JP2009206998A - Communications device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a communication device which can suppress the deterioration of content data. <P>SOLUTION: The communication device includes a receiving means 301 to receive packets which store content data from a first external equipment, a buffering means 304 to buffer the content data received by the receiving means 301, a detection means 351 to detect the packet loss of the packet received by the receiving means 301, a complement packet generating means 352 to generate complement packets for filling up the portion where the packet loss in the content data is generated, and a transmitting means 301 which sequentially transmits the content data buffered by the buffering means 352 as packets to a second external equipment, and at the same time, along with the detection of the packet loss by the detection means 351, transmits the retransmission request of the packets to the first external equipment. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a communication device.

  In recent years, communication systems that perform streaming distribution of content data via a network such as the Internet have become widespread. In such a communication system, a communication mode for relaying content data between terminal devices called P2P (Peer To Peer) is used, so that the load and the load can be increased without increasing the number of server devices that distribute content data. A communication system capable of reducing traffic concentration has been considered (see, for example, Patent Document 1).

  In streaming delivery by P2P, a plurality of terminal devices are logically connected in multiple layers with a terminal device storing content data as a vertex. The content data distributed from the server device is sequentially transferred between lower-layer terminal devices.

  Further, in a communication system that performs streaming distribution of content data, a packet loss occurs in which the content data being communicated is lost on a packet-by-packet basis when the amount of communication increases and exceeds the processing capacity of the lines and devices on the network. . As means for preventing the deterioration of content data due to packet loss, for example, there is an error correction coding technique.

In the error correction coding system, redundant data is added to content data to be transmitted by error correction coding, and the packet loss portion of the content data is corrected when decoding is performed on the receiving side. In general, in the error correction coding method, the larger the amount of redundant data is, the more packet loss can be corrected.
JP 2007-67814 A

  However, the error correction coding method cannot sufficiently solve the problem of repeating the transfer of content data between terminal devices. The error correction coding method can correct erroneous data to some extent, but if an error (packet loss, etc.) exceeding the correction capability occurs, it cannot be corrected, and data loss is still caused. Propagates to the lower level. That is, as the content data is transferred to the lower layer, the possibility that the packet loss accumulates and the content data deteriorates increases.

  Accordingly, an object of the present invention is to provide a communication apparatus capable of suppressing deterioration of content data in a lower hierarchy in a system that sequentially transfers a stream of content data between terminal apparatuses.

  In order to achieve the above object, the present invention is a communication device that receives content data from a first external device by streaming and transmits the received content data to a second external device by streaming. Receiving means for receiving a packet storing the content data from one external device; buffering means for buffering the content data received by the receiving means; and detecting packet loss of the packet received by the receiving means Detecting means for performing, replenishment packet generating means for generating a replenishment packet for replenishing a portion of the content data where the packet loss has occurred, and the content data buffered by the buffering means for the second external device Are sequentially transmitted as packets, and the detection means A transmission unit that transmits a packet retransmission request to the first external device in association with detection of the packet loss, and the transmission unit transmits the packet loss of the content data to the second external device. If the receiving means receives the retransmission packet of the packet loss part before the transmission of the packet, the retransmission packet is transmitted to the second external apparatus, and the second external apparatus of the part where the packet loss of the content data has occurred If the retransmission packet of the packet loss part cannot be received before transmission to the device, the supplement packet generated by the supplement packet generation means is transmitted to the second external device, and then received from the first external device. A retransmission packet is transmitted.

  ADVANTAGE OF THE INVENTION According to this invention, in the system which transfers the stream of content data sequentially between terminal devices, the communication apparatus which can suppress deterioration of the content data in a lower hierarchy can be provided.

The communication apparatus of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing a configuration of a communication system according to an embodiment of the present invention. For example, the communication system 1 shown in FIG. 1 includes a terminal device 2 that distributes content data and terminal devices 311 to 333 that receive the distributed content data.

  The terminal device 2 has a recording medium such as an HDD (Hard Disk Drive) that stores content data, and is a communication device that distributes content data stored in the recording medium in response to a distribution request. Further, the terminal device 2 has a function of retransmitting a lost packet in response to a packet retransmission request from the lower layer terminal devices 311 to 333.

