JP5276569B2 - Receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To convert an IP packet received from a transmitter through a unidirectional transmission line to the IP packet of FLUTE. <P>SOLUTION: The SDP generation part 23 of the receiver 2 takes out download control information from the IP packet on the basis of the destination port number of a UDP header and generates SDP information. An FDT generation part 24 selects the IP packet of a medium file on the basis of the destination port number of the UDP header, takes out the transmission file attribute information of the medium file from the IP packet on the basis of the block number and sequence number of a download header, and generates an FDT instance. An ALC/LCT header generation part 25 generates an ALC/LCT header on the basis of the IP packet storing the transmission file attribute information of the medium file or the like, and generates the IP packet of FLUTE. Thus, the IP packet is converted to the IP packet of the FLUTE, and a file is reconfigured. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a transmission system in which a packet is transmitted from a transmission device to a reception device via a one-way transmission path, and a reception device having a FLUTE (File Delivery over Unidirectional Transport) client function receives a received IP packet from the FLUTE. The present invention relates to a packet format conversion technique for converting into an IP packet conforming to a standard.

  Conventionally, a service for downloading content using a unidirectional transmission path such as a broadcast transmission path is known. In the content download service, a file is divided and stored in a plurality of packets for transmission. In this file transmission method, a transmission device generates and transmits redundant packets based on packets generated by dividing a file by an error correction method called FEC (Forward Error Correction). Then, the receiving device receives the redundant packet from the transmitting device and restores the missing packet. Thereby, it is possible to maintain a certain file transmission quality in the one-way transmission path without using a return channel (uplink from the receiving apparatus to the transmitting apparatus).

  FLUTE is known as a file transmission method using such a one-way transmission path (see Non-Patent Document 1 and Patent Document 1). FLUTE is a standard for transmitting file attribute information and a file body as one object each time a file is packetized and transmitted. The attribute information of the file is described as an FDT (File Delivery Table) instance, and is handled as one object as with the file body. That is, the transmission apparatus transmits a FLUTE packet of file attribute information as an object, and subsequently transmits a FLUTE packet of the file body as an object.

  This FLUTE is used for DVB-H IP datacast service and 3GPP MBMS service (see Non-Patent Documents 2 and 3). Accordingly, there are a large number of receiving apparatuses having a FLUTE client function for processing an IP packet conforming to the FLUTE standard (hereinafter referred to as a FLUTE IP packet) and reconstructing a file, and those widely spread internationally. It is assumed.

US Patent Application Publication No. 2004/0153468

IETF RFC3926, “FLUTE-file delivery over unidirectional transport”, Oct., 2004 ETSI TS 102 472, “Digital Video Broadcasting (DVB); IP Datacast over DVB-H: Content Delivery Protocols”, 2006-12 3GPP TS 26.346, “3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; Multimedia Broadcast / Multicast Service (MBMS); Protocols and codecs (Release 8)”, 2008-09

  On the other hand, among file transmission systems using a unidirectional transmission path such as a broadcast transmission path, there are many transmission apparatuses that comply with standards other than FLUTE. For example, Japanese Patent Application No. 2008-304375, which was made by the same applicant as the present application and has not been published at the time of the present application, is particularly applicable to high-speed transmission paths such as satellite broadcasting, and efficient file transmission with low overhead. An advanced BS download method, which is a method, has been proposed. It is possible to develop a receiving apparatus that can cope with such a transmitting apparatus using an efficient file transmission method with less overhead.

  However, instead of developing a new receiving apparatus corresponding to such a transmitting apparatus, if a receiving apparatus having a FLUTE client function that currently exists and is widely used can be used, reception opportunities may be increased. Development cost and development load are reduced, which is useful.

  Therefore, the present invention has been made in view of the above problems, and the object of the present invention is to receive from a transmitting device via a one-way transmission path in a receiving device having a FLUTE client function for reconstructing a file from a FLUTE packet. An object of the present invention is to provide a receiving apparatus capable of converting an IP packet into a FLUTE IP packet.

  In order to achieve the above object, a receiving apparatus according to the present invention divides a file into a plurality of data units, generates transmission file attribute information based on the file, and download control necessary for downloading the file. Information is divided into a plurality of data units, transmission file attribute information is generated based on the download control information, an identifier of the file and download control information, and a number used when transmitting the data unit and transmission file attribute information. A download header including the file data unit, the transmission file attribute information of the file, the data unit of the download control information or the transmission file attribute information of the download control information in a packet together with the download header and transmitted Do In a transmission system comprising: a transmission device, and a reception device that receives the packet through one-way transmission and restores the file by a client function that performs processing according to a FLUTE (File Delivery over Unidirectional Transport) standard Based on a packet in which the data unit of the download control information and the transmission file attribute information are stored, the reception device includes SDP (Session Description Protocol) information regarding a session when the file is transmitted as a FLUTE packet. When the file is transmitted as a FLUTE packet based on an SDP generation unit to be generated and a packet in which transmission file attribute information of the file is stored An FDT generation unit that generates an FDT (File Delivery Table) instance related to sex, an ALC / LCT header when transmitting the FDT instance based on a packet storing the data unit and transmission file attribute information of the file, and Generating an ALC / LCT header when the file is transmitted as an encoding symbol, generating an FLTE packet including an FDT instance generated by the FDT generation unit and an ALC / LCT header when transmitting the FDT instance; ALC / L in the case where the data unit of the file stored in the packet is taken out and treated as the encoding symbol, and the encoding symbol and the encoding symbol are transmitted An ALC / LCT header generation unit that generates a FLUTE packet including a T header, and an SLC information generated by the SDP generation unit, from the FLUTE packet generated by the ALC / LCT header generation unit, And a FLUTE client for restoring a file.

  In the receiving device according to the present invention, a UDP header in which a different destination port number is set in the transmission of the file and the download control information is added to the packet transmitted by the transmitting device, and the UDP added to the packet Based on the destination port number of the header, the packet storing the data unit of the file and the transmission file attribute information is distinguished from the packet storing the data unit of the download control information and the transmission file attribute information. To do.

  In the receiving device according to the present invention, the SDP generation unit extracts a source IP address, a destination IP address, a destination port number, a distribution start time and a distribution end time of the file from the download control information, and the SDP information It is characterized in that it is set for each item.

  The receiving apparatus according to the present invention is characterized in that the FDT generation unit extracts a content location and an expire attribute from the transmission file attribute information of the file, and sets them in each item of the FDT instance.

