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From: hvs@ee.upenn.edu (H.V. Sorensen)
Newsgroups: comp.dsp
Subject: Re: Hartley transforms
Keywords: transforms, Hartley, Fourier, FFT, FHT
Message-ID: <27843@netnews.upenn.edu>
Date: 5 Aug 90 14:58:06 GMT
References: <9711@life.ai.mit.edu>
Sender: news@netnews.upenn.edu
Reply-To: hvs@ee.upenn.edu (H.V. Sorensen)
Organization: University of Pennsylvania
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>tmb@wheaties.ai.mit.edu (Thomas M. Breuel) writes

>Also, does anyone have code for the FHT (C/Fortran)? Currently, I am
>using a REALFFT routine and re-arrange the output, which is probably
>not very inefficient, but not quite as fast as it could be.  Have the
>patent issues involving the FHT been resolved?

I am glad to see you solved your own problem, but will have to
dissapooint you. If you are interested in speed, you should stick with
the real-input FFTs. It has been shown several places, that the Hartley
transform requires more arithmetic operations than the real-input FFT.
(The number of multiplications are the same, while the number of
additions are N-2 more for the Hartley transform, where N is the
transform length).

Hope this helps you,   Henrik Sorensen

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*   Henrik Sorensen               Department of Electrical Enginering        *
*   Internet: hvs@ee.upenn.edu    University of Pennsylvania                 *
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