Questions tagged [frequency-domain]
28 questions
8
votes
3 answers
Fourier Domain - have I got my theory/terminology right?
In terms of images.
Fourier transform converts spatial to frequency (Fourier) domain.
DC value = average of sinusoids (sine waves), F(0,0) and average brightness/graylevel of image.
Fourier has a complex number output....you can get the [magnitude…
Cheetah
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4
votes
1 answer
Applying Gaussian blur to image in frequency domain
I've got torubles with appling gaussian blur to image in frequency domain.
For unknown reasons (probably I've dont something wrong) I recieve wired image instead of blurred one.
There's what i do step by step:
Load the image.
Split image into…
user2475983
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4
votes
2 answers
How do I interpret audio encoded binary data?
I have built a little program that encodes binary data into a sound. For example the following binary input:
00101101
will produce a 'sound' like this:
################..S.SS.S################
where each character represents a constant unit of…
Patrick Oscity
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3
votes
2 answers
Spectral Entropy and Spectral Energy of a vector in Matlab
I am going to use Spectral Energy and Spectral Entropy as features for window-based time-series data. However, I'm bit confused about the formula being used for it online, especially about the the special Entropy.
I used entropy from Matlab but…
utengr
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1
vote
1 answer
Why is audio file encryption done in frequency domain?
When we want to encrypt an audio file (wav/mp3), why is the encryption done in the frequency domain? I looked at some audio encryption methods and they use the Fourier Transform and then they do some encryption in the frequency domain. Why we dont…
Tenshi
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1
vote
1 answer
How to Extract the following Frequency-domain Features in Python?
Please feel free to point out any errors/improvements in the existing code
So this is a very basic question and I only have a beginner level understanding of signal processing. I have a 1.02 second accelerometer data sampled at 32000 Hz. I am…
Danish Anis
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1
vote
1 answer
Why convolution in spatial domain equal to multiplication in frequency domain?
Why it is said that "convolution of an image in spatial domain is equal to multiplication in frequency domain" ?
Could anyone please explain it briefly?
Linkon
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1
vote
0 answers
FFT result interpretation
I am developing an android app that will do human activity recognition. I am using Apache Commons to calculate my time domain features already. Now, I want to use Fast Fourier Transform method of the library to convert my time domain data (raw xyz…
Georgi Koemdzhiev
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1
vote
2 answers
Apply parabolic filter in frequency domain
What would be the effect on initial image of applying this filter:
in the frequency domain?
How can I determine the effect without using computer (on paper)?
This filter (H) is already in frequency domain.
wonderingdev
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0
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how to plot a centralize upconverted signal around the carrier frequency - Matlab
I have an upconverted signal that is around the carrier frequency fc.
I'm trying to plot this signal's FFT but failed to scale the frequency axis correctly as the signal's FFT is centered around the DC.
I tried:
f = 1;
fs = 10*f;
t = 0:1/fs:5;
fc =…
A.B.A
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0
votes
1 answer
How to do features extraction of ECG using mean frequency in python?
can you help me to correct this code below?
Here I tried to do features extraction of ecg by calculating the mean frequency.
First, I read the audio with this code:
Fs, data = read('ecg_file.wav')
output from data:
enter image description…
Ngr Wisnu
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0
votes
1 answer
How to calculate the num_fft value?
can you guys help me about this code,
fs = 1000
num_fft = 1024;
t = np.arange(0, 1, 1/fs)
f0 = 100
f1 = 200
x = np.cos(2*np.pi*f0*t) + 3*np.cos(2*np.pi*f1*t) + np.random.randn(t.size)
Y = fft(x, num_fft)
Y = np.abs(Y)
ps = Y**2 /…
Ngr Wisnu
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0
votes
1 answer
Why are edges high frequency components of an image?
The description of frequency on Wikipedia is:
Frequency is the number of occurrences of a repeating event per unit of time
Now, when talking about images, I suppose we're talking about spatial frequency, so it would be per unit of space, instead.…
Stefan Dimeski
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0
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1 answer
How can the ideal low pass filter from the frequency domain can be applied?
I have an image where I add a Gaussian noise. I need to use the ideal low pass filter to remove the noise but I cannot really see any examples on the official Matlab documentation. There examples but not with images and I cannot really grasp the…
Fiphe
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0
votes
1 answer
How can I use a linear filter from the frequency domain to remove noise in an image?
So I have worked with linear filters from the Spatial domain but in the Frequency domain I have troubles understanding how to implement any filter in Matlab. Could anybody explain me how to do that?
I want to see how I can use a filter from the…
Fiphe
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