Remultiplexing device, distribution system, and program

Abstract

To prevent a buffer underflow in a modulation device.SOLUTION: A re-multiplexing apparatus 12 comprises: a XMI packetized part 107 that generates a XMI packet housing a content signal in each hierarchy; and a packet transmission schedular part 112 that repeatedly outputs a first packet set that is formed by the XMI packet of one first hierarchy in the case where the number of XMI packets of the first hierarchy and a second hierarchy is K and L (K<L) in 1O FDM frames and the XMI packet of the second hierarchy of ceil (L / K), and a second packet set formed by the XMI packet of one first hierarchy and the XMI packet of the second hierarchy of a floor(L / K).SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a remultiplexing device, an OFDM (Orthogonal Frequency Division Multiplexing) frame generation device, and a program.

Background Art

[0002] In the advanced system of next-generation terrestrial digital television broadcasting (hereinafter referred to as the "advanced system"), it is considered to use IP (Internet Protocol)-based XMI (Extensible Modulator Interface) packets as a program transmission format from a performance venue to a broadcasting station (transmission station) (see, for example, Patent Document 1).

[0003] In the advanced system, similar to conventional terrestrial digital broadcasting, a method of multiplexing and transmitting a plurality of layers (services) such as a layer for mobile reception (mobile reception service) and a layer for fixed reception (fixed reception service) is being considered. A remultiplexing device is a device that multiplexes these multiple services and the control signal of the modulator at the broadcasting station and sends them as a stream of one program transmission signal toward the broadcasting station. In conventional terrestrial digital broadcasting, TS (Transport Stream) is multiplexed to output a broadcast TS, but in the advanced system, a method of multiplexing MMT (MPEG Media Transport) / TLV (Type Length Value) to output an XMI packet is being considered.

[0004] The current broadcast TS and XMI being considered in the advanced system form a multiplex frame that corresponds one-to-one with an OFDM frame in advance in the remultiplexing device, divides it into a fixed length for easy assembly at the broadcasting station, and further adds control information of the modulator and transmits it at a fixed rate in order to easily form the same OFDM waveform in the modulators of multiple broadcasting stations.

[0005] The modulation device of the broadcasting station constructs an OFDM frame from the received broadcast TS packet or XMI packet, emits it as radio waves, and delivers the radio waves to each household.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] In the remultiplexing device described in Patent Document 1, depending on specific parameters, the output ratio of XMI packets for each layer does not become constant at the end, and an operation called buffer underflow occurs due to the input packets being insufficient compared to the required packets in the buffer area at the input stage of the modulation device that receives the packets, and the modulation device may not operate

[0008] An object of the present invention made in view of such circumstances is to provide a remultiplexing device, a modulation device, and a program capable of preventing buffer underflow.

Means for Solving the Problems

[0009] A remultiplexing device according to an embodiment is a remultiplexing device that transmits packets to a modulation device, and includes an XMI packetization unit that generates XMI packets storing content signals for each layer in FEC block format, and when the number of XMI packets for the first layer and the second layer in one OFDM frame are K and L (K < L) respectively, a first packet set consisting of one XMI packet of the first layer and ceil(L / K) XMI packets of the second layer, and a second packet set consisting of one XMI packet of the first layer and floor(L / K) XMI packets of the second layer, and a packet transmission scheduler unit that repeatedly outputs them.

[0010] Also, a remultiplexing device according to an embodiment is a remultiplexing device that transmits packets to a modulation device, and includes an XMI packetization unit that generates XMI packets storing hierarchical content signals in the form of FEC blocks, and when the number of XMI packets in the first layer, second layer, and third layer in one OFDM frame is K, L, and M (K < M < L) respectively, a first packet set consisting of one XMI packet of the first layer, ceil(L / K) XMI packets of the second layer, and ceil(M / K) XMI packets of the third layer, a second packet set consisting of one XMI packet of the first layer, ceil(L / K) XMI packets of the second layer, and floor(M / K) XMI packets of the third layer, and a third packet set consisting of one XMI packet of the first layer, floor(L / K) XMI packets of the second layer, and floor(M / K) XMI packets of the third layer, and a packet transmission scheduler unit that repeatedly outputs them.

[0011] Also, one according to an embodiment Distribution system is The above-mentioned remultiplexing device, and from the said remultiplexing device, a modulation device that receives STLP packets storing hierarchical content signals in the form of TLV packets and equipped , The modulation device is and includes a packet reception unit that converts the received STLP packets into XMI packets storing hierarchical content signals in the form of FEC blocks, a data processing unit that performs error correction coding processing and interleaving processing on the FEC blocks, and an OFDM frame configuration unit that inserts a TMCC signal and a pilot signal into the data processed by the data processing unit to configure an OFDM frame.

[0012] Also, a program according to an embodiment causes a computer to function as the above remultiplexing device.

Advantages of the Invention

[0014] According to the present invention, it is possible to prevent buffer underflow in the modulation device.

