WO2010063950A1

WO2010063950A1 - Method and device for sending a digital data file in accordance with the dmb standard

Info

Publication number: WO2010063950A1
Application number: PCT/FR2009/052372
Authority: WO
Inventors: David Vincent; Jean-Claude Pacaud
Original assignee: Tdf
Priority date: 2008-12-02
Filing date: 2009-12-02
Publication date: 2010-06-10
Also published as: KR101661270B1; EP2361481A1; FR2939261B1; CN102301709A; FR2939261A1; KR20110096549A

Abstract

The invention relates to a method for inserting a digital file, said file including at least one digital data set (E1) which includes a first number of bits ((Nb(E1)), in a multimedia data transport stream (TS) in the context of digital multimedia broadcasting (DMB), said method including determining (120), in at least one transport packet (TS1) belonging to said multimedia data transport stream (TS), the presence of a redundancy of bits and, if the first number of bits is less than or equal to the number of bits for the occurrence of said redundancy, deleting (170) the bits, among said occurrences of redundancy, in a number corresponding to the first number of the insertion (180) of said digital data set (E1) into said transport packet (TS1). The invention also relates to the corresponding receiving method (200), devices (10, 1, 2), and computer program.

Description

Method and device for transmitting a digital data file according to the DMB standard

The invention relates to the field of transmission of digital data files, in particular files comprising digital text data, in the transport mode of a digital data broadcasting system according to the ETSI TS 102 428 standard.

Digital data broadcasting is a new data dissemination technique to replace the analogue broadcast used by analog amplitude or frequency modulation systems.

A first step in the implementation of such a digital data broadcasting method has been achieved with the standardization of digital audio broadcasting, under the usual name "DAB" (Digital Audio Broadcasting) corresponding to the ETSI 300 401 standard. specifies the transmission modalities of a digital audio signal, as for example the case for the transmission of radio transmission to digital radio receivers such as those which are embedded in motor vehicles.

Other standards, still dealing with the broadcasting of digital audio signals, followed, such as the "DAB +" or "DRM" standards, respectively corresponding to ETSI standards TS 102 536 and TS 201 980.

In the standards indicated above, it is intended to send text files, for example, in addition to purely audio information. If the receiver includes an alphanumeric screen, this screen may display the received text according to one of the standards used. To do this, text files are encoded in a format called "DLS" (acronym for "Dynamic Label Segment"), allowing the insertion of pieces of text files within digital audio data packets. A further evolution of digital broadcasting has been to implement digital video broadcasting. With such a broadcast, it becomes possible to receive videos in a motor vehicle for example. A new standard has been developed to allow this kind of broadcast, ETSI 102 428 otherwise known as "DMB" for "Digital Multimedia Broadcasting".

The DMB standard is based on the multiplexing of the various data to be broadcast, whether video or audio, within an MPEG-2 transport stream. Such a transport stream TS is presented in the first line of FIG. 1. This stream consists of several transport packets TSi, TS ₂ , of 188 bytes each, presenting a header of 4 bytes minimum and a part dedicated to media data of up to 184 bytes. The disadvantage of this standard DMB is that it is not intended, in transport packets, field specifically dedicated to the transport of files other than audio, video or related to these two types of files. This is so text messages for example. Thus, a user having a digital reception system according to the DMB standard will not be able to receive text messages transmitted by a transmitter using the DAB standard, for example.

The present invention aims to remedy this situation. It proposes for this purpose a method for inserting a digital file, comprising at least one set of digital data comprising a first number of bits, in a multimedia data transport stream in a digital multimedia broadcasting (DMB) context, comprising the following steps: determining, in at least one transport packet belonging to said multimedia data transport stream, the presence of a redundancy of bits;

if the first number of bits is less than or equal to the number of occurrence bits of said bit redundancy, deletion a number of bits corresponding to said first one of said redundant bits and inserting said set of digital data into said transport packet.

In an advantageous embodiment, when the bit redundancy is contained in the header field of the transport packet and has a determined number of occurrence bits, the determining step includes recognizing said stubborn field. In this mode, prior knowledge of the field where the bit redundancy in the transport packet is located, as well as the size of said redundancy, allows easy insertion of the digital data sets.

In another advantageous embodiment, the insertion method comprises, between the step of determining the presence of a redundancy of bits and the deletion step, the determination of a second number of bits of occurrences of said redundancy in the transport packet. In this further embodiment, the digital data sets may be flexibly inserted at any point in the transport packet having bit redundancies.