  Further, the receiving device according to the present invention includes a plurality of data units when a download header of a packet transmitted by the transmitting device transmits an identifier of the file and download control information, the data unit, and transmission file attribute information. It is composed of a block number consisting of transmission file attribute information and a sequence number indicating the number of transmission units in the block, and the ALC / LCT header generation unit determines the final transmission file attribute information from the transmission file attribute information of the file. Whether or not the packet number is the final packet in which the transmission file attribute information of the file is stored based on the sequence number and the final packet number in the download header of the packet in which the transmission file attribute information of the file is stored Information Generating a destination port number from the UDP header of the packet storing the transmission file attribute information of the file, calculating the data unit length in the packet storing the data unit of the file, and transmitting the file of the file The block number and sequence number are extracted from the download header of the packet in which attribute information is stored, the source block number and encoding symbol number defined by FLUTE are calculated based on the block number and sequence number, and the FDT instance is transmitted. The packet download header of the packet in which the data unit of the file is stored by extracting the number of packets in the block from the transmission file attribute information of the file. Based on the sequence number and the number of packets in the block, information indicating whether the data unit of the file is the last packet stored is generated, and from the UDP header of the packet in which the data unit of the file is stored The destination port number is extracted, the identifier is extracted from the download header of the packet storing the data unit of the file, the block number and the sequence number are extracted from the download header of the packet storing the data unit of the file, and the block number The source block number and the encoding symbol number defined by FLUTE are calculated based on the sequence number, and an ALC / LCT header for transmitting the encoding symbol is generated.

  As described above, according to the receiving apparatus of the present invention, an IP packet received from a transmitting apparatus via a one-way transmission path can be converted into a FLUTE IP packet to reconstruct a file. Therefore, for a transmission device using an efficient file transmission method with low overhead, a number of reception devices having a FLUTE client function that are present and widely used without developing a new reception device corresponding to the transmission device can be provided. Can be used to reconstruct the file. That is, development cost and development load can be reduced. In addition, the content transmitted from the transmission device by the advanced BS download method can be received by a reception device corresponding to a method such as DVB-H, 3GPP, or ISDB-Tmm.

It is a figure which shows schematic structure of the transmission system containing the receiver by embodiment of this invention. It is a block diagram which shows the structure of a transmitter. It is a figure which shows the structure of download control information. It is a block diagram which shows the structure of an IP packetization part. It is a figure explaining the process of an IP packetization part. It is a figure which shows the structure of transmission file attribute information. It is a figure which shows the structure of a download header. It is the figure which showed notionally the download control information and media file transmitted as a TLV (Type-Length-Value) packet. It is a block diagram which shows the structure of the receiver by embodiment of this invention. It is a flowchart which shows the conversion procedure to the IP packet of FLUTE. It is a figure which shows the structure of the IP packet of FLUTE which transmits an FDT instance. It is a figure which shows the structure of the IP packet of FLUTE which transmits an encoding symbol. It is a figure explaining the item and description method of SDP (Session Description Protocol) information. It is a figure explaining the item and description method of an FDT instance. It is a figure explaining the item and description method of an ALC / LCT header in the case of transmitting an FDT instance. It is a continuation of FIG. It is a figure explaining the item and description method of an ALC / LCT header in the case of transmitting an encoding symbol.

The best mode for carrying out the present invention will be described below with reference to the drawings.
[Transmission system]
First, a transmission system including a receiving device according to an embodiment of the present invention will be described. FIG. 1 is a diagram illustrating a schematic configuration of a transmission system. This transmission system is, for example, a system that realizes a file download service using an advanced BS download method, and includes a transmission device 1 and a reception device 2. The transmitter 1 and the receiver 2 are connected by a one-way transmission path 3.

  When transmitting the media file, the content file, the metadata file, the file package, and the like and the download control information (control information necessary for downloading the file), the transmission device 1 transmits the transmission file attribute information and the data unit. This is an apparatus that stores in an IP packet, encapsulates the IP packet in a TLV packet, and transmits the packet to the receiving apparatus 2 via the one-way transmission path 3. The receiving apparatus 2 has a FLUTE client function, receives the TLV packet transmitted by the transmitting apparatus 1 via the one-way transmission path 3, decapsulates the TLV packet into an IP packet, and converts the IP packet into a FLUTE It is a device that converts IP packets and reconstructs the original file.

[Transmitter]
Next, the transmitter 1 shown in FIG. 1 will be described in detail. FIG. 2 is a block diagram illustrating a configuration of the transmission device 1. The transmission device 1 includes IP packetization units 11 and 12, an IP / UDP header compression unit 13 and a TLV packetization unit 14, and when the download control information and the media file are transmitted, the download control information and the media file are transmitted. Then, a data unit and transmission file attribute information are generated from each, a download header is added to generate an IP packet, the IP packet is encapsulated in a TLV packet, and transmitted to the receiving device 2. In the embodiment of the present invention, the transmission device 1 transmits a TLV packet, but may transmit an IP packet. Hereinafter, an example in which a media file is transmitted from the transmission device 1 to the reception device 2 will be described.

  The IP packetization unit 11 inputs download control information, generates a data unit and transmission file attribute information, adds a download header to the data unit and transmission file attribute information, generates an IP packet, and generates an IP / UDP header. Output to the compression unit 13. Here, the IP packet output from the IP packetization unit 11 to the IP / UDP header compression unit 13 includes an IP packet storing a data unit of download control information and transmission file attribute information of download control information. There are two types of IP packets.

  FIG. 3 is a diagram showing a configuration of download control information. The download control information is information corresponding to a media file that is one content, and is control information necessary for downloading the media file from the transmission device 1 to the reception device 2. The download control information includes “content location information” “source IP address, destination IP address, destination port number” “distribution start time and distribution end time” “content ID” “license ID” “ECG metadata location information” “ It includes playback control information location information, location information of purchase attribute metadata, license location information, and the like.

  Returning to FIG. 2, the IP packetizing unit 12 inputs a media file, generates a data unit and transmission file attribute information, adds a download header, and generates an IP packet, like the IP packetizing unit 11. And output to the IP / UDP header compression unit 13. Here, the IP packet output from the IP packetization unit 12 to the IP / UDP header compression unit 13 includes an IP packet storing a data unit of a media file and an IP packet storing transmission file attribute information of the media file. There are two types.

