FR3001352A1 - Method for recording and playing broadcast digital service received in scrambled form by e.g. digital TV, involves generating replacement table, transferring output stream including table, and recording stream to host equipment - Google Patents

Abstract

The method involves extracting input transport stream from transport packets received from host equipment (1), and selecting the packets in the stream during recording phase. An identifier of table is recovered from a service listened by the equipment, and recording stream and the packets are received from an external memory medium (8). An identifier of elementary stream of the recorded service is recovered in the stream. A replacement table is generated from the identifiers. An output stream including the replacement table and recording stream is transferred to the equipment. Independent claims are also included for the following: (1) an access control module associated with host equipment for receiving an input transport stream (2) a data transport stream delivered by an access control module for reading a recording stream corresponding to a broadcasted digital service.

Description

The present invention relates to an improvement relating to the functionalities offered by the common interface modules for the access control of the services recorded by PCMCIA access control modules. digital television programs. Such a common interface module, also called PCMCIA module, is conventionally used in association with a host equipment (digital television, or any other digital television signal receiver equipment such as a decoder (satellite, terrestrial, cable) or a receiver. IP receiver, to descramble MPEG2 or IP type television / digital radio television signals that are received in scrambled form (DVB scrambling for MPEG2 standard, or AES scrambling for IP standard) by the host equipment .

The operation and interaction between any PCMCIA module and any host equipment equipment in which a PCMCIA module is inserted are defined by the "Common Interface" (EN50221) and "CI + V1.3" standards. FIG. 1 schematically illustrates the principal components of a host device 1 and a PCMCIA module 2 for controlling access to certain live channels, in the nonlimiting example of a broadcast according to the MPEG2 standard. In FIG. 1, as well as in all the appended figures, the optional components are represented by rectangles in broken lines. Firstly, the installation procedure of the host device 1 and its operation for the reception of a channel in the absence of the PCMCIA 2 module will be described: the host equipment 1, for example a digital television, conventionally comprises a digital receiver consisting mainly of a tuner 10, a demodulator 11, a demultiplexer 12 and an MPEG decoder 13. All of these elements operates under the control of a microcontroller 14. The signal RFIN television received at the input of the tuner 10 is demodulated by the demodulator 11 which consequently delivers a TSIN transport stream. Different data contained in this stream are separated by the demultiplexer 12, in particular the data relating to the audio and video signals likely to be present in the TSIN transport stream, these data then being decoded by the MPEG decoder 13 in order to be played on the speakers and the display (not shown) integrated or associated with the host equipment 1.

In the case of digital television, a transmission channel carries several services of different nature, each consisting of at least one elementary stream ES, as well as information that enables the receiving equipment to know the nature and composition of the services present in the transport stream. This information is carried in different tables. In particular, in accordance with the standard EN 300 468 V1.12.1, the MPEG-2 standard defines two types of mandatory tables that must be transmitted in the transport stream: - the program correspondence tables, or PMT tables (English initials); saxons set for Program Map Table), each PMT table being relative to a service (television or radio channel) present in the transport stream and thus including a description of the characteristics and components of this service (for example video, audio in French, audio in English, subtitling in French ...). Each PMT table also indicates whether the associated service is scrambled or not, by means of one or more encryption identifiers called CA_descriptors; the program association table, or PAT (Program Association Table) which associates each service present in the transport stream with a PMT table. The DVB standard imposes the use of the service description table, or SDT (set in English for Service Description Table) table, which makes it possible to match the name of a string (as known by the end user) and its program number ("program_number"). As shown diagrammatically in FIG. 2, the TSIN transport stream therefore comprises a succession of TP transport packets of different types, in particular TPES transport packets relating to the services themselves, and TPPMT, TPPAT and TPsDT transport packets relating to each other. PMT tables, the PAT table, and the SDT table. Whatever the type of TP transport packet, the latter is generally composed of 188 bytes and comprises: a header field 3 including a PID identifier for uniquely recognizing the nature of the packet. In particular, the standards require the use of a PID equal to 0 for the PAT table, a PID equal to 11 for the SDT table, the PID corresponding to the services being left to the discretion of the operators. - A data field 4 which corresponds to the content. To fix ideas, Table 1 below gives an example of the structure of TP transport packets received when the TSIN transport stream is intended to transmit two television channels named channel 1 and channel 2, each channel comprising a video signal and an audio signal, the channel 1 being scrambled DVB and the channel 2 being broadcast in clear. The two channels therefore each have two elementary streams ES (one for audio, the other for video). Nature PID packet TPPMT data field String 1 PMT1 PID_ES Type ES + CA_descriptor PID1 audio PID2 video TPPMT String 2 PMT2 PID_ES Type ES PID3 audio PID4 video TPPAT (PAT Table) 0 PID_PMT Program_number PMT1 1 PMT2 21 TPsDT (SDT Table) 11 Name of channel Program_number Channel 1 1 Channel 2 21 Audio Channel 1 PID1 Audio content Video Channel 1 PID2 Video content Audio Channel 2 PID3 Audio content Video Channel 2 PID4 Video content Table 1 Of course, there will usually be several PID1 identifier packets in the stream , PID2, PID3 and PID4. Similarly, the packets corresponding to the PMT, PAT and SDT tables are regularly transmitted to take account of possible updates.

