JP3822508B2 - Packet transmission system and data transmission device and data reception device thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a packet transmission system for transmitting data by UDP (User Datagram Protocol) in an IP (Internet Protocol) network configured using routers, switches, and the like, and a data transmission apparatus and data used in this system The present invention relates to a receiving device.
[0002]
[Prior art]
There are TCP (Transmission Control Protocol) and UDP as standard upper protocols of IP used in the IP network.
[0003]
TCP is a connection type protocol, a connection management function for setting a connection using a VC (Virtual Circuit), a response confirmation function for notifying a transmission source every time a destination receives a packet, and a sequence for each packet. A sequence function that identifies unarrived packets by numbering, a window control function that provides a buffer for storing multiple packets and confirms responses in units of buffers, and notifies the sender of the amount of packets that can be received by the destination in advance And a flow control function.
[0004]
FIG. 6 shows an outline of data transmission by TCP. In the figure, the data transmission device TSt on the transmission side (transmission source) assigns a sequence number to each packet and transmits it in sequence, and the data transmission device RSt on the reception side (destination) receives a response (ACK) every time a packet is received. ) Send it back. Then, the data transmission device TSt on the transmission side retransmits the packet for which no reception response is obtained, and the data transmission device RSt on the reception side reproduces each received packet in order according to the sequence number.
[0005]
Thus, TCP can realize highly reliable communication by 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, so that it is not suitable for communication of stream data that requires real-time properties such as moving images and voices. Further, it cannot be applied to multicast communication or the like that cannot perform retransmission control.
[0006]
On the other hand, unlike TCP, UDP does not have a connection management function, a response confirmation function, a sequence function, a window control function, and a flow control function, and is a connectionless type that does not set up a connection with a communication partner. Protocol.
[0007]
FIG. 7 shows an outline of data transmission by this UDP. In the figure, the data transmission device TSu on the transmission side (transmission source) packetizes and transmits the data generated by the higher-order application as it is in the generation order. At this time, it is not confirmed whether or not the data transmission device RSu on the receiving side (destination) has received the packet reliably. The data transmission device RSu on the receiving side (destination) reproduces the received packets in order.
[0008]
Therefore, UDP can perform data transmission with relatively light processing without requiring complicated control. Therefore, it is suitable for the communication of stream data that requires the real-time property such as the moving image and the voice as described above, and the point-to-multipoint communication using broadcast or multicast.
[0009]
[Problems to be solved by the invention]
However, since UDP does not have a function for ensuring communication reliability such as a response confirmation function and a sequence function as described above, even if a packet is lost during transmission, it is not retransmitted. For this reason, for example, if a packet is lost during the distribution of a moving image or sound, the reproduced image or sound is interrupted, resulting in degradation of data quality.
[0010]
The present invention has been made paying attention to the above circumstances, and its object is to provide a packet transmission system capable of improving transmission quality by simple control in data transmission using UDP, its data transmitting apparatus, and It is to provide a data receiving apparatus.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a packet transmission system for transmitting data to be transmitted from a transmission side to a reception side via a network using UDP (User Datagram Protocol). First and second packet generation means are provided. Then, the first packet generation unit generates a plurality of data packets based on the transmission target data, and the second packet generation unit generates a parity packet for each predetermined number of the plurality of data packets generated by the second packet generation unit. The plurality of generated data packets and parity packets are transmitted to the network.
On the other hand, the receiving side is provided with a means for determining whether or not a packet is dropped and a reproducing means. Then, the determination means performs a parity check based on the received data packet and parity packet to determine whether or not the data packet is dropped, and when the data packet drop is detected, the reproduction means performs the reception. The dropped data packet is reproduced based on the data packet and the parity packet.
[0012]
Therefore, according to the present invention, even if a packet is lost during packet transmission by UDP, the lost packet can be reproduced from the received packet and the parity packet. For this reason, it is possible to reproduce dropped packets with a relatively light processing load without generating extra traffic as in the case of using a response confirmation function or a sequence function. Therefore, it is possible to transmit stream-related data that requires real-time properties, such as moving images and audio, in real time and with good quality. The present invention can also be applied to point-to-multipoint communication using broadcast or multicast that cannot perform retransmission control, thereby realizing high-quality point-to-multipoint communication.