  The terminal devices 311 to 333 are communication devices that receive and decode content data distributed from the terminal device 2. The terminal devices 311 to 333 have a function of transferring content data to other terminal devices that are logically connected one layer below.

  When the terminal device 311 to 333 detects a packet loss in the process of receiving the content data, the terminal device 311 to 333 transmits a packet retransmission request to the terminal device 2 or another terminal device in the upper layer / same layer and the packet loss part. A dummy packet for supplementing is generated. Details of these processes will be described later with reference to FIGS. The terminal devices 311 to 333 can realize the same function as the terminal device 2 as long as the terminal devices 311 to 333 include a recording medium for storing content data.

  In FIG. 1, a terminal device 311, a terminal device 312, and a terminal device 313 are located in the first layer and directly receive content data distribution from the terminal device 2. The terminal device 321, the terminal device 322, and the terminal device 323 are located in the second layer and directly receive content data distribution from the terminal device 311 in the first layer. The terminal device 331, the terminal device 332, and the terminal device 333 are located in the third hierarchy, and directly receive content data distribution from the second hierarchy terminal apparatus 321.

  In FIG. 1, the terminal device 311, the terminal device 312, and the terminal device 313 are logically connected to the terminal device 2, and the terminal device 321, the terminal device 322, and the terminal device 323 are logically connected to the terminal device 311. 5 shows an example of a tree structure in which the terminal device 331, the terminal device 332, and the terminal device 333 are logically connected. However, the present invention is not limited to this, and another terminal device can be logically connected to each terminal device.

  In the communication system 1, the content data stored in the terminal device 2 in the 0th hierarchy is first distributed to the terminal devices 311 to 313 located in the 1st hierarchy. Next, the content data distributed to the terminal device 311 located in the first hierarchy is transferred to the second hierarchy terminal devices 321 to 323 logically connected to the respective terminal devices 311.

  As described above, in the communication system 1, the stream of content data distributed from the terminal device 2 in the 0th layer is sequentially transferred to the terminal devices 311 to 333 in the lower layer. In this embodiment, each device is connected by a network in which communication is performed by UDP (User Datagram Protocol) / IP (Internet Protocol) and RTP (Real-time Transport Protocol).

  Also, in this embodiment, when content is viewed on each terminal device 311 to 333, a certain amount of received packets are secured and decoded so that jitter such as fluctuations and distortions in video and audio does not occur. . In each of the terminal devices 311 to 333 according to the present embodiment, for example, in order to be able to transfer content data at a constant rate, packet transfer to the next terminal device is performed in accordance with the pace of decoding.

  Therefore, in each of the terminal devices 311 to 333, the content data decoding start time and transfer start time are delayed by the time from the start of content data reception until a predetermined amount of packets are accumulated. As a result, the delay time is accumulated in the terminal devices in the lower hierarchy, and the decoding start time of the content data is delayed.

  Therefore, in the terminal device 2 of this embodiment, when a connection request for a new terminal device is received, the connection destination is determined in consideration of the decoding start time of the content data in each layer. For example, when a terminal device that desires connection transmits a connection request to the terminal device 2, the terminal device 2 that receives the connection request considers the delay time in each layer, and is a layer that can be received from the first packet of content data, In addition, a connection destination is determined in a hierarchy having a short waiting time until the start of decoding.

  In this way, in the present embodiment, the tree structure of the communication system 1 is configured based on the instruction from the terminal device 2. Although the case where the terminal device 2 determines a suitable connection destination hierarchy is shown here, the present invention is not limited to this, and a terminal device that desires connection may determine a desired hierarchy.

  In the terminal device 2, for example, the time required to secure a certain amount of buffer from the communication speed on each line is calculated, and a suitable connection destination is searched by a method such as predicting the delay time of each layer. The method is not limited to this as long as it is a method for finding a suitable connection destination by grasping the delay time of the hierarchy. Therefore, in the present embodiment, it is possible to find a suitable connection destination by considering the decoding start time of content data in each layer when connecting a new terminal device.

