RU2249861C2 - Copy protection of compact disks with digital audio record - Google Patents

Abstract

FIELD: copy protection.

SUBSTANCE: control data are encoded on a CD. Copy protection method includes stage of playback of selected control data incorrectly and/or non-precisely. Said control data are inaccessible or not readable at all by sound player, which only can play sound data. Wrong control data make sound data absolutely not readable by data reading device. Copy-protected CD with digital sound record contains audio data and control data, encoded in above-mentioned way.

EFFECT: higher efficiency.

2 cl, 7 dwg

Description

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

Digital audio compact discs (CD-DAs) onto which music or other audio information is recorded can be played or read by a more sophisticated device, such as CD-ROM drives (read-only media on a CD). This means, for example, that data from a user-acquired CD-DA can be read on a personal computer via its ROM drive (read only memory) and thus copied to another disc or other recording medium. The increasing capabilities of CD recorders are therefore a huge threat to the music industry.

The present invention provides a copy protection method for a digital audio compact disc.

According to a first aspect of the present invention, there is provided a copy protection method of a digital audio compact disc, in which control data suitable for use by a data reader is encoded on a compact disc (CD), wherein the copy protection method comprises the step of playing back the selected control data incorrectly and / or inaccurate.

In an embodiment of the invention, incorrect data encoded on a CD is either inaccessible or not readable at all to the audio player. Therefore, a legitimate audio CD purchased by the user can be played normally on the audio player. However, incorrect data makes the CD not a reproducible data reader. This prevents copying data to a CD.

Of course, by making the audio CD non-playable on the data reader, the user is also prevented from using the CD-ROM drive, for example, by simply playing music or other audio information on the disk.

As used herein, the term “sound player” is used to refer to players and drives designed to play audio data on a digital audio CD. Such players should usually be commercially available music CD players, the functions of which are solely to play music or other audio information from the CD. It is required that incorrect data encoded on a CD do not “encroach” at all or affect the normal operation of, for example, a “sound player”.

As used herein, the term “data reader” is used to indicate all players and drives that are capable of reading data from a disk, for example, by retrieving or otherwise accessing data on a disk. Such players will therefore include CD-ROM drives. In general, and as allowed above, for a CD-ROM drive, for example, not only will an operation to create a usable copy of a legitimate CD-DA be prevented, but reproduction of a legitimate CD-DA will be generally prevented.

In one embodiment of the method of the invention, data encoded on a CD that has not been played correctly is navigation and / or synchronization data.

For example, data identifying the position on the disk of the final zone is not reproduced correctly on the zero track of the disk. Thus, data on track zero that indicates Atime (absolute time) at the beginning of the end zone may not be played correctly. For example, data on the null track may indicate that the (value) Atime at the beginning of the end zone is zero. Alternatively, the data on the zero track may matter to Atime at the beginning of the end zone, which occurs on the first audio track on the CD.

Additionally and / or alternatively, the data on the CD defining the nature of the tracks are not reproduced correctly.

In a preferred embodiment, CD data identifying the nature of the tracks incorrectly identifies each audio track as a data track.

In a preferred embodiment of the method of the invention, the data encoded on a disc that does not play correctly is data in the table of contents (TC) of the CD.

Preferably, the control data encoded on the CD is changed so that it is not reproduced correctly before the master disk is made.

The present invention also encompasses a copy-protected digital audio compact disc in which control data suitable for use by a data reader is encoded on a compact disc and in which the selected control data is reproduced incorrectly and / or inaccurately.

Preferably, the incorrect data encoded on the CD is either inaccessible or not readable at all by the audio player. This makes it possible to play normally a copy-protected disc on the sound player. However, the data encoded on the copy-protected CD makes the disc not a reproducible data reader at all. This prevents the use of a data reader to retrieve or read data on the disc, whereby copying the disc is also prevented. Of course, it is no longer possible to use a CD-ROM drive, for example, to play audio information on a legally acquired copy-protected disc.

In an embodiment, the incorrect control data on the copy-protected disk is navigation and / or synchronization data.

For example, on the zero track there are incorrect control data and identify the position on the disk of the end zone. Thus, incorrect control data on the zero track may indicate Atime incorrectly at the beginning of the end zone. For example, incorrect control data on a zero track may indicate that the (value) Atime at the beginning of the end zone is zero.

Alternatively, incorrect zero-track control data may make a difference to Atime at the beginning of the end zone, which occurs on the first audio track on the CD.

Additionally and / or alternatively, the copy-protected digital audio compact disc according to the invention may have incorrect control data encoded on a disc that determines the nature of the tracks on the disc.

In an embodiment, incorrect control data incorrectly identifies each audio track as a data track.

