WO2012039084A1 - Multicast delivery system as well as transmitter and receiver used for same - Google Patents

Multicast delivery system as well as transmitter and receiver used for same Download PDF

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Publication number
WO2012039084A1
WO2012039084A1 PCT/JP2011/003571 JP2011003571W WO2012039084A1 WO 2012039084 A1 WO2012039084 A1 WO 2012039084A1 JP 2011003571 W JP2011003571 W JP 2011003571W WO 2012039084 A1 WO2012039084 A1 WO 2012039084A1
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WO
WIPO (PCT)
Prior art keywords
unit
receiver
reception response
priority
transmitter
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PCT/JP2011/003571
Other languages
French (fr)
Japanese (ja)
Inventor
山崎　靖久
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パナソニック株式会社
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Publication of WO2012039084A1 publication Critical patent/WO2012039084A1/en

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/20—Servers specifically adapted for the distribution of content, e.g. VOD servers; Operations thereof
    • H04N21/23—Processing of content or additional data; Elementary server operations; Server middleware
    • H04N21/238—Interfacing the downstream path of the transmission network, e.g. adapting the transmission rate of a video stream to network bandwidth; Processing of multiplex streams
    • H04N21/23805—Controlling the feeding rate to the network, e.g. by controlling the video pump
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/20—Servers specifically adapted for the distribution of content, e.g. VOD servers; Operations thereof
    • H04N21/23—Processing of content or additional data; Elementary server operations; Server middleware
    • H04N21/24—Monitoring of processes or resources, e.g. monitoring of server load, available bandwidth, upstream requests
    • H04N21/2402—Monitoring of the downstream path of the transmission network, e.g. bandwidth available
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/40—Client devices specifically adapted for the reception of or interaction with content, e.g. set-top-box [STB]; Operations thereof
    • H04N21/43—Processing of content or additional data, e.g. demultiplexing additional data from a digital video stream; Elementary client operations, e.g. monitoring of home network or synchronising decoder's clock; Client middleware
    • H04N21/436—Interfacing a local distribution network, e.g. communicating with another STB or one or more peripheral devices inside the home
    • H04N21/4363—Adapting the video or multiplex stream to a specific local network, e.g. a IEEE 1394 or Bluetooth® network
    • H04N21/43637—Adapting the video or multiplex stream to a specific local network, e.g. a IEEE 1394 or Bluetooth® network involving a wireless protocol, e.g. Bluetooth, RF or wireless LAN [IEEE 802.11]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N21/00—Selective content distribution, e.g. interactive television or video on demand [VOD]
    • H04N21/60—Network structure or processes for video distribution between server and client or between remote clients; Control signalling between clients, server and network components; Transmission of management data between server and client, e.g. sending from server to client commands for recording incoming content stream; Communication details between server and client 
    • H04N21/63—Control signaling related to video distribution between client, server and network components; Network processes for video distribution between server and clients or between remote clients, e.g. transmitting basic layer and enhancement layers over different transmission paths, setting up a peer-to-peer communication via Internet between remote STB's; Communication protocols; Addressing
    • H04N21/64—Addressing
    • H04N21/6405—Multicasting
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/30—Resource management for broadcast services

Definitions

  • the present invention relates to a multicast distribution system that adjusts transmission conditions (encoding rate, image quality, retransmission limit, etc.) of transmission data according to wireless communication quality.
  • a transmission / reception system that adjusts the encoding rate of transmission data on the transmission side according to the communication quality of the transmission path is known (see, for example, Patent Document 1).
  • a transmitter wireless communication device
  • a reception side device through wireless communication of the encoded image.
  • the quality of the image to be encoded by the image encoding unit is determined according to the wireless communication unit to be transmitted to and the communication quality of the wireless communication (specifically, the response ratio and S / N ratio of ACK and NACK, etc.)
  • an image quality instruction unit for instructing the image encoding unit to encode an image with the determined quality.
  • this wireless communication apparatus since the encoding rate in the image encoding unit is determined according to the communication quality of wireless communication, it is possible to transmit image data that can be reproduced with optimum quality even when the communication quality deteriorates .
  • the conventional transmission system is premised on application to one-to-one communication. Therefore, when this system is applied to a multicast distribution system in which a transmitter transmits (distributes) transmission data to a plurality of receivers at the same time, there is only one receiver with very poor communication quality. However, there is a problem that a low encoding rate is set for the receiver.
  • the present invention has been made to solve the above-described conventional problems, and an object of the present invention is to provide a multicast distribution system capable of automatically adjusting transmission conditions according to wireless communication quality in the multicast distribution system. To do. Another object of the present invention is to provide a multicast distribution system that can specify which of the frame rate and the resolution is prioritized when automatically adjusting the transmission conditions according to the wireless communication quality.
  • the multicast distribution system of the present invention is a multicast distribution system that includes a transmitter and a plurality of receivers, and multicasts transmission data from the transmitter to the plurality of receivers. Some of the plurality of receivers are priority receivers, and others are non-priority receivers.
  • the priority receiver includes a reception response generation unit that generates a reception response to the transmission data received from the transmitter, and a reception response transmission unit that transmits the reception response generated by the reception response generation unit to the transmitter. have. Based on the reception response transmitted from the priority receiver, the transmitter estimates the communication quality of the priority receiver and the communication quality of the priority receiver estimated by the communication quality estimation unit.
  • a transmission condition determining unit that determines a transmission condition of transmission data based on the transmission data and a transmission data transmitting unit that transmits the transmission data are included.
  • the transmitter includes an encoding unit that encodes transmission data, and the transmission condition determining unit determines an encoding rate in the encoding unit as a transmission condition, and encodes the encoding unit.
  • the coding rate determination unit sets a lower coding rate than when the communication quality is good when the communication quality of the priority receiver is not good.
  • the transmitter includes a video photographing unit that generates video data as transmission data, and the transmission condition determining unit determines the image quality in the video photographing unit as the transmission condition, and the video photographing unit
  • the image quality determination unit sets a lower image quality when the communication quality of the priority receiver is not good than when the communication quality is good.
  • the transmitter includes a retransmission unit that retransmits the transmission data based on the reception status of the reception response from the priority receiver, and the transmission condition determination unit retransmits the transmission condition as a transmission condition.
  • a retransmission limit determination unit that determines the maximum number of retransmissions in the transmission unit and sets the retransmission limit in the retransmission unit. The retransmission limit determination unit is smaller than when the reception response is received when no reception response is received from the priority receiver. Set the maximum number of retransmissions.
  • the transmitter includes an encoding unit that encodes transmission data for one frame divided into a plurality of sub-blocks, and the retransmission limit determination unit is a retransmission unit as a transmission condition.
  • the frame retransmission limit determination unit that determines the upper limit number of retransmissions in units of frames and sets it in the retransmission unit, and the sub-block retransmission that determines the upper limit number of retransmissions in subblocks in the retransmission unit as transmission conditions and sets in the retransmission unit
  • the frame retransmission limit determination unit and the sub-block retransmission limit determination unit each include a limit determination unit, and set a smaller number of retransmission upper limits than when the reception response is received when the reception response is not received from the priority receiver.
  • the communication quality estimation unit estimates the communication quality of the priority receiver based on the sub-block error rate included in the reception response.
  • the priority receiver transmits a video parameter setting request and a video parameter setting request unit for generating a video parameter setting request indicating which of the video resolution and frame rate is to be prioritized.
  • a video parameter setting request transmitting unit that transmits video data as transmission data, and a code that encodes the video data using an intra-frame encoded frame and an inter-frame encoded frame.
  • a video parameter setting request determination unit that determines which of the video resolution and frame rate is prioritized based on the video parameter setting request received from the priority receiver, and the transmission condition determination unit includes: As a transmission condition, determine the maximum number of retransmissions in the retransmission unit for each frame type.
  • the number of times is set larger than the upper limit number of retransmissions of the inter-frame encoded frame.
  • a priority response receiver and a non-priority receiver among a plurality of receivers generate a reception response generation unit and whether or not a reception response is generated.
  • a reception response output setting unit to be set, and a reception response output setting unit of a receiver to be a priority receiver among a plurality of receivers sets the reception response generation unit to generate a reception response,
  • the reception response output setting unit of the receiver to be a non-priority receiver sets the reception response generation unit so as not to generate a reception response.
  • the reception response output setting unit sets in the reception response generation unit whether or not to generate a reception response in accordance with a user operation.
  • the transmitter further includes a reception response permission output unit that outputs a reception response permission that permits a reception response of a priority receiver among a plurality of receivers, and a reception response output setting is made.
  • the unit sets the reception response generation unit to generate a reception response when the reception response is permitted as a priority receiver in the reception response permission, and the reception response is not permitted to itself.
  • the reception response generator is set not to generate a reception response.
  • the transmitter includes a receiver identification number requesting unit that requests transmission of its own identification number held by each of the plurality of receivers, and a plurality of receivers.
  • An identification number of a receiver to be a priority receiver is stored, and a reception identification number transmitted from each of a plurality of receivers is received in response to a request from the receiver identification number request unit,
  • a priority receiver determination unit that determines a receiver to be received, and the reception response permission output unit permits a reception response to a receiver that is determined to be a priority receiver by the priority receiver determination unit.
  • the reception response permission is output.
  • Another aspect of the present invention is a transmitter that constitutes the above multicast distribution system, and yet another aspect is a receiver that constitutes the above multicast distribution system.
  • the present invention provides a multicast distribution system having an effect of automatically adjusting transmission conditions optimum for a group of receivers according to the communication quality of a transmission path when multicasting transmission data to a plurality of receivers wirelessly. It is something that can be done.
  • FIG. 1 is a diagram showing an overall configuration of a multicast distribution system according to a first embodiment of the present invention.
  • FIG. 2 is a block diagram showing the configuration of the transmitter according to the first embodiment of the present invention.
  • FIG. 3A is a block diagram showing a configuration of a priority receiver in the first exemplary embodiment of the present invention.
  • FIG. 3B is a block diagram showing the configuration of the non-priority receiver in the first embodiment of the present invention.
  • FIG. 3C is a block diagram showing the configuration of the receiver according to the first embodiment of the present invention.
  • FIG. 4 is a block diagram showing a configuration of a transmitter according to the second embodiment of the present invention.
  • FIG. 5 is a block diagram showing a configuration of a receiver according to the second embodiment of the present invention.
  • FIG. 6A is a diagram showing an overall configuration of a multicast distribution system according to the third embodiment of the present invention.
  • FIG. 6B is a diagram showing an overall configuration of a multicast distribution system according to the third embodiment of the present invention.
  • FIG. 7 is a block diagram showing a configuration of a transmitter according to the third embodiment of the present invention.
  • FIG. 8 is a diagram illustrating a format example of a sub-block reception response according to the third embodiment of the present invention.
  • FIG. 9 is a block diagram showing a configuration of a receiver according to the third embodiment of the present invention.
  • FIG. 10 is a diagram showing an overall configuration of a multicast distribution system according to the fourth embodiment of the present invention.
  • FIG. 11 is a block diagram showing a configuration of a transmitter according to the fourth embodiment of the present invention.
  • FIG. 12 is a block diagram showing a configuration of a receiver according to the fourth embodiment of the present invention.
  • the multicast distribution system is a multicast distribution system that includes a transmitter and a plurality of receivers, and multicasts transmission data from the transmitter to the plurality of receivers. Some of the plurality of receivers are priority receivers, and others are non-priority receivers.
  • the priority receiver includes a reception response generation unit that generates a reception response to the transmission data received from the transmitter, and a reception response transmission unit that transmits the reception response generated by the reception response generation unit to the transmitter. have. Based on the reception response transmitted from the priority receiver, the transmitter estimates the communication quality of the priority receiver and the communication quality of the priority receiver estimated by the communication quality estimation unit.
  • a transmission condition determining unit that determines a transmission condition of transmission data based on the transmission data and a transmission data transmitting unit that transmits the transmission data are included.
  • the transmitter determines the transmission condition of the transmission data considering only the communication quality of the priority receiver
  • the priority receiver with good communication quality is affected by the poor communication quality of the non-priority receiver. It is possible to avoid transmission of transmission data under poor transmission conditions.
  • the transmitter includes an encoding unit that encodes transmission data, and the transmission condition determining unit determines an encoding rate in the encoding unit as a transmission condition.
  • the coding rate determination unit sets a lower coding rate than when the communication quality is good when the communication quality of the priority receiver is not good. .
  • the encoding rate is lowered (the amount of data for error detection and error correction is increased), so that encoding is performed on the receiver side. Transmission data can be reliably reproduced.
  • such adjustment of the coding rate is performed considering only the communication quality of the priority receiver (ignoring the communication quality of the non-priority receiver), so that the communication quality of the priority receiver is reduced. If it is good, even if the communication quality of the non-priority receiver is poor, the coding rate is not set low for that reason.
  • the transmitter includes a video photographing unit that generates video data as transmission data, and the transmission condition determining unit determines the image quality in the video photographing unit as the transmission condition.
  • the image quality determining unit sets the image quality lower than when the communication quality is good when the communication quality of the priority receiver is not good.
  • the video shooting unit lowers the image quality (lowers the frame rate and / or lowers the resolution) and generates video data. Transmission data can be reproduced more reliably.
  • the image quality adjustment is performed considering only the communication quality of the priority receiver (ignoring the communication quality of the non-priority receiver)
  • the communication quality of the priority receiver is good. If so, even if the communication quality of the non-priority receiver is poor, the image quality is not set low for that reason.
