JP2006174299A - Data distribution method, receiver, computer program and recording medium recording computer program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the number of missing packets which cannot be restored by FEC when the state of a communication path changes. <P>SOLUTION: A receiver 30 is used for communication network for performing unicast distribution for distributing data to a single receiver from a transmitter 10 or multicast distribution for distributing the same data to a plurality of receivers via one or more relay apparatuses from the transmitter. The receiver 30 is also used for executing a data distribution method for restoring missing packets generated on a communication path due to a redundancy coding system. The receiver 30 has a redundant packet request generating unit 36 for calculating the number of redundant packets suitable for the state of the communication path on the basis of a rate of missing packets generated on the communication path. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention provides communication for performing unicast distribution for distributing data from a transmitting device to a single receiving device, or performing multicast distribution for distributing the same data from a transmitting device to a plurality of receiving devices via one or more relay devices. The present invention relates to a data distribution method, a receiving apparatus, a computer program, and a recording medium on which this computer program is recorded, which is used in a network and repairs packet loss that occurs in a communication path by a redundant encoding method and improves distribution quality.

  In recent years, there has been an increasing demand for applications that require wide bandwidth and low delay, such as video stream distribution. In addition, with the increase in the Internet population, there is an increasing demand for multicast that enables large-scale multipoint distribution. As a protocol for realizing multicast in an IP (Internet Protocol) network based on packet communication, IP multicast and application layer multicast (for example, see Patent Document 1) have been proposed. In these methods, a packet distributed from a transmission device is delivered to a plurality of reception devices by duplicating it in a multicast router arranged in the network.

However, in a best-effort network such as the Internet, packet loss frequently occurs, which may lead to deterioration in distribution quality. Considering the video stream distribution, packet loss causes video disturbance.
A typical technique for repairing packet loss is ARQ (Automatic Repeat reQuest).

  In ARQ, when a packet loss occurs, a retransmission request is transmitted from the reception device to the retransmission device, and the retransmission device that receives this retransmits the lost packet to the reception device. That is, at least a round-trip propagation delay between the receiving device and the retransmission device is required for retransmission, and the data reception delay becomes large in a large-scale network such as the Internet. When multicast distribution is considered, retransmission processing load is concentrated on the retransmission apparatus due to an increase in the number of reception apparatuses, and scalability with respect to the number of reception apparatuses is limited.

  On the other hand, there is a method called FEC (Forward Error Correction) that repairs lost packets by using a redundant encoding method. In FEC, data to be transmitted is encoded and transmitted, and even if packet loss occurs on the communication path, the original data is restored by decoding at the receiving device. In FEC, lost packets can be repaired only by processing in the receiving apparatus, so the repair time does not depend on the delay of the communication path. Also, since retransmission is not required, the load is not concentrated on a specific device, and the scalability with respect to the number of receiving devices is excellent.

  RS (Reed-Solomon) code is a typical FEC encoding method. When the RS code is used, the transmission apparatus divides the packet sequence to be transmitted into blocks for each k packet, performs encoding for each block, and distributes the blocks. Here, k is called a block size. By encoding, h redundant packets are added for each block, so that a total of n (= k + h) packets are obtained. Then, the receiving apparatus decodes the received packet sequence for each block, and extracts k source packets.

  Here, even if a packet is lost on the communication path, if the receiving apparatus can receive any k packets among n packets, k source packets can be restored by decoding. However, if only less than k packets can be received, decoding cannot be performed and lost packets cannot be recovered. Therefore, it is necessary to set the number of redundant packets suitable for the communication path conditions.

The Internet is a heterogeneous network, and the status of communication channels varies depending on time and place. Therefore, when performing distribution using FEC in such a network, it is necessary to change the number of redundant packets depending on time and place.
Therefore, a method called AFEC (see Non-Patent Document 1) that adaptively changes the number of redundant packets has been proposed. AFEC is a method for determining the number of redundant packets based on the difference between the number of packets received by the receiving apparatus and the target value of the number of received packets. Since the determination of the number of redundant packets is performed every time the receiving apparatus receives one block, it can cope with the time change of the communication path condition.