Referring back to FIG. 1, at the time of installation of the host device 1, the latter will first of all set up a filter to extract, via the demultiplexer 12, the TPSDT and TPPAT transport packets respectively corresponding to the SDT and PAT tables. By combining the information extracted from these two tables, he will be able to create and store in an integrated memory 15: - a list of channels, with the names of channels from the SDT, that he can propose to the user for the channel changes; - triplets associating the name of each string with its program number (Program_number in table 1 above) and its identifier in the PMT table (PID_PMT in table 1 above). When the user wishes to watch and / or listen to a particular service associated with a channel, for example by selecting this service by means of a remote control 16, the host device 1 receives the control signal from the user and retrieves from the memory 15 the program number (Program_number) of this string and its PMT identifier (PID_PMT). The host device 1 can then apply a filter to extract from the TSIN transport stream the TPPAT transport packets of the PMT table corresponding to this PMT identifier. From an analysis of the contents of these transport packets, the host device 1 can extract all the identifiers linked to the elementary streams ES of this chain (PID_ES in Table 1 above). It is then able to set a new filter to extract from the TSIN transport stream the TPES transport packets corresponding to each of the identifiers PID_ES linked to the elementary streams ES. The signals recovered at the demultiplexer 12 are then decoded by the MPEG decoder 13 to be played on the screen and the speakers integrated or associated with the host equipment. In the example given above, the channel 2 is broadcast in clear, so that the user who selected the channel 2 can actually see the images and hear the associated soundtrack. On the other hand, in the absence of the PCMCIA 2 module, the images and / or the sound associated with the string 1 will be unintelligible for the user since the latter is scrambled DVB (presence of the CA_descriptor in the PMT table of the string 1). It should be noted at this level that an elementary stream ES included in a service can be scrambled by several access control systems, each system being identified by a unique identifier (CA_system_id in the I5013818-1 standard). This practice, known as Anglo-Saxon Simulcrypt, allows to have several offers of subscriptions for the same service without having to send several times this service. As indicated above, the information relating to the fact that an elementary stream ES of a service is scrambled is indicated by the presence of a CA_descriptor identifier in the service's PMT table, this identifier including the CA_system_id identifier of the control system access used to scramble the flow. If an elementary stream is scrambled by several systems, a CA_descriptor identifier for each control service used, containing the CA_system_id identifier of the access control system, will be present in the service's PMT table. Of course, the PCMCIA module that must be used to descramble the stream must support at least one of the access control systems used to scramble the stream. The conventional procedure of installing the PCMCIA 2 module for access control and its operation to enable a user to make intelligible the images and / or the soundtrack associated with a scrambled DVB service will now be described: As shown on the right-hand part of FIG. 1, a conventional PCMCIA module 2 for access control comprises a demultiplexer 20, a software module 21 for descrambling DBV or AES according to whether the transport stream to be processed is an MPEG stream or an IP stream , and a software module 22 known as the CAS module (English initials set for Conditional Access Support) in connection with the demultiplexer 20 and the module 21 descrambling. All of these elements operate under the control of a microcontroller 23. The PCMCIA module 2 can furthermore also include a card reader 24 capable of receiving a smart card with which the CAS module 22 can communicate. To further improve security and avoid any hacking of the PCMCIA module output stream, the CI + specification has modified the EN50221 specification by requiring that the elementary streams descrambled by a PCMCA module be re-encrypted into AES or DES before transmission to the host equipment. . Also, if the PCMCIA 2 module is a CI + module, it must also include a software module 25 CI + encryption whose input is connected to the output of the module 21 descrambling. Of course, in this case, the host equipment 1 must also integrate a software module 17 decryption CI +. Finally, the PCMCIA module comprises a storage memory 26. The conventional PCMCIA module 2, whether it is CI or CI + compatible, is able to be connected to the host equipment 1, for example inserted in a slot or a cavity the host equipment 1 provided for this purpose, for exchanging transport streams and control signals. In particular, a bidirectional PCMCIA bus 5 is provided to allow the exchange of control signals between the two microcontrollers 14 and 23. In addition, a transport bus is used between the host equipment 1 and the PCMCIA module 2. On the Figure, this transport bus is referenced 6 to identify the TSIN transport stream transiting from the output of the demodulator 11 of the host equipment 1 to the input of the demultiplexer 20, and this same bus is referenced 7 to identify the transport stream TSouT in return.

