JP5966502B2 - Data receiving method and apparatus - Google Patents

Description

  The present invention relates to a data receiving method and apparatus.

  In video transmission using an IP network, when an error such as a bit error occurs in a packet during a propagation process in the network, a retransmission request (Automatic) of the packet is transmitted from a receiving device (hereinafter referred to as a decoder) to a transmitting device (hereinafter referred to as an encoder). Repeat reQuest (ARQ) is performed. The encoder that has received the retransmission request from the decoder transmits a packet corresponding to the retransmission request to the decoder again, so that the decoder can receive a normal packet. However, if the decoder makes a retransmission request to the encoder every time it receives an error packet, it takes a long time until the decoder receives all the data, which is inefficient.

  Therefore, in order to reduce the number of retransmission requests from the decoder when error data occurs, the encoder generates a packet called an FEC (Forward Error Correction) packet for every fixed number of packets. The FEC packet is a packet including redundant data for recovering a packet error.

  The correspondence between the video packet and the FEC packet is set in advance by the system administrator, and the encoder transmits the FEC packet together with the packet to the decoder in a predetermined order predetermined by the system administrator. The decoder that receives the packet recovers the error generated in the packet by the FEC packet based on the correspondence.

  One FEC packet is normally associated with a predetermined number of packets, and when an error occurs in one of the predetermined number of packets, the error of the packet can be recovered. In addition, a predetermined number of video packets are generally transmitted continuously in time. For this reason, when a burst error occurs in which a plurality of packets continuously error in time, the FEC packet can recover only an error that has occurred in one packet. Therefore, there is a possibility that the packet error cannot be recovered by the FEC packet.

  As a technique for recovering a packet error accompanying such a burst error, there is a technique described in Non-Patent Document 1. This technology uses two-dimensional FEC data (Pro-MPEG FEC) that combines FEC packets corresponding to a plurality of temporally continuous packets and FEC data corresponding to a plurality of temporally non-continuous packets. Error recovery.

  FIG. 20 shows an example of the correspondence between video packets and FEC packets in Pro-MPEG FEC. 20 shows a case where packets are transmitted from the encoder in the order of video packets 1... 5, FEC packet 1, video packets 6... 10, FEC packet 2, video packets 11. An example is shown. The decoder has table information as shown in FIG. 18 in its storage area, and the decoder can recognize the correspondence between each video packet and the FEC packet by referring to the table information. it can.

  For example, the video packet 9 is associated with the FEC packet 2 together with the video packets 6, 7, 8, and 10 which are video packets transmitted continuously in time with the packet. Further, the video packet 9 is associated with the FEC packet 7 together with the video packets 4 and 14 which are video packets transmitted discontinuously in time with the packet.

  The correspondence between such a packet and the FEC packet is set in advance by a system administrator or the like, and the encoder generates an FEC packet based on the correspondence and transmits it to the decoder together with the video packet in a predetermined order. To do. Further, based on the correspondence relationship, the decoder recovers an error occurring in the packet by one of the FEC packets corresponding to the packet.

  Here, an example of error packet recovery procedure by Pro-MPEG FEC is shown using FIG. FIG. 21A shows an example of a table representing the correspondence between video packets and FEC packets when the decoder receives video packet 3 that is an error packet. In FIG. 21, a packet represented by a white background represents a normal packet, a packet represented by a black background represents an error packet, and a packet represented by a hatched background represents an unreceived consultation packet. At this time, since neither FEC packet corresponding to the video packet has been received, error recovery at this time is not performed.

  FIG. 21B is a diagram for explaining the correspondence between the video packet and the FEC packet when the decoder receives the FEC packet F1. At this time, if the video packets 1, 2, 4, and 5 are all normal packets, the error of the video packet 3 can be recovered by the FEC packet 1. In the example of FIG. Is an error packet. Therefore, the error of the video packet 3 cannot be recovered by the FEC packet 1.

  Here, unlike conventional FEC packet transmission, Pro-MPEG FEC packet transmission is characterized in that two FEC packets correspond to one video packet. Therefore, in the example of FIG. 21B, in order to recover the error of the video packet 3, the reception of the FEC packet 6, which is another FEC packet corresponding to the video packet, is awaited.

  FIG. 21C is a diagram for explaining the correspondence between the video packet and the FEC packet when the decoder receives the FEC packet 6. In FIG. 21 (c), only the video packet 3 is the error packet among the video packets 3, 8, and 13, so that the error of the video packet 3 can be recovered by the FEC packet 6.

  FIG. 21D is a diagram for explaining the correspondence between the video packet and the FEC packet when the error of the video packet 3 is recovered. In FIG. 21D, since the error of the video packet 3 is recovered by the FEC packet 6, the error of the video packet 4 can be recovered by the FEC packet 1. Thus, by using Pro-MPEG FEC, even if a burst error occurs in the packet, it is possible to recover the error packet.

  However, there are cases where video packet errors cannot be recovered using Pro-MPEG FEC. The conditions under which error recovery by Pro-MPEG FEC cannot be performed will be described with reference to FIG. FIG. 22A is an example of a table showing the correspondence between the video packet and the FEC packet when the video packet 8 is received. Also in FIG. 22, a packet represented by a white background represents a normal packet, a packet represented by a black background represents an error packet, and a packet represented by a hatched background represents an unreceived packet.

  Unlike the example of FIG. 21, in FIG. 22A, in addition to the video packets 3 and 4, the video packet 8 is also an error packet. At this time, since two of the video packets supported by the FEC packet 6 are error packets, there is a concern that the error of the video packet 3 cannot be recovered by the FEC packet 6 as in the example of FIG. Is done.

  However, if the error of the video packet 8 is recovered, the error packet is only the video packet 3 among the video packets supported by the FEC packet 6, and therefore the video packet can be recovered. FIG. 22B is a diagram for explaining the correspondence between the video packet and the FEC packet when the decoder receives the FEC packet 2.

  In FIG. 22B, since only the video packet 8 is the error packet among the video packets 6 to 10, the error of the video packet 8 can be recovered by the FEC packet 2. If the error of the video packet 3 is recovered, all errors are recovered by the procedure described with reference to FIGS.

  However, if the video packet 9 is also an error packet, the video packet 8 cannot be recovered by the FEC data 2, and the error of the video packet 3 cannot be recovered. FIG. 22C is a diagram for explaining the correspondence between the video packet and the FEC packet when the FEC packet 2 is received when the video packet 9 is an error packet.