  FIG. 4 is a block diagram showing the configuration of the IP packetizing units 11 and 12. FIG. 5 is a diagram for explaining the processing of the IP packetizing units 11 and 12. The IP packetization units 11 and 12 include a data unit generation unit 31, an attribute information generation unit 32, a download header addition unit 33, and an IP packet generation unit 34.

  The data unit generation unit 31 receives download control information or a media file, divides the data unit into data units having a predetermined unit length, and generates a plurality of data units. Then, the data unit generation unit 31 generates a parity unit based on the generated plurality of data units, generates a block including the data unit and the parity unit, and sets the data unit and the parity unit for each block to the data units # 1 to # 1. The data is output to the download header adding unit 33 as #N (a data unit and a parity unit are collectively referred to as a data unit) (step S501). The size of the data unit can be freely set, for example, 1344 bytes and 4032 bytes.

  The attribute information generation unit 32 inputs download control information or a media file, generates transmission file attribute information including download control information or media file identification information and size based on the download control information or the media file, It outputs to the download header addition part 33 (step S502). In this case, the attribute information generation unit 32 generates the generated transmission file when the size of the generated transmission file attribute information is larger than the size of the data unit generated by the data unit generation unit 31 (size of a fixed length unit). The attribute information is divided into the same size as the data unit.

  FIG. 6 is a diagram showing a configuration of transmission file attribute information. Transmission file attribute information includes “number of bits in block number (Block Number) field in download header”, “number of packets in block”, “last sequence number of transmission file attribute information packet”, “identifier for specifying FEC method”, “ “Content-Location” (URI / name of the file body) ““ File Length ”“ Content Type ”“ Last block number for transmitting the file and last sequence number of the last block ”“ Storage ” Previous directory structure ”“ Content encoding ”“ Transfer length ”“ Content MD5 ”“ Content MD5 ” It consists of Spire (Expires) attributes ". In the description of FIG. 6, the download control information and the media file are referred to as files.

  The attribute information generation unit 32 sets a bit length set in advance according to the type and characteristics of the one-way transmission path 3 to “the number of bits in the block number field in the download header”. Details of the number of bits and the block number in the block number field will be described later. Further, the attribute information generation unit 32 sets the preset number of packets in the block to “number of packets in block”. The “number of packets in a block” is the number of packets that can be transmitted in a block in a block that is an aggregate of data units separated from a file and parity units generated from the data units.

  Further, when the generated transmission file attribute information is divided, the attribute information generation unit 32 sets the final packet number of the transmission file attribute information, which is the number of the divided transmission file attribute information, as “the final sequence number of the transmission file attribute information packet”. To "". When the size of the transmission file attribute information is equal to or smaller than the size of the data unit, the “last sequence number of the attribute information packet” is 0.

  Further, the attribute information generation unit 32 sets the file size to “File Length” and sets the content type of the file to “Content Type”. Further, the attribute information generation unit 32 calculates the number of blocks and the number of sequences based on the number of data units and parity units generated by the data unit generation unit 31, the size of the data unit set in advance, and the like. These are set to “the last block number for transmitting the file and the last sequence number of the last block”.

  In addition, when the attribute information generating unit 32 encodes and transmits a file, the attribute information generation unit 32 sets the method to “content encoding”, and when encoding and transmitting the file, the length of the original file and the file at the time of transmission Therefore, the length of the file at the time of transmission is set to “Transfer Length”. In addition, a checksum “content MD5 (content MD5)” for checking whether or not the receiving apparatus 2 has received the file correctly is set. Furthermore, “an identifier for specifying the FEC method”, “content location (Content-Location) (URI / name of file body)”, “directory configuration of storage destination”, and “Expires attribute” are also set.

  4 and 5, the download header adding unit 33 inputs the data units # 1 to #N from the data unit generating unit 31, inputs the transmission file attribute information from the attribute information generating unit 32, and receives the data unit #. A download header is added to 1 to #N and the transmission file attribute information (step S503).

  FIG. 7 is a diagram showing the configuration of the download header. The download header is a 64-bit header composed of three fields, and includes a “transport file identifier (TFID)”, a “block number”, and a “sequence number”. The number of bits (field width) allocated to the “TFID” field is 32. The total number of bits assigned to the “block number” and “sequence number” fields is 32, but each has a variable length, depending on the type and characteristics of the one-way transmission path 3, or transmitted download control information or It is preset according to the media file. Further, during transmission of the same download control information or media file, these field widths are not changed, and fixed values are used. The number of bits allocated to this “block number” field is set by the attribute information generation unit 32 to “number of bits in the block number field in the download header” of the transmission file attribute information shown in FIG. For example, by setting the number of bits in the “block number” field to 0, all 32 bits can be used as the “sequence number” field.

  “TFID” serves as a label for uniquely identifying download control information or a media file to be transmitted. Therefore, the download header adding unit 33 sets the same “TFID” for the same download control information, and sets the same “TFID” for the same media file.

  The “block number” indicates a block number which is a unit in which data units in the download control information or media file to be transmitted are collected. “Sequence number” indicates the number of data units # 1 to #N in the block and the number of transmission file attribute information (respective transmission file attribute information when divided). For example, for the first transmission file attribute information, block number = 0, sequence number = 0 is set, and when the next transmission file attribute information exists, block number = 0, sequence number = 1 is set, and the final The sequence number is incremented and set up to the transmission file attribute information. In the data unit following the transmission file attribute information, a sequence number subsequent to the sequence number set for the final transmission file attribute information is set.

  More specifically, when one piece of transmission file attribute information is generated by the attribute information generation unit 32, the download header addition unit 33 determines the block number for the transmission file attribute information in the first block (block number = 0). = 0, sequence number = 0 is set. The download header adding unit 33 sets block number = 0 and sequence number = 1 for the first data unit of the first block, and sets block number = 0 and sequence number = 2 for the next data unit. To do. The sequence number increases by one according to the number of data units. Then, in the next block (block number = 1), the download header adding unit 33 sets block number = 0 and sequence number = 0 for the same transmission file attribute information as the transmission file attribute information in the first block. . Then, the download header adding unit 33 sets block number = 1 and sequence number = 1 for the first data unit of the block (block number = 1), and block number = 1 and sequence for the next data unit. Set number = 2.

