Copy protected digital audio compact disc and method and system for producing same

• US 6,718,501 B1
• Filed: 05/28/2002
• Issued: 04/06/2004
• Est. Priority Date: 11/30/1999
• Status: Expired due to Term

• Current Assignee: Rovi Europe Limited (Adeia Inc.)
• Original Assignee: Macrovision Europe Limited
• Inventors: Sollish, Baruch, Brody, Moshe
• Primary Examiner(s): Tu, Christine T.
• Application Number:
  US10/148,502
• Time in Patent Office: 679 Days
• Field of Search: 714/752, 714/746, 714/800, 714/758, 714/803, 714/701, 714/702, 714/718, 714/719, 714/769, 714/770, 714/771, 386/94, 386/39, 386/40, 386/54, 386/96, 369/132, 369/133, 369/155, 369/166, 369/291, 369/275.5
• US Class Current: 714/752
• CPC Class Codes: G11B 20/00086 Circuits for prevention of unauthorised reproduction or copying, e.g. piracy indicating unauthorised use of record carriers in general G11B23/28; scrambling for television signal recording H04N5/913; network architectures or network protocols for network security H04L63/00; cryptographic mechanisms or cryptographic arrangements for secret or secure communication H04L9/00
• CPC Class Codes: G11B 20/0063 wherein the modification to the logical format mainly concerns management data, e.g., by changing the format of the TOC or the subcode
• CPC Class Codes: G11B 20/00927 wherein said defects or errors are generated on purpose, e.g. intended scratches
• CPC Class Codes: G11B 20/1217 on discs
• CPC Class Codes: G11B 20/1251 for continuous data, e.g. digitised analog information signals, pulse code modulated [PCM] data
• CPC Class Codes: G11B 20/1809 by interleaving
• CPC Class Codes: G11B 2020/10546 specifically adapted for audio data
• CPC Class Codes: G11B 2020/10916 Seeking data on the record carrier for preparing an access to a specific address
• CPC Class Codes: G11B 2220/213 Read-only discs
• CPC Class Codes: G11B 2220/2545 CDs

Abstract

A copy-protected digital audio compact disc and method for producing same, such that neither the proper playing of the original nor the enforcement of the copy-protection depends on the use of any special equipment. A pattern of latent noise is incorporated into a digital audio CD by overwriting some of the original audio signal data symbols with grossly-erroneous values, and then overwriting the corresponding error-correction parity symbols in such a way as to create an uncorrectable error in the codewords containing the erroneous values. An ordinary CD player of such a disc will therefore detect each occurrence of a latent noise value as an uncorrectable error and will apply interpolative error-concealment to prevent the output of the error. By appropriately choosing the locations for the overwriting of the erroneous values in such a way that the interpolated value will be substantially identical to the original value, the resulting sound output from the CD player will match that of the original audio signal, so that an ordinary CD audio player will properly reproduce the original audio signal from the protected disc without any superimposed noise. Most commercially-available CD-ROM drives for computers, however, do not employ error-concealment when reading a compact disc as a data source. Depending on the copying software employed with such CD-ROM drives, when an uncorrectable error is detected, either no data is read from the disc, or only the raw uncorrected data is read from the disc. Thus, either substantial portions of the original disc will be uncopyable because of the uncorrectable errors, or the uncorrected raw data of the original will be copied, which will place audible noise on the unauthorized copy. To inhibit unauthorized copying via CD-ROM drives that employ error-concealment, alterations are made to the channel Q mode and/or CRC to disable the ability of the CD-ROM drive to seek to the desired data position.

Claims

1. A method for producing a copy-protected audio compact disc containing a plurality of symbols within error-correction codewords representing audio data samples of an audio signal, by including latent noise on the copy-protected audio compact disc which does not interfere with the playback of the audio signal from the audio compact disc on an ordinary audio player, but which interferes with the unauthorized copying of the audio compact disc on an ordinary CD recorder and with the playback of an unauthorized copy of the audio compact disc made on an ordinary CD recorder, the method comprising the steps of:

(a) selecting at least one audio data sample of the audio signal;

(b) locating the data symbols representing said at least one audio data sample;

(c) overwriting said data symbols with erroneous symbols;

(d) locating the error-correction codewords which contain said data symbols; and

(e) disabling the error-correction of said error-correction codewords.