  In FIG. 22C, since there are two error packets (video packets 8 and 9) among the video packets corresponding to the FEC packet 2, the error packet cannot be recovered by the FEC packet 2. At this time, if the error of the video packet 9 is recovered, the error of the video packet 8 is recovered by the procedure described with reference to FIGS. 22 (a) and 22 (b), and will be described with reference to FIGS. 21 (c) and 21 (d). All errors are recovered by the procedure.

  Therefore, it waits for reception of FEC packet 7, which is another FEC packet corresponding to video packet 9. FIG. 22D is a diagram for explaining the correspondence between the video packet and the FEC packet when the FEC packet 7 is received.

  In FIG. 22D, since there are two error packets (video packets 4 and 9) among the video packets corresponding to the FEC packet 7, the error of the video packet 9 cannot be recovered by the FEC packet 7. Therefore, when all the FEC packets are received, the video packets 3, 4, 8, and 9 remain unrecovered.

  The above situation can occur when multiple burst errors occur. In this way, when a plurality of burst errors occur and an error packet that cannot be recovered even after receiving all FEC packets remains, the decoder makes a retransmission request of the error packet to the encoder, The error is recovered.

  In FIG. 21 and FIG. 22, a group of 15 video packets is formed, and eight FEC packets are added to each FEC group. That is, in FIG. 21 and FIG. 22, the video packets 1 to 15 form one group. When the decoder receives a packet of one group and all the FEC packets corresponding to the packet of the group, if an error packet remains in the group, the decoder requests retransmission of the error packet. In the following description, the group is referred to as “FEC recovery unit”.

  In the example of FIG. 22D, when the decoder receives all the video packets of the FEC recovery unit to which the video packets 3, 4, 8, and 9 belong and all the FEC packets corresponding to the video packets, A retransmission request for one of the video packets 3, 4, 8, and 9 is made. When the packet reaches the decoder in a normal state, the decoder can recover all remaining error packets with the FEC packet.

  For example, when a retransmission request is made for the video packet 3 and the packet is normally received, the video packet 4 can be recovered by the FEC packet 1 and the video packet 8 can be recovered by the FEC packet 6. When the video packet 4 or the video packet 8 is restored, the video packet 9 is restored by the FEC packet 7 or the FEC packet 2 and all error packets are restored. Note that the video packet to be retransmitted does not necessarily need to be the video packet 3, and the error can be recovered without any problem even if it is another error packet.

  Here, in a streaming service in which video data is received and played back at the same time, the decoder outputs video that has been successfully decoded to the display device in accordance with the playback timing in order not to prevent playback on the viewer side. There is a need. The error packet received by the decoder is automatically decoded and output to the display device regardless of whether or not the packet has been restored when a certain time has elapsed since the packet was received.

  Therefore, even if a packet error occurs in the propagation process in the network, it is necessary to shorten the time taken to recover each error packet. However, in order to reduce the load on the encoder, it is desirable to reduce the number of packet retransmissions from the encoder as much as possible. The fixed time is a value arbitrarily set by the user and stored in hardware, and is hereinafter referred to as a packet recovery time limit.

"Transmission of Professional MPEG-2 Transport Streams over IP Networks", Pro-MPEG Forum (2004): Pro-MPEG Code of Practice # 3 release 2

  FIG. 23 is a diagram for explaining the relationship between the video compression rate, the number of packets, and the amount of information included in each packet. In FIG. 23, an image 100 is composed of regions divided into 30 represented by A, B,... Z, α, β, γ, and δ. Note that in the above-described streaming, the image 100 corresponds to one frame of video.

  In FIG. 23, video packets 1 to 5, 7 to 11, 13 to 17, 24 to 28, 30 to 34, and 36 to 40 are obtained by encoding the image 100 in a compression format with a low compression rate such as MPEG-4. This is a total of 30 video packets obtained. Each video packet includes one piece of information divided into 30 pieces. For example, packet 1 contains information A and packet 38 contains information β. Note that the information contained in each packet does not overlap.

  In FIG. 23, FEC recovery units are formed for every 15 video packets, and eight FEC packets are added to each FEC recovery unit. For example, video packets 1 to 5, 7 to 11, and 13 to 17 are video packets forming one FEC recovery unit, and FEC packets 6, 12, 18, and 19 to 23 are associated with the FEC recovery unit. It has been added.

  In each FEC recovery unit, a plurality of video packets transmitted continuously in time form a group, and one FEC packet is associated with each group. Here, the FEC packet corresponding to each group is referred to as a “horizontal FEC packet”, and the FEC packet and the video packet corresponding to the FEC packet are collectively referred to as a “horizontal FEC group” or “row”. Shall.

  Further, in each FEC recovery unit, a plurality of video packets transmitted discontinuously in time form a group, and one FEC packet is associated with each group. Here, the FEC packet corresponding to the group is referred to as a “vertical FEC packet”, and the FEC packet and the video packet corresponding to the FEC packet are collectively referred to as “vertical FEC group” or “column”. Shall.

  In FIG. 23A, each FEC packet can recover one video packet error in the same row or column as the FEC packet. For example, the packet 12 that is an FEC packet can recover one error of the video packets 7 to 11 in the same row as the packet. Further, the packet 22 that is an FEC packet can recover one error of the video packets 4, 10, and 16 in the same column as the packet.

  In this way, in the example shown in FIG. 23 (a), by encoding a certain image in a compression format with a low compression rate such as MPEG-4, 30 video packets each containing one piece of information are obtained. A total of 46 packets of 16 error correcting FEC packets are generated.

  In FIG. 23B, video packets 101-105, 107-111, 113-117 represent the image 100 as H.264. This is a total of 15 video packets obtained by packet encoding in a compression format with a high compression rate such as H.264. Here, it is assumed that the high compression rate compression format in FIG. 23B can compress the video at a compression rate twice that of the low compression rate compression format in FIG. Each video packet includes any two pieces of information divided into 30 pieces. For example, the packet 101 includes information A and B, and the packet 116 includes information α and β. Note that the information contained in each packet does not overlap.

  In FIG. 23 (b), FEC recovery units are formed for every 15 video packets, and eight FEC packets are added to each FEC recovery unit. For example, the packets 101 to 105, 107 to 111, and 113 to 117 form one FEC recovery unit, and the FEC packets 106, 112, 118, and 119 to 123 are added to the FEC recovery unit.

  In FIG. 23B, each FEC packet can recover one video packet error in the same row or column as the FEC packet. For example, the packet 112 that is an FEC packet can recover one error of the video packets 107 to 111 in the same row as the packet.

  As described above, in the example of FIG. 23B, by encoding a certain image with a high compression rate, 15 video packets each including two pieces of information and 8 error correcting FEC packets are obtained. A total of 23 packets are generated.

