JP6517905B2 - Transmission system, transmission slotting apparatus, and transmission slot creation method - Google Patents

Description

  The embodiment of the present invention generates a transmission main signal by storing a TLV (Type Length Value) packet in a slot, and transmits a broadcast wave based on the transmission main signal, and a transmission slot used in the transmission system. FIELD OF THE INVENTION The present invention relates to a communication slotting apparatus used in a communication slotting apparatus.

  In current broadcasting systems, media transport methods such as MPEG-2 TS (Moving Picture Experts Group-2 Transport Stream) method and RTP (Real-time Transport Stream) method are widely used. In these systems, there are various limitations when trying to coordinate broadcasting and communication. Therefore, MMT (MPEG Media Transport), which is a new media transport method assuming use of various networks using MPEG, has been proposed.

  A transmission system using MMT TLV packetizes an MPEG Media Transport Protocol (MMTP) / User Datagram Protocol (UDP) / Internet Protocol (IP) packet. The transmission system stores the TLV packet in a slot to generate a transmission main signal. The transmission main signal is a signal generated on a slot basis, and for example, transmission control settings are updated for each frame configured of 120 slots. The transmission system performs processing such as modulation processing on the transmission main signal and transmits it as a broadcast wave.

  By the way, when the transmission system generates the transmission main signal by storing the TLV packet in the slot, it is conceivable that the remaining capacity of the last effective slot in the frame in the transmission main signal is less than 4 bytes. However, since the minimum capacity of the TLV packet is 4 bytes, when the remaining capacity is less than 4 bytes, it is impossible to store the TLV packet in this slot.

JP, 2011-103568, A

"Video coding, audio coding and multiplexing method in digital broadcasting", ARIB STD-B32 version 3.1 ARIB STD-B44 Version 2.0 "Transmission Method for Advanced Broadband Satellite Digital Broadcasting"

  As described above, when the remaining capacity is less than 4 bytes, it is impossible to store the TLV packet in this slot, which may hinder the transmission of the broadcast wave from the transmission system.

  Therefore, the purpose is to use a transmission system capable of avoiding that the remaining capacity of the last effective slot in the transmission main signal is less than 4 bytes, a transmission slotting apparatus used in this transmission system, and this transmission slotting apparatus It is to provide a transmission slot creation method.

  According to the embodiment, the transmission system comprises: a variable-length packet multiplexer for generating a variable-length packet including information indicating the type of data and information indicating the number of bytes of the data; and a plurality of transmission main signals. And a transmission slotting device for storing the variable-length packet in any one of the slots. The transmission slotting apparatus includes a capacity calculating unit, an extracting unit, a remaining capacity calculating unit, a selecting unit, and a slot information multiplexing unit. The capacity calculation unit receives setting information of one frame of the transmission main signal, and calculates a data capacity that can be included in the transmission main signal of one frame based on the setting information. The extraction unit extracts the number of bytes of the variable-length packet. The remaining capacity calculation unit calculates the remaining capacity of the transmission main signal based on the data capacity calculated by the capacity calculation unit and the number of bytes extracted by the extraction unit. When the variable length packet is stored in any one of the slots, the selection unit is null instead of the variable length packet if the remaining capacity of the transmission main signal is less than the minimum number of bytes that can be taken by the variable length packet. The packet is stored until the end of the slot, and the slot storing the null packet is output. The slot information multiplexing unit multiplexes slot information in the slot output by the selection unit.

FIG. 2 is a block diagram showing a transmission system and a reception system according to the first embodiment. It is a figure which shows the structure of the TLV packet which the TLV multiplexer shown by FIG. 1 produces | generates. It is a figure which shows the structure of the slot which concerns on 1st Embodiment. It is a block diagram which shows the example of a function structure of the transmission slotting apparatus shown by FIG. FIG. 5 is a diagram showing a slot configuration of a transmission main signal output from the slot information multiplexing unit shown in FIG. 4 to the transmission processing device. It is a flowchart which shows the process at the time of storing the data which the selection part shown by FIG. 4 received in a slot. FIG. 5 is a diagram showing a transmission main signal output from the selection unit shown in FIG. 4; FIG. 7 is a diagram showing another example of the transmission main signal output from the selection unit shown in FIG. 4; FIG. 7 is a diagram showing another example of the transmission main signal output from the selection unit shown in FIG. 4; It is a block diagram which shows the structure of the receiving system shown by FIG. It is a block diagram which shows the function structure of the transmission main signal receiver shown by FIG. It is a block diagram which shows the example of a function structure of the transmission slotting apparatus which concerns on 2nd Embodiment. It is a flowchart which shows the process at the time of storing the data which the selection part shown by FIG. 12 received in a slot.

  Embodiments will be described below with reference to the drawings.

First Embodiment
FIG. 1 is a block diagram showing a transmission system 10 and a reception system 20 according to the first embodiment. The transmission system 10 transmits a broadcast wave. The broadcast wave to be transmitted arrives at the receiving system 20 via a transmission path such as a broadcast network. The receiving system 20 receives a broadcast wave.

(Transmission system)
The transmission system 10 shown in FIG. 1 includes an encoder 11, an additional information generation device 12, an MMT (MPEG Media Transport) multiplexing device 13, an IP (Internet Protocol) multiplexing device 14, and a TLV (Type Length Value) multiplexing device 15. , A transmission slotting unit 16 and a transmission processing unit 17.

  The encoder 11 receives video and audio signals from, for example, a photographing device such as a camera or a server. The encoder 11 converts the video / audio signal into an encoded signal by encoding the received video / audio signal according to a preset method. The encoder 11 outputs the encoded signal to the MMT multiplexer 13.

  The additional information generation device 12 creates a program guide of the broadcast program and information about charging / encoding of the video delivery content, and outputs the information to the MMT multiplexing device 13 as additional information. In addition, although the encryption part (scrambler) is not described in the transmission system 10 shown by FIG. 1, it is provided between the MMT multiplexer 13 and the IP multiplexer 14, for example.

  The MMT multiplexer 13 includes, for example, a central processing unit (CPU), a memory used when the CPU executes processing, and an FPGA (field programmable gate array) which executes predetermined processing according to control from the CPU. . When the CPU causes the FPGA to execute predetermined processing, the MMT multiplexer 13 executes processing on the encoded signal. That is, the MMT multiplexer 13 adds additional information to the encoded signal, and stores the encoded signal to which the additional information is added in an MMTP (MPEG Media Transport Protocol) packet. The MMT multiplexer 13 outputs the MMTP packet to the IP multiplexer 14.

  The MMT multiplexer 13 may include an LSI (Large-Scale Integration) instead of the FPGA. The MMT multiplexer 13 may execute predetermined processing by software.

