CN102036123A - Synchronization method and system for single frequency network digital broadcast television system - Google Patents
Synchronization method and system for single frequency network digital broadcast television system Download PDFInfo
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Abstract
The invention provides a synchronization method and a synchronization system for a single frequency network digital broadcast television system. The synchronization method comprises the following steps of: 1) in a central station, stamping a time stamp on each transport stream (TS) packet of TS program stream, wherein the time stamp records absolute stamping time; and 2) when each transmitting station receives each TS packet, calculating absolute transmitting time of the TS packet according to the time stamp of the TS packet and preset delay time, and transmitting the TS packet according to the absolute transmitting time by using each transmitting station, wherein the absolute transmitting time is the sum of the absolute stamping time of the TS packet recorded by the time stamp of the TS packet and the preset delay time. In addition, the invention provides a corresponding synchronization system. The method and the system can avoid error accumulation, improve synchronization reliability, ensure that the transmitting stations are easy and convenient to debug, and avoid asynchronization caused by packet loss, wrong packets and the like in an exciter, and are particularly suitable for a complex hybrid network and a remote distributed network.
Description
Technical field
The present invention relates to the digital TV broadcast signal transmission technique field, specifically, the present invention relates to a kind of method for synchronous and system that is used for the digital broadcast television system of Single Frequency Network.
Background technology
At present, in the digital broadcast signal transmission system, the digital television broadcasting international standard of terrestrial transmission has DVB-T, ATSC-T, ISDT-T etc., the domestic terrestrial DTV transmission standard GB20600-2006 (hereinafter to be referred as the GB terrestrial digital TV standard) with independent intellectual property right that also issued, they can both realize the single frequency network transmission.Single Frequency Network (SFN) whole system only needs a frequency, and the user does not need to change channel in moving and receiving in network coverage, so the relative multi-frequency network of Single Frequency Network (MFN) can be saved frequency resource.But Single Frequency Network has strict demand to the website distance, its website density is relatively large, needs synchronizer to guarantee to be positioned at the transmitter synchronized transmissions of diverse location, to reduce the many through disturbing of signal overlap zone, improve signal and reliably cover, obtain the high-quality television-quality.Therefore one of core technology problem of single frequency network is exactly a stationary problem, and described stationary problem mainly comprises the synchronous of three aspects: Frequency Synchronization, and promptly the carrier frequency of all transmitting stations must be identical; Time synchronized, promptly each transmitting station broadcasts the same data byte of same program at one time; Symbol synchronization, promptly modulation signal must bit synchronous.What relate generally among the present invention is time synchronized and symbol synchronization.The Single Frequency Network system of GB terrestrial digital TV standard mainly is made up of SFN adapter, gps clock, exciter, transmitter etc., compares with the multi-frequency network system, and the Single Frequency Network system has increased SFN adapter and gps clock equipment.The synchronization principles of the Single Frequency Network of other standards and the method for synchronization and GB terrestrial digital TV standard are basic identical, are example with the GB terrestrial digital TV standard below therefore, briefly introduce method for synchronizing time of the prior art.
Fig. 1 shows traditional GB terrestrial digital TV standard Single Frequency Network system.This tradition Single Frequency Network system comprises central station subsystem 100, distributed network 300 and transmitting station subsystem 200.Central station subsystem 100 is connected by distributed network 300 with transmitting station subsystem 200.Central station subsystem 100 comprises digital TV front-end 101, Single Frequency Network adapter 102, network adapter 103 and common reference clock 104 (as gps clock).Single Frequency Network adapter 102 receives the TS bag program data stream of importing from digital TV front-end 101 (hereafter is a TS stream), according to 1 second commutator pulse (1PPS) insertion second frame initialization bag (SIP) in described TS stream of gps clock output.Simultaneously, also to utilize 10MHz reference frequency that gps clock provides that described TS stream is carried out code check adaptive for Single Frequency Network adapter 102.TS stream after Single Frequency Network adapter 102 is handled is input to network adapter 103, is transferred to each transmitting station subsystem 200 by distributed network 300.Transmitting station subsystem 200 comprises network adapter 201, terrestrial DTV exciter 202 and common reference clock 203.The TS that network adapter 201 is sent from distributed network 300 receiving center station subsystems 100 flows and exports this TS stream to terrestrial DTV exciter 202.TS stream as described in the 10MHz reference frequency that terrestrial DTV exciter 202 provides according to common reference clock 203 (as gps clock) and 1 second commutator pulse are launched.Contain the maximum delay time field in described frame initialization bag second (SIP), (maximum delay time is used T to described maximum delay time hereinafter sometimes
Delay_maxExpression) the TS program stream that is meant each transmitting station is unified dead time with respect to the 1PPS of GPS.At each transmitting station, exciter is resolved and is received that a second frame initialization bag (SIP) obtains maximum delay time, the 1PPS rising edge that provides with local gps clock is a benchmark then, postpone emission according to maximum delay time pair and this 1PPS frame initialization in corresponding second bag, thereby make each transmitting station synchronization broadcast the identical data byte of TS stream.
