WO1984003166A1

WO1984003166A1 - Device for the protection of magnetic tapes, or other recording media, or television or radio broadcastings against an authorized reading and/or reproduction

Info

Publication number: WO1984003166A1
Application number: PCT/FR1984/000029
Authority: WO
Inventors: Jacques Pierre Picard; Claude Alain Daguillon
Original assignee: Sisex Soc Int Servic Export; Sep Spec Elect Physiques; Rim Rech Integrees Marketing
Priority date: 1983-02-09
Filing date: 1984-02-09
Publication date: 1984-08-16
Also published as: EP0137801A1; JPS60500835A; BR8405175A; FR2540659A1; DK482984A; DK482984D0

Abstract

Device for the protection of a video tape on the "sound" track of which have been recorded coded messages, comprising a detector (9) for detecting said coded messages, means (7, 8) for inhibiting or enabling the reading or copying of the tape at each detection of a coded message corresponding to a preset program and means (analog delay lines) (3, 5) for transmitting the sound signal while eliminating the coded message.

Description

DEVICE FOR PROTECTING MAGNETIC TAPES, OR OTHER RECORDING MEDIA, OR TELEVISION OR RADIO TRANSMISSIONS FROM NON-SELF-READED READING AND / OR REPRODUCTION.

The invention relates to the protection of magnetic tapes or other recording media and, possibly, television or radio broadcasts, against unauthorized reading, reproduction or hearing.

An important, but not limiting, application concerns the protection of "video" cassettes against unauthorized duplication. This kind of piracy is carried out on a large scale and we have so far sought to prevent it by using synchronization signals recorded on the "video" channel of the mother band and which only authorized duplication can regenerate; the disappearance of these tops during successive unauthorized copies destroys the quality of the image. However, a fraudster informed of the possibility of regenerating these tops.

The invention proposes to record coded messages in locations distributed on the "sound" track or tracks and to detect these messages on reception of the signals to trigger an inhibition or scrambling and / or validation operation.

WIPO -

According to the invention, a protection device, associated with the receiving or recording device, comprises a device for detecting previously coded messages by means of a programmable encoder and distributed on the "sound" track or tracks and means for '' inhibit and / or validate the reception, recording or jamming upon each detection of a message conforming to the program registered in the detector organ.

According to a preferred embodiment, the protection device further comprises a channel for deleting the coded messages and for reconstituting an undisturbed sound signal, advantageously comprising two analog delay lines connected together in series by a first switch, a second switch connecting the output of the second delay line to its input, the first switch being closed and the second being open during the reception of the portions of the sound signal not comprising a coded message at the output of the first delay line, first means, responding to the detection of a coded message, to supply a control signal for the opening of the first switch and the closing of the second and second means, responding at the end of a predetermined delay interval to provide a control signal for closing the first switch and opening the second.

Other particularities, as well as the advantages of the invention, will become clear in the light of the description below.

In the attached drawing:

Figure 1 is a block diagram of a protection device according to a preferred embodiment of the invention; and

WIPO Figure 2 is a track diagram of signals "a" taken at various points of the device of ^"Figure 1.

In FIG. 1, the reference number 1 designates the sound playback head of a sound and / or image reproduction apparatus recorded on a magnetic tape in which the sound recording track or tracks have, at the time of recording, on portions of predetermined length, received a coded message.

In the described embodiment, this coded message is written on the medium, at the same time as the sound, by means of a programmable coder of the ED11 type sold by the company "Supertex Inc". This recording is carried out at a frequency fc such that it is in conformity with that of the intended receiver and in any case in the compatible bandwidth ensuring the greatest reliability of recognition of the code. The signal coded by the transmitter includes a fixed "preamble" from 46 binary clock signals followed by a white interval of duration equal to that of 18 clock periods and a message proper, of duration equal to 62 clock periods and corresponding to 16 bits of data; the assembly formed by the preamble, the interval and the message constitutes a coding block and is "in accordance with the code" Manchester "; on the condition that the reading frequency fc is the same as the coding frequency, a coding block will be recognized as valid if it conforms to the "Manchester" transmission format and will then allow the message to be used only. which the same 12-bit configuration has been recorded (so-called "primary" code), while the 4 least significant bits constitute a "secondary code" which can be used for other purposes.

The complete coded signal, of duration equal to 130 clock periods of specific frequency fc of the coder, has been recorded on the track or tracks "sound" of the band at the same time as other signals audible and / or video, with a random distribution preferably, and an ^intensity such that the mere reading of such a tape would produce, when passing coded signals, noise that is difficult to bear when hearing.

