Error detection/correction and fault detection/recovery – Pulse or data error handling – Digital data error correction
Reexamination Certificate
2002-05-28
2004-04-06
Tu, Christine T. (Department: 2133)
Error detection/correction and fault detection/recovery
Pulse or data error handling
Digital data error correction
C386S349000
Reexamination Certificate
active
06718501
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
The present invention relates to copy protection, and, more particularly, to a method and system for copy-protecting a digital audio compact disc as well as to the resulting copy-protected compact disc.
Types of Compact Disc
The familiar compact disc (CD) has become one of the most highly successful of modem consumer products, with current annual worldwide production and distribution in the billions. Low manufacturing costs, availability of inexpensive recording and playback equipment, reasonably high data densities, extremely high reliability, noise immunity, absence of contact wear during playback, and versatility of the medium underlie the wide popular acceptance of the compact disc. There are two principal kinds of compact disc, distinguished by the nature of the recorded material:
The first kind of compact disc is termed the “audio compact disc”, which herein denotes any compact disc on which audible sounds, such as music, speech, and other material in the audible spectrum can be recorded, and which substantially contains only information for reproducing audio signals. The audio compact disc is specified by the International Electrotechnical Commission (IEC) International Standard 908 “Compact disc Digital Audio System”, which is substantially the same as the original standard proprietary to Sony Corporation of Japan and Philips Electronics of the Netherlands. This standard is commonly known in the art, and denoted herein, as the “Red Book”, and is incorporated by reference for all purposes as if fully set forth herein. The Red Book contains the basic physical specifications for the compact disc as well as the fundamentals of the optical readout of digital audio data therefrom by laser, the “eight-to-fourteen modulation” (EFM) data encoding scheme, the data interleaving, and a concise formulation of the mathematics of the “Cross Interleave Reed-Solomon Code” (CIRC) digital error-correction method used to insure faithful sound reproduction in spite of scratches and other minor physical surface damage a compact disc can be expected to encounter during normal handling. More detailed information pertaining to the audio compact disc is available in popular publications, such as
Principles of Digital Audio
, by Ken C. Pohlman, published by McGraw-Hill, Inc., ISBN 0-07-0504687.
The basic Red Book format, recording, and playback processes for an audio compact disc are illustrated in FIG.
1
and
FIG. 2
, to which reference is now briefly made. In particular, the principal recording unit specified by the Red Book is a sector
150
. Because sector
150
corresponds to a record data block
110
(
FIG. 1
) containing 2,352 usable bytes of data, the playback of the audio compact disc results in a playback data block
235
(
FIG. 2
) which also contains 2,352 bytes of audio data. The Red Book standard parameters are such that 75 consecutive sectors of audio data represent one second of audio signal content, and at 2,352 bytes per sector this results in a data rate of 176,400 bytes per second. The Red Book specifies that each audio data sample contains 2 bytes (16 bits), and that two audio channels are simultaneously encoded for stereo. Thus, each channel has an audio data rate of 44,100 samples per second, corresponding to an upper frequency of 22 kHz according to the well-known Nyquist criterion. The 16-bit resolution provides a dynamic range in excess of 90 dB, from −32,768 to +32,767.
The second kind of compact disc is termed the “compact disc read-only memory” (CD-ROM), which herein denotes any compact disc oh which arbitrary digital data may be recorded. The data on a CD-ROM may represent audio information, but it may also represent images, video, graphics, text, executable computer programs and data therefor, as well as any other information which may be represented digitally. The CD-ROM is specified by ISO/IEC International Standard 10149 “Data Interchange on Read-Only 120 mm Optical Data Disks”, which is substantially the same as the original standard proprietary to Sony Corporation of Japan and Philips Electronics of the Netherlands. This standard is commonly known in the art, and denoted herein, as the “Yellow Book”, and is incorporated by reference for all purposes as if fully set forth herein. The Yellow Book standard is based upon the physical and fundamental data format specifications of the Red Book, and contains specifications for additional data formatting, sector addressing, mode specification, byte scrambling, an additional two levels of Reed-Solomon Product Code (RSPC) error-correction, error-detection encoding, and byte swapping. More detailed information pertaining to the CD-ROM as well as to compact discs in general is available in popular publications, such as
The Compact Disc Handbook
by Ken C. Pohlman, published by A-R Editions, Inc., ISBN 0-895-79-300-8.
(Although the present invention pertains only to audio compact discs as specified by the Red Book, some details of the Yellow Book are herein presented so that the limitations of the prior art as well as the functioning of the copy-protection afforded by the present invention may be better appreciated. It is not necessary, however, to take into consideration any details specific to the Yellow Book in order to carry out the method according to the present invention or to produce an audio compact disc with copy-protection according to the present invention.)
There are a number of formatting variations covered by the Yellow Book, and there are derivative formats covered by related standards. A conceptual view of the Yellow Book recording process and format is illustrated in general in
FIG. 3
, to which reference is now briefly made. In summary, Yellow Book recording from a computer
305
starts with an arbitrary record data block
310
containing from 2,048 bytes to 2,324 bytes of any kind of binary data. The presence or absence of the optional features indicated in
FIG. 3
depend on the specific mode in use, so that the actual number of bytes available for data varies according to the mode. Record data block
305
is given an optional additional error-correction
315
, a byte scrambling
320
, and a byte swapping
325
, and is then formatted into a Yellow Book record sector
330
containing a total of 2,352 bytes, including the original data from record data block
310
and additional data such as header, a sector address
330
-
2
, mode, and other optional information. The particular format of Yellow Book record sector
330
also depends on the details of the specific mode in use. Finally, Yellow Book record sector
330
is treated as a Red Book record data block, which is then recorded onto compact disc according to the Red Book standard. Playback of the recorded Yellow Book CD-ROM is illustrated in
FIG. 4
, and is essentially the reverse of the recording process shown in
FIG. 3. A
CD-ROM drive
400
reads a CD-ROM
440
via a laser reader
445
whose position relative to CD-ROM
440
is set by a sector selector
450
which receives an input from a computer
435
. A Red Book playback data block
405
is output from laser reader
445
and treated as a Yellow Book playback sector
410
, which undergoes a byte de-swapping
415
, a byte descrambling
420
, and an optional error-correction
425
to yield the arbitrary binary data of playback data block
430
for computer
435
. At the same time, sector address decoding
455
provides a reference input to sector selector
450
.
Recording an Audio Compact Disc
FIG. 1
illustrates the basic prior-art recording process for an audio compact disc. An audio sampling source
105
generates pairs of 16-bit samples of a two-channel (stereo) audio signal at a rate of 44,100 samples per second. These create a record data block
110
containing 2,352 bytes of data every {fraction (1/75)} second, which are then encoded by an EFM encoding
115
as specified in the Red Book and as is well-known in the art. The bytes then undergo a crossing and cross-delay
120
followed by a computation
125
of a C2 error-correction code
Brody Moshe
Sollish Baruch
Macrovision Europe Limited
Tu Christine T.
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