MXPA01010399A - The copy protection of digital audio compact discs - Google Patents

Abstract

The ability of a data reader, such as a CD ROM drive, to access, extract, or otherwise read the data on a digital audio compact disc provides a problem for the music industry. A user can use his CD ROM drive to read the data from an audio disc into a computer file, and then that data can be copied. To provide copy protection, errors are deliberately introduced into the data on a CD, but these errors are of a typewhich are generally transparent to an audio player but which will interfere with the reading of the audio data by a data reader. According to the standards, the data on a CD is encoded into frames by EFM (eight to fourteen modulation). Each frame has sync data, sub code bits providing control and display symbols, data bits and parity bits, and includes 24 bytes of data, which is audio data for a CD DA. The standard requires that 98 such frames are grouped into a sector. To provide copy protection, each sector is provided with a non standard number of frames, for example, has 99 rather than 98 frames. Then the S0 and S1 sub code synchronisation patterns are placed one frame later than they otherwise would be, but the data within each frame remains the same. An audio player would divide the 24 bytes of data from each frame of the sector into 4 byte samples and continue playing the disc, albeit with an inaccurate time display. Howewer, a data reader used to read audio data from the CD DA to enable a copy to be made, would produce a copy having a degraded quality of sound.

Description

\\ COPY PROTECTION FOR COMPACT DISCS 'DIGITAL AUDIO CAMBO OF THE INVENTION The present invention relates to a method for the protection against copies of a compact digital audio disc and with a compact digital audio disc protected against copies.

BACKGROUND OF THE INVENTION Digital audio CDs (CD-DAs) containing music or another audio signal can be played or read by more sophisticated devices, such as CD-ROM drives. This means / for example, that the data on a CD-DA acquired by a user can be read on a PC by means of its ROM unit and thus copied to another disk or other means for recording. This "increasing availability of • recorders capable of writing on CDs is therefore a major threat to the music industry." In a previously proposed method, a digital audio compact disc is a protected copy by making the control data encoded on the disc are incorrect and / or inaccurate Incorrect data encoded on the CD either inaccessible or in general can not be used by a CD-DA player. legitimate audio purchased by a user. can usually be played on a compact disc music player. However, - incorrect data means that the CD can not be played through a CD-ROM drive. However, as a compact disc can not be played back on a CD-ROM drive, the user is also prevented from using the legitimately simple CD-ROM drive to play the music or other audio signal on the CD-ROM. the disc .. Clearly it could be advantageous to provide a copy protection method for a digital audio compact disc that, while avoiding the production of usable copy discs, may not prevent or degenerate, the reproduction of legitimate audio discs in all the players that have the functionality to play audio discs.