  • the transmitter includes a retransmission unit that retransmits transmission data based on the reception status of the reception response from the priority receiver
  • the transmission condition determination unit includes: A retransmission limit determination unit that determines the upper limit number of retransmissions in the retransmission unit as a transmission condition and sets the retransmission limit in the retransmission unit.
  • the retransmission limit determination unit receives a reception response when no reception response is received from the priority receiver. Set a smaller number of retransmission upper limit times.
  • the retransmission upper limit count is set to a small value and unreceived transmission data is retransmitted. Can be avoided.
  • the adjustment of the number of retransmission upper limits is performed considering only the communication quality of the priority receiver (ignoring the communication quality of the non-priority receiver), the communication quality of the priority receiver is reduced. If it is satisfactory, even if the non-priority receiver is out of the communication range and cannot communicate, the upper limit number of retransmissions is not set low.
  • the transmitter includes an encoding unit that encodes transmission data for one frame divided into a plurality of sub-blocks
  • the retransmission limit determination unit includes transmission conditions.
  • the frame retransmission limit determination unit for determining the upper limit number of retransmissions for each frame in the retransmission unit and setting it in the retransmission unit, and as the transmission condition, determining the upper limit number of retransmissions for each subblock in the retransmission unit and setting it in the retransmission unit
  • a sub-block retransmission limit determination unit, and each of the frame retransmission limit determination unit and the sub-block retransmission limit determination unit has a smaller number of retransmission upper limits than when the reception response is received when the reception response is not received from the priority receiver.
  • the retransmission upper limit count is set to a small value and unreceived transmission data is retransmitted. Can be avoided.
  • the adjustment of the number of retransmission upper limits is performed considering only the communication quality of the priority receiver (ignoring the communication quality of the non-priority receiver)
  • the communication quality of the priority receiver is reduced. If it is good, it is assumed that the non-priority receiver is out of the communication range and communication is not possible because it is out of the communication range.
  • the encoding unit divides the transmission data for one frame into a plurality of sub-blocks, and the sub-block retransmission limit determination unit sets the retransmission upper limit number of sub-blocks in the retransmission unit. Compared with the case of performing retransmission, the retransmission overhead can be reduced.
  • the communication quality estimation unit preferably estimates the communication quality of the priority receiver based on the sub-block error rate included in the reception response. With this configuration, it is possible to estimate the communication quality more precisely.
  • the priority receiver includes a video parameter setting request unit that generates a video parameter setting request indicating which of the video resolution and the frame rate has priority, and a video parameter.
  • a video parameter setting request transmission unit for transmitting the setting request, and the transmitter uses a video photographing unit for generating video data as transmission data, and uses the intra-frame encoded frame and the inter-frame encoded frame for the video data.
  • An encoding unit for encoding, and a video parameter setting request determination unit that determines which of the video resolution and the frame rate is to be prioritized based on the video parameter setting request received from the priority receiver.
  • the decision unit sets the upper limit number of retransmissions in the retransmission unit as a transmission condition in the frame type.
  • a frame type retransmission limit determination unit that is determined separately and set in the retransmission unit.
  • the frame type retransmission limit determination unit performs intra-frame encoding when the video parameter setting request determination unit determines that priority is given to resolution.
  • the upper limit number of retransmissions of frames is set larger than the upper limit number of retransmissions of inter-coded frames.
  • the upper limit number of retransmissions of intra-frame encoded frames is set to be larger than the upper limit number of retransmissions of inter-frame encoded frames, the possibility that the inter-coded frames are lost and the video is disturbed is relatively high.
  • the period of the intra-coded frame there is a high possibility that a high-resolution video can be obtained, and a video parameter setting request that gives priority to resolution can be realized.
  • a priority receiver and a non-priority receiver among a plurality of receivers generate a reception response generation unit and whether or not to generate a reception response.
  • a reception response output setting unit to be set in the reception response generation unit, and the reception response output setting unit of the receiver that should be a priority receiver among the plurality of receivers, in the reception response generation unit to generate a reception response The reception response output setting unit of the receiver to be set and to become a non-priority receiver sets the reception response generation unit so as not to generate a reception response.
  • each of the plurality of receivers is not specified whether it is a priority receiver or a non-priority receiver at the time of manufacture, and in the course of use, for each individual receiver, Whether it is used as a priority receiver or a non-priority receiver can be arbitrarily set.
  • the reception response output setting unit sets whether or not to generate a reception response in response to a user operation in the reception response generation unit.
  • the user can arbitrarily set whether to use each receiver as a priority receiver or a non-priority receiver.
  • the transmitter further includes a reception response permission output unit that outputs a reception response permission that permits a reception response of a priority receiver among a plurality of receivers,
  • the reception response output setting unit sets the reception response generation unit to generate a reception response when the reception response is permitted as a priority receiver by the reception response permission, and permits the reception response to itself. If not, the reception response generation unit is set not to generate a reception response.
  • This configuration allows the transmitter to arbitrarily set which of a plurality of receivers is used as a priority receiver and which is used as a non-priority receiver.
  • the transmitter requests a receiver identification number requesting unit to transmit its own identification number held by each of the plurality of receivers, and a plurality of receptions.
  • the identification number of the receiver to be a priority receiver among the machines is stored, and the reception identification number transmitted from each of the plurality of receivers in response to the request by the receiver identification number request unit is received.
  • a priority receiver determination unit that determines a receiver that should be a priority receiver, and a reception response permission output unit for a receiver that is determined to be a priority receiver by the priority receiver determination unit.
  • the reception response permission that permits the reception response is output.
  • Another aspect of the present invention is a transmitter that constitutes the above multicast distribution system, and yet another aspect is a receiver that constitutes the above multicast distribution system.
  • FIG. 1 is a diagram illustrating an overall configuration of a multicast distribution system according to the first embodiment.
  • the multicast distribution system 1 includes a transmitter 101 as an access point (AP) and a plurality of receivers 301a1, 301a2, 301b1, and 301b2 as slave stations (Stations). .
  • the slave station is also called a terminal.
  • the transmitter 101 transmits transmission data by multicast.
  • data reproduced in time series is used as transmission data.
  • the transmission data is video data or audio data.
  • the video data may be accompanied by audio data, or may not be accompanied by audio data.
  • the receivers 301 a 1, 301 a 2, 301 b 1, 301 b 2 receive transmission data distributed from the transmitter 101 by multicast when they are within the communication range R of the transmitter 101.
  • receivers 301a1 and 301a2 are priority receivers
  • receivers 301b1 and 301b2 are non-priority receivers.
  • the priority receivers 301a1 and 301a2 return a reception response to the transmitter 101.
  • no reception response is returned.
  • the priority receiver and the non-priority receiver are not particularly distinguished with respect to the receiver, they are simply referred to as “receiver 301” or the like, and when the individual priority receivers are not distinguished, “priority receiver 301a”.
  • “b” is appended.
  • the transmitter 101 may function as a receiver and receive transmission data transmitted from other transmitters. For this reason, in FIG. 1, the transmitter 101 has the characters “STA” meaning slave stations as well as “AP” meaning parent stations.
  • the transmitter 101 has a function of automatically adjusting transmission conditions of transmission data based on a reception response from the receiver.
  • the “transmission condition” of transmission data includes the transmission data encoding rate, frame rate, resolution, and retransmission limit.
  • transmitter 101 automatically adjusts the encoding rate of transmission data as a transmission condition of transmission data.
  • the transmitter 101 adjusts the encoding rate of transmission data considering only the reception responses of the priority receivers 301a1 and 301a2.
  • the multicast distribution system 1 of the present embodiment can be applied, for example, at a disaster site.
  • the transmitter 101 is provided in a camera that captures the situation of a damaged site or a lifesaving situation, and distributes video captured by the camera to a plurality of receivers 301 by multicast.
  • the priority receiver 301a may be connected to, for example, a monitor installed at a command headquarters set up at the site.
  • the portable terminal carried by the person in charge of the command may be used as the priority receiver 301a.
  • an important receiver among the plurality of receivers 301 can be set as the priority receiver 301a.
  • the non-priority receiver 301b may be a portable terminal that is carried by a person who is saving lives at a disaster site, or may be connected to a monitor provided in a police vehicle, a fire engine, or an ambulance vehicle. In this way, among the plurality of receivers 301, a receiver having a relatively low importance can be set as the non-priority receiver 301b.
  • the encoding rate of transmission data in the transmitter 101 is adjusted in consideration of the communication quality of the priority receivers 301a1 and 301a2. Therefore, for example, the non-priority receiver 301b2 is in a state of poor communication quality, and the transmission data cannot be reproduced with high quality at the non-priority receiver 301b2 unless the transmission data encoding rate in the transmitter 101 is lowered. Even if the transmitter 101 is multicasted to transmit data having a low encoding rate by dragging the communication quality of the non-priority receiver 301b2, the important priority receiver 301a itself is high as a result. A situation in which only transmission data encoded at a low encoding rate can be received even though transmission data at the encoding rate can be received is avoided.
  • the transmitter 101 encodes transmission data distributed by multicast based on the communication quality of the priority receiver having the worst communication quality. Determine the rate.
  • FIG. 2 is a block diagram illustrating a configuration of the transmitter according to the first embodiment.
  • the transmitter 101 includes a transmission unit 11 that multicasts transmission data and a reception unit 12 that receives a reception response from a receiver in a communication area.
  • the transmitter 101 further includes a content providing unit 13, an encoding unit 14, and a transmission packet generating unit 15.
  • the content providing unit 13 generates and provides data of content to be transmitted.
  • the content providing unit 13 is a video shooting unit that generates and provides video data by shooting.
  • the encoding unit 14 encodes the video data provided from the content providing unit 13.
  • the encoded video data is provided to the transmission packet generator 15 as encoded data.
  • the transmission packet generator 15 divides the encoded data into packets and generates a transmission packet.
  • the transmitter 101 further includes a reception response determination unit 16 and a communication quality estimation unit 17.
  • the reception response determination unit 16 determines whether to retransmit the transmission packet based on the reception response from the receiver received by the reception unit 12.
  • the reception response determination unit 16 determines to retransmit the corresponding transmission packet when the reception response (ACK) is not received from the priority receiver 301a and when the reception response (NACK) is received from the priority receiver 301a.
  • the reception response determination unit 16 gives an instruction to the transmission packet generation unit 15.
  • the communication quality estimation unit 17 estimates the communication quality with the receiver based on the S / N ratio of the reception response from the receiver received by the reception unit 12.
  • the communication quality estimation unit 17 outputs the estimated communication quality to the coding rate determination unit 18.
  • the communication quality estimation unit 17 may estimate the communication quality with the receiver based on the reception rate of the reception response (ACK) or the S / N ratio of the reception response and the reception rate of the reception response (ACK). Good.
  • the coding rate determination unit 18 determines a coding rate based on the communication quality estimated by the communication quality estimation unit 17 and outputs the coding rate to the coding unit 14. At this time, the encoding rate determination unit 18 increases the encoding rate as the communication quality estimated by the communication quality estimation unit 17 increases, that is, the ratio of actual data (video data) in the encoded data. The coding rate is determined so that becomes higher.
  • the encoding unit 14 encodes the video data provided from the content providing unit 13 according to the encoding rate determined by the encoding rate determining unit 18.
  • the coding rate determination unit 18 determines the coding rate based on the lowest communication quality among the communication qualities of the plurality of receivers. To decide.
  • the coding rate determination unit 18 includes a receiver that transmits a reception response among a plurality of receivers to which the transmitter 101 should transmit transmission data by multicast, that is, a priority receiver 301a. The communication quality of all the priority receivers 301a is compared, and the lowest communication quality is adopted.
  • the reception response determination unit 16 causes the transmission packet generation unit 15 to retransmit the transmission packet based on the presence / absence of the reception response from the priority receiver 301a received by the reception unit 12. That is, when the reception response determination unit 16 does not receive the reception response (ACK) from the priority receiver 301a at the reception unit 12, or when the reception response (NACK) is received, the reception response determination unit 16 A transmission packet that has not been received by the receiver is retransmitted with a predetermined retransmission limit as the upper limit of the number of retransmissions.
  • the communication quality estimation unit 17 estimates the communication quality of each priority receiver 301a based on the reception response from the priority receiver 301a received by the reception unit 12. Then, the encoding rate determination unit 18 determines the encoding rate based on the estimated communication quality and sets it in the encoding unit 14. Next, the encoding unit 14 generates encoded data by encoding the video data provided from the content providing unit 13 at the set encoding rate. Next, the transmission packet generation unit 15 generates a transmission packet from the encoded data, and the transmission unit 11 transmits the transmission packet as transmission data. The transmitter 101 retransmits the transmission packet when necessary based on the reception response from the priority receiver 301a received by the reception unit 12.
  • FIG. 3A is a block diagram illustrating a configuration of the priority receiver 301a
  • FIG. 3B is a block diagram illustrating a configuration of the non-priority receiver 301b.
  • Each of the priority receiver 301a and the non-priority receiver 301b includes a reception unit 31, a decoding unit 32, an error determination unit 33, and a content reproduction unit 34.
  • the receiving unit 31 receives transmission data transmitted from the transmitter 101.
  • the decoding unit 32 decodes the transmission data received by the receiving unit 31.
  • the error determination unit 33 receives the data decoded by the decoding unit 32 and determines whether or not there is an error in the data. Data determined to be error-free by the error determination unit 33 is output to the content reproduction unit 34 and is reproduced by the content reproduction unit 34.
