The Time-Frequency Toolbox (TFTB) is a collection of about 100 scripts for GNU Octave and Matlab (R) developed for the analysis of non-stationary signals using time-frequency distributions. It is primary intended for researchers and engineers with some basic knowledge in signal processing.
The toolbox contains numerous algorithms performing time-frequency analysis with a special emphasis on quadratic energy distributions of the Cohen and affine classes, and their version enhanced by the reassignment method. The toolbox also includes signal generation procedures and processing/post-processing routines (with display utilities).
Important note for GNU Octave users'
The TFTB includes a Graphical User Interface for adjusting the layout of the time-frequency plots. This GUI is currently not supported by GNU Octave (version 2.70). This is linked to several limitations in GNU Octave graphics. GNU Octave's development team is preparing a major release (upcoming version 3) which will much improve the graphical functionalities. We expect that this will allow us to design a GUI working with GNU Octave as well.
As of today, the scripts for TFR computations and signal generations are expected to be fully compatible with GNU Octave, but the user has to write a few lines of codes to produce the time-frequency plots.
- Example
%% generate signal
fs=100; % Hz
N=128;
x=fmlin(N);
%% define time and frequency axes
t=1:N;
Nf=N;
f=(0:Nf/2)/Nf;
%% compute spectrogram
tfr=tfrsp(x,t,Nf);
%% select positive frequencies
tfr=tfr(1:Nf/2+1,:);
%% make image plots
colormap(jet);
imagesc(t/fs,fs*f,flipud(tfr));
%% make contour plots
contour(t/fs,fs*f,tfr);
axis('xy');