FR3091109A1 - Method and equipment for generating a transport stream for distribution to a plurality of broadcasting sites, method and site for broadcasting data, and corresponding computer program. - Google Patents

Abstract

Method and equipment for generating a transport stream for distribution to a plurality of broadcasting sites, method and site for broadcasting data, and corresponding computer program. The invention relates to a method for generating a transport stream intended for distribution to a plurality of broadcasting sites, comprising obtaining (23) a set of complex samples representative of a source signal, and a construction (24) of said transport flow, from said set of complex samples, said construction (24) implementing: - a division of said set of complex samples into fragments of complex samples; - for at least one fragment, a first encapsulation of the complex samples of said fragment in a fragmentation packet, the fragmentation packets having a variable length and carrying information representative of the number of complex samples associated with them; - a second encapsulation of the fragmentation packets in transport packets having a fixed length, delivering said transport stream. Figure for the abstract: Figure 2

Description

Description

Title of the invention: Method and equipment for generating a transport stream intended to be distributed to a plurality of broadcasting sites, method and site for distributing data, and corresponding computer program.

1. Field of the invention

The field of the invention is that of the distribution and dissemination of information, in a digital distribution and distribution network comprising at least one fixed reference site and a plurality of dissemination sites.

[0002] The term “fixed reference site” is understood here to mean an entity making it possible to format content and to distribute it in a distribution network. For example, such an entity is a network head (in English "head-end"), national or regional, located in a content creation studio.

The term “broadcasting site” is understood to mean an entity making it possible to receive the content distributed in the distribution network, and to distribute it in particular to individual receivers. For example, such an entity comprises at least one exciter (in English "exciter"). Conventionally, distribution sites are located on separate geographic sites.

The invention applies in particular, but not exclusively, to SFN networks ("Single Frequency Network" for "single frequency network"), whatever the broadcast standard used:

- DVB-T or DVB-T2 (in English "Digital Video Broadcasting - Terrestrial", in French "digital television broadcasting - terrestrial");

- T-DMB (in English “Terrestrial Digital Multimedia Broadcasting”, in French “terrestrial digital multimedia broadcasting”);

- ATSC (in English "Advanced Television Systems Committee", in French "committee of advanced television systems"), in particular ATSC 3.0;

- ISDB-T (in English "Integrated Services Digital Broadcasting - Terrestrial", in French "digital broadcasting of integrated services - terrestrial");

- DAB (in English "Digital Audio Broadcasting", in French "digital sound broadcasting");

- etc.

2. Prior art

We present below, in relation to FIG. 1, an example of a distribution network according to the ATSC 3.0 standard, implementing a fixed reference site, located for example in a content creation studio, and a plurality of dissemination sites SD1, SD2, SDN located on separate geographic sites.

At the studio level, the source data to be distributed 11 (source 1, source 2, ..., source i, for example of the data, audio, and / or video services type, etc.), supplied by one or more service providers, are pre-processed 12. For example, the source data is compressed, then formatted, so that at the level of the broadcasting sites, each physical layer modulator can effect a modulation in a deterministic manner. This preprocessing step can in particular be implemented in a broadcast gateway of a head end.

[0007] In particular, the source data is encapsulated in baseband packets ("baseband packets"). These baseband packets, with signaling information and synchronization information obtained by taking into account a universal reference time (UTR), such as the GPS signal or a signal according to the NTP protocol (“ Network Time Protocol ") and / or PTP (" Precision Time Protocol "), are distributed to SD1, SD2, SDN broadcasting sites via a STL interface (in English" studio-to-transmitter link ", in French "link studio - broadcast site").

In particular, STL packets, comprising baseband packets and signaling information, are transported in STL-TP transport packets on a link 13, for example Ethernet, satellite, etc.

The source data are therefore managed centrally at the studio level, in order to create a transport signal distributed to all the broadcasting sites, in particular allowing deterministic processing at the level of the different broadcasting sites. The structure of such a transport signal is detailed in particular in the document "ATSC Standard: Scheduler / Studio to Transmitter Link" - Document A / 324: 2018 - January 5, 2018.

Each broadcast site SD1, SD2, SDN receives the transport signal comprising the STL-TP transport packets, possibly delayed, and implements a processing allowing re-synchronization of the complex samples obtained at the output of the physical layer modulator. of each dissemination site, taking into account the universal reference time, and radiofrequency transmission of the resynchronized complex samples.

In particular, each broadcasting site SD1, SD2, SDN implements a modulator / exciter 141, 151, 161, delivering a radiofrequency signal, and a power amplifier 142, 152, 162 of the radiofrequency signal. Each modulator / exciter 141, 151, 161 comprises in particular:

- a physical layer modulator, integrating a time synchronization, delivering a flow of complex samples, and

- an exciter, integrating a quadratic modulator (also called modulator

I / Q). delivering a radio frequency signal.

3. Statement of the invention

The invention proposes, according to a particular embodiment, a method of generating a transport stream intended to be distributed to a plurality of broadcasting sites, comprising:

- obtaining a set of complex samples representative of a source signal, and

- a construction of the transport flow from the set of complex samples, implementing:

- a division of the set of complex samples into fragments of complex samples;

for at least one fragment, a first encapsulation of the complex samples of the fragment or of at least one piece of information representative of the complex samples of the fragment in a fragmentation packet, the fragmentation packets having a variable length and carrying information representative of the number d 'complex samples associated with them;

- A second encapsulation of the fragmentation packets in transport packages having a fixed length, delivering the transport flow.

In particular, such a transport stream can be a transport stream generated by a fixed reference site, and distributed to the various broadcasting sites. This is for example a transport flow of a national or regional program.

The invention according to this embodiment thus proposes to move, at a fixed reference site, part of the modulation processing conventionally implemented at the level of the physical layer modulators of each broadcasting site. By deporting part of the modulation processing at the head of the network, the complexity, and therefore the cost, of the exciters of each broadcasting site is reduced.

As a variant, such a transport stream can be generated by a constant sequence generator, for example a TxID identification sequence according to the ATSC 3.0 standard. In this case, the complex samples are for example obtained after sampling the identification sequence.

The invention thus proposes to transport, in the transport flow, complex samples (also called I and Q samples, or I / Q samples) or information representative of the complex samples, in particular when they are coded or compressed. .

In particular, the invention is based on the use of new packages for the transport of complex samples, called fragmentation packages or internal packages (in English "inner packets"), have a different structure from STL packages or packages MPEG-TS transport. In particular, such fragmentation packets have a variable length.

These fragmentation packets can then be encapsulated in transport packets having a fixed length, also called external packets (in English "outer packets"), transported for example on an Ethernet link to broadcast sites.

The use of new packets for the transport of complex samples makes it possible in particular to reduce the size of the headers of the fragmentation packets, in particular compared to the transport packets MPEG-TS or RTP / UDP / IP, which makes it possible to reduce the overhead (in English "overhead") between the different broadcasting sites.

Furthermore, the structure of the fragmentation packets, and in particular their variable length, offers flexibility making it possible to adapt to the needs of the distribution networks.

The invention also relates to equipment for generating a corresponding transport flow. Such equipment is in particular suitable for implementing the method of generating a transport flow described above. For example, such equipment is a fixed reference site, such as a national or regional headend, or a generator of a constant sequence.

The invention also relates to a data dissemination method, implemented at a dissemination site, comprising:

- reception of at least one transport stream comprising transport packages having a fixed length,

- a first de-encapsulation of the transport packets, delivering fragmentation packets, the fragmentation packets having a variable length and carrying information representative of the number of complex samples associated with them;

a second desencapsulation of the fragmentation packets, delivering, for a fragmentation packet, complex samples of a fragment of complex samples or at least information representative of the complex samples of a fragment, the set of fragments of samples being representative of a source signal; and

- a reconstruction of a signal to be broadcast from complex samples. Such a method, implemented at the level of the broadcasting sites, is in particular intended to receive one or more transport flows generated by the method of generating a transport flow described above.

The invention also relates to a corresponding data dissemination site. Such a dissemination site is particularly suitable for implementing the data dissemination method described above.

According to a particular embodiment, the method for generating a transport stream and the method for disseminating data are implemented in one or more separate devices, which can be co-located. In particular, several transport streams can be generated by one or more programs executed by a server. Such an embodiment can in particular be used for the broadcasting of several multiplexes.

The techniques for generating a transport or data flow stream according to the invention can therefore be implemented in various ways, in particular in hardware form and / or in software form.

For example, at least one step of the technique for generating a transport or broadcast stream according to an embodiment of the invention can be implemented: - on a reprogrammable calculation machine (a computer, a processor for example DSP (in English "Digital Signal Processor"), a microcontroller, etc.) executing a program comprising a sequence of instructions, - on a dedicated computing machine (for example a set of logic gates such as an FPGA (in English "Field Programmable Gate Array") or an ASIC (in English "Application-Specific Integrated Circuit"), or any other hardware module).

