JP2008131599A - Cast transmission apparatus and cast transmission method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a media information distribution system and a media information distribution method that can attain compatibility between the real time performance of real time distribution and the high reliability of stored information at the multicast distribution of a media information stream (time series data). <P>SOLUTION: At multicast distribution using the Internet or an intranet and multicast information distribution using a digital broadcast satellite communication satellite, a data receivers 200a, 200b and 200c store distribution information, detect positions where transmission errors occur, request the other data receiver to re-transmit a transmission error portion and receive the information so as to correct a transmission error existing in the stored distribution information. This allows to satisfy both the real time performance of multicast program distribution and the high reliability of information storage. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a cast transmission apparatus and the like for simultaneously distributing digital program information encoded with video, audio and the like to a large number of recipients for real-time viewing while redistributing information lost due to transmission errors during distribution.

  A technique for distributing the same information in real time to a large number of recipients using a digital communication network such as the Internet or an intranet is being actively developed as a multicast communication system. This is a communication method in which a signal transmitted from one sender is transmitted to a plurality of destinations by a relay device (router) in a communication network and distributed to a large number of receivers existing at the end in a tree form. At present, a multicast communication method is used in which a large number of receivers receive the same radio wave, such as information distribution using digital broadcasting satellites and communication satellites. However, multicast communication using the Internet is increasing in the future, and it is expected that broadcasting on the Internet will become the mainstream in the near future.

Generally, there are the following two means for preventing a transmission error in a digital communication network and realizing highly reliable communication.
(A) The signal is transmitted with redundancy to enable error recovery on the receiving side.
(B) The receiving side detects an error and requests the transmitting side to retransmit the corresponding part.

  Of these, in order to achieve reliable error recovery by means (a), considerable redundancy is required in the signal, and transmission efficiency is reduced. The recovery by is used together. For example, in TCP, which is a typical protocol in the Internet or an intranet, when a bit error or packet loss is detected on the receiving side, the transmission error is recovered by requesting the transmitting side to retransmit the packet. TCP is an abbreviation for Transmission Control Protocol.

  In addition, since the real-time property is important in the multicast communication method, the retransmission protocol such as the above-described TCP is not usually adopted because of the low speed and high load. In a multicast communication system in the Internet or an intranet, a high-speed and low-reliability protocol such as UDP (User Datagram Protocol) is generally used. In other words, real-time performance is high because it is unilaterally distributed from the sending side to the receiving side, but there is no means to recover the error by resending even if a bit error due to transmission error or packet loss due to congestion occurs. The video and audio are disturbed / missed on the receiving side. Similarly, in information distribution using digital broadcasting satellites / communication satellites, transmission errors occur due to weather conditions such as rainfall, and it is difficult to recover them by retransmission.

  Patent Document 1 describes a method in which an allowable amount of delay time due to retransmission is set in order to place importance on real-time properties, and retransmission is not performed for those exceeding the allowable time. Japanese Patent Application Laid-Open No. 2004-228561 describes a method of repairing an error after distribution is completed. However, this method has a problem that the transmission source requires a large storage unit.

JP 2002-84239 A JP 2003-60669 A

That is, the conventional technique has the following problems.
(1) In multicast program distribution using the Internet or an intranet, since real-time performance is important, a high-speed and low-reliability protocol represented by UDP is used. For this reason, there is no means for recovering transmission errors such as bit errors and packet loss. As a result, even when the receiver accumulates and uses the distribution program, the transmission error at the time of distribution remains. There is a problem that it must be.
(2) Although there is a method of requesting retransmission to the transmission source after distribution is completed, there is a problem that all distribution data sources are stored in the transmission source.

  The present invention provides a media information distribution system and a media information distribution method capable of realizing both real-time distribution of real-time distribution and high reliability of stored information in multicast distribution of media information streams (time-series data). With the goal.

