Anti-copy protection for a video signal

Apparatus for applying anti-copy-protection to a raster-scanned video signal to produce a modified video signal, the apparatus comprising:

• an input for receiving a video signal which is to be modified, the video signal having a vertical synchronisation pulse defined between a leading edge and a trailing edge, wherein the leading edge and the trailing edge are consecutive edges in the video signal;
• circuitry configured to modify the vertical synchronisation pulse between the leading edge and the trailing edge of the video signal received by the input to produce a modified video signal, the circuitry adding a waveform to the vertical synchronisation pulse with an amplitude at least equal to that of the vertical synchronisation pulse, wherein the circuitry is further configured to modify the vertical synchronisation pulse such that after recording by a recording device, the average voltage level of a modified vertical synchronisation pulse is shifted towards a blanking level in comparison to the average level before recording, and
• an output configured to output the modified video signal.

A method for applying anti-copy-protection to a raster-scanned video signal to produce a modified video signal, the method comprising:

• receiving a video signal which is to be modified, the video signal having a vertical synchronisation pulse defined between a leading edge and a trailing edge, wherein the leading edge and the trailing edge are consecutive edges in the video signal;
• modifying the vertical synchronisation pulse of the video signal received by the input to produce a modified video signal, the modifying means adding a waveform to the vertical synchronisation pulse with a frequency of at least 500 KHz and with an amplitude at least equal to that of the vertical synchronisation pulse, wherein modifying the vertical synchronisation pulse further includes modifying the vertical synchronisation pulse such that the average voltage level of a modified vertical synchronisation pulse is shifted towards the blanking level in a comparison to the average level before recording, and
• outputting the modified video signal.

A method comprising:

• outputting from an electronic device a raster-scanned video signal having a modified vertical synchronisation pulse defined between a leading edge and a trailing edge of the video signal such that the video signal can be viewed on a display device at or near the quality intended by the originator of the video signal, but such that after recording by a recording device, the recorded signal exhibits a reduction in vertical stability when played back and viewed on the display device, wherein the leading edge and the trailing edge are consecutive edges in the video signal prior to recording, and wherein the modified vertical synchronisation pulse is such that, after recording by the recording device, the average voltage level of a modified vertical synchronisation pulse is shifted towards the blanking level in comparison to the average level before recording.

An apparatus comprising:

• circuitry configured to output a raster scanned video signal having a vertical synchronisation pulse modified to include a waveform with an amplitude at least equal to that of the vertical synchronisation pulse such that a time duration of the modified vertical synchronisation pulse is substantially the same as a time duration of the vertical synchronisation pulse before modification, wherein the vertical synchronization pulse is defined between a leading edge and a trailing edge in the video signal, and wherein the leading edge and the trailing edge are consecutive edges in the video signal before modification, wherein the circuitry is further configured to modify the vertical synchronisation pulse such that after recording by a recording device, the average voltage level of a modified vertical synchronisation pulse is shifted towards a blanking level in comparison to the average level before recording.