JP2022066009A - Traffic smoother device, distribution system, and program - Google Patents

Abstract

To provide a traffic smoother device, a distribution system, and a program that can output packets at regular intervals even when the packets are transmitted via a communication path where jitter is generated.SOLUTION: A traffic smoother device 23 includes a control unit 31 that receives a packet containing a time stamp indicating transmission time serving as a reference for time when the packet should be transmitted, from another device via a network, updates the time stamp by delay time, which is time obtained by adding a predetermined delay to the transmission time indicated by the time stamp contained in the received packet, and outputs a packet containing the updated time stamp, at the delay time indicated by the updated time stamp.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to traffic smoother devices, distribution systems, and programs.

Broadcasting station modulators used in terrestrial digital broadcasting need to input content transmission signals at regular intervals in order to form an OFDM (Orthogonal Frequency Division Multiplexing) frame. That is, it is necessary to input the content transmission signal to the modulator in accordance with the time for forming the 1 OFDM frame (Non-Patent Document 1).

In the current terrestrial digital broadcasting, a content transmission signal is transmitted using a broadcast TS (Transport Stream) packet in a content transmission line in an STL / TTL (Studio to Transmitter Link / Transmitter to Transmitter Link) section. The STL / TTL section means a section from a performance station to a broadcasting station equipped with a transmitter, or a section between a plurality of broadcasting stations. In the content transmission line, the clock is periodically multiplexed and transmitted to the content transmission signal by PCR (Program Clock Reference), and the decoder on the receiving side reproduces this to synchronize the content with an error of ± 500 ns or less. It enables playback.

On the other hand, in the next-generation terrestrial digital broadcasting, the content transmission signal may be transmitted by an IP line using an IP (Internet Protocol) format packet (hereinafter referred to as "XMI packet") in the STL / TTL section. It is being considered. "XMI" is an abbreviation for eXtensible Modulator Interface.

"Information technology --Generic coding of moving pictures and associated audio information: Systems", Standards, ISO / IEC 13818-1, Second edition, 2000-12-01.

In the next-generation terrestrial digital broadcasting, it is also possible to multiplex the clock and transmit the XMI packet in the STL / TTL section as in the current terrestrial digital broadcasting. However, multiplexing the clock causes the system to become complicated, the cost increases due to the introduction of the dedicated hardware device, and the failure rate of the device increases.

Further, when an IP packet such as an XMI packet is transmitted using an IP line regardless of whether it is wireless or wired, the arrival interval of the XMI packet fluctuates due to fluctuation of the packet arrival interval called jitter. Therefore, even if the clocks are multiplexed, the arrival interval of the XMI packet is changed, so that the time for forming the 1 OFDM frame is deviated. Therefore, simply multiplexing the clocks makes it impossible for the modulator to form an OFDM frame, which may result in a modulation error.

An object of the present disclosure is to provide a traffic smoother device, a distribution system, and a program capable of outputting packets at regular intervals even if packets are transmitted via a communication path in which jitter occurs.

The traffic smoother device as one aspect of the present disclosure receives a packet from another device via a network and includes a packet including a time stamp indicating a transmission time as a reference of a time when the packet should be transmitted, and is included in the received packet. The time stamp is updated by a delay time which is a time obtained by adding a predetermined delay to the transmission time indicated by the time stamp, and the update is performed at the delay time indicated by the updated time stamp. It is provided with a control unit that outputs the packet including the time stamp.

In one embodiment, the control unit updates the time stamp with the delay time, which is the time obtained by adding a time larger than the transmission delay time in the network as the delay to the transmission time.

As one embodiment, the time stamp indicates the time when the packet is transmitted by the other device as the transmission time.

As one embodiment, the time stamp indicates the time set in the other device as the time at which the traffic smoother device should transmit the packet as the transmission time.

As one embodiment, the control unit acquires time information indicating a time from an external server device that manages the time, and the time is indicated by the updated time stamp with the time indicated by the time information as a reference. The packet including the updated time stamp is output at the delay time.

The distribution system as one aspect of the present disclosure is a distribution system including the plurality of traffic smoother devices, and is a first time stamp indicating a transmission time that is a reference of a time when a packet should be transmitted from the other device. A second time, which is the same packet as the first packet by the second communication line from the first receiver that receives the first packet including the above by the first communication line and the other device. The updated first time stamp of the second receiver receiving the second packet including the stamp and the first time stamp of the first packet received by the first receiver are updated. The first traffic smoother device that outputs the first packet including the updated first time stamp at the delay time indicated by the time stamp of the above, and the second receiver received by the second receiver. The second time stamp of the second packet is updated to indicate the same delay time as the delay time indicated by the first time stamp, and at the delay time, the updated second time stamp is used. A second traffic smoother device that outputs the second packet including a time stamp, a first output signal output by the first traffic smoother device, and a second output signal output by the second traffic smoother device. A redundant device for inputting an output signal and outputting the first output signal or the second output signal is provided, and the redundant device has a failure in the first communication line. Accordingly, the output signal is switched from the first output signal to the second output signal.

The program as one aspect of the present disclosure causes the computer to function as the traffic smoother device.

According to one embodiment of the present disclosure, a traffic smoother device, a distribution system, and a program capable of outputting packets at regular intervals even if packets are transmitted via a communication path in which jitter occurs can be programmed. ..

It is a figure which shows the configuration example of the distribution system which includes the IP traffic smoother which concerns on one Embodiment of this disclosure. It is a figure which shows the configuration example of the remultiplexing apparatus shown in FIG. It is a figure which shows the configuration example of a TLV packet. It is a figure which shows the structural example of the FEC block. It is a figure which shows the configuration example of the frame by hierarchy. It is a figure which shows the example of the division of the frame by layer by the XMI packetizing part shown in FIG. It is a figure which shows the configuration example of the XMI packet. It is a figure which shows the configuration example of the MMTP packet. It is a figure which shows the structural example of the XMI header. It is a figure which shows the structural example of the synchronization control information included in the MMTP payload. It is a figure which shows the structural example of the XMI packet which constitutes 1 OFDM frame. It is a figure which shows the configuration example of the IP traffic smoother shown in FIG. It is a figure which shows the time stamp correction processing by the IP traffic smoother shown in FIG. It is a figure which shows the configuration example of the distribution system which includes the IP traffic smoother which concerns on one Embodiment of this disclosure.

Hereinafter, one embodiment of the present disclosure will be described with reference to the drawings. In each drawing, the same or corresponding parts are designated by the same reference numerals. In the description of the present embodiment, the description will be omitted or simplified as appropriate for the same or corresponding parts.

