EP2243232A1 - Procede de diffusion d ' un flux de donnees dans un reseau comprenant une pluralite d ' emetteurs ainsi que produit programme d ' ordinateur, tete de reseau et systeme pour la mise en oeuvre de ce procede - Google Patents
Procede de diffusion d ' un flux de donnees dans un reseau comprenant une pluralite d ' emetteurs ainsi que produit programme d ' ordinateur, tete de reseau et systeme pour la mise en oeuvre de ce procedeInfo
- Publication number
- EP2243232A1 EP2243232A1 EP09712298A EP09712298A EP2243232A1 EP 2243232 A1 EP2243232 A1 EP 2243232A1 EP 09712298 A EP09712298 A EP 09712298A EP 09712298 A EP09712298 A EP 09712298A EP 2243232 A1 EP2243232 A1 EP 2243232A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- time
- data stream
- pps
- transmitters
- marker
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04H—BROADCAST COMMUNICATION
- H04H20/00—Arrangements for broadcast or for distribution combined with broadcast
- H04H20/65—Arrangements characterised by transmission systems for broadcast
- H04H20/67—Common-wave systems, i.e. using separate transmitters operating on substantially the same frequency
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04H—BROADCAST COMMUNICATION
- H04H20/00—Arrangements for broadcast or for distribution combined with broadcast
- H04H20/18—Arrangements for synchronising broadcast or distribution via plural systems
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
- H04N21/20—Servers specifically adapted for the distribution of content, e.g. VOD servers; Operations thereof
- H04N21/23—Processing of content or additional data; Elementary server operations; Server middleware
- H04N21/236—Assembling of a multiplex stream, e.g. transport stream, by combining a video stream with other content or additional data, e.g. inserting a URL [Uniform Resource Locator] into a video stream, multiplexing software data into a video stream; Remultiplexing of multiplex streams; Insertion of stuffing bits into the multiplex stream, e.g. to obtain a constant bit-rate; Assembling of a packetised elementary stream
- H04N21/23608—Remultiplexing multiplex streams, e.g. involving modifying time stamps or remapping the packet identifiers
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
- H04N21/20—Servers specifically adapted for the distribution of content, e.g. VOD servers; Operations thereof
- H04N21/23—Processing of content or additional data; Elementary server operations; Server middleware
- H04N21/238—Interfacing the downstream path of the transmission network, e.g. adapting the transmission rate of a video stream to network bandwidth; Processing of multiplex streams
- H04N21/2383—Channel coding or modulation of digital bit-stream, e.g. QPSK modulation
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
- H04N21/20—Servers specifically adapted for the distribution of content, e.g. VOD servers; Operations thereof
- H04N21/23—Processing of content or additional data; Elementary server operations; Server middleware
- H04N21/242—Synchronization processes, e.g. processing of PCR [Program Clock References]
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
- H04N21/60—Network structure or processes for video distribution between server and client or between remote clients; Control signalling between clients, server and network components; Transmission of management data between server and client, e.g. sending from server to client commands for recording incoming content stream; Communication details between server and client
- H04N21/63—Control signaling related to video distribution between client, server and network components; Network processes for video distribution between server and clients or between remote clients, e.g. transmitting basic layer and enhancement layers over different transmission paths, setting up a peer-to-peer communication via Internet between remote STB's; Communication protocols; Addressing
- H04N21/643—Communication protocols
- H04N21/64315—DVB-H
Definitions
- the field of the invention is that of the transmission and broadcasting of digital information, especially television or radio data, in a communication network comprising a plurality of transmitters.
- the invention relates to the synchronization of transmitters 10 of such a network.
- the invention applies more particularly, but not exclusively, to SFN ("Single Frequency Network") networks, regardless of the broadcast standard used:
- the invention is in the context of the ISO / IEC standard
- the vast majority of these networks are of the MFN ("Multi Frequency Network") type, which means that the different transmitters of such a network operate at different frequencies.
- the networks are of the SFN or isochronous type, which means that the different transmitters must be precisely synchronized in time, in frequency and in content.
- the operating principle of such SFN networks may consist in transmitting the same signal from at least two distinct geographical sites on each of which is implanted a transmitter.
- the objective is then to add the contribution of these two signals in reception, which requires that they be received at the same time, in a guard interval which is a function of the modulation profile and proportional to the symbol time width. , and at the same frequency, to prevent them from disturbing each other.
- a guard interval which is a function of the modulation profile and proportional to the symbol time width.
- FIG. 1 illustrates, according to this standard, a block diagram of an SFN-type digital terrestrial television broadcasting system implementing a broadcast of data in the MPEG-2-TS format. ("Motion Picture Expert Group - Transport Stream").
- FIG. 1 shows two transmitters 10 and 11, each comprising a synchronization equipment (system SYNC) 101, 111, and a DVB-T modulator 102, 112.
- the synchronization equipment 101, 1 1 1 is powered by two frequency and time reference signals, for example a signal corresponding to one pulse per second, or 1 pps (for "Puise Per Second"), and a 10 MHz signal resulting from the 1 pps. It is found that there are exactly 10 million periods of the frequency reference signal at 10 MHz between two pulses 1 pps.
- These signals can come from any reliable reference system 105 and 115, for example from the American Global Positioning System (GPS) or European Galileo, or from long wave radio carriers (DCF77 in Germany, MSF in the United Kingdom , France Inter in France, etc.) - registered trademarks.
