Linked Questions

19 votes
3 answers
18k views

How to Resample Audio Using FFT or DFT

I'm down sampling voice audio by first performing an FFT, then only taking the parts of the result that I need, and then performing an inverse FFT. However, it's only working properly when I'm using ...
user avatar
11 votes
4 answers
4k views

Whittaker-Shannon ($\mathrm{sinc}$) interpolation for a finite number of samples

Given an infinite number of samples $(N)$, a higher (or lower) number of samples $(cN)$ can be derived using sinc interpolation followed by sampling. How can this be applied to finite length signals? ...
Television's user avatar
1 vote
2 answers
7k views

Downsampling and Upsampling Using FFTW

I'm having 2 signals which have different sampling rates i.e., 1ms(A) and 4ms(B) and I've tried to upsample/downsample either of the signals based on the code snippet Resampling based on FFT which I ...
rahul's user avatar
  • 113
4 votes
2 answers
2k views

Sinc Interpolation Using DFT (FFT)

Lets say I want to double the number of points in an array f. I had the idea to do this: F=fft(f);N=length(f); FF=[F(1:N/2) zeros(1,N) F(N/2+1:N)]; f=ifft(FF); ...
Gappy Hilmore's user avatar
7 votes
2 answers
925 views

Why Zero Padding in the Center of the DFT Interpolates / Upsamples the Signal (Sinc Interpolation / DFT Interpolation / Periodic Interpolation)

I'm experimenting with the Inverse Discrete Fourier Transform. Starting from the two-cycles continuous $x(t)$ signal below: I have the discrete signal $x(n) = \{ 1, 0, -1, 0, 1, 0, -1, 0 \}$ leading ...
Sylvain Leroux's user avatar
3 votes
1 answer
4k views

Upsampling and Downsampling using IFFT and FFT (DFT Based Resampling)

Assume in OFDM , there are N=64 subcarriers. I would like to upsample my signal by Factor 8 after IFFT and pass it through channel then downsample it by factor 8 before FFT. I can use upsample, ...
user59419's user avatar
  • 353
2 votes
1 answer
3k views

Frequency Domain Interpolation: Convolution with Sinc Function

I am reading the paper, Design of an energy-efficient accelerator for training of convolutional neural networks using frequency-domain computation, and I came across the following definition of sinc ...
Eduardo Reis's user avatar
6 votes
2 answers
776 views

Fourier Like Spectral Analysis with Uneven Intervals and Redesigned DFT Matrix

I intended to use a discrete Fourier transform (DFT) on a time series sampled at uneven intervals. What I did was to calculate a DFT matrix where the elements are the values at the uneven locations ...
David Jonsson's user avatar
2 votes
3 answers
1k views

Zero Padding in Frequency Domain (Spectrum): How to Split the Middle Bin (Nyquist Frequency)?

When a complex digital signal is converted to its spectrum through an FFT, the result will contain a series op positive and negative frequencies. That is, when the spectrum has N bins. Bin 0 will be ...
user avatar
4 votes
2 answers
825 views

How is the DFT involved in downsampling?

I recently had my first proper class of DSP and upon completing the review of Signals and Systems my professor started working on the concepts of upsampling and downsampling. Of course as is their ...
Ahsan Yousaf's user avatar
  • 1,573
2 votes
1 answer
745 views

The Proper Way to Do Sinc Upsampling (DFT Upsampling) for Uniformly Sampled Discrete Signals with Finite Number of Samples

Given a signal $ \left\{ x [ 0 ], x [ 1 ], ..., x [ N - 1 ] \right\} $ what would be the correct way to upsample it in the frequency domain (Sinc interpolation)? Note: Added as a request by the answer ...
David's user avatar
  • 144
0 votes
1 answer
514 views

Generate an Ideal 2D Low Pass Filter in MATLAB

I've been tasked with creating a 32 x 32 half-band low-pass image filter in MATLAB. My thinking is to generate the ideal filter mask in the frequency domain and compute the corresponding convolution ...
Izzo's user avatar
  • 882
0 votes
1 answer
379 views

Applying 2D Sinc Interpolation for Downsampling in the Fourier Domain (DFT / FFT)

Related to The Proper Way to Do Sinc Downsampling (DFT Downsampling) for Uniformly Sampled Discrete Signals with Finite Number of Samples, how can one apply Sinc downsampling in the DFT / FFT domain ...
Eric Johnson's user avatar
1 vote
1 answer
123 views

Sinc Based Multi Dimension Signal Resampling on the Fourier Spectrum (DFT)

As a generalization of the following questions: The Proper Way to Do Sinc Downsampling (DFT Downsampling) for Uniformly Sampled Discrete Signals with Finite Number of Samples. The Proper Way to Do ...
Eric Johnson's user avatar