  In order to solve the above-described problems, the present invention provides a cast transmission method for simultaneously delivering a media information stream in which code information of at least video data, audio data, and other data is multiplexed from a single sender to a large number of receivers. A transmission error detection step for inspecting a received media information stream to detect an error or missing information, a transmission error position storage step for storing a position where a transmission error exists in the media information stream, and this transmission And a retransmission request transmission step for requesting another receiving device to retransmit a portion where a transmission error has occurred based on the error position storage.

  ADVANTAGE OF THE INVENTION According to this invention, in the multicast delivery of a media information stream, the real time property of real time delivery and the high reliability of stored information are compatible. As a result, it is possible to construct a more sophisticated digital program broadcasting system and software content distribution system using the Internet, an intranet, and a communication network such as a digital communication satellite / broadcast satellite. Specifically, the present invention can be applied to real-time transmission of an encoded stream such as MPEG-2 that efficiently compresses and encodes video and audio, and is used in the fields of surveillance camera systems and multimedia communication and broadcasting services. A big effect is acquired. As an example, it is possible to realize a system in which a digital satellite broadcast receiver is equipped with an Internet port and a retransmission request is made via the Internet and a transmission error part is retransmitted.

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

  FIG. 1 shows a media information distribution system according to an embodiment of the present invention. Reference numeral 50 denotes a camera, which has an interface for sending the captured media information stream 104 to the data transmission apparatus 100. Reference numeral 100 denotes a data transmission apparatus having an interface for receiving stream data from the camera 50 and an interface for outputting distribution information to the network. Reference numerals 200a, 200b, and 200c denote data receiving apparatuses, which are a plurality of data receiving apparatuses that each have an IP address. In this embodiment, the IP address of 200a is “192.168.0.10”, the IP address of 200b is “192.168.0.11”, and the IP address of 200c is “192.168.0.12”. To do. The data receiving device 200 has an interface to the output devices 400a, 400b, and 400c, and reproduces and stores stream data. For the sake of distinction in the following explanation, a, b, and c are appended. Reference numerals 400a, 400b, and 400c denote output devices that are connected to 200a, 200b, and 200c and have an image and sound output function. Reference numerals 300a to 300c denote wireless LANs. Reference numeral 300a denotes a multicast transmission link in the wireless LAN, and 300b and 300c denote unicast links between terminals. The network used in this embodiment is a wireless LAN, but any network such as a wired LAN capable of cast communication may be used.

  The internal configuration of the data transmission device 100 will be described with reference to FIG. Reference numeral 101 denotes a camera interface unit that receives and electrically converts the media information stream 104 sent from the camera unit 50, and logically transmits the same information to the transmission format generation unit 102. Reference numeral 102 denotes a transmission format generation unit that receives the media information stream 104 via the camera interface unit 101 and divides the media information stream 104. This transmission format generation unit 102 adds serial number information as distribution information, shapes it into a transmission format suitable for the connected transmission path, and distributes the information as distribution information 105 to the data reception device via the network transmission unit 103. Send. The transmission format generation unit 102 of this embodiment controls the UDP protocol, and data for detecting a transfer error is performed by UDP FCS (Frame Check Sequence).

  The frame configuration will be described later with reference to FIG.

  FIG. 3 shows an internal configuration of the data receiving apparatus 200. A network interface transmission / reception unit 201 transmits / receives data from the network 300. Reference numeral 202 denotes a distribution information receiving unit that receives distribution information transmitted from the data transmitting apparatus 100. Reference numeral 203 denotes a transmission error detection unit that detects an error part of distribution information from UDP FCS error information. An output interface unit 204 transmits distribution information to the output device 400. Reference numeral 205 denotes a transmission error position storage unit that stores the position of the transmission error detected by the transmission error detection unit. Reference numeral 206 denotes a retransmission information transmission unit that transmits a retransmission request.

  Reference numeral 207 denotes a retransmission information receiving unit that receives retransmission information sent from another data receiving apparatus. A transmission error repair unit 208 receives the retransmission data from the retransmission information reception unit and writes it in the storage unit. Reference numeral 209 denotes a retransmission information receiving unit that receives a retransmission request sent from another data receiving apparatus. A retransmission unit 210 retransmits distribution information when there is distribution information requested to be retransmitted. Reference numeral 211 denotes an accumulator that accumulates distribution information. A timer unit 212 manages time.

