JP2003264590A - Packet transmission system and its data transmitting device and data receiving device - Google Patents

Abstract

(57) [Problem] To improve transmission quality by simple control in packet transmission using UDP. SOLUTION: In a data transmission device TS, a parity packet is generated every four packets for a data packet to be transmitted, and the parity packet is inserted into the data packet and transmitted. On the other hand, in the data receiving device RS, every time a parity packet is received, the presence or absence of a data packet is determined using the parity packet. When the drop is detected, the dropped data packet is identified based on the sequence number assigned to the received data packet in place of the source port number, and the received data packet and the parity packet are identified. Then, the dropped data packet is reproduced based on the above.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an IP (Internet Protocol) configured by using a router, a switch and the like.
The present invention relates to a packet transmission system for transmitting data by UDP (User Datagram Protocol) in a network, and a data transmission device and a data reception device used in this system.

[0002]

2. Description of the Related Art TCP (Transmission Control) is a standard upper-layer protocol of IP used in an IP network.
Protocol) and UDP.

TCP is a connection-type protocol, and has a connection management function for setting a connection by using a VC (Virtual Circuit), a response confirmation function for notifying a source of a response each time a destination receives a packet, and a packet. A sequence function that assigns a sequence number to each packet to identify undelivered packets, a window control function that provides a buffer to store multiple packets and confirms responses in buffer units, and the amount of packets that the destination can receive is sent in advance. It has a flow control function to notify the original.

FIG. 6 shows an outline of this TCP data transmission. In the figure, the sender (source)
The data transmission apparatus TSt of 1 transmits a packet by sequentially assigning a sequence number to each packet, and the data transmission apparatus RSt of the receiving side (destination) receives a reception response (AC
K) Send it back. Then, the data transmission device TSt on the transmission side
Retransmits a packet for which no reception response is obtained, and the data transmission device RSt on the receiving side sequentially reproduces each received packet according to its sequence number.

As described above, TCP can realize highly reliable communication due to the sequence function, the flow control function and the like. However, on the other hand, the processing load is heavy and the packet delivery time varies. Therefore, it is not suitable for communication of stream data that requires real-time property such as video and audio. Further, it cannot be applied to multicast communication or the like in which retransmission control cannot be performed.

On the other hand, unlike TCP, UDP has a connection management function, a response confirmation function, a sequence function,
It is a connectionless protocol that does not have a window control function and a flow control function, and does not set a connection with a communication partner.

FIG. 7 shows an outline of data transmission by this UDP. In the figure, the sender (source)
The data transmission device TSu of the above-mentioned packetizes the data generated by the higher-level application in the generation order and transmits the packet. At that time, it is not confirmed whether or not the packet is certainly received by the data transmission device RSu on the receiving side (destination). The data transmission device RSu on the receiving side (destination) reproduces the received packets in order.

Therefore, the UDP can perform data transmission with a relatively light processing without requiring complicated control. Therefore, the points using the communication of stream data, which requires real-time processing such as moving images and audio, and the use of broadcast or multicast as described above,
Suitable for to multipoint communication.

[0009]

However, since UDP does not have a function for ensuring the reliability of communication such as a response confirmation function and a sequence function as described above, a packet is lost during transmission. But it is not resent. For this reason, for example, if packets are lost during the distribution of a moving image or audio, the reproduced image or audio will be interrupted and the data quality will be deteriorated.

The present invention has been made in view of the above circumstances. An object of the present invention is to provide a packet transmission system capable of improving the transmission quality by simple control in data transmission using UDP and its data. It is to provide a transmitter and a data receiver.

[0011]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention transfers data to be transmitted to a UDP (User Data).
In a packet transmission system for transmitting a packet from a transmission side to a reception side via a network using an agram protocol), the transmission side is provided with first and second packet generation means. Then, the first packet generating means generates a plurality of data packets based on the data to be transmitted, and the second packet generating means generates a parity packet for every predetermined number of the plurality of data packets generated. It generates and transmits the generated plurality of data packets and parity packets to the network. On the other hand, the receiving side is provided with a means for judging the presence / absence of dropped packets and a reproducing means. Then, the determining means performs a parity check on the basis of the received data packet and parity packet to determine whether or not the data packet is lost, and when the loss of the data packet is detected, the reproducing means performs the reception. The lost data packet is reproduced based on the data packet and the parity packet that have been deleted.

