Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04K—SECRET COMMUNICATION; JAMMING OF COMMUNICATION
  • H04K3/00—Jamming of communication; Counter-measures
  • H04K3/80—Jamming or countermeasure characterized by its function
  • H04K3/82—Jamming or countermeasure characterized by its function related to preventing surveillance, interception or detection
  • H04K3/825—Jamming or countermeasure characterized by its function related to preventing surveillance, interception or detection by jamming
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04K—SECRET COMMUNICATION; JAMMING OF COMMUNICATION
  • H04K1/00—Secret communication
  • H04K1/02—Secret communication by adding a second signal to make the desired signal unintelligible
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N7/00—Television systems
  • H04N7/16—Analogue secrecy systems; Analogue subscription systems
  • H04N7/166—Passage/non-passage of the television signal, e.g. jamming, band suppression
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N7/00—Television systems
  • H04N7/16—Analogue secrecy systems; Analogue subscription systems
  • H04N7/173—Analogue secrecy systems; Analogue subscription systems with two-way working, e.g. subscriber sending a programme selection signal
  • H04N7/17345—Control of the passage of the selected programme
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04K—SECRET COMMUNICATION; JAMMING OF COMMUNICATION
  • H04K2203/00—Jamming of communication; Countermeasures
  • H04K2203/10—Jamming or countermeasure used for a particular application
  • H04K2203/14—Jamming or countermeasure used for a particular application for the transfer of light or images, e.g. for video-surveillance, for television or from a computer screen

Definitions

• the present invention relates generally to the field of the distribution of signals, such as image or sound signals to users, and more particularly the control of access to these signals.
• a descrambling device is made available to the user and a useful signal, such as image and / or sound signal, is transmitted or broadcast after scrambling into a scrambled signal (for example US- A-5 228 082). After descrambling the scrambled signal in the descrambling device, the useful signal is restored to the user.
• a scrambled signal for example US- A-5 228 082.
• the user remotely controls the supply of the signal.
• the original unscrambled signal is supplied to it in response to this command for a short predetermined duration repeated a given number of times during a fixed period of time.
• the user receives the original signal free of charge three times a day each time for a period of five minutes.
• These free accesses to the original signal bring the content of the signal, such as image if it is an image signal, to the knowledge of the user.
• the user wishes to receive the original signal durably, he remote controls the reception of the signal then the stopping of this reception and is billed according to the duration of reception.
• This technique is more frequently used in structures of limited size, such as hotels or hospitals.
• the invention aims to remedy the aforementioned drawbacks by providing a method of controlling the access mode which differs from that according to the second aforementioned technique in that it allows the user to permanently access the image signal, not under its original form, but in a disturbed form, nonetheless intelligible, in order to allow it to know at all times the overall content of this signal.
• a method of controlling the mode of access to a useful signal by a user comprising the selective remote control by the user of several modes of access to the useful signal, one of the access modes consisting of supply of the useful signal to the user, is characterized in that another of the access modes consists in the alternative and periodic supply of the useful signal and of a disturbance signal to the user.
• the useful signal is an image signal.
• the disturbance signal can be a target signal or result from an overlay, a titration or an image overlay operated relative to said image signal.
• the useful signal is a sound signal and the disturbance signal is an audio frequency signal at fixed frequency.
• the invention also relates to a system for implementing the aforementioned method in switching grids for switching nodes intended for the distribution of image signals to users, such as television channels for a professional application, or connected households. to cable networks and customers in hotels for a general public application.
• a television channel remotely controls a switching grid to establish a link between an input and an output of the grid.
• the gate input constitutes an external image capture, for example to which one of the image signals read from an image bank is applied, or a live reporting signal.
• the grid output is connected to a control room of the television channel. An agent in the control room can select, subject to access restrictions, any of the grid entries to receive the corresponding image in the control room.
• each of the image signals received at respective inputs of the switching grid is distributed to all of the users, such as channels television, which allows each user to select one of the image signals and to decide how to broadcast it to viewers, in which case there is neither confidentiality nor selectivity in the distribution of the signals; or else the image signals are distributed to respective user groups according to rights allocated by the operator of the switching grid, in which case confidentiality and selectivity in the distribution of the signals are ensured, but access to signals offered to users are limited, which does not allow users to whom rights have not been allocated for certain signals to appreciate the interest of these signals and to become buyers of these signals.
• Another objective of the invention is also to provide a system for controlling the mode of access to useful signals, such as image or sound signals, at the output of the switching gate directly remote controlled by the user in order to allow it to freely select permanently according to the access modes which are granted to it, or else an unaltered useful signal coming from the switching grid, for example in the case where the user wishes to use this useful signal, or else a signal which alternates the unaltered useful signal and another signal called disturbance signal in the case where the user wishes to know succinctly the information supported by the signal before deciding on its sustainable use.
• the disturbance signal can be a rod target signal or the useful scrambled image signal.
• An objective complementary to the previous one according to the invention consists in taxing differently a transmission of information according to whether they are intended for a pre-analysis, that is to say for example for an image preview or pre-listening of sound or for a use, that is to say in function of the two modes of access to the information defined above.
• a system for controlling the mode of access to useful signals through a switching grid constituted by a matrix of switching cross points between several matrix line inputs receiving respectively useful signals and several matrix column outputs delivering useful signals, a single crossing point not being established at the same time in a matrix column between an output of said column and one of the inputs of the matrix is characterized in that 'it comprises, associated with each gate output, a switching means having a first input connected to said each gate output and a second input receiving an image disturbance signal, and an output to be connected to one of the inputs switching means, and a control means controlling the switching means in order to selectively connect to said output switching means, or else said first input or bie n periodically, alternately, said first and second entries.