  • the error determination unit 33 outputs the result of the error determination to the reception response generation unit 35.
  • the reception response generation unit 35 generates a reception response (ACK) indicating that the data has been received without error according to the result of the error determination, and indicates that there is an error when there is an error.
  • a reception response (NACK) is generated.
  • the transmission unit 36 transmits the generated reception response to the transmitter 101.
  • the non-priority receiver 301b includes a reception unit 31, a decoding unit 32, an error determination unit 33, and a content reproduction unit 34, as with the priority receiver 301a. However, since the non-priority receiver 301b does not transmit a reception response to the transmitter 101, the non-priority receiver 301b does not include a configuration related thereto, that is, the reception response generation unit 35 of the priority receiver 301a and the transmission unit 36 for transmitting the reception response. .
  • the difference between the priority receiver 301a and the non-priority receiver 301b is that the priority receiver 301a has a configuration for transmitting a reception response to the transmitter 101.
  • the non-priority receiver 301b is not provided with these configurations. That is, in the example of FIGS. 3A and 3B, the priority receiver 301a and the non-priority receiver 301b are distinguished at the time when they are manufactured.
  • FIG. 3C is a block diagram illustrating another example of the receiver 301 of the present embodiment.
  • the user can arbitrarily set whether to use the receiver 301 as the priority receiver 301a or the non-priority receiver 301b in the course of use.
  • the receiver 301 illustrated in FIG. 3C is similar to the priority receiver 301a illustrated in FIG. 3A in that the reception unit 31, the decoding unit 32, the error determination unit 33, the content reproduction unit 34, the reception response generation unit 35, and the transmission unit 36. And a reception response output setting unit 37.
  • the reception response output setting unit 37 sets, in the reception response generation unit 35, whether or not to generate a reception response according to a user operation. That is, when the receiver 301 is used as the priority receiver 301a, the user operates the reception response output setting unit 37 to set the reception response generation unit 35 so as to generate a reception response. Is used as the non-priority receiver 301b, the user operates the reception response output setting unit 37 to set the reception response generation unit 35 so as not to generate a reception response.
  • the transmitter 101 encodes content at a coding rate determined only considering the communication quality of the priority receiver 301a and distributes the multicast. Therefore, it is possible to avoid a situation in which a sufficient amount of information cannot be obtained by the priority receiver 301a which is an important receiver because the communication quality of the non-priority receiver 301b which is a less important receiver is poor.
  • the receiver 301 that can select whether to make it a priority receiver 301a or a non-priority receiver 301b by the user's operation, the user gives priority to the case when necessary.
  • Receiver and non-priority receiver can be set.
  • the transmitter 101 receives a reception response only from the priority receiver 301a, so that the transmitter 101 can communicate with the priority receiver 301a.
  • the coding rate is determined considering only the quality, reception responses may be transmitted from all the receivers 301 including the non-priority receiver 301b to the transmitter 101.
  • information indicating whether the receiver is a priority receiver or a non-priority receiver is added to the reception response.
  • the transmitter 101 Upon receiving the reception response, the transmitter 101 refers to the information added to the reception response to determine whether the receiver that transmitted the reception response is a priority receiver or a non-priority receiver, Only the reception response sent from the priority receiver is reflected in the determination of the coding rate.
  • which receiver is the priority receiver is stored on the transmitter 101 side, and among the reception responses received from all the receivers, only the reception response of the priority receiver is considered and the encoding rate is set. It may be determined.
  • FIG. 4 is a block diagram illustrating a configuration of the transmitter 102 according to the second embodiment
  • FIG. 5 is a block diagram illustrating a configuration of the receiver 302 according to the second embodiment.
  • the same components as those of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.
  • each receiver 302 is set with a receiver identification number for uniquely identifying each receiver 302 among at least the plurality of receivers, and each receiver 302 has its own identification. The number information is retained.
  • the transmitter 102 holds information on identification numbers of a plurality of receivers that are targets of multicast distribution.
  • the user operates the transmitter 102 to specify the receiver 302 that should be the priority receiver 302a.
  • the transmitter 102 specifies the identification number of the receiver that should be the priority receiver 302a among the plurality of receivers 302 that are the targets of multicast distribution.
  • the transmitter 102 includes a priority receiver determination unit 19, a reception response permission output unit 20, and a receiver identification number request unit 21. It has.
  • the receiver identification number request unit 21 generates a receiver identification number request for requesting transmission of its own identification number held by each receiver 302. This receiver identification number request is transmitted by the transmitter 11 by multicast.
  • the receiving unit 12 receives the reception identification number transmitted by the receiver 302 in response to the receiver identification number request, and outputs it to the priority receiver determination unit 19.
  • the priority receiver determination unit 19 stores the identification number of the receiver to be designated as the priority receiver 302a specified by the user.
  • the priority receiver determination unit 19 determines whether or not the reception identification number received by the reception unit 12 is the identification number of the receiver that should be the priority receiver 302a, and outputs the result to the reception response permission output unit 20 To do.
  • the reception response permission output unit 20 When the received reception identification number is the identification number of the receiver that should be the priority receiver 302a, the reception response permission output unit 20 generates a reception response permission that permits the reception response of the receiver.
  • the transmission unit 11 transmits the reception response permission generated by the reception response permission output unit 20 by multicast.
  • the receiver 302 includes a receiver identification number request determination unit 38, a receiver identification number output unit 39, and a reception response permission determination. Part 40 is provided.
  • the decryption unit 32 decrypts the data received by the reception unit 31 and outputs the decrypted data to the receiver identification number request determination unit 38.
  • the receiver identification number request determination unit 38 determines whether the data decoded by the decoding unit 32 includes a receiver identification number request, and outputs the result to the receiver identification number output unit 39. .
  • the receiver identification number output unit 39 stores its own receiver identification number. When there is a receiver identification number request according to the determination result in the receiver identification number request determination unit 38, the receiver identification number output unit 39 causes the transmission unit 36 to transmit the stored receiver identification number.
  • the decryption unit 32 decrypts it and outputs it to the reception response permission determination unit 40.
  • the reception response permission determination unit 40 stores its own receiver identification number.
  • the reception response permission determination unit 40 determines whether or not a reception response is permitted for its own reception identification number in the received reception response permission, and outputs the result to the reception response output setting unit 37.
  • the reception response output setting unit 37 sets the reception response generation unit 35 to generate a reception response when the reception response is permitted for itself according to the determination result output from the reception response permission determination unit 40. If the reception response is not permitted for itself, the reception response generation unit 35 is set so as not to generate the reception response.
  • the multicast distribution system As described above, according to the multicast distribution system of the present embodiment, at the transmitter 102, among the plurality of receivers 302, the receiver that should be the priority receiver 302a and the reception that should be the non-priority receiver 302b. You can specify the machine.
  • the multicast distribution system according to the present embodiment is a system for grasping the situation at the disaster site, and the transmitter 102 photographs the situation at the site where the damage (damage site) occurs or the situation of lifesaving. When the camera is equipped, it can be applied as follows.
  • the monitoring device of the command headquarters or the mobile terminal of the commander is set as the priority receiver 302a, so that the video can be reliably displayed at the command headquarters or the commander. Can be confirmed, and the work procedure can be instructed from the command headquarters or the command manager.
  • the receiver 102 installed in the ambulance is designated as the priority receiver 302a in the transmitter 102 of the victim site in order to ask for an ambulance crew member's instruction. This designation is set in the priority receiver determination unit 19, and the priority receiver 302a and the non-priority receiver 302b are set as described above.
  • the priority / non-priority is dynamically dynamically assigned particularly when the multicast distribution system is used. This is useful when you want to change
  • the receiver identification numbers of all the plurality of receivers 302 included in the multicast distribution system are stored in advance in the transmitter 102, the receiver identification number request unit 21 of the transmitter 102 and the priority receiver determination
  • the configurations of the unit 19, the receiver identification number request determination unit 38 of the receiver 302, and the receiver identification number output unit 39 can be omitted.
  • 6A and 6B are diagrams showing the overall configuration of the multicast distribution system 3 of the present embodiment.
  • 6A and 6B show only one priority receiver 303a and one non-priority terminal 303b, there may be a plurality of each.
  • 6A shows a situation where the priority receiver 303a is located outside the communication range R of the transmitter 103
  • FIG. 6B shows that the priority receiver 303a is located within the communication range R of the transmitter 103. Indicates the situation.
  • FIG. 7 is a block diagram illustrating a configuration of the transmitter 103 according to the third embodiment.
  • the transmitter 103 adjusts the transmission conditions in consideration of only the communication quality of the priority receiver 303a.
  • the transmission data retransmission limit and the image quality of video data are adjusted as transmission conditions.
  • the encoding unit 14 divides and encodes video data for one frame into a plurality of sub-blocks by using a block code such as a low density parity check (Low Density Parity Check: LDPC) code.
  • the transmission packet generation unit 15 generates a transmission packet, and the transmission unit 11 transmits the transmission packet by multicast.
  • the transmitter 103 includes a transmission frame retransmission limit determination unit 22 and a sub-block retransmission limit determination unit 23 in addition to the configuration of the transmitter 101 of the first embodiment.
  • the transmission frame retransmission limit determination unit 22 determines a transmission frame retransmission limit (retransmission upper limit number) based on the reception rate of the reception response in the communication quality estimation unit 17. As shown in FIG. 6A, when the priority receiver 303a is outside the communication range R and the reception response from the priority receiver 303a is not returned, the transmission frame retransmission limit determination unit 22 and the sub-block retransmission limit determination unit 23 sets a retransmission limit smaller than normal in the transmission packet generation unit 15 so that retransmission is completed with a smaller number of retransmissions than usual.
  • the transmission packet generation unit 15 retransmits the transmission data according to the determination result of the reception response determination unit 16, and the transmission frame retransmission limit determination unit 22 or the sub-block reproduction limit determination unit 23 determines the retransmission limit at this time. And set in the transmission packet generator 15.
  • the quality estimation unit 17 determines the presence / absence of a reception response from the priority receiver 303a, and outputs the determination result to the transmission frame retransmission limit determination unit 22 and the sub-block retransmission limit determination unit 23.
  • the transmission frame retransmission limit determination unit 22 and the sub-block retransmission limit determination unit 23 have not received a reception response from the priority receiver 303a according to the determination result in the communication quality estimation unit 17, the transmission frame retransmission limit determination unit 22 Thus, the retransmission limit of the transmission frame and the retransmission limit of the sub-block are set to be small.
  • FIG. 9 is a diagram illustrating an ACK format example of a sub-block of a reception response transmitted from the receiver 303.
  • the ACK format of the subblock includes a PLCP header, a MAC header, an error determination result of each subblock from # 1 to #N, and an error correction code CRC.
  • the error determination result of each sub-block represents, for example, the presence or absence of an error with 1 bit.
  • the communication quality estimator 17 obtains the ratio of subblocks with errors among the subblocks # 1 to #N in the reception response (ACK) as the block error rate.
  • the transmitter 103 includes an image quality determination unit 24 instead of the coding rate determination unit 18 of the above embodiment.
  • the communication quality estimation unit 17 outputs the block error rate to the image quality determination unit 24.
  • the image quality determination unit 24 sets the image quality (frame rate and resolution) for generating video data to the content providing unit 13. Specifically, the image quality determination unit 24 sets the content providing unit 13 to generate video data with a lower image quality than the normal image quality when the block error rate is high.
  • the reception response (ACK) is not received from the priority receiver 303a
  • the image quality determination unit 24 sets the content providing unit 13 to generate video data with normal image quality.
  • the priority receiver 303a For a receiver that is in the dead zone (outside the communication range R of the transmitter 103) and does not receive the reception response (ACK or NACK) to the transmitter 103, it is the priority receiver 303a.
  • the retransmission limit is set small. Further, when the priority receiver 303a returns a reception response (ACK or NACK), the transmitter 103, based on the content of the reception response, the sub-block reproduction limit, the transmission frame retransmission limit, and the content providing unit 13 automatically sets the image quality of the video data generated.
  • FIG. 8 is a block diagram illustrating a configuration of the receiver 303 according to the third embodiment. As shown in FIG. 8, the receiver 303 has a configuration similar to that of the first embodiment. Similarly to the first embodiment, the receiver 303 generates a reception response in the reception response generation unit 35 only when it is set as the priority receiver 303a by the reception response output setting unit 37. The transmitter 36 transmits the data to the transmitter 103.
  • the error determination unit 33 determines the presence / absence of an error for each sub-block, and outputs the determination result to the reception response generation unit 35.
  • the reception response generated by the reception response generation unit 35 is as described above with reference to FIG.
  • the transmitter reduces the image quality due to the priority receiver that cannot expect such communication, and as a result, the receiver that can communicate is affected by the receiver that cannot expect communication and the image quality is lower than necessary. The situation where only the suppressed transmission data can be received is avoided.
  • the transmitter 103 divides transmission data for one frame into a plurality of sub-blocks by using a block code, transmits the data, and transmits a reception response for each sub-block from the receiver 303.
  • Sub-block error rate is obtained based on this, and retransmission is performed for each sub-block. Therefore, communication quality can be estimated more finely than when only frame-based retransmission is performed based on only the error rate for each frame. This is possible, and retransmission overhead can be reduced.
  • an image quality determining unit 24 is used instead of the coding rate determining unit 18 according to the first and second embodiments, and a content providing unit is used according to the estimated communication quality.