Therefore, according to the present invention, even if a packet is lost during UDP packet transmission, the lost packet can be regenerated from the received packet and the parity packet. Therefore, it is possible to reproduce the dropped packet with a comparatively light processing load without generating extra traffic as in the case of using the response confirmation function or the sequence function. Therefore, it becomes possible to transmit stream data, such as a moving image or a sound, which requires real-time property, in real time and with good quality. Further, the present invention can be applied to point-to-multipoint communication using broadcast or multicast that cannot perform retransmission control, and can realize high-quality point-to-multipoint communication.

Specifically, in the first packet generating means, the data packet is transmitted with a sequence number reset for each parity packet. On the other hand, in the reproducing means, when the loss of the data packet is detected, the lost data packet is specified based on the sequence number given to the received data packet. This makes it possible to easily identify the dropped packet based on the sequence number of the data packet that could be received.

In the second packet generating means, a parity bit is calculated bit by bit for the payload of the predetermined number of data packets, and the calculated parity bit is inserted into the parity packet and transmitted.
On the other hand, in the reproducing means, when the loss of the data packet is detected, based on the information bit of the payload of the received data packet and the parity bit corresponding to the information bit of the received parity packet. , Reproduce the information bits of the payload of the lost data packet. By doing so, the information bits of the payload of the data packet can be reproduced in bit units.

Further, when the data packet generated by the first packet generating means has a variable length and the information indicating the packet length is inserted into the header of the data packet, the second packet generating means causes the predetermined packet to be transmitted. A parity bit is calculated bit by bit for information representing the packet length of a number of data packets, and the calculated parity bit is inserted into the parity packet and transmitted. On the other hand, in the reproducing means, when the loss of the data packet is detected, the information indicating the packet length inserted in the header of the received data packet and the information indicating the packet length of the received parity packet. The packet length of the dropped data packet is obtained based on the parity bit corresponding to. In this way, even if the data packet has a variable length, the packet length of the dropped data packet can be reproduced.

Further, when the data packet generated by the first packet generating means has a variable length, the second packet generating means causes the data packet shorter than the maximum length data packet of the predetermined number of data packets. Parity bits are obtained by regarding the short and small portions of the packet as "0" bits, and the obtained parity bits are inserted into the parity packet and transmitted. On the other hand, in the reproducing means, when the dropout of the data packet is detected, the short or small portion of the received data packet is regarded as the “0” bit, and the regarded “0” bit and the received parity packet are described above. The lost data packet is reproduced based on the parity bit corresponding to the short and small portions.

In this way, for example, even when the maximum length data packet is dropped, the lost maximum length data packet of the received data packet is regarded as the "0" bit and the corresponding parity bit of the parity packet. It becomes possible to reproduce all parts.

[0018]

1 is a schematic configuration diagram showing an embodiment of a packet transmission system according to the present invention.
The system of this embodiment includes a data transmission device (hereinafter referred to as a data transmission device) TS that is a transmission side (transmission source),
A plurality of data transmission devices (hereinafter, data receiving devices) RS1 to RSn on the receiving side (destination) are connected to the IP (Internet Pro
tocol) network NW to connect from data transmission device TS to data reception devices RS1 to RSn by UDP / IP (User
Data is transmitted in packets using the Datagram Protocol / Internet Protocol.

By the way, the data transmission device TS is constructed as follows. FIG. 2 is a block diagram showing the functional configuration. This data transmission device TS includes a data generation unit 1
1, a data packet generator 12, a parity packet generator 13, and a packet transmitter 14.

The data generation unit 11 converts a data stream formed by an application of an upper layer, for example, a data stream made up of images and audio, into MPEG (Moving Picture Experts G).
roup) and the like to encode transmission data to generate transmission data.

The data packet generator 12 takes in the transmission data generated by the data generator 11, packetizes the transmission data according to UDP / IP, and thereby generates a plurality of data packets DP11, DP12, .... As shown in FIG. 4, each of the data packets DP11, DP12, ...
It is composed of DP data. The UDP data (payload) has a variable length, and the encoded image and audio data is inserted.

A source port number field and a length field are provided in the UDP header. Information indicating the packet length of the data packet DP11, DP12, ... Is inserted in the length field. Meanwhile, a sequence number (for example, 0x0001, 0x0002, ...) Representing the transmission order of the data packets DP11, DP12, ... Is inserted in the source port number field. This sequence number is generated by the counter.
The counter counts up the count value as "1", "2", ... Each time the data packets DP11, DP12, ... Are generated, and counts at the timing when the parity packet is generated in the parity packet generation unit 13 described later. Reset the value.

