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I cant figure out why our output image is 257 * 32 , 32 I know why , but 257 I cant understand ? this is the exact word of this paper wich applied STFT on 3 channel of eeg signal :

Short time Fourier transform (STFT) was applied on the time series for each 2 s long trial. In case of 250 Hz signal this is corresponding to 500 samples. STFT was performed with window size equal to 64 and time lapses equal to 14. Starting from sample 1 toward sample 500, STFT is computed for 32 windows over 498 samples and the last 2 samples, remaining at the end, are simply ignored. This leads to a 257 × 32 image where 257 and 32 are the number of samples along the frequency and time axes respectively.

I really really appreciated if anyone could explain it to me

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  • $\begingroup$ There must be a mistake. 257 points to a window length of 512 with the spectrum being one sided. $\endgroup$ – Max Mar 22 '18 at 13:02
  • $\begingroup$ Overlap window. $\endgroup$ – Creator Mar 22 '18 at 22:50

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