Conference cookie::notes$archive:cd_v1

Re .0:

	Sure ... just like the cassette tape recorder replaced the record
	player.

	I'm sure the same type of article was printed when magnetic cassette
	tapes were introduced :-)

	Matt

	P.S.  Look elsewhere in this file ... others have mentioned digital
	taping (somewhere).

    There is a lengthy discussion on this in the AUDIO notes file
    (DSSDEV::AUDIO).  Relax.  CDs are in no danger.  Specifically,
    
    The R-DAT (Rotary head Digital Audio Tape) standard specifically
    prohibits giving players the ability to record at 41.5KHz, the sampling
    frequency used by CDs.  In other words, if you want to record a
    CD, you have to convert the signal to analog, as you would for normal
    playing, and then re-convert it to digital in the recorder. There
    is no provision for digital-digital recording.  (Of course, some
    inventive hackers will no doubt circumvent that restriction).  They
    did, however, allow for playback of tapes from 41.5KHz masters,
    to allow record companies to use the same masters for CDs and
    pre-recorded DATs.
    
    Also, just because it's digital doesn't mean DAT will be perfect.
    It will still be subject to stretching, wear, head-cleaning, etc.
    The analogy of casettes replacings records doesn't quite hold, since
    DAT will be closer to CD sound quality than casettes are to LPs.
    But, I wouldn't throw out the CD collection yet.

    Relax! I read the article too (booring...) and it was fairly obvious
    the author has barely grasped the buzzwords let alone shown the
    insight needed to make accurate predictions on the future of audio.
    
    Reminded me of Chicken Little...
    
    Walt (now watch somebody tell me this writer is his _____-in-law) 

    re: .2
    
    Okay, maybe these are dumb questions, but I'm really confused. 
    Icertainly do not know enough about DATs but why would there be
    any wearing problems or head cleaning problems?  Wouldn't DATs be
    read using the same laser technology used for CDs?
    
    Second, I don't see why they cant sample at 41.5kHz or 44.3kHz or
    whatever rate they record CDs at if this is so important.  But first,
    please answer me this, why do they have to use that rate at all?
    It seems to me that as long as they used a rate that was >= the
    sampling rate of the original (the CD in this case), then all of
    the music information that was on the CD will be transferred to
    the copy (the DAT).  Oversampling wont provide any additional info,
    of course, but I don't think it will lose any either.
    
    By the way, the original note was FYI only.  I *love* my CD player
    and certainly don't plan on getting rid of it anytime soon.  However,
    I think a digital tape deck would be a great convenience and would
    love to see them marketed just to add another dimension to the market.
    
    
    Mitch
    

    No, DAT does not use any laser technology.  It's a magnetic read
    and write process, similar to what's in video recorders.  That's
    why you still have wear and tear on tapes and heads.
    
    CDs use a 41.5KHz sampling frequency, and DAT uses 48KHz, I think.
    You can't simply copy from one to the other, or your music will
    be 1.15 % faster.  Either that, or you have to figure out something
    to do with the remaining 6.5K samples each second.

    Re .2:
       It's not true that there is no provision in R-DAT for digital-
    digital recording - it IS true that you can't do this at the
    CD sampling frequency - a deliberate move to thwart CD copying.
    Frankly, I'd be just as happy with recording the analog output
    of a high-quality CD player onto DAT - I doubt you could tell the
    difference in normal circumstances.
    					Steve

It would be possible to copy CDs to DAT even with the sampling frequency
differences.  I can think of two methods:

1) Do the copy CD->analog audio signal->DAT.  This involves some signal loss,
   of course.

2) Using the digital output so conveniently provided on many CD players, run
   the bits through an anti-aliasing algorithm to generate new bits at the
   DAT sampling frequency.  These algorithms are in extremely common use in
   graphics processing.  A 68010 processor with some minimal extra hardware
   (a couple of UARTs) could be programmed to do it, no problem.

I predict that if DAT becomes commonplace, somebody will market a box that
does (2), either that or some enterprising manufacturers will implement a
record head for CD sampling frequency in spite of what the standard says.
I know *I'd* buy one.