In particular, the computer program can use any programming language, and be in the form of source code, object code, or intermediate code between source code and object code, such as in a form partially compiled, or in any other desirable form.

Consequently, an embodiment of the invention also aims to protect one or more computer programs comprising instructions adapted to the implementation of methods for generating a transport stream or for broadcasting data such as as described above when this or these programs are executed by a processor, as well as at least one information medium readable by a computer comprising instructions from at least one computer program as mentioned above.

4. List of figures

Other characteristics and advantages of the invention will appear more clearly on reading the following description of a particular embodiment, given by way of simple illustrative and nonlimiting example, and of the attached drawings.

[Fig.l]

Figure 1, described in relation to the prior art, shows a block diagram of a distribution network according to the ATSC 3.0 standard.

[Fig.2]

FIG. 2 illustrates a distribution network according to an embodiment of the invention.

[Fig.3]

FIG. 3 illustrates more precisely the steps implemented by an ST2L adaptation block as illustrated in FIG. 2.

[Fig.4]

FIG. 4 shows an example header of a fragmentation package according to an embodiment of the invention.

[Fig.5]

FIG. 5 illustrates an example of a distribution network implementing a TxID identification sequence insertion and a regionalization according to an embodiment of the invention.

[Fig.6]

FIG. 6 illustrates the generation of the different transport flows according to an embodiment of the invention.

[Fig.7]

[Fig.8]

Figures 7 and 8 show respectively the simplified structure of a fixed reference site and a dissemination site according to an embodiment of the invention.

5. Description of embodiments of the invention

5.1 General principle

The invention takes place in the context of a digital distribution and broadcasting network comprising at least one fixed reference site and a plurality of broadcasting sites, according to which part of the physical layer modulation processing is implemented. works at the fixed reference site. This produces a set of complex samples (also called I and Q samples, or L / Q samples), intended to be distributed to a plurality of dissemination sites.

The general principle of the invention is based on the use of specific packets for the transport of complex samples, or of information representative of these complex samples (in particular when they are coded or compressed), from a site of fixed reference to a plurality of dissemination sites. Complex samples (or an encoded and / or compressed version of these samples) are thus encapsulated in fragmentation packets, of variable length, themselves encapsulated in transport packets, of fixed length. In particular, the fragmentation packets have a reduced length header compared to the MPEGTS or RTP / UDP / IP transport packets conventionally used for this type of distribution.

We present below, in relation to FIG. 2, an example of implementation of the invention, in a distribution network based on the ATSC 3.0 standard. Of course, the invention is not limited to this broadcast standard, and can be implemented with any digital broadcast standard, notably authorizing SFN operation of broadcast sites, regionalization or time multiplexing of frames of different types. , and / or the insertion of an identification sequence.

The distribution network illustrated in FIG. 2 comprises a fixed reference site, located for example in a content creation studio, and a plurality of broadcasting sites, for example two broadcasting sites SD1 and SD2, located on distinct geographic sites belonging to the same SFN network.

5.2 Method implemented on the equipment side for generating a transport flow

A. General principle

Equipment for generating a transport stream, for example a fixed reference site (“Studio” according to FIG. 2), implements the method for generating a transport stream according to one embodiment of the invention.

Thus, at the studio level, the source data to be distributed 21 (source 1, source 2, ..., source i, for example of the data, audio, and / or video services type, etc.), supplied by a or several service providers, can be preprocessed 22. For example, the source data are coded, multiplexed and ordered in a coding / multiplexing / scheduling block (in English "encoder / multiplexer / scheduler"). The preprocessing step 22 can in particular be implemented in a broadcast gateway.

The source data, possibly preprocessed, are then modulated 23 in a physical layer modulation block, delivering a modulated signal. Such a physical layer modulation block can implement a transformation of the source data, possibly pre-processed, from the frequency domain to the time domain, for example by means of a fast inverse Fourier transformation (IFFT for “Inverse fast Fourier transform ").

The complex samples (samples I and Q) representing the digital time signal are used by the adaptation block ST2L 24 (for "STL Like") to construct a transport stream intended to be distributed to the various broadcasting sites SD1 , SD2 via a distribution network 25 (Ethernet, satellite link, microwave, optical fiber, etc., possibly all physical interfaces allowing the transport of IP packets).

FIG. 3 illustrates more precisely the steps implemented by the ST2L adaptation block 24 according to an embodiment of the invention.

More specifically, such a block 24 obtains (31) a set of samples representative of a source signal, corresponding for example to the flow of complex samples at the output of the modulator 23.

The ST2L 24 adaptation block implements a construction of a transport flow, by:

- cutting (32) the set of samples into fragments,

- For at least one fragment, encapsulating (33) the complex samples of the fragment, possibly coded and / or compressed, in a fragmentation packet, also called an internal packet. Such a fragmentation package can carry any sequence of complex samples. This first encapsulation can be implemented for all the fragments, - encapsulating (34) the fragmentation packets in transport packets, also called external packets.

In particular, it should be noted that the division of all the samples into fragments may depend on the structure of a frame according to the standard considered, ATSC 3.0 for example. Thus, a first fragment, transported in a first fragmentation packet, corresponds for example to the "boot" (in English "bootstrap") of the ATSC 3.0 frame. Other fragments, transported by other fragmentation packets, carry the complex samples corresponding to the OEDM symbols for example. A fragmentation packet can thus transport a complete OEDM symbol, or, according to a particular embodiment, an OEDM symbol without its guard interval / cyclic prefix. In the latter case, this cyclic prefix can be reconstructed by copying part of the complex samples, at the broadcasting site.

The ST2L 24 adaptation block therefore makes it possible to construct a transport stream for complex samples generated by a physical layer modulator located at the studio level (for example an ATSC 3.0 modulator), intended for a set of exciters from the sites of diffusion. For example, if a transformation from the frequency domain to the time domain is implemented in the physical layer modulator located at the studio level, each broadcasting site directly obtains complex samples (I and Q), which makes it possible to dispense with implementing a transformation from the frequency domain to the time domain at each broadcasting site.

As illustrated in FIG. 3, a two-level encapsulation is therefore used for transporting the data:

- a first encapsulation of complex samples in specific packages, called fragmentation packages. This first encapsulation is not of the RTP / UDP / IP type. It is for example called internal ST2L layer, or “ST2L inner layer” in English. The internal ST2L layer fragmentation packets can in particular have different lengths;

- a second encapsulation of the fragmentation packets in transport packets. This second encapsulation can be of the RTP / UDP / IP type. It is for example called ST2L external layer, or “ST2L outer layer” in English. The outer ST2L layer fragmentation packets are all the same length. The use of transport packets of the same length thus offers the possibility of using control mechanisms such as those defined in the SMPTE-2022 standard to protect distribution over the IP network.

In particular, the transport packets of the external ST2L layer can be routed over an Ethernet link and have a maximum length of 1500 bytes (MTU, in French "maximal transfer unit", in English "Maximum Transfer Unit" 1500 bytes). The transport flow thus obtained is for example denoted ST2L-TP.

B. Internal ST2L layer

B.l Fragmentation packets and information and individual addressing packets

As indicated above, the method for generating a transport flow according to the invention can be implemented at a fixed reference site, to generate a transport flow from a national or regional program by example, or at the level of a constant sequence generator, to generate for example an identification sequence.

Three types of fragmentation packets are used, for example, to encapsulate complex samples, depending on the use of the method.

A first type of fragmentation packet makes it possible to transport a continuous flow of complex samples. This type of fragmentation packet can be used to transport a continuous stream of complex samples corresponding for example to a main / national program, without zero time interval or discontinuity between frames (ATSC 3.0 for example). It is noted that such a continuous flow is sufficient to supply an antenna.

A second type of fragmentation packet makes it possible to transport a “discontinuous” flow of complex samples. This type of fragmentation package can be used to transport one or more groups of complex samples, corresponding for example to a secondary / regional program, which can be used by at least one exciter from a dissemination site for insertion. regional or time multiplexing of different frames.

A third type of fragmentation packet makes it possible to transport a constant sequence. For example, a constant sequence can be used to transport a TxID identification sequence to be associated with a continuous or discontinuous flow of complex samples at the level of at least one exciter from a diffusion site. Such a constant sequence can be transmitted several times, for example according to a predefined period. It can in particular be used by the receiver of a signal, to enable it to identify the broadcasting site / the exciter which emitted the signal. It is generally added to the signal to be broadcast by the broadcasting site, possibly to a reduced set of samples from the latter.