The parity packet generator 13 fetches a predetermined number of data packets DP11, DP12, ... Generated by the data packet generator 12, for example, 4 packets each, and temporarily stores them in a buffer.
One parity packet PP1 is generated for each of the data packets DP11 to DP14.

As shown in FIG. 4, the parity packet PP1 is composed of an IP header, a UDP header, and UDP data, like the data packets DP11, DP12, ... It is set to the same length as the data packet DP11 having the maximum length among the data packets DP11 to DP14.

A specific number (for example, 0xffff) indicating a parity packet is inserted in the transmission source port number field of the UDP header. In the length field of the UDP header, a parity bit (for example, even parity) generated for the information indicating the packet length inserted in the length field of the four stored data packets DP11 to DP14 is inserted. Further UD
The four data packets D stored above are included in the P data.
A parity bit (for example, even parity) generated for the payload information inserted in the UDP data of P11 to DP14 is inserted. These parity bits are generated for each bit in the same position of the four data packets DP11 to DP14. Data packets DP12, DP13, DP14 shorter than the maximum length data packet DP11
Parity bits are generated by regarding the short portions a, b, and c of “0” as “0”.

The packet transmission unit 14 is configured to generate each data packet DP1 generated by the data packet generation unit 12 described above.
, And the parity packets PP1, ... Generated by the parity packet generating unit 13 are transmitted to the IP network NW in the order of generation.

On the other hand, the data receiving device RS is constructed as follows. FIG. 3 is a block diagram showing the functional configuration. This data receiving device RS is a packet receiving device RP.
And a data reproducing device RD.

The packet receiving device RP comprises a packet receiving unit 21, a parity check unit 22, a lost packet reproducing unit 23, and a packet output unit 24. The packet receiving unit 21 receives data from the data transmitting device TS from the IP network N.
Data packets DP11, DP12, transmitted via W,
... and parity packets PP1, ... Are respectively received.

The parity check unit 22 receives the plurality of data packets DP received by the packet receiving unit 21.
For 11, DP12, ..., Parity check is performed every four packets based on the parity packet. Then, by this parity check, it is determined whether or not a dropped packet has occurred.

The lost packet reproducing unit 23, when the parity check unit 22 determines that there is a lost packet, performs processing for specifying the lost packet,
A process for reproducing the specified lost packet is executed.

The lost packet identification process is performed by using the sequence number (for example, 0x0001, 0x000) from the source port number field of the UDP header of the plurality of received data packets.
(2, ...) is extracted and a gap is found from the continuity of the extracted sequence numbers.

The reproduction processing of the specified lost packet is performed by the information indicating the packet length inserted in the UDP header of the received data packet and the UDP of the parity packet.
The packet length information of the lost packet is reproduced based on the parity bit inserted in the header. At the same time, the payload information of the drop packet is reproduced based on the payload information inserted in the UDP data and the parity bit inserted in the UDP data of the parity packet. At this time, when the data packet has a variable length, the short or small portion of the received data packet is regarded as a “0” bit, and this regarded “0” bit corresponds to the short or small portion of the received parity packet. The lost data packet is reproduced based on the parity bit.

When the parity check unit 22 determines that there are no dropped packets, the packet output unit 24 receives the data packets DP11, DP12, ... Transfer to RD. On the other hand, when the parity check unit 22 determines that there is a lost packet, the data packet received by the packet receiving unit 21 and the data packet reproduced by the lost packet reproducing unit 23 are received in the order of reception. Are prepared and transferred to the data reproducing device RD. The parity packet is discarded.

The data reproducing device RD depacketizes and decodes the data packet transferred from the packet output unit 24, thereby reproducing the image and audio data streams.

Next, the operations of the packet transmission system and the data transmitting apparatus and the data receiving apparatus thereof configured as above will be described. Here, in the system shown in FIG. 1, the data transmission device TS is replaced by the data reception device RS1.
On the other hand, a case of transmitting data composed of a moving image and audio will be described as an example.

In the data transmission device TS, when an image data stream and an audio data stream are generated by an application (not shown), these data streams are encoded by the data generation unit 11 and then input to the data packet generation unit 12. Here, the data is packetized according to UDP / IP, and thereby data packets are sequentially generated.

