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GB2196167A - Encoded marking of a recording signal - Google Patents

Encoded marking of a recording signal Download PDF

Info

Publication number
GB2196167A
GB2196167A GB08623533A GB8623533A GB2196167A GB 2196167 A GB2196167 A GB 2196167A GB 08623533 A GB08623533 A GB 08623533A GB 8623533 A GB8623533 A GB 8623533A GB 2196167 A GB2196167 A GB 2196167A
Authority
GB
United Kingdom
Prior art keywords
signal
marking
recorded
binary elements
binary
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB08623533A
Other versions
GB2196167B (en
GB8623533D0 (en
Inventor
Lyn Holt
Barry Gordon Maufe
Anthony Wiener
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
EMI Group Ltd
Original Assignee
Thorn EMI PLC
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Thorn EMI PLC filed Critical Thorn EMI PLC
Priority to GB8623533A priority Critical patent/GB2196167B/en
Publication of GB8623533D0 publication Critical patent/GB8623533D0/en
Publication of GB2196167A publication Critical patent/GB2196167A/en
Application granted granted Critical
Publication of GB2196167B publication Critical patent/GB2196167B/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
    • G11B20/00086—Circuits for prevention of unauthorised reproduction or copying, e.g. piracy
    • G11B20/0071—Circuits for prevention of unauthorised reproduction or copying, e.g. piracy involving a purchase action
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
    • G11B20/00086—Circuits for prevention of unauthorised reproduction or copying, e.g. piracy
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
    • G11B20/00086—Circuits for prevention of unauthorised reproduction or copying, e.g. piracy
    • G11B20/00094—Circuits for prevention of unauthorised reproduction or copying, e.g. piracy involving measures which result in a restriction to authorised record carriers
    • G11B20/00123—Circuits for prevention of unauthorised reproduction or copying, e.g. piracy involving measures which result in a restriction to authorised record carriers the record carrier being identified by recognising some of its unique characteristics, e.g. a unique defect pattern serving as a physical signature of the record carrier
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
    • G11B20/00086—Circuits for prevention of unauthorised reproduction or copying, e.g. piracy
    • G11B20/00884—Circuits for prevention of unauthorised reproduction or copying, e.g. piracy involving a watermark, i.e. a barely perceptible transformation of the original data which can nevertheless be recognised by an algorithm

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  • Engineering & Computer Science (AREA)
  • Computer Security & Cryptography (AREA)
  • Signal Processing (AREA)
  • Signal Processing For Digital Recording And Reproducing (AREA)

Abstract

A marking signal 1 identifying the owner of a recording and formed by binary elements passes from a data store 2 to code generator 3, which translates each like binary element into a pseudo random sequence of binary elements, to produce an encoded marking signal and then, via low pass filter 4 and multiplier 5, passes to multiplier 6 with an audio signal 7 input to effect amplitude modulation thereof. After filtering by high pass filter 8, the signal is added to the audio signal channel by circuit 9. Decoder 11 (also Fig. 3) enables extraction of the marking signal for identification. The arrangement facilitates proof of ownership of illegal re-recordings and automatic logging of playback time for royalty purposes. <IMAGE>