Brief Description of the Drawings

[0015] [Figure 1] It is a block diagram showing a configuration example of a distribution system according to an embodiment of the present invention. [Figure 2] It is a block diagram showing a configuration example of a remultiplexing device according to an embodiment of the present invention. [Figure 3] It is a diagram showing the configuration of a TLV packet generated by the TLV packetization unit shown in FIG. 2. [Figure 4] It is a diagram showing a configuration example of an FEC block configured by the FEC block configuration unit shown in FIG. 2. [Figure 5] It is a diagram showing a configuration example of a hierarchical multiplexed frame configured by the hierarchical frame configuration unit shown in FIG. 2. [Figure 6] It is a diagram showing a configuration example of an XMI packet used in a distribution system according to an embodiment of the present invention. [Figure 7] It is a diagram showing an example of division of a hierarchical frame by the XMI packetization unit shown in FIG. 2. [Figure 8] It is a diagram showing an output example of an XMI packet by a conventional packet transmission scheduler unit when the number of layers is 2. [Figure 9] It is a diagram showing an output example of an XMI packet by a conventional packet transmission scheduler unit when the number of layers is 3. [Figure 10] It is a diagram showing an output example of an XMI packet by the packet transmission scheduler unit shown in FIG. 2 when the number of layers is 2. [Figure 11] It is a diagram showing an output example of an XMI packet by the packet transmission scheduler unit shown in FIG. 2 when the number of layers is 3. [Figure 12] It is a block diagram showing a configuration example of a modulation device according to an embodiment of the present invention. [Figure 13] It is a diagram showing an FEC block and an OFDM frame. [Figure 14] It is a diagram showing a configuration example of an STLP packet used in a distribution system according to a modified example of the present invention.

Embodiments for Carrying Out the Invention

[0016] Hereinafter, an embodiment will be described in detail with reference to the drawings.

[0017] (Distribution System) FIG. 1 is a diagram showing a configuration example of a distribution system 1 according to an embodiment of the present invention. The distribution system 1 shown in FIG. 1 includes a performance venue 10 and a broadcasting station 20. The performance venue 10 includes a multiplexing device 11 (11a, 11b) and a remultiplexing device 12. The broadcasting station 20 includes a modulation device 21 and a transmission device 22. The performance venue 10 and the broadcasting station 20 are connected via a content transmission line 30 as a network.

[0018] The performance venue 10 performs hierarchical transmission for transmitting data of a plurality of layers through one channel. In FIG. 1, data of two layers, namely, layer A and layer B, are transmitted, but the number of layers of the hierarchical transmission is not limited to two layers. Further, in order to deliver information with high immediacy such as an emergency earthquake warning to viewers with low latency, the performance venue 10 provides a low-latency transmission channel called LLch (Low Latency channel) that does not perform processing such as time interleaving, and transmits LLch data through the same one channel as layer A and layer B.

[0019] The multiplexing device 11a multiplexes the content signal (video / audio signal and subtitle signal) for layer A input from the outside, packetizes it into packets of a predetermined format, and outputs it to the remultiplexing device 12 as a package for layer A.

[0020] Similarly, the multiplexing device 11b multiplexes the content signal for layer B input from the outside, packetizes it into packets of a predetermined format, and outputs it to the remultiplexing device 12 as a package for layer B.

[0021] In this embodiment, the multiplexer 11 packets into MMTP (MMT Protocol) packets, which are MMT (MPEG Media Transport) format packets. The transmission path between the multiplexer 11 and the remultiplexer 12 is an IP (Internet Protocol) transmission path, and the multiplexer 11 stores the MMTP packets in IP packets and outputs them to the remultiplexer 12 as MMTP / IP packets.

[0022] The remultiplexer 12 generates XMI packets from the MMTP / IP packets input from the multiplexers 11a and 11b, and from the MMTP / IP packets of the LLch signal, and further remultiplexes them into one system before outputting them to the broadcasting station 20 as a content transmission signal.

[0023] The modulation device 21 modulates the XMI packets input from the remultiplexer 12 to form an OFDM frame, which is then output to the transmitter 22.

[0024] The transmitting device 22 generates a broadcast wave corresponding to the packet input from the modulation device 21 and transmits it to the outside of the broadcasting station 20 via the antenna.

[0025] (remultiplexer) Next, a remultiplexing device 12 according to one embodiment of the present invention will be described. The remultiplexing device 12 does not need to be dedicated hardware, but may be in the form of computer software.

[0026] Figure 2 is a block diagram showing an example configuration of the remultiplexer 12 when the number of layers is 2. The remultiplexer 12 shown in Figure 2 comprises a packet filter 101 (101a to 101c), an IP header compression unit 102 (102a to 102d), a TLV (Type Length Value) packetization unit 103 (103a to 103d), a FIFO (First in, First Out) buffer 104 (104a to 104d), an FEC (Forward Error Correction) block configuration unit 105 (105a, 105b), a layer-specific frame configuration unit 106 (106a, 106b), an XMI packetization unit 107, an L0 symbol configuration unit 108, an L1 symbol configuration unit 109, a synchronous control XMI packet configuration unit 110, a staff XMI packet configuration unit 111, and a packet transmission scheduler unit 112.

[0027] The packet filter 101a, IP header compression unit 102a, TLV packetization unit 103a, FIFO buffer 104a, FEC block configuration unit 105a, and hierarchical frame configuration unit 106a are provided in accordance with the A layer.

[0028] The packet filter 101a receives MMTP / IP packets containing content signals for the A layer from the multiplexer 11a. Based on the source IP address, destination IP address, protocol type, source port number, destination port number, etc. of the IP header of the input MMTP / IP packets, the packet filter 101a selects (filters) the packets to be transmitted and outputs the selected MMTP / IP packets to the IP header compression unit 102a.

[0029] The IP header compression unit 102a compresses the IP header of the MMTP / IP packet input from the packet filter 101a as needed, and outputs it to the TLV packetization unit 103a.

[0030] The TLV packetization unit 103a encapsulates the MMTP / IP packet input from the IP header compression unit 102a into a variable-length TLV packet to generate a TLV packet, which is then output to the FIFO buffer 104a.

[0031] Figure 3 shows an example of a TLV packet configuration. In the following, the numbers assigned to each field (area) indicate an example of the number of bits in each field.