The data packets generated by the data packet generation unit 12 are fetched into the parity packet generation unit 13 by four packets. The parity packet generation unit 13 generates one parity packet based on the fetched four data packets.

For example, assume that the four data packets DP11, DP12, DP13, DP14 shown in FIG. Then, in the parity packet generation unit 13,
First, the data packets DP11, DP12, DP13, DP
For the information indicating the packet length inserted in the 14 UDP headers, even parity is generated for each bit at the same position. Then, this even parity is inserted into the length field provided in the UDP header of the parity packet PP1.

Next, the four data packets DP11,
For the payload information inserted in the UDP data of DP12, DP13, DP14, even parity is generated for each bit at the same position. Then, this even parity is inserted into the UDP data of the parity packet PP1. At this time, the data packets DP11, DP1
Data packet D with the maximum length of 2, DP13, DP14
Data packets DP12, DP with packet length shorter than P11
The short portions a, b, and c of 13, DP14 are regarded as "0" and even parity is generated.

The four data packets DP11, DP12, D generated by the data packet generator 12 are
Sequence numbers 0x0001, 0x0002, 0x0003, 0x0004 counted by the counter of the data packet generation unit 12 are inserted in the transmission source port number fields of P13 and DP14. The parity packet generator 13 inserts a specific number, for example, 0xffff, indicating that the packet is a parity packet, in the source port number field of the parity packet PP1.

The four data packets DP11, DP12, DP generated by the data packet generator 12 in this way
13, DP14, and the parity packets PP1, ... Generated by the parity packet generation unit 13 are the IP network N in order.
Sent to W.

Similarly thereafter, the data packets generated by the data packet generation unit 12 are taken into the parity packet generation unit 13 by four packets, and the parity packet generation unit 13 generates the parity packets for the four data packets. To be done. And the above 4
Number of data packets followed by the parity packet I
It is transmitted to the P network NW.

On the other hand, in the data receiving device RS, the data receiving / reproducing operation is performed as follows. That is, when a packet is transmitted from the data transmission device TS via the IP network NW, this packet is received by the packet reception unit 21 and then input to the parity check unit 22. Every time a parity packet is input, the parity check unit 22 performs a parity check on a plurality of data packets received prior to the parity packet based on the parity packet, and thereby checks whether or not the data packet is dropped. To be judged. For example, when the parity packet PP1 shown in FIG. 4 is input, it is determined whether or not the four data packets DP11, DP12, DP13, DP14 to be received prior to the parity packet PP1 are dropped. If no data packet is dropped as a result of this determination, the four received data packets DP11, DP12, DP13, DP14 are transferred from the packet output unit 24 to the data reproduction device RD as they are.

On the other hand, it is assumed that the drop of the data packet is detected by the above parity check. Then, the lost packet reproducing unit 23 first extracts the sequence number from the source port number field of the data packet received prior to the parity packet PP1, and based on the extracted sequence number, the lost data packet Specified. For example, the sequence number extracted from the received data packet is “1”,
If it is "2" or "4", the sequence number is "3"
It is possible to specify that the data packet DP13 has been dropped.

Next, the reproduction processing of the specified lost data packet DP13 is performed. The dropped data packet DP13 is the received three data packets DP1.
Reproduction is possible based on 1, DP12, DP14 and parity packet PP1. That is, the packet length information of the lost data packet is reproduced from the length field information of the three received data packets DP11, DP12, DP14 and the parity bit inserted in the length field of the parity packet PP1. The packet length of the lost packet is reproduced based on the reproduced packet length information. Also, the three received data packets D
Information bits of UDP data of P11, DP12, DP14,
The UDP data of the dropped data packet is reproduced from the parity bit of the UDP data of the parity packet PP1. The data packet DP1 received at this time
2, DP14 short and small parts a and c are regarded as "0" and calculation for reproduction is performed. In this embodiment, if two or more data packets are dropped or the parity packet cannot be received, the data cannot be reproduced.

The reproduced data packet DP13 is
Received three data packets DP11, DP12, DP
It is input to the packet output unit 24 together with 14, is arranged in order based on the sequence number, and is then output to the data reproduction device RD.

In the data reproducing device RD, the four data packets DP11,
DP12, DP13, and DP14 are depacketed and then decoded, whereby image data and audio data are reproduced. The reproduced image data is displayed on the display, and the audio data is output from the speaker. Also,
These image data and audio data are stored in the memory as needed.