In a particular embodiment of the invention where the digital file comprises a plurality of sets of digital data, the steps of the above transmission method are repeated until the last set of the digital file to be transmitted is inserted into a data transport package. This particular mode of the invention makes it possible to transmit large files distributed over several transport packets.

Advantageously, this last set of data comprises data indicating the end of said file, the steps of the transmission method then being repeated until this data is detected, which makes it possible to optimize the progress of the insertion method. The present invention furthermore provides a method for receiving, in the context of digital multimedia broadcasting, a digital file comprising at least one set of digital data from at least one digital transmitter, comprising the reception steps of least one multimedia data transport packet comprising a plurality of data fields and transmitted by the digital transmitter, selecting at least one of said plurality of data fields and, if the selected data field contains at least one sets of data of the digital file to be received, extraction of said data set.

In a particular embodiment of the invention in which the digital file to be received comprises a plurality of sets of digital data, the steps of the above reception method are repeated until the last set of the digital file to be received is extracted from a selected field of a data transport packet.

Advantageously, this last set of the digital file to be received comprises at least one piece of data indicating the end of the file, the steps of the above reception method then being repeated until this datum is detected.

In a preferred embodiment, wherein the data transport packet comprises at least one header field and a field for holding multimedia data, the set of digital data is inserted into the header field. The choice of the stubborn field, free of multimedia data, makes it possible to guarantee a certain size available to receive the data to be inserted without influencing the data rate of the multimedia data. Advantageously, the header of the transport packet comprises at least one optional field of private transport data within which the set of digital data is inserted. The choice of such a private data transport field, for inserting the digital data sets, instead of the unused stuffing bits at the end of the transport packet, makes it possible to use the capacity usually lost for the distribution of texts. In a preferred manner, the digital data set is inserted into a data transport packet whose packet identifier has a value of zero. Indeed, such a transport packet contains no multimedia data, but only a few signaling data and a large number of unused stuffing bits, which guarantees a significant amount of space available to insert the digital data.

In a preferred embodiment, the file to be transmitted comprises at least one set of textual data, advantageously encoded in the DLS format. This makes it possible to compensate for the absence of a field specifically dedicated to the transmission of text messages in the DMB standard. A format such as the DLS format has error correction capabilities, as well as a flag indicating the beginning or end of the file, ensuring the quality of the file transmission.

The present invention also provides an insertion device adapted to perform the steps of the insertion method described above. It also proposes a transmission device comprising a means for generating a multimedia data stream, generated in the context of digital multimedia broadcasting and consisting of at least one transport packet, an insertion device capable of performing the steps of the insertion method described above, and a transport packet transmission means where the digital data sets have been inserted.

Similarly, the present invention provides a receiving device adapted to perform the steps of the reception method as described above. Finally, the present invention provides a computer program for carrying out one of the methods described above. Such a program may be downloadable via a telecommunication network intended to be stored in a memory of a digital transmission or reception device, or even stored on a storage medium intended to cooperate with a transmitting or receiving digital entity.

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

FIG. 1 illustrates a data stream according to the MPEG-2 transport protocol;

FIG. 2 illustrates a digital transmission system comprising a transmission device and a reception device in accordance with a preferred embodiment of the invention;

FIG. 3 illustrates the steps of the insertion and transmission methods in accordance with a preferred embodiment of the invention; FIG. 4 illustrates the steps of a reception method in accordance with a preferred embodiment of the invention;

FIGS. 5A-5C illustrate a transport packet TSi in which two sets of data E ₁ and E ₂ are successively inserted; and FIG. 6 illustrates a particular type of preferred digital file that can be transmitted with the devices and methods of FIGS. 2 and 3.

FIG. 2 illustrates a digital transmission system comprising a digital transmission device 1 as well as a digital reception device 2. It is however clear that the present invention could be applied to any system comprising any number of devices of transmission and any number of receiving devices.

The digital transmission device 1 comprises a means 14 for generating a multimedia data transport stream TS according to the DMB standard, an insertion means 10 and a transmission means 15.

The generation means 14 generates a multimedia data transport stream TS, according to the MPEG-2 standard, consisting of a series of transport packets TS ₁ , TS ₂ in which multimedia data, such as audio or video objects, are transported by example.

The insertion means 10 receive, on the one hand, the transport packets TS ₁ , TS ₂ belonging to this TS transport stream coming from the generation means 14. This insertion means 10 on the other hand receives a digital file F to transmitting, in the form of one or more sets of digital data Ei, E ₂ , ..., E _k .

