[b0dhi]

Anyone know of software that can do a spectrum analysis on a signal in very short repetitive time windows? What I'm trying to do is like this:

...except I wanna be able to catch changes within every cycle of a, say, 1300Hz signal, and observe the changes in detail.

 

[Publius]

You look like a smart young chap. Write it yourself.

YA RLY! It's a specialized enough analysis that you might be looking at a rather large chunk of change to find an app to do it. Instead, brush up on your signal processing skillz and learn Octave.

 

[b0dhi]

Ugh looks like I may have to. Turns out that what I'm after is a STFT (short-time fourier transform) or Spectrograph, except the display is just a regular 2D frequency/amplitude plot but with a scrollbar to travel back or forward in time. How can no one have done something like this before >_<

 

[deltaydeltax]

Have you looked at TrueRTA?

http:///www.trueaudio.com

 

[b0dhi]

Yea, looked at that and about a dozen others. There are a few that do realtime analysis but not to the degree that I'm after unfortunately.

I'm in the process of writing one myself atm. Most of it is re-writing what 99% of analysis software already does, but adding time-domain controls. Luckily I can get most of the processing done with stuff others have already built, like graphing, FFT, etc. The only thing I've had to write myself so far is the wav file decoder.

On another note, if anyone knows how to get Exocortex DSP to do a 1D FFT without crashing, PM me...

 

[asebastian0]

Write it in MATLAB. Easy enough if you use the signal processing toolkit as a jumping off point. There are also a ton of specialized MATLAB apps written by various people that can be modified for your specific needs.

Ugh.. seems like you are already started. Need to finish the thread before I start a post!

 

[b0dhi]

Bout half way through atm. Waveform and spectrum views are working. Just gotta program the windowing function and then the time travel scrollbar and it's time to get the electret microphone and take some measurements

 

[deltaydeltax]

Did you polish off your spectrum analyzer? How did it come out?

 

[b0dhi]

Wouldn't call it "polished" by any stretch of the imagination, but it works well for what I need it for.

Feel free if you want to have a play with it: http://members.iinet.net.au/~harargh...eDomainFFT.zip

The textbox on the right is the sample offset from beginning. It crashes if you slide all the way to the right. It only supports stereo WAV files. Also, the output is not normalised. It's just good for comparing files.