AU2007202302A1 - Prevention of CD-audio piracy using sub-code channels - Google Patents

Description

S&F Ref: 612570D2

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT Name and Address of Applicant Actual Inventor(s): Address for Service: Invention Title: Macrovision Europe Ltd., of Woodley House Crockhamwell Road, Reading, Berkshire, RG5 3JP, United Kingdom Ran Alcalay Philippe Selve Patrice Sinquin Spruson Ferguson St Martins Tower Level 31 Market Street Sydney NSW 2000 (CCN 3710000177) Prevention of CD-audio piracy using sub-code channels The following statement is a full description of this invention, including the best method of performing it known to me/us:- 5845c(799709 1) PREVENTION OF CD-AUDIO PIRACY USING SUB-CODE CHANNELS CROSS-REFERENCE TO RELATED APPLICATIONS This application is related to U.S. Patent Application 09/549,820, filed April 14, 2000, U.S. Patent Application 09/370,813, filed August 9, 1999, U.S.

Patent Application 09/175,255, filed October 20, 1998. All of these application are of incorporated herein by reference.

FIELD OF THE INVENTION The present invention relates generally to protection of intellectual property rights, and specifically to prevention of unauthorized copying of recorded audio, computer-readable media.

BACKGROUND OF THE INVENTION ij 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, also known as the Red Book, defines how audio data are to be enclosed 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, which may be recorded on CD, as well. For example, the Blue Book standard specifies multi-sessions recordings, that combine audio and other data on a single disk.

Original music CDs are produced by molding plastic blanks with a master stamp piece, which is produced using costly, specialized equipment.

Alternatively, a recordable CD (CDR) may be created by authorized plants according to customer request. Because of the high cost of CD recording equipment, CD recording were considered, until 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 [k \1.IBE}A04457 doc edg read out by the computer, byte by byte; from one CD, typically a legitimately-purchased originai CD, and then written to a blank CD so as to make a prate cop,'. Similar copying methods may be used with other media, suci as Digita! Video Disks (DVD). Financial losses to the recording and software industries due to such pirate copying are estimated to be in the billions of dollars.

Another common method for pirate copying is via the digital audio output provided by many CD players, such as the S/PDIT (Sony/Philips Digital Interconnect Format) output. This output format is specified by IEC standard 95, entitled "Digital Audio Interface" (Geneva, Switzerland. 1993), which is incorporated herein by reference. The S/PDIF output can be used legitimately to connect the CD player to high-quality converters, speakers and dther audio components. On the other hand, since it reprcduces the audio content of the CD bit by bit, the S/PDIF output is also easy for pirates to use in making illegal copies. In addition to the audio content, the S/PDIF data includes a sub-code, known as the serial copying management system (SCMS) sub-code, that indicates whether the source of the data is an original recording or a copy. According to SCMS, commercially-available recording equipment is not supposed to allow users to record audio from a S/PDIF stream that is marked as a copy. This protection, however, is easily circumvented by pirate copiers.

SULIM/LARY OF I THE INVENTI ON It is an object of some aspects 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 still a further object of some aspects of the present invention to provide methods and apparatus for preventing unauthorized digital copying of audio disks.

In preferred embodiments of the present invention, signals recorded on an original storage medium are protected against unauthorized copying by changes made in a sub-code channel, preferably the Q-channel. For this purpose, a data-writing unit comprises an encoding block, which receives audio signals and encodes the signals in accordance with standard 908 of the International Electrotechmical Commission (TEC). A modification-msertion block of the data-writing unt alters the encoded signals. by introducing a modification in a sub-code Q channel of the encoded signals. A recording block of the data-writing unit subsequently records the altered signals on the storaoe medium. wicb typicaly com prises a compact disk

(CD).

N IPreferably, the altered signas au-e erroneous according to standard 908. or according to implementations of the standard used in CD-ROiMl drives. but.L nevertheless do not prevent playback of the audio signas fromr the original Luediun following recording. Thus, the original CD is able to perform in a mantner substantially unaffected by the alteration. By NI contrast, the alteration causes a subs-tantially-unrecoverable error when an attempt is made to Screate an unauthorized copy of the CD. The error nanifests itself in that either the C 10 unauthorized copy cannlmot be produced at all, or the copy is corrupted in such a way as to render it substantially unusable. Preferably, authorized software residing in the data-writing unit or in other hardware is enabled to duplicate the CD, such that authorized copies also can be played back, unaffected by the alteratiolln.

