U.S. patent application number 13/659484 was filed with the patent office on 2013-03-14 for copy protection system for data carriers.
This patent application is currently assigned to FIRST 4 INTERNET LTD.. The applicant listed for this patent is FIRST 4 INTERNET LTD.. Invention is credited to Iain BENSON, Ceri COBURN, Ian DAVIES, Anthony MILES.
Application Number | 20130064055 13/659484 |
Document ID | / |
Family ID | 27589710 |
Filed Date | 2013-03-14 |
United States Patent
Application |
20130064055 |
Kind Code |
A1 |
MILES; Anthony ; et
al. |
March 14, 2013 |
Copy Protection System for Data Carriers
Abstract
A copy-protected compact disc includes, within a single session,
a table of contents (TOC) and a Video CD index (VI). Each track (T)
is prefaced by unrecoverable data (UD) at a track start position
(ATOC) indicated by the table of contents (TOC). However, the Video
CD index (VI) indicates the actual position (AP) of the tracks. DVD
players use the Video CD index (VI) to locate the tracks, while the
CD-ROM drives use the table of contents (TOC) and read the
unrecoverable data (UD), which prevents them from reading the
subsequent track (T). The unrecoverable data (UD) may be prefaced
by data pointers (DP) which cause the CD-ROM drive to load a player
program in response to the error condition. The player program can
be used to play the tracks (T), but restricts copying. Subchannel
data (P; DX) causes audio CD players to ignore the Video CD index
(VI) and the unrecoverable data (UD), and to play the tracks (T) at
their actual start positions (AP).
Inventors: |
MILES; Anthony; (Bridgend,
GB) ; BENSON; Iain; (Bridgend, GB) ; COBURN;
Ceri; (Bridgend, GB) ; DAVIES; Ian; (Rhiwbina,
GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
FIRST 4 INTERNET LTD.; |
Banbury |
|
GB |
|
|
Assignee: |
FIRST 4 INTERNET LTD.
Banbury
GB
|
Family ID: |
27589710 |
Appl. No.: |
13/659484 |
Filed: |
October 24, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13180596 |
Jul 12, 2011 |
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13659484 |
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10560316 |
May 2, 2006 |
7987508 |
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PCT/GB2004/002433 |
Jun 9, 2004 |
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13180596 |
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Current U.S.
Class: |
369/30.04 ;
G9B/27.05 |
Current CPC
Class: |
G11B 20/00086 20130101;
G11B 20/00956 20130101; G11B 20/00659 20130101; G11B 20/00688
20130101 |
Class at
Publication: |
369/30.04 ;
G9B/27.05 |
International
Class: |
G11B 27/32 20060101
G11B027/32 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 9, 2003 |
GB |
0313240.4 |
Claims
1-50. (canceled)
51. The optical disc carrying a session including a table of
contents and a program area containing at least one track, the
table of contents indicating a first start position, wherein: a. a
data portion is located at said first start position and is
arranged to cause a read failure by a first optical disc reader,
which reads at said first start position; b. the track is located
at a second start position different from said first start
position; and c. the session further includes an index indicating
said second start position, such that a second optical disc reader
is enabled to read the track by reading the second start position
from the index.
52. The optical disc according to claim 51, wherein the index is a
video CD index and said second optical disc reader is a video CD
compatible optical disc reader.
53. The optical disc according to claim 51, wherein the index is
located at a predetermined position within the session, such that
it is recognized by the second optical disc reader.
54. The optical disc according to claim 51, wherein the program
area includes one or more subchannels arranged to cause a third
optical disc reader to read the track and to ignore the data
portion.
55. The optical disc according to claim 54, wherein the one or more
sub channels are arranged to cause the third optical disc reader to
ignore the index.
56. The optical disc according to claim 54, wherein the third
optical disc reader is an audio CD player, and the track is an
audio track.
57. The optical disc according to claim 51, wherein the data
portion includes unrecoverable data arranged to cause a read error
in the first optical disc reader.
58. The optical disc according to claim 51, wherein the data
portion includes a pointer to a player program executable by the
first optical disc reader to play the track.
