PSOLA (Pitch Synchronous Overlap and Add) is a digital
signal processing
Signal processing is an electrical engineering subfield that focuses on analyzing, modifying and synthesizing ''signals'', such as sound, images, and scientific measurements. Signal processing techniques are used to optimize transmissions, ...
technique used for
speech processing
Speech processing is the study of speech signals and the processing methods of signals. The signals are usually processed in a digital representation, so speech processing can be regarded as a special case of digital signal processing, applied t ...
and more specifically
speech synthesis. It can be used to modify the
pitch and
duration of a speech signal. It was invented around 1986.
PSOLA works by dividing the speech waveform in small overlapping segments. To change the pitch of the signal, the segments are moved further apart (to decrease the pitch) or closer together (to increase the pitch). To change the duration of the signal, the segments are then repeated multiple times (to increase the duration) or some are eliminated (to decrease the duration). The segments are then combined using the
overlap add
Overlap may refer to:
* In set theory, an overlap of elements shared between sets is called an intersection (set theory), intersection, as in a Venn diagram.
* In music theory, overlap is a synonym for reinterpretation of a chord at the boundary o ...
technique.
PSOLA can be used to change the
prosody of a speech signal.
See also
*
Audio time stretching and pitch scaling
Time stretching is the process of changing the speed or duration of an audio signal without affecting its pitch. Pitch scaling is the opposite: the process of changing the pitch without affecting the speed. Pitch shift is pitch scaling implement ...
References
External links
Changing Pitch with PSOLA for Voice ConversionA thesis that discusses PSOLA with diagrams
(PDF format; see page 35, which is page 44 of the PDF)
Speech synthesis
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