Signal Processing Stack Exchange
Signal Processing Stack Exchange

Questions tagged [ifft]

251 questions
23
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4 answers

Reconstruction of audio signal from Spectrogram

I have a set of songs for which I extracted the magnitude spectrogram using a Hamming Window with 50% overlap. After extracting the spectrogram, I did some dimensionality reduction using Principal Components Analysis (PCA). After reducing it to…
user76170
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Intuitive explanation of cross-correlation in frequency domain

According to the cross-correlation theorem : the cross-correlation between two signals is equal to the product of fourier transform of one signal multiplied by complex conjugate of fourier transform of another signal. After doing this, when we take…
silver surfer
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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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3 answers

How to make a signal conjugate symmetric?

Take the simple frequency-domain band-pass filtering operation below . . . NFFT = 128; x = randn(NFFT,1); H = zeros(NFFT,1); H(10:20) = 1; y = ifft(H.*fft(x), 'symmetric'); This gives a real output because I'm using the conjugate symmetric flag to…
learnvst
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Does our brain constantly ifft to hear?

From my understanding our ears have hairs/cilia in the cochlea that resonate at frequencies within our hearing range. To me this means we are hearing in the frequency domain as opposed to the time domain. But does that mean we are constantly…
benathon
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7
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3 answers

Efficient calculation of correlation function every $N^{\rm th}$ point

I would like to calculate a long correlation function of length say, 1e6 points. I have a prior knowledge that the correlation peak will be in point k*1000. Is there an efficient way to apply this prior knowledge and perform a shorter calculation. I…
Vlad Sokolik
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7
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4 answers

Filter size vs. FFT size and Overlap add

First of all I would like to say that : I'm new to DSP and in a "learning curve" hence the "basicness" of my questions. I've read as many posts/articles as possible on the internet but still need "guidance". I'm french hence the bad formulation…
Arnaud
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Computation of the Inverse DCT (IDCT) Using DCT Or IFFT

Is there a way to compute the inverse discrete cosine transform (type-2) by leveraging either a DCT, FFT, or IFFT algorithm? I have seen ways to compute the DCT using FFTs, and I've seen ways to compute IFFT using FFT. I can't quite find a simple…
user2913869
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4 answers

How Do You Save / Convert an Image to Be in the Frequency Domain?

Quick Note: I don't believe this is a subjective question... however if it is I will gladly modify to be more objective In ImageJ, if I take the FFT of an image, how can I save this new frequency domain image? The goal being that I would like to be…
Kyle Swanson
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4
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1 answer

Multidimensional FFT with mixed directions

Let's say I have three-dimensional complex array $X[m,n,p]$, $m \in \{0, 1, \ldots, M-1\}$, $n \in \{0, 1, \ldots, N-1\}$, $p \in \{0, 1, \ldots, P-1\}$; i.e. $X \in \mathbb C^{M \times N \times P}$. I would like to take a three-dimensional DFT of…
Robert L.
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4
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1 answer

Zero padding effect on a FFT of gaussian noise

I have a gaussian noise $\nu(t)$ with variance $\sigma^2$. After a FFT I get $X(\omega)$. If now I do the IFFT on the $X(\omega)$ can I say that the result is still a gaussian noise of variance $\sigma^2$? What is the effect of zero padding on FFT?…
Riccardo.Alestra
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1 answer

Inverse Fourier transform - porting from MATLAB to Python

I am porting a script from MATLAB to Python, but I am failing when it comes to the inverse Fourier transform. The function in MATLAB (ifft) includes a 'symflag', which treats the data as conjugate symmetric and ensures that the output is real.…
Tim Blackmore
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4
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Implementing Frequency Domain Convolution in MATLAB (Convolution Theorem)

I'm trying to prove convolution in time domain is same as multiplication in frequency domain but I'm not getting the same answer in matlab. Here is the code:
bharath
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Filter - Spatial Domain Versus Frequency Domain

Note: This is a followup question of How can I create a custom band-pass filter?. Can you explain the following python source code?. Bandpass filter bank. Suppose, I have an equation of a filter as follows, $$ h(x, y) = \frac{1}{1 + 0.414 (x +…
user18425
4
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4 answers

Is it possible to apply inverse Fourier transform (I-FFT) to the following image?

Suppose, I have this image in my hand and nothing else. Clearly, this is a Magnitude-plot of some unknown image. Is it possible to apply an Inverse Fast Fourier Transform (I-FFT) operation to recover the original Grayscale image from this…
user18425
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