In any event, DAT in no way obsoletes CDs.  DAT will not be able to seek to
any track more or less instantaneously, for example.  The situation is
completely analogous to cassette tapes vs. records.

--PSW

    
    
    re -.1
    
    
    I dissagree.The sound quality from a record player is vastly
    superior to a cassette tape.Whereas DAT should offer comparable
     sound quality to CD,with the added attraction of being able to
    record.Admittadly tapes do suffer from wear/stretching/mangling,but
    unlike analogue tapes these won't result in a gradual degradation
    of sound.

    re .-1

<<    I dissagree.The sound quality from a record player is vastly
    superior to a cassette tape.Whereas DAT should offer comparable
    sound quality to CD,with the added attraction of being able to
    record.                                                          >>

    I disagree, disagree.
    They're working on CD's which you can record on at the moment. But
    the first versions are record-once-playback-forever kind of technology.
    (equivalent to PROM - Programmable Read Only Memory).

    Eventually I expect CD's will be able to record again and again,
    now that IS something worth waiting for...


    Peter (ROM..PROM..EPROM) Linton.  [8v)-

Re .8:

Although I agree with you that DAT will be somewhat equal to sound quality 
of CDs (during first use anyway), the point I was trying to make when I made
the analogy to records/cassettes was that some people will always prefer a
particular technology over another. 

Look at CDs ... when (if :-{ ) CDs are as available as records, I would think
that CDs would destroy the record market.  But, not everyone feels that this
is true (e.g., some say analog recordings sound better, etc).  

As pointed out by others, there is more to CD than sound quality.  One can't
forget instant track seek and permanent (practically) data retention.   DAT is
serial access (hence no instant track seek).  The heads touch the tape, which
*will* wear the tape out.  Now I know that the data is digital and probably
won't be as affected as with analog tape; however, I have my doubts that data
retention will be permanent as with CDs. 

Also, tape heads require more maintenance than a laser.  In normal use, it is
easier for tapes to crease, crinkle, stretch, etc. then for a CD to scratch or
crack. 

I'm not sure about this (somebody who knows please reply), but will the 
dynamic range of DAT be the same as CD?

As .9 pointed out, recording on CDs is being developed.  CD technology is in 
its infancy ... who knows what else the research will turn up.  :-)

Remember that the above is my opinion and, as such, I enjoy constructive 
feedback.

Matt

    The co-existance of CDs and records has nothing to do with opinions
    about analog vs. digital recordings.  After all, many LPs are digitally
    recorded, and many CDs are not.  When CDs have as vast a catalog,
    and are as cheap, as records, then I think there'll be trouble for
    good ol' vinyl after all.
    
    Yes, DAT tape will not gradually degrade as a result of tape wear,
    stretching, etc.  Instead, it'll fail suddenly, in some spots, and
    the number of spots will increase.
    
    I'd certainly settle for write-once/read-many (WORM) CDs, if the
    blanks are cheap enough.  However, I don't think even this is "just
    around the corner" as so many of you are saying.  Currently, it
    requires a clean room and vast amounts of equipment to produce CDs.
    The density of information requires the dust-free environment. How
    many of you have clean rooms at home?  Besides, there's no guaranty
    that writable optical audio discs would be compatible with today's
    CDs.
    
    I'm perfectly happy with read-only CDs.  I'd be happier if more
    titles were available, but that's situation's improving all the
    time.  I'd also be happier if they were cheaper.

    Good News!  Write once is real and it doesnt require cleanroom for
    the user.

    Bad News!   It is currently only being seriously developed for
    industry as an archive for big databases and the media is expensive.
    It will likely not be compatable with current CD players. 
    
    Walt

          Why should recording on a write once disc require a clean room?.I
    agree that manufacturing the disc will
    
          Write only CDs are available,but I understand that tracks are
    considerably wider than read only discs,so capacity is reduced.
  
      Surely any medium that is recordable will suffer degredation due
    to repeated reads,ie the read-laser will repolarise the data cells,
    much the same as repeated read of tape realigns the magnetic particles.
    
    The laser in a CD player has a finite life,can't remember how long,but
    it's years rather than 10s of years.The replacement cost is
    prohibitvely high,ie buy a new player time.....
    