Description

SPECIFICATION Apparatus for marking a recorded signal This invention relates to apparatus for marking a recorded signal and in particular, though not exclusively, for marking an audio signal being recorded on a recording medium, such as magnetic tape.
It has become important, particularly in the music recording industry, to be able to identify the source of an audio recording, especially for proving ownership of illegal re-recordings or for enabling automatic logging of play-back time of the recording for royalty purposes.
To achieve this, the recorded signal is marked by adding to the signal hidden information identifying the owner of the recording, the marking being carried out in such a way as to render the information substantially imperceptible to an ordinary listener of the recording. The spectrum, over which the added information is recorded, is made similar to that of the signal being recorded, so that it is difficult to remove, alter or destroy the added information without seriously impairing the recorded signal.
It is an object of the present invention to provide apparatus for marking a recorded signal, which apparatus provides improved protection from unauthorised detection and removal of the marking than that provided by known apparatus of this kind.
In accordance with the present invention, there is provided apparatus for marking a recorded signal, said apparatus including means for generating a marking signal comprising a sequence of binary elements and means for modulating the signal to be recorded, in accordance with said marking signal, such that said modulation is substantially imperceptible on play-back of the recorded signal, said apparatus also including means for translating each like binary element of said sequence into a randomised sequence of binary elements prior to said modulation.
The apparatus also preferably includes means for demodulating said modulated signal to produce a signal consisting of binary elements and means for correlating said signal with the randomised sequences generated by said translating means to produce said.marking signal.
The present invention enables relatively low levels of the marking signal to be applied, as well as enabling the marking signal to be spread across the recorded signal in a randomised manner to produce a marking of the recorded signal, which is considerably more difficult to detect, either electronically or audibly, than marking produced by known apparatus.
The invention will now be further described by way of example only with reference to the accompanying drawings wherein: Figure 1 shows a block circuit diagram of a preferred embodiment of the invention, Figures 2a and 2b show the signal waveform at respective points in the circuit shown in Fig. 1, and Figure 3 shows a more detailed block circuit diagram of one part of the circuit shown in Fig. 1.
In Fig. 1, a marking signal 1, indicative of an identification of the owner of a recording, comprises a sequence of binary elements, either "1" or "0", and is stored in a data store 2. The binary elements are passed to a code generator 3, which effectively translates each like binary element into a pseudorandom sequence of binary elements, to produce an encoded marking signal. Respective pseudorandom sequences are used for the two types of binary elements, such that a poor correlation between the two pseudorandom sequences is achieved. Each pseudorandom sequence typically comprises 31 binary elements and the clock rate of the binary elements is determined by an input to the code generator 3 from a clock generator (not shown in Fig.
1).
Fig. 2a shows a frequency spectrum of the output at point A in the circuit from the code generator 3, which, as shown in Fig. 2a, is a sin x x waveform. The clock rate from the clock generator also determines the frequency of the nulls of the waveform, i.e., as shown in Fig.
.2a, the nulls are produced at 1KHz intervals, thereby indicating a clock rate of 1KHz.
The output at point A is then filtered by low pass filter 4 and converted by multiplier 5, which is also has an input F1 from the clock generator (not shown in Fig. 1), to produce an output waveform at point B in the circuit, as shown in Fig. 2b, having a frequency spectrum of O to 2KHz.
The encoded marking signal is then passed to multiplier 6, which also has an input of audio signal 7, which is to be recorded. The audio signal 7 is amplitude modulated, in accordance with the encoded marking signal, and the modulated signal is filtered by high pass filter 8, to remove all low frequency components of below, for example, 1KHz, and attenuated, before being added back into the audio signal channel by circuit 9, taking care to avoid distortion of the audio signal. Output signal 10, which is subsequently recorded on any suitable recording medium, such as magnetic tape, thus consists of the audio signal modulated by the encoded marking signal.
Fig. 1 also shows a decoder 11 for extracting the marking signal from the modulated audio signal to enable subsequent identification of the owner of the recording.
The decoder 11 is shown in more detail in Fig. 3, wherein the output signal 10, from the recording, is passed through high pass filter 11 and multiplier 12, to be demodulated and rectified, and is then passed through low pass filter 13 to give the encoded marking signal.
The frequency spectrum of this signal is converted down by multiplier 14, which also has an input from clock generator 15, and the output of multiplier 14 is passed through another low pass filter 16 before being digitised by comparator 17.
A correlator 18, including a microcomputer 19, then correlates the digitised signal of binary elements with the pseudorandom sequences of binary elements generated by code generator 3 to produce the marking signal 1.
The microcomputer 19 also has an input to, and output from, the clock generator 15 to enable adjustment of the clock rate.
By employing the present apparatus for maring a recorded signal, the modulation depth, i.e. the change in amplitude of the recorded signal as a result of the modulation, can be lower than 0.14, whilst still providing an acceptable data rate of the marking signal.
The marking signal may be monitored during the encoding procedure by any suitable monitoring technique. It may also be preferable to devise suitable codes, which are capable of altering the data rate according to the natural amplitude modulation of the audio signal, which then acts as noise to the encoded marking signal.
To provide an enhanced performance, an A to D convertor (not shown) may be employed, instead of the comparator 17, in decoder 11 to digitise the signal.