- GPS Global Positioning System
- DCF77 long wave radio carriers
- the 10 MHz frequency reference signal can also be used at the head end, by an SFN adapter, to calibrate its output rate, so that it is stable and accurate, as well as transmitters in the transmit center to calibrate their output. debit.
- This reference can also be used by transmitters to synchronize their transmit frequency, which must be accurate to less than 1 Hz in DTT in an SFN network for optimal operation.
- the data to be broadcast by each of these transmitters 10, 11 are received in the form of an MPEG-2 TS transport stream (for "MPEG-2 Transport Stream "), from a receiver 12 also acting as a network adapter (" RX Network Adapter ").
- the MPEG-2 TS stream of data to be transmitted is constructed by an MPEG-2 multiplexer referenced 13, which performs the framing of the data.
- an MPEG-2 multiplexer is located for example in a national headend, from which are then transported by satellite (in a transport network, also called distribution network) the data to be broadcast by each of the transmitters 10, 11 , of the broadcast network.
- the data is processed by an SFN adapter 14, which realizes the time stamping of the frames from the same time and frequency reference system 15 as that 105, 115 which is used by the synchronization equipment 101, 1 1 1 transmitters 10 and 1 1.
- the SFN adapter 14 is the pendant, on transmission, the synchronization equipment 101, 111 in reception.
- the SFN adapter is also powered by a frequency reference signal at 10 MHz and by a time reference signal at one pulse per second.
- the data flow is therefore of the MPEG-2 TS type: it is then transmitted by a network adapter 16 ("TX network adapter"), and conveyed via the transport network or distribution 17 (for example a satellite distribution network), to the receivers 12, to be made available to the transmitters 10 and 11.
- TX network adapter for example a satellite distribution network
- the time stamping performed by the SFN adapter 14 consists, on the one hand, in constructing megatrames, each corresponding to 8 DVB-T frames in 8K mode, or 32 DVB-T frames in 2K mode, and on the other hand, to insert in any place of each of these mega-tows, a megatram initialization packet, also called "Mega-frame Initialization Packet", or MIP.
- MIP Mega-frame Initialization Packet
- the MIP packet of the megatram index n is identified by its own PID (for "Packet Identifier” or “packet identifier”) and comprises in particular: a two-byte word called “pointer”, which gives the number of data packets (TS packets) between the current MIP and the first TS packet of the next megatram; a three-byte word called “Synchronization time stamp", or STS, which gives the number of 10 MHz periods between the last pulse
- FIG. 2 illustrates more precisely these different notions for: the data flow at the output of the SFN adapter at the head of the network, referenced 21;
- the SFN adapter 14 organizes the data stream 21 into megatrames, and inserts one and only one MIP packet per megatram (MIP n- I for the megatram). -1, MIP n for megatram n).
- the system SYNC module 101, 102 receives at its input on the one hand the MPEG stream 22 which has been transported in the network, and on the other hand the time references 1 pps and frequency 10 MHz for example from the GPS receiver.
- the system SYNC module 101, 102 finds, thanks to the value STS and pulse 1 pps, when this first packet TS of the next megatram is out of the SFN adapter at the head of the network. This corresponds to the time (or time) of transport. Finally, the system SYNC module 101, 102 deduces the instant of broadcast, which corresponds to the time of exit of the SFN adapter at the head of the network to which is added a controlled delay common to all issuers of the transmission sites (maximum delay or "Max Delay", also carried in the packets MIP), as well as a delay that may be specific to each transmitter ("Tx_time_offset").
- the transmitters 10, 11 use the MIP signaling and a time reference (for example a signal 1 pps) identical to that used at the headend transmitter, to perform a comparative analysis of the signaling MIP and time stamps STS, and make the decision to delay more or less the received frame, output of the emitter of the site of emission.
- a time reference for example a signal 1 pps
- this deterministic method which is based on the same 1 pps time reference as at the head end, ensures the temporal synchronization of the output signals of transmit site transmitters.
- time references 1 pps and frequency 10 MHz are common at all points of the broadcast chain. They are thus deduced, conventionally from a GPS reception.
- the document WO 2006/084361 proposes inserting temporal information into the data stream to be broadcast at the headend, retrieving this information at each transmission site, and generating, from of this temporal information, a reference signal used by the different transmission sites to synchronize.
- this technique ensures the synchronization of different transmitters only if all transmission sites use the same synchronization technique. Therefore, this technique does not give correct synchronization of all transmitters if some transmitters use a 1 pps reference generated from a GPS receiver, and other transmitters regenerate a reference signal from the information temporal range in the broadcast stream.
- the transport time between the headend and the different emission sites varies.
- the transport time to a given transmitter center varies over time by about 270 ⁇ s, considering a geostationary satellite located at about 36,000 km whose position varies in a cube of about 80 km side.
- the time reference 1 pps regenerated according to the technique of document WO 2006/084361 is therefore no longer synchronized with the time reference 1 pps resulting from a GPS receiver.
- the displacement of the satellite induces frequency variations.
- the invention proposes a new solution that does not have all of these disadvantages of the prior art, in the form of a diffusion method.
- a data stream in a broadcast network comprising at least two separate transmitters powered by a headend, said stream being organized into data frames and comprising at least one time tag.
- such a method implements the following steps, at the head end:
- the invention thus proposes, according to at least one of these embodiments, a new synchronization technique for the different transmitters of a broadcast network, not requiring the use of a reliable time reference (for example from a GPS receiver) at each of these transmitters.