According to current standards, the output stream TSouT must include all the packets initially present in the TSIN input stream, except that the scrambled packets corresponding to the service listened to by the host device 1 have been replaced by descrambled packets, and possibly enciphered CI +. The role of the PCMCIA 2 module is therefore to descramble the packets of the service or services listened to, and to copy in the output stream the entire input stream while replacing the scrambled packets of the service or services listened to by descrambled packets.

At the time of installation of the module 2 in the host equipment 1, and each time the host equipment is started, a certain amount of information will be exchanged on the PCMCIA bus 5 between the two devices. In particular: the PCMCIA module 2 sends to the host device 1 a list of all the CA_system_id identifiers of the access control systems that it supports, by a specific message (CA_info message according to the EN50221 standard). This list can be stored in the CAS module 22 or in a smart card present in the reader 24. Once received, this list is stored by the host device 1 in its memory 15. - In the case of a PCMCIA module CI + compatible, the host device 1 and the PCMCIA 2 module constantly exchange the information used to define the CI + encryption keys. In addition, as soon as the host device 1 detects the presence of the PCMCIA 2 module, the TSIN transport stream necessarily passes through the PCMCIA bus 6. When, consequently, the user wishes to watch and / or listen to a particular service associated with a PCMCIA bus. scrambled channel, for example by selecting this service by means of the remote control 16, the host equipment 1 knows in particular: - recover the identifier PID_PMT of the PMT table associated with this service; and - determining that the string is scrambled according to one or more systems if one or more CA_descriptor identifiers appear in the PMT table associated with this service. The host device 1 can then compare the list of CA_system_id identifiers of the access control systems used for the scrambling to compare it with the list of CA_system_id identifiers of the systems supported by the module 2.

In case of correspondence with at least one system, the host device 1 sends to the module 2, via the PCMCIA bus 5, one or more requests for descrambling one or more services' in the form of one or more commands CA_PMT commands CA_PMT as defined in the EN50221 standard, each command containing the program number (Program_number) and the elementary streams of the service that must be descrambled. Once the commands have been received, the various program numbers are extracted and stored by the PCMCIA module 2 in its memory 26. Upon receipt of a CA_PMT command, the PCMCIA module 2 converts this CA_PMT into a request for the CAS module 22 which uses in turn the various resources available in the PCMCIA module 2 (smart card reader 24 if present, demultiplexer 20 and descrambling module 21) for controlling the selective descrambling of scrambled packets TPEs corresponding to the listened string and contained in the stream of transport received TSIN. At the output of the PCMCIA 2 module, the TSOUT transport stream thus comprises: in unchanged form, the TPE transport packets corresponding to elementary streams ES originally in the clear (not scrambled), as well as the TPE transport packets corresponding to ES elementary streams originally scrambled but for which either, the host device 1 made no decryption request, ie, the CAS module 22 could not find rights (unsupported or unsubscribed access control services ). in the descrambled form (and possibly CI +), the TPE transport packets corresponding to originally scrambled elementary streams ES for which the host equipment 1 has made a decryption request, and the CAS module 22 has been able to find rights. The TSOUT output stream is then supplied if necessary to the decoding module CI + 17, and in all cases to the demultiplexer 12 and to the decoder 13 of the host equipment 1, which finally delivers image and sound signals for the user, associated with the chain on listening. It will be understood from the foregoing that the above-mentioned operation of a host equipment in association with a control PCMCIA module only concerns the possibility of playing in clear and in real time the initially scrambled program (s) chosen by a user at the same time. the host equipment.

