JP2007214946A - Broadcast retransmitter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a broadcast retransmitter which deletes an unnecessary TSP, creates a TS at the optimal transmission rate and retransmits the TS to an IP network in retransmission of terrestrial digital broadcasting. <P>SOLUTION: The broadcast retransmitter 100 is constituted of: an OFDM tuner 101 which receives an OFDM signal to demodulate the TS; a packet filter part 102 which deletes a NULL packet from the TS; a clock generation part 103 which generates a clock based on information from the OFDM tuner; a TS buffer memory 104 which temporarily holds the TS packet; a NULL packet generation part 105 which generates the NULL packet; a speed conversion part 106 which converts speed of the TS; an IP packet generation part which makes the TS into an IP packet and an IP processing part 110 which performs IF processing with an IP network and the speed conversion part 106 is constituted of a TS generation part 107 which generates a TS to be output and a PCR conversion part 108 which converts PCR of the generated TS. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to IP retransmission in which terrestrial digital broadcasting is converted into IP packets and distributed to terminals in each home using a communication network such as FTTH.

  In recent years, digitalization of broadcasting has been progressing, and a form in which a transport stream (hereinafter abbreviated as TS) is converted to IP and transmitted using a communication network, so-called IP broadcasting has been put into practical use. Under such circumstances, studies on IP retransmission, in which terrestrial digital broadcasting is converted to IP and distributed using a communication network such as FTTH, have been started.

  In general, communication information of a personal computer or the like is usually transmitted to a communication network. Considering transmission of IP broadcasts using this communication network to homes, the transmission band of broadcasts is larger than that used in normal communications, so the transmission band can be reduced as much as possible. desired.

  On the other hand, as for broadcasting, Japanese terrestrial digital broadcasting is carried out by the ISDB-T system. In this method, a multiplex frame composed of n transport stream packets (hereinafter abbreviated as TSP) is formed and transmitted after OFDM modulation. This multiplex frame is configured to transmit TSPs of the A layer, B layer, and C layer of the OFDM signal, but to interface the TS with a constant clock regardless of the transmission parameter setting of each layer. Furthermore, it is supplemented with an appropriate number of NULL packets. Therefore, when the OFDM signal is demodulated on the receiving side, a TS supplemented with a NULL packet, that is, a TS composed of multiple frames is output, and the TS is converted into an IP as it is and transmitted to each home using a communication network. The extra transmission band will be used. As a method of deleting and transmitting the supplemented NULL packet, for example, a method as disclosed in Patent Document 1 is considered.

  The contents of the prior art will be described with reference to FIG.

  FIG. 5 shows an example of a method of transmitting by deleting a complemented NULL packet included in a multiplexed frame according to the prior art in transmission between an ISDB-T remultiplexing apparatus and an ISDB-T OFDM modulator. .

  The TSP filter 201 of the transmission side apparatus receives an ISDB-T format multi-frame TS signal in a DVB-ASI standard data packets format. In the present apparatus, the TSP filter 201 is controlled so as to delete the complemented NULL packet determined by the Frame synchronization signal and the TMCC, Mode, and Guard Interval information. The complemented NULL packet to be deleted is determined by the TSP filter control circuit 202 based on the Frame synchronization signal, TMCC, Mode, Guard Interval information, and the like. Note that the number of supplemented NULL packets to be deleted can be any number from 0 to the number of all complemented NULL packets. For example, if the goal is to reduce the transmission rate to the minimum, it is possible to delete all complemented NULL packets. In addition, when the purpose is to make the number of TSPs to be transmitted constant, it is possible to delete only the number of supplemented NULL packets that are unnecessary. By such an operation, the number of TSPs transmitted through the TS signal transmission path 206 is equal to or less than the number of TSPs of the multi-frame TS signal.

  The output signal of the transmission side apparatus is input to the TSP multiplexing circuit 204 of the reception side apparatus via the TS signal transmission path 206. Since an arbitrary number of complemented NULL packets are deleted from the output signal of the transmission side apparatus, it is necessary to newly multiplex a NULL packet at a location where the TSP is deleted. Therefore, first, a NULL packet to be multiplexed is generated by the NULL packet generator 203. Further, the multiplexing control circuit 205 determines the position where the NULL packet is multiplexed based on the Frame synchronization signal and TMCC, Mode, Guard Interval information, and the like. In the TSP multiplexing circuit 204, multiplexing is performed based on the signal input via the TS signal transmission path 206, the output of the NULL packet generator 203, and the output of the multiplexing control circuit 205. As a result, the same signal as the multiplexed frame TS signal input to the transmission side apparatus is output from the TSP multiplexing circuit 204.