- the first time reference is a pulse per second, derived from a positioning system
- the second time reference is a pulse per second, regenerated from the data stream.
- a reliable source is here understood to mean a time reference and / or frequency reference source, of the American GPS or European Galileo positioning system type, or long wave radio carriers (DCF77 in Germany, MSF in the UK, France Inter in France, etc.) - trademarks.
- a time shift is determined between the two time references obtained in different ways, at the head end, and this time offset is transmitted, or at least one time marker of the modified data flow as a function of this offset. , intended for issuers.
- the time offset determined for example for a mega-cluster of index n, can be taken into account to modify the temporal marker or markers in the rest of the data stream, ie the mega-beat time markers. of index n + 1, of index n + 2 and following.
- This modification of the time stamp (s) makes it possible to postpone this time shift, due in particular to the variation of the transport time between the headend and an emitter (due to variations of the satellite), on the modulated signal broadcast by the transmitter.
- the time stamp carries a timing stamp (STS).
- STS timing stamp
- the modified time marker (s) carries (s) a value representative of the time offset and of said synchronization time stamp (STS).
- the time markers are modified by adding the time offset to the value of the time stamp.
- the diffusion method comprises a step of pre-distortion of the first temporal reference, by adding to it said time offset.
- the modified time marker (s) then bear a value representative of the predistorted temporal reference and of said synchronization time stamp (STS).
- the modified time markers carry the value of said modified stamp according to the predistorted time reference.
- the diffusion method may comprise a step of obtaining a frequency reference from said first time reference, and a step of predistortion of said frequency reference, as a function of said time difference.
- the diffusion method comprises a step of determining a predistorted time reference from said frequency reference.
- the modified time marker (s) then bear a value representative of the predistorted temporal reference and of said synchronization time stamp (STS).
- the value of said stamp is thus modified according to said predistorted time reference.
- the time offset is transmitted to said transmitters via an external transmission means.
- this external transmission means implements an external link, such as a GPRS link, WIMAX ... using a data transmission protocol such as the IP protocol.
- an external link such as a GPRS link, WIMAX ... using a data transmission protocol such as the IP protocol.
- the time offset or said at least one modified time marker may also be inserted into the data stream prior to the transmission step.
- the time offset or said at least one time stamp is inserted by replacing a stuff packet of said data stream with a phantom packet prior to the transmitting step.
- the temporal offset or the said at least one marker temporal is inserted by replacing a packet of stuffing said data stream with a packet whose signaling does not change the nature of the flow, that is to say the final service associated with the flow.
- this or these marking-specific packets inserted in the stream before the transmission can be filtered before the extraction of the time markers, that is to say at the level of each transmitter, for example by overwriting these packets by a stuffing pack.
- this filtering of the specific packets is deterministic. Thus, in the context of a SFN type network, it does not modify the SFN aspect of the broadcast signal.
- the data frames are organized into megatrams, each megatram comprising a time marker, and the time marker is a megatram initialization packet (MIP).
- MIP megatram initialization packet
- the network is a SFN type network, in which each of said transmitters uses the same transmission frequency.
- the invention also relates to a computer program product downloadable from a communication network and / or recorded on a computer readable medium and / or executable by a processor comprising program code instructions for implementing the broadcast method. previously described.
- the invention in another embodiment, relates to a headend supplying at least two separate transmitters in a data stream broadcasting network, said stream being organized into data frames and comprising at least one time marker.
- the headend comprises:
- Such a headend is particularly adapted to implement the broadcasting method described above.
- such a headend comprises means for modifying said one or more time markers, depending on the result of said comparison.
- the comparison means and the means for modifying the time marker (s) can be included in an adapter of the type
- Yet another aspect of the invention relates to a system for transmitting a data stream in a network comprising at least one head-end supplying at least two different transmitters, said stream being organized into data frames and comprising at least one marker in which: said at least one headend comprises:
- means for synchronizing said data stream from said time reference; means for retransmitting said data stream; and at least one other of said transmitters comprises:
- the proposed technique thus makes it possible to use, in the same broadcast network, both transmitters using a time reference from a reliable source, and transmitters using a time reference from the data stream.
- FIG. 1 already described in relation with the prior art, presents a block diagram of a SFN-type digital terrestrial television broadcasting system implementing a broadcasting of data in the MPEG format.
- FIG. 2 illustrates, in the form of a time diagram, the principle of SFN synchronization implemented in the system of FIG. 1;
- Figure 3 shows the main steps of the diffusion method according to the invention;
- FIGS. 4A and 4B illustrate the regeneration of a time reference from the MPEG data stream;
- Figure 5 shows a regeneration technique of a frequency reference from the MPEG data stream;
- Figures 6 and 7 provide a block diagram of a headend and a timing diagram illustrating a first embodiment of the invention;
- Figures 8 and 9 provide a block diagram of a headend and a timing diagram illustrating a second embodiment of the invention;
- FIG. 10 shows a block diagram of a headend according to a third embodiment of the invention
- Figures 11 and 12 show a block diagram of a headend and a transmitter at a transmission site according to a fourth embodiment of the invention
- FIG. 13 shows the simplified structure of a headend implementing the broadcasting method according to a particular embodiment of the invention.
- the general principle of the invention rests on the determination, on the head side of network, a time lag between two time references obtained according to different techniques, and the transmission of a directly modified time marker in the data stream sent by the headend to take account of this offset, or on the transmission of this time shift to the different transmitters of the network, so that the transmitters modify their local time reference according to this offset.