  The frame structure will be described with reference to FIG. In the transmission format generating unit 102, the media information stream 104 is divided and mounted at the position of the distribution information division payload 402, and a distribution information division header 401 including serial number information is added. Further, the packet composed of the distribution information division header 401 and the payload 402 is divided and mounted on the UDP payload 404. The distribution information 105 includes a UDP header 403 and a UDP payload 404. The error check uses FCS in the UDP header. The distribution information 105 is divided by a network interface transmission unit, mounted on an IP payload 406, added with an IP header 405, and generated as an IP packet.

  The network interface unit also performs layer 2 and layer 1 processing, but the description is omitted because it depends on the network to be used. The number of bits of the serial number information is not limited because an appropriate bit field may be prepared for each system.

  The outline of a series of overall operations of the system according to the present embodiment will be described below.

  The media information stream 104 that is the target of multicast distribution sent from the camera unit 50 is input from the network interface unit 101 of the data transmission device 100. The input media information stream 104 is shaped into a transmission format suitable for the transmission path used by the transmission format generation unit 102. Further, the transmission format generation unit 102 adds information for detecting a transmission error and information for specifying a part in the media information stream to the distribution information 105. Then, the distribution information 105 is transmitted from the network interface transmission unit 103 to the data reception device 200 via the network 300.

  The data receiving device 200 that has received the distribution information 105 checks the type of the received data, and if it is distribution data, transfers the data to the output device 400 and the transmission error detection unit 203 determines whether there is an error. If a transmission error exists, the position information is written in the transmission error position storage 205 as an error. If there is no error and reception is normal, the distribution information is written in the storage 211. If an error exists, a retransmission request including error occurrence part information and error occurrence time is transmitted from the retransmission request transmission unit 206. The transmission destination is determined according to the device list. In this embodiment, the device list will be described as a multicast list. In this embodiment, the multicast list is given to each data receiving device by default, but a method of distributing the cast list from the data transmitting device may be used.

  The other data receiving apparatus that has received the retransmission request receives the retransmission request by the retransmission request receiving unit 209 and confirms whether data exists from the error occurrence part information. If data exists, the data requested by the retransmission unit 210 is transmitted to the data receiving apparatus 200.

  The data receiving apparatus 200 to which the requested data is returned receives the retransmission information at the retransmission information receiving unit 207. Based on this, the transmission error repair unit 208 replaces the portion of the media information recorded in the storage 211 that includes the transmission error with the correct media information that has been retransmitted.

  The sequence outline of the retransmission request in the system will be described with reference to FIG.

  S501 to S504 are distribution information by multicast communication, and are regularly cast to 200a, 200b, and 200c.

  When the data receiving apparatus 200a that has received the distribution information S501 performs error detection S516, the data receiving apparatus transmits a retransmission request S510 to the data receiving apparatus 200b according to the multicast list shown in FIG.

  The data receiving device 200b that has received the retransmission request S510 checks whether the requested distribution information is possessed, and if so, transmits the retransmission data S511 to the data receiving device 200a.

  The data receiving apparatus 200 a that has received the retransmission data S 511 records the data in the storage 211 by the transmission error repair unit 208.

  Next, when the error detection S517 is performed by the data reception device 200a in the distribution of the distribution information S502, a retransmission request S512 is transmitted to the data reception device 200b as in the case of the distribution information S501.

  The data reception device 200b confirms whether the distribution information is owned or not, and if it does not have the distribution information, transmits a retransmission request 413 to the data reception device 200c according to the multicast list.

  When receiving the retransmission request S513, the data receiving device 200c transmits the retransmission data S514 to the data receiving device 200b if it is requested and confirmed whether it has distribution information.

  The data receiving apparatus 200b that has received the retransmission data S514 records the retransmission data S515 to the data receiving apparatus 200a while recording it in the storage 211 by the transmission error repair unit 208.

  The data receiving apparatus 200 a that has received the retransmission data S 515 records the data in the storage 211 by the transmission error repair unit 208.