59. The optical disc according to claim 58, wherein the pointer
indicates a position on the optical disc at which the player
program is stored.
60. The optical disc according to claim 58, wherein the data
portion is arranged to cause the first optical disc reader to
execute the player program.
61. The optical disc according to claim 58, wherein the player
program is arranged to restrict copying of the track by the first
optical disc reader.
62. The optical disc according to claim 51, including a boot sector
arranged to cause a third optical disc player to execute a player
program when the optical disc is loaded into the third optical disc
player.
63. The optical disc according to claim 62, wherein the player
program is arranged to restrict copying of the track by the third
optical disc player.
64. The optical disc according to claim 62, wherein the player
program is stored on the optical disc at a position indicated by
the boot sector.
65. The optical disc according to claim 51, further including a
supervisory program arranged to be executed by the first optical
disc player when the optical disc is loaded therein, the
supervisory program being arranged selectively to prevent access to
the optical disc by the first optical disc player.
66. The optical disc according to claim 51, wherein the track is
able to be copied to another carrier via the first optical disc
reader.
67. The optical disc according to claim 51, wherein the track is
unable to be copied by the second optical disc reader to another
carrier.
68. The optical disc according to claim 51, wherein the program is
unable to be loaded and executed by the second optical disc
reader.
69. A method of manufacturing an optical disc, the method
comprising: formatting source data to create a session including a
table of contents and a program area containing at least one track,
the table of contents indicating a track start position; and
recording the formatted source data on the optical disc, wherein:
a. a data portion is located at said first start position and is
arranged to cause a read failure by a first optical disc reader,
which reads at said first start position; b. the track is located
at a second start position different from said first start
position; and c. the session further includes an index indicating
said second start position, such that a second optical disc reader
is enabled to read the track by reading the second start position
from the index.
70. The method according to claim 69, wherein the index is a video
CD index and said second optical disc reader is a video CD
compatible optical disc player.
Description
FIELD OF THE INVENTION
[0001] This invention concerns methods, software and formats for
preventing or restricting copying of data, particularly as recorded
in digital form on a carrier such as optical disc media. In this
description optical disc media is intended to include compact discs
(CDs), CD-ROMs and Digital Versatile Discs (DVDs), as well as
similar media that may be read using electromagnetic radiation
outside the visible range.
BACKGROUND OF THE INVENTION
[0002] CD audio discs contain at least a first session formatted in
compliance with the well known `Red Book`, also known as Standard
908 of the International Electrotechnical Commission (IEC) entitled
`Compact Disc Digital Audio System` (Geneva, Switzerland,
1987).
[0003] CD-ROMs contain one or more sessions formatted in compliance
with the `Yellow Book` standard and normally its extension `System
Description CD-ROM XA`, which includes a data retrieval structure
based on ISO 9660. The `Yellow Book` standard incorporates the `Red
Book` standard, so that CD data drives can play audio data as well
as read non-audio data. Multisession CD-R and CD-RW discs comply
with the Orange Book standard.
[0004] In this specification, a distinction will be made between
`audio CD players`, which need only be able to read CDs complying
with the Red Book standard, and `CD-ROM drives`, which are able to
read CD's complying with the Yellow Book standards, and normally
the Orange Book standard as well. Audio CD players are generally
stand-alone devices having no other functionality than audio
reproduction, although they may be integrated with other devices.
CD-ROM drives are peripherals for general-purpose computers or
other similar devices which are able to load and run application
programs selected by the user.
[0005] The advent of recordable CDs (CD-R) has made it generally
easy and inexpensive to make unauthorised copies of audio CDs and
CD-ROMs; for example by copying the entire contents of an audio CD
to a computer hard disc and then writing this to a CD-R. The
potential loss of revenue to recording companies from such
activities is considerable, and indeed its impact has already been
felt. Consequently, there is a need to prevent such unauthorised
copying.
[0006] Red Book compliant CDs contain a great deal of information
which is not necessary purely for playing audio tracks and which is
ignored by most audio-only players. Hence, one approach to
preventing unauthorised copying has been to deviate from Red Book
compliance in a way that is ignored by audio CD players, but causes
an error in a CD-ROM drive.