Similarly, the parity packets PP2, PP
Each time 3 ... Is received, the presence / absence of a data packet received prior to that is determined, and when the loss is detected, the lost packet reproducing unit 23 identifies the lost data packet and reproduces it. Then, the reproduced data packets are arranged in order by the packet output unit 24 together with the three received data packets,
The data is transferred to the data reproducing device RD and reproduced.

As described above, in this embodiment, in the data transmission device TS, the data packet D to be transmitted is transmitted.
Parity packets PP1, PP2, ... Are generated for every four packets of P11, DP12, ... And these parity packets PP1, PP2 ,.
It is inserted into DP12, ... And transmitted. Then, in the data receiving device RS, every time the parity packets PP1, PP2, ... Are received, it is determined whether or not the data packet is dropped using the parity packets PP1, PP2 ,. And when the dropout is detected,
The lost data packet is identified based on the sequence number given to the received data packet instead of the source port number, and the dropped data is based on the received data packet and parity packet. I am trying to replay the packet.

Therefore, even if a data packet is dropped during UDP / IP packet transmission, the dropped data packet can be regenerated from the three data packets that have been received and the parity packet. For this reason, it is possible to improve the transmission quality with simple control compared to the case of using the response confirmation function or the sequence function, and as a result, stream-based data or broadcast that requires real-time property such as video and audio. Alternatively, transmission data in point-to-multipoint communication using multicast or the like can be transmitted in real time and with good quality.

Further, in this embodiment, a sequence number is added to the UDP header of the data packet instead of the transmission source port number, and the data packet is transmitted, and the dropped data packet is specified based on this sequence number. Therefore, the dropped packet can be easily specified based on the sequence number of the data packet that can be received.

Further, in this embodiment, when the data packet has a variable length, the parity bit is also obtained in bit units for the information indicating the packet length inserted in each data packet, and the obtained parity bit is used as the parity packet. Insert and send. Then, the receiving side determines the packet length of the dropped data packet based on the parity bit of this parity packet. Therefore, even if the data packet has a variable length, the packet length of the dropped data packet can be accurately reproduced.

Furthermore, when transmitting a variable-length data packet, the parity bit is obtained by regarding the short and small portions of the data packet shorter than the maximum-length data packet as "0" bits, and the obtained parity bit is used as the parity packet. And send it. On the other hand, on the receiving side, the short and small portions of the received data packet are regarded as “0” bits, and based on the regarded “0” bit and the parity bit corresponding to the short and small portions of the received parity packet. , The lost data packet is reproduced. Therefore, for example, even when the maximum length data packet is dropped, all parts of the dropped maximum length data packet are reproduced from the deemed “0” bit of the received data packet and the corresponding parity bit of the parity packet. Is possible.

The present invention is not limited to the above embodiment. For example, in the above embodiment, the case where a variable-length data packet is transmitted has been described as an example.
However, the present invention is also applicable to the case of transmitting a fixed-length data packet. FIG. 5 shows an example of the format of the data packet and the parity packet in this case. As shown in the figure, the parity bit of the information indicating the packet length is not inserted in the parity packet, but only the parity bit generated for the UDP data (payload information) is inserted. Note that the insertion of the sequence number in the transmission source port number field of each data packet is the same as in the case of transmitting a variable-length data packet described above (FIG. 4).

In the above embodiment, one parity packet is generated and transmitted for every four data packets. However, one parity packet may be generated and transmitted for every two packets or three packets, or one parity packet may be generated and transmitted for every five or more data packets. Good. The number of data packets for which the parity packet is generated can be arbitrarily set according to the quality of the transmission path and the required transmission quality. In this case, the setting may be adaptively changed according to the transmission quality and the like.

Further, in the above-mentioned embodiment, the case where the data is transmitted from the data transmitting device to one data receiving device RS1 has been described as an example, but from the data transmitting device TS to the plurality of data receiving devices RS1, RS2 ,. The present invention can also be applied to the case of transmitting the same data by broadcast. The present invention is also applicable to the case where a network device such as a router device is interposed between the data transmitting device TS and the plurality of data receiving devices RS1, RS2, ....