(Distribution system)
FIG. 1 is a diagram showing a configuration example of a distribution system 1 including an IP traffic smoother 23 as a traffic smoother device according to an embodiment of the present disclosure. The distribution system 1 shown in FIG. 1 includes a performance station 10 and a broadcasting station 20. The playing room 10 includes a remultiplexing device 11 and an STL transmitter 12. The broadcasting station 20 includes an STL receiver 21, an XMI monitoring device 22, an IP traffic smoother (traffic smoother device) 23, a modulation device 24, and a transmitter 25. "STL" is an abbreviation for Studio to Transmitter Link. The performance station 10 and the broadcasting station 20 are connected to each other via a content transmission line 30 as a network. In the present embodiment, contents such as video and audio are distributed in the distribution system 1. The performance hall 10 does not necessarily have to be equipped with the XMI monitoring device 22. Further, in the present embodiment, the "content" includes not only video / audio signals, subtitle signals, and data (data transmitted by data broadcasting, etc.) but also control for controlling the operation of the modulation device 24 of the broadcasting station 20. Information (delay time, modulation parameters, etc.) is also included.

In the distribution system 1 according to the present embodiment, the XMI packet generated by the remultiplexing device 11 of the playing station 10 is transmitted by the STL transmitter 12 and distributed to the broadcasting station 20 via the content transmission line 30. .. The broadcasting station 20 receives the delivered XMI packet at the STL receiver 21, and monitors the time stamp and the like of the XMI packet at the XMI monitoring device 22. This time stamp functions as a time stamp indicating a transmission time that is a reference for the time when the IP traffic smoother 23 should transmit the XMI packet. The IP traffic smoother 23 corrects the time stamp of the XMI packet by using the time information acquired from an external GPS server, PTP server, NTP server, or the like. The IP traffic smoother 23 outputs the time-stamped XMI packet to the modulation device 24 at the transmission time indicated by the corrected time stamp. The modulation device 24 modulates the time stamped XMI packet. The transmitter 25 transmits a broadcast wave corresponding to the modulated XMI packet. "GPS" is an abbreviation for Global Positioning System. "PTP" is an abbreviation for Precision Time Protocol. "NTP" is an abbreviation for Network Time Protocol.

The XMI packets delivered from the playing station 10 are output at regular intervals, but fluctuations in the packet arrival intervals called jitter occur before reaching the broadcasting station 20 via the content transmission line 30. The IP traffic smoother 23 rewrites and corrects the transmission time stamp and the delivery time stamp of the XMI packet including the jitter that has reached the broadcasting station 20 with a value obtained by adding the fixed delay Δt. Then, the IP traffic smoother 23 outputs the XMI packet to the modulation device 24 at the transmission time indicated by the corrected time stamp. This makes it possible to input XMI packets to the modulation device 24 at the same intervals as the XMI packets output at the playing room 10.

(Remultiplexing device)
The re-multiplexing device 11 is a multiplexing device (not shown) provided for each layer of layered transmission, in which video / audio signals, subtitle signals, and data of each layer are multiplexed and packetized in a predetermined format. The packet (for example, MMTP (MPEG Media Transport Protocol) packet) is input. Further, the remultiplexing device 11 is a video / audio signal transmitted by Lch from a multiplexing device provided corresponding to a channel (Lch: Low latency channel) to be transmitted with a lower delay than the data of each layer. And the caption signal are multiplexed, and a packet (MMTP packet) packetized in a predetermined format is input. The transmission line between the multiplexing device and the remultiplexing device 11 is an IP line, and the IP packet (MMTP / IP packet) containing the MMTP packet is output from the multiplexing device to the remultiplexing device 11. To.

The remultiplexing device 11 remultiplexes the MMTP / IP packets output from each multiplexing device into one system. Specifically, the remultiplexing device 11 generates an XMI packet from the MMTP / IP packet output from each multiplexing device, multiplexes the XMI packet into one system, and transmits the XMI packet to the broadcasting station 20 via the content transmission line 30. do. Although only one broadcasting station 20 is shown in FIG. 1, in reality, the remultiplexing device 11 transmits XMI packets to a plurality of broadcasting stations 20. In order to realize SFN (Single Frequency Network), each of the plurality of broadcasting stations 20 transmits broadcast waves with a delay time and modulation parameters according to the output from the remultiplexing device 11. By transmitting the control information such as the delay time and the modulation parameter, it is possible to stably receive the broadcast wave from the plurality of broadcasting stations 20 even in the overlapping region.

FIG. 2 is a diagram showing a configuration example of the remultiplexing device 11. In the following, there are cases where three layers of A layer, B layer, and C layer are transmitted, and Lch data is transmitted on the same channel as the data of A layer, B layer, and C layer. Be explained.

The remultiplexing device 11 shown in FIG. 2 includes packet filters 301a, 301b, 301c, 301d, IP header compression units 302a, 302b, 302c, 302d, 302e, and TLV (Type Length Value) packetization units 303a, 303b, 303c, 303d, 303e, FIFA (First in, First Out) buffers 304a, 304b, 304c, 304d, 304e, FEC (Forward Error Correction) block configuration units 305a, 305b, 305c, and hierarchical frame configuration units 306a, 306b, 306c, XMI packetization units 307a, 307b, 307c, L0 symbol configuration unit 308, L1 symbol configuration unit 309, synchronization control XMI packet configuration unit 310, staff XMI packet configuration unit 311, and XMI packet transmission. It is provided with a scheduler unit 312.

The packet filter 301a, the IP header compression unit 302a, the TLV packetization unit 303a, the FIFO buffer 304a, the FEC block configuration unit 305a, the layer-specific frame configuration unit 306a, and the XMI packetization unit 307a are provided corresponding to the A layer. ..

In the packet filter 301a, the MMTP packet (MMTP / IP packet) of the A layer is input from the multiplexing device provided corresponding to the A layer. The packet filter 301a transmits based on the source IP address, destination IP address, protocol type, source port number of UDP (User Datagram Protocol) header, destination port number, etc. of the IP header of the input MMTP / IP packet. Packets are selected (packet filtering), and the selected MMTP packet is output to the IP header compression unit 302a.

The IP header compression unit 302a compresses the IP header of the MMTP / IP packet output from the packet filter 301a, if necessary, and outputs the IP header to the TLV packetization unit 303a.

The TLV packetization unit 303a encapsulates the MMTP / IP packet output from the IP header compression unit 302a into a TLV packet to generate a TLV packet.

FIG. 3 is a diagram showing a configuration example of a TLV packet. In the following, the numbers attached to each field indicate an example of the number of bits in each field.

As shown in FIG. 3, the TLV packet includes a reserved area, a packet type, a data length, and a data area. The packet type indicates the type of TLV packet. The data length indicates the size of the data stored in the data area. The TLV packetization unit 303a stores the IP packet output from the IP header compression unit 302a in the data area. For the reserved area, all bits are set to "1".

Referring to FIG. 2 again, the TLV packetization unit 303a outputs the generated TLV packet to the FIFO buffer 304a.

The FIFO buffer 304a stores the TLV packet output from the TLV packetization unit 303a, and outputs the stored TLV packet to the FEC block configuration unit 305a in the order of storage.

The FEC block component unit 305a constitutes an FEC block at a fixed cycle from the TLV packet output from the FIFO buffer 304a.

FIG. 4 is a diagram showing an example of the configuration of the FEC block.

As shown in FIG. 4, the FEC block includes an FEC block header, a main signal area, a BCH parity area, and an LDPC parity area. In FIG. 4, the main signal area and the BCH parity area are shown one by one, but each may be divided into a plurality of areas.

