JP2005184580A - COMMUNICATION SYSTEM, INFORMATION PROCESSING DEVICE AND METHOD, PROGRAM, AND RECORDING MEDIUM - Google Patents

Abstract

PROBLEM TO BE SOLVED: To optimally set a buffer time of a receiving side terminal according to a network environment.
A communication unit 21 transmits a measurement packet for measuring a round-trip time to and from a transmission-side terminal that transmits a packet of streaming data, and receives the measurement packet. The controller 22 calculates the buffer time based on the round trip time of the measurement packet. The reproduction data buffer unit 23 buffers the streaming data of the packet transmitted from the transmission side terminal, and starts reading the buffered streaming data after the buffer time has elapsed. The present invention can be applied to, for example, a videophone.
[Selection] Figure 2

Description

  The present invention relates to a communication system, an information processing apparatus and method, a program, and a recording medium, and more particularly, to a communication system, an information processing apparatus and method capable of adaptively setting an appropriate buffer time in a receiving apparatus, and The present invention relates to a program and a recording medium.

  In recent years, services for transmitting and providing image data or audio data via a network such as the Internet are generally performed. In particular, in recent years, many stream-type transmission scheme services that transmit data in real time have been provided.

  In a stream-type transmission method service, a transmission apparatus encodes image data and audio data from a camera or a microphone, stores a predetermined amount of data in one packet, and creates a plurality of packets. The transmitting device sequentially transmits the packets to the receiving device via the network. The receiving device receives the packet from the transmitting device via the network, and sequentially performs decoding processing and reproduces it. In the stream-type transmission method, the transmission device sequentially transmits data, and the reception device sequentially reproduces data from the transmission device, whereby the reception device can perform real-time image and audio reproduction. The stream type transmission method is used for Internet services such as Internet telephone, videophone, remote video conference, live video, and video on demand.

  In the stream type transmission method, data transmitted from a transmission device is generally referred to as streaming data.

  When a delay occurs during transmission through the network, fluctuation (jitter) occurs in the reproduction of streaming data at the receiving device. In addition, when a loss occurs during transmission over the network, playback of streaming data on the receiving device is interrupted.

  As a method of preventing such playback fluctuations and interruptions, there is a method of buffering streaming data received from a transmitting apparatus for a certain amount of time in a receiving apparatus. The buffer time for buffering streaming data by the receiving device can be specified by the user as appropriate depending on the network environment, or by specifying a certain amount of time in advance at the receiving device. can do.

  On the other hand, for example, Patent Literature 1 discloses a technique in which a transmission device calculates a buffer amount of each reception device and sets the reception device.

Japanese Patent Laid-Open No. 10-229429

  However, as described above, in the receiving apparatus, when the user specifies a buffer time that is large to some extent, the buffer time is secured more than necessary, and the time until playback of streaming data is started, that is, the delay time. There was a problem of increasing.

  On the other hand, when a sufficient buffer time is not secured, the delay time is shortened, but it becomes difficult to prevent fluctuations or interruptions in reproduction, that is, quality of reproduced images and sounds.

  For example, in a network in which packet loss occurs during transmission, such as the Internet, there is a trade-off between starting playback of streaming data with a low delay and ensuring the quality of the streaming data. It is difficult for the user to specify an appropriate buffer time.

  Further, when the transmission device calculates the buffer amount of each reception device, the processing overhead of the transmission device increases as the number of connections of the reception device increases.

  The present invention has been made in view of such a situation, and an object of the present invention is to adaptively set an appropriate buffer time in a receiving apparatus.

  In the communication system according to the present invention, the receiving device transmits a measurement packet for measuring a round trip time in which the packet reciprocates between the receiving device and the transmitting device, and receives the measurement packet, and the transmitting device. Buffer means for buffering data transmitted from the buffer, buffer time calculating means for calculating a buffer time for buffering data transmitted from the transmitting device to the buffer means based on the round trip time, and data by the buffer means And a reading means for starting reading of the data buffered in the buffer means after the buffer time has elapsed after the start of buffering, and the transmitting device receives a measurement packet from the receiving device via the network. And transmitting side communication means for transmitting the measurement packet to the receiving device. And butterflies.

  The information processing apparatus of the present invention transmits a measurement packet for measuring a round-trip time during which the packet reciprocates between the transmission apparatus and communication means for receiving the measurement packet, and data transmitted from the transmission apparatus Buffer means for buffering data, buffer time calculating means for calculating buffer time for buffering data transmitted from the transmission device in the buffer means based on the round-trip time, and after starting buffering of data by the buffer means And reading means for starting reading of the data buffered in the buffer means after the buffer time has elapsed.

  The data may be streaming data.

  The communication unit can cause the transmitter to transmit two or more measurement packets, and the buffer time calculation unit can calculate the buffer time based on the round trip time of the two or more measurement packets.

  The measurement packet includes an ID (Identification) unique to the measurement packet, and the communication unit can identify each of two or more measurement packets based on the ID.

  The buffer time calculation means can calculate the buffer time in consideration of the fluctuation of the round trip time.

  The buffer time calculation means can calculate the buffer time in consideration of the fluctuation of the round-trip delay time required for the measurement packet to be transmitted on the forward and return paths of the network.

  Further, the buffer time calculation means can calculate the buffer time in consideration of the variation in the processing time on the transmission side required until the transmission apparatus receives and transmits the measurement packet.

  The information processing method according to the present invention includes a communication step of transmitting a measurement packet for measuring a round trip time for a packet to and from the transmission device, and receiving the measurement packet; and data transmitted from the transmission device A buffer step for buffering data in a buffer means for buffering, a buffer time calculating step for calculating a buffer time for buffering data transmitted from the transmission device in the buffer means based on a round trip time, and a buffer And a reading step of starting reading of data buffered in the buffer means after a buffer time has elapsed after the start of data buffering by the means.

  The program of the present invention transmits a measurement packet for measuring a round-trip time during which the packet reciprocates between the transmitter and a communication step of receiving the measurement packet, and buffers data transmitted from the transmitter A buffer step for buffering data in the buffer means for ringing, a buffer time calculating step for calculating a buffer time for buffering data transmitted from the transmission device in the buffer means based on the round trip time, and a buffer means And a reading step of starting reading of data buffered in the buffer means after a buffer time has elapsed after the start of buffering of data.

  The recording medium of the present invention transmits a measurement packet for measuring the round-trip time during which the packet reciprocates between the transmission device and receives the measurement packet, and data transmitted from the transmission device A buffer step for buffering data in a buffer means for buffering, a buffer time calculating step for calculating a buffer time for buffering data transmitted from the transmission device in the buffer means based on a round trip time, and a buffer And a read step for starting reading of data buffered in the buffer means after a buffer time has elapsed after the start of data buffering by the means.

  In the communication system of the present invention, the receiving device transmits a measurement packet for measuring the round-trip time during which the packet reciprocates between the receiving device and the transmitting device, and receives the measurement packet. Also, the data transmitted from the transmission device is buffered. Furthermore, based on the round trip time, the buffer time for buffering the data transmitted from the transmission device is calculated, and after the buffer time has elapsed after the start of data buffering, the buffered data is reproduced. To start. Further, the transmission device receives the measurement packet from the reception device via the network and transmits the measurement packet to the reception device.

  In the information processing apparatus, the information processing method, the program, and the recording medium of the present invention, a measurement packet for measuring the round-trip time during which the packet reciprocates with the transmission apparatus is transmitted, and the measurement packet is received. In addition, data transmitted from the transmission device is buffered. Further, based on the round trip time, the buffer time for buffering the data transmitted from the transmission device is calculated, and after the buffer time has elapsed after the start of data buffering, the buffered data Playback starts.

  According to the present invention, an appropriate buffer time can be adaptively set on the receiving side.

  BEST MODE FOR CARRYING OUT THE INVENTION The best mode of the present invention will be described below. Correspondences between constituent features described in the claims and specific examples in the embodiments of the present invention are exemplified as follows. This description is to confirm that specific examples supporting the invention described in the claims are described in the embodiments of the invention. Therefore, even if there are specific examples that are described in the embodiment of the invention but are not described here as corresponding to the configuration requirements, the specific examples are not included in the configuration. It does not mean that it does not correspond to a requirement. On the contrary, even if a specific example is described here as corresponding to a configuration requirement, this means that the specific example does not correspond to a configuration requirement other than the configuration requirement. not.

