han `k` is returned.
If `left` is set than p_k * `hop` is returned else (p_k+1) * `hop`.

This method can be used to slice an input signal into chunks for
calculating the STFT and iSTFT incrementally.

See Also
--------
delta_t: Time increment of STFT (``hop*T``)
hop: Time increment in signal samples for sliding window.
T: Sampling interval of input signal and of the window (``1/fs``).
fs: Sampling frequency (being ``1/T``)
t: Times of STFT for an input signal with `n` samples.
ShortTimeFFT: Class this method belongs to.
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