WO2009000982A2

WO2009000982A2 - Methods for generating final streams and secondary streams of primary and secondary contents to be transmitted, for sfn networks, and associated generating devices and stations

Info

Publication number: WO2009000982A2
Application number: PCT/FR2008/050790
Authority: WO
Inventors: Pascal Gravoille; Stephane Guillemot; Stephane Fillod
Original assignee: Thomson Licensing
Priority date: 2007-06-25
Filing date: 2008-05-06
Publication date: 2008-12-31
Also published as: WO2009000982A3

Abstract

A method is dedicated to the transmission of primary and secondary contents between a central station (SC) of a supply network and groups (G1, G2) of sending station(s) (S11-S22) of distribution networks (at least one of which is of the SFN type). This method consists i) in constructing a reference stream with packets of a primary content, MIP packets and padding packets, ii) in the presence of N (N ≥ 2) secondary contents intended respectively for N chosen groups (G1, G2), in constructing N copies of the reference streams, which copies are associated respectively with these N groups, then in replacing in each of the N copies padding packets with packets of secondary content which is intended for the corresponding group, so as to construct N secondary streams, iii) in replacing in each of the N secondary streams initial values of packet identifiers, associated with the padding packets, MIP, of the secondary content and of the primary content, with replacement values, as a function of a correspondence table, then in constructing an optimized final stream, adapted to the transmission and decodeable by the sending stations with all the packets of one of the N secondary streams, the packets of the secondary contents and the MIP packets of certain at least of the other N-1 secondary streams, and iv) in transmitting the optimized final stream from the central station (SC) to the N groups.

Description

METHODS OF GENERATING FINAL FLOWS AND SECONDARY FLOWS OF PRIMARY AND SECONDARY CONTENT TO BE TRANSMITTED, FOR SFN NETWORKS, AND GENERATING DEVICES AND STATIONS THEREOF

Technical field of the invention

The invention relates to communication networks comprising a power supply network (wired or non-wired) coupled to at least two non-wired distribution networks of which at least one is said to be "single frequency" (better known by the acronym English SFN (for "Single Frequency Network")), and more precisely the generation and transmission of primary and secondary content streams from a central station of a power supply network to groups of stations transmission, respectively associated with different distribution networks, at least one of which is of the SFN type, then to reception equipment present in the coverage areas of these distribution networks.

It is recalled here that a power supply network is a wired or non-wired communication network comprising at least one central station (or "head-end"), responsible for generating and transmitting a primary and secondary content stream. (s) to at least two distribution networks of which at least one is SFN. In addition, a SFN distribution network is a wireless communication network associated with a single geographical area in which at least two transmitting stations are installed for transmitting to reception equipment, synchronously and in a single length of time. wave, the primary content (s) concerning all the zones and the secondary content (s) which concern only their own zone and which have been transmitted by a central station of a power network.

The invention relates to all non-wired distribution networks (or infrastructures) (including those of the SFN type), capable of broadcasting in continuously, for example by using a coded Orthogonal Frequency Division Multiplexing (COFDM) type of modulation or according to another standard (such as the ATSC (Advanced Television Systems) standard, for example). Committee ")), content in the form of MPEG-2 System data packets for receiving equipment. It may therefore be a radio communication network (for example WiFi, WiMAX or 4G), or a terrestrial broadcasting network (for example of the DVB-T, DVB-H, T-DBM or DAB type). or satellite or hybrid (that is to say, both terrestrial and satellite).

Furthermore, the invention relates to all power networks (or infrastructures) capable of streaming content in the form of data packets in the MPEG-2 System format, intended for at least two distribution networks. at least one of which is SFN. It may therefore be a wired network, such as for example a telecom loop, or a non-wired network, such as a satellite link.

Here "content" is understood to mean a set of data that defines a television or video or audio program (radio or musical) or games or multimedia, or a computer file (or "data").

In addition, "primary content" here means content that must be broadcast in all SFN and non-SFN areas of a power and distribution network, and "secondary content" means content that must be broadcast only in at least one of the areas (SFN and non-SFN) of a power and distribution network but not in all of its areas. For example, where zones are regions of a country, primary content (for the whole country) is usually called "national content", while secondary content (for a single region) is usually called "Regional content".

Finally, "receiving equipment" here refers to any type of communication equipment that can connect to an SFN distribution network in order at least to receive content broadcast in "broadcast" or "multicast" mode (point-to-multipoint). ). It may therefore be for example, fixed or mobile telephones (or cell phones), fixed or portable computers, personal digital assistants (or PDAs, including "pocket PCs"), content receivers (such as decoders, gateways "residential gateways", TV sets with built-in decoders, or STBs ("Set-Top Boxes")), provided that they are equipped with means of communication which are at least suitable for receiving content transmitted in the form of MPEG-2 System data packets.

State of the art

As known to those skilled in the art, so that the transmitting stations that are located in the area of a SFN distribution network can synchronously broadcast the same stream, it is inserted in this stream, at the level of the central station of the associated power network, a marker containing synchronization information, such as MIP ("Megaframe Initialization Packet") type packets. Specifically, it is an MPEG packet that contains a GPS time reference to allow transmission stations of a SFN distribution network to synchronize their transmissions with an accuracy of about 100 ns in order to broadcast. simultaneously the same received stream.

If this synchronization does not pose a real problem at the transmitting stations, on the other hand the transport of a stream to the transmitting stations proves difficult because the stream received by each of the transmitting stations an SFN field must be the same bitwise ("bit accurate").

To do this, one can for example create the stream in its final format (that is to say according to a given broadcast rate) at the central station of the power supply network and transmit it according to this rate to the various stations transmission without any modification in the transmission chain.

However, this solution is optimal neither in terms of costs nor in terms of architecture, because the needs of the operators are multiple. Indeed: - the transport media that must be used to reach the transmitting stations may have a bit rate that is not that of the stream they must broadcast, - to reach isolated transmitting stations one may be obliged to use satellite links,

in the case of a broadcast transport medium (satellite or other), the profitability of the broadcast link may require the use of the same transponder for the transport of several SFN streams,

- when regionalization is necessary, the packages of content broadcast may contain both national content common to the entire territory (ie identical for all SFN and non-SFN areas) and regional content specific to one or more regions (ie attached to one or more SFN or non-SFN areas). In this case, it is possible to constitute and transmit as many streams as there are SFN and non-SFN zones (one per SFN or non-SFN zone) to the different transmitting stations. However, this results in the duplication of national content, or even regional content intended for several regions, in each of the streams, which unnecessarily consumes bandwidth, and may require the use of multiple transponders in parallel.

Summary of the invention

The object of the invention is therefore to improve the situation, and more precisely to allow efficient transport of the primary and secondary content streams in terms of bandwidth utilization, while guaranteeing receptions of flows identical to the bit ready at the transmitting stations.

