FR2828976A1 - RECEPTION TERMINAL AND INTERACTIVE PROGRAM BROADCASTING CENTER, SIGNAL CONTAINING SUCH PROGRAMS AND METHOD FOR MONITORING INTERACTIVE PROGRAMS RECEIVED IN SUCH A TERMINAL - Google Patents

Abstract

The terminal (5) comprises an interactivity management module (51), and also a module (52) responsible for detecting a channel identifier (IDC) in the interactive programs received and responsible for notifying any change of channel identifier and/or any absence of channel identifier to the interactivity management module (51) so as to end an interactive application liable to be executed on the terminal when a change of channel identifier or the absence of such an identifier is detected. The broadcasting centre inserts the channel identifier into the interactive programs broadcast.

Description

<Desc / Clms Page number 1>

 The present invention relates to a terminal for receiving interactive programs and a center for broadcasting such programs. It also relates to a method for monitoring the interactive programs received implemented in such a terminal. It applies in particular to the field of interactive television.

 Interactive television allows a viewer to act on the progress of the programs he is watching. It can thus interact with interactive services. To do this, interactive consumer terminals are connected to one or two (as desired) communication networks from: - a bidirectional network (modem return cable, cable, etc.) of point-to-point type, such as in particular a network telephone, using one or more point-to-point servers, - and a unidirectional distribution network, such as a terrestrial TV broadcasting network, by cable or satellite, implementing one or more general broadcasting servers; By general broadcasting means the transmission of identical data to a set of destinations, whether this is carried out in particular by broadcasting, by cable or by Internet.

 The terminals considered are for example television receivers, DVB (Digital Video Broadcasting) decoders or Internet decoders.

 The interactive services are generally downloaded to the terminals by general broadcasting via the unidirectional network. They are broadcast either in addition to a traditional audiovisual program (enriched program), or on a dedicated channel without any associated audiovisual program being offered (virtual channel).

 The terminals can therefore receive: either conventional audiovisual programs, without associated interactive service; either enriched programs containing interactive services broadcast synchronously with audiovisual programs; or even interactive services broadcast on a virtual channel.

 In the following description, interactive programs will be used to designate enriched programs or interactive services broadcast on a virtual channel.

 A classic technique for broadcasting enriched programs consists of broadcasting an interactive service in a loop (broadcast in a carousel)

<Desc / Clms Page number 2>

 during the broadcast period of an associated audiovisual program. Generally, the interactive service is broadcast by a service operator via the broadcasting center of an affiliated broadcaster or broadcaster, which at the same time broadcasts the associated audiovisual program.

 The terminal first of all acquires the interactive service.

Then, the reception of a signal sent by the service operator (for example a trigger-or display-trigger signal within the framework of the ATVEF-specification for Advanced Television Enhancement Forum) causes the display a graphic or text element superimposed on the video to invite the viewer to interact with the interactive service. Optionally, at the operator's option, this invitation can be avoided and the service can then appear directly.

 The broadcasting of the interactive service is interrupted at the end of the associated audiovisual program by the sending of another signal (for example a signal to trigger the end of service or end trigger within the framework of the ATVEF) by the operator on duty. When the terminal receives this end of service signal, it eliminates the associated graphic or text display and the viewer can no longer access the interactive service.

 When interactive services are broadcast on a virtual channel, the broadcasting center reserves a particular channel on which one or more interactive services are broadcast in a loop. Generally, the broadcasting center performs a time division multiplexing of the interactive services to be broadcast and indicates, by signals broadcast on the particular channel, the start and the end of availability of the interactive services broadcast successively on the channel. Or, it performs a non-temporal multiplexing of interactive services. In this case, the terminal offers a list of services available to the user.

 It is important, in particular from the point of view of program broadcasters, that an interactive service, broadcast in an enriched program or on a virtual channel, never be displayed on a terminal at the same time as an audiovisual program to which it is not associated. Consequently, when the user of a terminal on which an interactive service is displayed changes channels (typically, when the viewer changes channels by zapping), the terminal must then interrupt the display of the interactive service (as when receives an end of service signal from the service operator) so that it does not persist at the same time as the audiovisual program broadcast on the new selected channel.

