GB2104701A - Method and apparatus for preventing unauthorised recording of source material (e.g. a gramophone recording) - Google Patents
Method and apparatus for preventing unauthorised recording of source material (e.g. a gramophone recording) Download PDFInfo
- Publication number
- GB2104701A GB2104701A GB08124048A GB8124048A GB2104701A GB 2104701 A GB2104701 A GB 2104701A GB 08124048 A GB08124048 A GB 08124048A GB 8124048 A GB8124048 A GB 8124048A GB 2104701 A GB2104701 A GB 2104701A
- Authority
- GB
- United Kingdom
- Prior art keywords
- signal
- recording
- source material
- machine according
- responsive
- 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
Links
- 239000000463 material Substances 0.000 title claims abstract description 32
- 238000000034 method Methods 0.000 title claims 8
- 239000003112 inhibitor Substances 0.000 claims description 17
- 230000002265 prevention Effects 0.000 claims description 6
- 230000005764 inhibitory process Effects 0.000 claims description 4
- 230000000694 effects Effects 0.000 claims description 3
- 238000001208 nuclear magnetic resonance pulse sequence Methods 0.000 claims description 2
- 230000005236 sound signal Effects 0.000 claims 2
- 238000001914 filtration Methods 0.000 description 2
- 230000002401 inhibitory effect Effects 0.000 description 2
- 230000004913 activation Effects 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 230000000873 masking effect Effects 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 230000001360 synchronised effect Effects 0.000 description 1
- 230000001052 transient effect Effects 0.000 description 1
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
- G11B20/00681—Circuits for prevention of unauthorised reproduction or copying, e.g. piracy involving measures which prevent a specific kind of data access
- G11B20/00688—Circuits for prevention of unauthorised reproduction or copying, e.g. piracy involving measures which prevent a specific kind of data access said measures preventing that a usable copy of recorded data can be made on another medium
-
- 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
- G11B20/00681—Circuits for prevention of unauthorised reproduction or copying, e.g. piracy involving measures which prevent a specific kind of data access
- G11B20/00695—Circuits for prevention of unauthorised reproduction or copying, e.g. piracy involving measures which prevent a specific kind of data access said measures preventing that data are read from the recording medium
-
- 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
- G11B20/00876—Circuits for prevention of unauthorised reproduction or copying, e.g. piracy wherein physical copy protection means are attached to the medium, e.g. holograms, sensors, or additional semiconductor circuitry
-
- 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
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B27/00—Editing; Indexing; Addressing; Timing or synchronising; Monitoring; Measuring tape travel
- G11B27/10—Indexing; Addressing; Timing or synchronising; Measuring tape travel
- G11B27/19—Indexing; Addressing; Timing or synchronising; Measuring tape travel by using information detectable on the record carrier
- G11B27/28—Indexing; Addressing; Timing or synchronising; Measuring tape travel by using information detectable on the record carrier by using information signals recorded by the same method as the main recording
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N5/00—Details of television systems
- H04N5/76—Television signal recording
- H04N5/91—Television signal processing therefor
- H04N5/913—Television signal processing therefor for scrambling ; for copy protection
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B23/00—Record carriers not specific to the method of recording or reproducing; Accessories, e.g. containers, specially adapted for co-operation with the recording or reproducing apparatus ; Intermediate mediums; Apparatus or processes specially adapted for their manufacture
- G11B23/28—Indicating or preventing prior or unauthorised use, e.g. cassettes with sealing or locking means, write-protect devices for discs
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N5/00—Details of television systems
- H04N5/76—Television signal recording
- H04N5/91—Television signal processing therefor
- H04N5/913—Television signal processing therefor for scrambling ; for copy protection
- H04N2005/91307—Television signal processing therefor for scrambling ; for copy protection by adding a copy protection signal to the video signal
- H04N2005/91321—Television signal processing therefor for scrambling ; for copy protection by adding a copy protection signal to the video signal the copy protection signal being a copy protection control signal, e.g. a record inhibit signal
Abstract
A system for preventing unauthorised recording of source material comprises putting onto a source signal, for example a gramophone recording, a coded signal and including in a tape recorder a detector circuit to mar or inhibit recording only of that source signal, the coded signal being such that it does not significantly detract from the source material quality when played through normal equipment. A detector 8 is activated by the coded signal on attempted recording (and/or on replay) and may inhibit an amplifier 5 or activate a spoiler oscillator 10 which adds a spoiling signal to the input through a mixer 6. The coded signal may be a discrete signal comprising a burst of fixed frequency and may be recorded in digital form (e.g., as an 8 bis code word). <IMAGE>
Description
SPECIFICATION
Preventing unauthorised recording from source
material
This invention relates to the prevention of
unauthorised recording or re-recording of "source
material" comprising, as example off-air radio or
television broadcasts or recorded material such as
audio gramophone records, tape recordings or video recordings in tape or disc form.