[0007] Examples of this approach are described in WO 00/74053, in
which selected control data is rendered inaccurate or incorrect;
the Table of Contents (TOC) may identify the audio tracks as data
tracks, or may incorrectly identify the position of the Lead-Out.
WO 02/075735 discloses identifying the first session as CD-ROM data
when it actually contains audio tracks. EP 1239472 also discloses
the idea of identifying audio tracks as data tracks in the TOC.
[0008] The techniques mentioned above are intended to prevent
reading of audio tracks by a CD-ROM drive, and thereby prevent
storage of the tracks on a computer and subsequent recording or
distribution on some other medium. However, some users would like
to play audio CDs on their computers. Hence, there is also a need
to provide audio tracks in such a way that they can be played on a
CD-ROM drive but cannot be re-recorded or distributed.
[0009] One solution to this problem has been to provide the audio
tracks in a first session which cannot be read by a CD-ROM drive,
and to provide an encrypted version of the audio tracks in a second
session. The encrypted tracks can only be decrypted and played by a
player program which plays the audio data by converting it to audio
signals.
[0010] However, certain multifunction devices such as DVD players
also conform to the Yellow Book standard and are therefore
prevented from reading the audio tracks. Furthermore, multifunction
devices may not be capable of loading and running a player program
to decrypt and read a second session. Hence, a multifunction device
such as a DVD player may not be able to reproduce any of the
content of a copy-protected CD, despite being incapable of
producing unauthorised copies. This problem is not unique to DVD
players. For example, MP3-enabled CD players, automotive audio
systems where the CD player is used to read mapping information for
a navigation system as well as to play audio CDs, and games
consoles may all be sensitive to modified control data in the first
session, but incapable of running a player program to decrypt a
second session. The sensitivity to modified control data in the
first session depends on whether a suitable recovery strategy is
programmed into the firmware of the device. Multifunction devices
which are not general-purpose computers are normally not
reprogrammable, but contain all of the necessary programs in
firmware, and cannot therefore load a new player program for
playing the second session.
[0011] Another problem is that the second session occupies a
significant proportion of the CD, and yet typically contains
duplicate content to the first session. Hence, the use of a second
session restricts the quantity of content which can be recorded on
a single CD.
STATEMENT OF THE INVENTION
[0012] According to one aspect of the present invention, a compact
disc includes, within a single session, different indexes each
recognisable by a different class of compact disc player. One index
gives the start addresses of the payloads of tracks, and allows the
class of player which reads that index to play the tracks. That
class may be Video CD compatible players. A second index gives
addresses for encapsulating data which prefaces some or all the
tracks, leading a second class of player to read the encapsulating
data instead of the tracks. The encapsulating data causes the
second class of player to start a player program which allows
playback but not copying of the tracks. The second class may be
CD-ROM drives. The encapsulating data and the other index are
recorded in such a way that a third class of player ignores them,
and plays the tracks. The third class may be audio CD players.
[0013] Thus, a single session may contain tracks which are readable
by each of the three different classes of CD player, but restricts
copying of the tracks by the second class of player, which is
otherwise able to copy the tracks.
[0014] According to another aspect of the present invention, there
is provided a method of preventing access to a removable storage
medium, such as a CD or DVD, by unauthorised applications,
comprising intercepting commands sent through an application
program interface to the drive, preventing normal operation of
standard commands, and enabling operation of non-standard commands
by converting non-standard commands to standard commands and
sending them to the drive. Unauthorised programs do not normally
generate non-standard commands, and are therefore prevented from
controlling the drive, while authorised programs use non-standard
commands to control the drive. This aspect of the invention
provides a convenient way of distinguishing between authorised and
unauthorised programs.