The TLV packet output from the FIFO buffer 304a is stored in the main signal area. The FEC block header is the position of the beginning of the first TLV packet stored in the main signal area of the FEC block, specifically, the position of the first byte of the first TLV packet stored in the FEC block, and the FEC block header. This is information indicated by the number of bytes from the beginning of the excluded FEC block. Bit "1" is stored in the BCH parity area and the LDPC parity area.

Three types of sizes of the FEC block are set according to the code length (Short, Middle, Long) of LDPC (Low Density Parity Check) coding performed by the transmitter 25. Further, the sizes of the main signal area and the LDPC parity area are determined according to the coding rate.

The FEC block component 305a concatenates the TLV packets output from the FIFO buffer 304a in the order of output and stores them in the main signal area, and sets the value of the FEC block header for each FEC block. If the TLV packet to be stored in the main signal area does not exist in the FIFO buffer 304a, the FEC block configuration unit 305a stores the null type TLV packet in the main signal area.

Referring to FIG. 2 again, the FEC block component unit 305a outputs the configured FEC block to the layer-based frame component unit 306a.

The layer-based frame component unit 306a constitutes a layer-specific frame from the FEC blocks output from the FEC block component unit 305a. FIG. 5 is a diagram showing a configuration example of a frame for each layer.

As shown in FIG. 5, the hierarchical frame is composed of an FEC block area. In the FEC block area, a concatenation of FEC blocks output from the FEC block component unit 305a and a fragment of the FEC block are stored.

Referring to FIG. 2 again, the layer-based frame configuration unit 306a outputs the configured layer-specific frame to the XMI packetization unit 307a.

The XMI packetization unit 307a constitutes an XMI packet from the layer-specific frames output from the layer-specific frame configuration unit 306a. Specifically, as shown in FIG. 6, the XMI packetization unit 307a divides the hierarchical frames into predetermined sizes (10448 bits in FIG. 6) to form a data unit. Although details will be described later, the XMI packet includes a header and a data unit area. The XMI packetization unit 307a stores the data unit in the data unit area. As shown in FIG. 6, the last data unit may be smaller than a predetermined size (less than 10448 bits in FIG. 6). In this case, the XMI packetization unit 307a adds a predetermined bit (stuff bit) to a data unit smaller than the predetermined size to make the data unit a predetermined size, and stores the data unit in the data unit area.

Referring to FIG. 2 again, the XMI packetization unit 307a outputs the generated XMI packet (A layer XMI packet) to the XMI packet transmission scheduler unit 312. The details of the configuration of the XMI packet will be described later.

The packet filter 301b, the IP header compression unit 302b, the TLV packetization unit 303b, the FIFO buffer 304b, the FEC block configuration unit 305b, the layer-specific frame configuration unit 306b, and the XMI packetization unit 307b are provided corresponding to the B layer. .. The packet filter 301c, the IP header compression unit 302c, the TLV packetization unit 303c, the FIFO buffer 304c, the FEC block configuration unit 305c, the layer-specific frame configuration unit 306c, and the XMI packetization unit 307c are provided corresponding to the C layer. .. Since the configuration corresponding to the A layer and the configuration corresponding to the B and C layers are the same, the description of the configuration corresponding to the B and C layers will be omitted.

The packet filter 301d, the IP header compression unit 302d, 302e, the TLV packetization unit 303d, 303e, the FIFO buffer 304d, 304e, the L0 symbol configuration unit 308, and the L1 symbol configuration unit 309 are provided corresponding to Lch.

The packet filter 301d receives Lch MMTP / IP packets from a multiplexing device provided corresponding to Lch. The packet filter 301d selects a packet to be transmitted based on the source IP address, destination IP address, protocol type, source port number of the UDP header, destination port number, etc. of the IP header of the input IP packet (packet filtering). Then, the selected MMTP / IP packet is output to the IP header compression unit 302d or the IP header compression unit 302e.

The IP header compression unit 302d compresses the IP header of the MMTP / IP packet output from the packet filter 301d as necessary, and outputs the IP header to the TLV packetization unit 303d. The IP header compression unit 302e compresses the IP header of the MMTP / IP packet output from the packet filter 301d as necessary, and outputs the IP header to the TLV packetization unit 303e.

The TLV packetization unit 303d encapsulates the MMTP / IP packet output from the IP header compression unit 302d into a TLV packet, generates a TLV packet, and outputs the TLV packet to the FIFO buffer 304d. The TLV packetization unit 303e encapsulates the MMTP / IP packet output from the IP header compression unit 302e into a TLV packet, generates a TLV packet, and outputs the TLV packet to the FIFO buffer 304e.

The FIFO buffer 304d stores the TLV packet output from the TLV packetization unit 303d, and outputs the stored TLV packet to the L0 symbol configuration unit 308 in the storage order. The FIFO buffer 304e stores the TLV packet output from the TLV packetization unit 303e, and outputs the stored TLV packet to the L1 symbol configuration unit 309 in the order of storage.

The L0 symbol configuration unit 308 configures a symbol (L0 symbol) from the TLV packet output from the FIFO buffer 304d, and outputs the symbol (L0 symbol) to the XMI packet transmission scheduler unit 312. The L1 symbol configuration unit 309 constructs a symbol (L1 symbol) from the TLV packet output from the FIFO buffer 304e, and outputs the symbol (L1 symbol) to the XMI packet transmission scheduler unit 312.

In the current ISDB-T system, the signal bandwidth is divided into 13 segments. On the other hand, in the next generation of terrestrial digital broadcasting, it is considered to divide the signal bandwidth into 33 or 35 segments. By increasing the number of segments, the bit rate of each layer can be finely adjusted, and flexibility can be improved. The L0 symbol is transmitted, for example, in 9 segments for partial reception, and the L1 symbol is transmitted in 24 or 26 segments for other non-partial reception. Therefore, packet filtering by the packet filter 301d is also performed according to such allocation.

Synchronous control The XMI packet configuration unit 310 data on synchronous control information indicating information related to transmission control such as transmission parameters for the transmitter 25 to configure an OFDM frame, timing of transmitting an OFDM frame, and TMCC (Transmission Multiplexing Configuration Control) information. An XMI packet (synchronous control XMI packet) stored in the unit area is configured and output to the XMI packet transmission scheduler unit 312. When the synchronization control information does not meet the predetermined size for dividing the frame for each layer, the synchronization control XMI packet configuration unit 310 adds a staff bit to the synchronization control information to make it a predetermined size and puts it in the data unit area. Store.

The stuff XMI packet configuration unit 311 configures an XMI packet (staff XMI packet) in which only stuff bits having the same size as the data unit are stored in the data unit area, and outputs the XMI packet to the XMI packet transmission scheduler unit 312. The stuff XMI packet is used to keep the number of XMI packets output by the remultiplexing device 11 per second constant even when the modulation method or the coding rate is different.

