EP0366381B1
Expired / Lapsed
EP
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Signal identification system
Assignee: Central Research Laboratories Ltd
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Filing: 1989-10-23
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Granted: 1995-03-15
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Expires: 2009-10-23
Abstract
Abstract A signal identification system, suitable for producing an identification code on a sound track recording is described. The system includes an encoder 209 effective to eliminate a variable sequence of frequency bands from an audio signal and insert a sequence of code signals into the frequency bands. As the sequence of frequency bands varies throughout the sound track recording, the presence of the code is difficult to detect.
Inventors
- 👤 Stuart John Best
- 👤 Nigel Johnson
- 👤 Adrian Miles Sandford
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 11:50
CPC Classifications
H; H04; H04H; H04H20/00; H04H20/28; H04H20/30; H04H20/31; G; G11; G11B; G11B20/00; G11B20/00086; G11B20/00884; G11B20/00891
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
167 words
A signal identification system comprising: encoding means including filter means (203, 207, 301, 303) for eliminating from a given signal a plurality of predetermined frequency bands within the bandwidth of the given signal to form corresponding notches in the bandwidth of the given signal, and means (205, 211, 311, 313) for inserting a sequence of code signals within the notches; and decoding means (401 - 409; 501 - 517) for determining whether the sequence of code signals is present in the given signal, characterized in that the filter means (203, 207, 301, 303) is controllable to selectively eliminate a subset of the plurality of predetermined frequency bands from the given signal at any given time, which subset is selectable from a plurality of such subsets which differ from each other in that at least one said frequency band is substituted by another said frequency band, the filter means (203, 207, 301, 303) being provided with control means (201) for selecting a plurality of said subsets in succession.
Claim 2
Dependent Claim
40 words
A system according to Claim 1, wherein the plurality of predetermined frequency bands consists of at least three predetermined frequency bands and wherein the control means (201) is arranged to select a subset containing two of these bands each time.
Claim 3
Dependent Claim
43 words
A system as claimed in Claim 2, wherein the means (205, 211, 311, 313) for inserting a sequence of code signals within the notches is arranged to insert code signals in a complementary manner into the two notches formed at any given time.
Claim 4
Dependent Claim
51 words
A system according to Claim 1, Claim 2 or Claim 3, wherein the decoding means (401 - 409) includes means (401, 403, 405) for simultaneously inspecting all the frequency bands of the given signal which are included in the selected subsets for the presence of the sequence of code signals therein.
Claim 5
Independent Claim
147 words
A system for incorporating a code into a given signal, comprising filter means (203, 207, 301, 303) for eliminating from the given signal a plurality of predetermined frequency bands within the bandwidth of the given signal to form corresponding notches in the bandwidth of the given signal, and means (205, 211, 311, 313) for inserting a sequence of code signals within the notches, characterized in that the filter means (203, 207, 301, 303) is controllable to selectively eliminate a subset of the plurality of predetermined frequency bands from the given signal at any given time, which subset is selectable from a plurality of such subsets which differ from each other in that at least one said frequency band is substituted by another said frequency band, the filter means (203, 207, 301, 303) being provided with control means (201) for selecting a plurality of said subsets in succession.
Claim 6
Dependent Claim
40 words
A system according to Claim 5, wherein the plurality of predetermined frequency bands consists of at least three predetermined frequency bands and wherein the control means (201) is arranged to select a subset containing two of these bands each time.
Claim 7
Dependent Claim
43 words
A system as claimed in Claim 6, wherein the means (205, 211, 311, 313) for inserting a sequence of code signals within the notches is arranged to insert code signals in a complementary manner into the two notches formed at any given time.
Claim 8
Dependent Claim
111 words
A system for decoding a given signal which has had a code incorporated therein by a system as claimed in Claim 5, which decoding system has an input for said given signal and comprises a respective decoder (401, 403, 405) corresponding to each selected subset, each decoder having an input coupled to the system input and being arranged to selectively decode any of the code signals which are present within its input signal within the corresponding subset of the plurality of frequency bands, and code recognition means (407) coupled to outputs of the decoders (401, 403, 405) for recognizing said code upon its decoding by any said decoder (401, 403, 405).
References Cited (Backward Citations)
No citation records indexed.
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