• the disturbance signal is a color test signal, an operator logo or any other predetermined image signal.
• a means associated with said each gate output can be provided for combining the useful signal delivered by said each gate output. grid with an additional signal, such as a title to be entered, into a resulting signal.
• the switching means associated with said each gate output then further comprises a third input receiving the resulting signal to be selectively connected to the output of the switching means under the control of the control means.
• the aforementioned system is particularly intended to be integrated into a switching node in the form of a local network to which is attached a plurality of local and / or remote stations transmitting first messages each including a crosspoint address word of grid detected by a grid control unit to establish a corresponding crossing point.
• Second messages transmitted by the stations each include a control word for access mode to the useful signal leaving the output of the gate connected to said crossing point when establishing said crossing point, said mode control word d access being received by a local network coupling means to be transmitted to said control means with the address of said output connected to said crossing point.
• each second message includes, in addition, a user identification word which is received by a central supervision means connected to said local network to increment a respective tax counter in said central means, addressed by said user identification word, with an increment frequency dependent on said access mode control word in said message.
• the invention also provides for deporting the switching means and the control means to the user.
• the control means then comprises a synchronization extraction means connected to said each gate output to detect and extract a synchronization signal in one of said image signals in order to selectively connecting said first and second inputs to said output from switching means alternately, depending on the detection and the failure to detect said synchronization signal in the image signal according to whether this useful image signal is respectively absent present at the input of the switching means.
• the invention also relates to a system for implementing the method according to the invention in a digital distribution network of useful signals, such as image signals.
• Digital fiber optic image distribution networks will replace the centralized architecture of the current switching grid image distribution in the future.
• the system comprises a serial-parallel conversion means for converting serial bit data words from an incoming digital useful signal into parallel bit data words of said useful signal, first and second validation means for validating respectively said words of parallel bit data of the useful signal and parallel data words of disturbance signal, in outgoing parallel bit words, means for selectively activating either said first validation means, or alternately and periodically said first means of validation and said second validation means, in response to a user access mode control signal, and parallel-to-serial conversion means for converting said outgoing parallel bit words into serialized bit words transmitted to the user.
• FIG. 1 is a block diagram of a system controlling mode of access to an image signal through a switching gate for a television center switching node according to the invention
• FIG. 2 shows a schematic block diagram of an image switching node including an access mode control system according to the invention
• FIG. 3 shows a detailed block diagram of an electronic card grouping means for combining image signals included in the access mode control system shown in Figure 2;
• FIG. 4 shows in detail a block diagram of a security module included in the card of Figure 3;
• FIG. 5 and 6 respectively show software architectures of a coupler on the one hand, and a control unit in the card of Figure 3 on the other hand, both belonging to the mode control system access according to the invention;
• FIG. 7 is a block diagram of a remote access control module to the user.
• FIG. 8 is a block diagram of an access control system for implementing the invention in a digital image distribution network.
• a switching grid GC also known as a video switching matrix
• a switching grid GC in a television center has M row line inputs E ⁇ to EJJ and N column column outputs ST; L to ST ⁇ , and thus (M x N) switching crossing points divided into M rows and N columns.
• the grid is produced by placing N switching bars side by side with M inputs.
• N is established by passing the crossing point (E m , ST n ) which, in practice, may be in the form of a gate field effect transistor ordered.
• the grid is distributive, that is to say any input can be switched to all outputs; the grid is also non-blocking since a connection is always possible between any input and any output.
• a GC switching grid in a television nodal center or in a central image distribution point such as the cable headend or a node of this network (EP-A-389 339 , Figure 1), or a cable television headend in a hotel, it is controlled either by a centralized system, or by individual desks, or by a programmed system or by a variegated set.
• the switching grid GC belongs to a switching node in a cable and / or radio video distribution network intended to provide a service for distributing images to users, such as television channels, homes connected to a cable network, or hotel guests.
• a user controls the switching grid GC to establish a link between an input of the grid, connected for example to a live external image source or to a video recorder of recorded images to be transmitted, and an output typically connected to local or remote control of a television channel, a television set from a household connected to the cable network, or from a hotel room.
• the user selects, subject to access restrictions (EP-A-389,339, col. 4, 1.41 to col. 5, 1.6 and col. 7, 1.36 to col.
• any of the grid entries to receive the corresponding image After selecting images, the user can use these images.
• agents of the switching node ensure, with users, the operation of remote consoles which remotely control the switching grid GC.
• the invention adds a switching stage consisting of switches COM ] _ to COM ⁇ j at the output of the switching grid GC.
• Each COM n switch, n being an integer between 1 and N, is shown diagrammatically by an electromechanical switch with two fixed input contacts and a movable output contact, although in practice this switch is an analog transistor circuit. .
• the inputs of the switch are respectively connected to an output ST n of the grid GC and to a source of image disturbance signal MIRE, such as bars pattern.
• the COM n switch is remotely controlled by the corresponding user by means of a specialized terminal or an unmarked terminal connected to a server in a professional application, or even by means of an unmarked videotex terminal of the MINITEL type (Registered trademark) for a home connected to a cable network or an indoor telephone for a hotel room as part of a consumer application.
• a user can have access to several switches.
• a user served by the output S n wishing to view images applied to the input E m at the same time selects the crossing point (E m , ST n ) in the grid to connect the terminals E m and ST n and controls the switch COM n corresponding to the ST n output of the GC grid.
• Two alternatives are offered to users for controlling the switch.