[0015]
The present invention also provides By the first packet generation means Generate a variable length data packet and insert the packet length information into its header, In the second packet generation means, a parity bit is obtained for each bit of information indicating the packet length of the predetermined number of data packets, and the obtained parity bit is inserted into the parity packet and transmitted. On the other hand, in the reproducing means, when the dropping of the data packet is detected, information indicating the packet length inserted in the header of the received data packet and information indicating the packet length of the received parity packet The packet length of the dropped data packet is calculated based on the parity bit corresponding to Reproduce. In this way, even when the data packet has a variable length, the packet length of the dropped data packet can be reproduced.
[0016]
Further, by the first packet generation means Generate variable length data packets, The second packet generation means obtains a parity bit by regarding a short portion of the data packet shorter than the maximum length data packet as a “0” bit out of the predetermined number of data packets, and obtains the obtained parity bit as a parity packet. Insert into and send. On the other hand, in the reproducing means, when the dropping of the data packet is detected, the short part of the received data packet is regarded as “0” bit, and the deemed “0” bit and the above-mentioned parity packet are received. The dropped data packet is reproduced based on the parity bit corresponding to the short and small part.
[0017]
In this way, for example, even when the maximum length data packet is dropped, all parts of the dropped maximum length data packet are taken from the considered “0” bit of the received data packet and the corresponding parity bit of the parity packet. Can be played.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 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 serving as a transmission side (transmission source) and a plurality of data transmission devices (hereinafter referred to as data reception devices) RS1 to RSn serving as reception sides (destinations). Are connected via an IP (Internet Protocol) network NW, and data is transmitted from the data transmission device TS to the data reception devices RS1 to RSn using UDP / IP (User Datagram Protocol / Internet Protocol). is there.
[0019]
By the way, the data transmission device TS is configured as follows. FIG. 2 is a block diagram showing the functional configuration. The data transmission device TS includes a data generation unit 11, a data packet generation unit 12, a parity packet generation unit 13, and a packet transmission unit 14.
[0020]
The data generation unit 11 generates transmission data by encoding a data stream composed of, for example, images and sounds created by an upper layer application according to a predetermined encoding method such as MPEG (Moving Picture Experts Group).
[0021]
The data packet generator 12 takes in the transmission data generated by the data generator 11 and packetizes the transmission data according to UDP / IP, thereby generating a plurality of data packets DP11, DP12,. Each data packet DP11, DP12,... Is composed of an IP header, a UDP header, and UDP data as shown in FIG. The UDP data (payload) has a variable length, and the encoded image and audio data are inserted.
[0022]
The UDP header is provided with a source port number field and a length field. Of these, information indicating the packet length of the data packet DP11, DP12,... Is inserted into the length field. On the other hand, a sequence number (for example, 0x0001, 0x0002,...) Representing the transmission order of the data packets DP11, DP12,. This sequence number is generated by a counter. Each time the data packets DP11, DP12,... Are generated, the counter counts up the count value to “1”, “2”,..., And is counted at the timing when the parity packet is generated in the parity packet generator 13 described later. Reset the value.
[0023]
The parity packet generation unit 13 takes in a predetermined number of data packets DP11, DP12,... Generated by the data packet generation unit 12, for example, four packets, and temporarily stores them in a buffer. The four stored data packets One parity packet PP1 is generated for DP11 to DP14.
[0024]
As shown in FIG. 4, the parity packet PP1 is composed of an IP header, a UDP header, and UDP data in the same manner as the data packets DP11, DP12,..., And the packet length is the four stored data. It is set to the same length as the data packet DP11 having the maximum length among the packets DP11 to DP14.
[0025]
A specific number (for example, 0xffff) representing a parity packet is inserted into the source port number field of the UDP header. In addition, a parity bit (for example, even parity) generated for information indicating the packet length inserted into the length fields of the four stored data packets DP11 to DP14 is inserted into the length field of the UDP header.
Further, parity bits (for example, even parity) generated for the payload information inserted into the UDP data of the four stored data packets DP11 to DP14 are inserted into the UDP data. These parity bits are generated for each bit in the same position of the four data packets DP11 to DP14. It should be noted that parity bits are generated by regarding “0” for the short and small portions a, b, c of the data packets DP12, DP13, DP14 shorter than the maximum length data packet DP11.