  As described above, the download header adding unit 33 adds a download header including the TFID, the block number, and the sequence number to the transmission file attribute information and the data unit. In this case, the download header addition unit 33 assigns the same transmission file attribute information to the plurality of blocks generated by the data unit generation unit 31, and the first transmission of the transmission file attribute information corresponding to one block. For file attribute information, block number = 0 and sequence number = 0 are unified and set. Thereby, the receiving terminal 2 determines whether or not the 32-bit data obtained by concatenating both the block number and sequence number fields in the download header is 0x00000000 for the received packet, and if it is determined that it is 0x00000000, Regardless of the setting of the number of bits in the block number field and the number of bits in the sequence number field, a packet having such a download header is a packet including transmission file attribute information (a packet including the first transmission file attribute information). Can be recognized.

  4 and 5, the IP packet generator 34 generates an IP packet by adding an IP header and a UDP header to the data unit to which the download header is added by the download header adding unit 33 and the transmission file attribute information. And output to the IP / UDP header compression unit 13 (step S504). Here, the IP packet generator 34 adds UDP headers having different destination port numbers to the IP packet storing the download control information and the IP packet storing the media file.

  Returning to FIG. 2, the IP / UDP header compression unit 13 inputs the IP packet storing the data unit of the download control information and the IP packet storing the transmission file attribute information of the download control information from the IP packetizing unit 11. Then, the IP packet storing unit 12 receives the IP packet storing the data unit of the media file and the IP packet storing the transmission file attribute information of the media file. Then, the IP / UDP header compression unit 13 compresses the IP header and UDP header added to the IP packet to generate a compressed header, and generates an IP packet with the compressed header added instead of the IP header and UDP header. , Output to the TLV packetization unit 14.

  The TLV packetization unit 14 receives the IP packet from the IP / UDP header compression unit 13, encapsulates the IP packet into a TLV packet, generates a TLV packet, and transmits the TLV packet to the receiving device 2 via the one-way transmission path 3. .

  The TLV packetizing unit 14 directly inputs the IP packet from the IP packetizing unit 11 and the IP packetizing unit 12, encapsulates the IP packet to which the uncompressed IP header and UDP header are added, and converts the TLV packet into the TLV packet. You may make it transmit to the receiver 2.

  FIG. 8 is a diagram conceptually showing download control information and media files transmitted as TLV packets. There are two types of TLV packets transmitted from the transmission apparatus 1 to the reception apparatus 2: a download control information packet and a media file packet. Specifically, a TLV packet in which a data unit of download control information is stored. And a TLV packet storing transmission file attribute information of download control information, a TLV packet storing media file data units, and a TLV packet storing media file transmission file attribute information. As shown in FIG. 8, for example, the destination port number in the TLV packet of the download control information is 50000, the destination port number of the TLV packet of the media file is 50001, and the IP packet generators of the IP packetizers 11 and 12 34 is set to a different number. Thereby, the receiving device 2 can distinguish the download control information from the media file based on the destination port number of the UDP header. An arbitrary number is set as the source port number.

  As described above, when transmitting the download control information and the media file, the transmission device 1 generates the data unit and the transmission file attribute information from the download control information and the media file, and generates the IP packet by adding the download header. Then, a TLV packet is generated and transmitted to the receiving device 2. This file transmission method can be used for a high-speed transmission line such as satellite broadcasting because it can perform efficient processing with little overhead by specializing in transmission specific to broadcasting.

[Receiver]
Next, the receiving apparatus 2 according to the embodiment of the present invention shown in FIG. 1 will be described in detail. FIG. 9 is a block diagram illustrating a configuration of the receiving device 2. The receiving apparatus 2 includes a TLV depacketization unit 21, an IP / UDP header restoration unit 22, an SDP generation unit 23, an FDT generation unit 24, an ALC / LCT header generation unit 25, and a FLUTE client 26. The receiving device 2 receives the TLV packet of the download control information and the TLV packet of the media file from the transmitting device 1 via the one-way transmission path 3, decapsulates the TLV packet into an IP packet, and converts the IP packet into a FLUTE IP packet. To reconstruct the original media file. Thereby, the media file in the transmission apparatus 1 can be restored.

  The TLV depacketization unit 21 receives a TLV packet from the transmission device 1 via the one-way transmission path 3, decapsulates the TLV packet in the TLV container format into an IP packet, and generates an IP packet with a compressed header added thereto. The data is output to the IP / UDP header restoration unit 22.

  The IP / UDP header restoration unit 22 receives the IP packet with the compressed header added from the TLV depacketization unit 21, restores the IP header and the UDP header from the compressed header, and receives the IP packet with the IP header and the UDP header added. And output to the SDP generation unit 23, the FDT generation unit 24 and the ALC / LCT header generation unit 25.

  When the IP header and the UDP header of the TLV packet transmitted from the transmission device 1 are not compressed, the TLV depacketization unit 21 decapsulates the received TLV packet and adds the IP header and the UDP header to the IP packet. Is directly output to the SDP generation unit 23, the FDT generation unit 24, and the ALC / LCT header generation unit 25. In addition, when an IP packet to which a compressed header is added is transmitted directly from the transmission apparatus 1 instead of a TLV packet, the IP / UDP header restoration unit 22 directly receives the IP packet from the transmission apparatus 1 and transmits the IP packet from the compression header. The header and the UDP header are restored, and the IP packet to which the IP header and the UDP header are added is output to the SDP generation unit 23, the FDT generation unit 24, and the ALC / LCT header generation unit 25.

Here, the IP packet output from the IP / UDP header restoration unit 22 to the SDP generation unit 23, the FDT generation unit 24, and the ALC / LCT header generation unit 25 is added to the payload in addition to the IP header, the UDP header, and the download header. Are four types of packets storing the data.
(1) Data unit of download control information (2) Transmission file attribute information of download control information (3) Data unit of media file (4) Transmission file attribute information of media file

  The SDP generation unit 23 receives the IP packet from the IP / UDP header restoration unit 22, determines whether the destination port number stored in the UDP header of the IP packet is 50000 or 50001, and stores the download control information The selected IP packet and the IP packet storing the media file are distinguished and selected, SDP information is generated based on the download control information and the like, and the IP packet of the SDP information is output to the FLUTE client 26. Here, as shown in FIG. 8, when the destination port number of the UDP header is 50000, the download control information is stored in the IP packet, and in the case of 50001, the media file is stored in the IP packet. . The SDP information is information indicating what IP packet the media file is transmitted in, and is information regarding a session when the media file is stored and transmitted in an IP packet of FLUTE. The SDP information is information necessary in advance for the FLUTE client 26 to perform processing for reconstructing a file. Details of the SDP information will be described later.