For this purpose, the invention firstly proposes a first method, dedicated to the transmission of sets of primary and secondary contents between a central station of a supply network, and at least two groups of at least one transmission station, associated respectively with distribution networks of which at least one is at a single frequency, and consisting of: i) constituting a reference flow with packets of at least one set of primary contents, packets of synchronization and stuffing packets, ii) in the presence of N (N ≥ 2) sets of secondary contents for N selected groups respectively, to constitute N copies of this flow of references associated respectively with the N groups, then replace in each of the N copies of packets packets by packets of the set of secondary contents for the corresponding group, to constitute N secondary streams, iii) to replace in each of these N secondary flows the initial values of packet identifiers, which are associated with the stuff packets, the synchronization packets, and the packets of the set of secondary contents and the set of primary contents, with replacement values, based on of a correspondence table, then to constitute at least one optimized final stream, adapted to the transmission and decodable by the transmitting stations, with all the packets of one of said N secondary streams, the packets of the sets of secondary contents at least some other N-1 secondary streams and synchronization packets contained therein, and iv) to transmit the optimized final stream of the stat central ion to the N groups. The first method according to the invention may comprise other characteristics that can be taken separately or in combination, and in particular:

in i) the reference flow can be constituted with packets of at least one set of primary contents, a first set of secondary contents intended for one of the N selected groups, synchronization packets and any stuffing packs. In this case, in ii) N copies of the reference stream, respectively associated with the N groups, can be constituted, then in N-1 of these copies, packets of the first set of secondary contents can be replaced by packets of the N-1s respectively. sets of secondary contents for the N-1 corresponding groups, to constitute N-1 secondary streams completing the Nth copy, which has not been replaced and which constitutes an Nth secondary flow;

ii) it is possible to adapt at least one temporal information field relating to the secondary contents of the set concerned,

- in ii) one can designate among the N secondary flows that which one must take (iii) all packets to begin to build the optimized end stream; ii) it is possible to modify in each of the N secondary flows a selected part of each synchronization packet which is not relative to temporal information;

> iii) can then remove the redundancy of packets between the secondary flows; iii) the secondary streams can be synchronized, and a pointer can be used for each secondary stream so as to point one of its temporally synchronous packets, then a step a) in which the packet of a secondary stream designated as the principal, then a step b) in which this read packet is placed in the optimized final stream, then if it was a packet of the set of secondary contents read the packets designated by the pointers other secondary streams in order to place them also in the optimized final stream, and a step c) in which the pointer of each secondary stream is moved to the next packet in order to repeat the steps a) and b); alternatively, iii) the secondary streams can be synchronized, and a pointer can be used for each secondary stream so as to point one of its temporally synchronous packets, then a step a) can be performed in which the packet is read. a secondary stream designated as the principal, and then a step b) in which the read packet is placed in the optimized final stream if it is a packet of the set of primary contents, then one goes to the step e), a step c) in which, if the read packet is a packet of a set of secondary contents, a finite number of packets of set (s) of secondary contents are read without going further than the preceding packet the next packet of the set of primary contents, and these packets of set (s) of secondary content read in the optimized final stream are placed, then a step d) in which step c) is repeated for all the others secondary flows, and a step e) in which the point is moved of each secondary stream of the finite number of read packets in order to repeat steps a) to d); iii), in the presence of a set of secondary contents common to several but not all groups, it is possible to eliminate the redundancy of the packets of this set of secondary contents present in the N secondary flows;

iii) the secondary flows can be synchronized temporally, and a pointer can be used for each secondary stream so as to point one of its temporally synchronous packets, then a step a) in which the packet of a secondary stream designated as the principal, then a step b) in which the read packet is placed in the optimized final stream if it is a packet of the set of primary contents, then one can proceed to a step f), or a step c) in which, if the read packet is a packet of a set of secondary contents intended for several groups but not all, and not yet placed in the optimized final flow, or a set of non-shared secondary content then one can read the package of the set of secondary contents and we can place this packet read in the optimized final stream and then go to step e), or a step d) in which, if the read packet is a package of a set of e secondary contents intended for several groups but not all and already placed in the optimized final flow, we can go to step e), a step e) in which we can repeat step c) for all other secondary flows , and a step f) in which the pointer of each secondary flow can be displaced by one increment in order to repeat the steps a) to e); (iii) the optimized end stream may be augmented with a worthless PAT packet (or referencing no service); iii) for each packet identifier, it can be indicated whether it is associated with a packet of the set of primary contents or a set of secondary contents; iii) the optimized final stream can be adapted to a selected rate by adding stuffing packets or packets of non-primary or secondary contents for at least one transmitting equipment; we can also transmit to the N groups, in the optimized final stream, at least part of each correspondence table;

in i) the stuffing packs can be placed in positions regularly spaced from the reference flow.

The invention also proposes a second method, dedicated to the transmission of sets of primary and secondary contents between a group of transmitting stations of a single frequency distribution network and reception equipment, and consisting, in the case of reception by the transmitting stations of an optimized final stream transmitted by means of a first method: i) extracting from this optimized final stream the packets of the set of primary contents, the packets of the set of secondary contents for the group, the packets of jam present in the initial secondary flows, and the synchronization packets corresponding to this group, then ii) to replace by initial values the replacement values of the packet identifiers of at least some extracted packets, according to a correspondence table, then iii) to constitute a secondary flow with the extracted packets, respecting the relative ordering that they had with each other compared to others in the optimized final stream, and iv) to transmit this secondary stream to the receiving equipment.

The second method according to the invention may comprise other characteristics that can be taken separately or in combination, and in particular:

in iv) this secondary stream can be transmitted to reception equipment taking into account the temporal information contained in its synchronization packets;

iv), before proceeding with the transmission of the secondary flow, the regeneration of a clock which is present in each transmitting station and used for the transmission of the secondary flow can be carried out;

i) it is also possible to extract from the optimized final flow received each correspondence table that it contains, in order to proceed to the ii) replacement of the values of the packet identifiers.

The invention also proposes a first device, dedicated to the generation of final flows of sets of primary and secondary contents (to be transmitted to at least two groups of at least one transmitting station), respectively associated with networks of a distribution of which at least one is single frequency, and comprising:

first loaded processing means, in the presence of at least one set of primary contents intended for N (N ≥ 2) selected groups and N sets of secondary contents intended for these N selected groups respectively, to constitute a reference flow; with packages of the primary content set, synchronization packets and stuffing packets,

second processing means responsible for constituting N copies of this reference stream, associated respectively with said N groups, and replacing in each of these N copies packet stuffing packets of the secondary content set intended for the corresponding group; , in order to constitute N secondary flows, and

third processing means responsible for replacing in each of the N secondary streams the initial values of packet identifiers associated with the stuffing packets, the synchronization packets, and the packets of the set of secondary contents and the set of primary contents, by replacement values, according to a correspondence table, and to constitute at least one optimized final stream, adapted to the transmission and decodable by the transmitting stations, with all the packets of the one N secondary streams, packets of secondary content sets of at least some other N-1 secondary streams and synchronization packets contained therein.

