Subject: Re: [linux-audio-user] Pitch shifting
From: Steve Harris (S.W.Harris_AT_ecs.soton.ac.uk)
Date: Mon Jan 28 2002 - 17:42:04 EET
On Mon, Jan 28, 2002 at 10:15:12 -0500, Dave Phillips wrote:
> Steve Harris wrote:
>
> > ...pitch_scale_1194.so, the quality is OK. The interface is frequency
> > ratios, it is easy to translate, but depends on what scale you are using.
> >
> > That's probably a good entry for the docs.
>
> Steve, what would be the best way to scale a Motif slider for that
> plugin ? I made one that goes from .50 to 2.00 on a linear scale, should
> I do it differently ?
Maybe. Its common to think of pitch shifting in octaves/semitones, so a
+-12 semitone scale might be better. You could probably assume equal
temprement:
s = 2**(p/12) [s = pow(2.0f, p * 0.0833333333f); in c]
where s is the scale coefficent and p is the pitch shift in semitones.
Ofcourse I could make the LADSPA interface semitones if people preferred.
I was thinking more of an SL2's +-n% when I wrote it.
- Steve
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