Further, in the above-mentioned embodiment, the packet receiving device RP and the data reproducing device RD are constructed separately, but the packet receiving device may be built in the data reproducing device and vice versa. May be built in the data reproducing device. Further, in the above-described embodiment, the case where the data generation unit is incorporated in the data transmission device has been described as an example, but the data generation device and the packet transmission device may be configured separately.

In addition, the types and configurations of the data transmitter and the data receiver, the types of networks, the types of transmission data, the configurations of data packets and parity packets, and the like are variously modified without departing from the scope of the present invention. Can be implemented.

[0059]

As described above in detail, according to the present invention, in the packet transmission system in which the data to be transmitted is packet-transmitted from the transmission side to the reception side through the network using UDP, the transmission side performs the transmission. A plurality of data packets are generated based on the target data, a parity packet is generated for each predetermined number of the generated plurality of data packets, and the generated plurality of data packets and parity packets are sent to the network. Send. On the other hand, on the receiving side, a parity check is performed based on the received data packet and parity packet to determine whether or not the data packet is dropped, and when the drop of the data packet is detected, the received data packet and The lost data packet is reproduced based on the parity packet.

Therefore, according to the present invention, it is possible to provide a packet transmission system capable of improving the transmission quality by simple control in data transmission using UDP, and a data transmitting apparatus and a data receiving apparatus thereof.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a packet transmission system according to the present invention.

FIG. 2 is a block diagram showing a functional configuration of a data transmission device of the packet transmission system shown in FIG.

FIG. 3 is a block diagram showing a functional configuration of a data receiving device of the packet transmission system shown in FIG.

FIG. 4 is a diagram showing a configuration of a data packet and a parity packet transmitted by the packet transmission system shown in FIG.

FIG. 5 is a diagram showing configurations of a data packet and a parity packet transmitted by the packet transmission system according to another embodiment of the present invention.

FIG. 6 is a diagram for explaining an outline of data transmission by TCP.

FIG. 7 is a diagram for explaining an outline of data transmission by UDP.

[Explanation of symbols]

TS ... Data transmission device RS1 to RSn ... Data receiving device RP ... Packet receiving device RD ... Data playback device NW ... IP network 11 ... Data generation unit 12 ... Data packet generator 13 ... Parity packet generator 14 ... Packet transmission unit 21 ... Packet receiving unit 22 ... Parity check unit 23 ... Dropped packet playback unit 24 ... Packet output unit

Continued front page    (72) Inventor Satoshi Shiozaki             2-3-1, Otemachi, Chiyoda-ku, Tokyo             Inside Telegraph and Telephone Corporation F-term (reference) 5K014 AA01 BA02 FA15                 5K030 HA08 JA05 LA01 LD06 MB13

Claims (16)

