Abstract: 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.

Abstract: The invention provides a device driver for monitoring and controlling access to data on a computer readable medium. The device driver comprises an interface for access to a device-driver stack for a media drive, a detector for detecting the insertion of a computer readable medium in said media drive, and a monitor for monitoring data transfer from said computer readable medium. The monitor evaluates a behavior characteristic of an application accessing data on said computer readable medium, and indicates when said behavior characteristic fulfills predetermined criteria. A control system is responsive to said monitor for issuing at least one control output when said behavior characteristic fulfills said predetermined criteria. The invention also provides a method of monitoring and controlling access to data on a computer readable medium by means of the device driver.

Abstract: A digital recording medium such as an optical disc is recorded using an encoding process this is modified to cause a peak or rapid change in the digital sum value in the encoded data for part of the recording data. This provides the corresponding part of the recorded medium with a modified DC characteristic that affects an operational characteristic of the recording medium. This modified DC characteristic will not be present in unauthorized copies of the recording medium because the normal encoding process will encode the recording data so as to minimize DC imbalance. Profile data is obtained from operational data acquired during operation of the recording medium. This profile data is compared with expected profile data that is the profile data that would be expected to be obtained if the modified DC characteristic is present. The results of this comparison are used to determine whether or not the recording medium is authentic.

Abstract: 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.

Abstract: The present invention relates to a method of copy protecting optical discs, such as CD-ROMs. Instead of encoding data onto the CD-ROMs in a 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 unbalanced dc content. Thus, for example, the DSV value of the encoded data may be changed rapidly in less than (100) frames to (FIG. 9). For an area of digital data on the optical disc in which the DSV has been caused to rise steeply (FIG. 10a), heavy distortions in audio arise (FIG. 10c) during an attempt to copy an audio track including the single segment of unbalanced dc content.