Short-Time Fourier Transform

Short-Time Fourier Transform (STFT) is a time-frequency analysis tool that repeatedly applies the Discrete Fourier Transform (DFT or FFT) to windowings of short snippets of a longer signal. It is equivalently convolutions with windowed complex sinusoids, or bandpass filtering, where the "hop" parameter is the stride or subsampling factor. It's a function of two independent variables: frequency in the DFT, and time of the center of the sliding window.