[0032] As shown in Figure 3, a TLV packet includes a reserved area, a packet type area, a data length area, and a data area. The packet type indicates the type of TLV packet. The packet type identifies whether the TLV packet is IPv4, IPv6, or compressed IP. The data length indicates the size of the data stored in the data area. The TLV packetization unit 103a stores the IP packet input from the IP header compression unit 102a in the data area. Note that, for example, all bits in the reserved area may be set to "1".

[0033] Referring again to Figure 2, the FIFO buffer 104a stores the TLV packets input from the TLV packetization unit 103a and outputs the stored TLV packets to the FEC block configuration unit 105a in the order they were stored.

[0034] The FEC block constructor 105a constructs FEC blocks at regular intervals from TLV packets input from the FIFO buffer 104a and outputs them to the hierarchical frame constructor 106a.

[0035] Figure 4 shows an example of the configuration of an FEC block. As shown in Figure 4, an FEC block includes an FEC block header area, a main signal area, a BCH parity area, and an LDPC (Low Density Parity Check) parity area, and may also include a stuff bit area. Note that in Figure 4, the main signal area and BCH parity area are shown as one each, but each may be divided into multiple parts.

[0036] The main signal area stores the TLV packets output from the FIFO buffer 104a. The FEC block header area stores information indicating the starting position 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, expressed as the number of bytes from the beginning of the FEC block excluding the FEC block header. The BCH parity area, staff bit area, and LDPC parity area all store bit "1".

[0037] The size of the FEC block is set to one of three sizes depending on the code length (Short, Middle, Long) of the LDPC encoding performed by the modulation device 21. The sizes of the main signal area, the stuff bit area, and the LDPC parity area are determined according to the coding rate. The BCH parity area is fixed at 24 bytes.

[0038] The FEC block component 105a concatenates the TLV packets input from the FIFO buffer 104a in output order and stores them in the main signal area, setting the value of the leading TLV instruction field for each FEC block. If no TLV packets to be stored in the main signal area exist in the FIFO buffer 104a, the FEC block component 105a stores a null-type TLV packet in the main signal area.

[0039] Referring again to Figure 2, the hierarchical frame constructor 106a constructs hierarchical frames from the FEC blocks input from the FEC block constructor 105a and outputs them to the XMI packetization unit 107.

[0040] Figure 5 shows the structure of a hierarchical frame. As shown in Figure 5, a hierarchical frame is composed of an FEC block area. The FEC block area stores linked FEC blocks output from the FEC block component 105a, or fragments of FEC blocks. The size of the hierarchical frame is determined according to the modulation scheme, FFT size, guard interval ratio, pilot signal ratio, and number of segments.

[0041] The hierarchical frame configuration unit 106a connects the FEC blocks input from the FEC block configuration unit 105a in the order they were input and stores them in the FEC block area.

[0042] Referring again to Figure 2, the packet filter 101b, IP header compression unit 102b, TLV packetization unit 103b, FIFO buffer 104b, FEC block configuration unit 105b, and hierarchical frame configuration unit 106b are provided in accordance with the B layer. Since the configuration corresponding to the A layer and the configuration corresponding to the B layer are the same, the explanation of the configuration corresponding to the B layer will be omitted.

[0043] The XMI packetization unit 107 generates XMI packets that store hierarchical content signals in FEC block format.

[0044] Figure 6 shows the packet structure of an XMI packet. An XMI packet includes a header and a data unit area. The header of an XMI packet includes an IPv4 header, a UDP header, an MMTP packet header (MMTP header), and an XMI header. There are four types of XMI packets: an XMI packet in which synchronization control information is included in the data unit area (Figure 6(a)), an XMI packet in which a data unit is included in the data unit area (Figure 6(b)), an XMI packet in which a data unit and stuff bits are included in the data unit area (Figure 6(c)), and an XMI packet in which the data unit area consists of stuff bits (Figure 6(d)).

[0045] Synchronization control information includes parameters for configuring OFDM frames, the timing for transmitting OFDM frames, and TMCC (Transmission and Multiplexing Configuration and Control) information. Data units are data obtained by dividing hierarchical frames into predetermined sizes. In addition, in Figures 6(b), (c), and (d), an LLch information area is provided for storing L0 and L1 symbols.

[0046] The XMI header contains data unit type information that indicates the type of data to be stored in the data unit area of ​​the XMI packet. Therefore, when the synchronous control XMI packet constructor 110 constructs the XMI packet, it sets the data unit type information to a value corresponding to the synchronous control XMI packet (e.g., '0'). The XMI packetization unit 107 also sets the data unit type information to a value corresponding to an A-level XMI packet (e.g., '1') or a B-level XMI packet (e.g., '2'). The staff XMI packet constructor 111 also sets the data unit type information to a value corresponding to the staff XMI packet (e.g., '4' or '15') when constructing the XMI packet. In this way, the type of data to be stored in the XMI packet can be identified.

[0047] Figure 7 shows an example of hierarchical frame division by the XMI packetization unit 107. As shown in Figure 7, the XMI packetization unit 107 divides the hierarchical frame into predetermined sizes (10448 bits in Figure 7) to form data units. The XMI packetization unit 107 stores the data units in the data unit area of ​​the XMI packet. As shown in Figure 7, the last data unit may be smaller than the predetermined size (less than 10448 bits in Figure 7). In this case, the XMI packetization unit 107 adds predetermined bits (stuff bits) to the data unit that is smaller than the predetermined size to make it the predetermined size and stores it in the data unit area.