  The FDT generation unit 24 receives the IP packet from the IP / UDP header restoration unit 22 and stores the IP packet and the media file storing the download control information based on the destination port number stored in the UDP header of the IP packet. The selected IP packet is selected and generated, an FDT instance is generated based on the transmission file attribute information of the media file, etc., and output to the ALC / LCT header generation unit 25. The FDT instance is attribute information of the media file body, and is stored in the payload in the FLUTE IP packet that transmits the FDT instance. Details of the FDT instance will be described later. Note that there are two types of FLUTE IP packets: a packet that transmits an FDT instance that is attribute information of the media file body, and a packet that transmits an encoding symbol that is the media file body. Details will be described later.

  The ALC / LCT header generation unit 25 inputs an IP packet from the IP / UDP header restoration unit 22, inputs an FDT instance from the FDT generation unit 24, and based on the destination port number stored in the UDP header of the IP packet, When the IP packet storing the download control information and the IP packet storing the media file are distinguished and selected, and the ALC / LCT header and the encoding symbol when transmitting the FDT instance are transmitted based on the UDP header or the like Generate ALC / LCT header. Further, the data unit of the media file stored in the IP packet is handled as an encoding symbol. Then, the ALC / LCT header generation unit 25 generates a FLUTE IP packet including the ALC / LCT header and the FDT instance when transmitting the FDT instance that is the attribute information of the media file body, and outputs the packet to the FLUTE client 26. The ALC / LCT header generation unit 25 generates a FLUTE IP packet including an ALC / LCT header and an encoding symbol when transmitting an encoding symbol that is a media file body, and outputs the packet to the FLUTE client 26.

  According to the FLUTE standard, on the transmission side, a file is divided into source symbols, parity symbols are generated by FEC, and the source symbols and parity symbols are stored in the packet as encoding symbols. Also, an FDT instance for restoring the encoding symbol to a file is stored in the packet. Both the encoding symbol and the FDT instance are transmitted to the receiving side as the same object. In addition, an ALC / LCT header is added to the packet transmitting each object. As described above, the FLUTE IP packet includes 2 packets including an ALC / LCT header and an FDT instance when transmitting an FDT instance, and a packet including an ALC / LCT header and an encoding symbol when transmitting an encoding symbol. There are types.

  FIG. 11 is a diagram illustrating a configuration of a FLUTE IP packet that transmits an FDT instance. As shown in FIG. 11, the FLUTE IP packet includes an IP header, a UDP header, an ALC / LCT header, and an FDT instance (FDT Instance). In addition to the default LCT header (Default LCT Header), the ALC / LCT header requires EXT_FDT and EXT_FTI of the LCT header extension (LCT Header Extension), and FEC payload (Payload) ID. -It consists of each item of encoding symbol ID (Encoding Symbol ID). Details of each item of the ALC / LCT header will be described later.

  FIG. 12 is a diagram showing a configuration of a FLUTE IP packet that transmits an encoding symbol. As shown in FIG. 12, this FLUTE IP packet is composed of an IP header, a UDP header, an ALC / LCT header, and an encoding symbol (Encoding Symbol). The ALC / LCT header requires a default LCT header (Default LCT Header) and an FEC payload (Payload) ID, and is composed of items V, C,..., Encoding symbol ID (Encoding Symbol ID). Details of each item of the ALC / LCT header will be described later.

  Returning to FIG. 9, the FLUTE client 26 inputs the IP packet of the SDP information from the SDP generation unit 23, starts the FLUTE client based on the SDP information, and the FLUTE client including the FDT instance from the ALC / LCT header generation unit 25. A FLUTE IP packet including an IP packet and an encoding symbol is input, and a file is reconfigured based on the FDT instance and the encoding symbol of the FLUTE IP packet.

  FIG. 10 is a flowchart showing a conversion procedure from the IP packet output by the IP / UDP header restoration unit 22 to the IP packet of FLUTE. This conversion process is performed by the SDP generation unit 23, the FDT generation unit 24, the ALC / LCT header generation unit 25, and the FLUTE client 26.

  The FLUTE client 26 is a processing unit that inputs the FLUTE IP packet defined in the above-mentioned Non-Patent Document 1 and reconstructs a file. The FLUTE client 26 needs SDP information indicating in what IP packet the file is transmitted in the file reconstruction process. Therefore, first, the SDP generation unit 23 generates SDP information.

  First, the SDP generation unit 23 inputs an IP packet from the IP / UDP header restoration unit 22, and selects an IP packet in which download control information is stored based on a destination port number stored in the UDP header of the IP packet. Based on the block number and sequence number of the download header, the IP packet storing the data unit of download control information and the IP packet storing the transmission file attribute information of download control information are selected, respectively, and the data unit and the transmission file are selected. Download control information is generated from attribute information. Then, the SDP generation unit 23 generates SDP information based on the download control information and preset information, and outputs an IP packet of the SDP information to the FLUTE client 26 (step S1001). As described above, when both the block number and the sequence number of the download header are 0, the transmission file attribute information is stored in the IP packet, and when the transmission file attribute information is divided, the transmission file Transmission file attribute information is stored in IP packets up to a sequence number indicated by “last sequence number of transmission file attribute information packet” in the attribute information. Data units are stored in subsequent IP packets.

  As described above, when the SDP generation unit 23 generates the SDP information from the download control information or the like, the FLUTE client 26 can start the reconfiguration of the file even in the receiving apparatus 2 that supports only the SDP information.

(SDP information)
FIG. 13 is a diagram illustrating items of SDP information and description methods (setting methods by the SDP generation unit 23). The SDP information includes “source IP address”, “number of channels used for session”, “destination IP address and destination port number for each channel”, “session identifier (Transport Session Identifier)”, “session start time and end time”, “protocol ID” Is comprised.

  “Source IP address” is the source IP address of the media file to be transmitted, and the source IP address (see FIG. 3) is extracted from the download control information and set in this item. In the item “number of channels used in session”, 1 is set regardless of the download control information. In the item “destination IP address and destination port number for each channel”, the destination IP address and the destination port number (see FIG. 3) are extracted from the download control information and set. The “session identifier (Transport Session Identifier)” is the destination port number of the IP packet that transmits the media file, and the destination port number is extracted from the download control information and set in this item. In the item “session start time and end time”, the distribution start time and the distribution end time are extracted from the download control information and set. In the item “Protocol ID”, FLUTE / UDP is set regardless of the download control information. Refer to the non-patent document “IETF RFC2327,“ SDP: Session Description Protocol ”, April, 1998” for details of the SDP information.