• the output ST n of the grid GC is connected to the output S n of the switch COM n of the switching stage so that the user receives clearly, without alternation with a disturbance signal, the signal of color television image entering the entrance E m .
• This first alternative is chosen for example when the user wishes to clearly visualize the images received at the input E m .
• the switch COM n is controlled according to a predetermined alternation mode so that the output S n alternately transmits the image signal selected at the output ST n of the switching gate GC and the disturbance signal MIRE.
• the alternation may consist of the transmission of one or more lines, respectively frames, successive of the image signal entering E m , followed by the transmission of one or more lines, respectively frames, successive of the signal MIRE.
• This second alternative is for example chosen when the user wishes to preview a sequence of images. Each image in the sequence, or group of successive images, is not directly usable by the user since the image is degraded by the disturbance signal. The rhythm of the alternation is nevertheless chosen so that the images entering E ro cannot be used while being recognizable, so that the user selects, if necessary, the first alternative.
• an image switching node is typically organized in the form of a local network RL consisting of a BUS bus to which is attached the switching grid GC, stations, or consoles, premises POL or remote PODs and central OS supervision computers.
• the remote POD stations are connected to the BUS bus through, for example, either a dedicated link LS, or a packet switching network by means of MO modems.
• the switching gates, local and remote stations POL and POD, and central supervision computers are attached to the BUS bus through respective IRL local network interfaces.
• IRL interfaces can be simple integrated or external physical interfaces, for example for local POL stations, or gateways for example for remote POD stations connected to the BUS bus through the packet switching network.
• the various POD remote stations are allocated to the users, who thus remotely control the GC switching grid.
• Local POL stations are assigned to central office agents.
• the switching gate GC receives crossing point address words from the various local POL and remote stations POD through its own local network interface. These crosspoint address words are applied to a gate control unit UCG of the switching gate GC.
• the UCG control unit establishes, that is to say makes conductive, or breaks, that is to say makes nonconductive, a crossing point (E m , ST n ) in the grid whose address (m, n) is contained in a received address word. Of in this way, connections are established and broken between inputs of the grid GC receiving images, and outputs of this same grid GC transmitting these images to the users.
• the central computers OS provide supervision of the local area network RL, and functions such as restriction of access rights to the switching grid GC by limiting the authorizations for establishing crossing points.
• This access mode control system comprises a management coupler CO and an MCOM access control module.
• the CO management coupler is connected to the BUS bus through an IRL local network interface.
• This management coupler CO is intended to receive access mode control words transmitted by the local and remote stations POL and POD, to interpret these access mode control words and control the MCOM access control module accordingly.
• a crossing point address word and an access mode control word are transmitted in respective first and second messages by a remote station POD of the user.
• These first and second messages transmitted by the remote stations POD are intended respectively for the grid control unit UCG and for the management coupler CO and central supervision computer OS.
• These messages are received through IRL local network interfaces.
• the first message is interpreted by the UCG unit to establish or break a crossing point of the switching grid GC between a given input E fl , and an output ST n assigned to a given user.
• the second message is processed by the coupler CO to be transmitted to the access control module MCOM, in order to select the mode of access to the image signal produced at said output assigned to the user in response to the establishment of the crossing point which is chosen by the user by means of his POD station, the access mode being a mode disturbed by a test pattern or by overlay, or an undisturbed mode, called clear mode.
• This second message is received as a whole by at least one of said central supervision computers OS which triggers in the latter a tax counter associated with the user.
• the second message also contains a user identification word field which identifies the user and which, after recognition in the computer, triggers a counting of clock pulses in the tax counter associated with this user.
• either one of two clock signals having different periods is applied to the clock input of the counter when the counter is non-programmable, or a single clock signal is applied to the counter which is programmed according to one of two increment rates of this counter according to the access mode chosen by the user which is read in the access mode command word included in the second message.
• the ratio between the periods of the two clock signals or the two increment rates is for example between 10 and 50.
• the MCOM access control module consists of L CA electronic cards; L to CA L.
• Each card CA ⁇ , 1 being an integer index between 1 and L, processes 4 successive respective outputs ST n to S n + 3 of the switching grid GC.
• the number N of grid outputs is equal to 4L.
• the cards CA ⁇ to CAL are interconnected in cascade by means of a link bus BL connected to the management coupler CO.
• Access mode command words in the second messages interpreted by the management module CO are transmitted to the cards CA; L to CAL • One of these cards, assigned to the output ST n of the switching gate GC for which is requested the establishment of a crossing point (E m , ST n ) selected from the points (EL, ST ⁇ ) to (E jj , ST n ), controls the access mode in correspondence with the address output n included in the cross point address word.
• the means for combining image signals are means for superimposing an image, called the foreground image, in another image, called the image 'background, represented by the image signal to be disturbed at the output ST n ; in this case, the foreground image replaces one or more determined zones of the behind the scene image and can be constituted by a title, designating for example the image sequence to be disturbed and / or a logo of the operator of the switching node.
• the means for combining image signals are means for superimposing a foreground image, such as hatching or checkerboard, entirely or partially on a background image, in order to obtain a resulting image in full screen or containing a window in which the background image is visible with a more or less accentuated blur through the foreground image.
• inlay means and overprinting means are combined to blur background image areas.
• the means for combining image signals in addition to the means for combining by switching between image and pattern signals, are constituted by titration modules in FIG. 3.
• a card CA ⁇ of the access mode control module MCOM is intended to process 4 outputs ST n to ST n + 3 of the GC switching grid.
