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Luca
Posts:
77
Registered:
6/6/12


Spectrogram: nfft vs. window. How's that??
Posted:
Mar 15, 2013 9:34 AM


I admit from the beginning that I do not have so much knowledge about stft and the topic. But anyway I need a "quick and dirty" spectrogram of a signal, and there's something I do not get. The parameters are : spectrogram (x,window,noverlap,nfft,.....); Now... What's the difference between window and nfft and how (therefore) am I supposed to set these two parameter? It seems pretty obvious to me that they are dependent. Arent't they?
I quote from the doc: "window is a Hamming window of length nfft." "nfft is the FFT length and is the maximum of 256 or the next power of 2 greater than the length of each segment of x. Instead of nfft, you can specify a vector of frequencies, F. See below for more information."
Why should I specify "window" then? And would it make sens to set it to anything different from fft?
Can anybody shed some light on it? And BTW... does anybody has a rule of thum on how to set these parameters in a "kinda optimal way" (depending on what I want to analyze)



