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Discussion Groups | Analog Devices DSPs | AW: AW: Reg...guitar tuner design...

Technical discussions related to Analog Devices DSPs (including Blackfin, TigerSHARC, SHARC and ADSP-21xx DSPs).

  

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AW: AW: Reg...guitar tuner design... - Bernhard Holzmayer - Oct 6 6:38:00 2004




> -----Ursprüngliche Nachricht-----
> Von: Jon Harris [SMTP:]
> Gesendet am: Dienstag, 5. Oktober 2004 21:07
> An: Bernhard Holzmayer; 'ayyam perumal';
> Betreff: Re: AW: [adsp] Reg...guitar tuner design... > >
> > Or, just evaluate the FFT of the signal, average it and find the
> > position of highest energy.
> >
> > Bernhard
>
> The main methods out there seem to be FFT, zero-crossing, and PLL.
> Here is a link that describes a zero-crossing method that is a
> bit smarter to try to deal with the overtone problem:
> http://www.xilinx.com/bvdocs/appnotes/xapp366.pdf
>
> I think the FFT method could work, though quite a large amount of
> processing power could be required for good accuracy on low frequencies. Hi Jon,
what about this?

Do a first FFT to roughly detect the tone range.
Then downsample the signal with an appropriate factor.

Another FFT at that new sampling rate should now provide a result,
where the accuracy is almost independent of the tone's frequency.

The accuracy should be comparable to that of a FFT at original rate
with the FFT length multiplied by the downsampling factor.

Bernhard





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