Transmitting device and receiving device

Abstract

To provide a transmission system that associates broadcasting with communication via an IP line without increasing the number of decoders in a receiving device and transmits via the IP line subordinate broadcast content indicating extension and auxiliary information with respect to main broadcast content transmitted by digital broadcasting, a transmitting device for the IP line, and the receiving device that receives the broadcast content having a main-subordinate relationship and stabilizes synchronization.SOLUTION: A transmission system 1 of the present invention includes: a transmitting device 2 (or 3) for digital broadcasting that generates a modulated wave signal by encoding and modulating main broadcast content using an error correction code for digital broadcasting and transmits it by broadcasting; a transmitting device 6 for an IP line that generates a variable-length packet for communication transmission of subordinate broadcast content, generates an encoded IP packet encoded using the same error correction code as digital broadcasting, and transmits it by communication; and a receiving device 5 that acquires the broadcast content having a main-subordinate relationship from each of the transmitting devices 2 (or 3) and 6, synchronizes them, and outputs them in a reproducible manner.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to the technical fields of satellite broadcasting, terrestrial broadcasting, fixed communication, and mobile communication, and in particular to a transmission system, transmitting device, and receiving device for efficient digital broadcasting and IP (Internet Protocol) communication by linking broadcasting and communication and applying a common error correcting code to address bit errors or packet losses that occur during signal transmission in the broadcasting and communication. [Background technology]

[0002] In digital broadcasting systems for satellite and terrestrial broadcasting, error correcting codes are used as a technology to improve transmission performance under white noise. For example, advanced wideband digital satellite broadcasting uses LDPC (Low Density Parity Check) codes, which are powerful error correcting codes with performance approaching the Shannon limit, which is the theoretical upper limit of utilization efficiency for the signal-to-noise ratio (see, for example, Non-Patent Documents 1 and 2).

[0003] Furthermore, since it is expected that packets will be lost due to some kind of failure such as line congestion in IP communication lines, and transmission information will be lost, error correcting codes dedicated to IP communication, which is an erasure channel, such as LDPC-CC (Convolutional Codes) (see, for example, Patent Document 1) and LDGM (Low-Density Generator Matrix) codes (see, for example, Patent Document 2) are used as error correcting codes to compensate for packet loss. These LDPC-CC and LDGM codes are error correcting codes based on LDPC codes, just like advanced wideband satellite digital broadcasting, but they are codes designed taking into consideration only IP communication, which is an erasure channel, and therefore it is necessary to prepare an encoder and decoder for the error correcting code dedicated to IP communication.

[0004] Although the signal transmission according to the present invention, which will be described in detail later, is not directly related to this technology, there is also known a technology called ARQ (Automatic Repeat reQuest) in which data is retransmitted from the transmitting side in response to a retransmission request from the receiving side in signal transmission using IP communication lines (see, for example, Patent Document 3). A transmission system has also been disclosed that applies this ARQ to link digital broadcasting and communication over IP lines, and makes error correction using LDPC codes common to both broadcasting and communication (see, for example, Patent Documents 4 and 5). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-050034 [Patent Document 2] International Publication No. 2007 / 069406 [Patent Document 3] International Publication No. 2015 / 048569 [Patent Document 4] Japanese Patent Publication No. 2021-34748 [Patent Document 5] Japanese Patent Publication No. 2020-188430 [Non-patent literature]

[0006] [Non-Patent Document 1] RG Gallager, “Low-Density Parity-Check Codes,” in Research Monograph series Cambridge, MIT Press, December 1963. [Non-patent document 2] "Advanced Wideband Satellite Digital Broadcasting Transmission Method (ISDB-S3) Standard ARIB STD-B44 Version 2.1," [online], revised March 25, 2016, ARIB, [searched July 5, 2021], Internet<URL:https: / / www.arib.or.jp / kikaku / kikaku_hoso / std-b44.html> Summary of the Invention [Problem to be solved by the invention]

[0007] As mentioned above, there is a known technique for dealing with bit errors or packet losses that occur in digital broadcasting and IP communication lines by using error-correcting codes based on LDPC codes for each transmission path. However, when transmitting extension and supplementary information for broadcast content over IP lines, it is necessary to build a transmission system that links broadcasting and communication. This requires separate error-correcting code encoders and decoders for digital broadcasting and encoders and decoders for IP communication, and a mechanism for coordinating them, which increases the scale of the equipment.

[0008] Therefore, by using "error correction codes used in digital broadcasting" for error correction on IP lines, it becomes possible to share encoders and decoders between broadcasting and communications, and it becomes possible to reduce the scale of the transmission system equipment assuming the cooperation of broadcasting and communications. Furthermore, by applying the powerful error correction used in digital broadcasting to IP lines, for example, by combining UDP (User Datagram Protocol) with error correction, it becomes possible to build a transmission system with smaller transmission delays and less overhead than retransmission-based TCP (Transmission Control Protocol) / IP.

[0009] Furthermore, the above-mentioned Patent Documents 4 and 5 also disclose a transmission system based on ARQ, in which an encoder and decoder are shared between broadcasting and communications by using "error correction codes used in digital broadcasting" for error correction on IP lines. Furthermore, when constructing a transmission system that transmits "secondary broadcast content" indicating extension and supplemental information for "primary broadcast content" transmitted via digital broadcasting over IP lines without using ARQ as the base, it is also effective to use "error correction codes used in digital broadcasting" for error correction on IP lines. However, in this case, some ingenuity is required to ensure that the receiving device can reliably synchronize and acquire the "secondary broadcast content" indicating extension and supplemental information with the "primary broadcast content" transmitted via digital broadcasting, thereby stabilizing reception performance.

[0010] Therefore, in view of the above-mentioned problems, the object of the present invention is to provide a transmission system that links digital broadcasting and communication via IP lines without increasing the size of the decoder in the receiving device, and transmits subordinate broadcast content that indicates extension and auxiliary information for the main broadcast content transmitted via digital broadcasting via IP lines, a transmitting device for IP lines, and a receiving device that can receive and stably synchronize the broadcast content that is in a master-slave relationship transmitted via broadcasting and communication. [Means for solving the problem]

