JP2013026917A - Content distribution device, receiving device, repeating device, content distribution system, and content distribution method and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a content distribution system which, in IP multicast based content distribution services, etc., helps to reduce a delay time by transferring packets in a repeating device efficiently.SOLUTION: The content distribution system encodes and multiplexes media content to generate a media payload, and generates an FEC payload on the basis of the media payload. Then, on the basis of the media payload and FEC payload, it generates a media packet and an FEC packet, respectively, according to the characteristics of a network to be transmitted, and transmits the generated packets to a receiving device. The receiving device receives the media and the FEC packets and restores the media and the FEC payloads. If the media payload contains an error, the error is corrected by using the FEC payload before the media payload is decoded and then demultiplexed, in which way the content is decoded.

Description

  The present invention relates to a content distribution device connected to a content distribution system in which IP multicast media content is distributed to at least one receiving device.

  In recent years, with the spread of broadband lines such as FTTH (Fiber to the Home) and ADSL (Asymmetric Digital Subscriber Line), broadcast services such as IP broadcasting that provide multimedia content such as large-capacity video and audio over IP networks. Is increasing.

  Such a distribution system is generally realized by using “IP multicast technology” capable of simultaneous distribution to a large number of recipients. The IP multicast technology is a method of simultaneously transmitting the same data packet from a single server to a plurality of receivers that have joined a specific multicast group. By using this IP multicast technology, the load on the server and the load on the distribution network are increased. Can be reduced.

  A multicast group is formed by a collection of recipients who are to be provided with specific multimedia content from a certain server, and participating recipients share the same multicast address within the group.

  When the router that controls the data transmission path in this group receives the multicast data, it reads the multicast address and retransmits it toward the path to which the receiver belonging to the corresponding multicast group is connected.

  At this time, when there are a plurality of recipients and they exist on different routes, the router duplicates information to be transmitted and transmits it to each route. Due to the operation of this router, the IP multicast technology can greatly reduce the amount of transmission information compared to the case where information is sent to all recipients belonging to the multicast group independently from the server, and can be transferred to the server or network. Can reduce the load.

  In addition, an application or a system that uses this IP multicast technology to receive multicast contents distributed from a large number of servers while switching between them at one receiving terminal is also conceivable.

  For example, an IP broadcast service system in which many programs are broadcast from a broadcast station in a multicast format and the program is switched to a program that the user wants to watch at a receiving terminal at home or facility, or the content from the broadcast station is composed of many camera videos. In addition, there is a video monitoring system in which each is distributed by a multicast method and a camera video can be selected by switching reception at a receiving terminal.

  In such a distribution system, various techniques are known for efficiently transmitting packets. For example, a packet transfer method as shown in Patent Document 1, or content data as shown in Patent Document 2 and FEC (Forward Error Correction) data for error correction are transmitted as different data series, and the receiving terminal A technique for selecting an appropriate data series from among them based on the reception state is known.

JP 2000-78197 A JP 2001-45098 A

  In recent years, the amount of data of media content has continued to expand, and a more efficient packet relay method is desired in order to prevent delay and effectively use resources.

  However, for example, in Patent Document 1 described above, it is necessary to determine an error resilience characteristic (for example, a packet header part or a payload part) for each packet segment by a repeater and to select a different error correction method according to the result. There is a problem that transmission delay time occurs in the repeater. In addition, for example, the WWW server and the access router, and the access router and the receiving terminal are in one-to-one communication, and it is possible to negotiate network conditions such as MTU (Maximum Transmission Unit) and to request retransmission. It is a technology that can be applied to cases.

  Therefore, when media content is multicast-transmitted from the server, since it is a one-to-many communication, negotiation cannot be performed. For example, an MTU of a transmission path such as path MTU discovery is acquired in advance. However, it was not possible to use a method of packetizing according to the minimum size.

  Furthermore, when Patent Document 2 is applied, when a repeater that can receive multicast data once and retransmit it to another network such as a home wireless network is introduced, the repeater has different network characteristics. When reconfiguring the corresponding transmission packet, it is necessary to newly calculate and add FEC data for each new transmission packet. Therefore, in this case, a transmission delay occurs for the receiving terminal via the repeater.

  In particular, it is necessary for one repeater to perform relay processing for packets from many networks. For example, if only one network is relayed to one network, one route is sufficient, but when relaying five networks to each other, 25 routes are used, and when 10 networks are relayed, 100 routes are used. It will be quite loaded.

  Therefore, there is a problem that transmission delay in the network occurs due to the load of the repeater.

  In view of the above-described problems, the present invention aims at a content distribution system or the like in which a delay time is reduced by efficiently transferring packets in a repeater in a media content distribution service using IP multicast. Is to provide.