  Next, the configuration of the terminal device 2 and the terminal devices 311 to 333 according to the present embodiment will be described with reference to FIGS. FIG. 2 is a diagram illustrating a configuration of the terminal device 2. The terminal device 2 includes, for example, a network communication unit 201, a HDD 202, an MPU (Micro Processing Unit) 203, a RAM (Random Access Memory) 204, a ROM (Read Only Memory) 205, and the like.

  The network communication unit 201 receives a distribution request for content data via the network, and transmits the content data to the terminal devices 311 to 313 one level below. Also, the network communication unit 201 receives the packet retransmission request and retransmits the packet specified by the request.

  The MPU 203 outputs commands for operating various functions in accordance with programs stored in the ROM 204. The MPU 204 controls the operation of the entire apparatus. The RAM 205 is used as a main memory that reads and writes electrical signals and provides a work area to the MPU 203.

  The ROM 204 stores various programs executed by the MPU 203. The ROM 204 includes, for example, a duplication unit 250 that duplicates content data, a decode time calculation unit 251, and the like. Note that the duplication unit 250 duplicates the content data in the HDD 202 in response to the content data distribution request, and generates a copy of the content data. When a new terminal device is connected, the decode time calculation unit 251 calculates a predicted decode start time of content data in each terminal device from the communication speed in each line.

Further, it is assumed that the terminal device 2 in the present embodiment records the address of each terminal device that receives streaming distribution of content data.
FIG. 3 is a diagram illustrating a configuration of the terminal devices 311 to 333. Here, for simplification of description, only the configuration of the terminal device 311 in the first layer is shown, but the terminal devices 311 to 333 in the present embodiment all have the same configuration. The terminal device 311 includes, for example, a network communication unit 341, an MPU 342, a RAM 343, a ROM 344, a decoder 345, and the like.

  The network communication unit 341 receives content data from a communication device (terminal device 2) that is one layer above the network. Then, the network communication unit 341 transmits the received content data to the communication devices (terminal devices 321 to 323) that are one layer below. The network communication unit 341 transmits / receives a packet retransmission request and transmits / receives a packet corresponding to the packet retransmission request.

  The MPU 342 outputs commands for operating various functions according to programs stored in the ROM 344. The MPU 342 controls the operation of the entire apparatus. The RAM 343 reads and writes electrical signals and is used as a main memory that provides a work area to the MPU 342. Further, the RAM 343 buffers content data received by the network communication unit 341 and adjusts the speed difference between the processing speed of the decoder 345 and the communication speed.

  The ROM 344 stores various programs executed by the MPU 342. The ROM 344 includes, for example, a duplication unit 350 that duplicates content data, a packet loss detection unit 351 that detects packet loss, a dummy packet generation unit 352 that generates dummy packets, and the like.

  Note that the duplicating unit 350 creates a duplication of the content data according to the number of terminal devices logically connected one level below. The packet loss detection unit 351 checks the sequence number written in the RTP header of each packet, for example, in the process of receiving content data for each packet, and detects packet loss. The dummy packet generation unit 352 generates a dummy packet that fills a gap between packets caused by packet loss. The implementation of the dummy packet will be described later with reference to FIGS.

The decoder 345 decodes the content data buffered by the RAM 343 and outputs it to the output device 400 such as a display device.
In the terminal devices 311 to 333 according to the present embodiment, when the buffered data is transmitted from the RAM 343 to the decoder 345, the copy of the content data generated by the copy unit 350 is transmitted to the terminal device one layer below. Further, since the terminal devices 311 to 333 in the present embodiment temporarily delete the decoded packets and then sequentially delete them, a recording medium such as the HDD 202 for storing content data is not required. The content data distribution method in the present embodiment will be described below with reference to FIG.

  FIG. 4 is a diagram illustrating a content data distribution method according to the present embodiment. Here, for example, a case is shown where content data distributed from the terminal device 2 in the 0th hierarchy flows to the terminal devices 331 to 333 in the 3rd hierarchy.

  When receiving the content data distribution request, the terminal device 2 according to the present embodiment divides the copy of the content data into a plurality of partial data, and stores the partial data in a plurality of packets for distribution. At this time, a sequence number is written in each packet so that the content data can be restored at the delivery destination.

