JP3405980B2 - Digital audio compact disc copy protection - Google Patents

Description

Detailed Description of the Invention

The present invention relates to a method for copy-protecting a digital audio compact disc and a copy-protected digital audio compact disc.

A digital audio compact disc (CD-DA) for carrying music and other audio is a CD-
It can be reproduced or read by a higher performance device such as a ROM drive. This is, for example, a CD obtained by the user.
It means that the data on the DA can be read by the ROM drive to the PC and then copied to another disk or other recording medium. The increasing availability of recording devices capable of writing to CDs is therefore a major threat to the music industry.

The present invention provides a method of copy protecting a digital audio compact disc.

According to a first aspect of the invention, there is provided a method of copy protecting a digital audio compact disc, wherein control data usable by a data reader is encoded on the compact disc, the copy protecting method being selected. And making the control data erroneous and / or inaccurate.

In an embodiment of the invention, the incorrect data encoded on the CD is either inaccessible by the audio player or generally not read.

Of course, by preventing the audio compact disc from being reproduced by the data reader,
The user cannot use the CD-ROM drive and legally simply plays music or other audio on the disc.

In this specification, the term "audio player" is used to refer to a player and drive adapted to reproduce audio data on a digital audio compact disc. Such players are generally commercially available CD music players, whose function is simply to play audio data or other audio on a CD. Wrong data encoded on the CD, and generally affecting the normal operation of such "audio players".

In this specification, the term "data reader"
Is used to refer to all players and drives that can read the data on the disc, for example by extracting or accessing the data on the disc. Accordingly, such players include a CD-ROM drive. Generally, and as known above, a CD-ROM drive is, for example, a legal CD-ROM.
Not only does it prevent making a usable copy of the DA,
Generally, it can also be prevented from playing legal CD-DA.

In one embodiment of the method of the present invention, the erroneous data encoded on the compact disc is navigation and / or timing data.

For example, the data identifying the position of the lead-out on the disc is erroneous in the lead-in.
In this way, the data in the lead-in showing the A time at the start of the lead-out is erroneous. For example, the data in the lead-in indicates that the A-time at the start of the lead-out is zero. Instead, the data in the lead-in has a value for the A time of the start of the lead-out that occurs in the first audio track of the compact disc.

Additionally and / or alternatively, the data on the CD defining the characteristics of the track is erroneous.

In the preferred embodiment, data on a CD that incorrectly identifies the characteristics of a track identifies the audio track as a data track.

In the preferred embodiment of the method of the present invention, the data encoded on the corrupted disc is the data in the table-off content (TOC) of the compact disc.

Preferably, the control data encoded on the compact disc is modified to be erroneous prior to mastering the disc. The invention also includes a copy protected digital audio compact disc in which the control data usable by the data reader is encoded on the compact disc and the selected control data is mistaken and / or inaccurate.

Preferably, the incorrect data encoded on the compact disc is either inaccessible by the audio player or generally not readable. This allows the copy protected disc to be played normally on an audio player. However, the data encoded on a copy protected compact disc generally makes it impossible for the data reader to play the disc. This prevents using a data reader to extract or read the data on the disc, which also prevents copying of the disc. Of course, it is no longer possible to use a CD-ROM drive, for example, to play audio on legally obtained copy-protected discs.

In an embodiment, the erroneous data on the copy protected disc is navigation and / or timing data.

For example, erroneous control data is provided during lead-in to identify the position of the lead-out on the disc. Thus, erroneous control data in the lead-in can erroneously indicate the A-time of the start of the lead-out. For example, erroneous control data in the lead-in may indicate that the A-time of the start of the lead-out is zero.

Alternatively, the erroneous data in the lead-in may have a value for the A-time of the start of the lead-out occurring in the first audio track of the compact disc.

Additionally and / or alternatively, the copy protected digital audio compact disc of the present invention may have erroneous control data encoded on the disc that defines the characteristics of the tracks on the disc.

In the preferred embodiment, the erroneous control data incorrectly identifies each audio track as a data track.

The copy protected digital audio compact disc of the present invention comprises a table-off content (T) of the disc encoded on the compact disc.
It may have erroneous control data which is control data in OC).

An embodiment of the present invention will be described with reference to the drawings.