- FIG. 3 illustrates more precisely the general principle of the invention, implemented in a communication network comprising at least two distinct transmitters powered by a headend.
- the headend receives as input on the one hand the data to be broadcast, and on the other hand a first time reference, obtained from an external source, such as a GPS receiver. It organizes the data in frames, and inserts at least one time marker in the data stream. The stream thus marked is then transported to the different transmission sites, via a satellite link, for example.
- the headend receives the data stream transported by the satellite. From the time marker (s) present in this stream, a second time reference is obtained.
- the first and second time references are then compared during a step 33, to determine a time shift between the first and second time references.
- this time offset is transmitted to the different transmitters, or else taken into account to modify the time marker (s) in the rest of the data flow transported to the different transmission sites. More precisely, the modification of the temporal markers makes it possible to to compensate, at the headend, the influence of the displacement of the satellite, so as to emulate the reception at the transmitters. It is also possible to transmit this time offset to the different transmitters, which can modify their local time reference according to this offset.
- these transmitters can be of different types, some using a reliable external source for the generation of a time reference (GPS type), others regenerating the time reference from the received data stream, and thus requiring not the use of an external reference type GPS.
- This technique thus makes it possible to compensate for variations in the transport time between the headend and the different transmission sites.
- the headend organizes the data to be broadcast in megatrames taking into account a 1 pps temporal reference from a reliable source, of GPS type, denoted 1 pps (GPS), and inserts at least one time stamp, in the form of a MIP packet, in the data stream.
- the stream thus marked, referenced 41, is then transported to the different emission sites.
- the transmitter receives the MPEG stream 42 which has been transported in the network.
- the sender looks for the MIP packet n . ⁇ .
- the transmitter Having found the MIP package n . i, it finds thanks to the value "point" the first TS packet of the next megatram n, referenced TS n J.
- the transmitter also extracts the STS value of the MIP packet.
- the transmitter regenerates the time reference 1 pps (denoted 1 pps (MPEG)), thanks to the value STS and to the value of the fixed delay, considered equal to the known and constant transport time .
- the transmitter at the transmission site or at the headend regenerates a time reference 1 pps by assigning the value of the transport time, considered constant, to the fixed delay. It is thus considered that a pulse (1 pps) occurs at the instant defined by the reception of the first bit of the first packet TS of the megatram following the packet MIP n . i, minus the time defined by the STS value, minus the fixed delay corresponding to the transport time.
- the time reference 1 pps (MPEG) regenerated by the transmitter is synchronized with the time reference 1 pps (GPS) from a reliable source.
- the transport time between the headend and the sending site is unknown or variable, which implies that the value of the fixed delay is no longer equal to the transport time.
- the time reference 1 pps (MPEG) regenerated by the transmitter is not synchronized with the time reference 1 pps (GPS) from a reliable source.
- FIG. 5 illustrates the main steps of the generation of a 10 MHz reference, from the data stream 42. For example, it is considered that this stream has a bitrate of 24.130 megabits per second.
- the generation of a 10 MHz reference implements the following steps:
- the 10 MHz frequency reference is very precisely at the same frequency as the 10 MHz frequency reference from a GPS receiver.
- the headend comprises: satellite reception means, such as those present on the transmission sites (RX network adapter), making it possible to follow the variations travel time related to satellite movements. These means make it possible to receive the MPEG stream 42 at the head end;
- a regeneration module 61 of the reference 1 pps from the MPEG stream 42 denoted 1 pps (MPEG), according to the technique described in section 5.2;
- GPS 1 pps time reference
- the comparison means belong to the SFN adapter 63.
- the SFN adapter 63 thus comprises, in addition to conventional inputs for the data to be broadcast 60 on the one hand, and for a first time reference ( 1 pps (GPS)) and a first frequency reference (10 MHz (GPS)) on the other hand, an additional input for a second time reference (1 pps (MPEG)).
- the data stream to be broadcast is organized into megatrams, comprising one or more MIP packets. These MIP packets bear an STS timing stamp, calculated according to the time reference 1 pps from the GPS receiver 62.
- the data flow 41 thus constructed is distributed in the transport network.
- the transported data stream, then referenced 42 is received by the satellite reception means of the headend.
- the module 61 then makes it possible to regenerate the time reference 1 pps (MPEG) from the MPEG stream 42.
- the comparison means (64) then compare the time reference 1 pps (MPEG) and the time reference 1 pps (GPS), determining the offset temporal ⁇ 1 pps between these two references.
- the SFN adapter 63 modifies the value STS (65) in the MIP packets, taking into account this time difference.
- the value of the STS stamp previously calculated according to the 1 pps (GPS) time reference, is modified by adding to it the time offset, such that:
- This new value STS ' which is inserted in the MIP packets, in the module 65. This time offset is therefore taken into account to modify the time markers or markers in the subsequent flow of data transported to the different sites of emission.
- the time reference 1 pps (MPEG) regenerated at the transmission sites from the MPEG stream comprising the modified markers, according to the technique described previously, is synchronized with the reference 1 pps (GPS) .
- the first bit of the megatram following the current MIP packet is not broadcast by the transmitter at the instant defined by the pulse 1 pps, to which the value STS and the delay Max Delay, but at the instant defined by the pulse 1 pps, which is added the value STS 'and the delay Max_Delay (ie 1 pps + STS + ⁇ 1 pps (t) + Max Delay).
- the broadcast signals remain well synchronized.
