Re: Newbie and AU plugin Dev
Re: Newbie and AU plugin Dev
- Subject: Re: Newbie and AU plugin Dev
- From: philippe wicker <email@hidden>
- Date: Tue, 20 Dec 2005 10:56:02 +0100
On Dec 20, 2005, at 9:54 AM, Nimalan Nandapalan wrote:
Hi Philippe,
As i understand there are two methods of Pitch shifting - using the
Fourier transform and varients, and stretching the audio and if needed
resampling to retain length. I haven't looked down the latter path.
Incase you haven't read my first post, i'm going to use the plugin in
garageband with my guitar to make it sound like a bass guitar (and
later like a 12 string guitar). Will the stretch/squish and resample
technique work well and easily and if i do as you suggest without
resampling to retain sample length
No. These polynomial interpolation algorithms are well fitted for
sample reader applications where you can accept a change in the
playback duration of the samples as most of the time these samples
are looped at some points and reshaped by an envelope generator
(ADSR). In your case, original audio samples are coming from an
instrument that is likely to be played live, so you'll have to use an
algorithm that uses in input as much samples as it provides at
output. Be aware also of the latency added by such kind of processing.
would i end up with a really weird
effect under the apple template AU effect, or would it be more normal
?
The second one can be used with small pitch amount
Is one octave down too much ?
Putting aside noise and aliasing, these algorithms shift the spectrum
left or right and it gives really bad results on complex sounds -
such as voice or piano - as soon as the pitch amount is more than -
say - a couple of tones (a story of formant). To make your 6 strings
guitar sounds like a bass guitar needs not only to resample one
octave down but also to reshape the spectral content of the signal.
I'm not a specialist of this kind of DSP so I cannot help you more on
this particular topic. Sorry.
Thanks a lot for responding and providing the above info
DKR
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