However, the technological evolution of the PCMCIA access control modules makes it possible to envisage the implementation of new functionalities, such as the integration of a USB type serial interface. With such an interface, it could in particular connect this PCMCIA module to an external hard drive, by a USB type connection. Such a PCMCIA module thus theoretically offers an additional function of digital recording on hard disk, and an additional function of replaying such a recording. In practice, however, the implementation of these recording / playback functionalities encounters various problems related to the operation of the host equipment on the one hand, and the PCMCIA modules on the other hand, as imposed by the current standards. In particular, the applicant's tests have shown that a recording method which consists of recording on a data medium a data stream comprising only the TPES transport packets descrambled by the PCMCIA module and corresponding to the registered service does not would allow the replay of this recorded data stream only if the host equipment listens, at the time of the replay, the same service as the one that was the subject of the recording. Indeed, most of the existing host equipment on the market can only listen to one service at a time. In rarer cases, some host devices know how to listen to two channels, a channel that is played live, and another channel that is either played as an overlay (PIP option, English initials set for Picture-In-Picture), recorded in a recorder built into the host equipment. As a result, it is not intended at this time to be able to replay a record provided via a PCMCIA module when the registered service is different from the current service (as listened to by the host equipment). . A solution to this problem must therefore be found. In addition, the solution must remain compatible with current standards which dictate that, when a host device provides a TSIN input stream to the PCMCIA module, the latter must output a TSout output stream corresponding to the input stream with certain TPES packets possibly replaced in case the current service is scrambled. The present invention fulfills these objectives by providing a method for recording a broadcast digital service received in scrambled form by a first host device and for replaying the recorded service, the method comprising: a recording phase in which a first access control PCMCIA module: - extracts from an input transport stream received from the first host device 10 transport packets corresponding to a PMT program matching table uniquely associated with the service to be recorded; - selects in said input transport stream transport packets corresponding to elementary streams uniquely associated with the service to be registered and descrambles the selected transport packets; Transferring the extracted transport packets and a recording stream composed of the descrambled transport packets to an external storage medium for recording; and a replay phase, on the first host device or a second host device, of the registered service, in which the first PCMCIA module or a second access control PCMCIA module: - retrieves a PID identifier from the PMT table of the current service listened to by the first or second host equipment; receives from the external storage medium the recording stream and the extracted transport packets; 25 - retrieves in the extracted transport packets PID identifiers of the elementary streams of the registered service; generates a replacement PMT table from the PID identifier of the PMT table of the current service and the PID identifiers of the retrieved elementary streams; and 30 - transfers to the first or second host equipment an output stream comprising only the replacement PMT table and the registration stream.

According to other particularly advantageous possible characteristics: the replacement PMT table is generated in the form of one or more transport packets each comprising a data field and a header field with a PID identifier uniquely associated with the PMT table of replacing the PID identifier of its header field comprising the PID identifier of the PMT table of the current service, and the data field comprising the PID identifiers of the retrieved elementary streams; an encryption identifier may further advantageously be inserted in the data field of the replacement PMT table; an encryption of the recording stream, for example according to an AES algorithm, can be carried out before its transfer for recording; in this case, the corresponding decryption of the recording stream must also be performed before it is transferred for replay; A CI + encryption of the output stream before it is transferred to the first or second host equipment. The subject of the invention is also a PCMCIA type access control module able to be associated with a host device, on the one hand, to receive an input transport stream comprising scrambled transport packets and on the other hand on the other hand, transmitting to the host equipment a first output stream corresponding to the input transport stream in which some of the scrambled transport packets have been optionally descrambled, characterized in that it includes, for recording purposes, a digital television service received in scrambled form, means for generating a recording stream, able to extract from the input transport stream transport packets corresponding to a PMT program matching table uniquely associated with service to be recorded, to select in said input transport stream transport packets corresponding to elementary streams of the service to be recorded, to Descrambling the selected transport packets and outputting the recording stream composed of the descrambled transport packets, and transfer means adapted to transfer the extracted transport packets and the recording stream to an external storage medium for recording; and, for purposes of replaying the recording stream on the first host device or a second host device, means for generating an output stream able to: - recover a PID identifier from the PMT table of the current service listened to by the first or second host equipment; receiving from the external storage medium the recording stream and the extracted transport packets; recovering in the extracted transport packets the PID identifiers of the elementary streams of the registered service; generating a replacement PMT table from the PID identifier of the PMT table of the current service and the PID identifiers of the retrieved elementary streams; and - generating a second output stream comprising only the replacement PMT table and the recording stream, for transfer to the first or second host equipment in place of the first output stream. In a preferred embodiment: the means for generating an output stream comprises a flow management injector adapted to simultaneously receive the recording stream to be replayed and a transport stream of a descrambling module of the control module. accessing and outputting only the replay record stream for transfer to the first or second host equipment in place of the first output stream; and / or the module is able to simultaneously generate the first output stream for the live playback of a first service listened to by the first host equipment, and a recording stream for recording the first service listened to, or another service received by the first host device; and / or the access control module also comprises means for programming the recording of the delayed service. The subject of the invention is also a data transport stream delivered by a PCMCIA module for controlling access to a host device for the replay of a recording stream corresponding to a digital television service, characterized in that it includes only the record flow composed of descrambled transport packets corresponding to streams elementary to said service, and a replacement PMT table generated from a PID of the PMT table of the current service listened to by the host equipment before replay , and PID identifiers of the elementary streams composing the recorded digital service. The invention and the advantages it provides will be better understood from the following description of a nonlimiting example of implementation of the invention, with reference to the appended figures, in which: FIG. described above, schematically represents the conventional interaction between a host equipment and a PCMCIA module for the control of direct access to encrypted television programs; FIG. 2, already described above, schematically illustrates the conventional structure of a transport stream transmitted by the host device of FIG. 1 to the PCMCIA module. FIG. 3 diagrammatically represents the physical interaction according to the invention between a host device and a PCMCIA module for recording on an external hard disk and replaying a service broadcast in scrambled form; FIG. 4 illustrates various steps that can be implemented according to the invention as part of a procedure for registering a service by the access control module of FIG. 3; FIG. 5 illustrates various steps that can be implemented according to the invention as part of a replay procedure of a service registered by the access control module of FIG. 3; FIG. 6 schematically illustrates an exemplary structure of a transport stream transmitted by the PCMCIA module to the host equipment of FIG. 3 in the case of a replay.