• It essentially comprises a control unit UC organized around a microprocessor 10, as well as 4 titration modules MT ⁇ to MT 4 , 4 safety modules MS ⁇ to MS 4 and 4 basic analog or digital switching matrices M ⁇ to MC 4 , all associated respectively with the four outputs ST n to ST n + 3 of the switching grid GC processed by the card CA ⁇ .
• the card shown in FIG. 3 constitutes the first card CA ⁇ of all the cards CA ] _ at CAL ; and is therefore intended to receive and process the first four outputs ST 1; ST, ST 3 and ST of the GC switching grid.
• the control unit UC comprises the microprocessor 10, an EPROM read-only memory 11 storing the operating program of the control unit UC, a random access memory RAM 12 , a synchronization unit 13, a clock 14, a parallel interface circuit 15 and an RS-422 type interface 16.
• the clock rates the microprocessor 10 and the asynchronous type data synchronization unit 13.
• the interface 16 constitutes a physical interface between the link bus BL and the control unit UC.
• Each access mode command word received in a second message is transmitted by the coupler CO to the access control module MCOM in order to select a particular mode of access to the image simultaneously with the establishment by the unit.
• An output address n is included in the command word which is transmitted simultaneously to all the cards CA ] _ to CA L.
• this output address n is compared to a stored address word associated with the card. If the output address contained in the control word is identical to the stored address word, then the control unit UC picks up and interprets the access mode control word.
• Wires RX- and RX + of the bus BL in FIG. 3 convey control words from the coupler CO to the cards CA ⁇ to which these control words are addressed according to a first direction of transmission.
• TX- and TX + wires of the BL bus are assigned to a second direction of transmission, opposite to the first, for transmitting data from the control units UC in the cards CA ⁇ to the coupler CO.
• the card CA ⁇ contains four parallel processing channels for respectively processing image signals at outputs ST to ST 4 of the switching grid GC, only the first processing channel consisting of the titration module MT] _ of the module security MS ⁇ and of the elementary analog switching matrix MC ⁇ is now detailed.
• the Titration modules MT 2 to MT, safety modules MS 2 to MS 4 and elementary switching dies MC to MC 4 are respectively identical to those in the first channel.
• the output ST ⁇ of the switching gate GC is connected to an input of the titration module MTT.
• the latter comprises a synchronization extraction circuit 21 and a titration circuit 22 preferably programmable.
• the synchronization extraction circuit 21 is for example made from a TDA 2595 or LM 1881 component while the titration circuit can for example be built around the MB 88303 component manufactured by FUJITSU.
• a color television image signal IMAGE is present on the output S - ⁇ of the switching grid GC as soon as the user commands the establishment of a crossing point of the grid of the type (E m , S ⁇ ).
• This IMAGE signal is applied to the input of the synchronization extraction circuit 21 which extracts a frame synchronization signal TSYNC and a line synchronization signal LSYNC from the image signal IMAGE.
• the synchronization signals TSYNC and LSYNC are applied to two respective inputs of the titration circuit 22 so that the latter locates predetermined lines in each of the even and odd fields in the image signal IMAGE, lines for which a predetermined title is embedded.
• Two other inputs of the titration circuit 22 respectively receive a data signal DATA and the image signal IMAGE.
• the data signal DATA corresponds to a predetermined text which is to be embedded in the image signal IMAGE and whose characters and their size are programmable in the titration circuit.
• the DATA signal is transmitted by the microprocessor 10 to the titration circuit 22 through a data bus forming part of an address / data bus BAD connecting the microprocessor 10, the read only memory, the random access memory 12, the synchronization circuit 13 and the parallel interface circuit 15 in the control unit UC.
• the data bus of the control unit UC being connected to all the titration circuits 22 in the modules T; L to MT 4 , a decoding logic associated with respective buffers for the titration modules MT ⁇ to MT is designed to transmit a data signal DATA only to the single titration circuit 22, in the titration module MT ] _ to MT4 which is connected to the output ST 2 to ST 4 of the switching grid GC for which the establishment of a crossing point was ordered by the user.
• the decoding logic and the buffer memories have not been shown.
• an analog switch with two inputs to which the image signal IM of the output ST lr is applied as a background image signal, and a title video signal, as the signal d 'stage, produced by the circuit 22 in order to deliver a signal resulting from combined images, called image signal titled IT.
• the selected title is embedded in the images represented by the IMAGE signal.
• the switch is for example constituted by two amplifiers connected to a summator and having variable gains controlled respectively by complementary gain control signals established by the titration circuit in dependence on the outline of the title to be embedded.
• the switch output of circuit 22 is connected to an input of the elementary switching matrix 40 of the module MC ⁇
• the analog or digital elementary switching matrix 40 has four inputs E] _, E, E 3 and E 4 respectively receiving the image signal IMAGE from the output ST ⁇ following the establishment of a crossing point by l in the column of points of the switching grid GC associated with the output ST ⁇ , the image signal titled IT coming from the titration circuit 22, and two bar pattern signals MIRE 1 and MIRE 2.
• Inputs of EC control of the matrix 40 receive from the security module MSI a two-bit matrix control word CMA1 in order to select at the output S of the matrix one of the four signals at the inputs E- to E 4 .
• the output S of the elementary switching matrix 40 is applied to an input of an amplification stage 41 having two outputs S ⁇ and S ' ⁇ , which each transmit a resulting image signal selected from among four through the matrix of switching 40, and corresponding to one of the modes of access to the image controlled by the corresponding user either to an unmodified image, or to an image disturbed by overlaying of title or switching with a test pattern.
• the output S ' ] _ constitutes a test terminal of the MCOM access control module.
• the parallel interface circuit 15 in the control unit UC (FIG. 3) has a register which serves an output port PA and in which the microprocessor 10 writes a six-bit address word via the address / data bus BAD.