- the comparison means (64) can regularly calculate the compensation ⁇ lpps to bring to the value STS, by the following recursion formula:
- ⁇ lpps (n + 1) ⁇ lpps (n) + measured instantaneous difference, where n is the index of the megatram.
- the compensation ⁇ 1 pps (n + 1) to be supplied to the megatram n + 1 is equal to the compensation ⁇ 1 pps (n) which was provided to the mega-band n, to which the measured instantaneous deviation (that is, the gap that still remained after providing the compensation ⁇ 1 pps (n)).
- the measured instantaneous deviation is zero, it means that the temporal offset ⁇ lpps between the time references 1 pps (GPS) and 1 pps (MPEG) has been correctly calculated and that the references lpps (GPS) and 1 pps (MPEG) ), after applying the correction, are synchronized.
- the time reference 1 pps generated from the MPEG signal is therefore correctly synchronized to the time reference 1 pps from the GPS.
- the SFN adapter works with references 1 pps and possibly 10 MHz from a reliable reception, type GPS. Its smooth operation is therefore assured. In particular, it can be noted that there are exactly 10 million periods of the 10 MHz reference between two 1 pps pulses.
- the headend comprises:
- the comparison means (64) make it possible to measure, at the head end of the network, the variation of the transport time, ie the time offset ⁇ 1 pps between the time reference 1 pps ( MPEG) and the time reference 1 pps (GPS).
- the headend comprises, according to this second embodiment, means 72 for pre-distortion of the first time reference, delivering a predefined temporal reference 1 pps.
- the SFN adapter 71 comprises three inputs, one for the data to be broadcast, and the other two for time and frequency references.
- the SFN adapter 71 is a conventional adapter, comprising a first input for the broadcast data 70, a second input for the frequency reference 10 MHz and a third input for the predefined time reference 1 pps.
- the data stream to be broadcast is organized into megatrams, comprising one or more MIP packets, as described for the first embodiment.
- the transported data stream, then referenced 42 is received by the satellite reception means of the headend.
- the module 61 then makes it possible to regenerate the time reference 1 pps (MPEG) from the MPEG stream 42.
- the comparison means (64) then compare the time reference 1 pps (MPEG) and the time reference 1 pps (GPS), determining the time shift ⁇ 1 pps between these two references.
- the time reference 1 pps (GPS) is then modified (72) taking into account this temporal offset, delivering a predefined time reference 1 pps:
- the SFN adapter 71 determines from this time reference 1 predefined pps an STS 'value, and modifies in the MIP packets the value STS in STS '.
- the time reference 1 pps (MPEG) regenerated at the transmission sites from the MPEG stream comprising the modified markers, according to the technique described previously, is synchronized with the reference 1 pps (GPS) .
- the time reference 1 pps generated from the MPEG signal is therefore correctly synchronized to the time reference 1 pps from the GPS.
- This second solution makes it possible to compensate for the variation of the transport time of the MPEG stream. It is therefore possible to use, in the same broadcast network, both transmitters using a time reference from a reliable source of GPS type, and transmitters using a time reference from the MPEG stream.
- the headend comprises:
- the comparison means (64) make it possible to measure, at the headend of the network, the variation of the transport time, that is, ie the time shift ⁇ 1 pps between the 1 pps (MPEG) time reference and the 1 pps (GPS) time reference.
- This time shift ⁇ 1 pps is used to regenerate, in a module 81, a frequency reference at 10 MHz predistorted. More specifically, the module 81 takes as input the frequency reference at 10MHz from the GPS receiver and the time shift ⁇ l pps predistord the frequency reference 10MHz (GPS) taking into account this shift, and delivers a frequency reference 10MHz predistorted.
- GPS time shift
- This predistorted 10MHz reference can for example be obtained by using a phase-locked loop ("Phase-Locked Loop”) or
- VCO voltage control
- the PLL can be slaved to the 10 MHz reference from the GPS. Then, once this control is achieved, the control voltage of the PLL (VCO) is increased or decreased according to the value of the time shift ⁇ l pps in order to minimize it, leading to an increase or a decrease of the frequency 10MHz.
- VCO control voltage of the PLL
- a predefined 1 pps time reference is regenerated in a module 82, starting from the predefined frequency reference 1 OMHz.
- the SFN adapter 83 which is a conventional adapter, then comprises inputs for the data to be broadcast 80, the predefined time reference 1 pps, and the predefined 10 MHz frequency reference.
- the data stream to be broadcast is organized in megatrams, comprising one or more MIP packets, during a first initialization phase.
- the transported data stream, then referenced 42 is received by the satellite reception means of the head of the network.
- the module 61 then makes it possible to regenerate the time reference 1 pps (MPEG) from the MPEG stream 42.
- the comparison means (64) then compare the time reference 1 pps (MPEG) and the time reference 1 pps (GPS), determining the time shift ⁇ 1 pps between these two references.
- the frequency reference 10 MHz from the GPS is then frequency-controlled from this time shift ⁇ 1 pps (81), delivering a predefined 10 MHz frequency reference, and a predefined 1 pps time reference.
- the SFN adapter 83 determines from this time reference 1 predefined pps an STS 'value, and modifies in the MIP packets the value STS in STS'.
- the time reference 1 pps generated from the MPEG signal is therefore correctly synchronized to the time reference 1 pps from the GPS.
- This third solution therefore makes it possible to compensate for the variation of the MPEG stream transport time, as well as the frequency difference of the 10 MHz frequency reference due to Doppler.