  By performing a retransmission request like a bucket tree array as in this operation, it is possible to restore data without congestion of information such as a retransmission request and retransmission data. In the worst case, it is conceivable that all the data receiving apparatuses cannot receive the distribution data, but in this case, the retransmission request is not sent and the retransmission data is not sent permanently.

  In this embodiment, a record of a retransmission request in another task process is constantly monitored, and a request that is not retransmitted even if the time set by the system is exceeded by comparing the time when the retransmission request occurs with the actual time. Erased. This waiting time varies depending on the system, but if it is a use case such as program distribution, the case of the next day is also expected. As described above, the communication for correcting the transmission error requires high reliability, but does not require real-time property, and therefore, a protocol (TCP or the like) according to the property is used.

  A processing flow of the data receiving apparatus 200 will be described with reference to FIG.

  In S600, it is determined whether a retransmission data request has been received. If it is a retransmission data request, the process proceeds to S607, and if it is not a retransmission data request, the process proceeds to S601.

  In step S601, it is determined whether retransmission data has been received.

  If it is retransmission data, the process proceeds to S605, and if it is different, the process proceeds to S602.

  In S602, it is determined whether it is distribution information. If it is distribution information, the process proceeds to S610, and if different, the process proceeds to S600.

  In S610, the distribution information is transmitted to the output device, and the process proceeds to S603.

  In S603, it is checked whether there is an error in the distribution information. If there is no error, the process proceeds to S604, and if an error is detected, the process proceeds to S608.

  In S604, the sent distribution information is accumulated, and the process proceeds to S600.

  In S605, it is confirmed whether there is a request for the retransmitted data sent from another data receiving apparatus. If there is no request from another, the process proceeds to S604, and if there is a request from another, the process proceeds to S606.

  In S606, the data is retransmitted (transferred) to another data receiving apparatus 200 that has requested retransmission based on information in the retransmitted data.

  In S607, a retransmission data request is received and it is confirmed whether or not the requested distribution data is owned. If so, the process proceeds to S609, and if not, the process proceeds to S608.

  In S608, the requested data receiving device is determined in accordance with the multicast list, a data retransmission request is made, and the process proceeds to S600. The determination flow of the retransmission request destination in S608 will be described later with reference to FIG.

  In S609, retransmission data of distribution information is transmitted, and the process proceeds to S600.

  The data receiving apparatus performs data receiving processing by the loop processing.

  FIG. 7 shows the data structure of the retransmission request packet transferred by the payload of the TCP frame. Reference numeral 706 denotes a TCP header, and reference numeral 707 denotes a TCP payload. Reference numeral 700 denotes control identification information for performing control identification, and a retransmission request packet is identified based on this information. Reference numeral 701 denotes request generation time information when a retransmission request is generated, and is used for selection of a transmission destination to which a retransmission request is made. Reference numeral 702 denotes packet length information. Reference numeral 703 denotes serial number information of distribution information for which retransmission is requested. Reference numerals 704 and 705 are the IP numbers of the data receiving apparatuses that requested the distribution information of the serial number information 703. When the retransmission request is received and not owned and the other data receiving apparatuses request retransmission, their own IP numbers Add a request and send the request. In the case of the retransmission request 413 in FIG. 5, the requesting device IPα 704 is “192.168.0.10”, and the requesting device IPβ 705 is “192.168.0.11”.

  FIG. 8 shows the data structure of a retransmission data packet transferred by the payload of the TCP frame. Reference numeral 807 denotes a TCP header, and reference numeral 808 denotes a TCP payload. Reference numeral 800 denotes control identification information for performing control identification, and retransmission data packets are identified based on this information. Reference numeral 801 denotes request generation time information when a retransmission request is generated, and may be used as approximate position information for accumulation. Reference numeral 802 denotes packet length information. Reference numeral 803 denotes serial number information of distribution information for which retransmission is requested. Reference numerals 804 and 805 denote the IP numbers of the data receiving apparatuses that have requested distribution information of the same serial number 703, and are arranged in the order of request. When transferring retransmission data, it does not matter whether the own IP number is deleted or transferred without change, or it is transferred without change. Reference numeral 806 denotes distribution information that has received a retransmission request.