By applying this transmission / reception device between the ISDB-T remultiplexing device and the ISDB-T OFDM modulator, transmission capacity can be reduced, or auxiliary information or the like can be multiplexed in place of the reduced NULL packet. We plan effective use of road.
JP 2003-115807 A

  However, the method as described above is a mechanism that assumes transmission between transmission station side apparatuses that can transmit one-to-one. When applying terrestrial digital broadcasts to IP and retransmitting them to each home, the frame synchronization signal and TMCC, Mode, Guard Interval information are transmitted as in the prior art, and these information are processed on the receiving side. It is quite difficult to realize a mechanism to do this, and it is not a realistic method.

  The object of the present invention is to delete unnecessary TSP, perform PCR conversion based on TMCC, Mode, and Guard Interval information, generate TS with the optimum transmission rate, and retransmit to the IP network. To provide an apparatus.

  In order to solve the above problems, a receiving apparatus according to an embodiment of the present invention receives an OFDM-modulated signal of digital terrestrial broadcasting, receives TS (Transport Stream) and TMCC (Transmission and Multiplexing Configuration Control) information, Mode information, and Guard. A receiving unit that outputs Interval information, a TS control unit that deletes a NULL packet from the TS output from the receiving unit, and a clock that generates a clock based on TMCC information, Mode information, and Guard Interval information output from the receiving unit Generation means, and speed conversion means for converting the TS output from the TS control means into a transmission rate corresponding to the clock generated by the clock generation means, IP conversion means for converting the TS output from the speed conversion means into an IP packet; and output means for output to an IP network. The speed conversion means performs PCR based on the clock generated by the clock generation means. (Program Clock Reference) conversion is performed.

  In the receiving apparatus according to an embodiment of the present invention, the clock generation means includes a plurality of fixed clock generation means for generating a predetermined frequency, and TMCC, Mode, and Guard Interval information output from the reception means. And a clock selection means for selecting an optimum clock from the plurality of fixed clock generation means.

  In the receiving apparatus according to an embodiment of the present invention, the TS control means includes a TS type setting means for setting the type of TS to be output, and the TS type setting means by analyzing the TS output from the receiving means. A NULL packet replacing unit that replaces TSs other than those set in step 1 with NULL packets and a NULL packet deleting unit that deletes NULL packets from the transport stream, and all but the desired TS are deleted.

  The receiving apparatus according to an embodiment of the present invention is characterized in that the receiving means outputs or does not output a NULL packet other than a TS packet transmitted in a desired layer.

  The receiving apparatus according to an embodiment of the present invention is characterized in that the speed conversion means generates a transport stream having a desired transmission rate by multiplexing a NULL packet on the input transport stream.

  According to the broadcast retransmission apparatus of the present invention, unnecessary TSP can be deleted, and a TS can be generated at an optimal transmission rate and retransmitted to the IP network, thereby suppressing the bandwidth necessary for transmission as much as possible. .

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a block configuration diagram of a broadcast retransmission apparatus for retransmitting terrestrial digital broadcasting to an IP network in Embodiment 1 of the present invention. In FIG. 1, a broadcast retransmission apparatus 100 generates a clock based on information from an OFDM tuner 101 that receives an OFDM signal and demodulates a TS, a packet filter unit 102 that deletes a NULL packet from the TS, and the OFDM tuner 101. Clock generation unit 103, TS buffer memory 104 that temporarily holds TS packets, NULL packet generation unit 105 that generates NULL packets, speed conversion unit 106 that performs TS speed conversion, and IP packet generation unit that converts TS into IP packets 109, an IP processing unit 110 that performs IF processing with an IP network, and a speed conversion unit 106 includes a TS generation unit 107 that generates an output TS and a PCR conversion unit 108 that converts a PCR of the generated TS. It is configured.

  Next, the operation of the broadcast retransmission apparatus 100 in the present embodiment will be described. An OFDM modulated signal of terrestrial digital broadcasting is input to the OFDM tuner 101 via an antenna (not shown). The OFDM tuner 101 demodulates the OFDM modulated signal and reproduces the TS. The TS transmitted by the OFDM signal is a TSP transmitted in the X layer of the OFDM signal (the X layer indicates any one of the A layer, the B layer, and the C layer). It is composed of multiple frames composed of TSPs belonging to any of the non-transmitted NULL packets. For example, in the case of Mode 1 and guard interval 1/8, FIG. 2 composed of A layer, B layer and NULL packet (In this example, the C layer is not transmitted). In FIG. 2, TSPB is a TSP in the B layer, TSPA is a TSP in the A layer, TSPnull is a TSP of a NULL packet, and # 1, # 2, # 1152, etc. are TSP numbers in one multiplexed frame. The OFDM tuner 101 reproduces and outputs a TS composed of the multiple frames.