An object of this invention is to provide a
means whereby a recording machine is inhibited or produces a "marred" recording or playback signal when an attempt is made to produce an unauthodsed recording but which can nevertheless be used in a normal manner for other recording purposes.
Broadly, according to this invention, there is provided an inhibitor means for a recording machine, more particularly a recording machine incorporating such a means for connection in the signal recording or possibly playback path, said means being responsive to a coded signal impressed periodically or possibly continuously on a source material signal to effect inhibition, or marring of the recorded or playback signal.
The means preferably comprises a signal detector circuit in the recording signal path and set to be responsive to a copy prevention signal impressed on the source material signal and serving to either disable the recording or to impose thereon a signal which marrs the recorded tape effectively making same unusable.
Preferably the copy prevention signal (CPS) will of sub or super sonic frequency and may be of digital form preferably a coded pulse sequence to which the inhibitor means is responsive.
Advantageously the CPS will be repeated in a random manner on the source material. The inhibitor means will normally be set to an "unarmed" condition on initial switch-on to record (or playback) of the recording machine.
To prevent unauthorised disarming of the inhibitor means same may comprise a portion of an integrated circuit which otherwise is a functional part of the recording circuitry, thus disconnection of the means is not possible in a simple manner.
By making use of a coded OPS provision of a simple filter circuit to remove the CPS prior to recording is difficult and furthermore the inhibitor means may then include a code recognising circuit to permit non-inhibition of certain permitted source material. The coding may be externally entered preferably by a magnetic "licence" card or by using a preprogramed integrated circuit e.g.
one including a ROM containing a code.
An alternative arrangement is to provide the non-inhibiting code on a blank tape used for recording the code being read into the inhibitor means to disarm same by making it nonresponsive to the CPS containing a defined code.
Thus a tape might be purchased enabling only recordings to be made from one source.
The tape may include the code in optical or magnetically recorded form on the leader for example.
By making the CPS of very short duration and outside normal audio range little, if any, degradation of the recording will be apparent. In this invention therefore the OPS is contained on the source material but in a manner not requiring filtering during normal playback thus for practical purposes the source material can be used normally. The arrangement is such that activation of inhibiting means in a recording machine is operated.
Alternatively the CPS may be of very low amplitude and impressed on the source material only during quiet or non-signal passages to prevent masking by the source material signal and to avoid reproduction of a strong signal which may produce cross-modulation and distortion.
For video sources the CPS is conventiently placed in the line flyback period or in the first line proper of the picture information.
In an embodiment the OPS is detected using a digital (matched) filter enabling the required known code to be detected from the source material signal which can be considered as noise.
A predefined code is required to be held in the inhibitor means to be matched with the CPS. If certain permitted codes are to be used so as not to inhibit recording then the CPS comprises a first coded standard portion which will operate the inhibitor means and a second non standard or discrete code which cancels the inhibitor assuming same is set to respond to this second code.
Conveniently the inhibitor circuit will also be operative in playback whereby replay of unauthorised recordings may be inhibited. For replay of legitimate recordings the prior mentioned leader coding may be included on the tape to prevent inhibition of the playback mode.
In the aforementioned arrangement therefore recordings made from source material on recording machines not having the inhibitor means will still include the CPS preventing playback on recording means with the inhibitor means installed.
An embodiment and modification thereof is shown by way of example in the accompanying schematic two Figures of drawing.
Referring to Figure 1 of the drawings an embodiment is shown for an audio tape recording machine comprising a record replay selector switch 1 to connect either the record input line 2 or playback head 3 to an input signal amplifier 4.
The amplifier output feeds a buffer amplifier 5 which passes the signal through a mixer 6 to the output stage 7 feeding either the record head or audio amplifier.
The input amplifier 4 also feeds a detector means 8 which is responsive to a certain discrete signal which may be present in the input signal.
The detector may comprise a very narrow bandwidth selective filter, a synchronous detector to operate on phase coherence between the discrete signal and a reference or a digital filter.
The discrete signal can be a burst of set frequency and this may form a digital, e.g. 8 bit code word.
