From: jeh@cmkrnl.com
Newsgroups: rec.audio
Subject: Re: DAT, DCC and MD
Date: 21 Jan 93 16:06:43 PST
Organization: Kernel Mode Systems, San Diego, CA

In article <GLAS.93Jan21081603@muresh.et.tudelft.nl>, glas@muresh.et.tudelft.nl (Jack Glas) writes:
> To do something about the disadvantages mentioned above Philips (one 'l') invented the 
> Digital Compact Cassette system. These players doesn't have rotating heads (so they can
> become cheaper than DAT recorders), and you can play (and record) you normal Compact 
> Cassettes in them. 

Nothing that I've read has indicated that a DCC deck that could record on
analog cassettes would be made.  The deck would have to use different heads for
recording depending on which media you were recording on.  This is possible but
mechanically complicated.  

> The system makes use of PASC (precision adaptive subband coding) to 
> compress data. 
> 
> PASC is based on two phenomena of the human ear:
> * One can only hear sound above a certain level, called the absolute hearing threshold.
> * Loud sounds hide, or mask, softer sounds in their vicinity. They dynamially adapt the
>   hearing threshold. This applies to the frequency domain (spectral masking) as well as to 
>   the tiem domain (temporal masking).
> So you have to be a GOD to hear the differences between CD and DCC.

That's quite a leap of faith.  (pardon the pun.)

Let me just add one drop of gasoline to this particular fire:  There is a
difference between what you can and cannot report hearing in a controlled test,
and what you can and cannot perceive at a subconscious level.  The stuff that
PASC claims you can't hear may very well contribute to the "listening
experience".  You can't prove that it doesn't, and I of course can't prove that
it can... 

> I think everyone who doesn't believe me (which of course is also a matter 
> of taste) should at least read one of the following articles:
> * Gerard C.P. Lokhoff: 'dcc-Digital Compact Cassette', IEEE transactions on consumer 
> 	electronics, Vol. CE-37, no. 3, pp 702-706, august 1991.
> * Gerard C.P. Lokhoff: 'Precision adaptive subband coding (PASC) for the digital compact
> 	cassette (DCC)', IEEE transactions on consumer electronics, Vol. CE-38, no. 4,
> 	pp 784-789, november 1992.

I find it really interesting that you don't suggest going out and *listening*
to a DCC deck!  

Tell me -- is it possible to determine, through chemical analysis, exactly what
a wine is going to taste like?  What would you say if I was selling wine that
had been shipped in "dehydrated" form (shipping water is expensive, after all,
and water is everywhere) -- "it's true that in the process we lose a few of the
really minor components of the wine, but don't worry, in blind taste tests
we've proven that those components can't be detected in the presence of the
stronger flavors in the wine."  Right!

For me it is enough to know that DCC and MD throw away *some* information which
*may* be part of the "listening experience".  And that CD and DAT are available,
and they don't throw away the stuff that DCC and MD do.  (They throw away other
things, but they're the best things available to the general public...)

	--- Jamie Hanrahan, Kernel Mode Systems, San Diego CA
Internet:  jeh@cmkrnl.com, or hanrahan@eisner.decus.org  Uucp: uunet!cmkrnl!jeh