  For example, in this embodiment, a sequence number of “1” is written in a packet that stores partial data located at the beginning of content data, and a sequence number of “2” is written in a packet that stores subsequent partial data. Thus, in each packet, a sequence number indicating a position in content data to which partial data to be stored is assigned is written.

  Therefore, in the terminal device of the present embodiment, the content data can be decoded by streaming in the distribution destination terminal device by distributing the packets in the order of the sequence numbers. In addition, each terminal device that receives distribution of content data can detect a packet loss by referring to the sequence number of each received packet.

  Here, the content data distributed from the terminal device 2 is shown as an aggregate of packets located in the 0th layer, and a copy of the content data buffered in each of the terminal devices 311 to 333 is shown in the 1st to 3rd layers, respectively. Shown by a collection of located packets.

  First, when the terminal device 2 in the 0th layer receives the content data distribution request, the terminal device 2 generates a copy of the content data and transmits it to the terminal devices 311 to 313 in the 1st layer. In this embodiment, the copy of the content data is transmitted in units of packets.

  The terminal devices 311 to 313 temporarily store the received packets in the respective RAMs 343. At this time, the terminal device 311 generates a copy of the packet according to the number of terminal devices in the second hierarchy.

  When a certain amount of received packets are accumulated in the RAM 343, the terminal devices 311 to 313 transfer the packets from the RAM 343 to the decoder 345 and decode them, so that the content data decoded by the output device 400 can be viewed. At the same time, the terminal device 311 transmits a copy of the generated packet to the terminal devices 321 to 323 in the second layer. Hereinafter, the terminal device in each layer distributes the content data by repeating the above-described processing.

  In this embodiment, packets stored in the RAM 343 are transferred to the decoder 345 at a constant pace. In addition, a packet copy is transmitted to the terminal device one layer lower along with the transfer to the decoder 345. As a result, the distribution timing of the content data to the lower-level terminal devices is also kept at a constant pace, and the streaming distribution of the content data between the terminal devices can be smoothed.

  Here, in streaming distribution of content data, packet loss occurs when the amount of communication exceeds the processing capability of each device. In a system such as the communication system 1, if no countermeasure is taken against this packet loss, the packet loss is accumulated as the content data is transferred to the lower layer, and the image quality of the content is increased as the terminal device is in the lower layer.・ Sound quality deteriorates. In order to avoid this accumulation of packet loss, in this embodiment, processing is performed according to the procedure shown in FIGS. 5 and 6 after detection of packet loss.

  Hereinafter, with reference to FIG. 5 and FIG. 6, the flow of processing after packet loss detection in the terminal device of the present embodiment will be described. Here, in order to simplify the description, the content data in the terminal devices of the 0th layer terminal device 2, the 1st layer terminal device 311, the 2nd layer terminal device 321, and the 3rd layer terminal device 331 The flow of distribution is shown as an example. Here, it is assumed that the packet with the sequence number 3 is lost in the content data transmitted from the terminal device 2 to the terminal device 311.

  FIG. 5 shows a flow in the case where a retransmission packet can be received in a time until it becomes an order of streaming the packet of sequence number 3 to the terminal device 321, and FIG. 6 shows the packet of sequence number 3 as the terminal device 321. The flow when the retransmission packet cannot be received in the time until the transmission order becomes the streaming is shown.

  The terminal device 2 receives the content data distribution request and starts distributing the content data. The terminal device 311 performs buffering of the received packet and sends a certain amount of accumulated packets to the decoder. For example, the terminal devices 311 to 331 transfer the data to the next delivery destination as 6 packets are accumulated.

  That is, the terminal devices 311 to 331 sequentially receive and buffer the packets of sequence numbers 1 to 6 and then receive the packet of sequence number 7 from the packet of sequence number 1 to the lower layer terminal device. Start streaming transfer.

  In the process of distributing content data from the terminal device 2 to the terminal device 311, for example, when a packet loss of sequence number 3 is detected, the terminal device 311 transmits a retransmission request for the packet of sequence number 3 to the terminal device 2, A dummy packet of sequence number 3 is generated to fill the gap between packets.