  • the coding rate is determined by employing the coding rate determining unit 18 as in the first and second embodiments, and the coding unit The encoding rate of 14 may be adjusted. In this case, the same effect as described above can be obtained.
  • the image quality determination unit 24 is used instead of the coding rate determination unit 18 as in the present embodiment.
  • the image quality of the video data generated by the content providing unit 13 may be adjusted according to the estimated communication quality.
  • FIG. 10 is a diagram illustrating an overall configuration of the multicast distribution system 4 according to the fourth embodiment.
  • the transmitter 104 adjusts the transmission conditions in consideration of only the communication quality of the priority receiver 304a.
  • transmitter 104 adjusts the retransmission limit for each frame type and the image quality of video data as transmission conditions.
  • This embodiment is effective when the priority receiver 304a is located at the edge portion of the communication range R of the transmitter 104 as shown in FIG.
  • the priority receiver 304a can communicate with the transmitter 104, but the communication quality is not good. Therefore, for example, when the transmission data is video data, the priority receiver 304a cannot reproduce high-quality video even if high-quality video data is sent.
  • the video data has better image quality as the frame rate is higher and the resolution of each frame is higher. That is, the higher the frame rate, the smoother the video, and the higher the resolution, the clearer the video.
  • the image quality improves, the amount of transmission data increases, and a receiver with poor communication quality cannot completely receive high-quality video data. In this case, by reducing the frame rate or reducing the resolution, the image quality can be lowered and the amount of transmission data can be suppressed.
  • an inter-frame encoded frame is reproduced using an intra-frame encoded frame. Therefore, as long as an intra-frame encoded frame is transmitted, the inter-frame encoded frame is transmitted reliably. This means that a smooth display of the video between the intra-frame encoded frames is ensured.
  • intra-frame encoded frames may be lost, which may prevent video from being reproduced until the next intra-frame encoded frame. As long as the frame is transmitted, a smoother image can be obtained. In this sense, giving priority to transmission of inter-frame encoded frames means giving priority to the frame rate.
  • the priority receiver 304a prioritizes resolution or frame rate.
  • a multicast distribution system that can be arbitrarily selected.
  • FIG. 11 is a block diagram illustrating a configuration of the transmitter 104 according to the fourth embodiment
  • FIG. 12 is a block diagram illustrating a configuration of the receiver 304 according to the fourth embodiment.
  • the receiver 304 is further provided with a reception response output setting unit 37 in addition to the configuration of the receiver 301 of the first embodiment.
  • the reception response output setting unit 37 sets the reception response generation unit 35 to generate a reception response in accordance with a user operation, thereby setting the receiver 304 as a priority receiver.
  • the reception response generation unit 35 When the receiver 304 is set as a priority receiver, the reception response generation unit 35 generates a reception response according to the result of error determination by the error determination unit 33.
  • the receiver 304 further includes a video parameter setting request unit 41.
  • the video parameter setting request unit 41 generates a video parameter setting request for requesting the setting of the video parameter in accordance with a user operation, and provides it to the reception response generation unit 35.
  • the reception response generation unit 35 generates a reception response including the video parameter setting request generated by the video parameter setting request unit 41.
  • the transmission unit 36 transmits the reception response generated by the reception response generation unit 35 to the transmitter 104.
  • video parameters include video resolution and frame rate.
  • the image quality of the video is determined by the resolution and the frame rate. The higher the resolution, the clearer the video, and the higher the frame rate, the smoother the video. In either case, the amount of transmitted data increases. If the resolution is to be increased with respect to the limited amount of transmission data, the frame rate must be lowered. Conversely, if the frame rate is increased, the resolution must be lowered.
  • a sufficient amount of data can be transmitted, the user can achieve a satisfactory resolution and frame rate, but if the communication quality is not good as in the situation of FIG. 10, the resolution is relatively high. It can be handled by lowering the frame rate while maintaining it, and conversely, it can be handled by lowering the resolution while keeping the frame rate relatively high, and further, both the resolution and the frame rate can be lowered appropriately. .
  • a user can arbitrarily set video parameters by operating video parameter setting request unit 41.
  • the video parameter setting request unit 41 may be capable of continuously specifying the priority of resolution or frame rate. For example, “resolution priority”, “frame rate priority”, or “resolution and frame rate are about the same”. (No priority) may be selected.
  • the priority may be expressed as a percentage, for example. For example, when the resolution is 70%, the frame rate is 30%.
  • the video parameter setting request includes information on the degree of priority.
  • the transmitter 104 further includes a video parameter setting request determination unit 25 and a frame type-specific retransmission limit determination unit 26 in addition to the configuration of the transmitter 101 of the first embodiment. .
  • the video parameter setting request determination unit 25 determines the content of the video parameter setting request included in the reception response received by the reception unit 12, and outputs the determination result to the image quality determination unit 24.
  • the communication quality estimation unit 17 estimates the communication quality with the receiver based on the reception rate of the reception response and the S / N ratio of the reception response, and outputs the estimation result to the image quality determination unit 24.
  • the image quality determination unit 24 obtains the image quality based on the estimation result by the communication quality estimation unit 17, and determines the resolution or frame rate based on the determination result obtained by the video parameter setting request determination unit 25 within the image quality range. Decide whether to give priority.
  • the image quality and resolution or frame rate priority determined by the image quality determination unit 24 are output to the content providing unit 13.
  • the content providing unit 13 generates video data at the resolution and frame rate determined by the image quality determining unit 24.
  • the communication quality estimation unit 17 may estimate the communication quality using the reception rate of the reception response as an index in addition to the S / N ratio of the reception response or instead of the S / N ratio of the reception response.
  • the transmitter 104 includes a retransmission limit determining unit 26 for each frame type.
  • the encoding unit 14 encodes the video data generated by the content providing unit 13 using an intra-frame encoded frame (I frame) and an inter-frame encoded frame (P frame or B frame).
  • the estimation result by the communication quality estimation unit 17 and the determination result by the video parameter setting request determination unit 25 are also output to the retransmission limit determination unit 26 by frame type.
  • the frame type retransmission limit determination unit 26 determines the frame type, that is, for each intra-frame encoded frame and inter-frame encoded frame. Determine retransmission limit.
  • the frame type retransmission limit determination unit 26 increases the retransmission limit of the intra-frame encoded frame and decreases the retransmission limit of the inter-frame encoded frame when priority is given to the resolution.
  • FIG. 10 shows such a situation.
  • the frame type retransmission limit determination unit 26 decreases the retransmission limit of the intra-frame encoded frame and increases the retransmission limit of the inter-frame encoded frame. By determining the retransmission limit in this way, a receiver with low communication quality may stop video during the period until the next intra-frame encoding due to the loss of the intra-frame encoded frame. If a frame can be received, a smoother video can be obtained. In addition, a receiver with high communication quality can obtain images with high resolution and frame rate.
  • the present embodiment it is possible to set the image quality of the video received by the priority receiver according to the user's request while ensuring the real-time property.
  • the multicast distribution system can automatically adjust the optimum transmission condition for the receiver group in accordance with the communication quality of the transmission path when the transmission data is wirelessly distributed to a plurality of receivers. It is useful as a multicast distribution system or the like that adjusts transmission conditions (encoding rate, image quality, retransmission limit, etc.) of transmission data according to wireless communication quality.

Abstract

Provided is a multicast delivery system capable of automatically performing adjustments of transmission conditions depending upon the quality of wireless communication. In a multicast delivery system (1) for multicast- delivering transmission data from a transmitter (101) to a plurality of receivers (301) including a priority receiver (301a) and a non-priority receiver (301b), the priority receiver (301a) is provided with a received response generation unit (35) for generating a received response for transmission data received from the transmitter (101), and a received response transmission unit (36) for transmitting the received response to the transmitter (101). The transmitter (101) is provided with a communication quality estimation unit (17) for estimating communication quality on the basis of received responses transmitted from the priority receiver (301a), an encoding rate determination unit (18) for determining the encoding rate for transmission data on the basis of the communication quality of the priority receiver (301a) as estimated at the communication quality estimation unit (17), and a transmission data transmitting unit (11) for transmitting the encoded transmission data.

Description

マルチキャスト配信システム、並びにそれに用いる送信機及び受信機Multicast distribution system and transmitter and receiver used therefor 関連する出願Related applications
本出願では、２０１０年９月２２日に日本国に出願された特許出願番号２０１０－２１１５６０の利益を主張し、当該出願の内容は引用することによりここに組み込まれているものとする。 This application claims the benefit of Patent Application No. 2010-2111560 filed in Japan on September 22, 2010, the contents of which are incorporated herein by reference.
　本発明は、無線通信品質に応じて伝送データの伝送条件（符号化レート、画質、再送リミット等）を調整するマルチキャスト配信システムに関するものである。 The present invention relates to a multicast distribution system that adjusts transmission conditions (encoding rate, image quality, retransmission limit, etc.) of transmission data according to wireless communication quality.
　従来から、伝送路の通信品質に応じて、送信側にて伝送データの符号化レートを調整する送受信システムが知られている（例えば特許文献１参照）。この伝送システムでは、送信機（無線通信装置）が、カメラで撮影した画像を、指示された品質の画像データに符号化する画像符号化部と、符号化された画像を無線通信により受信側装置へ送信する無線通信部と、無線通信の通信品質（具体的には、ＡＣＫおよびＮＡＣＫの応答比率やＳ／Ｎ比等）に応じて、画像符号化部にて符号化する画像の品質を決定する画像品質決定部と、決定された品質による画像の符号化を画像符号化部に指示する画像品質指示部とを備えている。 Conventionally, a transmission / reception system that adjusts the encoding rate of transmission data on the transmission side according to the communication quality of the transmission path is known (see, for example, Patent Document 1). In this transmission system, a transmitter (wireless communication device) encodes an image captured by a camera into image data of an instructed quality, and a reception side device through wireless communication of the encoded image. The quality of the image to be encoded by the image encoding unit is determined according to the wireless communication unit to be transmitted to and the communication quality of the wireless communication (specifically, the response ratio and S / N ratio of ACK and NACK, etc.) And an image quality instruction unit for instructing the image encoding unit to encode an image with the determined quality.
　この無線通信装置によれば、無線通信の通信品質に応じて画像符号化部における符号化レートが決定されるので、通信品質が悪化した場合にも最適な品質で再生可能な画像データを送信できる。 According to this wireless communication apparatus, since the encoding rate in the image encoding unit is determined according to the communication quality of wireless communication, it is possible to transmit image data that can be reproduced with optimum quality even when the communication quality deteriorates .
特開２００５－１４２７３５号公報JP 2005-142735 A
　しかしながら、上記従来の伝送システムは、一対一の通信への適用を前提としたものである。従って、このシステムを、送信機が伝送データを複数の受信機に同時に伝送（配信）するマルチキャスト配信システムに適用した場合には、通信品質が非常に悪い受信機が１つ存在するだけで、すべての受信機に対して、低い符号化レートが設定されてしまうという問題があった。 However, the conventional transmission system is premised on application to one-to-one communication. Therefore, when this system is applied to a multicast distribution system in which a transmitter transmits (distributes) transmission data to a plurality of receivers at the same time, there is only one receiver with very poor communication quality. However, there is a problem that a low encoding rate is set for the receiver.
　また、映像データは、単位時間当たりのフレーム数であるフレームレートが多いほど、また、各フレームの解像度が高いほど、受信機で再生される際の品質が高くなるが、上記従来の伝送システムでは、所定の符号化レート下でフレームレートと解像度の何れを優先するかを選択することができないという問題があった。 In addition, the higher the frame rate, which is the number of frames per unit time, and the higher the resolution of each frame, the higher the quality of video data when it is played back by the receiver. There is a problem that it is impossible to select which of the frame rate and the resolution is given priority under a predetermined encoding rate.
　本発明は、上記従来の問題を解決するためになされたもので、マルチキャスト配信システムにおいて、無線通信品質に応じて自動で伝送条件の調整を行うことができるマルチキャスト配信システムを提供することを目的とする。また、本発明の他の目的は、無線通信品質に応じて自動で伝送条件の調整を行う際に、フレームレートおよび解像度の何れを優先するかを指定できるマルチキャスト配信システムを提供することである。 The present invention has been made to solve the above-described conventional problems, and an object of the present invention is to provide a multicast distribution system capable of automatically adjusting transmission conditions according to wireless communication quality in the multicast distribution system. To do. Another object of the present invention is to provide a multicast distribution system that can specify which of the frame rate and the resolution is prioritized when automatically adjusting the transmission conditions according to the wireless communication quality.
　本発明のマルチキャスト配信システムは、送信機と複数の受信機とを含み、送信機から複数の受信機に伝送データをマルチキャスト配信するマルチキャスト配信システムである。複数の受信機のうちの一部は優先受信機であり、その他は非優先受信機である。優先受信機は、送信機から受信した伝送データに対する受信応答を生成する受信応答生成部と、受信応答生成部にて生成された受信応答を送信機に送信する受信応答送信部とを備えた構成を有している。送信機は、優先受信機から送信されてきた受信応答に基づいて、当該優先受信機の通信品質を推定する通信品質推定部と、通信品質推定部にて推定された優先受信機の通信品質に基づいて伝送データの伝送条件を決定する伝送条件決定部と、伝送データを送信する伝送データ送信部とを備えた構成を有している。 The multicast distribution system of the present invention is a multicast distribution system that includes a transmitter and a plurality of receivers, and multicasts transmission data from the transmitter to the plurality of receivers. Some of the plurality of receivers are priority receivers, and others are non-priority receivers. The priority receiver includes a reception response generation unit that generates a reception response to the transmission data received from the transmitter, and a reception response transmission unit that transmits the reception response generated by the reception response generation unit to the transmitter. have. Based on the reception response transmitted from the priority receiver, the transmitter estimates the communication quality of the priority receiver and the communication quality of the priority receiver estimated by the communication quality estimation unit. A transmission condition determining unit that determines a transmission condition of transmission data based on the transmission data and a transmission data transmitting unit that transmits the transmission data are included.