In view of the above-described problems, the content distribution apparatus of the present invention is
In a content distribution apparatus connected to a content distribution system in which IP multicast media content is distributed to at least one receiving apparatus,
A multiplexing unit that encodes and multiplexes media content to generate a media payload;
A media packaging unit that generates a media package by combining the media payloads;
Based on the media package, a media packet generation unit that generates a media packet according to characteristics of a network to be transmitted;
An FEC encoder that generates an FEC payload based on the media payload;
An FEC packaging unit that generates an FEC package by combining the FEC payloads;
An FEC packet generation unit that generates an FEC packet according to characteristics of a network to be transmitted based on the FEC package;
A transmitting unit for transmitting the media packet and the FEC packet to the receiving device,
It is characterized by providing.

The receiving apparatus of the present invention is
In a receiving device connected to a content distribution system for distributing IP multicast media content from a content distribution device,
A receiving unit for receiving media packets and FEC packets respectively;
A media package extraction unit for extracting a media package from the media packet;
An FEC package extraction unit for extracting an FEC package from the FEC packet;
A media payload restoration unit that decrypts the media package and restores the media payload;
An FEC payload restoring unit that decrypts the FEC package and restores the FEC payload;
If there is an error in the media payload, an error correction unit that performs error correction using the FEC payload;
A content decoding unit for decoding the media content by demultiplexing and decoding the media payload;
It is characterized by providing.

The relay device of the present invention
In a relay device connected to a content distribution system in which IP multicast media content is distributed from a content distribution device to at least one receiving device,
A receiving unit for receiving media packets and FEC packets from the content distribution device;
A repacketization unit for repacketizing the received media packet and FEC packet according to characteristics of a destination network;
A transmission unit that transmits the repacketized media packet and the FEC packet to the receiving device, respectively;
It is characterized by providing.

The content distribution system of the present invention includes:
In a content distribution system in which IP multicast media content is distributed from a content distribution device to at least one receiving device,
The content distribution device includes:
Encode and multiplex media content to generate media payload,
Combining the media payloads to generate a media package;
Based on the media package, generate a media packet according to the characteristics of the transmitted network,
Generating an FEC payload based on the media payload;
Combining the FEC payload to generate an FEC package,
Based on the FEC package, generate FEC packets according to the characteristics of the transmitted network,
Transmitting the generated media packet and the FEC packet to the receiving device, respectively;
The receiving device is:
Receiving media packets and FEC packets respectively;
Decode the received media packet to recover the media payload, decode the FEC packet to restore the FEC payload,
If there is an error in the media payload, error correction is performed using the FEC payload, and then the media payload is demultiplexed and decoded to decode the media content.
It is characterized by that.

Further, a relay device is further connected to the content distribution system of the present invention,
The relay device is
Each of the media packet and the FEC packet is received from the content distribution device,
The received media packet and FEC packet are repacketized according to the characteristics of the destination network, and the media packet and the FEC packet are transmitted to the receiving device, respectively.
It is characterized by that.

The content distribution method of the present invention includes:
A content distribution method in a content distribution system in which IP multicast media content is distributed from a content distribution device to at least one receiving device,
In the content distribution apparatus,
Encode and multiplex media content to generate media payload,
Combining the media payloads to generate a media package;
Based on the media package, generate a media packet according to the characteristics of the transmitted network,
Generating an FEC payload based on the media payload;
Combining the FEC payload to generate an FEC package,
Based on the FEC package, generate FEC packets according to the characteristics of the transmitted network,
Transmitting the generated media packet and the FEC packet to the receiving device, respectively;
In the receiving device,
Receiving media packets and FEC packets respectively;
Decode the received media packet to recover the media payload, decode the FEC packet to restore the FEC payload,
If there is an error in the media payload, error correction is performed using the FEC payload, and then the media payload is demultiplexed and decoded to decode the media content.
It is characterized by realizing this.

The program of the present invention
A computer that distributes media content connected to a content distribution system in which IP multicast media content is distributed to at least one receiving device;
A multiplexing function that encodes and multiplexes media content to generate a media payload;
A media package generation function for generating a media package by combining the media payloads;
Based on the media package, a media packet generation function that generates a media packet according to the characteristics of the network to be transmitted;
An FEC encoding function for generating an FEC payload based on the media payload;
An FEC package generation function for generating an FEC package by combining the FEC payloads;
An FEC packet generation function for generating an FEC packet according to the characteristics of a network to be transmitted based on the FEC package;
A transmission function for transmitting the media packet and the FEC packet to the receiving device;
It is characterized by realizing.

