Signal Processing Stack Exchange
Signal Processing Stack Exchange

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1500 questions
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3 answers

Can Gabor filter be used for detecting dents in cars?

I am doing some research on Gabor filters for detecting dents in cars. I know Gabor filters have had widespread use for pattern recognition, fingerprint recognition, etc. I have an image. Using some code from the MathWorks File Exchange site, I got…
vini
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A good mathematical explanation of Gibbs phenomenon

I was explaining to someone how Fourier series work in context of constructing signals that are not everywhere differentiable, e.g. square waves, sawtooth waves, etc. When I mentioned the Gibbs phenomenon however, I realized that I never really…
Phonon
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What are the differences between these two Gabor filter functions

I need to enhance the visibility of veins on dorsal hand vein images in my project. I use two different even-symmetric Gabor filters bank improve vein visibility. First bank consists of these gabor…
saglamp
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2 answers

How to recognize hexagonal tiling in boardgame?

I would like to recognize the boundaries of a hexagonal tiling in a photograph, like in image below: It seems to me, that a standard approach at a square grid is to first detect corners (e.g. canny) and then extract the longest lines via a Hough…
snalx
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How do I reconstruct text from an image using only morphological operations?

I want to reconstruct the text from the following image as best as possible. The tricky part is that I want to do it only using morphorogical operations on the image I tried using erosion, dilation, opening and closing but the result is not very…
Jackobsen
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16
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9 answers

Why do we use window in time domain rather than do FFT modify the spectrum and than inverse FFT

I thought that DSP would be done by using FFT of portions of a signal, modify the samples that result from FFT (since they represent the spectrum of our signal + noise) and remove any unwanted signals and than do an inverse FFT to get a time domain…
quantum231
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16
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4 answers

When concatenating sine waves, how do I phase shift in order to prevent "pops" caused by sudden jumps in amplitude?

I'm writing a synthesizer using numpy and python. I've run into a problem where concatenating sine waves causes 'pops' or 'clicks' when they are outputted to audio, say, via scipy.io.wavfile.write. Here is some example code that illustrates the…
Tim
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Why Wavelet developed when we already had Short-time Fourier transform

If we already had Short-time Fourier transform for better analysis of a signal than Discrete Fourier Transform, then what was the need that leads to development of Wavelet Transform ?
Sufiyan Ghori
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16
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1 answer

Converting frequency from $\textrm{Hz}$ to radians-per-sample

In MATLAB I have to pass cut-off frequency for designing a filter. But this Cut-off frequency is in radians-per-sample. How do I convert my analog Cut off frequency in $\textrm{Hz}$, into the required radians-per-sample for MATLAB?
gpuguy
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What data should I use to test an FFT implementation, and what accuracy should I expect?

I'm involved with an effort to implement an FFT algorithm, and am curious what the recommended advice is for the input test data to use -- and why! -- and what accuracy to expect. On test inputs, I've found a little guidance in old Usenet posts that…
Brooks Moses
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5 answers

When to consider double (64 bit) floating point for Audio

When synthesizing and processing audio on modern processors, when would one consider using something other than single precision (32 bit) floating point? Obviously, the audio coming in and going out to the real world is 16/24 bit, so I'm just…
user1849104
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2 answers

Bitmap alpha bevel algorithm?

I am looking to create an algorithm which adds a bevel effect to a bitmap using it's alpha as a bump map. How would I go doing something like this? I have tried specular lighting but I only get the highlight and not the shade. Here is the effect I…
Shedokan
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3 answers

How to decide what platform is best to implement real-time audio processing on?

When developing products I do all of my algorithm design in Matlab. They are usually pretty basic, an IIR or FIR filter or two, a couple FFTs, etc. When it comes time to move it to an embedded environment I always have a hard time deciding what…
Kellenjb
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Is wavelet analysis useful for 1D signals?

Wavelets seem to be very useful for image processing. Assuming that I'm only ever going to study signals of time, i.e. 1D signals, should I still take a course in wavelet analysis? Are they applicable to 1D signals?
Andreas
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What is normalized frequency

I am learning DSP and finding difficulty understanding the term Normalized frequency often used with DFT & DTFT. What does normalized frequency mean in DSP and how it is different from analog frequency? What is the significance of normalized…
user6363
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