 However, this synchronization of the change of channel with the end of interactivity is sometimes problematic, in particular when the function of

<Desc / Clms Page number 3>

 management of channel (or chain) changes, also called zapping function, and the interactivity management function are not implemented by the same terminal.

 This can be the case for example when the interactive programs are received by a first terminal, in particular a decoder, to be transmitted to a second terminal, in particular an interactive television receiver, via a connection (for example scart cord) through which the audio and video signals as well as any interactive services. The zapping function is in this case managed by the decoder while the management of interactivity is managed in the television receiver. In the event of a channel change requested by the viewer, the decoder tuner performs the channel change to transmit the audio and video signals corresponding to the new selected channel to the interactive television. A problem may then arise if a previous interactive service was being displayed on the interactive television because this service will persist in superimposition compared to the video corresponding to the new selected channel, which is not satisfactory.

 The invention aims to remedy this drawback.

 The invention relates to a terminal intended to receive interactive programs transmitted by a broadcasting center and comprising a module for managing interactivity.

 According to the invention, the terminal comprises a module responsible for detecting a channel identifier in the interactive programs received and responsible for notifying any change in channel identifier and / or any absence of channel identifier to the management module. interactivity so as to terminate an interactive application capable of being executed on the terminal when a change of channel identifier or the absence of such an identifier is detected.

 According to a preferred embodiment of the invention, the channel identifier detection module is only activated when the interactive programs are received from another terminal.

 In this case, in fact, the module for managing the channel changes of the terminal is not requested because of the use of another terminal upstream of the reception of the interactive programs. It is therefore impossible for the terminal to terminate an interactive application capable of being executed, following a command from the channel change management module.

<Desc / Clms Page number 4>

 According to a particular embodiment of the invention, the channel identifier detection module is only activated when an interactive application is executed on the terminal.

 The invention also relates to a center for broadcasting interactive programs to at least one terminal as above for an affiliated service operator, characterized in that it includes a device for inserting a channel identifier in the interactive programs. broadcast, the channel identifier uniquely identifying the channel on which the interactive programs are broadcast and being intended to be interpreted by the terminal to detect any change in channel.

 According to a preferred embodiment of the invention, the channel identifier is repeated regularly in the broadcast data containing the interactive programs.

 According to another particular embodiment of the invention, the broadcasting center comprises means for multiplexing the channel identifier with data containing interactive services, and means for transmitting the data originating from the multiplexing means repeatedly during the broadcasting of an associated audio / video program.

 According to yet another embodiment of the invention, the broadcasting center comprises means for inserting display triggering and end of display signals of the interactive service in the data containing transmitted interactive services and the identifier channel is inserted into an interactive program broadcast between a first display trigger signal and a last display end signal.

 The invention also relates to a signal containing interactive programs transmitted by a broadcasting center as above and intended to be received by a terminal as described above, characterized in that it comprises a channel identifier, the identifier channel uniquely identifying the channel on which interactive programs are broadcast and being intended to be interpreted by the terminal to detect any change in channel.

 The invention also relates to a method for monitoring interactive programs received by a terminal as described above. The method consists in detecting a channel identifier in the interactive programs received and in notifying any change of channel identifier and / or any absence of channel identifier to an interactivity management module so as to end a interactive application that can be executed

<Desc / Clms Page number 5>

 on the terminal when a change of channel identifier or the absence of such an identifier is detected.

 According to a particular embodiment of the invention, the method comprises the steps consisting in: (a) extracting from the received programs the digital data not containing an audiovisual program; (b) testing whether a channel identifier is contained in said extracted digital data; and (c1) in the event of a positive response to the test in step (b), memorize (103) the detected channel identifier, and (c2) in the event of a negative response to the test in step (b), memorize (102) a default value.