[0011] The present invention Transmitting device for IP lines divides broadcast content into a master-slave relationship and transmits signals by linking broadcasting and communications. Fora transmitting device for satellite broadcasting or terrestrial broadcasting relating to digital broadcasting, which encodes main broadcast content using a block code made of a concatenated code of an LDPC code and a BCH code as an error correcting code, generates a modulated wave signal modulated using a predetermined modulation method, and transmits the modulated wave signal to a receiving device via a broadcast transmission path, and generates variable-length packets in IP format or TLV format by adding a packet header indicating packet identification information to data of secondary broadcast content indicating extension and auxiliary information for the main broadcast content relating to the digital broadcasting, encodes the variable-length packets using an error correcting code of the same format as the digital broadcasting, and converts them into IP packets to generate coded IP packets, and transmits the coded IP packets a transmitter for an IP line that transmits the digital broadcast of the main broadcast content to the receiver via a communication line, a function of demodulating a modulated wave signal of the digital broadcast of the main broadcast content transmitted from the transmitter for satellite broadcasting or terrestrial broadcasting via a broadcast transmission line, correcting bit errors that occur on the broadcast transmission line by error correction decoding processing, and outputting the signal in a reproducible manner; and a function of receiving an encoded IP packet storing the secondary broadcast content transmitted from the transmitter for IP line via a communication transmission line and correcting bit errors by error correction decoding processing that operates with the same decoding algorithm as the digital broadcast, while providing resistance to packet loss that occurs on the communication transmission line, and long a receiving device having a function of extracting packets and outputting the secondary broadcast content in a reproducible manner in synchronization with the primary broadcast content. a header adding unit that generates variable-length packets by adding a packet header in IP format or TLV format indicating the packet identification information to the data of the subsidiary broadcast content; and a header adding unit that performs error correction coding processing on the variable-length packets in IP format or TLV format to which the packet header indicating the packet identification information has been added, using the same error correction code as digital broadcasting, at a coding rate according to a required packet loss rate, which is one of the indicators of IP line quality, to generate error correction code frames of the same fixed code length as digital broadcasting. an interleaved frame constructing unit that constructs an interleaved frame by sequentially inputting and stacking the error correcting code frames of the fixed code length; an IP packet generating unit that extracts one bit from the beginning of each error correcting code frame that constructs the interleaved frame and generates a predetermined number of coded IP packets to which an IP header for IP packetization, an interleaved frame identification number for identifying the interleaved frame, and a sequence number indicating the order in which the IP packets were packetized are added; and an interleaving unit that changes the sending order of the coded IP packets in the order of the sequence numbers in accordance with a predetermined interleaving standard and transmits the coded IP packets to the receiving device via a communication transmission path. It is characterized by:

[0014] In addition, in the transmitting device for IP lines of the present invention, the header adding unit is configured to, when adding a packet header consisting of a header detection unique word for transmission in IP format to the data of the secondary broadcast content, add the packet header as indicating the packet identification information with a head detection signal for synchronizing the head of the secondary broadcast content with the head of the main broadcast content and packet length information indicating the packet length of each variable-length packet, and when adding a packet header consisting of a header detection unique word for transmission in TLV format to the data of the secondary broadcast content, add as indicating the packet identification information with a predetermined head detection value for synchronizing the head of the secondary broadcast content with the head of the main broadcast content, packet type information for identifying that the information is digital broadcast extension / auxiliary information in combination with the predetermined head detection value, and packet length information indicating the packet length of each variable-length packet.

[0015] The receiving device of the present invention also includes: In order to divide broadcast contents into a master-slave relationship and transmit signals by linking broadcasting and communications, a transmitter for satellite broadcasting or terrestrial broadcasting related to digital broadcasting encodes the main broadcast contents using a block code made of a concatenated code made of an LDPC code and a BCH code as an error correcting code, generates a modulated wave signal modulated using a predetermined modulation method, and transmits the modulated wave signal to a receiving device via a broadcast transmission path, and generates variable-length packets in IP format or TLV format by adding a packet header indicating packet identification information to data of secondary broadcast contents indicating extension and auxiliary information for the main broadcast contents related to the digital broadcasting, encodes the variable-length packets using the error correcting code of the same format as the digital broadcasting, and converts them into IP packets to generate coded IP packets, which are then transmitted to the receiving device via a communication transmission path. a receiving device having a function of demodulating a modulated wave signal of the digital broadcast of the primary broadcast content transmitted from the transmitting device for satellite broadcasting or terrestrial broadcasting via a broadcast transmission path, correcting bit errors occurring on the broadcast transmission path by error correction decoding processing, and outputting the demodulated wave signal in a reproducible manner; and a receiving device having a function of receiving coded IP packets storing the secondary broadcast content transmitted from the transmitting device for IP line via a communication transmission path, correcting bit errors by error correction decoding processing that operates with the same decoding algorithm as the digital broadcast, while providing resistance to packet loss occurring on the communication transmission path, extracting the variable-length packets based on packet headers that indicate the packet identification information, and outputting the secondary broadcast content in a reproducible manner in synchronization with the primary broadcast content. A receiving device in a transmission system receives and demodulates a modulated wave signal of the main broadcast content transmitted from the transmitting device for satellite broadcasting or terrestrial broadcasting related to the digital broadcasting via a broadcast transmission path, and obtains an IQ signal. revengea first a priori LLR generating unit that generates an a priori log-likelihood ratio to be used for error correction decoding of the error correction code frame; an IP packet receiving unit that receives coded IP packets of the secondary broadcast content transmitted from the transmitting device for the IP line via a communication transmission path; a deinterleaving unit that stores the received coded IP packets based on an interleaved frame identification number added to the coded IP packets, reconstructs the interleaved frame generated by the transmitting device 6 for the IP line, and performs deinterleaving processing to rearrange the coded IP packets based on the sequence number; and a second a priori LLR generating unit that extracts an error correction code frame from the interleaved frame after the deinterleaving processing, and generates a priori log-likelihood ratio to be used for error correction decoding of the error correction code frame. an error correction decoding unit that performs error correction decoding processing on an error correction code frame related to the primary broadcast content based on the a priori log-likelihood ratio related to the primary broadcast content pertaining to digital broadcasting, and also performs error correction decoding processing on the error correction code frame related to the secondary broadcast content based on the a priori log-likelihood ratio related to the secondary broadcast content by error correction decoding processing that operates with the same decoding algorithm as that for digital broadcasting; a primary information output unit that outputs the primary broadcast content after the error correction decoding processing so as to be playable externally; and a secondary information output unit that extracts the variable-length packets based on a packet header that indicates the packet identification information obtained after the error correction decoding processing, and externally outputs the secondary broadcast content after the error correction decoding processing so as to be playable, with the display timing synchronized with that of the primary broadcast content. The subsidiary information output unit is configured to, when the variable-length packets stored in the coded IP packet and transmitted are in IP format, identify the packet identification information as being composed of a head detection signal for synchronizing the head of the subsidiary broadcast content with the head of the main broadcast content, and packet length information indicating the packet length of each variable-length packet, and, when the variable-length packets stored in the coded IP packet and transmitted are in TLV format, identify the packet identification information as being composed of a predetermined head detection value for synchronizing the head of the subsidiary broadcast content with the head of the main broadcast content, packet type information for identifying that the information is digital broadcast extension / auxiliary information in combination with the predetermined head detection value, and packet length information indicating the packet length of each variable-length packet, extract the variable-length packets based on the packet header indicating the packet identification information, and externally output the subsidiary broadcast content after error correction decoding processing so that the display timing is synchronized with that of the main broadcast content and can be played back. It is characterized by the following. [Effects of the Invention]