There is following defective in above-mentioned conventional synchronization mode:
(1) reliability is not high.In theory, the emission you is a benchmark with the 1PPS rising edge of this locality in the prior art, per second is done one subsynchronous to the frame initialization second bag in the TS stream, utilize single frequency adapter input code flow (being TS stream) to be fitted to the code check value of modulating mode defined simultaneously, code check with assurance central station and each transmitting station is consistent, thereby reaches the purpose of all TS bag time synchronized in the TS stream.But TS stream is the inevitable problems such as transmission shake, transmission error code that exist in the transmission course of reality, and this causes the time delay of each each transmitting station of TS bag arrival in the TS stream to have deviation, can't guarantee that therefore each TS bag can both synchronized transmissions.And because prior art can only utilize a second frame initialization bag to carry out synchronously, so each TS bag in the per second may accumulate owing to transmitting the error that shake and transmission error code cause, can cause more serious asynchronous problem like this.Moreover because also there are problems such as transmission shake, transmission error code in a second frame initialization bag itself, when frame initialization packet delay second was big, the moment that may cause transmitting station to receive the SIP bag was later than local corresponding 1PPS rising edge+T
Delay_maxThis causes realizing synchronously that therefore in fact prior art can't accomplish that per second synchronously once constantly.More seriously, may there be the transmission error code problem in a second frame initialization bag itself, may cause transmitting station can't receive a second frame initialization bag like this, and then cause synchronization mechanism thoroughly to be destroyed.
(2) debug difficulties.In the conventional synchronization mode, the maximum delay time field in the SIP bag need preestablish.Obtain maximum delay time and need know the transmission delay of each website (being transmitting station).Prior art can only be by the transmission delay that experience is estimated and site test draws each website repeatedly, so this brings very big difficulty for debugging work, and more when the transmitting station number, when distributed more widely, this problem is particularly outstanding.
(3) locking range of SIP bag is for only being 0 to 0.9999999 second.In large-scale net, because website is many and distributed more widely, 1 second situation may appear surpassing in transmission delay, in case the scope traditional approach that time-delay exceeds 1 second just can not be realized synchronously at all.In addition, in the hybrid network of multiple transmission link, also occur the problems referred to above easily and cause to realize synchronously.
Summary of the invention
Therefore, the purpose of this invention is to provide a kind of reliability height, need not the method for synchronous that is used for the Single Frequency Network digital broadcast television and the system of complicated debug process.This method for synchronous and system are particularly suitable for transmitting station number catenet more, distributed more widely.
For achieving the above object, the invention provides a kind of method for synchronous that is used for the Single Frequency Network digital broadcast television system, relate to central station and transmitting station, comprise the following steps:
1) at central station, in each TS bag of TS program stream, squeeze into timestamp, the absolute time of stabbing beaten in described timestamp record; In some embodiments of the invention, beat the absolute time of stabbing and be meant that being played the TS bag that stabs enters the absolute time of beating stamp equipment;
When 2) each transmitting station received each TS bag, according to the timestamp of this TS bag with draw the emission absolute time of this TS bag predefined time of delay, each transmitting station was all launched described TS bag according to described emission absolute time; Described emission absolute time is that the absolute time that TS bag this TS bag that timestamp write down is played stamp adds described predefined time of delay.
Wherein, in the described step 1), also be included in the debug phase, in each TS bag of TS program stream, squeeze into timestamp, draw the pairing propagation delay time of each transmitting station respectively according to the timestamp in the TS bag, then by more further drawing the maximum delay time of each transmitting station in the pairing propagation delay time, with described maximum delay time as described predefined time of delay.
Wherein, described step 1) and step 2) in, described absolute time obtains according to common reference clock and local clock, and common reference clock and local clock that central station and each transmitting station are adopted are in full accord.
