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Questions tagged [fftw]

FFTW, "The Fastest Fourier Transform in The West", is a C library which implements discrete Fourier Transforms. It is licensed under the GNU GPL.

FFTW homepage: http://www.fftw.org/
FAQ: http://www.fftw.org/faq/

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How to write a function to calculate 2D convolution between a template (T) and a 2D image (imin) by using fftw package?

I am doing a project in which I have a small template (T) and an image (imin). The aim is to use convolution along fft to find the location of the most similar pattern in imin. I want to use FFTW codes in C++ for this aim. But, I am new in C++ and…
user1555892
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How to use FFTW on loaded samples?

my ultimate goal is to extract all the sound information that is below 15KHz from a mono wave file. The program loads samples into memory and its represented as 16bit signed integer array. I used FFTW and it has several functions such as complex…
Maduranga E
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Centering 3D FFT

again I have a question concerning centering a FFT result. In this case in 3D space with FFTW Library. At the moment I have implemented the concept shown in the picture below. It shows the subdivided frequency space. Each sub cube (1-8) represents…
DerHandwerk
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Misunderstanding or typo in documentation for FFTW using OpenMP

This quote is from the FFTW Manual: [...] Third, before creating a plan that you want to parallelize, you should call: void fftw_plan_with_nthreads(int nthreads); The nthreads argument indicates the number of threads you want FFTW to use (or…
hanno
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ideal lowpass filter with fftw

again I am still trying to get my lowpass filter running, but I am at a point where I do not know why this is still not running. I oriented my code according to FFT Filters and my previous question FFT Question in order to apply an ideal low pass…
DerHandwerk
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3d c2c fft with fftw library

I am trying to do a 3D FFT with the FFTW library, but I have some difficulties with the inverse transformation. At first I do the foreword transformation via: fftwf_plan_dft_3d(_dimensions[0], _dimensions[1], _dimensions[2],…
DerHandwerk
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OpenMP: How can I increase the speedup with number of threads?

I am using fftw library along with OpenMP and the best speedup I was able to achieve is ~ 2-3x only. Even with 6 cores and 6 threads I still barely achieve ~ 2.5! I am simply following the documentation of fftw: HERE The example code I…
Jamie
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How do I reconstruct all Fourier coefficients from 2D r2hc transform in FFTW?

I have 3D real data, say, 64 * 64 * 64 real data points, and I want to do a 3D Fourier transform. Specifically, I want to do DFT (exponential transform, containing both sine and cosine terms) on two of the three dimensions and DCT (discrete cosine…
Dennis
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How to link files in qt throw pro file

I've got undefined reference to 'ffwf_malloc' and other functions fftw3 lib At first I installed fftw3 library to usr/local/lib. Then I included in my project. But I've got an error: Can't find file. In pro file I added LIBS +=…
Vadim Shestak
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fftw not working correctly with real data

I'm trying to use fftw3.3.5 for DFT in C. but i currently have trouble while applying DFT to real data, it results in something strange, like extremly large numbers, as well as something that isn't symmetric. here is the test code: #include…
tyker1
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calculate the precise, non integer frequencies from time series in (FFTW)

I want to calculate the frequency of time series precisely with at least 3 decimal value. This is a simple example that calculates the frequency of integer values. #include #include #include #include #include…
Abolfazl
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C++ error: “Windows has triggered a breakpoint in Espectrogramafrequencia.exe.”

I've been working on Microsoft Visual C++ 2010(32-bit system) The compilation phase is alright, but on execution I get an error that says: "Windows has triggered a breakpoint in Espectrogramafrequencia.exe. This may be due to corruption of the heap,…
Andres Girón Cruz
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float2 cufftcomplex to fftw_complex

I want to using FFTW library on my code. I have cast float2 data type to fftw_complex. But I get: Segmentation fault This is my code. test.cu typedef float2 cplx; int DoFFT_Operation( cplx* DatafftOneSlice, float* out, int *dim) { cout << "DO…
Khalif21
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Error when executing 2D DFT with FFTW

Good afternoon everyone, So I'm learning to use the FFTW and I was testing a 1D DFT from real to complex and everything was working fine. Then now I try doing the same with a 2D transformation and I find that my program fails. The thing is that I…
fdzglln
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Tiva C FFT Library

I'm carrying on a new embedded systems project that analyse input frequency and get the coefficients of the frequencies and produces some information based on this information. I will be using Tiva C TM4C Microcontroller, and I've done heaps of…
Michel Mina
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