JP3400681B2 - Data packet remultiplexing method and remultiplexing apparatus - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data packet re-multiplexing method and a multiplexing device, and more particularly to MPEG.
2-system single program transport stream (abbreviated as Single Program-Transport Stream SP-TS)
From Multiple Program Transport Stream (M
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data packet re-multiplexing method and a multiplexing device for converting into an ultimate-program-transport stream, abbreviated as MP-TS.

[0002]

2. Description of the Related Art Digital satellite broadcasting started in 1996, and terrestrial broadcasting and CATV are being planned for digitization. In digital broadcasting, video signals and audio signals are compression-coded and transmitted based on the MPEG-2 Video and Audio standards. By performing digital compression, compared to conventional analog broadcasting, it is possible to transmit a plurality of channels with the same quality as analog in the band in which one channel was transmitted in analog.

As described above, broadcasting is in the direction of multi-channel service. In current digital satellite broadcasting, one repeater (transponder) provides about 4 channels of service. The program is delivered to each subscriber and CAT
It is desired to distribute the program to another program distributor such as V and retransmit it to the CATV subscriber. As a method of retransmission, there is a method of transmitting digital data of one transponder band to the CATV network as it is.

However, in this case, since all the programs in the transponder are retransmitted, undesired programs are retransmitted. This method is inefficient because it consumes transmission bandwidth for unwanted programs. Therefore, by extracting only desired programs in the satellite broadcasting transponder, re-multiplexing them and transmitting them to the CATV transmission band, the band can be efficiently used. However, since this method performs multiplex processing, there is a problem that the packet transmission delay fluctuates. If the packet transmission delay fluctuates, the following problems occur.

The encoded signal is transmitted in packets called transport packets. The transport stream, which is the data stream of the transport packet, considers the transmission in the asynchronous network, and the counter value of the clock used at the time of encoding (abbreviated as Program Clock Reference PCR). Is described in the packet and transmitted. On the side that receives the transport stream, the clock on the encoding side (abbreviated as System Time Clock STC) is reproduced from the received PCR, decoding is performed using that STC, and the video display and audio signal are output. To do. On the receiving side, PLL (Phase Locked Loop) using the received PCR as a reference signal
Since the STC is reproduced by using, the STC fluctuates because the arrival interval fluctuates although there is no problem if the arrival interval of the packet including the PCR matches the output interval of the transmission side. The decoded video data needs to be converted into a video signal such as an NTSC television signal for display. The sync signal of this video signal is generated based on STC, but S
The fluctuation of TC makes the synchronization signal unstable. Since the color subcarrier is generated based on the sync signal, an unstable sync signal causes a problem that reproduction of a correct color tone is hindered.

As a technique for solving this problem, a multiplexing method in which the transmission delay of a packet including PCR is made constant is known ("Consideration on PCR at MPEG-2 TS re-multiplexing" (Baba et al., 1997 Electronics). However, the precondition for this multiplexing method is that the transmission bit rates of the multiple transport streams to be multiplexed and the stream after re-multiplexing are perfectly synchronized. Is the least common multiple of the input transmission bit rate as the transmission bit rate after multiplexing.For example, when the encoders of the transport stream to be multiplexed operate on the same clock source, this prerequisite is satisfied, but the satellite Since different transponders are operated by independent clock sources, transport streams that have passed through different transponders are synchronized. If the transmission bit rates are close to each other and slightly deviated from each other, the least common multiple will result in a considerably large bit rate after multiplexing, which makes transmission impossible in a limited transmission band. Further, although it is stipulated that PCR is sent at least once in 100 msec, the interval is indefinite within this range, and the output interval of PCR in different encoding devices is often not constant. The technique of making the transmission delay of the packet constant cannot handle the case where the packets including the PCRs are overlapped and input, and therefore, the problem that the PCR fluctuates when the asynchronous transport streams are multiplexed cannot be solved.

[0007]

SUMMARY OF THE INVENTION Therefore, the main object of the present invention is to solve the above problems and eliminate the adverse effects of PCR fluctuations of transport streams when remultiplexing multiple asynchronous transport streams. An object of the present invention is to provide a data packet re-multiplexing method and a multiplexing device that enable the side to normally reproduce STC.