SUMMARY OF THE INVENTION According to a first aspect of the present invention there is provided a method for the protection against copies of a compact digital audio disc, wherein the control data is encoded on the compact disc. he. method for protection against copying comprises - the step of making the selected control data < incorrect and / or inaccurate with which the incorrect data and / or inaccurate interfere with the reading of audio data from the digital audio compact disc. In general, incorrect and / or inaccurate control data are arranged in such a way that they can be corrected by the error correction provisions of available data readers. The error correction provisions of some data readers can ostensibly provide "corrections", although this will cause any data to be extracted incorrectly. Other data readers will avoid data extraction due to their inability to correct errors. With one embodiment of the invention, the incorrect data encoded on the CD could either be ignored or otherwise in general. Could have no effect on reproduction. of the. audio data on the disk. Therefore, a legitimate audio CD purchased by a user can be played normally on any player capable of playing audio data. However, when a copy is made of the copy-protected CD by reading the audio data, the reproduction of any CD made, or the sound it is capable of producing, is degenerated. In the description and claims of this specification, the term "audio player" is used to refer to players and units arranged or controlled to reproduce the audio data on a compact digital audio disc. These players will include ,. Thus, commercially available CD music players that work only to play music or other audio on the CD. It is required that the incorrect data encoded on the CD in general does not interfere with the audio player or cause effects on the normal operation of the same. In the description and claims of this specification, the term "data reader" is used to refer to all players or units arranged or controlled to read the data on a disk, for example, by extraction or otherwise access of the data on the disk. These players will therefore include CD-ROM drives when they are configured or controlled to read or extract data from the disk. In this regard, it is required to allow a CD-ROM drive, for example, to play a legitimate CD-DA, but prevent this CD-ROM drive from being used to make a usable copy of the disc. In one embodiment of a method of the present invention, the data encoded on the compact disk that has been made incorrect is the structure of a data sector on the compact disc. A method of the present invention additional and / or alternatively may have other control data which are incorrect and / or inaccurate. . It is well known that the data on a compact disk is encoded in tables, and convincingly 98 of these tables are grouped into a sector. In a preferred embodiment of a method of the present invention, the number of frames grouped in each sector is changed from the norm. • The applicants have established that the sound reproduced in an audio player of a compact disc having 97 or 99 frames per sector does not suffer from any degeneration in the quality. By contrast, if the data that has been recorded in this way is recorded again by using data reader, the quality of the sound is degenerated. Missing samples are displayed as a noise phase that tends to be unpleasant. Clearly, the number of tables per sector can be selected as required, to meet the particular circumstances. Preferably, the control data - encoded on the compact disc are altered before the asterization of the disk. Specifically,. he - encoder used in the mastering process has its parameters changed - to change the frame structure of the mastered disk. The present invention also extends to a compact digital audio disc, protected against copies, where the control data is encoded on the compact disc and where the selected control data has been made incorrect and / or inaccurate,. The incorrect and / or inaccurate control data will be arranged to interfere with the "reading of data" of audio from the digital audio compact disc.In general, incorrect and / or inaccurate control data is arranged in such a way that it can not be corrected by the error correction provisions of the available data readers .. In a preferred embodiment of a digital audio compact disc protected against copies of the present invention, the data is encoded on the compact disc. in tables and tables are grouped into sectors, where there is a non-standard number of tables in each sector.A compact digital audio disc protected from copies of the invention may have only non-standard sectors or may have other control data that is incorrect. and / or inaccurate.

BRIEF DESCRIPTION OF THE DRAWINGS. In . In the following, the modalities of the present invention will be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows schematically a compact disk that exposes the spiral data track, Figure 2 shows a schematic of an audio player for CDs, 'Figure 3' shows the structure of a data box encoded on a CD, the Figure 4 shows an individual sector in which a number of tables are grouped, Figure 5 shows a standard sector, as in Figure 4, together with a non-standard sector, Figures 6a and 6b show the way in which a reader data is associated 'with the sectors,' Figure 6a shows the reception of the standard sectors and Figure 6b shows the use of a non-standard sector, and Figure 7 illustrates the use, by means of an audio player, of data tables arranged in a non-standard sector.

DESCRIPTION OF PREFERRED MODALITIES A digital audio compact disc (CD-DA), which contains music and which will be played on an audio player such as a conventional CD player, is produced and recorded to a normal format known as the Red Book standards. In addition to defining - the physical properties of the disk, such as - its dimensions and its optical properties, such as the laser wavelength, the Red Book also defines the signal format and the data encoding that will be used. As is well known, the use of the Red Book standards ensures that any CD-DA produced with those standards will be reproduced on any audio player produced with those standards. Figure 1 schematically shows the spiral track 4 on a CD 6. This spiral track 4 on a CD-DA is divided into an Input 8, a number of music or audio tracks as 10 and an Output 12. The track of Entry 8 includes a- Table of Contents (TOC, for its acronym in English) that identifies the tracks to follow for the player, while Output 12 provides the warning that the spiral track 4 will end. An audio player always has access to Input 8 on power up. The music tracks can then be played consecutively as the playhead tracks 4. from the Input to the Output. Alternatively, - the player navigates from the read head at the start of each audio track as required. At first glance, 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 sophisticated and are capable of reading data, and processing the information, from each sector of the compact disc according to the nature of that data or information. A data reader can navigate when reading the information from each sector with which the 'reader head can be directed to access any part. of the spiral track 4 as required. To ensure that any data reader can read any CD-ROM, the compact disks and the readers are also produced according to the known standards, in this case, like the Yellow Book standards. These Yellow Book standards incorporate, although they extend, the Red Book standards. Therefore, a data reader, such as a CD-ROM drive, can be controlled to play a CD-DA :: La. The ability of a data 'reader' to access, extract or otherwise read the data on a CD-DA provides a problem for the music industry. A user can use their CD-ROM drive to read data from an audio disc, for example, into a computer file and then these data can be copied. The increasing availability of recorders capable of recording on compact discs means that individuals and organizations today have an easy access to technology to make perfect copies of audio CDs. . This is of great interest to the music industry.

