I would like to detect the change of the frequency content through a real signal using sliding window as shown in following figure.
Fixed size sliding window on a signal
However, applying fourier transform is costly for windowing operations. For example, at the above case assume window size is 50 samples; I need to calculate fourier transform 950 times. I wonder is there any mathematical workaround to shorten the calculation time.
I would really be happy if I gain some calculation time. Thanks in advance!