Signal Processing Stack Exchange
Signal Processing Stack Exchange

Most Popular

more tags
1500 questions
17
votes
4 answers

Scipy - Audio Processing

I am looking for good tools for Audio signal processing. e.g Speech & music analysis, automatic language identification, etc. Does the Scipy library provide functions for audio processing? Does it have a good tool for Audio Signal processing? Can…
PGupta
  • 183
  • 1
  • 1
  • 5
17
votes
2 answers

Fourier transform 4 times = original function (from Bracewell book)

I was glancing through "The Fourier Transform & Its Applications" by Ronald N. Bracewell, which is a good intro book on Fourier Transforms. In it, he says that if you take the Fourier transform of a function 4 times, you get back the original…
sambajetson
  • 373
  • 2
  • 7
17
votes
2 answers

Alternatives to Hough transform for detecting a grid-like structure

I have an image which is composed of multiple 'angles' which form a grid shape: After some searching, Hough seemed like a good fit, because it isn't troubled by breaks in lines. However, the problem I have is that my lines are 'fat', and any edge…
Benjol
  • 273
  • 2
  • 7
17
votes
1 answer

Using an error prediction filter for filtering a semi-known signal

I'm trying to wrap my head around the proper use of a Wiener or error-prediction filter for filtering data. It seems to me that it is only a whitening filter, so how is it used when the data you want to recover isn't an AWGN signal? For instance, I…
gallamine
  • 693
  • 1
  • 5
  • 10
17
votes
4 answers

How can I remove shadows from an image?

I have this image I would like to remove the shadow from the image. I know a lot of different methods like certain morphological operations have been used to remove shadows: I have created this mask for the same image Are there some other methods…
vini
  • 2,182
  • 4
  • 21
  • 37
17
votes
3 answers

How can I lowpass filter by only reducing peak data?

I have a 2D image, which I want to lowpass filter, with these constraints / quality metrics: I can not "add" light to the image, so each pixel in the result should be <= the corresponding pixel in the input. The lowpass cutoff frequency should be a…
Pieter-Jan Busschaert
  • 576
  • 5
  • 10
17
votes
4 answers

Intuitive explanation of tracking with Kalman filters

I would much appreciate an intuitive explanation for (visual) tracking with Kalman filters. what I know: Prediction step: Dynamic system state $\mathbf x_t$: target location at time $t$ Measurement $\mathbf z_t$: the image at time index $t$…
matlabit
  • 887
  • 1
  • 8
  • 16
17
votes
4 answers

Why is the Fourier transform of a Dirac comb a Dirac comb?

This doesn't make sense to me, because the Heisenberg inequality states that $\Delta t\Delta \omega$ ~ 1. Therefore when you have something perfectly localized in time, you get something completely distributed in frequency. Hence the basic…
Fraïssé
  • 601
  • 2
  • 9
  • 22
17
votes
2 answers

DFT with geometrically-spaced bins?

The traditional Discrete Fourier Transform (DFT) and its cousin, the FFT, produce bins that are spaced equally. In other words, you get something like the first 10 hertz in the first bin, 10.1 through 20 in the second, etc. However, I need something…
Brannon
  • 295
  • 1
  • 7
17
votes
8 answers

Why Does the DFT Assume the Transformed Signal Is Periodic?

In many signal processing books, it is claimed that the DFT assumes the transformed signal to be periodic (and that this is the reason why spectral leakage for example may occur). Now, if you look at the definition of the DFT, there is simply no…
user10839
  • 171
  • 1
  • 1
  • 3
17
votes
2 answers

What image-processing techniques are ideal for this particular shift/scale invariant template matching?

A problem I had originally discussed in What methodology to use for discrimination of different (musical?) tones has evolved, and might have gotten a little simpler as I studied it in some more and attained new information. Bottom line, I would like…
Spacey
  • 9,817
  • 8
  • 43
  • 79
17
votes
2 answers

Are there any good open-source (well, free) handwriting OCR programs?

The title asks it all. I have before me a data entry task that I'm not too enthusiastic about: 50-100 pages of handwritten sign out/sign in logs. The format of the logs may help. Pages are partitioned into clearly delineated rows and columns (13r x…
psoft
  • 271
  • 1
  • 2
  • 5
17
votes
6 answers

Can we break the Shannon capacity?

I have a friend working in wireless communications research. He told me that we can transmit more than one symbol in a given slot using one frequency (of course we can decode them at the receiver). The technique as he said uses a new modulation…
Learning
  • 289
  • 2
  • 6
17
votes
3 answers

How to Remove Gaussian Noise from an Image without Destroying the Edges?

What is the best filter for removing Gaussian noise without destroying the edges? I am using the standard Lena images with additive Gaussian noise and I want to denoise before applying anisotropic diffusion. I don't want to median filter because…
Aviral Kumar
  • 341
  • 2
  • 7
17
votes
5 answers

Why are FIR filters still stable even though they contain poles?

How come FIR filters are always stable? Since they contain poles, shouldn't they be more affected by stability issues than others?
user7277
  • 257
  • 1
  • 3
  • 10
1 2 3
…
99 100