The program of the present invention
From a content distribution device to a computer that receives media content connected to a content distribution system for distributing IP multicast media content,
A receiving function for receiving media packets and FEC packets respectively;
A media package extraction function for extracting a media package from the media packet;
An FEC package extraction function for extracting an FEC package from the FEC packet;
A media payload restoration function for decrypting the media package and restoring a media payload;
An FEC payload restoration function for decoding the FEC package and restoring the FEC payload;
If there is an error in the media payload, an error correction function that performs error correction using the FEC payload;
A content decoding function for decoding the media content by demultiplexing and decoding the media payload;
It is characterized by realizing.

The program of the present invention
From a content distribution device to a computer that relays packets connected to a content distribution system in which IP multicast media content is distributed to at least one receiving device;
A receiving function for receiving media packets and FEC packets from the content distribution device;
A repacketization function for repacketizing the received media packet and FEC packet according to characteristics of a destination network;
A transmission function for transmitting the repacketized media packet and FEC packet to the receiving device;
It is characterized by realizing.

  According to the present invention, in the content distribution system, the content distribution device encodes one or a plurality of media contents to generate media fragments, multiplexes them to generate an indefinite length media payload, The media payload is packaged to generate a media package, and based on the media package, an FEC packet and a media packet are generated with network characteristics (for example, MTU size) to be transmitted, and the generated media packet is generated. And the FEC packet are respectively transmitted to the receiving side network to which the receiving device is connected.

  Then, the receiving device receives the media packet and the FEC packet from the receiving side network, depackets the received media packet, depackages the media payload, and extracts the FEC payload from the FEC packet in the same procedure. If there is an error in the media payload, error correction is performed using the FEC payload, then the media payload is demultiplexed to extract the media fragment, and the media fragment is decoded to decode the media content.

  As described above, since the FEC encoding calculation is performed in the processing stage without the influence of the network characteristics prior to packetization, the influence of the network characteristics at the time of FEC encoding can be eliminated. Even in such a case, it is not necessary to perform an FEC calculation process such as decoding the FEC packet once, performing error correction processing, and then performing encoding again. Therefore, the processing in the relay device is merely repacketized according to the network characteristics, and content transmission can be realized with a small delay time.

  Further, error correction processing for lost packets and the like is performed by the receiving device at the media decoding stage, and efficient network transmission is possible while substantially maintaining the service quality.

It is a figure for demonstrating the whole content delivery system in this embodiment. It is a figure for demonstrating the parity FEC. It is a figure for demonstrating the parity FEC. It is a figure for demonstrating the function structure of a content delivery server. It is a figure for demonstrating the function structure of a repeater. It is a figure for demonstrating the function structure of a receiving terminal. It is a figure for demonstrating the flow of a process of a content delivery server. It is a figure for demonstrating the flow of a process of a repeater. It is a figure for demonstrating the flow of a process of a receiving terminal.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

[1. System configuration]
FIG. 1 shows an entire content distribution system 1 to which the present invention is applied. The content distribution system 1 includes a distribution side network 3 and a reception side network 5, and the networks are connected to each other by a repeater 20. The distribution side network 3 and the reception side network 5 are, for example, IP networks configured by optical fiber networks, and a multicast group that shares the multicast address for each media content is configured.

  The content distribution server is an example of a distribution server for the IP broadcast service system or the video monitoring system, and distributes media content to another multicast address for each program or each camera video. FIG. 1 shows a case where the number of programs or the number of camera videos is two.

  A repeater is a device that relays a network. For example, a wireless LAN router in a home can be considered. In this case, the receiving side network 5 indicates a home wireless LAN network.

  As another example, the repeater may be a base station for a mobile device such as a mobile phone. Of course, the receiving side network 5 does not need to be a wireless network, and a wired LAN in a home or a company is also conceivable.

  In any case, the repeater receives the necessary media content from the distribution side network and redistributes it to the reception side network by multicast technology, so that the media at a large number of reception terminals connected to the reception side network can be obtained. Content reception can be realized.

  In the present embodiment, as an example, media content is transmitted from the content distribution server 10 via the multicast group of the distribution side network 3 to the reception terminal 30 via the relay group 20 and further to the reception terminal 30 via the multicast group of the reception side network 5. A case of distribution will be described.

[1.1 About MTU]
Here, the MTU used in the present embodiment will be described. In an IP network, data to be transmitted is divided into units called packets and transmitted. The maximum size (MTU: Maximum Transfer Unit) of the size of this packet is determined according to the type of network to be transmitted.

  For example, it is 1,500 bytes for Ethernet, and 2,370 bytes for one 802.11b wireless LAN standard. Since this MTU is the maximum value, a packet having a size larger than that cannot be transmitted as it is, and in this case, the size change (packet reconfiguration) is required at the repeater or the distribution server. When the packet size is less than or equal to the MTU, data transmission can be performed without changing the size, but the amount of data transmitted in one packet is reduced, resulting in a decrease in transmission efficiency.