The copy-protected digital audio compact disc according to the invention may have incorrect control data encoded thereon, which is control data in the contents table (TS) of the disk.

Embodiments of the present invention are described below by way of example with reference to the accompanying drawings, in which:

figure 1 schematically shows a CD with a spiral data track,

figure 2 presents the structure of the frame data encoded on CD,

figure 3 presents the General data format of the Q-subchannel,

figure 4 presents the data format for the Q-subchannel in accordance with the mode

5 graphically shows Atime and Ttime on a CD,

on figa presents an example of determining the tracks of the CD-DA using the table of contents, and

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

A digital audio compact disc (CD-DA) on which music is recorded and which must be played on a sound player, such as a regular CD player, is made and recorded in a standard format relating to the well-known Red Book standards. Determining the physical properties of a disk, such as its size, and its optical properties, such as a laser wavelength, the Red Book also determines the signal format and the encoding of the data to be used.

As you know, the use of Red Book standards ensures that any CD-DA produced in accordance with these standards can be played on any sound player made in accordance with these standards.

Figure 1 schematically shows a spiral track 4 on CD 6. This spiral track 4 on a CD-DA is divided into track zero 8, a plurality of consecutive music or sound tracks 10 and the end zone 12. Track zero 8 includes a table of contents (TS) which identifies for the sound player the tracks to be followed further until the end zone 12 indicates that track 4 is to end.

When turned on, the audio player always accesses track zero 8. Music tracks can then be played back sequentially when the read head tracks track 4 from track zero to the end zone. Alternatively, if necessary, the player moves the read head to the beginning of each audio track.

All CD players and readers are programmed so as not to move the read head beyond the start of track 12 of the end zone. This should protect the read head.

Obviously, a CD-ROM looks exactly like a CD-DA, and has the same spiral track divided into sectors. However, data readers, such as CD-ROM drives, are much more complex and can read data and process information from each sector of the CD according to the nature of the data or information. The data reading devices can be moved by reading information from each sector, whereby the reading head can be controlled so as to access any corresponding part of the spiral track 4 if necessary.

To ensure that any data reader can read any CD-ROM, CDs and readers are also made in accordance with well-known standards, in this case called the Yellow Book standards. These Yellow Book standards include, but also extend, the Red Book standards. Therefore, a data reader, such as a CD-ROM drive, can be controlled to play CD-DA.

The ability of a data reader to access, retrieve, or otherwise read data on a CD-DA poses a problem for the music industry. The user can use the CD-ROM drive to read data from an audio disk, for example, into a computer file, and then this data can be copied. The increasing capabilities of recorders capable of burning to CDs mean that people and organizations now have free access to the technology for making perfect copies of audio CDs. This is a matter of great concern to the music industry.

An audio player, whether it is a dedicated music CD player or the more sophisticated CD-ROM drive that is controlled to play an audio disk, only views and uses data encoded in accordance with the Red Book standards. More importantly, if there is an inaccuracy in the data, the sound player will usually continue playing instead of trying to correct the error. For example, if the read head has moved to the beginning of a track and started playing that track, the sound player will continue to play that track to the end, even if it becomes obvious that there is some error in the time synchronization information, for example. In contrast, a data reader is designed to identify and correct errors.

The present invention therefore proposes that errors be deliberately inserted into encoded data. For example, errors can be inserted into Red Book data, but inserted errors must be of a type that is usually "transparent" to the sound player. Alternatively, audio discs may be encoded with selected and incorrect Yellow Book data that are not used by the audio player. In each case, the errors are selected such that the data reader is unable to read or play an audio disc. Obviously, the system according to the invention has the disadvantage that the user cannot reproduce a legally acquired audio disc having copy protection on a data reader in a legal manner, that is, simply play music recorded on a disc. However, in view of the potential losses from piracy, the music industry wants to accept this shortcoming.

Since the encoding of data on a CD-DA and on a CD-ROM is known and consistent with relevant standards, there is no need to describe it here in detail.

In short, CD data is encoded into frames by EFM (eight-to-fourteen modulation). FIG. 2 represents a frame format and, as is apparent from this drawing, each frame has timing data, sub-code bits providing control and display symbols, information bits and parity bits. Each frame includes 24 bytes of data, which for CD-DA are audio data.

There are 8 sub-code bits contained in each frame and denoted by P, Q, R, S, T, U, V, and W. Typically, only the P and Q sub-codes bits are used in audio format. The standard requires 98 frames, shown in FIG. 2 were grouped into a sector, and the 98-frame sub-code bits are combined to form sub-code blocks. That is, each block of the sub-code forms a byte of 98 consecutive frames simultaneously. Thus, 8 different P-W subchannels are formed. These subchannels contain control data for the disc. P- and Q-subchannels include synchronization and navigation data for tracks on a disc, and are typically the only subchannels used on a sound disc.

