Signal Processing Stack Exchange
Signal Processing Stack Exchange

Most Popular

more tags
1500 questions
19
votes
6 answers

Fit a Piecewise Linear Model to Data with Unknown Knots and Number of Segments

What is a robust way to fit piecewise linear but noisy data? I'm measuring a signal, which consists of several almost linear segments. I'd like to atomatically fit several lines to the data to detect the transitions. The dataset consists of a few…
P3trus
  • 351
  • 2
  • 6
19
votes
2 answers

Why do we say that "zero-padding doesn't really increase frequency resolution"

Here is a sinusoid of frequency f = 236.4 Hz (it is 10 milliseconds long; it has N=441 points at sampling rate fs=44100Hz) and its DFT, without zero-padding : The only conclusion we can give by looking at the DFT is: "The frequency is…
Basj
  • 1,277
  • 5
  • 22
  • 54
19
votes
2 answers

Why does spectral leakage arise in an FFT?

I've tried googling and wikipedia-ing it, but I haven't gotten any answers beyond 'it's because the frequency of the input signal is sitting between two bins'. I understand that this is the reason, but what I can't understand is why the leakage…
Kitchi
  • 721
  • 2
  • 8
  • 18
18
votes
1 answer

What mathematical tools exist for understanding modulated noise?

Suppose we have a signal $n$ that consists of Gaussian white noise. If we modulate this signal by multiplying it by $\sin 2\omega t$, the resulting signal still has a white power spectrum, but clearly the noise is now "bunched" in time. This is an…
nibot
  • 3,803
  • 5
  • 29
  • 40
18
votes
1 answer

How to Calculate the Color Temperature / Tint of the Colors in an Image?

How can I calculate the (black body equivalent) color temperature of the light source illuminating a given image? Below are screenshots of Adobe Lightroom manipulating color temperature and a shift in the RGB Histograms. Given RGB components of the…
Lord Loh.
  • 491
  • 1
  • 4
  • 18
18
votes
2 answers

Are there any standard implementation forms for tunable Butterworth filters?

One of the standard ways to implement a Butterworth filter is with a cascade of second-order sections, each corresponding to a pair of complex-conjugate poles. For a fourth-order filter, for example, there would be two second-order sections. If we…
datageist
  • 4,897
  • 4
  • 32
  • 53
18
votes
1 answer

What is the phase and magnitude response of white noise?

I would like to create white noise in the frequency domain, and then transform it to the time domain using python. To understand the problem, I simply generated white noise in the time domain, and transformed it to freq domain: import scipy.signal…
Uffe
  • 355
  • 1
  • 3
  • 7
18
votes
2 answers

Using continuous verses discrete wavelet transform in digital applications

I am familiar with much of the mathematical background behind wavelets. However when implementing algorithms on a computer with wavelets I am less certain about whether I should be using continuous or discrete wavelets. In all reality everything on…
John Robertson
  • 1,122
  • 1
  • 9
  • 13
18
votes
2 answers

How can I design Nyquist interpolation filters with the Parks-McClellan algorithm?

We can easily design interpolation filters that obey certain frequency-domain constraints using the Parks-McClellan algorithm. However, it's not immediately clear how to enforce time-domain constraints; in particular, I'm interested in generating…
Oliver Charlesworth
  • 281
  • 2
  • 7
18
votes
3 answers

How do I add AWGN to an I and Q representation of a signal?

I have a wireless communication system that I am simulating in Matlab. I am performing some watermarking through slightly adjusting the phase of the transmitted signal. My simulation takes the original I (inphase) and Q (quadrature) values and adds…
Kellenjb
  • 1,103
  • 1
  • 11
  • 19
18
votes
1 answer

What approximation techniques exist for the square super-root function?

I need to implement an approximation to the inverse of $x^x$, i.e. the square super-root (ssrt) function. For example, $\mathrm{ssrt}(2) \approx 1.56$ means that $1.56^{1.56} \approx 2$. I'm not as interested in any particular accuracy/bit-depth as…
datageist
  • 4,897
  • 4
  • 32
  • 53
18
votes
5 answers

what is smoothing in very basic terms

What is smoothing and how can I do it? I have an array in Matlab which is the magnitude spectrum of a speech signal (the magnitude of 128 points of FFT). How do I smooth this using a moving average? From what I understand, I should take a window…
user13267
18
votes
1 answer

Removing Glare from Image

Disclaimer: I am in NO way engaged in signal processing. Just very curious... Ny question is, very simply: is it possible to apply software processing to an image to remove or reduce headlight glare? It would be a picture such as this: If this…
BenCole
  • 283
  • 2
  • 4
18
votes
7 answers

What are some of the differences between DFT and FFT that make FFT so fast?

I'm trying to understand FFTs, here's what I have so far: In order to find the magnitude of frequencies in a waveform, one must probe for them by multiplying the wave by the frequency they are searching for, in two different phases (sin and cos) and…
Seph Reed
  • 305
  • 2
  • 13
18
votes
3 answers

How to Detect Gradients and Edges in Images?

I want to be able to find points in images that are the centre of a radial gradient like the one shown in the left picture below. Any ideas on how I could use a Hough transform or some other computer vision method? Thanks example search image:
waspinator
  • 743
  • 1
  • 8
  • 12
1 2 3
…
99 100