[0008]

In order to achieve the above object, the data packet re-multiplexing method of the present invention uses a PCR to convert a data packet of a desired specific channel from one or a plurality of transport streams, particularly a packet according to the MPEG2 standard. In a multiplexing method of selecting a data packet having the same and multiplexing it to create a new transport stream, PCR of a signal compressed and coded by a different clock or a signal of a different transmission bit rate is corrected at the re-multiplexing stage and received. Machine so that it can be used properly.
That is, a transport packet having a specific identifier is extracted from one or more input transport streams, the extracted data packet is converted into a new transport packet, and a re-multiplexed transport packet is re-multiplexed. In the multiplexing method, the generation of the new transport packet is performed by replacing the identifier of the extracted data packet with another identifier, and when the extracted data packet has a PCR, it is replaced with a correction PCR prepared in advance. , The data packet PC input when outputting as a transport packet of the new transport stream to be multiplexed
Replace R with the above PCR for correction.

The preferred form of generation of the correction PCR is: (1) PCR of the extracted data packet
Is set in the counter, and the counter is counted by the clock signal provided in the extraction unit until the output of the new transport packet, and the value of the counter is used as the correction PCR. (2) The difference value between the PCR of the extracted data packet and the counter is obtained over a plurality of transport packets having the PCR, the average value of the plurality of difference values is obtained, and the average value and the value of the counter are added to correct the above. For PCR. (3) There is a mode in which the value of the counter and a specific offset value are added to obtain the correction PCR.

Further, the data packet re-multiplexing apparatus of the present invention receives a transport stream including a plurality of programs as one input, extracts a packet identifier including a transport stream of a specific program from the transport stream, and performs PCR. A packet identifier extraction unit that outputs a PCR value when receiving, a packet filter unit that extracts a packet having an identifier of the output of the packet identifier extraction unit, a buffer unit that temporarily holds the output of the packet filter unit, and the packet identifier extraction unit A clock generation unit that generates a clock from the PCR value of the output, a correction PCR generation unit that performs a counter PCR by the output signal of the clock generation unit, and a packet including the PCR when the packet including the PCR is read from the buffer unit. Use the PCR value in the above as the correction PCR And a PCR exchange section for conversion.

[0011]

DETAILED DESCRIPTION OF THE INVENTION

<Embodiment 1> FIG. 1 is a block diagram showing an embodiment of a data packet remultiplexing apparatus according to the present invention. A plurality of channel processing units 10-1, 10-2 arranged in parallel,
10-3 and a plurality of channel processing units 10-1, 10-
It is composed of a multiplexing unit 5 for time-division multiplexing a plurality of transport packets output from Nos. 2 and 10-3, and a control unit 8 for controlling the multiplexing unit 5. Channel processing unit 10-1
The PCR extracts the packet identifier of the transport packet of the specific program to be newly multiplexed from the transport stream TS including a plurality of programs (channels), and PCR when the transport packet has PCR.
A packet identifier extraction unit 1 that outputs a value and a packet filter unit 1 that extracts a packet having an identifier output from the packet identifier extraction unit 1 from the transport stream TS.
1, the buffer unit 4 for temporarily holding the output of the packet filter unit 11, and the PCR of the output of the packet identifier extraction unit 1.
When a packet including a PCR is read from the clock generation unit 3 that generates a clock from the value, the counter unit 2 that performs the counting operation of the counter 2 based on the output clock signal of the clock generation unit 3, and the PCR in the packet A PCR replacement unit 9 that replaces the value of 2 with the counter value of the counter 2,
A transport packet generation unit 6 that generates a specific transport packet for channel generation and a packet generation control unit 7 that generates data to be output by the packet generation unit 6 are provided.