• a first part for two bits (CO, Cl) in the address word constitutes an elementary matrix input address which is included in the access mode control word of a second message received by the microprocessor 10 and which is applied as input of each of the four security modules MSI to MS4 by the parallel interface circuit 15.
• AD1 to AD4 in the address word are a combination of three bits in the state "1" and a single bit in the state "0” and are transmitted respectively in the form of four logic signals by the circuit 15 through four wires respectively to respective storage inputs of the security modules MSI to MS4.
• Only the security module MSI to MS4 addressed by the address validation bit AD1 to AD4 in the "0" state stores the matrix input address (C0, C1) as a matrix control word CMA1 to CMA4, to select one of the inputs E ⁇ to E 4 of the associated elementary switching matrix 40.
• All the image access mode command words transmitted by the user are received, after processing in the coupler CO, by the control unit UC through the link bus BL.
• the control unit UC switches, after reception of the access mode control word transmitted by the user and received through the bus BL, alternately the inputs E ] _ and E 3 or E 4 , respectively E ⁇ and E, of the switching matrix 40 respectively receiving the image signal IMAGE and the signal MIRE 1 or MIRE 2, respectively the image signal IMAGE and the image signal titled IT.
• the security module MSI mainly comprises three AND gates with two inputs 30a, 30b and 30c, a security switch 31, two monostable flip-flops 32 and 33, an inverter 34, two OR gates with two inputs 35 and 36, three D type flip-flops 37a, 37b and 37c, a bias resistor 38 and a pilot light in the form of a light-emitting diode LED 39.
• the first respective inputs of the AND gates 30a and 30b receive the bits CO and Cl composing the matrix entry address word.
• a first input of the AND gate 30c receives a respective one of the four address validation bits AD1 to AD4, ie here AD1 for the module MSI.
• Second inputs of the AND gates are connected to a supply terminal + V C c in the high logic state "1". Between this supply terminal and ground are connected in series the switch 31 and a directly polarized short-circuit protection diode 31a.
• the outputs of AND gates 30a and 30b are respectively applied to data inputs D of flip-flops 37a and 37b having clock inputs receiving from the output of gate 30c, through the inverter 34, the validation signal of address AD1 carried by a respective one of the four module address wires connected respectively to the modules MSI to MS4.
• the outputs Q of flip-flops 37a and 37b are connected to the control inputs EC of the matrix 40 of the first processing channel.
• the control unit UC produces a RESET signal initializing, in addition, the microprocessor 10.
• the monostable flip-flop 33 active on a falling edge, is triggered by the RESET signal applied to its input and has a stable state at the high state "1".
• the output of this monostable flip-flop 33 is connected to an input of the monostable flip-flop 32 and to the supply terminal + V DC *
• the monostable flip-flop 32 active on a falling edge, has a stable state in the low state "0 "and has an output connected to a first input of the OR gate 35, a second input of which receives the module address validation signal AD1 through the AND gate 30c.
• the output of the OR gate 35 is applied to a clock input of the D flip-flop 37c.
• the data input D of this flip-flop 37c is connected to the output of the OR gate 36 whose inputs are connected to the outputs Q of flip-flops 37a and 37b.
• the inverted output Q of the flip-flop D 37c is applied to ground M through the resistor 38 and the indicator LED diode 39 connected in cascade.
• the terminal common to the resistor 38 and to the inverted output Q of the flip-flop D 37c is looped back to one of four inputs of an input port PB of the parallel interface circuit 15 connected respectively to the security modules MSI to MS4 of the CA card ⁇ .
• the microprocessor 10 of the control unit UC periodically reads a register associated with the input port PB to verify that the last bits of input address (C0, C1) transmitted by the unit UC to the module MSI security and stored in RAM 12 correspond well to the matrix control word CMA1 stored at the output of flip-flops D 37a and 37b, and therefore that the control of the switching matrix 40 is correctly carried out.
• the operation of the MSI security module is as follows. During normal operation of all the circuits of the card CA ] _, the switch 31 is in the open position, which keeps the AND gates 30a, 30b and 30c open, including the second inputs are in the high state "1" or in the low state "0".
• the two matrix input address bits CO and Cl are thus transmitted by the open doors 30a and 30b to be memorized at the output of flip-flops 37a and 37b, in the matrix control word CMA1 in response to a falling edge of the ADl module address validation signal.
• the rising edge of the signal AD1 causes, through the OR gate 35, the memorization of the state (co + Cl) at output Q of the flip-flop 37c.
• the state (co + Cl) at output Q of flip-flop 37c is at "1" if and only if the switching matrix 40 is commanded to produce at output S the clear image signal IMAGE, nor disturbed by a signal of bars pattern, nor titrated.
• This state (co + Cl) at the output of flip-flop 37c is retransmitted in the form of a scan signal SCRUT to the input port PB of the parallel interface circuit 15, so that the microprocessor 10 detects a failure of the card. IT! when SCRUT is in state "0" while the user has requested to receive the IMAGE signal in clear.
• the RESET reset signal from the microprocessor 10 is applied to the input of the monostable flip-flop 33 which produces, in response to the falling edge of the RESET signal, a low state pulse "0" of duration ⁇ 2 .
• This low state pulse closes the AND gates 30a, 30b and 30c.
• a state "0" is provided at the outputs of the two AND gates 30a and 30b. Knowing that the validation signal ADl is in the high state "1", the setting in the low state "0" of the second input of the AND gate 30c for the duration ⁇ induces an initialization pulse in the state high "1" of duration ⁇ 2 at the output of the inverter 34.