　本発明のマルチキャスト配信システムにおいて、好ましくは、送信機は、伝送データを符号化する符号化部を備え、伝送条件決定部は、伝送条件として符号化部における符号化レートを決定して符号化部に設定する符号化レート決定部であり、符号化レート決定部は、優先受信機の通信品質が良好でないときに、通信品質が良好であるときよりも低い符号化レートを設定する。 In the multicast distribution system of the present invention, preferably, the transmitter includes an encoding unit that encodes transmission data, and the transmission condition determining unit determines an encoding rate in the encoding unit as a transmission condition, and encodes the encoding unit. The coding rate determination unit sets a lower coding rate than when the communication quality is good when the communication quality of the priority receiver is not good.
　本発明のマルチキャスト配信システムにおいて、好ましくは、送信機は、伝送データとして映像データを生成するビデオ撮影部を備え、伝送条件決定部は、伝送条件としてビデオ撮影部における画質を決定してビデオ撮影部に設定する画質決定部であり、画質決定部は、優先受信機の通信品質が良好でないときに、通信品質が良好であるときよりも低い画質を設定する。 In the multicast distribution system of the present invention, preferably, the transmitter includes a video photographing unit that generates video data as transmission data, and the transmission condition determining unit determines the image quality in the video photographing unit as the transmission condition, and the video photographing unit The image quality determination unit sets a lower image quality when the communication quality of the priority receiver is not good than when the communication quality is good.
　本発明のマルチキャスト配信システムにおいて、好ましくは、送信機は、優先受信機からの受信応答の受信状況に基づいて、伝送データを再送する再送信部を備え、伝送条件決定部は、伝送条件として再送信部における再送上限回数を決定して再送信部に設定する再送リミット決定部であり、再送リミット決定部は、優先受信機から受信応答を受信しないときに、受信応答を受信したときよりも小さい再送上限回数を設定する。 In the multicast distribution system of the present invention, preferably, the transmitter includes a retransmission unit that retransmits the transmission data based on the reception status of the reception response from the priority receiver, and the transmission condition determination unit retransmits the transmission condition as a transmission condition. A retransmission limit determination unit that determines the maximum number of retransmissions in the transmission unit and sets the retransmission limit in the retransmission unit. The retransmission limit determination unit is smaller than when the reception response is received when no reception response is received from the priority receiver. Set the maximum number of retransmissions.
　本発明のマルチキャスト配信システムにおいて、好ましくは、送信機は、１フレーム分の伝送データを複数のサブブロックに分けて符号化する符号化部を備え、再送リミット決定部は、伝送条件として再送信部におけるフレーム単位の再送上限回数を決定して再送信部に設定するフレーム再送リミット決定部及び伝送条件として再送信部におけるサブブロック単位の再送上限回数を決定して再送信部に設定するサブブロック再送リミット決定部を含み、フレーム再送リミット決定部及びサブブロック再送リミット決定部は、それぞれ優先受信機から受信応答を受信しないときに、受信応答を受信したときよりも小さい再送上限回数を設定する。 In the multicast distribution system of the present invention, preferably, the transmitter includes an encoding unit that encodes transmission data for one frame divided into a plurality of sub-blocks, and the retransmission limit determination unit is a retransmission unit as a transmission condition. The frame retransmission limit determination unit that determines the upper limit number of retransmissions in units of frames and sets it in the retransmission unit, and the sub-block retransmission that determines the upper limit number of retransmissions in subblocks in the retransmission unit as transmission conditions and sets in the retransmission unit The frame retransmission limit determination unit and the sub-block retransmission limit determination unit each include a limit determination unit, and set a smaller number of retransmission upper limits than when the reception response is received when the reception response is not received from the priority receiver.
　本発明のマルチキャスト配信システムにおいて、好ましくは、通信品質推定部は、受信応答に含まれるサブブロック誤り率に基づいて、優先受信機の通信品質を推定する。 In the multicast distribution system of the present invention, preferably, the communication quality estimation unit estimates the communication quality of the priority receiver based on the sub-block error rate included in the reception response.
　本発明のマルチキャスト配信システムにおいて、好ましくは、優先受信機は、映像の解像度およびフレームレートの何れを優先するかを示す映像パラメータ設定要求を生成する映像パラメータ設定要求部と、映像パラメータ設定要求を送信する映像パラメータ設定要求送信部とをさらに備え、送信機は、伝送データとして映像データを生成するビデオ撮影部と、映像データをフレーム内符号化フレーム及びフレーム間符号化フレームを用いて符号化する符号化部と、優先受信機より受信した映像パラメータ設定要求に基づいて、映像の解像度およびフレームレートの何れを優先するかを判定する映像パラメータ設定要求判定部とをさらに備え、伝送条件決定部は、伝送条件として再送信部における再送上限回数をフレームタイプ別に決定して再送信部に設定するフレームタイプ別再送リミット決定部であり、フレームタイプ別再送リミット決定部は、映像パラメータ設定要求判定部にて解像度を優先すると判定したときに、フレーム内符号化フレームの再送上限回数をフレーム間符号化フレームの再送上限回数よりも大きく設定する。 In the multicast distribution system of the present invention, preferably, the priority receiver transmits a video parameter setting request and a video parameter setting request unit for generating a video parameter setting request indicating which of the video resolution and frame rate is to be prioritized. A video parameter setting request transmitting unit that transmits video data as transmission data, and a code that encodes the video data using an intra-frame encoded frame and an inter-frame encoded frame. And a video parameter setting request determination unit that determines which of the video resolution and frame rate is prioritized based on the video parameter setting request received from the priority receiver, and the transmission condition determination unit includes: As a transmission condition, determine the maximum number of retransmissions in the retransmission unit for each frame type. This is a retransmission limit determining unit for each frame type set in the retransmission unit, and the retransmission limit determining unit for each frame type determines the retransmission upper limit of the intra-frame encoded frame when the video parameter setting request determining unit determines to give priority to resolution. The number of times is set larger than the upper limit number of retransmissions of the inter-frame encoded frame.
　本発明のマルチキャスト配信システムにおいて、好ましくは、複数の受信機のうちの優先受信機及び非優先受信機のいずれもが、受信応答生成部と、受信応答を生成するか否かを受信応答生成部に設定する受信応答出力設定部とを備え、複数の受信機のうちの優先受信機となるべき受信機の受信応答出力設定部は、受信応答を生成するよう受信応答生成部に設定をし、非優先受信機となるべき受信機の受信応答出力設定部は、受信応答を生成しないよう受信応答生成部に設定をする。 In the multicast distribution system of the present invention, it is preferable that a priority response receiver and a non-priority receiver among a plurality of receivers generate a reception response generation unit and whether or not a reception response is generated. And a reception response output setting unit to be set, and a reception response output setting unit of a receiver to be a priority receiver among a plurality of receivers sets the reception response generation unit to generate a reception response, The reception response output setting unit of the receiver to be a non-priority receiver sets the reception response generation unit so as not to generate a reception response.
　本発明のマルチキャスト配信システムにおいて、好ましくは、受信応答出力設定部は、ユーザの操作に応じて受信応答を生成するか否かを受信応答生成部に設定する。 In the multicast distribution system of the present invention, preferably, the reception response output setting unit sets in the reception response generation unit whether or not to generate a reception response in accordance with a user operation.
　本発明のマルチキャスト配信システムにおいて、好ましくは、送信機は、複数の受信機のうちの優先受信機の受信応答を許可する受信応答許可を出力する受信応答許可出力部をさらに備え、受信応答出力設定部は、受信応答許可にて自らが優先受信機として受信応答を許可されている場合に、受信応答を生成するよう受信応答生成部に設定し、自己に対して受信応答の許可がされていない場合は、受信応答を生成しないよう受信応答生成部に設定する。 In the multicast distribution system of the present invention, preferably, the transmitter further includes a reception response permission output unit that outputs a reception response permission that permits a reception response of a priority receiver among a plurality of receivers, and a reception response output setting is made. The unit sets the reception response generation unit to generate a reception response when the reception response is permitted as a priority receiver in the reception response permission, and the reception response is not permitted to itself. In this case, the reception response generator is set not to generate a reception response.
　本発明のマルチキャスト配信システムにおいて、好ましくは、送信機は、複数の受信機が各々保持している自己の識別番号を送信するよう要求する受信機識別番号要求部と、複数の受信機のうちの優先受信機とすべき受信機の識別番号が記憶されており、受信機識別番号要求部による要求に応じて複数の受信機の各々から送信された受信識別番号を受信して、優先受信機とすべき受信機を判定する優先受信機判定部とをさらに備え、受信応答許可出力部は、優先受信機判定部にて優先受信機とすべきと認定された受信機に対して受信応答を許可する受信応答許可を出力する。 In the multicast distribution system of the present invention, preferably, the transmitter includes a receiver identification number requesting unit that requests transmission of its own identification number held by each of the plurality of receivers, and a plurality of receivers. An identification number of a receiver to be a priority receiver is stored, and a reception identification number transmitted from each of a plurality of receivers is received in response to a request from the receiver identification number request unit, A priority receiver determination unit that determines a receiver to be received, and the reception response permission output unit permits a reception response to a receiver that is determined to be a priority receiver by the priority receiver determination unit. The reception response permission is output.
　本発明の別の態様は、上記のマルチキャスト配信システムを構成する送信機であり、更に別の態様は、上記のマルチキャスト配信システムを構成する受信機である。 Another aspect of the present invention is a transmitter that constitutes the above multicast distribution system, and yet another aspect is a receiver that constitutes the above multicast distribution system.
　本発明は、複数の受信機に伝送データを無線でマルチキャスト配信する際に、伝送路の通信品質に合わせて受信機群に最適な伝送条件を自動調整できるという効果を有するマルチキャスト配信システムを提供することができるものである。 The present invention provides a multicast distribution system having an effect of automatically adjusting transmission conditions optimum for a group of receivers according to the communication quality of a transmission path when multicasting transmission data to a plurality of receivers wirelessly. It is something that can be done.
以下に説明するように、本発明には他の態様が存在する。したがって、この発明の開示は、本発明の一部の提供を意図しており、ここで記述され請求される発明の範囲を制限することは意図していない。 As described below, there are other aspects of the present invention. Accordingly, the disclosure of the present invention is intended to provide part of the invention and is not intended to limit the scope of the invention described and claimed herein.
図１は、本発明の第１の実施の形態におけるマルチキャスト配信システムの全体構成を示す図FIG. 1 is a diagram showing an overall configuration of a multicast distribution system according to a first embodiment of the present invention. 図２は、本発明の第１の実施の形態における送信機の構成を示すブロック図FIG. 2 is a block diagram showing the configuration of the transmitter according to the first embodiment of the present invention. 図３Ａは、本発明の第１の実施の形態における優先受信機の構成を示すブロック図FIG. 3A is a block diagram showing a configuration of a priority receiver in the first exemplary embodiment of the present invention. 図３Ｂは、本発明の第１の実施の形態における非優先受信機の構成を示すブロック図FIG. 3B is a block diagram showing the configuration of the non-priority receiver in the first embodiment of the present invention. 図３Ｃは、本発明の第１の実施の形態における受信機の構成を示すブロック図FIG. 3C is a block diagram showing the configuration of the receiver according to the first embodiment of the present invention. 図４は、本発明の第２の実施の形態における送信機の構成を示すブロック図FIG. 4 is a block diagram showing a configuration of a transmitter according to the second embodiment of the present invention. 図５は、本発明の第２の実施の形態における受信機の構成を示すブロック図FIG. 5 is a block diagram showing a configuration of a receiver according to the second embodiment of the present invention. 図６Ａは、本発明の第３の実施の形態におけるマルチキャスト配信システムの全体構成を示す図FIG. 6A is a diagram showing an overall configuration of a multicast distribution system according to the third embodiment of the present invention. 図６Ｂは、本発明の第３の実施の形態におけるマルチキャスト配信システムの全体構成を示す図FIG. 6B is a diagram showing an overall configuration of a multicast distribution system according to the third embodiment of the present invention. 図７は、本発明の第３の実施の形態における送信機の構成を示すブロック図FIG. 7 is a block diagram showing a configuration of a transmitter according to the third embodiment of the present invention. 図８は、本発明の第３の実施の形態におけるサブブロック受信応答のフォーマット例を示す図FIG. 8 is a diagram illustrating a format example of a sub-block reception response according to the third embodiment of the present invention. 図９は、本発明の第３の実施の形態における受信機の構成を示すブロック図FIG. 9 is a block diagram showing a configuration of a receiver according to the third embodiment of the present invention. 図１０は、本発明の第４の実施の形態におけるマルチキャスト配信システムの全体構成を示す図FIG. 10 is a diagram showing an overall configuration of a multicast distribution system according to the fourth embodiment of the present invention. 図１１は、本発明の第４の実施の形態における送信機の構成を示すブロック図FIG. 11 is a block diagram showing a configuration of a transmitter according to the fourth embodiment of the present invention. 図１２は、本発明の第４の実施の形態における受信機の構成を示すブロック図FIG. 12 is a block diagram showing a configuration of a receiver according to the fourth embodiment of the present invention.
