Joost de Meij writes:
> How is SCMS-information stored on CD's and pre-recorded MD's?
Selected postings from the archives:
Re: MD: CD-r scms
_________________________________________________________________
From Ralph Smeets <[EMAIL PROTECTED]>
Date Wed, 13 Jan 1999 11:51:32 +0100
Organization STMicroelectronics
References <[EMAIL PROTECTED]>
Reply-To [EMAIL PROTECTED]
_________________________________________________________________
Jough Dempsey wrote:
>
> At 12:15 PM 1/12/99 +0000, stories wrote:
>
> >Thats not correct, ALL CD media can carry the SCMS data (If you burn a
> >disk with a computer CD-r drive
> >you'll notice the SCMS data is the same as the origanal),
>
> They *can*, but most *don't*.
>
> Does anyone know the first application of SCMS?
>
They all *do*. SCMS stands for Serial Copy Management System. The two
bits that make up the SCMS code are coded in every frame on the CD. I
thinks it's every 96th bit that represents on of these bits. It doesn't
mater what the SCMS code is on a CD, it's always there.
Cheers,
Ralph -> who was talking solely about pre-recorded-audio-CDs and copies
of them!
--
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Ralph Smeets STMicroelectronics
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Re: MD: CD-r scms
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From [EMAIL PROTECTED] (David W. Tamkin)
Date Wed, 13 Jan 1999 15:52:29 -0600 (CST)
Cc [EMAIL PROTECTED]
In-Reply-To <[EMAIL PROTECTED]> from "Ralph Smeets" at
Jan 13, 99 11:51:32 am
Reply-To [EMAIL PROTECTED]
_________________________________________________________________
Ralph Smeets wrote,
| The two bits that make up the SCMS code are coded in every frame on the CD.
Someone has posted here in the past that each word of CD subcode has only
one SCMS bit. 0 means unlimited, and 1 means final (or maybe I have those
two reversed); penultimate, the usual setting, is represented by 0 and 1 in
alternating frames, so the player has to read the subcode from two frames
to determine the SCMS status.
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Re: MD: CD-r scms
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From Ralph Smeets <[EMAIL PROTECTED]>
Date Thu, 14 Jan 1999 10:11:24 +0100
Organization STMicroelectronics
References <[EMAIL PROTECTED]>
Reply-To [EMAIL PROTECTED]
_________________________________________________________________
David W. Tamkin wrote:
>
> Ralph Smeets wrote,
>
> | The two bits that make up the SCMS code are coded in every frame on the
>CD.
>
> Someone has posted here in the past that each word of CD subcode has only
> one SCMS bit. 0 means unlimited, and 1 means final (or maybe I have those
> two reversed); penultimate, the usual setting, is represented by 0 and 1 in
> alternating frames, so the player has to read the subcode from two frames
> to determine the SCMS status.
Well, the even frames contain bit 1 and the uneven frames contain bit 0
(or visa versa). This is what I understood from a previous poster (I
believe somewhere in February during the SCMS-disable attempts on the
702).
I've got a copy somewhere of the email that contains the codding of
S/PDIF and CD frames. You'll see that an S/PDIF frame is almost the same
as a CD frame. It just contains some extra information in order to have
more than two channels etcetera..
Cheers,
Ralph -> Who needs a secretary to reply his other non md related
mails.....
--
=======================================================================
Ralph Smeets STMicroelectronics
Voice: (+33) (0)4 76 58 44 46 CMG Functional Verification Team
Fax: (+33) (0)4 76 58 40 11 5, chem de la Dhuy
Mobile: (+33) (0)6 82 66 62 70 38240 MEYLAN
E-Mail: [EMAIL PROTECTED] FRANCE
=======================================================================
"For many years, mankind lived just like the animals. And then some-
thing happened that unleashed the powers of our imagination: We learned
to talk."
-- Stephen Hawking, later used by Pink Floyd --
=======================================================================
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Re: MD: timing differences on CD/MD
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From Dan Hollis <[EMAIL PROTECTED]>
Date Thu, 23 Apr 1998 20:10:20 -0700 (PDT)
In-Reply-To <[EMAIL PROTECTED]>
Reply-To [EMAIL PROTECTED]
_________________________________________________________________
On Thu, 23 Apr 1998, Seth Lacy wrote:
> I don't know where you guys get these ideas, but cd's don't encode
> timing information on the disc.
Sorry. You are wrong. CDs _DO_ encode timing information.
Specifically, the timecode information is stored in the subcode channels.