  The multicast list structure will be described with reference to FIG.

  S900 is a field indicating a data receiving apparatus, and includes IP information S901 and a buffer type S902. S903 is IP information of the multicast address. S904 is a field indicating the distribution status to each terminal for each multicast IP.

  The line in S905 will be described. The IP is “192.168.0.10”, and the buffer type S902 is a memory. The received multicast IPs are “239.255.0.100” and “239.255.0.300”.

  Next, the line in S906 will be described. The IP is “192.168.0.11” and the buffer type is HD. The received multicast IPs are “239.255.0.100” and “239.255.0.200”.

  Next, the row of S907 will be described. The IP is “192.168.0.12”, and the buffer type is HD. The received multicast IPs are “239.255.0.100”, “239.255.0.200”, and “239.255.0.300”.

  In the present embodiment, the order in which retransmission requests are made is made by inquiring the lower IP shown in the list, and the data receiving device on the last line makes an inquiry to the highest data receiving device.

  The internal processing of S608 will be described with reference to FIG.

  In S650, it is checked whether the distribution information in error or the distribution information requested from another data receiving apparatus 200, which has transitioned from S603 and S607, has been inquired in the past. If not, the process proceeds to S651. If the inquiry is made, the process proceeds to S600.

  In S651, as described with reference to FIG. 7, the own IP is added, and the process proceeds to S652.

  In S652, as described with reference to FIG. 9, the next data receiving apparatus of its own IP is selected according to the list of the multicast list, and the process proceeds to S653.

  In S653, it is determined whether the buffer type of the data receiving apparatus selected in S652 is a memory. If it is not a memory, the process proceeds to S654, and if it is a memory, the process proceeds to S655.

  In S654, a transmission request is made according to the multicast list.

  In S655, the time elapsed from the request time 701 is measured, and the process proceeds to S656.

  In S656, it is determined whether the measurement result in S655 is 10 seconds or longer. If 10 seconds or more have not elapsed, the process proceeds to S654, and if 10 seconds or more, the process proceeds to S657. In this embodiment, the buffer time of the memory is 10 seconds, but the determination time differs depending on the system to be constructed. In addition, the multicast list information may be directly managed with a buffer time.

  In S657, one multicast list is updated, and the process proceeds to S653.

  As described above, in this embodiment, in the multicast distribution of the media information stream, each data receiving apparatus detects a transmission error while accumulating the distribution contents, and requests retransmission of data to other data receiving apparatuses that are cast. Yes. Therefore, according to the present embodiment, it is possible to perform distribution that can achieve both real-time distribution of real-time distribution and high reliability of stored information without congesting traffic. Specifically, it is effective in a monitoring system that requires real-time performance. In addition, a secondary effect that the transmission apparatus can be realized with a simple configuration can be obtained. When reproducing the data recorded by the monitoring system, it is also possible to expect the effect that the high-quality stream data can be viewed.

  These embodiments of the present invention can be realized by, for example, a computer executing a program. Also, means for supplying a program to a computer, for example, a computer-readable recording medium such as a CD-ROM recording such a program, or a transmission medium such as the Internet for transmitting such a program is also applied as an embodiment of the present invention. Can do. The above program can also be applied as an embodiment of the present invention. The above program, recording medium, transmission medium, and program product are included in the scope of the present invention.

It is a basic system block diagram. It is a data transmitter block diagram. It is a data receiver block diagram. It is a delivery information format block diagram. It is a retransmission sequence diagram. It is a data reception process flowchart. It is a resending request packet format figure. It is a resending data packet format figure. It is a figure which shows a multicast list. It is a resending request processing flowchart.

