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ANN: beta version of FFTW now available

I just noticed a new beta version of FFTW is available at www.fftw.org. I look forward to trying it. I am building it as I write this. Thanks for all your hard work Steven & Mateo. Considering how often FFTW is discussed on this newsgroup, I thought it worthy of an announcement. If you c...

FFTW in Visual Studio C++

I want to use FFTW in visual Studio 6.0 , and I have downloaded the FFTW 3.0.1 static library files from http://www.ece.cmu.edu/~franzf/fftw.org/. However, I cannot run the program as expected ? Did i do anything wrong ? I did not download the FFTW 3.0.1 VisualStudio 6.0 project files (req...

[FFTW] SSE is not used?

Hi, any FFTW experts reading this? :-) I'm using FFTW. But i cannot measure any difference between runs with FFTW_NO_SIMD and without. I'm trying to do in-place DFT, with plans created like this: fftw_complex *buf0 = fftw_malloc(...) fftw_plan_dft_1d(N, buf0, buf0, FFTW_FORWARD, 0) ...

Zero padding in FFTW

Dear All, I want to do zero padding of of the data and than do fft by FFTW(www.fftw.org). The dummiest way is to make an array which has more elements than the data set size. However, it takes more memory space and more computation time. I'm wondering if there is a way to tell FFTW do zero...

FFTW For VisualDSP

Hi, I'm looking to port FFTW to be used under VisualDSP. Has anyone done this before? If so, is it possible to send me the ported FFTW code at sbw@appsig.com? I found one post here: http://www.dsprelated.com/showmessage/35481/1.php I'm still trying to contact that person. Thank you! ...

FFTW velocity

Hi, I'm using FFTW. First of all I inform you that I have overcome my "Altivec assist" problem through a modification of simd-altivec.h. In particular I have defined #define VLITF(x0, x1, x2, x3) (vector float)(x0, x1, x2, x3) #define VLITUI(x0, x1, x2, x3) (vector unsigned int)(x0, x1, x2, x...

[ANNOUNCE] FFTW-3.1.3 released

Dear FFTW users, we are pleased to announce the availability of FFTW 3.1.3, which you can download from the web page: http://fftw.org/download.html This release fixes a bug that causes incorrect results to be computed in programs that use both REDFT11 (a.k.a. DCT-IV) and RODFT11 (...

Multi-threaded FFTW

I'm using the FFTW library implemented as DLL under Win XP. Now I'm writing (in C++) a multi-threaded application which call the FFTW functions from two function in my code at the same time and, obviously, the application crashes. Is there any way to use the FFTW library in a multi-threaded ap...

FFTW Real FFT

Hello, simple question: I have a time series with lots of entries (more than int). How can I use FFTW to do a FFT? The problem is, that FFTW can only handle up to "int n" entries in the datafile... Any idea? Thanks a lot! Mark ...

Re: FFTW Sample Project

FFTW is quite simple to use indeed, and it's well documented, but if you have a precise question then ask right away. ...

FFTW?

Hello, can anyone explain me how to perform the convolution of two dimentional array with fftw? Thanks ...

Matlab's fftw returns nothing?

Hi all, Matlab command "fftw" supposedly should return something, as described in the following help document. But when I tried these command examples, nothing happened, i.e. "fftw" returned nothing. What might be the problem? Thanks --------------------------------------------------...

FFTW, Imlib & OpenCV

Hi there, I am working on an image processing project. I am trying to represent an image in terms of signal and then calculate contrast using that signal representation of the image. I know that inorder to represent an image in terms of signal a FFT has to be performed. I am using FFTW to calc...

Is the output of FFTW in angular velocity domain?

Hi, I have a question in FFTW, I need to make the out put data in angular velocity domain, like 1/2*sqrt(pi)*exp(omiga**2/4) for exp(-x**2). I guess the FFTW output is in frequency domain, what do I need to do to change it? Thanks, Shuangyi ...

