Signal Processing Stack Exchange
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1500 questions
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3 answers

Texture Classification via DCT

How viable would it be to classify the texture of an image using features from a discrete cosine transform? Googling "texture classification dct" only finds a single academic paper on this topic, using a neural network. For my application, I have a…
Cerin
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Is a notch filter for 50 Hz without delay possible?

I am processing an EEG signal (2 kHz sampling frequency) from hardware and the built-in filter doesn't work as intended. FIR gives a delay, and IIR is unstable. The signal of interest is from 4 Hz to 360 Hz, with the goal to clear the utility signal…
Evil
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why should I scale the fft using 1/N?

I am writing a report, and my advisor asked me to explain why I scale the fft by a factor 1/N (where N is the length of the array). I used to use the scaling convention of multipling the fft by the time increment (dt), this convention was good for…
Luca Mirtanini
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4 answers

How to 'whiten' a time domain signal?

I am trying to understand how exactly to implement what is known as a 'pre-whitening' filter or simply a 'whitening' filter. I understand that the purpose is to make it have a delta as its autocorrelation function, but I am not sure how to do this…
Spacey
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13
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2 answers

Real-valued ringing when zero-padding odd-length FFT

So I'm trying to write a frequency-domain interpolator that zero-pads the frequency response of a signal and inverse transforms. There's two cases I have to deal with: Even-length response - have to split the $F_s/2$ bin because it's ambiguous. …
gct
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13
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2 answers

Calculating a homography based on detected lines

I know you can calculate homographies from image to camera plane using correspondence points between a "perfect model" and the image points. I'm doing it for a football pitch/field, and have used edge detection to find the white lines in the…
Henrik Kjus Alstad
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6 answers

Relation between signal processing and control systems engineering?

Control systems engineering and Digital signal processing are both important courses/subjects of electrical engineering But how these two subjects/courses are related to each other?? Also please kindly let me know,what are some recommended resources…
DSP_CS
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5 answers

Slicing and Recognition of book title and author from bookshelf image

I am trying, for my own learning purposes, to develop an implementation of an algorithm that would list books, given an image of a bookshelf like the following: The first step is to slice the image into individual books. My algorithm, in…
Oren Pinsky
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Image classification using SIFT features and SVM

I am hoping someone can explain how to use the bag of words model to perform image classification using SIFT/SURF/ORB features and a support vector machine? At the moment I can compute the SIFT feature vectors for an image, and have implemented a…
Jono Brogan
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The Scale Space Theory Understanding

In the scale-space theory the scale-space representation of the signal $f(x), x = (x_1, ..., x_d)$, (in case of image $d = 2$) is given as: $L(x, y; t) = g(x, y; t) * f(x, y)$ where $g(x, y; t)$ is a gaussian kernel with parameter $t$ and $*$ is a…
maximus
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3 answers

Savitzky–Golay filter vs. IIR or FIR linear filter

A traditional IIR / FIR filter (lowpass to remove the high freq oscillations), e.g. moving average, or a Savitzky-Golay filter can all be useful to smoothen a signal, such as an envelope signal: For which application would a Savitzky-Golay…
g6kxjv1ozn
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Does a simple photograph contain more information than a complex painting?

I hope this question is appropriate for this site. I came across this passage in The Three Body Problem, a novel by Liu Cixin: The professor had put up two pictures: One was the famous Song Dynasty painting Along the River During the Qingming…
RSS
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Why would one use a Hann or Bartlett window?

Suppose we're designing a low-pass FIR filter, and I want to use one of these three windows: Bartlett, Hann or Hamming. From Oppenheim & Schafer's Discrete-Time Signal Processing, 2nd Ed, p. 471:} All three of them provide the same transition…
Tendero
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Which transform most closely mimics the human auditory system?

The Fourier transform is commonly used for frequency analysis of sounds. However, it has some disadvantages when it comes to analyzing the human perception of sound. For example, its frequency bins are linear, whereas the human ear responds to…
user76284
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Covariance vs Autocorrelation

I'm trying to figure out if there is a direct relationship between these concepts. Strictly from the definitions, they appear to be different concepts in general. The more I think about it, however, the more I think they are very similar. Let $X,Y$…
rbell
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