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Questions tagged [convolution]

Convolution is a mathematical operation on two functions f and g, producing a third function that is typically viewed as a modified version of one of the original functions.

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Eigenvalues of a product of matrices with specific structures

I'm working on a multichannel feedback system with open-loop frequency response $\mathbf{A}(\omega) = \mathbf{B}(\omega)(\mathbf{C}(\omega)-\mathbf{D}(\omega))$. The time-domain convolution matrices ...
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Implementing blind deconvolution in MATLAB

I want to implement blind deconvolution for the signal $ r(n) = h(n) \star s(n) + a(n)$ in MATLAB where $r(n)$ is the recorded speech $h(n)$ is impulse response of room acoustics $s(n)$ is desired ...
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Blind 1D equalization/deconvolution with some knowledge of filter kernel

Let $s_{\rm out}[n]$ be the 1D output signal of a system, $s[n]$ be the input, and $k[n,q]$ be the filter kernel for an element $n$ and for fixed value $q$. Then: $s_{\rm out}[n] = s[n] \ast k[n,q]$ ...
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Convolution of signals sampled on a logarithmic grid

Is there a practical accelerated algorithm or a theoretical discrete (Fourier) transform based method to convolve discrete-time signals sampled on a logarithmic grid? What I mean is representing a ...
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maching convolution filters to results

I am practicing for an exam and I need help in the following question (it is just for me- no grade...) we get an input image, 6 convolution filters and 6 results. we need to find the matches between ...
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Wavelet computation with filter bank - differing results

I'm trying to get a grip on Wavelets. I've read "Wavelets, Their Friends, and What They Can Do for You" which lead me to an implementation of the discrete DWT with filter banks. Basically, I'm using ...
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Gaussian filter convolution giving unexpected results

I am trying to smooth a time series signal with a Gaussian filter and then differentiate the signal (this is for an application for edge detection). A nice property of convolution is: $$ \frac{d}{dx} \...
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679 views

Convolving two complex signals - relationship between phase

Suppose two continuous complex domain signals are convolved, how is the magnitude and phase of the resultant signal related to the magnitudes and phase of the original signals?
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Deconvolution of non-stationary, 1-D signal?

I have a time series that has been measured after convolution with a moving average filter. Knowing the parameters of the moving average filter, is it possible to reconstruct/constrain the values of ...
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Convolution - change of variables

I am struggling trying to understand the 3rd line of the expression below. The second line can be simply visualized by letting the kernel size be 3 and $i=2$ for eg. Then $ y_2 = \sum_a x_{2+a-1}...
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How to apply the convolution matrix of a filter of an image

When I am dealing with one dimensional signals I can apply a filter of that signal by multiplying the convolution matrix built with that filter times the signal itself. $x[n]$ column vector filter $...
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Where does convolution fit into tracking fluorescent photons using MC models?

I have been reading this old paper by Steven Jacques, a titan in the world of using Monte-Carlo methods for photon propagation and distributions. https://www.osapublishing.org/ao/abstract.cfm?uri=ao-...
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Imfilter, FFT-bsed convolution speed

I want to convolve two large matrices and it is working fast - as long as one of those matrixes contains only separate points (point sources). If I replace the points by eg. Gaussians (line "HERE" ...
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252 views

discrete fourier transform circular symmetry

I was reading digital signal processing. In topic Discrete Fourier Transform, circular symmetry it is said that circular advance is obtained by shifting x(n) in clockwise direction. i.e. to obtain x(n+...
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How to convert multi-band Energy Time Curve (ETC) to Impulse Response (IR)?

I am running my own sound simulator. Now I have obtained the Energy Time Curve (ETC, expressed by energy) by physical simulation, and they are stored in 8 discrete frequency bands (because decay of ...
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Recognize irregular repetition of unknown feature (stamps at random locations)

I have an image which is generated by convolution between (1) a simple small patch and (2) larger image composed of localized point-like features (e.g. slat-and-pepper noise, sum of shifted $\delta$-...
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Applying a frequency filter in dB onto an audio wav file in the frequency domain

I am working on a university project consisting of a C program supposed to apply a correction of the isophonic curves to an audio PCM file. So far, I have managed to code the most part of it (read/...
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Fastest way to subtract known music tracks from live videogame audio stream

I want to isolate video game "action" sounds from the video game soundtrack. Given all ~20 songs, I'd like to filter them out from any live audio stream during gameplay. What is a fast and robust way ...
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Can this robot trajectory smoothing function be expressed as a single convolution?

I have an Nx3 matrix of poses (x, y, theta) that I need to apply an algorithm on which will cause the trajectory to be smoothed. I am interested in performance and so would like to improve efficiency ...
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129 views

Appropriate digital filter for GPS tracks?

I have an open-source software project whose purpose is to analyze a GPS track, or a similar track made by an application such as google maps, and estimate the physical exertion required to hike or ...
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Locate first minima in signal

I have many datasets which all looks roughly like this: All the datasets have this in common. First there is an artifact around 0 with an unknown (but likely very high) intensity. Then there is some ...
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Feature maps for a Convolutional Neural Network

I hope this is the right place to ask this, so here goes: I am currently trying to implement a convolutional neural network in C++, but since I have no formal education in signal processing, image ...
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FFT Convolution: missing sample somewhere

For a piece of software I've been working on lately I need to implement FFT convolution for performance reasons. Doing so has been mildly succesfull but there is still a error somewhere causing lots ...
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Is there any library for convolution reverb software for Visual Studio besides Freeverb?

