Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!cs.utexas.edu!uunet!zephyr.ens.tek.com!orca!ka7axd.wv.tek.com 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> Sender: news@orca.WV.TEK.COM Reply-To: mhorne@ka7axd.wv.tek.com Organization: Horne's Happy Home of Heavy Hacking Lines: 14 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