A digital audio compact disc (CD-DA) that carries music and is played back by an audio player such as a conventional CD disc player is created and recorded in a standard format known as the Red Book standard. In addition to defining the physical properties of the disk and its dimensions and its optical properties such as laser wavelength, the Redbook also defines the signal format and data encoding used.

As is known, the use of the Red Book standard refers to any CD-DA manufactured in accordance with that standard.
Also guarantees that it can be played back by an audio player manufactured according to the standard.

FIG. 1 shows a schematic of a spiral track 4 on a CD 6. This spiral track 4 on the CD-DA is divided into a lead-in 8, a continuous music or audio track 10 and a lead-out 12. Lead-in 8
It has a table of contents (TOC) that identifies the track that the audio player follows, while the lead-out 12 marks the end of track 4.

The audio player always accesses the lead-in 8 at the start. The music tracks are continuously played as the read head follows the track 4 from lead-in to lead-out. Instead, the player manipulates the readhead to the beginning of each audio track when needed.

All compact disc players and readers are programmed to not move the readhead beyond the lead-out 12. This is to protect the read head.

To the naked eye, a CD-ROM looks exactly the same as a CD-DA and has the same spiral track divided into sectors. However, data readers such as CD-ROM drives are more sophisticated and capable of reading and processing information from each sector of a compact disc according to the nature of the data or information. The data reader can be operated by reading the information from each sector so that the read head can be driven to access the appropriate portion of the spiral track 4 when needed.

To ensure that any data reader can read any CD-ROM, the compact disc and reader are also made in a standard known in this case as the Yellow Book standard. The Yellow Book standard incorporates, but extends, the Red Book. Therefore, the CD-ROM
A data reader such as a drive can be controlled to play a CD-DA.

The ability of a data reader to access, extract or otherwise read data on a CD-DA poses a problem to the music industry. The user may use a CD-R to read the data from the audio disc, eg into a computer file.
An OM drive can be used and its data can be copied. The increased availability of recording devices that can write to compact discs means that individuals and organizations have easy access to the technology for making complete copies of audio compact discs. this is,
It is a big concern for the music industry.

A dedicated compact disc music player or advanced CD-ROM drive when controlled to play an audio disc retrieves and uses data encoded in the Redbook standard. Moreover, if there is inaccuracy in the data, the audio will generally continue to play rather than attempt to correct the error. For example, if the readhead is navigated to the beginning of the track, and the playback of the track begins, the audio player will continue to play the track to the end, even if it appears that there are some errors in the timing information, for example. . In contrast, the data reader is adapted to identify and correct errors.

Therefore, the present invention should intentionally introduce errors into the encoded data. For example, the error is
It can be introduced in the Redbook data, but it must generally be transparent to the error audio player that is introduced. Alternatively, the audio disc may be encoded with unused and selected yellow book data that is unused in the audio player. In either case, the error is chosen so that the data reader cannot read or play the audio disc. The system of the present invention does not allow the user to play legally obtained audio discs with copy protection on a data reader in a legitimate manner, ie not simply to play the music recorded on the disc. It is admitted that there is a drawback. However, in terms of potential loss from pirates, the music industry accepts this shortcoming.

The data encoding on the CD-DA and on the CD-ROM is known and in accordance with the appropriate standards and need not be described in detail here.

Briefly, the data on the CD is EFM (8-
14 modulation) to encode the frame. FIG. 2 shows the format of the frames, and as can be seen, each frame has synchronization data, subcode bits providing control and display symbols, data bits and parity bits. Each frame contains 24 bytes of data, which is audio data for CD-DA.

There are eight subcode bits for each frame, designated as P, Q, R, S, T, U, V, and W. Generally, P and Q subcode bits are used within the audio format. The standard is 9 in Figure 2.
Eight frames are required to be grouped into sectors, and the subcode bits from 98 frames are
Collected to form subcode blocks. That is, each subcode block consists of bytes from 98 consecutive frames at a given time. In this way, eight different sub-channels P to W are formed. These sub-channels contain the disc control data. P- and
The Q-subchannel incorporates timing and navigation data for tracks on the disc, and
Generally, there are only sub-channels used in audio discs.

A Q-subchannel block collected from 98 consecutive frames is shown in FIG. As is apparent, the beginning of the sub-channel block is indicated by the synchronization patterns S0 and S1 of the first two symbols. The next data bit is a control bit for defining the contents of the track. As such, the control bits may identify audio content and data content. Then follows the address information ADR which defines one of four modes for the Q-data bits. 72 bits of Q-data follows the address information and is used for error detection of control, address and Q-data bits 16C
There is an RC or check bit.