The first device according to the invention may comprise other characteristics that can be taken separately or in combination, and in particular:

its first processing means may be responsible for constituting the reference flow with packets of at least one set of contents primary, a first set of secondary contents for one of N selected groups, synchronization packets and possible packets stuffing. In this case, its second processing means may be responsible for constituting N copies of the reference stream, associated respectively with the N groups, and for replacing in N-1 these copies of the packets of the first set of secondary contents with respectively packets of the N-1 sets of secondary contents for the N-1 corresponding groups, to constitute N-1 secondary streams completing the Nth copy, not being replaced and constituting an Nth secondary flow;

its second processing means may be responsible for adapting at least one temporal information field relating to the secondary contents of the set concerned,

its second processing means may be responsible for designating, among the N secondary flows, the one in which the third processing means must take all the packets in order to start constituting the optimized final flow;

its third processing means may be responsible for modifying in each of the N secondary flows a selected part of each synchronization packet which is not relative to temporal information;

its third processing means may be responsible for adding to the optimized final stream a packet of PAT type with no value (or referencing any service);

its third processing means may be responsible for indicating for each packet identifier whether it is associated with a packet of the set of primary contents or a set of secondary contents;

its third processing means may be responsible for integrating into the optimized final flow at least part of each correspondence table;

its first processing means may be responsible for placing the stuffing packets at positions regularly spaced from the reference flow.

The invention also proposes a central station equipped with a first end stream generation device of the type presented above, and transmission means responsible for transmitting each optimized final stream generated by the first device to groups of transmitting stations.

The invention also proposes a second device, dedicated to the generation of secondary streams of sets of primary and secondary contents to be transmitted to reception equipment, within a transmission station of a frequency distribution network. unique, and comprising:

first loaded processing means, in the event of reception by the transmitting station of an optimized final stream transmitted by a central station of the type of the one presented above, of extracting from this optimized final stream the packets of the set of primary contents, the packets of the set of secondary contents intended for the distribution network, the packets of stuffing present in the initial secondary flows, and the synchronization packets corresponding to this distribution network, and to replace by values initials the replacement values of the packet identifiers of at least some of said extracted packets, according to a look-up table, and

second processing means responsible for constituting a secondary stream with the extracted packets, respecting the relative ordering that they had with respect to each other in the optimized final stream received.

The second device according to the invention may comprise other characteristics that can be taken separately or in combination, and in particular:

its second processing means can be responsible for regenerating the clock of the transmitting station and the initial clock of the secondary flow;

its first processing means may be responsible for extracting also from the optimized final stream received each correspondence table that it contains, in order to proceed with the replacement of the values of the packet identifiers.

The invention also proposes a transmitting station equipped with a second secondary flow generation device of the type of the one presented above, and transmission means responsible for transmitting each secondary flow generated by the second device to the receiving equipment located in the area, taking into account the time information contained in its synchronization packets.

Brief description of the drawings

Other features and advantages of the invention will appear on examining the detailed description below, and the attached drawings, in which:

FIG. 1 diagrammatically and functionally illustrates an example of a power supply network comprising a central station according to the invention and coupled to two SFN distribution networks comprising transmitting stations according to the invention,

FIG. 2 schematically and functionally illustrates an exemplary embodiment of a transmitting station according to the invention,

FIG. 3 schematically illustrates different flows constituted during successive steps of the two methods according to the invention, in the case where the supply network supplies two SFN distribution networks associated with two zones (or regions), such as is the case in the example illustrated in Figure 1, and

FIG. 4 schematically illustrates a variant of the optimized final flow (FF) illustrated in FIG. 3.

The attached drawings may not only serve to complete the invention, but also contribute to its definition, if any.

detailed description

The object of the invention is to enable efficient and bit-wise transport by a power supply network coupled to at least two distribution networks, at least one of which is of SFN type, of streams of sets of primary contents and secondary. In what follows, it is considered by way of non-limiting example that the power supply network is a satellite link network (SA), for example DVB-S or DVB-S2 type. However, the invention is not limited to this type of supply network. It concerns any type of wired or non-wired feed network (or infrastructure) capable of streaming content in the form of MPEG-2 System data packets for at least two distribution networks of which at least one is of the SFN type. It may also be a wired network, such as a telecom loop.

Furthermore, it is considered in the following, by way of non-limiting example, that the distribution networks are both of the SFN type and that they are DVF-T terrestrial networks with COFDM modulation. , adapted to the transport of content of the television program type. However, the invention is not limited to this type of COFDM-modulated SFN network. It concerns in fact any type of non-wired SFN network (or infrastructure) capable of broadcasting continuously, for example by using COFDM type modulation or answering another standard, for example the ATSC standard, content in the form MPEG-2 System data packets for receiving equipment. It may therefore also be a radio communication network (for example WiFi type, WiMAX or 4G), or a satellite or hybrid broadcast network.

Given the choice of distribution networks (here all SFN type) carried out above, the contents are television programs. But, the invention is not limited to this type of content. It concerns any type of content that can be broadcast in broadcast mode or multicast, including video or audio programs (radio or music) or gaming programs or multimedia, or computer files (or "data").

FIG. 1 schematically illustrates a nonlimiting example of a satellite link power supply network SA responsible for broadcasting at least one optimized (or final) satellite stream FF to two (distribution) networks SFN associated respectively with two zones (or regions) SFN Zk (k = 1 or 2). We consider in the following, by way of non-limiting example, that the two zones SFN Zk are two regions of a country (or a nation). But, it will be understood that it could be sub-parts of a region, or any other subdivision of a space. It will also be understood that the invention is not limited to broadcasting to two SFN Zk zones. It concerns indeed the diffusion towards at least two zones of which at least one is of type SFN.

As illustrated, a satellite link power supply network comprises a central station (or head-end) SC and a satellite SA, and each SFN network comprises a group Gk of at least two transmission stations Skj, located in an area (SFN) Zk. It will be noted that when one of the distribution networks is not of the SFN type, it may comprise a group Gk of a single transmission station Skj, implanted in a zone (non-SFN) Zk.

In the nonlimiting example illustrated, a first group G1 comprises three transmitting stations S11 to S13 (k = 1, j = 1 to 3) located in fixed locations and known to the first area (SFN) Z1 of the first network. SFN, and a second group G2 comprises two transmitting stations S21 and S22 (k = 2, j = 1 or 2) located in fixed locations and known from the second zone (SFN) Z2 of the second SFN network.

The central station SC is responsible for generating and transmitting at least one optimized (or final) satellite stream FF of primary and secondary content sets for the satellite SA, which is responsible for retransmitting it to the transmitting stations Skj implanted in Zk areas. The transmitting stations Skj, of the same zone Zk, are responsible for (re) constituting a secondary stream FSk from the final stream (or satellite) FF received from the satellite SA, and broadcasting this secondary stream FSk (re) constituted, synchronously and in a single wavelength, to receive equipment Ei which are implanted or present in their zone Zk.

Here, "primary content" is intended to mean content that must be broadcast in all zones Zk, and "secondary content" content that must only be broadcast in at least one of the zones Zk but not in all. In the example described, a primary content is a national program, while a secondary content is a regional program. Therefore, a final flow (optimized) FF comprises packets of a set of at least one national (or primary) program and packets of at least two sets of at least one regional (or secondary) program, while a secondary FSk stream includes packets of a set of at least one national (or primary) program and packets of a set of at least one regional (or secondary) program.