The XMI packet transmission scheduler unit 312 includes an A-layer XMI packet output from the XMI packetization unit 307a, a B-layer XMI packet output from the XMI packetization unit 307b, and a C-layer XMI packet output from the XMI packetization unit 307c. The L0 symbol output from the L0 symbol configuration unit 308, the L1 symbol output from the L1 symbol configuration unit 309, the synchronization control XMI packet output from the synchronization control XMI packet configuration unit 310, and the staff XMI packet configuration unit 311 output. The stuff XMI packet is transmitted to the transmitter 25 via the content transmission line 30.

The XMI packet transmission scheduler unit 312 outputs one synchronization control XMI packet at the beginning of the OFDM frame. Subsequently, the XMI packet transmission scheduler unit 312 outputs XMI packets of each layer (A layer XMI packet, B layer XMI packet, and C layer XMI packet). When all the XMI packets of each layer are output, the XMI packet transmission scheduler unit 312 may output the staff XMI packet so that the number of XMI packets constituting the OFDM frame becomes a fixed number. The XMI packet transmission scheduler unit 312 may output, for example, at least one stuff XMI packet in order to indicate the end of the output of the XMI packet in the OFDM frame.

Here, in the data unit area of the A-layer XMI packet, the B-layer XMI packet, and the C-layer XMI packet (XMI packet for transmitting the data unit), a predetermined number of bytes (for example, for example) for storing the L0 symbol and the L1 symbol. A channel information area (L0 symbol storage area and L1 symbol storage area) of 4 bytes) is provided. When the L0 symbol is output from the L0 symbol configuration unit 308, the XMI packet transmission scheduler unit 312 promptly (with low delay) the input L0 symbol in the L0 symbol storage area of the XMI packet that transmits the data unit. Allocate and output to transmitter 25. Further, when the L1 symbol is output from the L1 symbol configuration unit 309, the XMI packet transmission scheduler unit 312 promptly (low delay) the input L1 symbol in the L1 symbol storage area of the XMI packet that transmits the data unit. ) Assign and output to the transmitter 25. By doing so, the Lch data can be output to the transmitter 25 with low delay. When there is no Lch TLV packet, the XMI packet transmission scheduler unit 312 stores the null TLV packet for Lch data in the channel information area.

(Composition of XMI packet)
Next, the configuration of the XMI packet generated by the remultiplexing device 11 will be described with reference to FIG. 7. FIG. 7 is a diagram showing an example of the configuration of the XMI packet.

As shown in FIG. 7, an exemplary configuration of an XMI packet includes an IPv4 header, a UDP header, an MMTP header, and an MMTP payload. The MMTP payload includes an XMI header and a data unit area. In the data unit area, synchronization control information (with stuff bits added), a data unit with a predetermined number of bits, a data unit with stuff bits added to a predetermined number of bits, or a staff with a predetermined number of bits. Bits are stored. As described above, for the XMI packet in which information other than the synchronization control information (with the stuff bit added) is stored in the data unit area, the channel information area for storing the L0 symbol and the L1 symbol is stored in the data unit area. Although it is provided, the description is omitted in FIG.

The IPv4 header has the same configuration as the IPv4 header part defined in the third part of ARIB STD-B32. The UDP header has the same configuration as the UDP header portion defined in the third part of ARIB STD-B32. The MMTP packet has the same configuration as the MMTP packet defined in ARIB STD-B60, except that the XMI packet is stored in the payload. That is, the XMI header and below are stored in the payload of the MMTP packet (MMTP payload).

FIG. 8 is a diagram showing an example of the configuration of the MMTP packet included in the XMI packet.

As shown in FIG. 8, exemplary configurations of MMTP packets include version, packet counter flag, FEC flag, reserve area, extended header flag, RAP flag, payload type, packet identifier, and delivery. It includes a time stamp, a packet sequence number, a packet counter, an extended area, and a data subregion.

The version indicates the version of the MMT protocol. The packet counter flag indicates whether or not a packet counter exists. The FEC flag indicates information regarding AL-FEC (Application Layer-Forward Error Correction) of the MMTP packet. AL-FEC is a method in which a repair packet is generated on the transmitting side using an error correction code based on a packet (source packet) containing data such as video or audio, and the generated repair packet is transmitted together with the source packet. Even if some packets are lost during transmission, the receiving side can generate the lost packets based on the received source packets and repair packets. The FEC flag indicates whether the MMTP packet is a packet not protected by AL-FEC, a source packet among packets protected by AL-FEC, or a repair packet among packets protected by AL-FEC. And so on.

The extended header flag indicates whether or not to extend the header of the packet. The RAP flag indicates whether or not the payload of the MMTP packet (MMTP payload) includes the beginning of a random access point. The RAP flag may be set to 1 when storing synchronization control information, and 0 in other cases. The payload type indicates the type of MMTP payload. When the MMTP packet is an XMI packet, the payload type may be set to 0x20 indicating the XMI packet. When synchronization control information (with stuff bits added) is stored in the data unit area of the MMTP payload, the payload type is data_unit_type = 0. When a data unit having a predetermined number of bits or a data unit having a predetermined number of bits added with stuff bits is stored in the data unit area of the MMTP payload, the payload type is data_unit_type = 1 to 3. data_unit_type = 1 indicates the A layer, data_unit_type = 2 indicates the B layer, and data_unit_type = 3 indicates the C layer. When a predetermined number of stuff bits are stored in the data unit area of the MMTP payload, data_unit_type = 15. The packet identifier indicates the type of data in the payload. For the XMI packet, the packet identifier may be set to 0x9801 indicating that it is XMI data. The delivery time stamp indicates the time when the first byte of the MMTP packet is output from the transmitting entity (remultiplexing device 11). That is, the delivery time stamp indicates the time when the XMI packet is transmitted by the other device (remultiplexing device 11) as the transmission time. The packet sequence number indicates the order of MMTP packets having the same packet identifier. The packet counter indicates the order of MMTP packets in the same IP data flow regardless of the value of the packet identifier. If the packet counter flag indicates that the packet counter does not exist, then the packet counter is not included in the MMTP packet.

The data subregion corresponds to the MMTP payload shown in FIG. When the XMI packet is a synchronous control XMI packet, the MMTP payload of the MMTP packet included in the XMI packet includes synchronization control information as shown in FIG. 7. The synchronization control information includes the next frame synchronization control information which is the synchronization control information of the next OFDM frame.

FIG. 9 is a diagram showing a configuration example of an 88-bit XMI header included in the MMTP payload. As shown in FIG. 9, an exemplary configuration of the XMI header includes an L0 head symbol flag, an L0 symbol start flag, an L1 head symbol flag, an L1 symbol start flag, a reservation, a frame number, and a data unit type. , Sequence number, CRC32, and data unit length. The L0 first symbol flag indicates that it is the beginning of the L0 symbol. The L0 symbol start flag indicates that the L0 symbol starts. The L1 first symbol flag indicates that it is the beginning of the L1 symbol. The L1 symbol start flag indicates that the L1 symbol starts. The reservation is a bit prepared for future expansion, and all bits may be set to 0. The frame number indicates a number that identifies the OFDM frame. The data unit type indicates the type of the data unit. The sequence number is a serial number of the packet. The CRC 32 is a Cyclic Redundancy Check (CRC) code having a bit length of 32 bits. The data unit length indicates the length of the data in the data unit.