In sSome preferred embodiments of the present invention. the modification-insertion block inserts the modification in the sub-code Q channel by specif:ting a modified absolute or relative track tine of the audio sianals recorded on the CD. CD copying algorithms known in the art rely on non-corrupted track times, and are therefore unable to make unauthorized copies of CDs which are orepared using these emabodiments of the nresenr invention. Ourionallv. the original track time is stored on the original CD in reserved bits of the sub-code channels that are defined by standard 908. Authorized copying software retrieves the original track time from the reserved bits, and is thereby enabled to make fily---nctioing copies of the original

CD.

Xlternativel or additionally, the minodification is introduced by adding one or more additional sessions on the disk. with a lead-in that point to tracks in the prorgram area of the first session and includes special modes to block an unauthorized comuter from reading the sessio11.

Further alternatively or additionally. the inodification-insertion block inserts the modification in the sub-code Q channel by specifying a modified index number of a track of the audio signals recorded on the CD. CD copyung algorithms known in the art rely on the non-corrupted index number of the track, and are therefore unable to make unauthorized copies of CDs which are prepared using these enbodirnents of the present invention.

Optionally, the original index number of a track is stored on the orisinal CD in reserved bits of the sub-code channels that are defined by standard 908. Authorized copying software retrieves the original index number of the frack from the reserved bits or from a second session on the disk, and is thereby enabled to make ftdiy-fuiictioning copies of the original

CD.

Preferably, in order to allow an authorionzed personal computer (PC) to play the contens of the protected disk, the original contents are protected by digital rights rumanagement

(DRM)

technology, typically by compressing (using any suitable formnat known in the art, such as MP3 or VQF) and encrypting the contents. fThese encrypted data are stored in a manner that is hidden to conventional CD driver software. fir example in reserved sub-code channel bits, in the pause area or lead-out area, or in a second session on the CD. The data can be decrypted and played back only by using authorized software, which is preferably stored in the second session.

Further preferably, the modifications iroduced in the CD are suchb as to cause changes in a S/PDIF output or other digital output generated by a CD player Li which the protected

CD

is played. The changes in the digital output do not interfere with audio playback of the CD recording by compatible equipment, such as audio speakers with a digitalianalog converter.

The changes do, however, prevent unauthorized copying of the CD conteru using the dicital output, tor example, as a digital input to a recorder.

-0 Optionally, in addition to the modifications introduced in the sub-code channel, further mrodifications are intenhtionall introduced iM, the audio data an idded impediment to unauthorized copying. The modifications are introduced in such a way that ancillary data on the disk, such as error detection codes. which are provided by the 908 standard (or other applicable standard), enable a CD player either to correct or conceal die modifications during playback or to ignore thenm altogether. When an unauthorized copy is made of the medium.

however, the ancillary data are ineffective in overcoming the intentional modifications in the original medium, with the result that faults occur in the copy that are substantially unrecoverable. Methods for intr-oducing such modifications are described in the above-mentioned U.S. Patent Applications 09/175,255 and 09/370.813.

There is therefore provided, in accordance with a preferred embodiment of the present Lnvention a method for protecting data recorded on an original storage medium against copying using an unauthorized data readout device, the method, inciuincg: receivin data encoded un accordance with Standard 908 of the International Elecrrotechnical Commission.

altering a portion of the encoded data to introduce a modification in a sub-code Q channel of the data, such that the altered data are inconsistem with an implementation of Standard 908 used in the data readout device, but do not prevent playback of the data following recording thereof; and recording the data, including the altered data, on the original storage medium, whereby an application which plays back the recorded data runs in a manier substantially unaffected 'by the alteration of the data, but a substantially unrecoverable error occurs in unauthorized copying of the original storage medium.

Preferably, the medium includes a compact disk, and the data include digital audio data.

In a preferred embodiment, altering the data includes modifying an absolute time in the data to be recorded on the medium. Preferably, a correct absolute timne is stored in reserved sub-code bits on the medium. Most preferably, modiing the absolute time includes altering absolute times recorded in a plurality of consecutive blocks of a selected track.

In another preferred embodiment, altering the data includes duplicating one or more blocks of the data to a new location on the :toraae medium, without changing the absolute ime recorded in the sub-code Q channel of the one or more blocks.

In still another preferred embodiment, altering the data includes modifying a point index number in a track of the data to be recorded on the medium. Preferably, the method includes storing a correct index number in reserved sub-code bits on the medium.

In yet anoiher preferred embodirnmen, altering the data includes generating a multiple-session recording, including one or more audio and data sessions, wherein the modification in the sub-code Q channel is introduced in one or more of the data and audio sessions. Preferably, generating the multiple-session recording includes creating a lead-in to one of the sessions that points to one or more tracks located in a first audio session on the mediun. ,Aternatively or additionally, generating the multiple-session recording includes creating a lead-in to one of the sessions that includes a laerer number of tracks than is specified by the standard. Furher alternatively or additionally, generating the multiple-session recording includes creating f% lead-in to one of the sessions that hidicates that the recording medium is shorter than it is in actuality. Stll further altematively or additionally, generating the multiple-session recording includes insertmng a modified absolute time at a start of one of the sessions. Yet further alternatively or additionally, generating the multiple-session recording includes creating multiple sessions at least two of which are identified as audio sessions.