The "sound" signal from the sensor 1 is, after passing through the conventional equalization pre-amplifier 2 that such a device includes, transmitted to two parallel channels. The first channel comprises, connected in series, a first delay member 3, a first electronic switch 4, a second delay member 5, a filtering device 6, a second electronic switch 7 and an output member 8. The second channel comprises a programmable decoder 9 of the ED11 type, controlled by a clock 93 and having at 94 twelve programmable input lines; an output 90 validated each time a coding block has been detected, a primary code compliance output 91 and four secondary code outputs 92. A secondary code memory 11 has data inputs connected to output 92. programming of the primary code, by the lines 94, is carried out using a member 10 which can be advantageously carried out, either by wiring, or by positioning of switches or any other switching means, such as card reader, (perforated, optical, magnetic ...).

The output 90 is connected to the trigger input S of a flip-flop 12, the output of which is connected to the control terminal of the electronic switch 4, and to the initialization input of a counter at preset 13, the output of which is connected to the reset input R of the flip-flop 12. A clock 14 is connected to the clock inputs of the delay members 3 and 5 and of the counter 13.

The output of the flip-flop 12 is also connected, via a logic inverter 19, to the control input of a third electronic switch 15, which connects the output of the delay member 5 to its input through - £ -

through an operational amplifier 50 intended to restore the amplitude of the signal.

The output 91 is connected, on the one hand, to the input of a memory of the signal ^for recognition of the identity of primary code 16, on the other hand, to an input for validation of the memory 11.

The output of memory 16 is connected to a member 17 which processes the primary code and provides, after processing, on the one hand, an erase signal from memory 16, on the other hand, a control signal applied to the control input of switch 7.

The output of the memory 11 is likewise connected to a member 18 which optionally decodes into sixteen decimal pieces of information the part of the message from the four binary lines of the secondary code, possibly compares it to a pre-established code and commands the execution of a particular function, either independent of the processing of the primary code, or in combination with it; after execution of the secondary code available in 18a_ the member 11 is deleted.

In a preferred embodiment, the delay members 3 and 5 are each constituted by an analog delay line for processing audio-frequency signals, of the TDA1022, TDA2104, TDA2107 or 2110 type sold by the company "RIC" , or an equivalent type.

A frequency such as the delay is of the order of 10 to 40 ms is adopted for the clock 14 and it is arranged so that this duration is greater than the duration of a coding block whose presence is detected by the appearance of a specific signal at the output 90 of the decoder 9.

The operation of the device in FIG. 1 will be better understood by referring to FIG. 2.

A "sound" track is represented in A composed of information blocks of equal duration 1, 2, 3 etc. This division of "sound" information has no physical reality on the tape: each block simply corresponds to a sequence of duration equal to that of the delay Δ T introduced by each of the -

delay lines 3 and 5. The hatched part of block 5 expresses the fact that at this location of the track, there is a coding block which has been arranged so that the duration is less than that of a block.

The signal observed at the output of switch 4 is shown in B.

During the time interval which precedes the instant td of validation of the output 90 of the decoder, the switch 4 is closed and therefore transmits the "sound" signal offset by the delay Δ T.

^" At time td, the signal which appears on the output 90 positions the rocker 12 on 1, which has the effect, on the one hand of opening the switch 4, on the other hand, of closing the switch 15, which was previously open, which results in signal C being interrupted.

The signal observed at the output of the delay line 5 is shown in C. Until the instant td, it is obviously the initial "sound" signal, shifted by 2 Δ T. From the ins ¬ as long as td, the delay line 5 ceases to receive the signal B and returns to its input the output signal C recorded during the preceding interval ΔT.

It follows that, during an interval ΔT + Σ, defined as will be indicated below and which follows the instant td, the “sound” signal portion comprising here the end 3b of block 3 and the start 4a of block 4 is transmitted to the output of delay line 5.

At time td, the counter 13 is initialized and, as its capacity is pre-selected to correspond to a duration of filling by the pulses of the clock 14 equal to T + Σ, Σ corresponding to the short duration necessary to hold account of the transmission times, at the end of Δ T + Σ, it resets the flip-flop 12 to zero, which has the effect of closing the switch 4 again and of reopening the switch 5. In other words , the transmission then takes place normally, as during the time interval which precedes the instant td. Now, during the time interval between td and td + Δ T + ∑, the delay line 3 has moved the end 5b of block 5, and the start 6a of block 6, without however that they can be observed in C. Therefore, during the interval td + ΔT + ∑ to td + 2 AT + Σ which follows, 5b and 6a_ are transmitted from the delay line 3 to the delay line 5 and the ^'during the time interval td + 2ΔT + Σà td + 3 + Σ .DELTA.T, the latter returns this information.