[0048] The packet filter 101c, IP header compression units 102c, 102d, TLV packetization units 103c, 103d, FIFO buffers 104c, 104d, L0 symbol configuration unit 108, and L1 symbol configuration unit 109 are provided in correspondence with LLch.

[0049] Packet filter 101c receives MMTP / IP packets on LLch. Based on the source IP address, destination IP address, protocol type in the IP header of the input IP packet, the source port number, destination port number in the UDP header, etc., packet filter 101c selects (filters) the packets to be transmitted and outputs the selected MMTP / IP packets to IP header compression unit 102c or IP header compression unit 102d.

[0050] The IP header compression unit 102c compresses the IP header of the MMTP / IP packet input from the packet filter 101c as needed and outputs it to the TLV packetization unit 103c. The IP header compression unit 102d compresses the IP header of the MMTP / IP packet input from the packet filter 101c as needed and outputs it to the TLV packetization unit 103d.

[0051] The TLV packetization unit 103c encapsulates the MMTP / IP packet input from the IP header compression unit 102c into a TLV packet to generate a TLV packet, which is then output to the FIFO buffer 104c. The TLV packetization unit 103d encapsulates the MMTP / IP packet input from the IP header compression unit 102d into a TLV packet to generate a TLV packet, which is then output to the FIFO buffer 104d.

[0052] The FIFO buffer 104c stores the TLV packets input from the TLV packetization unit 103c and outputs the stored TLV packets to the L0 symbol constructor 108 in the order they were stored. The FIFO buffer 104d stores the TLV packets input from the TLV packetization unit 103d and outputs the stored TLV packets to the L1 symbol constructor 109 in the order they were stored.

[0053] The L0 symbol constructor 108 constructs a symbol (L0 symbol) from the TLV packet input from the FIFO buffer 104c and outputs it to the XMI packetization unit 107. The L1 symbol constructor 109 constructs a symbol (L1 symbol) from the TLV packet input from the FIFO buffer 104d and outputs it to the XMI packetization unit 107.

[0054] L0 symbols are transmitted, for example, on 9 segments for partial reception, while L1 symbols are transmitted on the remaining 24 or 26 segments. Therefore, packet filtering by packet filter 101c is also performed according to this allocation.

[0055] The number of bits in an L0 symbol and an L1 symbol per 1 OFDM frame is 4 × N × 223 bits for 8K FFT, 8 × N × 111 bits for 16K FFT, and 16 × 55 × N bits for 32K FFT, where N is the number of segments. In other words, when 9 segments are allocated to an L0 symbol and 24 segments to an L1 symbol, in the case of 16K FFT, the size of an L0 symbol per 1 OFDM frame is 7992 bits and the size of an L1 symbol is 21312 bits. The L0 symbol configuration unit 108 configures an L0 symbol of this size by allocating each byte of the TLV packet input from the FIFO buffer 104c in MSB (Most Significant Bit) first, and outputs it to the packet transmission scheduler unit 112. Similarly, the L1 symbol constructor 109 assigns each byte of the TLV packet input from the FIFO buffer 104d in MSB-first order to an L1 symbol of this size, constructs an L1 symbol, and outputs it to the packet transmission scheduler 112. Here, MSB-first means that the most significant bit of each byte constituting the TLV packet is placed at the beginning of the bit sequence.

[0056] The synchronous control XMI packet configuration unit 110 generates an XMI packet (synchronous control XMI packet) in which synchronous control information, which indicates transmission control information such as transmission parameters for the modulation device 21 to configure OFDM frames, the timing for transmitting OFDM frames, and TMCC information, is stored in the data unit area, and outputs it to the packet transmission scheduler unit 112. If the synchronous control information does not meet the predetermined size for dividing the hierarchical frame, the synchronous control XMI packet configuration unit 110 adds stuff bits to the synchronous control information to make it the predetermined size and stores it in the data unit area.

[0057] The staff XMI packet constructor 111 constructs an XMI packet (staff XMI packet) in which only staff bits of the same size as the data unit are stored in the data unit area, and outputs it to the packet transmission scheduler 112. The staff XMI packet is used to keep the number of XMI packets output per second by the remultiplexer 12 constant, even when the modulation scheme and coding rate are different.

[0058] The packet transmission scheduler unit 112 outputs XMI packets input from the XMI packetization unit 107, XMI packets input from the synchronous control XMI packet configuration unit 110 (synchronous control XMI packets), and XMI packets input from the staff XMI packet configuration unit 111 (staff XMI packets) to the modulation device 21.

[0059] The packet transmission scheduler unit 112 outputs one synchronous control XMI packet at the beginning of the OFDM frame. Subsequently, the packet transmission scheduler unit 112 outputs XMI packets for each layer (A-layer XMI packets and B-layer XMI packets). Once all XMI packets for each layer have been output, the packet transmission scheduler unit 112 outputs staff XMI packets so that the number of XMI packets constituting the OFDM frame remains constant. The packet transmission scheduler unit 112 may also output, for example, at least one staff XMI packet to indicate the end of outputting XMI packets within the OFDM frame.

[0060] (Conventional XMI packet transmission algorithm) For comparison with the present invention, a conventional XMI packet transmission algorithm of a packet transmission scheduler unit will be described.

[0061] Figure 8 shows an example of XMI packet output by a conventional packet transmission scheduler when the number of layers is 2. Let K and L be the number of XMI packets in layer A and layer B in one OFDM frame. The conventional packet transmission scheduler outputs ceil(L / K) XMI packets from layer B for every XMI packet from layer A, so that the output ratio (number of outputs per unit time) of XMI packets from each layer is approximately constant. Here, ceil(x) is a ceiling function and represents the smallest integer greater than or equal to the argument x. When the OFDM transmission parameters are the values ​​shown in Table 1, as shown in Figure 8, K=311, L=1050, and ceil(L / K)=4.