- the 1 pps and 10 MHz frequency references supplied to the SFN adapter 83 are linked, which means that there are exactly 10 million periods of the 10 MHz frequency reference between two 1 pps pulses. .
- GPS GPS, and transmitters using a time reference from the MPEG stream, reporting the variation of the duration of the transport time on the modulated signal broadcast by the transmitters.
- the first bit of the megatram following the current MIP packet is not broadcast by the transmitter at the instant defined by the pulse 1 pps, to which the value STS and the delay Max Delay are added, but at the same time. moment defined by the pulse 1 pps, which is added the value STS 'and the delay Max Delay (either 1 pps + STS + ⁇ 1 pps (t) + Max_Delay).
- a fourth embodiment is presented. This embodiment makes it possible to synchronize the two temporal references, and possibly frequency references, without causing distortion of the reference coming from the external source. As described above, this fourth embodiment makes it possible to measure at the head end the time offset between a time reference provided by an external source and a temporal reference provided by the data stream.
- this time difference is transmitted directly to the different transmitters.
- the transmitters present at the transmission sites comprise, according to this embodiment, means for obtaining this time offset, and for modifying their local time reference to take account of this offset.
- the network head A comprises:
- a regeneration module 61 of the reference 1 pps from the MPEG stream 42 denoted 1 pps (MPEG), according to the technique described in section 5.2;
- GPS 1 pps time reference
- the temporal shift between the temporal references 1 pps (MPEG) and 1 pps (GPS), resulting from the comparison means 64, is transmitted to at least one transmission site B, using a means external transmission 111.
- This external transmission means 111 is for example a GPRS link or an IP transmission.
- the received MPEG stream 42 is used to regenerate the reference 1 pps, according to the technique described in section 5.2.
- the time offset obtained at the transmission site is then added (112) to the regenerated signal 1 pps (MPEG) at the transmission site, corresponding to the local time reference.
- the time reference 1 pps (MPEG) is found aligned with an external time reference (for example 1 pps (GPS)), compensating for the time shift ⁇ 1 pps.
- the headend A comprises, in addition to the elements mentioned in relation to the first variant, means 121 for modifying the data flow.
- this time shift is inserted into a packet TS having a PID, that is to say a TS packet identifier, dedicated.
- this time shift is inserted by replacing a packet of stuffing of the stream with a packet identified by a phantom PID, that is, a packet with a PID that is not described in the tables and which does not. is not reserved by the standard.
- this time shift is inserted by replacing a packet of stuffing of the stream with a packet whose signaling does not modify the nature of the signal to be broadcast.
- the transmitter knows the specific packets carrying the time offset (phantom PIDs or packets whose signaling does not modify the nature of the signal to be broadcast). It is also possible to insert several time offset values in the stream by introducing tag-specific packets in each of the megatrams.
- This insertion step is for example implemented by a slightly modified MIP inserter.
- the MPEG stream received is used to regenerate the reference 1 pps, according to the technique described in paragraph 5.2.
- An extraction module 122 is also provided, making it possible to extract, in the specific packets marking, the time offset measured at the head of the network.
- the extracted time offset is then added (123) to the regenerated signal 1 pps (MPEG) at the transmission site, thus delivering a compensated 1 pps time reference.
- the time reference 1 pps (MPEG) is then aligned with the 1 pps (GPS) time reference, compensating for the time shift ⁇ 1 pps. It may also be noted that the TS packet dedicated to the marking is transparently processed by the modulators (for example referenced 102 and 112 in connection with FIG. 1), at the transmission sites B.
- marking-specific TS packets it is also possible to insert one or more modified time marker (s) as described in connection with the first three embodiments in one or more marking-specific TS packets.
- these marking-specific packets are identified by a phantom PID or a packet whose signaling does not change the nature of the signal to be broadcast.
- specific tagging packets for example, phantom MIPs
- STS' STS + ⁇ 1 pps
- This insertion step is for example implemented by a slightly modified MIP inserter, making it possible to introduce marking-specific packets into the MPEG stream.
- the flow of data transported from the headend to the different transmitters thus has a double MIP marking:
- the "conventional" MIP marking used by the modulators for example referenced 102 and 112 in connection with FIG. 1; the specific MIP marking, transparent for the modulators, and used only during the synchronization of the system in the transmission centers to generate a reference 1 pps aligned with the reference 1 pps resulting from a reliable source (GPS).
- GPS reliable source
- the tagging specific packets inserted in the stream before the transmission can be filtered before the extraction of the "conventional" MIP time markers, that is to say at the level of each transmitter, for example by overwriting this or these packets specific to marking by a stuffing pack.
- this filtering of the specific packets is deterministic. Thus, in the context of a SFN type network, it does not modify the SFN aspect of the broadcast signal.
- the time reference 1 pps (MPEG) regenerated from the data stream will be determined from the time markers bearing the value STS '.
- the time reference 1 pps (MPEG) is found aligned with an external time reference (for example 1 pps (GPS)).
- FIG. 13 the simplified structure of a headend implementing a broadcasting method according to one of the particular embodiments described above.
- Such a headend comprises a memory 131, a processing unit 132, equipped for example with a microprocessor ⁇ P, and driven by the computer program 133, implementing the diffusion method according to the invention.
- the code instructions of the computer program 133 are for example loaded into a RAM memory before being executed by the processor of the processing unit 132.
- the processing unit 132 receives as input the data to broadcast D, as well as a time reference 1 pps (and possibly frequency 10 MHz).
