I have never tried autotune. I gather from what you wrote that it can be used in realtime? It sounds a bit like the whammy pedal for a guitar to me, because the sound is altered. I always thought the signal was split in two parts, one used to analyse the spectrum, and one to analyse the pitch. In this model the pitch would be modified according to some rules and the timbre would be stamped back on it. That's what it sounds like to me, but i may be mistaken to a great extent.

Pierre

2010/8/17 martin brinkmann <mnb@martin-brinkmann.de>
On 08/16/2010 06:21 PM, Pierre Massat wrote:
> Hi,
>
> I've been thinking of writing a pd version of autotune, but before i get
> started i m wondering if anybody as ever tried doing this?

not in pd, but in reaktor and c. combining pitch-detection and a
pitchshifter (and some quantization) works quite well, and should
be not too hard to do in pd (fiddle and the pitchshifter from
the docs).
though this is quite good for subtle pitch correction, it does
not create the typical, metallic, vocoder-like "cher-effect".

maybe something like taking single-cycle-samples of the input,
when a constant pitch  is detected, and playing these instead
of the original audio would do better, but i have not tried
yet. (and i think detecting zero-crossings in pd (vanilla) is
rather difficult...)

> I m assuming
> they're making a ton of money selling it, so there 's probably not much
> information available as to how it actually works, but i guess Miller
> Puckette's Phase vocoder example could be a good starting point.

i do not think that autotune uses fft-based methods,
since it has very little latency (and does not need too much cpu).

bis denn!
       martin

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