An audio player, it is a player. of compact disc music, a more sophisticated CD-ROM drive when controlled to play an audip disc, only searches and uses data encoded for Red Book standards. What's more, if it seems that. there is an inaccuracy in the data, an audio player '"in general will continue - playback instead of trying to correct the error, for example, if the playhead navigated at the beginning of a track and starts playing that track, The audio player will continue to play the track to completion, even if it becomes evident that there is some 'error in the sync information * for example, by contrast, a reader of., data is available to identify and correct. - Errors The present invention therefore suggests that errors must be made, deliberately entered into the data network.

Book, although these errors must be of a type that in general are transparent, for an audio player but that interfere with the extraction or reading of the audio data by a data reader. This means that the data reader is either unable to read the audio disc and / or produces copies with degenerate sound. As the data that is encoded in a CD-DA and on a CD-ROM is well known and agrees with the appropriate standards, it is not necessary to describe it in detail here. Briefly, the data in a CD is coded in frames by means of EFM (modulation eight to fourteen). Figure .2 shows the format of a frame and as is evident from it, each frame has synchronization data, sub-coded bits that provide control and display symbols, data bits and parity bits. Each frame includes 24 bytes of data, which, for a CD-DA, is the audio data. The symbols. sub-coded, P, Q ', R, S, T, U, V, W are arranged in sub-coded blocks and each, one has the patterns of synchronization SO and SI as the first two symbols. The standard requires that 98 of these tables be grouped in one sector. The start of each sector is defined by the appearance of the symbol SO 'as the sub-coded symbol of the first frame and by the appearance of the - symbol SI as the sub-coded symbol of the following frame, as shown in Figure 4. The Figure 2 schematically shows an audio player for a CD 6. As can be seen, the analog signal detected by the optical system, generally designated 14, is converted by the converter 1.6 into the digital EFM form. The EFM data is decoded in '. the decoder 18 and is subjected to a correction of error in stage '20. The 24 bytes resulting from the data obtained from each frame are divided into 4-byte samples and put on time at a constant speed in a digital-to-analog converter 22 to produce the output signal of .audio . The present invention proposes that each sector have a number of non-standard tables as illustrated in Figure 5, where a sector of 98 standard tables is shown adjacent to the sector having 99 frames. In the non-standard arrangement shown in Figure 5, the patterns. synchronization sub-coded SO and SI are placed a box after that 'otherwise they could be. The data inside each box remains the same. Therefore, this means that there is an extra F table in each sector. We have observed that in an audio player, the 24 bytes of data coming from each frame of a sector are divided into 4-byte samples. The audio player could treat a sector of 99 frames, as shown in Figure 5, in a similar way as indicated in Figure 7. However, an arbitrary data reader decides how to break each sector of 2352 bytes (98 frames x 24 bytes) and the data reader is prepared to acquire and manipulate sectors of 2352 bytes. With an extended sector. which has 99 frames, as shown in Figure 5, the data reader will have to omit some of the bytes that you have acquired from a sector .: Effectively, the reader. of data will omit six samples from each sector, or six samples of l / 75th of a sector, and these samples omitted 5. They show a noise phase. In this way, if a data reader is used to read audio data from the CD-r to allow a copy to be made, the sound quality of the resulting copy will degenerate. 10 A conventional audio player will be. affects by. the large number of frames in which the timer. It will be somewhat slower when the disc is playing. This means that any elapsed time that is exhibited in the audio player can be inaccurate. This invention shows that the use of sectors with a non-standard number of frames is effective for the copy protection of the CD-DAs. Clearly, the number of tables in a sector is . You can select to meet particular circumstances. The. upper or lower limits for. Changes that can be made will depend, for example, on such factors - such as the design of a particular data reader and whether or not there are other incorrect or inaccessible control data added additionally to the disk. It will be evident that the method described and illustrated is only an example of a method in which - the audio data obtained by reading a copy protected disc can be corrupted by the use of non-standard sectors. Other examples are possible. Furthermore, the nature of the resulting corruption will depend not only on the variations made to the structure of the data sectors, but will also depend on the design of the data reader used. It will be appreciated that sectors n can be incorporated? standard on a compact disc to provide copy protection. Alternatively, other incorrect or inaccessible control data can be additionally incorporated into the compact disc. It will be appreciated that variations can be made. and modifications to the modalities described and illustrated within the scope of this application.

