DAT and SCMS, some info
sohl,william h
A recent poster asked for some SCMS information. Here's a file
I've had for some time which is still pretty accurate I belive.
The following was published in a past issue
of UPDATE, the newsletter of the Home Recording Rights
Coalition, Volume 5 No. 2 and is posted with HRRC's permission.
HRRC encourages the further dissemination of this information.
The Serial Copy Management System (SCMS)
SCMS is a system, for the first time, that will allow Digital
Audio Tape recorders (DATs) to make direct digital-to-digital
copies of compact discs. It does not allow digital-to-digital
copies of these copies to be made.
A DAT with SCMS circuitry is programmed to read certain subcode
channels of digital source material (eg. CDs). These subcode
channels are separate from the music channels and include: a
"catagory code" indicating what type of digital device is being
used, a "flag" indicating whether or not copyright is asserted,
and an "L" bit indicating whether the material is from an album
(eg. original CD) or a copy of an album. DAT recorders with SCMS
use the combination of this information to determine if
digital-to-digital copying is permitted. If copying is allowed,
the DAT recorder inserts new codes onto the DAT tape being
recorded to indicate if future copies are permitted.
Essentially, SCMS guarantees that direct digital-to-digital
tapes of CDs, prerecorded digital tapes and future digital
radio broadcasts will be made on consumer DAT recorders. The
only restriction introduced by SCMS is on digital copies of
digital copies, and then only if the maker of the original
digital source asserts the copy protection.
Congressional Report Vindicates Home Taping
In an October 30, 1989 report, "Copyright & Home Copying:
Technology Challenges the Law," Congress's Office of Technology
Assessment (OTA) concludes: "although home taping may reduce
recording industry's revenue, a ban on home audio taping would be
even more harmful to consumers, and would result in an outright
loss of benefits to society, at least in the short term, in the
billions of dollars."
The OTA study was done at the request of Congress in response to
the debate about home music taping. The key part of the report
presents the results of a national survey designed to gather
objective data about actual consumer use of home recording equipment.
Some of the OTA principal findings included:
1. "Place Shifting" is the most common reason for album taping;
home tapers usually tape their own records or CDs so that they
can play them in their cars, Walkmans, or cassette players.
2. Nearly 3 out of 4 home taping occasions do NOT involve
pre-recorded music or copyrighted material.
3. Home tapers listen to more music and PURCHASE more
prerecorded music than nontapers.
4. Home taping stimulates album purchases. A substantial number
of music buyers first hear the recording or artist they
eventually purchase on a homemade tape, and many buy recordings with
the expectation of taping from them.
5. The availability of dual cassette and high-speed dubbing
technology does not generate increased home taping.
6. Overwhelmingly, consumers would strongly oppose legislation
that would impose royalty taxes (on blank tape or recording
equipment) or that would prevent home taping.
(1992 update - we all know how much congress considered the
concerns and/or opinion of consumers.
In developing the survey, OTA gave industry and consumer groups of
all viewpoints, including HRRC, extensive opportunity for comment
and advice. Earlier surveys by HRRC and the music industry had
reached some conflicting results. HRRC strongly applauded the OTA
findings as confirming everything HRRC had been saying since 1981!
In short, home tapers act responsibly and are the music industry's
best customers.
--------------------
Anyone interested in contacting the Home Recording Rights
Coalition (HRRC) can do so as follows:
Telephone: 1-800-282-TAPE
Address: HRRC, 1145 19th Street NW, PO Box 33576, Wash DC 20033
Paul S. Winalski
In article <1992Nov16.1...@porthos.cc.bellcore.com>,
wh...@dancer.cc.bellcore.com (sohl,william h) writes:
|>
|>Essentially, SCMS guarantees that direct digital-to-digital
|>tapes of CDs, prerecorded digital tapes and future digital
|>radio broadcasts will be made on consumer DAT recorders. The
|>only restriction introduced by SCMS is on digital copies of
|>digital copies, and then only if the maker of the original
|>digital source asserts the copy protection.
Alas, this isn't quite entirely true. A SCMS-implementing DAT deck recording
from analog sources records a SCMS code of 11 (one more generation of digital
copying allowed). This means that if you are, for example, using a SCMS DAT
deck to make a recording of yourself singing or playing an instrument, you
can make copies of the original DAT tape, but you cannot make copies of the
copies, even if you, as holder of the copyright for the material, desire to
do so. The maker of an original digital source on an SCMS-implementing DAT
has no choice about asserting the copy protection--it will be asserted, whether
the maker wants it to be or not.