[0015] The present invention extends to a method of recording the
compact disc, a computer program for performing the method, and the
data structure of the compact disc.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] A detailed description of the preferred embodiments will now
be described with reference to the accompanying drawings, in
which:
[0017] FIG. 1 is a diagram of a session format in an embodiment of
the invention;
[0018] FIG. 2a is a diagram of a driver chain between an
application and a CD-ROM drive;
[0019] FIG. 2b is a diagram showing the insertion of a supervisory
program in the driver chain;
[0020] FIG. 3a is a diagram showing the action of a command proxy
function in the supervisory program when receiving a command proxy
from a higher layer;
[0021] FIG. 3b is a diagram showing the action of a command proxy
function in the supervisory program when receiving a standard
command from the higher layer, and
[0022] FIG. 4 is diagram illustrating the stages of manufacture of
a compact disc according to the embodiment.
DESCRIPTION OF THE EMBODIMENTS
Multiple File Systems in Single Session
[0023] In an embodiment of the invention, a compact disc (CD)
carries a single session incorporating multiple data structures
each complying with a filing system of a different standard. In
this embodiment, the single session includes multiple different
data structures readable by PC-compatible computers, Mac.TM.
computers, Red Book standard audio CD players, and White Book
standard video CD players. The track format is compatible with the
relevant standard for that track type. In this way, a player can
recognise one of the data structures in order to access the tracks,
and can play the tracks if it is able to decode their format.
However, the data structures readable by PC-compatible and Mac.TM.
computers include unrecoverable data, which prevent the computer
from reading the tracks unless by means of a dedicated player
program which prevents unauthorised copying of the tracks.
[0024] FIG. 1 shows a sample format of a single session in an
embodiment of the invention. The single session contains a lead-in
LI, a program area PA containing one or more tracks T1-TN, and a
lead-out LO. The lead-in LI includes a table of contents (TOC),
identifying the absolute times (ATIME) of the start of each track
and of the lead-out LO.
[0025] The tracks T1-TN conform to the Red, Yellow and White Book
standards as appropriate to each track. These formats are well
known, but the relevant parts are recited here for ease of
understanding. Each frame of data which is modulated and recorded
on the CD includes one subcode byte. Each bit of the subcode byte
corresponds to a different subcode channel, labelled from P to W.
The P-channel is a single bit that goes high during an optional
pause between tracks and goes low during the track. The Q-channel
contains time codes, track type and catalogue information and, in
the Lead-in, the TOC. The time codes include ATIME, the absolute
time elapsed since the start of the session in the format M:S:F
denoting minutes, seconds and frames. The Q channel also indicates
the track number TNO, which increments during the pause preceding a
track, and the index IDX which changes from `00` indicating a pause
to `01` indicating a track.
[0026] As shown in FIG. 1, there is an extended pre-gap area PG
containing multiple different data structures preceding the first
track T1. The first data structure is a Mac.TM. boot sector MB
containing a pointer to an HFS sector HS containing a Mac.TM.
compatible player application, as described below. Thus, a Mac.TM.
class computer, on mounting the CD, will load and run the Mac.TM.
compatible player application.
[0027] Next, there are recorded data pointers DP required by the
ISO 9660 standard: the Primary Volume Descriptor (PVD),
Supplementary Volume Descriptor (SVD), and Volume Set Descriptor
(VSD). The data pointers DP point to ISO 9660/Joliet files JF,
containing a PC-compatible player application, as described below,
and to duplicate data pointers DP preceding unrecoverable data UD
as will be described below under the heading `Data
Encapsulation`.
[0028] Next, there is recorded a Video CD index section VI
containing the files `info.vcd` and `entries.vcd`, recorded at
ATIME of respectively 00:04:00 and 00:04:01. According to the White
Book standard, this section VI would normally be included in a
segment play area of the disc, but in this embodiment, it is
included in the extended pre-gap area PG. As a result, the index
section VI is ignored by CD audio players and is not visible in the
ISO 9660 Joliet or HFS filing systems.
[0029] Most DVD players identify a VCD type disc by looking for the
files `info.vcd` and `entries.vcd` at ATIME of respectively
00:04:00 and 00:04:01, and will therefore find these files at the
expected position and disregard the ISO 9660 data structure. The
VCD index section VI is not indexed in the HFS or Joliet filing
systems, and will therefore not be found by PC-compatible and
Mac.TM. class computers.