  However, AFEC has a problem that the follow-up performance with respect to the change in the communication path status, that is, the time until the target value of the number of received packets is changed, due to the magnitude of the packet loss rate generated in the communication path. . For example, when the packet loss rate occurring on the communication path is 1%, the difference between the number of received packets and the target value is 5 packets, and when the packet loss rate is 10%, the difference is 5 packets. In some cases, both increase the number of redundant packets by the same number.

However, in practice, redundant packets are also discarded according to the packet loss rate of the communication path, so the latter requires more redundant packets. For this reason, the larger the packet loss rate of the communication path, the longer the time until the target value is achieved.
JP 2003-032300 A K. Park and W. Wang, “AFFC: An adaptive forward error correction protocol for end-to-end transport of real-time traffic Possible Transmission Error Correction Protocol ”, in Proc. Int. Conf. Computer Communications and Networks, Lafayette, LA (Lafayette, LA, USA), October 1997

On the other hand, in the multicast distribution, the present invention has already proposed a data distribution method corresponding to the difference in communication channel status depending on the location of each receiving device (Japanese Patent Application No. 2003-295308). In this data distribution method, first, the number of redundant packets required by each receiving apparatus is requested upstream. The notification of the number of redundant packets from each receiving device is aggregated by the multicast relay device, and the maximum redundancy is notified to the transmitting device.
The transmitting apparatus generates and distributes the notified maximum number of redundant packets. Then, the relay device discards excessive redundant packets based on the notification from each receiving device, whereby data distribution with redundancy suitable for each receiving device can be performed.

However, even in this data distribution method, since each receiving apparatus uses the AFEC method as a method for determining the number of redundant packets, the larger the packet loss rate in the communication path, the longer the time until the target value is achieved. .
As described above, in the method of adaptively updating the redundancy based on AFEC, as the packet loss rate in the communication channel is larger, the time until the target value of the number of received packets is achieved becomes longer. There is.

  The present invention has been made in view of such circumstances, and by quickly achieving the target value of the number of received packets regardless of the size of the packet loss rate, FEC can be used when the communication path conditions change. An object of the present invention is to provide a data distribution method, a receiving apparatus, a computer program, and a recording medium on which this computer program is recorded, which can reduce the number of lost packets that cannot be repaired by the above.

  In order to achieve the above object, the invention described in claim 1 is used in a communication network that performs unicast distribution in which data is distributed from a transmission device to a single reception device, and is generated in a communication channel by a redundant encoding method. In the data distribution method for repairing packet loss, the receiving device constantly monitors the packet loss state, calculates the number of redundant packets suitable for the communication path condition based on the packet loss rate occurring in the communication path, and The transmission device is notified.

The invention according to claim 2 is used in a communication network for performing multicast distribution in which the same data is distributed from a transmitting apparatus to a plurality of receiving apparatuses via one or more relay apparatuses, and is communicated by a redundant encoding method. In a data distribution method for repairing packet loss occurring on a channel, the receiving device calculates the number of redundant packets suitable for the channel status based on a packet loss rate occurring on the channel and notifies the transmitting device It is characterized by doing.
According to the first and second aspects of the present invention, by calculating the redundant packet based on the packet loss rate occurring in the communication path in the receiving device, the communication path state is obtained regardless of the magnitude of the packet loss rate. It is possible to quickly obtain the number of redundant packets suitable for the above.

According to a third aspect of the present invention, the same data is transmitted to a plurality of receiving devices from a transmitting device through one or more relay devices. A receiving device used in a communication network that performs multicast distribution and is used to implement a data distribution method that repairs packet loss that occurs in a communication path by a redundant encoding method, and is generated in the communication path It has a redundant packet request generation unit that calculates the number of redundant packets suitable for the communication path condition based on the packet loss rate.
According to the third aspect of the present invention, the receiving device calculates the redundant packet based on the packet loss rate occurring in the communication path, so that the communication path condition is maintained regardless of the size of the packet loss rate. A suitable number of redundant packets can be quickly obtained.