[0062] [Table 1]

[0063] As shown in Figure 8, in the example, the conventional packet transmission scheduler repeatedly outputs a packet set consisting of one A-layer XMI packet and four B-layer XMI packets 262 times. However, if L / K is not an integer, as in this example, a fractional amount will be generated at the end. To send all of the fractional XMI packets, the conventional packet transmission scheduler then outputs one A-layer XMI packet, two B-layer XMI packets, and finally outputs the remaining 48 A-layer XMI packets.

[0064] Figure 9 shows an example of XMI packet output by a conventional packet transmission scheduler when the number of layers is 3. Let the number of XMI packets in layers A, B, and C in one OFDM frame be K, L, and M, respectively. The conventional packet transmission scheduler outputs ceil(L / K) XMI packets from layer B and ceil(M / K) XMI packets from layer C for each XMI packet from layer A, so that the output ratio (number of outputs per unit time) of XMI packets for each layer is approximately constant. Here, if the OFDM transmission parameters are the values ​​shown in Table 2, then as shown in Figure 9, K=311, L=1050, M=388, and ceil(L / K)=4, ceil(M / K)=2.

[0065] [Table 2]

[0066] As shown in Figure 9, the conventional packet transmission scheduler repeatedly outputs a packet set consisting of one A-layer XMI packet, four B-layer XMI packets, and two C-layer XMI packets 194 times. In cases where L / K and M / K are not integers, as in this example, a fractional amount remains at the end. To send all the fractional XMI packets, the conventional packet transmission scheduler then repeats a packet set consisting of one A-layer XMI packet and four B-layer XMI packets 68 times. After outputting one A-layer XMI packet and two B-layer XMI packets, it outputs the remaining 48 A-layer XMI packets.

[0067] By outputting XMI packets in this manner, the output ratio of XMI packets at each layer remains constant, except when sending fractional packets. However, this results in a biased transmission where A-layer XMI packets are consecutive at the end of the transmission. This can cause a buffer underflow, where the number of incoming packets falls short of the required number of packets in the buffer area of ​​the input stage of the receiving modulator, potentially causing the modulator to malfunction.

[0068] (XMI Packet Transmission Algorithm According to the Present Invention) Therefore, the packet transmission scheduler unit 112 according to the present invention changes the XMI packet transmission algorithm.

[0069] First, the case where the number of layers is 2 will be described. In 1 OFDM frame, let the number of XMI packets in the first layer (layer A) be K, and the number of XMI packets in the second layer (layer B) that is more than the first layer be L. That is, K < L. The packet transmission scheduler unit 112 repeatedly outputs a first packet set composed of one XMI packet of layer A and ceil(L / K) XMI packets of layer B, and a second packet set composed of one XMI packet of layer A and floor(L / K) XMI packets of layer B. Here, floor(x) is the floor function, which represents the largest integer less than or equal to the argument x.

[0070] The packet transmission scheduler unit 112 outputs the first packet set and the second packet set a predetermined number of times each. For example, the packet transmission scheduler unit 112 may repeatedly output one of the first packet set and the second packet one or more times and then repeatedly output the other one or more times, or may repeatedly output the first packet set collectively and then repeatedly output the second packet set collectively, or may repeatedly output the second packet set collectively and then repeatedly output the first packet set collectively. Also, in each packet set, the position of the XMI packet of the first layer is not limited to the head and may be arranged at any position.

[0071] FIG. 10 is a diagram showing an output example of XMI packets by the packet transmission scheduler unit 112 according to the present invention when the number of layers is 2. Here, similar to the example shown in FIG. 8, if the number of XMI packets of layer A in 1 OFDM frame is K = 311 and the number of XMI packets of layer B is L = 1050, then ceil(L / K) = 4 and floor(L / K) = 3.

[0072] In the example shown in FIG. 10, the packet transmission scheduler unit 112 repeatedly outputs a first packet set consisting of one XMI packet of the A layer and four XMI packets of the B layer 117 times, and then repeatedly outputs a second packet set consisting of one XMI packet of the A layer and three XMI packets of the B layer 194 times.

[0073] The number of repetitions K* of the second packet set and the number of repetitions K** of the first packet set are represented by the following equations. K*=(K×floor(L / K))+K-L=194 K**=K-K*=117

[0074] Next, the case where the number of layers is 3 will be described. Let the number of XMI packets of the first layer (A layer) in one OFDM frame be K, the number of XMI packets of the second layer (B layer) with more XMI packets than the first layer be L, and the number of XMI packets of the third layer (C layer) with more XMI packets than the first layer and less than the second layer be M. That is, K<M<L. The packet transmission scheduler unit 112 repeatedly outputs a first packet set consisting of one XMI packet of the A layer, ceil(L / K) XMI packets of the B layer, and ceil(M / K) XMI packets of the C layer, a second packet set consisting of one XMI packet of the A layer, ceil(L / K) XMI packets of the B layer, and floor(M / K) XMI packets of the C layer, and a third packet set consisting of one XMI packet of the A layer, floor(L / K) XMI packets of the B layer, and floor(M / K) XMI packets of the C layer. The packet transmission scheduler unit 112 outputs the first packet set, the second packet set, and the third packet set a predetermined number of times respectively.