  In the case of unicast content transmission in which the distribution server and the receiving terminal perform one-to-one communication, the MTUs of all the networks from the server to the receiving terminal are checked in advance, and the packet is transmitted with the minimum size packet. It is possible to use a method called a path MTU discovery method. However, when performing multicast distribution, the network involved in transmission may vary, so it is practically impossible to check the MTU in advance.

  Therefore, when data is transmitted by IP multicast, packets are reconstructed by a repeater that can grasp the network types on both the input and output sides.

[1.2 About FEC]
The FEC used in this embodiment will be described. The IP multicast technology generally uses UDP (User Datagram Protocol) as a transport layer protocol, and thus has a drawback of being vulnerable to data loss.

  Therefore, it is necessary to recover the missing data by some method. Typical error recovery techniques include automatic retransmission request (ARQ: Automatic Report reQuest) that resends and recovers the error part in response to a request from the receiving side, and redundant data by encoding according to a specific algorithm on the transmitting side. FEC (Forward Error Correction) for correcting errors on the receiving side.

  However, when considering a large-scale multicast group that takes advantage of the IP multicast feature of simultaneous content delivery to multiple recipients, the technology that sends a retransmission request to the server, such as ARQ, does not exchange requests and responses. The possibility to increase explosively increases. For this reason, FEC is generally used for error recovery technology in order not to increase the server load rapidly even in a large-scale multicast group. When an error exceeding the FEC error recovery limit occurs, the error recovery capability may be improved by using both ARQ and FEC in multicast.

  The FEC technique is realized by adding redundant data according to a preset algorithm to content data. Specific algorithms include various algorithms such as a parity FEC method, a Hamming code method, a Reed-Solomon method, and an LDPC (Low Density Parity Check Codes) code method.

[1.2.1 Parity FEC]
The parity code is simple among error detection / correction codes, and can be mathematically described by exclusive OR (XOR) of each bit of data. In this XOR operation, if the input value changes by one, the output value also changes. Therefore, one error can be detected by one parity bit.

  Therefore, if a plurality of parity bits are used, a plurality of errors can be detected and corrected. For example, if data A and B are present and A XOR B is also transmitted, even if data is corrupted for some reason, any two of A, B, and A XOR B are received. , A and B can be recovered.

  This is the same even if the transmission data is a bit stream of an arbitrary length. For example, as shown in FIG. 2, if “data A XOR B” is transmitted as a parity code in addition to “data A” and “data B”, for example, “data B” is lost during transmission. However, “data B” can be recovered (decoded) from “data A” and “data A XOR B”.

  In addition, as shown in FIG. 3, for example, when one FEC packet is calculated from four packets, even if one of the original four packets is lost, the FEC packet and another Three packets can be used to recover missing packets. The case of FIG. 3 shows a case where the packet 3 is lost, and the packet 3 is recovered (decoded) by the packet 1, the packet 2, the packet 4, and the FEC packet.

  However, the actual recovery of missing packets is generally performed in a two-stage process. In order to recover the lost packet, it is necessary to first determine the correct combination of the original data packet and the FEC packet, and then, in the second stage, data reconstruction is performed.

  At that time, in order to determine the correct combination of packets, it is necessary to use an appropriate algorithm. For example, when an FEC packet is received, its base sequence number and mask are checked to determine a data packet to be protected.

  If all the data packets have been received, the FEC packet is unnecessary and is discarded. If a portion of the data packet is missing and these sequence numbers are less than the maximum sequence number of the received packet, a recovery operation is attempted.

  When the recovery is successful, the FEC packet is discarded, and the recovered packet is stored in the reproduction buffer. If the sequence number of the data packet is greater than the maximum sequence number of the received packet, the FEC packet is stored so that it can be reused later. After that, when the data packet is received, the stored FEC packet is checked to check whether the recovery can be executed by this new data packet. If it is executed, the FEC packet is discarded after the recovery, and the recovered packet is Put in playback buffer.

  That is, in order for such an algorithm to function, it must be possible to determine whether or not a lost packet can be recovered by a specific data packet and an FEC packet. All the referenced packets need to be examined.

[1.2.2 Separate transmission of FEC and data]
Considering that the old receiving terminal that does not perform the data recovery process by FEC receives data, in many cases, the FEC packet is transmitted as a separate stream to the same destination address as the original packet through a different UDP port. The method is done.

  In addition, when the receiving terminal performs data recovery by FEC, if the network quality is poor and there are many omissions, it may be possible to solve the problem by receiving more FEC packets. For example, in that case, FEC packets with different error correction capabilities may be transmitted in separate streams, and the receiving terminal may receive the necessary FEC packets as necessary.