Since the transmission stations Skj are responsible for broadcasting the secondary streams FSk by waves, the reception equipment Ei are communication equipment (or terminals) at least adapted to receive sets of contents diffused by wave broadcast or multicast mode. It may therefore be, for example, fixed or mobile (or cellular) telephones, fixed or portable computers, personal digital assistants (or PDAs, including "pocket PCs"), content receivers ( such as decoders, residential gateways (or "residential gateways"), TVs with integrated decoders or STBs ("Set-Top Boxes"), provided that they are equipped with at least one radio communication means receiving wave-transmitted contents in the form of data packets in the MPEG-2 System format.

The invention proposes to implement a first method on the side of the central station SC, and a second method on the side of the transmitting stations Skj.

The first method is dedicated to the transmission of primary and secondary contents between the central station SC and Gk groups of transmitting station (s) Skj, implanted in different areas (SFN or not SFN) Zk.

This first method comprises four main steps. It will be noted that this decomposition into four main stages is not limiting. It is indeed given to facilitate understanding. But, all or part of these main steps could be merged together.

A first main step of the first method (i) consists in constituting a reference stream FR (see FIG. 3) with packets of at least one set of primary (or national) contents CN, synchronization packets (for example of the type MIP (Megaframe Initialization Packet)) and stuffing packets (or stuffing) PB.

Here, by way of illustrative example, the set of primary (or national) contents CN and secondary (or regional) content sets CRk arrive at the central station SC in the form of MPEG-2 packets. System.

A non-limiting example of reference stream FR is schematically illustrated in the upper part of FIG. 3. In this example, the letter N denotes a national content packet CN, the letter S denotes a stuffing packet, and the letter M designates a synchronization packet. In the following, by way of nonlimiting example, the synchronization packets are considered to be MIP type packets.

As illustrated, the reference flow FR is adapted (i.e. identical) to the transmission mode rate (here DVB-T) which is used by the transmitting stations Skj to join the reception equipment Ei of their zone Zk. As illustrated, this DVB-T rate of the reference stream FR is decomposable into a stuffing rate (PB), a rate of national contents (CN) and a MIP packet rate (for example at 3 kbps). It will therefore be understood that the object of the first main step is to allow the definition of the broadcast rate (in this case DVB-T) in the zones Zk as well as the contents of the MIP packets, which notably contain synchronization information (time reference GPS provided by a GPS receiver RG from the central station SC).

It will be noted, as illustrated, that the stuffing packs PB are preferentially placed in the reference flow FR at positions which are regularly spaced apart. This makes it possible, in fact during the second main step, to avoid constituting flows comprising bursts of CN national content packets and bursts of regional content packets CRk.

This first step is implemented by a first device D1 which is coupled to the central station SC, or, as illustrated, which is located in this central station SC.

Such a first device D1 comprises a first processing module MT1 which is more particularly responsible for implementing the first main step of the first method. For this purpose, it is powered at least by set (s) of CN national content. But, it could also be fed with the CRk regional content set that is destined for one of the Zk zones. Indeed, it can be envisaged that the first processing module MT1 receives at least one set of national contents CN and a first set of regional contents (for example CR1), and that it constitutes the reference flow FR with packets N of this set of CN national contents, R1 packets of this first set of regional contents CR1 (for the first group G1), MIP type packets, and possible packets S stuffing (PB).

A second main step of the first method (ii) consists first of all, when one has N (with N ≥ 2) sets of regional content (or secondary) CRk intended respectively for N groups Gk selected to form N copies of the reference flow FR respectively associated with the N groups Gk.

Here is meant by "constituting N copies of the reference stream FR" both the fact of keeping the reference stream FR and of copying N-1 times, that actually creating N copies of the reference stream FR without preserving this latest.

Note that in the illustrated example, N is equal to 2, so that two copies of the reference stream FR are constituted.

Once N identical copies of the reference stream FR are available, in each of these N copies S (or PB) stuffing packets are replaced by packets Rk of the set of regional contents CRk which is intended for corresponding Gk group.

It will be noted that this replacement may be accompanied by an adaptation of at least one temporal information field which is relative to the secondary contents CRk of the object set of the replacement. This field can be the one called PCR ("Program Clock Reference"), and whose information is used at least by reception equipment Ei to regenerate their local clock. The adaptation of the PCR field makes it possible to obtain a signal of the MPEG-2 TS type which is temporally compliant with the MPEG-2 System standard and thus allows decoding and correct rendering. content by a reception equipment Ei.

This replacement and this PCR field adaptation thus make it possible to constitute N secondary flux FSk (here FS1 and FS2 because N = 2), compliant with the MPEG-2 System standard. Nonlimiting examples of secondary flows FS1 and FS2 are schematically illustrated in the upper part of FIG. 3. In this example, the alphanumeric reference R1 denotes a packet of the first set of regional contents CR1, the alphanumeric reference R2 designates a packet of the second set of regional contents CR2, the alphanumeric reference M1 designates a packet of the MIP type of the first secondary stream FS1, and the alphanumeric reference M2 designates a packet of the MIP type of the second secondary stream FS2.

It should be noted that the packets R2 of the second set of regional contents CR2, which are placed in the second secondary stream FS2, are not necessarily placed in the same places as those where the packets R1 of the first set of regional contents CR1 are placed in the first set. FS1 secondary stream. There may indeed be variations, especially when the rate of Rk packets of regional content CRk does not require the replacement of all stuffing packets S. However, it is preferable to ensure that a maximum of packets S jam will be common to all FSk secondary flows in order to increase the redundancy between the streams, and thus facilitate the search phase of redundancy (of packets of a set of national contents CN) and optimization.

It will also be noted that when in the first step a reference stream FR has been constituted with packets N of a set of national contents CN and packets R1 of a (first) set of regional contents CR1 (intended for the (first) group G1), once N copies of this reference stream FR (associated with the N groups Gk respectively) have been constituted, it is possible for example to replace, in N-1, these copies of the packets R1 of the first set of regional contents. CR1 as well as possibly stuffing packets S by respectively packets Rk of N-1 sets of regional contents CRk (with k ≠ 1) intended for the N-1 groups Gk corresponding, adapting at least the PCR field. The R1 packets of the first set of regional content CR1 thus play the role of stuffing packets S. It will be noted that, in a variant, it is possible for example to replace in N-1 copies R1 packets of the first set of regional contents CR1 by stuffing packets S, then replacing at least some stuffing packets S with packets Rk of N-1 sets of regional contents CRk (with k ≠ 1) intended for the corresponding N-1 groups Gk, adapting at least the field PCR .

Once the replacements have been made, there are N-1 secondary flows which complete the Nth copy (or the original reference flow FR) which it has not been replaced but which then constitutes a Nth secondary stream.

In other words, in the example described and illustrated, the original reference stream FR gives the first secondary stream FS1, and one replaces in the single copy (N-1 = 1 when N = 2) of this original reference stream FR, the packets R1 (of the first set of regional contents CR1) and the stuffing packets S by the packets R2 of the second set of regional contents CR2, in order to constitute the second secondary stream FS2.