The data format for the Q-subchannel block assembled from 98 consecutive frames is shown in FIG. As you can see, the beginning of the subchannel block is indicated by the appearance of the synchronization pattern S0 and S1 as the first 2 characters. The following information bits are overhead bits for determining the contents of a track. In this way, overhead bits can identify audio content or data content. This is followed by address information, ADR, which defines one of four modes for Q-data bits. 72 bits of Q data follow the address information, and then there are 16 bits of cyclic redundancy check or check, which are used to detect errors in the control bits, address, and Q data.

Figure 4 represents the data content of the Q-subchannel block in each of the four modes indicated by address information, ADR. In mode 0, all Q data is zero. In mode 0, the P-subchannel data is also set to zero. In mode 2, the Q-data contains the catalog number for the disk, for example, the barcode of the Universal Product Code. In addition, in mode 2, the Atime countdown from adjacent blocks continues. Mode 3 is used to obtain a code for storing and retrieving information (KHPI, ISR) to identify each music track. In addition, and as shown, in mode 3, the absolute time count, Atime, continues.

As shown in FIG. 4, in mode 1, the Q data in each block of the subchannel contains program and temporal information for the individual audio tracks and for the information area of the disc. As shown, there are various formats for Q data for the start track for data in the program and end zones. However, in both formats in mode 1, the Q data provides information about the time along the track. The current time of the track is called Ttime, measured in minutes, seconds and frames, and Cumin, Tsek and Tkadr are components of Ttime. In the software and end zones, Q data additionally includes absolute time information, Atime, on the disk in minutes, seconds and frames, and Amin, Asek and Akadr are components of Atime.

Figure 5 shows graphically how Atime and Ttime vary within a disk. Atime is the absolute time within the disk and starts at zero at the beginning of the program area. Ttime is the current time within each track and thus starts at zero at the beginning of each track. Thus, and as depicted in FIG. 5, Atime increases monotonically within the disk, while Ttime increases for each individual track. As also shown in FIG. 5, the P-subchannel includes flags F, each of which indicates the start of a corresponding track. Flags of the P-subchannel also define the end zone.

As indicated in FIG. 4, in mode 1, each Q-subchannel block contains the following sequential values for Atime and Ttime. When the sound player is to play the soundtrack, the head moves to the beginning of the track. The movement can be carried out by means of Atime, Ttime, and / or flags of the P-subchannel or some combination thereof. In general, as soon as the sound player has started playing a track, this playback continues. Track playback usually does not stop if there are any errors in the data, and thus the sound player effectively ignores any errors in the data that are encountered. Thus, if the audio player can be reliably oriented towards the beginning of the track, you can expect to receive a continuous audio output from this track without any problems.

As noted above, in mode 1, the Q-data provides the vehicle in the zero track. Part of a typical vehicle is shown in the form of a table in figa. It can be seen from it that each track (14) is specified by (16) the start address in (units) of time and frames from the end of the zero track. Each track also has a logical block address (LAB) 18, which is counted from Atime and provides the address of the beginning of the track on the disk. The sound drive TS also identifies Atime from the beginning of the program area to the start of the end zone, as indicated by 20. However, applicants have determined that usually sound players do not read or use the time stamp of the end zone from the TS.

On fig.6b presents in tabular form part of the vehicle depicted in figa, after it was changed to protect the disk from copying. In particular, it can be seen that the Atime value (20) from the beginning of the program area of the disk to the end zone was set to zero, indicating that the end zone is at the beginning of the zone located at the beginning of the first audio track. The data reader therefore, referring to disc 6, will read from the zero track information indicating that the disk does not have a program area and that the final zone immediately follows the zero track. The data reader will refuse to move the read head from the beginning of the audio track because it believes that the first track begins within the end zone. The data reader will therefore be unable to read or play back the drive of the vehicle shown in FIG. 6b.

Obviously, the values in the tables of FIGS. 6a and 6b are provided only to illustrate how information is manipulated to provide copy protection. Actual values (for) disks in practice may differ from those indicated in the tables.

The vehicle shown in FIG. 6b has been modified in a second way, which also prevents the data reader from using the disk information properly. In this regard, and as can be seen from FIGS. 6a and 6b, all tracks on the audio disc are audio tracks, which is indicated by reference 22. In the vehicle of FIG. 6b, these tracks are erroneously identified as data tracks. Thus, even if the data reader is controlled to ignore false information about the end zone in the vehicle, it indicates that each of the following tracks contains digital data instead of the audio counterpart. Any reading of these tracks will therefore fail, because the player tries to read the data, but cannot find the corresponding SYNC synchronization headers or sectors. Therefore, errors appear and the reading is unsatisfactory.