The digital file F to be transmitted may consist of a single set of digital data Ei, or several successive sets, in which case it is possible to signal the beginning sets, as well as the end of the file. This can be done by means of a start or end flag, inserted at a specific place of the concerned ensembles, in their header for example.

The digital file F may be of any type for which there is at present no field specifically provided for in the DBM standard. An example, presented in detail later in Figure 6, is a DLS type text file for messages such as those used in the DAB standard and for which the DMB standard has nothing planned. However, the present invention can be applied to any other type of file not specifically managed by the DBM standard and comprising digital data. The insertion means 10 will take one or more sets E ₁ of the digital file to insert them within the transport stream TS, MPEG-2 type. Such a transport stream is broken down into a series of transport packets TSi, TS ₂ having an HE ₁ SUiVi header field of a PAYL field ₁ able to receive multimedia data, as already seen in FIG.

The insertion of the data sets E ₁ of the file to be transmitted will take place at locations of these transport packets TS ₁ , TS ₂ not interfering with the transmission of the multimedia data. In other words, the bit rate of the multimedia data must not be modified by the insertion of these additional digital data packets.

To do this, we will use data fields in which the multimedia data are not found. These fields will be selected either directly during transmission or in advance.

It is possible to envisage a direct case-by-case selection in which the insertion means 12 observes each TS ₁ transport packet and identifies the fields of these packets that do not contain multimedia data in order to insert one or more sets.

E ₁ of data of the file to be transmitted. Such a selection method makes it possible to have a maximum insertion capacity.

However, it then requires the signaling of the selected field to be able to extract, on reception, the inserted set.

Another preferred mode of selection, since it does not require signaling, consists in choosing in advance a particular place where to place the sets to be inserted, a place intended not to receive multimedia data according to the MPEG-2 standard.

For example, a data field belonging to the header HE ₁ of a transport packet TS _{1 may be used} . multimedia data not intended to be contained therein according to DMB.

Such a header includes an optional ADAP adaptation field, illustrated in the third line of FIG. 1, the size of which may be inversely proportional to the size of the multimedia data contained in the same transport packet

TS ₁ .

If, in a transport packet TS ₁ , the multimedia data field PAYL ₁ is filled to its maximum, that is to say if it contains 184 bytes, then the header HE ₁ is limited to the minimum 4 bytes and necessary in the MPEG-2 standard, and the ADAP field does not exist. It will not be possible to insert a data set E ₁ in such a packet TS ₁ .

If, on the other hand, in a transport packet TS ₁ , the multimedia data field PAYL ₁ is not completely filled, that is to say if it contains less than 184 bytes, then normally the last bytes not filled with data. Multimedia PAYL field ₁ are filled with stuffing bits, to maintain the synchronization of transport packets, represented by the redundancy of an OxFF bit in hexadecimal, for example. This usually ruined ability can be used here to insert the data sets to be transmitted. In these cases, the optional ADAP field may exist and contain data to carry, replacing the stuffing bits.

In an extreme first case, some transport packets TS ₁ may contain only stuffing bits, that is, 180 bytes of stuffing bits, in addition to the 4 bytes of the header. Such a case is optimal in terms of space for inserting data sets E ₁ , but is irregular and not guaranteed.

Another advantageous case consists in using the first transport packet TS ₁ , which has an identification number of packet (PID), which contains no multimedia data, but only signaling data and stuffing bits instead. Since the header of such a TSi packet contains 4 bytes and this signaling data comprises a maximum of 20 bytes, there is at least 164 bytes of stuffing bits available in such a packet.

Using this package TS ₁ is particularly advantageous because such a package has a guarantee of available space (164 bytes), occurring at a certain guaranteed frequency of occurrence. It is therefore possible to guarantee a certain data rate inserted using such packets, unlike other transport packets whose insertion capacity is variable, irregular and unsecured.

The ADAP adaptation field, when it exists, notably comprises at least one private transport data field, illustrated by the PRIV field of the fourth line of FIG. 1 and reserved as its name indicates for the transport of private data. For example, it is possible to use such a field to insert the data packets of the digital file to be transmitted, before the multimedia data possibly contained in the PAYL ₁ field and instead of the stuffing bits added at the end of this PAYL ₁ field.