[Claims] 1. Data to be transmitted is transmitted by UDP (User Data).
In a packet transmission system for transmitting a packet from a transmission side to a reception side via a network using an agram protocol), the transmission side generates a plurality of data packets based on the transmission target data. Generating means; second packet generating means for generating, for each predetermined number of data packets generated by the first packet generating means, a parity packet including parity information based on the predetermined number of data packets; And a transmitting unit for transmitting the data packet and the parity packet generated by the first and second packet generating units to the network, the receiving side receiving the data packet and the parity packet arriving via the network. Means and the data packets received by the receiving means and the Paris. And a received data packet and a parity packet when the dropout of the data packet is detected by the decision means. And a reproducing means for reproducing the dropped data packet. 2. The first packet generating means assigns a sequence number to each of the predetermined number of data packets, which is reset for each parity packet, and the reproducing means detects the loss of the data packet. The packet transmission system according to claim 1, wherein the dropped data packet is specified based on the sequence number given to the received data packet. 3. The second packet generation means calculates a parity bit in bit units for the payloads of the predetermined number of data packets, inserts the calculated parity bit into the parity packet, and the reproduction means determines the data. When packet loss is detected, based on the information bit of the payload of the received data packet and the parity bit corresponding to the information bit of the received parity packet, the payload of the lost data packet is The packet transmission system according to claim 1, wherein the information bit is reproduced. 4. When the data packet generated by the first packet generation means has a variable length and information indicating the packet length is inserted in the header of the data packet, the second packet generation means is configured to perform the predetermined packet processing. A parity bit is obtained for each bit of information representing the packet length of the number of data packets, and the obtained parity bit is inserted into the parity packet, and the reproducing means receives the data packet when the dropout is detected. The packet length of the dropped data packet is obtained based on the information indicating the packet length inserted in the header of the data packet and the parity bit corresponding to the information indicating the packet length of the received parity packet. The packet transmission system according to claim 1, wherein: 5. When the data packet generated by the first packet generating means has a variable length, the second packet generating means is shorter than the maximum length data packet of the predetermined number of data packets. The short and small portions of the data packet are regarded as "0" bits, the parity bit is obtained, the obtained parity bit is inserted into the parity packet, and the reproducing means receives the data packet when the dropout is detected. The short and small portions of the data packet are regarded as "0" bits, and the dropped data packet is reproduced based on the regarded bit and the parity bit corresponding to the short and small portions of the received parity packet. The packet transmission system according to claim 1. 6. The data to be transmitted is transmitted by UDP (User Data).
In a data transmitting device for transmitting a packet to a receiving side using an agram protocol), the first packet generating means for generating a plurality of data packets based on the data to be transmitted, and the first packet generating means Second packet generating means for generating a parity packet containing parity information based on the predetermined number of data packets, and the first and second packet generating means. A data transmitting apparatus comprising: a transmitting unit that transmits a data packet and a parity packet to the receiving side. 7. The data transmitting apparatus according to claim 6, wherein the first packet generating means gives a sequence number that is reset for each parity packet to each of the predetermined number of data packets. . 8. The second packet generation means obtains a parity bit in bit units for the payloads of the predetermined number of data packets, and reproduces the obtained parity bit of the payload of the data packet dropped by the receiving side. 7. The data transmitting apparatus according to claim 6, wherein the data transmitting apparatus inserts the information into a parity packet. 9. When the data packet generated by the first packet generating means has a variable length and information indicating the packet length is inserted in the header of the data packet, the second packet generating means is operable to perform the predetermined packet. It is characterized in that a parity bit is obtained for each bit of information representing the packet length of a number of data packets, and the obtained parity bit is inserted into the parity packet as information for obtaining the packet length of the data packet dropped by the receiving side. The data transmission device according to claim 6. 10. The data packet generated by the first packet generation means has a variable length, and the second packet generation means is shorter than the maximum length data packet of the predetermined number of data packets. A parity bit is obtained by regarding the short portion of the data packet as a “0” bit, and the obtained parity bit is inserted into the parity packet as information for temporarily reproducing the short portion of the data packet that the receiving side has dropped. The data transmission device according to claim 6, characterized in that 11. The data transmission device according to claim 6,
A data receiving device for receiving a packet transmitted using UDP (User Datagram Protocol), and a receiving means for receiving the data packet and the parity packet transmitted from the data transmitting device, and a receiving means for receiving the data packet and the parity packet. Determining means for determining whether or not the data packet is lost by performing a parity check based on the data packet and the parity packet, and the received data packet when the loss of the data packet is detected by this determining means. And a reproducing means for reproducing the dropped data packet based on a parity packet. 12. A data receiving device for receiving a packet transmitted from the data transmitting device according to claim 7, wherein the reproducing means adds the received data packet to the received data packet when the dropout of the data packet is detected. The data receiving device according to claim 11, wherein the dropped data packet is specified based on the given sequence number. 13. A data receiving device for receiving a packet transmitted from the data transmitting device according to claim 8, wherein said reproducing means detects the received data packet when the dropout of the data packet is detected. 12. The data bit according to claim 11, wherein the information bit of the payload of the lost data packet is reproduced based on the information bit of the payload and the parity bit corresponding to the information bit of the received parity packet. Receiver. 14. A data receiving device for receiving a packet transmitted from the data transmitting device according to claim 9, wherein said reproducing means detects the received data packet when a drop of the data packet is detected. The packet length of the dropped data packet is obtained based on information indicating the packet length inserted in the header and a parity bit corresponding to the information indicating the packet length of the received parity packet. The data receiving device according to claim 11. 15. A data receiving device for receiving a packet transmitted from the data transmitting device according to claim 10, wherein said reproducing means detects the received data packet when the dropout of the data packet is detected. The short and small portions are regarded as "0" bits, and the short and small portions of the dropped data packet are temporarily reproduced based on the regarded bit and the parity bit corresponding to the short and small portions of the received parity packet. The data receiving device according to claim 11. 16. A data reproducing means for reproducing data to be transmitted by a data transmitting device based on the data packet received by the receiving means and the data packet reproduced by the reproducing means. The data receiving device according to claim 11, wherein: