Prevention of disk piracy

Details Prevention of disk piracy Prevention of disk piracy

1999-08-09

2002-07-23

Robertson, David L. (Department: 2187)

Error detection/correction and fault detection/recovery

Pulse or data error handling

C705S057000, C713S193000, C369S053210

Reexamination Certificate

active

06425098

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to protection of intellectual property rights, and specifically to prevention of unauthorized copying of recorded, computer-readable media.
BACKGROUND OF THE INVENTION
Compact disk (CD) recordings are a preferred means for distributing both digital audio recordings and computer software. CD audio recordings are almost universally made in accordance with standard 908 of the International Electrotechnical Commission (IEC), entitled “Compact Disc Digital Audio System” (Geneva, Switzerland, 1987), which is incorporated herein by reference. The 908 standard defines how audio data are to be encoded and recorded on the disk, enabling the data to be played back using standard digital decoding chips. Different standards apply to other types of data, such as computer software and video, which may be recorded on CD, as well. The various types of CDs and standards for CD recording and data storage are described, for example, in a booklet entitled “The CD Family,” published by Philips Consumer Electronics B.V. (Eindhoven, Netherlands), which is incorporated herein by reference. A “road map” shown on page 29 of the booklet lists different formats that exist among members of the “CD family.”
FIG. 1
is a block diagram illustrating the structure of a frame
20
of audio data for storage on an audio CD, in accordance with the IEC 908 standard. Each such frame comprises one control symbol
24
, followed by thirty-two data symbols
28
. Each symbol is spaced from the preceding one by a separator
30
comprising three auxiliary bits. A block of data on the CD comprises ninety-eight frames, each of which is separated from the preceding frame by a twenty-four-bit synchronization pattern
22
.
Each symbol
28
recorded on the CD in frame
20
comprises fourteen channel bits, which correspond to a single byte of binary input data. Each of the 256 possible byte values is encoded in a process of eight-to-fourteen bit modulation (known as “EFM” modulation) as a fourteen-bit code, specified in the IEC 908 standard. A characteristic of the EFM codes is that over a run of coded data of a specified maximum length T
max
, including successive symbols
28
and separators
30
, there will always be at least one transition (from zero to one or from one to zero). T
max
is specified by the standard to be 11 channel bits long. When the data are read out from the CD, any absence of such a transition over the course of 12 successive bits will be noted as a medium error.
Following control symbol
24
, each frame
20
comprises two data segments
26
and
34
and two error correction segments
32
and
36
. Each data segment comprises twelve symbols, containing data and parity information, typically corresponding to digitized audio data. Error corrections segments
32
and
36
each comprise four symbols, which are calculated based on the data in segments
26
and
34
using a Cross Interleave Reed Solomon Code (CIRC), as specified by the 908 standard. The CIRC segments are read during playback and are used to identify errors in the corresponding data segments. Dedicated, proprietary processors, typically based on custom integrated circuit chips, are used in CD players to correct the errors if possible and to conceal those errors that cannot be corrected, as described further hereinbelow.
FIG. 2
is a schematic block diagram illustrating the functions of an integrated circuit (IC) processor
40
used for digital processing of data read from a CD, as is known in the art. The functional blocks shown in
FIG. 2
are typical of commercially-available ICs, such as the SAA7345 and SAA7348 devices produced by Philips Semiconductors (Eindhoven, The Netherlands), which are used in common audio CD players.
Data are read from the CD by an optical reading head (not shown) and are input to a phase locked loop (PLL)
42
for synchronization purposes. Fourteen-bit data segments
28
are converted to eight-bit symbols by an EFM demodulator
44
and are then stored by a first-in-first-out (FIFO) memory
46
. An error corrector
48
compares the audio data read from data segments
26
and
34
to the corresponding CIRC data in segments
32
and
36
. If an error is found, corrector
48
attempts to correct the data, using the CIRC information. Such correction is not always possible, however. Corrector
48
sets indicator flags
50
depending on whether an error was detected and whether it could be corrected.
Data from error corrector
48
is input to a digital audio processing circuit
52
. If flags
50
indicate that there was an uncorrectable error in the data, an interpolator
54
conceals the erroneous value either by holding a preceding data value or by interpolating between adjacent values. The erroneous value itself is discarded. A filter
56
processes the data to enhance audio quality, and a data interface
58
formats the data for conversion to analog form by a digital/analog converter (DAC)
59
. Although some processing circuits can provide a digital output of the “raw” data, without error correction or concealment, special equipment is required to deal with this digital output, and such equipment is generally available only to established recording studios.
Original CDs are produced by stamping plastic blanks with a master mold piece, which is produced using costly, specialized equipment. Because of the high cost of CD recording equipment, CD recordings were considered, until recently, to be relatively secure against unauthorized copying. This situation has changed recently, as inexpensive CD recording devices and read/write media have become available to consumers. Thus, it is now easy, using a conventional personal computer with a read/write CD drive, or with one read drive and one write drive, to make exact, digital copies of all types of CDs. The CD content is read out by the computer, byte by byte, from one CD, typically a legitimately-purchased original CD, and then written to a blank CD so as to make a pirate copy. Similar copying methods may be used with other media, such as DVD (Digital Video Disks, also known as Digital Versatile Disks). Financial losses to the recording and software industries due to such pirate copying are estimated to be in the billions of dollars.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide improved methods and apparatus for preventing unauthorized copying of recorded, computer-readable media.
It is a further object of some aspects of the present invention to provide methods and apparatus for producing compact disks that are resistant to unauthorized copying.
It is yet another object of some aspects of the present invention to provide methods and apparatus for preventing unauthorized digital copying of audio disks.
It is still a further object of some aspects of the present invention to provide methods and apparatus to preventing unauthorized copying of software disks.
In preferred embodiments of the present invention, errors are intentionally introduced into the coded content of an original digitally-recorded medium. The content of the medium further includes ancillary data, such as error detection codes or a program routine, that enable a processor in a conventional playback device, reading the original medium in accordance with a given recording standard, to automatically overcome the errors. Typically the ancillary data enable the processor either to correct or conceal the errors during playback or to ignore them altogether. When an unauthorized copy is made of the medium, however, the ancillary data are ineffective in overcoming the intentional errors in the original medium, with the result that faults occur in the copy that are substantially unrecoverable. In other words, the present invention takes advantage of error-avoidance features of the recording standard in an unexpected way, using recoverable errors introduced in the original medium to cause more serious, unrecoverable faults to be generated in the copy.
Preferred embodiments of the present invention are described hereinbelow with

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