 The method further includes the steps of: (d) waiting for n seconds, where n is an integer less than or equal to 10, and preferably less than or equal to 5; (e) reading the last value which was memorized in step (c1) or (c2); (f1) if the last value read is the default value, terminate an interactive application that can be executed on the terminal; (f2) if the last value read is not the default value, test if the last value read is different from the previous last value read, and - in the event of a positive response to said test, terminate an interactive application likely to '' be executed on the terminal; - in the event of a negative response to said test, repeat step (d).

 Preferably, steps (a), (b) and (c1) or (c2) are executed in parallel with steps (d), (e) and (f1) or (f2).

 The invention will be better understood on reading the description which follows, given solely by way of example and made with reference to the appended drawings in which: - Figure 1 schematically shows a set of program transmission and reception interactive devices comprising an interactive terminal and a broadcasting center in accordance with the invention; - Figure 2 shows a broadcasting center according to the invention; - Figure 3 shows an interactive terminal according to the invention; FIGS. 4A and 4B illustrate methods implemented in the terminal of FIG. 3.

<Desc / Clms Page number 6>

 In FIG. 1, a broadcasting center 1 of a broadcaster (or broadcaster) affiliated to a service operator 2 is represented. The service operator 2 broadcasts interactive services via the broadcasting center 1 which inserts the data containing interactive services in audiovisual programs that it broadcasts. The broadcasting center can also broadcast interactive services on a dedicated channel that does not contain an audiovisual program (virtual channel).

 In general, several different broadcasters are affiliated with a service operator who can thus broadcast a large number of services in different interactive programs, but for the simplicity of the description, we have only represented a single broadcasting center in FIG.

 The broadcasting center 1 transmits, through a unidirectional network 3, interactive programs (or conventional audiovisual programs) to reception devices such as the interactive television 5 or the decoder 6.

 The interactive television 5 is also connected to the service operator 2 via a bidirectional network 4, such as the switched telephone network (PSTN). This forms what is commonly called the return path for interactivity which in particular allows the viewer to interact with the interactive services broadcast by the service operator, for example to participate in a vote or a game.

 It will be noted that the invention applies both to the transmission of audiovisual programs in analog form and in digital form.

When the programs are transmitted in analog form, interactive services can be transmitted in a known manner in the VBI (for Vertical Blanking Interval), that is to say in lines of the image which do not contain no video information. The interactive services are transmitted in the form of digital data packets which are contained in several VBI lines allocated by the broadcaster to the service operator.

 When the programs are transmitted in digital form, using for example DVB technology (for Digital Video Broadcasting), the interactive services are transmitted in data packets available for auxiliary data alongside the audio-video data packets.

 Returning to FIG. 1, the interactive television 5 and the decoder 6 which are represented therein are linked together by a cord 8, for example a scart cord, through which audio and video signals pass, as well as, possibly, interactive services. .

<Desc / Clms Page number 7>

 In the example of FIG. 1, it is assumed that interactive programs are received by the decoder 6 which includes a tuner 64 and a module 65 for managing channel changes (or zapping management). When the viewer actuates his remote control 7 to choose a particular channel or to change the channel, the zapping management module 65 transmits the information to the tuner 64 which selects the chosen channel. The signals containing the interactive programs are then transmitted to the interactive television 5 via the cord 8.

 The interactive television 5 also includes a tuner 54 and a zapping management module 55 but these are shown in dotted lines in FIG. 1 because they are not used in the example described since the programs are received by the decoder 6 which transmits them to the interactive television 5.

 It will be noted that this configuration is advantageous when, for example, the decoder 6 contains a conditional access system (software embedded in the decoder and associated smart card containing a secret decryption key for example) to pay television programs. In this case, if the user wants to zap between pay channels (which he can only receive through his decoder 6) and non-pay channels (which he can receive as desired, directly on his television 5 or else via its decoder 6), it will prefer to permanently receive the programs on its decoder 6 and use the remote control 7 of its decoder to zap between the channels.

 The interactive television 5 also includes an interactivity management module 51 (for example a French browser) which manages in particular the display of interactive services on the television screen.

 According to the invention, the interactive television 5 further comprises a module 52 for detecting an IDC channel identifier. This module 52 scans the signals received by the television containing interactive programs (or conventional audiovisual programs) to detect a channel identifier there.