To provide some of the technical details on SCMS, it is encoded as two bits
of the subcode 6 field of the header information for each block. The four
SCMS codes are:
code meaning
00 unlimited digital copying allowed
01 (this code is not used)
10 digital copying prohibited
11 one more generation of digital copying allowed
If a DAT deck receives digital input with a SCMS code of 10, copying is
prohibited. If the digital input has a SCMS code of 00, copying is allowed and
the result will also have a SCMS code of 00. If the digital input has a SCMS
code of 11, copying is allowed and the result will have a SCMS code of 10.
If input is from an analog source, recording is allowed and the result will
have a SCMS code of 11.
Note that SCMS is not unique to DAT. DCC and MD also must implement SCMS
in consumer units.
--PSW
copying is allowed
Curt Welch
>The maker of an original digital source on an SCMS-implementing DAT
>has no choice about asserting the copy protection--it will be asserted, whether
>the maker wants it to be or not.
I've got some SCMS questions (sorry of this has already been discussed - I
haven't been reading this thread).
What happens when an SCMS DAT deck is sent a digital source that's
marked "unrestricted"? Does it create an unrestricted copy or
does it treat it the same as the analog input - i.e marking it with
the code that allows one digital copy?
If so, are they any outboard A/D converts that produce a data stream
with the SCMS code set to unrestricted? I guess that even if these do
exist, they will cost more than a pro (i.e., non SCMS) DAT deck so it's
not really an option for someone that wants to make their own
unrestricted recordings.
I have a pre SCMS DAT deck. What happens when I feed the digital
output of this deck to an SCMS deck? Does it look like an unrestricted
source?
Is the coding of the SCMS data such that the receiving deck can tell
that there is "no SCMS code" in the data stream and treat the input
differently? Or is was the SCMS code just assigned to bits that
were always set to a constant value (like 0) in older equipment?
Curt
sohl,william h
>
>Note that SCMS is not unique to DAT. DCC and MD also must implement SCMS
>in consumer units.
If that is so, then doesn't that imply a "digital" interface. I knew
DCC was a digital encoded signal, but I thought the inputs and
outputs of a DCC deck would be analog only.
If the DCC output is always analog, then what does the SCMS
coding provide or do for the recording industry? Or is there some
type of analog SCMS encoding been developed that we haven't heard
about (that is, an SCMS encoding that is present in the analog
mode at the audio out of a DCC deck?)
Standard Disclaimer- Any opinions, etc. are mine and NOT my employer's.
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Steven Walsh
-------------------------
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AC adaptor
Rechargable battery (lasts 2 hours)
Backlit display (blue)
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Digital cable (optical) for digital masters
Mini jack to RCA plugs (gold)
***Includes a pack of 10 one hour tapes***
Short and Long play modes (16bit/12bit)
$500
Steven Walsh
wal...@cs.uwp.edu
(414) 654-4473
Stephe Lewis Foskett
william> I knew DCC was a digital encoded signal, but I thought the
william> inputs and outputs of a DCC deck would be analog only.
No one's mentioned it yet, so here's Radio Shack's plug (from the
latest direct-mail ad) for it's version of the Phillips DCC deck:
(emphasis added)
--
DIGITAL AUDIO BREAKTHROUGH!
Introducing the DCC - the world's first Digital Compact Casette recorder
*Records and plays _CD-quality_ digital stereo on convenient DCC tapes
*Plays standard analog casettes, too - _won't obsolete your existing
tape library_
*Programmable memory stores 20 selections to play in any order you desire
*Once/continuous auto-reverse
*One-touch automatic music search
*64-times oversampling provides _purest playback of DCC tapes_
*Drawer loading
*Dolby B-C system for analog tape playback
*Quality-made in the USA
Optimus DCT-2000. Enjoy the best of both worlds-true digital home
recordings and compatibility with your existing casettes. The DTC-2000
records up to 90 minutes of pure digital stereo per DCC tape,
_delivering perfect copies of your compact discs_ plus superb
recordings from LPs and analog tapes. The drawer-loading deck is
simple to use combining the familiar features of CD players and
casette decks, like a 20-selection programmable memory, auto-reverse
and music search. There's even a unique text display that shows titles
and performers' names on prerecorded DCC tapes. Features fiber-optic,
coaxial and analog inputs for recording from both digital and analog
sources, a headphone jack with a volume control and a wireless remote.
contact your nearby radio shack for availability in your area
--
So there you have it.
now my comments:
* There's NO MENTION of the compression scheme. They promise
"CD-quality" sound and "perfect copies of CDs". This is simply not
true, but maybe they just didn't want to get into specifics with the
mindless masses...
