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Is this a correct method for fixed pattern noise correction?

I am currently involved in a project involving programming an imaging sensor. Our sensor is giving us noise, so we want to correct for it. Someone else on the project came up with the idea to take a "black" image i.e. put the lens cap on and take an…
NominSim
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Filtering 50Hz using a notch filter in MATLAB

I've read up a lot about this, but haven't been able to piece everything together successfully, so I'm looking for some help. I need to filter 50 Hz from a signal. It looks like the best options are either a notch filter or a LMS filter, but I don't…
Dororo
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Graphical fourier series of a square wave

This is probably off-topic since it isn't really a question, but I thought that this GIF of the fourier series of a square wave was too cool not to share.
Jim Clay
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What is spectral whitening?

What is meant by "spectral whitening" in DSP? What effect does spectral whitening have when used in image processing? (visually or otherwise...) Where might spectral whitening be useful in audio processing or analysis? What would a spectrally…
hotpaw2
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Power spectral density vs Energy spectral density

I read the following on Wikipedia: Power spectral density: The above definition of energy spectral density is most suitable for transients, i.e., pulse-like signals, for which the Fourier transforms of the signals exist. For continued signals…
Amelio Vazquez-Reina
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What exactly is a complex envelope?

I have seen this be mentioned a couple of times in some books I read, so I want to make sure. Is the complex envelope simply the summation of the real and quadrature components of a signal, whereby the absolute value is the (real) envelope? I have…
TheGrapeBeyond
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"Low-pass filter" in non-EE, software API contexts

I am an experienced software engineer and am working on smartphone sensors. I've taken fundamental EE classes in DSP and am trying to apply my knowledge. I believe that I understand convolution, transfer functions, z-transform, etc. I know a little…
stackoverflowuser2010
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How to find smoothed estimates of the derivative and second derivative of a signal?

I have a signal sampled at $\Delta t$: $f_i(t_i=i\Delta t)$ where $i = 0,\ldots,n-1$. I want to find the first and second derivative of the signal: $f'(t)$ and $f''(t)$. My first thought was to estimate the derivatives by central…
Andy
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Smoothing signal / detecting bumps in a data stream

(EDIT: This question follows from Extracting Binary Magnetic-Strip Card Data from raw WAV) Here is my signal (top line) and a basic IIR filter applied (bottom line) (EDIT: my task is to break the signal into binary 0 (frequency F) and binary 1…
P i
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Artifacts in FFT

I recently realized that FFT's aren't perfect. Meaning if I take a signal and then take it's FFT, and then do an inverse FFT, the resulting output isn't exactly the same as the input. Here's an image to show you what I mean : I think the image is…
Kitchi
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Conditions for precoding matrix to preserve complex conjugate symmetry on DFT vector

Suppose there is a DFT vector $\mathbf{X}$ with length N, which presents complex conjugate symmetry around its middle point, i.e., $X(1) = X(N-1)^*$, $X(2) = X(N - 2)^*$ and so forth. $X(0)$ and $X(N/2)$ are the DC and Nyquist frequency…
igorauad
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Why does adding a time delayed version of a signal to itself create a filtered signal?

I was asked this question and couldn't come up with an answer on the spot which didn't involve the frequency domain (basically that the co-efficients of the delay sequence are the impulse response of a FIR filter). Does anyone have any insight…
Tom Kealy
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Implementing a Kalman filter for position, velocity, acceleration

I've used Kalman filters for various things in the past, but I'm now interested in using one to track position, speed and acceleration in the context of tracking position for smartphone apps. It strikes me that this should be a text book example of…
Stochastically
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What information does the Hilbert transform give?

The Hilbert transform of a function is defined as : $$\mathscr{H}\big\{f(t)\big\} = \lim_{T\rightarrow \infty}\frac{1}{\pi}\int\limits_{-T/2}^{T/2}\frac{f(\tau)}{t-\tau}\, \mathrm{d}\tau$$ Okay but what does it do exactly? What information do we…
Volpina
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Counting vechicles in an image

I have been trying to implement an algorithm for successfully counting cars in an image. I have tried implementing A Method for Vehicle Count in the Presence of Multiple-Vehicle Occlusions in Traffic Images It estimates the background from a set of…
krammer
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