In a preferred embodiment, recording the data includes compressing and storing the data mi a data session on the medium, for use in making an authorized copy of the medium.

In a further preferred embodiment, the encoded data include encoded audio data, and the method includes altering a portion of the encoded audio data such that the altered data are inconsistent with the implementation of Standard 908 used in the data readout device, wherein recording the data on the medium includes recording ancillary data which are used by a processor in the application to operate upon the altered portion of the encoded audio data such that the application plays back the data in a manner substantially unaffected by the alteration of the encoded audio data, but which ancillary data are ineffective in correcting the altered portion of the encoded audio data upon copying of the data. so that the alteration causes a further substantially unrecoverable error in the unauthorized copying of the original medium.

Preferably, the ancillary data include error detection codes.

There is further provided, in accordance with a preferred embodiment of the present invention, a method for protecting data recorded on an original storage medium against unauthorized copying including: receiving data encoded in accordance with Standard 908 of the International Electrotechnical Commission: altering a portion of the encoded data to introduce a modification in the data, so that a digital output of the altered data will be inconsistent with an unplementation of a digital output standard, such as Standard 958 of the International Electrotechnical Commission, but the modification will not prevent playback of the data following recording thereof; and recording the data, including the altered data. on the original storage medium, whereby an application which plays back the recorded data runs in a manner substantially ulaffected by the modification in the cdara, but a subsinialy unrecoverable en-or occurs in unauthorized copymg of the original storae nmediunm based on the digital output.

a Preferably, altering tihe Iportion of the encoded data includeis altering one or more control bits in the encoded data, whch control bits are reproduced in tie digital output.

Addiionlla y or alternatively, alering the portion of the encoded data includes manipulating bits of audio data within a frrame otde encoded data.

Tlher is also provided, in accordance with a prefe-rred embodiment of the present nvention, apparatus for protecting data recorded on an original data storage medium against copymng usinmg an unauthorized data readout device, including: an encoder, adapted to receive a strearn of data for recording on the medium and encodes the data in accordance vritl Standard 908 of tie International Electroteclinical Commission; a sub-code generator, operaive to alter a lpor-ioin of tine encoded data by intoducing a nodification in a sub-code Q channel of the data, such dial the altered data are inconsistent with an implementation of Standard 908 used in ithe data readout device, but do not prevent playback of tihe data fIbllowing recording thereof: and an eight-to-fourteen bit (EFM) modulator, coupled to modulate the altered data for recording on the original storage medium, whereby an application which plays back the recorded data runs in a manmner substantially unaffected by hie alteration of die data. but a substannalkl unrecoverable en-or occurs in unauihorized copy ing of the oricinal storage meciiun.

in a preferied embodiment, tine apparatus includes a data session generator, operative to provide a data session to thie EFM for recording on thie original storage medium, so that the data recorded on thie mediun include multiple-session data, and thie defect in the sub-code

Q

channel is introduced in at least one of the multiple sessions.

There is additionally provided, in accordance with a preferred embodiment of the present invention, a data storage mnediun that is resistant to copying using an unaudthorized readout device, on which medium data encoded in accordance with Standard 908 of the International Eleen-otechnical Conmmission are stored, a portion of which encoded data is altered by introducing a modification i a sub-code Q channel of the data, such that the altered data are identified as inconsistent with an iimplementation of Standard 908 used in the data readout device, but do not prevent playback of the data following recording thereof, whereby an application which plays back the recorded data runs in a manner substantially unaffected by the alteration of the data, but a subsantially unrecoverable error occurs in unauthorized copying of the original storage medium.

The present invention will be more illy understood from the followine detailed description of tie preferred embodiments thereof, taken together with the drawings in which: BRIEF DESCRIPTION OF TIE DRAWINGS Fig. 1 is a schematic, sectional view of a compact disk in accordance with recording practice known in the art: Fig. 2 is a schematic block diagram that illustrates apparatus for producing a copy-resistant CD, in accordance wid a preferred embodimem of the present invention; Fi. 3 is a schematic illustr-ation of details of a data structure written to a CD, in accordance with recording practice knor, in the art; and Fig. 4 is a block diagram that schematically illustrates duplication of data on a CD for the purpose of preventing unauthorized copying, in accordance with a preferred embodiment of the present invenion.