    The disc themselves MAY have a finite life.I recall reading an article
   suggesting that the plastic crazes with age.Philips dispute this.
    
    As for instant track selection,random order etc.I'm afraid I have
    to admit that I normally just stick a disc in and play it from start
    to finish..boring eh?.
    
    Bob

Re .13:
>                            the read-laser will repolarise the data cells,
>    much the same as repeated read of tape realigns the magnetic particles.
    
Ahhhhh, I'm confused ... "repolarize the data cells"?  That's not how I thought
CDs were made!  I thought the dimples were stamped/pressed.  Somebody else 
wish to comment?


>    The laser in a CD player has a finite life,can't remember how long,but
>    it's years rather than 10s of years.The replacement cost is
>    prohibitvely high,ie buy a new player time.....
    
By that time, the price of players will have dropped alot more, probably less
than the price of a good replacement stylus. :-)   Also, I was refering to
regular maintenance of a tape head vs. laser.  Tape heads require more.


>    The disc themselves MAY have a finite life.I recall reading an article
>   suggesting that the plastic crazes with age.Philips dispute this.
    
I thought I read somewhere that CDs will last for >1M plays, >100 years, or as
far as I'm concerned a life time.  BTW, do you think a tape would last as
many plays or as long?  Not me.  Also, it seems to me that the probability of 
a tape being eaten by its player is *much* greater than the probability of a
disk being trashed by its player. 


>    As for instant track selection,random order etc.I'm afraid I have
>    to admit that I normally just stick a disc in and play it from start
>    to finish..boring eh?.

I've hardly used this feature either, but *in context* within the reply it was
mentioned, it is a feature that some people like/use. 

I'm holding my stand ... both DAT and CD will exist side by side.  Although DAT
may be generally available way before CD write capability, I think CD is here
to stay and has many attributes that DAT just can't provide.

Now ... if only more titles would be on CD ... :-(

    Re .14:
        The pits on a CD ARE stamped, and polarization has nothing to
    do with it.  The data is read from the interference caused by
    the different distances the reflection travels.  There is no reason
    that reading a CD should make ANY difference in the media.
    
         There's a good article on how CDs are made in the latest
    Stereo Review.
    					Steve

There seems to be some confusion about the read only CD's now generally
available and the WORM (write once read many) CD's.

The read only CD's are made by stamping little pits.

WORM CD's work by changing the physical properties of the material
in the disk from reflective to nonreflective (or is it vice versa?)
under the influence of a write laser blast.

Bob

    As I recall most the writable stuff cannot approach the read only
    regarding the amount of phase rotation of the return beam (90 degrees
    being optimum I guess).  A technology called Magneto Optic was
    introduced to enhance this. I also understand this has the most
    promise as far as being erasable.   This is at least grade C
    information (third hand - and fermenting in my brain for a while).
    
    Walt 

    Gee, it seems pretty easy to grind vinyl at home.  My stylus does
    it all the time!  How come there are no record-it-yourself vinyl
    turntables out there?  With the original Edison tinfoil or wax
    cylinder, you did have that capability.  Did the Japanese threaten
    him until he withdrew those models from the market?
    
    :-)
    
    Carl
    

    Some of the confusion may be because there are several different
    technologies (and applications) for CD's.
    
    CD's work by noticing changes in a reflected laser beam.  In the
    case of audio CD's, pits (or holes) are stamped in the disk.  Since
    the circuitry is digital/binary, all the system does is sense
    hole/nohole (or reflection/noreflection).  Write Once Read Many
    (WORM) CD's work by having a laser actually melt pits into a metal
    disk -- there are two ways to do this: either with a very strong
    laser which can melt holes in anything, or with a special disk that
    can be easily melted (usually using a tellurium alloy).
    
    In either case, writing to the disk requires enough power to actually
    melt portions of the disk, while reads only require enough power
    to bounce light off of the disk.  Since the read laser is below
    the threshold of melting the disk, it causes no changes and allows
    an unlimited number of reads.
    