Re: Calculate MACs in MATLAB

> Agree the tic toc is useful but I am doing one method by hand and the > other practically on matlab so I can't use it. Well, you can time your functions then use an approximation to calculate the equivalent FLOP count. FFTW uses MFLOPS = 5*N*log2(N)/time (in us) for complex data, divide by 2 ...

FFTW + low pass filtering + reverse FFTW

Dear FFTW experts, I'm using 2d r2c fftw on images, and now I would like to do a low pass filtering. I compute the module (sqrt(realpart*realpart+imagpart*imagpart)) of my data, and if it exceeds a threshold, I set it to zero. Therefore, I get an array of real data, and I don't know if I can use ...

FFTW question about larger output array than input

Hi, I am using FFTW to obtain freq values from an input signal. The input and output arrays are the same size. However, I need more precision (i need to detect frequencies which aren't whole numbers) therefore as i understand it i need a larger output array than my input one. i am using FFTW 3...

Re: FFT of 0s and 1s signal

On Apr 22, 5:12 pm, "markt" wrote: > That can be said for any pre-determined case and hence a lookup would > suffice. There are implementations that are faster than others, depending > upon the radices required for the given FFT (the FFTW folks discuss all > this, with prime radices up t...

FFTW on DSP

Hello All, I'm planning to use FFTW library on the DSP....has anybody used it with code composer studio to generate the coff file for the DSP ??..please share your experiences Thanks bngguy ...

Partial Derivative for 3D function by FFTW

Dear FFTW experts, I want to do the partial derivative for a 3D function by FFTW. For example, I have a 3D function P(x,y,z), and I want to compute dP/dx and dP/dy (I can not find the symbol for partial so I use "d" here). As I remembered: 1. Determine dP/dx:(P is a 3D data) (1)I should do f...

Re: FFT for sequences of arbitrary lengths

Zero-padding produces a result different from the DFT of the original data. You probably want to use an FFT code that supports non-power-of-two sizes. There are several such FFT programs freely available, so there is no reason to write your own. (One possibility is our FFTW, www.fftw.org, w...

FFTW Accuracy vs Matlab Accuracy

Hi, i'm using FFTW to computer determine the SNR of a recorded sinusoidal signal. (1khz sinus for 5seconds @ 48khz) I'm experiencing a strange behaviour: if i compute the fft with FFTW i obtain really different values from what matlab compute. To be more specific: i compute a real 2 rea...

Re: decomposing of an unknow signal?

Rune Allnor wrote: > Well, I would certainly start with a Fourier analysis. In good > implementations the FFT routines will work withe general data lengths, > not only powers of 2. Unfortunately, I don't know if such FFT routines > are available for free. There are several "general-leng...

Compile process of FFTW3 on vxWorks O.S.

Good morning, I need help about the compile process of FFTW3 source files. I'm working on vxWorks operating system. I have edit a new config.h file using the #define I need. I'm using Altivec optimization so I have #define the HAVE_ALTIVEC option. I have follow all the advices in "Installation...

Using FFTW to do analysis of a WAV file

Hi, I'm extremely new to DSP, I just read about the FFT for the first time a couple of days ago. :) I wanted to construct a program will add filter effects to a WAV file. No, I'm not interested in a freeware/shareware program, I want to learn how to do this. I found that I would need a FFT an...

Convolution of two one-dimensional arrays

hello everyone, i just downloaded the FFTW library, and i read the tutorial (well..i skimmed through it). i'm using dev-C++. in c++, i constructed 2 vectors, and i have to convolve them using the FFTW library. the stuff in the tutorial seems much more complex than what i want to do, and i am a ...

Re: fftw and dct/idct

> Hi Markus, there are two sources to check which immediately reveal the > answer: the Matlab manual and the FFTW manual. In particular, if you > look in the two manuals, they give the exact mathematical definitions > of the transforms as computed by Matlab and FFTW: > > http://www.mathworks....