[0017] According to the present invention, a common LDPC code is used for digital broadcasting and communication via IP lines, which makes it possible to avoid an increase in the equipment size of the decoder in the receiving device and to link signal transmission via broadcasting and communication, thereby enabling the receiving device to stably receive synchronously broadcast content that is transmitted via broadcasting and communication in a master-slave relationship. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a block diagram showing a schematic configuration of a transmission system according to an embodiment of the present invention; [Figure 2] 1 is a block diagram showing a schematic configuration of a transmitting device for an IP line according to an embodiment of the present invention; [Figure 3] FIG. 1A is a diagram showing the operation of a slave information input unit and a header addition unit of Example 1 in a transmitting device for an IP line of one embodiment according to the present invention, and FIG. 1B is a diagram showing the operation of a slave information input unit and a header addition unit of Example 2 in a transmitting device for an IP line of one embodiment according to the present invention. [Figure 4] 1A is a diagram showing the operation of an error correction coding unit in a transmitting device for an IP line according to one embodiment of the present invention, and FIG. 1B is a diagram showing the relationship between the coding rate of an LDPC code that can be used in the error correction coding unit and the required packet loss rate. [Figure 5] 10 is a diagram illustrating the operation of an interleaved frame construction unit in a transmitting device for an IP line according to an embodiment of the present invention. FIG. [Figure 6] 1A is a diagram showing the operation of an IP packet generator in a transmitting device for an IP line according to an embodiment of the present invention, and FIG. 1B is a diagram showing the signal format of an IP packet generated by the IP packet generator. [Figure 7] FIG. 2A is a diagram showing the operation of an interleave unit in a transmitting device for an IP line according to an embodiment of the present invention, and FIG. 2B is a diagram showing the interleave processing executed by the interleave unit. [Figure 8] 1 is a block diagram showing a schematic configuration of a receiving device according to an embodiment of the present invention; [Figure 9] 4 is a flowchart illustrating an operation of a receiving device according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] [Transmission System] Fig. 1 is a block diagram showing a schematic configuration of a transmission system 1 according to an embodiment of the present invention. The transmission system 1 shown in Fig. 1 is configured to divide broadcast content into a master-slave relationship, link broadcasting and communication, and transmit signals, and includes a transmitter 2 for satellite broadcasting, a transmitter 3 for terrestrial broadcasting, a receiver 5, and a transmitter 6 for IP lines.

[0020] In the transmission system 1 shown in Fig. 1, a transmitter 2 for satellite broadcasting related to digital broadcasting and a transmitter 3 for terrestrial broadcasting are configured to encode main broadcast content (main information for digital broadcasting) using a block code formed by concatenating an LDPC code and a BCH code as an error correcting code, respectively, generate a modulated wave signal modulated using a predetermined modulation method, and transmit the modulated wave signal via a broadcast transmission path to a receiver 5. On the other hand, a transmitter 6 for IP lines is configured to encode secondary broadcast content indicating extension and auxiliary information for the main broadcast content using an error correcting code of the same format as that of the digital broadcasting, generate coded IP packets, and transmit the coded IP packets to a receiver 5 via a communication transmission path (IP line). The primary broadcast content (main information for digital broadcasting) is the broadcast program itself, and the secondary broadcast content (extended / auxiliary information) is one or more of AR content, VR content, and 3D content. By distinguishing between broadcast content transmitted by signal via broadcast and communication in this primary-subordinate relationship, it becomes possible to provide broadcast services without adversely affecting not only the receiving device 5 of this embodiment that can receive both the primary broadcast content and the secondary broadcast content, but also existing receiving devices that can only receive the primary broadcast content.

[0021] The receiving device 5 has a function of demodulating the modulated wave signal of the digital broadcast of the primary broadcast content (main information for digital broadcast) transmitted via a broadcast transmission path from the transmitting device 2 for satellite broadcasting or the transmitting device 3 for terrestrial broadcasting, correcting bit errors that occur on the broadcast transmission path by error correction decoding processing, and outputting the demodulated wave signal in a playable manner.The receiving device 5 also has a function of receiving coded IP packets storing the secondary broadcast content (extension and supplemental information) transmitted via a communication transmission path from the transmitting device 6 for IP lines, correcting bit errors by error correction decoding processing that operates with the same decoding algorithm as digital broadcasting, making the secondary broadcast content resistant to packet loss that occurs on the communication transmission path, and outputting the secondary broadcast content (extension and supplemental information) in a playable manner in synchronization with the primary broadcast content (main information for digital broadcasting).

[0022] More specifically, the satellite broadcast transmitter 2 performs error correction coding (concatenated coding using LDPC code and BCH code) on transmission data of primary broadcast content related to digital broadcasting, adding error correction code parity to generate coded data, digitally modulates the coded data using a predetermined modulation method to generate a modulated wave signal, and emits radio waves related to digital broadcasting via a transmission antenna 2a over a satellite broadcast transmission path including a broadcast satellite 4. The satellite broadcast transmitter 2 also stores transmission control information indicating the LDPC coding rate and modulation method used to generate the modulated wave signal related to the primary broadcast content in a transmission control signal (TMCC signal), multiplexes the transmission control information on the modulated wave signal related to the primary broadcast content, and transmits it. For example, the satellite broadcast transmitter 2 can be a transmitter for advanced wideband digital satellite broadcasting.

[0023] The terrestrial broadcast transmitter 3 performs error correction coding (concatenated coding using LDPC and BCH codes) on transmission data of the main broadcast content of digital broadcasting, adding error correction code parity to generate coded data, digitally modulates the coded data using a predetermined modulation method to generate a modulated wave signal, and emits radio waves related to the digital broadcasting via a transmission antenna 3a and a terrestrial broadcast transmission path. The satellite broadcast transmitter 2 stores transmission control information indicating the LDPC coding rate and modulation method used to generate the modulated wave signal related to the main broadcast content in a transmission control signal (TMCC signal), multiplexes the TMCC signal on the modulated wave signal related to the main broadcast content, and transmits it. For example, the terrestrial broadcast transmitter 3 can be a transmitter for next-generation terrestrial digital broadcasting that uses concatenated coding using LDPC and BCH codes.