[2. Functional configuration]
Subsequently, the functional configuration of each apparatus will be described with reference to the drawings.

[2.1 Content distribution server]
First, the content distribution server 10 will be described with reference to FIG. As shown in FIG. 4, the content distribution server 10 includes a media content storage unit 102, an encoding unit 104, a multiplexing unit 106, an FEC encoding unit 108, a packaging unit 110 (a packaging unit 110a, a package). 110b), packetizer 112 (packetizer 112a, packetizer 112b), and transmitter 114.

  First, the media content storage unit 102 is a functional unit that stores media content. Note that media content may be temporarily stored in the media content storage unit 102 from the outside, or may be stored in advance. Furthermore, a configuration may be adopted in which media content is input from the outside in real time and output to the encoding unit 104.

  That is, it is only necessary to input media content to the encoding unit 104. Note that the media content is multimedia content in which content such as images, video, audio, and text is appropriately single or combined.

  The encoding unit 104 is a functional unit that converts and compresses the input multimedia content according to a specific encoding method. There are various encoding methods depending on the type of content. For example, JPEG, JPEG2000, PNG, etc. for images, MPEG audio, LPCM, ATRAC, WMA, etc. for audio, MPEG-1,-for video. 2, -4, H.I. If the text such as H.264, VP8, DivX, WMV, etc. is Japanese, for example, Shift-JIS, EUC-JP, UTF-8, etc. can be used.

  Media fragments that have undergone this encoding process are multiplexed by the multiplexing unit 106. For example, for a plurality of media fragments in units of video frames output from the encoding unit, the multiplexing unit combines them according to information such as their characteristics, time, order, synchronization, etc., and outputs them as a media payload.

  The media payload is packaged by the packaging unit 110a in a combination of, for example, image and text, video and audio, video and audio and text, and is output to the packeting unit 112a as a media package.

  Here, packaging is a mechanism that enables a plurality of content data streams to be collected and sent out at a higher data transfer rate. By this process, a plurality of content data is transferred from one place to another. It can be sent with one link.

  The media packages collected by the packaging unit 110a are converted into appropriate packet data (media packets) by the packetizing unit 112a in accordance with the characteristics of the network that is the transmission destination of the content distribution server 10.

  Then, the converted packet data (media packet) is transmitted to the distribution side network 3 via the transmission unit 114.

  One of the network characteristics is the above-described MTU, where packet information is added to the header, and packet data having a size matching the MTU is generated. In the conventional distribution server, the above-described FEC encoding process is performed for each packet data, and the calculated redundant packet data is output to the network as an FEC packet.

  However, the content distribution server according to the present embodiment is characterized in that content data is subjected to FEC encoding processing at the above-described media payload stage to generate redundant data (FEC payload) in units of media payload. In other words, since the characteristics of the network such as the MTU are considered in the processing in the packetizing unit, the FEC encoding can be performed regardless of the network characteristics. This makes it possible to reduce transmission delay when the repeater connected to the distribution-side network relays data to the heterogeneous network.

  Specifically, the FEC encoding unit 108 generates an FEC payload for each media payload. Then, the generated FEC payload is output to the packaging unit 110b.

  The packaging unit 110b packages the FEC payload and outputs it as an FEC package to the packetizing unit 112b. The FEC package is converted into appropriate packet data by the packetizing unit 112b in accordance with the characteristics of the network that is the destination of the content distribution server 10.

  Then, the converted FEC packet is transmitted to the distribution side network 3 via the transmission unit 114.

[2.2 Repeater]
Next, the configuration of the repeater 20 will be described with reference to FIG. The repeater 20 has a role of acquiring data from the distribution side network and retransmitting the data to the reception side network, and includes a reception unit 202, a depacketization unit 204, a packetization unit 206, and a transmission unit 208. It is configured.

  Here, a case where the MTU sizes are different is illustrated as a difference in network characteristics between the distribution side network and the reception side network before and after the repeater. First, the receiving unit 202 receives media packets and FEC packets having a packet size a from the distribution-side network 3 whose MTU is a. Then, the media packet is output to the depacketizer 204a, and the FEC packet is output to the depacketizer 204b.

  The depacketizing unit 204 once restores the media package and the FEC package based on the header information of the packet data. The packetizing unit 206 again sets the packet size b to match the characteristics of the receiving network 5 where the MTU is b. The packetizing unit 206 a generates the media packet, and the packetizing unit 206 b generates the FEC packet, and outputs the generated packet to the transmitting unit 208. Then, the data is transmitted from the transmission unit 208 to the reception-side network 5.