[0030] The file `entries.vcd` comprises an index of the positions
of tracks readable under the VCD format in the disc. The index
includes the actual start positions AP of each of the tracks T1-TN,
but may also include the positions of video segments VS stored
within the pre-gap area PG. Hence, a DVD player is able to locate
and play the tracks T1-TN, and any video segments VS. According to
the White Book, audio tracks conforming to the Red Book standard
can be played.
Data Encapsulation
[0031] Since the tracks T1-TN are recorded in standard formats, it
is desirable to prevent unrestricted access to the tracks by
PC-compatible and Mac.TM. class computers. This is achieved by a
format which will be referred to as `data encapsulation`. In
outline, data encapsulation involves prefacing a track with
unrecoverable data and a pointer to a player program which is able
to ignore the unrecoverable data, but which restricts copying of
the tracks T1-TN. The unrecoverable data and pointer are recorded
in a format which is ignored by players which do not conform to the
Yellow Book standard, such as audio CD players. Data encapsulation
can be applied to some or all tracks in a session.
[0032] In this embodiment, data encapsulation is achieved as
follows. Immediately preceding the first track T1, there is
recorded encapsulating data ED. The absolute time position ATOC of
first track T1, as indicated in the TOC, indicates the first sector
of the encapsulating data ED. Therefore, Yellow Book standard
drives will interpret the first Track T1 as beginning at ATOC, and
will start to read the track from that point. The encapsulating
data ED comprises, in sequence: blank data BD; the duplicate data
pointers DP; unrecoverable data UD, and audio silence AS.
[0033] The unrecoverable data UD may be unrecoverable due to one or
more of sync information, error detection code (EDC) or error
correction code (ECC) being corrupted. Alternatively, an
inconsistent value of ATIME may be written in each sector header,
while the EDC and the ECC do not indicate any error in this
value.
[0034] The encapsulating data ED is followed sequentially at an
absolute time position AP by the first track T1, which conforms
entirely with the appropriate standard for the relevant track
type.
[0035] The P channel bit stays high at the position ATOC, but goes
low at the position AP. At this point, the index IDX changes from
00 (indicating a pause) to 01 (indicating a track). Throughout the
pre-gap area PG, the track number TNO indicates the track number of
the following track (in this case, it has the value 1). As shown in
FIG. 1, each of the subsequent tracks may be prefaced by the
encapsulating data ED.
[0036] When an encapsulated track is played by a CD-ROM drive, the
drive reads the position ATOC from the TOC and starts reading at
that position. First, the duplicate data pointers DP are read; the
duplicate data pointers DP are included here because some CD-ROM
drives may not be able to recognise the pointers in the pre-gap
area PG. When the unrecoverable data UD is read, the data reading
operation is aborted. The CD-ROM drive will then implement a
recovery strategy, which includes reading from the position
indicated by the data pointers DP. Hence, the player program is
loaded automatically.
[0037] When the track is played by an audio CD player, the player
starts to look for the track T at the position ATOC but also
examines other control data, such as the P channel and the index
IDX, to determine the start position of the track T. The player
therefore starts to read the track from the time AP, thereby
avoiding the encapsulating data ED and playing the track as a
normal audio track.
[0038] By this method, a CD-ROM drive encounters an error in the
data itself, rather than in the control information. The method
cannot be circumvented simply by ignoring all data errors, because
there may be unintentional data errors elsewhere on the CD which
cannot be ignored.
[0039] A multifunction device which detects video CDs by looking
for the files `info.vcd` and `entries.vcd` at a predetermined
position on the compact disc will use the track index contained
within those files; as the track index indicates the start position
as AP, rather than ATOC, the encapsulating data ED is not read by
the multifunction device.
Player Program
[0040] As described above, the CD contains both a Mac.TM. player
program and a PC-compatible player program, each arranged so that
it is only identified by the relevant filing system. The player
program is designed to read the CD in the same manner as a DVD
player, by reading the VCD index section VI at the predetermined
position as described above. The player program does not attempt to
read the encapsulating data ED. However, the player program is
arranged to play the tracks only if a supervisory program, as
described below, is running on the computer.