  Here, as shown in FIG. 5, if the retransmission packet can be received in the time until the packet of sequence number 3 is streamed to the terminal device 321, the terminal device 311 generates the dummy packet of sequence number 3. And replace the retransmitted packet instead.

  However, as shown in FIG. 6, if the retransmission packet cannot be received in the time until the packet of sequence number 3 is streamed to the terminal device 321, the terminal device 311 generates the generated sequence number 3. The content data supplemented with the dummy packet is distributed to the terminal device 321. After that, when the retransmitted packet with the sequence number 3 is received, the terminal device 311 preferentially transfers the packet to the terminal device 321.

  For example, in the terminal device 321, when a packet retransmitted in the time until the packet in sequence number 3 is transmitted to the terminal device 331 can be received, a dummy packet having the same sequence number as the retransmitted packet is received. Delete and replace the retransmitted packet instead.

  Thus, in this embodiment, the retransmitted packet is preferentially transferred. Since the retransmitted packet is transferred faster than the content data transferred while buffering in each terminal device, it can catch up with the content data transmitted earlier. As a result, even if the terminal device in the upper hierarchy does not make it in time, the terminal device in the lower hierarchy can catch up with the content data and supplement the portion where the packet loss has occurred. Therefore, in the present embodiment, it is possible to realize a mechanism for avoiding accumulation of packet loss in streaming delivery by P2P.

  Also, if the content data is transferred without supplementing the portion where the packet loss has occurred, a new packet retransmission request is transmitted at the transfer destination terminal device. As a result, there is a possibility that the traffic on the network increases and becomes congested.

  In this embodiment, each time a terminal device that receives content data detects a packet loss, a new packet retransmission request is received from the lower layer by sequentially replenishing the portion where the packet loss has occurred and transferring it to the next terminal device. It is possible to avoid being transmitted.

  In addition, in this embodiment, since the decoded content data is temporarily stored and then deleted, the terminal device in the second layer or lower layer can receive the desired packet in the upper layer terminal device even if the packet retransmission request is transmitted. May be deleted and not retransmitted. In this case, it is assumed that the terminal device that has detected the packet loss can transmit a packet retransmission request to the terminal device 2 or another terminal device in the same hierarchy.

  In the present embodiment, the terminal device that receives the streaming distribution of the content data has a hierarchy in which the terminal device 2 is located from the terminal device 2 or another terminal device in the upper hierarchy, and the terminal device 2 or the upper hierarchy. -It is assumed that information such as addresses of other terminal devices in the same hierarchy has been acquired.

  Next, a dummy packet mounting method of this embodiment will be described with reference to FIGS. FIG. 7 shows a configuration example of RTP in this embodiment. In this embodiment, a packet transmitted and received between terminal devices stores, for example, an IP (Internet Protocol) address for identifying the device, a UDP header in which control information used in UDP is stored, and control information used in RTP. RTP header and RTP payload in which partial data is stored.

  The RTP header 700 of this embodiment includes, for example, the current RTP version (V; version), padding (P; padding), extension (X; extension), the number of CSRCs (CC; contributing source count), a marker (M; Marker, payload type (PT), sequence number, time stamp, SSRC (synchronization source) and other data are written.

  Padding indicates whether there is padding at the end of the RTP payload. Here, a value of “1” is written when there is padding at the end of the RTP payload.

The extension indicates whether an RTP extension header is used. Here, a value of “1” is written when the RTP extension header is used.
The number of CSRCs indicates the number of merged information sources when a plurality of RTP streams are merged by entering a mixer or a translator in the middle.
Markers are used to mark important events in the RTP stream. The method of using this bit depends on the RTP profile and RTP payload format used.

The sequence number is incremented every time an RTP packet is transmitted, and is used for detecting a packet loss.
In this embodiment, when a packet loss is detected, an extension header 800 shown in FIG. 8 is added to the RTP header 700 to generate a dummy packet. FIG. 8 is an example of an extension header 800 added to the RTP header 700. FIG. 9 shows a configuration example of a dummy packet in the present embodiment. In the present embodiment, the dummy packet is mounted so as to be shorter than a normal packet to reduce network traffic. For example, in this embodiment, the payload size is set to zero using an RTP extension header.

