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The proposed purchase of Manchester United Football Club by media tycoon
Rupert Murdoch will give his TV stations worldwide rights to screen all the
Reds’ matches. But protecting TV rights is expensive, as broadcasters have to
pay licence fees to use Macrovision’s industry standard anti-pirating
system.

So engineers at Murdoch-owned NDS are patenting their own copy protection
system for digital TV (GB 2 319 683). Macrovision adds spurious pulses to video
signals to confuse a VCR into making unplayable tapes, but pirates can strip out
these pulses.

NDS proposes rapidly fluctuating, or dithering, the timing signal in a
digital set-top receiver. TV sets can compensate for the variation, but the
electromechanical systems in VCRs are not so adaptable, resulting in copies of
poor quality.