To do this, the insertion device 10 comprises a first receiving means (11), which will serve to receive the set or sets Ei, Σ ₂ , ..., E _k and will determine a first number of bits Nb ( E ₁ ) of each of these sets. This can be done simply by counting these bits, or by reading a field indicating the number of bits or the length of the set E ₁ . Such fields exist in text files encoded according to usual formats, such as the DLS format explained below.

The device 10 also comprises a second reception means 12 which receives the data transport packets Multimedia TSi, TS2 belonging to the TS transport stream and detects therein a redundancy of bits, indicating the presence of stuffing bits that can be replaced by digital data to be transmitted. This means 12 will then determine a second number of occurrence Nb (TS ₁ ) of the stuffing bits in this redundancy, for example by counting the occurrences of the typical stuffing bit OxFF.

The device 10 finally comprises a means of substitution 13. For a first packet TSi and a first set E ₁ , the substitution means 13 will compare the first number Nb (Ei) determined by the first means 11 with the second number Nb (TSi ) determined by the second means. If the first number of bits Nb (Ei) is less than or equal to the second number of bits Nb (TSi), this means that there is enough room to insert the set Ei in the transport packet TSi. The means 13 will then remove, among the stuffing bits placed at the end of the transport packet TSi, Nb (Ei) stuffing bits. The stuffing bits to be deleted can be chosen successively, but not necessarily, and preferably at the end of the transport packet TSi, in order to constitute a modified packet TSi 'always containing stuffing bits located precisely at the end of this packet, but in reduced numbers.

The means 13 will then insert the set of digital data Ei in the HEi header of the TSi transport packet, creating an ADAPi adaptation field and adding the set Ei in the private data transport field PRIV of this ADAP field.

Preferably, the first transport packets TS i of the transport streams TS will be used to insert the sets E ₁ , since these packets TS i do not contain multimedia data, but only the program allocation table, designated by the acronym PAT in English. Also, in such a TSi transport package, the optional adaptation field ADAP may have some guaranteed capacity of 164 bytes, corresponding to the total amount of bytes in the packet minus the byte quantities of the header and the signaling data of such a packet, as previously seen. It will therefore be possible to insert in its transport field PRIV private data, either larger data sets E ₁ or more data sets E ₁ than in conventional transport packets TS ₁ containing a certain amount of data. multimedia. Once at least one set of the digital file E ₁ has been inserted into a transport packet TS ₁ by the insertion means 10, this transport packet TS ₁ is sent to the transmission means 15 which will transmit, by radio broadcast for example, this TS ₁ transport packet to a digital reception device 2.

This reception device comprises a digital reception means 20 and an extraction means 21. The digital reception means 20 can receive a transport stream TS ', defined according to the MPEG-2 standard and comprising one or more packet of TS ₁ 'transport, for example from a digital transmitter 1 broadcast over the air multimedia data according to the DMB standard. Once the packets TS ₁ 'have been received, the means 20 supplies them to the extraction means 21.

This extraction means 21 is responsible for extracting, from within the transport packets TS ₁ 'received by the receiving means 20, any sets of digital data of a digital file inserted by a device 1 as described below. before.

To do this, the extraction means 21 will monitor one or more selected fields within a transport packet TS ₁ '. Again, as in the transmission device 1, the selection of the fields to be monitored can be done directly during the transmission, on a case by case basis, or well by choice made in advance of one or more particular fields.

In the first case, as previously seen, signaling is necessarily performed by the transmission device 1. The extraction means 21 must then be able to receive this signaling indicating the field to be monitored.

In the second case, one or more particular fields will be chosen, as seen previously, as being able to contain sets of inserted digital data. The extraction means 21 will therefore monitor this or these precise fields, and in the case where there is a set of inserted text data, extract it from this field.

In the case where the inserted digital file comprises several sets of inserted text data Ei, E ₂ ,..., E _k , one way of knowing the last inserted set E _k is to locate a flag signaling the end of this file and present in this set E _k , for example.

The text data sets E ₁ , once extracted, are sent to a device 22 external to the device 2, for receiving the text data, for processing, decode or for example display them directly on an alphanumeric screen. If the digital file consists of several sets Ei, E ₂ , this external device

23 can either directly process, or for example display, the different sets as they arrive, or aggregate them and store them while waiting to receive the last set of textual data E _k . Once the last one together

E _k received, the external device 22 will reconstruct the extracted file in full and may for example display it on an alphanumeric screen or send the entire file to another device.

The flowchart of FIG. 3 illustrates methods of insertion and transmission according to an example of the invention, such as could be implemented in the transmission device 1 described in Figure 2, and is likely to represent an exemplary flowchart of a computer program for the implementation of the invention. This flowchart illustrates the steps of the method of insertion 100 according to an example of the invention.

