摘要:
A l'émission le signal de télévision est codé, pour chaque ligne, par décalage pseudo-aléatoire du signal d'image par rapport au signal de synchronisation ligne. Le circuit de décodage comprend une ligne à retard (12) dont le retard est commandé pour rétablir le décalage correct entre le signal de synchronisation et le signal d'image. La ligne à retard est du type à transfert de charge (DTC). Elle a la capacité d'une ligne de signal vidéo de durée P. La fréquence du signal d'horloge est telle qu'une ligne vidéo est retardée d'une valeur du même ordre de grandeur que la durée d'une telle ligne vidéo. Un moyen (18, 19) est prévu pour bloquer le signal d'horloge pendant un temps qui, à chaque ligne, est fonction du décalage à effectuer pour rétablir la phase correcte entre le signal de synchronisation et le signal d'image.
摘要:
A video signal is encoded in a pattern which changes 'rom field to field. The encoding pattern starts at the Nth line where N is a random number generated afresh for each 'ield, and thereafter alternate lines have their video portions ioninverted and inverted. Further encoding may be achieved by shifting the horizontal synchronisation pulses of certain lines starting from the Nth line and this shifting is applied to bands of lines separated by bands of lines in which the synchronisation pulse is left unchanged, in a regular pattern. In a transmission system, the encoded video signal is combined with the encoding data and an audio signal for modulation of an rf carrier. The decoding information may be applied to a sub-carrier.
摘要:
The invention uses digital techniques for defeating the effects of the analog copy protected signal while the signal is in the digital domain. The types of copy protection signals includes pseudo sync pulses and AGC pulses. Additionally digital techniques may be used for reducing or eliminating the effects of a chroma copy protection process (Figs. 10-14). A digital video copy protection eliminator allows removal of substantially all pseudo sync pulses and/or AGC pulses in the digital domain. The location of pseudo syncs and/or AGC pulses are determined, while the signal is in the digital domain. These known pixel locations of all or some of the pseudo syncs and/or AGC pulses are used to digitally modify the signal so as to effectively remove the pseudo sync pulses and/or AGC pulses.
摘要:
A anti-copy programme signal is provided. Copies of the anti-copy video pulses made on a video recorder experience 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 28 added to each line 6 of the signal throughout both the visible picture region and throughout the vertical blanking region 12, as well as a first modulated wave-form 34 added to the vertical synchronisation pulses 16 of the signal and a second modulated wave-form 36 added to several lines 6 of the picture signal before the vertical blanking section 12. The presence of all three of these features 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 separately.
摘要:
In a known copy protection process for preventing recording of video signals, pseudo sync and AGC pulses (Fig. 2) are present on predetermined lines within the blanking intervals of the video signal so that any subsequent video signal shows a picture of very low entertainment quality. The location of the video lines containing the copy protection is determined by using the color burst signal or chroma in the horizontal blanking interval. Then some or all of the lines including copy protection signals may be modified so as to render the overall video signal recordable. The modification is accomplished in a number of ways, including gain shifting portions of the video signal, level shifting portions of the video signal, bandwidth limiting certain portions of the video signal or replacing certain portions of the video signal with other video elements.
摘要:
In a known copy protection process for preventing recording of video signals, pseudo sync and AGC pulses (Fig. 2) are present on predetermined lines within the blanking intervals of the video signal so that any subsequent video signal shows a picture of very low entertainment quality. The location of the video lines containing the copy protection is determined by using the color burst signal or chroma in the horizontal blanking interval. Then some or all of the lines including copy protection signals may be modified so as to render the overall video signal recordable. In an embodiment, a copy protected video signal is input to a chroma band pass amplifier (16) whose output is applied to a chroma envelope detector (20). The output chroma envelope signal is used to generate a non-retriggerable one shot pulse, and a retriggerable one shot pulse. The retriggerable one shot pulse is applied to a multi line one shot pulse generator (26) to generate a multi line one shot pulse. The non-retriggerable one shot pulse and the multi line one shot pulse are then anded to produce a control signal representing the location of the copy protection pulses.