The detector 8 when activated may simply inhibit the amplifier 5 (line 9) or preferably activates a spoiler oscillator 10 which adds a signal to the input through mixer 6. Essential information in the recording can still be heard but the quality is otherwise marred and indentifiable.
It will be apparent that the circuit operates from source material from external inputs as well as from already recorded tape replayed through the machine.
The form of detector/discrete signal used will be selected to have little or no detectable effect on the original material but readily capable detection in a simple manner. A burst signal is preferred this
being possibly randomly presented on the input as a periodically repeating signal so that the detector
may have a reasonable "failure to respond" rate to
one given burst.
Optionally the detector 8 may have a disabling
input which can be actuated by a replayed signal
amplified through a second input signal path 1 1 and disabling detector 12. The leader portion of a
tape may include a coded recorded signal which is
detected by 12. The coded signal may be present
on a tape cassette package and read as the
cassette is inserted into the machine. This
arrangement serves to detect a tape on which, for
example, a copyright fee has been paid. The
disable is preferably reset at 13 when the
recorded is put into a stop-mode.
In a further embodiment shown in part in Figure
2 the input 11 feeds the disable detector 1 2 which
offers the coded signal to a comparator 14. The
detector normally enables the spoiler 10 but if a
second coded portion is included in the burst
signal this can be compared with the coded signal
and if the codes agree the detector is disabled.
Thus tape may be coded to record only certain
source material.
By using a coded burst response to transient
passages in a signal is much reduced, preventing
marring of otherwise permitted recordings. Further
disabling by filtering of the burst signal is difficult.
The burst signal will preferably be at the extreme
upper end of the frequency response and will be full amplitude recorded. The burst will be of short
duration.
The circuitry comprising units 4, 5, 6, 8, 10 and 1 2, if used will preferably be integrated into a single circuit to prevent tampering.
Broadly, therefore, the invention comprises putting onto a source signal, for example a gramophone recording, a coded signal and including in a tape recorded a detector circuit to
mar or inhibit recording only of that signal, the
signal being such that it does not significantly
detract from the source material quality when
played through normal equipment.
In a further embodiment the source material
includes a burst signal impressed thereon only
when the signal is at or near a no-signal level. The
detector becomes operative during such no-signal
condition to look for the burst which thereafter enables the spoiler oscillator. The burst signal could be of a low level in such a case there being a phase synchronisable associated with the detector to identify the burst from noise, and lock to the frequency thereof to enable the burst or a following signal to be decoded.
Alternatively, or additionally, the coded burst signal can be superimposed on a part of the source material having high amplitude such as a percussive passage, which predominantly will be "noise" and thus not detectably distorted by impression of a further signal part thereon.
Claims (14)
1. Method for the prevention of unauthorised copying by recording of source material, the method comprising:~
a) impressing onto the source material signal a discrete signal which is not significantly discernable during the normal use of the source material,
b) providing a recording apparatus with detector means integrated with the normal recording circuit of the apparatus and responsive only to said discrete signal to inhibit or spoil the recorded signal.
2. Method in accordance with Claim 1, wherein the discrete signal is digital.
3. Method in accordance with Claim 1 or 2, wherein the source material comprises an audio signal, the discrete signal being present with the audio signal but impressed thereon in a manner which is inaudible.
4. Method in accordance with any preceding claim, wherein the detector means is operative to continuously monitor the signal being recorded and is responsive to the discrete signal when present.
5. A recording machine for use in the method of any preceding claim and including an inhibitor means connected in the signal recording or possibly playback path, said means being responsive to a coded signal impressed periodically or possibly continuously on a source material signal to effect inhibition, or marring of the recorded or playback signal.
6. A recording machine according to Claim 5, wherein the inhibitor means comprises a signal detector circuit in the recording signal path and set to be responsive to a copy prevention signal impressed on the source material signal and serving to either disable the recording or to impose thereon a signal which marrs the recorded tape effectively making same unusable.
7. A recording-machine according to Claim 6, wherein the copy prevention signal (CPS) is of sub or super sonic frequency and may be of digital form preferably a coded pulse sequence to which the inhibitor means is responsive.
8. A recording machine according to any preceding Claim 5 to 7, wherein the CPS is repeated in a random manner on the source material.
9. A recording machine according to any preceding claim, wherein the inhibitor means comprises a portion of an integrated circuit which is otherwise a functional part of the recording circuitry.
10. A recording machine according to any preceding claim, wherein the inhibitor means includes a code recognising circuit to permit noninhibition of certain permitted source material.