  Further, this description does not mean that all the inventions corresponding to the specific examples described in the embodiments of the invention are described in the claims. In other words, this description is an invention corresponding to the specific example described in the embodiment of the invention, and the existence of an invention not described in the claims of this application, that is, it may be divided in the future. It does not deny the existence of an invention which appears by amendment and is added.

The communication system according to claim 1 comprises:
In a communication system in which a transmitting device that transmits data in packets and a receiving device that receives the data are connected via a network,
The receiving device is:
A communication means (for example, the communication unit 21 in FIG. 2) that transmits a measurement packet for measuring a round-trip time during which the packet reciprocates between the reception device and the transmission device, and receives the measurement packet;
Buffer means for buffering data transmitted from the transmission device (for example, the reproduction data buffer unit 23 in FIG. 2);
Based on the round trip time, buffer time calculating means for calculating buffer time for buffering data transmitted from the transmitting device in the buffer means (for example, the buffer time calculating unit 53 in FIG. 2);
Read means (for example, the controller 22 in FIG. 2) that starts reading the data buffered in the buffer means after the buffer time has elapsed after the buffer means starts buffering the data. Prepared,
The transmitter is
A transmission-side communication means (for example, the communication unit 313 in FIG. 3) that receives the measurement packet from the reception device via the network and transmits the measurement packet to the reception device.
It is characterized by providing.

The information processing apparatus according to claim 2
In an information processing apparatus that receives data transmitted via a network from a transmission apparatus that transmits data in packets,
A communication means (for example, the communication unit 21 in FIG. 2) that transmits a measurement packet for measuring a round-trip time during which the packet reciprocates between the transmission device and receives the measurement packet;
Buffer means for buffering data transmitted from the transmission device (for example, the reproduction data buffer unit 23 in FIG. 2);
Based on the round trip time, buffer time calculating means for calculating buffer time for buffering data transmitted from the transmitting device in the buffer means (for example, the buffer time calculating unit 53 in FIG. 2);
Read means (for example, the controller 22 in FIG. 2) that starts reading the data buffered in the buffer means after the buffer time has elapsed after the buffer means starts buffering the data. It is characterized by providing.

The information processing method according to claim 9 comprises:
In an information processing method of an information processing apparatus that receives data transmitted from a transmission apparatus that transmits data in a packet via a network,
A communication step (for example, processing in steps S103 and S104 in FIG. 10) for transmitting a measurement packet for measuring a round trip time for the packet to and from the transmitting device and receiving the measurement packet;
A buffer step for buffering the data to the buffer means for buffering the data transmitted from the transmission device (for example, the process of step S109 in FIG. 10);
A buffer time calculating step for calculating a buffer time for buffering data transmitted from the transmitting device in the buffer means based on the round-trip time (for example, the process of step S107 in FIG. 10);
A read step (for example, the process of step S111 in FIG. 10) that starts reading the data buffered in the buffer means after the buffer time has elapsed after the buffer means starts buffering the data. It is characterized by including and.

The program according to claim 10 is:
A program for causing a computer to perform processing for receiving data transmitted from a transmission device that transmits data in packets via a network,
A communication step (for example, processing in steps S103 and S104 in FIG. 10) for transmitting a measurement packet for measuring a round trip time for the packet to and from the transmitting device and receiving the measurement packet;
A buffer step for buffering the data to the buffer means for buffering the data transmitted from the transmission device (for example, the process of step S109 in FIG. 10);
A buffer time calculating step for calculating a buffer time for buffering data transmitted from the transmitting device in the buffer means based on the round-trip time (for example, the process of step S107 in FIG. 10);
A read step (for example, the process of step S111 in FIG. 10) that starts reading the data buffered in the buffer means after the buffer time has elapsed after the buffer means starts buffering the data. It is characterized by including and.

  The correspondence relationship between each step of the program recorded on the recording medium according to claim 11 and the embodiment is the same as that of the program according to claim 10.

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

  FIG. 1 shows a configuration example of an embodiment of a communication system to which the present invention is applied.

  The network 1 is a transmission path including the Internet. The network 1 may be either wired or wireless, and may be a mixture of wired and wireless.

  In FIG. 1A, one receiving-side terminal 10 that receives streaming data and one transmitting-side terminal 301 that transmits streaming data are connected via a network 1 to form a one-to-one communication system. . Examples of streaming data transmitted by such a one-to-one communication system include an Internet phone and a video phone.

  In FIG. 1B, a receiving terminal 10 that receives streaming data, a receiving terminal 11 and one or more other receiving terminals (not shown) via a network 1, and one transmitting terminal 301 that transmits streaming data Are connected to form a one-to-many communication system.

  When the network 1 is a public line network such as the Internet, a one-to-many communication system as shown in FIG. 1B is configured. Examples of streaming data transmitted in such a one-to-many communication system include remote video conference video and live video.

  FIG. 2 shows a configuration example of the receiving terminal 10.

  The receiving terminal 10 includes a communication unit 21, a controller 22, a reproduction data buffer unit 23, a decoding processing unit 24, and an output unit 25. The controller 22 includes a packet creation unit 51, a time measurement unit 52, a buffer time calculation unit 53, and a packet loss detection time holding unit 54. The receiving side terminal 10 receives the streaming data from the transmitting side terminal 301 and outputs it to the monitor 31 and the speaker 32.

  The communication unit 21 transmits a packet created by the packet creation unit 51 via the network 1. The packet created by the packet creation unit 51 includes a round-trip delay measurement packet for measuring a round-trip time during which the packet travels back and forth between the reception-side terminal 10 and the transmission-side terminal 301. The packet created by the packet creation unit 51 includes a retransmission request packet for requesting retransmission of streaming data. The communication unit 21 transmits a round trip delay measurement packet and a retransmission request packet to the transmission side terminal 301 via the network 1. Further, the communication unit 21 receives and analyzes a round-trip delay measurement packet transmitted from the transmission-side terminal 301 via the network 1 and a packet storing streaming data.

  When the communication unit 21 receives the round trip delay measurement packet, the communication unit 21 notifies the controller 22 that the round trip delay measurement packet has been received, and further outputs the time data stored in the round trip delay measurement packet to the controller 22. . Further, when the communication unit 21 receives a packet in which streaming data is stored, the communication unit 21 supplies the streaming data stored in the packet to the reproduction data buffer unit 23. Further, the communication unit 21 notifies the controller 22 that the supply of streaming data to the reproduction data buffer unit 23 has started.

  The communication unit 21 monitors packet loss. When the communication unit 21 detects a loss, the communication unit 21 notifies the controller 22 accordingly.

  The controller 22 includes a packet creation unit 51, a time counting unit 52, a buffer time calculation unit 53, and a packet loss detection time holding unit 54, and controls packets transmitted and received by the receiving terminal 10. That is, the packet creation unit 51 creates a round trip delay measurement packet and a retransmission request packet. When the controller 22 receives notification from the communication unit 21 that a loss has been detected, the controller 22 creates a retransmission request packet for requesting retransmission of the lost packet, and supplies the packet to the communication unit 21. Further, the controller 22 creates a round trip delay measurement packet by the packet creation unit 51 and supplies the round trip delay measurement packet to the communication unit 21 when connecting to the transmission side terminal 301 via the network 1 according to a user instruction or the like.

  The time counter 52 measures time. When the communication unit 21 transmits the round-trip delay measurement packet, the controller 22 stores the data of the time counted by the time counting unit 52 in the payload of the round-trip delay measurement packet or in its own storage area. Further, when the communication unit 21 receives the round-trip delay measurement packet, the controller 22 stores the time data counted by the time counting unit 52 in its own storage area. The time data counted by the time counting unit 52 is, for example, 64-bit data.

  The buffer time calculation unit 53 calculates the buffering time and the time for buffering the streaming data transmitted from the transmission side terminal 301 in the reproduction data buffer unit 23. That is, the controller 22 associates the time data stored in the round-trip delay measurement packet from the communication unit 21 with the time data stored in its own storage area, and supplies the data to the buffer time calculation unit 53. To do. The buffer time calculation unit 53 calculates the buffer time using the time data from the controller 22.

