Questions tagged [cross-correlation]

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Convolution theorem for cross-correlation

Forgive me is this is an ill-posed question. Is there any such thing as a 'convolution theorem' for the cross-correlation. Namely, the convolution theorem states that: $$ x[n] * h[n] = \sum_{k=0}^{...
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1answer
818 views

identification of sounds within audio signals

I am looking for methods to identify sounds within audio files. I was hoping to find some ready-made user-friendly software to do this but haven't found it yet. I am familiar with Matlab and some C++...
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1answer
1k views

Real-time delay between signals

I currently have a real-time noise suppression algorithm based on two inputs from different microphones. It has passed most tests that I have thrown at it, however when the signal I am trying to ...
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277 views

Fast Normalized Cross-Correlation for Stream-Data

I read some papers about fast normalized cross-correlation techniques. Most of them are used to identify a template in an original image. I was not able to find information about input-data in a ...
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1answer
368 views

Code generation for `sum` function in MATLAB

In cross correlation we use the below command to calculate the sum after elementary multiplication of the vectors. But when we try to convert this Matlab code to vhdl using HDL coder, this command is ...
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2answers
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Python - Normalized cross-correlation to measure similarites in 2 images

I'm trying to measure per-pixel similarities in two images (same array shape and type) using Python. In many scientific papers (like this one), normalized cross-correlation is used. Here's an image ...
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469 views

Problem in hardware implementation of cross correlation without xcorr

Sorry for any thing silly! Matlab uses the built in function called 'xcorr' to find correlation of two signals.In VHDL xcorr is not defined then correlation can be written using for loop ...
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1answer
764 views

Calculating similarity between bit strings/signal

I have a project I'm working on where I'm trying to efficiently compare sequences of binary data to determine how similar they are. Basically, a sequence might look like this: 1001010010100011110... ...
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3answers
921 views

Estimate changing time lag between signals

Suppose I have two timeseries $x_1(t)$ and $x_2(t)$, shown in the image that I drew below. They look almost identical in general form, except some features are shifted slightly in time from one series ...
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1answer
340 views

Can anyone help with cross correlation error in Simulink?

I am sorry if I say any thing silly. I have a vector x below and trying to implement correlation with itself (lets say x2) in Simulink, but getting error. I am ...
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0answers
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Why correlation coefficient template matching perfoms better than cross-correlation and square-differences method

I am using this template in OpenCv's match template function by converting all images to grayscale. Here are my result using sum of square differences,cross correlation and correlation coefficient....
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Detecting a Signal Inside a Time Series Using MATLAB's $ \tt xcorr() $

I would like to find the exact replica of signal A in time series B. I am working with the simple toy example below, in which A is located starting at the 4th position in B. I thought that using <...
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1answer
143 views

Applying a window to input signal

I am sorry if I say any thing silly .Please forgive me.I want to apply a window to input signals.I have two signals each of which contains zeros (462 samples) and non zeros data (38 samples).I want my ...
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1answer
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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 ...
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1answer
284 views

find cross correlation lag by optimization

I have data from many closely located sensors (geophones). These are often contaminated with coherent noise which I need to remove. Some of the most effective de-noising methodologies work if the ...
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1answer
617 views

Bartlett's and Welch's Method for PSD

Lets say. I have an image of 100 samples, and I want to find the presence of smaller image of 24 sample using cross-correlation in the fourier domain. I use Bartlett's and Welch's method for PSD, ...
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1answer
207 views

Mismatched offset when computing cross-correlation using FFT

In MATLAB if I compute the cross-correlation of 2 arbitrary signals using the xcorr function I get exactly the answer I expect. If I then calculate the cross-correlation using element-wise fft ...
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1answer
258 views

How to compare the syllable extracted from the audio

I need to recognize just one bird. I am trying to compare the syllables extracted from the sound samples. As a result of the spectrogram function, the power spectral density is taken from the sound. ...
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2answers
635 views

Audio template matching - power correlation?

I'm looking at some code that matches audio templates in a longer audio file. The calculation correlates the power spectra of the template and audio file, maximizing over the possible alignments. This ...
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1answer
396 views

Scaling Data before Fourier transform

I am doing an experiment, where I am trying to get the same results from correlating two matrices in the fourier domain and then scaling the data by some constant. Method_1: Do FFT, Correlate the ...
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2answers
914 views

How to Match 2 Signals which Are a Shifted and Scaled Version of Each Other

I have 2 signals S1 and S2 that contain the same information, but S2 is shifted and scaled compared to S1 by an unknown amount (but small; eg shift would be of the order of 1-10 samples). What is the ...
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1answer
358 views

Cross-Correlation to find the similartity of songs

I have been working on a problem where I am given two songs which are of the same category but there is a time difference between them. Eg. one song starts at x sec and other song starts at y sec. So ...
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1answer
230 views

Is jointly wss (wide sense stationary) a transitive relation?

I've been try to either prove or find a counter-example to the idea of jointly-wss being transitive. In other words: does ($x$ and $y$ are jointly wss) $\wedge$ ($y$ and $z$ are jointly wss) imply ...
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1answer
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Computing cross-correlation of two images using OpenCV

I have a program that uses OpenCV to compute either the convolution or cross-correlation of an image with a specified kernel. I compute cross-correlation by setting the conjB flag to true when calling ...
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1answer
2k views

Baseline correlation for template matching

In normal cross-correlation or convolution between a signal and a template(say a small portion of the signal) the template is moved along length of the signal without changing the amplitude offset of ...
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1answer
900 views

PSS convertion from Frequency to time domain

Hi I have a question regarding primary sync signal in LTE. It is generated in frequency domain and its length is 63. How to convert this signals frim frequency to time domain. Should I use IFFT? what ...
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1answer
479 views

Finding dependence between two sparse signals

I am new to signal processing and would really appreciate your help. happy to provide more context/details. In my research, I have a system that has many sensors $X_1, \ldots, X_N$ and using this ...
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1answer
162 views

Is there any reason that cross correlation would perform well or poorly on sparse binary arrays?

