WO1999063538A1

WO1999063538A1 - Apparatus and method for copy protection for recordable digital media

Info

Publication number: WO1999063538A1
Application number: PCT/US1999/011721
Authority: WO
Inventors: Shogo Karitani
Original assignee: Enterprise Corporation International
Priority date: 1998-06-01
Filing date: 1999-05-27
Publication date: 1999-12-09
Also published as: AU4100499A

Abstract

In a method for preventing unauthorized use of a recording medium having intentionally implanted error information, first, information is read and the error information is compared with a key code. It is then concluded that the recording medium is a true recording medium (lawfully produced medium). A true recording medium with implanted error information (Master Data) contains error information that can be corrected by the Error Correction circuit of the optical disc apparatus. When Master Data is copied by a recorder, Master Data is copied through the Error Correction circuit. Master Data is corrected by the Error Correction circuit of the recorder to create Copy Data. Thus Copy Data contains the same data of the Master Data but without the original error information of the Master Data. By detecting a lack of the error information, it is then concluded that the Copy Data is not a lawfully produced medium. Alternatively, a predetermined sequence or placement of error data in Master Data can be detected and used to determine if a copy is a lawfully produced medium.

Description

TITLE: APPARATUSAND METHOD FOR COPYPROTECTION FOR RECORDABLE DIGITAL MEDIA

BACKGROUND OF THE INVENTION

Field Of The Invention

The present invention generally relates to optical discs, and more particularly to an unauthorized use prevention method, and an optical disc having an unauthorized use prevention function. Further, the present invention is concerned with an optical disc apparatus for reading data from an optical disc having such an unauthorized use prevention function, and an optical disc apparatus for recording data to an optical disc to generate such an unauthorized use prevention function.

Problems In The Art

An optical disc has a large data storage capacity, and data can be easily read from the optical disc and recorded thereon by a random access method. From the above point of view, optical discs have been widely used. In the specification, the term "an optical disc" includes a magneto-optical disc. With the spread of use of optical discs, the problem of data recorded on an optical disc being unlawfully copied onto another recording medium or other optical disc becomes significant. Hence, it is necessary to provide an unauthorized use prevention method in order to facilitate the spread of use of optical discs while the copyright of data and programs recorded on the optical disc is protected.

Music audio, video, movie, computer software, and multimedia information are recorded on optical discs and sold worldwide. The development and production of such music audio and other information require a large sum of money and time. Such music audio and other information are recorded on optical discs as digital information. Thus, as is well known in the art, it is easy to make an identical copy of the optical disc by acquiring a master disc. To prevent an unauthorized copy of optical discs, a watermark method and a key code method have been used in the market place.

A watermark method allows the identification of the original author, however it does not prevent the making of the unauthorized copies. A key code method prevents the use of the copy discs without a key code. However a key code method does not prevent making copies of the master disc. A key code is open to the master disc owner, thus it is easy to know the key code. Thus prior attempts do not have effective prevention methods when a master disc is digitally copied.

Due to the lack of effective unauthorized copy prevention methods, unlawful copies of optical discs are spread worldwide, and the copyright protections can not be achieved. Further, unauthorized copies of optical discs are not effectively deterred in the countries which have no copyright laws or in the countries which have no effective copyright laws.

Another method of attempted copy protection is disclosed in U.S. Patent No. 5,418,852 to Itami et. al. issued May 23, 1995. Its abstract states that first information is read from the user inaccessible area of the recording medium and compared with second information concerning a true recording medium, and a conclusion is made whether the recording medium is the true recording medium. The information regarding the unauthorized use protection, however, is available in the optical disc, and therefore, if obtained can allow copying to occur. U.S. Patent No. 5,418,852 discusses the basic process involved in reading and recording optical discs, and is incorporated by reference herein.

SUMMARY OF THE INVENTION

It is a general object of the present invention to provide an unauthorized use prevention method in which the above disadvantages of prior inventions are eliminated. A more specific object of the present invention is to provide an unauthorized use prevention method capable of effectively preventing unlawful copying of master discs, having digital information including but not necessarily limited to music audio, movie, video, computer software, computer data, and multimedia information. Further the present invention provides an easy method to detect an unauthorized copy of the master disc. The above objects of the present invention are achieved by a method for preventing unauthorized use of a recording medium having intentionally implanted correctable error information. The feature of the present invention is that the master data and copy data have no difference when compared. In the present invention, the master disc identification is implanted in the correctable error information. The error information is within correctable errors, and the error information is eliminated through the standard error correction circuit currently in optical disk playback machines. Thus the data can be retrieved without an error. When an unauthorized copy is made, the master data without error information is recorded. Therefore the copy data does not contain the implanted error information.

Optical discs can contain various errors caused by scratches, dust, defects of the media, or errors during recording. Thus without an error correction circuit, it is impossible to effectively use optical discs. For this reason, effective error correction methods and error correction circuits are designed and implemented in present optical disc recorders/players to correct such errors. Therefore majority of errors can be corrected with such error correction circuits.