A fourth type of packet intended to be encapsulated in one or more transport packets is also defined, making it possible to transport flow information and individual addressing. This package is for example called SIIA package (in English "Stream Information and Individual Addressing data"). It does not carry complex samples. Such SIIA packets can therefore be distributed in the transport packets with other fragmentation packages carrying complex samples, such as the fragmentation packages associated with a continuous flow of complex samples, with a discontinuous flow of complex samples, or at a constant sequence.

Thus, according to a particular embodiment, at least one of the fragmentation packets is of a type belonging to the group comprising:

- a fragmentation package associated with a continuous flow of complex samples;

- a fragmentation package associated with a discontinuous flow of complex samples;

- a fragmentation package associated with a constant sequence.

For example, all the fragmentation packets of the internal ST2L layer belong to one of the types mentioned above.

In particular, the internal ST2L layer transports either fragmentation packets associated with a continuous flow of complex samples, or fragmentation packets associated with a discontinuous flow of complex samples, or fragmentation packets associated with a constant sequence , as well as possibly SIIA packages.

According to another particular embodiment, the length of the header of the fragmentation packets is strictly less than 40 bytes, and preferably equal to 8 bytes. Indeed, since the fragmentation packets are not transport packets, the length of their header is strictly less than that of transport packets, conventionally equal to 40 bytes for transport packets of RTP / UDP / IP type.

According to a first embodiment, the proposed solution allows broadcasting sites to reconstruct a transport package (i.e. belonging to the external STL2 layer), in particular in the event of the loss of a transport package.

To do this, according to this first embodiment, at least one of the fragmentation packets carries at least one item of information relating to at least one other fragmentation packet.

For example, the information relating to at least one other fragmentation package ap11 belongs to the group comprising:

- the type of the following fragmentation package;

- the length of the next fragmentation packet;

- the number of complex samples associated with a next fragmentation package of the same type; and

- the size of a guard interval associated with complex samples associated with a following fragmentation packet of the same type.

It is thus possible to use the information of another fragmentation package to build a substitution package to replace a fragmentation package encapsulated in a corrupt transport package, i.e. a lost or erroneous package. Such a substitution package has a length identical to that of the fragmentation package it replaces. However, its content may be different.

According to a second embodiment, the proposed solution makes it possible to ensure time synchronization of the broadcasting sites and in particular to transmit a continuous stream of samples.

To do this, according to this second embodiment, at least one of the fragmentation packets carries at least time synchronization information from the broadcasting sites.

The insertion of such synchronization information in a fragmentation packet associated with a fragment, or in a set of fragmentation packets associated with a set of fragments forming a frame, makes it possible in particular to ensure SFN operation of the broadcast sites receiving the transport stream.

Frequency synchronization of the broadcasting sites can be ensured in a conventional manner, from a reference signal such as GPS.

At least one of the fragmentation packets can also carry at least one item of information belonging to the group comprising:

- information relating to the start of a frame;

- information relating to the strength of the signal represented by the complex samples of the fragmentation packet.

It is noted that the information relating to the start of a frame can in particular be used as a reference to define a shift between the start of the frame (corresponding to the first complex sample of the first fragment) and the start of a constant sequence to be inserted in the transport flow.

It is also noted that the information relating to the power can in particular be used to determine whether certain treatments at the exciter level can or must be applied to the samples of the fragment concerned, for example an automatic gain control.

According to a third embodiment, the proposed solution makes it possible to ensure time synchronization of the broadcasting sites, in particular in the case of replacement of fragmentation packets by other fragmentation packets, or of multiplexing of sample streams complex.

To do this, according to this third embodiment, at least one of the fragmentation packets carries at least one piece of time synchronization information for the fragmentation packets belonging to the group comprising:

- information relating to the replacement of the fragmentation package by another fragmentation package;

information relating to the multiplexing of the flow of complex samples from which said fragmentation packet is constructed, with another flow of complex samples. In particular, multiplexed sample streams are discontinuous sample streams.

For example, the information relating to the replacement or multiplexing of the fragmentation package belongs to the group comprising:

- an indicator indicating that the current fragmentation package can be replaced by another fragmentation package at one of the dissemination sites;

- an indicator indicating that the complex samples associated with the current fragmentation packet directly follow the complex samples associated with the previous fragmentation package, without time lag, after replacement or multiplexing;

- an indicator indicating that the complex samples associated with the current fragmentation package are directly followed by the complex samples associated with the next fragmentation package, without time difference, after replacement or multiplexing.

According to a fourth embodiment, the proposed solution makes it possible not to transmit the guard interval and to reduce the bit rate in the case of a signal based on the use of a guard interval.

To do this, according to this fourth embodiment, at least one of the fragmentation packets carries at least one item of information relating to the length of a guard interval associated with the complex samples associated with the fragmentation packet.

According to a fifth embodiment, the proposed solution makes it possible to monitor the delay introduced by the network, in particular by indicating the time of transmission of the fragmentation packet.

To do this, according to this fifth embodiment, at least one of the fragmentation packets carries at least one item of information relating to the time of transmission of the fragmentation packet.

It is noted that the various embodiments described above can be taken in13 individually or combined.

An example of a structure of fragmentation packets implementing these different embodiments is described below.

B.2 General structure of the packets of the internal ST2L layer

A fragmentation package includes a header ("Header"), a "data structure" field ("Structure_data"), and a "data" field ("Data").

The header comprises for example 8 bytes. It carries the type T (“type”) of the current fragmentation packet and the length L (“length”) of the payload of the current fragmentation packet (ie the length of the “data structure” and “data” fields), as well as a version number V (“version”) and a sequence number Seq (“sequence number”).

The length and content of the "data structure" field depend on the type of the fragmentation packet. Likewise, the length and content of the "data" field depend on the type of fragmentation packet.

In particular, as illustrated in FIG. 4, information “type of a next fragmentation packet” NT (“NextType”) and “length of a next fragmentation packet” NL (“NextLength”) can be carried. by the header of the current fragmentation packet.

As indicated above, it is thus possible according to the first embodiment to use the information of another fragmentation package to build a substitution package to replace a fragmentation package encapsulated in a corrupt transport package. , ie a lost or wrong package.

B. 3 Example of the structure of the fragmentation packets associated with a continuous or discontinuous flow of complex samples

An example of the structure of the fragmentation packets of the first or second type according to the invention is presented below, allowing respectively to carry a continuous flow of complex samples or a discontinuous flow of complex samples (ie a group of 'complex samples).

We note these fragmentation packets "IQS packets" or "IQ_stream". More specifically, we denote "IQS-C packets" the fragmentation packets associated with a continuous flow of complex samples, and "IQS-D packets" the fragmentation packets associated with a discontinuous flow of complex samples.

[Tables 1]

Syntax Number of bits Lormat Iq_stream (IQS) () { Header () { Type 4 uimsbf Version 4 uimsbf Sequence 4 uimsbf Reserved 2 for (i = 0; i <2; i ++) ‘1’ Length 18 uimsbf Next_type 4 uimsbf reserved 10 for (i = 0; i <10; i ++) ‘1’ Next_length 18 uimsbf } Structure_Data () { Start_of_frame 1 uimsbf Regional_slot 1 uimsbf Stuck_to_previous 1 uimsbf Stuck_to_next 1 uimsbf Nominal_power 1 uimsbf Num_samples 16 uimsbf Gi_size 14 uimsbf Next_num_samples 16 uimsbf Next_gi_size 14 uimsbf Timestamp_seconds 32 uimsbf Timestamp_nanoseconds 32 uimsbf Pkt_rls_seconds 4 uimsbf Pkt_rls_a-milliseconds 10 uimsbf reserved 17 for (i = 0; i <17; i ++) ‘1’ } Iq_samples () {

for (i = 0; i <num_samples; i ++) { I_s ample not tcimsbf Q_sample not tcimsbf } Padding x for (i = 0; i <x; i ++) ‘1’ } }

In this example, the header includes several fields:

- the "Type" field indicates the type of the fragmentation packet. For example, a type equal to 1 indicates that the fragmentation packet is associated with a continuous flow of complex samples, and a type equal to 2 indicates that the fragmentation package is associated with a continuous flow of complex samples;

- the "Version" field indicates the version of the fragmentation package. For example, the current version is noted 0x0;

- the "Sequence" field indicates the sequence number. For example, this is a number specific to each type of fragmentation packet. Such a number can be used to detect a disorganization or a loss of a fragmentation packet of a given type;

- the "Length" field indicates the length of the payload of the fragmentation packet (counted from the byte following the "Next_length" field of the current fragmentation packet);

- the “Next_type” field indicates the type of the next fragmentation packet, i.e. of the fragmentation packet which directly follows the current fragmentation packet;

- the “Next_length” field indicates the length of the payload of the next fragmentation packet, ie of the fragmentation packet which directly follows the current fragmentation packet (counted from the byte following the “Next_length” field of the next packet of fragmentation).