DETALED DESCRIPTION OF PREFERRED EMBODIMENTS Reference is now made to Fig. 1, which is a schematic sectional view of an audio compact disk (CD) 20, showing the overall layout of the disk, in accordance with recording practice known in the art. An information area 22 includes a lead-in (LI) area 24, a program area (PA) 26 and a lead-out (LO) area 2S. Information area 22 progresses outwards in. a wideng spiral and contains all of the recorded contents of CD 20. Lead-in area 24 and lead-out area 28 both contain P and Q channels, which include tiirung and track information used during playback of the CD. Program area 26 consists of up to 99 tracks of audio information music), as well as accompanying sub-code information.

Preferred embodiments of thl present invention provide a nrunber of different, compleme-ntary techniques for modifying the data in CD 20 in order to frustrate pirate copiers.

A numLnber of these embodunents are described in detail hereinbelow. Generally speaking, the modifications fal into the folowin categories: G neral disk IlVout moCdiiciions for example, recording several sessions on an ar:dio CD. The second session can be used to mislead personal computers (PCs) that are colnm only used in pirate copying, typically by adding conflicting pointers in the lead-in of thile second session. Preferably, the last session on the CD is a data session tlat contais the nusic in con1mpressed form. Most preferably, the music is encrypted so as to enable playback directly from the disk and/or encoded using digital wrapper technology (also known as digital rights management DRM) to enable download and playback through secure software froin the disk of an authorized user.

Modifications of the audio data. by insertion of noise, preferably as described in the above-mentioned U.S. Parent Application 09/370.813 Modifications of the subcode information, particularly in the Q channel. These modifications inmay include, for example, changing the absolute or relative time, index poners, table of contents (TOC) information (listing too many or too few tracks, or irusieding pointers bet ween miuiile sessions), control bvye modifications, pregap length manipulation. Other such modifications will be apparent to those skilled in the 2 art.

Low-level moifications to the structure of the bits recorded on the CD. Such modifications are described in detail in the above-mentioned U.S. Patent Applications 09/175,255 and 09/370:S,3. They, typicallv involve recording sequences of bir the CD dthat cause hardware enrors in some CD-R.OMN drives used in PCs, or prevent them Prom interpolating over erroneous audio data. Alternatively or additionally, bit sequences mnay be recorded on the CD that do not appear in thile conventional eight-to-fourteen bit (EFIM) loolcup table specified by the 908 standard.

These modifications may be used in CD 20 in different combinations, depending on application needs.

Fig. 2 is a schematic block diagram that illustrates apparatus 40 for producing a S copy-resistant CD, in accordance with a preferred embodiment of the present invention. The original sound, or analog audio, is converted to digital format suitable for encoding on a disk.

such that the informatidn can subsequently be played back (decoded) by a standard player of 1 5 audio CD 20. In a first stage of encoding, a digital bit stream is generated which represents the continuous analog sound signal. The analog signal is converted into discrete digital samples 1 by an analog-to-digital converter 4 To enable detection and correction of errors during playback, parity bits are added to q the bit stream. An error-correction encoder 32 employs the commonly used Cross-Interleaved 0 Reed-Solomon Code (CIRC) to reorder the digital data. A sub-code generator 36 adds a byte 1 of sub-code for every thirty-two bytes of error-corrected audio. The 908 standard prescribes the contents of the sub-code channels to be added at this stage. Sub-code generator 36, however, alters the standard sub-codes in such a manner that ordhiary playback of the CD is substantially unaffected, but unauthorized copying is prevented. In particular, the alterations do not compromise the integrity of the bit stream and do not generate CIRC errors on the disk.

Methods of such alteration are described hereinbelow.

Apparatus 40 is also shown to include an optional data session generator 37, for use in producing multiple-session disks that include both audio and data sessions. As described hereinbelow, the data session is configured so as to prevent an unauthorized computer from reading the CD. An audio compressor 35 is optionally provided to compress the audio input for inclusion in such a multiple-session disk in an encoded form.

It is known in the art to map a standard sixteen-bit word of sound data into two fourteen-bit 'optical" symbols, and to include in the recording additional information, such as playback control and display functions. An eight-to-fourteen modulator (EFM) 34 combines the output of error-correction encoder 32 with the output of sub-code generator 36 and data session generator 37. Each bit of encoded data i:i preferably physically inscribed onto a master for producing CD 20, using a laser beam recorder (LBR) 38 to create a series of microscopic pits on the master. Alternatively, a dedicated burner 39 is used to produce CD 20 directly on a recordable CD (CDR).