  The packet loss detection time holding unit 54 stores a loss detection time α until the communication unit 21 detects a packet loss. The packet loss detection time holding unit 54 supplies the loss detection time α to the buffer time calculation unit 53. The buffer time calculation unit 53 also calculates the buffer time using the loss detection time α from the packet loss detection time holding unit 54.

  The controller 22 acquires that the streaming data is started to be supplied to the reproduction data buffer unit 23 from the communication unit 21, and then buffers the reproduction data buffer unit 23 after the buffer time calculated by the buffer time calculation unit 53 has elapsed. The ringed streaming data is read out and output to the decoding processing unit 24, and the reproduction is started.

  The decode processing unit 24 receives streaming data from the reproduction data buffer unit 23, performs a decoding process, and supplies it to the output unit 25. The output unit 25 acquires the streaming data from the decode processing unit 24 and outputs it to the monitor 31 or the speaker 32.

  FIG. 3 shows a configuration example of the transmission side terminal 301.

  The transmission side terminal 301 includes a data capture unit 311, an encoding processing unit 312, a communication unit 313, a controller 314, and an output data buffer unit 315. The controller 314 includes a time measuring unit 341 that measures time.

  For example, the camera 308 captures a moving image and supplies image data corresponding to the moving image to the transmission-side terminal 301. The microphone 309 collects sound and supplies sound data corresponding to the collected sound to the transmitting terminal 301. Image data and audio data are examples of streaming data. As streaming data, there is data such as real-time control data and the like that are sequentially requested to be transmitted or received in accordance with the passage of time, in addition to image data and audio data.

  The data capture unit 311 acquires image data from the camera 308 and audio data from the microphone 309 and captures them at predetermined time intervals. The data capture unit 311 captures image data and audio data, converts them into digital data that can be handled by a personal computer or the like, and outputs the digital data to the encoding processing unit 312. The encoding processing unit 312 encodes image data and audio data from the data capture unit 311. The encoding processing unit 312 stores the encoded image data and audio data in a packet of a predetermined method for transmitting streaming data, and outputs the packet to the communication unit 313.

  The communication unit 313 transmits the packet storing the streaming data from the encoding processing unit 312 via the network 1. The communication unit 313 causes the output data buffer unit 315 to buffer the copy of the packet. Further, the communication unit 313 receives a retransmission request packet from the receiving terminal 10. When the communication unit 313 receives the retransmission request packet, the communication unit 313 reads the packet requested by the retransmission request packet from the output data buffer unit 315 and transmits the packet to the receiving terminal 10 via the network 1.

  In addition, the communication unit 313 receives a round trip delay measurement packet from the receiving terminal 10 via the network 1. When the communication unit 313 receives the round trip delay measurement packet, the communication unit 313 supplies the round trip delay measurement packet to the controller 314. Further, the communication unit 313 processes the round-trip delay measurement packet from the controller 314 and transmits (replies) the round-trip delay measurement packet after processing to the receiving terminal 10 that has transmitted the processed round-trip delay measurement packet.

  The controller 314 includes a time counter 341. The controller 314 stores the data of the time measured by the time measuring unit 341 when the communication unit 313 receives the round trip delay measurement packet in the payload of the round trip delay measurement packet or stores it in its own storage area. . In addition, the controller 314 can store the data of the time measured by the time measuring unit 341 when the communication unit 313 transmits the round trip delay measurement packet in the payload of the round trip delay measurement packet. The time data counted by the time measuring unit 341 is, for example, 64-bit data.

  As will be described later, the controller 314 calculates the difference between the time when the communication unit 313 receives the round trip delay measurement packet and the time when the communication unit 313 transmits the round trip delay measurement packet, that is, the transmission side processing time. Then, the data on the transmission side processing time is stored in the round trip delay measurement packet.

  The output data buffer unit 315 buffers packets in which streaming data from the communication unit 313 is stored. The output data buffer unit 315 outputs a packet storing the requested streaming data to the communication unit 313 in response to the packet request from the communication unit 313.

  In the reception side terminal 10 and the transmission side terminal 301 configured as described above, the reception side terminal 10 requests streaming data from the transmission side terminal 301, and the transmission side terminal 301 responds to the request, A packet storing streaming data is transmitted.

  The communication unit 21 of the reception side terminal 10 starts receiving the packet storing the streaming data from the transmission side terminal 301 and outputs the streaming data stored in the packet to the reproduction data buffer unit 23. The reproduction data buffer unit 23 buffers the streaming data after starting buffering of the streaming data until the buffer time elapses. Then, when the buffer time has elapsed, the reproduction data buffer unit 23 starts reading the buffered streaming data and outputs it to the decoding processing unit 24.

  In addition, when the communication unit 21 detects a loss of a packet in which streaming data is stored, the communication unit 21 transmits a retransmission request packet to the transmission side terminal 301. When the communication unit 313 receives a retransmission request packet from the receiving terminal 10, the communication unit 313 reads the requested packet from the output data buffer unit 315 and retransmits the packet via the network 1. The communication unit 21 receives the packet retransmitted from the transmission side terminal 301 and compensates the streaming data stored in the packet by adding it to the streaming data buffered in the reproduction data buffer unit 23.

  Note that the playback data buffer unit 23 discards the streaming data when the time at which the retransmitted streaming data is filled has passed the time at which the streaming data is output (the playback time of the streaming data).

  Next, transmission / reception of a round-trip delay measurement packet between the receiving terminal 10 and the transmitting terminal 301 will be described with reference to FIG.

  The communication unit 21 of the receiving terminal 10 transmits the round trip delay measurement packet to the transmitting terminal 301 via the network 1. The transmission time of the round trip delay measurement packet by the reception side terminal 10 is described as reception side packet transmission time T1.

  The communication unit 313 of the transmission side terminal 301 receives a packet transmitted from the reception side terminal 10 via the network 1. The reception time of this round trip delay measurement packet is described as a transmission side packet reception time T2.

  The controller 314 of the transmission-side terminal 301 processes the round-trip delay measurement packet received from the reception-side terminal 10, and controls the communication unit 313 to process the round-trip delay measurement packet after the processing via the network 1. Transmit to the terminal 10. The transmission time of this round trip delay measurement packet is described as a transmission side packet transmission time T3.

  The communication unit 21 of the receiving terminal 10 receives the round trip delay measurement packet from the transmitting terminal 301 via the network 1. The reception time of this round-trip delay measurement packet is described as reception-side packet reception time T4.

  Also, the time required for the transmission side terminal 301 to process and transmit the round trip delay measurement packet after receiving the round trip delay measurement packet from the reception side terminal 10, that is, the transmission side packet transmission time T3 and the transmission side The difference from the packet reception time T2 is described as a transmission side processing time (T3-T2).

  Next, the format of the round trip delay measurement packet will be described.

  FIG. 5 is a diagram for explaining a first format of the round-trip delay measurement packet.

  The round trip delay measurement packet shown in FIG. 5 is, for example, a UDP (User Datagram Protocol) packet, and stores a payload for storing a 64-bit reception side packet transmission time T1, and a 64-bit transmission side packet reception time T2. And a payload for storing a 64-bit transmission side packet transmission time T3.

  The controller 22 of the reception-side terminal 10 stores the reception-side packet transmission time T1 that is measured by the time measuring unit 52 when transmitting the round-trip delay measurement packet in the payload for storing the reception-side packet transmission time T1. In addition, the controller 314 of the transmission side terminal 301 stores, in the payload for storing the transmission side packet reception time T2, the transmission side packet reception time T2 that is timed by the time measuring unit 341 when the round trip delay measurement packet is received. . The controller 314 stores, in the payload for storing the transmission side packet reception time T3, the transmission side packet reception time T3 that the time measuring unit 341 measures when transmitting the round trip delay measurement packet.

  FIG. 6 is a diagram for explaining a second format of the round trip delay measurement packet.

  The round-trip delay measurement packet shown in FIG. 6 is, for example, a UDP packet, and stores a payload for storing a 64-bit reception side packet transmission time T1, and a 64-bit transmission side processing time (T3-T2). Includes payload.

  The controller 314 of the transmission side terminal 301 calculates a transmission side processing time (T3−T2) that is a time difference between the transmission side packet reception time T2 and the transmission side packet transmission time T3, and the round trip delay measurement packet of FIG. Of (T3-T2) in the payload.