The “data structure” field also includes several fields:

- the "Start_of_frame" field carries information relating to the start of a frame. For example, it is equal to 1 if the first sample of the current fragmentation packet is the first sample of a frame, i.e. the first sample of the first fragmentation packet;

- the “Regional_slot” field carries information relating to the replacement of the current fragmentation package. For example, it is equal to 1 if the current fragmentation package can be replaced locally by another fragmentation package (for regionalization for example);

the “Stuck_to_previous” field also carries information relating to the replacement or multiplexing of the current fragmentation package. For example, it is equal to 1 if the complex samples associated with the current fragmentation packet directly follow the complex samples associated with the previous fragmentation package (which could have been replaced or multiplexed), without time lag;

the “Stuck_to_next” field also carries information relating to the replacement or multiplexing of the current fragmentation packet. For example, it is equal to 1 if the complex samples associated with the previous fragmentation packet directly the complex samples associated with the next fragmentation packet (which could be replaced or multiplexed), without time shift;

the “Nominal_power” field carries information relating to the signal strength represented by the complex samples of the fragmentation packet. For example, it is equal to 1 if the sample sequence has a nominal effective power and an automatic gain control mechanism can be implemented;

the "Num_samples" field carries information relating to the number of complex samples associated with the current fragmentation package. For example, it is between 0 and 65535 and is equal to the number of complex samples contained in the fragmentation packet, minus one;

the "Gi_size" field carries information relating to the length of a guard interval associated with the fragmentation packet. For example, it indicates the number of complex samples of a fragmentation packet which must be copied to serve as a cyclic prefix / guard interval at the level of the dissemination sites, and therefore inserted before the payload (for example the last N fragmentation package samples). A null value indicates that there is no guard interval to insert.

the “Next_num_samples” field carries information relating to another fragmentation package. For example, it is between 0 and 65535 and is equal to the number of complex samples contained in the next fragmentation packet carrying complex samples, minus one;

the "Next_gi_size" field also carries information relating to another fragmentation packet, and more precisely information relating to the length of a guard interval associated with a next fragmentation packet. For example, it indicates the number of complex samples of the following similar fragmentation package that can be copied to serve as a cyclic prefix / guard interval at broadcast sites, and therefore inserted before the payload. A null value indicates that there is no guard interval to insert;

- the “Timestamp_seconds” field carries at least time synchronization information from the broadcasting sites. It indicates for example the time of radiofrequency emission of the data carried by the current fragmentation packet, in seconds;

- the "Timestamp_nanoseconds" field also carries at least time synchronization information from the broadcasting sites. It indicates for example the instant of transmission of the data carried by the current fragmentation packet, in nanoseconds;

If time synchronization information "Timestamp_seconds" or "Timestamp_nanoseconds", more generally called "timestamp" is not available, this field can be set to the value OxFFFFFFFF. In particular, it should be noted that the use of such a "timestamp" is optional for transmission in an MFN ("Multi-frequency Network"). On the other hand, in an SFN network, at least one timestamp per frame is useful for ensuring the synchronization of the broadcasting sites. In particular, the insertion of a timestamp per fragmentation packet makes it possible to accelerate the synchronization of the broadcasting sites, since it is not necessary to wait for the start of a next frame to synchronize the broadcasting sites ( exciters can use any fragmentation packet to ensure synchronization);

- the "Pkt_rls_seconds" field contains information relating to the time of transmission of the fragmentation packet. For example, it indicates the second at which the fragmentation packet leaves the generating equipment of a transport stream;

- the "Pkt_rls_a-millseconds" field also carries information relating to the time of transmission of the fragmentation packet. For example, it indicates the millisecond at which the fragmentation packet leaves the generating equipment of a transport stream.

Finally, the "data" field also includes several fields:

- the "I_sample" field carries the phase component of a complex sample of the fragmentation package;

- the "Q_sample" field carries the quadrature component of a complex sample of the fragmentation package;

- the padding field can be used to complete the last byte. Note that some fields are optional.

For example, the “Next_type”, “Next_length”, “Next_Num_Samples” and “Next_gi_size” fields can be used according to the first embodiment allowing the broadcasting sites to reconstruct a transport package, in particular in the event of loss of 'a transport package.

The “Type”, “Length”, “Start_of_frame”, “Nominal_power”, “Num_samples”, “Timestamp_seconds” and “Timestamp_nanoseconds” fields can be used according to the second embodiment allowing time synchronization of the sites. diffusion and in particular to transmit a continuous flow of samples.

The “Regional_slot”, “Stuck_to_previous” and “Stuck_to_next” ”fields can be used according to the third embodiment making it possible to ensure time synchronization of the broadcasting sites, in particular in the case of replacement of fragmentation packets by other fragmentation packets, or multiplexing complex sample streams.

The "GI_size" field can be used according to the fourth embodiment which allows the guard interval not to be transmitted.

The “Pkt_rls_seconds” and “Pkt_rls_a-millseconds” fields can be used according to the fifth embodiment making it possible to monitor the delay introduced by the network.

As already indicated, these different embodiments can be implemented individually or in combination.

According to at least one particular embodiment, the "Type", "Length", and "Num_samples" fields are mandatory.

[ΟΠΟ] B. 4 Example of the structure of fragmentation packets associated with a constant sequence

An example of the structure of the third type fragmentation packets according to the invention is presented below, making it possible to transport a constant sequence of complex samples, a fragmentation packet carrying for example an identification sequence of a dissemination site.

We note these fragmentation packets "CSIQ packets" or "Constant_Sequence_iq".

[Paintings!]

Syntax Number of bits Format Constant_Sequence_iq (CSIQ) () { Header () { Type 4 uimsbf Version 4 uimsbf Sequence 4 uimsbf Reserved 2 for (i = 0; i <2; i ++) ‘1’ Length 18 uimsbf Next_type 4 uimsbf reserved 10 for (i = 0; i <10; i ++) ‘1’ Next_length 18 uimsbf } Structure_Data () { Nominal_power 1 uimsbf Num_samples 16 uimsbf Num_repeat 8 uimsbf Lrame_offset 20 uimsbf reserved 19 for (i = 0; i <19; i ++) ‘1’ } Iq_samples () { for (i = 0; i <num_samples; i ++) { I_s ample not tcimsbf Q_sample not tcimsbf } Padding X for (i = 0; i <x; i ++) ‘1’ } }

According to this example, the header includes fields similar to those defined for the fragmentation packets associated with a continuous or discontinuous flow of complex samples. These different fields are therefore not repeated in detail here. In particular, we note that a value equal to 3 for the "Type" field indicates that the fragmentation packet is associated with a constant sequence (CSIQ).

The “data structure” field comprises various fields:

- the "Nominal_power" and "Num_samples" fields as defined above;

- the field “Num_repeat” carries information relating to the number of repetitions of the constant sequence in the signal to be broadcast. For example, a value of 0 indicates that the sequence should be inserted only once by the exciter;

- the “Frame_offset” field carries information relating to the offset between the first complex sample of the frame (ie start of the frame, indicated for example in the “Start_of_frame” field of the “data structure” field of an associated fragmentation packet to a continuous or discontinuous flow of complex samples), and the complex sample to which the first complex sample of the constant sequence must be added. For example, an offset value of 0 indicates that the first complex sample in the constant sequence should be added to the first sample in the frame, for example by the broadcast site exciter.

Finally, the "data" field also includes fields similar to those defined for the fragmentation packets associated with a continuous or discontinuous flow of complex samples. These different fields are therefore not repeated in detail here.

Thus, according to one embodiment, at least one of the fragmentation packets is of the fragmentation packet type associated with a constant sequence, and carries a sequence of identification of at least one of the broadcasting sites.

For example, such a sequence is of the TxID type. It is noted that such a sequence does not need to be distributed, in the transport stream, for each frame of the signal to be broadcast. On the other hand, on the broadcasting site side, an exciter can insert this TxID sequence into each frame of the signal to be broadcast. It is also possible to repeat the sequence TxID several times successively.

As with the IQS fragmentation packets, certain fields of the CQIS fragmentation packets are optional.

[0119] B. 5 Example of Structure of Flow Information Packets and Individual Addressing [0120] Finally, an example of structure of packets of the fourth type according to the invention is presented, making it possible to transport flow information and d '' individual addressing.

We note these packages "SIIA packages".

[0122] In particular, such SIIA packets carry configuration parameters for at least one of the broadcasting sites. For example, SIIA packets carry:

- individual parameters for each broadcast site / exciter in the network, including the identifier (s) of the transport stream (s) (ST2L-TP) to be used by the broadcast site;

- parameters associated with each transport stream (ST2-TP) of the network, for example the destination multicast IP address and the destination UDP port number.

