Questions tagged [cross-correlation]

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27 views

Map time/scene differences between two similar videos

Goal: Given two videos that are episodes from series but in different format (one Bluray/one TV for example), map the time differences between the two (which scenes are not in one of the two) and be ...
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1answer
2k views

When to use cross spectral density versus cross correlation?

All my life, I've used cross-correlation to analyze the strength of the relationship between an input signal and the output signal. I use this to determine which ...
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0answers
25 views

Is it possible to normalize an un-normalized cross-correlation vector after computation

I have a C++ code that computes cross-correlation for a given 2 vectors as input. It doesn't have an implicit normalization or normalized implementation of cross-correlation. But I would prefer a ...
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1answer
36 views

CWT at low scales: PyWavelets vs Scipy

Low scales are arguably the most challenging to implement due to limitations in discretized representations. Detailed comparison here; the principal difference is in how the two handle wavelets at ...
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1answer
63 views

Proving the upper bound of cross correlation

I am reading about cross-correlation from this document and equation (5) states that The maximum value of the crosscorrelation is not always when the shift equals zero; however, we can prove the ...
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1answer
30 views

Finding delay where squared error between signal and data is minimal

I have a set of points which correspond to part of a known signal. What I want to do is estimate the delay between the set of points and the known signal. In this case, I don't think cross ...
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1answer
51 views

Convolution and Cross Correlation Blackbox

Suppose I was handed a blackbox that I know is either a Convolution filter or Cross-Correlation filter, and my job is to find out which it is. My idea is to pretend that it's Cross-Correlation and ...
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1answer
30 views

Detecting multi-path propagation when one acoustic signal is dominant

I am sending an acoustic signal from a source to a receiver where there are limited number of paths the signal can travel. I want to detect if there has been multipath propagation or not when one path ...
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2answers
493 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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1answer
68 views

Produce musical signal from instantaneous frequency

I'm implementing the Yin Algorithm in Python so as to extract the pitch of my voice when whistling or humming. My goal is to produce the Gate (Envelop Control) and CV (Pitch Control) signals which can ...
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0answers
38 views

How to use cross-correlation to verify speech data and determine delay

I have been experimenting with cross-correlation function to verify the presence of speech in a recorded file wrt a source file. I tried the following in Matlab: <...
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2answers
6k views

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 ...
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1answer
84 views

Fourier Transforms, Convolution, Cross-correlation: what is their physical unit exactly?

Let us assume we are talking about real, deterministic, electrical signals $x(t)$ and $y(t)$ (magnitude in Volts). There are different kind of Fourier Transforms. I made a table to summarize: NB: By ...
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5answers
45k views

What is the difference between convolution and cross-correlation?

I've found on multiple sites that convolution and cross-correlation are similar (including the tag wiki for convolution), but I didn't find anywhere how they differ. What is the difference between ...
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2answers
688 views

Why can Sum of Squared Differences (SSD) seen as cross-correlation?

In this slides, on page 4, the SSD can be seen as cross-correlation: http://www.lira.dist.unige.it/teaching/SINA/slides-current/pyramids.pdf http://www.cse.yorku.ca/~kosta/CompVis_Notes/ssd_cross-...
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1answer
314 views

Time delay estimation between two complex signals(IQ)

I need to time align two complex signals. The two signals obtained were at different RF frequency before digitisation. So,I have two complex signals(IQ) and I need to do delay estimation and apply ...
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2answers
86 views

audio signal time delay estimation(TDE) in indiviual and separate mics

common TDE problems algorithms(such as GCC) often require audio signals in different mics concurrently, however, is it possible to estimate audio signal time of arrivals(ToA) in different mics ...
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1answer
499 views

Confusion with data after cross correlation

Surely this question has been answered before in parts but I cannot find one solid answer. Ultimately I am trying to calculate the audio delay between two signals I am recording on USB microphones. ...
5
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1answer
482 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 ...
3
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2answers
660 views