In a first step 110 of this method of 100, a multimedia data transport packet TSi according to the MPEG-2 standard is obtained. This can be done by generating the transport packet when it is necessary to transmit a digital file of text data, or by taking a transport packet from an already active MPEG-2 stream independently of the digital file to be transmitted. The internal organization of such a packet is illustrated for example in Figure 1, which shows the different data fields composing such a transport packet.

In a second step 120, it will be determined whether the TSi packet contains stuffing bits, usually located at the end of this packet. When it is previously known that the transport packet TSi contains a determined number of stuffing bits, for example in its stubborn field, as is the case for the first transport packets comprising only the table of FIG. allocation designated by PAT in English, that is to say those for which the PID parameter is equal to 0 according to ETSI TS 102 428, this step 120 of determination is simply to recognize the stubborn field of such transport packet, which in itself guarantees the presence of a number Nb (TSi) of stuffing bits. Such a determination step 120 can then be assimilated to an "indirect" detection, insofar as the redundancy of stuffing bits does not necessarily need to be detected directly, but it is sufficient here to detect the specific packet ensuring the presence of a predetermined number of stuffing bits for insertion.

Alternatively, without such prior knowledge of the possible presence of stuffing bits, for example when it is considered to perform an insertion in a transport packet that is not specific (ie other than that including the PAT), the Step 120 of determination is to detect the presence of stuffing bits on a case by case basis, for example by searching for a specific type of stuffing bit type OxFF.

Such a determination step 120 can then be likened to a "direct" detection, insofar as the redundancy of stuffing bits is detected in order to determine, on the one hand, whether such a redundancy of bits is present and, d on the other hand, if there are enough stuffing bits to allow insertion.

If no stuffing bit is detected by this way in the TSi packet, this TSi packet is filled with multimedia data and can therefore not receive set E ₁ . We then return to the previous step to obtain another transport packet.

If on the other hand the TSi packet contains stuffing bits, then we will determine, during a third step 130, the number of stuffing bits contained in this packet, counting them by means of a bit counter for example . Such a packet TSi, comprising stuffing bits at the end, is illustrated in FIG. 5A. By counting these final stuffing bits, the number Nb (TSi) already explained above is then obtained.

In order to enable insertion, during a step 140, one of the sets of textual data E i received from the source of transmission or encoding of the file F to be inserted is taken. In a step 150, the first number of bits Nb (Ei) of this set Ei is determined. This can be done, as with Nb (TSi), by counting the bits by means of a counter, or by reading a field of the set Ei indicating the length of this set or the number of bits that it contains, as is normally indicated in the headers of the sets Ei encoded according to usual formats, of the DLS type for example.

A comparison step 160, between the numbers Nb (TSi) and Nb (Ei), is performed next. If the number Nb (Ei) is strictly greater than the number Nb (TSi), then there is not enough room, in the stuffing bits, to insert the set Ei, and we return to the stage 110 to try to find another transport package that can contain this set.

On the other hand, if the number Nb (Ei) is less than or equal to the number Nb (TSi), we can insert the set Ei in the packet TSi. To do this, we will first delete, in a step 170, a number of stuffing bits corresponding to the size of the set Ei, that is to say the number Nb (Ei). This can be done by removing the last Nb (Ei) stuffing bits from the TSi packet. Thus, the new packet will still contain a number Nb (TSi) - Nb (Ei) of stuffing bits, and may possibly receive a second set E ₂ , provided that Nb (E ₂ ) ≤ Nb (TSi) -Nb ( Ei), that is to say that there is still enough room to receive the set E ₂ . We can continue so, until there is no more room, in the same packet TSi, to receive another set E ₁ . Following the deletion step 170, we can then insert the Nb (Ei) bits of the set Ei within the header of the transport packet TSi, more particularly in the private transport data field PRIV of the optional ADAP adaptation field. We then obtain a TSi 'packet as illustrated in Figure 5B.

Finally, in a last step 190, it is checked whether the last set E ₁ inserted is a final set E _k of the file F to be inserted. Such a final set E _k may comprise a datum of signaling as an end flag, for example, in the case of a set encoded by DLS format. We can also count the number of set E ₁ inserted and compare this value to a set number to insert transmitted or read initially. If this is the case, then we can proceed to the step of transmitting the TSi packet by the transmission means 15, to one or more receiving units.