  FIG. 24 is a diagram for explaining the relationship between the compression rate and the transmission rate. In FIG. 24, when a packet is transmitted by a method with a high compression rate, the transmission interval of each packet is wider than when a packet is transmitted by a method with a low compression rate. This is because, in real-time video distribution, the video playback timing is predetermined, so that the time required to transmit all information must be substantially constant regardless of the compression format.

  FIG. 25 is a diagram for explaining the relationship between the compression rate and the error packet recovery time. FIG. 25 shows that the packet corresponding to the information D, E, N, O has an error in each of the high compression rate method and the low compression rate, so that the packet including the information D is requested to be retransmitted. The time required until the error packet is recovered based on the above is shown.

  In the method with a low compression rate, the packets corresponding to the information D, E, N, and O are the packets 4, 5, 16, and 17, respectively, and these four packets are error packets. Furthermore, each packet cannot be recovered by the FEC packet corresponding to the packet. Here, the FEC packet corresponding to each packet is an FEC packet located in the same row or column as each packet in FIG. For example, the FEC packet corresponding to the packet 4 is the packet 6 and the packet 22, the FEC packet corresponding to the packet 5 is the packet 6 and the packet 23, the FEC packet corresponding to the packet 16 is the FEC corresponding to the packet 18, the packet 22, and the packet 17. The packets are packet 18 and packet 23.

  In the method with a high compression rate, the packets corresponding to the information D, E, N, and O are the packets 102, 103, 108, and 109, respectively, and these four packets are error packets. Further, each packet cannot be recovered by the FEC packet corresponding to the packet, as in the case of the method having a low compression rate. For example, the FEC packet corresponding to the packet 102 corresponds to the packet 106 and the packet 120, the FEC packet corresponding to the packet 103 corresponds to the packet 106 and the packet 121, and the FEC packet corresponding to the packet 108 corresponds to the packet 112, the packet 120, and the packet 109. The FEC packets to be performed are the packet 112 and the packet 121.

  In data transmission by Pro-MPEG FEC, when the decoder receives all the FEC packets corresponding to one video packet of one FEC recovery unit, the decoder determines whether there is an error packet that could not be recovered by the FEC packet. If an unrecovered error packet still exists, the decoder determines that the error packet needs to be retransmitted and makes a retransmission request for the packet.

  As described above, in a streaming service in which video data is received and played back at the same time, in order not to prevent playback on the viewer side, the decoder sends the video that has been normally decoded in accordance with the playback timing to the display device. It is necessary to output. The error packet received by the decoder is automatically decoded and output to the display device regardless of whether or not the packet has been restored when a certain time has elapsed since the packet was received.

  Therefore, in FIG. 25, when a packet is transmitted by a method with a low compression rate, if the error packet can be recovered by the FEC packet, the decoder can quickly receive the FEC packet corresponding to each error packet. Even when an error packet cannot be recovered by the FEC packet, the decoder can determine whether or not the packet 4 (or any of the packets 5, 16, and 17) needs to be retransmitted when the packet 23 is received. It can be carried out. Accordingly, since it takes a short time to recover the packet after receiving the packet 4 as an error packet, it is unlikely that the packet is automatically decoded before the packet is recovered.

  On the other hand, if the error packet can be recovered by the FEC packet when the packet is transmitted by a method with a high compression rate, the decoder takes a long time to receive the FEC packet corresponding to each error packet. In addition, even when the error packet cannot be recovered by the FEC packet, the decoder determines whether retransmission of the packet 102 (or one of the packets 103, 108, and 109) is necessary when the packet 123 is received. Becomes slower. Therefore, since it takes a long time until the packet is recovered after receiving the packet 102 which is an error packet, there is a high possibility that the packet is automatically decoded before the packet is recovered.

  In recent years, with the improvement of image compression technology, H.264, which has a higher compression rate than MPEG-4, which is a conventional image compression technology, has been widely used. Therefore, in packet transmission in which a packet encoded at a high compression rate is transmitted using Pro-MPEG FEC, it is necessary to reduce the time required from the reception of the error packet until the packet is restored. However, since MPEG-4, which has a low compression rate, is often used at present, settings such as FEC recovery unit and packet recovery time limit have been changed to ensure compatibility with MPEG-4. It is desirable not to. Furthermore, if the packet recovery time limit is long, the time until video display becomes long and the real-time performance of video distribution is impaired. Therefore, from the viewpoint of video playback in real time, the packet recovery time limit is preferably as short as possible.

  Accordingly, an aspect of the present invention is to speed up the timing for transmitting a retransmission request in order to prevent an error packet from being decoded without being restored.

  In order to achieve the above object, a data receiving method and apparatus according to the present invention includes one or more other packets generated by dividing original data and divided from the original data. When a decoder that receives a packet belonging to a group together with an error correction packet receives the first packet from the transmitter, the decoder determines whether an error exists in the first packet, and the first packet has an error. When it is determined that the packet exists, the error of the first packet cannot be recovered even if all the error correction packets are received with reference to the number of error packets existing in the group to which the first packet belongs. If it is determined that the error of the first packet cannot be recovered even if the error correction packet is received by all hands, the first transmitter is sent to the transmitter. Requesting retransmission of packets, it receives the first packet retransmitted from the transmitter.

  According to the present invention, it is possible to prevent the error packet from being decoded in an unrecovered state by advancing the timing for transmitting the retransmission request.

The figure for demonstrating the flow of the error correction in this invention. The figure for demonstrating the whole structure of the video transmission system concerning this invention. The functional block diagram showing the function of the encoder 1 in this invention. The figure showing the correspondence of the video packet and FEC packet in this invention. The figure for demonstrating the transmission order of a packet. The block diagram showing an example of the hardware constitutions of the encoder 1 in this invention. The functional block diagram showing the function of the decoder 2 in this invention. The block diagram showing an example of the hardware constitutions of the decoder 2 in this invention. The flowchart showing an example of the procedure of the reception data confirmation process concerning this invention. Example of a table for entering data error information. The flowchart showing the procedure of a data error information update process. An example of data error information when video packet 1 is received. The example of the data error information at the time of video packet 2 reception. An example of data error information when video packet 3 is received. An example of data error information when video packet 4 is received. An example of data error information when the video packet 8 is received. An example of data error information when the video packet 9 is received. The flowchart showing the procedure of a resending request search process. The flowchart showing the procedure of the data error information update process at the time of a resending request. The figure for demonstrating the correspondence of the video packet and FEC packet in Pro-MPEG FEC. The figure for demonstrating the correspondence of a video packet and a FEC packet when a decoder receives the video packet. The figure for demonstrating the correspondence of a video packet and a FEC packet when a decoder receives the FEC packet. The figure for demonstrating the relationship between a compression rate, the number of packets, and the information content contained in each packet. The figure for demonstrating the relationship between a compression rate and a transmission rate. The figure for demonstrating the relationship between a compression rate and error packet recovery time.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram for explaining the flow of error correction in the present invention. In FIG. 1, in the prior art, after receiving the packet 123 (after receiving all video packets of the same FEC recovery unit and the FEC packet corresponding to the packet), it is determined whether or not there is an error packet remaining, and a retransmission request is made. Had gone.