[0075] Figure 11 shows an example of XMI packet output by the packet transmission scheduler unit 112 according to the present invention when the number of layers is 3. Here, as in the example shown in Figure 9, if the number of XMI packets in layer A in one OFDM frame is K=311, the number of XMI packets in layer B is L=1050, and the number of XMI packets in layer C is M=388, then ceil(L / K)=4, floor(L / K)=3, ceil(M / K)=2, and floor(M / K)=1.

[0076] In the example shown in Figure 11, the packet transmission scheduler unit 112 repeatedly outputs a first packet set consisting of one A-tier XMI packet, four B-tier XMI packets, and two C-tier XMI packets 77 times, then repeatedly outputs a second packet set consisting of one A-tier XMI packet, four B-tier XMI packets, and one C-tier XMI packet 40 times, and then repeatedly outputs a third packet set consisting of one A-tier XMI packet, three B-tier XMI packets, and one C-tier XMI packet 194 times.

[0077] The number of times h is output for ceil(L / K) layers B XMI packets per layer A XMI packet, and the number of times i is output for floor(L / K) layers B XMI packets per layer A XMI packet, are expressed by the following formulas. h = L - (K * floor (L / K)) = 117 i=Kh=194 Furthermore, the number of times j is output for ceil(M / K) C-layer XMI packets per A-layer XMI packet, and the number of times k is output for floor(M / K) C-layer XMI packets per A-layer XMI packet, are expressed by the following formulas. j = M - (K*floor(M / K)) = 77 k=Kj=234

[0078] (Modulation device) Next, a modulation device 21 according to one embodiment of the present invention will be described. The modulation device 21 does not need to be dedicated hardware, but may be in the form of computer software.

[0079] Figure 12 is a block diagram showing an example configuration of a modulation device 21 when the number of layers is 2. The modulation device 21 shown in Figure 12 comprises a packet receiving unit 201, a layer separation unit 202, a layer-specific frame generation unit 203, an FEC block formation unit 204, an energy diffusion unit 205, an error correction coding unit 206, a bit interleave unit 207, a mapping unit 208, a layer synthesis unit 209, a frame header addition unit 210, a time-frequency interleave unit 211, a TMCC analysis unit 212, an LLch frame generation unit 213, an LLch modulation unit 214, a pilot signal generation unit 215, an OFDM frame configuration unit 216, and an OFDM transmission processing unit 217.

[0080] The packet receiving unit 201 receives the content transmission signal from the remultiplexing device 12, removes the IPv4 header and UDP header from the XMI packet, and outputs it to the hierarchical separation unit 202.

[0081] The hierarchical separation unit 202 identifies the type of each XMI packet by referring to the data unit type information contained in the XMI header of the XMI packet. The hierarchical separation unit 202 then separates packets belonging to each layer and distributes them to the processing system of each layer. It also outputs data for channels that are transmitted with lower latency compared to each layer (for example, earthquake early warnings) to the LLch frame generation unit 213. The hierarchical separation unit 202 also outputs synchronization control information to the TMCC analysis unit 212.

[0082] The hierarchical frame generation unit 203 concatenates the data units contained in the A-layer XMI packets input from the hierarchical separation unit 202 to generate an A-layer frame and outputs it to the FEC block formation unit 204. The hierarchical frame generation unit 203 also concatenates the data units contained in the B-layer XMI packets input from the hierarchical separation unit 202 to generate a B-layer frame and outputs it to the FEC block formation unit 204.

[0083] The FEC block forming unit 204 forms FEC blocks at each level and outputs them to the energy diffusion unit 205.

[0084] The energy diffusion unit 205 applies energy diffusion processing to the FEC block input from the FEC block formation unit 204 and outputs it to the error correction coding unit 206.

[0085] The error correction coding unit 206 generates an encoded signal by error-correcting the signal input from the energy diffusion unit 205 (LDPC encoding in this embodiment) in order to enable the OFDM signal receiver to correct transmission errors. The error correction coding unit 206 then outputs the generated encoded signal to the bit interleave unit 207.

[0086] The bit interleaving unit 207 generates bit data by interleaving the encoded signal input from the error correction encoding unit 206 bit by bit in order to improve the performance of the error correction code. The bit interleaving unit 207 then outputs the generated bit data to the mapping unit 208.

[0087] The mapping unit 208 maps the bit data input from the bit interleaving unit 207 to the IQ plane and generates a carrier symbol with carrier modulation according to the modulation scheme. The mapping unit 208 then outputs the generated carrier symbol to the hierarchical synthesis unit 209.

[0088] The hierarchical synthesis unit 209 synthesizes the carrier symbols input from the mapping unit 208 of each hierarchical level and outputs them to the frame header addition unit 210.

[0089] The frame header addition unit 210 adds a frame header to the carrier symbols input from the hierarchical synthesis unit 209 and outputs it to the time-frequency interleaving unit 211.

[0090] The time-frequency interleaving unit 211 rearranges the order of carrier symbols input from the frame header addition unit 210 in the time and frequency directions to generate an interleaved signal. The time-frequency interleaving unit 211 then outputs the generated interleaved signal to the OFDM frame constructor unit 216.

[0091] The TMCC analysis unit 212 generates a TMCC signal from the synchronization control information input from the hierarchical separation unit 202 and outputs it to the OFDM frame configuration unit 216.

[0092] The LLch frame generation unit 213 concatenates the L0 and L1 symbols contained in the XMI packet input from the hierarchical separation unit 202 to generate an LLch frame, which is then output to the LLch modulation unit 214.

[0093] The LLch modulation unit 214 modulates the data input from the hierarchical separation unit 202 using a predetermined modulation scheme (e.g., DBPSK) to generate symbols, and outputs them to the OFDM frame constructor 216.