  In the prior art, after acquiring the media packet and the FEC packet from the distribution side network, the error correction processing unit determines whether the media packet needs to be corrected. If necessary, the FEC packet required for the error correction processing is determined. After the media packet is repaired using the packet packet, the packet packet is converted into a media package by the depacketizer, and the packetizer generates packet data that matches the characteristics of the receiving network whose MTU is b. On the other hand, it is necessary to newly calculate and generate redundant data again by the FEC encoder and send it to the receiving network.

  In the repeater, it is not necessary to reproduce the multimedia content that is generally transmitted. Therefore, it is not necessary to perform error correction processing by FEC decoding to completely restore the media package once, and to repacketize and FEC recalculate. However, when performing packet reconfiguration processing in accordance with network characteristics such as MTU, the conventional method had to perform the above processing.

  On the other hand, the repeater 20 in the present embodiment simply changes the packet size, for example, and eliminates unnecessary calculation processing such as FEC decoding / encoding. It is possible to relay the content reproduction at the connected receiving terminal or the receiving terminal connected to the receiving side network 5 without causing an extra delay.

  Also, if any of the receiving terminals connected to the receiving side network 5 has its reception quality lowered due to the state of the network, it confirms whether there is an FEC packet with a higher redundancy in the distribution side network 3. There is a case.

When there is an FEC packet with a high degree of redundancy, it may request acquisition of another FEC packet. In this case, the input at the repeater is, for example, a media packet and two different FEC packets, and the processing in the conventional method requires processing of FEC decoding / encoding using these three data. It becomes complicated. In contrast, the repeater 20 of the present embodiment can be realized by simply adding one set of packet reconstruction processing (depacketization and packetization).
[2.3 Receiving terminal]
Next, the receiving terminal 30 will be described with reference to FIG. The receiving terminal 30 includes a receiving unit 300, a depacketizing unit 302, a depackaging unit 304, an error correction processing unit 306, an FEC decoding unit 308, a demultiplexing unit 310, a decoding unit 312, and media content. And an output unit 314.

  Here, the receiving terminal 30 basically performs the reverse process of the distribution server 10. In other words, depending on the multimedia content to be received, it joins one of the multicast groups redistributed from the repeater 20 to the receiving network 5, and receives the media packet and the FEC packet from there.

  The received packet is output to depacketization section 302. Here, based on each packet header information, the media packet is restored to the media package by the depacketization unit 302a, and the FEC packet is restored to the FEC package by the depacketization unit 302b.

  These media package and FEC package are further output to the depackaging unit 304. Based on the header information at the time of packaging, the depackaging unit 304a restores the media payload, and the depackaging unit 304b restores the FEC payload. The media payload is output to the error correction processing unit 306, and the FEC payload is output to the FEC decoding unit 308.

  The necessity of error correction processing is determined by the error correction processing unit 306 for each payload, and when error correction processing is necessary, the FEC payload necessary for the processing is acquired from the FEC decoding unit 308.

  After the error correction processing is performed, the media content is restored by extracting the media fragment from the media payload by the demultiplexing unit 310 and restoring the data encoded by the decoding unit 312, and the media content output unit To 314.

  The media content output unit 314 outputs media content based on the input media content. For example, video data or text data is output to a display device, and audio data is output to an audio output device. Further, the media content output unit 314 may output the media content to the storage device once and store it, for example.

[3. Process flow]
Subsequently, the flow of processing in each apparatus will be described with reference to the drawings.

[3.1 Content distribution server]
First, the processing flow of the content distribution server 10 will be described with reference to FIG. First, media content is input (step S100). The input of media content means that the media content to be distributed is input to a service (processing) distributed by the content distribution server 10. The media content may be stored content or content distributed in real time from a broadcasting station, a video camera, or the like. In other words, the content distributed by the content distribution service 10 may be input.

  Next, the distributed media content is encoded to generate a media fragment (step S102). Then, the media fragment is multiplexed to generate a media payload (step S104).

  Next, an FEC payload based on the FEC code is generated based on the media payload (step S106). An FEC package is created from the FEC payload (step S108), and an FEC packet is generated from the FEC package at the MTU in the distribution side network 3 (step S110).

  In addition, a media package is generated from the media payload (step S114), and a media packet is generated from the media package in the MTU in the distribution side network 3 (step S116). Then, the media packet and the FEC packet are transmitted to the distribution side network 3 (step S112).

  Here, regarding the MTU of the distribution side network 3, the content distribution server 3 may store the MTU of the network in advance or inquire about the network. It may also be included in the request signal from the distribution network 3 side.

[3.2 Repeater]
Next, the processing flow of the repeater 20 will be described with reference to FIG. First, when the relay device 20 receives a packet from the distribution side network 3 (step S200), the relay device 20 analyzes the packet and determines the type of the packet (step S202).