Explanation of symbols

50: Camera 100: Data transmission device 101: Camera interface unit 102: Transmission format unit 103: Network interface transmission unit 104: Media information stream 105: Distribution information 200: Data reception device 201: Network interface transmission / reception unit 202: Distribution information reception unit 203: Transmission error detection unit 204: Output device interface unit 205: Transmission error position storage unit 206: Retransmission request transmission unit 207: Retransmission information reception unit 208: Transmission error repair unit 209: Retransmission request reception unit 210: Retransmission unit 211: Accumulation 212: Timer unit 300: Network
300a: Multicast link 300b: Unicast link b
300c: Unicast link c
400a: output device a
400b: output device b
400c: Output device c
401: Distribution information division header 402: Distribution information division payload 403: UDP header 404: UDP payload 405: UDP header 406: IP header 407: IP payload 700: Control identification 701: Control identification 702: Packet length 703: Distribution number 704: Request device IPα
705: Requesting device IPβ
706: TCP header 707: TCP payload 800: Control identification 801: Control identification 802: Packet length 803: Delivery number 804: Requesting device IPα
805: Requesting device IPβ
806: Distribution retransmission information 807: TCP header 808: TCP payload

Claims (9)

A cast transmission device that simultaneously distributes a media information stream in which code information of at least video data and audio data is multiplexed from a single sender to a large number of receivers,
To the sender's transmitter,
An input unit for inputting stream data;
A transmission format generator for dividing the stream data and adding serial number information to generate a format suitable for transmission;
A network interface transmitter for transmitting to the network;
Comprising
In the receiver of the recipient,
A network interface transmission / reception unit for transmitting / receiving a media information stream via a network;
A distribution information receiver for receiving the media information stream;
An accumulator that sequentially accumulates received media information streams;
An output device interface unit for transmitting the received media information stream to the output device;
A transmission error detector that inspects the received media information stream and detects at least information errors and omissions;
A transmission error position storage unit for storing a position where a transmission error exists in the media information stream;
Based on this transmission error position storage, a retransmission request transmission unit that requests retransmission of a part where a transmission error has occurred to another receiving device;
A retransmission information receiving unit for receiving media information retransmitted from the other receiving device;
Based on the received media information, a transmission error repair unit that repairs a transmission error of the media information stream stored in the accumulator,
A retransmission request accepting unit that receives a partial retransmission request of a media information stream issued from the receiver of the receiver;
A retransmission unit that transmits a corresponding part of a media information stream to a reception device that has requested retransmission according to an instruction from the reception device;
A cast transmission apparatus comprising:   The cast transmission apparatus according to claim 1, further comprising a timer unit having real time information.   The cast transmission apparatus according to claim 1, wherein the retransmission request transmission unit includes a distributed apparatus list.   The cast transmission apparatus according to claim 1, wherein the retransmission request transmission unit makes an inquiry in a relay manner according to the apparatus list.   The cast transmission apparatus according to claim 2, wherein the retransmission request transmission unit controls an inquiry destination according to a retransmission request time of the apparatus list information and information of a timer unit.   The cast transmission apparatus according to claim 1 or 2, wherein the receiving apparatus primarily accumulates data even when the signal to the output apparatus is stopped.   The serial number information is added to the packet storing the media information stream in order to identify a part in the media information stream and to detect the loss of the packet storing the media information stream. The cast transmission device according to 1. A cast transmission method for simultaneously delivering a media information stream in which code information of at least video data and audio data is multiplexed from a single sender to many receivers,
A transmission error detection step of inspecting the received media information stream and detecting at least information errors and omissions;
A transmission error position storage step for storing a position where a transmission error exists in the media information stream;
Based on this transmission error position storage, a retransmission request transmission step for requesting retransmission of the part where the transmission error has occurred to another receiving device;
A cast transmission method comprising: A program for causing a computer to execute cast transmission for simultaneously delivering a media information stream in which code information of at least video data and audio data is multiplexed from a single sender to many receivers,
In the computer,
A transmission error detection process that inspects the received media information stream and detects at least information errors and omissions;
A transmission error position storage process for storing a position where a transmission error exists in the media information stream;
Based on this transmission error position storage, a retransmission request transmission process for requesting retransmission of a part where a transmission error has occurred to another receiving device;
A program characterized in that is executed.

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