Signal Processing Stack Exchange
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1500 questions
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4 answers

Fast approximate optical flow / image shift

I need to detect how fast a camera is panning (either horizontal/vertical) to give a warning to the operator to slow down. The entire image is moving as a block, I don't need an actual direction (although H or V would be a bonus) and I only need an…
Martin Beckett
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How to do De-Houghing of a Hough transform'ed Image?

I'm working with code found at Rosetta Code for creating a Hough transform. I now want to find all the lines in an image. To do so I need the ρ and θ values of each of the peaks in the Hough space. A sample output for a pentagon looks like…
waspinator
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How do I use a Savitzky Golay filter to find local maxima (in between samples) in a discretely sampled 1D signal?

I have a seismic signal y(i): Here I have found one maximum: i=152.54, y=222.29 manually and plotted it in red. I want to find all maxima automatically. I read that the Savitzky Golay Filter (SGF) can be used to find smoothed estimates of both a…
Andy
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The small red peak in the CIE standard observer

The human eye has 3 types of color cones: red, green and blue. Their spectral sensitivity peaks in short (S, 420–440 nm), middle (M, 530–540 nm), and long (L, 560–580 nm) wavelengths. See diagram below. Then we have the CIE standard observer.…
Julian
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Good features / algorithms for recognizing car-models in images

I have a question concerning object recognition, especially recognizing car-models! I am at the beginning of a work about identifying the same car-model in different images. At the moment I think one of the best algorithm for 3D object recognition…
Hans Sperker
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What is the $\mathcal Z$-transform of Bessel function $J_0(\alpha n)$ sequence

What is the $\mathcal Z$-transform of the sequence $J_0(\alpha n)$ for $n \in \mathbb{Z}$? The Fourier transform of zero$^{\rm th}$ order Bessel function $J_0(\alpha x)$ is known to be $\frac{2}{\sqrt{\alpha^2 - \omega^2}}$ for $|\omega| < \alpha$.…
sauravrt
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python; audio; detecting silence in audio signal

I have real-time audio application written in python, and I have question about detecting silence. What's the most efficient way to distinguish silence from non-silence, in an input audio signal? By non-silence I mean any sound, even noise. I need…
user155
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How to get started with fingerprint recognition?

I have started with Matlab and Digital Image Processing. I am trying to do Fingerprint recognition. I found many research papers regarding this but I am unsure where to start. Concisely, what is the most basic approach/algorithm for doing…
krammer
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Number of DFT (FFT) Points Required for a Specific Frequency Resolution for an Oversampled Signal

I have a bandpass signal centered at 2 MHz and bandwidth of 50 kHz (the signal frequency varies from 2 MHz - 25 kHz to 2 MHz + 25 kHz). This signal is being sampled at 10 MHz. I want a frequency resolution of 100 Hz in FFT. I want to know: How many…
Vinod
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3D Position estimation using 2D camera

I have a camera (iPhone), I have a 3D control object in the image that I know its properties very well. (My control object). There is also a secondary object in motion. The ultimate goal is to establish the 3D trajectory of the moving object for a…
Ktuncer
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Finding radius r of the overlappable sphere(s) in 3D image

My current problem: I have an input 3D binary image (a 3D matrix that has only 0 and 1) that consists of random numbers of sphere with radius r. We do not know how many spheres are there in the image. All spheres have the same radius r, but we do…
Karl
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Is it possible to convert from 2D to 3D form?

I have captured car positions at different frames from the video. Suppose car's(e.g.left side car which is coming towards us in the images) centroid at video frame1 is P(x1,y1) and Q(x2,y2) at video frame4. Is it possible to represent P and Q…
sagar
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Functional analysis for signal processing engineers

It seems that the most advanced pure mathematics course most EE engineers take is Fourier analysis, and after that it's basically 'applied' courses. There's probably a good reason for this, but I'm not sure what it is. Functional analysis seems like…
Benjamin Lindqvist
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Deconvolution by Convolution

This is now a second time I am attempting to ask this very important but simple question here. What I want to know is can you do deconvolution by convolving a signal. It is often stated that, for example by cutting and boosting the same frequency on…
Tony
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Non Uniform FFT / DFT with FFTW?

Can FFTW perform the FFT on data which is not uniform in time? I can't seem to find a straight-forward answer to this question anywhere online.
John
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