During the time interval td to td + 2 Δ t + Σ, the delay line 5 continuously recycles the information which was stored there at the instant td, that is to say the block 3 and the portion 4a. of block 4.

Finally, at the input of the filter 6, intended to eliminate the switching transients, a signal is present comprising a cyclic reproduction of the block 3 and the portion 4a of the block 4 and comprising neither the terminal portion 4b of the block 4, nor the 5a_ portion of block 5, nor the coded message. Experience shows that such a "sound" signal is not discernible, on hearing, from the original "sound" signal. The code detected by the decoder 9 is moreover, internally compared with a code pre-established by the member 10 and, in the event of coincidence, a signal is supplied to the switch 7, either to close it or to open, possibly in combination with the secondary code. One can, indeed, consider using the device described, either to prohibit or to authorize the exploitation of the prerecorded document according to the presence or absence of a code or a combination of codes which were detected or not. In the first case, the protection device is incorporated in a recorder and the "sound" signal comprising the coded message can come either from another video recorder (or tape recorder) or from a television (or radio) receiver . It can also come from any other medium (mechanical, optical, magnetic recording, etc.). In the second case, the device is incorporated into a reader or receiver and is arranged to authorize reading. The practical way of acting on the recording or reading heads, or on any other element of the circuit of the protected device, is within the reach of the skilled person. û

Advantageously, the distribution of the coded messages on the "sound" track is random, which makes it more difficult to eliminate them by unauthorized means, and the coded message has a sufficient amplitude to seriously disturb reception by a device not equipped with the protection. - „- - _ -.

It is obvious that the conformity of the frequency of the signals of the coding block detected with the natural frequency fc of the device as imposed by the clock 93 already implies a first level of accounting, that is to say of auto ¬ rization or / and prohibition.

The output signal 18a_ resulting from the processing of the secondary code can be used for various purposes. In particular, its presence can be used to revalidate the device which has been inhibited by the primary code; it is thus possible to prohibit the recording of a television program and then authorize the recording of the following program, as was authorized the recording of the previous program.

The primary and secondary codes could also be used to simultaneously validate and / or inhibit two different devices, for example a reader device and a recorder.

It goes without saying that many variants can be imagined by a person skilled in the art, without departing from the spirit of the invention.

O PI IPO

Claims

Patent claims

1. Device for protecting magnetic tapes, or video information carriers, characterized in that it includes means for recording, on at least one "sound" track of the support, at least one mes¬ sage coded according to a predetermined arbitrary code capable of rendering the support unusable by causing an unacceptable disturbance to the hearing when it is present, this message being composed of separate coded blocks distributed all along the support and arranged so that their elimination does not deteriorate not substantially the quality of the information during operation, and means of detecting the presence of blocks having a code conforming to said arbitrary code and of extracting them from the signal read at the time of operation.

2. Device according to claim 1, characterized in that said extraction means comprise a channel for deleting the blocks of the coded message and for reconstituting an undisturbed sound signal, comprising: two analog delay lines connected together by a first switch; a second switch connecting the output of the second delay line to its input, the first switch being closed and the second being open during the reception of the portions of the sound signal not comprising coded blocks; first means, responding to the detection of a block, to supply a control signal for the opening of the first switch and the closing of the second and second means, responding to the end of a predetermined delay interval , to provide a control signal for the closing of the first switch and the opening of the second.

3. Device according to claim 2, characterized in that said registration means are arranged to generate a message comprising a primai¬ re code and a secondary code.

WIPO

4. Device according to claim 2 or 3, characterized in that said analog delay lines are synchronized by a first clock (14) and said detector means are synchronized by a second clock

(93) _T the frequencies of these two clocks being determined so that the delay introduced by the delay lines is greater than the duration of a coded block.

5. Device according to one of claims 2 to 4, characterized in that said first means comprise a rocker (12) and a logic inverter (19), while the second means comprise a synchronized preselection counter (13) by the first clock (14).

6. Device according to one of claims 1 to 5, characterized in that said coded blocks are distributed almost randomly along the support.

WIPO