FIG. 3 shows some of the elements already described above with reference to FIG. 1, in particular: the host equipment 1, identical at all points with the host equipment of FIG. 1; a PCMCIA access control module 2, which is CI + or at least CI compatible, comprising all the elements already described in the context of FIG. 1; the PCMCIA bus 5 allowing the host equipment 1 and the PCMCI module 2 to exchange control signals; the transport buses 6 and 7 for transporting the TSIN and TS ouT streams. In the context of the invention, the access control PCMCIA module 2 is furthermore capable of being connected to an external memory device 8, such as external hard disk, via a connection port managed by a controller 27 and an additional digital link, for example USB type. Given the congestion constraints related to the module 2, the connection port can be advantageously provided at an accessory (not shown) which cooperates with the module 2. The PCMCIA module 2 further comprises the following elements: a software module 28 for human-machine interface or MMI (English initials set for Man-Machine Interface); a software module 29 for controlling in particular the CAS module 22 during the recording or playback of a registered service; an injector 30 for the management of the transport flows during the replay of a registered service; optionally, an AES type encryption software module 31 and its associated decryption software module 32. The operation of the PCMCIA module 2 for a registration of a service chosen by the user will now be described with reference to FIG. 4. A registration procedure first requires a phase 100 of selection by the user of the service in question. save. Two scenarios are then to consider. The first case is where the user wants to record live a service, even while simultaneously watching this service on the host equipment, or any other service broadcast in parallel. The second case is where the user has programmed a recording (delayed recording). In both cases, the selection or programming is carried out via a user interface GUI displayed on the screen associated with the host equipment 1 under the control of the MMI module 28. At the moment when the recording must begin (immediately in the first case, at the programmed time and stored in the memories 15 and 26 respectively associated with the host equipment 1 and the PCMCIA module 2 in the second case), the PCMCIA 2 module receives on the bus 6 a stream TSIN input transport (step 110 in FIG. 4). As previously indicated, this TSIN input transport stream comprises TPES transport packets carrying ES elementary stream contents associated with a plurality of digital services (including the service to be recorded), received by the first host equipment 1 , transport packets TPpmT carrying contents of PMT program matching tables, each PMT table being uniquely associated with one of the plurality of digital services, transport packets TRDAT carrying contents of a PAT table program association, and TPSDT transport packets carrying contents of an SDT service description table, each of said TPES, TPPMT, TRDAT, TPSDT transport packets having a header field with a PID identifier uniquely associated with the type of the package. The PCMCIA module 2 then extracts from the TSIN input transport stream the TPpmT transport packets corresponding to the PMT table of the service to be recorded, and selects in the TSIN input transport stream the TPES transport packets corresponding to the elementary streams ES of the service to be recorded (steps 120 and 130). These steps 120 and 130 have been shown as performed in parallel but can of course be done successively and in any order. In practice, these steps are triggered by a particular command of the module 29 asking the CAS module 22 to descramble the service to be recorded, possibly in addition to a service listened in parallel on the host equipment 1. This particular command is similar to a CA_PMT type command that would have been received by the PCMCIA bus 5 as part of a conventional descrambling of a live channel. The CAS module 22 can then control the demultiplexer 20 so that it is interested in TPpmT and TPES transport packets of the service to be recorded.