• the switch 31 is closed for example under the control of a local station POL of an agent of the switching node via the local area network RL, or else under the action of a push button (not shown) on the card CA ⁇
• the second inputs of AND gates 30a and 30b are thus set to the state bottom "0" through the diode 31a.
• the output of the AND gate 30c previously in state "1”, is forced to state "0".
• a pulse in the high state "1" is thus supplied at the output of the inverter 34.
• the monostable flip-flop 33 is used, for each initialization or detection of failure, to produce a clock pulse applied to the clock inputs of flip-flops 37a and 37b in order to store at the output of said flip-flops the states "0" and "0" for the matrix control word CMA1 in order to select an image access mode without disturbance or titration.
• FIG. 5 relates to the software architecture of the CO coupler.
• the second control messages each comprising an access mode control word transmitted by a user are received through the bus of the local area network RL by a CO LOW CO Q module which manages the physical layer of access to the BUS bus, and of the link layer relating to the flow regulation and the shaping of the frames constituting the MESSAGE command messages.
• MESSAGE messages other than access mode messages are also received by the CO coupler, in particular for the purpose of configuring the latter.
• a CO ⁇ filtering module classifies the messages according to their category, according to whether they are intended for the CO coupler, whether they are control messages intended for the MCOM control module, or whether they are erroneous messages. For an erroneous message, the filter module C ⁇ !
• an alarm management module C0 4 which forms an ALARM alarm message which is returned to the user who transmitted the MESSAGE message to inform him of the impossibility of processing his message.
• this is transmitted by the filtering module to a command interpreter C0 in the CO coupler.
• the interpreter C0 translates the message in the form of elementary commands which are transmitted to a command establishment module CO5 which reads beforehand a static configuration database B2 relating to the declared hardware structure (chosen access modes, address on local bus, number of cards, text of the titration module, etc.) and a database of state variables relating to the availability of the cards declared in B2 and of the switching matrices 40.
• a message intended for the coupler is by example a LEC read request message of an entry address word of an elementary switching matrix CMA stored in the base of state variables B4. It is recalled that the microprocessor 10 of the card CA ⁇ periodically reads, via the parallel interface circuit 15, inter alia, the states constituting the words of address of entry of matrix CMA for the four processing channels in the card CA ⁇ . These input address word states are stored in the database B 4 as state variables.
• a message intended to control the MCOM module in particular in order to control a given access mode to the image, this is transmitted by the filtering module CO ⁇ to a CO 3 analysis automaton.
• the automaton reads two databases Bl and B3 respectively constituting a sequence descriptor and a grid state table TEG, for, on the one hand, identifying the sequence SEQ to be established and, on the other hand, for checking in the updated table B3, in response to each received command message. access, that a crossing point establishment was requested in the grid column serving the output ST n corresponding to the controlled access mode.
• the sequence SEQ to be established is transmitted to the command establishment module C0 5 which supplies, via a shaping module CO, a control frame CDE in the bus BL to all the cards CA ⁇ to CAL ⁇ u module MCOM control unit.
• This CDE control frame further contains information representative of the input address bits of matrix CO and Cl for controlling an elementary switching matrix 40, and the address of the card CAi recipient of the address bits accompanied of the address AD1, that is to say in practice the address of the gate output ST n .
• the software architecture of a control unit UC in a card CAi is as follows.
• a management module UC 0 takes among the CDE control frames transmitted in the link bus BL, the CDE control frames which are intended for the card CAi to which the control unit UC belongs.
• each picked control frame is deprived of the information relating to the link layer concerning the transport of the frames, such as the address of the card, to constitute a command [CDE].
• This command [CDE] is applied to a UCi command interpretation module.
• the latter activates in particular a programmable timing module UC 4 which determines a switching period equal to the sum of a first duration Tl during which the output S of the matrix 40 is connected to the first input E i and of a second duration T3 during which the output S is connected to one of the test pattern inputs E 3 and E 4 or E 2 , when the user commands an access mode of the type disturbed by the alternation between the useful image signal IMAGE and one of the test pattern signals MIRE, or the signal image titled IT.
• a programmable timing module UC 4 which determines a switching period equal to the sum of a first duration Tl during which the output S of the matrix 40 is connected to the first input E i and of a second duration T3 during which the output S is connected to one of the test pattern inputs E 3 and E 4 or E 2 , when the user commands an access mode of the type disturbed by the alternation between the useful image signal IMAGE and one of the test pattern signals MIRE, or the signal image titled IT.
• the UC i module also provides a search for specific personalized text relating to the at least partial marking of the image by combination of images, such as titration of the image in the MTi titration module ”
• the [CDE] command cannot be interpreted , that is to say erroneous, it is transmitted to an alarm module UC 7 responsible for forming an alarm message which is sent back to the coupler CO through the management module UC Q which completes it beforehand in a frame .
• the UC Q management module manages the permanent dialogue with the CO coupler. If this dialogue is interrupted by causing a silence greater than a predetermined duration, the UC Q module is responsible for forming a command [CDE] transmitted to the UC module and intended to guarantee the user an optimal access mode to the signal. image IMAGE, neither disturbed nor titled alternately.
• the command interpretation module UCi delivers a two-bit address word (C0, C1) to a command establishment module UC 3 .
• This module UC 3 controls the elementary switching matrix 40 in order to select one of the four inputs Ei to E 4 of this matrix 40 to be connected to the output S.
• the timer module UC4 periodically activates the module UC 3 , so that the latter controls the grid switching 40 by alternately selecting, at each delay period, the input Ei during said first duration T1 and then the other matrix input E3 or E 4 , respectively El and E2, during the second duration T3.