Wherein, described common reference clock is according to GPS, GLONASS, Galileo or dipper system provided that 1 second commutator pulse obtains.
Wherein, described local clock adopts 27M clock, the zero clearing when receiving described 1 second commutator pulse of described local clock.
Wherein, in the described step 1), also be included in central station described TS bag carried out serial number, and with described number record in described TS bag; Described step 2) in,, when the TS packet number that receives is discontinuous, generates corresponding to institute and lack the TS sync packet of numbering and number the pairing moment at this and launch described TS sync packet at transmitting station; Described TS sync packet is the filling bag that adopts the TS bag of error correcting technique recovery or do not have content.
The present invention also provides a kind of synchro system that is used for the Single Frequency Network digital broadcast television system, comprises central station subsystem and transmitting station subsystem, and described central station subsystem is connected with a plurality of transmitting station subsystems by distributed network, it is characterized in that,
Described central station subsystem comprises TS bag expanding element, is used for squeezing into timestamp at each TS bag of the TS program stream of importing described central station subsystem output expansion TS bag; The absolute time of stabbing beaten in described timestamp record;
Described transmitting station subsystem comprises TS bag resolution unit and lock unit, described TS bag resolution unit is used for resolving expansion TS bag and obtains the entrained timestamp of TS bag, described lock unit is used for according to the timestamp of this TS bag and draws the emission absolute time that this TS wraps predefined time of delay, and each transmitting station is all launched described TS bag according to described emission absolute time; Described emission absolute time is that the absolute time that TS bag this TS bag that timestamp write down is played stamp adds described predefined time of delay.
Wherein, be the maximum delay time of each transmitting station in the pairing propagation delay time described predefined time of delay.
Wherein, TS bag expanding element also is used to write down the numbering of described TS bag, the described serial number that is numbered; Described TS bag resolution unit also is used to obtain the numbering of described TS bag, described lock unit also is used for when the TS packet number that receives is discontinuous, generates corresponding to institute to lack the TS sync packet of numbering and encourage the modulate emission unit to number the pairing moment at this and launch described TS sync packet; Described TS sync packet is the filling bag that adopts the TS bag of error correcting technique recovery or do not have content.
Wherein, the expansion TS bag that described TS bag expanding element is exported is to increase extended field on former TS package base, and described extended field length is 16 bytes.
The present invention has following technique effect:
1, can avoid the accumulation of error, improve synchronous reliability.
2, debugging is simple and convenient.
3, can avoid in exciter because of situations such as packet loss, wrong bag cause asynchronous.
4, the delay time scope can surpass 1S, is particularly suitable for COMPLEX MIXED network and remote distributed network.
5, synchro system is separated with the stimulated emission system, can adopt the stimulated emission system of different vendor in same Single Frequency Network.
6, synchro system is separated with the stimulated emission system, makes each emission excitation system to set up single frequency network under the mode of operation of multiple frequency network, MFN.
Description of drawings
Below, describe embodiments of the invention in conjunction with the accompanying drawings in detail, wherein:
Fig. 1 shows the traditional Single Frequency Network system of traditional GB terrestrial digital TV standard;
Fig. 2 shows the method for synchronous flow process of Single Frequency Network system in the one embodiment of the invention;
Fig. 3 shows the sequential schematic diagram of absolute time in the one embodiment of the invention.
Embodiment
Below in conjunction with the drawings and specific embodiments the present invention is done to describe further.
Present embodiment provides a kind of synchro system that is used for the Single Frequency Network digital broadcast television system, comprise central station subsystem and transmitting station subsystem, described central station subsystem comprises TS bag expanding element, and described transmitting station subsystem comprises TS bag resolution unit and lock unit.
Synchro system of the present invention need be linked in the Single Frequency Network digital broadcast television system and use, in the present embodiment, described TS bag expanding element is embedded in the Single Frequency Network adapter, increase a Single Frequency Network adapter receiving terminal at the transmitting station subsystem simultaneously, embed TS bag resolution unit and lock unit therein to realize the time synchronized of all TS bags in the TS stream.Owing to increased Single Frequency Network adapter receiving terminal, present embodiment is called Single Frequency Network adapter transmitting terminal with the Single Frequency Network adapter of central station subsystem.