  Here, if the received packet is a media packet (step S204; Yes), it is depacketized and a media package is extracted (step S206). Then, the extracted media package is packetized again at the MTU of the receiving network 5 this time, and a media packet suitable for the receiving network 5 is generated (step S208).

  On the other hand, when the received packet is an FEC packet (step S204; No), it is depacketized and an FEC package is extracted (step S210). Then, the extracted FEC package is packetized again at the MTU of the receiving network 5 this time, and an FEC packet suitable for the receiving network is generated (step S212).

  Then, the generated media packet and FEC packet are transmitted to the receiving network 3 (step S214).

[3.3 Receiving terminal]
Next, the processing flow of the receiving terminal 30 will be described with reference to FIG. First, a packet is received at the receiving terminal 30 (step S300). By analyzing the received packet, if the packet is a media packet (step S302; Yes), it is depacketized and a media package is extracted (step S304). Then, the media payload is restored from the media package (step S306).

  On the other hand, when the received packet is an FEC packet (step S302; No), it is depacketized and an FEC package is extracted (step S308). Then, the FEC payload is restored from the FEC package (step S310).

  Here, if there is an error in the media payload (step S312; Yes), the error location is specified, and the error correction processing is performed according to the FEC encoding algorithm using the FEC payload necessary for the correction. Execute (step S314). Subsequently, the media payload that has been subjected to error correction processing is demultiplexed to extract media fragments (step S316).

  The media content is decrypted from the extracted media fragment (step S318), and the decrypted media content is output (step S320).

  As described above, according to the present embodiment, the FEC packet is once decoded in the repeater, the FEC calculation process for correcting the error of the media packet is performed, the media package is extracted once, and the media package is extracted again. Thus, the packet can be relayed without performing processing such as packetizing the media packet and re-encoding the FEC packet using the media packet.

  As a result, the load on the repeater is reduced, so that it is possible to prevent a delay when distributing content, and it is possible to further save resources. In particular, the effect becomes more remarkable as the number of packets relayed by the repeater increases.

  In addition, by applying the above-described embodiment, for example, in a service such as VOD, in an IP multicast environment in which media content can be simultaneously transmitted to a large number of receiving terminals, the media content is further relayed to a home wireless LAN or a mobile network. In this case, it is necessary to reconstruct the transmission packet in the repeater (retransmitter). At this time, it is not necessary to recalculate the error correction code in the repeater. Media content can be transmitted to a larger number of receiving terminals with a small delay time.

[4. Modified example]
The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and the design and the like within the scope of the present invention are also within the scope of the claims. include.

  Further, in the processing executed in the above-described embodiment, each functional unit may be configured as hardware or may be realized as software. That is, it is good also as implement | achieving by memorize | storing the program which performs the process of FIGS. 7-9 in each apparatus, and being executed by a control part (for example, CPU etc.).

Moreover, you may implement | achieve part or all of each apparatus in embodiment mentioned above as LSI (Large Scale Integration) which is typically an integrated circuit. Each functional block of each device may be individually formed as a chip, or a part or all of them may be integrated into a chip. Further, the method of circuit integration is not limited to LSI, and may be realized by a dedicated circuit or a general-purpose processor. In addition, when integrated circuit technology that replaces LSI appears due to progress in semiconductor technology, it is of course possible to use an integrated circuit based on this technology.

DESCRIPTION OF SYMBOLS 1 Content distribution system 3 Distribution side network 5 Reception side network 10 Content distribution server 102 Media content storage part 104 Encoding part 106 Multiplexing part 108 FEC encoding part 110, 110a, 110b Packaging part 112, 112a, 112b Packetization part 114 Transmitter 20 Repeater 202 Receiver 204, 204a, 204b Depacketizer 206, 206a, 206b Packetizer 208 Transmitter 30 Receiver 30 Receiver 302, 302a, 302b Depacketizer 304, 304a, 304b Depackaged Unit 306 error correction processing unit 308 FEC decoding unit 310 demultiplexing unit 312 decoding unit 314 media content output unit

Claims (9)

