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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...

Double precision in FFTW

Hi all, I am relatively new to using FFTW.. I have been using FFTW to take fft for a few complex matrices. My problem is that I am not gettign the same values in Matlab and C++, the values seem to be differing after the sixth or seventh significant bit. When we use fftw_plan are we using double p...

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 ...

FFTW Help

Hi All, I'm doing some tests with FFTW and it seems to be working ok, but I am seeing something that's a little odd and was wondering if my reasoning for it happening was correct. Basically, I have a 3 second 440hz sine wave file created in Audacity at 44.1khz sampling rate. I am running F...

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 ...

FFTW 3.3-beta1 available

Dear DSP and numerics folks, You might be interested to know that a beta release of FFTW 3.3 is now available from www.fftw.org, with the final 3.3 release scheduled for July 25. This release includes several major new features, including support for 256-bit AVX instructions on recent Intel/A...

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 tuning

The documentation for Matlab's fftw interface states that: fftw('planner', method) sets the method by which the tuning algorithm searches for a good FFT algorithm when the dimension of the FFT is _not_ a power of 2. So when the input dimension _is_ a power of 2 there is no potential spe...

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 multi-threaded routines, what's use case for them?

I'm creating a web application that accepts client requests to crunch math on a server. The application will receive multiple client requests simultaneously. Was FFTW's multi-threaded routines intended to: (A) process all client requests serially through FFTW, but for the current client process b...

fft 'n' size

Hi. I'm using fftw in my code for my signal analysis. In fftw (1D), one of the parameters is 'n'. And the document says, "size n can be any positive integer, but sizes that are products of small factors are transformed most efficiently (although prime sizes still use an O(n log n) algorithm)" ...

FFTW and VB.NET

Hi, I don't know where to post this (since FFTW developers do not provide help with VB, and posting on MSDN for non-VB related question is kinda dumb) so I decided to ask you guys. :) I really can't import FFTW library in VB.NET 9 (VS 2008). When trying to reference to it i get this error mess...

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 ...

benchmarking advanced interface using fftw bench

Hi, I would like to use the fftw bench program to time the following. Use plan_many_dft from Advanced interface to calculate a bunch of ffts on a contiguous array of complex numbers. Can some one help me with the options i need to pass on to fftw bench program to be able to choose plan_many opti...

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 small difference for r2c ?

Hello, I am using FFTW v3.2 in C++ to compute the 3d DFT of a real image. I use the FFT as part of an iterative algorithm in which high accuracy is a must, so I checked the outputs of the FFTW and found some very small difference depending on whether I used the r2c or not. By small difference...

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...

Convolution and FFTW question.

Seems dumb*, but what the hey: (data sets are 1D PCM audio data) Convolution is O(n*m) where n is the length of one vector to be convolved, m is the length of the other vector. Convolution using FFT is alleged to be O(n log(n))... *part of this is things I can't easily find in the FFTW docs...

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: Zero padding fftw

simwes wrote: > I am writing a code to transform an array from the frequency domain to time > domain using the fftw. In order to increase the resolution of the signal in > the time domain I am adding zero in the frequency before sending it to the > fftw. > The problem is that the s...

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...