 In fact, according to the principle of the invention, an IDC channel identifier is inserted, in addition to the interactive service, in each interactive program broadcast by the broadcasting center. This IDC identifier, which uniquely identifies the channel on which the interactive service is broadcast, is repeated regularly during the broadcast of the interactive program, for example every four or five seconds. We then speak of diffusion in a carousel.

<Desc / Clms Page number 8>

 When an interactive program is received by the television 5, the interactivity management module 51 is responsible for displaying the content of the interactive service on the television screen and the IDC detection module 52 examines the signal received to detect and store the identifier of the IDC channel corresponding to the interactive program received.

 When the viewer actuates his remote control 7 to change the channel (or channel), the detection module 52 detects either a new IDC identifier (for example when the viewer zaps on another channel of a broadcaster affiliated with the service operator ) by comparing it to the one previously stored, ie no IDC identifier (for example when the viewer zaps on a channel of a broadcaster not affiliated with the service operator).

 In these two cases (new identifier detected or no identifier detected), the detection module 52 notifies the interactivity management module 51 that it must end the display of the interactive service in progress on the screen of the TV. This prevents an interactive service broadcast with a program on a first channel from persisting in being superimposed on a program broadcast on a second channel.

 We will now describe the implementation of the invention in the broadcasting center 1 in conjunction with FIG. 2.

 FIG. 2 illustrates the example of a center for broadcasting interactive programs in analog form. Only the elements necessary for understanding the invention have been shown in FIG. 2.

 The broadcasting center 1 comprises equipment for broadcasting audiovisual programs such as a video server 11, an automaton for executing an event list 10, an encoder 13 and a modulator 14. It also includes a data server 12 for the distribution of interactive services.

 The broadcasting center 1 is affiliated with a service operator 2 and the data server 12 of the broadcasting center is connected via a link 15, for example of the TCP / IP type (for Transmission Controi Protocol / Internet Protocol), to a system supervising the broadcasting of interactive services 21 of the service operator.

The broadcasting of an enriched program P'by the broadcasting center 1 is carried out as follows:
The broadcaster creates an execution list of events on a traffic system (not shown). The execution list is used to define the time scheduling of the programs. It is then executed by

<Desc / Clms Page number 9>

 the event list executing machine 10 which controls the devices of the broadcasting center involved in the broadcasting of the programs, that is to say the video server 11 and the data server 12 in our example, according to the information contained in this execution list (for example start / end times of programs, device to be controlled, etc.).

 The service operator 2 makes the interactive service SI available to the data server 12 a few hours before its broadcasting and it programs the data server so that it starts the broadcasting of the interactive service SI on command from the data controller. event list execution 10.

 At the programmed time, the automaton 10 controls the video server 11 and the data server 12 to synchronize the broadcasting of the audiovisual program P with that of the interactive service SI.

 The VBI encoder 13 then performs the insertion of data packets of the interactive service SI into the frame blanking intervals (VBI) of the video signal containing the program P to provide the enriched program P '. This is then modulated by the modulator 14 to be broadcast, in particular via the terrestrial radio network, to reception equipment such as interactive televisions or decoders.

 In an alternative embodiment (digital mode), the data packets containing the interactive service SI are multiplexed with the data packets containing the program P to then be broadcast according to DVB technology for example.

 According to the principle of the invention, so that the reception terminals can identify the channel on which the interactive program P is broadcast, a channel identifier IDC is added to the interactive services SI which are provided by the service operator 2 to the data server 12.

 Thus, this channel identifier IDC is inserted, with the data packets containing the interactive service SI, in the program P to form the enriched program P '.

 According to a preferred embodiment, the IDC identifier is coded on two bytes and it has the following form: PPCCC where: - PP represents the code of the country in which the broadcaster is established according to the ISO 3166-1 standard; and where - CCC represents a sequential number from 000 to 999 allowing to code 1000 different channels by country.