　以下に、本発明の詳細な説明を述べる。以下に説明する実施の形態は本発明の単なる例であり、本発明は様々な態様に変形することができる。従って、以下に開示する特定の構成および機能は、特許請求の範囲を限定するものではない。 The detailed description of the present invention will be described below. The embodiments described below are merely examples of the present invention, and the present invention can be modified in various ways. Accordingly, the specific configurations and functions disclosed below do not limit the scope of the claims.
　本発明の実施の形態のマルチキャスト配信システムは、送信機と複数の受信機とを含み、送信機から複数の受信機に伝送データをマルチキャスト配信するマルチキャスト配信システムである。複数の受信機のうちの一部は優先受信機であり、その他は非優先受信機である。優先受信機は、送信機から受信した伝送データに対する受信応答を生成する受信応答生成部と、受信応答生成部にて生成された受信応答を送信機に送信する受信応答送信部とを備えた構成を有している。送信機は、優先受信機から送信されてきた受信応答に基づいて、当該優先受信機の通信品質を推定する通信品質推定部と、通信品質推定部にて推定された優先受信機の通信品質に基づいて伝送データの伝送条件を決定する伝送条件決定部と、伝送データを送信する伝送データ送信部とを備えた構成を有している。 The multicast distribution system according to the embodiment of the present invention is a multicast distribution system that includes a transmitter and a plurality of receivers, and multicasts transmission data from the transmitter to the plurality of receivers. Some of the plurality of receivers are priority receivers, and others are non-priority receivers. The priority receiver includes a reception response generation unit that generates a reception response to the transmission data received from the transmitter, and a reception response transmission unit that transmits the reception response generated by the reception response generation unit to the transmitter. have. Based on the reception response transmitted from the priority receiver, the transmitter estimates the communication quality of the priority receiver and the communication quality of the priority receiver estimated by the communication quality estimation unit. A transmission condition determining unit that determines a transmission condition of transmission data based on the transmission data and a transmission data transmitting unit that transmits the transmission data are included.
　この構成により、送信機では優先受信機の通信品質のみを考慮して伝送データの伝送条件を決定するので、非優先受信機の通信品質が悪いことに影響されて通信品質が良好な優先受信機に悪い伝送条件で伝送データが伝送されることを回避できる。 With this configuration, since the transmitter determines the transmission condition of the transmission data considering only the communication quality of the priority receiver, the priority receiver with good communication quality is affected by the poor communication quality of the non-priority receiver. It is possible to avoid transmission of transmission data under poor transmission conditions.
　本発明の実施の形態のマルチキャスト配信システムにおいて、好ましくは、送信機は、伝送データを符号化する符号化部を備え、伝送条件決定部は、伝送条件として符号化部における符号化レートを決定して符号化部に設定する符号化レート決定部であり、符号化レート決定部は、優先受信機の通信品質が良好でないときに、通信品質が良好であるときよりも低い符号化レートを設定する。 In the multicast distribution system according to the embodiment of the present invention, preferably, the transmitter includes an encoding unit that encodes transmission data, and the transmission condition determining unit determines an encoding rate in the encoding unit as a transmission condition. The coding rate determination unit sets a lower coding rate than when the communication quality is good when the communication quality of the priority receiver is not good. .
　この構成により、受信機の通信品質が良好でないときは、符号化レートを低くして（誤り検出や誤り訂正のためのデータ量を多くして）符号化を行うので、受信機側にてより確実に伝送データを再生できる。しかも、上述のように、このような符号化レートの調整を優先受信機の通信品質のみを考慮して（非優先受信機の通信品質は無視して）行うので、優先受信機の通信品質が良好であれば、非優先受信機の通信品質が悪いとしてもそれを理由として符号化レートが低く設定されることはない。 With this configuration, when the communication quality of the receiver is not good, the encoding rate is lowered (the amount of data for error detection and error correction is increased), so that encoding is performed on the receiver side. Transmission data can be reliably reproduced. In addition, as described above, such adjustment of the coding rate is performed considering only the communication quality of the priority receiver (ignoring the communication quality of the non-priority receiver), so that the communication quality of the priority receiver is reduced. If it is good, even if the communication quality of the non-priority receiver is poor, the coding rate is not set low for that reason.
　本発明の実施の形態のマルチキャスト配信システムにおいて、好ましくは、送信機は、伝送データとして映像データを生成するビデオ撮影部を備え、伝送条件決定部は、伝送条件としてビデオ撮影部における画質を決定してビデオ撮影部に設定する画質決定部であり、画質決定部は、優先受信機の通信品質が良好でないときに、通信品質が良好であるときよりも低い画質を設定する。 In the multicast distribution system according to the embodiment of the present invention, preferably, the transmitter includes a video photographing unit that generates video data as transmission data, and the transmission condition determining unit determines the image quality in the video photographing unit as the transmission condition. The image quality determining unit sets the image quality lower than when the communication quality is good when the communication quality of the priority receiver is not good.
　この構成により、受信機の通信品質が良好でないときは、ビデオ撮影部にて画質を低くして（フレームレートを下げる、及び／又は解像度を下げる）映像データを生成するので、受信機側では、より確実に伝送データを再生できる。しかも、上述のように、このような画質の調整を優先受信機の通信品質のみを考慮して（非優先受信機の通信品質は無視して）行うので、優先受信機の通信品質が良好であれば、非優先受信機の通信品質が悪いとしてもそれを理由として画質が低く設定されることはない。 With this configuration, when the communication quality of the receiver is not good, the video shooting unit lowers the image quality (lowers the frame rate and / or lowers the resolution) and generates video data. Transmission data can be reproduced more reliably. In addition, as described above, since the image quality adjustment is performed considering only the communication quality of the priority receiver (ignoring the communication quality of the non-priority receiver), the communication quality of the priority receiver is good. If so, even if the communication quality of the non-priority receiver is poor, the image quality is not set low for that reason.
　本発明の実施の形態のマルチキャスト配信システムにおいて、好ましくは、送信機は、優先受信機からの受信応答の受信状況に基づいて、伝送データを再送する再送信部を備え、伝送条件決定部は、伝送条件として再送信部における再送上限回数を決定して再送信部に設定する再送リミット決定部であり、再送リミット決定部は、優先受信機から受信応答を受信しないときに、受信応答を受信したときよりも小さい再送上限回数を設定する。 In the multicast distribution system according to the embodiment of the present invention, preferably, the transmitter includes a retransmission unit that retransmits transmission data based on the reception status of the reception response from the priority receiver, and the transmission condition determination unit includes: A retransmission limit determination unit that determines the upper limit number of retransmissions in the retransmission unit as a transmission condition and sets the retransmission limit in the retransmission unit. The retransmission limit determination unit receives a reception response when no reception response is received from the priority receiver. Set a smaller number of retransmission upper limit times.
　この構成により、優先受信機の通信品質が良好でないときは、再送上限回数を少なく設定して未受信の伝送データを再送するので、受信できる見込みの無い優先受信機に多数回の再送を行うことが避けられる。しかも、上述のように、このような再送上限回数の調整を優先受信機の通信品質のみを考慮して（非優先受信機の通信品質は無視して）行うので、優先受信機の通信品質が良好であれば、非優先受信機が通信範囲外にいる等の理由で通信できない状況にあったとしてもそれを理由として再送上限回数が少なく設定されることはない。 With this configuration, when the communication quality of the priority receiver is not good, the retransmission upper limit count is set to a small value and unreceived transmission data is retransmitted. Can be avoided. In addition, as described above, since the adjustment of the number of retransmission upper limits is performed considering only the communication quality of the priority receiver (ignoring the communication quality of the non-priority receiver), the communication quality of the priority receiver is reduced. If it is satisfactory, even if the non-priority receiver is out of the communication range and cannot communicate, the upper limit number of retransmissions is not set low.
　本発明の実施の形態のマルチキャスト配信システムにおいて、好ましくは、送信機は、１フレーム分の伝送データを複数のサブブロックに分けて符号化する符号化部を備え、再送リミット決定部は、伝送条件として再送信部におけるフレーム単位の再送上限回数を決定して再送信部に設定するフレーム再送リミット決定部及び伝送条件として再送信部におけるサブブロック単位の再送上限回数を決定して再送信部に設定するサブブロック再送リミット決定部を含み、フレーム再送リミット決定部及びサブブロック再送リミット決定部は、それぞれ優先受信機から受信応答を受信しないときに、受信応答を受信したときよりも小さい再送上限回数を設定する。 In the multicast distribution system according to the embodiment of the present invention, preferably, the transmitter includes an encoding unit that encodes transmission data for one frame divided into a plurality of sub-blocks, and the retransmission limit determination unit includes transmission conditions. As the frame retransmission limit determination unit for determining the upper limit number of retransmissions for each frame in the retransmission unit and setting it in the retransmission unit, and as the transmission condition, determining the upper limit number of retransmissions for each subblock in the retransmission unit and setting it in the retransmission unit A sub-block retransmission limit determination unit, and each of the frame retransmission limit determination unit and the sub-block retransmission limit determination unit has a smaller number of retransmission upper limits than when the reception response is received when the reception response is not received from the priority receiver. Set.
　この構成により、優先受信機の通信品質が良好でないときは、再送上限回数を少なく設定して未受信の伝送データを再送するので、受信できる見込みの無い優先受信機に多数回の再送を行うことが避けられる。しかも、上述のように、このような再送上限回数の調整を優先受信機の通信品質のみを考慮して（非優先受信機の通信品質は無視して）行うので、優先受信機の通信品質が良好であれば、非優先受信機が通信範囲外にいる等の理由で通信できない状況にあったとしてそれを理由として再送上限回数が少なく設定されることはない。さらに、符号化部が１フレーム分の伝送データを複数のサブブロックに分けて符号化し、サブブロック再送リミット決定部がサブブロック単位の再送上限回数を再送信部に設定するので、単にフレーム単位で再送を行う場合と比較して、再送オーバーヘッドが少なくて済む。 With this configuration, when the communication quality of the priority receiver is not good, the retransmission upper limit count is set to a small value and unreceived transmission data is retransmitted. Can be avoided. In addition, as described above, since the adjustment of the number of retransmission upper limits is performed considering only the communication quality of the priority receiver (ignoring the communication quality of the non-priority receiver), the communication quality of the priority receiver is reduced. If it is good, it is assumed that the non-priority receiver is out of the communication range and communication is not possible because it is out of the communication range. Furthermore, the encoding unit divides the transmission data for one frame into a plurality of sub-blocks, and the sub-block retransmission limit determination unit sets the retransmission upper limit number of sub-blocks in the retransmission unit. Compared with the case of performing retransmission, the retransmission overhead can be reduced.
　本発明の実施の形態のマルチキャスト配信システムにおいて、好ましくは、通信品質推定部は、受信応答に含まれるサブブロック誤り率に基づいて、優先受信機の通信品質を推定する。この構成により、通信品質をより細かく推定することが可能となる。 In the multicast distribution system according to the embodiment of the present invention, the communication quality estimation unit preferably estimates the communication quality of the priority receiver based on the sub-block error rate included in the reception response. With this configuration, it is possible to estimate the communication quality more precisely.
　本発明の実施の形態のマルチキャスト配信システムにおいて、好ましくは、優先受信機は、映像の解像度およびフレームレートの何れを優先するかを示す映像パラメータ設定要求を生成する映像パラメータ設定要求部と、映像パラメータ設定要求を送信する映像パラメータ設定要求送信部とをさらに備え、送信機は、伝送データとして映像データを生成するビデオ撮影部と、映像データをフレーム内符号化フレーム及びフレーム間符号化フレームを用いて符号化する符号化部と、優先受信機より受信した映像パラメータ設定要求に基づいて、映像の解像度およびフレームレートの何れを優先するかを判定する映像パラメータ設定要求判定部とをさらに備え、伝送条件決定部は、伝送条件として再送信部における再送上限回数をフレームタイプ別に決定して再送信部に設定するフレームタイプ別再送リミット決定部であり、フレームタイプ別再送リミット決定部は、映像パラメータ設定要求判定部にて解像度を優先すると判定したときに、フレーム内符号化フレームの再送上限回数をフレーム間符号化フレームの再送上限回数よりも大きく設定する。 In the multicast distribution system according to the embodiment of the present invention, preferably, the priority receiver includes a video parameter setting request unit that generates a video parameter setting request indicating which of the video resolution and the frame rate has priority, and a video parameter. A video parameter setting request transmission unit for transmitting the setting request, and the transmitter uses a video photographing unit for generating video data as transmission data, and uses the intra-frame encoded frame and the inter-frame encoded frame for the video data. An encoding unit for encoding, and a video parameter setting request determination unit that determines which of the video resolution and the frame rate is to be prioritized based on the video parameter setting request received from the priority receiver. The decision unit sets the upper limit number of retransmissions in the retransmission unit as a transmission condition in the frame type. A frame type retransmission limit determination unit that is determined separately and set in the retransmission unit. The frame type retransmission limit determination unit performs intra-frame encoding when the video parameter setting request determination unit determines that priority is given to resolution. The upper limit number of retransmissions of frames is set larger than the upper limit number of retransmissions of inter-coded frames.