  Returning to FIG. 10, next, the FLUTE client 26 inputs the SDP information from the SDP generation unit 23 and starts the FLULE client (step S1002). As a result, the FLUTE client 26 can acquire the FLUTE IP packet in which the media file is stored, based on the SDP information. That is, the transmitting device 1 transmits download control information instead of transmitting SDP information, and the receiving device 2 interprets the received download control information and virtually generates SDP information based on the download control information. . As a result, the FLUTE client 26 can acquire the FLUTE IP packet in which the media file is stored, and can start reconstructing the file.

  In FLUTE, a media file is divided into source symbols, parity symbols are generated by FEC, and the source symbols and parity symbols are stored in the packet as encoding symbols. On the other hand, an FDT instance necessary for restoring an encoding symbol to a media file is transmitted as an object similar to the media file. As shown in FIGS. 11 and 12, the packet for transmitting each object includes an ALC / LCT header.

Therefore, the ALC / LCT header generation unit 25 configures the FLUTE IP packet in order to convert the IP packet storing the data unit and the transmission file attribute information into a FLUTE IP packet that can be processed by the FLUTE client 26. It is necessary to generate an FLC instance, an encoding symbol, an ALC / LCT header when transmitting an FDT instance, and an ALC / LCT header when transmitting an encoding symbol. Here, since the encoding unit uses the data unit of the media file stored in the IP packet as it is, the following processing is required except for this encoding symbol.
(A) An FDT instance is generated from transmission file attribute information or the like.
(B) An ALC / LCT header for transmitting an FDT instance is generated from the download header and transmission file attribute information.
(C) An ALC / LCT header for transmitting an encoding symbol is generated from a download header or the like.

  The FDT generation unit 24 inputs the IP packet from the IP / UDP header restoration unit 22, selects an IP packet in which the media file is stored based on the destination port number stored in the UDP header of the IP packet, and download header The IP packet storing the transmission file attribute information of the media file is selected based on the block number and the sequence number. Then, the FDT generation unit 24 generates an FDT instance based on the transmission file attribute information of the media file and preset information, and outputs the FDT instance to the ALC / LCT header generation unit 25 (step S1003).

  As described above, when the FDT generation unit 24 generates the FDT instance from the transmission file attribute information of the media file, the ALC / LCT header generation unit 25 can generate the FLUTE IP packet for transmitting the FDT instance. .

(FDT instance)
FIG. 14 is a diagram for explaining items (attributes) and description methods (setting methods by the FDT generation unit 24) of FDT instances. The FDT instance is composed of “content location (Content-Location)”, “TOI (Transport Object Identifier)”, and “Expires”.

  In the item “content location (Content-Location)”, the content location (Content-Location) (URI / name of the file body) (see FIG. 6) is set from the transmission file attribute information of the media file. . In the item of “TOI (Transport Object Identifier)”, 0 is set regardless of the transmission file attribute information of the media file. The item “Expires” is set by extracting an Expires attribute (see FIG. 6) from the transmission file attribute information of the media file.

  Returning to FIG. 10, next, the ALC / LCT header generation unit 25 inputs the IP packet from the IP / UDP header restoration unit 22, inputs the FDT instance from the FDT generation unit 24, and stores it in the UDP header of the IP packet. Based on the destination port number, the IP packet storing the download control information and the IP packet storing the media file are distinguished and selected. Then, the ALC / LCT header generation unit 25 generates an ALC / LCT header when transmitting an FDT instance, and generates an ALC / LCT header when transmitting an encoding symbol (step S1004).

(ALC / LCT header when transmitting FDT instance)
15 and 16 show items (field names), sizes (bit lengths), item outlines and description methods (setting methods by the ALC / LCT header generation unit 25) of the ALC / LCT header when transmitting an FDT instance. It is a figure explaining. As shown in FIG. 11, the ALC / LCT header when transmitting the FDT instance includes the EXT_FDT and EXT_FTI in the LCT header extension (LCT Header Extension), and the FEC payload in addition to the default LCT header (Default LCT Header). (Payload) ID is required, and “V” “C” “R” “S” “O” “H” “T” “R” “A” “B” “HDR length (HDR_LEN)” “code point ( Code_Point) ”“ CCI ”“ TSI ”“ TOI ”“ SCT ”“ ERT ”“ V ”“ FDT instance (Instance) ID ”“ HEL ”“ Transfer Length ”“ FEC instance (Instance) ID ”“ Encode ” Din Symbol length (Encoding Symbol Length) "consists of" maximum source block number (Maximum Source Block Length) "," the source block number (Source Block Number) "," encoding symbol number (Encoding Symbol Number) ".

  Referring to FIG. 15, a version number 1 is set in the item “V”. In the item “C”, 0 which is the CCI field length is set. “R” is a reserved field, and 0 is set in the item. In the item “S”, 1 which is the TSI field length is set. In the item “O”, 1 which is the TOI field length is set. In the item “H”, 0 which is the TSI / TOI field length is set. The item “T” is set to 0 (no) in the presence or absence of the SCT field. The item “R” is set to 0 (no) in the presence or absence of the ERT field.

  In the item “A”, 0 is set as a close session flag (Close Session Flag). In the item “B”, as a close object flag (Close Object Flag), the IP packet storing the transmission file attribute information of the media file is set to 1 corresponding to the final IP packet storing the transmission file attribute information. Is set, and 0 is set corresponding to other IP packets. Specifically, the sequence number (see FIG. 7) of the download header of the IP packet storing the transmission file attribute information (see FIG. 7) is included in the “last sequence number of the transmission file attribute information packet” (FIG. 6). 1) is set in the same case. As described with reference to FIG. 7, in the transmission apparatus 1, when the first transmission file attribute information is set with block number = 0 and sequence number = 0 in the download header, and the next transmission file attribute information exists, Number = 0, Sequence number = 1 is set, the sequence number is set up to the final transmission file attribute information, and the sequence number set for the final transmission file attribute information is set in the data unit following the transmission file attribute information This is because the sequence number subsequent to is set.

