[CM] Stereo and time stretch HQ

Bill Schottstaedt bil@ccrma.Stanford.EDU
Thu, 06 May 2004 04:06:44 -0700

 > 2) I'm looking for a good algorithm for time stretching and pitching the sound with a High Quality.

There are three, but each has problems.  I would try the granular
synthesis approach first (the "expand" control); there are
functions to separate the pitch shift from the time stretch --
expsrc, expsnd, etc.  Then I'd try rubber-sound in rubber.scm --
it looks for stable portions of a sound and tries to add or
delete periods until the desired time stretch is reached, but
it's not robust (and it's very slow).  As a last resort, try
the phase vocoder -- some people claim it works.  On the pitch
shift side -- use src (the sample-rate-change generator), src-sound, etc.