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1500 questions
9
votes
1 answer
How to expand on and deepen a basic skill set for image/video processing?
I didn't take any class on image processing but I studied the subject based on lecture notes and important books for last three months. So at this point, I would like to sharp my image processing skills. Of course, I am practicing a lot of image…
Tae-Sung Shin
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9
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1 answer
Auto Correlation vs Cross Correlation vs Convolution and their applications
I know from wikipedia that auto correlation in done on the same signal while cross correlation is done on different signals.But what does this actually imply in terms of application.I can always apply cross correlation on same signals and get same…
Chirag Ahuja
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9
votes
2 answers
How do I create a frequency vs time plot?
I'm a chemical engineer, not an EE, so this is a bit difficult.
I'm trying to figure out how to take amplitude vs time data and transform it into frequency vs time. My first instinct is to slice my data into chunks, perform the FFT on each chunk,…
Nick
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How do real-time convolution plugins process audio so quickly
Okay, so in Logic Pro I can load up a Space Designer plugin (convolution reverb) with an impulse that's 9.1 seconds long, turn my mic on, and get real-time convolution reverb as the mic records incoming audio.
My question is: How could this be…
Aaron Dawson
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9
votes
2 answers
Fourier transform artifacts
My starting point in what follows is a radially symmetric random field. Taking the Fourier transform of this (and plotting it in logarithm to highlight the patterns), I obtain the following image in Fourier space:
As you can see, there is a…
user1991
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9
votes
2 answers
Statistical properties of the Kalman estimates under Gaussian noise
For a linear state-space model with independent Gaussian state and output noises and perfect guess for initial state, do Kalman estimates have the following properties:
$$
E(\hat{x}_{k|k} - x_k) = 0
$$
$$
P_{k|k} = Var(\hat{x}_{k|k} - x_k),\text{ or…
Tim
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9
votes
2 answers
Why Should the Sum of Masks / Kernel / Filter in Image Processing be One?
I am studying pyramids (expanding and reducing) and I am a newbie.
Why should the sum of the convolution mask be one when we are using gaussian distribution?
According to When should the sum of all elements of a gaussian kernel be zero? and Why is…
David
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9
votes
1 answer
Speech Compression - In LPC how does the linear predictive filter work on a general level?
Hi I'm taking a multimedia systems course and I'm preparing for my exam on tuesday. I'm trying to get my head around LPC compression on a general level, but I'm having trouble with what is going on with the linear predictive filter part. This is…
user1058210
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9
votes
1 answer
Zero Padding of FFT
There are many question related to the zero padding a time domain signal to get more frequency bins after performing Fourier transform. As I understand this process is equivalent to trigonometric interpolation in the frequency domain. However, I am…
Creator
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9
votes
1 answer
Theory behind Linear Predictive Coding (LPC)
What is the theory behind LPC?
Why are(were) certain implementations of LPC said to be more tolerant of transmission or encoding errors quantization than other compressed voice encoding schemes?
Can LPC methods also be used for smoothing or…
hotpaw2
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9
votes
2 answers
Best way to evaluate "quality" of autocorrelation?
This is a side-trip from my snoring app.
I had a crack at producing an autocorrelation of the audio signal, to see if that "correlates" with snoring/breathing very well. I have a simple algorithm going (produces 1.0 as the zeroth element, which is…
Daniel R Hicks
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9
votes
2 answers
What are some face detection (not recognition) algorithms suitable for limited (embedded) processors?
I am looking at a hardware based platform for surveillance class of applications. I want to identify faces of people as they appear in the scene.
I don't intend to really apply face recognition (then or later). Also orientation of faces can be…
Dipan Mehta
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9
votes
1 answer
Conjugation in Fourier Transform
I have a very simple question.
In Oppenheim book, it says that:
If CT Fourier transform of $x(t)$ is $X(j\omega)$ then, CT Fourier
transform of $x^*(t)$ is $X^*(-j\omega)$.
What I can't understand is what is $X^*(-j\omega)$? Or what is…
jason
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9
votes
3 answers
FFT for line detection
I am trying use the FFT in a different way then most people ask about. I want to be able to take a picture of a graph with regular repeating vertical lines, and to process the image to determine how far in pixels the lines are apart on average. I…
justagruvn
9
votes
2 answers
What is the meaning of Mutual Information beyond the numerical calculation?
Beyond the raw equation for calculating mutual information, what does it mean in physical terms?
For example:
From Information Theory, we know that entropy is the smallest loss-less compression scheme that we can use on a alphabet with a specific…
CyberMen
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