Claims (14)

1. NOVELTY GIVE IT THE. INVENTION Having described the present invention, it is considered as a novelty and, therefore, the content of the following is claimed as property. 5 CLAIMS. 1. A method for protection against copies of a digital audio compact disc, wherein the control data is encoded on the compact disc, the method for copy protection comprises the 10 step of making the selected control data incorrect and / or inaccurate, whereby the incorrect and / or inaccurate control data interfere with the reading of audio data from the digital audio compact disc. 15. The method for protection against copying of a digital audio compact disc according to claim 1, wherein the incorrect and / or inaccurate control data are arranged in such a way that they can not be corrected, by means of the provisions 20 correction, error of available data readers. The method for copy protection according to claim 1 or claim 2, wherein the incorrect data encoded on the disk 25 -. 25 -compact are arranged either to be ignored or otherwise have in general no effect on the playback of the audio data on the disc. '4. The method for protection against copies. according to any of the preceding claims, wherein the data encoded in the compact disk that has been made incorrect is the structure of. a sector of data on the compact disc. 5. The method for protection against copies according to any preceding claim, wherein the data on the compact disc is encoded in frames that are grouped into a s stor, and wherein the number of frames grouped in each sector are changed from the standard. The method for copy protection according to any preceding claim, wherein the control data encoded on the compact disc has been altered before the mastering of the disk. The method for copy protection according to claim 6, comprising the step, of changing the parameters of an encoder used in the mastering process to change the frame structure of the mastered disk. 8. A copy-protected digital audio compact disc, where the control data is encoded on the compact disc, and where the selected control data has been made incorrect and / or inaccurate, the incorrect and / or inaccurate control data are arranged to interfere with the reading audio data from the digital audio compact disc. . 9. The digital copy protected compact disc according to claim 8, wherein the incorrect and / or inaccurate control data are arranged in such a way that they can not be corrected by the error correction provisions of the available data readers. . 10.- The. compact copy-protected digital audio disc according to claim 8 or claim 9, wherein the data is encoded on the compact disc in frames, and the frames are grouped into sectors, where there is a non-standard number of frames in each sector. 11. The digital audio compact disc protected against copies according to any of claims 8 to 10, wherein the compact disk has only non-standard sectors. . 1-2. The copy-protected digital audio compact disc according to any of claims 8 to 10, wherein the compact disk has non-standard sectors and additionally has other control data that is incorrect and / or inaccurate. ' 13. A method for the protection against copies of a compact digital audio disc practically as described above with. reference to the accompanying drawings. 14. A compact disc of digital audio protected against copies practically like the '. described above with reference-, to the accompanying drawings. '-'-' - - '•' ' SUMMARY OF THE INVENTION The. The ability of a data reader, such as, for example, a CD-ROM drive to access, extract or otherwise read, data on a digital audio compact disc provides a problem for the music industry. A user can use their CD-ROM drive to read the data from an audio disc into a computer file and then that data can be copied. To provide copy protection, errors are deliberately entered into the data about • a CD, although these errors are of a type that are generally transparent to an audio player but will interfere with the reading of the audio data by means of a data reader. From., According to the standards, the data on a CD is encoded in frames by EFM (modulation-- from eight to fourteen). Each frame has synchronization data, subcoded bits that. they provide control and display symbols, • data bits and parity bits and include 24 bytes of data, which is audio data for a CD-DA. The standard requires that 98 of these tables be grouped into one sector. To provide copy protection, each sector is provided with a number of frames' without standard, for example, it has 99 instead of 98 frames. Then - the synchronized synchronization patterns SO and SI are placed in a box after which they could be otherwise, although the data within each picture remain the same. An audio player could divide the 24 bytes of data from each sector frame into 4-byte samples and continue playing the disc even though with an inaccurate time display. However, a data reader used to read audio data from the CD-DA to allow a copy to be made, could produce a copy that has a degenerate quality of. sound.