Questions tagged [correlation]

Correlation or Cross-Correlation is a measure of similarity of two waveforms as a function of a time-lag applied to one of them.

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Difference Between Correlation and Convolution in the Context of Image Processing

Could you please clearly explain what is the difference between correlation and convolution that is done by a filter on an image? I mean in terms of signal processing definition I know that ...
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Calculating similarity between two signal plots

I have two plots, each having frequency as x-axis and Gain as y-axis. By taking one data set as a reference I have to calculate similarity between them. The graphs have same values on the x-axis and ...
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Need help understanding convolution indexing

Ok, this is leaving me increasingly frustrated. This builds on a previous question here but I am still not getting the indexing, although I learned from that question all the same. Case 1: First ...
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2 votes
2 answers
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Comparing two small audio files (e.g., hand clap) Android

Dears, I am new in signal processing and I am dealing with an Android application that should do some audio files (having the same "small" duration) comparison in real time. My main focus is ...
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How do I calculate the eigenvalues of a covariance matrix which contains harmonic functions

I have read that $ce^{-\frac{\phi_i-\phi_j}{\rho}}$ is a harmonic function of the form $e^{-in\phi_i}$, and therefore it's eigenvalues are one of the Fourier components of $(|\phi_i-\phi_j|)$. My ...
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Deciding if the received packet is valid or not valid [closed]

I have sampled RF wireless packets as IQ samples file, those RF packets has patterns like preamable|syncword|data|crc , I'm doing cross correlation with my constant syncword (after I did the ...
LiamLony's user avatar
14 votes
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What Does It Mean Exactly When Two Parts of a Signal Are Correlated?

I stumble quite often upon the notion that two or more parts of a signal are correlated to describe semi-formally that they belong together. For example in image processing, two pixels on an edge ...
Lenar Hoyt's user avatar
13 votes
2 answers
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Why do we need to conjugate complex signals in autocorrelation and cross correlation

Why is it necessary to conjugate $f(t)$ while performing auto correlation or cross correlation with respect to $g(t)$, if $f(t)$ and $g(t)$ are complex signals?
Vinayak Killedar's user avatar
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Phase Correlation - Poor Performance on Noisy/Blurred Images?

I have successfully tested 1D phase correlation algorithm to determine vertical shift between two synthetic images. When I moved to real images, however, it is not able to detect translation at all (...
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Correlation : How is correlation analogous to dot product?

Till now I know correlation tells about similarity. I was watching a video lecture on image similarity in which I came to know that correlation is analogous to dot product. And hence correlation of ...
No Sound's user avatar
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How does DCT decorrelate images?

I've read in multiple places that DCT decorrelates Toeplitz matrices and images usually have Toeplitz structure. Can you explain with an example how DCT decorrelates a Toeplitz matrix? Example for DFT:...
Nagabhushan S N's user avatar
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6 answers
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Find Short Clip of Audio Within Longer Clip Of Audio

I need help figuring out a way to automatically synchronize two audio files that are both different recordings of the same source. More info below. This example is from a concert, where there is only ...
Mitch Chaiet's user avatar
5 votes
2 answers
1k views

Time Alignment of 2 Sensors Sampling the Same Signal with Different Hardware Delays

I have two radios sampling simultaneously, and I am trying to time-align their two signals (they will always start sampling at slightly different times with random delays due to hardware differences). ...
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1 answer
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Cross correlation with FFT and fftshift

When I calculate the cross correlation between two vectors with the following code ...
Pedro G.'s user avatar
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3 votes
1 answer
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Proving that FFT (and by extension any correlation based estimator) is unbiased

I have a pretty simple question which i should have been able to answer. Just wanted to check if people here have a better solution to it. I am trying to establish that FFT as a frequency estimator (...
Khurram's user avatar
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3 votes
1 answer
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explanation of correlation of stationary stochastic processes

I have some doubts about correlation in stationary stochastic processes. I know that the expectation of a random variable is $$E(x)=\int_{-\infty}^{+\infty} a f_x(...
Andrea's user avatar
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2 votes
2 answers
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minimum sampling rate for very short duration signals

I understand that sampling rate should be twice the signal bandwidth for successful reconstruction. But what I don't get is how this translates in the time domain. For example, I have a sine wave ...
user4673's user avatar
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Designing an efficient curve-matching algorithm

I'm currently designing a curve-matching algorithm and as I already explored many ideas I'm requesting your help. So, if you got some advices about how to handle this problem, feel free to answer! ...
Louis Lac's user avatar
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3 answers
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Synchronization of two audio tracks via Mel-frequency cepstral coefficients (MFCCs)

I am trying to solve the (common) problem of synchronizing (i.e. measuring the delay between) two audio tracks recorded from different sources during a conference talk (about 1h of audio). One track ...
charlie80's user avatar
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1 vote
2 answers
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How to interpret values of the autocorrelation sequence?

I know that (auto)correlation indicates the "degree of predictability" of a variable with respect of another. However, this is a vague notion. I know that a blank process should have an ...
MPA95's user avatar
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Find Syncword (pattern) in signal, using Correlation

I have a signal which always has the same syncword ([93 0b 51 de] in hexa). I also have a signal with additive noise(attacing it, and I want to find my syncword in that a noisy signal using corelation(...
Ryan's user avatar
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3 answers
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How do I know quantitatively if the correlation of two time series is significant?

I computed the correlation coefficient of two time series of daily observations, x and y, but noticed that the more sampling ...
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Estimate the time delay of two signals

I am having 2 sets of data data1 and data2 .I wanted to find the delay between the two datasets. Assume data1=[1 2 3 4 5 6 7 8 9 10] and data2=[0 0 0 0 1 2 3 4 5 6].From the data I know that, data2 is ...
Deepa's user avatar
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Find Preamble (pattern) in signal, using Corelation

I have a signal which always has the same preamble (4x 0xAA - 10101010...). I also have a signal with additive noise, and I want to find my preamble in that a noisy signal using corelation. U used ...
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Correlation between Sin and Square wave

I would like to know how $\frac T2$ came for time period in the image below.Because I think the frequncy is 1 so time period should be 1.Is that correct? or can anyone help me.. The article from ...
justin's user avatar
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Autocorrelation - Understanding reduced correlation at periodic time shifts using np.correlate (versus statistical autocorrelation)?

I'm going through the Think DSP by Allen B. Downey, and I'm struggling to understand a specific aspect of np.correlate and how it differs from statistic autocorrelation. The question is at the bottom, ...
minifigmaster125's user avatar
0 votes
1 answer
87 views

packet encoder RF packets by using LPF for determining if it's zero or one [closed]

I'm transmitting RF packets with frequency 868MHZ , symbol rate (it's the same as bit rate) is 50KBaud , and Im sampling them by a dongle (fs=20480KHZ) to capture those RF packets, the captured ...
LiamLony's user avatar