It is important to note that the MIP type packet M 1 of the first secondary stream FS 1 and / or the packet of the MIP type M2 of the second secondary stream FS 2 may possibly be different from the packet of the MIP type M of the reference flow FR. Indeed, it can be envisaged that the MIP type packet M, which is inserted into the reference stream FR (by a MIP packet insertion function of the first processing means MT1), can be modified during the second main step.

The modification of a MIP type packet can only relate to a selected part that is not relative to temporal information. Indeed, it is not necessary that this modification causes an alteration of the modulation scheme.

This modification is optional because it is necessary only when it is necessary to regionalize the private information (for the sending equipment Skj) that are contained in the MIP packets, because the MIP table becomes too large ( Too many equipment of issue Skj to be addressed). It should be noted that in the case where the MIP packet is common to all secondary streams FSk, then it is considered as a packet of national content and therefore it is present only once in the optimized final stream.

It will be noted that in the second main step, it is possible to designate, among the N secondary flows FSk, the one in which all the packets will have to be taken during the third main step to begin constituting the final flow FF. In the absence of such a designation, we will systematically take all the packets of one of the N secondary streams FSk, always the same, for example the first FS1, or we can take those of a secondary stream FSk among the N, chosen by random draw.

This second main step is implemented by the first device D1, and more specifically by a second processing module MT2 that it comprises. For this purpose, the second processing module MT2 is fed at least by N-1 sets of regional contents CRk and by the reference flow FR which is constituted by the first processing module MT1. It will be noted that when the reference stream FR does not contain packets Rk of a set of regional contents CRk, then the second processing module MT2 must be supplied with the N sets of regional contents CRk and the reference stream FR, as shown in Figure 1.

A third main step of the first method (iii) consists first of replacing with replacement values, in each of the N secondary streams FSk (constituted during the second main step), the initial values of packet identifiers, called PID (for "Packet Identifier") and which are associated with the stuffing packets S, the synchronization packets M (here MIP type), and the packets of the set of regional contents CRk and the set of national contents CN .

This replacement is based on at least one lookup table that defines a match between initial PID values and replacement PID values. It should be noted that one can provide either a single correspondence table (possibly subdivided into 2 or N + 1 subparts) for the PIDs of the regional content sets. CRk and the set of national contents CN, a first table of correspondence for the PIDs of the set of national contents CN and N tables of correspondence for the PIDs of N sets of regional contents CRk, is still a first table of correspondence for the PIDs of the set of national contents CN and a second correspondence table (possibly subdivided into N subparts) for the PIDs of N sets of regional contents CRk.

Once this PID replacement has been carried out, at least one optimized final stream FF, adapted for transmission to the transmitting stations Skj (here via a satellite SA), with all the packets N and Rk of one of the Ns, is constituted. secondary streams FSk and packets of the MIP type Mk of the latter if they have not been modified during its constitution (otherwise they are considered as Rk packets), and the packets Rk 'regional content sets CRk' ( k '≠ k) of at least some of the N-1 other secondary streams FSk', and the MIP type packets Mk contained therein (FSk '). Indeed, if the number of regional content Rk packets CRk is too large, we must constitute several final flows optimized FFm to contain all.

In the illustrated example, if one chooses to use (or if one must use, by configuration or designation) all the packets of the first secondary stream FS1, then one can for example start by placing all the packets (N , R1, M1) of the first secondary stream FS1 in the final stream FF, then it is possible to extract from the second secondary stream FS2 the packets R2 of the second set of regional contents CR2 and the associated MIP packet M2, in order to place them in selected locations of the final stream optimized FF.

The places where the different packets are placed in an optimized final stream FF can for example be chosen by means of one of the two algorithms described below.

A first algorithm makes it possible to constitute an optimized final stream FF of the type of that illustrated in FIG. 3. It consists, once the secondary streams FSk (or N copies) have been synchronized, to use a pointer for each secondary stream. FSk so as to point one of its temporally synchronous packets, then: a) to read the packet of a secondary stream FSk designated as principal, b) if this packet read is a packet N of national content CN then it is placed in the final stream FF, while if this packet read is a packet Rk of regional content CRk it is placed in the final stream FF and all the packets Rk 'which are pointed by the pointers of all the other secondary streams FSk', and c) the pointer of each secondary stream FSk is moved to the next packet in order to repeat steps a) and b).

A nonlimiting example of optimized final stream FF, resulting from the optimized combination of the packets from the secondary streams FS1 and FS2 by means of this first algorithm, is schematically illustrated in the central part of FIG. 3. The flow rate of the MIP packets Mk is here the double (2x3 kbps) of the secondary flux FSk because the final flow FF results from the multiplexing of two regional content sets CR1 and CR2 for which the content of the MIP packets is different.

A second algorithm consists, once synchronized secondary streams FSk (or N copies), to use a pointer for each secondary stream FSk so as to point one of its temporally synchronous packets, then: a) to read the packet of a secondary stream FSk designated as principal, b) if this packet read is a packet N of the national content CN then it is placed in the final stream FF, and we go to a step e), c) if this read packet is a packet Rk of a regional content CRk then one reads a finite number of regional content CRk packets CRk without going further than the packet preceding the next packet N of the national content CN, and these packets Rk content are placed regional CRk read in the final stream FF, then d) we repeat the operation c) for all the other secondary stream FSk 'by placing in the final stream an equivalent number of packets, and e) we move the pointer of each secondary stream FSk of the finite number of read packets in order to reiterate the apes a) to d).

A non-limiting example of optimized final flow FF, resulting from the optimized combination of the packets from secondary streams FS1 and FS2 by means of this second algorithm, is schematically illustrated in FIG.

It will be noted, as illustrated in FIGS. 3 and 4, that it is advantageous to add to the final flow FF a packet (referenced P) of the PAT (Program Association Table) type with no value. It is recalled that the PAT is one of four PSI (Program Specified Information) tables in MPEG-2 format. The PAT packets of the source FSk secondary streams are replaced like all the other packets and therefore have a non-zero value PID.

This addition of a worthless packet PAT (P) is intended to prevent that when receiving a final stream FF at a transmission station Skj, the MPEG analysis module detects an error (of type "ETR290 PAT Error") due to the absence of a PAT packet having the value PID 0 following the deletion of this last value induced by the replacement of the values of the PIDs. With such a worthless PAT packet, the final stream FF becomes a regular (or correct) MPEG stream from a signaling point of view.

In general, it is preferable to replace the values of the PIDs that are associated with all the packets that are inserted in the final flow FF, including the PAT and MIP packets and generally all the packets. signaling.

Moreover, when it is desired to adapt the final flow FF to a chosen rate, it can for example be added stuffing packets (referenced P in Figures 3 and 4). But, the values of the PIDs that are associated with these stuffing packets (P) are original values (8191) and not replacement values. Alternatively, instead of using stuffing packs, packets of non-SFN content for at least one receiving equipment can be used to fill the residual flow rate.

It will be noted, as illustrated, that it is advantageous to indicate for each PID whether it is associated with a packet of the set of national contents CN or a set of regional contents CRk. This makes it possible to facilitate the reconstitution of the secondary streams FSk at the transmitting stations Skj.