 Preferably, the IDC identifier is multiplexed with the data containing the interactive service SI and it is broadcast in a loop, or in

<Desc / Clms Page number 10>

 carousel)), being repeated regularly, for example every four seconds.

 In the case where the interactive service SI and the channel identifier IDC are transmitted in the VBI lines of an analog video program, the bandwidth allocated by the broadcaster to the service operator for this transmission is limited. We can therefore advantageously apply the method of managing the bandwidth of a service multiplex in an analog stream which is described in French patent application No. 99 13890, filed in the name of THOMSON multimedia, with the title Method and device. allocating bandwidth to data streams in a broadcasting network and published under No. FR 2 800 960.

 For example, we could choose to assign 2% of the bandwidth to the IDC identifier and 98% of the bandwidth to the interactive service. As the IDC identifier has a reduced size (for example 2 bytes), with a minimum of 2% of allocated bandwidth, it is ensured that the IDC identifier can be transmitted regularly with the data containing the interactive services.

 Preferably, the maximum transmission period of the IDC is 5 seconds. This ensures that at most 5 seconds after zapping on a different channel, the viewer will see the interactive application he previously viewed disappear from the screen of his television.

 On the other hand, also in order to reduce the use of bandwidth for the transmission of the IDC identifier, it is only broadcast when an interactive application is displayed on the screens of viewers. In practice, the identifier IDC is broadcast by the service operator between a display trigger signal of the interactive service SI and an end of service signal.

 As part of the ATVEF specification, the service operator broadcasts a display trigger signal several times during the broadcast of the interactive service. This signal causes either the display of a graphic or text element on the interactive TV screen to invite the viewer to interact with the service, or directly the display of the interactive service itself (for example a game or a vote concerning the audiovisual program broadcast at the same time). If the operator wishes to make the service available to viewers throughout the associated program, then the display trigger is broadcast in a carousel during the entire broadcast of the associated audiovisual program. If, on the other hand, the operator wishes the interactive service to be available only to viewers

<Desc / Clms Page number 11>

 having followed the broadcast from the start, then the operator stops broadcasting the display trigger after a few seconds.

 The interruption of the display of the interactive service is then caused by the transmission of end of service signals (end trigger) by the service operator. The end trigger is transmitted several times to ensure that all interactive terminals receive it even in the event of poor transmission quality.

 According to a preferred embodiment of the invention, the channel identifier IDC is therefore broadcast between the first transmission of the display trigger signal and the last transmission of the end signal of the interactive service SI.

 Thanks to this arrangement, it is possible to have all of the bandwidth when no interactive service is broadcast, for example to update, via the general broadcasting network 3, the software embedded on the terminals. interactive service reception.

 The implementation of the invention in an interactive terminal such as the television 5 will now be described in conjunction with FIG. 3 and with FIGS. 4A and 4B.

 In Figure 3 have been shown the various software components necessary for the implementation of the invention.

 The interactive terminal 50 is for example an analog analog television such as the television 5 of FIG. 1. It comprises a component called Driver VBI (or pilot VBI in French) 56 responsible for extracting the digital data packets transported in the VBI lines of the received video signal. In an alternative embodiment (digital mode), this component is replaced by a demultiplexer which extracts the digital data packets containing the interactive service and the channel identifier from the rest of the digital data containing the video and the audio.

 The VBI Driver retrieves on the one hand the interactive service SI which it transmits to a 510 component called Browser (or navigator in French) implementing the management of interactivity and on the other hand the IDC channel identifier that it transmits to a component 520 called Middleware (or intermediate software in French). It will be noted that similar software components are used when working in digital for the reception of interactive programs.

 The Browser 510 manages the interactive services. It causes interactive applications to be displayed or deleted on the terminal screen (or on the screen

<Desc / Clms Page number 12>

 a display device connected to the terminal if the latter is not a television for example), it processes the commands it receives from the user via a remote control (not shown) and executes the actions requested (such as hyper-navigation, script execution, etc.).

de scripts JavaScript (JavaScript est défini par les normes ECMA-262 et ISO 10262) ou d'applicatifs en byte-code (ou code 8 bits ) de type OpenTVTM ou Java. ( OpenTV et Java sont des marques déposées respectivement par OpenTV et Sun Microsystems. An interactive application 53 is also represented in FIG. 3. These can be HTML pages (for Hypertext Markup Language),

JavaScript scripts (JavaScript is defined by ECMA-262 and ISO 10262 standards) or applications in byte-code (or 8-bit code) of OpenTVTM or Java type. (OpenTV and Java are registered trademarks of OpenTV and Sun Microsystems respectively.