FIG. 4 shows the data content of the Q-subchannel block in each of the four modes specified by the address information ADR. In mode 0, all Q-data has a value of zero. In mode 0, the P-subchannel data is also set to zero. In mode 2, the Q-data has a disc catalog number, such as a universal product code bar code. In addition, in mode data 2, A time counts from adjacent blocks are continuous. In mode 3, it is used to give an ISR code to identify each music track. Further, as shown in the figure, in mode 3, the absolute time count A time continues.

As shown in FIG. 4, in mode 1, the Q-data in each sub-channel block contains individual information tracks and program and time information for the information area of the disc. As shown, the Q-data in the lead-in area and the Q in the program and lead-out area
-The data is in a different format. However, in both formats of Mode 1, Q-data gives information along the track. The playback time of a track is called T time, and it is minutes, seconds, and frames. TMin, TSec
And, TFrame is a component of T time.
In the program and lead-out area, the Q-data further relates to the disc in minutes, seconds and frames,
Absolute time, which has information about A time, Amin, As
ec and Aframe are all components of A time. .

FIG. 5 shows how the A and T times vary across the disc. The A-time is the absolute time across the disc, starting at zero at the beginning of the program area. T-time is the elapsed time in each track, starting at zero at the beginning of each track. As shown in FIG. 5, A-time increases monotonically across the disc, while T-time increases along each track. As shown in FIG. 5, the P-subcode channel includes a flag F indicating the start of each track. As shown in FIG. 4, in mode 1, each Q-
The sub-channel block contains the next consecutive values for A-time and T-time. When the audio player plays an audio track, the head is operated to start the track. Navigation is by A-time, T-time and / or P-subchannel flags or combinations thereof. In general, once the audio player starts playing a track, it continues. Track playback generally does not stop even if there is a data error. This then effectively ignores any data errors that appear in the audio player. Thus, an audio player is expected to provide continuous audio output from a track without problems if operated reliably at the beginning of the track.

As mentioned above, in mode 1, the Q-data provides the TOC in the lead-in area. Typical TO
A portion of C is shown in tabular form in Figure 6a. Than that
It can be seen that at 14 each track is given and at 16 the starting address from the end of the lead-in is given in time and frame. Each track also has a logical block address (LBA) 18 calculated from the A time, which provides the address for the beginning of the track on the disc. The TOC of the audio disc also identifies the A time from the beginning of the program area to the beginning of the lead-out indicated by 20. However, applicants have generally stated that audio players do not read or use the lead-out time from the TOC.

FIG. 6b shows the tabular portion of the TOC from FIG. 6a after being modified to copy protect the disc. In particular, it can be seen that at 20, the A time from the beginning of the disc program area to the lead-out area is set to zero, indicating that the lead-out is the beginning of the pre-gap of the first audio track. Therefore, the data reader accessing the disc 6 reads the lead-in information, which means that the disc has no program area and its lead-in is directly followed by lead-out. The data reader refuses to move the readhead past the beginning of the audio track because it believes the first track starts in the leadout. Therefore, the data reader cannot read or play the disc with the TOC of FIG. 6b.

It is understood that the values in the tables of FIGS. 6a and 6b are provided only to indicate how the information is manipulated to provide copy protection. The actual value of the disc may actually differ from the value shown in the table.

The TOC of FIG. 6b is modified in a second way which also prevents the proper use of the information on the disc by the data reader. In this regard, and as can be seen from Figures 6a and 6b, there are 2 tracks on an audio disc.
All are audio tracks, as indicated by 2. In the TOC of Figure 6b, these tracks were erroneously identified as data tracks. Thus, if the data reader is operated to ignore spurious lead-out information in the TOC, each subsequent track is told to contain digital information rather than analog audio. Therefore, reading those tracks is confusing because the player tries to read the data but cannot find the proper SYNC or sector header.

In the illustrated embodiment, the A-time is set to zero indicating that the lead-out is at the beginning of the pregap of the first audio track. Alternatively, the lead-out A-time can be set to an incorrect value. Such incorrect values confuse the data reader and generally prevent moving the readhead further across the disk than the position indicated by the incorrect readout time. For example, the A-time value provided in the TOC for the lead-out may indicate the position within the first or subsequent audio track.

