Short-time Fourier transform for IDL
Basically a small program for personal use
Syntax:
Result = stft(input [,window overlap] [,window lengh] [,input timeline]
[,sampling] [,window_function = scalar] [,timeline = variable]
[,frequency = variable] [,/two_way] [,/inverse] [,/remove_dc])
Return Value:
STFT return a two-dimensional vector which is Short-time Fourier
transform result of input array or return a inverse STFT of input array.
Arguments:
Input:
An one-dimensional vector of original time domaim signal.
Input timeline:
The time axis corresponding to the original signal.
If not spectified or 0, the converted timeline will not be output.
Window length:
The length of window function, or the sampling length of STFT.
If not spectified, it will be preset to 512.
Window overlap:
The length of overlap part between two window function.
If not spectified, it will be preset to 256.
Sampling:
Sampling period of input signal.
If not spectified, it will be automatically determination.
Keywords:
Window_function:
0 or not spectified:Hanning
1:Rectangular
2:Hamming
3:Nuttall
Timeline:
Return timeline of the spectrogram, in julday.
Frequency:
Return frequency of the spectrogram.
Two_way:
Set this keyword to do STFT both fellow and reverse the timeline
of original data, the result will be the average of the two.
Inverse:
Set this keyword to do inverse STFT, meanwhile, other keywords and
arguments except Window overlap are no effect, and default value of
overlap will be 0.
Remove_dc:
Remove the DC component of the input waveform.