In the above structure, the counter 2, the clock generator 3 and the PCR replacement unit 9 form a correction PCR generator. Since the channel processing units 10-2 and 10-3 have the same configuration as the channel processing unit 10-1, they are shown only by blocks. Depending on the embodiment, the input of each channel processing unit may be applied to a case in which one transport stream TS including a plurality of programs (channels) is commonly added to a plurality of channel processing units, or some channel processing units use other transports. Port stream may be input.

For the convenience of explanation of the configuration and operation of the above-mentioned multiplexer, the format of the transport stream TS and its generation will be described below. Fig. 2 shows the multiple transport streams (MP-TS: Multiple-Trans) defined by the MPEG2 system standard, which is a global standard.
port stream) configuration is shown. Further, FIG. 3 shows a configuration of a transmitter that creates a transport stream TS from video and audio information and a receiver that reproduces video and audio information from the transport stream TS. Since these are conventionally known, only the parts necessary for explaining the present invention will be described.

As shown in FIG. 2A, it is composed of a sequence of fixed length transport packets of 188 bytes.
Each transport packet is composed of a 4-byte fixed length header, a variable length adaptation field and a payload. The number in parentheses indicates the number of bits. The presence or absence of an adaptation field and payload below the packet header is indicated by an adaptation field flag (2 bits) in the header. Further, the header has PID (13 bits) which is identification information of the packet. The adaptation field can carry information of an individual stream, and in particular, the PCR (4
2 + 6 bits). The PCR is information for setting and configuring the value of STC (reference synchronization information) as a time reference to a value intended by the encoder side in a decoder of the MPEG2 system including a video and audio decoder. Transport packet with PCR is 100m
It is specified to transmit at least once per second.

The transmitter for generating the transport stream TS and the receiver for reproducing the video and audio information from the transport stream TS are configured by the device shown in FIG. In the transmitter, the video source 13 and the audio source 14 such as a VTR and a camera are compression-encoded by encoders 15 and 16, respectively. The compression encoding is based on the world standard MPEG-2. Furthermore, each packetizing unit 1
7 and 18 are packetized in a specific unit. In the packetizing units 17 and 18, the receiving unit receives a decoding time stamp (DTS) indicating the decoding start time of the encoded signal and the PTS (Presenta indicating the time at which the decoded video and audio signals are displayed and reproduced.
tion Time Stamp) is added. Packetizing units 17 and 1
8 output signal is PES (Packetized Elementary Stream)
Called. Transport stream encoder unit 1
At 9 and 20, the transport packet of FIG. 2 (b) is created. At this time, PCR is added at a cycle of 100 ms or less. In the multiplexing unit 21, the transport packet TP
Are time-division-multiplexed and sent to the transmission medium as the transport stream TS of FIG.

In the receiving section, the transport stream TS received via the transmission medium is separated into video, audio and PCR by the separating section 24. The separated coded video and audio signals are temporarily held in buffers 26 and 27, respectively, and then reproduced in video signals and audio signals by decoding units 28 and 29, respectively. Further, the PCR output from the separation unit 24 generates a signal STC synchronized with the clock on the encoding side in the phase locked loop PLL 25, the decoding units 28 and 29 are driven by this clock, and the images are displayed on the monitor 30 and the speaker 31, respectively. And play sound.

FIG. 4 is a timing chart for explaining the effect of the PCR correction by re-multiplexing according to the present invention. It is assumed that transport packets 100, 101, 102 including PCR are output from the transmitting side at times t0, t1, t2. When the transmission delay is fixed such as in a synchronous communication network, the received transport packets 103, 101, 102 corresponding to the transport packets 100, 101, 102, respectively.
If the arrival times of 104 and 105 are t0 ', t1', and t2 ', t1-t0 = t1'-t0', t2-t1 = t
2'-t1 ', PC included in these packets
When the R value is input to the phase locked loop PLL, a clock synchronized with the clock on the transmission side can be obtained.

However, when the arrival delay time of transport packets fluctuates, such as in an asynchronous communication network, the arrival times of the reception transport packets 106, 107, 108 corresponding to the transmission transport packets 100, 101, 102 transport packets are determined. t0 ", t1",
If t2 ″, then t1-t0 ≠ t1 ″ -t0 ″, t2-
When t1 ≠ t2 ″ −t1 ″, and these PCR values are input to the phase locked loop PLL, the frequency deviation of the PLL becomes large. Therefore, the synchronization signal becomes unstable, which causes a problem that the video and audio signals cannot be reproduced correctly.