• the matrix is controlled by means of the parallel interface circuit 15, by loading the register associated with the corresponding processing channel and serving the output port PA of said circuit 15.
• the module UC 3 controls the switching matrix 40, simultaneously the corresponding two-bit word (C0, C1) is stored in a state storage table UC 5 .
• the matrix control words CMA1 and the address words (CO, Cl) which are stored in the table UC 5 are compared in a monitoring module UCg in order to detect a malfunction of the CA card ⁇
• the switch 31 is closed in order to guarantee the user an optimal mode of access to the image.
• the invention is also applicable to video signals other than analog video signals in color, or in black and white, of a SECAM, PAL or NTSC television standard.
• the incoming IMAGE signals in the switching grid can be primary red R, green V and blue B signals, or MAC signals (analog component multiplexing) based on compression and time multiplexing of the analog luminance and chrominance components, or digital signals.
• MAC signals the combination of images such as titration circuits are modified so that the titled signal is of the MAC type and the capturing of the title is carried out, at each of predetermined lines of an image frame, in predetermined intervals of the signal compressed luminance and compressed chrominance signal.
• each IMAGE signal processing channel in CAi to AC cards is fully implemented as digital circuits when the incoming IMAGE signals are digital.
• the application which has just been described for implementing the method of the invention in a switching grid is not limited to an image signal. It can be extended to a useful sound signal which accompanies for example the image signal, in which case the two image signals and sound form an audiovisual program.
• the alternation perturbation then applying to the useful sound signal is then for example an audio frequency signal at a fixed frequency of sinusoidal nature.
• the image disturbance signal and the fixed frequency disturbance signal can be transmitted during the same half-wave, or respectively with the useful sound signal during one half-wave and with the useful image signal IMAGE during the other half-wave.
• the main disturbance function performed in the access control module MCOM is deported to an access control module installed with a user.
• the user orders only the establishment of a crossing point in the switching grid.
• the access control module 5 mainly comprises a switching means 51 of which first and second inputs ei and e 2 respectively receive a useful image signal in response the establishment of a crossing point and a titration signal supplied by a titration module 52 or any other image disturbance module.
• This module 52 comprises a circuit 521 with programmable read-only memory EPROM and counter, scanned by line and frame synchronization signals HS and VS supplied by a time base 522 piloted by quartz.
• a line synchronization extraction circuit 53 extracts from the useful image signal a line synchronization signal which, through a low-pass filter 54, is applied in the form of a continuous signal to a direct input of a comparator 55.
• the continuous signal is compared with a predetermined voltage threshold VS in the comparator 55 which delivers a logic signal to a control input e c of the switching means 51.
• the switching means is controlled to connect the first input ei or the second input e to its output S C0M .
• the useful image signal and the titration signal are supplied alternately when a crossing point is established in the switching gate and an image signal is received by the remote access control module.
• the user ends this alternation, appearing by default, by an appropriate command transmitted to the server of the switching node which stabilizes the crossing point in the grid GC, or which authorizes the supply of the useful signal with its synchronization signals. , which therefore triggers separate pricing.
• the invention is not limited to the implementation of the method in a switching grid, but also provides for its implementation in a digital distribution network by optical fiber.
• the invention provides two different access modes to an image signal which are a disturbed access mode and an optimal or clear access mode.
• the useful IMAGE image signal is supplied alternately with a disturbance image signal.
• This access mode is selected by the user to consult the content of the image signal, for example to know the subject of a film or a documentary magazine. As soon as the user wishes to receive the image signal clearly, undisturbed by the disturbance signal, he selects the optimal access mode.
• FIG. 8 shows an access control system for implementing the method according to the invention in a digital image distribution network.
• the system comprises a time insertion device 6, a serial-parallel conversion deserializer 7a, a parallel-series conversion serializer 7b, and a safety circuit 8.
• This system is for example inserted between a switching node (not shown ) of the digital image distribution network and the user. It is assumed that the IMAGE image signal produced at the output of the switching node is of the 4.2.2 type according to Recommendation 601 of the CCIR (International Radiocommunication Advisory Committee) and comprises 625 lines per image at the rate of 50 interlaced frames per second .
• This image signal consists of a series of 10-bit multiplex binary words relating either to the content of the image, or to time marks for synchronization and suppression of line and frame.
• Each of the words relating to the content of the image consists, on the one hand, of an 8-bit word resulting from sampling and quantification over 256 levels of a luminance signal at a frequency of 13, 5 MHz or a chrominance signal at a frequency of 6.75 MHz for each of the blue and red components, and on the other hand, two bits introduced for synchronization purposes for the serial transmission of the image signal .
• the line frequency is 15 625 Hz.
• Each digital image line comprises 1728 words of which 288 are assigned to digital horizontal suppression and 1440 of which are assigned to the active part.
• 720 luminance words are alternated with the 2 x 360 words of both chrominance components.
• the deserializer 7a is designed for example around the SBX 1602 circuit of the company THOMSON and receives the image signal IMAGE formed from 10-bit binary words in series.
• the deserializer further comprises clock recovery means, decoding means and series-parallel conversion means for reproducing on 8 parallel outputs, at the frequency of 10-bit words of the incoming IMAGE signal, words to 8 parallel bits of useful signal which are contained respectively in the 10-bit words and which have been subtracted from the two bits introduced for synchronization purposes for the serial transmission of the image signal.
• the deserializer 7a also produces, at two respective clock outputs SY and CL, a frame synchronization signal SYT in response to frame time references included in the first and last lines of the even and odd frames, and a parallel clock signal HP synchronous with the 8-bit parallel words produced at the outputs of the deserializer 7a.
