Time-Scale Modification Using a WOLA Phase Vocoder

[Note that much of this section is still in the form of terse ``bulleted lists'' intended for overhead projection in class. I.e., the book version remains ``under construction''.]

1. Perform a short-time Fourier transform (STFT) using hop size .

2. To slow down by the factor , resynthesize using hop size , creating the new spectral frames by interpolating the original STFT.
   • Spectral magnitude may be interpolated in a straightforward manner (e.g., using linear interpolation of nearest adjacent spectral frames).

   • Spectral phase is tricky, since there's no exact way to do it.

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written by Julius Orion Smith III
Julius Smith's background is in electrical engineering (BS Rice 1975, PhD Stanford 1983). He is presently Professor of Music and Associate Professor (by courtesy) of Electrical Engineering at Stanford's Center for Computer Research in Music and Acoustics (CCRMA), teaching courses and pursuing research related to signal processing applied to music and audio systems. See http://ccrma.stanford.edu/~jos/ for details.