  The IP multiplexer 14 includes, for example, a CPU, a memory used when the CPU executes a process, and an FPGA which executes a predetermined process according to control from the CPU. When the CPU causes the FPGA to execute predetermined processing, the IP multiplexer 14 executes processing on the MMTP packet. That is, the IP multiplexer 14 stores the MMTP packet in the IP packet. The IP multiplexer 14 outputs the IP packet to the TLV multiplexer 15.

  The IP multiplexer 14 may include an LSI instead of the FPGA. Also, the IP multiplexer 14 may execute predetermined processing by software.

  The TLV multiplexer 15 includes, for example, a CPU, a memory used when the CPU executes a process, and an FPGA which executes a predetermined process according to control from the CPU. When the CPU causes the FPGA to execute predetermined processing, the TLV multiplexer 15 executes processing on the IP packet. That is, the TLV multiplexer 15 generates a TLV packet based on the IP packet.

  FIG. 2 is a schematic view showing the configuration of a TLV packet generated by the TLV multiplexer 15. As shown in FIG. As shown in FIG. 2, the TLV packet has 2 bits of "01", 6 bits of "111111", 8 bits of "packet type" for identifying the type of packet stored in the TLV, and the following data byte It consists of data in which the number of data bytes is indicated by the “data length” of 16 bits and the data length in which the number is written. When the data length is 0, ie, the number of data bytes is 0 bytes, the capacity of the TLV packet is the minimum 4 bytes (2 bits + 6 bits + 8 bits + 16 bits + 0 bytes).

  The TLV multiplexer 15 outputs the TLV packet to the transmission slotter 16.

  The TLV multiplexer 15 may include an LSI instead of the FPGA. Further, the TLV multiplexer 15 may execute predetermined processing by software.

  The transmission slotting apparatus 16 includes, for example, a CPU, a memory used when the CPU executes a process, and an FPGA which executes a predetermined process according to control from the CPU. When the CPU causes the FPGA to execute a predetermined process, the transmission slotting apparatus 16 executes a process for the TLV packet. That is, the transmission slotting apparatus 16 generates a transmission main signal by storing the TLV packet in any of the slots constituting the transmission main signal. The transmission slotting apparatus 16 outputs the generated transmission main signal to the transmission processing apparatus 17.

  The transmission main signal is a signal generated in units of slots. The setting of the transmission mode for the transmission main signal is updated for each frame configured of 120 slots based on the setting information. The setting information includes information on a modulation mode and a transmission mode such as a coding rate for 120 slots in the transmission main signal.

  FIG. 3 is a schematic view showing a configuration example of the slot. A slot is a signal obtained by adding an error correction outer code and a stuff bit to a slot header and a main signal, and adding an error correction inner code to this signal. The main signal stores at least one of a TLV packet, an NTP packet, a TLV NULL packet, and a slot padding byte, as described later.

  FIG. 4 is a block diagram showing an example of the functional configuration of the transmission slotting apparatus 16 shown in FIG. The slot number counter 161, setting information reception unit 162, capacity calculation unit 163, transmission slot generation unit 164, TLV packet reception unit 165, NTP (Network Time Protocol) packet generation unit 166, slot padding byte generation unit 167 shown in FIG. The function of the TLV NULL packet generation unit 168 is realized by the CPU causing the FPGA to execute a predetermined process. The transmission slotting apparatus 16 may realize the function shown in FIG. 4 by providing an LSI instead of the FPGA. Further, the transmission slotting apparatus 16 may realize the function shown in FIG. 4 by software.

  When the slot number counter 161 receives the frame synchronization signal, the count value is set to 1, and then the count is restarted using the transmission clock. The slot number counter 161 increments the slot number by 1 and counts the number of transmission clocks of the next slot when the number of clocks for transmitting data of the slot structure shown in FIG. 3 has elapsed. This will start counting at the start of the frame. The slot number counter 161 outputs the count value to the capacity calculation unit 163 and the selection unit 1641.

  The setting information receiving unit 162 receives setting information for setting a transmission mode for each frame of the transmission main signal. The setting information receiving unit 162 outputs the setting information to the capacity calculating unit 163 and the transmission slotting unit 164.

  The coding rate included in the setting information can be set, for example, as shown by the coding rate in FIG. 3, and the number of main signal bits also changes according to the change of the coding rate.

  The modulation method included in the setting information is, for example, 16-value amplitude phase modulation method (16APSK), 8-phase phase modulation method (8PSK), 4-phase phase modulation method (QPSK), and π-shift two-phase modulation method of two minutes. (.Pi. / 2 shift BPSK) or the like. In 16APSK, when the slot unit is 5, the number of available slots is 4 and the number of invalid slots is 1. In 8PSK, when the slot unit is 5, the number of valid slots is 3, and the number of invalid slots is 2. Further, in QPSK, when the slot unit is 5, the number of valid slots is 2, and the number of invalid slots is 3. In the π / 2 shift BPSK, when the slot unit is 5, the number of valid slots is 1, and the number of invalid slots is 4. The total number of main signal bits for every five slots is determined by the combination of the modulation scheme and the coding rate included in the setting information.

  Further, the combination of the modulation scheme and the coding rate included in the setting information is not limited to one type. The combination of the modulation scheme and the coding rate included in the setting information may be two or more types. When there are a plurality of combinations, transmission modes are assigned to slots in ascending order from slot number 1, in the order of modulation schemes with large multi-level numbers, and in the case of the same modulation scheme, in order from the highest coding rate.

  The capacity calculation unit 163 receives the count value output from the slot number counter 161 and the setting information output from the setting information receiving unit 162. When receiving the first count value in the frame, that is, “1”, capacity calculating section 163 determines the number of main signal bits determined by the coding rate, and the ratio of the effective slot to the ineffective slot determined from the modulation scheme. And the capacity of the effective main signal for the frame is calculated as the frame main signal capacity. Also, upon receiving the count value output from the slot number counter 161, the capacity calculation unit 163 calculates the capacity of the effective main signal in the slot indicated by the number indicated by the count value as the slot main signal capacity. When calculating the frame main signal capacity and the slot main signal capacity, the capacity calculating section 163 outputs information on the calculated frame main signal capacity and information on the calculated slot main signal capacity to the transmission slotting section 164.

  When there are two or more types of combinations of the modulation scheme and the coding rate included in the setting information, the capacity calculating unit 163 calculates a pseudo frame main signal capacity for each combination. The capacity calculation unit 163 uses the pseudo slot main signal capacity at the slot start position allocated according to the combination of the modulation scheme and the coding rate included in the setting information.

  The TLV packet receiving unit 165 receives the TLV packet output from the TLV multiplexer 15. The TLV packet receiving unit 165 includes a buffer (not shown), and holds the received TLV packet in the buffer. The TLV packet receiving unit 165 outputs the held TLV packet to the transmission slotting unit 164 according to the instruction from the transmission slotting unit 164.

  The NTP packet generation unit 166 generates an IP packet in NTP format. The NTP packet generation unit 166 generates an NTP packet by storing an IP packet including the NTP format in a TLV packet.