In the present invention, the fluctuation of the arrival delay time at the time of re-multiplexing, for example, in the case of FIG. 4, the time t1 ″ corresponding to the fluctuation.
Since −t1 ′ is obtained and the received PCR value is corrected, when the PCR value received and included in the packet is input to the phase locked loop PLL due to the time relationship of the received transport packets 106, 107, 108, the frequency deviation of the PLL is lost. There is no shift, and an accurate STC that serves as a time reference can be obtained. Therefore, the synchronization signal becomes stable and the video and audio signals can be reproduced correctly.

The data packet re-multiplexing method according to the present invention will be described below with reference to FIG. The packet identifier extraction unit 1 extracts the information described about the packet identifier of the input multiple transport stream TS by the packet identifier extraction unit 1, and sets the packet identifier including the desired program in the packet filter 11. The packet filter 11 selects only the packet having the set packet identifier. Further, the packet identifier extraction unit 1 sets the PCR value that arrived first after the start of processing as the initial value of the counter 2.

The clock generating section 3 generates a clock for operating the counter section 2. The clock generation unit 3 generates a clock by using a PLL to generate a signal synchronized with the clock on the transmission side, or replaces the counter value of the counter unit 2 with the arrived PCR every time PCR arrives, and the clock is on the transmission side. And a method that uses a clock independent of. In the latter method, the packet containing PCR is TS
During the processing from the input from the multiplexer 5 to the output from the multiplexer 5, the clock is asynchronous with the clock on the transmission side. However, this processing time is on the order of a few milliseconds, and it has little effect on the counter value. Further, from the perspective of the whole, since the value of the counter unit 2 is updated every time the PCR arrives, it can be said that it is synchronized with the clock on the transmitting side.

The output of the packet filter unit 11 is temporarily held in the buffer 4. When the reading from the multiplexing unit 5 is started, the packet is output from the buffer 4 and the replacing unit 9 performs the process of replacing the PCR portion in the packet with the value of the counter unit 2.

Further, when a program is retransmitted to a new communication network such as a CATV network, it is necessary to multiplex information about the new communication network. The packet generation control unit 7 generates necessary information and outputs the information to the transport packet generation unit 6. Transport packet generator 6
Then, the transport packet is generated, and the packet is held until the multiplexing unit 5 reads it. The multiplexer 5 reads out the packet of the channel selected by the controller 8 from the buffer 4 and outputs it.

As the channel selection method in the control section 8, any one of the following methods is adopted. (1) The empty signal of the buffer 4 of each channel is sequentially detected, and the channel having packet information in the buffer 4 is selected. (2) Channels are selected in descending order of the number of packets held in the buffer 4 of each channel. In this case, a counter for counting the number of packets held in the buffer 4 of each channel is provided. (3) Select the channel having the longest time held in the buffer 4 of each channel. In this case, a timer for counting the storage period of the packet input to the buffer 4 is provided. (4) The selection interval is set for each channel, and the selection is performed at regular intervals. This method can effectively perform multiplexing when the transmission bit rate is predetermined. With these methods, channels with different transmission bit rates can be multiplexed.

FIG. 5 shows an algorithm of the multiplexing process by the multiplexing unit 5 and the control unit 8. First, a channel to be multiplexed is selected (5-1). Read the 4 bytes of the transport packet header from the selected channel (5-2). Check the 27th bit from the beginning of the read transport packet header. The 27th bit is a flag indicating the presence or absence of the TS adaptation field.

When there is no adaptation field,
That is, when the flag is "0", 184 bytes other than the header are read and output. After the output, the operation from the selected channel is stopped for a certain fixed time, that is, the remaining time of the time allocated to the processing of one channel (5-4).

