Re: stretch time, keeping pitch
Re: stretch time, keeping pitch
- Subject: Re: stretch time, keeping pitch
- From: Jose Commins <email@hidden>
- Date: Tue, 30 Nov 2004 21:08:43 +0000
Two methods are popular, one being FFT as you mentioned and the other
granular synthesis.
With the FFT method, you convert your time-domain sound to
frequencies; as an example, if we stretch it in time by x2, which
lowers the pitch accordingly, then adjust the pitch up in your FFT data
and then convert it back to a time domain sample.
With granular synthesis, you have a buffer which holds as small a
time-domain sample as it can, down to one cycle is ideal, then repeat
until you have to move onto your next cycle in the full sample. This
method, although faster by far, requires some well-judged merging
between one cycle and the next.
Regards,
Jose.
--
Arguing with an engineer is like wrestling with a pig in mud.
After a while, you realize the pig is enjoying it.
On 30 Nov 2004, at 20:04, Michael Hanna wrote:
Hi, my app loads a sound via NSSound and manipulates it via Quicktime.
I'd like to take a subregion of the sound/movie and play it back
slowly, but keeping pitch like the original.
First of all, is it possible to get a 'subregion' or piece of the
sound? I'd imagine that's a Quicktime call? From the light research
I've done on this, does this sound have to have 1:1 frame/packet
ratio(such as wav or aiff) in order to properly apply the dsp
technique? Do I apply a FFT for this.. not sure where to start on this.
regards,
Michael
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