[Tables3]

Syntax Number of bits Format Stream_Information_Individual_addressing (SIIA) () { Header () { Type 4 uimsbf Version 4 uimsbf Sequence 4 uimsbf Reserved 2 for (i = 0; i <2; i ++) ‘1’ Length 18 uimsbf Next_type 4 uimsbf reserved 10 for (i = 0; i <10; i ++) ‘1’ Next_length 18 uimsbf } Structure_Data () { num_xmtrs_in_group 6 uimsbf xmtr_group_num 7 uimsbf reserved 5 for (i = 0; i <5; i ++) ‘1’ tx_carrier_offset 2 tcimsbf Num_streams 8 uimsbf reserved 4 for (i = 0; i <4; i ++) ‘1’ } Per_Transmitter_Data () { for (i = 0; i <= num_xmtrs_in_group; i ++) { xmtr_id 13 uimsbf tx_time_offset 16 tcimsbf txid_inj ection_l vl 4 uimsbf

Reserved 7 for (i = 0; i <7; i ++) ‘1’ main_stream_id 8 Uimsbf tx_id_stream_id 8 Uimsbf reg_stream_id 8 Uimsbf } } IQ_Compression_Data () { Nb_bits_iq 4 uimsbf Comp_law 4 uimsbf Sample_frequency_standard 7 uimsbf B andwidth_code 7 uimsbf reserved 10 for (i = 0; i <10; i ++) ‘1’ } Stream_information_Data () { for (i = 0; i <num_streams; i ++) { stream_id 8 uimsbf stream_ip_addre s s 32 uimsbf stream_udp_port 16 uimsbf reserved 8 for (i = 0; i <8; i ++) ‘1’ } } Error_Check_Data () { crcl6 16 uimsbf } }

According to this example, the header includes fields similar to those defined for the fragmentation packets associated with a continuous or discontinuous flow of complex samples. These different fields are therefore not repeated in detail here. In particular, we note that a value equal to 4 for the "Type" field indicates that the packet is a packet of flow information and individual addressing (SIIA).

The “data structure” field includes:

- the fields “num_xmtrs_in_group”, “xmtr_group_num”, “tx_carrier_offset”, known and described in document A / 324 “Scheduler / studio to transmitter link” mentioned above;

- the "Num_streams" field carrying information relating to the number of transport flows described in the "Stream_information_data" field. For example, a value of 0 indicates that there is no "Stream_information_data" field. A value between 1 and 255 indicates the number of streams that can be identified.

According to this example, there are three types of data fields for a SIIA packet:

- the "Per_Transmitter_Data" field allowing individual configuration of the different exciters from the modulator as well as identifying the flows intended for one of them;

- the “IQ_compression_data” field used to define the complex sample coding rule and possibly a compression method;

- the "Stream_information_data" field used to identify the destination multicast IP address and the UDP destination port number.

The “Per_Transmitter_Data” field includes:

- the fields "xmtr_id", "tx_time_offset", "txid_injection_lvl", known and described in document A324;

- the “Main_Steam_id” field carrying information representative of an identifier of a transport stream carrying a main complex sample stream for the distribution site considered (from 0 to 255), for example a transport stream of a National program ;

- the "Tx_id_stream_id" field carrying information representative of an identifier of a transport stream carrying a constant sequence of complex samples for the distribution site considered (from 0 to 255);

the “Reg_Stream_id” field carrying information representative of an identifier of a transport stream carrying a stream of secondary complex samples for the distribution site considered (from 0 to 255), for example a transport stream of a regional program.

The “IQ_compression_data” field includes:

- a “Nb_bits_iq” field indicating the number of bits used to encode each component (phase and quadrature) of the complex samples;

- a “Comp_law” field indicating the type of compression used to compress each component (phase and quadrature) of complex samples. For example, a value of 0 indicates that no compression is implemented;

- a "Sample_frequency_standard" field indicating the basic sampling frequency according to the standard considered. For example: [Tables4]

Sample_frequency_standard Base frequency (Base_frequency) Standard 0 384 kHz ATSC-3 1 8/7 MHz DVB-T2

- a “Bandwidth_code” field indicating the bandwidth of the channel according to the standard considered. The coding also depends on the value of the "Sample_frequency_standard" field.

[0128] For example, the sampling frequency can be calculated as follows:

[Tables5]

S ample_frequen cy_standard Sampling frequency Note 0 (ATSC-3) Ps = Base_frequency x (16 + Bandwidth_code) The value of the "Bandwidth_code" field corresponds to the coefficient "Bsr_coefficient" used to calculate the sampling frequency, called the system frequency, as defined in the document "ATSC Standard: A / 321, System Discovery and Signaling", A / 321: 2016, March 23 2O16. For example, the value of the “Bandwidth_code” field is equal to 2 for a channel width of 6 MHz with a sampling frequency of the order of 6912 MHz. 1 (DVB-T / T2) Ps = Base_Prequency x B andwidth_code The value of the “Bandwidth_code” field corresponds to the channel width, in MHz. For example, the value of the “Bandwidth_code” field is equal to 8 for a channel width of 8 MHz with a sampling frequency of the order of 91,428 MHz.

[0129]

[0130]

[0131]

The "Stream_information_data" field includes:

- a "stream_id" field carrying information representative of an identifier of a transport stream (from 0 to 255);

- a "stream_ip_address" field indicating the multicast IP address for the transport stream identified in the "stream_id" field;

- a “stream_udp_port” field indicating the UDP destination port number of the transport stream identified in the “stream_id” field;

- a "crcl6" field carrying the value resulting from the implementation of a 16-bit redundancy check, applied to all the fields of the SIIA packet preceding the "crcl6" field.

As with IQS fragmentation packets, some fields in SIIA packets are optional.

C. External ST2L layer

Once the complex samples have been encapsulated in fragmentation packets, the fragmentation packets are encapsulated in transport packets, also denoted ST2L-TP packets.

For example, these transport packets can be transmitted over an Ethernet link, and are of the RTP / UDP / IP type. These transport packets have a fixed length, less than or equal to 1500 bytes, configurable by the user.

The use of such transport packages in particular ensures compatibility of the proposed technique with the SMPTE-2022 standard. A forward error correction (FEC) module can thus be implemented to protect distribution over an IP network.

For MISO, ΜΙΜΟ transmissions or link aggregation (in English "channel bonding"), the different streams of complex samples are encapsulated in fragmentation packets encapsulated in different transport streams: for example a stream of transport of a national program carrying fragmentation packages associated with a continuous flow of samples, a transport flow of a regional program carrying fragmentation packages associated with a discontinuous flow of samples, several transport flows each carrying a constant sequence associated with a separate broadcast site, etc.

In the same network implementing MISO transmission, ΜΙΜΟ or link aggregation, the different transport flows carry the same flow information and individual addressing, i.e. the same SIIA packets.

In particular, a transport stream encapsulating fragmentation packets associated with a constant sequence (CQIS packets) can supplement an RTP packet with an RTP stuffing sequence. In this case, a P flag in the header of the RTP / UDP / IP packet indicates the presence of a padding sequence.

In contrast, a transport stream encapsulating fragmentation packets associated with a continuous or discontinuous stream of samples (IQS-C or IQS-D packets) does not need to complete the last RTP packet with a sequence of RTP jam.

5.3 Process implemented on the broadcasting site side

Returning to FIG. 2, the transport stream or streams thus generated are distributed to the various broadcasting sites SD1, SD2 via the distribution network 25.

Each dissemination site can implement the data dissemination method according to an embodiment of the invention. In particular, the post-processing linked to the amplification of the power of the radiofrequency signal for broadcasting remains managed by broadcasting sites.

Each broadcasting site SD1, SD2 therefore receives one or more transport streams.

For example, each broadcasting site SD1, SD2 includes an adaptation block ST2L 261, 262, implementing:

[0144] - reception of at least one transport stream comprising transport packages having a fixed length,

A first de-encapsulation of the transport packets, delivering fragmentation packets, the fragmentation packets having a variable length and carrying information representative of the number of complex samples associated with them;

A second de-encapsulation of the fragmentation packets, delivering, for a fragmentation packet, complex samples of a fragment of complex samples or at least information representative of the complex samples of a fragment, the set of fragments samples being representative of a source signal; and

[0147] - a reconstruction of a signal to be broadcast from complex samples.

Each broadcasting site SD1, SD2, also implements a quadratic modulator (also called I / Q modulator) 271, 272, delivering a radiofrequency signal, and a power amplifier 281, 282 of the radiofrequency signal.

For example, the adaptation block ST2L 261 (respectively 262) and the quadratic modulator 271 (respectively 272), present at the level of the broadcasting site SD1 (respectively SD2) belong to an exciter of the broadcasting site SD1 (respectively SD2).

In particular, the quadratic modulator 271, 272, present at each broadcasting site, implements a quadrature modulation of a transmission carrier, with the complex samples extracted from the transport stream, and a digital conversion analog DAC.

