[no subject]

[tothl@xxxxxxxxxxxxxxx]

>From tothl Tue Jun 22 10:13:05 +0200 1999 remote from inf.u-szeged.hu
Date: Tue, 22 Jun 1999 10:13:05 +0200 (MET DST)
From: Toth Laszlo <tothl@inf.u-szeged.hu>
X-Sender: tothl@csilla
To: auditory@lists.mcgill.ca
Subject: Re: Cepstrum computation
In-Reply-To: <4.1.19990621105041.00a58450@ricochet.net>
Message-ID: <Pine.SV4.3.91.990622100611.7290B-100000@csilla>
MIME-Version: 1.0
Received: from inf.u-szeged.hu by inf.u-szeged.hu; Tue, 22 Jun 1999 10:13 MET
Content-Type: TEXT/PLAIN; charset=US-ASCII
Content-Length: 1102

On Mon, 21 Jun 1999, Richard F. Lyon wrote:

> >                          C(t)=|| FFT( log( ||FFT(x)|| ) ) ||
> >
> >My question is: what happens when ||FFT(x)||=0 for some x?
> >Then we have to compute log(0), which is undefined (as we all know).
> >
> Yes, isn't it ridiculous that people sort of define things part way
> and then pretend they're OK?
>
Yes, ridiculous indeed. A mathematician would definitely add a comment like
"and if ||FFT(x)||=0 then ...".
When I wrote my first cepstrum code it took me many hours to figure out
why I get black lines in my images...
My solution was an if:

if(||FFT(x)||==0) { y=-BigNumber}
else {y=log(||FFT(x)||)

Where "BigNumber" is some big constant. Yes, it's terrible, but what could
have I done?

               Laszlo Toth
        Hungarian Academy of Sciences         *   "Military intelligence:
  Research Group on Artificial Intelligence   *    two words combined that
     e-mail: tothl@inf.u-szeged.hu            *    can't make sense"
     http://www.inf.u-szeged.hu/~tothl        *