RECORD CARRIER, RECORDING METHOD AND PLAYBACK DEVICE FOR CONTROLLING COPYRIGHT

摘要

When duplicating the record carrier the angle between the sync words S1 S2 can be preserved at the cost of a change in bit length, or the bit length can be preserved at the expense of changes in the angle between the sync words S1 S2. Consequently a playback device that checks for both changes in the angle between the sync words S1 S2, or between other marks, and for changes in bit length can detect an illegally duplicated record carrier with a high certainty.