  In ARIB STD-B 44 version 2.0, it is defined that the NTP packet is placed at the head of the first slot in the frame among the slots allocated for each TLV stream ID. This is to suppress the delay variation of the NTP packet. The NTP packet does not have to be included for each frame. When there are two or more combinations of modulation scheme and coding rate in the same TLV stream ID, an NTP packet may be placed at the beginning of the first slot of the slot with the highest combination of error tolerance.

  The NTP packet generation unit 166 receives the notification of the timing for inserting the NTP packet from the transmission slot generation unit 164, and outputs the NTP packet including the NTP time (system time) at that time to the transmission slot formation unit 164. The NTP time may be corrected by adding or subtracting an offset set from the outside.

  The slot padding byte generation unit 167 generates a data string set in advance as a slot padding byte in accordance with an instruction from the transmission slotting unit 164. The first byte of the TLV packet is “0x7f” as described in FIG. The slot padding byte generation unit 167 generates a data string different from “0x7f”, for example, “0x7e” as a slot padding byte. The slot padding byte is not limited to "0x7e", and may be other than "0x7f".

  Also, the slot padding byte generation unit 167 sets the slot padding byte when the remaining capacity of the last effective slot in the transmission main signal is 3 bytes as “0x7e” and the slot padding byte when the remaining capacity is 2 bytes. The slot padding byte when the remaining capacity is 1 byte may be “0x7 d”, and the lower 2 bits may represent the remaining capacity. The slot padding byte generation unit 167 outputs the generated slot padding byte to the transmission slotting unit 164.

  The TLV NULL packet generation unit 168 receives the instruction from the transmission slotting unit 164, and generates a TLV NULL packet of the instructed capacity. The TLV NULL packet generation unit 168 outputs the generated TLV NULL packet to the transmission slot generation unit 164.

  The transmission slotting unit 164 includes a selecting unit 1641, a TLV byte number extracting unit 1642, a remaining amount calculating unit 1643, and a slot information multiplexing unit 1644.

  The TLV byte number extraction unit 1642 receives the TLV packet output from the TLV packet reception unit 165 or the NTP packet output from the NTP packet generation unit 166. The TLV byte number extraction unit 1642 extracts the data length shown in FIG. 2 from the received TLV packet or NTP packet, and acquires the data capacity included in the TLV packet or NTP packet. The TLV byte number extraction unit 1642 outputs information on the acquired data capacity to the remaining amount calculation unit 1643.

  The remaining amount calculating unit 1643 is information from the capacity calculating unit 163 about the frame main signal capacity, information from the capacity calculating unit 163 about the slot main signal capacity, and the TLV byte number extraction unit 1642. Receive information about the amount of data The remaining amount calculation unit 1643 calculates the remaining frame capacity by sequentially subtracting the data capacity from the frame main signal capacity. The remaining amount calculation unit 1643 outputs the calculated remaining frame capacity to the selection unit 1641. The remaining capacity calculation unit 1643 calculates the remaining slot capacity by sequentially subtracting the data capacity from the frame main signal capacity. The remaining capacity calculation unit 1643 outputs the calculated remaining capacity of the slot to the selection unit 1641.

  The selection unit 1641 stores the TLV packet, the NTP packet, or the TLV NULL packet in the slot represented by the number indicated by the count value output from the slot number counter 161.

  When the selecting unit 1641 stores the TLV packet, NTP packet or TLV NULL packet in the slot, the current slot remaining capacity is obtained by subtracting the capacity of the stored data from the slot remaining capacity output from the remaining capacity calculating unit 1643. Calculate Also, when the TLV packet, NTP packet or TLV NULL packet is stored in the slot, the selection unit 1641 subtracts the capacity of the stored data from the remaining capacity of the frame output from the remaining capacity calculation unit 1643 to obtain the current frame. Calculate the remaining capacity.

  The selection unit 1641 stores the TLV packet, the NTP packet, or the TLV NULL packet in the slot, so when the remaining slot capacity of the last effective slot in the frame is less than 4 bytes, the slot padding byte generation unit 167 performs slot padding. Output a request for bytes. At this time, the selection unit 1641 may request the slot padding byte generation unit 167 for the same slot padding byte, for example, “0x7e” for a plurality of bytes.

  In addition, the selection unit 1641 requests “0x7e” for 3 bytes when the slot remaining capacity is 3 bytes, and requests “0x7d” for 2 bytes when the slot remaining capacity is 2 bytes, and the slot remaining capacity When 1 is one byte, "0x7c" may be requested for one byte. The request for the slot padding byte by the selection unit 1641 is not limited to the above, and various aspects can be assumed. For example, the selection unit 1641 requests “0x7e”, “0x7d” and “0x7c” when the slot remaining capacity is 3 bytes, and “0x7d” and “0x7c” when the slot remaining capacity is 2 bytes. If it is requested and the remaining slot capacity is 1 byte, "0x7c" may be requested.

  Whether the selecting unit 1641 is required to store an NTP packet at the head of the slot represented by the number indicated by the count value output from the slot number counter 161 based on the setting information output from the setting information receiving unit 162 To judge. If it is determined that it is necessary, the selection unit 1641 issues an NTP packet request instruction to the NTP packet generation unit 166. The selection unit 1641 stores the NTP packet output from the NTP packet generation unit 166 in the slot.

  The selection unit 1641 instructs the TLV NULL packet generation unit 168 to generate a TLV NULL packet of a capacity according to the remaining frame capacity and the remaining slot capacity. When the selecting unit 1641 receives the TLV NULL packet output from the TLV NULL packet generating unit 168, the selecting unit 1641 stores the received TLV NULL packet in the slot.

  Selection section 1641 outputs the slot storing the data to slot information multiplexing section 1644.

  The slot information multiplexing unit 1644 is information on the frame main signal capacity output from the capacity calculation unit 163, information on the slot main signal capacity output from the capacity calculation unit 163, and setting information output from the setting information reception unit 162. And the slot output from the selection unit 1641 is received. The slot information multiplexing unit 1644 creates slot information for the received slot based on the received frame main signal capacity, slot main signal capacity, and setting information. The slot information includes synchronization signals, signal point arrangement information and TMCC information. The signal point arrangement information indicates the start position of the first packet included in each slot and the end position of the last packet included in each slot. The TMCC information includes information on a transmission mode including a coding rate and a modulation scheme, information on a TLV stream ID, and the like. The slot information multiplexing unit 1644 multiplexes the generated slot information in the received slot, and outputs the slot in which the slot information is multiplexed to the transmission processing device 17. FIG. 5 is a schematic diagram showing the slot configuration of the transmission main signal output from the slot information multiplexing unit 1644 to the transmission processing device 17. As shown in FIG.