　この構成により、フレーム内符号化フレームの再送上限回数をフレーム間符号化フレームの再送上限回数よりも大きく設定することで、フレーム間符号化フレームが抜けて映像が乱れる可能性は比較的高くなるものの、フレーム内符号化フレームの周期では解像度の高い映像が得られる可能性が高くなり、解像度優先という映像パラメータ設定要求を実現できる。 With this configuration, although the upper limit number of retransmissions of intra-frame encoded frames is set to be larger than the upper limit number of retransmissions of inter-frame encoded frames, the possibility that the inter-coded frames are lost and the video is disturbed is relatively high. In the period of the intra-coded frame, there is a high possibility that a high-resolution video can be obtained, and a video parameter setting request that gives priority to resolution can be realized.
　本発明の実施の形態のマルチキャスト配信システムにおいて、好ましくは、複数の受信機のうちの優先受信機及び非優先受信機のいずれもが、受信応答生成部と、受信応答を生成するか否かを受信応答生成部に設定する受信応答出力設定部とを備え、複数の受信機のうちの優先受信機となるべき受信機の受信応答出力設定部は、受信応答を生成するよう受信応答生成部に設定をし、非優先受信機となるべき受信機の受信応答出力設定部は、受信応答を生成しないよう受信応答生成部に設定をする。 In the multicast distribution system according to the embodiment of the present invention, preferably, a priority receiver and a non-priority receiver among a plurality of receivers generate a reception response generation unit and whether or not to generate a reception response. A reception response output setting unit to be set in the reception response generation unit, and the reception response output setting unit of the receiver that should be a priority receiver among the plurality of receivers, in the reception response generation unit to generate a reception response The reception response output setting unit of the receiver to be set and to become a non-priority receiver sets the reception response generation unit so as not to generate a reception response.
　この構成により、複数の受信機の各々は、製造された時点ではそれが優先受信機であるか非優先受信機であるかは特定されておらず、使用の過程で、個々の受信機について、それを優先受信機として利用するか非優先受信機として利用するかを任意に設定できる。 With this configuration, each of the plurality of receivers is not specified whether it is a priority receiver or a non-priority receiver at the time of manufacture, and in the course of use, for each individual receiver, Whether it is used as a priority receiver or a non-priority receiver can be arbitrarily set.
　本発明の実施の形態のマルチキャスト配信システムにおいて、好ましくは、受信応答出力設定部は、ユーザの操作に応じて受信応答を生成するか否かを受信応答生成部に設定する。 In the multicast distribution system according to the embodiment of the present invention, preferably, the reception response output setting unit sets whether or not to generate a reception response in response to a user operation in the reception response generation unit.
　この構成により、個々の受信機について、ユーザが、それを優先受信機として利用するか非優先受信機として利用するかを任意に設定できる。 With this configuration, the user can arbitrarily set whether to use each receiver as a priority receiver or a non-priority receiver.
　本発明の実施の形態のマルチキャスト配信システムにおいて、好ましくは、送信機は、複数の受信機のうちの優先受信機の受信応答を許可する受信応答許可を出力する受信応答許可出力部をさらに備え、受信応答出力設定部は、受信応答許可にて自らが優先受信機として受信応答を許可されている場合に、受信応答を生成するよう受信応答生成部に設定し、自己に対して受信応答の許可がされていない場合は、受信応答を生成しないよう受信応答生成部に設定する。 In the multicast distribution system according to the embodiment of the present invention, preferably, the transmitter further includes a reception response permission output unit that outputs a reception response permission that permits a reception response of a priority receiver among a plurality of receivers, The reception response output setting unit sets the reception response generation unit to generate a reception response when the reception response is permitted as a priority receiver by the reception response permission, and permits the reception response to itself. If not, the reception response generation unit is set not to generate a reception response.
　この構成により、送信機側で、複数の受信機のいずれを優先受信機として利用し、いずれを非優先受信機として利用するかを任意に設定できる。 This configuration allows the transmitter to arbitrarily set which of a plurality of receivers is used as a priority receiver and which is used as a non-priority receiver.
　本発明の実施の形態のマルチキャスト配信システムにおいて、好ましくは、送信機は、複数の受信機が各々保持している自己の識別番号を送信するよう要求する受信機識別番号要求部と、複数の受信機のうちの優先受信機とすべき受信機の識別番号が記憶されており、受信機識別番号要求部による要求に応じて複数の受信機の各々から送信された受信識別番号を受信して、優先受信機とすべき受信機を判定する優先受信機判定部とをさらに備え、受信応答許可出力部は、優先受信機判定部にて優先受信機とすべきと認定された受信機に対して受信応答を許可する受信応答許可を出力する。 In the multicast distribution system according to the embodiment of the present invention, preferably, the transmitter requests a receiver identification number requesting unit to transmit its own identification number held by each of the plurality of receivers, and a plurality of receptions. The identification number of the receiver to be a priority receiver among the machines is stored, and the reception identification number transmitted from each of the plurality of receivers in response to the request by the receiver identification number request unit is received. A priority receiver determination unit that determines a receiver that should be a priority receiver, and a reception response permission output unit for a receiver that is determined to be a priority receiver by the priority receiver determination unit. The reception response permission that permits the reception response is output.
　この構成により、送信機側で、複数の受信機のいずれを優先受信機として利用し、いずれを非優先受信機として利用するかを識別番号によって管理できる。 With this configuration, on the transmitter side, which of a plurality of receivers is used as a priority receiver and which is used as a non-priority receiver can be managed by an identification number.
　本発明の別の態様は、上記のマルチキャスト配信システムを構成する送信機であり、更に別の態様は、上記のマルチキャスト配信システムを構成する受信機である。 Another aspect of the present invention is a transmitter that constitutes the above multicast distribution system, and yet another aspect is a receiver that constitutes the above multicast distribution system.
　以下、本発明の実施の形態のマルチキャスト配信システムについて、図面を用いて説明する。 Hereinafter, a multicast distribution system according to an embodiment of the present invention will be described with reference to the drawings.
（第１の実施の形態）
　図１は、第１の実施の形態におけるマルチキャスト配信システムの全体構成を示す図である。図１に示すように、マルチキャスト配信システム１は、親局（ＡｃｃｅｓｓＰｏｉｎｔ：ＡＰ）としての送信機１０１と、子局（Ｓｔａｔｉｏｎ：ＳＴＡ）としての複数の受信機３０１ａ１，３０１ａ２，３０１ｂ１，３０１ｂ２とからなる。子局は端末とも呼ばれる。送信機１０１は、伝送データをマルチキャストで送信する。本実施の形態では、伝送データとして、時系列で再生されるデータが用いられる。伝送データは、映像データ又は音声データである。映像データは音声データを伴っていてもよいし、音声データを伴っていなくてもよい。 (First embodiment)
FIG. 1 is a diagram illustrating an overall configuration of a multicast distribution system according to the first embodiment. As shown in FIG. 1, the multicast distribution system 1 includes a transmitter 101 as an access point (AP) and a plurality of receivers 301a1, 301a2, 301b1, and 301b2 as slave stations (Stations). . The slave station is also called a terminal. The transmitter 101 transmits transmission data by multicast. In the present embodiment, data reproduced in time series is used as transmission data. The transmission data is video data or audio data. The video data may be accompanied by audio data, or may not be accompanied by audio data.
　受信機３０１ａ１，３０１ａ２，３０１ｂ１，３０１ｂ２は、それらが送信機１０１の通信範囲Ｒ内にあるときに、送信機１０１からマルチキャスト配信された伝送データを受信する。受信機には、優先受信機と非優先受信機の２種類がある。図１において、受信機３０１ａ１，３０１ａ２は優先受信機であり、受信機３０１ｂ１，３０１ｂ２は非優先受信機である。優先受信機３０１ａ１，３０１ａ２は、送信機１０１からの伝送データを受信すると、送信機１０１に対して受信応答を返信する。一方、非優先受信機３０１ｂ１，３０１ｂ２は、送信機１０１からの伝送データを受信しても受信応答は返信しない。 The receivers 301 a 1, 301 a 2, 301 b 1, 301 b 2 receive transmission data distributed from the transmitter 101 by multicast when they are within the communication range R of the transmitter 101. There are two types of receivers, a priority receiver and a non-priority receiver. In FIG. 1, receivers 301a1 and 301a2 are priority receivers, and receivers 301b1 and 301b2 are non-priority receivers. Upon receiving the transmission data from the transmitter 101, the priority receivers 301a1 and 301a2 return a reception response to the transmitter 101. On the other hand, even if the non-priority receivers 301b1 and 301b2 receive the transmission data from the transmitter 101, no reception response is returned.
　以下では、受信機について、優先受信機と非優先受信機とを特に区別しないときは、単に「受信機３０１」等と表記し、個々の優先受信機を区別しないときには、「優先受信機３０１ａ」等のように「ａ」を付けて表記し、個々の非優先受信機を区別しないときには、「非優先受信機３０１ｂ」等のように「ｂ」を付けて表記する。なお、送信機１０１は、受信機としての機能を有して、他の送信機から送信された伝送データを受信してもよい。このため、図１では、送信機１０１には、親局を意味する「ＡＰ」とともに子局を意味する「ＳＴＡ」という文字を表記している。 Hereinafter, when the priority receiver and the non-priority receiver are not particularly distinguished with respect to the receiver, they are simply referred to as “receiver 301” or the like, and when the individual priority receivers are not distinguished, “priority receiver 301a”. When not distinguishing individual non-priority receivers, such as “non-priority receiver 301b” or the like, “b” is appended. The transmitter 101 may function as a receiver and receive transmission data transmitted from other transmitters. For this reason, in FIG. 1, the transmitter 101 has the characters “STA” meaning slave stations as well as “AP” meaning parent stations.
　送信機１０１は、受信機からの受信応答に基づいて、伝送データの伝送条件を自動調整する機能を有する。本願において、伝送データの「伝送条件」には、伝送データの符号化レート、フレームレート、解像度、再送リミットが含まれる。本実施の形態では、送信機１０１は、伝送データの伝送条件として伝送データの符号化レートを自動調整する。 The transmitter 101 has a function of automatically adjusting transmission conditions of transmission data based on a reception response from the receiver. In the present application, the “transmission condition” of transmission data includes the transmission data encoding rate, frame rate, resolution, and retransmission limit. In the present embodiment, transmitter 101 automatically adjusts the encoding rate of transmission data as a transmission condition of transmission data.
　本実施の形態では、複数の受信機のうち、優先受信機３０１ａ１，３０１ａ２のみが送信機１０１に受信応答を送信し、非優先受信機３０１ｂ１，３０１ｂ２は送信機１０１に受信応答を送信しない。よって、送信機１０１は、優先受信機３０１ａ１，３０１ａ２の受信応答のみを考慮して、伝送データの符号化レートを調整する。この構成により、送信機１０１から複数の受信機３０１ａ１，３０１ａ２，３０１ｂ１，３０１ｂ２にマルチキャストで伝送データを送信する場合において、通信範囲Ｒ内にある受信機のうちの優先度は低いが通信品質の悪い受信機に引きずられて、すべての受信機が低い符号化レートで符号化された伝送データしか受信できないという事態が回避される。 In this embodiment, among the plurality of receivers, only the priority receivers 301a1 and 301a2 transmit a reception response to the transmitter 101, and the non-priority receivers 301b1 and 301b2 do not transmit a reception response to the transmitter 101. Therefore, the transmitter 101 adjusts the encoding rate of transmission data considering only the reception responses of the priority receivers 301a1 and 301a2. With this configuration, when transmission data is transmitted from the transmitter 101 to the plurality of receivers 301a1, 301a2, 301b1, and 301b2 by multicast, the priority among the receivers within the communication range R is low but the communication quality is poor. A situation in which all receivers can only receive transmission data encoded at a low encoding rate by being dragged by the receivers is avoided.
　本実施の形態のマルチキャスト配信システム１は、例えば、災害現場にて応用され得る。この場合に、送信機１０１は、例えば、被害が生じている現場の状況又は人命救助の状況を撮影するカメラに備えられて、カメラで撮影した映像を複数の受信機３０１にマルチキャストで配信する。 The multicast distribution system 1 of the present embodiment can be applied, for example, at a disaster site. In this case, for example, the transmitter 101 is provided in a camera that captures the situation of a damaged site or a lifesaving situation, and distributes video captured by the camera to a plurality of receivers 301 by multicast.
　受信機３０１のうち、優先受信機３０１ａは、例えば、現場に設営された指揮本部に設置されるモニタに接続されてよい。指揮責任者が携帯する携帯端末を優先受信機３０１ａとしてもよい。このように、複数の受信機３０１のなかで、重要な受信機を優先受信機３０１ａとすることができる。非優先受信機３０１ｂは、災害現場で人命救助等にあたっている者が携帯する携帯端末であってよく、又は警察車両や消防車両や救急車両に備えられたモニタに接続されていてもよい。このように、複数の受信機３０１のなかで、重要性が比較的低い受信機を非優先受信機３０１ｂとすることができる。 Among the receivers 301, the priority receiver 301a may be connected to, for example, a monitor installed at a command headquarters set up at the site. The portable terminal carried by the person in charge of the command may be used as the priority receiver 301a. Thus, an important receiver among the plurality of receivers 301 can be set as the priority receiver 301a. The non-priority receiver 301b may be a portable terminal that is carried by a person who is saving lives at a disaster site, or may be connected to a monitor provided in a police vehicle, a fire engine, or an ambulance vehicle. In this way, among the plurality of receivers 301, a receiver having a relatively low importance can be set as the non-priority receiver 301b.