• the eight bits of each parallel word produced at the respective outputs of the deserializer 7a are applied to respective inputs of eight AND gates with two inputs 600a to 607a in a useful signal validation circuit 60a.
• the outputs of AND gates 600a to 607a are applied respectively to the first inputs of eight gates OR to two inputs 600c to 607c.
• Second inputs of the eight OR gates 600c to 607c are respectively connected to outputs of eight AND gates with two inputs 600b to 607b in a disturbance signal validation circuit 60b.
• First inputs of the AND gates 600b to 607b receive, at the frequency of the parallel clock signal HP, 8 parallel bits of disturbance signal words stored in a PROM memory 63, through the data bus BD of this memory 63.
• These eight-bit parallel disturbance signal words are supplied by the memory 63 in a periodic sequence of (1728 x 625/2) or (1728 x 625) eight-bit words constituting one or two image frames.
• a counter 62 whose outputs address said memory 63.
• This counter 62 is incremented by the parallel clock signal HP coming from the deserializer 7a and is reset to zero (RESET) by the frame synchronization signal SYT.
• image signal word frames and signal signal word frames disturbances are periodically multiplexed at a frequency multiple of the duration of a frame.
• a modulo-2 ° - 61 counter is incremented by the frame synchronization signal SYT, and has a qth output Sg_ ⁇ applied to a first input of an AND gate with two inputs 611, the index q being chosen arbitrarily between 1 and 1 integer Q which can be of the order of 3 to 8 for example.
• This output Sg_ ⁇ is alternately and periodically at a state "0" during 2 ⁇ ⁇ -1 successive pulses of the frame synchronization signal SYT and at a high state "1" during (2 ⁇ - 2 ⁇ 3 ⁇ 1 ) successive successive pulses of the SYT signal.
• the output of the AND gate 611 applies a validation signal through an inverter 64 to second inputs of the AND gates 600a to 607a and directly to respective second inputs of the AND gates 600b to 607b of the circuit 60b respectively.
• the AND gate 611 When the AND gate 611 is open, the gates 600a to 607a and 600b to 607b are alternately opened respectively during (2 ⁇ 3 ⁇ 1 ) successive pulses of the signal SYT and (2 Q - 2 ( 3 ⁇ 1 ) successive successive pulses of this SYT signal.
• the outputs of circuits 60a and 60b are thus validated alternately and periodically 8-bit parallel word sequences of the image signal and the disturbance signal, which are applied to eight parallel inputs of the serializer 7b through the OR gates 600c to 607c.
• the serializer 7b is designed for example around the circuit SX 1601 of the Company THOMSON. It also includes clock recovery means, parallel-to-serial conversion means and coding means, and receives at two other parallel inputs (not shown) a low state signal "0" to form with the eight bits from the OR gates 600c to 607c, 10-bit words.
• the means of coding the serializer 5b modify the state "0" of the two bits applied to the other two parallel inputs to form a synchronization digit in the 10-bit words supplied in series at an output of the serializer 7b.
• a CDE access mode control signal delivered by the user is applied to a second input of the AND gate 611.
• the CDE signal opens the gate 611 to provide at the output of the serializer 7b a image signal IMAGE 'corresponding to the disturbed access mode and resulting from an alternation of the useful image signal IMAGE and the disturbance signal.
• the CDE signal closes the door 611 and the serializer 7b delivers to the user an image signal IMAGE 'identical to the original image signal IMAGE .
• the second input of the AND gate 611 is also connected to a terminal of a safety circuit 8 comprising a voltage source + Vcc at a high state "1", a switch 80 and a protection diode 81 identical and arranged to the same way as the elements Vcc, 31 and 31a in FIG. 4.
• This safety circuit 8 is used to force, by closing the switch 80, the state of the control signal CDE applied to the second input of the door AND 61a in the low state "0" upon detection of a malfunction, in order to guarantee the user an optimal mode of access to the image.
• the output CL of the deserializer 7a applies the parallel clock signal HP to delay compensation means connected to a clock input CL of the serializer 7b intended to receive another parallel synchronization clock signal HP '. Knowing that following a rising edge of the parallel clock signal HP produced by the deserializer 7a, an 8-bit word of disturbance signal does not appear in the data bus BD of the PROM memory 63 until after a delay due to reading the memory 63, it is necessary to delay the parallel clock signal HP produced by the deserializer 7a appropriately by the parallel clock signal HP 'applied to the serializer 7b.
• This delay function is provided by the delay compensation means comprising a shift register 65, an inverter 66, two AND gates with two inputs 67a and 67b and an OR gate with two inputs 68.
• First inputs of the AND gates 67a and 67b receive the validation signal from the AND gate 611 respectively directly and through the inverter 66.
• Second inputs from the gates 67a and 67b receive the HP signal respectively through the register 65 and directly.
• the two outputs of AND gates 67a and 67b are applied through the OR gate to the clock input CL of the serializer 7b.
• the gate 67a When the validation signal from the AND gate 611 is in a high state "1" to validate the parallel words of disturbance signal at the outputs of the AND gates 600b to 607b, the gate 67a is open, and the clock signal of parallel synchronization HP is delayed by the register 65 by a duration equal to the delay in reading a word in the memory 63.
• the validation signal from the AND gate 611 is at a low state "0" to validate the words image signal useful at the outputs of the AND gates 600a to 607a, the gate 67b is open, and the parallel synchronization signal HP is reproduced without modification into the signal HP 'at the output of the OR gate 68.

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