  The transmission processing device 17 includes, for example, a CPU, a memory used when the CPU executes a process, and an FPGA which executes a predetermined process according to control from the CPU. The CPU causes the FPGA to execute predetermined processing, whereby the transmission processing device 17 executes processing on the transmission main signal. That is, the transmission processing unit 17 receives the transmission main signal output from the transmission slotting unit 16 and modulates the received transmission main signal according to the modulation scheme assigned to each slot. The transmission processing device 17 performs predetermined transmission processing on the modulated signal to generate a broadcast wave. The transmission processing device 17 transmits a broadcast wave.

  The transmission processing device 17 may include an LSI instead of the FPGA. Further, the transmission processing device 17 may execute predetermined processing by software.

  Next, the operation of the transmission slotting apparatus 16 configured as described above will be described in detail. FIG. 6 is a flowchart showing an example of processing when storing data received by the selection unit 1641 shown in FIG. 4 in a slot. In FIG. 6, an example will be described in which there is one transmission mode in a frame, that is, one combination of the modulation scheme and the coding rate included in the setting information.

  First, the selection unit 1641 receives the count value from the slot number counter 161 (step S61). The selection unit 1641 determines whether the received count value is 1 (step S62). If the received count value is 1 (Yes in step S62), the selection unit 1641 recognizes that a new frame has started (step S63). If the received count value is not 1 (No in step S62), the selecting unit 1641 determines whether the NTP packet is stored in the slot indicated by the number indicated by the count value (step S64).

  If the NTP packet needs to be stored in the slot (Yes in step S64), the selecting unit 1641 stores the NTP packet at the beginning of the current slot (step S65). When it is not necessary to store the NTP packet in the slot (No in step S64), the selecting unit 1641 determines whether the current slot is the last valid slot in the current frame (step S66).

  When the data is stored in the current slot, the selection unit 1641 subtracts the capacity of stored data from the slot remaining capacity output from the remaining capacity calculating unit 1643, thereby updating the current slot remaining capacity. In addition, when data is stored in the current slot, selection unit 1641 updates the current frame remaining capacity by subtracting the capacity of the stored data from the frame remaining capacity output from remaining capacity calculation unit 1643 (step S67).

  Subsequently, the selection unit 1641 determines whether the remaining slot capacity in the current slot is 0 (step S68). If the slot remaining capacity in the current slot is 0 (Yes in step S68), the selecting unit 1641 determines whether the frame remaining capacity in the current frame is 0 (step S69). If the slot remaining capacity in the current slot is not 0 (No in step S68), the selection unit 1641 shifts the processing to step S66.

  If the frame remaining capacity in the current frame is 0 (Yes in step S69), the selecting unit 1641 waits until the next frame is started (step S610). If the frame remaining capacity in the current frame is not 0 (No in step S69), the selection unit 1641 shifts the processing to step S61.

  In step S66, if the current slot is the last valid slot in the current frame (Yes in step S66), the selecting unit 1641 determines whether the remaining slot capacity of the current slot is less than 4 bytes (step S611). ). If the current slot is not the last valid slot in the current frame (No in step S66), the selecting unit 1641 determines whether there is a TLV packet to be stored in the current slot (step S612).

  In step S611, when the slot remaining capacity of the current slot is less than 4 bytes (Yes in step S611), the selection unit 1641 sets the slot padding byte output from the slot padding byte generation unit 167 in an area less than 4 bytes. After storing (step S613), the process proceeds to step S610.

  In step S612, when there is a TLV packet to be stored in the current slot (Yes in step S612), the selecting unit 1641 determines whether the TLV packet can not be stored in the current frame, that is, stores the TLV packet in the current slot. Then, it is determined whether the remaining frame capacity of the current frame is less than 0 (step S614). If there is no TLV packet to be stored in the current slot (No in step S612), the selecting unit 1641 stores the TLV NULL packet output from the TLV NULL packet generation unit 168 in the current slot (step S615). It transfers to step S67.

  If the TLV packet is stored in the current slot and the remaining frame capacity of the current frame falls below 0 (Yes in step S614), the selecting unit 1641 links the current slot and the last valid slot in the current frame, and this connected slot Stores the TLV null packet instead of the TLV packet (step S616). If the remaining frame capacity of the current frame is less than 0 when storing the TLV packet in the current slot (No in step S614), whether the remaining slot capacity of the current slot is less than 0 when the TLV packet is stored in the current slot It is determined whether or not it is (step S617).

  When the TLV packet is stored in the current slot and the slot remaining capacity of the current slot falls below 0 (Yes in step S617), the selecting unit 1641 selects the TLV packet as the first TLV packet of the capacity that can be stored in the current slot. It is divided into other second TLV packets (step S618). The selection unit 1641 stores the divided first TLV packet in the current slot (step S619), and the process proceeds to step S67. When the TLV packet is stored in the current slot and the slot remaining capacity of the current slot becomes 0 or more (No in step S617), the selecting unit 1641 stores the TLV packet in the current slot (step S620), and the process proceeds to step S67. Transition.

  When the selecting unit 1641 executes the process described in FIG. 6, a slot group as shown in FIG. 7 is output to the slot information multiplexing unit 1644. According to FIG. 7, the slot padding byte is stored at the end of the last valid slot.

  In addition, in FIG. 6, the case where the transmission mode in a flame | frame is one was demonstrated to the example. However, it is not limited to this. The selection unit 1641 can perform the same operation even when there are two or more transmission modes in a frame.

  When there are two or more transmission modes in a frame, the capacity calculation unit 163 calculates the capacity of the main signal effective for each transmission mode as the frame main signal capacity according to the setting information.

  The remaining amount calculation unit 1643 calculates the remaining frame capacity for each transmission mode by subtracting the data capacity output from the TLV byte number extraction unit 1642 from the frame main signal capacity calculated for each transmission mode.

  The selection unit 1641 stores the TLV packet in the slot while referring to the remaining frame capacity and the remaining slot capacity according to the assignment of the transmission mode to the slot indicated in the setting information.

  FIG. 8 is a diagram showing a slot configuration in the case where there is one TLV stream and two transmission modes. In FIG. 8, it is assumed that the multilevel number of the modulation mode of the transmission mode allocated to slots # 1 to # 60 is larger than the multilevel number of the modulation mode of the transmission mode allocated to slots # 61 to # 120. At this time, since the transmission mode assigned to slots # 61 to # 120 is more resistant to interference, the NTP packet is placed at the head of slot # 61. Also, according to FIG. 8, the slot padding byte is stored at the end of the last valid slot in each transmission mode.

  FIG. 9 is a diagram showing a slot configuration in the case where there are three TLV streams and three transmission modes. 9, NTP packets for transmission modes assigned to slots # 1 to # 40 are stored at the beginning of slot # 1, and NTP packets for transmission modes assigned to slots # 41 to # 80 are at the head for slot # 41. The NTP packet for the transmission mode stored in and assigned to slots # 81 to # 1200 is stored at the beginning of slot # 81. Further, according to FIG. 9, the slot padding byte is stored at the end of the last valid slot in the transmission mode allocated to the slots # 1 to # 40.

