To: WSFAlist at KeithLynch.net
Date: Sat, 23 Dec 2006 01:13:59 -0500
Subject: [WSFA] Data processing by the human brain (was: modems)
From: ronkean at juno.com
Reply-To: WSFA members <WSFAlist at KeithLynch.net>

On Thu, 21 Dec 2006 23:14:37 -0500 (EST) "Keith F. Lynch"
<kfl at KeithLynch.net> writes:
> Ron Kean wrote:
> > Keith F. Lynch wrote:
> >> ... Just don't try to store modem signals as MP3s.  That trick
> >> never works.
>
> > To contrive a counterexample, ...

> Just because there's enough room for an elephant in your living
> room
> doesn't mean there's one there, or even that one would fit through
> the door.
>
> MP3 and competing standards are designed to compress sounds by
> discarding subtleties that human ears don't notice.  ... MP3 and
competing standards may
> not capture enough information to uniquely reconstruct the signal.
>

I contrived the counterexample because you wrote 'that trick never
works', thinking that you meant 'that procedure would never work', that
the compressed signal would not be readable at all.  But I realize now
that your choice of the word 'trick' probably implies that you were
thinking about a case of using MP3 compression to usefully compress data
indirectly by compressing an audio modem signal.  I agree that _that_
trick would not achieve the goal of ultimately compressing the underlying
data, even though the compressed audio might in some cases be readable.

> I have heard of people who can read 75 bps modem signals by ear, so
> presumably if you crank down the speed enough, it would work.

That's what I was thinking.

While on the subject of 300 bps data streams, I note that 300 bps happens
to be roughly the speed limit at which a person can read English text,
assuming that each character of text represents 7 or 8 bits.  Since
English text can be data compressed by a ratio of about three to one, I
would conclude that a human reader can handle a true data input rate of
only about 100 bps.  That estimate is roughly consistent with the
estimate that conversational speech has a data content rate of about 50
bps, and that most people can probably follow rapid speech at two or
three times the normal conversational rate.

So, here's the question.  If people can accept information input only up
to a rate of about 100 bps, reading text, why is it that people can
easily 'take in' a movie, which requires a streaming data rate of perhaps
tens of millions of bits per second, for a wide screen movie theater
presentation?

Ron Kean

.