Method and product for copy protection of optical discs using unbalanced DC content
View Patent ↗The present invention relates to a method of copy protecting optical discs, such as CDs or DVDs. Instead of encoding data onto the CD-ROMs in a conventional manner which ensures balanced dc content, for copy protection the digital data is encoded and recorded onto the optical disc such that it is arranged to give some of the recorded digital data highly unbalanced dc content. Thus, for example, the DSV (digital sum value) value of the encoded data is recorded so that the DSV value changes continuously once 50 frames of data or more.
1. A method of copy protecting an optical disc on which encoded digital data is recorded, the method comprising:
encoding and recording the digital data onto the optical disc in a manner which is arranged to give some of the recorded digital data unbalanced dc content;
wherein the unbalanced dc content allows playing of the digital data but prevents extracting the digital data from the disc and the unbalanced dc content is given to selected areas of the recorded digital data on the disc; and
wherein the unbalanced dc content changes strictly monotonically over at least 50 frames of the selected area, each frame including 24 bytes of data.
2. The method of copy protecting an optical disc according to claim 1 , further comprising predetermining the selected areas of the recorded digital data which are to be given the unbalanced dc content.
3. The method of copy protecting an optical disc according to claim 1 , further comprising randomly selected the selected areas of the recorded digital data which are to be given the unbalanced dc content.
4. The method of copy protecting an optical disc according to claim 1 , further comprising recording the digital data onto the optical disc in frames arranged into sectors each having a plurality of frames, and providing that each selected area having the unbalanced dc content contains less than 2 sectors.
5. The method of copy protecting an optical disc according to claim 4 , wherein each sector contains 98 frames.
6. The method of copy protecting an optical disc according to claim 1 , wherein some of the recorded digital data is given the unbalanced dc content by providing the recorded digital data with poor DSV (digital sum value) characteristics.
7. The method of copy protecting an optical disc according to claim 6 , wherein the DSV of the recorded digital data has substantial low frequency components.
8. The method of copy protecting an optical disc according to claim 1 , wherein the recorded digital data on the optical disc is given the unbalanced dc content by encoding the selected areas of the digital data to have poor DSV (digital sum value) characteristics.
9. The method of copy protecting an optical disc according to claim 8 , wherein the DSV of the recorded digital data has a rapid rate of change.
10. The method of copy protecting an optical disc according to claim 8 , wherein the DSV of the recorded digital data has high absolute values.
11. The method according to claim 1 , wherein the digital data is encoded using EFM encoding where merge bits chosen during the encoding are inserted between successive channel bits, and wherein the merge bits are chosen to give poor DSV (digital sum value) characteristics to the selected digital data.
12. The method according to claim 1 , wherein the digital data is encoded using EFMPlus encoding where each 8 bit data word is encoded into one of a choice of four 16 bit channel words, and wherein the 16 bit channel words are chosen to give poor DSV (digital sum value) characteristics to the selected digital data.
13. The method of copy protecting an optical disc according to claim 1 , wherein the change is increasing or decreasing.
14. A copy protected optical disc having data comprising encoded digital data recorded thereon, wherein some of the recorded digital data have unbalanced dc content, wherein the unbalanced dc content is given to selected areas of the digital data and wherein the unbalanced dc content allows playing of the digital data but prevents extracting the digital data from the disc and wherein the unbalanced dc content changes strictly monotonically over at least 50 frames of the selected area, each frame including 24 bytes of data.
15. The copy protected optical disc according to claim 14 , further comprising predetermining the selected areas of the recorded digital data which are to be given the unbalanced dc content.
16. The copy protected optical disc according to claim 14 , further comprising randomly selected the selected areas of the recorded digital data which are to be given the unbalanced dc content.
17. The copy protected optical disc according to claim 14 , further comprising recording the digital data onto the optical disc in frames arranged into sectors each having a plurality of frames, and providing that each selected area having the unbalanced dc content contains less than 2 sectors.
18. The copy protected optical disc according to claim 14 , wherein each sector contains 98 frames.
19. The copy protected optical disc according to claim 14 , wherein some of the recorded digital data is given the unbalanced dc content by providing the recorded digital data with poor DSV (digital sum value) characteristics.
20. The copy protected optical disc according to claim 14 , wherein the recorded digital data on the optical disc is given the unbalanced dc content by encoding the selected areas of the digital data to have poor DSV (digital sum value) characteristics.
21. The copy protected optical disc according to claim 20 , wherein the DSV of the recorded digital data has a rapid rate of change.
22. The copy protected optical disc according to claim 20 , wherein the DSV of the recorded digital data has high absolute values.
23. The copy protected optical disc according to claim 20 , wherein the DSV of the recorded digital data has substantial low frequency components.
24. The copy protected optical disc according to claim 14 , wherein the selected areas of the recorded digital data which have the unbalanced dc content are predetermined.
25. The copy protected optical disc according to claim 14 , wherein the selected areas of the recorded digital data which have the unbalanced dc content are randomly selected.
26. The copy protected optical disc according to claim 14 , wherein the optical disc is a CD (compact disc) and the encoded digital data has been subjected to EFM encoding.
27. The copy protected optical disc according to claim 14 , wherein the optical disc is a DVD (digital video disc) and has been subjected to EFMPlus encoding.
28. The copy protected optical disc according to claim 14 , wherein the digital data recorded on the optical disc is one or more of audio data, video data, graphics data, visual data, animation data, numerical data, program data, control and access data, and/or any other data.
29. The copy protected optical disc according to claim 14 , wherein the digital data is encoded using EFM encoding where merge bits chosen during the encoding are inserted between successive channel bits, and wherein the merge bits are chosen to give poor DSV (digital sum value) characteristics to the selected digital data.
30. The copy protected optical disc according to claim 14 , wherein the digital data is encoded using EFMPlus encoding where each 8 bit data word is encoded into one of a choice of four 16 bit channel words, and wherein the 16 bit channel words are chosen to give poor DSV (digital sum value) characteristics to the selected digital data.
31. The copy protected optical disc according to claim 14 , wherein the change is increasing or decreasing.