UC San Diego

This research describes and implements new techniques for objective analysis and comparison of common time stretching algorithms. A set of test signals and samples is used in conjunction with spectral analysis to generate objective error measurements and subsequent comparisons of the algorithms. The time stretching techniques are treated as black-box processes, and are regarded as members within a general family of analyze-modify- resynthesize algorithms. This black-box approach of output signal analysis provides a basis for objective evaluation of the more general class of algorithms. Six common time stretching algorithms are analyzed: the Classic Phase Vocoder, Oscillator Bank Phase Vocoder, Peak Tracking Phase Vocoder, Phase-Locked Vocoder, Synchronous Overlap Add technique, and Overlap Add technique. The six algorithms are then compared within a uniform framework to provide greater insight regarding the behavior of their output signals. Subjective listening evaluations are also performed, then all results contribute to the development of criteria that evaluate and rank the algorithms⁰́₉ suitability in various signal processing situations