From: rlk@underprize.think.com (Robert Krawitz)
Newsgroups: alt.atheism
Subject: Re: Chaotic brain behaviour and its influence on duplicating a perso
Date: 15 Nov 92 20:17:49
Organization: Thinking Machines Corporation, Cambridge Mass., USA
	<3g50TB4w165w@mantis.co.uk> <1992Nov15.170101.20546@doug.cae.wisc.edu>
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In-reply-to: mccullou@cae.wisc.edu's message of 15 Nov 92 17:01:00 CST

This is a bit off the subject, but...

In article <1992Nov15.170101.20546@doug.cae.wisc.edu> mccullou@cae.wisc.edu (Mark McCullough) writes:

   Few things.  1.  It is not the human genome that dictates what you remember.
   Two, I know people who remember all the music from several pieces of music
   that fill up a CD.  A CD contains 1 gigabyte.

They do not remember all the bits that make up that music, though; they
remember "the music" in a highly compressed form.  A conductor may
actually have memorized a large number of the notes in a score, but this
is still a lot less information than the raw number of bits on the CD.
With most music, there are harmonic relationships between various notes
that reduce the amount of information needed; there are also time
relationships (e. g. the first violins are playing a melody, but the
second violins and violas are playing C and E tremolo for 8 bars).
Second generation digital audio techniques (e. g. those used in digital
compact cassettes) use compression techniques that reduce the
information needed tremendously, yet they don't even begin to attain the
amount of compression possible (just look at a musical score to see what
I mean -- sure, it can be complex, but it certainly doesn't require a
gigabyte of storage).  The score, plus a relatively small amount of
information (small changes in the tempo here and there, a particularly
rich string sound, etc.) contains all the information that anyone can
hear about a piece of music, which is a lot less than that same piece of
music sampled digitally 44,100 times/second at 16 bits.
						  
						  For those who don't know
   computer jargon, a byte is a character.  giga normally means billion, but
   not here.  Here, it means 2^30.  That is somewhat more than a billion.
   That translates to 1073741824 characters, or about 214748364.8 words (at
   five characters per word.)  This seems like a tremendous amount, but how
   much memory does it take to represent visual images?  Lots.

Not so.  Once again, there are image compression techniques that can
achieve remarkable reductions in storage needs.  There was a fractal
based technique that I read about a few years ago (don't have the
reference handy; it may have been in Scientific American) that could
reduce storage needs by a factor of 10,000 in some (non-trivial) cases.
As far as I know, the company that invented this is still in business.
There are industry groups (JPEG and MPEG for still and motion pictures,
respectively) that are working on techniques to reduce storage needs
tremendously.  Many of these techniques are actually lossy (they lose
information) but they're designed to lose the information which people
don't remember anyhow.

Several years ago, as part of an internal demonstration, I wrote a
program to Fourier transform an image, and display the image and its
transform, along with the original image and its transform, on a screen.
The program had simple filtering capabilities.  For a while I thought my
program had a bug in it, because I could remove a remarkable amount of
high frequency information without visibly degrading the picture.  I had
to look very closely to determine that in fact the image was changing
when I filtered it.  This wasn't even intended as a compression
technique, merely as another way to analyze an image.
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