Fig. 3 is a schematic illustration of details of the data structure received by EFMI modulator 34, in accordance with the 908 standard. A block 58 of data for recording on a CD contains 98 frames, each frame made up of 32 bytes of data, or symbols, received from encoder 32 (or from the daia session generator'37) and one eight-bit '"sub-code" word. The cigh bits Lln each sub-code word are respectively called P, Q, R, S. T U. V, and W.

C The Q bits fi-rom 98 uonsecutive flames are collectively called a sub-code Q channel 64.

The sub-code Q channel contains program and timing information, including synchronization

C

bits SO and S 1 4 control bits, 4 address bits, 72 data bits, and a 16-bit cyclic redundancy check code (CRCC). In lead- rea 24, the 72 dat bits include relative time (R-Time, or trck t-ime) data 74 and track position. while in program area 26, relative time and absolute time (A-Time, or diskic time) data are stored. The relative time for each block indicates the length of time from the beginning of a current track to the beginning of the block. The absolute time indicates the length of time from the beginning of program area 26 to the beginling of the block. Time is measured in units of minutes, seconds and frames (different from the 98 data frames in a block)i, with 75 time fi-ames in a second. The Q channel also includes a track number (TNO) and 1-track indices, also referred to as point indices. In lead-in area 24, the Q channel carries a table of contents (TOC).

Table .1 below schematically illustrates alteration of absolute time values of sub-code Q channel 64, in accordance with a preferred embodiment of the present invention. In typical .0 encoding of CD 20 according to standard 908, absolute time starts at the beginning of program area 26 and increases linearly to the end of lead-out area 28. Copying software lmnown in the art uses the absolute time as a pointer. in order to cnsure smooth reproduction of the original audio and synchroniciry of t iming between recorded frames andi played-back frames.

Preferably embodied, a modification is inntoduced into the absolute time values of the sub-code Q channel, as shown in the "altered" column in the table, thereby increasing the speed at which time appears to pass in tis track.

TABLE 1 Oripinal time Altered time Nin Sec Frame lin Sec Franme 0(star 0 0 0 0 0 track) ci0 0 0 0 0 0 3 0 0 6 0- 0 0 7 cI0 1 0 4 1 00_ S0 0 T 71 0 T 74 N0 -1 -72 K 01 -'(end 3425 36 track) (pause) 30 1 43 5 30 43 1 0 44, 1 30 44 So as 1)ot To ddversely affect stereo play-back of the audio, thet absolute time for original CD 20 is nreferablv inlcreased in2 sevtra consecutive bl1ockcs out of tevery 150 consecutive blocks, anid retuned to nonnal in a pause area btween tracks, as shown inl the table above. A standard CD player will be unaf-fected by these intentional distortions of the ,absolute tune. An u-nauthI-) o ri zed copy of CD 20 however, wilconta*i discontinuities in1 the music,. for examnple. wlire absolute time jumps from frame 2 to framne 4 to frame 6, in the table above. The resulting signal on the CD cony wil have a serlies of constant-amnpliude.

audible, distorted and generally unnelodious sounds.

Opionally, the- original. correct absolute ti-me 'information is stored i~n the reserved bits of the sub-codle R.-W channels (Fig. which are cur-rently unassigned acecording to standaird 908. Authorized soffnvare is e-nabled to make copies of oiginal CD 20 by accessing the data stored in the R- W channels.

-Alternatively, rather than intioducing modificaions in the absolute time, mo difi cations If that produce audible effects in unauthorized copies ar-e introduced in sub-code Q channel 64 by changing point index and/or mode v'alues. Like the absolute track time, the poit index provIdes a series of "checkpouiis" within a track. A modified seties of Doint indices will cause mute areas iii an unauthorized copy of CD 20, but will not affect the playback of the original CD. Optionally, as described above. the correct indices are stored mi the R-W channels, and authorize software is enabled to copy the original CD by recrieving the indices from these channels.

Preferably, modifications iztroduced in the CD are such as to cause changes in a digital output, such as a S/PDIF output, generated by a CD plavyer in which the protected CD is played. The digiul outnout data stream comnprises a sequence of 32-bit words, knon as sub-frares, eaclh carryin between 16 and 24 bits of audio data, along with preamble and control bits. One of the control bits in each sub-frame is a sub-code bit. sinilar to the sub-code bits in each frame of data on the CD. The sub-code bits in a block of 192 frames (typically 384 sub-fr-ames) in the S/PDIF data stream cary most of the contents of the sub-code Q channel being played on the CD, icluding control bytes, the track number and the rIde.

Preferably, The minodifications that ari-e introduced in the Q channel on the disk are such as to be carried over to the S/PDYF data. Although these modifications do not interfere with audio playback of the CD recording by speakers and other compatible equipment, they do impede unauthorized copying of the CD content using the digital outpur.