The error information for the present invention is such that periodical errors having predetermined frequencies, pseudo random errors, or errors implanted to predetermined sectors or data are intentionally placed on the optical disc. Thus the error information can be easily distinguished from the errors caused by scratches, dust and other random errors because of the predetermined or preknown nature of the error information (as opposed to the purely random nature of scratches, dust, recording errors, etc.). Further by implanting key codes and/or identification codes, it is possible to read key codes and/or identification codes from the error information. Or, from the error information, the sector or data containing key codes and/or identification codes can be determined.

It can therefore be seen that the present invention, relying in part on already existent circuitry in the optical disc players, provides an economical unauthorized use prevention method and apparatus.

The above objects of the present invention are achieved by the following components:

1. Master data disc having the correctable error information.

2. Optical disc apparatus having an error correction circuit and an error information detection circuit.

3. An identification circuit that determines the master data or copy data based on the information from an error information detection circuit.

The following describes the method of determining the master data and the copy data:

1. RF signal that is optically detected from optical discs, such as CD- ROM discs, is amplified to the appropriate amplitude, and sent to the date slice/sampling circuit.

2. The RF signal is converted to the digital data by the data slice/sampling circuit, and sent to the error correction circuit.

3. The digital data input to the error correction circuit is corrected by the circuit. The data without error is generated and the error information is extracted from the detected errors.

4. Based on the error information extracted by the error correction circuit, the master data is identified. Or, the key code and/or identification code is extracted from the error information. Further by identifying the data blocks or sectors containing the key code and/or identification code, the key code and/or identification code can be extracted.

5. By determining the existence of the intentional error information, or by detecting the presence of the key code and/or identification code, the distinction of the master data and copy data can be performed.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings, in which:

Fig. 1 is a block diagram of the master data prior to the implant of the error information (Fig. 1.1), a block diagram of the master data with the error information by the present invention (Fig. 1.2), and the copy data from the master data with the error information by the present invention (Fig. 1.3). FI, F2, ..., and Fn represent the data frame numbers and indicate the data frames without the implanted error information. Ql, Q2, ..., and Qn represent the data frame numbers with the error information of the present invention.

Fig. 2 is an example block diagram of an optical disc reader apparatus that reads the master data disc with the error information of the present invention, and determines the master data or the copy data.

Fig. 3 is the detailed example block diagram of the error correction circuit of Fig. 2.

Fig. 4 is an example block diagram of an optical recorder apparatus. Fig. 5 is the detailed example block diagram of the error correction encoding circuit of Fig. 4. Fig. 6 is an example block diagram of an optical disc recording apparatus with the error correction encoding circuit of the present invention. Fig. 7 is a block diagram of a method according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Fig. 1.1 illustrates the master data with 16 frames. Fig. 1.2 illustrates the master data with a periodic (in this example, every other frame) correctable error information implanted to prevent unlawful copying of the master data. Other sequences or schemes could be used. The optical disc contains the recorded master data with correctable error information. For the purpose of copy protection, the error information can be implanted in any or all of data recorded in the optical disc, such as Program Area, TOC, Subcode, Header, Lead In Area, and/or Lead Out Area. The error information can be implanted by utilizing the bit patterns not used for EFM encoding.

The optical disc data are read by the optical disc reader apparatus, the errors are corrected in the error correction circuit, and the master data without error is output. On the other hand, the error detector circuit in the present invention detects the periodic errors. Thus the data disc is identified as the master data disc.

A standard, commercially available optical disc recorder apparatus inputs the master data without error, and copies it to the recording medium. Therefore the resulting copy data disc does not contain the error information contained in the master data disc. Fig. 1.3 illustrates the data frames of the copy data disc. By measuring the presence of the error information sequences, the master data disc with the error information of the present invention and the copy data disc can be easily distinguished.

Fig. 2 is an example block diagram of the optical disc reader apparatus (10) with the master data detector circuit (12) of the present invention. Phase lock loop (21), Motor Driver (25), and Disc Motor (23) are standard components. They allow for constant linear velocity (CLV) to be maintained as the optical disc is rotated and the optical pickup follows the spiral path of the disc. This is all well-known in the art. Disc Motor (23) is controlled by Motor Driver (25) which can receive signal (30) from Master Data Detector (12) and stop operation of disc motor 23 if an unauthorized recording is detected. The optical pickup (14) detects the RF signal of the optical disc (20) with the laser beam (18). The RF signal detected by the optical pickup (14) is amplified by the RF Amplifier circuit (22), and converted to the digital data by the A/D converter/data sampling circuit (24). The digital data is corrected by the error correction circuit (26), and the data without error is output. At the same time, the error information is given to the master data detector/key code ID detector (12) of the present invention. The detector (12) determines whether the error is caused by scratches, dust, or other defects, or by the error information implanted in the master data disc. The detector (12) issues the master/copy detection result signal (30). Based on the detection result, the optical disc reader apparatus (10) stops reading or playing the copy data disc if an unauthorized copy is detected.