DOA estimation 2 sources time delay estimation uniform array

I am new to signal processing, so sorry if the question is superbanal. I have been spending more days than I would admit on this and can't find the error. I have two triangle waves that are emitted ...
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1answer
40 views

GCC-PHAT always peaks at zero when estimating delay offset

My question is that when I used gcc-phat to estimate delay between two audio signals, it always returns zero offset. However normal cross correlation Xcorr gives a good result. I don't know the reason....
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1answer
571 views

Cramer Rao Lower Bound for Cross Correlation (Time Shift Estimation)

UPDATE 2 Okay, I think I understand now why the defined CRLB is not applying to my use case. In my use case, we have very high SNR, and the the first signal $x_1$ is always the same. So the classical ...
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2answers
3k views

Correlation Using FFT / IFFT (Convolution in Frequency Domain) in Java

I try to find about the delay between two audio files using Cross Correlation in Java. I've already done this algorithm so far that i get a idea about how many samples is the delay. FFT x1 -> Zero ...
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1answer
935 views

Cross Correlation in Java (Android) Using FFT (Frequency Domain Convolution / Correlation)

I want to implement cross-correlation with the start-symbol and the signal using FFT. I zero-pad both signals to length N = x.len + y.len -1 Using the convolution theorem: ...
5
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2answers
919 views

How to calculate the phase shift AND time delay of non-periodic signals

Say I have two non-periodic signals, $f_1(t)$ and $f_2(t)$, with Fourier transforms $F_1(\omega)$ and $F_2(\omega)$. Basically, I need to line up $f_1(t)$ and $f_2(t)$ as close as possible, and I am ...
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1answer
419 views

Finding baseline (reference) of nosiy data and lag/lead between 2 signals

I have 2 datasets which vary with time as shown in the figure - Sa – Red , Sb – BLACK . I am doing the analysis in R. The entire dataset and a segment of data from 30 - 31 s are shown below - - As ...
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2answers
775 views

Downsampling from 100Hz to 60 Hz

I have two sensors measuring a single time varying signal . The first sensor (reference sensor) is sampling the data at 60 Hz and the second sensor (test sensor) is sampling the data at 60 Hz. I ...
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2answers
82 views

Interpolation of missing audio signal in a video sequence

Suppose there is a video sequence and there are some frames for which the audio data is missing. I want to interpolate the missing audio data on the basis of the correlation of the audio signal with ...
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0answers
24 views

The normalized cross-correlation of two signals

I wanted to calculate the normalized cross-correlation function of two signals. I use the command ...
2
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0answers
36 views

Strange behavior in fixed-point FFT

This is a problem I encountered some time ago while doing my thesis, which still now, I am not sure to understand. By then, I was implementing the circular correlation in an FPGA using this Xilinx FFT ...
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1answer
33 views

Variance of circular vector correlation

Say I have two zero-mean vectors, with a size of N and the translation between them is k. Say the image signal std is $\sigma_s$ and the noise std is given by $\sigma_n$. What is the variance of the ...
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1answer
30 views

Having Problem about DownConversion

I hope, you are doing well. I want to ask question about baseband conversion. Background: I generated two AM signals in MATLAB, which one of them is shifted in time. I multiply the signals with $\cos(...
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2answers
44 views

Comparing similarity of two simultaneously recorded EEGs in freq domain

I have two EEG signals that are simultaneously recorded during the night (sleep). Imagine one device recorded from channel F4 and the other from Fp2. Now I would like to check the similarity of these ...
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1answer
74 views

SVD vs matched filter

Reading about singular value decomposition (SVD) in the context of signal processing applications, one can separate the signal from the noise into orthogonal subspaces. On the surface this sounds like ...
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0answers
67 views

Fast calculation of normalization factor for normalized cross correlation

There has been a number of posts here I've browsed through that explain implementations of normalized cross-correlation in Python. One such implementation that is frequently cited is found below. <...
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1answer
38 views

Interpreting the cross correlation results

I am new to this forum. I am just trying to understand how to calculate delay (in terms of samples) between two signals using cross-correlation function. I wrote a small Matlab code in order to ...
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2answers
509 views

Why does the addition of noise improve coherence between two signals?