FIG. 10 is a diagram showing an example of the configuration of synchronization control information included in the MMTP payload. As shown in FIG. 10, the synchronization control information includes a transmission time stamp, a leap second indicator, a reservation, the number of L0 information field bytes, the number of L1 information field bytes, the next frame synchronization control information, and stuffing. include. The transmission time stamp indicates the time when the broadcasting station 20 should transmit the packet. The leap second indicator indicates when the transmission time stamp is set based on the system clock when the leap second adjustment is performed on the system clock of the remultiplexing device 11. For example, if the transmission time stamp is set based on the system clock in Japan time from 9:00 am on the day before the leap second insertion date to 8:59:59 am on the leap second insertion date, the leap second is set. The second specifier may be set to 1. If the transmission time stamp is set based on the system clock from 9:00 am on the day before the leap second deletion date to 8:59:58 am on the leap second deletion date, the leap second specifier is 2 May be set. In other cases, the leap second specifier may be set to 0. The reservation is a bit prepared for future expansion, and for example, all bits may be set to 0. The number of bytes in the L0 information field indicates the data length of the L0 information field in bytes. The number of bytes in the L1 information field indicates the data length of the L1 information field in bytes. The next frame synchronization control information indicates the synchronization control information of the next OFDM frame of this synchronization frame. Stuffing is a bit that does not have the information inserted to adjust the bit length.

The next frame synchronization control information includes switching timing index, transmission mode, guard interval (GI) ratio, TMCC information (non-partial reception band), TMCC information (partial reception band), and network synchronization information. Includes 4 reservations. The switching timing index is an index indicating the timing at which the parameters of the transmission mode and the GI ratio are switched. Normally, 0x15 is set as the switching timing index, but the value is decremented one by one each time one OFDM frame is transmitted from 15 frames before the switching timing. In this way, the switching timing index counts down the switching of the parameters of the transmission mode and the GI ratio in units of OFDM frames from 15 frames before the switching. The first timing at which the switching timing index returns from 0 to 15 corresponds to the start timing of the OFDM frame. The transmission mode is 2-bit information indicating the coding size. The transmission mode "00" indicates mode 3 (FFT size is 8192). The transmission mode "01" indicates mode 4 (FFT size is 16384). The transmission mode "10" indicates mode 5 (FFT size is 32768). The transmission mode "11" indicates a reserve. The guard interval (GI) ratio is a section provided so as not to interfere with the data of the time before and after. The GI ratio is represented by 3 bits. The GI ratio of "000" is 1/4, "001" is 1/8, "010" is 800/8192, "011" is 1/16, "100" is 800/16384, and "101". "" Indicates 1/32, "110" indicates 800/32768, and "111" indicates 1/256. The TMCC information (non-partial reception band) is TMCC information for a terminal that receives all segments such as a general TV (television) receiver. The TMCC information (partial reception band) is TMCC information for terminals that receive only a narrow band receiver (central 9 segments). The network synchronization information is synchronization control information including control of the delay time for constructing the SFN. All four reservations are bits prepared for future expansion, and all bits may be set to 0.

The XMI packet (with data_unit_type = 0 in the XMI header) containing the synchronization control information has a 64-bit transmission timestamp field in addition to the 32-bit delivery timestamp field. As described above, the delivery time stamp field exists in the MMTP header (FIG. 8) and indicates the transmission time when the XMI packet is output from the remultiplexing device 11. On the other hand, the transmission time stamp field exists in the MMTP payload of the XMI packet (data_unit_type = 0) containing the synchronization control information (FIG. 9), and indicates the time when the XMI packet should be transmitted from the transmitter 25 of the broadcasting station 20. show. That is, the transmission time stamp indicates the time set by the other device (remultiplexing device 11) as the time at which the IP traffic smoother 23 should transmit the XMI packet as the transmission time. In the present embodiment, the delivery time stamp and the transmission time stamp function as a time stamp indicating a transmission time that is a reference of the time when the packet should be transmitted.

The XMI packet has a constant rate, and the time interval between the XMI packets is constant. Therefore, the remultiplexing device 11 stamps the transmission time in the transmission time stamp field and the delivery time stamp field of the XMI packet at regular intervals, and transmits the XMI packet. By stamping the transmission time stamp and the distribution time stamp which are the output times of the performance station, the broadcasting station 20 can use the transmission time stamp and the distribution time stamp to measure the transmission delay time and the jitter of the arrived packet. Is. The transmission time stamp is used only in the synchronization control XMI packet, whereas the delivery time stamp is described in all XMI packets. Therefore, only the delivery time stamp may be used for measuring the jitter (fluctuation of the packet arrival interval for each packet). Hereinafter, a method of outputting an XMI packet received at the broadcasting station 20 to each device of the broadcasting station 20 at a fixed time interval based on the time indicated by the transmission time stamp and the distribution time stamp stamped at the performance station 10. Is explained.

FIG. 11 is a diagram showing an example of the configuration of XMI packets constituting 1 OFDM frame. As described above, the XMI packet includes a synchronization control XMI packet with data_unit_type = 0, a data XMI packet with data_unit_type = 1 to 3, and a staff XMI packet with data_unit_type = 15. As shown in FIG. 11, the XMI packets constituting the 1 OFDM frame are first transmitted in the order of the synchronization control XMI packet, then the data XMI packet, and finally the stuff XMI packet.

(IP traffic smoother)
Synchronous control XMI packets need to be accurately input to the modulation device 24 at intervals at which the modulation device 24 forms one OFDM frame. However, as described above, due to the jitter in the content transmission line 30, the arrival interval of the XMI packet in the broadcasting station 20 fluctuates, which may cause a deviation in the time constituting the 1 OFDM frame in the modulation device 24. Therefore, the IP traffic smoother 23 according to the present embodiment rewrites the transmission time stamp and the delivery time stamp of the XMI packet including the jitter that has reached the broadcasting station 20 with a value obtained by adding only the fixed delay Δt. Then, the IP traffic smoother 23 outputs each XMI packet to the modulation device 24 at the time indicated by the rewritten transmission time stamp or distribution time stamp. This makes it possible to input XMI packets to the modulation device 24 at the same intervals as the XMI packets output from the playing room 10.

As a premise of such processing, the IP traffic smoother 23 needs to synchronize the system clock of the device or the dedicated hardware or software having the function thereof with UTC (Coordinated Universal Time). However, if the system clock of the IP traffic smoother 23 is constructed by dedicated hardware or software independent of the outside, a time error may occur between the system clock of the IP traffic smoother 23 and UTC. Therefore, in the present embodiment, the IP traffic smoother 23 receives time information from the GPS server, PTP server, or NTP server, and synchronizes the system clock based on the received time information.

FIG. 12 is a diagram showing a configuration example of the IP traffic smoother 23. The IP traffic smoother 23 includes components such as a control unit 31, a storage unit 32, a communication unit 33, an input unit 34, and an output unit 35.

