FR2540659A1 - DEVICE FOR PROTECTING MAGNETIC TAPES, OR OTHER RECORDING MEDIA, OR TELEVISION OR RADIO TRANSMISSION AGAINST UNAUTHORIZED READING AND / OR REPRODUCTION - Google Patents

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

PROTECTION DEVICE FOR MAGNETIC STRIPS, OR THE LIKE
RECORDING MEDIA, TELEVISION BROADCAST OR
OF RADIO AGAINST NON-AUTO READING AND / OR REPRODUCTION
RISEES.

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 application, but not limiting, relates to the protection of video cassettes "against unauthorized duplication. This kind of piracy is done on a large scale and we have so far sought to prevent it by using recorded synchronization tops on the "video" channel of the mother band and that 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.

According to the invention, a protection device, associated with the receiving or recording device, comprises a device for detecting messages previously coded by means of a programmable coder and distributed on the "sound" track or tracks and means for inhibiting and / or to 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 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 signal for controlling 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.

Other features, as well as the advantages of the invention, will become apparent in the light of the description below.

In the attached drawing:
Figure 1 is a block diagram of a device
protection according to a preferred embodiment
of the invention; and
Figure 2 is a diagram of the runway signals
"sound" taken, at different 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 registration, 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 marketed 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 comprises a "preamble9 "fixed from 46 binary clock signals followed by a white interval of duration equal to that of 18 clock periods and of 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"; under the condition that the reading frequency fc is the same as the coding frequency, a coding block will be recognized valid if it conforms to the "Manchester" format of transmission and will then and only allow the exploitation of the message. the Eu11 model, the 12 most significant bits of the message used to validate the receiver in which the same 12-bit configuration was 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, was recorded on the "sound" track (s) of the tape at the same time as the other sound and / or video signals, with a distribution. preferably random, and an intensity such as pure and simple reading of such a band would produce, during the passage of the coded signals, a noise difficult to bear at 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 Eu11 type, controlled by a clock 93 and having at 94 twelve programmable input lines g an output 9.0 validated each time a coding block has been detected, a compliance output of primary code 91 and four outputs of secondary code 92. A secondary code memory 11 has data inputs connected to output 92. The programming of the primary code, by lines 94, is carried out using a device 10 which can advantageously be realized, either by wiring, either by positioning of switches or any other switching means, such as card reader (perforated, optical, magnetic, etc.).

 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 input for initializing a preset counter. 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 via 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 recognition signal of the primary code identity 16, on the other hand, to an input of 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 a particular function, either independent of the processing of the primary code, or in combination with it t after, execution of the secondary code available in 18a the organ It is erased.

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 type
TDA1022, Ta2104, TDA2107 or 2110 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 arrangements are made for this duration to be greater than the duration of a coding block the presence of which is detected by the appearance of a specific signal at output 90 of 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 information n sound n has no physical reality on the tape: each block simply corresponds to a sequence of duration equal to that of the delay A T introduced by each of the delay lines 3 and 3. The hatched part of the 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 signal gson "shifted by the delay A
At the instant 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 opened. As a result, signal C is interrupted.

The signal observed at the output of the delay line 5 has been shown in C. Until the instant td, it is obviously the initial "son'2 signal, shifted by 2 A T. From the instant td, the delay line 5 stops receiving the signal B and returns to its input the output signal C recorded during the preceding interval AT.

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

At time td, the counter 13 is initialized and, as its capacity is preselected to correspond to a duration of filling by the pulses of the clock 14 equal to
AT + Z, Z corresponding to the short duration necessary to take account of the transmission times, at the end of A T + X, it resets the flip-flop 12 to zero, which has the effect of closing switch 4 and d again '' again open the switch 5. In other words, the transmission then operates normally, as during the time interval which preceded the instant td.Or, during the time interval comprised -between td and td + AT + C, the delay line 3 has endowed the end 5b of block 5, and the start 6a of block 6, without however being able to be observed in C. Therefore, during the interval td + AT + z to td + 2 At + z which follows, 5b and 6a are transmitted from delay line 3 to delay line 5 and, during the time interval td + 28T + Zà td + 3 QT + Z, the latter restores this information.

During the time interval td tottd + 2A t +, the delay line 5 permanently recycles the information which was stored there at the instant td, that is to say the block 3 and the portion 4a of the 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 Sa portion of block 5, nor the coded message.

Experience shows that such a sign # l "sound" 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, in fact, 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 that have been detected or not. In the first case, the protection device is incorporated in a recorder and the "sound" signal C # including the coded message can come either from another video recorder (or tape recorder), or from a television receiver (or from radio). 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.

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

It is obvious that the conformity of the frequency of the signals of the detected coding block 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 authorization or / and ban.

 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 that 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 those skilled in the art, without departing from the spirit of the invention.

Claims (6)

Patent claims  1. Device for protecting magnetic tapes, or other recording media, or television or radio broadcasts against unauthorized reading and / or reproduction, characterized in that it has a detector member (9) messages previously coded by means of a programmable coder and distributed on the "sound" track (s) and means (7, 8) of inhibiting and / or validating the reception or the recording each time a message is detected in accordance with the program registered in the detector unit.  2. Device according to claim 1, characterized in that it further comprises a channel for deleting the coded messages and for reconstituting an undisturbed sound signal, advantageously comprising two analog delay lines linked 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 a coding block of the first means, responding to the detection of '' a coding block, to provide a control signal for the opening of the first switch and the closure of the second and second means, responding to the end of a predetermined delay interval to provide a control signal of the closure of the first switch and the opening of the second.  3. Device according to claim 2, characterized in that said programmable encoder generates messages comprising a primary code and a secondary code.  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 member is synchronized by a second clock (93), the frequencies of these two clocks being determined so that the delay introduced by the delay lines is greater than the duration of a coding 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 messages are distributed randomly.