Claims (4)

1. Apparatus for marking a recorded signal, said apparatus including means for generating a marking signal comprising a sequence of binary elements and means for modulating the signal to be recorded, in accordance with said marking signal, such that said modulation is substantially imperceptible on play-back of the recorded signal, said apparatus also including means for translating each like binary element of said sequence into a randomised sequence of binary elements prior to said modulation.
2. Apparatus as claimed in Claim 1 and including means for demodulating said modulated signal to produce a signal consisting of binary elements and means for correlating said signal with the randomised sequences generated by said translating means to produce said marking signal.
3. Apparatus as claimed in Claim 1 or 2 wherein said translating means comprises a code generator connected to a data store for storing the marking signal.
4. Apparatus for marking a recorded signal, said apparatus being substantially as herein described with reference to the accompanying drawings.
GB8623533A 1986-10-01 1986-10-01 Apparatus for marking a recorded signal Expired - Lifetime GB2196167B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB8623533A GB2196167B (en) 1986-10-01 1986-10-01 Apparatus for marking a recorded signal

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB8623533A GB2196167B (en) 1986-10-01 1986-10-01 Apparatus for marking a recorded signal

Publications (3)

Publication Number Publication Date
GB8623533D0 GB8623533D0 (en) 1986-11-05
GB2196167A true GB2196167A (en) 1988-04-20
GB2196167B GB2196167B (en) 1991-01-02

Family

ID=10605059

Family Applications (1)

Application Number Title Priority Date Filing Date
GB8623533A Expired - Lifetime GB2196167B (en) 1986-10-01 1986-10-01 Apparatus for marking a recorded signal

Country Status (1)

Country Link
GB (1) GB2196167B (en)

Cited By (44)

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EP0298691A2 (en) * 1987-07-08 1989-01-11 Matsushita Electric Industrial Co., Ltd. Method and apparatus for protection of signal copy
EP0338794A2 (en) * 1988-04-20 1989-10-25 THORN EMI plc Apparatus for marking a recorded signal
FR2658022A1 (en) * 1990-02-07 1991-08-09 Telediffusion Fse METHOD AND SYSTEM FOR MARKING AND IDENTIFYING DIGITAL INFORMATION.
EP0606703A1 (en) * 1993-01-12 1994-07-20 Lee S. Weinblatt Method for surveying a radio or a television audience, carrying programme identification signals in the sound channel
WO1994017609A1 (en) * 1991-07-19 1994-08-04 John Barrett Kiefl Television viewer monitoring system
US5382970A (en) * 1991-07-19 1995-01-17 Kiefl; John B. Television viewer monitoring system including portable data meter for each viewer
WO1995014289A2 (en) * 1993-11-18 1995-05-26 Pinecone Imaging Corporation Identification/authentication coding method and apparatus
WO1996027191A1 (en) * 1995-02-28 1996-09-06 Isis Innovation Limited Covert identification
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US6301369B2 (en) 1992-07-31 2001-10-09 Digimarc Corporation Image marking to permit later identification
US6317505B1 (en) 1992-07-31 2001-11-13 Digimarc Corporation Image marking with error correction
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Cited By (88)