Particularly, as shown in Figure 2, the Single Frequency Network digital broadcast television system that present embodiment relates to comprises central station subsystem 100, distributed network 300 and transmitting station subsystem 200.Wherein central station subsystem 100 comprises elementary cells such as digital TV front-end 101, common reference clock 104, Single Frequency Network adapter TX105 (Single Frequency Network adapter transmitting terminal) and network adapter 103, and transmitting station subsystem 200 comprises network adapter 201, common reference clock 203, Single Frequency Network adapter RX204 (Single Frequency Network adapter receiving terminal) and terrestrial DTV exciter 202.Wherein, Single Frequency Network adapter RX204 is connected between network adapter 201 and the terrestrial DTV exciter 202.
Wherein, embed TS bag expanding element among the Single Frequency Network adapter TX105, TS bag expanding element is used for squeezing into timestamp at each TS bag of the TS program stream of the described central station subsystem 100 of input, output expansion TS bag; The absolute time of stabbing beaten in described timestamp record.
Embed TS bag resolution unit and lock unit among the Single Frequency Network adapter RX204.Described TS bag resolution unit is used for resolving expansion TS bag and obtains the entrained timestamp of TS bag, described lock unit is used for according to the timestamp of this TS bag and draws the emission absolute time that this TS wraps predefined time of delay, and each transmitting station is all launched described TS bag according to described emission absolute time; Described emission absolute time is that the absolute time that TS bag this TS bag that timestamp write down is played stamp adds described predefined time of delay.Be the maximum delay time of each transmitting station in the pairing propagation delay time described predefined time of delay.
In addition, TS bag expanding element also is used to write down the numbering of described TS bag, the described serial number that is numbered; Described TS bag resolution unit also is used to obtain the numbering of described TS bag, described lock unit also is used for when the TS packet number that receives is discontinuous, generation corresponding to lack the numbering the TS sync packet and encourage modulate emission unit (in the present embodiment, the modulate emission unit is a terrestrial DTV exciter 202) to number the pairing moment and launch described TS sync packet at this; Described TS sync packet is the filling bag that adopts the TS bag of error correcting technique recovery or do not have content.
Introduce each elementary cell of Single Frequency Network digital broadcast television system below further.
1. digital TV front-end 101: be mainly used in to MPEG2 code stream (being the TS program stream) filter, multiplexing, add functions such as digital television service information (SI), scrambling, broadcast.Present embodiment directly adopts digital TV front-end of the prior art to get final product.
2. the common reference clock 104: the common reference clock is the canonical reference clock that global any place can both obtain, mainly contain Galileo, the following Chinese dipper system in GPS of USA, Muscovite GLONASS, Europe, this clock provides the 1PPS standard time of a pulse of per second.The 1PPS standard time is the international standard time T second IME of corresponding 1PPS rising edge of a pulse, time T IME generally sent to receiving equipment with the RS232 interface before the 1PPS signal arrives, and parsing time T IME by receiving equipment, time T IME represents the etalon time of corresponding 1PPS rising edge.The Single Frequency Network adapter transmitting terminal of present embodiment and receiving terminal can obtain unified time, frequency and the pulse per second (PPS) of synchronization criterion based on time T IME.At present, the common reference clock mainly adopts the GPS of USA signal, and gps signal can reach the 1E-12 magnitude in lock-out state lower frequency stability, and time precision reaches ± 50nS, can satisfy the requirement of radio data system.The common reference clock also need to provide other absolute time information (time, minute, second, month, day, year information etc.).These absolute time informations are generally by the RS232 transmission, and message information uses the output of NMEA-0183 form usually, are extensive use of the V2.0 version at present, and the data code of output is an ASC II code character.During output, minute, second, month, day, year information.Selecting for use on the market accurately at present, gps time frequency standard and clock product can both satisfy digital broadcast television Single Frequency Network system requirements.
3. Single Frequency Network adapter TX105: Single Frequency Network adapter TX will finish that code check is adaptive, SIP inserts, beat time stamp and close function such as road.Wherein, beat the function of time stamp and finished by the TS bag expanding element that is embedded into Single Frequency Network adapter TX, this function is that the present invention is peculiar.In the present embodiment, need beat time stamp to each TS bag (the Various types of data bag in the TS program stream that the TS bag refers in the present embodiment had both comprised the TS bag that carries programme content, also comprised the SIP bag of insertion) that enters TS bag expanding element.For this reason, the Single Frequency Network adapter TX inside of present embodiment also needs to set up a standard local clock, is used to write down 1 second with interior accurate absolute time.This local clock is a benchmark with a high accuracy 27M clock, with the form realization of counter.When each 1PPS rising edge arrived, described counter carried out synchronous clear ' 0 '.The time stamp precision of TS bag can reach 1/27000000 second like this.