  The extension header 800 added to the RTP header 700 is divided into areas 811, 812, 813, and 814 in which data is written. Each area has a data length of 2 bytes (16 bits).

  In the area 811, for example, a specific value indicating a dummy packet is written so that it can be determined that the packet is a dummy packet. In the area 812, the size of the payload is written. In this embodiment, since the payload size of the dummy packet is zero, a value of “0” is written here.

  In the area 813, the sequence number of the lost packet is written. Further, when packet loss occurs continuously, the sequence number of the first packet lost first in the continuous packet loss is written. In the area 814, the number of lost packets at the time when packet loss occurs continuously is written. When packet loss is not continuous, a value of “1” is written in the area 814.

  Normally, each time a packet loss occurs, a dummy packet corresponding to the lost sequence number is generated. For example, when packet loss occurs continuously, a dummy packet corresponding to each number is generated. The amount of communication can be reduced by replenishing the gaps collectively with one dummy packet rather than replenishing the gaps between the packets.

  Therefore, in this embodiment, when packet loss occurs continuously, the number of packets continuously lost is written in the area 813 in which the sequence number of the first packet lost first in the continuous packet loss is written. Referring to the area 814, a dummy packet that can replenish gaps between the packets at once is generated.

  Next, the flow of content data transfer processing in each of the terminal devices 311 to 333 will be described with reference to FIGS. FIG. 10 is a flowchart illustrating a procedure of content data transfer processing in the terminal device 311. In order to simplify the description, the flow of content data distribution in each terminal device of the terminal device 2, the terminal device 311, the terminal device 321, and the terminal device 331 is shown as an example. Here, although the processing of the terminal device 311 is mainly shown, each terminal device in the present embodiment is assumed to perform the same processing.

  When receiving a packet from the terminal device 2 (S1001), the MPU 342 of the terminal device 311 confirms whether or not the received packet is a retransmitted packet (S1002). If the received packet is a retransmitted packet (Yes in S1002), the MPU 342 of the terminal device 311 confirms the sequence number of the retransmitted packet, and this sequence number is the number of each packet currently buffered in the RAM 343. It is confirmed whether or not the value is smaller than the smallest sequence number among the sequence numbers, that is, whether or not the retransmitted packet is in time for the time scheduled to be decoded by the terminal device 311 (S1003). ).

  When the sequence number of the retransmitted packet is a value smaller than the smallest sequence number among the respective sequence numbers of each packet currently buffered in the RAM 343, that is, this retransmitted packet is the terminal device 311. In step S1010, the MPU 342 of the terminal device 311 preferentially transmits the retransmitted packet to the terminal device 321 without buffering (S1010). .

  When the sequence number of the retransmitted packet is larger than the smallest sequence number among the respective sequence numbers buffered in the RAM 343 in the processing of S1003, that is, the retransmitted packet Is in time for the terminal device 311 to be decoded by streaming (No in S1003), the MPU 342 of the terminal device 311 deletes the dummy packet having the same sequence number as the retransmitted packet from the RAM 343, and instead The retransmitted packet is buffer-recorded in the RAM 343 (S1004).

  If the packet received in S1002 is not a retransmitted packet (No in S1002), the MPU 342 of the terminal device 311 confirms the sequence number written in the RTP header of this packet, and detects packet loss (S1005).

  When the packet loss is detected (Yes in S1005), the MPU 342 of the terminal device 311 transmits a packet retransmission request including the sequence number of the lost packet to the terminal device 2 (S1006). Further, the MPU 342 of the terminal device 311 generates a dummy packet having a sequence number in which the packet loss is detected in order to supplement the portion where the packet loss has occurred (S1006), and records the buffer in the RAM 343 (S1008).

  When packet loss is not detected in S1004 (No in S1002), the MPU 342 of the terminal device 311 records the received packet in a buffer (S1008). At this time, the MPU 342 of the terminal device 311 generates a copy of the packet according to the number of terminal devices connected one layer below.

