Most Popular
1500 questions
24
votes
3 answers
Pink ($1/f$) pseudo-random noise generation
What are some algorithms for generating a good pseudo-random approximation to $1/f$ (pink) noise, yet suitable for implementation with low computational cost on an integer DSP?
hotpaw2
- 35,346
- 9
- 47
- 90
24
votes
1 answer
What is the difference between Remez exchange and Parks-McClellan filter design?
A question recently came up regarding Parks-McClellan and some of the comments point out that the wikipedia article on Parks-McClellan states,
...the Parks-McClellan algorithm is a variation of the Remez algorithm or Remez exchange algorithm. …
Mark Borgerding
- 3,020
- 19
- 26
24
votes
6 answers
What Is the Walsh Hadamard Transform? How Could One Use It in Image Processing?
I am trying to teach myself about the WHT but there dont seem to be many good explanations of it online anywhere. I think I have figured out how to calculate the WHT, but I am really trying to understand why it is considered useful within the image…
Spacey
- 9,817
- 8
- 43
- 79
24
votes
6 answers
Savitzky-Golay smoothing filter for not equally spaced data
I have a signal that is measured at 100Hz and I need to apply the Savitzky-Golay smoothing filter on this signal. However, on closer inspection my signal is not measured at perfectly constant rate, the delta between measurements ranges between 9.7…
VLC
- 343
- 1
- 2
- 5
24
votes
4 answers
Peak detection approach
What are the peak detection algorithms in existence? I have noisy data, and I would like to implement peak detection for this data. Data is in reverse, actually I am trying to determine the bottom.
Here is a snapshot of the data in Excel. I like to…
Ktuncer
- 816
- 2
- 11
- 18
24
votes
3 answers
How can I reconstruct a 3D structure from a set of images?
I have a set of contours (set of line segments) grouped in the following way:
$S_i = \{I^0, I^\frac{\pi}{4}, I^\frac{2\pi}{4}, \ldots, I^\frac{7\pi}{4} \}$
where
$S_i$ denote sequence of photos of one concrete object.
$I^j$ denote an image, with…
om-nom-nom
- 446
- 3
- 11
23
votes
2 answers
Synchrosqueezing Wavelet Transform explanation?
How does Synchrosqueezing Wavelet Transform work, intuitively? What does the "synchrosqueezed" part do, and how is it different from simply the (continuous) Wavelet Transform?
OverLordGoldDragon
- 8,912
- 5
- 23
- 74
23
votes
3 answers
What Is the Difference between Difference of Gaussian, Laplace of Gaussian, and Mexican Hat Wavelet?
There are three techniques used in CV that seem very similar to each other, but with subtle differences:
Laplacian of Gaussian: $\nabla^2\left[g(x,y,t)\ast f(x,y)\right]$
Difference of Gaussians: $ \left[g_1(x,y,t)\ast f(x,y)\right] -…
DeusXMachina
- 378
- 1
- 2
- 8
23
votes
3 answers
What is a good example of an ergodic process?
I'm trying to find simple examples of an ergodic process. What process comes to your mind as a good illustration of its properties?
A quick research (Wikipedia, another answer) mainly gives examples of non-ergodic processes. Also, I'm wondering…
bluenote10
- 605
- 1
- 5
- 13
23
votes
2 answers
How should I pre-process a real valued signal in order to use Kay's estimator?
I have 100,000 samples of a signal $x[n]$ that was sampled at 20kHz. The data is vibration data from a rotating machine, and contains a significant spectral component related to the speed of the machine's rotation.
Because the speed of the machine…
Peter K.
- 25,714
- 9
- 46
- 91
23
votes
2 answers
How can I compute a log-spaced power spectrum?
I would like to compute a power spectrum in which the frequencies are logarithmically spaced.
In Welch's method there is a trade-off between the frequency resolution of the resulting power spectrum and the number of averages (i.e. error in the…
nibot
- 3,803
- 5
- 29
- 40
23
votes
6 answers
What are the problems with designing an FIR filter using FFT?
I'm trying to get an understanding of the relationship between an FIR filter designed from "first principles" using a filter kernel with convolution, and a filter designed in one of two ways using FFT (see below).
As far as I understand, the impulse…
bryhoyt
- 1,423
- 3
- 13
- 14
22
votes
4 answers
Which IIR filters approximate a Gaussian filter?
So it recently dawned on me that Bessel filters, despite being listed along with the other common types, are really an oddball that belongs in a different "class", and I'm trying to learn more about it.
The rectangular magnitude response represents…
endolith
- 15,759
- 8
- 67
- 118
22
votes
4 answers
How do I detect distinct objects when their edges touch each other?
I need to find all the contours in an image retrieved from the camera. So I first use the canny edge detector to find the edges and then find the contours. Pretty simple.
However, my contours get "merged". For example, in the image below, I clearly…
user650
22
votes
5 answers
Why would I leave a signal oversampled?
I can't think of a better way for asking this question so I will start with an example. Suppose that I have an input signal with a max frequency of 50Hz (sampled at 100Hz). Now the signals of interest lie in the range 0-5Hz, so I can add a low-pass…
anasimtiaz
- 1,059
- 2
- 10
- 17