Signal Processing Stack Exchange
Signal Processing Stack Exchange

Questions tagged [feature-extraction]

74 questions
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What's the correct graphical interpretation of a series of MFCC vectors?

I'm studying speech-recognition, in particular the use of MFCC for feature extraction. All examples I've found online tend to graph a series of MFCC extracted from a particular utterance as follows (graph generated by me from the software I'm…
jotadepicas
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Palm Pilot Graffiti

I have been completely unable to find details on the underlying model that is used for the Palm Pilot Graffiti handwriting recognition. Given the computing power available for handheld PDA technology, I have always been quite surprised this was…
adfriedman
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What Are the Differences in Four Different Types of Third Order Image Moments (Skewness)?

I am attempting to analyze images using the third order image moment (aka skewness), but I am having trouble figuring out how to do so. As it turns out, there are four different types of third order image moments: $$ \begin{array}{rcl} \mu_{21} &=&…
cadams
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Using Convolution as Feature Extraction

I am now studying image processing in my spare time. My understanding of convolution is about 'response to a specific filter': When we have a raw image, or raw signal; and a filter, aka kernel; we apply a 'moving dot product' between the image and…
user152503
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Accurate phase calculation in sinusoidal linear regression?

I've been trying to work out a way to minimize the error in phase calculation. The underlying model is the following $$s(t) = \sum_{i=1}^{M} A_i\sin\left(\frac{2\pi t}{T_i} + \phi_i\right) + \epsilon_t,$$ where $\epsilon_t\sim N(0,\sigma^2)$. I'm…
Cifer
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How to Describe the Color of an Image Patch?

I want to describe the color of an image patch (say, of size 5x5) centered around a pixel of an RGB image. The most straightforward way to do that is to calculate the average color over that patch and have a 3D vector, where each component…
S.E.K.
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ORB Algorithm: What Is Intensity Centroid?

So, I am reading a paper about ORB: An Efficient Alternative to SIFT or SURF and it happens to calculate the direction of corner from it center . According to Rosin the author of the paper;moments of a patch is given by and the centroid is of the…
motiur
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How to Extrapolate a 1D Chirped Signal?

Following a past question, I'd like to extrapolate a signal like the one below: (red is signal, blue is the the extrapolated ) t1 = 0:0.1:30; t2 = 0:0.1:40; s = @(t) sin(0.2*t)+sin(0.5*t+0.05*t.^2); figure; plot(t2,s(t2)); hold…
bla
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Common Spatial Pattern for EEG Signals

I am having difficulty in understanding the use of CSP for EEG signal feature extraction and subsequently. Since I am using two classes, this query will be restricted to it. In essence CSP requires 2 classes of trial data, i.e C1, the covariance…
Kartik
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How to extract features of individual spikes in non-negative signal?

I have data of non-negative (in the sense there's no signal below baseline) spiking waveforms, which are in the form of a 1D array of numbers: Spikes that cross some threshold are considered real signal events and I want to be able to measure the…
Brandon Brown
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MFCC delta: How to compute delta, in real time, with no future frames?

I am trying to compute Delta coefficients for real-time audio analysis. As far as I know, a valid formula is: $$d_t= \frac{\displaystyle\sum_{n=1}^{N}n\left(c_{t+n}-c_{t-n}\right)}{2\displaystyle\sum_{n=1}^{N}n^2}$$ It seems that I need $n$ future…
Marvin Ler
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Is there a way to extract the difference between the 2 signals? Fitting?

I'm very new to signal processing and have been struggling this far. I have a device that measures the signal due to the magnetization of iron particles. In order to calculate the response of the particles, I did 2 measurements: Background…
Tassou
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Should i normalize FFT signal with z-score?

I am working with EEG data (time domain) in a machine learning task, where each input signal must be mapped to a class/frequency. I am using FFT in order to get data in frequency domain and make classification easier. I'd like to know if it is…
heresthebuzz
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SURF normalisation and Haar wavelet

I am reading the SURF paper (Speeded-Up Robust Features (SURF)) but can't understand two things. In 3.2 it says: Furthermore, the filter responses are normalised with respect to their size. This guarantees a constant Frobenius norm for any filter…
sucicf1
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Understanding GCC-PHAT as a Feature

I'm working on a sound source localization project and am interested in using GCC-PHAT as a feature. I'm quite new to this transformation and I've been reading a few papers about it and I'm still struggling with understanding what it actually is.…
user25758
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