When there is an adaptation field, that is, when the flag is "1", 2 bytes of the flag are read (5-5) and the 44th bit from the head of the packet is checked (5-6). This is a flag indicating whether the PCR field is present. When the 44th bit is "0", that is, when the PCR field does not exist, after the remaining 182 bytes are read, the selection operation is stopped for a certain period of time (5-7). When the 44th bit is "1", that is, when the PCR field is present, the value of the counter unit 2 is output (5-8), and then the remaining bits of the packet are output.

By processing these operations for a certain period of time, it is possible to perform the processing for a certain period of time whether the PCR is present or not, and to perform the processing time of the PCR for a certain period of time. Therefore, even if the PCR is corrected, the time from immediately after the correction to the output is constant for each packet, and the jitter is less likely to occur after the PCR is corrected.

<Second Embodiment> FIG. 6 shows a PCR in another embodiment of the data packet re-multiplexing apparatus according to the present invention.
It is a block diagram showing the configuration of the correction unit. PC that arrived
The difference value between the count values of R and the counter 2 is calculated by the calculation means 32, the calculated difference value is held by the holding means 33, and the average value calculated by the calculation part 35 for calculating the average of the difference values is added to the value of the counter 2. The PCR is corrected by the adding means 35. The corrected PCR is added to the multiplexing unit 5.

<Third Embodiment> FIG. 7 is a block diagram of a data packet re-multiplexing apparatus according to another embodiment of the present invention.
It is a block diagram which shows the structure of the correction | amendment part of CR. By adding the value of the counter 2 and the specific offset value from the offset control unit 38 by the addition calculation means 37, the PCR transmitted and the PCR having a certain offset can be added. Therefore, the PTS is added. And PCR timing can be adjusted.

<Fourth Embodiment> FIG. 8 is a block diagram showing an embodiment of a communication system in which a data packet re-multiplexing method and a multiplexing device according to the present invention are implemented. This communication system uses the antenna 50 for broadcasting transmitted by a digital satellite.
And a receiver 51, and a desired program among broadcast programs is re-multiplexed by a re-multiplexer 52 of the present invention, modulated by a modulator 53, and a CATV network including a cable transmission line 54, an STB 55, and a monitor 56. It is a transmitting system.

<Fifth Embodiment> FIG. 9 is a block diagram showing another embodiment of a communication system in which the data packet re-multiplexing method and the multiplexing device according to the present invention are implemented. This communication system uses the antenna 5 for broadcasting transmitted by digital satellite.
0 and the receiver 51, and a multi-transport stream obtained by re-multiplexing the transport stream obtained by encoding the audiovisual sources 61 and 62 of the ground station by the encoding devices 63 and 64 by the re-multiplexing device 65 of the present invention. This is a system for transmitting a TS to a CATV network including a cable transmission line 54, STB 55, and monitor 56.

[0033]

According to the present invention, TSs compressed and encoded by the same clock are multiplexed, and a plurality of TSs compressed and encoded by different clocks are multiplexed and output as one multi-transport stream TS, and The clock recovery of the receiver can operate stably. In addition, it is possible to perform multiplexing at different transmission bit rates by performing multiplexing control. Further, even if the input of the multiplexer is fluctuating, the fluctuation of PCR can be absorbed by obtaining the error average.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a data packet remultiplexing device according to the present invention.

FIG. 2 is a configuration diagram of a transport stream (TS) defined by the MPEG2 system standard.

FIG. 3 is a transmission unit that generates a transport stream,
Block diagram showing the configuration of a receiving unit that reproduces information from a transport stream

FIG. 4 is a timing chart for explaining the effect of PCR correction by re-multiplexing according to the present invention.

FIG. 5 is a diagram showing an algorithm of a multiplexing process by the multiplexing unit 5 and the control unit 8.

FIG. 6 is a block diagram showing the configuration of a PCR correction unit in another embodiment of the data packet remultiplexing device according to the present invention.

FIG. 7 is a block diagram showing a configuration of a PCR correction unit in still another embodiment of the data packet remultiplexing device according to the present invention.

FIG. 8 is a block diagram showing an embodiment of a communication system in which a data packet re-multiplexing method and a multiplexing device according to the present invention are implemented.