Re: Mistake on FFTW3 - Transform size > 16

(I apologize to comp.dsp about the offtopic thread. I regularly refer FFTW users to comp.dsp if they have DSP-related questions, but I don't encourage them to come here for FFTW-specific compiling/debugging advice.) m.baldasseroni wrote: > I'm using FFTW3 and I have noted that it's very fas...

FFTW question about larger output array than input

Hi, I am using FFTW to obtain freq values from an audio signal.The input and output arrays are the same size. However, I need more precision (i need to detect frequencies which aren't whole numbers) therefore as i understand it i need a larger output array than my input one. i am using t...

IFFT conversion using FFTW libraries

Hi, I am trying to convert a FFT and IFFT Matlab code to C using the fftw libraries. Hoiwever, I am stuck at a particular step: The Matlab command is: G = ifftn(P21,'symmetric'); ow do I convert this statement to C using the fftw library. I have tried the following steps: 1.I used fftw_plan_dft_...

one dimensional FFT of a MATRIX

Hello every one I am new to FFTW library and currently i am using version FFTW3.1.2. My problem is i have a real no matrix of size 32 x 2048 and i want to calculate one-dimensional real to complex FFT of all 32 rows(each with 2048 points) using FFTW library. One simple approach in my mind i...

Re: fft implementation in c with altivec support

mittalvivek42 wrote: > if anyone knows a site or has code for fft implementation written in c with > altivec instructions, please do reply. thank you > > I think FFTW has AltiVec support these days: . Paul ...

Re: FFT TMS320F2812

Have you tried FFTW (MIT's FFT Library in C)? I made a FFTW based plugin for Image Apprentice: http://divyarathore.googlepages.com/fftwpluginforimageapprentice Source code is there for you to have a look, though the wrapperclass 'CFFTWWrapper' that I have made currently handles only 2D FFT. ...

FFTw Forward/Backwards :s

Hello, I'm having some trouble to use FFTw library... I'm using two plans like this: fftw_plan fftw_plan_r2r_1d(SIZE_OF_IN, in, out, R2HC, FFTW_FORWARD); fftw_plan fftw_plan_r2r_1d(2*SIZE_OF_IN +2, out, originalInput, HC2R, FFTW_BACKWARD); If i'm not wrong, i should be getting, after...

Weird results from FFTW -- banding and large roundoff

I have been struggling to figure out some strange results from FFTW. I get a angled banding in the DFT and the inverse gives an image that looks generally OK except that the signal varies periodically, consistent with those bands, by up to 1% above and below the original image signal. I have put ...

Questions about fftw

Hi, I am using the FFTW library to do some image processing. I am using the r2c plan to get the fourier transform. The documentation clearly states that the size of the output for a m*n input is m*(n/2+1). Also, the dc component of the result is the (0,0) element, rather than at the centre of...

undersampling and FFTW

Hello, I have a problem with my fftw complex transform (1d) when I want to undersample my signal. I start with initial signal (Dimension 16384points), and get the FFT of this signal in complex with fftw_plan_dft_1d (result is a 16384points dimension too). This signal has 128 first non-zero va...

[FFTW] Cyclic results with FFTW?

Dear all, I implemented some test FFT's from various libraries, having decomposed and reconstructed a simple signal (sine), my code worked for all of them however, the signal I got using fftw was not reconstructed correctly, indeed, the transform is not cyclic. How to get cyclic output fro...

Faster fft on P4 + winxp?

Hello, I am using fftw in a fluid simulation code for doing 1D,2D ffts and cosine transforms associaciated with Chebyshev differentiation. All this is done on a P4 pc with winxp. Code written in C on the dev-C++ IDE i.e. the compiler is gcc. To my surprise, it turns out that the s...

Re: Decimation in Frequency FFT

I heard that MATLAB has switched to the FFTW FFT which is very fast. If I remember correctly, other MATLAB-like programs, some free, also use FFTW. You may be blaming the slow FFT speed on the FFT algorithm instead of the built in lack of speed in MATLAB. Or you might be using an old versio...