The PCMCIA module 2 then descrambles the selected TPES transport packets (step 140), in practice by a particular command from the CAS module 22 which requests the descrambling module 21 to effectively descramble these transport packets. The record stream TS2ouT composed of the descrambled transport packets the extracted TPPMT transport packets corresponding to the service to be recorded are then transferred to the external storage medium 8 for recording (step 160). Optionally, but nevertheless preferred because the operators generally require that it is not possible to record in plaintext a scrambled program, an encryption, for example of the AES type, the recording stream TS2ouT is performed before its transfer for recording (step 150). It should be noted at this point that the registration procedure as described above remains compatible with the standards. Indeed, the standards require that if we look at an input stream, then we must have an output flow corresponding to the input stream with some packets replaced, the goal being that the host equipment can always play any service. Here, if a recording is done while the user is also watching television (either the same channel as the one recorded, or more generally another channel), the output of the PCMCIA 2 module is: - a first output stream transferred to the bus 7, in all respects identical to the TSout output stream described in relation to FIG. 1, ie comprising: in unchanged form, the TPES transport packets corresponding to elementary streams ES originally in the clear (not scrambled), as well as the TPES transport packets corresponding to originally scrambled ES elementary streams but for which either the host device 1 made no decryption request, or the CAS module 22 could not find rights (control services unsupported or unsupported access). in the form of descrambled (and possibly re-encrypted CI +) TPES transport packets corresponding to originally scrambled elementary streams ES for which the host equipment 1 has made a decryption request, and the CAS module 22 was able to find rights. a second TS2ouT output stream intended for recording. During a delayed recording (ie without simultaneously watching the TV), the output of the PCMCIA module 2: - a first output stream transferred on the bus 7, identical in all respects to the input stream TSIN, however, this is not a problem because in this case the host equipment does not need to play a service. a second TS2ouT output stream intended for recording. The operation of the PCMCIA module 2 for the playback of a registered service will now be described with reference to FIG. 5. It should be noted here that the host equipment 1 on which the registered service is going to be read can be the same as that used for registration or other equipment. Similarly, the PCMCIA 2 module used for replay may be the same as that used for recording, or another PCMCIA module. A replay procedure requires a prior phase 200 selection by the user of the recorded service to reread. The selection is made via a user interface GUI displayed on the screen associated with the host equipment 1, for example under the control of the MMI module 28. The PCMCIA module 2 first retrieves the PID identifier of the PMT of the current service listened to by the host equipment 1 (step 210). To do this, it first retrieves the program number (Program_number) of the current service as listened to by the host equipment 1 (step 211). As previously mentioned, this program number was normally stored in its memory 26 at the time the service was selected by the user on the host equipment 1, the host equipment 1 then transmitting this information to the module via the bus. PCMCIA 5. As the PCMCIA module 2 also receives the TSIN input stream (step 212) comprising in particular the program association PAT table, it can then command the extraction of the PID identifier of the PMT of this service. current using the received PAT table (step 213).

The PCMCIA module 2 then receives from the external memory support 8 the recording stream TS2IN, which corresponds to the recording stream TS2ouT, and the extracted TPPMT transport packets associated with the registered service (step 220). If the packets of the recording stream have been encrypted at the time of recording (step 150 of FIG. 4), then they are again decrypted according to the corresponding algorithm (step 230). AES encryption / decryption can be defined so that only the PCMCIA module used to register the service can re-read the registered service. Alternatively, PCMCIA modules of the same group may be allowed to replay services registered by any of the modules in the group. The PCMCIA module 2 can then retrieve in the extracted TPPMT transport packets that have been stored in the external storage medium 8 the identifiers PID_ES of the elementary streams ES of the registered service (step 240).