[0026]
The packet transmitter 14 sends the data packets DP11, DP12,... Generated by the data packet generator 12 and the parity packets PP1,... Generated by the parity packet generator 13 to the IP network NW in the order of generation. Send to.
[0027]
On the other hand, the data receiving device RS is configured as follows. FIG. 3 is a block diagram showing the functional configuration. The data receiving device RS is composed of a packet receiving device RP and a data reproducing device RD.
[0028]
The packet reception device RP includes a packet reception unit 21, a parity check unit 22, a dropped packet reproduction unit 23, and a packet output unit 24. The packet receiver 21 receives data packets DP11, DP12,... And parity packets PP1,... Transmitted from the data transmitter TS via the IP network NW.
[0029]
The parity check unit 22 performs a parity check on the plurality of data packets DP11, DP12,... Received by the packet receiving unit 21 based on the parity packet every four packets. Then, the presence / absence of a dropped packet is determined by this parity check.
[0030]
When the parity check unit 22 determines that there is a dropped packet, the dropped packet reproduction unit 23 performs a process for identifying the dropped packet and a process for reproducing the identified dropped packet, respectively. Execute.
[0031]
The process of identifying dropped packets extracts sequence numbers (for example, 0x0001, 0x0002,...) From the source port number field of the UDP header of a plurality of received data packets, and escapes from the continuity of the extracted sequence numbers. Do by finding.
[0032]
The replay processing of the specified dropped packet is performed based on the information indicating the packet length inserted in the UDP header of the received data packet and the parity bit inserted in the UDP header of the parity packet. Play packet length information of packet. At the same time, based on the payload information inserted into the UDP data and the parity bits inserted into the UDP data of the parity packet, the payload information of the dropped packet is reproduced.
At this time, if the data packet has a variable length, the short portion of the received data packet is regarded as “0” bits, and this regarded “0” bit corresponds to the short portion of the received parity packet. Based on the parity bit, the dropped data packet is reproduced.
[0033]
When the parity check unit 22 determines that there is no dropped packet, the packet output unit 24 transfers the data packets DP11, DP12,... Received by the packet receiving unit 21 to the data reproduction device RD in the order received. To do. On the other hand, when the parity check unit 22 determines that there is a dropped packet, the data packet received by the packet receiving unit 21 and the data packet reproduced by the dropped packet reproducing unit 23 are received in the order of reception. Are transferred to the data reproducing device RD. The parity packet is discarded.
[0034]
The data reproduction device RD depackets and decodes the data packet transferred from the packet output unit 24, thereby reproducing the image and audio data streams.
[0035]
Next, the operation of the packet transmission system configured as described above and the data transmission apparatus and data reception apparatus will be described.
Here, in the system shown in FIG. 1, a case where the data transmission device TS transmits data composed of moving images and audio to the data reception device RS1 will be described as an example.
[0036]
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 where It is packetized according to UDP / IP, and thereby data packets are sequentially generated.
[0037]
The data packet generated by the data packet generator 12 is taken into the parity packet generator 13 by four packets. In the parity packet generation unit 13, one parity packet is generated based on the captured four data packets.
[0038]
For example, assume that four data packets DP11, DP12, DP13, and DP14 shown in FIG. Then, the parity packet generation unit 13 first generates even parity for each bit at the same position for information indicating the packet length inserted in the UDP header of the data packets DP11, DP12, DP13, and DP14. The even parity is inserted into a length field provided in the UDP header of the parity packet PP1.
[0039]
Next, for the payload information inserted into the UDP data of the four data packets DP11, DP12, DP13, and DP14, even parity is generated for each bit at the same position. This even parity is inserted into the UDP data of the parity packet PP1. At this time, among the data packets DP11, DP12, DP13, and DP14, “0” is used for the short portions i, b, and c of the data packets DP12, DP13, and DP14 having a shorter packet length than the maximum data packet DP11. Even parity is generated.
[0040]
The transmission source port number fields of the four data packets DP11, DP12, DP13, and DP14 generated by the data packet generation unit 12 include sequence numbers 0x0001, 0x0002, 0x0003 and 0x0004 are inserted. Further, a specific number indicating that the packet is a parity packet, for example, 0xffff, is inserted into the source port number field of the parity packet PP1 by the parity packet generator 13.
