From: znpt01@trc.amoco.com (Norman P. Tracy)
Subject: Re: questions on new digital formats
Originator: znpt01@gpss43
Organization: Amoco Production Company, Tulsa Research
Date: Wed, 16 Dec 1992 14:51:36 GMT


In article <lisfn9INNgm@exodus.Eng.Sun.COM>, drp@reed.Eng.Sun.COM (Darrell Parham) writes:
> I have some questions about the new recordable digital formats
> (MD, DCC, DAT):
> 
> - The claim is that you can play analog cassettes in DCC
>   machines. Can you also record analog cassettes in DCC
>   machines?

	No, its playback only.  And the reviews I've seen have been
	none too complementary of the analog playback.  After all
	Philips can't have you noticing your ACC sound is almost as good
	as DCC or feeding it blank $3 ACC instead of $15 DCC blanks
	now can they?

> I would like the capability of recording
>   cassettes for friends who might not have DCC yet?

	Save your ACC (analog compact cassette) deck.  Philips' marketing
	concept is that you buy a DCC deck and STOP using ACC except to
	play back your existing collection.
> 
> - I am under the impression that a magnetic format like
>   tape will degrade over time, while this isn't much of
>   a problem with an optical format like CD's.
>   Do people generally agree with this?

	It all comes down to how careful and smart the media manufacturers
	are. i.e. the big Q (Quality).  There are 40+ year old magnetic
	tapes that play just fine.  Then there are the tapes from the 70's
	(just after they took the whale oil out and replaced it with other
	less stable chemicals) that are falling apart in storage.  Optical
	media can degrade with time if every step of the complex process
	is not fully understood and looked after.  Look at the problems
	Laser Disks had with 'laser rot' when some of the glues used to
	stick the two sided LDs together attacked the data surface.  It
	now appears CD had a close call with 'laser rot' when pressing plants
	proliferated, costs dropped, and corners were being cut.  Premature
	reports in the British press based on the LD experience caused
	Philips to crack down on the new pressing plants to keep their QC
	up to standard.
 
>   How do the Mini-Disks fare in this respect?

	The only way to know for sure is ask again in 10 years.  My opinion
	is that they try very hard for excellent QC when the media is new
	and the cheaper less stable stuff hits the market as the price drops.

>   I hear they use a combination of magnetic and
>   optical recording (which I have a poor understanding of)
>   Could one expect them to degrade over time very much?
>   Would this differ between pre-recorded and home-recorded
>   mini-disks (is the same mechanism used) ?

	A pre-recorded MD uses exactly the same pressing technology as CD.
	The only differences are disk size and the carrier.  Recordable MD
	uses MO (magna-optical) technology which is very young. Stability
	of MO should be ok if you believe in the chemists involved.

>   Is degradation less of an issue with any digital format
>   than it is with an analog format?

	To the degree the 'digital' format has error detection/correction
	yes.  As long as the degradation does not exceed the error correction
	scheme's ability to reconstruct the data you're home free. Once that
	threshold is crossed you've lost data.  In contrast analog formats
	tent to slowly degrade with the loss of information immediately
	evident.  I work in the geophysical seismic industry which went
	digital in the 1960s and I can assure you digital data storage
	formats can degrade into an unuseable state.

	This raises an issue I have yet to see addressed anywhere.  What
	happens (i.e. what does it sound like) when an uncorrected error
	gets through to the 'data-de-compresser-reconstructor' chip in
	a MD or DCC player?
> 
> Any comments?

	I'm waiting for affordable Recordable-CD. DAT and Nakamichi ACC
	will tide me over this format war.

	IF I were considering buying a MD or DCC recorder I'd buy a blank,
	record it then scratch it and see what happens on playback.

> Thanks.
	Your welcome.
	
	Norman Tracy
	znpt01@trc.amoco.com
Newsgroups: rec.audio,sci.electronics