Method and apparatus for preparing recorded program material to prevent unauthorized duplication by magnetic tape recording
First Claim
1. A method for preparing recorded audible program material which does not interfere with normal playback of the material but which renders detectable any unauthorized copies of the audible program material upon a magnetic recording tape which are made by magnetic tape recording with conventional high frequency bias, said method comprising:
- recording the audible program material for providing a predetermined information passband of frequencies of such recorded material;
generating a high frequency modulated signal which varies in a predetermined manner over a selected spectrum of frequencies lying just above and outside of said information passband of frequencies; and
recording the modulated signal together with the audible program material;
whereby copying of the recorded audible program material onto magnetic tape will produce on the tape copy detectable interference signals between the modulated signal and the conventional recording bias signal.
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Accused Products
Abstract
Unauthorized duplication of recorded audible program material upon magnetic tape, commonly known as tape piracy, is prevented and rendered detectable by the present method and apparatus for preparing the program material. The method and apparatus prepare recorded audible program material by generating a high frequency modulated signal which varies in a predetermined manner over a selected spectrum of frequencies, and by recording the modulated signal together with the audible program material so that subsequent copying of the program material and modulated signal onto magnetic tape with conventional high frequency bias will produce on the copied tape detectable and identifiable interference signals arising between the modulated signal and the conventional recording bias. The modulated signal may sweep a range of frequencies at a rate which will produce an audible playback noise spoiling the copied tape, and the modulated signal can be coded to identify the origin of the program material. In one embodiment, the method and apparatus record the modulated signal in superposition upon recorded program material, applying the modulated signal in square wave form to reduce modulation noise and rocking the recording head to intercept any azimuth deviation of subsequent playback means. In another embodiment, a frequency modulated signal is arranged to form the bias signal during the recording of the program material. The method and apparatus do not interfere with normal playback of the recorded program material since the modulated signal is beyond the audible range, but when copying onto magnetic tape is attempted, unacceptable interference signals, such as beat signals and cross-modulation signals, arise either to spoil the copy or to mark it in a detectable fashion as pirated copy.
50 Citations
26 Claims
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1. A method for preparing recorded audible program material which does not interfere with normal playback of the material but which renders detectable any unauthorized copies of the audible program material upon a magnetic recording tape which are made by magnetic tape recording with conventional high frequency bias, said method comprising:
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recording the audible program material for providing a predetermined information passband of frequencies of such recorded material; generating a high frequency modulated signal which varies in a predetermined manner over a selected spectrum of frequencies lying just above and outside of said information passband of frequencies; and recording the modulated signal together with the audible program material; whereby copying of the recorded audible program material onto magnetic tape will produce on the tape copy detectable interference signals between the modulated signal and the conventional recording bias signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. Apparatus for preparing recorded audible program material which does not interfere with normal playback of the material but which renders detectable any unauthorized copies of the material which are made by magnetic tape recording with conventional high frequency bias, said apparatus comprising:
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means for generating a high frequency modulated signal which varies in a predetermined manner over a selected spectrum of frequencies; and means for recording the modulated signal together with the audible program material; whereby copying of the recorded material onto magnetic tape will produce on the tape detectable interference signals between the modulated signal and the conventional recording bias. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. A method for preparing recorded audible program material upon magnetic recording tape which renders detectable any unauthorized copies of the audible program material upon a magnetic recording tape which are made by magnetic tape recording with a conventional high frequency bias signal, said method comprising:
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recording the audible program material upon a first magnetic recording tape for providing a predetermined information passband of frequencies of such recorded material; generating a square wave high frequency modulatable signal having a quiescent frequency lying above said passband; recording said modulatable signal on the tape together with the audible program material; sensing the presence of passages of program material suitable for audibly masking the presence of a modulated signal in the upper end of said passband; when said masking passages of program material are available, frequency modulating said square wave high frequency modulatable signal to produce frequency excursions thereof down into the upper frequencies of said passband; whereby copying of the recorded audible program material onto another magnetic tape will produce on the tape copy detectable interference signals between the modulated signal and the conventional recording bias signal; and whereby the modulated signal is impossible to be removed in the process of making such tape copy. - View Dependent Claims (23, 24, 25)
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26. A method for preparing recorded audible program material on a magnetic recording tape comprising:
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recording the audible program material on said tape for providing a predetermined information passband of frequencies of such recorded material, said recording being applied by a first magnetic recording head having a predetermined gap width, generating a square-wave high frequency modulated signal which varies in a predetermined manner over a selected spectrum of frequencies higher than said information passband of frequencies, said square wave having a transition time which is 1/6 or less of the dwell time thereof, and recording said square-wave modulated signal on said tape using a second magnetic recording head having a narrower gap width than said first head and being positioned for engaging said tape after said recorded material has been applied by said first head.
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Specification