t) and S (t) is defined as integral (-infinity to +infinity) with inside integral we have A(T)S(t-T)dT, now suppose if we have A(T)S(vt-vT) inside that intergal, where 'v' is a constant. Can we still call it as a convolution? if yes how can we take care of 'v' and if its not a convolution how can we manipulate it to make it convolution? This message was sent usi...

## convolution

Started by in comp.dsp11 years ago 4 replies

Hi all, I need to convolve a sine wave with random signal. I made use of the conv function in matlab. I am expecting a dual-dirac histogram for...

Hi all, I need to convolve a sine wave with random signal. I made use of the conv function in matlab. I am expecting a dual-dirac histogram for the resulting convolution. But I keep getting the gaussian histogram of the random signal as the result of the convolution. Can anyone suggest a proper code for performing the convolution between them? Thanks, Nitin

## Convolution

Started by in comp.dsp14 years ago 2 replies

This is just a curious doubt. What is the statistical significance of convolution? For instance, we define the auto correlation in terms...

This is just a curious doubt. What is the statistical significance of convolution? For instance, we define the auto correlation in terms of expectation as R(u) = E(X.Xu). Similarly, do we have any expression for convolution of two signals? Can I have it as something like (sorry, if it is completely absurd): Conv(Xu, Yv) = E(Xu-v.Yu) - Krishna

## help! Using discrete convolution to approximate continuous convolution...?

Started by in comp.dsp10 years ago 1 reply

Hi all, I am helping a friend on this. We would like to evaluate the convolution of f(x)=exp(3 * x) / (1 + exp(x) ^ 5). However, in...

Hi all, I am helping a friend on this. We would like to evaluate the convolution of f(x)=exp(3 * x) / (1 + exp(x) ^ 5). However, in Maple and Mathematica, using symbolic calculations, the convolution results in numerical oscillation (lots of spikeness). We don't know why. We just couldn't get rid of the spikeness. And we thought at the end of day, our end-goal is to numerically evalua...

## Bi-dimensional time-domain convolution

Started by in comp.dsp13 years ago

Hi, I have implemented 1D convolution in many ways before, in the time-domain, by FFT, or by FFT with overlap-add, but I have never did that...

Hi, I have implemented 1D convolution in many ways before, in the time-domain, by FFT, or by FFT with overlap-add, but I have never did that in 2D until now. I tried to but I have a problem that I just cannot solve. The vertical convolution works properly, but the problem with the horizontal convolution is that the last kernel_width-1 bins stay to 0. I'm pretty sure that I have made a d...

## circular convolution and wraparound error....

Started by in comp.dsp10 years ago 4 replies

Hello forum, another basic questions, but you experts are better than any book. Give two finite sequences X and Y of duration, respectively...

Hello forum, another basic questions, but you experts are better than any book. Give two finite sequences X and Y of duration, respectively N and M samples, the convolution will be a new sequence G of length M+N-1 samples. that said, what is the wraparound error? The discrete convolution assumes that both X and Y are periodic sequences. (That way we can approximate the convolution ...

## Convolution Tutorial

Started by in comp.dsp9 years ago 101 replies

I have created a tutorial on the convolution integral. It uses an interactive flash program with embedded audio files. It is located...

I have created a tutorial on the convolution integral. It uses an interactive flash program with embedded audio files. It is located here: http://www.fourier-series.com/Convolution/index.html

## Questions about Convolution of Spectra and Matlab 'conv()' function

Started by in comp.dsp14 years ago 6 replies

Hello. I would like to obtain the convolution of two spectra. I have the complex form Fourier coefficients for the first 300 harmonics of each...

Hello. I would like to obtain the convolution of two spectra. I have the complex form Fourier coefficients for the first 300 harmonics of each spectra. I was looking at the definition of convolution in one of my books and the sumation term goes from -infinity to infinity. Can I obtain a good accurate convolution with the terms i have or do I have to also calculate the terms for the negative...

## FFT convolution giving different results from convolution

Started by in comp.dsp14 years ago 46 replies

I read the chapter about FFT convolution (chapter 18) on dspguide.com and from what I understood, to perform a FFT convolution, you perform...

I read the chapter about FFT convolution (chapter 18) on dspguide.com and from what I understood, to perform a FFT convolution, you perform a FFT on your filter kernel and on your signal (after you have changed their size and zero padded), you multiply each real and imaginary part of the two signals, and then you perform an IFFT, and with that you're supposed to get the same result as with a ...