* There's NO MENTION of SCMS. See above...
* They indicate that the "standard" tape use is pretty good. I was
expecting it to suck, but if they promise Dolby B and C, perhaps they
put some thought into it after all. It's still not going to "obsolete
_my_ tape library", though, since I've already got a perfectly goot
casette deck... :)
* "Purest playback of DCC tapes"??? I thought all decks would sound
more or less the same... Advertising hyperbole?
* "Made in the USA"? Like the rest of RatShack's products, more like
"assembled a little bit in the USA"...
* It's got fiber and coax ins, but no mention of the outs... Hmmm...
Anyone know if there'll be a fiber out?
Now my comments on DCC:
I'm not convinced. MD sounds good (MAYBE even good enough for me to
buy in a few years) but not DCC. The audio advantages (and,
compression or none, I DO see advantages in DCC) are not balanced by
the packaging ones. Tape snarls and wear are SERIOUS considerations
in my book, and I'm not convinced that DCC decks are immune... Also,
the lack of an immediate portable unit and the larger size are
detractions to me. In 5 years I see myself listening to my CDs at
home and my MDs in my car and at work. Sorry, Philips.
Now, about SCMS and compression:
What if you open the decks up and physically wire the digital out
(before the DAC or "uncompressor") to the digital in (after the ADC or
"compressor") on another deck? What would happen? I'm no expert (so
don't flame _ME_ for not reading so-and-so-lab's PI314159 report on
how they work) but there must be some pretty easy way to get around
SCMS and the MD and DCC's compression schemes...
And a final overheard comment:
"DCC? Is that a computer? DAT? No? Oh, you mean the little disks,
right? I thought that was called MD! Oh? There's something that can
record digitally on regular casettes? NOT regular casettes?
Something LIKE regular casettes? Nope, never heard of it but it
sounds confusing..."
(I heard this yesterday afternoon. Makes me wonder about Philips
advertising and head start and all...)
.s.
--
- so spake lan...@wpi.wpi.edu - In the Mean Time -
- To die unsung would really bring you down although wet eyes -
- would never suit you - walk through no archetypal suicide -
- To die young is far too boring these days... -
Curt Welch
>Note that SCMS is not unique to DAT. DCC and MD also must implement SCMS
>in consumer units.
In rec.audio, wh...@dancer.cc.bellcore.com (sohl,william h) writes:
>If that is so, then doesn't that imply a "digital" interface.
Yes.
>I knew
>DCC was a digital encoded signal, but I thought the inputs and
>outputs of a DCC deck would be analog only.
They have standard digital input and output ports like DAT and CD
along with the analog ports.
But you can't get them to send the raw data off the media out this
port. The data always go through the compress/uncompress algorithm.
Curt
Paul S. Winalski
In article <27...@oasys.dt.navy.mil>,
cu...@oasys.dt.navy.mil (Curt Welch) writes:
|>
|>What happens when an SCMS DAT deck is sent a digital source that's
|>marked "unrestricted"? Does it create an unrestricted copy or
|>does it treat it the same as the analog input - i.e marking it with
|>the code that allows one digital copy?
SCMS code 00 is "unrestricted". A SCMS-compliant DAT deck will allow
recording and the output DAT will have SCMS code 00.
|>If so, are they any outboard A/D converts that produce a data stream
|>with the SCMS code set to unrestricted? I guess that even if these do
|>exist, they will cost more than a pro (i.e., non SCMS) DAT deck so it's
|>not really an option for someone that wants to make their own
|>unrestricted recordings.
I think this is what a lot of the real pros use.
|>I have a pre SCMS DAT deck. What happens when I feed the digital
|>output of this deck to an SCMS deck? Does it look like an unrestricted
|>source?
It depends on the bits that are in the digital data stream. Some pre-SCMS DATs
appear to some SCMS-compliant DATs as "digital from an unknown source" and so
the output is given SCMS code of 11 (same as for analog input).
|>Is the coding of the SCMS data such that the receiving deck can tell
|>that there is "no SCMS code" in the data stream and treat the input
|>differently? Or is was the SCMS code just assigned to bits that
|>were always set to a constant value (like 0) in older equipment?