  On the other hand, in the present invention, the decoder determines at the timing when each video packet is received whether the packet is an error packet, and even if all the FEC packets are received, the error cannot be recovered. When it is determined that a packet (packet 209) is an error packet and the error cannot be recovered even if all FEC packets are received, the decoder requests retransmission of the packet at that time. I do. As a result, the timing for performing the recovery process of each error packet can be advanced, so that the time from the reception of each error packet to the recovery can be shortened.

  FIG. 2 is a diagram for explaining the overall configuration of the video transmission system according to the present invention. The video transmission system according to the present invention includes an encoder 1, a decoder 2, and a network 3, and a camera 4 is connected to the encoder 1 and a monitor 5 is connected to the decoder 2.

  In the present invention, a transmitting terminal (hereinafter referred to as encoder 1) encodes a video packet acquired by an imaging device (hereinafter referred to as camera 4) and transmits the encoded video packet to a receiving terminal (hereinafter referred to as decoder 2) through the network 3. Then, the decoder 2 decodes the received video packet and outputs it to an output device such as the monitor 5.

  FIG. 3 is a functional block diagram showing functions of the encoder 1 in the present invention. In FIG. 3, the encoder 1 includes a transmission unit 10, a video input processing unit 11, an encoding processing unit 12, an FEC processing unit 13, a storage unit 14, a retransmission request analysis unit 15, and a reception unit 16.

  The video input processing unit 11 has a function of inputting video acquired by the camera 4 or the like. The encoding processing unit 12 has a function of packet-coding the video input to the video input processing unit 11 and storing it in the storage unit 14. Here, a serial number is assigned to each video packet, and in order to simplify the following description, in the present invention, a total of 30 video packets represented by video packet 30 from video packet 1 are generated. Will be described.

  The FEC processing unit 13 uses a predetermined number of packets (for example, 15 packets) among the generated video packets as one FEC recovery unit, generates a Pro-MPEG FEC code in each FEC recovery unit, and stores it. The function of storing in the unit 14 is provided. In other words, when the above-described example is used, video packet 1 to video packet 15 belong to the same FEC recovery unit, and FEC packet 1 to FEC packet 8 described later correspond to error recovery of those packets. . Similarly, video packet 16 to video packet 30 belong to the same FEC recovery unit, and FEC packet 9 to FEC packet 16 described later correspond to error recovery of those packets.

  FIG. 4 is a diagram showing an example of inserting two-dimensional FEC packet data in the present invention. In FIG. 4, all video packets belong to the horizontal FEC group and the vertical FEC group at the same time. Each FEC packet is assigned a serial number. Each FEC packet corrects an error that has occurred in one of the video packets in the same row (or column) as itself. In the example of FIG. 5, the horizontal FEC packet 2 corrects the error of any one of the five packets from the video packet 6 to the video packet 10, and the FEC packet 5 is the three packets of the video packets 2, 7, and 12. Among them, any one packet error is corrected.

  Returning to the description of FIG. 3, the storage unit 14 has a function of storing the generated video packet and FEC packet. The video packet and the FEC packet stored in the storage unit 14 are held in preparation for a retransmission request from the decoder even after the data transmission operation is completed.

  The transmission unit 10 has a function of transmitting the video packets and FEC packets stored in the storage unit 14 in a predetermined order based on the serial numbers assigned to the video packets and the FEC packets.

  FIG. 5 is a diagram illustrating an example of the transmission order of each packet and the FEC packet. For example, in the above-described example, the transmission unit 10 transmits the video packets 1... 5, the FEC packet 1, the video packets 6... 10, the FEC packet 2, the video packets 11. ... packet transmission in the order of 8.

  For the sake of explanation, the case where video packets and FEC packets are transmitted one packet at a time will be described below, but the transmission operation does not necessarily have to be performed one packet at a time. For example, a plurality of packets may be transmitted at the same time, or the number of packets to be transmitted at the same time may be varied according to the availability of the storage unit of the decoder.

  Returning to the description of FIG. 3, the transmission unit 10 has a function of retransmitting a packet when the retransmission request analysis unit 15 is notified that a retransmission request for a video packet or an FEC packet has been received.

  Further, the receiving unit 16 has a function of receiving a retransmission request sent from the decoder. The retransmission request analysis unit 15 has a function of analyzing the content of the packet retransmission request, notifying the transmission unit 10 of the presence of the retransmission request, and notifying which packet is requested for retransmission.

  FIG. 6 is a block diagram illustrating a hardware configuration example of the encoder 1 according to the present invention. In FIG. 6, an encoder 1 includes a CPU (Central Processing Unit) 101, an HDD (Hard Disc Drive) 102, a transmission port 103, a reception port 104, a RAM (Random Access Memory) 105, and an input port 107. Have. Each component is electrically connected by a bus 106.

  Here, the CPU 101 is a calculation unit that controls the entire encoder 1. The HDD 102 stores a program for operating the encoder 1 and data necessary for operating the program. Further, the HDD 102 also stores information indicating the correspondence between video packets and FEC packets. A transmission port 103, a reception port 104, and an input port 107 are interfaces for the encoder 1 to transmit and receive data to and from other devices, and are connected to the decoder 2 via the network 3. The RAM 105 is a storage unit used as a work area for the CPU 101.

  Specifically, the encoder 1 realizes the function of the storage unit 14 by, for example, the RAM 105 or the HDD 102 illustrated in FIG. 6. The encoder 1 realizes the function of the video input processing unit 11 when the CPU 101 that has read the program stored in the HDD 102 executes processing for inputting video from the camera 4 via the input port 107.

  Further, the encoder 1 executes a process in which the CPU 101 that has read the program stored in the HDD 102 illustrated in FIG. 6 transmits the packet stored in the RAM 105 or the HDD 102 via the transmission port 103, for example. 10 functions are realized. The encoder 1 realizes the function of the reception unit 16 by the CPU 101 reading the program stored in the HDD 102 illustrated in FIG. 4 executing a process of receiving a retransmission request via the reception port 104, for example.