Supervisory Program
[0041] Preferably, a disc produced according to the embodiment
contains software that is activated when the computer operating
system first accesses the disc; this may be done automatically
using an `autorun` function of the operating system. The software
may comprise visible, hidden, or a combination of visible and
hidden files on the disc. The software may comprise multiple files,
packaged into a single package file.
[0042] The software may conceal critical registry entries by
deploying filters within the host operating system. This makes it
difficult to inhibit the software by changing registry entries.
[0043] The software instantiates a memory resident supervisory
program that monitors access to the protected disc. When the disc
is removed, the supervisory program is removed from the memory of
the PC. The supervisory program is also designed to monitor the
activity of the disc, including disc speed and disc access type
(digital or audio) and to ensure reliable playback of the disc
content.
[0044] The supervisory program inserts itself or part of itself
into the operating system driver chain. As illustrated in FIG. 2b,
a driver chain is a computer operating system feature, where an
application APP communicates with a higher level HL of the chain.
This higher level HL communicates with a lower level LL which
communicates with the CD-ROM drive. The driver chain presents a
standard application program interface API to the application
program APP for communicating with a large variety of hardware
devices. As shown in FIG. 2b, the supervisory program SP inserts
itself into this driver chain by modifying the chain pointers in
the next highest and lowest levels, and can therefore monitor all
communications from the application program APP to the CD-ROM
drive. The supervisory program SP performs command monitoring and
disc monitoring functions.
Command Monitoring
[0045] The command monitoring function intercepts commands, such as
SCSI or ATAPI commands, sent by the application APP to the CD-ROM
drive and determines whether the commands indicate an unauthorised
activity, such as the reading of data from the disc by an
application that is not the player program. If an unauthorised
activity is detected, the relevant command is blocked by the
supervisory program and cannot continue down the driver chain to
the CD-ROM. A command response is generated by the supervisory
program and is returned up the driver chain to the application. The
response may be an error message or dummy data, which appear to
have originated from the CD-ROM drive, and prevent the application
from performing the desired operation.
[0046] Alternatively, the command monitoring function may pass a
read command to the disc, but may corrupt the data read from the
disc if the read operation is not authorised, so that the
application receives corrupt data.
Command Proxy
[0047] The command monitoring function is able to handle
non-standard commands, referred to as `Command Proxies`, sent by
the application to the drive. Command proxies are not recognisable
by the drive and are only used by authorised applications. The
codes for command proxies may be kept secret, so that unauthorised
applications cannot be programmed to use them.
[0048] As shown in FIG. 3a, when the command monitoring function of
the supervisory program SP receives a command proxy CP, it alters
the command proxy to a standard drive command and passes the
standard command C on to the drive. The drive processes this
command as normal and returns the result D to the supervisory
program SP, which generates a corresponding result D to send to the
application program APP. For example, a `read` command proxy CP
causes the command monitoring program to send a standard read
command C to the drive. The drive returns the read data D which is
passed on to the application program.
[0049] Conversely, as shown in FIG. 3b, the command monitoring
function of the supervisory program SP blocks standard commands,
which are recognisable by the drive, received from an application
program. For example, when the normal read command C is used, its
operation is blocked by the command monitoring program, and an
error message E may be returned.
[0050] In a more specific example, the commands C are standard SCSI
commands such as defined in draft standard ANSI T10 MMC and the
SCSI Primary Commands standards SCP-2 and SCP-3. Both SCSI and
ATAPI drives use the standard SCSI command set. The command proxies
CP conform with the SCSI command standard, except that their
command codes do not have any standard meaning and are therefore
not recognisable by drives conforming to the SCP standards.
However, the command monitoring function accesses a conversion
table that converts command proxies CP to standard commands C, and
is therefore able to recognise command proxies CP and send
equivalent standard commands to the drive.