The control unit 31 is one or more processors. The processor is a general-purpose processor such as a CPU, or a dedicated processor specialized for a specific process. "CPU" is an abbreviation for Central Processing Unit. The control unit 31 may include one or more dedicated circuits, or the control unit 31 may replace one or more processors with one or more dedicated circuits. The dedicated circuit is, for example, FPGA or ASIC. "FPGA" is an abbreviation for Field-Programmable Gate Array. "ASIC" is an abbreviation for Application Specific Integrated Circuit. The control unit 31 executes information processing related to the operation of the IP traffic smoother 23 while controlling each unit of the IP traffic smoother 23.

The storage unit 32 is one or more semiconductor memories, one or more magnetic memories, one or more optical memories, or a combination of at least two of them. The semiconductor memory is, for example, RAM or ROM. "RAM" is an abbreviation for Random Access Memory (writable memory). "ROM" is an abbreviation for Read Only Memory. The RAM is, for example, an SRAM or a DRAM. "SRAM" is an abbreviation for Static Random Access Memory. "DRAM" is an abbreviation for Dynamic Random Access Memory. The ROM is, for example, EEPROM. "EEPROM" is an abbreviation for Electrically Erasable Programmable Read Only Memory. The storage unit 32 functions as, for example, a main storage device, an auxiliary storage device, or a cache memory. The storage unit 32 stores information used for the operation of the IP traffic smoother 23 and information obtained by the operation of the IP traffic smoother 23.

The communication unit 33 is one or more communication interfaces. The communication unit 33 is used when transmitting / receiving XMI packets between the XMI monitoring device 22 and the modulation device 24. The communication unit 33 is a wired LAN interface, a wireless LAN interface, or an interface for transmitting and receiving other information. "LAN" is an abbreviation for Local Area Network.

The input unit 34 is one or more input interfaces. The input interface is, for example, a USB interface or an HDMI® interface. "HDMI®" is an abbreviation for High-Definition Multimedia Interface. "LAN" is an abbreviation for Local Area Network. The input unit 34 is used as an interface when the user inputs information used for the operation of the IP traffic smoother 23. For example, a keyboard and a pointing device are connected to the input unit 34. If the user is not expected to input information, the input unit 34 may not be provided.

The output unit 35 is one or more output interfaces. The output interface is, for example, a USB interface or an HDMI® interface. The output unit 35 outputs the information obtained by the operation of the IP traffic smoother 23. In the present embodiment, a display as a display unit is connected to the HDMI (registered trademark) interface included in the output unit 35. If information output to the user is not expected, the output unit 35 may not be provided.

The function of the IP traffic smoother 23 is realized by executing the program according to the present embodiment on the processor included in the control unit 31. That is, the function of the IP traffic smoother 23 can be realized by software. The program is a program for causing a computer to execute a process of a step included in the operation of the IP traffic smoother 23, and to realize a function corresponding to the process of the step on the computer. That is, the program is a program for making the computer function as an IP traffic smoother 23.

The program can be recorded on a computer-readable recording medium. A computer-readable recording medium is, for example, a magnetic recording device, an optical disk, a photomagnetic recording medium, or a semiconductor memory. The distribution of the program is carried out, for example, by selling, transferring, or renting a portable recording medium such as a DVD or a CD-ROM in which the program is recorded. "DVD" is an abbreviation for Digital Versatile Disc. "CD-ROM" is an abbreviation for Compact Disc Read Only Memory. The program may be distributed by storing the program in the storage of the server and transferring the program from the server to another computer via the network. The program may be provided as a program product.

For example, the computer temporarily stores the program recorded on the portable recording medium or the program transferred from the server in the main storage device. Then, the computer reads the program stored in the main storage device by the processor, and executes the processing according to the read program by the processor. The computer may read the program directly from the portable recording medium and perform processing according to the program. The computer may sequentially execute processing according to the received program each time the program is transferred from the server to the computer. The program includes information used for processing by a computer and equivalent to the program. For example, data that is not a direct command to the computer but has the property of defining the processing of the computer corresponds to "a program-like data".

Some or all of the functions of the IP traffic smoother 23 may be realized by a dedicated circuit included in the control unit 31. That is, some or all of the functions of the IP traffic smoother 23 may be realized by hardware. Further, the IP traffic smoother 23 may be realized by a single information processing device or may be realized by the cooperation of a plurality of information processing devices.

FIG. 13 is a diagram showing a time stamp correction process by the IP traffic smoother 23. Each process of steps S1 to S3 in FIG. 13 is executed based on the control of the control unit 31 of the IP traffic smoother 23.

In step S0, the remultiplexing device 11 of the playing room 10 stamps the output time on the transmission time stamp in the synchronous control XMI packet 41 and the delivery time stamp in the MMTP of all the XMI packets when the XMI packet is output. .. All XMI packets include a synchronization control XMI packet 41 (data_unit_type = 0), a data XMI packet 42 (data_unit_type = 1-3), and a staff XMI packet 43 (data_unit_type = 15). When the remultiplexing device 11 outputs the XMI packet, that is, when the XMI packet is transmitted from the playing room 10, the time interval 44 of the XMI packet is constant. Therefore, the time interval between the transmission time stamp and the delivery time stamp between the XMI packets is also constant.

The XMI packet transmitted from the playing station 10 reaches the broadcasting station 20 via the content transmission line 30. In step S1, the XMI packet that has reached the broadcasting station 20 is received by the STL receiver 21, passes through the XMI monitoring device 22, and is input to the IP traffic smoother 23. The XMI packet input to the IP traffic smoother 23 is delayed by the transmission delay time 45 from the transmission time of the performance center 10 due to the transmission delay. As described above, since the transmission delay time 45 differs for each XMI packet due to packet fluctuation due to jitter, the time interval 46 of each XMI packet is undefined.

Therefore, in step S2, the IP traffic smoother 23 rewrites the time (transmission time) indicated by the time stamp of the XMI packet with the time (delay time) obtained by adding the fixed delay Δt, and corrects (updates) the time stamp again. Perform transmission correction processing. That is, the IP traffic smoother 23 updates the transmission time stamp by adding the fixed delay Δt expressed in 64 bits to the transmission time indicated by the transmission time stamp of the received synchronization control XMI packet 41. Further, the IP traffic smoother 23 updates the delivery time stamp by adding the fixed delay Δt expressed in 32 bits to the transmission time indicated by the delivery time stamps of all the XMI packets 41, 42, 43. The IP traffic smoother 23 may not use the transmission time stamp as the time stamp used for absorbing the jitter, but may use only the update of the delivery time stamp. In that case, it is not always necessary to update the transmission time stamp.

