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Re: [Octal-dev] Pitch Shifter / Extracting Fourier Description
From: |
Davíð B Franzson |
Subject: |
Re: [Octal-dev] Pitch Shifter / Extracting Fourier Description |
Date: |
Tue, 16 May 2000 16:28:57 +0100 |
There is some analysis method called LPC (f i remember it correctly) but it
is waaayayayyyy to slow to use in software on a resonable computer ( needs
some gHz to work) Maybe we can use it in octal y3k
----- Original Message -----
From: <address@hidden>
To: <address@hidden>
Sent: 16. maí 2000 17:11
Subject: [Octal-dev] Pitch Shifter / Extracting Fourier Description
>
> Steve Mosher wrote:
>
> [ I have a question, does anyone know how to write a reasonable
> [ pitch-shifter? I know that pitch shifting audio data (i.e.
> [ -withoutchanging its speed/duration) is gruesome work, but it can
> [ be a good correctional component for many effects.
>
> Pitch shifting without changing the sampling rate would seem to re-
> quire an identification of the pitch as frequency and amplitude
> (Fourier description) and then changing the frequency in the sampl-
> ing generate phase (reverse Fourier transform).
>
> I have been experimenting with code to identify the complete Fourier
> description of a sample sequence. Does anyone on the list know of
> code to perform this process? Some of my observations are:
>
> (1) The Fast Fourier Transform only detects frequencies in whole
> numbered values of which useful frequencies in general are not.
> What is required is a more precise frequency detection sequence.
> The full Fourier transform can be used to more precisely analyze
> fractional ranges after the FFT identifies nearby high-amplitude
> areas.
>
> (2) The precision of frequency identification correlates to the num-
> ber of samples used. I.e., though one may address any frequency
> below half the sampling rate, the degree of distinction from
> nearby (fractional) frequencies depends on how long (how many
> samples in which) the frequency is present, and would appear to
> be an aspect fundamental to all frequency detection systems such
> as human hearing.
>
> Neil Nelson address@hidden
>
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