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Publication number Priority date Publication date Assignee Title
EP0298691A2 (en) * 1987-07-08 1989-01-11 Matsushita Electric Industrial Co., Ltd. Method and apparatus for protection of signal copy
EP0298691A3 (en) * 1987-07-08 1990-08-22 Matsushita Electric Industrial Co., Ltd. Method and apparatus for protection of signal copy
US5073925A (en) * 1987-07-08 1991-12-17 Matsushita Electric Industrial Co., Ltd. Method and apparatus for the protection of signal copy
EP0338794A2 (en) * 1988-04-20 1989-10-25 THORN EMI plc Apparatus for marking a recorded signal
EP0338794A3 (en) * 1988-04-20 1992-01-29 THORN EMI plc Apparatus for marking a recorded signal
FR2658022A1 (en) * 1990-02-07 1991-08-09 Telediffusion Fse METHOD AND SYSTEM FOR MARKING AND IDENTIFYING DIGITAL INFORMATION.
EP0441702A1 (en) * 1990-02-07 1991-08-14 Telediffusion De France Method and system for marking and identifying data
WO1994017609A1 (en) * 1991-07-19 1994-08-04 John Barrett Kiefl Television viewer monitoring system
US5382970A (en) * 1991-07-19 1995-01-17 Kiefl; John B. Television viewer monitoring system including portable data meter for each viewer
US6628801B2 (en) 1992-07-31 2003-09-30 Digimarc Corporation Image marking with pixel modification
US6459803B1 (en) 1992-07-31 2002-10-01 Digimarc Corporation Method for encoding auxiliary data within a source signal
US6317505B1 (en) 1992-07-31 2001-11-13 Digimarc Corporation Image marking with error correction
US6301369B2 (en) 1992-07-31 2001-10-09 Digimarc Corporation Image marking to permit later identification
US7978876B2 (en) 1992-07-31 2011-07-12 Digimarc Corporation Hiding codes in input data
EP0606703A1 (en) * 1993-01-12 1994-07-20 Lee S. Weinblatt Method for surveying a radio or a television audience, carrying programme identification signals in the sound channel
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US6983051B1 (en) 1993-11-18 2006-01-03 Digimarc Corporation Methods for audio watermarking and decoding
US7103197B2 (en) * 1993-11-18 2006-09-05 Digimarc Corporation Arrangement for embedding subliminal data in imaging
US7181022B2 (en) * 1993-11-18 2007-02-20 Digimarc Corporation Audio watermarking to convey auxiliary information, and media embodying same
US8055012B2 (en) 1993-11-18 2011-11-08 Digimarc Corporation Hiding and detecting messages in media signals
US7987094B2 (en) 1993-11-18 2011-07-26 Digimarc Corporation Audio encoding to convey auxiliary information, and decoding of same
US6675146B2 (en) 1993-11-18 2004-01-06 Digimarc Corporation Audio steganography
US6647129B2 (en) 1993-11-18 2003-11-11 Digimarc Corporation Method and system for encoding image and audio content
WO1995014289A2 (en) * 1993-11-18 1995-05-26 Pinecone Imaging Corporation Identification/authentication coding method and apparatus
US6587821B1 (en) * 1993-11-18 2003-07-01 Digimarc Corp Methods for decoding watermark data from audio, and controlling audio devices in accordance therewith
US6567780B2 (en) 1993-11-18 2003-05-20 Digimarc Corporation Audio with hidden in-band digital data
US6363159B1 (en) 1993-11-18 2002-03-26 Digimarc Corporation Consumer audio appliance responsive to watermark data
US6542620B1 (en) 1993-11-18 2003-04-01 Digimarc Corporation Signal processing to hide plural-bit information in image, video, and audio data
US6400827B1 (en) 1993-11-18 2002-06-04 Digimarc Corporation Methods for hiding in-band digital data in images and video
US6404898B1 (en) 1993-11-18 2002-06-11 Digimarc Corporation Method and system for encoding image and audio content
US6430302B2 (en) 1993-11-18 2002-08-06 Digimarc Corporation Steganographically encoding a first image in accordance with a second image
US7974439B2 (en) 1993-11-18 2011-07-05 Digimarc Corporation Embedding hidden auxiliary information in media
US7672477B2 (en) 1993-11-18 2010-03-02 Digimarc Corporation Detecting hidden auxiliary code signals in media
WO1995014289A3 (en) * 1993-11-18 1995-06-29 Pinecone Imaging Corp Identification/authentication coding method and apparatus
US6496591B1 (en) 1993-11-18 2002-12-17 Digimarc Corporation Video copy-control with plural embedded signals
US7054465B2 (en) 1993-11-18 2006-05-30 Digimarc Corporation Data hiding method and system for embedding and extracting information in signals
US6560349B1 (en) * 1994-10-21 2003-05-06 Digimarc Corporation Audio monitoring using steganographic information
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