Next, in step S3, the IP traffic smoother 23 compares the signal received from the GPS, PTP, or NTP server with the transmission time stamp and the delivery time stamp of the XMI packet. The IP traffic smoother 23 outputs a synchronization control XMI packet at the time of the transmission time stamp or the time of the delivery time stamp as the delay time to which the fixed delay Δt is added. Although the transmission time stamp and the delivery time stamp have different numbers of bits, usually the same value is described in these time stamps, so that the IP traffic smoother 23 refers to one of the time stamps and synchronize control XMI. Determines the packet output timing. The IP traffic smoother 23 outputs a data XMI packet and a staff XMI packet at the timing of the delivery time stamp to which a fixed delay is added. That is, the IP traffic smoother 23 acquires time information indicating the time from an external server device that manages the time. Then, the IP traffic smoother 23 outputs a packet including the updated time stamp at the delay time indicated by the updated time stamp based on the time indicated by the time information.

As described above, since the time intervals of the transmission time stamps and the delivery time stamps between the XMI packets at the time of transmission of the performance center 10 are constant, the time intervals of these time stamps are constant even after the fixed delay Δt is added. be. Therefore, the IP traffic smoother 23 of the present embodiment absorbs jitter with a fixed delay Δt, outputs synchronous control XMI packets at regular intervals without using PCR, and causes the modulation device 24 to generate OFDM frames. It is possible. In particular, in the synchronous control XMI packet at the beginning of the OFDM frame, it is possible to output the XMI packet at a more accurate time by using a 64-bit transmission time stamp.

The value of the fixed delay Δt is set automatically or manually. When setting automatically, a value obtained by adding a margin as a processing delay to the maximum value (t_max) of the transmission delay time may be set. For example, if the margin is 1 ms, Δt = t_max + 1 ms. When configuring a network similar to the current terrestrial digital broadcasting, the fixed delay time can be set to 60 ms. As described above, the fixed delay Δt can be set to a value exceeding the maximum value of the transmission delay time 45, for example. That is, the IP traffic smoother 23 updates the time stamp with the delay time, which is the time obtained by adding a time larger than the transmission delay time in the network as a predetermined delay to the transmission time indicated by the time stamp. ..

As a result, the IP traffic smoother 23 can absorb the jitter of all XMI packets with a fixed delay Δt. That is, the IP traffic smoother 23 can set the transmission time to the modulation device 24 to a predetermined timing regardless of the magnitude of the transmission delay time of the content transmission line 30. Therefore, since the XMI packet always arrives at the time when each XMI packet should be transmitted from the broadcasting station 20, the IP traffic smoother 23 does not drop the XMI packet and keeps the time interval. It can be input to the modulator 24.

When a buffer such as a FIFO (First In, First Out) is installed in the input stage of the modulator 24, the buffer amount cannot be adjusted, which may increase the delay time and waste the buffer. On the other hand, according to the IP traffic smoother 23 of the present embodiment, XMI packets can be input to the modulation device 24 at regular time intervals while minimizing the delay time.

Further, according to the IP traffic smoother 23 of the present embodiment, it is possible to suppress complication of the system due to conventional clock multiplexing such as PCR. In addition, by reducing the dedicated hardware, the failure rate of the entire system can be reduced, and the cost can be reduced.

Further, since the IP traffic smoother 23 outputs XMI packets at regular intervals based on an accurate time stamp, it is possible to reduce the fluctuation of the time for forming a 1 OFDM frame at the time of input of the modulation device 24. Therefore, it is possible to form an accurate OFDM modulated wave. If an OFDM modulated wave is formed at an accurate timing, it is possible to construct an SFN (Single Frequency Network).

Further, since the IP traffic smoother 23 outputs the XMI packet based on the time information received from the GPS, PTP, or NTP server, the IP traffic smoother 23 can output the XMI packet at an accurate time.

The method of absorbing jitter fluctuations and realizing synchronization by correcting the time stamp described in the present embodiment can be applied not only to XMI packets but also to various types of packets that retain the time stamp. can. In the above embodiment, an example in which the IP traffic smoother 23 corrects both the transmission time stamp and the delivery time stamp of the XMI packet in order to absorb the influence of jitter has been described, but one of the time stamps has been described. May be used. For example, the IP traffic smoother 23 may correct only the delivery time stamp and transmit the XMI packet, and the device that receives the XMI packet may control the timing of retransmission or reproduction by paying attention only to the delivery time stamp.

(Distribution system with redundant lines)
In terrestrial digital broadcasting, in addition to the wireless STL line of the main line, it is conceivable to provide a wired IP line of the sub line to make the line redundant and switch to the sub line when a problem occurs in the main line. However, in such a configuration, since the transmission delay time differs between the wireless line and the wired line, XMI switching can be performed when the line is disconnected due to a trouble in the wireless line which is the main line or packet loss due to fading occurs. , It is impossible to switch seamlessly with the current configuration. Since such an effect affects the lower stations of the broadcasting station, the effect is large. That is, due to the accompanying TTL line, the image may be interrupted due to switching to the lower station, or the image may freeze.

Therefore, in a distribution system with redundant lines, a configuration capable of seamless line switching by using the IP traffic smoother 23 according to the present disclosure will be described.
FIG. 14 is a diagram showing a configuration example of a distribution system 2 in which a line is made redundant according to an embodiment of the present disclosure.

The distribution system 2 includes a performance station 50, a master station broadcasting station 60, and a relay broadcasting station 70. The playing station 50 and the master station broadcasting station 60 are connected via a line made redundant by a wired (IP) line 82 in addition to the wireless (STL) line 81. The master station broadcasting station 60 and the relay broadcasting station 70 are connected via a wireless (TTL) line 83. "TTL" is an abbreviation for Transmitter to Transmitter Link. The content generated at the performance center is delivered to the master station broadcasting station 60 via the wireless (STL) line 81 and the wired (IP) line 82 by the XMI packet. The content delivered to the master station broadcasting station 60 is transmitted from the transmitter 68 by the XMI packet after the time stamp of the XMI packet is corrected and updated by the IP traffic smoothers 64a and 64b, and is also wireless (TTL). It is delivered to the relay broadcasting station 70 via the line 83. The content delivered to the relay broadcasting station 70 is transmitted from the transmitter 75 by the XMI packet after the time stamp of the XMI packet is corrected and updated by the IP traffic smoother 73.

The playing place 50 includes a remultiplexing device 51, a line redundancy device 52, an STL transmitter 53, and an IP transmitter 54. The master station broadcasting station 60 includes an STL receiver 61, an IP receiver 62, XMI monitoring devices 63a and 63b, IP traffic smoothers 64a and 64b, a line redundancy device 65, a modulation device 66, and a TTL transmitter. 67 and a transmitter 68 are provided. The relay station 70 includes a TTL receiver 71, an XMI monitoring device 72, an IP traffic smoother 73, a modulation device 74, and a transmitter 75. The remultiplexing device 51 has the same functions as the remultiplexing device 11. The STL transmitter 53 and the TTL transmitter 67 have the same functions as the STL transmitter 12. The STL receiver 61 and the TTL receiver 71 have the same functions as the STL receiver 21. The XMI monitoring devices 63a, 63b, 72 have the same functions as the XMI monitoring device 22. The IP traffic smoothers 64a, 64b, and 73 have the same functions as the IP traffic smoother 23. The modulators 66 and 74 have the same functions as the modulator 24. The transmitter 68 has the same functions as the transmitter 25. The master station broadcasting station 60 and the relay broadcasting station 70 do not necessarily have to be equipped with the XMI monitoring devices 63a, 63b, 72.