According to a fourth aspect of the present invention, the same data is transmitted to a plurality of receiving devices from a transmitting device through one or more relay devices. A computer program executed on a receiving device used for implementing a data distribution method used for a communication network for performing multicast distribution and for repairing packet loss generated in a communication path by a redundant encoding method, The computer is caused to execute a step of calculating the number of redundant packets suitable for the communication path condition based on the packet loss rate generated in the communication path.
According to the invention described in claim 4, by causing the computer constituting the receiving apparatus to execute the computer program, the receiving apparatus calculates a redundant packet based on the packet loss rate generated in the communication path. As a result, the number of redundant packets suitable for the communication path condition can be quickly obtained regardless of the size of the packet loss rate.

In the invention according to claim 5, the same data is transmitted to a plurality of receiving apparatuses from a transmitting apparatus via a unicast distribution that distributes data to a single receiving apparatus or from one transmitting apparatus to one or more relay apparatuses. Computer for recording a computer program to be executed on a receiving apparatus used for implementing a data distribution method for repairing packet loss generated in a communication path by a redundant encoding method, used in a communication network that performs multicast distribution A readable recording medium, characterized by recording a computer program that causes a computer to execute a step of calculating the number of redundant packets suitable for a communication path condition based on a packet loss rate occurring in the communication path. .
According to the fifth aspect of the present invention, the computer program is read from the recording medium on which the computer program is recorded, and the computer program is read out and executed. By calculating redundant packets based on the packet loss rate, the number of redundant packets suitable for the communication path condition can be quickly obtained regardless of the size of the packet loss rate.

  According to the present invention, in a communication network that performs unicast distribution or multicast distribution to which FEC is applied, the time until the target value of the number of received packets is achieved increases as the packet loss rate in the communication path increases. By calculating redundant packets based on the packet loss rate occurring on the communication path in the receiving device, the number of redundant packets suitable for the communication path status regardless of the size of the packet loss rate And the number of lost packets that cannot be repaired by FEC when the communication path status changes.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a distribution form of a communication system that performs unicast distribution to which the present invention is applied. Here, packet communication in the IP network is assumed.
In FIG. 1, data distributed from the transmission device 10 is received by the reception device 30 via the plurality of routers 20. In FIG. 1, two routers 20 are connected between the transmission device 10 and the reception device 30, but this is for simplification of explanation, and an arbitrary number may exist.

FIG. 2 shows a distribution form of a communication system that performs multicast distribution to which the present invention is applied. In FIG. 2, data distributed from the transmission device 10 is received by the plurality of reception devices 30 via the plurality of relay devices 40 and the multicast router 50 using the multicast protocol.
Here, the multicast protocol is the aforementioned IP multicast, application layer multicast, or the like.
The multicast router 50 is a router corresponding to the multicast protocol to be used.

The relay device 40 is a router corresponding to the multicast protocol used for distribution, and the aggregation of redundant packet requests and redundancy described in Japanese Patent Application No. 2003-295308 already proposed by the present inventor as described above. This device has a function to adjust the number of packets.
In FIG. 2, one or two relay devices 20, multicast routers 30, or receivers 40 are connected downstream of the relay device 20 and the multicast router 30, but this is for simplicity of explanation. In reality, more units can be connected. This is limited by the multicast protocol or the performance of the relay device 20 or the multicast router 30.

  FIG. 3 is a block diagram showing functional expansion of the inside of the receiving apparatus 30 constituting the communication system shown in FIGS. In FIG. 3, the receiving device 30 is directly connected to the transmitting device 10. However, as in FIGS. 1 and 2, a plurality of routers 20, relay devices 40, or multicasts between the transmitting device 10 and the receiving device 30. A router 50 may be connected.

  The receiving device 30 receives a packet distributed from an upstream device in the communication path, and notifies the upstream device of a request for the number of generated redundant packets, and decodes the received distribution packet by FEC. FEC decoding unit 32, a packet receiving unit 33 that extracts distribution data from the decoded packet, a data reception unit 34 that outputs the extracted data to a display device if it is, for example, video data, and the received distribution A packet loss detection unit 35 that detects packet loss from the packet and measures the packet loss rate, obtains the required number of redundant packets from the measured packet loss rate, and generates a request for the number of redundant packets to the upstream device A redundant packet request generation unit is provided.

  The redundant packet request generation unit of the receiving device 30 determines the number of redundant packets requested by the following equation, for example.