Fig. 3 illustrates the detailed block diagram of the error correction circuit (26) of Fig. 2. These are all standard components and well known in the art as to their function and operation, as well as their physical make-up. The input digital data (32) is EFM decoded (block 34), then Cl corrected (block 36). After de-interleaved (block 38), the data is C2 corrected (block 40). The C2 corrected data is de-scrambled (block 42), and passed to the data decoder circuit (block 37) which sends a signal for further processing (for example by an audio playback component). Fig. 4 is an example block diagram of an optical disc recorder apparatus

(50) without the present invention. Fig. 5 is the detailed block diagram of the error correction encoder circuit (52) of Fig. 4. The input digital data (54) is scrambled (block 56), then C2 encoded (block 57). The C2 encoded data is interleaved (block 58), then Cl encoded (block 60). After the data is Cl encoded, the data is EFM encoded (block 62) and passed to the RF write amplifier circuit (64 in Fig. 4). Fig. 6 is an example block diagram of an optical disc recorder apparatus with the present invention error data encoding/key code ID encoding circuit (70). The encoding circuit (70) embeds/implants the correctable error information during Cl encoding. Fig. 7 illustrates a practical example block diagram of the present invention. With Fig. 7 block diagram:

1. While the master data is encoded, the correctable error information is implanted in the CD-ROM disc. An error is implanted in a frame out of every m-frames. The intentional error is one error per frame; where m is an integer number and m>0.

2. The CD-ROM disc created in Step 1, is inserted in the CD-ROM drive having a master data detection microcomputer.

3. The CD-ROM disc is read optically by the optical pickup (14) of the CD-ROM drive. The detected RF signal is amplified to the necessary amplitude by the RF amplifier circuit (22).

4. The RF signal is A/D converted by the data slice and sampling circuit (24), and the EFM digital data is extracted.

5. The EFM signal is decoded by the EFM decoder (34). Cl error is detected by the Cl decoder (36).

6. The Cl error is tested on every frame of the CD-ROM disc.

7. Upon collection of 98 frames of Cl data, the master data detector microprocessor (80) determines the master data or copy data.

8. Cl error is detected in a frame out of every m-frames on the CD- ROM disc. In the case of the master disc, the Cl error occurs every

98/m frame. If more than n (where n is less than or equal to (98/m)) errors are detected, the disc may be the master disc. If the errors are less than n, the disc is a copy disc.

9. When the probability of the master disc is detected more than k times continuously by the master data detector microcomputer (80), it is determined as the master disc. If not it is determined as a copy disc. The master data detector microcomputer (80) issues the master disc detection signal (82) to the system control microcomputer (84). If determined as a copy disc, the master data detector microprocessor (80) issues the copy disc detection signal (82) to the system control microcomputer (84).

10. Receiving the master/copy disc detection signal (82), the system control microcomputer (80) continues the read operation in the case of the master disc detection signal (82), otherwise the read operation stops. For example, the read operation stops by the sending of a Disc Motor On/Off Signal (86) to Disc Motor Driver

(25) which stops rotation of the optical disc and thus playback of the information on the optical disc.

It is to be understood that in Figure 7 two microprocessors are used. This allows on the fly detection. However, one processor could be eliminated and the method could work. The microcomputers used are standard, as are used in standard, commercially available optical disc recorders/players. It is further to be understood that the error correction circuitry of standard commercial optical disc apparatus can not be turned on and off. Therefore, the present invention can not be overridden by such a step.

The set up parameters shown in Figure 7 could take on different forms. The examples given herein (parameters m, n, and k) show some of those possible forms.

Another practical example of the present invention with Fig. 7:

1. While the master data is encoded, the correctable error information, based on the key code, is implanted in the CD-ROM disc.

2. The key code is recorded p times in the CD-ROM disc.

3. The master disc detector microcomputer (80) assigns 1-bit Cl error information per frame.

4. 98 bits information is obtained per 98 frames. 5. Within 98 bits information, 64 bits are used for the key code, 34 bits are used for the synchronization signal, parity, and header.

6. If the key code is detected k times (where k is less than or equal to p), the master disc detector microcomputer (80) determines the key code.

7. The obtained key code is compared with the pre-determined key code. If the key codes are identical, the CD-ROM disc is determined as the master disc, otherwise the disc is determined as a copy disc.

Claims

I Claim:

1. A method for deterring use of unauthorized copies of data on optical disks comprising: Intentionally implanting correctable error information in a predetermined manner with master data on one or more authorized optical disks; reading the data from an optical disk; if correctable error information in the predetermined manner is detected on the optical disk, considering the optical disk an authorized optical disk; if correctable error information in the predetermined manner is not detected on the optical disk; considering the optical disk an unauthorized optical disk.

2. A system for deterring use of unauthorized copies of data on optical disks comprising: one or more optical disks with intentionally implanted correctable error information in a predetermined manner with master disk, the one or more disks comprising authorized optical disks; an optical disk apparatus with an error correction circuit and error detection circuit; so that any optical disk read by the optical disk apparatus can determine if the optical disk is authorized by detecting the intentionally implanted correctable error information or unauthorized if it does not contain the intentionally implanted correctable error information.

3. The system of claim 2 further comprising a circuit to discontinue operation of the optical disk apparatus if an unauthorized disk is detected.