In the present embodiment, described Single Frequency Network adapter TX can utilize programmable controller (FPGA) to carry out hardware programming and realize.At first, set up one 32 bit time counter as inner clock with 27MHz in programmable controller (FPGA), this clock is with the timing that adds up of 27MHz count value.Programmable controller (FPGA) read the data in the RS232 interface before pulse per second (PPS) on the other hand, parsed TOD information, was buffered in then among the FPGA, when the rising edge of 1PPS pulse per second (PPS) arrives, the every minute and second data was write inner clock as the zero-time timing.Thereby inner clock can refresh once according to per 1 second of common reference time, guaranteed the total system time synchronized like this.It is adaptive to carry out code check after the TS bag enters into FPGA earlier, insert the SIP bag, the value that each TS is wrapped according to current inner clock (provides a second above absolute time by the common reference clock, provide second the absolute time that is accurate to 1/27000000 second with interior by local clock, squeeze into as shown in Figure 3) time stamp and add the continuity count value.In the present embodiment, the absolute time that TS wraps the moment that enters described Single Frequency Network adapter TX is stabbed in being beaten of described timestamp record.
4. network adapter 103,201: comprise network adapter TX (transmitting terminal), network adapter RX (receiving terminal), the two is the interface equipment that carries out Network Transmission.Directly adopt network adapter of the prior art to get final product.
5. distributed network 300: the circuit that carries out the signal transmission.Present embodiment is optional with various transmission channels such as optical fiber, copper cable, microwave, satellites.
6. Single Frequency Network adapter RX204: this equipment finish TS stream shunt, buffer memory, time-delay, to the time and output.Output unit when there are inner clock, buffer memory and school in the major function unit, output unit comprises TS bag resolution unit and lock unit during its lieutenant colonel.Single Frequency Network adapter RX is the newly added equipment of present embodiment.
Inner clock: TX is the same with the Single Frequency Network adapter, finishes the synchronous and timing of internal standard time.The implementation of inner clock is also in full accord with the inside clock of Single Frequency Network adapter TX.
Buffer unit: the collection that is mainly used in data is temporary.
Export during the school: be used to resolve TS bag (the TS bag is meant the TS expanding packet) here, determine the output time that this TS wraps according to the time stamp and the delay parameter of TS bag.
In the present embodiment,, thereby preferably adopt the hardware structure of microprocessor (CPU)+programmable controller (FPGA) to finish because Single Frequency Network adapter RX requirement is data cached.Inner clock is the same with Single Frequency Network adapter TX, is used to obtain unified lock in time.Because the time stamp of TS bag is the absolute time count value, add on this basis that therefore maximum delay time is exactly the absolute time that can determine this TS bag output.Maximum delay time is the maximum of all website transmission delays.Be formulated as follows:
T
transmitter＝T
time_stamp+T
delay_max
T
TransmitterAbsolute time for the output of TS bag
T
Time_stampTimestamp for the TS bag
T
Delay_maxBe the maximum delay time, by the transmission delay decision of maximum.
The Single Frequency Network method for synchronous of present embodiment is on implementation, in programmable controller (FPGA), by judging T
TransmitterWith current absolute clock count value, the TS bag is directly exported by decision circuit when both are equal; In theory, do not allow local absolute time greater than T
Delay_maxSituation take place.If take place then directly export this TS bag, come delayed data stream in this way, make each Single Frequency Network adapter RX at unified T
TransmitterThe identical TS of time output wraps, thereby reaches the purpose of time synchronized.
7. the terrestrial DTV exciter 202: the excitation of Single Frequency Network and transmitter.In the present embodiment, can directly adopt terrestrial DTV exciter of the prior art.In addition, present embodiment is owing to use Single Frequency Network adapter RX that TS stream is carried out synchronized transmissions, therefore, in fact present embodiment does not need the terrestrial DTV exciter to carry out synchronously according to 1 second commutator pulse, therefore, the terrestrial DTV exciter of present embodiment also can not need 1 second commutator pulse that the common reference clock provides.This moment, the terrestrial DTV exciter was operated under the multiple frequency network, MFN pattern.