  As described above, in the transmission system 10 according to the first embodiment, the capacity calculating unit 163 of the transmission slotting apparatus 16 calculates the frame main signal capacity and the slot main signal capacity. The remaining capacity calculation unit 1643 subtracts the data capacity of the TLV packet from the frame main signal capacity to calculate the frame remaining capacity, and subtracts the data capacity of the TLV packet from the slot main signal capacity to calculate the slot remaining capacity. calculate. Then, when the slot remaining capacity in the last effective slot in the frame is less than 4 bytes, the selecting unit 1641 stores the slot padding byte in the remaining area. Thus, in the transmission system 10 according to the first embodiment, even if the remaining slot capacity in the last effective slot in the frame is less than 4 bytes by storing the TLV packet in the effective slot, the frame It is possible to store data up to the end of the last valid slot in the middle.

  Therefore, according to the transmission system 10 of the first embodiment, even if the remaining capacity of the last effective slot in the frame becomes less than 4 bytes by storing the TLV packet in the effective slot in the frame It can be sent successfully.

  Note that the 3-byte area left in the last effective slot in the first frame is connected to the first slot of the second frame following the first frame, and the TLV NULL packet is stored in the connected slot. Countermeasures to However, when storing an NTP packet, its position is defined as the beginning of the first slot, so this countermeasure does not extend to the functions achieved by the transmission system according to the first embodiment.

  Also, in the first embodiment, the slot padding byte generation unit 167 generates a plurality of types of slot padding bytes according to the remaining capacity. Then, the selection unit 1641 stores slot padding bytes according to the remaining capacity. As a result, when the receiving system 20 receives the slot padding byte included in the transmission main signal, it is possible to grasp how many bytes of the slot padding byte are stored.

(Receiver system)
FIG. 10 is a block diagram showing a configuration of reception system 20 shown in FIG. The reception system 20 shown in FIG. 10 comprises a reception processing unit 21, a transmission main signal reception unit 22, a TLV separation unit 23, an IP separation unit 24, an MMT separation unit 25, a decoder 26 and an additional information interpretation unit 27.

  The reception processing device 21 receives an incoming broadcast wave via a transmission line such as a broadcast network. The reception processing device 21 mainly transmits the broadcast wave by performing predetermined reception processing on the received broadcast wave and performing demodulation processing using a demodulation method corresponding to the modulation method assigned to each slot. Convert to a signal. The reception processing device 21 outputs the transmission main signal to the transmission main signal receiving device 22.

  FIG. 11 is a block diagram showing an example of a functional configuration of the transmission main signal receiving device 22 shown in FIG. The functions of the data separation unit 221, the NTP time reproduction unit 222, the slot information interpretation unit 223, and the slot padding byte removal unit 224 shown in FIG. 10 are realized by causing the FPGA to execute predetermined processing. The transmission main signal receiving apparatus 22 may realize the function shown in FIG. 11 by providing an LSI instead of the FPGA. Also, the transmission main signal receiving apparatus 22 may realize the function shown in FIG. 11 by software.

  The data separation unit 221 receives the transmission main signal output from the reception processing device 21. The data separation unit 221 separates slot information added to the slot from the slots included in the received transmission main signal. The data separation unit 221 outputs the separated slot information to the slot information interpretation unit 223.

  Further, the data separation unit 221 refers to the slot header of the slot included in the received transmission main signal, and extracts the main signal from the slot. The data separation unit 221 outputs the NTP packet included in the main signal to the NTP time recovery unit 222. Also, the data separation unit 221 outputs data other than the NTP packet included in the main signal to the slot padding byte removal unit 224.

  The NTP time reproduction unit 222 generates NTP time information based on the NTP packet output from the data separation unit 221. The NTP time recovery unit 222 adjusts a clock that is internally counted so that the generated NTP time information and time information that is internally counted are synchronized, and outputs the internally counted time information to the device of the subsequent stage. The clock is adjusted, for example, when NTP time information is received, compared with the value of time information counted internally, and if the time information counted internally is advanced, the clock is lowered, and if delayed, the clock is delayed Control the oscillation frequency of VCXO (Voltage Controlled Xtal Oscillator) so as to increase

  The slot information interpretation unit 223 receives the slot information output from the data separation unit 221. The slot information interpretation unit 223 interprets the signal point arrangement information and the TMCC information included in the slot information from the received slot information. The slot information interpretation unit 223 outputs the signal point arrangement information and the TMCC information to the slot padding byte removal unit 224.

  The slot padding byte removing unit 224 stores in advance a data string to be a slot padding byte, for example, “0x7e”. The slot padding byte removal unit 224 receives signal point arrangement information and TMCC information output from the slot information interpretation unit 223. The slot padding byte removing unit 224 recognizes the transmission mode of the transmission main signal, the position of the end of the last packet in the last effective slot in the frame, and the like based on the received signal point arrangement information and TMCC information. When the slot padding byte removing unit 224 receives the data output from the data separation unit 221, the slot padding byte removal unit 224 determines whether the stored data string is present at the end position. If there is a slot padding byte in the received data, the slot padding byte removing unit 224 removes the slot padding byte which is arranged by at most 3 bytes from the end position in the received data. The slot padding byte removing unit 224 outputs the data after removing the slot padding byte, that is, the TLV packet or the TLV NULL packet to the TLV separation device.

  The information stored in the slot padding byte removing unit 224 is not limited to only the data string. For example, the slot padding byte removing unit 224 needs 3 bytes of data including “0x7e” when the slot includes “0x7e”, and “0x7d” when the slot includes “0x7d”. If 2 bytes of data are unnecessary and the slot contains "0x7c", information may be stored in advance that 1 byte of unnecessary data is included including "0x7c". At this time, the slot padding byte removing unit 224 removes unnecessary data included in the data according to the slot padding byte included in the data output from the data separation unit 221.

  The TLV separation device 23 receives the TLV packet and the TLV NULL packet output from the transmission main signal reception device 22. The TLV separation device 23 extracts an IP packet from the received TLV packet. The TLV separation device 23 outputs the extracted IP packet to the IP separation device 24.

  The IP separation device 24 receives the IP packet output from the TLV separation device 23. The IP separation device 24 extracts the MMTP packet from the received IP packet. The IP separation device 24 outputs the taken MMTP packet to the MMT separation device 25.

  The MMT separation device 25 receives the MMTP packet output from the IP separation device 24. The MMT separation device 25 extracts the encoded signal and the additional information from the received MMTP packet. The MMT separation device 25 outputs the extracted encoded signal to the decoder 26, and outputs the extracted additional information to the additional information interpretation unit 27.