[0024] The IP line transmitting device 6, the details of which will be described later, generates variable-length packets in IP or TLV format by adding packet headers indicating packet identification information to data of secondary broadcast content indicating extension and supplemental information for the primary broadcast content of the digital broadcast, encodes the variable-length packets using the same error correction code format as the digital broadcast, and converts them into IP packets to generate coded IP packets, which are then transmitted to the receiving device 5 via a communication transmission path. The packet identification information serves as a marker (a break between packets) for the receiving device 5 when extracting the variable-length packets from the LDPC block, allowing the receiving device 5 to reliably extract the variable-length packets and achieve stable synchronization of the master-slave content by managing the reception of the variable-length packets (managing the number of received packets). While such packet headers indicating packet identification information are unnecessary for fixed-length packets, the IP line transmitting device 6 of this embodiment generates variable-length packets in IP or TLV format with packet headers indicating packet identification information added.

[0025] The receiver 5 has a function of receiving and demodulating a modulated wave signal radiated by radio waves from the transmitter 2 for satellite broadcasting via the receiving antenna 5a, performing a decoding process corresponding to the error correction coding process in the transmitter 2 for satellite broadcasting to generate received data and output it in a reproducible manner, a function of receiving and demodulating a modulated wave signal radiated by radio waves from the transmitter 3 for terrestrial broadcasting via the receiving antenna 5b, performing a decoding process corresponding to the error correction coding process in the transmitter 3 for terrestrial broadcasting to generate received data and output it in a reproducible manner, and a function of receiving and demodulating a secondary broadcast code transmitted from the transmitter 6 for IP line via a communication transmission path (IP network 7). The receiver receives coded IP packets that store the content (extension and supplementary information), and performs error correction for bit errors or packet losses that occur on the communication channel using an error correction decoding process that operates using the same decoding algorithm as digital broadcasting. After that, it extracts the variable-length packets using the packet headers added to the secondary broadcast content (extension and supplementary information), and by managing the reception of the variable-length packets (managing the number of received packets), it synchronizes the display timing with the main broadcast content (main information for digital broadcasting) and outputs the secondary broadcast content (extension and supplementary information) so that it can be played back.

[0026] 1, the transmission system 1 is configured to digitally broadcast the main broadcast content (main information for digital broadcast) from a transmitter 2 for satellite broadcast or a transmitter 3 for terrestrial broadcast to a receiver 5, and the transmitter 2 for satellite broadcast or the transmitter 3 for terrestrial broadcast can be a conventionally known transmitter that uses concatenated codes based on LDPC codes and BCH codes. Note that the general data format of broadcast content for digital broadcast is TS (a sequence of TS packets with a fixed length or a variable length) format or TLV (Type Length Value) format, and in this embodiment as well, the main broadcast content (main information for digital broadcast) related to the digital broadcast is stored in packets of a predetermined format, such as TS (a sequence of TS packets with a fixed length or a variable length) format or TLV format, and is input to the transmitter 2 for satellite broadcast or the transmitter 3 for terrestrial broadcast.

[0027] Therefore, the configurations and operations of the IP line transmitter 6 and the receiver 5 will be described in detail below with reference to the drawings. In the following description, although not limited thereto, the error correction code used when transmitting signals in the satellite broadcast transmitter 2 or the terrestrial broadcast transmitter 3, and the IP line transmitter 6 is in accordance with ARIB STD-B44 (ISDB-S3), and an example will be described in which an inner code is a concatenated code of an LDPC code (code length 44880 bits) and an outer code is a BCH (65535, 65343, correction capability t=12). The receiver 5 is previously registered for a service that enables reception from the IP line transmitter 6, and previously stores information related to a check matrix used for decoding the error correction code (check matrix initial value table). The receiver 5 then exchanges test communication or communication log information with the IP line transmitter 6, and the information on the required packet loss rate in the communication transmission path is recorded and updated in the IP line transmitter 6 as the required packet loss rate.

[0028] [Transmitting device for IP lines] FIG. 2 is a block diagram showing a schematic configuration of a transmitting device 6 for an IP line according to an embodiment of the present invention.

[0029] The transmitting device 6 for an IP line of this embodiment shown in FIG. 2 includes a sub information input unit 61, a header adding unit 62, an error correction coding unit 63, an interleaved frame constructing unit 64, an IP packet generating unit 65, and an interleaving unit 66.

[0030] The subsidiary information input unit 61 inputs subsidiary broadcast content (extension / auxiliary information) in one of the following packet formats: IP packet format, fixed-length or variable-length TS packet format, and TLV format, and outputs the data in the payload area sequentially to the header addition unit 62.

[0031] The header addition unit 62 generates a variable-length packet by adding an IP format or TLV format packet header indicating packet identification information to the data of the secondary broadcast content (extension / auxiliary information) input from the secondary information input unit 61, and outputs it to the error correction coding unit 63.

[0032] Here, FIG. 3(a) shows the operations of the sub information input unit 61 and the header adding unit 62 of the first embodiment, and FIG. 3(b) shows the operations of the sub information input unit 61 and the header adding unit 62 of the second embodiment.

[0033] First, in the first embodiment shown in Fig. 3(a), when data of secondary broadcast content (extension and auxiliary information) is input from a secondary information input unit 61 to a header adding unit 62 in time sequence ("S1," "S2," "S3," ... shown in the figure), the header adding unit 62 adds packet headers in sequence ("S1'," "S2'," "S3'," ... shown in the figure) each made up of a header detection unique word for transmission in IP format, and outputs the packet as a variable-length packet in IP format. More specifically, the IP-format packet header shown in Fig. 3(a) is a total of 10 bytes long, and includes a "heading detection signal (8 bytes)" for synchronizing the beginning of the secondary broadcast content (extension and auxiliary information) with the beginning of the main broadcast content (main information for digital broadcasting) and "packet length information (2 bytes)" indicating the packet length of each variable-length packet, and these are added as packet identification information.

[0034] On the other hand, in the second embodiment shown in FIG. 3(b), when data of the secondary broadcast content (extension / auxiliary information) is input from the secondary information input unit 61 to the header adding unit 62 in time sequence ("S1", "S2", "S3", ... shown in the figure), the header adding unit 62 adds packet headers in sequence ("S1'", "S2'", "S3'", ... shown in the figure) made up of unique words for header detection for transmission in TLV format (see the ARIB STD-B44 or ARIB-STD B32 standard), and outputs them as variable-length packets in TLV format. More specifically, the TLV-format packet header shown in Figure 3(b) contains a predetermined start detection value "0x7F (1 byte)" for synchronizing the start of the secondary broadcast content (extension / auxiliary information) with the start of the primary broadcast content (digital broadcast main information), "packet type information (1 byte)" for identifying that the information is digital broadcast extension / auxiliary information in combination with the predetermined start detection value, and packet length information (2 bytes) indicating the packet length of each variable-length packet, for a total of 4 bytes, which are added as packet identification information. By adding a packet header indicating such packet identification information to the data of the secondary broadcast content (extension / auxiliary information), after decoding by the receiving device 5, it becomes possible to reliably extract the variable-length packets based on the packet header and stably synchronize the primary and secondary broadcast contents.

