Audio copy protection system
AssigneeDCS Copy Protection Limited
InventorsDavid John Michael Robinson, Baolin Tan
Life of this patent
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Abstract
An apparatus for applying an anti-copy protection signal for use with switchable head recorders, such as Video Hi-Fi recorders, is described. A high frequency pulsed signal is added to an original signal. The pulses interfere with the compensator circuitry such that the switching of the record head cannot adequately be masked on recording of a signal. On playback, the switching of the recording heads can subsequently be heard. In Video Hi-Fi recorders, the effect of the high frequency signals also interferes with the compressor-expander circuits to worsen the sound of the head switching.
Claims18
An apparatus to copy a received signal, comprising:
- an input for receiving the signal, wherein the signal comprises an audio component;
- a recording circuit configured to record the signal for later playback such that when the signal is recorded, at least the audio component of the signal is recorded with discontinuities;
- and
- an output for outputting the protected recorded signal for playback, wherein a protection signal in the audio component of the received signal causes attempts to mask the discontinuities of the audio component to become audible on playback of the recorded signal.
An anti-copy signal protection method for use by a recording device in which at least an audio component of the signal is recorded with discontinuities, and in which a compensating circuit is employed by the recording device to mask the discontinuities on recording and/or playback, the method comprising adding a protection signal to the audio component of the signal that impairs the operation of the compensating circuit of the recording device such that the attempts to mask the discontinuities in the recorded signal are audible on playback of a copy.
A detector for detecting an anti-copy protection signal in a received signal, the detector comprising:
- a pulse detector arranged to identify pulses occurring in an audio portion of the received signal, wherein the audio portion of the received signal is recorded with discontinuities that are masked during playback and wherein the pulses are configured to interfere with the masking of the discontinuities;
- an analyzer for determining values for one or more parameters of the pulses detected by the pulse detector;
- control logic associating different values of each parameter with a control instruction for a recording device;
- and
- an output for outputting a signal indicative of the control instruction associated with the values of the parameters of the analyzed pulse to the recording device.
Dependencies are inferred from the claim text.