  In the item “HDR length (HDR_LEN)”, a default LCT header (Default LCT Header), EXT_FDT, and EXT_FTI length 9 (which means 9 × 32 bits) are set. In the item of “code point (Code_Point)”, 0 is set as an FEC encoding (Encoding) ID indicating that parity symbol generation by FEC is not performed (Compact No code_FEC). In the item of “CCI”, 0 indicating that congestion control is not performed is set as the congestion control information (Congestion Control Information). In the item “TSI”, the destination port number is extracted and set from the UDP header added to the IP packet in which the transmission file attribute information of the media file is stored as the transport session ID. In the item of “TOI”, 0 is set as the transport object ID. “SCT” and “ERT” are not used.

  Referring to FIG. 16, the version number 1 is set in the item “V”. “FDT instance (Instance) ID” is the number of the FDT instance, and this item is set to a value that starts with 0 and is incremented by 1 for each FDT instance (for each FLUTE IP packet in which the FDT instance is stored). . “HEL” is a header extension length (Header Extension Length), and 4 is set in this item. “Transmission length” is a file length, and the length of the FDT instance is set in this item. In the item of “FEC instance (Instance) ID”, 0 is set when FEC encoding (Encoding) ID = 0.

  “Encoding Symbol Length” is a data unit length that is the length of the encoding symbol. In this item, the length of the data unit is calculated from the IP packet in which the data unit of the media file is stored. Is set. “Maximum Source Block Length” is the number of source symbols in the source block. In this item, the number of packets in the block (see FIG. 6) is extracted from the transmission file attribute information of the media file. Is set.

  “Source Block Number” is a 16-bit number when the FEC encoding (Encoding) ID is 0, and the block number and the block number and the transmission header of the IP file storing the transmission file attribute information of the media file are stored. Sequence numbers are extracted and calculated based on these numbers. “Encoding Symbol Number” is a 16-bit number when the FEC encoding (Encoding) ID is 0, and the block number and the block number from the download header of the IP packet storing the transmission file attribute information of the media file are stored. Sequence numbers are extracted and calculated based on these numbers.

As shown in FIG. 7, in the transmission apparatus 1, the total number of bits assigned to the block number and sequence number fields of the download header added to the IP packet is 32, but each has a variable length. On the other hand, in FLUTE, when the source block number corresponds to the block number of the download header, the encoding symbol number corresponds to the sequence number of the download header, and the FEC encoding (Encoding) ID is 0, each has a fixed length of 16 bits. It is. The ALC / LCT header generation unit 25, when BN is a block number, SN is a sequence number, x is a bit length of the block number, and A = BN × 2 ^x + SN, the source block number (SBN) is calculated by the following formula: And an encoding symbol number (ESN) is calculated.
SBN = INT (A / 2 ¹⁶ )
ESN = A-SBN

(ALC / LCT header when transmitting encoding symbols)
FIG. 17 is a diagram for explaining an ALC / LCT header item (field name), size (bit length), item outline, and description method (setting method by the ALC / LCT header generation unit 25) when transmitting an encoding symbol. It is. As shown in FIG. 12, the ALC / LCT header in the case of transmitting an encoding symbol requires a default LCT header (Default LCT Header) and an FEC payload (Payload) ID, and “V”, “C”, “R”. “S” “O” “H” “T” “R” “A” “B” “HDR Length (HDR_LEN)” “Code Point (Code_Point)” “CCI” “TSI” “TOI” “SCT” “ERT” It is composed of “source block number” and “encoding symbol number”.

  “V” “C” “R” “S” “O” “H” “T” “R” “Code Point (Code_Point)” “CCI” “SCT” “ERT” are the same as those shown in FIG. Therefore, explanation is omitted. In the item “A”, 1 is set as the close session flag (Close Session Flag) corresponding to the IP packet having the final sequence number of the final block for the IP packet in which the data unit of the media file is stored. 0 is set corresponding to other IP packets. Specifically, the block number and sequence number (see FIG. 7) of the download header of the IP packet in which the media file is stored are included in the transmission file attribute information “the last block number for transmitting the file and the last block of the last block. When it is the same as the “sequence number” (see FIG. 6), 1 is set. In the item “B”, as in the item “A”, an IP packet having the final sequence number of the final block is stored as an IP packet in which a data unit of a media file is stored as a close object flag (Close Object Flag). Is set to 1 and 0 is set to other IP packets. In the item “HDR length (HDR_LEN)”, 4 which is the LCT header length is set. In the item “TSI”, the destination port number is extracted and set as a transport session ID from the UDP header added to the IP packet storing the data unit of the media file. In the item of “TOI”, a transport file ID (Transport File ID) (see FIG. 7) is extracted from the download header of the IP packet in which the data unit of the media file is stored as a transport object (Transport Object) ID. Is set.

  “Source Block Number” is a 16-bit number when the FEC encoding (Encoding) ID is 0, and the block number and sequence number from the download header of the IP packet in which the data unit of the media file is stored. Is extracted and calculated based on these numbers. “Encoding Symbol Number” is a 16-bit number when the FEC encoding (Encoding) ID is 0, and the block number and sequence number from the download header of the IP packet in which the data unit of the media file is stored. Is extracted and calculated based on these numbers. The calculation method is the same as that described with reference to FIG.

  Returning to FIG. 10, the ALC / LCT header generation unit 25 generates an FDT instance (step S1003), and generates an ALC / LCT header for transmitting the FDT instance and an ALC / LCT header for transmitting the encoding symbol. After (step S1004), an IP packet of FLUTE is generated (step S1005). Specifically, the ALC / LCT header generation unit 25 generates an FLUTE IP packet including an ALC / LCT header and an FDT instance when transmitting an FDT instance, and outputs the packet to the FLUTE client 26. Further, the data unit of the media file stored in the IP packet is treated as an encoding symbol, and a FLUTE IP packet including the ALC / LCT header and the encoding symbol when transmitting the encoding symbol is generated and output to the FLUTE client 26.

  The FLUTE client 26 inputs the FLUTE IP packet including the FDT instance and the FLUTE IP packet including the encoding symbol from the ALC / LCT header generation unit 25, and outputs the file based on the FDT instance and the encoding symbol of the FLUTE IP packet. Reconfigure. Thereby, the media file in the transmission device 1 can be restored (step S1006).

  As described above, according to the receiving device 2 according to the embodiment of the present invention, the download control information and the media file transmitted from the transmitting device 1 via the one-way transmission path 3 include the transmission file attribute information and the data unit. Received as an IP packet, the SDP generator 23, the FDT generator 24 and the ALC / LCT header generator 25 convert the IP packet into a FLUTE IP packet, and the FLUTE client 26 reconstructs the original media file. I made it.