As specified by the above-mentioneci EC 958 standard, the S/PDIF signal contains four control bytes copied fromn the CD. Therefore, in an alternative embodiment of the present invention, these control bytes are used to fiustrate illega! copying of the audio contents. For this purpose in recording the conuoi bytes on the CD, in accordance with the Red Book standard, the rack mode is set to "'data" for a number of blocks, typically between one and ten blocks, in a repetitive cycle. The CR.CC is then recalculated so that this control byte is valid from the standpoint of data accuracy. When a recording is made ioiri the S/PDIF output of the CD player, however, this control byte setting will typically cause inmutes or clicks to appear in the resudting audicho stream.

In a further alternative embodiment, the bits in the S/PDIF envelope are shifted or otherwise manipulated in order to confound unauthorized recording of the CD contents. When the 32 bits in a S/PDIF sub-franeIC are fed to a digital/analog converter for audio playback. the converter takes all 32 bits and plays back the audio irrespective of the shift A digital recorder, 0 however, will seek the audio data in a given subset of the bits of the sub-frame, and the control Cl data in another subset, disjoint from the audio data, where these data are supposed to be according to the standard. Therefore, manipulating the bit order can block recorders while still enabling audio playback.

C

5 Fig. 4 is a block diagram that schematically illustrates another method for preventing unauthorized copying of a CD, using data session generator 37, in accordance with a preferred COl 0 embodi.ment of the present invention. Whereas an audio CD has only a smigle session Ce¢ Cl apparatus 40 with session generator 37 can produce CDs having multiple sessions, including, for example, one or more audio sessions 100 and at least one data session 102 Audio CD players read only the first session on a multiple-session CD, in this case session 100 and ignore the rest. DVD players read and are "aware" of data session 102, as well, but still play back audio session 100. When the CD is inserted into a CD-ROM drive, however, the computer can access any of the sessions and therefore will be confused by the modifications embedded in the second or subsequent sessions. The present embodiment therefore operates by introducing conflicting data into the sub-code Q channel of data session 102 or of additional audio sessions, subsequent to the first audio session. Most preferably, there are at least two audio sessions out of a total of three or more sessions on fhe disk.

Preferably, modified data are miroduced into audio session 100, as well. The modifications are introduced in such a way that ancillary data on the disk, such as Cross nterleave Reed Solomon Code (CIRC) error detection codes, which are provided by the 908 standard (or other appLicabie standard), enable a CD player either to correct or conceal the modifications 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 modifications in the original medium, with die result that faults occur in the copy that are substantially unrecoverable. Methods for inntoducing such modifications are described in the above-mentioned U.S. Patent Applications 09 /175,255 and 09/370,813.

Despite the modifications in the sub-code channels and/or audio data, an audio CD player will reproduce the audio signals on the disk without difficulty. A computer CD drive, however, will be confused by either the multiple sessions on the CD or the modified data m audio session 100 (or by both) mad will not be able to load or play the disk., et alone copy it.

Modifications in the added audio and/or data sessions are preferably introduced by one or more of the following mechanisms: Generating a lead-in that points to tracks located in the program area of the first session.

Generating a lead-in with a larger niunber of tracks than is allowed by the 908 standard.

Modifying the lead-in to simulate a shorter CD.

Modifying the absolute time at the begianning of the session.

Following these methods. Tabie ii beiow describes changes made in the sub-code Q channel of a multiple-session CD. in order to prevent computer copying of the audio content without interfering with audio playback. The first session on the CD is an audio session, based on the Red Book standard, while the second and subsequent sessions may be audio or data sessions, based on the Blue Book, as described above.

TABLB I] Session Standard Modification mnj sessions, per Blue Book format.

Pause length 2 Use different pregap length., per Blue Book format, sec preferably set to value between I and 3 sec.

Accurate Staru A-Time at non-zero value, 10 sec. to mask A-Time beogining of -'dis for computer CD drive.

S Audio track Audio track length .4 sec (minimum time per Red Book).

I

Lead-in

(I

min) TOC points to 99 non-existent data tracks at time 00:02.

NModif* lead-out pointer (A2) to a \value between 00:01 and 00:07.

Audio track Data track lngth sec. plus fill to a total CD length.

As a result of these changes, a computer CD-ROM or DVD-ROMN drive, upon reading the sub-code Q channel data in session 3, will either fail to nount the CD entirely, or will go into an endless loo: lookne ifor the non-exi,:ent data tracks listed in the TOC. if the drive does succeed in accessing sesston 1. which holds the nonral audio content, it is still 1i to be confused by the I sec pregap (wich is outside the Red Book specification) ar, by the distorted A-time. CD audio and DVD players, however, will be largely unaffected by these changes. In dis regard, session 2 is iImprtant. since without it, some Blue Book-compliant DVD players might refuse to mount the CD. It wWL be understood that the specific modifications noted in the table are listed by way of example. Alternative combinations of modifications and settings of the time values and other parameters will be apparent to those skilled in the art.

