NONPARAMETRIC TECHNIQUES FOR PITCH-SCALE AND TIME-SCALE MODIFICATION OF SPEECH

Time-scale and, to a lesser extent, pitch-scale modifications of speec h and audio signals are the subject of major theoretical and practical interest. Applications are numerous, including, to name but a few, te xt-to-speech synthesis (based on acoustical unit concatenation), trans formation of voice characteristics, foreign language learning but also audio monitoring or film/soundtrack post-synchronization. To fulfill the need for high-quality time and pitch-sealing, a number of algorith ms have been proposed recently, along with their real-time implementat ion, sometimes for very inexpensive hardware. It appears that most of these algorithms can be viewed as slight variations of a small number of basic schemes. This contribution reviews frequency-domain algorithm s (phase-vocoder) and time-domain algorithms (Time-Domain Pitch-Synchr onous Overlap/Add and the like) in the same framework. More recent var iations of these schemes are also presented.