Disc Monitoring
[0051] The disc monitoring functions involve monitoring data read
by the CD-ROM and passed along the driver chain to the application.
If unauthorised activity is detected, the read operation is
prevented.
[0052] The supervisory program SP may, for example calculate the
average data transfer rate, disc speed or the type of read
operation that is being attempted. When a disc is being played in a
computer using the player program, the average data reading speed
of the disc will be approximately the same as the speed at which
the player program plays the data. The data may read from the disc
in blocks at a high speed (burst speed), followed by a much longer
period of inactivity. The burst speed could in fact be anything up
to and including the maximum read speed of the CD-ROM drive, but
for very short periods. On the other hand, CD copying software
typically will try to copy at the highest speed possible for a
sustained period. The supervisory program monitors the average data
reading speed over a predetermined period, such as ten seconds. If
the average speed exceeds a threshold, then the read operation is
prevented.
[0053] The supervisory program may monitor the position of the read
head of the CD-ROM and compare the position to a range of positions
that the player program should not need to access. If a position
within that range of positions is being accessed, the supervisory
program prevents the read operation. For example, the player
program should not attempt to read the encapsulating data, so the
range of positions may include the positions of the encapsulating
data ED. If the supervisory program detects that the player program
is running but the encapsulating data is being read, then the
reading operation is inhibited. The read operation may be prevented
by blocking the data from reaching the application, and returning
an error message, dummy data or corrupt data as described above.
The supervisory program may shut down the unauthorised application.
An eject command may also be sent to the CD-ROM.
[0054] The supervisory program interacts with the player program to
prevent unauthorised activities. If the player program is not open,
or is closed by the user while the disc is still in the CD-ROM
drive, then the supervisory program sends an eject command to the
CD-ROM drive. Likewise, if a protected disc is no longer present in
the CD-ROM drive, the supervisory program closes itself down.
[0055] The supervisory program may comprise multiple program
components, each of which checks for the presence of some or all of
the other components and restores any of the other components which
have been removed or corrupted. This makes it very difficult for
the supervisory program to be removed in an unauthorised
manner.
[0056] Where there is more than one protected disc accessible to
the computer at the same time in different drives, the supervisory
program, when launched by the insertion of a protected disc,
determines whether there is another instance of itself already
running. If so, the drive containing the new disc is added to a
list of drives monitored by the other instance. If not, the new
instance of the supervisory program is deployed. Once all of the
monitored drives no longer contain a protected disc, the
supervisory program removes itself from the system.
[0057] In general, the supervisory program is designed to detect
any access to a protected disc other than the player program
accessing the disc. If the disc is accessed in any other way the
activity will be judged illegal and interventionary action will be
taken by the supervisory program. The supervisory program
identifies a protected disc by recognising a signature which forms
part of the disc format structure, and does not prevent the copying
of an ordinary disc or interfere with the general performance
and/or activities of the computer.
CD Production
[0058] To produce a CD formatted according to an embodiment of the
invention requires special software to be used during the mastering
process, which is illustrated in FIG. 4. The source data D for one
or more tracks is provided on a carrier, which may itself be a
recordable CD or a digital tape. The source data is formatted (S10)
by software to generate a session and associated data in the format
described above, for recording on the CD. The formatted data is
recorded (S20) on a CD master, using for example a laser beam
recorder which writes the data on a coated glass master. The glass
master is developed (S30) to produce a metallized glass master M.
The master may be used to produce one or more stampers S by an
electroforming process (S40). CDs are mass-produced from the
stamper S by a stamping process (S50). In an alternative embodiment
suitable for low volume production, recordable CD's may be recorded
directly with the formatted data.
[0059] The formatted data may be recorded as a data set for input
to the recorder at a subsequent time.
[0060] Embodiments of the invention include CD production software
for formatting data and/or controlling a recording process to
generate one or more CD's having a format in accordance with an
embodiment of the invention. Embodiments also include formatted
data having a structure as defined above.
[0061] The above embodiments are provided purely by way of example.
Alternatives, which may be apparent to the skilled person on
reading the specification, may nevertheless fall within the
invention as defined by the claims.
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