If this is not the case, we will continue to obtain sets E ₁ , returning to step 150 of the insertion process 100. As already seen above and illustrated in FIG. 5B, after the insertion of a first set E ₂ , the modified transport packet TS ₂ 'will still contain a number Nb (TSi) -Nb (E ₁ ) of stuffing bits at the end, and may possibly receive a second set E ₂ , provided that Nb (E ₂ ) ≤ Nb (TSi) -Nb (E ₁ ), that is to say that there is still enough room to receive the set E ₂ . If this is the case, we can insert the set E ₂ in the TSi 'package, which will give a modified transport packet TSi'', as shown in Figure 5C. We can continue so, until there is no more room, in the same packet TSi, to receive another set E ₁ .

Selecting a field that does not contain multimedia data, and therefore is usually filled with "stuffing" data, will make it possible to use normally unused transmission capabilities and not to affect the rate of data transmission. multimedia proper.

In the case where the digital file consists of a single set Ei of data whose size is smaller than the number of stuffing bits in the transport packet TSi, this set will be both the first and the last to be transmitted. with the packet TSi, and the transmission method 100 can then be terminated by a step 200 of transmission of the data packet TSiContaining the unique packet Ei of data to be transmitted.

In the case where the digital file consists of several sets of textual data Ei, E ₂ , if the cumulative size of these sets is smaller than the number Nb (TSi) of stuffing bits in the packet TSi, we will be able to place all datasets of the digital file in the same transport packet TS1, and thus the entire file will be transmitted with the single TSi transport packet. In the case where the sets E ₁ have a fixed size

Nb (E ₁ ), it is possible to define a parameter N corresponding to the maximum capacity of a selected packet TS ₁ , that is to say to the maximum number of textual data sets E _i that this packet may contain. If Nb (TSi) is the number of stuffing bits of a TS ₁ packet, then the maximum capacity N of this packet will be the integer respecting the relation N * Nb (E _x ) ≤ Nb (TS ₁ ) <(N +1) * Nb (E ₁ )

Thus, if the digital file F consists of k sets of textual data E ₁ , and if k * Nb (E _x ) ≤ Nb (TS ₁ ), that is to say if k N N, then all the sets of the digital file can hold in a single transport packet TS ₁ , and the transmission of this single transport packet TS ₁ will suffice to transmit the entire file F.

On the other hand, if k> N, that is to say if all data sets Ei can not fit in a single TS ₁ packet, then it will be necessary to distribute the data sets Ei between different packets TS ₁ . If the total number k of sets of data E ₁ of the digital file exceeds the maximum capacity Ni of a first packet TSi of this field, then it will be necessary to fill the private data transport field of this packet TSi with Ni sets E ₁ , then fill the private transport data field of another transport packet TS ₂ , for example the following in the stream TS, with N ₂ other sets E ₁ , and so on, until what happens to the TS ₁ transport packet where the number of remaining text data sets to be inserted is less than the maximum capacity N ₁ of the selected field in this TSi packet. The insertion of the data sets E ₁ in the consecutive fields can be done in any order, preferably in the order of arrival of the packets at the level of the insertion means 10.

In a first example, steps 110 to 190 may be repeated as long as there are sets of text data to be inserted in a transport packet TS ₁ of an MPEG-2 data stream TS, in complete independence with this stream TS. If the stream TS is active, the data packets of the file are inserted into the transport packets TSi of the stream TS. If the stream TS is inactive, that is to say if no multimedia data is broadcast for example, the insertion of the text data can be interrupted until the TS stream is reactivated, and then resume.

It is also possible to condition the method to the number k of sets of textual data Ei of the digital file. By knowing this number k, either by prior definition or by signaling this number by the external source 14 of these sets of data Ei, it is possible to deduce the number of TSi transport packets necessary for the total transmission of the file, as a function of the number and size of the selectable data fields in each transport packet. The implementation of a count of TS ₁ transport packets in which a set of text data E i is inserted will then send the number of TSi transport packets necessary for the total transmission of the file. This saves the transmission resources.

FIG. 4 also illustrates the method of receiving 200 a digital file inserted in a multimedia data stream according to the DMB standard. This reception method 200 includes a first step

210 for receiving a media stream TS 'according to the DMB standard, comprising one or more transport packets TSi', TS2 'comprising a number of data fields and capable of carrying multimedia data.