According to a first embodiment, discussed above, the proposed solution allows broadcast sites to reconstruct a transport packet (i.e. belonging to the external STL2 layer), in particular in the event of the loss of a transport packet.

To do this, on the broadcasting site side, the broadcasting method implements:

- detection of a problem of reception of at least one transport packet, said corrupt transport packet;

a replacement, by a determined sequence of samples, of the complex samples encapsulated, during the generation of the transport stream, in at least one fragmentation packet encapsulated in the corrupt transport packet, taking account of information relating to the packet of fragmentation encapsulated in the corrupt transport package carried by another fragmentation package encapsulated in another transport package.

By “corrupted package” is meant here a transport package having undergone a problem during transmission: either this transport package is lost and is not received by the broadcasting site, or this transport package is erroneous . When such a transport package is lost, it is thus possible to construct a substitution package for a fragmentation package that it was transporting, from another fragmentation package transported by another transport package.

In particular, it is possible to detect that a transport packet is lost using the sequence number of the packet, or that a transport packet is lost or erroneous using a mechanism for verifying a sum of control.

In particular, the determined sequence of samples can be a stuffing sequence comprising harmful samples, a pre-defined sequence or a sequence meeting certain characteristics necessary for the exciter to function properly, etc.

According to a second embodiment also discussed previously, the proposed solution makes it possible to ensure a temporal synchronization of the broadcasting sites and in particular to transmit a continuous stream of samples.

To do this, on the broadcasting site side, the broadcasting method implements an extraction of at least one piece of time synchronization information from the broadcasting sites carried by at least one of the fragmentation packets (for example in the fields " Timestamp_seconds "and / or" Timestamp_nanoseconds ").

In particular, the diffusion method comprises the detection of the first complex sample of a frame from information relating to the start of a frame carried by at least one of the fragmentation packets (for example in the field " Start_of_frame ”).

According to a third embodiment also discussed above, the proposed solution makes it possible to ensure time synchronization of the broadcasting sites, in particular in the event of replacement of fragmentation packets by other fragmentation packets, or of multiplexing of flows complex samples.

To do this, on the broadcasting site side, the broadcasting method implements the replacement of a fragmentation packet obtained from the transport stream, by another fragmentation packet obtained from another stream of transport, or the multiplexing of complex sample streams, taking account of information relating to the replacement or multiplexing of the fragmentation packet obtained from the transport stream (for example in the fields "Regional_slot", "Stuck_to_previous", "Stuck_to_next" and Timestamp).

According to a fourth embodiment also discussed above, the proposed solution makes it possible not to transmit the guard interval but to reconstruct it at the level of the broadcasting sites, in the case of a signal based on the use of 'a guard interval.

To do this, according to this fourth embodiment, the diffusion method comprises the reconstruction of a guard interval associated with the complex samples associated with a fragmentation packet obtained from the transport stream, from a information relating to the length of the guard interval carried by the fragmentation packet.

According to a fifth embodiment also discussed previously, the proposed solution makes it possible to monitor the delay introduced by the network ("network delay").

To do this, according to this fifth embodiment, the broadcasting method comprises extracting at least one item of information relating to the time of transmission of this fragmentation packet. From this information, the exciter can determine the travel time of the fragmentation packet on the network.

It is noted that the various embodiments described above can be taken individually or combined.

5.4 Examples of implementation

We now present, in relation to FIGS. 5 and 6, an example of implementation of the invention according to at least one embodiment, implementing an insertion of TxID identification sequence and regionalization.

More precisely, FIG. 5 illustrates an example of a distribution network, based on the ATSC 3.0 standard, comprising: - three fixed reference sites:

• a first 511 reference site generating two transport streams for national distribution or distribution in a first “Regionl” region, using two modulators and two transmitting antennas (ΜΙΜΟ TX1 5111, ΜΙΜΟ TX2 5112), • a second reference site 512 generating two transport streams for distribution in a second region "Region2", using two modulators and two transmitting antennas (ΜΙΜΟ TX1 5121, ΜΙΜΟ TX2 5122), • a third reference site 513 generating two transport streams for broadcasting in a third region "Region3", using two modulators and two transmitting antennas (ΜΙΜΟ TX1 5131, ΜΙΜΟ TX2 5132),

- three SFN plates:

• a first plate 52 associated with the first region “Regionl” comprising two dissemination sites 521 (“Regionl_siteA”) and 522 (“Regionl_siteB”) each using two exciters (ΜΙΜΟ TX1 5211, ΜΙΜΟ TX 5212 for the first site broadcast 521 and ΜΙΜΟ TX1 5221, ΜΙΜΟ TX 5222 for the second broadcast site 522), • a second plate 53 associated with the second region "Region2" comprising two broadcast sites 531 ("Region2_siteA") and 532 ("Region2_siteB") each using two exciters (ΜΙΜΟ TX1 5311, ΜΙΜΟ TX 5312 for the first broadcasting site 531 and ΜΙΜΟ TX1 5321, ΜΙΜΟ TX 5322 for the second broadcasting site 532), • a third plate 54 associated with the third region “Region3 »Comprising two broadcasting sites 541 (“ Region3_siteA ”) and 542 (“ Region3_siteB ”) each using two exciters (ΜΙΜΟ TX1 5411, ΜΙΜΟ TX 5412 for the first broadcasting site 541 and ΜΙΜΟ TX1 5421, ΜΙΜΟ TX 5422 for the second broadcast site 542) ;

- twelve constant sequence generators:

• a generator 551 associated with the first exciter ΜΙΜΟ TX1 5211 of the first diffusion site 521 of the first region (R1A);

• a generator 552 associated with the second exciter ΜΙΜΟ TX2 5212 of the first diffusion site 521 of the first region (R1A);

• a generator 553 associated with the first exciter ΜΙΜΟ TX1 5221 of the second diffusion site 522 of the first region (R1B);

• a generator 554 associated with the second exciter ΜΙΜΟ TX2 5222 of the second broadcasting site 522 of the first region (R1B);

• And so on for the two other reference sites 512 and 513. The outgoing flows from the fixed reference sites 511 to 513 and from the constant sequence generators are ST2L-TP transport flows, as described above. They are distributed to the various broadcasting sites 521, 522, 531, 532, 541, 542 through a distribution network 56.

FIG. 6 illustrates more precisely the structure of the different streams, and the processing implemented broadcasting site by broadcasting site to extract the information carried by the transport flows, and reconstruct a signal to be broadcast.

We consider for example a first set 61 of complex samples representative of a main program, corresponding for example to an OFDM signal obtained at the output of a modulator of the first fixed reference site 511 ("Main IQ stream") . Such a set can be divided into fragments of complex samples: for example, the first fragment 611 corresponds to the "bootstrap" BS of the ATSC 3.0 frame. It is encased in an IQS-C 621 fragmentation package associated with a continuous flow of complex samples. The second fragment 612 corresponds to the first Symboll symbol with its guard interval GI1. According to a particular embodiment, the first Symboll symbol can be embedded in an IQS-C 622 fragmentation packet without its GIL guard interval The "Gi-Size" field of this IQS-C 622 fragmentation packet makes it possible to define the size guard interval, and can be used on the broadcast site side to reconstruct the broadcast signal. Likewise, the second Symbol2 symbol can be embedded in an IQS-C 623 fragmentation packet without its GI2 guard interval, the third Symbol3 symbol can be embedded in an IQS-C 624 fragmentation packet without its GI3 guard interval , the fourth Symbol4 symbol can be embedded in an IQS-C 625 fragmentation packet without its GI4 guard interval, and so on. In particular, the first fragmentation packet 621 carries an indicator indicating that its first sample is the first complex sample of the bootstrap of the frame. For example, the “Start_of_frame” field 6211 of the first fragmentation packet 621 is equal to 1. The “Start_of_frame” field of the following fragmentation packets is equal to 0.

According to the example illustrated in FIG. 6, the fragmentation packets 624 and 625, associated respectively with the fourth and the fifth fragments, each carry an indicator indicating that these fragmentation packages can be replaced by other fragmentation packages at level of a dissemination site. For example, the field "Regional_slot" 6241 of the fragmentation package 624 is equal to 1 to indicate that this fragmentation package 624 can be replaced by another fragmentation package at a broadcast site, and the field "Regional_slot" 6251 of the 625 fragmentation package is equal to 1 to indicate that this 625 fragmentation package can be replaced by another fragmentation package at a broadcast site.

A SIIA 626 individual addressing and flow information packet can also be defined. Examples of values of the "Per_Transmitter_Data" and "Stream_Information_Data" fields are given in particular in Figure 6.

The internal ST2L layer 62 of the main transport stream (carrying a continuous stream of complex samples, or “STL2 continous stream”) is therefore composed of fragmentation packets having a variable length, including the IQS-C fragmentation packets 621 to 625 and the SIIA packet 626. These fragmentation packets are then encapsulated in transport packets of the RTP / UDP / IP type.