Note also that it is advantageous to insert in the signaling packets of the final flow FF at least part of each table of match that was used to perform a PID replacement. It will be understood that it is not necessary to transmit the entirety of each correspondence table used. It is indeed possible to transmit the parts of the tables that will be useful to the transmission stations Skj to reconstruct the initial FSk secondary streams (constituted during the second main stage to serve to constitute the final flow FF during the third main stage).

It will also be noted that when the final stream FF can not contain the packets of all the N regional content sets CRk, then there must be several (at least two) final flows FFm (m ≥ 2) from the reference stream. FR and FSk secondary flows formed in the second step.

It will also be noted that the final stream FF can also be optimized during the third main step when a set of regional contents CRk is common to several of the groups Gk but not all. In this case, the redundancy of the packets of this set of regional contents CRk which are present in the N regional streams CRk is suppressed. To do this, one can for example implement the algorithm described below.

Firstly, the secondary streams FSk are first synchronized, and a pointer is used for each secondary stream FSk in order to point one of its temporally synchronous packets. Then, we perform a step a) in which we read the packet of a secondary stream FSk which has been designated as principal.

Then, one performs either a step b), a step c), or a step d). In step b), the read packet is placed in the optimized final stream FF if it is a packet of the set of national contents CN, and then one goes on to a step T). If the read packet is a package of a set of regional contents CRk intended for one or more groups Gk but not all, and not yet placed in the final stream optimized FF, or a set of regional content not shared then one performs step c). The latter (c) consists in reading the packet of the regional content set CRk and placing this read packet in the optimized final stream FF and then moving to step e). If the read packet is a package of a set of regional contents CRk intended for several groups Gk but not all and already placed in the final stream optimized FF, then one performs step d). The latter (d) simply consists of going to step e).

This step e) consists in repeating step c) for all the other secondary flows.

Finally, step f) consists of moving the pointer of each secondary stream FSk by one increment in order to repeat the steps a) to e).

This third main step is implemented by the first device D1, and more specifically by a third processing module MT3 that it comprises. For this purpose, the third processing module MT3 receives the N secondary flows FSk constituted by the second processing module MT2. It will be noted that when the reference stream FR does not contain packets Rk of a set of regional contents CRk, then the second processing module MT2 must be supplied with the N sets of regional contents CRk and the reference stream FR, as shown in Figure 1.

A fourth main step of the first method (iv) consists of transmitting the optimized final stream FF (constituted during the third main stage) of the central station SC to the N groups Gk of transmission stations Skj, here via the satellite link SA .

This fourth main step is implemented by transmission means MX1 (with transponder (s)) that includes the central station SC and which are powered by the first device D1.

It will be noted that when it is necessary to transmit several optimized final streams FFm, then the transmission means MX1 of the central station SC must comprise several transponders.

It will be noted that a first device D1, according to the invention, can be realized in the form of a combination of software modules and electronic circuits ("hardware"), or electronic circuits, or even software modules.

In order to allow the reconstitution of a secondary stream FSk from an optimized final stream FF in the sending stations Skj of a zone Zk, then its synchronous transmission to reception equipment Ei located in this zone Zk, l The invention proposes a second method. This second method comprises four main steps. It will be noted that this decomposition into four main stages is not limiting. It is indeed given to facilitate understanding. But, all or part of these main steps could be merged together.

A first main step of the second method (i) consists, in the case of reception of a final stream FF by a transmission station Skj of a group Gk, to extract from the latter the packets (N) of the set of national contents CN, the packets (Rk) of the set of regional contents CRk which is destined to the zone Zk of the group Gk, the packets of jam present in the initial FSk secondary streams (or originals) and the synchronization packets (here of the MIP type) Mk corresponding to all these aforementioned packets. All other packets are ignored.

It will be understood that this task is facilitated when it has been taken care, during the third main step of the first method, to indicate for each PID whether it is associated with a packet (N) of the set of primary CN contents. or a packet (Rk) of a set of secondary contents CRk.

When the final flow FF contains signaling packets that define one or more parts of one or more correspondence tables, they are transmitted in the form of packets of national contents N or regional Rk. Therefore, they are extracted like the other packages N and Rk during the first main step, to serve in the second main step.

This first step is implemented by a second device D2 which is coupled to a transmission station Skj, or, as illustrated in FIGS. 1 and 2, which is located in a transmission station Skj.

Such a second device D2 comprises a first processing module MT4 which is more particularly responsible for implementing the first main step of the second method. For this purpose, it is coupled to the reception means MR of its transmission station Skj, which feeds it into the final streams FF they receive.

A second main step of the second method (ii) is to replace with initial values the replacement values of the identifiers packets (PIDs) of at least some of the packets extracted in the first main step. It is important to note that this (inverse) replacement is done using at least one lookup table. As indicated above, each correspondence table useful for the replacements is either locally available (because transmitted previously or defined by configuration (static)), or extracted from the final flow FF considered during the first main step.

Each extracted packet whose associated PID includes a replacement value is replaced by the latter with its corresponding initial PID value in the corresponding correspondence table.

This second main step is implemented by the first processing module MT1 of the second device D2.

A third main step of the second method (iii) consists in (re) constituting a secondary stream FSk with the packets that have been extracted, respecting the relative scheduling and temporal scheduling they had with respect to each other in the initial (or original) FSk secondary stream constituted by the central station SC. The first main step i) of the second method (which includes a simple decimation) keeps the relative order of the packets in the signal. It will be understood that the objective of this third main step is to reconstitute identically the original FSk secondary flow, that is to say previously constituted during the second main step of the first method (by the second module of MT2 treatment of the first device D1).

This reconstitution is done by means of the time information and the initial PIDs (resulting from the replacement) which are associated with the packets extracted from the final stream FF, and of a possible GPS time reference provided by a GPS receiver RG of the transmitting station. Skj (and therefore that allows with said extracted temporal information to find the local clock and the initial clock of the signal corresponding to the secondary stream FSk), and taking into account the diffusion rate (here DVB-T) which must be respected.

The secondary flow FS1, reconstituted from the example of the final flow FF of FIG. 3, is schematically illustrated in the lower part of this last.

This third main step is implemented by the second device D2, and more specifically by a second processing module MT5 that it comprises. For this purpose, the second processing module MT5 is fed by the first processing module MT4 extracted packets and replaced PIDs.

A fourth main step of the first method (iv) consists in transmitting the secondary flux FSk to the receiving equipment Ei situated in the zone Zk. It is recalled that it is during this fourth main step that all transmitting stations Skj of a zone Zk must synchronously diffuse the secondary stream FSk they have reconstituted by means of their respective second devices.

It will be noted that the transmission may take into account the time information contained in the MIP packet that corresponds to the zone Zk. It is the modulator that takes into account this temporal information.

Note that when the transmission of the final flow FF is ASI type ("Asynchronous Serial Interface"), each transmitting station Skj must, before transmitting the secondary stream FSk, regenerate its clock. This regeneration can for example be done according to the initial value of the clock, which is defined in the optimized final stream FF received, or by means of the PCR information and / or a mechanism based on the filling rate of memory (s) buffer (s) (or "buffer (s)") combined with a mechanism of phase locked loop (or PLL) (for example software type), or by using the information contained in the correlated packets if necessary with a GPS time reference.