[0035] The error correction coding unit 63 performs error correction coding processing on the variable-length packets in IP format or TLV format, obtained from the header adding unit 62 and to which a packet header indicating packet identification information has been added, using the same error correction code as used in digital broadcasting (a concatenated code of an LDPC code and a BCH code) at a coding rate according to the required packet loss rate, which is one of the indicators of IP line quality, to create an error correction code frame of the same fixed code length as used in digital broadcasting, and outputs the result to the interleaved frame creating unit 64.

[0036] Here, Fig. 4(a) shows the operation of the error correction coding unit 63, and Fig. 4(b) shows the relationship between the coding rate of the LDPC code that can be used in the error correction coding unit 63 and the required packet loss rate. As shown in Fig. 4(a), variable-length packets in IP format or TLV format, to which a packet header indicating packet identification information is added, are allocated to each of the error correction code frames #1, #2, #3, ... of fixed code length N (N=44880 bits in this example), to the maximum extent possible according to the coding rate (for example, coding rate 9 / 10), and after adjusting with dummy bits, parity bits of the coding rate (for example, coding rate 9 / 10) coded by the same error correction code method as digital broadcasting are added.

[0037] In the configuration according to the present embodiment that complies with ARIB STD-B44 (ISDB-S3), LDPC coding rates corresponding to coding rates 1 / 2 to 9 / 10 shown in the upper part of Fig. 4(b) can be used for digital broadcasting, but in addition, the transmission device 6 for IP lines can use LDPC coding rates corresponding to 110 / 120 to 117 / 120 shown in the lower part of Fig. 4(b) in the error correction coding unit 63. As described above, in the transmission device 6 for IP lines, information on the required packet loss rate in the communication transmission path is recorded and updated as the required packet loss rate through test communication with the reception device 5 or through exchange of communication log information obtained from the reception device 5, and the coding rate (i.e., LDPC coding rate) used in the error correction coding unit 63 is determined based on this required packet loss rate.

[0038] The interleaved frame constructing unit 64 sequentially inputs and stacks the coded block codes (error correction code frames of fixed code length N) from the error correction coding unit 63, constructing an N×m-bit interleaved frame when the code length of the block code is N bits and the number of block codes to be stacked is m, and outputs the frame sequentially to the IP packet generating unit 65.

[0039] 5 shows the operation of the interleaved frame constructing unit 64. The interleaved frame constructing unit 64 sequentially inputs error correction code frames with a code length of N bits from the error correction coding unit 63, constructs a predetermined number of frames (m frames) of error correction code frames as N×m-bit interleaved frames, and sequentially outputs them to the IP packet generating unit 65.

[0040] The IP packet generation unit 65 sequentially inputs N×m-bit interleaved frames, with N bits horizontally and m bits vertically, from the interleaved frame configuration unit 64, extracts one bit vertically from the beginning of each error correction code frame that makes up the N×m-bit interleaved frame, generates N packets of coded IP packets to which an IP header for IP packetization, an interleaved frame identification number (1 byte) for identifying the N×m-bit interleaved frame, and a sequence number indicating the order in which the IP packets were packetized (in this example, #1 to 44880 (2 bytes) to comply with ISDB-S3) are added, and outputs the coded IP packets to the interleaving unit 66 according to the sequence number.

[0041] 6(a) shows the operation of the IP packet generator 65, and FIG. 6(b) shows the signal format of the IP packet generated by the IP packet generator 65. As shown in FIGS. 6(a) and 6(b), the IP packet generator 65 sequentially inputs N×m-bit interleaved frames from the interleaved frame constructor 64, extracts one bit from the beginning of each of the N×m-bit interleaved frames, which constitutes the code length of the error-correcting code frame, and uses m-bit data as the payload. The IP packet generator 65 then generates N packets of IP packets by adding, to the beginning of each payload, an IP header for IP packetization, an interleaved frame (IF) number (1 byte) for identifying the N×m-bit interleaved frame, and sequence numbers #1 to #44880 (2 bytes) indicating the order of IP packetization, and outputs the IP packets to the interleaving unit 66 according to the sequence numbers.

[0042] However, in this embodiment, for the sake of convenience, the IP packet generating unit 65 is described as generating N packets of coded IP packets, but the number of packets can be reduced by not transmitting redundant parity bits through puncturing.In this case, the above-mentioned error correction coding unit 63 can be configured to use the LDPC coding rate within the range of 1 / 2 to 9 / 10 used in digital broadcasting, as shown in the upper part of Figure 4(b), and not use the LDPC coding rate corresponding to 110 / 120 to 117 / 120, as shown in the lower part of Figure 4(b).For example, when the quality of the IP line is good enough to allow error correction with a coding rate of 9 / 10 and the required packet loss rate is low (in this example, the required packet loss rate is lower than 11.8%), the above-mentioned error correction coding unit 63 is configured to add parity bits with a coding rate of 9 / 10. In this case, the IP packet generator 65 may shorten the IP packet by a predetermined amount by puncturing, which removes redundant bits from the area corresponding to the parity bits with a coding rate of 9 / 10, before generating a coded IP packet. Since the maximum LDPC coding rate specified in ISDB-S3 is 9 / 10, the IP packet generator 65 shortens the area corresponding to the parity bits by puncturing before packetizing the IP packet. This makes it possible to generate fewer coded IP packets than N packets for the N×m-bit interleaved frame, effectively achieving a coding rate of 9 / 10 or higher. Since puncturing eliminates the need to transmit redundant parity bits, this has the effect of reducing congestion on IP lines.

[0043] The interleaving unit 66 changes the sending order of the coded IP packets obtained from the IP packet generating unit 65 in the order of sequence numbers according to a predetermined interleaving standard, and transmits them to the receiving device 5 via the communication transmission path (IP network 7).

[0044] Here, Fig. 7(a) shows the operation of the interleave unit 66, and Fig. 7(b) shows the interleave processing. As shown in Fig. 7(a) and (b), the interleave unit 66 changes (shuffles) the sending order of the coded IP packets in the order of sequence numbers for each N × m bit interleave frame in accordance with a predetermined interleave standard, and transmits the packets to the receiving device 5 via the communication transmission path.

[0045] [Receiving device] Fig. 8 is a block diagram showing a schematic configuration of a receiving device 5 according to an embodiment of the present invention. The receiving device 5 shown in Fig. 8 includes a demodulator 51, a preliminary LLR generator 52, an IP packet receiver 53, a deinterleaver 54, a preliminary LLR generator 55, an error correction decoder 56, a main information output unit 57, and a secondary information output unit 58. The receiving device 5 demodulates and decodes the main broadcast content in the same manner as conventional digital broadcast reception, and first demodulates and decodes a transmission control signal (TMCC signal) to obtain transmission control information, and identifies the LDPC coding rate and modulation scheme used to generate the modulated wave signal from the transmission control information.