The Single Frequency Network time synchronized working mechanism of present embodiment is as follows: at first set up unified fiducial time in Single Frequency Network adapter and synchronizer with common reference time reference 1PPS, GPS TOD time, make each equipment in the system according to the 27MHz timing, synchronous with universal time, obtain identical timing time.With this count value and GPS absolute time each TS that enters bag is beaten time stamp and continuity count value.When this packet arrives Single Frequency Network adapter RX equipment by network adapter and distributed network, because the path difference of process, the time of delay that arrives synchronizer is different, if output immediately, will cause the time and the bit of Single Frequency Network asynchronous, thereby require packet in Single Frequency Network adapter RX equipment, to carry out certain delay, because each TS bag has been squeezed into the time stamp with absolute time information, therefore can determine the absolute time that this bag is exported as long as add the maximum delay time value at this moment on the basis of stabbing.The absolute time of each website is identical all to be set up with reference to GPS, so the code stream time and the bit synchronous of final output realize symbol synchronization with Frequency Synchronization, thereby realize the synchronized transmissions of Single Frequency Network, reduce Single Frequency Network and cover down many through disturbing the raising signal quality.
Narration is based on the method for synchronizing time of above-mentioned digital broadcast television Single Frequency Network below, and described method for synchronizing time comprises the following steps:
1) at central station, in each TS bag of TS program stream, squeeze into timestamp, the absolute time of stabbing beaten in described timestamp record; Described absolute time obtains according to common reference clock and local clock, when wherein the common reference clock provides, minute, second, month, day, year information, and the time precision of local clock is 1/27000000 second, mode with counter realizes that each count value is represented 1/27000000 second.
When 2) each transmitting station receives each TS bag, wrap timestamp and draw the emission absolute time that this TS wraps predefined time of delay according to this TS, each transmitting station is all launched described TS bag according to described emission absolute time; Described emission absolute time is that the absolute time that TS bag this TS bag that timestamp write down is played stamp adds described maximum delay time.In this step, absolute time also is to obtain according to common reference clock and local clock.For guaranteeing precise synchronization, common reference clock and local clock that central station and each transmitting station are adopted should be in full accord.Because present embodiment can carry out therefore with respect to the per second synchronization mechanism based on 1PPS, having strengthened synchronous reliability greatly synchronously by timestamp to each TS bag.
In addition, in the described step 1), can also carry out serial number to described TS bag at central station, and with described number record in described TS bag; Described step 2) in,, when the TS packet number that receives is discontinuous, generates corresponding to institute and lack the TS sync packet of numbering and number the pairing moment at this and launch described TS sync packet at transmitting station; Described TS sync packet is the filling bag that adopts the TS bag of error correcting technique recovery or do not have content.In the present embodiment,, under the situation that the TS packet loss occurs, still can guarantee the synchronous of TS program stream by generating the TS sync packet.
Present embodiment need be to stab and the TS packet number TS bag joining day by Single Frequency Network adapter RX, and a kind of method is to add extended field to form expansion TS bag on the basis of existing TS bag, and described timestamp and TS packet number are recorded in the described extended field.Especially,, increase the extended field of 16 bytes in therefore can 188 byte TS bag, so just can realize compatibility existing protocol because existing digital television protocol supports 188 bytes and two kinds of TS of 204 bytes to pack formula.In the extended field of 16 bytes, 4 bytes are used for logging timestamp, and 2 bytes are used to write down the TS packet number
Further, described step 2) in, can be the maximum delay time of each transmitting station in the pairing propagation delay time described predefined time of delay.Described maximum delay time can draw in the debug phase.Particularly, in the present embodiment, can draw the pairing propagation delay time of each transmitting station respectively according to the timestamp in the TS bag, then by more further drawing the maximum delay time of each transmitting station in the pairing propagation delay time.Certainly, the method that the present invention obtains maximum delay time is not limited to this, and this is that those skilled in the art are understandable.
Present embodiment is as follows with respect to the advantage of existing Single Frequency Network system and method for synchronous:
(1) introduce the common clock benchmark with GPS TOD absolute time, set up the absolute time value in internal system, all comprise the TOD absolute time in the time stamp of each TS bag, make the delay time scope can surpass 1S, only be subjected to the restriction of physical memory size in theory.This is at the COMPLEX MIXED net and realize that time synchronized has absolute predominance in the distributed network transmission at a distance.