Preferably, in order to allow an authorized personal computer (PC) to play the contents of the protected disk, the original contents are compressed (using any suitable format known in the art, such as MP3 or VQF) and enrrypmed, by audio compressor 35 (Fig. These encrypted data are stored using a "digital wrapper" technique, so that the data are idden from conventional CD driver sofrware. For exatmpie, the data may be stored in the reserved sub-code channel bits, as described above, or in one of the data sessions on the CD, or in a lead-in, lead-out or pause area. The data can be decrypted anild played back only by using aumhoriz ed softw. art. .vhichi is I Ll-- Q1 -CI ~nrp s e red in t-e second sessioi Is rnade available on>y to appropriately-licensed users and/or equipment. The authorized will prevent the decryption of the data if its source is not dthe original CD or if the distributing and using the data are otherwise violated.

It will be appreciated thai the preferred embodiments described above are cited by way of example, and that the presem invention is not limited to what has been particularly shown and described hereinabove. R.ather, the scope of the present invention includes both combinations and sub-combinations of the various features described hereinabove, as well as variations and modifications thereof which would occur to persons skilled in the art upon reading the foregoing description and which are not disclosed in the prior art.

Claims (19)

1. 2. A method according to claim 1, wherein the medium comprises a compact disk.
2. 3. A method according to claim 1, wherein the data comprise digital audio data.
3. 4. A method according to claim I, wherein altering the data comprises modifying an absolute time in the data to be recorded on the medium. A method according to claim 4, and comprising storing a correct absolute time in reserved sub-code bits on the medium.
4. 6. A method according to claim 4, wherein modifying the absolute time comprises altering absolute times recorded in a plurality of consecutive blocks of a selected track.
5. 7. A method according to claim 1, wherein altering the data comprises duplicating one or more blocks of the data to a new location on the storage medium, without changing the absolute time recorded in the sub-code Q channel of the one or more blocks.
6. 8. A method according to claim 1, wherein altering the data comprises modifying a point index number in a track of the data to be recorded on the medium.
7. 9. A method according to claim 8, and comprising storing a correct index number in reserved sub-code bits on the medium. A method according to claim 1, wherein altering the data comprises generating a multiple-session recording, including audio and data sessions, wherein the modification in the S sub-code Q channel is introduced in at least one of the sessions.
8. 11. A method according to claim 10, wherein the sessions comprise a first audio session, and wherein generating the multiple-session recording comprises creating a lead-in to one of "1 the sessions that points to one or more tracks located in the first audio session. A 12. A method according to claim 10, wherein generating the multiple-session recording ,I comprises creating a lead-in to one of the sessions that includes a larger number of tracks than is specified by the standard.
9. 13. A method according to claim 10, wherein the modification is introduced in both the audio and data sessions.
10. 14. A method according to claim 10, wherein generating the multiple-session recording comprises inserting a modified absolute time at a start of one of the sessions. A method according to claim 10, wherein generating the multiple-session recording comprises creating multiple sessions at least two of which are identified as audio sessions.
11. 16. A method according to claim 1, wherein recording the data comprises compressing and storing the data in a data session on the medium, for use in making an authorized copy of the medium.
12. 17. A method according to claim 1, wherein the encoded data comprise encoded audio .0 data, and comprising altering a portion of the encoded audio data such that the altered data are identified as inconsistent with the implementation of Standard 908 used in the data readout device, wherein recording the data on the medium comprises recording ancillary data which are used by a processor in the application to operate upon the altered portion of the encoded audio data such that the application plays back the data in a manner substantially unaffected by the alteration of the encoded audio data, but which ancillary data are ineffective in correcting the altered portion of the encoded audio data upon copying of the data, so that the alteration causes a further substantially unrecoverable error in the unauthorized copying of the original medium.
13. 18. A method according to claim 17, wherein the ancillary data comprise error detection codes.
14. 19. A method according to claim 1, wherein altering the portion of the encoded data comprises altering the data so as to create the modification in a standard digital output generated from the medium. A method according to claim 19, wherein the standard digital output is generated in accordance with Standard 958 of the International Electrotechnical Commission. i0
15. 21. Apparatus for protecting data recorded on an original data storage medium against copying using an unauthorized data readout device, the apparatus comprising: an encoder, adapted to receive a stream of data for recording on the medium and to encode the data in accordance with Standard 908 of the International Electrotechnical is Commission; a sub-code generator, operative to alter a portion of the encoded data by introducing a modification in a sub-code Q channel of the data, such that the altered data are inconsistent with an implementation of Standard 908 used in the data readout device, but do not prevent playback of the data following recording thereof; and an eight-to-fourteen bit (EFM) modulator, coupled to modulate the altered data for recording on the original storage medium, whereby an application which plays back the recorded data runs in a manner substantially unaffected by the alteration of the data, but a substantially unrecoverable error occurs in unauthorized copying of the original storage medium.