    Another technology being developed involves organic dyes that polarize
    the light when it is reflected.  Thus, you sense the polarity of
    the reflected light, rather than its presence/absence.  The advantage
    of this technology is that the dyes can be altered many times, allowing
    data to be changed.  So far, they are less stable and less dense
    than the WORM disks.
    
    All of the writable tachnologies are being developed for computer
    storage -- I haven't seen anything about using them in audio systems.
    
    I suspect that DAT will be the only way to record digital audio 
    for quite some time.
    
    (A digression -- I haven't been able to decide whether to get a
    good cassette deck today or wait for DAT!!!)
    
    Russ Doty

      
    Re .14 (mainly)
    
    
    		If you want your CD to be recordable more than once,you
    can't go blowing bloody great holes in the aluminium layer with
    a laser cannon.This may well be ok for WORM discs,and is I beleive
    the system used..As for stamping pits,wouldn't this make recording
    something rather noisy,then what do you do to erase the music,attack
    it with a rolling pin?

    	 	One of the re-recordable systems works on the principal
    of a laser switching some clever plastic layer into a reflective
     or non-reflective state,ie binary.Each bit is a cell.Simple eh?
    
    
    
     As for DAT and CD coexisting,well I expect they will both be wiped
    out by ROM/RAM chips or something..
    
    ps   How did you get bits of my reply into yours??
    
    Bob    

    re:.18
    
    Actually, my father *did* have a vinyl record-cutting turntable
    up until maybe 10 years ago. It hadn't been working for some time
    before that, though. He and a friend of his used to make their
    own records way back when, and I remember being fascinated as a
    kid by the blank discs.
    
    --- jerry

re:  "read/write compact disks"

I'd like to try to clear up some misconceptions from some previous
replies.

There is not yet such a thing as "read/write".  The technology should
be called "erasable", because you cannot effectively "write over" the
existing data, as you can with magnetic tape.  I will explain how
it works.

[Disclaimer/flame:  there are at least two systems proposed, magneto-optic
and dye.  The magneto-optic system seems to have far more promise.
I will ignore the dye system here.]

Magneto-optic disks are exactly that.  They are made from a material
whose properties, specifically polarization shift on reflection, change
based on the state of local magnetic domain.  

These materials are _not_ ferromagnetic, i. e., almost any credible magnetic
field alone will not affect the disk in any way.

The disk is written this way:  a "biasing" magnet is provided
under the disk, and a (rather high power) laser is focussed on a sopt on
the disk from above.  The biasing magnet does not "focus" in any way on
any particular spot of the disk, nor is it switched on/off rapidly.

The laser raises the temperature of the material
past the Curie point, just high enough to align the domain of the heated
spot to the applied field from below.  "Surrounding" domains are, therefore,
unaffected, by the biasing magnet.

You can write, then, at any data rate consistent with modulating the
laser and heating the surface.  However, the resulting bit pattern is
the inclusive "or" of what was on the disk previously with the new data.

The way one "overwrites" sich a disk is to reverse the biasing magnet, then
write onto all the bits of the field which one wants to erase.  This
sets the bits to logical "0".  Then, any "normal" writing into that
field will appear as the new data IOR "0", that is, the desired data.

The only way, currently, do to direct R/W with magneto-optic disks would
be to switch the biasing field direction at the incoming data rate.
This is a tall order.

"R/W" will be slow in coming for home use for at least four reasons:

	1) The media are _very_ expensive -- perhaps as much as $50 -
		$100 or more each.

	2) The read electronics are expensive.  The polarization
		shift is not very high.  A "very, very good" polarization
		shift is considered to be 2 or 3 degrees.  So, reading
		the disk with a very high effective S/N ratio is a
		bit of an achievement.

	3) The drive mechanism is more expensive than for CD; it
		has to do more than "track" pits -- rather, it has
		to have precision ( about +/- 0.3 uM) servo 
		for the positioning of the R/W head.  

	4) The laser is significantly more expensive.  CD semiconductor
		lasers are only a few milliwatts; these are easily
		produceable, and cheaply.  R/W will require laser
		powers in the 25 to 35 mW region.  This is _much_ more
		expensive (like $hundreds against $ones), and
		_much_ less reliable.