In the present embodiment, Atime was set to zero to indicate that the ending zone is at the beginning of the zone located at the beginning of the first audio track. It is also possible to set the Atime for the end zone to an alternate, incorrect value. Such an incorrect value will “baffle” the data reader and will generally prevent the reading head from moving further along the disk, in contrast to the position indicated by the incorrect time stamp of the end zone. For example, the Atime value set in the TS for the end zone could indicate the position within the first or subsequent audio track.

Where an incorrect Atime value for the start time of the end zone indicates a position in the program area of the disk, the data reader may access the audio data on the disk at the positions before the indicated incorrect Atime value. However, the amount of available audio data can be kept small. In the future, audio players will be able to read the time point of the end zone, for example, and in these circumstances, having the time zone of the end zone incorrectly identified, the position within the first audio track will ensure that the audio player is able to play a copy-protected disc.

The embodiments described and depicted above identify two options that can be implemented with respect to data on the zero track of an audio disc in order to protect this disc from copying. Obviously, any data that is “transparent” to the sound player can be changed to prevent the data reader from working. Additionally and / or alternatively, it is possible to provide data on a sound disc to prevent the generation of a digital output signal from the sound player. It is also obvious that, if necessary, alternative or additional errors in these Red Book or Yellow Book standards may be presented.

Other modifications or changes to the embodiments described above may be made within the scope of the appended claims of the present application.

Claims (19)

1. A method for protecting against copying a compact disc (CD) of digital audio recording containing audio data and control data, the control data being encoded on a compact disc, the copy protection method comprising the step of reproducing the selected control data incorrectly and / or inaccurately, wherein said selected control data is unavailable or not readable by the sound player at all, so that the sound player can play sound data, while incorrect control data makes the sound data Posted in General not reproducible data readout device. 2. The method according to claim 1, in which the control data is encoded on a CD that does not play correctly, are navigation and / or synchronizing. 3. The method according to claim 2, in which the control data is located on the zero track on the disk, and incorrect control data located on the zero track identifies the position on the disk of the end zone. 4. The method according to claim 3, in which the control data on the zero track indicate that Atime (absolute time) at the beginning of the end zone is not reproduced correctly. 5. The method according to claim 4, in which the control data on the zero track indicate that Atime (absolute time) at the beginning of the end zone should be zero. 6. The method according to claim 4, in which the control data on the zero track have a value for Atime (absolute time) equal to the value at the beginning of the end zone, which takes place on the first audio track on the CD. 7. The method according to any one of claims 1 to 6, in which the control data encoded on a CD that determines the nature of the tracks is not reproduced correctly. 8. The method according to claim 7, in which the control data on the CD, identifying the nature of the tracks, incorrectly identify each sound track as a data track. 9. The method according to any one of claims 1 to 8, in which the control data encoded on a CD that does not reproduce correctly is the control data in the table of contents (TS) of the CD. 10. The method according to any one of claims 1 to 9, in which the control data encoded on a compact disc is changed so that it is not reproduced correctly, before making the master disc. 11. A copy-protected digital audio compact disc carrying audio data and control data, the control data being encoded to a CD, and the selected control data not reproducing correctly and / or inaccurately, said selected control data being either inaccessible or not readable at all audio player so that the audio player can play audio data, while incorrect control data makes the audio data not playable by the reader at all OF DATA. 12. A copy-protected compact disc with digital audio recording according to claim 11, wherein the incorrect control data on the disc is navigation and / or synchronization data. 13. The copy-protected digital audio compact disc of claim 12, wherein the control data is located on the track zero on the disc, and the incorrect control data located on the track zero identify the position on the disc of the end zone. 14. A copy-protected CD with digital audio recording according to claim 13, in which incorrect control data on the zero track indicates incorrect Atime (absolute time) at the beginning of the end zone. 15. The copy-protected digital audio compact disc of claim 14, wherein the incorrect control data on the track zero indicates that Atime (absolute time) at the beginning of the end zone is zero. 16. The copy-protected digital audio compact disc of claim 14, wherein the incorrect control data on the zero track matters to Atime (absolute time) at the beginning of the end zone, which is located on the first audio track on the CD. 17. A copy-protected digital audio compact disc according to any one of claims 11-16, wherein the incorrect control data encoded on the compact disc determines the nature of the tracks on the disc. 18. The copy-protected digital audio compact disc of claim 17, wherein the incorrect control data incorrectly identifies each audio track as a data track. 19. A copy-protected digital audio compact disc according to any one of claims 11-18, wherein the incorrect control data encoded on the CD is control data in the contents table (TS) of the disk.

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