Patent ID: 8019598

Claim:
A method of converting an input digital audio signal into an output digital audio signal having a modified time scale comprising the steps of: receiving input digital audio data having a first time scale; calculating a discrete Fourier transform of first equally spaced, overlapping time windows having a first overlap amount of the input digital audio signal; partitioning the spectrum into a plurality of contiguous spectral bands according to a Bark scale where each spectral band has an extent dependent upon human frequency perception; identifying a dominant spectral line having the greatest magnitude within each spectral band; calculating a phase difference for the dominant spectral line of each spectral band by a phase vocoder algorithm; calculating a phase difference for each of a predetermined number of spectral lines near the dominant spectral line within each spectral band as the phase difference of the corresponding dominant spectral line; calculating a phase difference for other spectral lines of each spectral band by the phase vocoder algorithm; calculating an inverse discrete Fourier transform resulting in equally spaced, overlapping time windows having a second overlap amount employing the calculated phase difference for each spectral line thereby producing the output digital audio signal, the second overlap selected having a ratio to the first overlap amount to achieve a desired time scale modification; and converting the output digital audio signal into sound having a second time scale according to the desired time scale modification.