 Middleware 520 acts as an intermediary between interactive applications and a low-level software layer that controls the components of the terminal. In the context of the invention, the Middleware implements the method for detecting the IDC channel identifier and stopping the interactive application in the event of a channel change.

 In practice, two series of instructions illustrated by FIGS. 4A and 4B are executed in parallel by the Middleware 520 to implement this method.

 The first series of instructions (FIG. 4A) comprises a step 100 during which the data contained in the lines V81 of the video signal received by the terminal are recovered by the Middleware. Note that as a variant (digital mode), this is data from a demultiplexer.

 In step 101, a test is carried out to find out whether an IDC channel identifier is contained in the data received.

 If an IDC is detected (answer yes to test 101) then the value of the IDC identifier is stored in a memory 57, for example a RAM memory (of Random Access Memory) of the terminal, in step 103.

 If no IDC is detected (response no to test 101), then a default value, for example -1, is stored in memory 57 in step 102.

 The series of instructions continues with a return to step 100.

 The second series of instructions executed in parallel by the Middleware 520 (Figure 4B) comprises a first step 200 which consists in triggering a timer (or timer in French) expiring after n seconds and, at the expiration of these n seconds , to read the last value of IDC stored in memory 57 during a step 201. The value of n depends on the frequency of broadcasting of the channel identifier chosen by the service operator. We could for example choose n = 4. Indeed, this value must remain

<Desc / Clms Page number 13>

 low because it is directly linked to the time during which an interactive application will continue to be displayed on the screen despite a change of channel.

 In the next step 202, a test is carried out to find out whether the IDC identifier read is equal to -1 (the default value) or not. If the answer is no, then the series of instructions continues with step 203 where a test is carried out to find out whether the IDC identifier read in step 201 is different from the previously stored IDC (which is also stored in memory 57). It will be noted that two IDC identifier values are permanently memorized: the last value acquired as well as the previous value.

 If the answer to this test 203 is yes, that is to say if the viewer has zapped on another channel of a broadcaster affiliated with the service operator, then the series of instructions continues with step 204 during from which a message is sent to Browser 510 to end the interactive application 53 being displayed, if there is one.

 If the answer to test 202 is yes, that is to say if the viewer has zapped on a channel of a broadcaster not affiliated with the service operator, then the series of instructions continues with step 204 as follows -above.

 If, on the other hand, the response to test 203 is no, that is to say if the viewer has not zapped on another channel during the last n seconds, the series of instructions continues with a return to step 200.

 It will be noted that, in a preferred embodiment of the invention, the method which has just been described is executed by the Middleware 520 only when an interactive application is displayed on the screen. The information according to which an application is or is not being displayed is for example given by the Browser 510 to the Middleware 520.

 Furthermore, still according to this preferred embodiment, the method of detecting the channel identifier and stopping the interactive application in the event of a channel change described above is only executed when the interactive programs are received from 'another terminal. In other words, the method is only executed when one is in a situation such as that described in FIG. 1 where the programs are received by a decoder 6 which manages the channel changes to be transmitted to a interactive television 5 in which the interactivity management is carried out. Middleware has the possibility of knowing how it is supplied with interactive programs. If the interactive program stream arrives at it via an auxiliary baseband input, this means that the programs are received via another terminal and that the method must be implemented.

<Desc / Clms Page number 14>

 previously described. On the other hand, if the stream of interactive programs arrives at it via its main modulated input, this means that the programs are received directly by the terminal.

 The rest of the time, the part of software which executes the method described above is inactive, which saves the load of the central processor (not shown) of the terminal.