A second selection step 220 then takes place, in which a specific field of a transport packet TSi 'is selected. To be selected, this field must not include any multimedia data. As already seen in the transmission method, this selection can be done either by signaling the field chosen by the transmitter 10 or by predetermining a field that does not influence the bit rate of multimedia data, typically the private data field. transport, as explained above.

Following this selection step 220, it is observed during a step 230 whether the selected field (typically the private transport data field) contains at least one set E ₁ of the file to be received. If this field does not contain sets E ₁ of the file to be received, then we will consider a next packet, on which we repeat the selection step 220.

If, on the contrary, the selected field contains one or more sets E ₁ , then an extraction step 240 of this or these sets E ₁ takes place. Then there is a detection step 250, aiming at verifying whether the last set E _k of the file to be received was extracted during step 240, by the detection of a flag for example, or by counting the number of sets already received for a predetermined number of sets. If this is the case, then the process of receiving the file as such is finished, otherwise we return to step 210 to receive another transport packet TS ₁ . The extracted sets E ₁ may be used on the fly, for example displayed on an alphanumeric screen as they arrive, or aggregate, during a last aggregation step 250, so as to retrieve the file. initial digital This can then be used in its entirety, for example displayed in full or transferred entirely to another device.

The transport packets of an MPEG-2 stream all having a unique associated packet identifier, designated by the acronym PID (for "Packet Identification" in English), it will be advantageous to choose the transport packets of which this PID identifier is zero. Such a transport packet TSi is indeed intended to contain the program association table, designated by the acronym PAT (Program Association Table in English), and therefore does not contain multimedia data, but a certain number of bits of jam (Nb (TS ₁ ) then has a guaranteed value corresponding to 160 bytes of stuffing) unlike other transport packets having a non-zero PID identifier.

Since the size of the adaptation field, optional, depends inversely on the size allocated to the payload field, it is then guaranteed to have the optimum size for a private transport data field belonging to this null PID segment, which makes it possible to integrate more data packets into this private transport data field than into a private transport data field of a non-zero PID segment.

Conversely, the determination 130 and selection 220 steps can also be done transport packet transport packet, observing for each packet, with a non-zero PID, whether the private transport data field can receive, or no, one or more sets E ₁ of the digital file to be transmitted. This can be done by individual analysis of the transport packets to determine the number of stuff bits contained in each packet. We can counting the occurrence number of an OxFF bit specifically indicating a stuffing bit, or using any other method known to those skilled in the art.

The digital file F to be inserted and transmitted may contain digital data of any type, for which no field is specifically provided for in the standard

DMB. A typical example is text messages as they exist in other standards such as the DAB standard, consisting of textual digital data packets. But the present invention is not limited to the insertion of such text messages, and may be suitable for any type of digital data sets.

FIG. 6 illustrates a particular example of a set of X-PaCl ₁ text data encoded according to the DLS format and that can be transmitted with the devices and methods of the invention, as illustrated in FIGS. 2 to 4.

Indeed, the external source device 16 may for example receive a digital file F containing textual content and encode it in the form of a plurality of data sets X-Pad _x DLS format, acronym for "Dynamic Label Segment"" in English. In this case, the external source device 16 will be a DLS encoder.

Such an X-Pad _{x data set} includes a 2-byte PREF prefix, a CHAR CHAR field of n bytes, and a 2-byte CRC error correction field. X-Pad _x may be used in place of sets Ei described above.

A first advantage of using this DLS format for text files is to ensure the error control of the transmission through the presence of an error correction code.

Another advantage of this DLS format is to contain intrinsic signaling of start and end of file. Indeed, the PREF prefix of X-Pad sets _x contains a field BEG / END 2-bit, located in the second position of the prefix, to indicate whether the corresponding set X-Pad _x is the first or the last set of a file to be transmitted. This field will therefore provide the flag signaling the end of the file necessary for a particular embodiment of the invention as described above.

Of course, the invention is not limited to the embodiments described above and shown, from which we can provide other modes and other embodiments, without departing from the scope of the invention. .

Thus, it will be understood that any file format can be transmitted through the present invention. The term "file", throughout the description above, a group of digital data consisting of one or more sets of digital data, without necessarily a particular format is allocated to this group of data.