    
    
    Re: .20
    
    	Now there's an idea that I can relate to -- using ROMs/RAMs
    for audio.  Of course getting 2G on a chip may be tough, but I can
    envision it already.  Told my friends a few months ago that in a
    few years we'll all be wearing Sony Chip-men (or is that Chip-mans?)
    around our necks like lockets that are about the size of a big pink
    pencil eraser with earphones coming right off the neck chain at
    the sides.  Everyone will be carrying the evuivalent of about 10
    albums in their pocket.  I caught some strange looks...but I can't
    wait to get one!!! ;-)
    
    

    From DESIGN NEWS, December 15,1986 (reprinted without permission)
    
    		CHIPPING AWAY AT AUDIO PIRACY
    
    The specter of digital audio tape (DAT) has recording industry
    officials scurrying to bar the door.  The new technology- all the
    rage at this Fall's Tokyo Audio Fair and Japan Electronics Show-
    provides home audio recording recording systems with digital quality,
    until now found on compact disks.  Without some way to prvent transfer
    of the digital signal from CD to audio tape, industry officials
    fear greater piracy of copyright material.  Present loss: $1.5 billion
    yearly- nearly 25% of industry revenue.  Patricia Heimers of the
    Recording Industry Association of America (RIAA) in New York, says
    a meeting on the issue was scheduled December 11 in Vancouver, BC,
    between RIAA and other groups, including the Electronics Industry
    Association of Japan.  RIAA wants a mutually agreeable solution-
    preferably a "copy code chip," an electronic component in the recorder
    that would detect an electronic gap in the signal of copyright material
    and refuse to record it.  They're looking to Congress to require
    either the chip or a 35% tariff penalty on imports, but time is
    of the essence, since electronics industry sources say DAT units
    could start showing up as early as next spring.
    
    Ain't that a bitch.  (not reprinted)

                           By Richard Doherty
       (reprinted without permission from Electronic Engineering Times)
                       Monday, December 22, 1986
    
