Re: Spectragrams and stft's, oh my

[Peter Søndergaard]

You can also download the Linear Time Frequency Analysis toolbox, 

http://www.univie.ac.at/nuhag-php/ltfat/

it works in both Octave and Matlab.

It is still in development, but if there is something you can figure out
(or does not work as expected) you are more than welcome to send me an
email.

In the toolbox, the spectrogram is called "spectrogram" :-). In Octave,
the spectrogram looks much better if you call "colormap(jet)" before
invoking the spectrogram.

The short time Fourier transform is called "dgt" and its inverse is
"idgt".

There is online help avaliable here:

http://www.univie.ac.at/nuhag-php/ltfat/doc/m/Contents.php

Cheers,

Peter.

tir, 30 05 2006 kl. 03:38 -0700, skrev Rich E:
> I'm taking a class on computer music that is based on Matlab, and I'm
> trying to do everything in Octave.  It's been tough because we start
> in a new language with digital signal processing.  I know matlab to an
> ok degree, but I hate it and its memory problems.  But, the functions
> don't seem to operate the same, so I was wondering if anyone could
> point me towards any tutorials that use spectragrams and stft
> manipulations in octave. 
> 
> My biggest problem, other than syntax, is getting the imagesc()  to
> make something that is worth looking at.  The example in the
> specgram.m comments works fine, but everything I try to do on my own
> produces 2 images; one that is really zoomed in, and another tiny one
> that controls the zoomed in one.  Not that useful because I can't get
> an overall look of the spectragram.  
> 
> 
> So here is what I attempted without specgram.  Don't know why it won't
> work.
> 
> x is 3 seconds long at 44k sr
> wx = 512, hopx = 128, nfft = wx;
> 
> [ X,xc] = stft(x,wx,hopx,nfft);
> 
> If I try imagesc(log(abs(X)+ eps));  I get errors that don't tell me
> much, other than this is not how to do it.  But, this is how it is
> done in matlab. 
> 
> Any guidance is appreciated.
> Regards,
> Richie
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