FIG. 9 is a block diagram showing another embodiment of a communication system in which a data packet re-multiplexing method and a multiplexing device according to the present invention are implemented.

[Explanation of symbols]

1 ... Packet identifier extraction unit, 2 ... Counter unit, 3 ... Clock generation unit 4 ... Buffer, 5 ... Multiplexing unit, 6 ... Transport packet generation unit 7 ... Packet generation control unit, 8 ... Multiplexing control unit, 9 ... Replacement unit, 10 ... Channel processing unit, 11 ... Packet filter unit, 13 ... Video source 14 ... Audio source, 15 ... Video coding unit, 16 ... Acoustic coding unit, 17, 18 ... Packetization unit, 19, 20 ... Transport stream encoder 21 ... Multiplexing unit, 22 ... DTS control unit, 23 ... PTS control unit,
24 ... Separation unit, 25 ... PLL, 26, 27 ... Buffer, 2
8, 29 ... Decoding section, 32 ... Difference calculator, 33 ... Difference value holding section, 34 ... PCR control section, 35 ... Difference average calculating section, 3
6, 37 ... Addition calculation unit, 38 ... Offset control unit, 50
... antenna, 51 ... receiver, 52, 65 ... remultiplexing device,
53 ... Modulator, 61, 62 ... Audiovisual source, 63, 6
4 ... Encoding device.

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Claims (8)

(57) [Claims] 1. A process of extracting a packet having a specific identifier from an input transport stream, a process of replacing the identifier of the extracted packet with another identifier and holding the same, and a PCR of the extracted packet. A PCR correction step of preparing a corrected PCR by using the PCR , a step of replacing the PCR of the held packet with the corrected PCR when the transport packet is output, a selection step of selecting a channel of the transport packet, and the selection A data packet re-multiplexing method comprising a transport packet of a channel selected in the process and a multiplexing process of multiplexing another selected channel or a newly generated transport packet. 2. The PC corrected in the PCR correction step by setting the PCR of the extracted packet in a counter and correcting the coefficient of the counter by a time clock signal from the input to output of the transport stream.
The data packet remultiplexing method according to claim 1, wherein R is obtained. 3. The PCR correction step of obtaining a difference value between a PCR value of the extracted packet and a counter, a step of holding a plurality of the difference values, and an average difference value from the plurality of difference values. 2. The data packet re-multiplexing method according to claim 1, further comprising: a step of obtaining the value and a step of correcting the counter value from the average difference value. 4. The data packet re-multiplexing method according to claim 1, wherein the PCR correction step is a step of adding a specific offset value to a counter value of the counter. 5. A multiplexing device having a plurality of channel processing units for generating transport packets forming a transport stream, and a multiplexing unit for selecting the plurality of channel processing units and time division multiplexing the transport packets. At least one of the plurality of channel processing units is a packet identifier extraction unit that extracts a packet identifier from a transport packet of a specific channel from a transport stream having a plurality of input channels and outputs a PCR value when a PCR is received. , A packet filter unit that extracts a packet having an identifier of the output of the packet identifier extraction unit, a buffer unit that temporarily holds the output of the packet filter unit, and a correction P that creates a PCR value for correction.
A data packet re-multiplexing device comprising: a CR generation unit; and a PCR replacement unit that replaces the PCR of the buffer unit with the PCR value for correction when a packet including the PCR is read from the buffer unit. 6. The correction PCR generation section has a clock generation section that generates a clock from the PCR value output from the packet identifier extraction section, and a counter section that performs a counter operation based on the output signal of the clock generation section. 6. The data packet remultiplexing device according to claim 5, wherein the counter value at the time of reading a packet including a PCR from the buffer unit is used as the correction PCR value. 7. The clock generation unit has its own oscillation source, and is configured to operate by setting the PCR value as an initial value of the counter when a packet is received. Data packet remultiplexer. 8. The PCR for the channel filtered by the packet filter unit in the clock generation unit.
7. The data packet remultiplexing device according to claim 6, further comprising a PLL that generates a clock synchronized with a clock on the transmission side based on the above.