[sdiy] OT:Running stand alone autotune

[Richie Burnett]

Do you mean Vocal Autotune like used on Cher's song "Believe" (and countless 
others since!)?  Or something to automatically tune an instrument before a 
performance, more like a guitar tuner?

Real-time autotune of an audio input is very computationally intensive 
because it uses an algorithm called Autocorrelation (or AMDF) to determine 
the actual pitch of the audio input.  Only then can it can calculate the 
pitch error and finally shift the incoming audio to the nearest correct 
pitch on whatever scale it's set to work with.  The original patent in 
Harold Hildebrand's name is available on the net and gives an overview of 
Antares Autotune operation, but many of the details are glossed over as you 
might expect in a disclosure like this.

Autocorrelation is something that DSPs really excel at, so I'd be surprised 
if you could get real-time autotune to run on a Raspberry Pi without needing 
a lot of in-depth assembly optimisation of SIMD instructions or whatever the 
equivalent is on an R-Pi.  I think the original Autotune patent might have 
expired now, as there seem to be a lot of copycat autotune pedals on the 
market now from companies like Digitech, Electroharmonix, Eventide, etc. 
Your best bet would almost certainly be to purchase one of these!

-Richie,



-----Original Message----- 
From: Joe Frey
Sent: Tuesday, April 14, 2015 3:53 PM
To: Synth-diy at dropmix.xs4all.nl
Subject: [sdiy] OT:Running stand alone autotune

Hello, Is there someone on the list that would give me some advice on
running a stand alone autotune in a box for live performances. Maybe on
Raspberry Pi or something? Thanks. I really don't want to use a big
computer and a daw. Is this do-able? Is there another different way?

-- 
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"Anything worth doing, is worth doing badly, because it might make it better 
the next time." --anon

Joe Frey
A.K.A. Bitter Relic of a Bygone Era
joe.frey at radioles.com
http://radioles.com
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