From: fineberg@win31.nas.nasa.gov (Samuel A. Fineberg)
Subject: Re: DCC -- JUST SAY NO!  (was: The end of cassettes,
Organization: CSC, NASA Ames Research Center, NAS Division
Date: Wed, 18 Nov 92 17:38:14 GMT
Reply-To: fineberg@nas.nasa.gov

In article <1992Nov17.231246.137@nas.nasa.gov>, fineberg@win31.nas.nasa.gov (Samuel A. Fineberg) writes:
|> In article <27617@oasys.dt.navy.mil>, curt@oasys.dt.navy.mil (Curt Welch) writes:
|> |> In rec.audio, jj@alice.att.com (jj, curmudgeon and all-around grouch) writes:
|> |> >Must I again point out that a second-generation DCC (analog interface
|> |> >between decks) is going to sound pretty bad? (Well,
|> |> >"bad" is relative, perhaps I'm picky.)
|> |> 
|> |> Yes you must.  But you don't explaing why you think this.  I don't expect
|> |> multiple generation (analog or digital) copies on DCC or MD to be bad.  Why
|> |> do you?
|> |> 
|> |> Are you thinking that the first generation will compress the data by
|> |> throwing away 80%, so therefore the second generation must throw away
|> |> another 80% of the 20% left, leaving only 4% of the original music?
|> |> 
|> |> If this is your thinking, then here's mine.  The first compression
|> |> will remove 80% of the information, but the second time through the
|> |> system, almost nothing will be removed, because it was all removed
|> |> in the first pass.
|> |> 
|> |> I don't expect multiple analog DCC or MD copies to hold up as well as
|> |> DAT, but I expect it to be better than any cassette format.
|> |> 
|> |> Have you heard (:-)) otherwise?
|> |> 
|> |> If you have some evidence that multiple generation copies will be
|> |> bad, please let us know about it.  If you don't, please stop passing your
|> |> theories along as if they were facts.
|> |> 
|> |> Curt
|> I think he's partly right.  The fact is that the loss from compression is only 
|> where the information content of the signal is greater than the tapes capacity. 
|> After the signal has been reduced to a signal that can be stored on the tape 
|> (i.e., after the first time it is compressed), all further generations should
|> be exactly the same.  
|>             _______________			   _____________
|> 
|> Signal  --> | compression | --> signal on tape --> | expansion | --> tape output
|>             _______________                        _____________
|> 
|> In theory, any signal that can be expanded from one on a DCC (or MD) tape should
|> be compressible to exactly the same signal from which it was created unless if
|> some part of the expansion process is generating new information that wasn't
|> part of the original signal.  Therefore, all generations of a DCC or MD tape
|> should sound identical.  Its too bad the first generation copy will 
|> sound so bad.
|> 
|> Sam
|> 
I take this back.  I was using knowledge of information theory and assumed
as is stated above that nothing extra is added to the signal by expansion.
In fact, as other posters have pointed out, noise is added in expansion.  This
noise is not part of the original signal and will propagte error.  Personally,
I don't see why this can't be eliminated by using digital-digital copying,
but maybe they are doing something stupid for "psychoacustic" reasons.  Get
a clue, stick to CDs.  Think about how many CDs you could buy for the $700
a DCC deck will cost, you could even buy two car CD players for the same money.

Sam
Xref: sparky rec.audio:15569 rec.music.folk:8077 rec.arts.wobegon:429