I think there's a bit in the ID field that says "this is a SCMS-compliant data
stream". A SCMS deck that sees this in the ID then will expect SCMS codes in
the subcode 6 field. If the data stream either doesn't contain the SCMS ID or
doesn't have a subcode 6, then the receiving deck can detect this. In that
case, it's supposed to record a SCMS code of 11.
--PSW
Robert Krawitz
an SCMS 10 code (no digital copies) on digital media?
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ames >>>>>>>>> | Robert Krawitz <r...@think.com> 245 First St.
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sohl,william h
>I'm curious as to whether the HRRA forbids record companies from putting
>an SCMS 10 code (no digital copies) on digital media?
A recording company is under no legal obligation to code original
material as uncopieable or otherwise. In other words, if someone
wants to sell a CD or DAT tape which doesn't prohibit multiple
generations of copying, then the producer/originator of that CD
or DAT is perfectly free to encode the SCMS with an 00 coding
for unlimited copying.
Robert Krawitz
In article <RLK.92No...@underprize.think.com> r...@underprize.think.com (Robert Krawitz) writes:
>I'm curious as to whether the HRRA forbids record companies from putting
>an SCMS 10 code (no digital copies) on digital media?
A recording company is under no legal obligation to code original
material as uncopieable or otherwise. In other words, if someone
wants to sell a CD or DAT tape which doesn't prohibit multiple
generations of copying, then the producer/originator of that CD
or DAT is perfectly free to encode the SCMS with an 00 coding
for unlimited copying.
I understand that. My question is whether a record company is legally
prohibited from using the 10 code, forbidding ANY copying.
sohl,william h
>In article <1992Nov19.2...@porthos.cc.bellcore.com> wh...@dancer.cc.bellcore.com (sohl,william h) writes:
>
> In article <RLK.92No...@underprize.think.com> r...@underprize.think.com (Robert Krawitz) writes:
> >I'm curious as to whether the HRRA forbids record companies from putting
> >an SCMS 10 code (no digital copies) on digital media?
>
> A recording company is under no legal obligation to code original
> material as uncopieable or otherwise. In other words, if someone
> wants to sell a CD or DAT tape which doesn't prohibit multiple
> generations of copying, then the producer/originator of that CD
> or DAT is perfectly free to encode the SCMS with an 00 coding
> for unlimited copying.
>
>I understand that. My question is whether a record company is legally
>prohibited from using the 10 code, forbidding ANY copying.
Oops, sorry I misread what you were asking. I just browsed through my
copy of the HRRA and can't see anything that would seemingly state that
a producer of CDs, DATs, etc. can't encode with a 10 code (the codes
themselves aren't even mentioned). If, howver, a company did that, it
still wouldn't stop the digital-analog-digital copying, AND, it would
become known pretty fast that XXX CD is encoded with a "prohibit all
digital copies" coding and might then actually result in a lower
number of sales.
As several others have mentioned, the real gain for the recording
industry is the royalty tax on blank digital tapes. I suspect the
industry fully knows it can't stop any of the taping that generally
goes on by individuals for their own use and they won't really try
to either. The thing to watch is the probable cry for higher
royalty taxes in the future as well as an extension of royalty taxes
on other blank media (eg. analog cassettes, computer discs, etc.)
Don Reid
: prohibited from using the 10 code, forbidding ANY copying.
I doubt it, but it would seem fair to demand that they also forgo their
share of the DAT recorder/tape royalty.
Don Reid HP - ICBD - Product Design
750-2726 (telnet) 1050 NE Circle Blvd.
do...@cv.hp.com Corvallis, OR 97330
Paul S. Winalski
In article <RLK.92No...@underprize.think.com>,
r...@underprize.think.com (Robert Krawitz) writes:
|>
|>I'm curious as to whether the HRRA forbids record companies from putting
|>an SCMS 10 code (no digital copies) on digital media?
No, it does not. Owners of copyright on a work are allowed to set the
protection as they see fit.
--PSW
Gordon Van Huizen
writes:
>
> They have standard digital input and output ports like DAT and CD
> along with the analog ports.
>
When you say 'standard' I assume you mean S/PDIF. Surely there won't be any
'pro' decks with AES/EBU... :-)
Gordon
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