ここでｔは時刻を示しており、ＦＥＣの１ブロックを受信する時間で正規化した整数である。ｈ（ｔ）は受信装置３０が時刻ｔに受信するストリームの冗長パケット数、Ｔは受信装置３０が冗長パケット数を上流に要求し、その冗長パケット数が反映されたストリームを受信するまでの時間である。つまり受信装置３０は、時刻ｔに、時刻ｔ＋Ｔの冗長パケット数ｈ（ｔ＋Ｔ）を要求する。
ｑ（ｔ）は時刻ｔにおける通信路の通過率と呼び、パケット消失検出部３５で測定された時刻ｔにおける通信路でのパケット消失率をｐ（ｔ）とすると、ｑ（ｔ）＝１−ｐ（ｔ）で求まる。β（≧１）は余裕度とよばれる。

Here, t represents time, and is an integer normalized by the time for receiving one block of FEC. h (t) is the number of redundant packets of the stream received by the receiving device 30 at time t, and T is the time until the receiving device 30 requests the number of redundant packets upstream and receives the stream reflecting the number of redundant packets. It is. That is, the receiving device 30 requests the number of redundant packets h (t + T) at time t + T at time t.
q (t) is referred to as the passage rate of the communication path at time t, and when the packet loss rate on the communication path at time t measured by the packet loss detection unit 35 is p (t), q (t) = 1− It is obtained by p (t). β (≧ 1) is called a margin.

In the above equation, the target value of the number of packets received by the receiving device 30 is set to kβ, and the number of redundant packets that can achieve this target value at time t + T is obtained. As described above, in FEC, if k packets can be received per block, the original k packets can be restored. Therefore, the target value of the number of received packets may be k, but there is a margin for fluctuations in the communication path. Therefore, β is introduced.
In the above equation, the number of redundant packets is determined based on the packet loss rate (1-pass rate) of the communication path, and the target value of the number of received packets is achieved regardless of the size of the packet loss rate of the communication path. It is possible to quickly obtain the number of redundant packets.

FIG. 4 shows a distribution form when the communication channel condition of the communication system performing unicast distribution to which the present invention is applied varies. As shown in the figure, a case is considered where data is distributed from the transmission device 10 to the reception device 30 via the two routers 20.
First, transmission of distribution data from the transmission device 10 to the router 20 is started. Here, since the transmitter 10 has not yet been notified of the redundant packet request from the downstream, in the encoding, for example, an appropriate number of predetermined redundant packets such as 16 packets are generated and transmitted together with the distribution data. To do.

The two routers 20 transfer the packet distributed from the transmission device 10 to the reception device 30.
The receiving device 30 receives a packet transferred from the router 20 and decodes it every time one block is received to obtain original distribution data. Further, packet loss is detected from the received packet. Packet loss is detected, for example, by monitoring the sequence number in the received packet at the receiving device 30 by including a sequence number when generating a packet in the transmitting device 10, and detecting whether the number is interrupted. This can be achieved.

Then, for example, every second, the packet loss rate is obtained from the average value of the number of lost packets periodically every predetermined time, and further, the number of redundant packets requested based on this packet loss rate is obtained upstream. Notice.
The two routers 20 transfer the redundant packet request from the receiving device 30 to the transmitting device 10.
The transmission device 10 generates the number of redundant packets notified from the reception device at the time of encoding by FEC, and transmits the redundant packets together with the distribution data.
With these operations, it is possible to distribute to the receiving device 30 with the number of redundant packets suitable for the communication path condition.

  Here, let us consider a case where the channel condition changes and the packet loss rate on the channel changes. In this case, since the packet loss rate measured by the packet loss detection unit of the receiving device 30 changes, the redundant packet request generation unit 36 uses this value to determine a new number of redundant packets suitable for the changed communication path condition. Is calculated and notified to the upstream transmitting device 10. As a result, the receiving apparatus 30 is distributed with the number of redundant packets suitable for the changed communication path condition, and can cope with the time fluctuation of the communication path condition.

When AFEC is used here, as described above, there is a problem that the time until the target value of the number of received packets is reached increases as the packet loss rate in the communication path increases.
In contrast, in the present invention, redundant packets are calculated based on the packet loss rate occurring in the communication path, so that the number of redundant packets suitable for the communication path condition can be quickly obtained regardless of the size of the packet loss rate. And can respond quickly to fluctuations in the communication channel over time.
The same operation is performed even in a configuration in which an arbitrary number of routers 20 exist between the transmission device 10 and the reception device 30.