[0041]
The four data packets DP11, DP12, DP13, DP14 generated by the data packet generator 12 and the parity packets PP1,... Generated by the parity packet generator 13 are sequentially transmitted to the IP network NW. The
[0042]
Thereafter, similarly, the data packets generated by the data packet generator 12 are taken into the parity packet generator 13 by four packets, and the parity packet generator 13 generates parity packets for the four data packets. Then, the parity packet is transmitted to the IP network NW following the four data packets.
[0043]
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, the packet is received by the packet receiving unit 21 and then input to the parity check unit 22. Each 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, thereby confirming whether the data packet is dropped or not. Determined.
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, and DP14 to be received prior to the parity packet PP1 are dropped. If the data packet is not dropped as a result of this determination, the four received data packets DP11, DP12, DP13, DP14 are transferred as they are from the packet output unit 24 to the data reproducing device RD.
[0044]
On the other hand, it is assumed that dropped data packets are detected by the parity check. Then, the dropped packet reproduction unit 23 first extracts the sequence number from the transmission source port number field of the data packet received prior to the parity packet PP1, and based on the extracted sequence number, the dropped data packet Identified. For example, if the sequence numbers extracted from the received data packet are “1”, “2”, and “4”, it can be specified that the data packet DP13 with the sequence number “3” is dropped.
[0045]
Next, the reproduction process of the specified dropped data packet DP13 is performed. The dropped data packet DP13 can be reproduced based on the received three data packets DP11, DP12, DP14 and the parity packet PP1.
That is, the packet length information of the dropped 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 dropped packet is reproduced based on the reproduced packet length information.
Further, the UDP data of the dropped data packet is reproduced from the received information bits of the UDP data of the three data packets DP11, DP12, DP14 and the parity bit of the UDP data of the parity packet PP1. Note that the short and small portions a and c of the data packets DP12 and DP14 received at this time are regarded as “0” and calculation for reproduction is performed.
In this embodiment, when two or more data packets are dropped or when a parity packet cannot be received, reproduction is impossible.
[0046]
The regenerated data packet DP13 is input to the packet output unit 24 together with the three received data packets DP11, DP12, DP14, where the order is adjusted based on the sequence number, and then the data regenerating device RD. Is output.
[0047]
In the data reproducing device RD, the four data packets DP11, DP12, DP13, DP14 transferred from the packet output unit 24 are depacketized and then decoded, thereby reproducing the image data and the audio data. The reproduced image data is displayed on the display, and the audio data is output from the speaker. Further, these image data and audio data are stored in a memory as necessary.
[0048]
Thereafter, each time the parity packets PP2, PP3,... Are received in the same manner, it is determined whether or not the received data packet is dropped. When the dropped packet is detected, the dropped packet reproducing unit 23 identifies the dropped data packet. It is played after being played. The reproduced data packets are arranged in order by the packet output unit 24 together with the three received data packets, and then transferred to the data reproduction device RD for reproduction processing.
[0049]
As described above, in this embodiment, in the data transmission device TS, parity packets PP1, PP2,... Are generated for every four packets for the data packets DP11, DP12, etc. to be transmitted, and the parity packets PP1, PP2,. Are inserted into the data packets DP11, DP12,. Then, each time the parity packet PP1, PP2,... Is received, the data receiving device RS determines whether or not the data packet is dropped using the parity packets PP1, PP2,. When a drop is detected, the dropped data packet is identified based on the sequence number assigned to the received data packet in place of the transmission source port number, and the received data packet and parity packet are identified. Based on the above, the dropped data packet is reproduced.
[0050]
Therefore, even if a data packet is dropped during packet transmission by UDP / IP, the dropped data packet can be reproduced from the three received data packets and the parity packet. For this reason, transmission quality can be improved by simple control compared to the case of using a response confirmation function, sequence function, etc. As a result, stream data that requires real-time properties such as video and audio, broadcast, etc. Alternatively, transmission data in point-to-multipoint communication using multicast or the like can be transmitted in real time with good quality.
