Questions tagged [cross-correlation]

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1answer
519 views

Cross-correlation of time compressed 1D signal

If I ave 2 otherwise identical 1D signals that are phase shifted from each other then cross-correlation is a perfect way to identify the time lag between the 2 signals. Now supposing I double the ...
2
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1answer
623 views

Normalized-cross correlation operation

According to my question about separability of Gabor filters in this link, I want now to convolve my image with this separable filter by using the normalized cross correlation operation. Assume my <...
6
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1answer
1k views

Ambiguous results of phase correlation in pattern recognition

We are using phase correlation to find pattern on image and what we get is 15% of results is spurious. Ours pattern has 32x32 pixels and image for research has 32x512 pixels. So we put Pattern to ...
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1answer
527 views

Detecting a frequency pattern in the frequency domain

I am looking to detect a combination of frequencies in the frequency domain. For example, here is my spectrum: And I'm trying to detect the pilot tone. I have the FFT of the pilot tone: which zoomed ...
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2answers
12k views

Applications of Correlation in Signal Processing

There have been discussions on the differences between convolution and correlation, autocorrelation, cross-correlation, et al. In spite of looking at the visualizations, and understanding the formula ...
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1answer
210 views

how to calculate cross correlation of transient signal?

there. Let me have a noisy speech signal $y(k)$ as below. $$ y(k) = x(k) + v(k) $$ where, $k$ is the discrete-time index, $x(k)$ is clean speech signal, $v(k)$ is a zero-mean random process, ...
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1answer
4k views

How can I compute a time-frequency cross-spectrum in MATLAB?

MATLAB has a spectrogram function for the time-frequency analysis of a single signal. It also has a cpsd function for estimating the cross-frequency spectrum for two signals. However, cpsd averages ...
1
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1answer
3k views

Signal compare - cross corelation in frequency domain matlab

I need compare two signals. Signals have simliar shapes but completely different values (as on picture): So I think cross corelation in frequency domain should gave me a number that shows me how the ...
0
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2answers
718 views

Normalized cross-correlation in detail

I'm trying to implement a normalized cross-correlation algorithm but I don't get what in fact is this measure. What confuses is the wikipedia definition: $\frac{1}{n} \sum \frac{(f(x,y)- \overline{f})...
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0answers
275 views

Train Pulse Recognition in Medium Voltage Networks

I just started a project in the Smart Grids area. It involves the recognition and quick extinction of earth faults in a medium voltage system. The system works automatically and pretty much gets rid ...
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0answers
841 views

Similarity of signals

I have a question concerning methods to find different aspects of "similarity" of signals. So, first, I'd like to characterize the signals to be dealt with: We have a number of close to rectangular ...
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2answers
258 views

Correlation between 2 functions

I have a periodical function $f(x)$ that is sampled in time, at a rate of 1 millisecond. Together with this, I also have a second function $t(x)$. I want to find the correlations between periods ...
3
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1answer
830 views

how could correlation-based image patches matching works?

In general, correlation-based image matching can be referred to as $$c(I_1,I_2) = \sum_{x \in patch} f(I_1(x), I_2(x))$$ , I do think normalized cross-correlation like $$ncc(I_1, I_2) = \sum_{x \in ...
0
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1answer
332 views

Find the time lag for a wave

suppose that we have a wave which has some peaks in some indexes like 2,12,25,... and otherwise zero. I want to extract the time lag or lags between peaks of a signal. could anyone help me ?
2
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2answers
370 views

Given an experimental FFT plot, how to find the best match from a set of generated FFT plots?

What I'm trying to do is, given some experimental data and it's (magnitude normalized to 1) FFT, match the FFT with one of say 1000 other (magnitude normalized to 1) FFT plots. Please note that the ...
3
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1answer
348 views

How do you find signal similarity when one signal has zero values? Correlation alternative?

I'm using cross-correlation to look for a Barker code in a BPSK signal. It occurred to me that if I send out a zero DC valued signal proceeding the barker code, it won't affect the correlation ...
2
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0answers
135 views

Iterative Auto and Cross Correleation Estimates

I'm looking for literature or other information that covers iteratively estimating the auto- and cross-correlation vectors and the auto-correlation matrix. Initially, I can assume the signal is wide-...
2
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3answers
823 views

Is possible to compare to audio samples with cross-correlation [duplicate]

Is it possible to compare two audio samples(meaning find word from one in another) realtime with cross-correlation?
2
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2answers
4k views

Cross-correlation peak

How get cross-correlation peak and based on it calculate correlation score for similarity of two audio samples. SO far I've FFT two samples complex conjugate second multiply results IFFT cross-...
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1answer
447 views

What is the significance of first zero upcrossing of a cross correlation?

What is the significance of the first zero up-crossing of a cross-correlation? The signals being correlated are cosines signals with some phase difference. EDIT 1 : Cross-correlation plot attached. ...
2
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1answer
427 views

Embedded Correlation Function

I'm trying to write a correlation function on an embedded device. Because its embedded, I need to make sure that the memory/CPU usage is minimum. Here's the deal: - I have a saved waveform sampled ...
2
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2answers
1k views

Why is image blurring called convolution and not cross correlation?