  FIG. 5 shows a distribution form in the case where the channel conditions of a communication system performing multicast distribution to which the present invention is applied fluctuate. As shown in the figure, a case is considered where data is distributed from the transmission apparatus 10 to three reception apparatuses 30 (these are referred to as reception apparatuses 30a, 30b, and 30c). Packets for data distribution are multicast-distributed from the transmission device 10 to the reception device 30a via the relay device 40, and to the reception devices 30b and 30c via the relay device 40 and the multicast router 50 downstream thereof. The

First, multicast of distribution data from the transmission device 10 to the relay device 40 is started. Here, since the transmitter 10 has not yet been notified of the redundant packet request from the downstream, in the encoding, for example, an appropriate number of predetermined redundant packets such as 16 packets are generated and transmitted together with the distribution data. To do.
The relay device 40 duplicates the packet distributed from the upstream transmission device 10 and transfers it to the reception device 30 a and the multicast router 50.

As described above, the relay device 40 has a function of adjusting the number of redundant packets, but since a redundancy packet request has not been notified from the downstream side, an appropriate redundant packet determined in advance, such as 16 packets, is used. The number is adjusted to the number, or the number of redundant packets is not adjusted.
The multicast router 50 duplicates the distribution data transferred from the relay device 40 and transfers it to the receiving devices 30b and 30c.
The receiving devices 30a, 30b, and 30c receive a packet transferred from each upstream device, decode it every time one block is received, and obtain original distribution data.

  Further, packet loss is detected from the received packet. Packet loss is detected, for example, by monitoring the sequence number in the received packet at the receiving device 30 by including a sequence number when generating a packet in the transmitting device 10, and detecting whether the number is interrupted. This can be achieved. Then, for example, every second, the packet loss rate is obtained from the average value of the number of lost packets periodically every predetermined time, and further, the number of requested redundant packets is obtained based on this packet loss rate and notified upstream. To do.

As described above, since the relay device 40 has a redundant packet request aggregation function, it stores redundant packet requests from the receiving devices 30a, 30b, and 30c, respectively, and stores the maximum value in the upstream transmitting device 10 as a maximum value. Forward.
The transmitter 10 generates the maximum number of redundant packets at the time of encoding by FEC, and transmits them together with the distribution data.
The relay device 40 adjusts and transfers the number of redundant packets of distribution data from upstream to the number of redundant packets requested from the stored receiving devices 30a, 30b, and 30c. That is, only the required number of redundant packets are transferred to the receiving devices 30a, 30b, and 30c, and the rest are discarded.

By these operations, it is possible to distribute to the receiving devices 30a, 30b, and 30c with the number of redundant packets suitable for the respective communication path conditions.
Here, a case is considered where the communication path state between the relay device 40 and the receiving device 30a changes and the packet loss rate changes. In this case, since the packet loss rate measured by the packet loss detector 35 changes in the receiving device 30a, the redundant packet request generator 36 creates a new redundancy suitable for the changed communication path status based on this value. The number of packets is calculated and notified to the upstream relay device 40.

  The relay device 40 requests the transmitting device 10 for the maximum number of requested redundant packets from the receiving devices 30a, 30b, and 30c as before, and determines the number of redundant packets of distribution data from the transmitting device 10 as the receiving devices 30a, 30a, The number of redundant packets requested from 30b and 30c is adjusted and transferred. As a result, the receiving device 30a is distributed with the number of redundant packets suitable for the changed communication path condition, and the receiving devices 30b and 30c are distributed with the same number of redundant packets as before. The number of redundant packets can be adjusted.

Here, when the number of redundant packets is calculated by the same method as AFEC as in the data distribution method (Japanese Patent Application No. 2003-295308) already proposed by the present inventor, as described above, There is a problem that the time until the target value of the number of received packets is achieved becomes longer as the packet loss rate becomes larger.
On the other hand, in the data distribution method and the receiving device according to the present invention, since the redundant packet is calculated based on the packet loss rate occurring in the communication path, the communication path condition is maintained regardless of the size of the packet loss rate. A suitable number of redundant packets can be quickly obtained, and it is possible to quickly cope with time fluctuations in the communication path.
The same operation is performed even in a configuration in which an arbitrary number of relay devices 40 or multicast routers 50 exist between the transmission device 10 and each reception device 30.