[0051]
In this embodiment, a sequence number is assigned to the UDP header of the data packet instead of the transmission source port number for transmission, and the dropped data packet is specified based on the sequence number. Therefore, the dropped packet can be easily identified based on the sequence number of the data packet that can be received.
[0052]
Furthermore, in this embodiment, when the data packet has a variable length, a parity bit is obtained for each bit of information indicating the packet length inserted into each data packet, and the obtained parity bit is inserted into the parity packet. Send. The receiving side obtains the packet length of the dropped data packet based on the parity bit of the parity packet.
Therefore, even when the data packet has a variable length, the packet length of the dropped data packet can be accurately reproduced.
[0053]
Further, when transmitting a variable-length data packet, a parity bit is obtained by regarding the short part of the data packet shorter than the maximum-length data packet as “0” bits, and the obtained parity bit is inserted into the parity packet. To send. On the other hand, the receiving side regards the short part of the received data packet as a “0” bit, and based on the deemed “0” bit and the parity bit corresponding to the short part of the received parity packet. The dropped data packet is played back.
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.
[0054]
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 fixed-length data packets.
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 into the parity packet, and only the parity bit generated for the UDP data (payload information) is inserted. Note that the sequence number is inserted into the source port number field of each data packet, as in the case of transmitting the variable-length data packet described above (FIG. 4).
[0055]
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 every 2 or 3 packets, and one parity packet is generated and transmitted every 5 or more data packets. Also good. The number of data packets generated for each parity packet 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 transmission quality or the like.
[0056]
Further, in the above-described embodiment, the case where data is transmitted from the data transmission device to one data reception device RS1 has been described as an example. However, the same data is transmitted from the data transmission device TS to a plurality of data reception devices RS1, RS2,. The present invention is also applicable when data is broadcast. The present invention is also applicable when a network device such as a router device is interposed between the data transmission device TS and a plurality of data reception devices RS1, RS2,.
[0057]
Further, in the above embodiment, the packet receiving device RP and the data reproducing device RD are configured separately. However, the packet receiving device may be configured to incorporate the data reproducing device. You may comprise so that it may incorporate in an apparatus.
Moreover, although the case where the data generation unit is built in the data transmission device has been described as an example in the embodiment, the data generation device and the packet transmission device may be configured separately.
[0058]
In addition, the type and configuration of the data transmitting device and the data receiving device, the type of network, the type of transmission data, the configuration of the data packet and the parity packet, and the like can be variously modified without departing from the scope of the present invention. .
[0059]
【The invention's effect】
As described above in detail, according to the present invention, in the packet transmission system for transmitting the data to be transmitted from the transmission side to the reception side through the network using UDP, the transmission side also stores the data to be transmitted. In addition, a plurality of data packets are generated, and a parity packet is generated for each predetermined number of the generated data packets, and the generated data packets and parity packets are transmitted to the network. 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 the data packet is dropped, and when the dropped data packet is detected, the received data packet and The dropped data packet is reproduced based on the parity packet.
[0060]
Therefore, according to the present invention, it is possible to provide a packet transmission system capable of improving transmission quality by simple control, data transmission apparatus and data reception apparatus in data transmission using UDP.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an embodiment of a packet transmission system according to the present invention.
2 is a block diagram showing a functional configuration of a data transmission device of the packet transmission system shown in FIG. 1;
3 is a block diagram showing a functional configuration of a data reception device of the packet transmission system shown in FIG.