The external ST2L layer 63 of the main transport stream (or “ST2L-TP main stream”) is therefore composed of transport packets having a fixed length.

In particular, the transport packets carry in their header an indicator M indicating whether this packet contains the start of a new fragmentation packet (therefore, if a new internal packet begins in this external packet). When this indicator is active (M = l, illustrated by a point in FIG. 6), the header also contains a pointer indicating the position of the start of this fragmentation packet (illustrated by an arrow in the transport flow 63 in FIG. 6 ).

Optionally, the SIIA 626 packet can be transmitted in a separate transport stream.

Still in relation to FIG. 6, we also consider a second set 64 of complex samples representative of a secondary program, corresponding for example to an OFDM signal obtained at the output of a modulator of the second fixed reference site 512 ("Regional IQ stream").

For example, a first fragment 641 of the second set of complex samples corresponds to a first regional replacement symbol, denoted RegionalSymbol3, and a second fragment 642 of the second set of complex samples corresponds to a second regional replacement symbol, noted RegionalSymbol4. The first regional replacement symbol can be embedded in a fragmentation packet associated with a discontinuous flow of complex samples, noted IQS-D 651. Likewise, the second regional replacement symbol can be embedded in an associated fragmentation package to a discontinuous flow of complex samples, noted IQS-D 652.

The internal ST2L layer 65 of the secondary transport stream (carrying a discontinuous stream of complex samples, or “ST2L discontinous stream”) is therefore composed of fragmentation packets having a variable length, including the IQS-D fragmentation packets 651 and 652. These fragmentation packets are then encapsulated in transport packets of the RTP / UDP / IP type.

The external ST2L layer 66 of the secondary transport stream (or "ST2L-TP regional stream") is composed of transport packets having a fixed length. In particular, it is possible to complete an RTP / UDP / IP transport packet with a padding sequence. In this case, a P 661 flag is provided in the header of the RTP packet to indicate that a padding sequence has been added.

Still in relation to FIG. 6, we finally consider a third set 67 of complex samples representative of a constant sequence, corresponding for example to an identification sequence TxID generated by the constant sequence generator 511 ("TxID IQ sequence ”). For example, complex samples corresponding to the TxID identification sequence are encapsulated in a CSIQ 681 fragmentation packet.

In particular, the CSIQ 681 fragmentation packet carries a "Num_repeat" field defining the number of times that the constant sequence must be repeated in the (added to) signal to be broadcast, equal to 3 according to the example illustrated. In addition, the CSIQ 681 fragmentation package has a "Frame_offset" field indicating an offset between the start of the frame ("Start_of_Frame") and the complex sample from which the constant sequence can be added.

The internal ST2L layer 68 of the transport stream of the constant sequence ("STL2 constant sequence") is therefore composed of the CSIQ 681 fragmentation packet.

The external ST2L layer 69 of the transport stream of the constant sequence (or "ST2L-TP TxID") is for example composed of two transport packets having a fixed length. In particular, it is possible to complete an RTP / UDP / IP packet with a padding sequence. In this case, a P 691 flag is provided in the header of the RTP / UDP / IP packet to indicate that a padding sequence has been added to it.

When a broadcasting site, for example the first broadcasting site 521 of the first region, has obtained the main transport flow 63, and possibly the secondary transport flow 66, and / or the transport flow of the constant sequence 69 (which may or may not be received simultaneously), it can decapsulate the stream or streams received to reconstruct a signal to be broadcast. Such de-encapsulation is for example implemented in an ST2L adaptation module.

In particular, according to one embodiment, the de-encapsulation of the transport packets delivers at least one packet of flow information and individual addressing, and the method implemented on the broadcasting site side comprises the configuration of the distribution site. broadcast from the configuration parameters carried by the SIIA packet.

For example, the ST2L adaptation module can extract the SIIA 626 packet to obtain the values of the "Per_transmitter_Data" and "Stream_Information_Data" fields in particular. For example, from the "Per_transmitter_Data" field, for a value in the "Xmtr_Id" field equal to 100, we obtain:

- a value in the “Main_Steam_id” field identifying the main transport flow equal to 20,

- a value from the "Tx_id_stream_id" field identifying the transport flow of a constant sequence equal to 100, and

- a value in the "Reg_Stream_id" field identifying the secondary transport flow equal to 50.

From the “Stream_Information_Data” field, we obtain:

- for the main transport stream, identified by the value 20, the destination multicast IP address 239: 0: 0: 20 and the destination UDP port 1234;

- for the transport stream of a constant sequence, identified by the value 100, the destination multicast IP address 239: 0: 0: 100 and the destination UDP port 1600; and

- for the secondary transport stream, identified by the value 50, the destination multicast IP address 239: 0: 0: 5 0 and the destination UDP port 1456.

The ST2L adaptation module of the broadcast site can also extract the CSIQ 681 fragmentation packet, to obtain the TxID sequence to be added to the signal to be broadcast, as well as the number of repetitions of this sequence. This addition can in particular be implemented by the exciter of the broadcasting site. For example, the value of the “Frame_offset” field of the CSIQ 681 fragmentation packet defines the position where the constant sequence is added to the signal to be broadcast relative to the position of the “Start_of_frame” indicating the first sample of the frame.

The ST2L adaptation module of the broadcast site can also extract the IQS-C 624 and 625 fragmentation packets bearing an indicator indicating that these fragmentation packages can be replaced by other fragmentation packages.

For example, the exciter replaces the IQS-C 624 and 625 fragmentation packets of the main transport stream with the IQS-D 651 and 652 fragmentation packets of the secondary transport stream.

In other words, regionalization can be implemented locally at the level of the broadcasting sites, by replacing fragmentation packets belonging to the internal ST2L layer by other fragmentation packets. For example, in ATSC 3.0, all fragmentation packets associated with OFDM symbols of a subframe can be replaced. It is recalled for this purpose that an ATSC 3.0 frame consists of one or more sub-frames, each sub-frame consisting of one or more OFDM symbols. In the event of regionalization, all the OFDM symbols of a subframe must be replaced. The “Timestamp_seconds” and / or “Timestamp_nanoseconds” field of the fragmentation packets can be used to synchronize / temporally align the symbols associated with the fragmentation packets of the regional transport stream on the signal to be broadcast by the broadcasting sites.

Furthermore, as already indicated, the use of transport packets of the RTP / UDP / IP type allows the use of an FEC layer (for example of the SMPTE-2022 type conventionally used for the STL ATSC 3.0 interface. ), allowing to manage packet loss on the IP network. However, such a layer introduces an overhead associated with the addition of FEC packets.

According to at least one embodiment of the invention, it is possible to overcome this layer in order to limit the overhead by using the fields "Next_type", "Next_length", "Next_num_samples" and "Next_GI_size" of the fragmentation packages. The use of these fields makes it possible in particular to avoid a loss of synchronization of the fragmentation packets in the event of the loss of one (or even more) ST2L-TP transport packets. Complex samples lost can be replaced by harmful samples, a pre-defined sequence or a sequence meeting certain characteristics necessary for the exciter to function properly, etc.

It is also possible to use both the "Next_type", "Next_length", "Next_num_samples" and "Next_GI_size" fields of the fragmentation packets and the FEC layer to increase the robustness of the network.

In order to increase the robustness of the transmission, it is also possible to transmit the same transport stream twice, for example via two separate networks, to introduce redundancy and protect the transmission in the event of a failure. networks in particular.

On the broadcasting site side, redundancy can be managed in different ways:

- mixing of the two transport streams: The sequence number of the RTP layer of the transport packets makes it possible to detect packet duplications. Each transport packet is considered duplicated when the two transport streams are received. This mode implies that the two transport flows are identical at the level of the second RTP / UDP / IP encapsulation, both at the header and payload level. If the two transport flows are obtained from two modulators, the modulators must be perfectly synchronized so that the second RTP / UDP / IP encapsulation is the same for the two flows;

- using the sequence number of the fragmentation packets to pair the two transport streams. This mode implies that the internal ST2L layer of the two flows is identical. If the two transport flows are obtained from two modulators, the modulators must be perfectly synchronized so that the first encapsulation is the same for the two flows;

- by using synchronization time information, for example the “timesamp” of the fragmentation packets to temporally align the two streams of complex samples. This mode implies that the modulators must be perfectly synchronized so that the timestamp-based timestamp is the same for both streams.

5.5 Structures

Finally, in relation to FIGS. 7 and 8, we present the simplified structure of a piece of equipment for generating a transport stream and of a broadcasting site according to an embodiment of the invention.

As illustrated in FIG. 7, an equipment for generating a transport stream according to an embodiment of the invention comprises a memory 71 (comprising for example a buffer memory) and a processing unit 72 (equipped for example at least one processor, FPGA, or DSP), controlled or pre-programmed by an application or a computer program 73 implementing the method of generating a transport stream according to an embodiment of the invention .

