Hi, I'm currently a 17-year-old student trying to do a project, involving embedding data within an audio file. Hopefully, it will survive MP3 compression... so I've come to the conclusion I will have to convert all the samples to the freq. domain to do any analysis. I downloaded FFTW and I have it working, but it assumes that the user knows what he's doing (which I do not really). I found this software kit at http://www.eobj.com/eofft-dll.html that would be perfect, except it costs $60... Basically, it will calculate forward and inverse FFT and can add extra output tasks such as different windowing functions, converting output of forward FFT to magnitude (dB) or power. Is there any software kit (preferably in C/C++ or Java) for free that can provide similar features? Actually, all I really need are examples showing me how to do the above tasks I mentioned (mainly converting output of forward FFT to magnitude, after using a windowing function). Thanks. David Chen

# Seeking Free Frequency analysis toolkit or examples

Started by ●June 26, 2003

Reply by ●June 27, 20032003-06-27

David Chen wrote:> I found this software kit at http://www.eobj.com/eofft-dll.html that would > be perfect, except it costs $60... Basically, it will calculate forward and > inverse FFT and can add extra output tasks such as different windowing > functions, converting output of forward FFT to magnitude (dB) or power.This might do what you want: http://www.iowegian.com/scopedsp.htm Also, there's a lot of tutorial info at www.dspguru.com that you might find interesting. -- Jim Thomas Principal Applications Engineer Bittware, Inc jthomas@bittware.com http://www.bittware.com (703) 779-7770 There are 10 kinds of people: the ones who understand binary code, and the ones who don't.

Reply by ●June 27, 20032003-06-27

David, you should look into the examples for the FFT provided on my http://www.dspdimension.com pages. I am using the FFT to do pitch shifting (sic!) which involves calculating the magnintudes from the Fourier transform. Maybe this is of help. --sms> Actually, all I really need are examples showing > me how to do the above tasks I mentioned (mainly converting output of > forward FFT to magnitude, after using a windowing function).

Reply by ●June 27, 20032003-06-27

"David Chen" <david_c11@yahoo.com> wrote in message news:qvLKa.4$BS4.2700474@newssvr21.news.prodigy.com...> Hi, > > I'm currently a 17-year-old student trying to do a project, involving > embedding data within an audio file. Hopefully, it will survive MP3 > compression... so I've come to the conclusion I will have to convert allthe> samples to the freq. domain to do any analysis. > > I downloaded FFTW and I have it working, but it assumes that the userknows> what he's doing (which I do not really). > > I found this software kit at http://www.eobj.com/eofft-dll.html that would > be perfect, except it costs $60... Basically, it will calculate forwardand> inverse FFT and can add extra output tasks such as different windowing > functions, converting output of forward FFT to magnitude (dB) or power. > > Is there any software kit (preferably in C/C++ or Java) for free that can > provide similar features? Actually, all I really need are examples showing > me how to do the above tasks I mentioned (mainly converting output of > forward FFT to magnitude, after using a windowing function).Take a look at Cool Edit. Not exactly what you've asked for but could be useful in some situations. You can adjust the sample values manually with a mouse or external to the program as a file manipulation. Fred

Reply by ●July 9, 20032003-07-09

I'm not sure what you are trying to do though it sounds like you are attempting to fingerprint recordings. Designing signals that survive conversion to MP3 requires an expert understanding of the conversion process and only indirectly would be helped by understanding frequency analysis. If you have a real signal organized as single or double precision real data, you can fill a buffer of length N and compute the FFT using the rfftw series of functions. The output of rfftw is complex organized as follows: Real (0) DC Real frequency (1) Real frequency (2) . Real frequency (N) Nyquist frequency Imaginary frequency (N-1) Imaginary frequency (N-2) .. Imaginary frequency (1) The magnitude at a frequency I is mangitude(I) = sqrt(Real(I) * Real(I) + Imaginary(I) * Imaginary(I)) QED Windowing may be done in the time domain by multiplying the input series by the window function on a point by point basis or in the frequency domain by convolution. It is generally easier to window in the time domain. The Harris paper on windowing mentioned in the comp.dsp FAQ is a good starting point on the subject of windowing. In fact, the comp.dsp FAQ is a good starting point for any question you might want to ask in this group. In article <qvLKa.4$BS4.2700474@newssvr21.news.prodigy.com>, "David Chen" <david_c11@yahoo.com> wrote:>Hi, > >I'm currently a 17-year-old student trying to do a project, involving >embedding data within an audio file. Hopefully, it will survive MP3 >compression... so I've come to the conclusion I will have to convert all the >samples to the freq. domain to do any analysis. > >I downloaded FFTW and I have it working, but it assumes that the user knows >what he's doing (which I do not really). > >I found this software kit at http://www.eobj.com/eofft-dll.html that would >be perfect, except it costs $60... Basically, it will calculate forward and >inverse FFT and can add extra output tasks such as different windowing >functions, converting output of forward FFT to magnitude (dB) or power. > >Is there any software kit (preferably in C/C++ or Java) for free that can >provide similar features? Actually, all I really need are examples showing >me how to do the above tasks I mentioned (mainly converting output of >forward FFT to magnitude, after using a windowing function). > > >Thanks. > > >David Chen > > >

Reply by ●July 10, 20032003-07-10

"David Chen" <david_c11@yahoo.com> wrote in message news:<qvLKa.4$BS4.2700474@newssvr21.news.prodigy.com>...> Hi, > > I'm currently a 17-year-old student trying to do a project, involving > embedding data within an audio file. Hopefully, it will survive MP3 > compression... so I've come to the conclusion I will have to convert all the > samples to the freq. domain to do any analysis. > > I downloaded FFTW and I have it working, but it assumes that the user knows > what he's doing (which I do not really). > > I found this software kit at http://www.eobj.com/eofft-dll.html that would > be perfect, except it costs $60... Basically, it will calculate forward and > inverse FFT and can add extra output tasks such as different windowing > functions, converting output of forward FFT to magnitude (dB) or power. > > Is there any software kit (preferably in C/C++ or Java) for free that can > provide similar features? Actually, all I really need are examples showing > me how to do the above tasks I mentioned (mainly converting output of > forward FFT to magnitude, after using a windowing function). > > > Thanks. > > > David ChenHi David u may want to try the software called Autosignal. U can download the trial version for free from the web. just search for it in google. -Nithin