[0094] The pilot signal generation unit 215 generates pilot signals (SP signals and CP signals) and outputs them to the OFDM frame configuration unit 216.

[0095] The OFDM frame constructor 216 constructs an OFDM frame by inserting the TMCC signal input from the TMCC analysis unit 212, the symbol input from the LLch modulation unit 214, and the pilot signal input from the pilot signal generation unit 215 into the interleaved signal input from the time-frequency interleaving unit 211. The OFDM frame constructor 216 then outputs the generated OFDM frame to the OFDM transmission processing unit 217.

[0096] The OFDM transmission processing unit 217 generates an OFDM signal by performing OFDM modulation processing on the OFDM frame input from the OFDM frame constructor 216, and transmits the generated OFDM signal to the receiving device. More specifically, the OFDM transmission processing unit 217 generates a time-domain active symbol signal by performing IFFT (Inverse Fast Fourier Transform) processing on the OFDM symbols of the OFDM frame input from the OFDM frame constructor 216. Then, the OFDM transmission processing unit 217 inserts a guard section at the beginning of the active symbol signal, and then performs quadrature modulation processing and D / A conversion processing to generate an OFDM signal.

[0097] As described above, according to the present invention, the bias in the output ratio of XMI packets for each layer can be suppressed in the remultiplexer 12, thereby preventing buffer underflow in the modulation device 21.

[0098] (modified version) Next, a modified version of the distribution system 1 described above will be explained. As explained with reference to Figure 6, in order to maintain a fixed length, XMI packets are stuffed by adding synchronization control information and stuff bits to data units that do not meet the packet length. Also, if no data exists, a stuff bit is sent as shown in Figure 6(d) to maintain a constant rate. However, in this configuration, the parity area of ​​the FEC block is filled with nulls, resulting in unnecessary packets being sent to the line, which increases the transmission rate and carries risks such as packet loss on the line.

[0099] Figure 13 shows an FEC block and an OFDM frame. Here, an example with a coding rate of 7 / 16 and a code length of medium is shown. In this case, the LDPC parity occupies 9 / 16 (4860 bytes) of the 8640 bytes of the FEC block.

[0100] Therefore, the modified distribution system 1 uses STLP (Studio to Transmitter Link Protocol) packets, which are a streamlined version of XMI packets, instead of XMI packets for content transmission and reception. The remultiplexer 12 constructs FEC blocks and OFDM frames from TLV packets as described above (see Figures 4 and 5), and divides the OFDM frames into XMI packets (see Figure 7). On the other hand, STLP packets store TLV packets without using FEC blocks. In other words, STLP packets are packets that store hierarchical content signals in the form of TLV packets.

[0101] The packet receiving unit 201 of the modified modulation device 21 converts the received STLP packet into an XMI packet. If the modulation device 21 is capable of receiving both XMI packets and STLP packets, the packet receiving unit 201 determines whether the received packet is an XMI packet or an STLP packet. If the received packet is an XMI packet, the packet receiving unit 201 removes the IPv4 header and UDP header from the XMI packet and outputs it to the hierarchical separation unit 202. If the received packet is an STLP packet, the packet receiving unit 201 converts the STLP packet into an XMI packet, removes the IPv4 header and UDP header from the XMI packet, and outputs it to the hierarchical separation unit 202. The subsequent processing is the same as that of the modulation device 21 described above.

[0102] Next, we will explain specific examples of STLP packets. Figure 14 shows an example of the structure of an STLP packet. Figure 14(a) shows a synchronous control STLP packet containing synchronous control information, Figure 14(b) shows an example of a hierarchical data STLP packet containing hierarchical data TLV packets, Figure 14(c) shows a null STLP packet containing a null TLV packet, and Figure 14(d) shows an LLch data STLP packet containing LLch data TLV packets. Note that the structure of an STLP packet is not limited to these examples.

[0103] An STLP packet includes an IPv4 header, a UDP header, packet type information, a sequence number, and a timestamp. The packet type information and sequence number are the same as those included in the XMI header. An STLP packet may also include a frame number indicating the frame number of an OFDM frame, and a frame number flag indicating the presence or absence of a frame number.

[0104] The synchronous control STLP packet shown in Figure 14(a) includes synchronous control information. This synchronous control information includes FEC block byte offset information, which indicates the byte offset from the beginning of the OFDM frame in the FEC block. This makes it possible for the broadcasting station 20, which receives the content transmission signal, to configure the FEC block. The synchronous control information also includes TMCC information, time information indicating the time when the next OFDM frame should be transmitted, and so on.

[0105] The hierarchical data STLP packet shown in Figure 14(b) and the null STLP packet shown in Figure 14(c) include TLV storage byte offset information indicating the storage location of the hierarchical data TLV packet in the FEC block, a synchronization signal, and a hierarchical data TLV packet or a null TLV packet. By transmitting the input IP packet in TLV format without stuffing it to a fixed length, it is possible to slim down the packet. By placing the TLV storage byte offset information before the TLV packet and obtaining the byte offset information from the beginning of the OFDM frame, it is possible to know the beginning of the OFDM frame.

[0106] The LLch data STLP packet shown in Figure 14(d) includes LLch offset information, a synchronization signal, and an LLch data TLV packet. There are two types of LLch data STLP packets: L0ch data STLP packets for partial reception and L1ch data STLP packets for fixed reception, but these are collectively referred to as LLch data STLP packets. The LLch data TLV packet allows for packet streamlining by transmitting the input IP packet in TLV format without stuffing it to a fixed length.