2. The method as in claim 1, wherein said selecting at least one audio data sample selects a perfectly-concealable audio data sample having a previous audio data sample and a subsequent audio data sample, such that the value of said perfectly-concealable audio data sample substantially corresponds to a linear interpolation between said previous audio data sample and said subsequent audio data sample.

3. The method as in claim 1, wherein said erroneous symbols correspond to superimposed impulses.

4. The method as in claim 1, wherein the audio compact disc has a plurality of sectors and said selecting at least one audio data sample selects at least one audio data sample within each of a group of sectors selected from said plurality of sectors.

5. The method as in claim 1, wherein said error-correction codewords contain a plurality of parity symbols, said disabling the error-correction of said error-correction codewords comprising the step of overwriting at least one of said parity symbols with an arbitrary erroneous symbol.

6. The method as in claim 1, wherein said error-correction codewords contain a plurality of parity symbols, said disabling the error-correction of said error-correction codewords comprising the step of overwriting at least one of said parity symbols with an erasure.

7. The method as in claim 1, wherein the audio compact disc also contains a channel Q having positioning information, the method further comprising the step of disabling the positioning information of channel Q.

8. The method as in claim 7, wherein channel Q has a selectable mode including mode 1, said disabling the positioning information of channel Q comprising the selecting of the channel Q mode to exclude mode 1.

9. The method as in claim 7, wherein channel Q has a CRC, said disabling the positioning information of channel Q comprising the putting of an invalid value into the CRC.

10. A copy-protected audio compact disc containing a plurality of symbols representing audio data samples of an audio signal, and including latent noise which does not interfere with the playback of the audio signal from the audio compact disc on an ordinary audio player, but which interferes with the unauthorized copying of the audio compact disc on an ordinary CD recorder and with the playback of an unauthorized copy of the audio compact disc made on an ordinary CD recorder, the copy-protected audio compact disc comprising at least one erroneous symbol that does not correspond to the audio signal, and wherein said at least one erroneous symbol is contained within a disabled error-correction codeword.

11. The copy-protected audio compact disc as in claim 10, wherein said disabled error-correction codeword contains at least one arbitrary erroneous symbol.

12. The copy-protected audio compact disc as in claim 10, wherein said disabled error-correction codeword contains at least one erasure.

13. The copy-protected audio compact disc as in claim 10, further comprising a position-disabled channel Q.

14. The copy-protected audio compact disc as in claim 13, wherein said position-disabled channel Q comprises a mode other than mode 1.

15. The copy-protected audio compact disc as in claim 13, wherein said position-disabled channel Q comprises an invalid CRC.

16. A system for producing a copy-protected audio compact disc containing a plurality of symbols within error-correction codewords representing audio data samples of an audio signal, for including latent noise on the copy-protected audio compact disc which does not interfere with the playback of the audio signal from the audio compact disc on an ordinary audio player, but which interferes with the unauthorized copying of the audio compact disc on an ordinary CD recorder and with the playback of an unauthorized copy of the audio compact disc made on an ordinary CD recorder, the system comprising:

(a) an audio data source providing audio data samples to be recorded onto a copy-protected audio compact disc;

(b) a Red Book encoder for encoding said audio data samples;

(c) a noise generator for generating the latent noise;

(d) a codeword disabling unit for disabling error-correction codewords;

(e) a recording laser;

(f) a laser controller for controlling said recording laser;

(g) a switch for selecting between the output of said Red Book encoder and the output of said codeword disabling unit, and for passing the selected output to said laser controller.

17. The system as in claim 16, wherein the audio compact disc contains a channel Q, the system further comprising a channel Q disabling unit.

18. The system as in claim 17, wherein the channel Q has a selectable mode including mode 1, said channel Q disabling unit further operative to excluding mode 1.

19. The system as in claim 17, wherein the channel Q has a CRC, said channel Q disabling unit further operative to putting an invalid value into the CRC.