  That is, in the round trip delay measurement packet of FIG. 6, instead of the transmission side packet reception time T2 and the transmission side packet reception time T3 stored in the round trip delay measurement packet of FIG. Stored.

  FIG. 7 is a diagram for explaining a third format of the round trip delay measurement packet. FIG. 8 is a diagram for explaining a fourth format of the round trip delay measurement packet.

  The round trip delay measurement packet shown in FIGS. 7 and 8 includes a payload for storing a 32-bit ID in place of the payload for storing the reception side packet transmission time T1. The round trip delay measurement packet including the payload for storing the ID shown in FIG. 7 and FIG. 8 is hereinafter appropriately referred to as a round trip delay measurement packet with ID.

  When transmitting the round trip delay packet with ID in the receiving side terminal 10, the controller 22 stores the ID unique to the round trip delay measurement packet with ID in the payload for storing the ID of the round trip delay measurement packet with ID. Further, the controller 22 recognizes the reception side packet transmission time T1 timed by the time measuring unit 52 when transmitting the round trip delay measurement packet with ID, and as shown in the ID list of FIG. The time T1 is stored in association with each other.

  In the round trip delay packet with ID shown in FIG. 7, as in the round trip delay measurement packet shown in FIG. 5, the controller 314 of the transmission side terminal 301 includes the transmission side packet in the payload for storing the transmission side packet reception time T2. The reception time T2 is stored. Further, the controller 314 stores the transmission side packet transmission time T3 in the payload for storing the transmission side packet transmission time T3.

  In the round-trip delay packet with ID shown in FIG. 8, the controller 314 of the transmission-side terminal 301, in the payload for storing the transmission-side processing time (T3-T2), as in the round-trip delay measurement packet shown in FIG. The transmission side processing time (T3-T2) is calculated and stored.

  Here, the buffer time calculation unit 53 of the receiving terminal 10 can calculate the buffer time by transmitting a plurality of round trip delay measurement packets, as will be described later. Each needs to recognize the time transmitted and received between the receiving terminal 10 and the transmitting terminal 301.

  That is, when the round trip delay measurement packet shown in FIG. 5 is transmitted and received between the receiving side terminal 10 and the transmitting side terminal 301, the controller 22 receives the round trip delay from the transmitting side terminal 301 received by the communication unit 21. The reception side packet transmission time T1, the transmission side packet reception time T2, and the transmission side packet transmission time T3 stored in the payload of the measurement packet are acquired and supplied to the buffer time calculation unit 53. In addition, the controller 22 stores the reception side packet reception time T4 when the communication unit 21 receives the round trip delay measurement packet from the transmission side terminal 301 in its own storage area, and supplies it to the buffer time calculation unit 53. As described above, the buffer time calculation unit 53 makes the reception side packet transmission time T1, the transmission side packet reception time T2, the transmission side packet reception time T3, and the reception side packet reception time T4 supplied from the controller 22 the same. Are recognized as a reception side packet transmission time T1, a transmission side packet reception time T2, a transmission side packet reception time T3, and a reception side packet reception time T4.

  When the round trip delay measurement packet shown in FIG. 6 is transmitted and received between the reception side terminal 10 and the transmission side terminal 301, the controller 22 receives the round trip delay measurement packet from the transmission side terminal 301 received by the communication unit 21. The reception side packet transmission time T1 and the transmission side processing time (T3-T2) stored in the payload are acquired and supplied to the buffer time calculation unit 53. In addition, the controller 22 stores the reception side packet reception time T4 when the communication unit 21 receives the round trip delay measurement packet from the transmission side terminal 301 in its own storage area, and supplies it to the buffer time calculation unit 53. The buffer time calculation unit 53 uses the same round trip delay measurement packet for the reception side packet transmission time T1, the transmission side processing time (T3-T2), and the reception side packet reception time T4 supplied from the controller 22 as described above. Are recognized as a reception side packet transmission time T1, a transmission side processing time (T3-T2), and a reception side packet reception time T4.

  When the round trip delay measurement packet with ID shown in FIG. 7 is transmitted and received between the reception side terminal 10 and the transmission side terminal 301, the controller 22 receives the round trip delay measurement packet with ID when receiving the round trip delay measurement packet with ID. The transmission time T1 and the ID stored in the payload of the roundtrip delay measurement packet with ID are associated with each other and stored in the ID list (FIG. 9). Thereafter, the controller 22 obtains the ID, the transmission side packet reception time T2, and the transmission side packet transmission time T3 stored in the payload of the round trip delay measurement packet with ID received from the transmission side terminal 301 received by the communication unit 21. Then, the transmission side packet reception time T2 and the transmission side packet transmission time T3 are stored in association with the ID of the round trip delay measurement packet with ID. Further, the controller 22 associates the reception side packet reception time T4 when the communication unit 21 receives the round trip delay measurement packet with ID from the transmission side terminal 301 with the ID of the round trip delay measurement packet with ID. Store in the storage area. Then, the controller 22 calculates the buffer time for the reception side packet transmission time T1, the transmission side packet reception time T2, the transmission side packet reception time T3, and the reception side packet reception time T4 stored in association with the same ID. To the unit 53. As described above, the buffer time calculation unit 53 makes the reception side packet transmission time T1, the transmission side packet reception time T2, the transmission side packet reception time T3, and the reception side packet reception time T4 supplied from the controller 22 the same. Are recognized as a reception side packet transmission time T1, a transmission side packet reception time T2, a transmission side packet reception time T3, and a reception side packet reception time T4.

  When the round trip delay measurement packet with ID shown in FIG. 8 is transmitted and received between the reception side terminal 10 and the transmission side terminal 301, the controller 22 receives the round trip delay measurement packet with ID when receiving the round trip delay measurement packet with ID. The transmission time T1 and the ID stored in the payload of the roundtrip delay measurement packet with ID are associated with each other and stored in the ID list (FIG. 9). Thereafter, the controller 22 acquires the ID and the transmission side processing time (T3-T2) stored in the payload of the round trip delay measurement packet with ID received from the transmission side terminal 301 received by the communication unit 21, and transmits the transmission. The side processing time (T3-T2) is stored in association with the ID of the round trip delay measurement packet with ID. Further, the controller 22 associates the reception side packet reception time T4 when the communication unit 21 receives the round trip delay measurement packet with ID from the transmission side terminal 301 with the ID of the round trip delay measurement packet with ID. Store in the storage area. Then, the controller 22 supplies the reception side packet transmission time T1, the transmission side processing time (T3-T2), and the reception side packet reception time T4 stored in association with the same ID to the buffer time calculation unit 53. To do. The buffer time calculation unit 53 uses the same ID round-trip delay for the reception side packet transmission time T1, the transmission side processing time (T3-T2), and the reception side packet reception time T4 supplied from the controller 22 as described above. The measurement packet is recognized as the reception side packet transmission time T1, the transmission side processing time (T3-T2), and the reception side packet reception time T4.

  When a plurality of round-trip delay measurement packets are transmitted / received between the reception-side terminal 10 and the transmission-side terminal 301, as described above, the buffer time calculation unit 53 uses the reception side for each of the plurality of round-trip delay measurement packets. It is necessary to recognize the time transmitted and received between the terminal 10 and the transmitting terminal 301.

  However, the round trip delay measurement packet that is a UDP packet is transmitted to the transmission side terminal 301 by the round trip delay measurement packet transmitted from the reception side terminal 10 or the round trip delay measurement packet transmitted from the transmission side terminal 301 to the reception side terminal 10. It is not guaranteed to arrive.

  Therefore, for the round trip delay measurement packet shown in FIG. 5, the controller 22 causes the communication unit 21 to send the round trip delay measurement packet to the transmission side terminal 301, and then transmits the transmission side packet reception time T <b> 2 from the transmission side terminal 301 and A corresponding round trip delay measurement packet storing the transmission side packet transmission time T3 is received. Then, the controller 22 transmits the next round trip delay measurement packet. Thus, by waiting for the reception of the round-trip delay measurement packet transmitted last time and transmitting the next round-trip delay measurement packet, the reception-side packet transmission time T1 and the transmission-side packet reception time for each of the plurality of round-trip delay measurement packets. T2, the transmission side packet reception time T3, and the reception side packet reception time T4 can be recognized.