## Want to Understand Convolution

Started by in comp.dsp16 years ago 3 replies

I've looked at the equations for convolution and correlation and, yes, I can work them. And I've heard that common illustration of clapping your...

I've looked at the equations for convolution and correlation and, yes, I can work them. And I've heard that common illustration of clapping your hands in an echo chamber. But I just can't get my brain around just what it happening there. Anyone know of a book giving a good intuitive grasp of convolution, preferably with lots of handwaving, examples, and problems? Cheers, Wendell

## linear n circular convolution relation

Started by in comp.dsp11 years ago 6 replies

I have the knowledge of fourier transform of the circular convoluion of two vectors say h and s, ie i know FFT (s ** h) [saying ** stands for...

I have the knowledge of fourier transform of the circular convoluion of two vectors say h and s, ie i know FFT (s ** h) [saying ** stands for circular convolution]. I want to know FFT of linear convolution of s and h ie my target is to calculate FFT(s*h) [where * is the linear convolution]. I neither know s nor h. Is it possible and if yes then how?

## Comparison between FFT and Convolution

Started by in comp.dsp11 years ago 3 replies

Hi, Convolution in time domain is equal to multiplication in Frequency domain. I am using convolution in neural network. As many papers...

Hi, Convolution in time domain is equal to multiplication in Frequency domain. I am using convolution in neural network. As many papers says that converting image and weight matrix in frequency domain, multiply and inverse the result will take less process time comparable to convolution in Time domain. But the process time is increased instead of decreasing in my program. I have given the d...

## Newbie seeking some help understanding convolution

Started by in comp.dsp16 years ago 2 replies

I am somewhat new to DSP and have some general questions about convolution in regards to FIR filtering. First, when it is desired to filter a...

I am somewhat new to DSP and have some general questions about convolution in regards to FIR filtering. First, when it is desired to filter a signal and convolution is to be used, how do I interpret the fact that the output sequence is longer than the input? I guess it never occured to me that whenever you filter a signal you get more out than you put in. For example, if my data is x...

## Convolution and Correlation

Started by in comp.dsp16 years ago 2 replies

Hello all, When the two sequances are symmetrical then the correlation and the convolution are same from the classical definitions. My...

Hello all, When the two sequances are symmetrical then the correlation and the convolution are same from the classical definitions. My query is that, the correlation (if not ergodic) has joint pdf term in its definition which is not there in convolution. So can I assume that the above definition as limited to ergodicity or there is something more to it. Thanks, Merry Christmas and ...

## Java fft (not power of 2)

Started by in comp.dsp11 years ago 6 replies

Hi to all, I've been writing an application in JAVA that uses the Fourier Transform, and performs several operations, such as the...

Hi to all, I've been writing an application in JAVA that uses the Fourier Transform, and performs several operations, such as the convolution. The convolution is being processed in the time domain, so when signals lenths are big (i.e. 1000 values or more), it takes very long to process the convolution. So the best way to do this is by working in the frequency domain. Does anybody know ...

## Convolution property of DFT

Started by in comp.dsp9 years ago 4 replies

Hi, I'm trying fast convolution property but there seems to be some mistake (with the answer). Here is the Matlab code for it, clear all;...

Hi, I'm trying fast convolution property but there seems to be some mistake (with the answer). Here is the Matlab code for it, clear all; clc; % Test Vector Convolution a = [1 2 3 4 5]; b = [10 20 30 40 50]; c= conv(a,b) A = [1 2 3 4 5 zeros(1,5)]; B = [10 20 30 40 50 zeros(1,5)]; d= ifft(fft(A) .* fft(B)) c - d(1:9) The results are: c = 10 40 100 200 350 ...

## 2D Convolution using FFTW

Started by in comp.dsp14 years ago 1 reply

Hello everyone, I am implementing a fast convolution program using FFTW library. I understand the constraints of the Discrete Convolution...

Hello everyone, I am implementing a fast convolution program using FFTW library. I understand the constraints of the Discrete Convolution Theorem, and the issues of wrap around error and periodicity. Hence, I am taking the following approach at the moment. /*-------------------*/ Image: image[sizeX][sizeY] (Symmetrical)Filter: kernel[2k + 1][2k + 1] Step(1) Define padX = siz...