        VANCOUVER, British Columbia -
    Things are heating up between the audio equipment industry and the
    recording companies that feed it with hi-fi software.
        Last week, members of the Electronic Industries Associateion
    of Japan[,] who whant to bring ultrahigh-fidelity digital audio
    tape (DAT) to market[,] respectfully declined recording industry
    requests that they build anti-dopy circuitry into consumer DAT decks.
        International recording groups, represented at a meeting here
    by the International Federation of Phonogram and Vidogram Producers
    (IFPI), have sought an agreement that would place an anticopy VLSI
    circuit inside each DAT system.  The chip would inhibit the DAT
    system from recording copyrighted musical software.
        Member companies represented by IFPI include EMI, Warner Brothers,
    CBS Records International, Polygram International, Chrysalis Group
    plc, WEA International and CBS Records Group.
        Earlier this year, DAT manufacturing companies established a
    special playback-only mode, following initial discussions with record
    industry executives last year.  And the DAT digitization sampling
    frequency deliberately was made different from that of CD audio
    disks [sic] to make commercial piracy more difficult.  The EIAJ
    members intend no digital music ports on the DAT systems:  all music
    in and out will be in the analog domain.
        But, despite the creation of the special play-only format, and
    the deliberate removal of any direct digital-to-digital record dubbing
    capability, music producers have turned thumbs down on DAT
    commercialization.  The programmers' chief concerns:  commercial
    pirating and rampant consumer copying of CD audio albums.
        EIAJ members said they cannot accept IFPI's position, which
    puts at-home taping in the same league as commercial piracy.  The
    IFPI also claims that the practice of home taping suppresses the
    sales of records and prerecorded tapes.  EIAJ says IFPI has not
    presented hard financial evidence of the claim to its satisfaction.
    EIAJ's own surveys show home taping bufs purchase mroe records
    than other consumers and it expect the same synergy to happen with
    DAT machines.
        The meeting between the EIAJ and the IFPI was convened at the
    urging of member EIAJ companies.  Forty-four companies have endorsed
    the technological and potential commercial promise of DAT systems.
     Prototypes were shoen at the Janpan Electonics Show (see EE Times,
    Oct. 13, Page 12).  Manufacturers said commercial DAT systems could
    debut early in 1987.
        EIAJ chairman Shoichi Saba said the electronics industry is
    moving toward an era of all-digital products.  "To cripple or delay
    any one of the key elements of this era would simply mean less groth,
    less progress and a poorer environment for consumers and the industries
    that serve them."
        And the EIAJ reminded record producers that they also were
    skeptical on the arrival of the analog cassette tape and the CD
    platter.  Saba reminded delegates that the advent of every new consumer
    electronic product had opened vast worldwide markets for programming
    suppliers.  He said he hopes the IFPI will "delineate" the problem
    of commercial tape piracy from consumer's rights, and said his member
    companies are willing to help that effort.  Saba said he expects
    the traditional audio tape market (now largely cassette) will "be
    phased out in favor of DAT."  But "the development of the CBS
    anti-taping device is against this technological trend," he said.
    "In the long run, as I believe, the system cannot overcome the
    beneficial flow of technology.["]
        "Consumers have the right to enjoy the best quality music and
    video; the latest developments whenever advanced technology is
    available," said Saba.  "The software and hardware industries cannot
    prosper if they ignore this basic right of consumers....It is a
    custom established over a period of 20 to 30 years."
        Saba said the EIAJ is firmly opposed to piracy, but respects
    the rights of consumers to record their own musical selections in
    a personal, preferential order.
        Heading up the EIAJ delegation were Saba; Matsushita Electric
    Industrial Co. Ltd. chaiman Akio Tanii; Seiji Sudo, president of
    Hitachi Sales Corp.; and Sony co-founder and chairman Akio Morita.
    Morita is recognized by recording executives as the man who started
    the Walkman portable audio player phenomenon seven years agao. 
    That product spurred production of new cassette titles at a time
    when the record industry was in a deep slump.
        EIAJ president Toshio Takai reaffirmed his belief that the
    equipment makers and recording industry are interdependent, and
    welcomed any suggestions for a cooperative effort.  If there's no
    agreement, Saba said, the two groups should take the matter to the
    consumers of both industries and let them decide.
        Next month, the U.S. Congress is expected to act on a[n] appeal
    from the motion picture industry that anti-copy chips be placed
    in all new VCRs.  The commercial effect of any industry action,
    or pending legislation, is expected to be a popular topic at the
    Consumer Electronics Show in Las Vegas, Nev., in two weeks.

    Re: .25  (Also from EE Times article reprint)
    
              Audio       Digital    Data       Size      Playing
            Bandwidth    Sampling  Capacity                Time
    ------------------------------------------------------------------
    CD      20Hz-20kHz    44.1kHz   CD-ROM    4.72" Dia.   72 min
                                  600 Mbytes
    ------------------------------------------------------------------
    DAT     20Hz-22kHz    48kHz    >1GByte    4mm tape    120 min
    ------------------------------------------------------------------

    120 min. tape?  They don't even sell 2 hour conventional cassettes
    anymore do they?  I wonder if it will suffer from the problems
    associated with >90 min. cassette tape.  I've seen some tape decks with
    warnings that the use of any cassettes over 60 min. could void the
    warranty due to overstress of the motors. 

    Well, if the machines are designed for 120 min tape, I don't think
    there'll be a problem.  I don't even know if they will have rotating
    heads or not.  If so, the tape will move a lost slower and won't
    have to be as long or as thin.  Certainly these are newly-designed
    cassettes for DAT players only.  Does anyone know if the new cassettes
    will be more like video tape, where the tape is not exposed when
    its not playing?  I always thought it was a poor design to require
    cassette boxes instead of making them like video tapes...
       Steve

    It was my understanding that they will use cassettes similar to
    those used by the Sony 8mm video.                
    
    						-Dave

    The DAT cassettes are indeed very similar to the 8mm video cassettes,
    including a mechanism that completely surrounds the tape when removed
    from the device.
    
    It seems that only the rotating-head DAT format (R-DAT) is going
    to make it - S-DAT seems to have died already.
    					Steve

    At the CES, three companies were showing the DAT.  We only saw the
    Onkyo DAT in operation, but apparently Sony's was working also.
     I forget who the third was...
    
