NOTE: THIS DOCUMENT IS OBSOLETE, PLEASE CHECK THE NEW VERSION: "Mathematics of the Discrete Fourier Transform (DFT), with Audio Applications --- Second Edition", by Julius O. Smith III, W3K Publishing, 2007, ISBN 978-0-9745607-4-8. - Copyright © 2017-09-28 by Julius O. Smith III - Center for Computer Research in Music and Acoustics (CCRMA), Stanford University
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Stretch OperatorUnlike all previous operators, the
operator maps a length
signal to a length
signal, where
and
are integers. We use ''
'' instead of ''
'' as the time index to underscore this fact.
Definition: A stretch by factoris defined by
Thus, to stretch a signal by the factor, insert
zeros between each pair of samples. An example of a stretch by factor three is shown in Fig. 8.4. The example is
The stretch operator is used to describe and analyze upsampling, i.e., increasing the sampling rate by an integer factor.