fft and zero pad
Hi list,
I have a question concerning the choice of a window during analysis and the zero-pad.
Why increasing the window size with zeroes instead of, more simply,
increasing the window size (without append zeroes)?
I think a window size of 8 samples + 8 zeroes is not much more different than a
16 samples window size which have not zeroes. The only difference between these
two windows should be that a 16 sample window size without
zeroes contains more signal than the one with the same size containing zeroes.
So, a 16 samples window containing only signal without zeroes should be
better than a 16 samples signal containings 8 sample + 8 zeroes.
So, I don't understand why this zero-padding technique is so useful.
I hope someone could help me.
Best
fv
An easy point of confusion is the difference between FFT size and Window Size (which are fixed to be the same in pfft~ I believe).
You are right that you would not want to pad your window with zeros, but often you may want to have a smaller window size than FFT size (so you can analyze small chuncks at a time, but sill use a large FFT). For example, if you were using an FFT size of 2048 and a window size of 1024, the last 1024 samples of your FFT would be zero padded.