  The regenerated TS is temporarily stored in the TS buffer memory 104 after the NULL packet is deleted by the packet filter unit 102.

  On the other hand, in the OFDM transmission, the number of TSPs that can be transmitted per unit time takes various values depending on the transmission parameter settings of each layer. For this reason, by complementing an appropriate number of NULL packets, the TS interface can be taken with a constant clock regardless of the transmission parameter setting, but this TS contains unnecessary NULL packets. It will be. Actually, it is sufficient that there is a band that can transmit the number of TSPs excluding this unnecessary NULL packet, and this band, that is, the information rate, can be obtained from TMCC information, Mode, and Guard Interval information. In ISDB-T, the information rate of one segment is defined as shown in FIG. The clock generation unit 103 holds the information in FIG. 3, acquires TMCC, Mode, and Guard Interval information from the OFDM tuner 101, and generates a clock corresponding to a desired information rate from the information. For example, when the carrier modulation is 64QAM, the convolutional code is 3/4, the guard ratio is 1/8, and the 13 segments are the same parameters, 140.29 (kbit / s) is multiplied by 13 to 18.255 (Mbit / s) is the desired information rate.

  The speed conversion unit 106 generates a TS at the original information rate based on the clock supplied from the clock generation unit 103. This operation will be specifically described. First, the TS buffer memory 104 holds the TSP from which the NULL packet has been deleted. The NULL packet is included in the original TS separately from the unnecessary NULL packet added for complementation. There is a NULL packet required as a TS. Since the NULL packet deletion unit 102 also deletes the valid NULL packet included in the original TS, it is necessary to reproduce the NULL packet in order to generate a TS at the original information rate. . First, the TS generation unit 107 checks the TS buffer memory 104. If data of 1 TSP or more is accumulated, the TS generation unit 107 switches the switch to the TS buffer memory 104 side to read the data of 1 TSP in accordance with the information rate. When there is no data in the memory 104, the switch is switched to the NULL packet generator 105, and a NULL packet for 1 TSP is read according to the information rate. By repeating this operation every 1 TSP, the TS at the original information rate including the necessary NULL packet can be reproduced.

  The PCR value contained in the TS of the reproduced TS is corrected by the PCR conversion unit 108. PCR is the value of the system clock that the sending side has attached to a specific number of specific packets in the TS. Based on this value, the pace of the system clock on the receiving side is adjusted to the pace of the system clock on the sending side. The PCR included in the regenerated TS is a value attached on the transmission side in accordance with the rate of the TS composed of multiple frames. However, since the TSP is received at the information rate on the receiving side, it is necessary to correct the PCR value corresponding to the information rate in the broadcast retransmission apparatus. Therefore, when the TSP is output according to the information rate in accordance with the clock generated by the clock generation unit 103 in the broadcast retransmitting apparatus, the PCR conversion unit 108 replaces the PCR part of the TSP with its own system clock value. I do.

  In this way, the speed conversion unit 106 generates a TS at the original information rate based on the clock supplied from the clock generation unit 103.

  The TS generated by the speed converting unit 106 is converted into an IP packet by the IP packet generating unit 109 and then transmitted to the IP network through the IP processing unit 110.

  Through the above operation, a terrestrial digital broadcast signal transmitted by OFDM modulation is received, unnecessary TSP is deleted, TS is reconstructed and converted to IP at the original information rate, and retransmitted to the IP network. A retransmission apparatus can be provided.

  In the present embodiment, an example is shown in which all NULL packets are deleted by the packet filter unit 102, but only unnecessary NULL packets may be deleted. Further, the packet filter unit 102 may be configured to delete other than the TSP included in the necessary hierarchy. Specific methods include analyzing the TS and replacing all TSPs other than the necessary layers with NULL packets, and then deleting all NULL packets, or only TSPs with a specified packet ID (PID). A configuration is possible in which only TSPs of a necessary hierarchy are extracted by the PID filter to be extracted. The clock generation unit 103 can cope with the problem by generating a clock corresponding to the information rate according to the number of segments transmitted in a desired hierarchy. Thereby, for example, when the receiving side is a fixed receiver, it is only necessary to transmit the fixed reception service, and more efficient transmission is possible by deleting other than the fixed reception service layer.

(Embodiment 2)
A second embodiment of the present invention will be described with reference to FIG. In FIG. 4, a clock 111a, b clock 111b, and c clock 111c which are fixed clocks generate predetermined clocks, and the clock selection unit 112 selects an optimal clock based on information from the OFDM tuner 101. I do. The present embodiment is different from the first embodiment in that a plurality of fixed clocks are prepared and an optimum clock is selected.

  Hereinafter, a method for generating a clock to be supplied to the speed conversion unit 106 will be described in detail.