[0107] The distinction between synchronous control STLP packets, hierarchical data STLP packets, null STLP packets, and LLch data STLP packets may be made using 3 bits of packet type information. For example, as shown in Table 3, the type of STLP packet can be determined by pre-defining the STLP packets corresponding to the values ​​of the packet type information.

[0108] [Table 3]

[0109] The LLch offset information shown in Figure 14(d) includes a 1-bit LLch start flag, a 1-bit LLch end flag, a 5-bit reserved area, a 9-bit LLch symbol offset, and an 8-bit LLch byte offset.

[0110] The LLch symbol offset indicates the starting symbol position to which LLch data is allocated, and the LLch byte offset indicates the starting carrier position to which LLch data is allocated. In other words, the LLch symbol offset and LLch byte offset allow us to identify the starting position of the carrier symbol when allocating LLch data to an OFDM frame.

[0111] The LLch start flag and LLch end flag indicate whether each LLch data TLV packet after splitting is the beginning, the end, or neither. Table 4 shows specific examples of the LLch start flag and LLch end flag.

[0112] [Table 4]

[0113] As described above, according to the modified configuration, content transmission is performed with a streamlined packet configuration, and FEC blocks and OFDM frames are generated on the broadcasting station 20 (modulator 21) side, making it possible to transmit at a transmission rate close to the data capacity of the original video and audio data.

[0114] (program) To enable the above-mentioned remultiplexing device 12 or modulation device 21 to function, a computer capable of executing program instructions can also be used. The computer stores a program in its memory that describes the processing content for realizing each function of the remultiplexing device 12 or modulation device 21, and the computer's processor reads and executes this program. Some of these processing contents may be implemented in hardware. Here, the computer may be a general-purpose computer, a dedicated computer, a workstation, a PC (Personal Computer), an electronic notepad, etc. The program instructions may be program code, code segments, etc., for executing the necessary tasks. The processor may be a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), a DSP (Digital Signal Processor), etc.

[0115] Furthermore, this program may be recorded on a computer-readable recording medium. Using such a recording medium, the program can be installed on a computer. Here, the recording medium on which the program is recorded may be a non-transient recording medium. A non-transient recording medium is not particularly limited, but may be a CD-ROM, DVD-ROM, or similar recording medium. This program can also be provided by download over a network.

[0116] Although the embodiments described above are representative examples, it will be apparent to those skilled in the art that many modifications and substitutions are possible within the spirit and scope of the present invention. Therefore, the present invention should not be interpreted as being limited by the embodiments described above, and various modifications or changes are possible without departing from the scope of the claims. For example, it is possible to integrate multiple component blocks shown in the configuration diagram of the embodiments, or to divide a single component block. [Explanation of Symbols]

[0117] 1. Distribution System 10 Performance hall 11 Multiplexer 12 Remultiplexer 20 Broadcasting Stations 21 Modulator 22 Transmitters 30 Content transmission lines 101 Packet Filter 102 IP Header Compression Section 103 TLV Packeting Section 104 FIFO buffer 105 FEC Block Components 106 Layered Frame Structure 107 XMI Packeting Unit 108 L0 Symbol Components 109 L1 Symbol Components 110 Synchronous Control XMI Packet Configuration Unit 111 Staff XMI Packet Configuration Section 112 Packet transmission scheduler section 201 Packet Receiver 202 Hierarchical separation section 203 Hierarchical Frame Generation Unit 204 FEC block forming section 205 Energy Diffusion Section 206 Error Correction Encoding Unit 207-bit interleaved section 208 Mapping section 209 Layered Synthesis Unit 210 Frame Header Addition Section 211 Time-Frequency Interleaving Section 212 TMCC Analysis Department 213 LLch frame generation unit 214 LLch modulation section 215 Pilot signal generation unit 216 OFDM Frame Components 217 OFDM transmission processing unit

Claims

1. A remultiplexer that transmits packets to a modulation device, An XMI packetization unit that generates XMI packets containing hierarchical content signals in FEC block format, When the number of XMI packets in the first and second layers of a single OFDM frame is K and L, respectively (K < L), A first packet set consisting of one first-tier XMI packet and ceil(L / K) second-tier XMI packets, A second packet set consisting of one first-tier XMI packet and floor(L / K) second-tier XMI packets, A packet transmission scheduler unit that repeatedly outputs, A remultiplexing device equipped with the following features.

2. A remultiplexer that transmits packets to a modulation device, An XMI packetization unit that generates XMI packets containing hierarchical content signals in FEC block format, If the number of XMI packets in the first, second, and third layers of one OFDM frame is K, L, and M respectively (K < M < L), A first packet set consisting of one first-tier XMI packet, ceil(L / K) second-tier XMI packets, and ceil(M / K) third-tier XMI packets, A second packet set consisting of one first-tier XMI packet, ceil(L / K) second-tier XMI packets, and floor(M / K) third-tier XMI packets, A third packet set consisting of one first-tier XMI packet, floor(L / K) second-tier XMI packets, and floor(M / K) third-tier XMI packets, A packet transmission scheduler unit that repeatedly outputs, A remultiplexing device equipped with the following features.

3. A remultiplexing device according to claim 1 or 2, The remultiplexing device includes a modulation device that receives STLP packets containing hierarchical content signals in the form of TLV packets, The modulation device is A packet receiving unit converts the received STLP packet into an XMI packet containing hierarchical content signals in FEC block format, A data processing unit that performs error correction coding and interleaving processing on the FEC block, An OFDM frame constructing unit that inserts a TMCC signal and a pilot signal into the data processed by the data processing unit to construct an OFDM frame, A distribution system equipped with these features.

4. A program for causing a computer to function as a remultiplexing device according to claim 1 or 2.

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