Taking a simple example of the coherence between two signals, each composed of two sinusoids of frequency 100 and 200 Hz, I expect the coherence to show two peaks in the spectrum located at precisely ...
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1answer
34 views

Matlab: xcorr: Having trouble when I try to calculate delay between two sinusoids

I have a problem when I try to use Matlab built-in function for cross-correlation 'xcorr'. Background: I created two sinusoids, one of them delayed in time. I choose center frequencies of these ...
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0answers
26 views

aperiodic auto correlation properties

I'm reading about PSC (primary synchronization code) in UMTS. It is a so-called Golay sequence. It is said it has a good aperiodic auto correlation properties. What does it mean (in terms of aperiodic)...
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1answer
32 views

Calculating the bit period

I want to calculate the bit period in my RF packets that I transmit them with 50Kbaud (Symbol rate=bit rate in my case) , how can I calculate the bit period?
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1answer
23 views

Spectral analysis of a cross correlation function [duplicate]

So it's widely known that the Cross Correlation of 2 signals helps us in figuring out the time delay in those signals by analyzing the peak of the correlation coefficient in the time domain. For ...
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0answers
60 views

Probability of similarity for two random white noises

I'm looking for the method to calculate theoretical similarity of two random noises $x$ and $y$ with mean $0$ and standard deviation $1$, I've got also $12500$ samples of signal, sampled $2.5$ Ga/s. ...
0
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1answer
32 views

Cross-correlation with SDPSK modulation

I'm trying to detect a sync word in a signal using Symmetrical Differential PSK (bit 0 = +90° phase, bit 1 = -90° phase). Given the signal is encoded in the phase difference between two symbols, the ...
0
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1answer
50 views

Get the lag of a signal with respect to the other with cross correlation

I have 2 vector of length 20 each. The first 15 entries of $a$ are exactly the same as the last 15 entries of $b$. There is random noise in the 5 last entries of $a$ as well as the 5 first entries of $...
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0answers
26 views

Instantaneous frequency, PLLs, frequency mixing, cross-correlation and the cross-correlation matrix

This is as much a request for comment and critique as anything else. I am looking at tracking how a system perturbs an input that is a (real) sinoid of varying frequency. ...
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0answers
7 views

Clipping cross correlation peak range in noisy signal

The result of a cross-correlating a signal of deltas (period N) with a signal of white noise that's containing a periodic signal (of period N, Length and Position) is plotted in the image. I want to ...
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2answers
29 views

Cross Correlation of output with input is equivalent to impulse response of a large bandwidth input (LTI System)?

What is the practical way to found the impulse response of a system ? As impulse function has a very large amplitude at zero time (analog signal). So the cross corelation of output of a large ...
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3answers
157 views

Cross correlation and cross power spectrum for signal + noise

Quick question about my understanding of cross correlations and cross spectral densities. Let $C_{ab}$ be the cross correlation between the signals $a$ and $b$, i.e., $C_{ab}(\tau) = \langle a(t)b(t+\...
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1answer
31 views

Correlation of discrete time periodic sequences

So I was reading this textbook - Digital Signal Processing by Proakis and Manolakis. The authors define the cross-correlation operation for 2 energy signals $x(n)$ and $y(n)$ in section 2.6.1 as: $$ ...
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2answers
51 views

Why Convolve instead of Cross-Correlate for Detection of Known Signal?

I am reading a journal on optimal signal detection by mobile sensor. It is mentioned: How should we plan to robots’ motion in order to maximize the detection probability? Assuming the source emits ...

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