[0046] The demodulation unit 51 receives and demodulates the modulated wave signal of the main broadcast content (main information for digital broadcasting) transmitted via a broadcast transmission path from a transmitter 2 for satellite broadcasting related to digital broadcasting or a transmitter 3 for terrestrial broadcasting, obtains an IQ signal (a digital data signal represented by a signal point sequence of an in-phase component I and a quadrature phase component Q and capable of being represented as signal points on an IQ plane) and outputs it to the pre-LLR generation unit 52.

[0047] The a priori LLR generating unit 52 constructs an error correction code frame from the IQ signal obtained from the demodulating unit 51, generates a priori LLR (log-likelihood ratio) to be used for error correction decoding of the error correction code frame, and outputs it to the error correction decoding unit 55.

[0048] On the other hand, the IP packet receiving unit 53 receives the coded IP packets of the secondary broadcast content (extension and auxiliary information) transmitted from the IP line transmitting device 6 via the communication transmission line, and outputs them to the deinterleaving unit .

[0049] The deinterleave unit 54 accumulates the received IP packets based on the interleaved frame identification numbers added to the coded IP packets received from the IP packet receiver 53, constructs an N×m-bit interleaved frame, and performs deinterleaving to rearrange the coded IP packets based on the sequence numbers (the rearrangement is performed according to a predetermined interleaving standard that is the reverse of the processing performed by the interleave unit 66 on the IP line transmitter 6 side). The deinterleave unit 54 then outputs the deinterleaved IP packets to the pre-LLR generator 55. This interleaving operation between the transmitter and receiver can randomize burst packet losses. However, the horizontal size N of the interleaved frame, which corresponds to the number of packets, becomes smaller if the above-mentioned puncturing processing has been performed or if packet losses occur in the IP network 7. However, the error correction decoding processing by the error correction decoder 56, which will be described later, can recover bit errors caused by packet losses without being affected by the puncturing processing.

[0050] The a priori LLR generation unit 55 inputs an N×m-bit interleaved frame having N bits horizontally and m bits vertically after deinterleaving processing from the deinterleaving unit 54, reads the N×m-bit interleaved frame horizontally to extract an error correction code frame, generates a priori LLR to be used for error correction decoding of the error correction code frame, and outputs it to the error correction decoding unit 56 in units of N×m-bit interleaved frames.

[0051] Here, the a priori LLR generation unit 55 reads the N×m-bit interleaved frame horizontally to extract an error-correcting code frame, and when generating a priori LLRs to be used for error correction decoding of the error-correcting code frame, it treats lost packets as bit loss in the error-correcting code frame, and defines the a priori LLR as 0. Where IP packets are correctly received, bits of 0 or 1 are obtained in the error-correcting code frame, so these a priori LLRs are normally set to +∞ or −∞, but the a priori LLRs are set to +15 and −15 as values ​​that can be handled in actual calculations. In other words, the a priori LLRs output by the a priori LLR generation unit 55 are +15, −15, and 0. These three a priori LLRs are output to the error-correction decoding unit 56, the same as for digital broadcasting.

[0052] The error correction decoding unit 56 performs error correction decoding processing on the error correction code frame based on the preliminary LLR related to the main broadcast content (main information for digital broadcasting) related to the digital broadcast obtained from the preliminary LLR generation unit 52, obtains a packet of a predetermined format (a packet of TS format or TLV format) that stores the main broadcast content (main information for digital broadcasting), and outputs it to the main information output unit 57.

[0053] Furthermore, the error correction decoding unit 56 performs error correction decoding processing on the error correction code frame based on the preliminary LLRs for the secondary broadcast content (extension / auxiliary information) obtained from the preliminary LLR generation unit 55 using an error correction decoding process that operates using the same decoding algorithm as that used for digital broadcasting, obtains a packet header indicating packet identification information and a decoded bit string for a variable-length packet that stores the secondary broadcast content (extension / auxiliary information), and outputs the obtained bit string to the secondary information output unit 58.

[0054] The main information output unit 57 extracts the main broadcast content (main information for digital broadcast) from the packets in a predetermined format obtained from the error correction decoding unit 56, and outputs it externally so that it can be played back.

[0055] The subsidiary information output unit 58 extracts variable-length packets that store the subsidiary broadcast content (extension / auxiliary information) from the decoded bit string obtained from the error correction decoding unit 56 based on the packet header that indicates packet identification information, and outputs the subsidiary broadcast content (extension / auxiliary information) to the outside in a playable manner by synchronizing the display timing of the subsidiary broadcast content (extension / auxiliary information) with the main broadcast content (main information for digital broadcasting) in a manner that synchronizes the output with the main information output unit 57.

[0056] More specifically, when the variable-length packets stored in the encoded IP packets and transmitted are in IP format (see FIG. 3(a)), the subsidiary information output unit 58 recognizes that the packet identification information in the packet header is composed of a head detection signal for synchronizing the head of the subsidiary broadcast content (extension / auxiliary information) with the head of the primary broadcast content (digital broadcast main information) and packet length information indicating the packet length of each variable-length packet. On the other hand, when the variable-length packets stored in the encoded IP packets and transmitted are in TLV format (see FIG. 3(b)), the subsidiary information output unit 58 recognizes that the packet identification information in the packet header is composed of a predetermined head detection value for synchronizing the head of the subsidiary broadcast content (extension / auxiliary information) with the head of the primary broadcast content (digital broadcast main information), packet type information for identifying the packet as digital broadcast extension / auxiliary information in combination with the predetermined head detection value, and packet length information indicating the packet length of each variable-length packet. The subsidiary information output unit 58 then extracts the variable-length packet based on the identified packet identification information, and outputs the subsidiary broadcast content (extension / auxiliary information) after error correction decoding processing to the outside in a playable manner, with the display timing synchronized with that of the main broadcast content (main information for digital broadcasting).

[0057] That is, the subsidiary information output unit 58 extracts variable-length packets of the subsidiary broadcast content (extension / auxiliary information) while recognizing the packet length based on the packet header indicating the packet identification information, and by managing the reception of the variable-length packets (managing the number of received packets), synchronizes the beginning of the subsidiary broadcast content (extension / auxiliary information) with the beginning of the main broadcast content (main information for digital broadcast), and outputs the subsidiary broadcast content (extension / auxiliary information) by synchronizing the display timing with that of the main broadcast content (main information for digital broadcast).

[0058] (Example of receiving operation) FIG. 9 is a flowchart showing the operation of the receiving device 5 according to an embodiment of the present invention.

