Audio copy protection system
AssigneeDCS Copy Protection Limited
InventorsDavid John Michael Robinson, Baolin Tan
Life of this patent
Estimating the term…
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.
Claims45
An apparatus for applying an anti-copy signal to a signal to be protected, comprising:
- an input for receiving a signal to be protected;
- means for adding a protection signal to the audio component of the signal to form a protected signal such that on recording by a tape recorder in which at least an audio component of the signal is recorded with discontinuities, and in which a compensating circuit of the tape recorder is employed to mask the discontinuities on recording and/or playback by the tape recorder, the protection signal impairs the operation of the compensating circuit such that the attempts to mask the discontinuities are audible on playback of a copy;
- and
- an output for outputting the protected signal.
An apparatus for protecting a signal having an audio component against recording by a tape recorder in which a plurality of recording heads are successively switched during the recording of a signal onto tape, the system comprising:
- an input for receiving a signal to be protected;
- means for adding a pulsed signal to the audio component of the signal to form a protected signal, the pulses of the protection signal occurring at or near the rate at which the recording heads are switched, such that when the protected signal is recorded on the tape recorder, one or more artefacts are produced which result in a reduced quality of the recorded signal on playback;
- and
- an output for outputting the protected signal.
An apparatus for protecting a signal having an audio component against recording on a video Hi-Fi cassette recorder, comprising:
- an input for receiving a signal to be protected;
- means for adding a pulsed signal to the audio component of the signal at or near the vertical synchronisation rate of the video Hi-Fi cassette recorder to form a protected signal, such that when the protected signal is recorded on the video Hi-Fi cassette recorder, one or more artefacts are produced which result in a reduced quality of the recorded signal on playback;
- and
- an output for outputting the protected signal.
An apparatus for protecting a signal having an audio component against recording on a video Hi-Fi cassette recorder, comprising;
- an input for receiving a signal to be protected;
- means for adding a signal to the audio component of the signal at or near an integer multiple of the line synchronisation rate of the video Hi-Fi cassette recorder to form a protected signal, such that when the protected signal is recorded on the video Hi-Fi cassette recorder, one or more artefacts are produced which result in a reduced quality of the recorded signal on playback;
- and
- an output for outputting a protected signal.
An anti-copy signal protection method for use with a tape recorders in which at least an audio component of the signal is recorded with discontinuities, and in which a compensating circuit of the tape recorder is employed to mask the discontinuities on recording and/or playback by the tape recorder, the method comprising adding a protection signal to the audio component of the signal which on recording impairs the operation of the compensating circuit such that the attempts to mask the discontinuities are audible on playback of a copy.
A method of protecting a signal having an audio component against recording by a tape recorder, wherein the tape recorder comprises a plurality of recording heads which are successively switched during the recording of a signal onto tape, the method comprising adding a pulsed signal to the audio component of the signal, the pulses of the pulsed signal occurring at or near the rate at which the recording heads of the tape recorder are switched to form a protected signal, such that when the protected signal is recorded on the tape recorder, one or more artefacts are produced which result in a reduced quality of the recorded signal on playback.
A method of protecting a signal having an audio component against recording on a video Hi-Fi cassette recorder, comprising adding a pulsed signal to the audio component of the signal at or near the vertical synchronisation rate of the video Hi-Fi cassette recorder to form a protected signal, such that when the protected signal is recorded on the video Hi-Fi cassette recorder, one or more artefacts are produced which result in a reduced quality of the recorded signal on playback.
A method of protecting a signal having an audio component against recording on a video Hi-Fi cassette recorder, comprising adding a signal to the audio component of the signal at or near an integer multiple of the line synchronisation rate of the video Hi-Fi cassette recorder to form a protected signal, such that when the protected signal is recorded on the video Hi-Fi cassette recorder, one or more artefacts are produced which result in a reduced quality of the recorded signal on playback.
A detector for detecting an anti-copy protection signal, comprising:
- a pulse detector arranged to identify pulses occurring in a received signal, at or near the frequency at which recording heads in a video tape recorder are switched;
- wherein
- the anti-copy protection is produced by an apparatus comprising:
- an input for receiving a signal to be protected;
- means for adding a protection signal to the audio component of the signal to form a protected signal such that, on recording by the video tape recorder in which at least an audio component of the signal is recorded with discontinuities, and in which a compensating circuit of the video tape recorder is employed to mask the discontinuities on recording and/or playback, the protection signal impairs the operation of the compensating circuit such that the attempts to mask the discontinuities are audible on playback of a copy;
- and
- an output for outputting the protected signal.
A digital recording device comprising:
- recording heads configured to record a copy of received signal onto a tape, wherein at least an audio component of the received signal is recorded with discontinuities;
- a compensating circuit employed to mask the discontinuities on recording and/or playback of the copy;
- a pulse detector arranged to identify pulses occurring in the received signal, at or near the frequency at which the recording heads are switched;
- wherein
- the anti-copy protection is produced by an apparatus comprising:
- an input for receiving a signal to be protected;
- means for adding a protection signal to the audio component of the signal to form a protected signal such that, on recording by the recording heads, the protection signal impairs the operation of the compensating circuit such that the attempts to mask the discontinuities are audible on playback of a copy;
- and
- an output for outputting the protected signal.
A first apparatus for removing an anti-copy protection signal applied by a second apparatus, the second apparatus comprising:
- an input for receiving a signal to be protected;
- means for adding a protection signal to the audio component of the signal to form a protected signal such that, on recording by a tape recorder in which at least an audio component of the signal is recorded with discontinuities, and in which a compensating circuit is employed to mask the discontinuities on recording and/or playback, the protection signal impairs the operation of the compensating circuit such that the attempts to mask the discontinuities are audible on playback of a copy;
- and
- an output for outputting the protected signal, the first apparatus comprising:
- an input for receiving an anti-copy protected signal;
- a processor for removing the protection signal such that on recording, the masking of discontinuities in the signal by the compensating circuit is inaudible on playback;
- and
- an output for outputting the unprotected signal.
Dependencies are inferred from the claim text.