  Furthermore, the encoder 1 realizes the functions of the encoding processing unit 12, the FEC processing unit 13, and the retransmission request analysis unit 15 when the CPU 101 executes a program stored in the HDD 102 shown in FIG. 6, for example. As described above, the CPU 101 uses the RAM 105 as a work area in the process.

  FIG. 7 is a functional block diagram showing functions of the decoder 2 in the present invention. In FIG. 7, the decoder 2 includes a receiving unit 20, a storage unit 21, an error recovery processing unit 22, a decoding processing unit 23, a video output processing unit 24, a retransmission request analysis unit 25, and a transmission unit 26.

  The receiving unit 20 has a function of receiving the video packet and the FEC packet sent from the encoder 1 and storing the received video packet and the FEC packet in the storage unit 21. The storage unit 21 has a function of storing packets received by the receiving unit 20.

  The error recovery processing unit 22 holds data error information, which will be described later, and a function of performing reception data confirmation processing, which will be described later, on the video packet and the FEC packet stored in the storage unit 21 based on the data error information. Have The error recovery processing unit 22 indicates to the retransmission request analysis unit 25 that a retransmission request for the packet is necessary when the presence of a packet that cannot be recovered by the two-dimensional FEC is recognized by the received data confirmation processing. It has a function. Further, the error recovery processing unit 22 has a function of recovering the packets sequentially and sending them to the decoding processing unit 23 when there is an error packet that can be recovered by FEC in parallel with the received data confirmation processing. Further, the error recovery processing unit 22 has a function of counting an elapsed time after receiving each packet and sending an error packet that has not been recovered even after a certain time has elapsed after reception to the decoding processing unit 23. .

  The decoding processing unit 23 has a function of sequentially decoding the video packets sent from the error recovery processing unit 22, and the video output processing unit 24 has a function of outputting the video packets to an external device such as the monitor 5.

  The retransmission request analysis unit 25 checks the presence / absence of a packet that requires a retransmission request based on information from the error recovery processing unit. When there is a packet that requires a retransmission request, the transmission unit 26 has a function of transmitting a retransmission request for the packet to the encoder. Further, the retransmission request analysis unit 25 has a function of indicating to the error recovery processing unit 22 that a retransmission request for the packet has been made to the encoder after transmitting the retransmission request.

  FIG. 8 is a block diagram showing a hardware configuration example of the decoder 2 in the present invention. In FIG. 8, the decoder 2 includes a CPU 201, an HDD 202, a transmission port 203, a reception port 204, a RAM 205, and an output port 207. Each component is electrically connected by a bus 206.

  Here, the CPU 201 is a calculation unit that controls the entire decoder 2. The HDD 202 stores a program for operating the decoder 2, data necessary for operating the program, and table information for entering data error information described later. A transmission port 203, a reception port 204, and an output port 207 are interfaces for the decoder 2 to transmit and receive data to and from other devices, and are connected to the encoder 1 via the network 3. A RAM 205 is a storage unit used as a work area for the CPU 201.

  Specifically, the decoder 2 realizes the function of the storage unit 21 by, for example, the RAM 205 or the HDD 202 shown in FIG. The decoder 2 realizes the function of the reception unit 20 by the CPU 201 reading the program stored in the HDD 202 executing a process of receiving a packet via the reception port 204.

  Further, the decoder 2 realizes the function of the transmission unit 26 when the CPU 201 that has read the program stored in the HDD 202 illustrated in FIG. 8 executes a process of transmitting a retransmission request via the transmission port 203, for example. . The decoder 2 implements the function of the video output processing unit 24 when the CPU 201 that has read a program stored in the HDD 202 executes a process of outputting a video to the monitor 5 via the output port 207, for example.

  Further, the decoder 2 reads the program stored in the HDD 202 shown in FIG. 8, for example, so that the CPU 201 refers to the table information stored in the HDD 202 and executes a process based on the program to perform error recovery processing. The function of the unit 22 is realized. The decoder 2 implements the functions of the decryption processing unit 23 and the retransmission request analysis unit 25 when the CPU 201 executes a program stored in the HDD 202, for example. As described above, the CPU 201 uses the RAM 205 as a work area in the process.

  Next, received data confirmation processing in the present invention will be described. As a specific example, a case where 23 packets shown in FIG. 5 are transmitted to the decoder in the order shown in FIG. 5 and the video packets 3, 4, 7, 8, 9 are error packets will be described. Of these five error packets, the video packet 7 can be recovered by the FEC packet as soon as the necessary FEC packets are prepared, but the remaining four packets cannot be recovered by the FEC packet (FIG. 22C). d)).

  As described above, in the prior art, after receiving all video packets and FEC packets, a packet that requires a retransmission request is searched, and if there is a packet that requires a retransmission request, a retransmission request for the packet is performed. Then, recover the error packet. In the specific example, if a retransmission request for any one of the video packets 3, 4, 8, and 9 is made, the remaining three error packets can be recovered by FEC.

  However, as in the present invention, when it is determined whether or not a retransmission request for the packet is necessary at the timing when the error packet is received, the retransmission request for the data cannot be performed when the video packets 3, 4, and 8 are received. . This is because at this stage, it is not determined that the video packet 9 is in error, and if the video packet 9 is not in error, the three error packets can also be recovered by the FEC packet sent later. (See FIGS. 22A and 22B). For this reason, if a retransmission request is made at this point, packet transmission in the next data recovery unit may be delayed due to retransmission of a packet that is not necessary.

  Therefore, in the received data confirmation processing according to the present invention, it is necessary to determine the reception of the video packet 9, which is an error packet for which it is determined that recovery by the FEC packet is impossible, and to request retransmission of the packet.

  FIG. 9 is a flowchart showing an example of the procedure of received data confirmation processing according to the present invention. First, when the receiving unit 20 receives the video packet or the FEC packet transmitted from the encoder 1 (step S10), the error recovery processing unit 22 sets the received packet in the same FEC recovery unit as the packet received immediately before. It is determined whether it belongs (step S20). When the received packet belongs to a different FEC recovery unit from the packet received immediately before, the error recovery processing unit 22 initializes data error information described later (step S30).

  Next, the error recovery processing unit 22 determines whether there is a bit mismatch in the received packet or whether a bit missing has occurred in the received packet (hereinafter, the bit mismatch and missing are collectively referred to as an error). Determination) (step S40). Specifically, when the content of the received packet and the content of an error detection code such as a parity code included in the packet are inconsistent, the error recovery processing unit 22 determines that the packet is an error packet.

  If it is determined that no error has occurred in the received packet, the error recovery processing unit 22 repeats the processing from step S10 for the next received packet. If it is determined that an error has occurred in the received packet, the error recovery processing unit 22 performs data error information update processing at the time of error reception, which will be described later, for the error packet (step S50).