  For the round trip delay measurement packet shown in FIG. 6, the controller 22 causes the communication unit 21 to send the round trip delay measurement packet to the transmission side terminal 301, and then the transmission side processing time (T 3 -T 2) from the transmission side terminal 301. Is received in the corresponding round trip delay measurement packet. Then, the controller 22 transmits the next round trip delay measurement packet. In this way, by waiting for the reception of the round-trip delay measurement packet transmitted last time and transmitting the next round-trip delay measurement packet, the reception-side packet transmission time T1, the transmission-side processing time ( T3-T2) and the reception side packet reception time T4 can be recognized.

  On the other hand, for the round trip delay measurement packet with ID shown in FIGS. 7 and 8, the reception side packet transmission time T1 of each of the round trip delay measurement packets with ID can be identified by the ID of the round trip delay measurement packet with ID. Therefore, the controller 22 transmits the next round trip delay measurement packet with ID without waiting for the reception of the round trip delay measurement packet with ID transmitted last time, as in the round trip delay measurement packet of FIG. 5 or FIG. As a result, a plurality of reception side packet transmission times T1, transmission side packet reception times T2, transmission side packet reception times T3, and reception side packet reception times T4, or reception side packet transmission times T1, It becomes possible to recognize the transmission side processing time (T3-T2) and the reception side packet reception time T4.

  Here, hereinafter, the time required for the round trip delay measurement packet to travel back and forth between the receiving terminal 10 and the transmitting terminal 301 via the network 1 will be described as a round trip time. The round-trip time is expressed by equation (1).

    Round trip time = T4-T1 (1)

  The transmission side terminal 301 transmits and receives the round trip delay measurement packet until the transmission side terminal 301 receives the round trip delay measurement packet transmitted by the reception side terminal 10 and the round trip delay measurement packet. The sum of the time required for transmission on the return path of the network 1 until the side terminal 10 receives is described as a round-trip delay time. The round-trip delay time is expressed by equation (2).

    Round trip time = T4-T1- (T3-T2) (2)

  Further, as described above, the transmission-side processing time is expressed by Expression (3).

    Transmission side processing time = T3-T2 (3)

  The round trip time of the formula (1) is represented by the sum of the round trip delay time of the formula (2) and the transmission side processing time of the formula (3).

  The buffer time calculation unit 53 calculates the buffer time based on the round trip time. In other words, the buffer time calculation unit 53 calculates the buffer time according to the equation (4), for example.

    Buffer time = round trip time + reception side processing delay (4)

  Here, the reception-side processing delay of Expression (4) will be described later.

  The round trip time can be the round trip time of Equation (1) obtained by transmitting / receiving one round trip delay measurement packet, or Equation (1) obtained by sending / receiving multiple round trip delay measurement packets. It is also possible to use an average value of round-trip times.

  As described above, since the round trip time is the sum of the round trip delay time and the transmission side processing time, the equation (4) can be expressed by the equation (5).

    Buffer time = round trip delay time + transmission side processing time + reception side processing delay (5)

  The buffer time can also be calculated according to equation (5).

  The round trip delay time can be the round trip delay time of the formula (2) obtained by transmitting / receiving one round trip delay measurement packet, or the formula (2) obtained by sending / receiving a plurality of round trip delay measurement packets ( The average value of the round trip delay time of 2) can also be used. Similarly, the transmission side processing time can be the transmission side processing time of Expression (3) obtained by transmitting one round trip delay measurement packet, or can be obtained by transmitting and receiving a plurality of round trip delay measurement packets. It is also possible to use the average value of the processing time on the transmission side in equation (3). Similarly, the transmission side processing time can be an average value of the transmission side processing times obtained by transmitting and receiving a plurality of round trip delay measurement packets.

  Here, the reception-side processing delays of Expression (4) and Expression (5) can be expressed by Expression (6), for example. Α in Expression (6) is a loss detection time which is a time required for the receiving side terminal 10 to detect a packet loss.

    Processing delay on reception side = α (6)

  The receiving terminal 10 holds the loss detection time α in the packet loss detection time holding unit 54. The loss detection time α can be set to a positive value (time) such as 10 msec, for example. Also, the loss detection time α can be set by the user of the receiving terminal 10.

  The processing delay on the receiving side can be set to a time that takes into account the loss detection time α and the value (time) β that absorbs the jitter of the network 1. The processing delay on the receiving side when taking into account the jitter of the network 1 is expressed by Expression (7).

    Reception side processing delay = α + β (7)

  The value β that absorbs the jitter of the network 1 is described, for example, as a maximum value of the round trip time (hereinafter referred to as the maximum value of the round trip time as appropriate) and a minimum value of the round trip time (hereinafter referred to as the minimum value of the round trip time as appropriate). ) And the value represented by the difference. A value β that absorbs the jitter of the network 1 based on the maximum value of the round trip time and the minimum value of the round trip time is expressed by Expression (8).

    β = maximum round trip time−minimum round trip time (8)

  By substituting the value β that absorbs the jitter of the network 1 shown in Equation (8) into the value β that absorbs the jitter of the network 1 shown in Equation (7), the fluctuation in the round trip time is absorbed in the processing delay on the reception side. can do.

  In the buffer time calculation unit 53, the value β that absorbs the jitter of the network 1 shown in the equation (8) is substituted into the value β that absorbs the jitter of the network 1 in the equation (7). The buffer time can be calculated based on equation (5) by substituting the delay into the reception-side processing delay of equation (5). In this case, it is possible to calculate the buffer time taking into account (considering) the fluctuation of the round-trip time. Therefore, the receiving side terminal 10 can absorb the fluctuation of the round trip time.

  Further, the value β for absorbing the jitter of the network 1 is, for example, the maximum value of the round trip delay time (hereinafter referred to as the maximum round trip delay value) and the minimum value of the round trip delay time (hereinafter referred to as the round trip delay minimum as appropriate). It can be a value represented by the difference between the value and the value. A value β that absorbs the jitter of the network 1 based on the maximum value of the round trip delay and the minimum value of the round trip delay is expressed by Expression (9).

    β = maximum round trip delay−minimum round trip delay (9)

  By substituting the value β that absorbs the jitter of the network 1 shown in Equation (9) into the value β that absorbs the jitter of the network 1 shown in Equation (7), the fluctuation amount of the round-trip delay time is absorbed in the processing delay on the receiving side. can do.

  In the buffer time calculation unit 53, the value β that absorbs the jitter of the network 1 shown in the equation (9) is substituted into the value β that absorbs the jitter of the network 1 in the equation (7), and the reception side processing of the equation (7) is performed. The buffer time can be calculated based on equation (5) by substituting the delay into the reception-side processing delay of equation (5). In this case, it is possible to calculate the buffer time taking into account (considering) the fluctuation of the round trip delay time. Therefore, the receiving side terminal 10 can absorb the fluctuation of the round trip delay time.

  Further, the value β that absorbs the jitter of the network 1 is, for example, the difference between the maximum round-trip delay time value and the minimum round-trip delay time value, and further the maximum value on the transmission side processing time (hereinafter referred to as the maximum on the transmission side processing delay as appropriate) And a value that takes into account the difference between the minimum value of the transmission side processing time (hereinafter referred to as the minimum value of the transmission side processing delay as appropriate). The value β that absorbs the jitter of the network 1 based on the maximum round-trip delay value and the minimum round-trip delay value, and the transmission-side delay maximum value and the transmission-side delay minimum value is expressed by Expression (10).

    β = Maximum round trip delay−Minimum round trip delay + (Maximum transmission processing delay−Minimum transmission processing delay) (10)

  By substituting the value β that absorbs the jitter of the network 1 shown in the equation (10) into the value β that absorbs the jitter of the network 1 shown in the equation (7), It is possible to absorb fluctuations in processing delay on the transmission side.

  In the buffer time calculation unit 53, the value β that absorbs the jitter of the network 1 shown in the equation (10) is substituted into the value β that absorbs the jitter of the network 1 in the equation (7). The buffer time can be calculated based on equation (5) by substituting the delay into the reception-side processing delay of equation (5). In this case, it is possible to calculate the buffer time in consideration (consideration) of the fluctuation of the round trip delay time and the fluctuation of the transmission side processing time. Therefore, the receiving side terminal 10 can absorb the fluctuation of the round trip delay time and the fluctuation of the transmission side processing time.