  The decoder 26 receives the encoded signal output from the MMT separation device 25 and converts the encoded signal into a video / audio signal by decoding in accordance with a preset scheme. The decoder 26 outputs the video / audio signal to the device at the subsequent stage.

  The additional information interpretation unit 27 receives the additional information output from the MMT separation device 25. The additional information interpretation unit 27 outputs the information read out from the received additional information to the device at the subsequent stage.

  As described above, in the receiving system 20 according to the first embodiment, the transmission main signal receiving apparatus 22 takes out the main signal from the slot. The transmission main signal reception device 22 stores in advance a data string to be a slot padding byte. Then, when the main signal includes the slot padding byte, the transmission main signal receiving apparatus 22 removes the slot padding byte from the main signal. As a result, the transmission main signal reception apparatus 22 can properly extract the TLV packet from the transmission main signal even when the slot constituting the transmission main signal includes the slot padding byte.

  Therefore, according to the transmission main signal receiving apparatus 22 according to the first embodiment, the broadcast wave in the receiving system 20 is obtained even if the transmission main signal transmitted from the transmission system 10 includes the slot padding byte. Normal reception can be realized.

Second Embodiment
In the first embodiment, it has been described that the transmission slotting apparatus 16 stores the slot padding byte in the vacant area when the remaining slot capacity of the last effective slot in the transmission main signal is less than 4 bytes. In the second embodiment, a case will be described where the transmission slotting apparatus 18 stores a packet in a slot so that the remaining slot capacity of the last effective slot in the transmission main signal is not less than 4 bytes.

  FIG. 12 is a block diagram showing an example of a functional configuration of the transmission slotting apparatus 18 according to the second embodiment. The functions of the slot number counter 161, setting information reception unit 162, capacity calculation unit 163, transmission slot generation unit 181, TLV packet reception unit 165, NTP packet generation unit 166, and TLV NULL packet generation unit 168 shown in FIG. Is realized by causing the FPGA to execute a predetermined process. The transmission slotting apparatus 18 may realize the function shown in FIG. 12 by providing an LSI instead of the FPGA. The transmission slotting apparatus 18 may also realize the function shown in FIG. 12 by software.

  The transmission slot generation unit 181 includes a selection unit 1811, a TLV byte number extraction unit 1642, a remaining amount calculation unit 1643, and a slot information multiplexing unit 1644.

  The selection unit 1811 stores the TLV packet, the NTP packet, or the TLV NULL packet in the slot represented by the number indicated by the count value output from the slot number counter 161.

  When the TLV packet, NTP packet or TLV NULL packet is stored in the slot, the selection unit 1811 subtracts the capacity of the stored data from the remaining capacity of the slot output from the remaining capacity calculation unit 1643 to obtain the current remaining capacity of the slot. Calculate Also, when the TLV packet, NTP packet or TLV NULL packet is stored in the slot, the selection unit 1811 subtracts the capacity of the stored data from the remaining capacity of the frame output from the remaining capacity calculation unit 1643 to obtain the current frame. Calculate the remaining capacity.

  Whether the selecting unit 1811 needs to store an NTP packet at the head of the slot represented by the number indicated by the count value output from the slot number counter 161 based on the setting information output from the setting information receiving unit 162 To judge. If it is determined that it is necessary, the selection unit 1811 instructs the NTP packet generation unit 166 to request an NTP packet. The selection unit 1811 stores the NTP packet output from the NTP packet generation unit 166 in the slot.

  The selection unit 1811 instructs the TLV NULL packet generation unit 168 to generate a TLV NULL packet of a capacity according to the remaining frame capacity and the remaining slot capacity. When the selecting unit 1811 receives the TLV NULL packet output from the TLV NULL packet generating unit 168, the selecting unit 1811 stores the received TLV NULL packet in the slot.

  Selection section 1811 outputs the slot storing the data to slot information multiplexing section 1644.

  Next, processing when the selecting unit 1811 shown in FIG. 12 stores the received packet in the slot will be described in detail. FIG. 13 is a flowchart showing processing when the selecting unit 1811 stores a packet in a slot. Note that, in FIG. 13, the case of one transmission mode in a frame will be described as an example.

  First, the selection unit 1811 receives the count value from the slot number counter 161 (step S131). The selection unit 1811 determines whether the received count value is 1 or not (step S132). If the received count value is 1 (Yes in step S132), the selecting unit 1811 recognizes that a new frame has started (step S133). If the received count value is not 1 (No in step S132), the selecting unit 1811 determines whether the NTP packet is stored in the slot indicated by the number indicated by the count value (step S134).

  If the NTP packet needs to be stored in the slot (Yes in step S134), the selecting unit 1811 stores the NTP packet at the beginning of the current slot (step S135). If it is not necessary to store the NTP packet in the slot (No in step S134), the selecting unit 1811 determines whether there is a TLV packet to be stored in the current slot (step S136).

  When the data is stored in the current slot, the selection unit 1811 subtracts the capacity of the stored data from the slot remaining capacity output from the remaining capacity calculating unit 1643, thereby updating the current slot remaining capacity. In addition, when data is stored in the current slot, the selection unit 1811 updates the current frame remaining capacity by subtracting the capacity of the stored data from the frame remaining capacity output from the remaining capacity calculation unit 1643 ( Step S137).

  Subsequently, the selection unit 1811 determines whether the remaining slot capacity in the current slot is 0 (step S138). If the slot remaining capacity in the current slot is 0 (Yes in step S138), the selecting unit 1811 determines whether the frame remaining capacity in the current frame is 0 (step S139). If the slot remaining capacity in the current slot is not 0 (Yes in step S138), the selecting unit 1811 shifts the processing to step S136.

  If the frame remaining capacity in the current frame is 0 (Yes in step S139), the selecting unit 1811 stands by until the next frame is started (step S1310). If the frame remaining capacity in the current frame is not 0 (No in step S139), the selecting unit 1811 shifts the processing to step S131.

  In step S136, when there is a TLV packet to be stored in the current slot (Yes in step S136), the selection unit 1811 determines whether the remaining frame capacity of the current frame is less than 4 bytes when the TLV packet is stored in the current slot. It is determined (step S1311). If there is no TLV packet to be stored in the current slot (No in step S136), the selecting unit 1811 stores the TLV NULL packet output from the TLV NULL packet generation unit 168 in the current slot (step S1312). It transfers to step S137.

  If the TLV packet is stored in the current slot and the remaining frame capacity of the current frame is less than 4 bytes (Yes in step S1311), the selecting unit 1811 links the current slot and the last valid slot in the current frame. The TLV NULL packet is stored in the concatenation slot (step S1313). When the TLV packet is stored in the current slot and the frame remaining capacity of the current frame is 4 bytes or more (No in step S1311), the selecting unit 1811 stores the TLV packet in the current slot as 0 in the current slot. It is determined whether it falls below (step S1314).