[0059] First, the receiving device 5 receives and demodulates the modulated wave signal of the main broadcast content (main information for digital broadcasting) transmitted via the broadcast transmission path from the transmitting device 2 for satellite broadcasting related to digital broadcasting or the transmitting device 3 for terrestrial broadcasting, using the demodulation unit 51, to obtain an IQ signal (step S1).

[0060] Next, the receiving device 5 causes the a priori LLR generating unit 52 to construct an error correcting code frame from the IQ signal obtained by demodulation, and generates a priori LLRs to be used for error correction decoding of the error correcting code frame (step S2).

[0061] Meanwhile, the receiving device 5 receives, via the IP packet receiving unit 53, the encoded IP packets of the secondary broadcast content (extension and auxiliary information) transmitted from the transmitting device 6 for the IP line via the communication transmission path (step S3).

[0062] Next, the receiving device 5 uses the deinterleaving unit 54 to store the received coded IP packets based on the interleaved frame identification number attached to the coded IP packets, reconstruct the interleaved frames generated by the transmitting device 6 for the IP line, and perform deinterleaving processing to rearrange the coded IP packets based on the sequence numbers (step S4).

[0063] Next, the reception device 5 causes the a priori LLR generating unit 55 to extract an error correction code frame from the interleaved frame after the deinterleaving process, and generates a priori LLR to be used for error correction decoding of the error correction code frame (step S5).

[0064] Next, the receiving device 5 performs error correction decoding processing on the error correction code frame based on the preliminary LLR related to the main broadcast content (main information for digital broadcast) related to the digital broadcast using the error correction decoding unit 56, and also performs error correction decoding processing on the error correction code frame based on the preliminary LLR related to the secondary broadcast content (extension / auxiliary information) using the error correction decoding processing that operates using the same decoding algorithm as that for digital broadcast (step S6).

[0065] Next, the receiving device 5 outputs the main broadcast content (main information for digital broadcasting) after error correction decoding processing to the outside in a playable manner using the main information output unit 57, and the sub information output unit 58 extracts variable-length packets based on the packet header indicating the packet identification information obtained after error correction decoding processing, and synchronizes the display timing of the broadcast content in a master-slave relationship by managing the reception of the variable-length packets (managing the number of received packets), i.e., synchronizes the display timing of the sub broadcast content (extension / auxiliary information) after error correction decoding processing with the main broadcast content (main information for digital broadcasting) and outputs it to the outside in a playable manner (step S7).

[0066] By configuring the transmission system 1 of this embodiment as described above and using a common error correction code for the error correction code related to digital broadcasting and the error correction code used in signal transmission over IP lines, the receiving device 5 can achieve error correction for both transmission paths by simply providing a single error correction decoder, and can link signal transmission via broadcasting and communication while reducing the equipment scale of the receiving device 5. Furthermore, by configuring the variable-length packets related to signal transmission over IP lines to have packet headers indicating packet identification information of broadcast content in a master-slave relationship, the receiving device 5 can stably and synchronously receive broadcast content in a master-slave relationship transmitted over broadcast and communication by managing the reception of variable-length packets (managing the number of received packets).

[0067] In the above-described embodiment and example, the IP line transmitting device 6 may be a computer, and the computer may preferably use a program for causing each means of the IP line transmitting device 6 to function. Similarly, the receiving device 5 may be a computer, and the computer may preferably use a program for causing the IP line signal processing means to function. Specifically, a control unit for controlling each means may be configured with a central processing unit (CPU) within the computer, and a storage unit for appropriately storing programs required to operate each means may be configured with at least one memory. That is, each of the above-described means can be realized by having the CPU execute the program on such a computer. Furthermore, the program for realizing each means may be stored in a predetermined area of ​​the storage unit (memory). Such a storage unit may be configured with RAM or ROM within the device, or may be configured with an external storage device (e.g., a hard disk). Furthermore, such a program may be configured as part of the software on the operating system used by the computer (stored in ROM or an external storage device). Furthermore, the program for causing such a computer to function as each means may be recorded on a computer-readable recording medium. Furthermore, each of the above-described means can be configured as part of hardware or software, and can be realized by combining each of them.

[0068] The above-described examples, applications, and modifications of one embodiment have been described as representative examples, but it will be apparent to those skilled in the art that many modifications and substitutions can be made within the spirit and scope of the present invention. For example, the above-described embodiment has been described as being compliant with ARIB STD-B44 (ISDB-S3), but the present invention can be applied to various transmission systems as long as it uses an error correction code of any code length that utilizes a concatenated code of an inner code LDPC code and an outer code BCH as a block code. Therefore, the present invention should not be construed as being limited by the above-described examples, but is limited only by the claims. [Industrial Applicability]

[0069] According to the present invention, broadcast contents that are transmitted via broadcasting and communication and have a master-slave relationship can be stably synchronized, and therefore the present invention is useful for applications in a transmission system that links signal transmission via broadcasting and communication. [Explanation of symbols]

[0070] 1 Transmission System 2. Satellite broadcasting transmitter 2a Transmitting antenna 3. Transmitting equipment for terrestrial broadcasting 3a Transmitting antenna 4. Broadcasting satellite 5. Receiving device 5a, 5b Receiving antenna 6. Transmitting equipment for IP lines 7 IP network 51 Demodulation section 52 Pre-LLR generator 53 IP packet receiver 54 Deinterleave section 55 Pre-LLR generator 56 Error correction decoding unit 57 Main information output section 58 Sub information output unit 61 Sub information input unit 62 Header Addition Section 63 Error correction coding section 64 Interleaved frame configuration section 65 IP packet generator 66 Interleave section