- the microprocessor of the processing unit 132 implements the steps of the diffusion method described above, according to the instructions of the computer program 133.
- the head end includes, in addition to the memory 131, means for obtaining a first time reference, from an external source, means for obtaining a second time reference, from said stream data received by the headend, means for comparing said first and second time references, and means for transmitting said time offset or at least one of said modified time markers according to said time offset.
- means for obtaining a first time reference from an external source
- means for obtaining a second time reference from said stream data received by the headend
- means for comparing said first and second time references means for transmitting said time offset or at least one of said modified time markers according to said time offset.
- the processing unit 132 outputs the time offset or the data stream comprising at least one modified time marker.
Landscapes
- Engineering & Computer Science (AREA)
- Signal Processing (AREA)
- Multimedia (AREA)
- Synchronisation In Digital Transmission Systems (AREA)
- Two-Way Televisions, Distribution Of Moving Picture Or The Like (AREA)
Abstract
Description
Claims
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR0851047A FR2927747B1 (fr) | 2008-02-19 | 2008-02-19 | Procede de diffusion d'un flux de donnees dans un reseau comprenant une pluralite d'emetteurs, produit programme d'ordinateur, tete de reseau et systeme correspondants. |
PCT/EP2009/051561 WO2009103638A1 (fr) | 2008-02-19 | 2009-02-11 | Procede de diffusion d ' un flux de donnees dans un reseau comprenant une pluralite d ' emetteurs ainsi que produit programme d ' ordinateur, tete de reseau et systeme pour la mise en oeuvre de ce procede |
Publications (1)
Publication Number | Publication Date |
---|---|
EP2243232A1 true EP2243232A1 (fr) | 2010-10-27 |
Family
ID=39817094
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP09712298A Withdrawn EP2243232A1 (fr) | 2008-02-19 | 2009-02-11 | Procede de diffusion d ' un flux de donnees dans un reseau comprenant une pluralite d ' emetteurs ainsi que produit programme d ' ordinateur, tete de reseau et systeme pour la mise en oeuvre de ce procede |
Country Status (4)
Country | Link |
---|---|
US (1) | US8683069B2 (fr) |
EP (1) | EP2243232A1 (fr) |
FR (1) | FR2927747B1 (fr) |
WO (1) | WO2009103638A1 (fr) |
Families Citing this family (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2992507B1 (fr) * | 2012-06-26 | 2015-03-13 | Tdf | Procede et dispositif d'horodatage d'un flux de donnees dans un reseau de diffusion radiophonique, procede et dispositif d'insertion, programmes d'ordinateur et medium de stockage correspondants. |
CN103336712B (zh) * | 2013-05-28 | 2017-04-19 | 广州中大电讯科技有限公司 | 一种用于数字电视单频网适配器的控制方法 |
FR3015739B1 (fr) * | 2013-12-19 | 2017-05-26 | Enensys Tech | Procede de generation d’un marquage temporel pour une diffusion terrestre synchrone |
FR3019701B1 (fr) * | 2014-04-04 | 2017-09-15 | Tdf | Procede et dispositif de synchronisation de donnees, procede et dispositif de generation d'un flux de donnees, et programmes d'ordinateur correspondants. |
CN111436048B (zh) * | 2019-02-03 | 2022-03-01 | 维沃移动通信有限公司 | 支持时间敏感通信的方法及通信设备 |
Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0042144A1 (fr) * | 1980-06-14 | 1981-12-23 | Licentia Patent-Verwaltungs-GmbH | Méthode et dispositif pour la transmission simultanée d'informations par plusieurs émetteurs à ondes communes |
EP1026519A1 (fr) * | 1999-02-08 | 2000-08-09 | Société Européenne des Satellites | Système et procédé pour la mesure de distance pour satellites |
US20020054611A1 (en) * | 1998-07-07 | 2002-05-09 | Mitsuru Seta | Time synchronization method in cdma system |
WO2006084361A1 (fr) * | 2005-02-09 | 2006-08-17 | Alex Dolgonos | Systeme et procede de mise en oeuvre d'un reseau monofrequence a diversite de transmission sans recepteurs gps |
US20060200852A1 (en) * | 2005-03-02 | 2006-09-07 | Rohde & Schwarz, Inc. | Apparatus, systems and methods for producing coherent symbols in a single frequency network |
Family Cites Families (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE69232530T2 (de) * | 1991-03-27 | 2002-11-07 | Matsushita Electric Industrial Co., Ltd. | Signalübertragungssystem |
KR950701783A (ko) * | 1992-05-29 | 1995-04-28 | 존 에이치. 무어 | 동시방송 전송 시스템을 동기화하기 위한 방법 및 장치(Method and Apparatus for Synchronizing a Simulcast Transmission System) |
FR2725860A1 (fr) | 1994-10-17 | 1996-04-19 | Telediffusion Fse | Procede et systeme de synchronisation d'un reseau de telecommunication |
US6011977A (en) * | 1995-11-30 | 2000-01-04 | Ericsson Inc. | RF simulcasting system with dynamic wide-range automatic synchronization |
TW507428B (en) | 1999-03-31 | 2002-10-21 | Harris Corp | Method and system for extending broadcast coverage on a single frequency network |
US7336646B2 (en) | 2004-10-26 | 2008-02-26 | Nokia Corporation | System and method for synchronizing a transport stream in a single frequency network |
-
2008
- 2008-02-19 FR FR0851047A patent/FR2927747B1/fr active Active