  After completion of the data error information update process, the error recovery processing unit 22 performs a retransmission request search process to be described later for the error packet (step S60). After completion of the retransmission request search process, the error recovery processing unit 22 determines a value of a retransmission request flag indicating whether or not the error packet needs to be retransmitted (step S70).

  When the value of the retransmission request flag of the error packet indicates that it is not necessary to retransmit the packet, the error recovery processing unit 22 repeats the processing from step S10 for the next received packet. When the value of the retransmission request flag of the error packet indicates that the packet needs to be retransmitted, the error recovery processing unit 22 performs data error information update processing at the time of retransmission request described later (step S80). . Thereafter, the error recovery processing unit 22 repeats the processing from step S10 for the next received packet. In the following description, it is assumed that the retransmission request flag is set to 1 when the error packet needs to be retransmitted, and is set to 0 otherwise. As long as it is possible to uniquely identify whether or not retransmission is necessary, other values may be used.

  Here, the data error information update processing in the present invention will be described. In the present invention, the error recovery processing unit 22 has a table for entering data error information. FIG. 10 is an example of a table for entering data error information. The data error information is information including an error flag, a retransmission request flag, an X direction error counter, and a Y direction error counter, and represents information related to an error of each packet.

  In the table, items for entering the data error information of each packet are arranged according to the correspondence between each video packet and each FEC packet, and the error recovery processing unit 22 Data error information of each packet is entered by the update process. Since the table can take any form, the system administrator obtains information about the correspondence relationship in advance from the encoder 1 and the decoder 2, and the encoder 1 generates an FEC packet based on the information to generate a video packet. It is inserted at a predetermined position between them and transmitted to the decoder 2.

  Note that “X direction” and “Y direction” in the description of the present invention correspond to “horizontal FEC group” and “vertical FEC group”, respectively. That is, for example, when the value of the X direction error counter corresponding to a certain packet is “2”, it indicates that there are two error packets in the horizontal FEC group to which the packet belongs.

  The error flag indicates whether or not there is an error in its own data. If it is an error packet, its value is set to 1; otherwise, it is set to 0. The error flag may take another value as long as the presence or absence of the error can be uniquely identified. The retransmission request flag indicates whether or not the packet itself requires a retransmission request. As described above, the value is set to 1 when a retransmission request is required for the packet, and is set to 0 otherwise. Is done.

  The X direction error counter indicates the number of error packets existing in the X direction (row direction) including itself. For example, if there is an error in the video packets 3 and 4 and the video packets 1, 2, and 5 are not error packets or have not been received, the values of the X-direction error counters corresponding to the video packets 1 to 5 are all “ 2 ”. Note that the X-direction error counter may take other values for each packet as long as the number of error packets existing in the horizontal FEC group to which the packet belongs can be uniquely identified.

  The Y direction error counter indicates the number of error packets existing in the Y direction (column direction) including itself. For example, if there is an error in the video packets 3 and 8 and the video packet 13 is not an error packet or has not been received, the values of the Y-direction error counters corresponding to the video packets 3, 8 and 13 are all “ 2 ”. The Y-direction error counter may take other values as long as the number of error packets existing in the vertical FEC group to which the packet belongs can be uniquely identified.

  Also, the numbers in each data in FIG. 10 represent the values of the error flag, the retransmission request flag, the X direction error counter, and the Y direction error counter, respectively, from the left. In the drawing, the error flag may be denoted as A, the retransmission request flag as B, the X direction error counter as C, and the Y direction error counter as D.

  FIG. 11 is a flowchart showing the procedure of the data error information update process. First, the error recovery processing unit 22 determines whether the type of the received error packet is a video packet or an FEC packet (step S51). If it is determined that the received error packet is a video packet, the error recovery processing unit 22 sets 1 to the value of the data error information corresponding to the data (step S52). For example, when the decoder receives video packets 1 ... 3 and video packet 3 is an error packet, data error information at the time of receiving each video packet is expressed as shown in FIGS. 12, 13, and 14, respectively. .

  After performing the processing of step S52, the error recovery processing unit 22 increments the values of the X direction error counter and the Y direction error counter of the data error information corresponding to the data (step S53). The error recovery processing unit 22 further increments the value of the X direction error counter of the video packet belonging to the same horizontal FEC group as the data and the value of the Y direction error counter of the video packet belonging to the same vertical FEC group as the data. (Step S54), the process is terminated. Therefore, for example, when the error video packet 3 is received, the value of the X direction error counter of the video packets 1... 5 and the value of the Y direction error counter of the video packets 8 and 13 are incremented.

  If the received error packet is an FEC packet, the error recovery processing unit 22 determines the direction of the error FEC packet (step S55). It is assumed that the direction of the FEC packet corresponds to the FEC group to which the FEC packet belongs. For example, in the case of FEC packets belonging to the horizontal FEC group, the FEC direction of the data is horizontal (X direction), and in the case of FEC packets belonging to the vertical FEC group, the FEC direction of the data is vertical (Y Direction). Further, in both the X direction and the Y direction, the direction in which time passes, that is, the direction in which the serial number added to the data increases is defined as the positive direction.

  When the direction of the error FEC packet is the vertical direction (Y direction), the error recovery processing unit 22 increments the data and the value of the Y direction error counter corresponding to the data in the Y direction of the data (step S56). The process is terminated. For example, when the FEC packet 6 is an error packet, the value of the Y direction error counter of the video packets 3, 8, and 13 is incremented.

  When the direction of the error FEC packet is the horizontal direction (X direction), the error recovery processing unit 22 increments the data and the value of the X direction error counter corresponding to the data in the Y direction of the data (step S57). The process is terminated. For example, when the FEC packet 3 is an error packet, the value of the X direction error counter of the video packets 11... 15 is incremented.

  Next, the retransmission request search process in the present invention will be described. When the decoder 2 receives the first error packet, the retransmission request search process determines whether or not the error packet needs to be retransmitted. If it is determined that the error packet needs to be retransmitted, the error packet Is set to 1.

  As a specific example, a description will be given below with an explanation of the processing flow in the retransmission request search process when each of the error video packets 4, 8, and 9 is received. FIGS. 15, 16, and 17 show data error information when receiving video packets 4, 8, and 9, respectively.

  However, since error information of unreceived packets cannot be considered, for example, in the data error information when receiving video packet 4, error information of video packet 3 is described, but error information of video packets 7 ... 9 is included. Absent.

