Copy protection for video signal using narrowed horizontal synchronization signals and amplitude modulation
AssigneeMacrovision Corporation
InventorRonald Quan
Life of this patent
Estimating the term…
Abstract
Enhancements to a video anticopying process that causes an abnormally low amplitude video signal to be recorded on a illegal copy. The enhancement in one version include a negative going waveform that appears to the television receiver or videotape recorder to be a sync signal, thereby causing an early horizontal or vertical retrace. In another version, selected horizontal sync pulses are narrowed, causing irregular vertical retraces. In another version, post-pseudo sync pulses that have a minimum level above the minimum level of sync pulses are added to enhance anti-copy effectiveness. The post pseudo-sync pulses may be amplitude modulated.
Claims21
A method of modifying a copy protected video signal that includes horizontal sync pulses, wherein the copy protected video signal includes positive going pulses which cause a reduced amplitude in a recording of a copy projected video signal, the method comprising the act of:
- reducing the duration of at least one horizontal sync pulse, whereby the resulting video signal is enhanced in terms of its copy protection effects;
- wherein a first set of horizontal sync pulses is reduced in pulse width at one or more associated scan lines in an active portion of a video field;
- and, whereby another set of horizontal sync pulses associated with one or more scan lines in an overscan portion of the video field has a greater sync pulse width reduction than the first set.
A method of modifying a copy protected video signal that includes horizontal sync pulses, wherein the copy protected video signal includes positive going pulses which cause a reduced amplitude in a recording of a copy protected video signal, the method comprising the act of:
- reducing the duration of at least one horizontal sync pulse, whereby the resulting video signal is enhanced in terms of its copy protection effects;
- wherein in a video field, a first set of associated scan lines has a particular sync pulse width reduction while a second set of associated scan lines has a different sync pulse width reduction.
A method of modifying a copy protected video signal that includes horizontal sync pulses, wherein the copy protected video signal includes positive going pulses which cause a reduced amplitude in a recording of a copy protected video signal, the method comprising the act of:
- reducing the duration of at least one horizontal sync pulse, whereby the resulting video signal is enhanced in terms of its copy protection effects;
- whereby selected horizontal sync pulses are reduced to less than 600 nano second duration in pulse width.
A method of modifying a copy protected video signal that includes horizontal sync pulses, wherein the copy protected video signal includes positive going pulses which cause a reduced amplitude in a recording of a copy protected video signal, the method comprising the act of:
- reducing the duration of at least one horizontal sync pulse, whereby the resulting video signal is enhanced in terms of its copy protection effects;
- whereby a selected number of horizontal sync pulses toward the end of a video field are reduced to less than half of a width of a standard horizontal sync pulse.
A method of modifying a copy protected video signal that includes horizontal sync pulses, wherein the copy protected video signal includes positive going pulses which cause a reduced amplitude in a recording of a copy protected video signal, the method comprising the act of:
- reducing the duration of at least one horizontal sync pulse, whereby the resulting video signal is enhanced in terms of its copy protection effects;
- further comprising the act of adding amplitude modulated negative going pulses to the copy protected video signal after selected color burst signals.
A method of providing a copy protected video signal having horizontal sync pulses and a vertical blanking interval, comprising the acts of:
- adding AGC pulses to a selected set of scan lines in the video signal;
- reducing the duration of selected horizontal sync pulses of the video signal;
- and,
- adding a negative going pulse following a color burst to modify copy protection in the video signal including AGC pulses and/or pseudo-sync and AGC pulses.
A method of providing a copy protected video signal that includes horizontal sync pulses, the method comprising the acts of:
- adding positive going pulses which cause a reduced amplitude in a recording of the video signal;
- reducing the duration of at least one horizontal sync pulse, whereby copy protection of the resulting video signal is enhanced;
- further comprising the act of adding amplitude modulated negative going pulses to the copy protected video signal after selected color burst signals.
Dependencies are inferred from the claim text.