16. 22. Apparatus according to claim 21, wherein the medium comprises a compact disk.
17. 23. Apparatus according to claim 21, wvherein the data comprise digital audio data.
18. 24. Apparatus according to claim 21, wherein the modification in the sub-code Q channel comprises an altered value of the absolute time of a track of the data to be recorded on the medium. 19
19. 783347-1 Apparatus according to claim 21, wherein the modification in the sub-code Q channel is engendered by duplicating one or more blocks of the data to a new location on (,i the storage medium, without changing the absolute time recorded in the Q channel of the one or more blocks. ri 26. Apparatus according to claim 21, wherein the modification in the sub-code Q channel comprises a modified value of the point index number of a track of the data to be N recorded on the medium. i0 27. Apparatus according to claim 21, and comprising a data session generator, (,i operative to provide a data session to the EFM for recording on the original storage medium, so that the data recorded on the medium comprise multiple sessions; and the (Ni defect in the sub-code Q channel is introduced in at least one of the multiple sessions. 28. Apparatus according to claim 21, wherein the encoded data comprise encoded audio data, and the encoder is further operative to alter a portion of the encoded audio data such that the altered data are identified as inconsistent with the implementation of Standard 908 used in the data readout device, wherein the data recorded on the medium comprise ancillary data which are used by a processor in the application to operate upon the altered portion of the encoded audio data such that the application plays back the data in a manner substantially unaffected by the alteration of the encoded audio data, but which ancillary data re ineffective in correcting the altered portion of the encoded audio data upon copying of the data, so that the alteration causes a further substantially unrecoverable error in the unauthorized copying of the original medium. 29. Apparatus according to claim 21, wherein the defect in the sub-code Q channel is such as to create the modification in digital output generated from the medium in accordance with Standard 958 of the International Electrotechnical Commission. A data storage medium that is resistant to copying using an unauthorized readout device, on which medium data encoded in accordance with the Standard 908 of the International Electrotechnical Commission are stored, a portion of which encoded data is altered by introducing a modification in a sub-code Q channel of the data, such that the 783347-1 altered data are inconsistent with an implementation of Standard 908 used in the data readout device, but do not prevent playback of the data following recording thereof, whereby an application which plays back the recorded data runs in a manner substantially unaffected by the alteration of the data, but a substantially unrecoverable error occurs in unauthorized copying of the original storage medium. 31. A medium according to claim 30, wherein the medium comprises a compact disk. io 32. A medium according to claim 30, wherein the data comprise digital audio data. 33. A medium according to claim 30, wherein the data are encoded on the medium in a multiple-session format, including both audio and data sessions, and wherein the defect is introduced in at least one of the audio and data sessions. 34. A medium according to claim 30, wherein the data are encoded on the medium in a multiple-session format, including first and second sessions, and wherein the second session contains the data from the first session in a compressed form, for use in making an authorized copy of the first session. A medium according to claim 30, wherein the encoded data comprise encoded audio data, and wherein a portion of the encoded audio data is altered such that the altered data are identified as inconsistent with the implementation of Standard 908 used in the data readout device, wherein the data recorded on the medium comprise ancillary data which are used by a processor in the application to operate upon the altered portion of the encoded audio data such that the application plays back the data in a manner substantially unaffected by the alteration of the encoded audio data, but which ancillary data are ineffective in correcting the altered portion of the encoded audio data upon copying of the data, so that the alteration causes a further substantially unrecoverable error in the unauthorized copying of the original medium. 36. A method for protecting data recorded on an original storage medium against copying using an unauthorized data readout device, said method being substantially as 21 783347-I herein before described with reference to any one of the embodiments, as that embodiment is shown in the accompanying drawings. 37. An apparatus for protecting data recorded on an original storage medium against copying using an unauthorized data readout device, said apparatus being substantially as herein before described with reference to any one of the embodiments, as that embodiment is shown in the accompanying drawings. 38. A data storage medium substantially as herein before described with reference to any one of the embodiments, as that embodiment is shown in the accompanying drawings. DATED this Twenty-second Day of May, 2007 Macrovision Europe Ltd. Patent Attorneys for the Applicant SPRUSON FERGUSON 22 783347.1