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7
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Which Noise Reduction Algorithms Are Used in Commercial RAW Image Processors?
I'm trying to guess what noise reduction algorithms are used in commercial processors for raw images from digital cameras. I find this fairly easy to do for the sharpening algorithms (most use unsharp mask as at least one option, for example, and…
Potato
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7
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What is a Kravchuk transform and how is it related to Fourier transforms?
It has been stated here, that the the so-called Kravchuk transform is very important in the field of image processing and possibly in signal processing in general.
I can hardly find any description about this (e.g. not mentioned in Wikipedia, etc.).…
SheppLogan
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7
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How exactly to implement the fractional part of a 'fractional equalizer'?
I have written my own LSE equalizer (that works on the bit level), and literature I have read says that 'fractional' based ones are much better. So how exactly does one get 'fractional' bits? Is it as simple as resampling the softbit decisions to…
Spacey
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7
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What are i-vectors and x-vectors in the context of Speech Recognition?
I have read that i-vectors and x-vectors are widely used in speaker recognition tasks but I don't get the difference between them and how exactly they work. Can someone explain it starting from the ground to a bit technical?
I came across following…
mausamsion
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7
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2 answers
Should I use ideal or non-ideal filters for offline filtering?
I've got an offline signal that I want to high-pass filter. Should I use a Butterworth filter, or could I use the fact that the whole signal is known and use an ideal (step) filter?
Using a high-degree Butterworth filter is, I think, practically the…
Andreas
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7
votes
2 answers
Whats the optimal window function to use for analyzing real-time data samples?
Say you wanted to run a X point FFT on the last X audio samples that were played. The problem being, using a normal hann window function would place emphasis on the "middle" of the audio sample. However, the most current audio samples played (the…
Steve Barna
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7
votes
2 answers
Fourier Transform of Alternating Periodic Rectangular Pulse
I'm having trouble determining Fourier transform of signal. I have 2 ideas on how to solve this problem.
Given the signal is periodic I could use formula for Fourier transform of periodic signals:
$$X(j\omega) = \sum\limits_{k=-\infty}^{\infty} C_k…
Aleksandar Simonović
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7
votes
2 answers
Eigen Function of Linear Time Invariant (LTI) System
Whenever I try to find the derivation of eigen signal of a LTI system, they always start with assumption that the input signal is complex exponential. Is there any other way to prove that this is the case starting from the basic equation of LTI…
Interception
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7
votes
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Which unit does the power spectrum of microphone output have?
If I sample sound with a microphone and find the absolute square of the (non-normalized) DFT, I get the discrete power spectrum (correct me if I'm wrong). Which unit does it have?
Andreas
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7
votes
2 answers
Single-pole IIR low-pass filter - which is the correct formula for the decay coefficient?
A single-pole IIR low-pass filter can be defined in discrete time as y += a * (x - y), where y is the output sample, x is the input sample and a is the decay coefficient.
However, the definition of a varies.
On Wikipedia, it's defined as…
Mark
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7
votes
3 answers
Distribution of $e^{j\theta}$
Is there a canonical or analytic expression for the probability distribution for the circularly-symmetric complex random variable $Z$:
$$
Z = e^{j\theta},
$$
where $\theta \sim \mathcal U(0, 2\pi)$?
Side notes:
It is known that the real and…
Robert L.
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7
votes
1 answer
How to discern the distribution function of mean-squared coherence values?
This probably walks a fine line between Cross Validated and this site, but I think the practical application of it lies more on the signal processing side.
I have had the occasion to record some EEG data for an experiment, and determined the…
jonsca
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7
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1 answer
"Bi Directional" Kalman Filter - Kalman Filter for Smoothing
I am working on a project in Object Tracking, i.e. need to predict the location of next bounding box.
I used a Hungarian algorithm with a Kalman Filter (which is a common method in this domain) which produced decent results. However, lots of the…
Anuar Y
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7
votes
3 answers
Derivative with respect to complex conjugate
I have a real function $C$ of a complex vector $x$. While taking the gradient of the function $C$ for minimising the same, why do we take the derivatives with respect to the complex conjugate of $x$, i.e. $\bar{x}$ and not the actual vector $x$?
I…
Sal
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7
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3 answers
Weird results out of fourier transform of unknown signal, what am I doing wrong?
It has been a long time since I studied engineering, please forgive my mistakes.
I got data sampled from a digital accelerometer. It is sampled at 20 hz, then collapsed into 1 second epochs. The data is then filtered to remove noise. The system…
Alex Stone
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