(2) adopt synchronously absolute time carry out to the time, can avoid like this accumulation of error reach more accurate synchronously.Because all Single Frequency Network adapter TX, Single Frequency Network adapter RX equipment adopt unified reference clock, reach bit synchronous truly like this.
(3) adding of bag continuous counter value can be monitored the packet loss of transmission network, wrong bag situation accurately and be revised, and avoids finally causing the time bit asynchronous because of situations such as packet loss, wrong bags in exciter.
(4) can obtain each website transmission delay value accurately according to timestamp by Single Frequency Network adapter RX, carry out the setting of maximum delay, debug simple and convenient according to this value.
(5) synchro system is separated with the stimulated emission system, can adopt the stimulated emission system of different vendor in same Single Frequency Network.
(6) synchro system is separated with the stimulated emission system, makes each emission excitation system to set up single frequency network under the mode of operation of multiple frequency network, MFN.
It should be noted last that above embodiment is only unrestricted in order to technical scheme of the present invention to be described.Although the present invention is had been described in detail with reference to embodiment, those of ordinary skill in the art is to be understood that, technical scheme of the present invention is made amendment or is equal to replacement, do not break away from the spirit and scope of technical solution of the present invention, it all should be encompassed in the middle of the claim scope of the present invention.
Claims (10)
1. method for synchronous that is used for the Single Frequency Network digital broadcast television system, described Single Frequency Network digital broadcast television system comprises central station and transmitting station, described method for synchronous comprises the following steps:
1) at central station, in each TS bag of TS program stream, squeeze into timestamp, the absolute time of stabbing beaten in described timestamp record;
When 2) each transmitting station received each TS bag, according to the timestamp of this TS bag with draw the emission absolute time of this TS bag predefined time of delay, each transmitting station was all launched described TS bag according to described emission absolute time; Described emission absolute time is that the absolute time that TS bag this TS bag that timestamp write down is played stamp adds described predefined time of delay.
2. the method for synchronous that is used for the Single Frequency Network digital broadcast television according to claim 1, it is characterized in that, in the described step 1), also be included in the debug phase, in each TS bag of TS program stream, squeeze into timestamp, draw the pairing propagation delay time of each transmitting station respectively according to the timestamp in the TS bag, then by more further drawing the maximum delay time of each transmitting station in the pairing propagation delay time, with described maximum delay time as described predefined time of delay.
3. the method for synchronous that is used for the Single Frequency Network digital broadcast television according to claim 1, it is characterized in that, described step 1) and step 2) in, described absolute time obtains according to common reference clock and local clock, and common reference clock and local clock that central station and each transmitting station are adopted are in full accord.
4. the method for synchronous that is used for the Single Frequency Network digital broadcast television according to claim 3 is characterized in that, described common reference clock is according to GPS, GLONASS, Galileo or dipper system provided that 1 second commutator pulse obtains.
5. the method for synchronous that is used for the Single Frequency Network digital broadcast television according to claim 4 is characterized in that, described local clock adopts 27M clock, the zero clearing when receiving described 1 second commutator pulse of described local clock.
6. the method for synchronous that is used for the Single Frequency Network digital broadcast television according to claim 1 is characterized in that, in the described step 1), also be included in central station described TS bag carried out serial number, and with described number record in described TS bag; Described step 2) in,, when the TS packet number that receives is discontinuous, generates corresponding to institute and lack the TS sync packet of numbering and number the pairing moment at this and launch described TS sync packet at transmitting station; Described TS sync packet is the filling bag that adopts the TS bag of error correcting technique recovery or do not have content.
7. a synchro system that is used for the Single Frequency Network digital broadcast television system comprises central station subsystem and transmitting station subsystem, and described central station subsystem is connected with a plurality of transmitting station subsystems by distributed network, it is characterized in that,
Described central station subsystem comprises TS bag expanding element, is used for squeezing into timestamp at each TS bag of the TS program stream of importing described central station subsystem output expansion TS bag; The absolute time of stabbing beaten in described timestamp record;
Described transmitting station subsystem comprises TS bag resolution unit and lock unit, described TS bag resolution unit is used for resolving expansion TS bag and obtains the entrained timestamp of TS bag, described lock unit is used for according to the timestamp of this TS bag and draws the emission absolute time that this TS wraps predefined time of delay, and each transmitting station is all launched described TS bag according to described emission absolute time; Described emission absolute time is that the absolute time that TS bag this TS bag that timestamp write down is played stamp adds described predefined time of delay.