11. A recording machine according to any preceding claim, wherein the CPS is detected using a digital (matched) filter enabling the required known code to be detected from the source material signal.
12. A recording machine in accordance with any preceding claim, wherein the inhibit means is activated during passages or the source material having a predetermined amplitude level to look for the coded signal.
1 3. A method for preventing unauthorised recording substantially as herein described and exemplified.
14. A recording machine constructed and arranged to function substantially as herein described and with reference to the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08124048A GB2104701B (en) | 1981-08-06 | 1981-08-06 | Method and apparatus for preventing unauthorised recording of source material (eg, a gramophone recording) |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08124048A GB2104701B (en) | 1981-08-06 | 1981-08-06 | Method and apparatus for preventing unauthorised recording of source material (eg, a gramophone recording) |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2104701A true GB2104701A (en) | 1983-03-09 |
| GB2104701B GB2104701B (en) | 1985-06-05 |
Family
ID=10523738
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08124048A Expired GB2104701B (en) | 1981-08-06 | 1981-08-06 | Method and apparatus for preventing unauthorised recording of source material (eg, a gramophone recording) |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2104701B (en) |
Cited By (17)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1985002293A1 (en) * | 1983-11-21 | 1985-05-23 | Haute Securite Video Hsv S.A. | Antipiracy device and method for cinematographic and video carriers |
| EP0224929A2 (en) * | 1985-12-04 | 1987-06-10 | Sony Corporation | Apparatus and method for preventing unauthorized dubbing of a recording signal |
| EP0256753A2 (en) * | 1986-08-11 | 1988-02-24 | Macrovision Corporation | Method and apparatus for preventing the copying of a video program |
| GB2196167A (en) * | 1986-10-01 | 1988-04-20 | Emi Plc Thorn | Encoded marking of a recording signal |
| GB2199689A (en) * | 1987-01-05 | 1988-07-13 | Thomas Claude Henry Keen | Recording of an information signal |
| DE3707608A1 (en) * | 1987-03-10 | 1988-09-22 | Hormann Franz Juergen | Method of coding to prevent video and audio piracy |
| EP0298691A2 (en) * | 1987-07-08 | 1989-01-11 | Matsushita Electric Industrial Co., Ltd. | Method and apparatus for protection of signal copy |
| DE3806413A1 (en) * | 1988-02-29 | 1989-09-07 | Thomson Brandt Gmbh | Recorder with copy protection |
| EP0338794A2 (en) * | 1988-04-20 | 1989-10-25 | THORN EMI plc | Apparatus for marking a recorded signal |
| EP0342748A1 (en) * | 1988-05-18 | 1989-11-23 | Koninklijke Philips Electronics N.V. | Recording system as well as record carrier and recording apparatus for use in the system |
| EP0392612A1 (en) * | 1989-04-14 | 1990-10-17 | Koninklijke Philips Electronics N.V. | Arrangement for recording an audio signal |
| DE3912998A1 (en) * | 1989-04-20 | 1990-10-25 | Thomson Brandt Gmbh | Digital audio tape recorder with copy protection - uses amplitude reduction of supplied analogue signal before recording |
| GB2254952A (en) * | 1991-04-19 | 1992-10-21 | Samsung Electronics Co Ltd | A system for controlling the recording of a copy protected video signal. |
| US5418853A (en) * | 1992-07-24 | 1995-05-23 | Sony Corporation | Apparatus and method for preventing unauthorized copying of video signals |
| US6539095B1 (en) | 1993-11-18 | 2003-03-25 | Geoffrey B. Rhoads | Audio watermarking to convey auxiliary control information, and media embodying same |
| US6542620B1 (en) | 1993-11-18 | 2003-04-01 | Digimarc Corporation | Signal processing to hide plural-bit information in image, video, and audio data |
| US6675146B2 (en) | 1993-11-18 | 2004-01-06 | Digimarc Corporation | Audio steganography |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6944298B1 (en) | 1993-11-18 | 2005-09-13 | Digimare Corporation | Steganographic encoding and decoding of auxiliary codes in media signals |
| US6614914B1 (en) | 1995-05-08 | 2003-09-02 | Digimarc Corporation | Watermark embedder and reader |
| US6611607B1 (en) | 1993-11-18 | 2003-08-26 | Digimarc Corporation | Integrating digital watermarks in multimedia content |
