Error detection/correction and fault detection/recovery – Pulse or data error handling – Digital data error correction
Reexamination Certificate
2000-05-30
2004-11-16
Ton, David (Department: 2133)
Error detection/correction and fault detection/recovery
Pulse or data error handling
Digital data error correction
C714S772000
Reexamination Certificate
active
06820229
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to authenticity verification of optical media in general and to generating bistable symbols in particular.
BACKGROUND OF THE INVENTION
Digital data written to Compact Discs (CD), and Digital Video optical Discs (DVD) undergoes a well-defined series of processing steps including interleaving, Reed-Solomon encoding, and Eight-to-Fourteen-Modulation (EFM) encoding in the case of CDs or eight-to-sixteen encoding (known as EFM-Plus), for DVDs. International standards applicable to CDs are defined in the CD Colored Book series (Red Book. Yellow Book, and Green Book, for example) and also available as ISO/IEC standards. The DVD standard is defined in a series of books owned by the DVD Consortium (now known as the DVD Forum), available through Toshiba Co, of Japan. In particular, reference should be made to the ISO/IEC publication CD-information technology—Data interchange on read-only 120 mm optical data disks (CD-ROM), ISO/IEC 10149, 2
nd
ed., 1995, and to DVD Specifications for Read-Only Disc, Part 1 Physical Specifications Version 1.0, August 1996, respectively.
Additional information on data processing in optical media can be found in Chaps. 3 and 4 of
The Compact Disc Handbook
, 2
nd
ed., by Ken C. Pohlmann, published by A-R Editions Inc., Madison, Wis., 1992 and Chaps. 5 and 9 of
Principles of Digital Audio
, 3
rd
ed., by Ken C. Pohlmann published by McGraw-Hill Inc., New York, 1995.
In corresponding patent applications U.S. patent application Ser. No. 08/869,209 and U.S. Provisional Patent Application No. 60/038,080 to the present Applicant, which are herein incorporated by reference, methods for producing and reading bistable (ambiguous) data on pressed and recordable optical media are described.
It is difficult to faithfully reproduce the locations and values of bistable data without access to specially modified mastering or recording equipment. Therefore, bistable data on a disc cannot be readily reproduced on illicit copies of the disc. Software that checks for the presence of bistable data can determine if a particular disc is genuine (has bistable data of the correct values in the correct locations on the disc) or is counterfeit (no bistable data, or bistable data in the wrong locations or having the wrong values). Furthermore, the pattern of bistable data locations and values can represent a key to be used in decrypting the contents of a genuine disc. This key cannot be extracted from a counterfeit disc.
Definitions
The following definitions are used throughout this application:
“symbol”—a data byte or a channel word, depending on the context
“data symbol”—8-bit data that is represented on a disc as a channel word
“data value”—a value of a data symbol read from a disc (after demodulation and Reed-Solomon error detection)
“bistable symbol”—a symbol that, if read more than once, returns more than one data value
“channel word”—the 14-bit (EFM) or 16-bit (EFM Plus) binary representation of a data symbol
“companion symbols”—a pair of data symbols whose respective channel words differ solely by a shift of a single ‘1’ bit by one bit position
“main symbol”—the first companion symbol
“alternate symbol”—the second companion symbol
“augmented symbol”—a channel word with a ‘1’ that if shifted to the left by ½ bit position corresponds to one data symbol and if shifted to the right by ½ bit position corresponds to the companion symbol of the first symbol representation. Special hardware and software are required to produce an augmented symbol.
“displaced symbol”—a channel word that does not violate run-length rules, but has no corresponding data symbol. Essentially, a channel word comprised of one of the 9 unused EFM symbols.
“substituted symbol”—a channel word that has been replaced by another channel word representing a different data symbol different than that represented by the original channel word.
“erasure”—a potentially erroneous symbol whose location is known
“error”—an erroneous symbol whose location is not known.