Claims

claims

A method of inserting a digital file (F), comprising at least one set of digital data (Ei) comprising a first number of bits (Nb (Ei)), in a transport stream (TS) of multimedia data in the context of digital multimedia broadcasting (DMB), comprising the following steps: a) determining (120), in at least one transport packet (TSi) belonging to said multimedia data transport (TS) flow, the presence of a bit redundancy; and b) if the first number of bits is less than or equal to (160) the number of occurrence bits of said bit redundancy, deleting (170) a number of bits corresponding to said first one of said redundant and inserting bits ( 180) of said set (Ei) of digital data in said transport packet (TSi) •

An insertion method according to claim 1, wherein said bit redundancy is contained in the header (HEi) field of the transport packet (TSi) and has a determined number of occurrence bits (Nb (TSi) ), characterized in that the determining step (120) comprises recognizing said stubborn field (HEi).

3. An insertion method according to claim 1, characterized in that it comprises, between the step of determining (120) the presence of a bit redundancy and the deleting step (170), the determination ( 130) of a second number (Nb (TSi)) of occurrence bits of said bit redundancy in the transport packet.

4. Inserting method according to one of claims 1 to 3, wherein the digital file (F) comprises a plurality of digital data sets (Ei, E ₂ ), characterized in that the steps of the insertion method are repeated until the last set (E _k ) of the digital file (F) to be transmitted is inserted into a data transport packet (TS ₂ ).

5. Method according to claim 4, wherein the last set (E _k ) of the digital file (F) to be transmitted comprises at least one piece of data indicating the end of said file, characterized in that the steps of the insertion method are repeated until said data is detected.

6. A method of receiving (200), in the context of digital multimedia broadcasting, a digital file (F) comprising at least one set of digital data (E ₁ ) originating from at least one digital transmitter (1), comprising the following steps :

a) receiving (210) at least one multimedia data transport packet (TSi) comprising a plurality of data fields and transmitted by the digital transmitter (1),

b) selecting (220) at least one of said plurality of data fields,

c) if the selected data field contains at least one of the data sets (Ei) of the digital file to be received, extracting (240) said set of data.

The reception method (200) according to claim 6, wherein the digital file (F) to be received comprises a plurality of digital data sets (Ei, E ₂ , E _k ), characterized in that the steps of the method insertion are repeated until the last set (E _k ) of the file digital receiver (F) to be received from a selected field of a data transport packet (TSi).

The method according to one of the preceding claims, wherein the header field (HEi) of the transport packet (TSi) contains an optional private transport data field (PRIV) for holding private data, characterized in that that the digital data set (Ei) is inserted in said optional private transport data field (PRIV).

9. Method according to one of the preceding claims, wherein a packet identifier (PID) is associated with the data transport packet (TSi), characterized in that said packet identifier (PID) has a zero value.

10. Method according to one of the preceding claims, characterized in that at least said data sets (Ei) of the digital file (F) is a set of text data.

11. Method according to the preceding claim, characterized in that said set of textual data (Ei) is encoded in the DLS format.

An insertion device (10) for a digital file (F), comprising at least one set of digital data (Ei) comprising a first number of bits, in a multimedia data stream (TS) generated in the context of digital multimedia broadcasting (DMB), comprising:

a first reception means (11), able to receive at least one of the sets (Ei) and to determine a first number of bits of said set (Ei),

a second reception means (12), able to receive at least one multimedia data transport packet (TSi) belonging to said stream (TS), to detect in said transport packet (TSi) a bit redundancy, and

a substitution means (13) adapted, if the first number of bits is less than or equal to the number of occurrence bits of said bit redundancy, to be deleted from among said occurrence bits of said redundancy in the transport packet; (TSi), bits in number corresponding to the first number and inserting said set of digital data (Ei) in said transport packet (TSi) •

13. A transmission device (1), in digital multimedia broadcasting (DMB) context, of a digital file (F) comprising at least one set of digital data (Ei), intended for at least one receiving entity (20). ), comprising: - means for generating (14) a multimedia data stream (TS), generated in the context of digital multimedia broadcasting (DMB) and consisting of at least one transport packet (TSi),

an insertion device (10) according to the preceding claim, to which the generating means provides the transport packet (TSi) and adapted to receive at least one of the data sets (Ei) of the digital file (F) to be transmitted, and

a transmission means (15) capable of transmitting the data transport packet (TSi '), in which the data set (Ei) has been inserted, destined for the receiving entity (20).

14. Reception device (2) comprising means adapted to implement the reception method according to one of claims 4 to 11.

15. Computer program for the implementation of the method according to one of claims 1 to 10, downloadable via a telecommunications network and / or intended to be stored in a network. memory of a digital transmission or reception device and / or stored on a storage medium intended to cooperate with a transmitting or receiving digital entity.