Marked recorded signals

• US 5,079,648 A
• Filed: 04/20/1989
• Issued: 01/07/1992
• Est. Priority Date: 04/20/1988
• Status: Expired due to Fees

• Current Assignee: Thorn EMI Plc (Universal Music Group NV)
• Original Assignee: Thorn EMI Plc (Universal Music Group NV)
• Inventors: Maufe, Barry G.
• Primary Examiner(s): Psitos, Aristotelis
• Assistant Examiner(s): Kim, Won Tae C.
• Application Number:
  US07/340,800
• Time in Patent Office: 992 Days
• Field of Search: 360/31, 360/60, 360/53, 380/2, 380/4, 380/22, 235/375, 235/419, 235/462, 340/825.44, 340/825.62, 371/6
• US Class Current: 360/31
• CPC Class Codes: G11B 20/00086 Circuits for prevention of unauthorised reproduction or copying, e.g. piracy indicating unauthorised use of record carriers in general G11B23/28; scrambling for television signal recording H04N5/913; network architectures or network protocols for network security H04L63/00; cryptographic mechanisms or cryptographic arrangements for secret or secure communication H04L9/00
• CPC Class Codes: G11B 20/00884 involving a watermark, i.e. a barely perceptible transformation of the original data which can nevertheless be recognised by an algorithm
• CPC Class Codes: G11B 2220/20 Disc-shaped record carriers
• CPC Class Codes: G11B 2220/90 Tape-like record carriers
• CPC Class Codes: G11B 27/3027 used signal is digitally coded
• CPC Class Codes: G11B 27/36 Monitoring, i.e. supervising the progress of recording or reproducing for digital recording G11B20/00 and s.gr.; for monitoring, testing or measuring of TV recorders of the type covered by H04N5/76 and subgroups, see H04N17/06

Abstract

An apparatus for monitoring the marking of a recorded signal includes a data store containing marking information and a code selector for selecting any one of three orthogonal codes for marking the recorded signal and a demodulator for demodulating the marked signal and comparing this with the orthogonal codes. The demodulated marked signals are then fed to matched filters and accumulators wherein the marking process may be repeated dependent upon the value of the accumulation.

Claims

1. Apparatus for monitoring marking of a recorded signal including:

generating means for generating a plurality of marking signals;

modulating means for modulating the recorded signal with one of the marking signals;

monitoring means for monitoring the modulated marked signal, which means includes a demodulator which provides a demodulated signal comprising the recoreded signal and the one marking signal, comparisonmeans for comparing the magnitude of the one marking signal with the plurality of marking signals thereby to produce an output in dependence upon the differences between the magnitudes such that if the difference does not exceed a predetermined margin, the recorded signal is again modulated with the one marking signal.

2. Apparatus according to claim 1 wherein the comparison means includes matched filters and accumulators.

3. Apparatus according to claim 1 wherein the generating means for generating a plurality of marking signals comprises a code generator for generating three orthogonal codes.

4. Apparatus according to claim 3 wherein the generating means further comprises a binary data store.

5. A method of monitoring marking of a recorded signal, the method including:

generating a plurality of marking signals;

modulating the recorded signal with one of the marking signals;

monitoring the marked signal including demodulating the marked signal providing the recorded signal and said one marking signal;

comparing the magnitude of said one marked signal with the plurality of marking signals thereby producing an output in dependence upon the differences between the magnitudes such that if the difference does not exceed a predetermined margin, the recorded signal is again modulated with the one marking signal.