The PCMCIA module 2 then generates a replacement PMTR table from the PID identifier of the current service PMT and the PID identifiers of the recovered elementary streams (step 250); In particular, the replacement PMTR table is generated so that the PID identifier of its header field 3 comprises the PID identifier of the current service PMT, and its data field 4 comprises the identifiers PID_ES of the elementary streams recovered. . Finally, the PCMCIA module 2 transfers (step 260) to the first or second host device 1 a TSout output stream comprising only the replacement PMT table and the recording stream TS2 or T-FIG. 6 illustrates by way of nonlimiting example. the format an output flow structure 9 including the replacement PMTR table and the output recording stream packets noted TPTS2IN- Thanks to the generation of a replacement PMTR table, the PCMCIA 2 module forces the host equipment 1 to actually listen to the stream of recorded service, even if he was listening to another service. The host device 1 will thus begin to listen to the ES elementary streams defined in this replacement PMTR table, namely those corresponding to the registered service, in place of the elementary streams ES of the current channel. These recorded elementary streams will then be decoded by the MPEG decoder 13, then played on the screen and the speakers associated with the host equipment. In a preferred embodiment, an encryption identifier is further inserted into the data field of the replacement PMTR table, even though the recorded stream that is transferred to the host equipment 1 has already been descrambled. This precaution is necessary to overcome the difference in intrinsic operation of the host equipment with regard to the management of TSIN and TSouT flows. Indeed, when no PCMCIA module is inserted into the host equipment 1, the stream from the tuner 10 and the demodulator 11 of the host equipment is sent directly to the demultiplexer 12 of the host equipment. When a PCMCIA module for access control is inserted in one of the host equipment, the stream coming from the tuner of the host equipment must be sent to the PCMCIA module. However, for some host equipment, the flow management will differ depending on whether the listened to is clear or scrambled. In particular: - if the string is scrambled by an access control system supported by the PCMCIA module 2, the host device 1 must send a module CA_PMT command to request descrambling. In this case, the host equipment cuts the flow between the output of the demodulator 11 and the input of the demultiplexer 12, and is only interested in the flow passing through the transport bus 7. - If the string is scrambled by a access control system not supported by the PCMCIA 2 module, or if the string is not scrambled, the standards do not then require the host device 1 to send the module a command CA_PMT. If no command is sent, some host devices will cut the flow passing through the transport bus 7, and only look at the flow between the output of the demodulator 11 and the input of the demultiplexer 12.

As a result, for these equipments, the reception of a recording stream without an encryption identifier will immediately be interpreted as the reception of an undisclosed string, and the host equipment will stop being interested in the stream of recording.

Inserting an encryption ID into the data field of the replacement PMTR will ensure that the host device is using the record stream correctly. The encryption identifier will for example be chosen from the list of all the CA_system_id identifiers of the access control systems that the module supports. As a variant, this identifier will preferably be a proprietary specific identifier, in order to differentiate it from an encryption identifier used by the access control systems. It should be noted that the replay procedure as described above remains compatible with the standards. Indeed, when a replay is made, the host device 1 transmits a TSIN input stream, but this stream does not need to end up on the output bus 7 since it must at this precise moment replay than the registered service. The TSIN input stream can nevertheless be used by the PCMCIA 2 module to perform, in parallel, a recording of any current service. The injector 30 for the flow management makes it possible, under the command in particular of the CAS module 22, to cut any TSiouT stream so that only the recording stream TS2ouT and the replacement table PMTR are actually delivered to the host equipment 1 on the bus 7. On the other hand, if no replay of a registered service is in progress, the injector authorizes this stream TS1ouT- Thanks to the recording and playback method according to the invention, a user is allowed to to extend the possibilities of its host equipment. The CAS software module 22 is sized to allow the simultaneous processing of at least two streams (for example a stream for a live read by the host equipment and a stream for a record, or a stream for a replay and a stream for a recording).

Preferably, three or even four streams can be managed simultaneously, to take into account including recording options or PIP integrated into the host equipment.

Claims (12)