  FIG. 18 is a flowchart showing the procedure of the retransmission request search process. First, the error recovery processing unit 22 determines whether the values of the X-direction error counter and the Y-direction error counter corresponding to the first error packet to be processed are 2 or more (step S61). If the values of the X direction error counter and the Y direction error counter are both 2 or more, it is determined that the error packet cannot be recovered by the FEC packet unless other error packets are recovered first, and the process proceeds to step S62 described below. . If not, the process ends.

  For example, when the error video packet 4 is received, the values of the X-direction error counter and the Y-direction error counter corresponding to the error packet are not 2 or more, so it is determined that there is a possibility that the error can be recovered by FEC. Exit. That is, the error recovery processing unit 22 determines that a retransmission request for the video packet 4 at this time is unnecessary. However, when the error video packet 8 and D9 are received, both the X-direction error counter and the Y-direction error counter have a value of 2 or more. Therefore, unless the other error packets are recovered first, the error cannot be recovered using the FEC packet. Judge and proceed to the next decision.

  If the determination in step S61 is “Yes”, the error recovery processing unit 22 has already received the data and belongs to the horizontal FEC group common to the first error packet. The presence / absence of a packet having both direction error counter values of 2 or more is determined (step S62). When there is a second error packet that satisfies the condition, the error recovery processing unit 22 determines that the second error packet is not recovered unless another error packet belonging to the vertical FEC group common to the second error packet is recovered first. It is determined that recovery is not possible with the FEC packet, and the process proceeds to step S63 described below. If not, the process ends.

  For example, when the error video packet 8 is received, both the X-direction and Y-direction error counter values are 2 or more in the data error information corresponding to the received packet belonging to the common horizontal FEC group with the error packet 8. Since there is nothing, the process is terminated. That is, the error recovery processing unit 22 determines that there is a possibility that the error packet can be recovered by the FEC packet, and that a retransmission request is unnecessary. However, when the error video packet 9 is received, among the received data belonging to the common horizontal FEC group with the error packet 9, data in which both the X-direction and Y-direction error counter values are 2 or more (video packet 8 ) Exists. For this reason, the error recovery processing unit 22 determines that the error packet 8 cannot be recovered by the FEC packet unless other error packets are recovered first, and proceeds to the next determination.

  If the determination in step S62 is “Yes”, the error recovery processing unit 22 includes the X direction and the Y direction in the data corresponding to the received packet belonging to the vertical FEC group common to the second error packet. It is determined whether there is data having both error counter values of 2 or more (step S63). When there is a third error packet that satisfies the condition, the error recovery processing unit 22 does not recover the third error packet unless the other error packets belonging to the horizontal FEC group common to the third error packet are recovered first. It is determined that it cannot be recovered by the FEC packet, and the process proceeds to step S64 described below. If not, the process ends.

  For example, when the error video packet 9 is received, among the received data belonging to the vertical FEC group common to the error packet 8, the data (video packet 3) whose X direction and Y direction error counter values are both 2 or more. ) Exists. For this reason, the error recovery processing unit 22 determines that the error packet 3 cannot be recovered by the FEC packet unless other error packets are recovered first, and proceeds to the next determination.

  If the determination in step S63 is “Yes”, the error recovery processing unit 22 includes the X direction and the Y direction in the data corresponding to the received packet belonging to the horizontal FEC group common to the third error packet. It is determined whether there is data having both error counter values of 2 or more (step S64). If there is a fourth error packet that satisfies the condition, the error recovery processing unit 22 will return the third error packet unless other error packets belonging to the vertical FEC group common to the fourth error packet are recovered first. It is determined that the FEC packet cannot be restored, and the process proceeds to step S65 described below. If not, the process ends.

  For example, when the error video packet 9 is received, among the received packets belonging to the same horizontal FEC group as the error packet 3, a packet (video packet 4) whose X direction and Y direction error counter values are both 2 or more. ) Exists. For this reason, the error recovery processing unit 22 determines that the error packet 4 cannot be recovered by the FEC packet unless other error packets are recovered first, and proceeds to the next determination.

  If the determination in step S64 is “Yes”, the error recovery processing unit 22 determines whether the first error packet exists in the received packets belonging to the vertical FEC group common to the fourth error packet. Determination is made (step S65). If the condition is satisfied, the error recovery processing unit 23 determines that it is necessary to request retransmission of the data because the first error packet cannot be recovered even if all the unreceived FEC packets are received. Then, the process proceeds to step S66 described below. If not, the process ends.

  For example, when the error video packet 9 is received, it is determined that the video packet 9 needs to be retransmitted because the error packet 9 exists in the received packets belonging to the common horizontal FEC group with the error packet 4. The process proceeds to the next determination.

  If the determination in step S65 is “Yes”, since the first error packet needs to be retransmitted, the error recovery processing unit 22 sets 1 to the value of the retransmission request flag corresponding to the packet (step S66). ), A retransmission request flag for the packet data is established.

  For example, since the video packet 9 needs to be retransmitted when the error video packet 9 is received, the error recovery processing unit 22 sets the value of the retransmission request flag of the video packet 9 to 1 and the retransmission request flag is established. When the video packet 9 is retransmitted by the retransmission request, the video packets 3, 4, and 8 are also corrected by the FEC packet.

  In this way, by performing a retransmission request search process based on the above procedure, there is no need for a retransmission request (there is a possibility of error recovery by an FEC packet depending on the data reception status after receiving the data). When a packet (video packets 4 and 8 in the above example) is received, a retransmission request flag is not established, and a packet that cannot be recovered by an FEC packet regardless of the subsequent reception status (in the above example, video packet 9). The retransmission request flag can be established for the packet only when it is received.

  Next, data error information update processing at the time of retransmission request in the present invention will be described. If a retransmission request is made for a certain error packet, it can be considered that the error packet is correctly retransmitted, so that a deviation occurs between the data error information recorded in the table and the actual situation. Therefore, in order to perform accurate received data confirmation processing for subsequent received packets, it is necessary to update the contents of the table every time a retransmission request is made.

  FIG. 19 is a flowchart showing a procedure of data error information update processing at the time of a retransmission request. First, when the retransmission request analysis unit 25 confirms that a retransmission request for a packet for which a retransmission request flag has been established (hereinafter referred to as a retransmission target packet) has been made by the transmission unit 26, the data recovery is performed. Inform the processing unit 22 (step S71). Recognizing that the retransmission request for the retransmission target packet has been made, the data recovery processing unit 22 returns the values of the error flag and the retransmission request flag corresponding to the retransmission target packet to 0 (step S72).

  Next, the data recovery processing unit 22 determines the type of the retransmission target packet (step S73). If the retransmission target packet is a video packet, the values of the X direction error counter and the Y direction error counter corresponding to the retransmission target packet are decremented (step S74). If the decrement result is negative, it is set to zero. For example, when the retransmission target packet is the video packet 9, the data recovery processing unit 22 decrements the values of the X direction error counter and the Y direction error counter corresponding to the video packet 9.