I am using matlab xcorr to correlate simulated photon count data that has some Gaussian random noise set on top of it and it is working fine when the average value ...
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3answers
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Cross correlation with short or non periodic signals?

I am a total newbe to signal processing and i have a problem which may be quite trivial to most of you guys. I want to align two short sensor signals (speaking of max. 1000 samples recorded with ...
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0answers
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Compare two voices and outline their similarity

I am trying to develop an application which records the voice of someone through a microphone. I will have a preset recorded voices for the same words. I then need to compare the real time recorded ...
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2answers
491 views

Efficient calculation of correlation function every $N^{\rm th}$ point

I would like to calculate a long correlation function of length say, 1e6 points. I have a prior knowledge that the correlation peak will be in point k*1000. Is there an efficient way to apply this ...
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0answers
384 views

“Circular shift - invariant” distance

Couldn't decide whether the question belongs on Mathematics or here, but I guess I'll ask it here. I've got a discrete - valued function defined on a finite segment of a line that looks like this: ...
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0answers
54 views

filter out an expected but not regular signal

I am stuck with a case where I need to get rid of a portion of sinusoidal signal that suddenly appears in my main signal (sine wave). my total signal will look like: $ s(n) = \begin{cases} A\sin(\...
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3answers
823 views

Least Squares and Auto and Cross Correlation

I am trying to understand why auto and cross correlation helps find the best fit line in least squares. I have an equation as stated here: $Ax=b$ -- I have not exact solution, so I use the least ...
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2answers
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Cross correlation peak value

I would like to measure the time delay between two signals. By applying the cross correlation I get the time delay or number of samples by the location of the cross correlation peak, however I am ...
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1answer
241 views

Auto/cross correlation of a cosine in the context of an adaptive beamformer

I am currently reading chapter 13 of 'Adaptive Signal Processing' by Widrow and Stearns, so if anyone happens to have a copy of the book to hand it could be helpful. I am reading the chapter on "...
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1answer
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Efficient Marker Detection for Images

I need to detect a known number of simple markers (chessboard patterns) in a color image efficiently. I implemented normalized cross correlation (NCC) as a pixel shader via WebGL since I need this to ...
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0answers
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Why Normalized Cross Correlation Score of different templates is high?

I am using OpenCv's built in template matching function to search for an object in image. I am using Normalized Cross Correlation Method.The function is returning a value which I think indication of ...
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2answers
205 views

“Perfect waveform” for cross-correlations?

I am well versed in cross-correlations, as my masters thesis heavily relied on them for music classification and beat detection. So this question focuses more on the signals that I am running an ...
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2answers
575 views

Range and motion in received signals by radar

I've got two signals which are consecutive received signals by a radar system. The signals' values are complex (in form $x+\textrm iy$). I have generated a trasmitted signal using the info available. ...
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2answers
770 views

Map time difference between two similar videos

Question: Is there any software, source-code, or well documented and easily implementable research (I am not afraid for a little bit of Python) to do the following: Take two similar videos from ...
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1answer
3k views

Cross correlation vs FFT for finding phase between 2 signals

I have been struggling with this issue for months now, trying to understand which one to pick: FFT or cross correlation. I am given a sine wave (with phase, amplitude, frequency and time vector ...
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2answers
2k views

Difference Between Correlation / Convolution and Matrix Multiplication

Can anyone please clarify the difference between correlation/convolution and matrix multiplication? As I thought either convolution or correlation is similar to matrix multiplication. I read this ...
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4answers
388 views

“cascaded” cross-correlation

so, first let's do this for the circular correlation case (it might be easier). let's say we have three real and periodic functions or signals $x(t)$, $y(t)$, $z(t)$ all with period $2 \pi$: $$ x(t+...
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1answer
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Solution to Cross-correlation problem of 2 audio signals

There are 2 audio signals, X & Y. X is of 15 second duration. The duration of Y is not given. Y is a part of signal X (ie a small part of audio X is extracted & made into audio Y) I have to ...
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1answer
81 views

Avoid saturated pixels in cross-correlation computation

I am doing template maching using Normalized Cross-Correlation for measuring similarity between template and image. However, some images from my dataset contain saturated pixels (overshoot) which ...
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0answers
941 views

GCC-PHAT cross correlation

I am trying to implement GCC-PHAT in python. The approach is similar to the following two links: link1 and link2 It seems the only difference between GCC-PHAT and normal cross-correlation using FFT ...
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1answer
49 views

How to decode speaker gender from spoken transcript

I have 20 audio recordings (raw format) of people reciting the same ~50 word transcript. I would like to use audio signal analysis to decode speaker gender from audio recording. Intuitively, it ...
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1answer
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Cross-Correlation : Comparing two signals or finding the location of a target

I read across places that cross-correlation of two signal (a radar sending a signal and receiving it back) one can detect the location (distance) of a target from a point and that cross-correlation ...
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1answer
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Correlation : Cross correlation why we need to multiply the samples

I understand what books states about cross-correlation of signals and their mathematical representation: For continuous functions f and g, the cross-correlation is defined as: $(f \star g)(\tau)\ \...

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