Claims (14)

1. Terminal (5) intended to receive interactive programs transmitted by a broadcasting center (1) and comprising an interactivity management module (51), characterized in that it comprises a module (52) responsible for detecting a channel identifier (IDC) in said interactive programs received and responsible for notifying any change of channel identifier and / or any absence of channel identifier to said interactivity management module (51) so as to terminate an interactive application capable of being executed on said terminal when a change of channel identifier or the absence of such an identifier is detected.  2. Terminal according to claim 1, characterized in that said module (52) for channel identifier detection is activated only when said interactive programs are received from another terminal (6).  3. Terminal according to one of claims 1 or 2, characterized in that said module (52) of channel identifier detection is activated only when an interactive application is executed on said terminal.  4. Broadcast center (1) of interactive programs to at least one terminal according to one of claims 1 to 3 for an affiliated service operator (2), characterized in that it comprises a device (12,13) d insertion of a channel identifier (IDC) in said interactive programs broadcast, said channel identifier (IDC) uniquely identifying the channel on which said interactive programs are broadcast and being intended to be interpreted by said terminal to detect any change in channel.  5. Broadcast center according to claim 4, characterized in that said channel identifier (IDC) is repeated regularly in the broadcast data containing said interactive programs.  6. Broadcasting center according to one of claims 4 or 5, characterized in that it comprises means (12) for multiplexing said channel identifier (IDC) with data (SI) containing interactive services, and means (13) to transmit said data from <Desc / Clms Page number 16>  means for multiplexing repeatedly during the broadcast of an associated audio / video program.  7. Broadcasting center according to one of claims 4 to 6, said broadcasting center comprising means for inserting display triggering and end of display signals of the interactive service in the data containing transmitted interactive services, characterized in that the channel identifier (IDC) is inserted into an interactive program broadcast between a first display trigger signal and a last display end signal.  8. Signal containing interactive programs transmitted by a broadcasting center according to one of claims 4 to 7 and intended to be received by a terminal according to one of claims 1 to 3, characterized in that it comprises an identifier of channel (IDC), said channel identifier (IDC) uniquely identifying the channel on which said interactive programs are broadcast and being intended to be interpreted by said terminal to detect any change in channel.  9. Signal according to claim 8, characterized in that said channel identifier (IDC) is coded on two bytes.  10. Signal according to one of claims 8 or 9, characterized in that the channel identifier (IDC) has the following format: PPCCC where PP represents a country code and where CCC is a sequential number from 000 to 999.  11. Method for monitoring interactive programs received by a terminal according to one of claims 1 to 3, characterized in that it consists in detecting a channel identifier (IDC) in said interactive programs received and in notifying any change of channel identifier and / or any absence of a channel identifier in an interactivity management module so as to terminate an interactive application capable of being executed on said terminal when a change in channel identifier or the the absence of such an identifier is detected.  12. Method according to claim 11, characterized in that it comprises the steps consisting in: <Desc / Clms Page number 17>  (a) extracting (100) from the received programs the digital data not containing an audiovisual program; (b) testing (101) if a channel identifier (IDC) is contained in said extracted digital data; and (c1) in the event of a positive response to the test in step (b), memorizing (103) the channel identifier (IDC) detected, and (c2) in the event of a negative response to the test in step (b ), store (102) a default value (-1).  13. Method according to claim 12, characterized in that it further comprises the steps consisting in: (d) waiting for n seconds (200), where n is an integer less than or equal to 10, and preferably less than or equal to 5 ; (e) reading (201) the last value which was memorized in step (c1) or (c2);

 (f1) if the last value read is the default value (-1), terminate (204) an interactive application capable of being executed on said terminal; (f2) if the last value read is not the default value (-1), test (203) if the last value read is different from the last previous value read, and - in the event of a positive response to said test (203 ), terminate (204) an interactive application capable of being executed on said terminal; - in the event of a negative response to said test (203), repeat step (d).  14. Method according to claim 13, characterized in that steps (a), (b) and (c1) or (c2) are executed in parallel with steps (d), (e) and (f1) or (f2 ).