  When a margin for fluctuations in round-trip time, fluctuations in round-trip delay time, or fluctuations in processing time on the transmission side is required, for example, the loss detection time α can be obtained by equation (11). good.

α = time required for receiving terminal 10 to detect loss + margin for fluctuation
(11)

  Here, for example, when reading of streaming data from the reproduction data buffer unit 23 to the decoding processing unit 24 is performed at a constant time interval (a constant reading rate), the reproduction data buffer unit 23 stores the streaming data. When the time fluctuates, fluctuations occur in the reproduction of the streaming data. Therefore, as described above, the receiving side terminal 10 has a round trip time fluctuation, a round trip delay time fluctuation, a transmission side processing time fluctuation, and a buffer time considering a margin for these fluctuations. The streaming data from the transmission-side terminal 301 is stored in the reproduction data buffer unit 23 for this buffer time after being calculated, and then read out to the decoding processing unit 24 to absorb the fluctuations described above, and the reproduction data buffer It is possible to say the streaming data to the unit 23, store the time, and read (output) it to the decoding processing unit 24.

  A process in which the receiving terminal 10 calculates the buffer time and reproduces the streaming data will be described with reference to the flowchart of FIG. Here, it is assumed that the round trip delay measurement packet of FIG. 5 or 6 is adopted as the round trip delay measurement packet.

  In step S101, the communication unit 21 transmits a connection request to the transmitting terminal 301 via the network 1, and the process proceeds to step S102. In step S <b> 102, the communication unit 21 determines whether the connection to the transmission-side terminal 301 has been successful via the network 1. In step S102, when the communication unit 21 determines that the connection with the transmission side terminal 301 has succeeded via the network 1, the communication unit 21 proceeds to step S103, and the controller 22 sets the reception side packet transmission time T1 in the round trip delay measurement packet. Stored and supplied to the communication unit 21. The communication unit 21 immediately transmits the round-trip delay measurement packet to the transmission side terminal 301 via the network 1.

  After waiting for the round trip delay measurement packet to be transmitted from the transmission side terminal 301, the process proceeds from step S 103 to S 104, and the communication unit 21 receives the round trip delay measurement packet from the transmission side terminal 301. The communication unit 21 supplies the controller 22 with the reception side packet transmission time T1, the transmission side packet reception time T2, and the transmission side packet transmission time T3 stored in the payload of the round trip delay measurement packet. Further, the controller 22 stores a reception side packet reception time T4 that is a time when the round-trip delay measurement packet is received. Then, the controller 22 supplies the reception side packet transmission time T1 to the reception side packet reception time T4 to the buffer time calculation unit 53.

  When the round trip delay measurement packet transmitted from the receiving side terminal 10 to the sending side terminal 301 is the round trip delay measuring packet shown in FIG. 6, the communication unit 21 sends the transmission side packet reception time T2 and the transmission side packet transmission time T3. Instead, the transmission side processing time (T3-T2) is supplied to the controller 22.

  Proceeding from step S104 to S105, the buffer time calculation unit 53 uses the reception side packet transmission time T1, the transmission side packet reception time T2, the transmission side packet reception time T3, and the reception side packet reception time T4, and follows equation (1). Calculate the round trip time. Alternatively, the buffer time calculation unit 53 calculates the round trip delay time according to the equation (2), and calculates the transmission side processing time according to the equation (3). When the round trip delay measurement packet transmitted by the receiving terminal 10 is the round trip delay measurement packet of FIG. 6, it is not necessary to calculate the transmission processing time.

  Proceeding from step S105 to S106, the controller 22 determines whether or not the number of receptions of the round-trip delay measurement packet from the transmission-side terminal 301 satisfies a predetermined number. If the controller 22 determines in step S106 that the number of times the round-trip delay measurement packet has been received does not yet satisfy the predetermined number, the controller 22 returns to step S103 and performs processing for transmitting the next round-trip delay measurement packet.

  If it is determined in step S106 that the number of times the round-trip delay measurement packet has been received satisfies the predetermined number, the process proceeds to step S107, where the buffer time calculation unit 53 calculates the buffer time and supplies it to the reproduction data buffer unit 23. To do. The process for calculating the buffer time will be described later with reference to FIG.

  After waiting for a packet to be transmitted from the transmitting terminal 301, the process proceeds from step S107 to S108, and the communication unit 21 starts receiving the packet storing the streaming data from the transmitting terminal 301 via the network 1. To do. The streaming data stored in the packet received by the communication unit 21 is supplied to the reproduction data buffer unit 23. Proceeding from step S108 to S109, the reproduction data buffer unit 23 starts buffering of streaming data supplied from the communication unit 21.

  Proceeding from step S109 to S110, the controller 22 determines whether or not the buffer time calculated in step S107 has elapsed since the reproduction data buffer 23 started buffering the streaming data. In step S110, when the controller 22 determines that the buffer time calculated in step S107 has not elapsed since the reproduction data buffer unit 23 started buffering the streaming data, the process returns to step S110.

  On the other hand, if it is determined in step S110 that the buffer time calculated in step S107 has elapsed since the playback data buffer unit 23 started buffering the streaming data, the process proceeds to step S111, where the controller 22 By controlling the data buffer unit 23, the reproduction data buffer unit 23 is caused to start outputting streaming data to the decoding processing unit 24. As a result, the reproduction data buffer unit 23 reads the buffered streaming data at a constant reading rate, and supplies it to the decoding processing unit 24. The decode processing unit 24 decodes the streaming data from the reproduction data buffer unit 23 and supplies the decoded data to the output unit 25. The output unit 25 outputs the streaming data to the monitor 31 and the speaker 32 (FIG. 2), and ends the process.

  In step S102, if the communication unit 21 determines that the connection to the transmission side terminal 301 is not successful, that is, if the connection with the transmission side terminal 301 is not established via the network 1, the communication unit 21 It is assumed that connection is not possible, and the process ends.

  Next, processing in which the transmission side terminal 301 transmits streaming data to the reception side terminal 10 via the network 1 will be described with reference to the flowchart of FIG.

  In step S551, the communication unit 313 is in a state of waiting for a connection request from the receiving terminal 10, and determines whether or not a connection request from the receiving terminal 10 has been received. In step S551, when the communication unit 313 determines that a connection request from the receiving terminal 10 has been received via the network 1, the communication unit 313 establishes a connection with the receiving terminal 10, and proceeds to step S552. Waiting for reception of a round-trip delay measurement packet from the terminal 10.

  The communication unit 313 waits for the round trip delay measurement packet to be transmitted from the receiving terminal 10 and receives the round trip delay measurement packet in step S552. The controller 314 stores the time when the communication unit 313 receives the round trip delay measurement packet as the transmission side packet reception time T2. Proceeding from step S552 to S553, the controller 314 predicts, for example, the time at which the communication unit 313 transmits the round-trip delay measurement packet in step S554, which will be described later, and stores it as the transmission side packet transmission time T3. Then, the controller 314 stores the transmission side packet reception time T2 and the transmission side packet transmission time T3 or the transmission side processing time (T3-T2) in a predetermined payload of the round trip delay measurement packet received from the reception side terminal 10. To do.

  In step S554, the communication unit 313 transmits the round trip delay measurement packet to the reception side terminal 10 via the network 1, and proceeds to step S555.

  In step S555, the controller 314 determines whether or not the round trip delay measurement packet has been transmitted a predetermined number of times. If the controller 314 determines in step S555 that the round trip delay measurement packet has not been transmitted a predetermined number of times, the controller 314 returns to step S552 and waits until the next round trip delay measurement packet is received.

  If it is determined in step S555 that the round trip delay measurement packet has been transmitted a predetermined number of times, the process proceeds to step S556, the controller 314 notifies the communication unit 313 of the start of transmission of streaming data, and the process proceeds to step S556. In step S556, the communication unit 313 receives a notification from the controller 314, and receives a packet storing image data and audio data (streaming data) created by the encoding processing unit 312 via the network 1 on the receiving side terminal. 10 is started, and the process proceeds to step S557.

  In step S557, the communication unit 313 supplies a copy of the packet storing the transmitted streaming data to the output data buffer unit 315. The output data buffer unit 315 starts storing the packet in which the streaming data from the communication unit 313 is stored, and ends the process.