This fourth main step is implemented by transmission means MX2 (transponder) that includes each transmitting station Skj and which are powered by its second device D2.

It will be noted that a second device D2, according to the invention, can be produced in the form of a combination of software modules and electronic circuits ("hardware"), or electronic circuits, or even software modules. The invention is not limited to the embodiments of the first end stream generation device, the second secondary stream generation device, the central station, the transmitting station, the first end stream generation method, and the second method of generating secondary flows described above, only by way of example, but it encompasses all the variants that may be considered by those skilled in the art within the scope of the claims below.

Claims

A method of transmitting sets of primary and secondary contents between a central station (SC) of a power supply network and at least two groups (Gk) of at least one transmitting station (Skj) respectively belonging to distribution networks of which at least one is single-frequency, characterized in that it consists of i) constituting a reference flow with packets of at least one set of primary contents, synchronization packets and stuffing packets, ii) in the presence of N (N ≥ 2) sets of secondary contents for N selected groups (Gk) respectively, to form N copies of said reference stream respectively associated with said N groups (Gk), and then to replace in each of said N copies of the stuffing packets by packets of the set of secondary contents for said corresponding group (Gk), so as to constitute N secondary streams, iii) to be substituted in each of said N secondary streams initial values of packet identifiers, associated with the stuff packets, the sync packets, and the packets of the set of secondary contents and the set of primary contents, with replacement values, based on a correspondence table, then to constitute at least one optimized final stream, adapted to the transmission and decodable by said transmitting stations (Skj), with all the packets of one of said N secondary streams, the packets of secondary content sets at least some of said N-1 other secondary streams and synchronization packets contained therein, and iv) transmitting said optimized end stream from the central station (SC) to said N groups (Gk).

2. Method according to claim 1, characterized in that iii) in the presence of a set of secondary contents common to several of said groups (Gk) but not all, it removes redundancy packets of this set of secondary contents present in said N secondary streams.

3. Method according to claim 2, characterized in that iii) temporally synchronizes said secondary streams, and using a pointer for each secondary stream so as to point one of its temporally synchronous packets, then a step a) is performed in which the packet of a secondary stream designated as principal is read, then a step b) in which said packet is placed read in said optimized final stream if it is a packet of said set of primary contents, then one goes to a step f), or a step c) in which, if said read packet is a package of a set secondary content intended for several groups but not all, and not yet placed in said optimized final stream, or a set of non-shared secondary content then reads the packet of said set of secondary contents and place this packet read in said final stream optimized and go to step e), or a step d) in which, if said read packet is a package of a secondary content set intended for several groups but not all and already placed in said stream final optimis , we go to said step e), a step e) in which step c) is repeated for all said other secondary flows, and a step f) in which the pointer of each secondary flow is displaced by one increment in order to repeating said steps a) to e).

4. Method according to one of claims 1 to 3, characterized in that i) is constituted said reference flow with packets of at least one set of primary contents, a first set of secondary contents for one of said N groups (Gk) chosen, synchronization packets and possible stuffing packets, and that ii) N copies of said reference stream associated respectively with said N groups (Gk) are formed, and then replaces in N-1 said copies of the packets of the first set of secondary contents by respectively packets of the N-1 sets of secondary contents for said N-1 groups (Gk) corresponding to form N-1 secondary streams completing the Nth copy, having not been replaced and constituting an Nth secondary stream.

5. Method according to one of claims 1 to 4, characterized in that ii) can be adapted to at least one field of temporal information relative to the secondary contents of the set concerned.

6. Method according to one of claims 1 to 5, characterized in that ii) is designated among the N secondary flows that in which one must take at iii) all packets to begin to constitute said optimized final stream.

7. Method according to one of claims 1 to 6, characterized in that ii) modifying a selected portion of each synchronization packet, which is not related to time information, in each of said N secondary flows.

8. Method according to one of claims 1 to 7, characterized in that iii) synchronizing said secondary streams, and using a pointer for each secondary stream so as to point one of its time synchronous packets, then a step a) is performed in which the packet of a secondary stream designated as principal is read, then a step b) in which said read packet is placed in said optimized final stream, and then if it is a packet said set of secondary contents reads the packets designated by the pointers of the other secondary streams in order to place them also in said optimized final stream, and a step c) in which the pointer of each secondary stream is moved to the next packet in order to reiterate said steps a) and b).

9. Method according to one of claims 1 to 7, characterized in that iii) said secondary streams are synchronized, and a pointer is used for each secondary stream so as to point one of its temporally synchronous packets, then a step a) in which the packet of a secondary stream designated as principal is read, then a step b) in which said packet read is placed in said optimized final stream if it is a packet of said set from primary contents, then to a step e), a step c) in which, if said read packet is a packet of a set of secondary contents, a finite number of packets of set (s) of contents are read without going further than the packet preceding the next packet of the set of primary contents, and placing these packages of set (s) of secondary content read in said optimized final stream, then a step d) in which is repeated step c) for all said others and a step e) in which the pointer of each secondary stream is moved from said finite number of read packets to repeat said steps a) to d).

10. Method according to one of claims 1 to 9, characterized in that iii) an optimized final stream is added to an invalid PAT packet.

11. Method according to one of claims 1 to 10, characterized in that iii) is indicated for each packet identifier if it is associated with a packet of the set of primary contents or a set of secondary contents .

12. Method according to one of claims 1 to 11, characterized in that iii) adapts said optimized final stream to a selected rate by adding to it stuffing packets.

13. Method according to one of claims 1 to 11, characterized in that iii) adapting said optimized final stream to a selected rate by adding to it packets of contents neither primary nor secondary for at least one piece of equipment. broadcast (Skj).

14. Method according to one of claims 1 to 13, characterized in that is also transmitted to said N groups (Gk) in said optimized final stream, at least a portion of each correspondence table.

15. Method according to one of claims 1 to 14, characterized in that i) placing said stuffing packets at regularly spaced positions of said reference flow.

A method of transmitting sets of primary and secondary contents between a group (Gk) of transmitting stations (Skj) of a single frequency distribution network and receiving equipment (Ei), characterized in that it consists, in the event of reception by said transmitting stations (Skj) of an optimized final stream transmitted by means of a method according to one of the preceding claims, of i) extracting from said optimized final stream the packets of the set of primary contents, the packets of the secondary content set intended for said group (Gk), the packets of stuffing present in the initial secondary streams, and the synchronization packets corresponding to said group (Gk), then ii) to be replaced by initial values the replacement values of the packet identifiers of at least some of said extracted packets, according to a correspondence table, and iii) to constitute a secondary stream with said extracted packets, re observing the relative ordering they had with each other in the said optimized final stream, and iv) transmitting said secondary stream to said receiving equipment (Ei).

17. The method of claim 16, characterized in that iv) is carried out a regeneration of a clock present in each transmitting station (Skj) and used for the transmission of the secondary stream, before proceeding to said transmission secondary flow.

18. Method according to one of claims 16 and 17, characterized in that i) is also extracted from said optimized final flow received each correspondence table it contains so as to proceed to ii) the replacement of the values of the identifiers of package.