  When the processing of S1007 is performed, the MPU 342 of the terminal device 311 confirms whether a certain amount of packets have accumulated in the RAM 343 (S1009). If a certain amount of packets are not accumulated (No in S1008), the MPU 342 of the terminal device 311 returns the process to S1001.

  If a certain amount of packets have accumulated (Yes in S1009), the MPU 342 of the terminal device 311 reads out the packet having the smallest sequence number from the RAM 343, transfers it to the decoder 345, and copies the packet to the lower layer. It transmits to the terminal device 321 (S1010).

  Next, the MPU 342 of the terminal device 311 confirms whether or not the content data has been decoded (S1011). If the decoding of the content data has not been completed (No in S1011), the MPU 342 of the terminal device 311 returns the process to S1001. If the decoding of the content data is completed (Yes in S1011), the MPU 342 of the terminal device 311 ends the process.

  Further, the terminal device according to the present embodiment has a function of retransmitting a packet of a packet loss portion in response to a packet retransmission request from the same layer or a lower layer. Next, the flow of packet retransmission in this embodiment will be described with reference to FIG. FIG. 11 is a flowchart showing a flow of packet retransmission in the terminal device 311. Here, for example, it is assumed that the terminal device 311 receives a packet retransmission request. Here, for simplification of explanation, only the processing of the terminal device 311 in the first layer is shown, but all the terminal devices in the present embodiment perform the same processing as the terminal device 311.

  In the process of transferring the content data to the terminal devices 321 to 323, the terminal device 311 confirms whether or not a packet retransmission request has been received from the terminal devices 312 and 313 in the same layer or the terminal devices 321 to 333 in the lower layer. (S1101). When the packet retransmission request is not received (No in S1101), the MPU 342 of the terminal device 311 repeats the process of S1101 and stands by.

  When the packet retransmission request is received in S1101 (Yes in S1101), the MPU 342 of the terminal device 311 refers to the sequence number of the lost packet included in the packet retransmission request signal, and the packet with the corresponding sequence number is stored in the RAM 343. It is confirmed whether or not there is (S1102). When there is no packet with the corresponding sequence number in the RAM 343 (No in S1102), the MPU 342 of the terminal device 131 notifies that there is no packet with the corresponding sequence number in the lower layer terminal device that transmitted the packet retransmission request. Is transmitted (S1105), and the process returns to S1101.

  If there is a packet with a sequence number corresponding to the RAM 343 in the processing of S1102 (Yes in S1102), the MPU 342 of the terminal device 311 reads out the packet with the sequence number from the RAM 343, generates a duplicate (S1104), and requests a packet retransmission Is transmitted to the lower-layer terminal devices 321 to 323 that have transmitted (S1105).

  Next, the MPU 342 of the terminal device 311 confirms whether or not the content data has been decoded (S1106). If the decoding of the content data has not been completed (No in S1106), the MPU 342 of the terminal device 311 returns the process to S1001. If the decoding of the content data is completed (Yes in S1106), the MPU 342 of the terminal device 311 ends the process.

As described above, according to the present embodiment, it is possible to realize a mechanism for avoiding accumulation of packet loss in streaming delivery by P2P.
According to this embodiment, when packet retransmission is not in time, a gap between packets is supplemented with a dummy packet and content data is transferred, so that a new packet retransmission request can be avoided from being transmitted from the lower layer. Accordingly, it is possible to provide a communication device that can distribute data while avoiding network congestion.

  In the terminal device of the present embodiment, the data is erased after the distributed content data is decoded, and therefore it is not necessary to provide a large-capacity recording medium such as an HDD. Further, since only the terminal device that reproduces the content data is targeted for distribution, the network bandwidth can be reduced.

In the present embodiment, a packet retransmission request can be transmitted to other terminal devices in the upper layer and the same layer. Thereby, the packet loss handling process can be executed between the terminal devices.
In this embodiment, since decoding is performed after a certain amount of buffer is secured, occurrence of jitter such as fluctuation and distortion in video / audio can be avoided when viewing content on the output device. Further, in this embodiment, a copy of the packet is transmitted to the terminal device one layer lower along with the transfer to the decoder. Thereby, the timing which distributes content data to the terminal device of a lower hierarchy is also maintained at a fixed pace, and the data communication between each terminal device can be smoothed.

