Signal Processing Stack Exchange
Signal Processing Stack Exchange

Most Popular

more tags
1500 questions
7
votes
1 answer

How to determine if the system is invertible

Is there any systematic way to determine if the system is invertible? My general approach is first trying to find the inverse system by using mathematical method; that is, solving for the output in terms of input. If this is difficult, my guess…
IgNite
  • 175
  • 1
  • 1
  • 6
7
votes
3 answers

Subpixel - what is it?

I'm studying SuperResolution techniques, and I read often "subpixel"/"subpixel registration"/"subpixel accuracy". I don't find what exactly it means; Wikipedia says that is one of the three RGB channel in the pixel, but I think it isn't the right…
volperossa
  • 227
  • 1
  • 2
  • 5
7
votes
3 answers

Applying Photoshop's "Shadow / Highlight" Correction Using Standard Image Processing Algorithms

Adobe's Photoshop has an excelent filter called "Shadow/Highlight" used to correct, in one step, dark areas AND overexposed areas of a photo. By simple analysis, I suppose it uses some radius-dependent adaptive contrast algorithm (halo effect is…
heltonbiker
  • 1,097
  • 11
  • 22
7
votes
1 answer

Confusion Related to the Laplacian Filter

I have this confusion related to Laplacian filter. It states that it uses second derivative and finds the point of zero crossing(where the second derivative is zero) for which the first derivative has the high peak. I have seen them using kernels…
user34790
  • 169
  • 3
7
votes
1 answer

For a discrete LTI system, does "bounded memory" imply "rational transfer function?"

Every LTI system with a $\mathcal Z$-domain transfer function that is a rational function - aka a quotient of two polynomials in $z$ - can be implemented using a bounded amount of memory. Is the converse true? That is, are there any LTI systems that…
Mike Battaglia
  • 507
  • 2
  • 11
7
votes
3 answers

Choosing the length of a signal when calculating the FFT

I'm trying to transforming an already know signal from time domain to frequency domain using fft function in MATLAB. And I got different values of amplitude when I change the value of length of signal $L$. I'm therefore wondering if there is a rule…
Mai
  • 329
  • 1
  • 5
  • 9
7
votes
2 answers

Variance of periodogram estimate of the power spectrum

I have been reading chapter 13.4. ("Power Spectrum Estimation Using the FFT") of the Numerical Recipies Book. Some things related to the expectation value of the "periodogram estimate of the power spectrum" became not clear to me…
Tobias
  • 173
  • 1
  • 5
7
votes
1 answer

laser speckle noise reduction

I'm trying to process an 1D signal containing a waveform of 100000 pixel. As it was acquired with a laser scanning system, and therefore it is corrupted by some annoying speckle noise. I tried to prefilter it with a well-known type of non-linear…
Alfatau
  • 91
  • 4
7
votes
2 answers

Frequency Analysis (DFT / FFT) of a Signal Without a Constant Sampling Frequency (Non Uniform Sampling in Time Domain)

I'm a stack exchange user for some time and now I'm registering to ask a simple question (I think!). I have a vibration signal with an amplitude and time (sampling frequency not constant) in a $10000\times 2$ double variable. The data is available…
Pedro
  • 73
  • 1
  • 4
7
votes
3 answers

GCC-PHAT (Generalized cross correlation MATLAB)

I've been trying to implement generalized cross correlation with a PHAT weighting function for a while now, and cannot get it to work. I have tried correlating using MATLAB's xcorr.m file, and it works for getting a correct delay tau (on simulated…
CN railfan
  • 81
  • 1
  • 7
7
votes
2 answers

Can you turn a square wave into a sine wave using a low pass filter?

And if it could, would it make the sound of the square wave thinner than before because of losing its harmonics?
Mark
  • 71
  • 1
  • 1
  • 4
7
votes
1 answer

Location of Matched Filter

In a digital communication receiver, matched filter(SRRC filter) is used. In different literatures, the location of the matched filter is mentioned in two different places. One is just after the ADC followed by the resampler of a timing recovery…
avi1987
  • 181
  • 1
  • 11
7
votes
1 answer

Library to differentiate people by their voice timbre

Say there are 3 people in the room. Each of them have a unique voice timbre. I want to recognize people by their timbre and know who's speaking.
Dmitry
  • 173
  • 1
  • 4
7
votes
1 answer

Difference between a digital lock-in amplifier and a FFT when extracting phase of a signal?

I am trying to measure the relative phase of a sine wave fixed at a particular frequency in a noisy environment. My initial approach is to simply collect $N$ samples, take an FFT, and then just extract the phase at the operating frequency (which I…
Sergiy
  • 173
  • 1
  • 4
7
votes
1 answer

Convolution involving turning each pixel value to the most represented pixel value of the neighbourhood

In order to correct gradual changes of intensities in the background of grey-scales images, I have been blurring them and then subtracting the original images from the convolved one. In some cases, I have seen improvement using median blur instead…
Quentin Geissmann
  • 243
  • 1
  • 5
1 2 3
…
99 100