Note that the transmission device 10, the router 20, the reception device 30, the relay device 40, and the multicast router 50 according to the embodiment of the present invention described above have a computer system therein.
The operation processes of the transmission device 10, the router 20, the reception device 30, the relay device 40, and the multicast router 50 are stored in a computer-readable recording medium in the form of a program. Is read and executed, the above processing is performed.

The computer system here includes an OS and hardware such as peripheral devices.
In addition to ROM, “computer-readable recording medium” refers to a portable medium such as a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, or a storage device such as a hard disk built in a computer system. That means.
Further, the “computer-readable recording medium” refers to a volatile memory (RAM) in a computer system serving as a system or a client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. In addition, those holding a program for a certain period of time are also included.

The program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line.
The program may be for realizing a part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, and what is called a difference file (difference program) may be sufficient.

The block diagram which shows an example of the delivery form of the communication system which performs the unicast delivery to which this invention is applied. The block diagram which shows an example of the delivery form of the communication system which performs the multicast delivery to which this invention is applied. The block diagram which shows the specific structure of an example of the receiver which comprises the communication system which performs the unicast delivery to which this invention is applied, or multicast delivery. The block diagram which shows an example of a delivery form when the channel conditions of the communication system which performs the unicast delivery to which this invention is applied fluctuate | variate. The block diagram which shows an example of a delivery form when the channel conditions of the communication system which performs the multicast delivery to which this invention is applied fluctuate | variate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Transmitting device 20 ... Router 30, 30a, 30b, 30c ... Receiving device 31 ... Communication I / F
32 ... FEC decoding unit 33 ... packet receiving unit 34 ... data receiving unit 35 ... packet loss detecting unit 36 ... redundant packet request generating unit 40 ... relay device 50 ... multicast router

Claims (5)

In a data distribution method that is used in a communication network that performs unicast distribution that performs data distribution from a transmission device to a single reception device, and that repairs packet loss that occurs in a communication path using a redundant encoding method,
The receiving device constantly monitors the packet loss state, calculates the number of redundant packets suitable for the communication channel state based on the packet loss rate occurring in the communication channel, and notifies the transmission device Data delivery method. Data distribution that is used in a communication network that performs multicast distribution in which the same data is distributed from a transmitting device to a plurality of receiving devices via one or more relay devices, and that repairs packet loss that occurs in the communication path using a redundant coding scheme In the method
The receiving apparatus calculates a number of redundant packets suitable for a communication path condition based on a packet loss rate generated in the communication path and notifies the transmitting apparatus of the number of redundant packets. Used in communication networks that perform unicast distribution that distributes data from a transmission device to a single reception device, or multicast distribution that distributes the same data from a transmission device to multiple reception devices via one or more relay devices. A receiving apparatus used to implement a data distribution method for repairing packet loss that occurs in a communication path by a redundant encoding method,
A receiving apparatus comprising: a redundant packet request generation unit that calculates a number of redundant packets suitable for a communication path condition based on a packet loss rate generated in the communication path. Used in communication networks that perform unicast distribution that distributes data from a transmission device to a single reception device, or multicast distribution that distributes the same data from a transmission device to multiple reception devices via one or more relay devices. A computer program executed on a receiving device used to implement a data distribution method for repairing packet loss that occurs in a communication path by a redundant encoding method,
Calculating the number of redundant packets suitable for the channel conditions based on the packet loss rate occurring in the channel;
A computer program for causing a computer to execute. Used in communication networks that perform unicast distribution that distributes data from a transmission device to a single reception device, or multicast distribution that distributes the same data from a transmission device to multiple reception devices via one or more relay devices. A computer-readable recording medium recording a computer program executed on a receiving apparatus used to implement a data distribution method for repairing packet loss occurring in a communication path by a redundant encoding method,
Calculating the number of redundant packets suitable for the channel conditions based on the packet loss rate occurring in the channel;
A recording medium for recording a computer program for causing a computer to execute.

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