-
2009
- 2009-02-11 EP EP09712298A patent/EP2243232A1/fr not_active Withdrawn
- 2009-02-11 US US12/735,831 patent/US8683069B2/en active Active
- 2009-02-11 WO PCT/EP2009/051561 patent/WO2009103638A1/fr active Application Filing
Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0042144A1 (fr) * | 1980-06-14 | 1981-12-23 | Licentia Patent-Verwaltungs-GmbH | Méthode et dispositif pour la transmission simultanée d'informations par plusieurs émetteurs à ondes communes |
US20020054611A1 (en) * | 1998-07-07 | 2002-05-09 | Mitsuru Seta | Time synchronization method in cdma system |
EP1026519A1 (fr) * | 1999-02-08 | 2000-08-09 | Société Européenne des Satellites | Système et procédé pour la mesure de distance pour satellites |
WO2006084361A1 (fr) * | 2005-02-09 | 2006-08-17 | Alex Dolgonos | Systeme et procede de mise en oeuvre d'un reseau monofrequence a diversite de transmission sans recepteurs gps |
US20060200852A1 (en) * | 2005-03-02 | 2006-09-07 | Rohde & Schwarz, Inc. | Apparatus, systems and methods for producing coherent symbols in a single frequency network |
Also Published As
Publication number | Publication date |
---|---|
US20110055414A1 (en) | 2011-03-03 |
FR2927747B1 (fr) | 2010-03-19 |
US8683069B2 (en) | 2014-03-25 |
WO2009103638A1 (fr) | 2009-08-27 |
FR2927747A1 (fr) | 2009-08-21 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
WO2007042574A1 (fr) | Procede de generation et demultiplexage d'un signal de contribution optimise, et systeme de diffusion regionalisee de donnees | |
FR2919775A1 (fr) | Procede et dispositif pour la synchronisation d'un flux de donnees dans un reseau a frequence unique | |
EP2347588B1 (fr) | Horodatage d' un flux de donnees dans un reseau a frequence unique | |
EP2243232A1 (fr) | Procede de diffusion d ' un flux de donnees dans un reseau comprenant une pluralite d ' emetteurs ainsi que produit programme d ' ordinateur, tete de reseau et systeme pour la mise en oeuvre de ce procede | |
EP1040670A1 (fr) | Procede et systeme de mesure de la qualite de signaux de television numerique | |
EP2030449B1 (fr) | Procede d'insertion d'au moins une composante dans un flux numerique, dispositif d'insertion et produit programme d'ordinateur correspondants | |
EP2735167A1 (fr) | Système de diffusion de programmes vidéos | |
FR2930396A1 (fr) | Marquage temporel associe a une synchronisation d'equipements connectes a un reseau | |
FR2898452A1 (fr) | Procede de generation d'un double descripteur temporel pour la transmission d'un signal genlock sur un reseau ip | |
EP3284260B1 (fr) | Procédé de remplacement d'un contenu principal par au moins un contenu secondaire, équipement de remplacement de contenus et programme d'ordinateur correspondants | |
WO2009000982A2 (fr) | Procédés de génération de flux finaux et de flux secondaires de contenus primaires et secondaires à transmettre, pour des réseaux sfn, et dispositifs de génération et stations associés | |
WO2015150587A1 (fr) | Procédé et dispositif de synchronisation de données, procédé et dispositif de génération d'un flux de données, et programmes d'ordinateur correspondants | |
EP1927206B1 (fr) | Mesurer la synchronisation d'emetteurs dans un reseau a frequence unique a l'aide d'une reference externe | |
EP2865189B1 (fr) | Procédé et dispositif d'horodatage d'un flux de données, procédé et dispositif d'insertion, produits programme d'ordinateur et médium de stockage correspondants | |
EP3643072A1 (fr) | Procédé et équipement de génération d'un flux de transport, procédé et site de diffusion, et programme d'ordinateur correspondants. | |
EP2359507B1 (fr) | Procedes de diffusion et de re-diffusion d'un signal dans un reseau de diffusion radiophonique, ainsi que diffuseur et re-diffuseur, signal et programme d'ordinateur mettant en oeuvre ce procédé | |
EP2614655B1 (fr) | Diffusion synchronisee de flux | |
EP2345250B1 (fr) | Modification du debit d'un flux de donnees diffuse dans un reseau monofrequence | |
EP4091331A1 (fr) | Procédé de décrochage d'un flux dans un multiplex à débit variable, ledit flux étant constitué d'une pluralité de chunks, site de diffusion et dispositifs associés |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
|
17P | Request for examination filed |
Effective date: 20100730 |
|
AK | Designated contracting states |
Kind code of ref document: A1 Designated state(s): AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO SE SI SK TR |
|
AX | Request for extension of the european patent |
Extension state: AL BA RS |
|
DAX | Request for extension of the european patent (deleted) | ||
17Q | First examination report despatched |
Effective date: 20141009 |
|
RIC1 | Information provided on ipc code assigned before grant |
Ipc: H04H 20/67 20080101ALN20190521BHEP Ipc: H04H 20/18 20080101AFI20190521BHEP |
|
GRAP | Despatch of communication of intention to grant a patent |
Free format text: ORIGINAL CODE: EPIDOSNIGR1 |
|
INTG | Intention to grant announced |
Effective date: 20190724 |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN |
|
18D | Application deemed to be withdrawn |
Effective date: 20191204 |