Signal Processing Stack Exchange
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Alias frequency Formula

I'm taking a multimedia systems class in my MSc Computer Science, and I'm having some trouble understanding the formula for the alias frequency - this could stem from my misunderstanding of the alias signal. My understanding of an alias signal is…
user1058210
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What is the connection between analog signal to noise ratio and signal to noise ratio in the IQ plane in a quadrature demodulation system?

We would like to compute the quantitative relation between analog noise near the LO frequency and the statistics of points found in the IQ plane after IQ demodulation. In order to completely understand the question we first give a detailed…
DanielSank
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Vehicle counting from a video

Disclaimer: I posted this question on StackOverFlow but learned that it is better suited here. I am a bit new to image processing so I'd like to ask you about finding the optimal solution for my problem, not help for code. I couldn't think of a good…
Horizon1710
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decision rule for image segmentation

Let $Y$ be a measured (noisy) image $Y= X+ noise$, where $X$ is an image contains $0$(Background) and $200$(object). I need to create a decision rule that determines whether the true pixel value was $0$ or $200$ given the image $Y$. the noise is…
HforHesham
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Counting the number of objects intersected by the image border in MATLAB

I have an RGB image with various signs. My main goal is to count the signs that are in contact with the image borders. Approach and problem I started by loading the image [Fig. 1], then converted it to grayscale and applied a median filter to get…
Rui Trovisco
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What is the effect of aliasing on the magnitude of the autocorrelation?

I've a question about the effect of aliasing on the magnitude of autocorrelations. From a simulation in MATLAB, I don't see any effect of aliasing or any need to anti-alias filter when I take the magnitude of the autocorrelation. Which means I can…
Hossein
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Is it valid to increase amplitude (and presumably FFT quality) by simply scaling the data?

I'm using a version of "KISS FFT" by Mark Borgerding. It accepts an array of 16-bit fixed-point input values and produces a 32-bit float result array. I've discovered that if the input amplitudes are low many of the float result values come out…
Daniel R Hicks
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Meaning of the Transpose of Convolution

I have an $n \times n$ asymmetric convolution kernel, $k(t_1,t_2)$. $k$ is zero everywhere except for in small regions near the corners. I also have an $n \times n$ image, $f$. Let $*$ denote circular convolution so that the convolution operator,…
dranxo
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What is a good FFT window function to reject DC?

I'm using an FFT to analyze what is essentially the power envelope of a signal (see here for info on the containing project), and, since power numbers are always positive, to eliminate the DC component I'd like to use a window function that is 50/50…
Daniel R Hicks
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Phase shift and phase spectrum terms in multidimensional signal

I know about phase of a 1D signal. But when I go into higher dimensions like 2D,3D etc, it becomes headache to grasp the concept. What are the terms phase shift and phase spectrum mean in case of multidimensional(2D,3D etc.) signal like an Image…
devraj
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Isolate the non blurred part of foucsed image

I have an image taken by a mobile phone camera with focus on a part of it let say a face or whatever. I want to know -approximately- where is the focused area. For example, a bounding box around the focused area. example :
Humam Helfawi
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Are there any computer vision algorithms specifically targeting depth images?

I've been looking into marker detection algorithms to use with a kinect based application, and the majority of the work I've been able to find is obviously focused on feature detection in 'normal' images. However, the kinect hardware provides…
Doug
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Advise on detecting anatomical landmarks in a CT reconstructed volume

I'm trying to automatically detect some medical defined anatomical landmarks in a CT reconstructed volume. Medical doctors use these landmarks to measure some patient specific parameters. I have attempted to use the SIFT feature descriptor, since…
Federico
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Can I use independent component analysis if I have two discrete populations of signal sources mixed together?

I understand (mostly) how independent component analysis (ICA) works on a set of signals from one population, but I am failing to make it work if my observations (X matrix) includes signals from two different populations (having different means) and…
Edward
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Deconvolution Question on Article "Deriving Intrinsic Images from Image Sequences" by Yair Weiss

there are n derivative filters: $f_i$, and denote $f_i^r$ as $f_i$'s reverse filter such that $$f_i(x,y)=f_i^r(-x, -y)$$ $r_i, f_i$ given, to find $r$ from the equations: $$f_i * r = r_i, (1 \leq i \leq n)$$ Professor Weiss recovers $r$ using the…
Jiapei Huang
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