    Onkyo salesman was riding the fence about availability and price
    for their DAT; the best we could get was a year and <$2000 for the
    first generation.
    
    And, yes, it uses rotating heads and an 8mm-type tape.
    
    				Vernon Miller
    

   FOR THOSE OF YOU WHO DO NOT GET THE BOSTON GLOBE:

	Copied from The Boston Sunday Globe, Feb 8th 1987  Page 86.


	ANTIDISC RECORDING MEASURE EXPECTED.
	Associated Press
	WASHINGTON - President Reagan will propose legislation de-
	signed to foil future home recording of Compact discs and
	other digitally recorded audio material, administration of-
	ficials said Friday.
	The Proposal, to apply to a new generation of digital tape
	recorders and not to most machines now on the market or in 
	homes, is part of a competitiveness and trade package to be
	submitted to Congress in late February, said the officials.
	Under the proposal, digital tape recorders could NOT be
	imported or sold in the U.S.A. unless they contained a device
	that automatically would block the recording of certain
	copywright-protected material.
	This device, a computer chip circuit called a "Copy code
	scanner",, would "read" a special signal encoded onto compact
	doiscs and other audio sources at the time of manufacture.
	Although this signal would be inaudible, once its presence
	was detected the tape would refuse to record the material.
	(end)

	(Am I glad to live in Canada !)


	Vince.

    
    Am I missing something here?  Does this "protection" only apply
    to digital-digital medium transfers?  How can they possibly keep
    you from copying a CD to DAT by running it thru a converter - like
    any amplifier?  Sure, you'd lose a little bit of sound quality due
    to D-A and then A-D conversion, but wouldn't this work??

    re .33
    
    The technique involves removing a narrow notch of frequencies
    from the recorded signal. The CLAIM is that this would not be
    audible (I'd like to hear some opinions on this, especially from
    the `analog is audibly superior' contingent).
    
    My belief is that the net result would be that the DAT medium
    would not catch on in the US, and go the way of quadraphonics
    and the PDP-11/60. Why buy a tape over a CD if (1) you're not
    a musician that does a lot of live recording and (2) the only
    thing you can play on it is prerecorded material?

Either that, or Mod Squad & co. will clean up on selling bypasses to the
anti-record chip.

--PSW

    I read in Wednesday's local newspaper (in Holland) that DATs were
    available in the shops in Japan from Monday and that by Tuesday,
    most shops were sold out.
    I also read that the DAT manufacturors were again meeting the "Record
    Industry" this week, after their failed attempt at control in
    Vancouver. Has anyone heard the outcome of this meeting ? - I hope
    they don't decide on the CBS chip protection.             
    
    Alan

    Hi I'm a new reader of the CD file and would like to mention that
    even if the cbs chip is installed which I think it won't be. It
    will be a simple process to disable or eliminate the offending signal.
    Once the frequency of the signal is determined a simple notch filter
    between the CD and the DAT will take care of the problem.
    
    STeve

   RE .37
    
    I thought the proposed chip in effect WAS a notch filter, and
    to defeat it you'd have to ADD some signal.
    
    Time to go back and read these notes again (if I remember wrong,
    this note will be short-lived).

    The way I understand what I have heard is that the CD's will have
    some frequency (Ultra Sonic I assume) encoded into the CD. The DAT's
    will pick this up and not allow the record mechanism function.
    
    If I am wrong correct me, but everything I have seen or heard points
    in this direction. 
    
    Steve

    If it's ultrasonic, then it's a matter of minutes before someone
    designs a filter to get rid of it.

    There's an article in the April Digital Audio which discusses this.
    
    The "notch filter" notion was only for cassette decks.  I've never
    seen this suggested for DAT.  The DAT and CD standards do include
    a coding in the control data that indicates "do not copy" - DA suggests
    that most CDs produced today include this coding.
    
    The argument is whether or not DAT recorders should include a circuit
    that recognizes the "no-copy" signal.  My reading shows that the
    industry is only concerned about digital-digital copies - why, I
    don't know, as a copy from a CD player's analog output would be
    very good indeed.
    
    					Steve