I've always thought that image convolution is a weighted sum of the nearby pixels using the convolution kernel as weights. But from the description on Wikipedia, this is what cross correlation does. ...
2
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1answer
547 views

Normalized cross correlation via FHT - how can I get correlation score?

I'm using the 2D Fast Hartley Transform to do fast correlation of two images in the frequency domain, which is the equivalent of NCC (normalized cross correlation) in the spatial domain. However, ...
1
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1answer
629 views

Calculating an impulse response in a stable environment

I would like to estimate the impulse response of a simple environment (room, two speakers, one microphone). I am aware of the issues/limitations of working with "near" LTI systems. That said, I have a ...
5
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2answers
378 views

Using reference objects to estimate the point spread function?

I have a well-defined object and a clear image matrix of it. In subsequent frames the object moves, causing motion blur. I want to use the object as a reference to "guide" the deconvolution and ...
9
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1answer
6k views

Measuring time delay of audio signals

Before anyone yells at me I fully realize that this question has been asked numerous times. I assure you that I've read through the existing questions and answers but I am still confused about part of ...
5
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1answer
366 views

Cross Power Spectral Density of Unevenly Sampled Data

Here's my problem. The input signals $x$ and $y$ will be having the time value aligned with each other. However, the data are not evenly sampled. I would like to calculate CPSD of both signals. The ...
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1answer
3k views

Finding periodicity of spikes, matlab

In my time series data, I have often spikes with regular periods. Sometimes, I get two or three different periodical spike sequences (two electrical noise sources), some with T1 seconds period, some ...
2
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1answer
276 views

How can I detect clicks/ticks in a wav file?

I have a long recording of a train (here is a small sample) there are a number of clicks as the wheels go over joins in the tracks. I would like to detect the location of these. Looking at the ...
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1answer
1k views

get amplitude difference via cross correlation?

im currently comparing 2 signals: A = some music B = A + noise and ive implemented cross correlation in frequency domain via complex multiplication to determine the time offset, which works ...
14
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2answers
3k views

Finding symmetric regions/patterns in image

I have a set of images representing the mean curvature of a human back surface. What I want to do is to "scan" the image for points which have similar, reflected "counterparts" in some other part of ...
0
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1answer
844 views

Is there any example or existing resource for using matlab in audio comparison (cross correlation)?

I am new to MATLAB. I have the audio files A and B, B is recorded using a mic while playing audio file A. The length of file B is different from A. A does not always start from 0 second. My program is ...
2
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1answer
669 views

determine background noise level via cross correlation

The setup: Sound is being played by the speaker on the iphone. At the same moment i record sound via the microphone. Obviously the speaker sound will be recorded in addition to all the external noise. ...
3
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2answers
502 views

Why is there a mismatch between normalized cross-correlation and perception for basic waveforms?

To my ears, sawtooth and square waves are more similar to each other than either one is to a triangle wave. However, when I compare their magnitude spectra against each other using normalized cross-...
2
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1answer
165 views

When might looking at rising edges perform better than cross-correlation?

A simple question as the title indicates: Let us assume that we have two signals, measured from two different sensors that are close together. (For this application, the sensors are measuring blood/...
3
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1answer
2k views

Finding Peaks in an Autocorrelation Function

I'm trying to find the period of a signal. I've used FFT to compute the autocorrelation of the signal. As can be seen from the autocorrelation function (plotted below) I obtained, there are 70 sample ...
9
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1answer
2k views

Directly compare subpixel shifts between two spectra — and get believable errors

I have two spectra of the same astronomical object. The essential question is this: How can I calculate the relative shift between these spectra and get an accurate error on that shift? Some more ...
3
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1answer
2k views

Time delay estimation of two sensor signals

I have two sensors which are placed around 30 to 40 cm apart , both of them measure the same signal say 'lambda signal'. so there is a delay in the measurement of the signal from the second sensor. ...
5
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1answer
1k views

Finding the Wiener filter transfer function

I am trying to understand the mechanism of finding the transfer function for a Wiener function. ...
6
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2answers
746 views

Probability distribution of windowed cross-correlation

This question is in the context of time-delay estimation. Say I have a stationary Gaussian stochastic process $g$, and I know its autocorrelation function $R_g(\tau)$. To do time-delay estimation, I'm ...
5
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2answers
261 views

Coarse summary of various methods for detecting when a signal 'starts'

My question is basically in regards to how to detect when (in time) a signal 'starts', and it might also be called 'transient detection', or, as I have read in some papers regarding music, the 'onset' ...
5
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1answer
2k views

What is the cross-correlation of a WSS signal and the LTI filtered signal?

I remember a result about the cross-correlation function of a stationary signal and that same signal, filtered through a linear time-invariant filter. There might have been an assumption that the ...