  In this embodiment, when packet losses occur continuously, the gap between packets is replenished at once by referring to the sequence number of the first packet lost and the number of lost packets in the continuous packet loss. A dummy packet can be generated.

In this embodiment, when a new terminal device is connected, a suitable connection destination can be determined in consideration of the content reproduction start time in each layer.
The present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine a component suitably in different embodiment.

The figure which shows the structure of the communication system which concerns on the Example of this invention. The figure which shows the structure of the terminal device 2 which distributes the content data based on the Example of this invention. The figure which shows the structure of the terminal device 311 which concerns on the Example of this invention. The figure which shows the delivery method of the content data based on a present Example. The figure which shows the flow of the process after the packet loss detection which concerns on the Example of this invention. The figure which shows the flow of the process after the packet loss detection which concerns on the Example of this invention. The figure which shows the structural example of the RTP header which concerns on the Example of this invention. The figure which shows an example of the extension header added to the RTP header which concerns on the Example of this invention. The figure which shows the structural example of the dummy packet in a present Example. The flowchart which shows the process sequence of the content data transfer in the terminal device which concerns on the Example of this invention. The flowchart which shows the flow of the packet resending in the terminal device which concerns on the Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Communication system 2, 311, 312, 313, 321, 322, 323, 331, 332, 333 ... Terminal device 201, 341 ... Network communication part 202 ... HDD
203, 342... MPU
204, 343 ... ROM
205, 344 ... RAM
250, 350 ... duplication unit 345 ... decoder 351 ... packet loss detection unit 352 ... dummy packet generation unit 400 ... output device 700 ... RTP header 800 ... extension headers 811 and 812 , 813, 814... Data writing area in the extension header

Claims (7)

A communication device that receives content data from a first external device by streaming and transmits the received content data to a second external device by streaming,
Receiving means for receiving a packet storing the content data from the first external device;
Buffering means for buffering the content data received by the receiving means;
Detecting means for detecting a packet loss of a packet received by the receiving means;
Replenishment packet generation means for generating a replenishment packet for replenishing a portion of the content data where a packet loss has occurred;
The content data to be buffered by the buffering means is sequentially transmitted as a packet to the second external device, and a packet retransmission request is transmitted to the first external device when the packet loss is detected by the detecting means. Transmission means for
The transmission means receives the retransmission packet of the packet loss portion by the reception means before transmission to the second external device of the portion where the packet loss of the content data has occurred. The replenishment packet generated by the replenishment packet generator means if the retransmitted packet of the packet loss part cannot be received before the transmission to the second external device of the part where the packet loss of the content data has occurred. A communication apparatus that transmits a packet to the second external apparatus, and then transmits a retransmission packet received from the first external apparatus.   The transmission unit transmits a packet retransmission request to a third external device that receives the content data from the first external device in accordance with the detection of the packet loss by the detection unit. The communication device described. The receiving means receives a packet retransmission request from the second external device;
3. The communication apparatus according to claim 2, wherein the transmission unit transmits the packet designated by the packet retransmission request received by the reception unit to the second external device. 4. The communication apparatus according to claim 3, wherein when the packet loss occurs continuously, the supplement packet generation unit generates a supplement packet that replenishes a portion where the packet loss continuously occurs. . A recording device for storing the content data;
5. The communication device according to claim 4, wherein the transmission unit transmits the content data stored in the recording device to the second external device in response to a content data distribution request. Further comprising a connection destination determination means for determining a connection destination device of an external device to which a new connection is desired from the reception destination information of the content data,
The transmission means transmits the address of the connection destination device determined by the connection destination determination means in response to a connection request from the external device that desires a new connection to the external device that desires a new connection. The communication device according to claim 5, wherein: The connection destination determining means determines the connection destination device of the external device to which the connection is newly desired from the predicted content data reproduction start time of each external device currently connected to the network as the reception destination information. The communication device according to claim 6.

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