REVENDICATIONS1. A method for recording a broadcast digital service received in scrambled form by a first host device (1) and for playback of the recorded service, the method comprising: a recording phase in which a first PCMCIA module (2) access control: - extract (120) of an input transport stream (TSIN) received from the first host (1) of the transport packets (TPPMT) corresponding to a PMT program matching table correspondingly unique to the service to be registered; - selects (130) in said input transport stream (TSIN) transport packets (TPES) corresponding to elementary streams (ES) uniquely associated with the service to be recorded and descrambled (140) the selected transport packets; - transfers (160) to an external storage medium (8) for recording the extracted transport packets (TPPMT) and a recording stream (TS2ouT) composed of the descrambled transport packets; and a replay phase, on the first host device (1) or a second host device, of the registered service, in which the first PCMCIA module (2) or a second access control PCMCIA module: - retrieves (210) a PID identifier of the PMT table of the current service listened to by the first or second host equipment (1); - receives (220) the external storage medium (8) the recording stream (TS2IN) and the extracted transport packets (TPPMT); retrieves (240) in the transport packets (TPPMT) extracted from the PID identifiers of the elementary streams of the registered service; generates (250) a replacement PMT table from the PID identifier of the PMT table of the current service and the PID identifiers of the recovered elementary streams; and- transfers (260) to the first or second host equipment (1) an output stream (TSouT) comprising only the replacement PMT table and the record stream (TSoouT) - 2. Method according to claim 1, characterized in that the replacement PMT table is generated in the form of one or more transport packets each comprising a data field (4) and a header field (3) with an associated PID identifier. uniquely at the replacement PMT table, the PID identifier of its header field (3) including the PID identifier of the PMT table of the current service, and the data field (4) comprising the PID identifiers of the elementary streams recovered. . 3. Method according to claim 2, characterized in that an encryption identifier is further inserted in the data field of the replacement PMT table. 4. Method according to any one of claims 1 to 3, characterized in that it further comprises a step of encrypting (150) the recording stream (TS2ouT) before transfer for recording, and a decryption step (230) of said recording stream before being transferred for replay. 5. Method according to claim 4, characterized in that the encryption (150) and decryption (230) are performed according to an AES algorithm. 6. Method according to any one of the preceding claims, characterized in that it further comprises a step of encryption CI + output stream (TSouT) before its transfer to the first or second host equipment (1). 7. Method according to any one of the preceding claims, characterized in that the input transport stream (TSIN) received is in the MPEG or IP format, in which the services are scrambled according to a standard DVB type, respectively AES. 8. PCMCIA access control module (2) adapted to be associated with a host device (1), on the one hand, to receive an input transport stream (TSIN) comprising scrambled transport packets and on the other hand, transmitting to the host equipment (1) a first output stream (TSOUT) corresponding to the input transport stream (TSIN) in which some of the scrambled transport packets were optionally descrambled, characterized in that it includes, for the purpose of recording a digital television service received in scrambled form, means (20, 21, 22, 23, 29, 31) for generating a recording stream (TS2ou-r), adapted to extract from the transport transport input (TSIN) transport packet (TPPMT) corresponding to a PMT program matching table uniquely associated with the service to be recorded, to be selected in said input transport stream (TSIN) ) corresponding transport packets (TPES) to elementary streams (ES) of the service to be recorded, to descramble the selected transport packets and to deliver the recording stream (TS2ou-r) composed of the descrambled transport packets, and transfer means (23, 27) capable of forwarding the extracted transport packets (TPPMT) and the recording stream (TS2ouT) to an external storage medium (8) for recording; and, for replaying the recording stream (TS2ou-r) on the first host equipment (1) or a second host equipment, means (22, 23, 27, 29, 30) for generating a stream output device (TSouT) capable of: recovering a PID identifier from the PMT table of the current service listened to by the first or second host device (1); - Receive from the external storage medium (8) the recording stream (TS2IN) and the extracted transport packets (TPPMT); retrieving the PID identifiers of the recorded service elementary streams in the transport packets (TPPMT); generating a replacement PMT table from the PID identifier of the current service PMT table and the PID identifiers of the recovered elementary streams; ; and - generating a second output stream (TSOUT) comprising only the replacement PMT table and the recording stream (TS2IN), for transfer to the first or second host equipment (1) in place of the first output stream. Access control module (2) according to claim 8, characterized in that the means (22, 23, 27, 29, 30) for generating an output flow comprise an injector (30) for managing the stream adapted to simultaneously receive the replay recording stream (TS2IN) and a transport stream (TS1ouT) of a descrambling module (21) of the access control module (2) and to output only the stream recording replay (TS2IN) for transfer to the first or second host equipment (1) in place of the first output stream. 10.Module (2) access control according to any one of claims 8 or 9, characterized in that it is able to simultaneously generate the first output stream (TS2ouT) for the live playback of a first service listened to by the first host device, and a record stream (TS2ouT) for recording the first service listened to, or a second service received by the first host device (1). 11.Module (2) for access control according to any one of claims 8 to 10, characterized in that it further comprises means (28) for programming the recording of the service delayed. 12. Data transport stream (9) delivered by a host equipment access control module (PCMCIA) (2) for playback of a recording stream corresponding to a digital broadcast service, characterized in that it comprises only the record stream (TS2ouT) composed of descrambled transport packets (TPTS2IN) corresponding to elementary streams (ES) to said service, and a replacement PMT table (TPPMT R) generated from an identifier PID of the PMT table of the current service listened to by the host equipment (1) before replay, and of PID identifiers of the elementary streams composing the registered digital service.