This is a collection of Matlab files for computing time-frequency distributions or time-frequency representations. (However, if you don't have Matlab, you can try Octave or SciLab.)

These programs are either a result of my research or something that I found useful enough to spend the time to implement. Included are a rigorous implementation of time-frequency distributions (Cohen class), some quartic time-frequency distributions, chirplet decomposition based on maximum likelihood estimation, fractional Fourier transform, time-varying filtering, and other useful utilities.

The image on the right is a spectrogram of a hermite function.
x = hermite(63,15); s = spec2(x,1,64,1,2.2); ptfd(s)

Please support this project.

Screenshot

The image on the right shows example output from DiscreteTFDs. The main image is a spectrogram of a whale whistle. Below the spectrogram is the envelope of the time series and to the left of the spectrogram is spectrum in dBs. You can listen to the whale whistle.

For more examples, see the demonstration of chirplet decomposition of whale whistles.

Download

Version 0.8 is available for download at the Mathworks site.

Documentation

There is no manual, but there are several sources to obtain information about the software:

• See the Contents.m file.
• Use the "help" function in matlab.
• See the various demonstrations in the Demos directory.
• See papers I have written:
  • Shift-Covariant Time-Frequency Distributions of Discrete Signals
  • On the Existence of Disrete Wigner Distributions
  • A Function of Time, Frequency, Lag, and Doppler
  • Virtues and Vices of Quartic Time-Frequency Distributions
  • Sparse Representations with Chirplets via Maximum Likelihood Estimation