There are several channels reserved as follows:
P - Designates beginning and ending of tracks (A variation on the P
channel is where CD-Text data is stored)
Q - Track number, Time-In-Band (timecode)
R - CD+G graphics
S to W - Currently (as far as I know) unused.
Coincidentally, the Q subcode channel is also where the SCMS copy
permit/deny information is stored.
> That data is left out to save space (this is waht allows a cd to hold
> 750 meg of wavfiles in CD audio format, but only 650 as data). Anyhow
> the player just runs a clock along with the music or it may count
> samples.
Nope.
> That is why they will get off.
No. They get off, because subcode channels aren't transmitted in S/PDIF.
> I don't know if MD stores timing information in the data, but CD's
> don't.
Nope.
> That is why audiophiles love to talk about "jitter".
Nope. This isnt related to jitter at all.
> The data lacks a timing signal to sychonize it. That is why cheap
> cd-roms suck at ripping cd's. They can't read it at a constant enough
> data rate to get a good wav file extraction. That is also why most
> new CD-roms only rip at 1x.
Nope. The reason why CDDA audio is hard to rip is because the sectors
aren't numbered - unlike data CDs. The lack of timecode has nothing to do
with it (besides the fact that CD audio doesnt lack timecode).
-Dan
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MD: timing differences on CD/MD (plus SCMS on cd info in here)
_________________________________________________________________
From Seth Lacy <[EMAIL PROTECTED]>
Date Fri, 24 Apr 1998 14:11:26 -0700 (PDT)
Reply-To [EMAIL PROTECTED]
_________________________________________________________________
I am going to stand by my original statement that CD's don't have
time coding embeded in the data. The TOC contains the length of track
and number of them. The data on the disc only has frame
sychronization words in it that the player reads to keep the disc
linear velocity within spec. The CD player doesn't look at "timing
info" (because it isn't there) only the data bit rate. It must
achieve a bit rate of 4.3128MHz.
The presumption that you are working under is that each piece of
data (block) that comes off they disc has an additional info telling
the player where it goes. This not the case. That is why "jitter"
exists and is a problem. If the data had a "time code" like 8mm's
R.C. Time code. Every frame would have the time attatched to it.
That would take up more space than the music itself.
FOR THE SCMS on CD crowd the subcode block that immediately
follows the 27 bit sync information, has 8 bits consisting of P, Q, R,
S, T, U, V, W. The P bit tells the player whether there is data music
there or not. It is 0 (zero) wherever there is music. These serve as
flags to indicate the space between tracks. They are usually 2 seconds.
The Q channel (READ THIS HERE!!!!!! PERTAINS TO SCMS ON CD's)
contains several functions. 1) control 2) Address 3) Q data 4) Error
detection code. The 3rd bit in the control channel part of the Q data
channel (which consists of 98 bit chunks gather 1 bit at a time from
the frames) is the COPY BIT. When it is set to 0 NO COPY. When it is
set to 1 COPY PERMIT.
-Seth
p.s. if you really want to know all there is to know get the book The
Compact Disc Handbook by Ken Pohlmann. There are all sorts of diagram
as to what I am saying.
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MD: SCMS info (no opinions, just info)
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From Seth Lacy <[EMAIL PROTECTED]>
Date Fri, 24 Apr 1998 18:11:28 -0700 (PDT)
Reply-To [EMAIL PROTECTED]
_________________________________________________________________
First off SCMS had a provision made for it in the very beginning all
they way back to the first CD's. Copy protection bits are in the
red-book CD format decided on in 1980. To clarify all this stuff that
I've seen about SCMS let me share the information that is sitting on
the SPDIF (Sony/Philips Digital Interface Format) spec sheet.
The SCMS data is not two bits next to each other. SCMS is contained
in bits 0, 2 and 15 of the control word that is in the 98 bit subcode
block found on all digital audio devices. Bit 0 must be set to 0
indicating a consumer interface. Bit 2 is a copyright bit. Second
generation copying can't occur if the bit is 0. (Almost all CD's are
apparently set to 0) Bit 15 indicates whether the program is original
or copied. A CD player outputs 0 for itself about a cd, but a MD/DAT
records a 1. All other category codes other than CD (defined in bits
8-14) work the opposite. When a CD (with bit2 = 0 and bit 15 = 0 is
copied digitally, with bit 0 = 0 (on consumer equiptment), the data
from the cd is thought of as original and 1 copy is allowed. The
recorder will set bit 15 to 0, marking it as copied, preventing a
copy. If the CD's bit15 = 1 than no copied are allowed. If the CD's
bit2 = infinite copies are allowed.
-Seth
I will post the entire SPDIF subcode block later.
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