In a content distribution apparatus connected to a content distribution system in which IP multicast media content is distributed to at least one receiving apparatus,
A multiplexing unit that encodes and multiplexes media content to generate a media payload;
A media packaging unit that generates a media package by combining the media payloads;
Based on the media package, a media packet generation unit that generates a media packet according to characteristics of a network to be transmitted;
An FEC encoder that generates an FEC payload based on the media payload;
An FEC packaging unit that generates an FEC package by combining the FEC payloads;
An FEC packet generation unit that generates an FEC packet according to characteristics of a network to be transmitted based on the FEC package;
A transmitting unit for transmitting the media packet and the FEC packet to the receiving device,
A content distribution apparatus comprising: In a receiving device connected to a content distribution system for distributing IP multicast media content from a content distribution device,
A receiving unit for receiving media packets and FEC packets respectively;
A media package extraction unit for extracting a media package from the media packet;
An FEC package extraction unit for extracting an FEC package from the FEC packet;
A media payload restoration unit that decrypts the media package and restores the media payload;
An FEC payload restoring unit that decrypts the FEC package and restores the FEC payload;
If there is an error in the media payload, an error correction unit that performs error correction using the FEC payload;
A content decoding unit for decoding the media content by demultiplexing and decoding the media payload;
A receiving apparatus comprising: In a relay device connected to a content distribution system in which IP multicast media content is distributed from a content distribution device to at least one receiving device,
A receiving unit for receiving media packets and FEC packets from the content distribution device;
A repacketization unit for repacketizing the received media packet and FEC packet according to characteristics of a destination network;
A transmission unit that transmits the repacketized media packet and the FEC packet to the receiving device, respectively;
A relay device comprising: In a content distribution system in which IP multicast media content is distributed from a content distribution device to at least one receiving device,
The content distribution device includes:
Encode and multiplex media content to generate media payload,
Combining the media payloads to generate a media package;
Based on the media package, generate a media packet according to the characteristics of the transmitted network,
Generating an FEC payload based on the media payload;
Combining the FEC payload to generate an FEC package,
Based on the FEC package, generate FEC packets according to the characteristics of the transmitted network,
Transmitting the generated media packet and the FEC packet to the receiving device, respectively;
The receiving device is:
Receiving media packets and FEC packets respectively;
Decode the received media packet to recover the media payload, decode the FEC packet to restore the FEC payload,
If there is an error in the media payload, error correction is performed using the FEC payload, and then the media payload is demultiplexed and decoded to decode the media content.
A content distribution system characterized by that. A relay device is further connected to the content distribution system,
The relay device is
Each of the media packet and the FEC packet is received from the content distribution device,
The received media packet and FEC packet are repacketized according to the characteristics of the destination network, and the media packet and the FEC packet are transmitted to the receiving device, respectively.
The content distribution system according to claim 4, wherein: A content distribution method in a content distribution system in which IP multicast media content is distributed from a content distribution device to at least one receiving device,
In the content distribution apparatus,
Encode and multiplex media content to generate media payload,
Combining the media payloads to generate a media package;
Based on the media package, generate a media packet according to the characteristics of the transmitted network,
Generating an FEC payload based on the media payload;
Combining the FEC payload to generate an FEC package,
Based on the FEC package, generate FEC packets according to the characteristics of the transmitted network,
Transmitting the generated media packet and the FEC packet to the receiving device, respectively;
In the receiving device,
Receiving media packets and FEC packets respectively;
Decode the received media packet to recover the media payload, decode the FEC packet to restore the FEC payload,
If there is an error in the media payload, error correction is performed using the FEC payload, and then the media payload is demultiplexed and decoded to decode the media content.
A content distribution method that achieves this. A computer that distributes media content connected to a content distribution system in which IP multicast media content is distributed to at least one receiving device;
A multiplexing function that encodes and multiplexes media content to generate a media payload;
A media package generation function for generating a media package by combining the media payloads;
Based on the media package, a media packet generation function that generates a media packet according to the characteristics of the network to be transmitted;
An FEC encoding function for generating an FEC payload based on the media payload;
An FEC package generation function for generating an FEC package by combining the FEC payloads;
An FEC packet generation function for generating an FEC packet according to the characteristics of a network to be transmitted based on the FEC package;
A transmission function for transmitting the media packet and the FEC packet to the receiving device;
A program to realize From a content distribution device to a computer that receives media content connected to a content distribution system for distributing IP multicast media content,
A receiving function for receiving media packets and FEC packets respectively;
A media package extraction function for extracting a media package from the media packet;
An FEC package extraction function for extracting an FEC package from the FEC packet;
A media payload restoration function for decrypting the media package and restoring a media payload;
An FEC payload restoration function for decoding the FEC package and restoring the FEC payload;
If there is an error in the media payload, an error correction function that performs error correction using the FEC payload;
A content decoding function for decoding the media content by demultiplexing and decoding the media payload;
A program to realize From a content distribution device to a computer that relays packets connected to a content distribution system in which IP multicast media content is distributed to at least one receiving device;
A receiving function for receiving media packets and FEC packets from the content distribution device;
A repacketization function for repacketizing the received media packet and FEC packet according to characteristics of a destination network;
A transmission function for transmitting the repacketized media packet and FEC packet to the receiving device;
A program to realize

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