c++,windows,visual-studio-2012,fftw

For single precision routines in FFTW you need to use routines with an fftwf_ prefix rather than fftw_, so your call to fftw_plan_dft_r2c_2d() should actually be fftwf_plan_dft_r2c_2d().

fortran,fft,fortran90,subroutine,fftw

To this end, I usually write a Fortran module in which I put plans and allocatable arrays that will contain the in and out of FFTW3. Then, I can simply USE the module wherever I want. Here is an example for 3dimensional FFT of real data: MODULE modfft IMPLICIT NONE...

c++,matlab,fft,fftw,frequency-analysis

If you have a real signal consisting of 1024 samples, the contribution from the 16 frequency bins of interest could be obtained by multiplying the frequency spectrum by a rectangular window then taking the IFFT. This essentially amounts to: filling a buffer with zeros before and after the frequency bins...

Here are some lines of your code : char* interferogram = new char[imN]; ... double value = 0; double window = 0; for (int y = 0; y < imSize; y++) { for (int x = 0; x < imSize; x++) { value = 127.5 + 127.5 * cos((2*PI) /...

Why reinvent the wheel? Academic purposes You have time to waste, see 1. You are a code wizard and you know your code is superior in all ways. Why not reinvent the wheel? Speed of development: writing everything from scratch is just not doable Accuracy of result: you are bound...

The problem is that you are planning on array (Real, Imag) but you are executing with (Imag, Real), in an attempt to use the same plan for the forward and inverse transforms. This is not allowed, as per manual Section 4.6: For split arrays, the separations between the real and...

As you have noted, the fftw_plan_dft_1d function computes the standard FFT Yk of the complex input sequence Xn defined as where j=sqrt(-1), for all values k=0,...,N-1 (thus generating N complex outputs in the array out), . You may notice that since the input happens to be real, the output exhibits...

Like @VladimirF already said, the ordering of the values is a bit different, than you might expect. The first half of the array holds the positive frequencies, the second half holds the negative frequencies in reverse order (see this link). And you might have to check the sign convention used...

From documentation you must set two pointers to data that build the curve and the size (number of samples in your case). void QwtPlotCurve::setSamples(const double *xData, const double *yData, int size) In your case yData is the data from FFT, the xData is an array that sweep from min to...

This is a known problem in FFTW 3.3 whereby the FFTW headers misidentify that they are being compiled with a gcc version >=4.6 which has 128bit floating point support. It has been reported to effect compilation with icc, and it looks like nvcc steered compilation has the same problem. The...

You need to specify where fftw3.f03 is located! On my machine, it is in /usr/include, so I use: gfortran -I/usr/include -o "executable_ename" main.f90 BTW: the implicit none must go in front of the include: program fft use, intrinsic :: iso_c_binding implicit none include 'fftw3.f03' end program fft ...

c++,wolfram-mathematica,gaussian,convolution,fftw

Using FFT to do convolutions is only efficient when you have very large convolution kernels. In most blurring applications the kernel is much much smaller than the image, e.g. 3x3, so FFT would be significantly slower. There are many implementations for doing small-kernel convolutions. Most modern hardware supports such intrinsic...

You need to implement two different methods of converting. One for int32 to float and another from int16 to float. As currently implemented it is using the int32 conversion in the int16 case. One problem with this is that the scaling factor for conversion to float is wrong. The other...

c,signal-processing,fft,fftw,dft

There are a lot of good questions and answers on this subject on SO already, but a few general pointers: the spectrum of your sample will typically be time-varying you usually choose a window size (== FFT size) where there will be little short-term change in the spectrum, e.g. 10...

c++,pattern-matching,image-recognition,fftw,cross-correlation

This question would probably be more appropriately posted on another site like cross validated (metaoptimize.com used to also be a good one, but it appears to be gone) That said: There's two similar operations you can perform with FFT: convolution and correlation. Convolution is used for determining how two signals...

The n2fv_64 stands for the forward discrete Fourier transform (fv=forward vector).

You need to match a 64-bit FFTW library with 64-bit MATLAB (you are building a .mexw64 file). Your build command mex '-LC:\fftw-3.3.4-dll32' -llibfftw3-3.lib test.c Should point to a folder with the 64-bit FFTW libraries. For example: mex -LC:\fftw-3.3.4-dll64 -llibfftw3-3.lib test.c...

Your have several problems. The calling sequence for fftw_plan_dft_c2r_1d is as follows: The inverse transforms, taking complex input (storing the non-redundant half of a logically Hermitian array) to real output, are given by: fftw_plan fftw_plan_dft_c2r_1d(int n0, fftw_complex *in, double *out, unsigned flags); Thus, you have the following problems: You never...

c,multidimensional-array,fft,fftw

I ended up solving this problem by making separate real and imaginary 2D arrays. Functions were then written to take in the arrays, create double length 1D arrays with alternating real and imaginary values representing the rows and columns. This allowed me to use the simple in-code FFT four1 function...

It's complaining that it the type of complex_ny isn't the same as complex (and it doesn't know the conversion). If you cast complex_ny to a complex* first, then assign the pointer to a memoryview it's happier: complex_ny = fftw_alloc_complex(input.size) cdef complex[::1] view_of_complex_ny = <complex[:input.size]>(<complex*>complex_ny) view_of_complex_ny[:] = input As I'm sure...

by First Error, the configure should be like this: ./configure --host=arm-apple-darwin --target=arm-apple-darwin --enable-float ( without --enable-neon ) and the second Error, its because the libraries are all from the arch x86_64. they should have the right architecture ( libfftw3f_i386.a should have the arch. i386.a and libfftw3f_armv7s.a the arch. armv7s.a and...

If x is a 2N signal padded with zeros above N , its DFT writes : If k is even : Hence, the coefficients of even frequencies arise from the N-point discrete Fourier transform of x(n). if k is odd : Hence, the coefficients of odd frequencies arise from the...

c++,file,import,signal-processing,fftw

According to FFTW's documentation: Wisdom is automatically used for any size to which it is applicable, as long as the planner flags are not more “patient” than those with which the wisdom was created. In other words, if you would like to import wisdom for plans to be created with...