8. the synchro system that is used for the Single Frequency Network digital broadcast television system according to claim 7 is characterized in that, be the maximum delay time of each transmitting station in the pairing propagation delay time described predefined time of delay.
9. the synchro system that is used for the Single Frequency Network digital broadcast television system according to claim 7 is characterized in that, TS bag expanding element also is used to write down the numbering of described TS bag, the described serial number that is numbered; Described TS bag resolution unit also is used to obtain the numbering of described TS bag, described lock unit also is used for when the TS packet number that receives is discontinuous, generates corresponding to institute to lack the TS sync packet of numbering and encourage the modulate emission unit to number the pairing moment at this and launch described TS sync packet; Described TS sync packet is the filling bag that adopts the TS bag of error correcting technique recovery or do not have content.
10. the synchro system that is used for the Single Frequency Network digital broadcast television system according to claim 7 is characterized in that, the expansion TS bag that described TS bag expanding element is exported is to increase extended field on former TS package base, and described extended field length is 16 bytes.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2009102352019A CN102036123A (en) | 2009-09-27 | 2009-09-27 | Synchronization method and system for single frequency network digital broadcast television system |
Applications Claiming Priority (1)
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Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102186106A (en) * | 2011-05-04 | 2011-09-14 | 苏州全波通信技术有限公司 | Clock synchronization device in single-frequency network |
| CN102291193A (en) * | 2011-07-27 | 2011-12-21 | 合肥海清广电科技有限公司 | Digital single frequency synchronous coverage system and single frequency synchronous coverage method for amplitude modulation broadcast |
| CN103796079A (en) * | 2013-12-26 | 2014-05-14 | 国家广播电影电视总局广播科学研究院 | Channel damage simulation method of terrestrial digital TV transmission distribution network |
| CN103795589A (en) * | 2013-12-26 | 2014-05-14 | 国家广播电影电视总局广播科学研究院 | Channel damage testing method of radio and television transmission distribution network |
| CN105612757A (en) * | 2013-10-31 | 2016-05-25 | 松下电器（美国）知识产权公司 | Packet transmission method, content play method, packet transmission system, and terminal |
| CN103796039B (en) * | 2013-12-26 | 2017-02-22 | 国家广播电影电视总局广播科学研究院 | Channel damage simulation device of terrestrial digital TV transmission distribution network |
| CN106506108A (en) * | 2016-12-06 | 2017-03-15 | 全球能源互联网研究院 | Sync message dispatching method and device based on software defined network SDN |
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Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102186106A (en) * | 2011-05-04 | 2011-09-14 | 苏州全波通信技术有限公司 | Clock synchronization device in single-frequency network |
| CN102186106B (en) * | 2011-05-04 | 2014-01-22 | 苏州全波通信技术有限公司 | Clock synchronization device in single-frequency network |
| CN102291193A (en) * | 2011-07-27 | 2011-12-21 | 合肥海清广电科技有限公司 | Digital single frequency synchronous coverage system and single frequency synchronous coverage method for amplitude modulation broadcast |
| CN105612757A (en) * | 2013-10-31 | 2016-05-25 | 松下电器（美国）知识产权公司 | Packet transmission method, content play method, packet transmission system, and terminal |
| CN105612757B (en) * | 2013-10-31 | 2020-06-23 | 松下电器（美国）知识产权公司 | Method for transmitting broadcast content and line content to be displayed in synchronization and content reproducing method |
| CN103796079A (en) * | 2013-12-26 | 2014-05-14 | 国家广播电影电视总局广播科学研究院 | Channel damage simulation method of terrestrial digital TV transmission distribution network |
| CN103795589A (en) * | 2013-12-26 | 2014-05-14 | 国家广播电影电视总局广播科学研究院 | Channel damage testing method of radio and television transmission distribution network |
| CN103796039B (en) * | 2013-12-26 | 2017-02-22 | 国家广播电影电视总局广播科学研究院 | Channel damage simulation device of terrestrial digital TV transmission distribution network |
| CN103796079B (en) * | 2013-12-26 | 2017-03-22 | 国家新闻出版广电总局广播科学研究院 | Channel damage simulation method of terrestrial digital TV transmission distribution network |
| CN106506108A (en) * | 2016-12-06 | 2017-03-15 | 全球能源互联网研究院 | Sync message dispatching method and device based on software defined network SDN |
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