  When the TLV packet is stored in the current slot and the slot remaining capacity of the current slot falls below 0 (Yes in step S1314), the selecting unit 1811 selects the TLV packet as the first TLV packet of the capacity that can be stored in the current slot. It is divided into other second TLV packets (step S1315). The selection unit 1811 stores the divided first TLV packet in the current slot (step S1316), and the process proceeds to step S137. When the TLV packet is stored in the current slot and the slot remaining capacity of the current slot becomes 0 or more (No in step S1314), the selecting unit 1811 stores the TLV packet in the current slot (step S1317), and the process proceeds to step S137. Transition.

  In FIG. 13, the case where the number of transmission modes in a frame is one has been described as an example. However, it is not limited to this. The selection unit 1811 can perform the same operation even when there are two or more transmission modes in a frame.

  As described above, in the transmission system 10 according to the second embodiment, the capacity calculation unit 163 of the transmission slotting apparatus 18 calculates the frame main signal capacity and the slot main signal capacity. The remaining capacity calculation unit 1643 subtracts the data capacity of the TLV packet from the frame main signal capacity to calculate the frame remaining capacity, and subtracts the data capacity of the TLV packet from the slot main signal capacity to calculate the slot remaining capacity. calculate. When the TLV packet is stored in the slot and the remaining frame capacity of the current frame is less than 4 bytes, the selection unit 1811 stores the TLV NULL packet up to the end of the slot without storing the TLV packet in the slot. ing. This enables the transmission system 10 according to the second embodiment to store TLV packets and TLV NULL packets up to the end of the last valid slot in the frame.

  Therefore, according to the transmission system 10 of the second embodiment, it is possible to prevent the remaining capacity in the last effective slot in the frame from being less than 4 bytes.

  In the first and second embodiments, the case where the transmission slotting apparatus 16 and 18 store TLV packets in the main signal of the slot has been described as an example. However, the TLV packet is shown as an example of a variable-length packet including information indicating the data type and information indicating the number of data bytes. As a variable-length packet including information indicating the data type and information indicating the number of data bytes, for example, a GSE (Generic Stream Encapsulated) packet can be mentioned in addition to the TLV packet. The TLV multiplexer 15 may be described as a variable-length packet multiplexer.

  In the first and second embodiments, it is assumed that the minimum number of bytes that the TLV packet can take is 4 bytes, and whether or not the remaining capacity of the last effective slot is less than 4 bytes by the selection units 1641 and 1811. It is made to process according to. However, the number of bytes used by the selection units 1641 and 1811 as a criterion for determination is not limited to less than 4 bytes. The minimum number of bytes that a variable-length packet can take is not limited to 4 bytes. If the minimum number of bytes that can be taken by the variable-length packet is, for example, 2 bytes, the selecting units 1641 and 1811 perform processing in accordance with whether or not the remaining capacity of the last valid slot is less than 2 bytes. May be

While certain embodiments of the present invention have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the invention. These embodiments can be implemented in other various forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the invention described in the claims and the equivalents thereof as well as included in the scope and the gist of the invention.
The invention described in the claims at the time of filing of the original application is appended below.
[C1]
A variable-length packet multiplexer for generating a variable-length packet including information indicating the type of data and information indicating the number of bytes of the data;
And a transmission slotting apparatus for storing the variable-length packet in any of a plurality of slots constituting a transmission main signal.
The transmission slotting device
A capacity calculator configured to receive setting information of one frame of the transmission main signal and calculate a data capacity that can be included in the transmission main signal of one frame based on the setting information;
An extraction unit that extracts the number of bytes of the variable-length packet;
A remaining capacity calculation unit that calculates a remaining capacity of the transmission main signal based on the data capacity calculated by the capacity calculation unit and the number of bytes extracted by the extraction unit;
When the variable length packet is stored in any of the slots, if the remaining capacity of the transmission main signal is less than the minimum number of bytes that can be taken by the variable length packet, a null packet instead of the variable length packet is used to terminate the slot. Up to and including the slot storing the null packet, and
And a slot information multiplexing unit for multiplexing slot information in a slot output by the selection unit.
[C2]
The transmission system according to C1, wherein the variable-length packet is a TLV (Type Length Value) packet.
[C3]
When the variable length packet is stored in any of the slots, and the remaining capacity of the transmission main signal is less than 4 bytes, the selection unit stores a null packet up to the end of the slot instead of the variable length packet. The transmission system according to C2, wherein the slot storing the null packet is output.
[C4]
A plurality of combinations of modulation rate and modulation scheme are set in the setting information,
The capacity calculation unit calculates the data capacity for each of the combinations,
The remaining capacity calculation unit calculates the remaining capacity for each of the combinations,
When the variable length packet is stored in any of the slots, the selection unit determines whether the remaining capacity calculated for each combination is less than the minimum number of bytes of the variable length packet, and the remaining capacity is The transmission system according to any one of claims C1 to C3 wherein a null packet is stored up to the end of the slot instead of the variable length packet if the number of bytes of the variable length packet is less than the minimum number of bytes.
[C5]
The transmission system according to any one of C1 to C4, wherein the selection unit stores an NTP packet at the beginning of a first slot constituting the transmission main signal of one frame.
[C6]
A capacity calculator configured to receive setting information of one frame of a transmission main signal configured of a plurality of slots, and calculate a data capacity that can be included in the transmission main signal of one frame based on the setting information; ,
An extraction unit for extracting the number of bytes of a variable-length packet including information indicating the type of data and information indicating the number of bytes of the data;
A remaining capacity calculation unit that calculates a remaining capacity of the transmission main signal based on the data capacity calculated by the capacity calculation unit and the number of bytes extracted by the extraction unit;
When the variable length packet is stored in any of the slots, if the remaining capacity of the transmission main signal is less than the minimum number of bytes that can be taken by the variable length packet, a null packet instead of the variable length packet is used to terminate the slot. Up to and including the slot storing the null packet, and
A transmission slotting apparatus comprising: a slot information multiplexing unit that multiplexes slot information in a slot output by the selection unit.
[C7]
The transmission slotting device according to C6, wherein the variable length packet is a TLV (Type Length Value) packet.
[C8]
When the variable length packet is stored in any of the slots, and the remaining capacity of the transmission main signal is less than 4 bytes, the selection unit stores a null packet up to the end of the slot instead of the variable length packet. The transmission slotting apparatus according to C7, wherein the slot storing the null packet is output.
[C9]
A plurality of combinations of modulation rate and modulation scheme are set in the setting information,
The capacity calculation unit calculates the data capacity for each of the combinations,
The remaining capacity calculation unit calculates the remaining capacity for each of the combinations,
When the variable length packet is stored in any of the slots, the selection unit determines whether the remaining capacity calculated for each combination is less than the minimum number of bytes of the variable length packet, and the remaining capacity is The transmission slotting apparatus according to any one of C6 to C8, wherein a null packet is stored up to the end of the slot instead of the variable length packet if the number of bytes of the variable length packet is less than the minimum number of bytes.
[C10]
The transmission slotting apparatus according to any one of C6 to C9, wherein the selection unit stores an NTP packet at the beginning of a first slot constituting the transmission main signal of one frame.
[C11]
Calculating a data capacity that can be included in the transmission main signal of one frame based on setting information for one frame of the transmission main signal configured of a plurality of slots;
Extracting the number of bytes of a variable-length packet including information indicating the type of data and information indicating the number of bytes of the data;
The remaining capacity of the transmission main signal is calculated based on the data capacity and the number of bytes,
Store the variable length packet in one of the slots,
When the variable length packet is stored in any of the slots, if the remaining capacity of the transmission main signal is less than the minimum number of bytes that can be taken by the variable length packet, a null packet is used instead of the variable length packet. Store to the end,
A transmission slot creation method for multiplexing slot information in a slot storing the null packet.