19. Device (D 1) for generating final flows of sets of primary and secondary contents to be transmitted to at least two groups (Gk) of at least one transmission station (Skj) associated respectively with distribution networks at least one of which is single-frequency, characterized in that it comprises i) first processing means (MT1) arranged, in the presence of at least one set of primary contents intended for N (N ≥ 2) groups (Gk) and N sets of secondary contents respectively for said N groups (Gk) selected, to constitute a reference flow with packets of said set of primary contents, synchronization packets, and stuffing packets, ii) second processing means (MT2) arranged to constitute N copies of said reference stream respectively associated with said N groups (Gk), and to replace in each of said N copies of stuffing packets by packets of the set of cont secondary signals for said corresponding group (Gk), so as to constitute N secondary streams, and iii) third processing means (MT3) arranged to replace in each of said N secondary streams initial values of packet identifiers associated with the packets. stuffing, synchronization packets, and packets of the set of secondary contents and the set of primary contents, by replacement values, according to a correspondence table, and to constitute at least one final stream optimized, adapted to the transmission and decodable by said transmitting stations (Skj), with all the packets of one said N secondary streams, the packets of the secondary content sets of at least one of said N-1 other secondary streams and the synchronization packets contained therein.

20. Device according to claim 19, characterized in that said third processing means (MT3) are arranged, in the presence of a set of secondary contents common to several of said groups (Gk) but not all, to eliminate a redundancy of packets of this set of secondary contents present in said N secondary streams.

21. Device according to claim 20, characterized in that said third processing means (MT3) are arranged to temporally synchronize said secondary streams, and to use a pointer for each secondary stream so as to point one of its temporally synchronous packets then to perform a step a) of reading the packet of a secondary stream designated as principal, or a step b) of placing said packet read in said optimized final stream if it is a packet of said set of primary contents, then to go to a step f), or step c) consisting, if said read packet is a packet of a set of secondary contents intended for several groups but not all, and not yet placed in said stream finalized, or non-shared secondary content set, to read the packet of said set of secondary contents and to place that read packet in said optimized end stream and move to the next step e), a step d) consisting, if said read packet is a packet of a set of secondary content intended for several groups but not all and already placed in said optimized final stream, to go to said step e), a step e) of repeating step c) for all said other secondary flows, and a step f) of incrementally moving the pointer of each secondary flow to repeat said steps a) to e).

22. Device according to one of claims 19 to 21, characterized in that said first processing means (MT1) are arranged to constitute said reference flow with packets of at least one set of primary contents, a first set of secondary contents for one of said N groups (Gk) chosen, synchronization packets and possible packets of stuffing, and in that said second processing means (MT2) are arranged to constitute N copies of said reference stream associated respectively with said N groups (Gk), and to replace in N-1 said copies of the packets of the first set of secondary contents respectively by packets of the N-1 sets of secondary contents for said N-1 groups (Gk) corresponding, so as to constitute N-1 secondary flows completing the Nth copy, not having been the subject of a replacement and constituting an Nth secondary flow.

23. Device according to one of claims 19 to 22, characterized in that said second processing means (MT2) are arranged to adapt at least one field of temporal information relative to the secondary contents of the set concerned.

24. Device according to one of claims 19 to 23, characterized in that said second processing means (MT2) are arranged to designate among N secondary flows that in which said third processing means (MT3) must take all the packets to begin to constitute said optimized final stream.

25. Device according to one of claims 19 to 24, characterized in that said third processing means (MT3) are arranged to synchronize said secondary streams, and to point each temporally synchronous packet of a secondary stream by means of a pointer, then to perform a step a) of reading the packet of a secondary stream designated as principal, then a step b) of placing said packet read in said optimized final stream, then if it was a packet of said set of secondary contents to read the packets designated by the pointers of said other secondary streams to also place them in said optimized final stream, and a step c) of moving the pointer of each secondary stream to the next packet to reiterate said steps a) and b).

26. Device according to one of claims 19 to 24, characterized in that said third processing means (MT3) are arranged to synchronize said secondary flows, and to point each temporally synchronous packet of a secondary stream by means of a pointer then to perform a step a) of reading the packet of a secondary stream designated as principal, then a step b) of placing said packet read in said optimized final stream if it is a packet of said set of primary contents, then proceeding to a step e), a step c) consisting, if said read packet is a packet of a set of secondary contents, reading a finite number of packets of set (s) of secondary contents without to go further than the packet preceding the next packet of the set of primary contents, and to place these packets of set (s) of secondary content read in said optimized final stream, then a step d) of repeating the step c) for all said other secondary streams, and a step e) of moving the pointer of each secondary stream of said finite number of read packets to repeat said steps a) to d).

27. Device according to one of claims 19 to 26, characterized in that said third processing means (MT3) are arranged to modify in each of said N secondary streams a selected part of each synchronization packet which is not relative to temporal information.

28. Device according to one of claims 19 to 27, characterized in that said third processing means (MT3) are arranged to add to said optimized final stream a worthless PAT type packet.

29. Device according to one of claims 19 to 28, characterized in that said third processing means (MT3) are arranged to indicate for each packet identifier whether it is associated with a packet of the set of primary contents or of a set of secondary contents.

30. Device according to one of claims 19 to 29, characterized in that said third processing means (MT3) are arranged to integrate in said optimized final stream at least part of each correspondence table.

31. Device according to one of claims 19 to 30, characterized in that said first processing means (MT1) are arranged to place said stuffing packets at regularly spaced positions of said reference flow.

32. Central station (SC) of a power supply network, characterized in that it comprises a generation device (D1) according to one of claims 19 to 31 and transmission means (MX1) arranged to transmit each optimized final stream generated by said device (D1) to groups (Gk) of transmitting stations (Skj).

33. Device (D2) for generating secondary flows of sets of primary and secondary contents to be transmitted to reception equipment (Ei), for a transmission station (Skj) of a single frequency distribution network, characterized in that it comprises i) first processing means (MT4) arranged, in the event of reception by said transmitting station (Skj) of an optimized final stream transmitted by a central station (SC) according to claim 32, for extracting from said optimized final stream the packets of the set of primary contents, the packets of the set of secondary contents intended for said distribution network, the packets of stuffing present in the initial secondary streams, and the synchronization packets corresponding to said network for replacing, by initial values, the replacement values of the packet identifiers of at least some of the extracted packets, according to a correspondence table and ii) second processing means (MT5) arranged to constitute a secondary stream with said extracted packets, respecting the relative scheduling that they had with respect to each other in said optimized final stream.

34. Device according to claim 33, characterized in that said second processing means (MT5) are arranged to regenerate a clock of said transmitting station (Skj) and the initial clock of the secondary stream.

35. Device according to one of claims 33 and 34, characterized in that said first processing means (MT4) are arranged to extract also from said optimized final flow received each correspondence table it contains so as to proceed with the replacement of values of the packet identifiers.

36. Transmitting station (Skj) for a single frequency distribution network, characterized in that it comprises a generation device (D2) according to one of claims 33 to 35, and transmission means (MX2). arranged to transmit each secondary stream generated by said device (D2) receiving equipment (Ei) of said distribution network, taking into account the time information contained in its synchronization packets.