| US7305104B2 (en) | 2000-04-21 | 2007-12-04 | Digimarc Corporation | Authentication of identification documents using digital watermarks |
-
1981
- 1981-08-06 GB GB08124048A patent/GB2104701B/en not_active Expired
Cited By (31)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1985002293A1 (en) * | 1983-11-21 | 1985-05-23 | Haute Securite Video Hsv S.A. | Antipiracy device and method for cinematographic and video carriers |
| EP0224929A2 (en) * | 1985-12-04 | 1987-06-10 | Sony Corporation | Apparatus and method for preventing unauthorized dubbing of a recording signal |
| EP0224929A3 (en) * | 1985-12-04 | 1987-10-07 | Sony Corporation | Apparatus and method for preventing unauthorized dubbing of a recording signal |
| EP0256753A2 (en) * | 1986-08-11 | 1988-02-24 | Macrovision Corporation | Method and apparatus for preventing the copying of a video program |
| EP0256753A3 (en) * | 1986-08-11 | 1988-08-24 | Macrovision Corporation | Method and apparatus for preventing the copying of a video program |
| GB2196167A (en) * | 1986-10-01 | 1988-04-20 | Emi Plc Thorn | Encoded marking of a recording signal |
| GB2196167B (en) * | 1986-10-01 | 1991-01-02 | Emi Plc Thorn | Apparatus for marking a recorded signal |
| GB2199689A (en) * | 1987-01-05 | 1988-07-13 | Thomas Claude Henry Keen | Recording of an information signal |
| DE3707608A1 (en) * | 1987-03-10 | 1988-09-22 | Hormann Franz Juergen | Method of coding to prevent video and audio piracy |
| 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 |
| DE3806413A1 (en) * | 1988-02-29 | 1989-09-07 | Thomson Brandt Gmbh | Recorder with copy protection |
| 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 |
| EP0342748A1 (en) * | 1988-05-18 | 1989-11-23 | Koninklijke Philips Electronics N.V. | Recording system as well as record carrier and recording apparatus for use in the system |
| AU634709B2 (en) * | 1988-05-18 | 1993-03-04 | Philips Electronics N.V. | Recording system as well as record carrier and recording apparatus for use in the system |
| US5060219A (en) * | 1988-05-18 | 1991-10-22 | U.S. Philips Corporation | Recording system for recording only those types of information which are specified by the record carrier |
| EP0392612A1 (en) * | 1989-04-14 | 1990-10-17 | Koninklijke Philips Electronics N.V. | Arrangement for recording an audio signal |
| DE3912998A1 (en) * | 1989-04-20 | 1990-10-25 | Thomson Brandt Gmbh | Digital audio tape recorder with copy protection - uses amplitude reduction of supplied analogue signal before recording |
| GB2254952A (en) * | 1991-04-19 | 1992-10-21 | Samsung Electronics Co Ltd | A system for controlling the recording of a copy protected video signal. |
| GB2254952B (en) * | 1991-04-19 | 1995-02-15 | Samsung Electronics Co Ltd | A system for controlling the recording of a copy protected video signal |
| US5418853A (en) * | 1992-07-24 | 1995-05-23 | Sony Corporation | Apparatus and method for preventing unauthorized copying of video signals |
| USRE36763E (en) * | 1992-07-24 | 2000-07-04 | Sony Corporation | Apparatus and method for preventing unauthorized copying of video signals |
| US6539095B1 (en) | 1993-11-18 | 2003-03-25 | Geoffrey B. Rhoads | Audio watermarking to convey auxiliary control information, and media embodying same |
| US6542620B1 (en) | 1993-11-18 | 2003-04-01 | Digimarc Corporation | Signal processing to hide plural-bit information in image, video, and audio data |
| US6587821B1 (en) | 1993-11-18 | 2003-07-01 | Digimarc Corp | Methods for decoding watermark data from audio, and controlling audio devices in accordance therewith |
| US6654480B2 (en) | 1993-11-18 | 2003-11-25 | Digimarc Corporation | Audio appliance and monitoring device responsive to watermark data |
| US6675146B2 (en) | 1993-11-18 | 2004-01-06 | Digimarc Corporation | Audio steganography |
| US7987094B2 (en) | 1993-11-18 | 2011-07-26 | Digimarc Corporation | Audio encoding to convey auxiliary information, and decoding of same |
| US8055012B2 (en) | 1993-11-18 | 2011-11-08 | Digimarc Corporation | Hiding and detecting messages in media signals |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2104701B (en) | 1985-06-05 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| 746 | Register noted 'licences of right' (sect. 46/1977) | ||
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19940806 |