  In this way, the transmission side terminal 301 simply stores the time data in the round trip delay measurement packet from the reception side terminal 10 and returns the round trip delay measurement packet, and the reception side terminal 10 calculates the buffer time. Do. Since the transmission side terminal 301 does not perform the process of calculating the buffer time, an increase in load on the transmission side terminal 301 can be reduced even when connecting to a plurality of reception side terminals.

  The buffer time calculation process performed by the buffer time calculation unit 53 in step S107 of FIG. 10 will be described with reference to the flowchart of FIG.

  When the receiving-side terminal 10 transmits and receives a predetermined number of round-trip delay measurement packets, the buffer time calculation unit 53 holds a set of the predetermined number of round-trip delay times and transmission-side processing times.

  In step S201, the buffer time calculation unit 53 obtains an average value of round trip delay times, a round trip delay maximum value, and a round trip delay minimum value from a predetermined number of round trip delay times, and then proceeds to step S202.

  In step S202, the buffer time calculation unit 53 obtains an average value of the transmission side processing time, a transmission side processing maximum value, and a transmission side processing minimum value from a predetermined number of transmission side processing times.

  Proceeding from step S202 to S203, the buffer time calculation unit 53 uses the maximum round-trip delay value and the round-trip delay minimum value obtained in step S201, and the transmission-side processing maximum value and the transmission-side processing minimum value obtained in step S202. Then, the value β for absorbing the jitter of the network 1 is calculated according to the equation (10), and the process proceeds to step S204.

  In step S204, the buffer time calculation unit 53 obtains the loss detection time α held in the packet loss detection time holding unit 54.

  Proceeding from step S204 to S205, the buffer time calculation unit 53 uses the average value of the round-trip delay time, the average value of the processing time on the transmission side, the loss detection time α, and the value β that absorbs jitter of the network 1 to obtain an equation ( Calculate buffer time according to 5) and return.

  The buffer time calculation unit 53 calculates the reception-side processing delay used in Expression (5) according to Expression (7) using the loss detection time α and the value β that absorbs jitter of the network 1.

  For example, the loss detection time α and the like can be set freely to some extent in the receiving terminal 10. In this case, the buffer time can be set according to the purpose of the user who views the streaming data. That is, for example, when the user desires high quality reproduction, α is set to a large value and the buffer time is set to be long, and when reproduction with low delay is desired, α is set to a small value and the buffer time is set to be small. Should be set short.

  Processing of the receiving terminal 10 and the transmitting terminal 301 when a packet transmitted from the transmitting terminal 301 to the receiving terminal 10 is lost will be described with reference to the flowchart of FIG.

  In step S601, the communication unit 313 responds to the notification of the start of transmission of streaming data from the controller 314, and receives packet # 1, which is a packet in which the first streaming data created by the encoding processing unit 312 is stored. Then, the process of transmitting to the receiving terminal 10 via the network 1 is started, and the process proceeds to step S602. Note that the processing in step S601 corresponds to step S556 in FIG.

  In step S602, the communication unit 313 transmits the packet # 2, which is a packet storing the second streaming data, to the receiving terminal 10 via the network 1 after the transmission of the packet # 1 is completed. To proceed to step S603. In addition, the communication unit 313 causes the output data buffer unit 315 to hold the packet # 1 that has been transmitted.

  In step S603, the communication unit 313 transmits the packet # 3, which is a packet storing the third streaming data, to the receiving terminal 10 via the network 1 after the transmission of the packet # 2 is completed. To start. Further, the communication unit 313 causes the output data buffer unit 315 to buffer the transmitted packet # 2. Hereinafter, the communication unit 313 similarly transmits the fourth and subsequent streaming data to the receiving terminal 10 and causes the output data buffer unit 315 to buffer the data.

  In step S251, the communication unit 21 receives the packet # 1 in response to the arrival of the packet # 1 from the transmission-side terminal 301 via the network 1. Further, the communication unit 21 waits for the arrival of the second packet # 2. The communication unit 21 outputs the streaming data stored in the received packet # 1 to the reproduction data buffer unit 23. The reproduction data buffer unit 23 buffers the streaming data of packet # 1.

  Proceeding from step S251 to S252, the communication unit 21 waits for the arrival of the packet # 2 and responds to the arrival of the packet # 3 from the transmission side terminal 301 via the network 1 in response to the arrival of the packet # 3. Receive. The communication unit 21 outputs the streaming data stored in the received packet # 3 to the reproduction data buffer unit 23. The reproduction data buffer unit 23 buffers the streaming data of packet # 3. Similarly, the communication unit 21 outputs the streaming data stored in the packet to the reproduction data buffer unit 23 for the fourth and subsequent packets. Then, the reproduction data buffer unit 23 buffers the streaming data.

  On the other hand, the communication unit 21 detects that the packet # 2 is lost during transmission through the network 1 in response to the arrival of the packet # 3. In this case, in step S253, the communication unit 21 transmits a retransmission request packet to the transmitting terminal 301 via the network 1. The time when the communication unit 21 requests retransmission of the packet # 2 corresponds to the reception side packet transmission time T1 shown in FIG.

  Here, as described above, the loss of the packet # 2 is detected after the arrival of the packet # 3. The loss detection time α corresponds to the time for increasing the arrival of the packet # 3.

  In step S <b> 604, the communication unit 313 receives a retransmission request packet from the receiving terminal 10 via the network 1. In response to the retransmission request packet, the communication unit 313 reads the packet # 2 (second streaming data) stored in the output data buffer unit 315 and supplies it to the communication unit 313. Proceeding from step S604 to S605, the communication unit 313 transmits the packet # 2 to the receiving terminal 10 via the network 1.

  Note that the time at which the communication unit 313 receives the retransmission request packet from the reception side terminal 10 in step S604 corresponds to the transmission side packet reception time T2 illustrated in FIG. The time when the communication unit 313 transmits packet # 2 in step S605 corresponds to the transmission side packet transmission time T3.

  In step S254, the communication unit 21 receives the packet # 2 in response to the arrival of the packet # 2, which is a retransmission packet from the transmission side terminal 301, via the network 1. The communication unit 21 outputs the streaming data of the packet # 2 to the reproduction data buffer unit 23. The reproduction data buffer unit 23 supplements the streaming data of the packet # 2.

  Note that the time at which the communication unit 21 receives packet # 2 in step S254 corresponds to the reception side packet reception time T4 shown in FIG.

  In step S255, the reproduction data buffer unit 23 starts to read the buffered streaming data after the buffer time has elapsed after buffering the streaming data of the packet # 1, and outputs it to the decoding processing unit 24. The

  Therefore, even when the packet # 2 is lost, it is possible to receive the retransmission of the lost packet # 2 in time for reproduction. That is, it is possible to prevent the reproduction from being interrupted.

  As described above, the receiving terminal 10 transmits the round trip delay measurement packet to the transmitting terminal 301 and receives the round trip measurement packet. Then, the buffer time calculation unit 53 calculates the buffer time for buffering the streaming data based on the round trip time of the round trip delay measurement packet. Then, the reproduction data buffer unit 23 buffers the streaming data, buffers the streaming data for the buffer time, and then starts reading and reproducing the streaming data. Further, the transmission side terminal 301 receives the round trip delay measurement packet from the reception side terminal 10 via the network 1 and transmits the round trip delay measurement packet to the reception side terminal 10.

  Therefore, an appropriate value can be adaptively set (calculated) as the buffer time, and the delay time until the streaming data reproduction is started at the receiving terminal 10 can be shortened.

  Furthermore, since the receiving side terminal 10 calculates the buffer time, for example, even when the transmitting side terminal 301 has access from a plurality of receiving side devices, it is possible to suppress the processing overhead of the transmitting side terminal 301 as much as possible. It becomes. In addition, the buffer time can be calculated to some extent at the discretion of the receiving terminal 10 and, for example, according to the purpose of the user who views the streaming data, high quality playback or a short delay time (responsiveness is low). High) playback is possible.