At initialization, the code instructions of the computer program 73 are for example loaded into a RAM memory before being executed by the processing unit 72. The processing unit 72 receives as input a stream complex samples. The processing unit 72 implements the steps of the generation method described above, according to the instructions of the computer program 73, to generate a transport stream.

To do this, according to one embodiment, the processing unit 72 is configured for:

- obtain a set of complex samples representative of a source signal and

- build the transport flow from the set of complex samples, by:

- cutting the set of complex samples into fragments of complex samples;

- for at least one fragment, encapsulating the complex samples of the fragment or of at least one piece of information representative of the complex samples of the fragment in a fragmentation packet, the fragmentation packets having a variable length and carrying information representative of the number of samples associated with them;

- encapsulating the fragmentation packages in transport packages having a fixed length, delivering the transport flow. As illustrated in FIG. 8, a broadcasting site according to a particular embodiment of the invention comprises a memory 81 (comprising for example a buffer memory) and a processing unit 82 (equipped for example with at least one processor, LPGA, or DSP), controlled or pre-programmed by an application or a computer program 83 implementing the data broadcasting method according to an embodiment of the invention.

At initialization, the code instructions of the computer program 83 are for example loaded into a RAM memory before being executed by the processing unit 82. The processing unit 82 receives as input at least a transport flow. The processing unit 82 implements the steps of the data broadcasting method described above, according to the instructions of the computer program 83, to reconstruct a signal to be broadcast.

[0205] To do this, according to one embodiment, the processing unit 82 is configured for:

- receive at least one transport stream comprising transport packages having a fixed length,

- unwrapping the transport packets, delivering fragmentation packets, the fragmentation packets having a variable length and carrying information representative of the number of complex samples associated with them;

decapsulating the fragmentation packets, delivering, for a fragmentation packet, complex samples of a fragment of complex samples or at least information representative of the complex samples of a fragment, the set of fragments of samples being representative of 'a source signal; and reconstruct a signal to be broadcast from complex samples.

Claims (1)

Claims [Claim 1] Method for generating a transport stream intended to be distributed to a plurality of broadcasting sites, characterized in that it comprises: - obtaining (23, 31) a set of complex samples representative of a signal source, and - a construction (24) of said transport flow, from said set of complex samples, said construction (24) implementing: - a cutting (32) of said set of complex samples into fragments of complex samples; - For at least one fragment, a first encapsulation (33) of the complex samples of said fragment or of at least one piece of information representative of the complex samples of said fragment in a fragmentation packet, the fragmentation packets having a variable length and carrying representative information the number of complex samples associated with them; - A second encapsulation (34) of the fragmentation packets in transport packages having a fixed length, delivering said transport stream. [Claim 2] Method according to claim 1, characterized in that at least one of said fragmentation packets is of a type belonging to the group comprising: - a fragmentation package associated with a continuous flow of complex samples; - a fragmentation package associated with a discontinuous flow of complex samples; - a fragmentation package associated with a constant sequence. [Claim 3] Method according to either of Claims 1 and 2, characterized in that the length of the header of the said fragmentation packets is strictly less than 40 bytes. [Claim 4] Method according to any one of claims 1 to 3, characterized in that at least one of said fragmentation packets carries at least information relating to at least one other fragmentation packet. [Claim 5] Method according to claim 4, characterized in that said information relating to at least one other fragmentation packet belongs to the group comprising: - the type of the following fragmentation package; - the length of the next fragmentation packet; - the number of complex samples associated with a next fragmentation package of the same type; and - the size of a guard interval associated with the next fragmentation packet of the same type. [Claim 6] Method according to any one of Claims 1 to 5, characterized in that at least one of the said fragmentation packets carries at least time synchronization information from the broadcasting sites. [Claim 7] Method according to any one of Claims 1 to 6, characterized in that at least one of said fragmentation packets carries at least one piece of time synchronization information for the fragmentation packets belonging to the group comprising: - information relating to the replacement of said fragmentation package by another fragmentation package; information relating to the multiplexing of the flow of complex samples from which said fragmentation packet is constructed with another flow of complex samples. [Claim 8] Method according to Claim 7, characterized in that the said information relating to the replacement or the multiplexing of the said fragmentation packet belongs to the group comprising: - an indicator indicating that the current fragmentation package can be replaced by another fragmentation package at one of said dissemination sites; - an indicator indicating that the complex samples associated with said current fragmentation packet directly follow the complex samples associated with the preceding fragmentation package, without time lag, after replacement or multiplexing; an indicator indicating that the complex samples associated with said current fragmentation package are directly followed by the complex samples associated with the next fragmentation package, without time difference, after replacement or multiplexing. [Claim 9] Method according to any one of Claims 1 to 8, characterized in that at least one of said fragmentation packets carries at least one item of information belonging to the group comprising: - information relating to the length of a guard interval associated with said fragmentation packet; - information relating to the start of a frame; - information relating to the strength of the signal represented by the complex samples of said fragmentation package; - information relating to the time of transmission of said fragmentation packet. [Claim 10] Method according to any one of Claims 1 to 9, characterized in that at least one packet of flow information and individual addressing, carrying configuration parameters of at least one of said broadcasting sites, is encapsulated in at least one transport package. [Claim 11] Method according to claim 2 and any one of the preceding claims, characterized in that at least one of said fragmentation packets is of the fragmentation packet type associated with a constant sequence, and carries an identification sequence of at least one said dissemination sites. [Claim 12] Data dissemination method, implemented at a dissemination site, characterized in that it comprises: - a reception (261, 262) of at least one transport stream comprising transport packages having a fixed length, - a first de-encapsulation of the transport packets, delivering fragmentation packets, the fragmentation packets having a variable length and carrying information representative of the number of complex samples associated with them; a second desencapsulation of the fragmentation packets, delivering, for a fragmentation packet, complex samples of a fragment of complex samples or at least information representative of the complex samples of a fragment, the set of fragments of samples being representative of a source signal; and - a reconstruction (271, 272) of a signal to be broadcast from said complex samples. [Claim 13] Method according to claim 12, characterized in that it comprises: - a detection of a problem of reception of at least one transport packet, said corrupt transport packet; a replacement, by a determined sequence of samples, of the complex samples encapsulated, during the generation of the transport stream, in at least one fragmentation packet encapsulated in said corrupt transport packet, taking account of information relating to the packet of fragmentation encapsulated in said corrupt transport package carried by another fragmentation package encapsulated in another transport package. [Claim 14] Method according to any of claims 12 and 13, characterized in that it includes replacing a fragmentation packet obtained from said transport stream with another fragmentation packet obtained from another transport stream, or multiplexing the flow of complex samples from from which said fragmentation packet is constructed, with another stream of complex samples, taking account of information relating to the replacement or multiplexing of said fragmentation packet obtained from said transport stream. [Claim 15] Method according to any one of Claims 12 to 14, characterized in that it comprises the reconstruction of a guard interval associated with the complex samples associated with a fragmentation packet obtained from said transport stream, from a information relating to the length of the guard interval carried by said fragmentation packet. [Claim 16] Method according to any one of Claims 12 to 15, characterized in that said de-encapsulation of the transport packets delivers at least one packet of flow information and individual addressing, and in that said method comprises the configuration of said delivery site. broadcasting from the configuration parameters carried by said flow information and individual addressing packet. [Claim 17] Computer program comprising instructions for the implementation of a method according to any one of Claims 1 to 16 when this program is executed by a processor. [Claim 18] Equipment for generating a transport stream intended to be distributed to a plurality of broadcasting sites, comprising at least one processor operatively coupled to a memory, and configured to: - obtain (23, 31) a set of samples complexes representative of a source signal and - construct (24) said transport flow, from said set of complex samples, by: - cutting (32) said set of complex samples into fragments of complex samples; - For at least one fragment, encapsulating (33) the complex samples of said fragment or of at least one piece of information representative of the complex samples of said fragment in a fragmentation packet, the fragmentation packets having a variable length and carrying information representative of the number complex samples associated with them; - encapsulating (34) the fragmentation packets in transport packages having a fixed length, delivering said transport stream. [Claim 19] Data broadcasting site comprising at least one processor operatively coupled to a memory, and configured for: - receiving (261, 262) at least one transport stream comprising transport packages having a fixed length, - unencapsulate the transport packages, delivering fragmentation packages, the fragmentation packages having a variable length and carrying information representative of the number of complex samples associated with them; - encapsulate the fragmentation packets, delivering, for a fragmentation packet, complex samples of a fragment of complex samples or at least information representative of the complex samples of a fragment, the set of fragments of samples being representative a source signal; and - reconstructing (271, 272) a signal to be broadcast from said complex samples.