  DESCRIPTION OF SYMBOLS 10 ... Transmission system, 11 ... Encoder, 12 ... Additional information generation apparatus, 13 ... MMT multiplexer, 14 ... IP multiplexer, 15 ... TLV multiplexer, 16, 18 ... Transmission slotting apparatus, 161 ... Slot number Counter 162: setting information reception unit 163: capacity calculation unit 164, 181 transmission slot generation unit 1641, 1811 selection unit 1642 byte number extraction unit 1643 remaining amount calculation unit 1644: slot information multiplexing , 165 ... TLV packet receiver, 166 ... NTP packet generator, 167 ... slot padding byte generator, 168 ... TLV NULL packet generator, 17 ... transmission processor, 20 ... reception system, 21 ... reception processor, 22 ... Transmission main signal reception device, 221 ... Data separation unit, 222 ... Time reproduction unit, 223 ... Slot information Interpretation unit, 224 ... slot padding bytes removal unit, 23 ... TLV separator, 24 ... IP separator, 25 ... MMT separator, 26 ... decoder, 27 ... additional information interpreter

Claims (11)

A variable-length packet multiplexer for generating a variable-length packet including information indicating the type of data and information indicating the number of bytes of the data;
A transmission slotting apparatus for storing the variable-length packet in any one of a plurality of slots constituting a transmission main signal;
The transmission slotting device
A capacity calculator configured to receive setting information of one frame of the transmission main signal and calculate a data capacity that can be included in the transmission main signal of one frame based on the setting information;
An extraction unit that extracts the number of bytes of the variable-length packet;
A remaining capacity calculation unit that calculates a remaining capacity of the transmission main signal based on the data capacity calculated by the capacity calculation unit and the number of bytes extracted by the extraction unit;
When the variable length packet is stored in any one of the slots, if the remaining capacity of the transmission main signal is less than the minimum number of bytes that the variable length packet can take, the null packet is replaced with the slot instead of the variable length packet. A selection unit which stores up to the end of the frame and outputs a slot storing the null packet;
And a slot information multiplexing unit for multiplexing slot information in a slot output by the selection unit.   The transmission system according to claim 1, wherein the variable-length packet is a TLV (Type Length Value) packet.   When the variable length packet is stored in any one of the slots, when the remaining capacity of the transmission main signal is less than 4 bytes, the selection unit replaces the variable length packet with a null packet until the end of the slot. The transmission system according to claim 2, wherein the slot storing the null packet is output. A plurality of combinations of coding rate and modulation scheme are set in the setting information,
The capacity calculation unit calculates the data capacity for each of the combinations,
The remaining capacity calculation unit calculates the remaining capacity for each of the combinations,
The selection unit, when storing the variable-length packet to said one of the slots in each of the combinations, whether the remaining capacity calculated for thereby corresponding combination is less than the minimum number of bytes of the variable-length packets The transmission system according to any one of claims 1 to 3, wherein if the remaining capacity is less than the minimum number of bytes of the variable-length packet, a null packet is stored up to the end of the slot instead of the variable-length packet. .   The transmission system according to any one of claims 1 to 4, wherein the selection unit stores an NTP packet at the beginning of a first slot constituting the transmission main signal of one frame. A capacity calculator configured to receive setting information of one frame of a transmission main signal configured of a plurality of slots, and calculate a data capacity that can be included in the transmission main signal of one frame based on the setting information; ,
An extraction unit for extracting the number of bytes of a variable-length packet including information indicating the type of data and information indicating the number of bytes of the data;
A remaining capacity calculation unit that calculates a remaining capacity of the transmission main signal based on the data capacity calculated by the capacity calculation unit and the number of bytes extracted by the extraction unit;
When the variable length packet is stored in any one of the slots, if the remaining capacity of the transmission main signal is less than the minimum number of bytes that the variable length packet can take, the null packet is replaced with the slot instead of the variable length packet. A selection unit which stores up to the end of the frame and outputs a slot storing the null packet;
A transmission slotting apparatus comprising: a slot information multiplexing unit that multiplexes slot information in a slot output by the selection unit.   The transmission slotting apparatus according to claim 6, wherein the variable-length packet is a TLV (Type Length Value) packet.   When the variable length packet is stored in any one of the slots, when the remaining capacity of the transmission main signal is less than 4 bytes, the selection unit replaces the variable length packet with a null packet until the end of the slot. 8. The transmission slotting apparatus according to claim 7, which stores and outputs a slot storing the null packet. A plurality of combinations of coding rate and modulation scheme are set in the setting information,
The capacity calculation unit calculates the data capacity for each of the combinations,
The remaining capacity calculation unit calculates the remaining capacity for each of the combinations,
The selection unit, when storing the variable-length packet to said one of the slots in each of the combinations, whether the remaining capacity calculated for thereby corresponding combination is less than the minimum number of bytes of the variable-length packets The transmission slot according to any one of claims 6 to 8, wherein if the remaining capacity is less than the minimum number of bytes of the variable-length packet, a null packet is stored up to the end of the slot instead of the variable-length packet. Device.   The transmission slotting apparatus according to any one of claims 6 to 9, wherein the selection unit stores an NTP packet at the beginning of a first slot constituting the transmission main signal of one frame. Calculating a data capacity that can be included in the transmission main signal of one frame based on setting information for one frame of the transmission main signal configured of a plurality of slots;
Extracting the number of bytes of a variable-length packet including information indicating the type of data and information indicating the number of bytes of the data;
The remaining capacity of the transmission main signal is calculated based on the data capacity and the number of bytes,
Store the variable length packet in any one of the slots,
When the variable length packet is stored in any one of the slots, if the remaining capacity of the transmission main signal is less than the minimum number of bytes that the variable length packet can take, the null packet is replaced with the null packet instead of the variable length packet. Store to the end of the slot,
A transmission slot creation method for multiplexing slot information in a slot storing the null packet.