In the distribution system 2, the XMI packet generated by the remultiplexing device 51 of the playing room 50 is made redundant by the line redundancy device 52, and the same XMI packet is input to the STL transmitter 53 and the IP transmitter 54. .. The same XML packet is transmitted from the STL transmitter 53 via the wireless (STL) line 81 and from the IP transmitter 54 via the wired (IP) line 82, both of which are transmitted to the master station broadcasting station 60. It will be delivered.

The XMI packet delivered via the wireless (STL) line 81 is received by the STL receiver 61 of the master station broadcasting station 60, and its time stamp or the like is monitored by the XMI monitoring device 63a. Further, in the XMI packet delivered via the wireless (STL) line 81, the IP traffic smoother 64a updates the time stamp and adjusts the output timing. In parallel with this, the XMI packet delivered via the wired (IP) line 82 is received by the IP receiver 62, and its time stamp or the like is monitored by the XMI monitoring device 63b. Further, in the XMI packet delivered via the wired (IP) line 82, the time stamp is updated and the output timing is adjusted in the IP traffic smoother 64b. Here, the IP traffic smoothers 64a and 64b update the time stamps of the input XMI packets so as to indicate the same delay time, and output the time stamps to the line redundancy device 65 at the same delay time. The line redundancy device 65 inputs a first output signal output by the IP traffic smoother 64a and a second output signal output by the IP traffic smoother 64b, and inputs a first output signal or a second output signal. Output. The line redundancy device 65 switches the output signal from the first output signal to the second output signal in response to the failure of the wireless (STL) line 81. The output of the line redundancy device 65 is input to the modulation device 66 and the TTL transmitter 67.

In the distribution system 2, the IP traffic smoothers 64a and 64b update the time stamp of the input XMI packet to the same delay time and output it at that time. Therefore, the input timing of the line redundancy device 65 is a wireless line. And the wired line will be the same. Therefore, even if the input selection is switched, it is possible to switch seamlessly. Therefore, it is possible to switch the XMI without affecting the lower station. That is, by passing through the IP traffic smoother, the input timing of the line redundancy device becomes the same for the wireless line and the wired line, so that the input selection can be switched seamlessly. Therefore, it is possible to switch the XMI without affecting the lower station.

The IP traffic smoother may be provided as a device built in the XMI monitoring device 22 or a device built in the front stage of the line redundancy device 65.

Further, in each of the above embodiments, the configuration and operation of the IP traffic smoother have been described, but the present invention is not limited to this, and as a method of absorbing jitter fluctuations and realizing synchronization by correcting a time stamp. It may be configured.

The present disclosure is not limited to the embodiments described above. For example, the plurality of blocks shown in the block diagram may be integrated, or one block may be divided. The plurality of steps described in the flowchart may be executed in parallel or in a different order depending on the processing power of the device that executes each step, or as necessary, instead of executing the steps in chronological order according to the description. .. Other changes are possible without departing from the spirit of this disclosure.

1, 2 Distribution system 10 Performance station 11 Remultiplexing device 12 STL transmitter 20 Broadcasting station 21 STL receiver 22 XMI monitoring device 23 IP traffic smoother 24 Modulator 25 Transmitter 30 Content transmission line 31 Control unit 32 Storage unit 33 Communication Part 34 Input part 35 Output part 41 Synchronous control XMI packet 42 Data XMI packet 43 Staff XMI packet 44, 46, 47 XMI packet time interval 45 Transmission delay time 50 Playground 51 Remultiplexing device 52 Line redundancy device 53 STL transmission 54 IP transmitter 60 Master station broadcasting station 61 STL receiver 62 IP receiver 63a, 63b XMI monitoring device 64a, 64b IP traffic smoother 65 Line redundancy device 66 Modulator 67 TTL transmitter 68 Transmitter 70 Relay broadcasting station 71 TTL receiver 72 XMI monitoring device 73 IP traffic smoother 74 Modulator 75 Transmitter 81 Wireless STL line 82 Wired STL line 83 Wireless TTL line 301a, 301b, 301c, 301d Packet filter 302a, 302b, 302c, 302d, 302e IP header compression Part 303a, 303b, 303c, 303d, 303e TLV packetizing part 304a, 304b, 304c, 304d, 304e FIFO buffer 305a, 305b, 305c FEC block component part 306a, 306b, 306c Layer-based frame component part 307a, 307b, 307c XMI Packetization unit 308 L0 Symbol configuration unit 309 L1 Symbol configuration unit 310 Synchronous control XMI packet configuration unit 311 Staff XMI packet configuration unit 312 XMI packet transmission scheduler unit

Claims (7)

A packet containing a time stamp indicating the transmission time, which is the reference time for transmitting the packet, is received from another device via the network.
The time stamp is updated by the delay time, which is the time obtained by adding a predetermined delay to the transmission time indicated by the time stamp included in the received packet.
The packet containing the updated time stamp is output at the delay time indicated by the updated time stamp.
A traffic smoother device with a control unit. The control unit
The time stamp is updated by the delay time, which is the time obtained by adding a time larger than the transmission delay time in the network as the delay to the transmission time.
The traffic smoother device according to claim 1. The traffic smoother device according to claim 1 or 2, wherein the time stamp indicates the time when the packet is transmitted by the other device as the transmission time. The traffic smoother device according to claim 1 or 2, wherein the time stamp indicates a time set in the other device as a time at which the traffic smoother device should transmit the packet as the transmission time. The control unit
Obtains time information indicating the time from an external server device that manages the time, and obtains time information.
With respect to the time indicated by the time information, the packet including the updated time stamp is output at the delay time indicated by the updated time stamp.
The traffic smoother device according to any one of claims 1 to 4. A distribution system including the plurality of traffic smoother devices according to any one of claims 1 to 5.
A first receiver that receives a first packet from the other device, including a first time stamp indicating a transmission time that is a reference time for transmitting the packet, by the first communication line.
A second receiver that receives a second packet including a second time stamp, which is the same packet as the first packet, from the other device by the second communication line.
The updated first time stamp of the first packet received by the first receiver is updated and the updated first time stamp is set to the delay time indicated by the updated first time stamp. A first traffic smoother device that outputs the first packet including a time stamp of 1, and a first traffic smoother device.
The second time stamp of the second packet received by the second receiver is updated to indicate the same delay time as the delay time indicated by the first time stamp, and the delay is caused. A second traffic smoother device that outputs the second packet including the updated second time stamp at the time.
The first output signal output by the first traffic smoother device and the second output signal output by the second traffic smoother device are input, and the first output signal or the second output signal is input. And a redundancy device that outputs
Equipped with
The redundancy device switches an output signal from the first output signal to the second output signal in response to a failure in the first communication line.
Delivery system. A program for causing a computer to function as the traffic smoother device according to any one of claims 1 to 5.

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