Claims

1. In order to divide broadcast content into a master-slave relationship and link broadcasting and communications for signal transmission, a transmitting device for satellite broadcasting or terrestrial broadcasting relating to digital broadcasting, which encodes main broadcast content using a block code formed by concatenating an LDPC code and a BCH code as an error correction code, generates a modulated wave signal modulated using a predetermined modulation method, and transmits the modulated wave signal to a receiving device via a broadcast transmission path; a transmitting device for an IP line that generates variable-length packets in an IP format or a TLV format by adding a packet header indicating packet identification information to data of secondary broadcast content indicating extension and auxiliary information for the primary broadcast content related to the digital broadcast, encodes the variable-length packets using an error correction code of the same format as that of the digital broadcast to generate coded IP packets, and transmits the coded IP packets to the receiving device via a communication transmission line; a receiving device having a function of demodulating a modulated wave signal of the digital broadcast of the primary broadcast content transmitted from the transmitting device for satellite broadcasting or terrestrial broadcasting via a broadcast transmission line, correcting bit errors that occur on the broadcast transmission line by error correction decoding processing, and outputting the primary broadcast content in a reproducible manner; and a function of receiving coded IP packets storing the secondary broadcast content transmitted from the transmitting device for IP line via a communication transmission line, correcting bit errors by error correction decoding processing that operates with the same decoding algorithm as the digital broadcast, while providing resistance to packet loss that occurs on the communication transmission line, extracting the variable-length packets based on packet headers that indicate the packet identification information, and outputting the secondary broadcast content in a reproducible manner in synchronization with the primary broadcast content; A transmitting device for an IP line in a transmission system configured to include: a subsidiary information input unit that inputs the subsidiary broadcast content in any one of an IP packet format, a fixed-length or variable-length TS packet format, and a TLV format; a header adding unit that generates a variable-length packet by adding a packet header in IP format or TLV format indicating the packet identification information to the data of the secondary broadcast content; an error correction coding unit that performs error correction coding processing on the variable-length packets in IP format or TLV format to which a packet header indicating the packet identification information is added, using the same error correction code as that used in digital broadcasting, at a coding rate according to a required packet loss rate, which is one of the indicators of IP line quality, to form an error correction code frame with the same fixed code length as that used in digital broadcasting; an interleave frame constructing unit that sequentially inputs and stacks the error correction code frames of the fixed code length to construct an interleave frame; an IP packet generator that extracts one bit from the beginning of each error-correcting code frame that constitutes the interleaved frame, and generates a predetermined number of coded IP packets to which an IP header for IP packetization, an interleaved frame identification number for identifying the interleaved frame, and a sequence number indicating the order in which the IP packets are packetized are added; an interleaving unit that changes the transmission order of the coded IP packets in the order of the sequence numbers in accordance with a predetermined interleaving standard and transmits the coded IP packets to the receiving device via a communication transmission path; A transmitting device for an IP line, comprising:

2. The header adding unit When a packet header consisting of a header detection unique word for transmission in IP format is added to the data of the subsidiary broadcast content, the packet header is added as indicating the packet identification information by a head detection signal for synchronizing the head of the subsidiary broadcast content with the head of the main broadcast content and packet length information indicating the packet length of each variable-length packet; 2. The transmitting device for an IP line according to claim 1, characterized in that when a packet header consisting of a header detection unique word for transmission in TLV format is added to the data of the secondary broadcast content, the transmitting device is configured to add, as the packet identification information, a predetermined start detection value for synchronizing the start of the secondary broadcast content with the start of the main broadcast content, packet type information for identifying that the information is digital broadcast extension / auxiliary information in combination with the predetermined start detection value, and packet length information indicating the packet length of each variable-length packet.

3. In order to divide broadcast content into a master-slave relationship and link broadcasting and communication for signal transmission, a transmitting device for satellite broadcasting or terrestrial broadcasting relating to digital broadcasting, which encodes main broadcast content using a block code formed by concatenating an LDPC code and a BCH code as an error correction code, generates a modulated wave signal modulated using a predetermined modulation method, and transmits the modulated wave signal to a receiving device via a broadcast transmission path; a transmitting device for an IP line that generates variable-length packets in an IP format or a TLV format by adding a packet header indicating packet identification information to data of secondary broadcast content indicating extension and auxiliary information for the primary broadcast content related to the digital broadcast, encodes the variable-length packets using an error correction code of the same format as that of the digital broadcast to generate coded IP packets, and transmits the coded IP packets to the receiving device via a communication transmission line; a receiving device having a function of demodulating a modulated wave signal of the digital broadcast of the primary broadcast content transmitted from the transmitting device for satellite broadcasting or terrestrial broadcasting via a broadcast transmission line, correcting bit errors that occur on the broadcast transmission line by error correction decoding processing, and outputting the primary broadcast content in a reproducible manner; and a function of receiving coded IP packets storing the secondary broadcast content transmitted from the transmitting device for IP line via a communication transmission line, correcting bit errors by error correction decoding processing that operates with the same decoding algorithm as the digital broadcast, while providing resistance to packet loss that occurs on the communication transmission line, extracting the variable-length packets based on packet headers that indicate the packet identification information, and outputting the secondary broadcast content in a reproducible manner in synchronization with the primary broadcast content; A receiving device in a transmission system configured to include: a demodulation unit that receives and demodulates a modulated wave signal of the main broadcast content transmitted from the transmitting device for satellite broadcasting or terrestrial broadcasting related to the digital broadcasting via a broadcast transmission path, and acquires an IQ signal; a first a priori LLR generating unit that generates an error correction code frame from the IQ signal obtained by demodulation and generates a priori log-likelihood ratios to be used for error correction decoding of the error correction code frame; an IP packet receiving unit that receives encoded IP packets of the secondary broadcast content transmitted from the IP line transmitting device via a communication transmission path; a deinterleaving unit that stores the received coded IP packets based on the interleaved frame identification numbers added to the coded IP packets, reconstructs the interleaved frames generated by the transmitting device 6 for the IP line, and performs deinterleaving processing to rearrange the coded IP packets based on the sequence numbers; a second a priori LLR generator that extracts an error correction code frame from the interleaved frame after the deinterleaving process and generates a priori log-likelihood ratios to be used for error correction decoding of the error correction code frame; an error correction decoding unit that performs error correction decoding processing on an error correction code frame related to the primary broadcast content based on a priori log-likelihood ratios related to the primary broadcast content pertaining to digital broadcasting, and also performs error correction decoding processing on an error correction code frame related to the secondary broadcast content based on a priori log-likelihood ratios related to the secondary broadcast content by error correction decoding processing that operates using the same decoding algorithm as that for digital broadcasting; a main information output unit that outputs the main broadcast content after error correction decoding processing in a reproducible manner to an external device; a subsidiary information output unit that extracts the variable-length packets based on a packet header indicating the packet identification information obtained after the error correction decoding process, and outputs the subsidiary broadcast content after the error correction decoding process to an external device so as to be playable in synchronization with the display timing of the main broadcast content; Equipped with The sub information output unit If the variable-length packet stored in the encoded IP packet and transmitted is in IP format, the packet identification information is identified as being composed of a head detection signal for synchronizing the head of the subsidiary broadcast content with the head of the primary broadcast content, and packet length information indicating the packet length of each variable-length packet; If the variable-length packet stored in the encoded IP packet and transmitted is in TLV format, the packet identification information is identified as being composed of a predetermined start detection value for synchronizing the start of the subsidiary broadcast content with the start of the primary broadcast content, packet type information for identifying that the packet is digital broadcast extension / auxiliary information in combination with the predetermined start detection value, and packet length information indicating the packet length of each variable-length packet; A receiving device characterized in that it is configured to extract the variable-length packet based on a packet header indicating the packet identification information, and to output the secondary broadcast content after error correction decoding processing externally in a playable manner by synchronizing the display timing with that of the main broadcast content.

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