I am currently working on a simulation of a virtual scene. I calculate the IR of the direct path and the early reflections and want to convolute them with the input signal. My problem now is that ...
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Size obtained by applying Linear convolution

We know that applying a filter on an image is called correlation or convolution depending on the filter angle. In Gonzalez I have read that we can apply linear convolution on an image. Here I have a ...
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What is the difference between Time-Frequency Represenation and TF Decomposition

I'm asking as I'm looking at Wavelet transforms, and I see that it is possible to have a TF decomposition or a representation of the signal. Looking for example at the code here we can see that the ...
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Impact of different padding schemes in Frequency domain image filtering

I understand, that image padding is necessary in order to prevent wrap-around effects due to circular convolution. My set of questions are related to different padding schemes. Zero Padding is easy ...
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118 views

How do I combine a copy of a signal with the original to achieve a chorus effect in a .wav file using Python?

Can you please explain or point the right way to think about how to implement two sound effects in a .wav file. So I read a .wav file and converted it to int values (in ...
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Savitzky-Golay Filter Coefficients and Wikipedia

I am trying to implement a Savitzky-Golay filter by following this Wikipedia page and in the first instance I have written the following Octave software code to create the convolution coefficients <...
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Reconstruction from Convolution

I am trying to implement Wavelet transform in an embedded environment. The problem I face goes like this: Two vectors, A and B. A is input samples. B is vector co-efficients. I take convolution of A ...
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203 views

Applying a filter kernel defined by a continuous equation in the frequency domain

I have a filter kernel $K(\omega)$ completely defined in the frequency domain as a continuous function of angular frequency $\omega$. I know $K(\omega)$ defined as a continuous mathematical equation. ...
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How to implement freq convolution layer?

I am referring the paper https://pdfs.semanticscholar.org/31c7/4962122ba5fe1c469101b5bc2ae6d88c9c18.pdf. In the paper, for CLDNN network first layer is freq convolution. How to implement the same for ...
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Wide-Band Lorentzian FDTD Algorithm

I want to convert a simulated gain/absorption of a material, which can be understood as a discreet (dispersive?) function $g_i(f_i)$ ($f$ is for frequency) or $g_i(\lambda_i)$, into $\tilde g(t)$ for ...
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Convolution in the Hartley Domain

The convolution Theorem of the Hartley Transform is given by $$ Y_{Ha}(k) = X_{Ha}(k)H_{Ha}^{e}(k) + X_{Ha}(-k)H_{Ha}^{o}(k) $$ where, $$ H_{Ha}^{e}(k) = \frac{H_{Ha}(k) + H_{Ha}(-k)}{2} $$ $$ H_{...
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Applying a filter on an input sequence in matlab

Given a input sequence $x = {x_1, ... x_n}$ and a filter with l elements $h = [h_1, ..., h_l]$ with l < n. We want to filter the input sequence with the specified filter. My first thought was to ...
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Why convolution in time and frequency domain are not equal?

I was writing this Jupyter Notebook. Then, I unexpectedly faced two visually similar output, but their numerical results were very different. This is the code I used for convolution in the time ...
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Convolution with rectangular function

I have a system $h(t)=4e^{-4(t-4)}u(t-4)$ and I want to response of the system to $x(t)=rect(2(t+4))$. I have followed those steps: $y(t)=x(t){*}h(t)$ $=rect(2(t+4)){*}4e^{-4(t-4)}u(t-4)$ $=4[u(t)-...
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Noising audio in MFCC space

I am training up an audio recognition neural network using MFCCs. Its been shown to be very beneficial to artifically add noising and reverb of the original audio when training a neural network (Data ...
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245 views

How can I improve the Canny edge detection code?

I have converted this Matlab code for Canny edge detection into C# given that the Matlab version gives out a good output. The output from Matlab code is as follows: And my C# version's outputs are ...
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115 views

Matrix cross correlation in python

I'm currently performing matrix cross correlation in python using : C = scipy.signal.correlate2d(A,A) where A is a 2D matrix, typically a picture. As you can ...
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25 views

Applying BCJR equalization for LDPC encoded information

I want to apply BCJR decoder for LDPC encoded information. How can I change the BCJR originally for convolutional codes for this purpose?
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172 views

Circular Convolution, modulo N smaller than Length

I am having a small Problem here, which I can't figure out on my own. I am supposed to perform a circular convolution y[n] with three different modulo N values N =...
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23 views

Generating synthetic zero offset seismic data

Essentially, I am struggling with producing the depth model for this problem, which is a finite reflector dipping at an angle in the subsurface. I just started using matlab so I am not quite sure what ...
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45 views

Create colour-coding filter for Fourier transformations

I have to conduct a Fourier transform on a 2D-RGB-image, filter out low frequencies and then apply a colour-coding filter so that the remaining frequency peaks are represented by different colours. I ...
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37 views

Recursive systematic convolutional code with TCM

My question is: What are the outputs from the TCM encoder ?
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42 views

Matrix used for a transposed convolution?

I was wondering what would be the matrix used for a transposed convolution? I understand that the matrix for Conv2d given the initialization below: ...
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84 views

Amplitude is affected by the sampling interval in convolution of input signal with impulse response?

I simulated convolution using an application, I then wanted to see if the output would match the derived mathematical output. The square wave below is being convoluted with itself, the impulse ...
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265 views

Zero Padding FFT: ifft(fft(x)) is unequal to x

I implemented an iterative radix-4 FFT and IFFT, and after performing these on zero padded, but further unchanged signal, the output differs. What am i getting wrong? Problem Description: A signal ...
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42 views

Basic question about Block Diagrams and Scale factor

I am doing a project about controlling a thermoelectric module, and for doing so I must reverse the current direction. This is achieved changing the voltage polarity. So the output of the controller (...
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Applying the inverse FFT to even out a room's sound - What is the more efficient algorithm?

I have a way (the standard way) to correct for my room's acoustics, but I'm wondering if there's a more efficient algorithm, something that doesn't involve going to the frequency domain maybe? I ...