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1500 questions
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3 answers

Purpose of image feature detection and matching

I'm a new guy in image processing and computer vision, so this question might be stupid to you. I just learned some feature detection and description algorithms, such as Harris, Hessian, SIFT, SURF, they process images to find out those keypoints…
avocado
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Detecting a fixed template image out of a semi-constant frame of video

There are a number of videos that I'm looking to process of different video games to detect various "states" in them. The first game that I am tackling is any edition of Super Street Fighter 4. In it, I'd like to detect when the "vs" character…
casperOne
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Higher order spline interpolation

I noticed that spline interpolation with a degree higher than 3 (everything beyond cubic splines) have a very high interpolation error, hence the prediction is mostly awful. I've come across various lecture notes, slides and Youtube videos that…
goocreations
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Difference between a wavelet transform and a wavelet decomposition

I'm confused about the difference between a wavelet transform and a wavelet decomposition is. For example load woman [cA1,cH1,cV1,cD1] = dwt2(X,'db1'); [c,s] = wavedec2(X,2,'db1'); What's the difference between these two matlab commands, and when…
Tom Kealy
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kernels to compute second order derivative of digital image

For an image $I$, its first order derivatives can be computed using several oprators, such as $$K_{sobel} = \left[ \begin{array}{ccc} -1 &0 &1 \\ -2 &0 &2 \\ -1 &0 &1 \end{array}\right]$$ $$I_{x} = I * K_{sobel},\ I_{y} = I * K_{sobel}.T$$. And to…
avocado
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How can I remove random dots from an image?

I recently received some scanned pictures which are in a pretty good state, with OK resolution, but they are randomly spattered with a bunch of black dots. These cover everything (clothes, faces, walls, windows, and so on) except for a few very…
Emilio Pisanty
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Help implementing audio dynamic range compression

I am trying to implement audio dynamic range compression in JavaScript (not using web audio API). There is a lot of articles for sound technicians, and some high level documentation, but I couldn't find any helpful reference for actually…
sebpiq
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What are high frequencies and low frequencies in a signal?

I'm new to signal processing. I'm plotting a signal in the time-domain in matlab. I don't understand which parts of the signal are high frequencies and low frequencies, can someone explain what a high and low frequency is, and how to see high…
user1117262
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what is proper setting for Fb,Fc in Complex morlet wavelet (cmor)?

I am using Cmor-Fb-FC wavelet transform in matlab environment. Fb is bandwidth and Fc is center frequency parameters. with trail and error procedure I select Fb-Fc as 5-1, and I've got rational output. But I want to know whats the rule of selecting…
SAH
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Example of Fourier Transform not existing for real-life signals?

I got curious based on this question here, but basically, is there ever a real-life signal that exists where its Fourier transform does not exist? If a signal is not finite energy, then its Fourier Transform does not exist, so what might be an…
TheGrapeBeyond
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why eigenvalues concerned in Harris corner detection?

In Harris corner detection, as I see, the goal is to find out those points $(x,y)$ which makes $S(x,y)$ a large value for any direction of shifting, $$ S(x,y) = [\Delta x , \Delta y]M\left[ \begin{array}{c} \Delta x \\ \Delta y \\ \end{array}…
avocado
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"Ensemble averaging ... cannot track dynamic changes"?

A book claims this as a motivation for introducing exponential averaging: A disadvantage of ensemble averaging is that the resulting estimate cannot track dynamic changes occurring in the observed signal. -- L. Sörnmo and P. Laguna, Bioelectrical…
user42
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How can I perform object tracking using noisy images?

The problem Take 50+ of Lena images, add gaussian noise to them to the point that you couldn't say it is Lena. I insist, gaussian noise, not gaussian blurring. Now imagine a cropping window randomly moving around Lena's face (like a video camera…
user1637
7
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2 answers

Simple beat detection algorithm for microcontroller

For the purpose of controlling DIY disco lighting, I'm looking at implementing beat detection in a microcontroller with limited computing power (i.e. Arduino Uno). While detecting all beats would be a plus (for one, it would allow measuring BPM,…
abey
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Can I simultaneously remove salt and pepper noise and improve the image resolution?

What should my approach be towards designing a filter that can simultaneously remove salt & pepper noise and improve the resolution?
vini
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