  Specifically, the SDP generation unit 23 distinguishes between the IP packet storing the download control information and the IP packet storing the media file based on the destination port number stored in the UDP header of the IP packet, Download control information is extracted from the packet, and SDP information is generated based on the download control information and the like. In addition, the FDT generation unit 24 selects an IP packet in which a media file is stored based on the destination port number of the UDP header as described above, and transmits the media file based on the block number and sequence number of the download header. An IP packet in which file attribute information is stored is selected, and an FDT instance is generated based on the transmission file attribute information of the media file. The ALC / LCT header generation unit 25 generates an ALC / LCT header for transmitting an FDT instance from a media file download header, a media file transmission file attribute information, and the like. An ALC / LCT header for transmitting an encoding symbol is generated. Then, the ALC / LCT header generation unit 25 generates a FLUTE IP packet including the ALC / LCT header and the FDT instance when transmitting the FDT instance, and uses the data unit of the media file stored in the IP packet as an encoding symbol. The FLUTE IP packet including the ALC / LCT header and the encoding symbol when the encoding symbol is transmitted is handled. Thereby, the receiving device 2 can convert the IP packet received from the transmitting device 1 via the one-way transmission path 3 into a FLUTE IP packet.

  Then, the FLUTE client 26 reconstructs the original media file based on the FLUTE IP packet. Thereby, the receiving device 2 having the FLUTE client function can restore the media file in the transmitting device 1. Therefore, for the transmission apparatus 1 using an efficient file transmission method with low overhead, a large number of reception apparatuses having a FLUTE client function that are present and widely used without developing new reception means corresponding to the transmission apparatus 1 Can be used. That is, the development cost and development load of the receiving device 2 can be reduced. In addition, the content transmitted from the transmission device 1 by the advanced BS download method can be received by the reception device 2 corresponding to a method such as DVB-H, 3GPP, or ISDB-Tmm.

DESCRIPTION OF SYMBOLS 1 Transmission apparatus 2 Reception apparatus 3 Unidirectional transmission path 11, 12 IP packetization part 13 IP / UDP header compression part 14 TLV packetization part 21 TLV depacketization part 22 IP / UDP header restoration part 23 SDP generation part 24 FDT generation part 25 ALC / LCT header generation unit 26 FLUTE client 31 data unit generation unit 32 attribute information generation unit 33 download header addition unit 34 IP packet generation unit

Claims (5)

A file is divided into a plurality of data units, transmission file attribute information is generated based on the file, and download control information necessary for downloading the file is divided into a plurality of data units, and the download control information is Based on this, the transmission file attribute information is generated, a download header including an identifier of the file and download control information, and a number for transmitting the data unit and transmission file attribute information is generated, and the data unit of the file, the file The transmission file attribute information, the data unit of the download control information or the transmission file attribute information of the download control information is stored in a packet together with the download header and transmitted.
A receiving device that receives the packet via one-way transmission and restores the file by a client function that performs processing according to a FLUTE (File Delivery over Unidirectional Transport) standard; There,
An SDP generation unit that generates SDP (Session Description Protocol) information related to a session when the file is transmitted as a FLUTE packet, based on a packet storing the data unit of the download control information and transmission file attribute information;
An FDT generation unit that generates an FDT (File Delivery Table) instance related to an attribute when the file is transmitted as a FLUTE packet based on a packet storing transmission file attribute information of the file;
An ALC / LCT header for transmitting the FDT instance and an ALC / LCT header for transmitting the file as an encoding symbol are generated based on the packet storing the data unit and transmission file attribute information of the file. Generating a FLUTE packet including the FDT instance generated by the FDT generation unit and the ALC / LCT header when transmitting the FDT instance, and taking out the data unit of the file stored in the packet as the encoding symbol An ALC / LCT header generation unit that generates a FLUTE packet including the encoding symbol and an ALC / LCT header when transmitting the encoding symbol;
A FLUTE client that restores the original file from the FLUTE packet generated by the ALC / LCT header generation unit using the SDP information generated by the SDP generation unit;
A receiving apparatus comprising: The receiving device according to claim 1,
The packet transmitted by the transmission device is appended with a UDP header in which a different destination port number is set in the transmission of the file and the download control information,
Based on the destination port number of the UDP header added to the packet, a packet storing a file data unit and transmission file attribute information, and a packet storing a data unit of download control information and transmission file attribute information. A receiving device characterized by distinguishing. The receiving device according to claim 1,
The SDP generation unit takes out a transmission source IP address, a destination IP address, a destination port number, a distribution start time and a distribution end time of the file from the download control information, and sets each item of the SDP information. A receiving device. The receiving device according to claim 1,
The receiving apparatus, wherein the FDT generation unit extracts a content location and an expire attribute from transmission file attribute information of the file and sets the content location and each item in the FDT instance. The receiving device according to claim 2,
The download header of the packet transmitted by the transmission device includes an identifier of the file and download control information, and a block number consisting of a plurality of data units and transmission file attribute information when transmitting the data unit and transmission file attribute information. And a sequence number indicating the number of transmission units in the block,
The ALC / LCT header generation unit extracts the final packet number of the transmission file attribute information from the transmission file attribute information of the file, the sequence number in the download header of the packet storing the transmission file attribute information of the file, and the final Based on the packet number, information indicating whether or not the transmission file attribute information of the file is the last packet stored is generated, and the destination port number is determined from the UDP header of the packet in which the transmission file attribute information of the file is stored. Taking out, calculating the data unit length in the packet storing the data unit of the file, extracting the block number and sequence number from the download header of the packet storing the transmission file attribute information of the file, and the block number Based on the fine sequence number, it calculates the source block number and the encoding symbol number defined by FLUTE, and set in each item of the ALC / LCT header for transmitting the FDT instance,
The number of packets in the block is extracted from the transmission file attribute information of the file, and the data unit of the file stores based on the sequence number in the download header of the packet in which the data unit of the file is stored and the number of packets in the block Information indicating whether the file is a final packet, the destination port number is extracted from the UDP header of the packet in which the data unit of the file is stored, and the download header of the packet in which the data unit of the file is stored The identifier is extracted, the block number and the sequence number are extracted from the download header of the packet in which the data unit of the file is stored, and the source block defined by FLUTE based on the block number and the sequence number is extracted. Calculating a metric number and encoding symbol number, generates the ALC / LCT header for transmitting the encoded symbols, receiving apparatus according to claim.

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