  Further, the data recovery processing unit 22 sets the X direction error counter value corresponding to the packet belonging to the common FEC group and the Y direction error counter corresponding to the packet belonging to the common vertical FEC group. Each value is decremented (step S75), and the process ends. As in step S74, 0 is set when the decrement result is negative. For example, when the retransmission target packet is the video packet 9, the data recovery processing unit 22 determines the X-direction error counter value corresponding to the video packets 6... 8, 10 and the Y-direction error corresponding to the video packets 4 and 14. Decrement each counter value.

  If the retransmission target data is an FEC packet, the data recovery processing unit 22 determines the direction of the FEC packet (step S76). When the direction of the packet is the vertical direction (Y direction), the data recovery processing unit 22 decrements the value of the Y direction error counter corresponding to the packet belonging to the common vertical FEC group with the packet (step S77). The process is terminated. As in step S74, 0 is set when the decrement result is negative. For example, when the retransmission target packet is the FEC packet 6, the data restoration processing unit 22 decrements the value of the Y direction error counter corresponding to the video packets 3, 8, and 13.

  When the direction of the retransmission target FEC packet is the horizontal direction (X direction), the data recovery processing unit 22 decrements the value of the X direction error counter corresponding to the packet belonging to the horizontal FEC group common to the packet ( Step S78) and the process ends. As in step S74, 0 is set when the decrement result is negative. For example, when the retransmission target packet is the FEC packet 3, the data recovery processing unit 22 decrements the value of the X direction error counter corresponding to the video packets 11.

  As described above, the video transmission system according to the present invention determines whether an error exists in the packet at the timing when the decoder receives each packet, and if the result of the determination is true, all FECs It is determined whether the packet error can be recovered even if the packet is received, and only when the result of the determination is true, a retransmission request for the packet is made. As a result, the recovery process for each error packet can be started earlier, so the time required to recover each error packet can be shortened and the error packet can be decoded without being recovered. Can be prevented.

  Needless to say, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the invention.

1 Encoder 2 Decoder 3 Network 4 Camera 5 Monitor 10 Transmitter 11 Video Input Processor 12 Encoding Processor 13 FEC Processor 14 Storage Unit 15 Retransmission Request Analysis Unit 16 Receiver 20 Receiver 21 Storage Unit 22 Error Recovery Processor 23 Decoding processor 24 Video output processor 25 Retransmission request analyzer 26 Transmitter 100 Image 101 CPU
102 HDD
103 Transmission port 104 Reception port 105 RAM
106 Bus 107 Input port 201 CPU
202 HDD
203 Transmission port 204 Reception port 205 RAM
206 Bus 207 Output port

Claims (6)

In a data receiving apparatus that receives a packet generated by dividing predetermined data,
When receiving a first packet from the transmitter, determine if there is an error in the first packet;
When it is determined that an error exists in the first packet, the error packet information indicating the number of error packets existing in the group to which the first packet belongs is referred to. Determine if the first packet error can be recovered,
Based on the result of the determination, request the transmitter to retransmit the first packet ;
Said first packet belongs to a first group together with one or more other packets;
And the first packet belongs to a second group together with one or more other packets not belonging to the first group;
The error packet information includes, for each packet received by the data receiving apparatus, identification information of the packet, presence / absence of an error of the packet, presence / absence of necessity of retransmission request of the packet, and the first group. A data receiving method characterized in that the number of error packets existing and the number of error packets existing in the second group are managed by a table associated with each other. When it is determined that an error exists in the first packet ,
There is a second packet containing an error in the first group to which the first packet belongs, and a third packet containing an error is in the second group to which the second packet belongs. There is a fourth packet containing an error in the third group to which the third packet belongs, and the first packet in the fourth group to which the fourth packet belongs. Is determined to exist,
The data receiving method according to claim 1 , wherein the transmitter is requested to retransmit the first packet based on a result of the determination . In a data receiving apparatus that receives a packet generated by dividing predetermined data,
A receiver for receiving the first packet from the transmitter;
It is determined whether there is an error in the first packet, and when it is determined that there is an error in the first packet, an error indicating the number of error packets existing in the group to which the first packet belongs An error recovery processing unit that refers to the packet information and determines whether the error of the first packet can be recovered even if all packets are received;
Based on the result of the determination, a transmitter that requests the transmitter to retransmit the first packet;
Including
Said first packet belongs to a first group together with one or more other packets;
And the first packet belongs to a second group together with one or more other packets not belonging to the first group;
The error packet information includes, for each packet received by the data receiving apparatus, identification information of the packet, presence / absence of an error of the packet, presence / absence of necessity of retransmission request of the packet, and the first group. A table in which the number of existing error packets and the number of error packets existing in the second group are associated with each other is managed
A data receiving apparatus. When it is determined that an error exists in the first packet,
The error recovery processing unit sends an error to the second group to which the second packet belongs, and the second packet to which the second packet belongs has an error in the first group to which the first packet belongs. A fourth group including an error, and a fourth group including an error in a third group to which the third packet belongs and a fourth group to which the fourth packet belongs. To determine whether the first packet exists,
The transmitter requests the transmitter to retransmit the first packet based on the determination result
The data receiving apparatus according to claim 3, wherein: In a data receiving apparatus that receives a packet generated by dividing predetermined data,
When receiving a first packet from the transmitter, determine if there is an error in the first packet;
When it is determined that an error exists in the first packet, the error packet information indicating the number of error packets existing in the group to which the first packet belongs is referred to. Determine if the first packet error can be recovered,
Based on the result of the determination, request the transmitter to retransmit the first packet.
Let the data receiver perform the process,
Said first packet belongs to a first group together with one or more other packets;
And the first packet belongs to a second group together with one or more other packets not belonging to the first group;
The error packet information includes, for each packet received by the data receiving apparatus, identification information of the packet, presence / absence of an error of the packet, presence / absence of necessity of retransmission request of the packet, and the first group. A table in which the number of existing error packets and the number of error packets existing in the second group are associated with each other is managed
A data receiving program characterized by the above. When it is determined that an error exists in the first packet,
There is a second packet containing an error in the first group to which the first packet belongs, and a third packet containing an error is in the second group to which the second packet belongs. There is a fourth packet containing an error in the third group to which the third packet belongs, and the first packet in the fourth group to which the fourth packet belongs. Is determined to exist,
Based on the result of the determination, request the transmitter to retransmit the first packet.
The data receiving program according to claim 5, wherein the data receiving device is caused to execute processing.

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