enkitec@gmail.com wrote:
> On 30-Mar-10 10:51, Dave Tweed wrote:
> > I would also point out that in a tone-detection application, in which you
> > only care about magnitude and not about phase, the low-pass filtering
> > doesn't need to be a separate step. Instead of an IIR low-pass filter at
> > the output, you can create an implicit FIR low-pass filter by applying a
> > "window" function directly to the sine/cosine coefficients. Essentially,
> > what you then have is a pair of narrow quadrature-phase bandpass filters
> > for each frequency, and you're measuring the magnitude of their combined
> > outputs (sum of squares).
> 
> Isn't Goertzel algorithm like that?

No, not really.

The Goertzel algorithm converts a one-bin nonrecursive DFT calculation
into an equivalent recursive form (requiring much less data storage and very
few CPU cycles per sample) that comes up with the same answer. As a result,
it cannot be implemented as a sliding-window version.

-- Dave Tweed
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