If the incorrect A-time value for the start time of the lead-out indicates the position of the program area in the disc, the data reader will cause the data reader to move on the disc at a position earlier than indicated by the incorrect A-time value. You can access the audio data of. However, the amount of accessible audio data is kept small. In the future, the audio player will be able to read, for example, the lead-out time, so in this case making the incorrect lead-out time aware of the position in the first audio track will cause the audio player to copy. Ensure that you can play protected discs.

The above embodiment shows two changes made to the data in the lead-in of an audio disc in order to copy protect the disc. It will be appreciated that data, such as transparency, etc., can be modified to prevent the operation of the data reader as it extends to the audio player.
Additionally and / or alternatively, data may be provided on the audio disc to prevent digital output from the audio player. Alternative or further errors in the Red Book or Yellow Book standard data may be introduced if desired.

Further variations or modifications of the above described embodiments are understood to be within the scope of the application as claimed. [Brief description of drawings]

FIG. 1 is a schematic diagram of a compact disc having spiral data tracks.

FIG. 2 is a diagram showing the structure of a frame of data encoded on a CD.

FIG. 3 is a diagram showing a general data format of a Q subchannel.

FIG. 4 is a diagram showing a data format of a Q sub channel according to modes.

FIG. 5 is a diagram graphically showing both A time and T time on a compact disc.

FIG. 6a is a diagram showing an example of a track definition having a table of contents of CD-DA.

FIG. 6b shows the table-of-contents of the CD-DA shown in FIG. 6a when the disc is copy protected.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-11-328851 (JP, A) JP-A-11-96676 (JP, A) JP-A-10-326462 (JP, A) JP-A-8- 147766 (JP, A) International Publication 98/003973 (WO, A1) International Publication 98/52114 (WO, A1) International Publication 96/05595 (WO, A1) US Patent 6256738 (US, A) US Patent 6208598 (US, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G11B 20/10

Claims (13)

(57) [Claims] 1. A digital audio compact disc (CD-DA) carrying audio data and control data.
Is a method of copy-protecting a CD, in which the control data is
-Encoded on the DA, the copy protection method will erroneously select / control the selected control data on the CD-DA.
Or inaccurate, the selected control data is not accessible or generally read by an audio player, and the audio player can play the audio data on its CD-DA. However, the wrong control data makes it impossible for audio data on the same CD-DA to be generally reproduced by a data reader. 2. The method according to claim 1, wherein the control data encoded on the compact disc and erroneous is navigation and / or timing data. 3. The method of claim 2 wherein the control data provided during the lead-in that identifies the location of the lead-out on the disc is erroneous. 4. The method of claim 3, wherein the control data in the lead-in that indicates the A-time of the start of the lead-out is erroneous. 5. The control data encoded on the compact disc defining the nature of the track is erroneous,
And the method according to any one of claims 1 to 4, wherein each audio track is incorrectly identified as a data track. 6. The method according to claim 1, wherein the erroneous control data encoded on the compact disc is data in the table-off content (TOC) of the compact disc. 7. A method according to claim 1, wherein the control data encoded on the compact disc is modified to make it incorrect prior to mastering the disc. 8. Carrying audio data and control data,
A digital audio compact disc (CD-DA) which is copy protected and whose control data is the CD-
Encoded on the DA, the selected control data has been erroneous and / or inaccurate, and the selected control data is not accessible by the audio player or is generally not read. Either, the audio player can play the audio data on its CD-DA, but the incorrect control data makes it impossible for the audio data on the CD-DA to be generally played by a data reader. A copy-protected digital audio compact disc. 9. The copy protected digital audio compact disc of claim 8, wherein the erroneous control data on the disc is navigation and / or timing data. 10. A copy protected digital audio compact disc as claimed in claim 9 in which incorrect control data is provided in the lead-in and identifies the position of the lead-out on the disc. 11. The copy protected digital audio compact disc of claim 10 wherein the erroneous control data in the lead-in incorrectly indicates the A-time of the start of the lead-out. 12. Incorrect control data encoded on a compact disc defines the nature of the tracks on the disc and incorrectly identifies each audio track as a data track. A copy protected digital audio compact disc according to claim 1. 13. The control data of the error coded on the compact disc is control data in the table of contents (TOC) of the disc.
A copy protected digital audio compact disc according to any one of the preceding claims.