An improved method and apparatus for providing a copy-protected video signal

摘要

P kOPERXSE W2K9VIlU0 I 53k) disiond pages doc-24)7/2( 9 A anti-copy programme signal is provided. Copies of the anti-copy video pulses made on a video recorder experience 5 reduced quality and interference in playback making them unpleasant to watch. The uncopied signal can be viewed without any material effect on picture quality. The signal comprises a pulse added to each line of the signal throughout both the visible picture region and throughout 10 the vertical blanking region, as well as a first modulated wave-form added to the vertical synchronisation pulses of the signal and a second modulated wave-form added to several lines of the picture signal before the vertical blanking section. The presence of all three of these features 15 together has been found to be provide a surprising accumulative effectiveness in causing interference in the reproduction of the modified video signal during playback of the copied video signal, that is greater than the effectiveness provided by the different features taken 20 separately. it / 6 SUBSTITUTE SHEET (RULE 26)