US 6,982,377 B2
Time-scale modification of music signals based on polyphase filterbanks and constrained time-domain processing
Atsuhiro Sakurai, Tsukuba (Japan); Steven Trautmann, Ibaraki (Japan); and Daniel L. Zelazo, Shibuya-ku (Japan)
Assigned to Texas Instruments Incorporated, Dallas, Tex. (US)
Filed on Dec. 18, 2003, as Appl. No. 10/739,632.
Prior Publication US 2005/0132870 A1, Jun. 23, 2005
Int. Cl. G10H 5/00 (2006.01)
U.S. Cl. 84—654 12 Claims
OG exemplary drawing
 
1. A method of time-scale modification of a digital audio signal comprising the steps of:
separating the digital audio signal into a plurality of frequency bands;
detecting the energy in each frequency band;
determining the frequency band having the highest energy;
separately time-scale modifying each of the plurality of frequency bands producing corresponding time-scale modified frequency band signals by
analyzing each frequency band in a set of first equally spaced, overlapping time windows having a first overlap amount Sa,
selecting a base overlap Ss for output synthesis corresponding to a desired time scale modification,
calculating a measure of similarity between overlapping frames of the frequency band having the highest energy for a range of overlaps between Ss+kmin to Ss+kmax of the single audio signal, where kmin is a minimum overlap deviation and kmax is a maximum overlap deviation,
determining an overlap deviation km yielding the largest measure of similarity for the frequency band having the highest energy,
calculating a measure of similarity between overlapping frames of frequency bands other than the highest energy frequency band for a range of overlaps around km smaller than the range between Ss+kmin to Ss+kmax,
determining an overlap deviation ki yielding the largest measure of similarity for each frequency band other than having the highest energy frequency band,
synthesizing an output signal for each frequency band in a set of second equally spaced, overlapping time windows having the corresponding determined overlap amount; and
combining the separate time-scale modified frequency band signals.