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From: mhorne@ka7axd.wv.tek.com (Michael T.Horne)
Newsgroups: comp.dsp
Subject: Re: FFT / FHT (was Re: Adjust-Speed CD player?)
Message-ID: <4755@orca.WV.TEK.COM>
Date: 29 Sep 89 08:33:22 GMT
References: <698@lakart.UUCP>
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Organization: Horne's Happy Home of Heavy Hacking
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In a recent article by David Goodenough:
> ...But does anyone know anything of FHT - the Fast Hartley Transform, which
> is supposed to do the same job as the FFT, but in about 1/2 the time?

The FHT is an interesting transform, saving you computation time by reducing
the time to compute the DFT kernel (by avoiding a complex multiply/sum).
However, there are techniques available for reducing the computation time for
a normal FFT down to that of the FHT, such as (for real data sets) transforming
two data sets of size N using a single N-point FFT, transforming a data set of
size N using an N/2-point FFT, etc.  In short, FFT techniques are available
that minimize the purported computation-time advantage of the FHT.

Mike