Reference is now made to
FIG. 1
which is a high level block diagram illustration of the method of data detection and decoding as implemented for optical data storage for CD-ROM (referenced
10
). In the case of a CD (FIG.
1
), data
12
being read is detected and demodulated (step
14
) using EFM tables. The demodulated data
12
a
then passes through the two stages of Reed-Solomon error detection, known as C
1
and C
2
decoding and correction, (steps
16
and
18
, respectively). The Reed-Solomon error detection can correct up to two errors. That is, at each error correction step, the demodulated data
12
a
is corrected (referenced
12
b
and
12
c
). Finally, the CD-ROM reader firmware makes the corrected data
12
c
accessible to the computer program as data
12
d
. Based on the number and type of errors, if any, reported by the C
2
decoder, and in compliance with possible Error Recovery Modes specified by the accessing software, the drive firmware may or may not actually permit data to leave the drive.
The output during each data processing stage (steps
14
-
20
) includes data (
12
a
,
12
b
,
12
c
and
12
d
) plus flags, referenced
22
a
,
22
b
,
22
c
and
22
d
, which indicate the status (such as the error condition) of the data
12
.
The method of data detection and decoding for DVD-ROM
30
, illustrated in
FIG. 2
, is similar to that described for a CD-ROM
10
(FIG.
1
). Briefly, data
32
is detected and demodulated (step
34
) using EFM Plus tables. The demodulated data
32
a
then passes through the two stages of Reed-Solomon error detection, known as PI and PO decoding and correction, (steps
36
and
38
, respectively), before being read by the DVD reader firmware (step
40
) allowing the data
32
d
to be accessible to the computer program.
The object of the present and referenced inventions is to write one or more augmented symbols on a disc that will be read by ordinary readers as bistable symbols. This requires that each of the companion symbols derived from an augmented symbol pass untouched through Reed-Solomon error correction,
Reference is now made to
FIG. 3
which schematically illustrates a single bistable symbol, designated D
AB
, and its associated C
1
and C
2
codewords, referenced
42
and
44
, shown horizontally and vertically, respectively.
Bistable symbol D
AB
represents the data read from the augmented symbol previously written. Bistable symbol D
AB
can be read as either of its two companion symbols, D
A
(main) and D
B
(alternate). Each C
1
codeword contains 28 data symbols and 4 parity symbols, and each C
2
codeword contains 24 data symbols and 4 parity symbols. For the purposes of clarity, only the bistable symbol D
AB
and the relevant parity symbols are shown.
In accordance with the Cross Interleaved Reed-Solomon Coding (CIRC), any given data symbol is contained in exactly one C
1
codeword and exactly one C
2
codeword. The C
1
and C
2
codewords which contain D
AB
(hereinafter referred to as primary codewords),
42
and
44
, respectively, intersect at the bistable symbol D
AB
.
For the purposes of example, the four parity symbols, referenced P
A1
, P
A2
, P
A3
and P
A4
, of the primary C
1
codeword
42
and the four parity symbols, referenced Q
A1
, Q
A2
, Q
A3
and Q
A4
, of the primary C
2
codeword
44
are erased as shown. These erasures are effectively generated by displacing the EFM symbols of the respective parity symbols.
The four parity symbols (Q
A1
, Q
A2
, Q
A3
and Q
A4
) of the primary C
2
codeword
44
are also contained in four additional C
1
codewords, designated
45
,
46
,
47
and
48
, referred to as secondary C
2
codewords. In order to prevent the erased primary C
2
codeword parity symbols (Q
A1
, Q
A2
, Q
A3
and Q
A4
) from being corrected by their companion secondary C
1
codewords (
45
,
46
,
47
and
48
), the four parity symbols, generally designated P
A11
-P
A14
, P
A21
-P
A24
, P
A31
-P
A34
and P
A41
-P
A44
, of each of the four secondary C
1
codewords, are also erased by the aforementione
Macrovision Europe
Ton David
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