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3 answers

MATLAB: $\tt fft$ and $\tt ifft$ scaling

In MATLAB, the outputs of the fft and/or ifft functions often require additional processing before being considered for analysis. I have heard many differing opinions on what is correct: Scaling Mathworks states that fft and ifft functions are…
kando
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Z-transform of a downsampler

In this paper or multirate filtering, the author establishes the following mathematical relationship. Let $y_D$ be the output of a downsampler such that $$y_D[n] = x[Mn]$$ where $M$ is the downsampling factor. In other words, we keep every $M$-th…
Phonon
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Slow Down Music Playing While Maintaining Frequency

Playing a piece of music audio at a slower speed would lower its pitch (frequency). Is there a tool and theory to slow down the song playing while keep the frequency the same? I suppose one can do windowed Fourier transform or wavelet transform. It…
Hans
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Is a leaky integrator the same thing as a low pass filter?

The equation governing a leaky integrator (according to Wikipedia at least) is $\frac{d\mathcal{O}}{dt} + A\mathcal{O}(t) = \mathcal{I}(t)$. Is a continuous-time leaky integrator thus the same thing as a low pass filter with time-constant $A$, up…
Kris
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Why do digital filters work?

So I just started reading on FIR and IIR filters and am amazed by how "simple" the theory seems, so far. But what confuses me is, why does filtering work by creating a weighted sum of previous samples? What intuition makes one think this can…
mavavilj
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Why are some JPEG files of the same scene much larger than others?

I'm using a Foscam FI8910W ip camera to view a static scene under constant lighting conditions. When I pull back a frame grab, it's about 35 KB in size. I can do this over and over and it's always around 35 KB, but fluctuates somewhat due to…
Paul Uszak
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FSK Demodulation, Bit Timing Recovery

I am currently implementing acoustic FSK modulation and demodulation. I am not a signal processing guy so any help about the bit timing recovery would be very appreciated. Currently I implemented the demodulator using two matched filters for each…
peter
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Kalman Filter - Implementation, Parameters and Tuning

First of all, this is the first time I try to make a Kalman filter. I earlier posted the follwoing question Filter out noise and variations from speed values on StackOverflow which describes the background for this post. This is a typical sample of…
Ole-M
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Removing Noise from Dental Radiography

I'm working on a project of applying Active Shape Model to locate tooth in dental radiograph. For those familiar with the technique, I'm currently trying to sample along normal vectors for each landmark. The paper recommends to take derivatives of…
Raven
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Sampling of a continuous function: Kronecker's or Dirac's delta?

I've been reading some papers in signal proccesing and I'm very confused about the issue in the title of my question. Consider a continuous function of time $t$, $f(t)$, that I sample at uneven times $t_k$, where $k=1,2,...,N$. To me, it makes sense…
Néstor
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Recommendation for book - Writing DSP code in C

I am looking for some good book, that simply show how you actually write a code in C, to do all the main DSP methods . FFT. Low-pass and high-pass filters. Auto-correlation. Noise processing. And all the basics of DSP, from theory into a real code…
Curnelious
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How does the quantization error generate noise?

I'm learning about sampling and DSP on my own. I have a hard time to understand how the quantization error results in noise. I think I miss a fundamental understanding but can't tell what it is. So how does the quantization error generate noise?
Jan Deinhard
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Detection of number of yarns in the fabric image

I am a novice user in image processing and working on a project to determine number of yarns in a fabric image i.e. warps and wefts (Perpendicular and parallel yarns to x-axis). I am trying to detect the yarns by taking the sum of columns and rows…
user1509018
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3 answers

Can edge detection be done in the frequency domain?

Can we take advantage of the fact that high frequency components in the FFT of an image generally correspond to edges, to implement an edge detection algorithm in the fourier domain? I did try multiplying a high pass filter with the FFT of an…
rounak
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High quality reverb algorithm

I did a bit of searching on this site but surprisingly, I didn't find much relevant information, and my knowledge of DSP is very very limited. My goal is quite simple : I want to program an algorithmic reverb in C++ which sounds really good. Or…
Dinaiz
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