  Further, since the buffer time is calculated based on the round trip time, for example, in the network 1 in which packet loss occurs such as the Internet, the receiving side terminal 10 transmits a retransmission request packet to the transmitting side terminal 301, and the lost packet It is possible to set the buffer time assuming the time required to receive the signal. Therefore, even when a loss occurs, streaming data can be reproduced after waiting for retransmission of the lost packet. Even when a delay occurs in the network 1, the reproduction data buffer unit 23 can absorb jitter due to the delay.

  The series of processes described above can also be executed by software. When a series of processing is executed by software, a program constituting the software may execute various functions by installing a computer incorporated in dedicated hardware or various programs. For example, it is installed from a recording medium in a general-purpose personal computer or the like.

  FIG. 14 shows an internal configuration example of a general-purpose computer. A CPU (Central Processing Unit) 131 of the computer executes various processes according to a program recorded in a ROM (Read Only Memory) 132 or a program loaded from a storage unit 138 to a RAM (Random Access Memory) 133. The RAM 133 also appropriately stores data necessary for the CPU 131 to execute various processes.

  The CPU 131, ROM 132, and RAM 133 are connected to each other via a bus 134. An input / output interface 135 is also connected to the bus 134.

  The input / output interface 135 includes an input unit 136 including buttons, switches, a keyboard or a mouse, a display including CRT (Cathode Ray Tube) and LCD (Liquid Crystal Display), and a speaker. An output unit 137, a storage unit 138 composed of a hard disk or the like, and a communication unit 139 composed of a modem or a terminal adapter are connected. The communication unit 139 performs communication processing via a network such as the Internet.

  A drive 140 is connected to the input / output interface 135 as necessary, and includes a magnetic disk (including a flexible disk) 151, an optical disk (including a CD-ROM (Computer Disk Read Only Memory) and a DVD (Digital Video Disk)). 152, a magneto-optical disk (including MD (Mini-Disk) (including registered trademark)) 153, or a removable disk 154 made of a semiconductor memory or the like is appropriately mounted, and a computer program read from the disk is installed in the storage unit 138. Is done.

  As shown in FIG. 14, a recording medium that records a program that is installed in a computer and can be executed by the computer is distributed to provide a program to a user separately from the apparatus main body. A ROM 132 that stores a program that is provided not only to the magnetic disk 151, the optical disk 152, the magneto-optical disk 153, and the removable disk 154 but is provided in advance to the apparatus main body. Alternatively, it is composed of a recording unit 138 such as a hard disk.

  In the present specification, the step of describing the program recorded on the recording medium is not limited to the processing performed in chronological order according to the described order, but is not necessarily performed in chronological order. It also includes processes that are executed individually.

  Further, in the present specification, the system represents the entire apparatus constituted by one or more apparatuses.

It is a figure which shows the structural example of one Embodiment of the communication system to which this invention is applied. It is a block diagram which shows the structural example of a receiving side terminal. It is a block diagram which shows the structural example of a transmission side terminal. It is a figure for demonstrating the round trip of a round trip delay measurement packet. It is a figure for demonstrating the 1st format of a round-trip delay measurement packet. It is a figure for demonstrating the 2nd format of a roundtrip delay measurement packet. It is a figure for demonstrating the 3rd format of a round-trip delay measurement packet. It is a figure for demonstrating the 4th format of a round-trip delay measurement packet. It is a figure for demonstrating the ID list | wrist of delay measurement packet with ID. It is a flowchart for demonstrating the process of the receiving side terminal. It is a flowchart for demonstrating the process of the transmission side terminal. It is a flowchart for demonstrating a buffer time calculation process. It is a flowchart for demonstrating the transmission process and reception process of the packet in which streaming data were stored. FIG. 3 is a diagram illustrating an internal configuration example of a general-purpose computer.

Explanation of symbols

  1 network, 10, 11 receiving side terminal, 21 communication unit, 22 controller, 23 reproduction data buffer unit, 51 packet creation unit, 52 time measurement unit, 53 buffer time calculation unit, 54 packet loss detection time holding unit, 131 CPU, 132 ROM, 133 RAM, 151 magnetic disk, 152 optical disk, 153 magneto-optical disk, 154 semiconductor memory, 301 transmission side terminal, 313 communication unit, 314 controller, 315 output data buffer unit, 341 time measurement unit, T1 reception side packet transmission Time, T2 Transmission side packet reception time T3 Transmission side packet transmission time, T4 Reception side packet reception time, α loss detection time, β Value that absorbs jitter of network 1

Claims (11)

In a communication system in which a transmitting device that transmits data in packets and a receiving device that receives the data are connected via a network,
The receiving device is:
A communication means for transmitting a measurement packet for measuring a round-trip time during which the packet reciprocates between the reception device and the transmission device, and receiving the measurement packet;
Buffer means for buffering data transmitted from the transmitter;
A buffer time calculating means for calculating a buffer time for buffering the data transmitted from the transmitting device in the buffer means based on the round trip time;
A read means for starting reading of the data buffered in the buffer means after the buffer time has elapsed after the buffer means starts buffering the data;
The transmitter is
A communication system comprising: a transmission-side communication unit that receives the measurement packet from the reception device via the network and transmits the measurement packet to the reception device. In an information processing apparatus that receives data transmitted via a network from a transmission apparatus that transmits data in packets,
Communication means for transmitting a measurement packet for measuring a round trip time for the packet to and from the transmitting device, and receiving the measurement packet;
Buffer means for buffering data transmitted from the transmitter;
A buffer time calculating means for calculating a buffer time for buffering the data transmitted from the transmitting device in the buffer means based on the round trip time;
An information processing apparatus comprising: a reading unit configured to start reading data buffered in the buffer unit after the buffer time has elapsed after the buffer unit starts buffering the data. . The information processing apparatus according to claim 2, wherein the data is streaming data. The communication means transmits two or more measurement packets to the transmission device,
The information processing apparatus according to claim 2, wherein the buffer time calculation unit calculates the buffer time based on a round trip time of the two or more measurement packets. The measurement packet includes an ID (Identification) unique to the measurement packet,
The information processing apparatus according to claim 4, wherein the communication unit identifies each of the two or more measurement packets based on the ID. The information processing apparatus according to claim 2, wherein the buffer time calculation unit calculates the buffer time in consideration of a change in the round-trip time. 3. The information according to claim 2, wherein the buffer time calculating unit calculates the buffer time in consideration of a fluctuation amount of a round-trip delay time required for the measurement packet to be transmitted on a forward path and a return path of a network. Processing equipment. The buffer time calculating means further calculates the buffer time in consideration of a change in processing time on the transmission side required until the transmission apparatus receives and transmits the measurement packet. 8. The information processing apparatus according to 7. In an information processing method of an information processing apparatus that receives data transmitted from a transmission apparatus that transmits data in a packet via a network,
A communication step of transmitting a measurement packet for measuring a round-trip time during which the packet reciprocates between the transmission device and receiving the measurement packet;
Buffer means for buffering the data in buffer means for buffering data transmitted from the transmitter; and
Based on the round trip time, a buffer time calculating step for calculating a buffer time for buffering data transmitted from the transmitting device in the buffer means;
And a reading step of starting reading of the data buffered in the buffer means after the buffer time has elapsed after the buffering of the data is started by the buffer means. . A program for causing a computer to perform processing for receiving data transmitted from a transmission device that transmits data in packets via a network,
A communication step of transmitting a measurement packet for measuring a round-trip time during which the packet reciprocates between the transmission device and receiving the measurement packet;
Buffer means for buffering the data in buffer means for buffering data transmitted from the transmitter; and
Based on the round trip time, a buffer time calculating step for calculating a buffer time for buffering data transmitted from the transmitting device in the buffer means;
And a reading step of starting reading of the data buffered in the buffer means after the buffer time has elapsed after the buffering of the data is started by the buffer means. A recording medium in which a program for causing a computer to perform processing for receiving data transmitted from a transmission device that transmits data in packets via a network is recorded,
A communication step of transmitting a measurement packet for measuring a round-trip time during which the packet reciprocates between the transmission device and receiving the measurement packet;
Buffer means for buffering the data in buffer means for buffering data transmitted from the transmitter; and
Based on the round trip time, a buffer time calculating step for calculating a buffer time for buffering data transmitted from the transmitting device in the buffer means;
And a reading step of starting reading of the data buffered in the buffer means after the buffer time has elapsed after the buffering of the data is started by the buffer means. Recording media.

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