  FIG. 4 is a block configuration diagram of a broadcast retransmission apparatus for retransmitting terrestrial digital broadcasting to an IP network in Embodiment 2 of the present invention. For example, a clock 111a is 15 MHz, b clock 111b is 20 MHz, c In this example, three clocks with 25 MHz are prepared for the clock 111c. The clock selection unit 112 holds the information shown in FIG. 3 and selects an optimal clock from the OFDM tuner 101 based on the TMCC, Mode, and Guard Interval information. For example, when the carrier modulation is 64QAM, the convolutional code is 3/4, the guard ratio is 1/8, and the 13 segments are the same parameters, 140.29 (kbit / s) is multiplied by 13 to 18.255 (Mbit / Since s) is the actual information rate, the b clock 111b optimum for the information rate is selected and supplied to the speed converter 106 as a clock.

  Since other operations are the same as those in the first embodiment, description thereof is omitted.

  As described above, according to the second embodiment, a plurality of fixed clocks can be generated based on TMCC, Mode, and Guard Interval information without using a complicated means that accurately generates a clock corresponding to the information rate. By means for selecting the clock, it is possible to generate a clock with a simple configuration.

  Although three fixed clocks are used in the present embodiment, there is no problem with other numbers.

  In this embodiment, the values of the fixed clocks are 15 MHz, 20 MHz, and 25 MHz. However, other values do not cause any problem in operation.

  In this embodiment, a plurality of fixed clocks are prepared and selected. However, one fixed clock is prepared and the clock is replaced with TMCC, instead of the clock selection unit 112. A clock may be generated in accordance with the information rate by providing a function of multiplying or dividing based on the Mode / Guard Interval information.

  According to the broadcast retransmission apparatus according to the present invention, unnecessary TSPs can be deleted and a TS can be constructed at an optimum transmission rate. Therefore, communication data and efficient transmission can be efficiently performed in terrestrial digital broadcast retransmission using an IP network. Thus, it is possible to construct a retransmission system that can share the bandwidth.

The block diagram which shows the structure of the broadcast retransmission apparatus in Embodiment 1 of this invention. The figure which shows an example of a structure of the multiplex frame in Embodiment 1 of this invention The figure which shows the information rate of 1 segment defined by ISDB-T The block diagram which shows the structure of the broadcast retransmission apparatus in Embodiment 2 of this invention. Block diagram showing a conventional multi-frame transmission system

Explanation of symbols

100 Broadcast Retransmission Device 101 OFDM Tuner 102 Packet Filter Unit 103 Clock Generation Unit 104 TS Buffer Memory 105 NULL Packet Generation Unit 106 Speed Conversion Unit 107 TS Generation Unit 108 PCR Conversion Unit 109 IP Packet Generation Unit 110 IP Processing Unit 111a Fixed Clock 111b Fixed clock 111c Fixed clock 112 Clock selection unit

Claims (5)

A broadcast retransmitting apparatus that receives an OFDM modulated signal of terrestrial digital broadcasting, outputs a TS (Transport Stream) into an IP packet, and outputs the packet.
A receiver that receives the OFDM modulated signal and outputs TS and TMCC (Transmission and Multiplexing Configuration Control) information, Mode information, and Guard Interval information;
A packet filter unit for deleting a NULL packet from the TS output from the receiving unit;
A clock generation unit that generates a clock based on TMCC information, Mode information, and Guard Interval information output from the reception unit;
A speed conversion unit that converts TS output from the packet filter unit into a transmission rate according to the clock generated by the clock generation unit;
An IP packet generation unit that converts the TS output from the speed conversion unit into an IP packet,
The broadcast conversion apparatus, wherein the speed conversion unit converts a value of a PCR (Program Clock Reference) included in the TS based on the clock generated by the clock generation unit. The clock generation unit includes a plurality of fixed clock generation units that generate a predetermined frequency;
The broadcast retransmission according to claim 1, further comprising a clock selection unit that selects an optimal clock from the plurality of fixed clock generation units according to TMCC, Mode, and Guard Interval information output from the reception unit. apparatus. The packet filter unit includes: a TS type setting unit that sets a type of TS to be output; and a NULL that analyzes a TS output from the receiving unit and replaces a TS other than that set by the TS type setting unit with a NULL packet. A packet replacement unit and a NULL packet deletion unit that deletes a NULL packet from the transport stream;
3. The broadcast retransmitting apparatus according to claim 1, wherein all but the desired TS are deleted. 4. The broadcast retransmission apparatus according to claim 1, wherein the receiving unit outputs or does not output a NULL packet other than a TS packet transmitted in a desired layer. 5. . The broadcast according to any one of claims 1 to 4, wherein the speed conversion unit generates a transport stream having a desired transmission rate by multiplexing NULL packets on the input transport stream. Retransmission device.

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