4 is a diagram showing a configuration of data packets and parity packets transmitted by the packet transmission system shown in FIG. 1;
FIG. 5 is a diagram showing a configuration of data packets and parity packets transmitted by a 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 receiver
RD: Data reproduction device
NW ... IP network
11: Data generator
12: Data packet generator
13: Parity packet generator
14 ... Packet transmitter
21 ... Packet receiver
22 ... Parity check section
23. Dropped packet playback unit
24 ... Packet output section

Claims (7)

In a packet transmission system that transmits data to be transmitted from a transmission side to a reception side via a network using UDP (User Datagram Protocol),
The sender side
First packet generating means for generating a plurality of data packets having a variable length and information indicating the packet length inserted in a header based on the data to be transmitted;
For each of a predetermined number of data packets generated by the first packet generation means , a parity bit is obtained in bit units for information representing the packet length, and a second parity packet including the obtained parity bit is generated. Packet generation means;
Transmission means for transmitting data packets and parity packets generated by the first and second packet generation means to the network;
The receiving side
Receiving means for receiving data packets and parity packets arriving via the network;
A determination unit that performs a parity check based on the data packet and the parity packet received by the reception unit, and determines whether or not the data packet is dropped;
When the drop of the data packet is detected by this determination means, it corresponds to information indicating the packet length inserted in the header of the received data packet and information indicating the packet length of the received parity packet A packet transmission system comprising: reproducing means for reproducing the packet length of the dropped data packet based on a parity bit . In a packet transmission system that transmits data to be transmitted from a transmission side to a reception side via a network using UDP (User Datagram Protocol),
The sender side
First packet generation means for generating a plurality of variable-length data packets based on the data to be transmitted;
Of the predetermined number of data packets generated by the first packet generation means, a short portion of the data packet shorter than the maximum length data packet is regarded as a “0” bit to obtain a parity bit, and the obtained parity bit Second packet generation means for generating a parity packet including:
Transmission means for transmitting data packets and parity packets generated by the first and second packet generation means to the network;
The receiving side
Receiving means for receiving data packets and parity packets arriving via the network;
A determination unit that performs a parity check based on the data packet and the parity packet received by the reception unit, and determines whether or not the data packet is dropped;
When the drop of the data packet is detected by this determination means, the short portion of the received data packet is regarded as a “0” bit, and this deemed bit corresponds to the short portion of the received parity packet. A packet transmission system comprising: reproducing means for reproducing the dropped data packet based on a parity bit . In a data transmission device that transmits data to be transmitted to the receiving side using UDP (User Datagram Protocol),
First packet generation means for generating a plurality of data packets, which are variable-length based on the data to be transmitted and in which information indicating the packet length is inserted in the header ;
Wherein every predetermined number of data packets generated by the first packet generating means, the the packet information representing a length determined parity bits in bit units, packets of this the obtained parity bit, data packet receiver dropped Second packet generating means for generating a parity packet including information for determining the length ;
A data transmission apparatus comprising: a transmission unit configured to transmit the data packet and the parity packet generated by the first and second packet generation units to the reception side. In a data transmission device that transmits data to be transmitted to the receiving side using UDP (User Datagram Protocol),
First packet generation means for generating a plurality of variable-length data packets based on the data to be transmitted;
Of the predetermined number of data packets generated by the first packet generation means, a short portion of the data packet shorter than the maximum length data packet is regarded as a “0” bit to obtain a parity bit, and the obtained parity bit A second packet generation means for generating a parity packet that includes, as information for temporarily reproducing a short portion of a data packet dropped by the receiving side ,
A data transmission apparatus comprising: a transmission unit configured to transmit the data packet and the parity packet generated by the first and second packet generation units to the reception side. A data receiving device for receiving a packet transmitted using UDP (User Datagram Protocol) from the data transmitting device according to claim 3 ,
Receiving means for receiving data packets and parity packets transmitted from the data transmitting device;
A determination unit that performs a parity check based on the data packet and the parity packet received by the reception unit, and determines whether or not the data packet is dropped;
When the drop of the data packet is detected by this determination means, it corresponds to information indicating the packet length inserted in the header of the received data packet and information indicating the packet length of the received parity packet A data receiving apparatus comprising: reproducing means for reproducing a packet length of the dropped data packet based on a parity bit . A data receiving device for receiving a packet transmitted using UDP (User Datagram Protocol) from the data transmitting device according to claim 4 ,
Receiving means for receiving data packets and parity packets transmitted from the data transmitting device;
A determination unit that performs a parity check based on the data packet and the parity packet received by the reception unit, and determines whether or not the data packet is dropped;
When a drop of the data packet is detected by this determination means, the short part of the received data packet is regarded as a “0” bit, and the deemed bit and the parity bit corresponding to the short part of the received parity packet And a reproducing means for reproducing the dropped data packet . Based on the reproduced data packets by the received data packet and said reproducing means by said receiving means, wherein the data transmission device is characterized in that the data reproducing means for reproducing the data with the transmission target, and further comprising Item 7. A data receiving device according to item 5 or 6 .

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