　本実施の形態のマルチキャスト配信システム１では、優先受信機３０１ａ１，３０１ａ２の通信品質を優先的に考慮して、送信機１０１における伝送データの符号化レートを調整する。従って、例えば、非優先受信機３０１ｂ２が通信品質の悪い状況にあり、送信機１０１における伝送データの符号化レートを低くしなければ非優先受信機３０１ｂ２にて伝送データの高画質な再生ができない状態にあったとしても、送信機１０１が非優先受信機３０１ｂ２の通信品質に引きずられて符号化レートの低い伝送データをマルチキャスト配信することで、結果として、重要な優先受信機３０１ａがそれ自体は高い符号化レートの伝送データが受信できるにもかかわらず低い符号化レートで符号化された伝送データしか受信できないという事態が回避される。 In the multicast distribution system 1 of the present embodiment, the encoding rate of transmission data in the transmitter 101 is adjusted in consideration of the communication quality of the priority receivers 301a1 and 301a2. Therefore, for example, the non-priority receiver 301b2 is in a state of poor communication quality, and the transmission data cannot be reproduced with high quality at the non-priority receiver 301b2 unless the transmission data encoding rate in the transmitter 101 is lowered. Even if the transmitter 101 is multicasted to transmit data having a low encoding rate by dragging the communication quality of the non-priority receiver 301b2, the important priority receiver 301a itself is high as a result. A situation in which only transmission data encoded at a low encoding rate can be received even though transmission data at the encoding rate can be received is avoided.
　なお、図１に示すように優先受信機３０１ａが複数ある場合には、送信機１０１は、そのうちの通信品質が最も悪い優先受信機の通信品質に基づいて、マルチキャスト配信される伝送データの符号化レートを決定する。 As shown in FIG. 1, when there are a plurality of priority receivers 301a, the transmitter 101 encodes transmission data distributed by multicast based on the communication quality of the priority receiver having the worst communication quality. Determine the rate.
　次に、送信機１０１の構成を説明する。図２は、第１の実施の形態における送信機の構成を示すブロック図である。送信機１０１は、伝送データをマルチキャスト配信する送信部１１と、通信エリア内の受信機から受信応答を受信するための受信部１２とを備えている。 Next, the configuration of the transmitter 101 will be described. FIG. 2 is a block diagram illustrating a configuration of the transmitter according to the first embodiment. The transmitter 101 includes a transmission unit 11 that multicasts transmission data and a reception unit 12 that receives a reception response from a receiver in a communication area.
　送信機１０１は、さらに、コンテンツ提供部１３、符号化部１４、および送信パケット生成部１５を備えている。コンテンツ提供部１３は、送信すべきコンテンツのデータを生成して提供するものであり、本実施の形態では、撮影により映像データを生成して提供するビデオ撮影部である。符号化部１４は、コンテンツ提供部１３から提供された映像データを符号化する。符号化された映像データは符号化データとして送信パケット生成部１５に提供される。送信パケット生成部１５は、符号化データをパケットに分けて送信パケットを生成する。 The transmitter 101 further includes a content providing unit 13, an encoding unit 14, and a transmission packet generating unit 15. The content providing unit 13 generates and provides data of content to be transmitted. In the present embodiment, the content providing unit 13 is a video shooting unit that generates and provides video data by shooting. The encoding unit 14 encodes the video data provided from the content providing unit 13. The encoded video data is provided to the transmission packet generator 15 as encoded data. The transmission packet generator 15 divides the encoded data into packets and generates a transmission packet.
　送信機１０１は、さらに、受信応答判定部１６および通信品質推定部１７を備えている。受信応答判定部１６は、受信部１２で受信した受信機からの受信応答に基づいて、送信パケットを再送するか否かを判断する。受信応答判定部１６は、優先受信機３０１ａから受信応答（ＡＣＫ）を受けていない場合、及び優先受信機３０１ａから受信応答（ＮＡＣＫ）を受けた場合に、該当する送信パケットを再送するよう判断する。受信応答判定部１６は、送信パケットを再送すると判断したときは、送信パケット生成部１５にその指示をする。 The transmitter 101 further includes a reception response determination unit 16 and a communication quality estimation unit 17. The reception response determination unit 16 determines whether to retransmit the transmission packet based on the reception response from the receiver received by the reception unit 12. The reception response determination unit 16 determines to retransmit the corresponding transmission packet when the reception response (ACK) is not received from the priority receiver 301a and when the reception response (NACK) is received from the priority receiver 301a. . When the reception response determination unit 16 determines to retransmit the transmission packet, the reception response determination unit 16 gives an instruction to the transmission packet generation unit 15.
　通信品質推定部１７は、受信部１２で受信した受信機からの受信応答のＳ／Ｎ比に基づいて、当該受信機との間の通信品質を推定する。通信品質推定部１７は、推定した通信品質を符号化レート決定部１８に出力する。通信品質推定部１７は、受信応答（ＡＣＫ）の受信率、又は受信応答のＳ／Ｎ比及び受信応答（ＡＣＫ）の受信率に基づいて当該受信機との間の通信品質を推定してもよい。 The communication quality estimation unit 17 estimates the communication quality with the receiver based on the S / N ratio of the reception response from the receiver received by the reception unit 12. The communication quality estimation unit 17 outputs the estimated communication quality to the coding rate determination unit 18. The communication quality estimation unit 17 may estimate the communication quality with the receiver based on the reception rate of the reception response (ACK) or the S / N ratio of the reception response and the reception rate of the reception response (ACK). Good.
　符号化レート決定部１８は、通信品質推定部１７にて推定された通信品質に基づいて符号化レートを決定し、符号化部１４に出力する。このとき、符号化レート決定部１８は、通信品質推定部１７にて推定された通信品質が高いほど、符号化レートが高くなるように、すなわち、符号化データにおいて実データ（映像データ）の比率が高くなるように、符号化レートを決定する。符号化部１４は、符号化レート決定部１８にて決定された符号化レートに従って、コンテンツ提供部１３から提供された映像データを符号化する。 The coding rate determination unit 18 determines a coding rate based on the communication quality estimated by the communication quality estimation unit 17 and outputs the coding rate to the coding unit 14. At this time, the encoding rate determination unit 18 increases the encoding rate as the communication quality estimated by the communication quality estimation unit 17 increases, that is, the ratio of actual data (video data) in the encoded data. The coding rate is determined so that becomes higher. The encoding unit 14 encodes the video data provided from the content providing unit 13 according to the encoding rate determined by the encoding rate determining unit 18.
　符号化レート決定部１８は、通信品質推定部１７が複数の受信機についてそれぞれ通信品質を推定したときは、それらの複数の受信機の通信品質のうちの最も低い通信品質に基づいて符号化レートを決定する。このために、符号化レート決定部１８には、予め送信機１０１がマルチキャストで伝送データを送信すべき複数の受信機の中に、受信の応答を送信してくる受信機、即ち優先受信機３０１ａの情報を有しており、すべての優先受信機３０１ａの通信品質を比較して、最も低い通信品質を採用する。 When the communication quality estimation unit 17 estimates the communication quality for each of the plurality of receivers, the coding rate determination unit 18 determines the coding rate based on the lowest communication quality among the communication qualities of the plurality of receivers. To decide. For this purpose, the coding rate determination unit 18 includes a receiver that transmits a reception response among a plurality of receivers to which the transmitter 101 should transmit transmission data by multicast, that is, a priority receiver 301a. The communication quality of all the priority receivers 301a is compared, and the lowest communication quality is adopted.
　受信応答判定部１６は、受信部１２にて受信した優先受信機３０１ａからの受信応答の有無に基づいて、送信パケット生成部１５に送信パケットを再送させる。即ち、受信応答判定部１６は、受信部１２にて優先受信機３０１ａから受信応答（ＡＣＫ）を受信していない場合、または受信応答（ＮＡＣＫ）を受信した場合に、送信パケット生成部１５に、所定の再送リミットを再送回数の上限として、受信機にて受信されなかった送信パケットを再送させる。 The reception response determination unit 16 causes the transmission packet generation unit 15 to retransmit the transmission packet based on the presence / absence of the reception response from the priority receiver 301a received by the reception unit 12. That is, when the reception response determination unit 16 does not receive the reception response (ACK) from the priority receiver 301a at the reception unit 12, or when the reception response (NACK) is received, the reception response determination unit 16 A transmission packet that has not been received by the receiver is retransmitted with a predetermined retransmission limit as the upper limit of the number of retransmissions.
　このような構成により、送信機１０１では、まず、通信品質推定部１７が、受信部１２で受信した優先受信機３０１ａからの受信応答に基づいて、各優先受信機３０１ａの通信品質を推定する。そして、符号化レート決定部１８が、推定された通信品質に基づいて符号化レートを決定して、符号化部１４に設定する。次に、符号化部１４が、設定された符号化レートで、コンテンツ提供部１３から提供された映像データを符号化して符号化データを生成する。次に、送信パケット生成部１５が符号化データから送信パケットを生成し、送信部１１が送信パケットを伝送データとして送信する。また、送信機１０１は、受信部１２にて受信した優先受信機３０１ａからの受信応答に基づいて、必要なときには送信パケットを再送する。 With such a configuration, in the transmitter 101, first, the communication quality estimation unit 17 estimates the communication quality of each priority receiver 301a based on the reception response from the priority receiver 301a received by the reception unit 12. Then, the encoding rate determination unit 18 determines the encoding rate based on the estimated communication quality and sets it in the encoding unit 14. Next, the encoding unit 14 generates encoded data by encoding the video data provided from the content providing unit 13 at the set encoding rate. Next, the transmission packet generation unit 15 generates a transmission packet from the encoded data, and the transmission unit 11 transmits the transmission packet as transmission data. The transmitter 101 retransmits the transmission packet when necessary based on the reception response from the priority receiver 301a received by the reception unit 12.
　次に、受信機３０１の構成を説明する。図３Ａは、優先受信機３０１ａの構成を示すブロック図であり、図３Ｂは、非優先受信機３０１ｂの構成を示すブロック図である。優先受信機３０１ａおよび非優先受信機３０１ｂは、いずれも受信部３１と、復号化部３２と、誤り判定部３３と、コンテンツ再生部３４とを備えている。 Next, the configuration of the receiver 301 will be described. FIG. 3A is a block diagram illustrating a configuration of the priority receiver 301a, and FIG. 3B is a block diagram illustrating a configuration of the non-priority receiver 301b. Each of the priority receiver 301a and the non-priority receiver 301b includes a reception unit 31, a decoding unit 32, an error determination unit 33, and a content reproduction unit 34.
　受信部３１は、送信機１０１から送信された伝送データを受信する。復号化部３２は、受信部３１で受信した伝送データを復号化する。誤り判定部３３は、復号化部３２で復号化されたデータを受けて、データに誤りがあるか否かを判定する。誤り判定部３３で誤りがないと判定されたデータは、コンテンツ再生部３４に出力され、コンテンツ再生部３４で再生される。 The receiving unit 31 receives transmission data transmitted from the transmitter 101. The decoding unit 32 decodes the transmission data received by the receiving unit 31. The error determination unit 33 receives the data decoded by the decoding unit 32 and determines whether or not there is an error in the data. Data determined to be error-free by the error determination unit 33 is output to the content reproduction unit 34 and is reproduced by the content reproduction unit 34.
　誤り判定部３３は、誤り判定の結果を受信応答生成部３５に出力する。受信応答生成部３５は、誤り判定の結果に従って、誤りがない場合は、誤りなくデータを受信したことを示す受信応答（ＡＣＫ）を生成し、誤りがある場合には、誤りがあったことを示す受信応答（ＮＡＣＫ）を生成する。送信部３６は、生成された受信応答を送信機１０１に送信する。 The error determination unit 33 outputs the result of the error determination to the reception response generation unit 35. The reception response generation unit 35 generates a reception response (ACK) indicating that the data has been received without error according to the result of the error determination, and indicates that there is an error when there is an error. A reception response (NACK) is generated. The transmission unit 36 transmits the generated reception response to the transmitter 101.
　非優先受信機３０１ｂは、優先受信機３０１ａと同様に、受信部３１、復号化部３２、誤り判定部３３、およびコンテンツ再生部３４を備えている。但し、非優先受信機３０１ｂは、送信機１０１に受信応答を送信しないので、これに関する構成、即ち優先受信機３０１ａの受信応答生成部３５および受信応答を送信するための送信部３６を備えていない。 The non-priority receiver 301b includes a reception unit 31, a decoding unit 32, an error determination unit 33, and a content reproduction unit 34, as with the priority receiver 301a. However, since the non-priority receiver 301b does not transmit a reception response to the transmitter 101, the non-priority receiver 301b does not include a configuration related thereto, that is, the reception response generation unit 35 of the priority receiver 301a and the transmission unit 36 for transmitting the reception response. .
　以上、図３ＡおよびＢを参照して説明したとおり、優先受信機３０１ａと非優先受信機３０１ｂとの相違は、優先受信機３０１ａは受信応答を送信機１０１に送信するための構成を備えているのに対して、非優先受信機３０１ｂはこれらの構成を備えていないという点にある。即ち、図３ＡおよびＢの例では、優先受信機３０１ａと非優先受信機３０１ｂとは、それらが製造される時点で区別されている。 As described above with reference to FIGS. 3A and 3B, the difference between the priority receiver 301a and the non-priority receiver 301b is that the priority receiver 301a has a configuration for transmitting a reception response to the transmitter 101. On the other hand, the non-priority receiver 301b is not provided with these configurations. That is, in the example of FIGS. 3A and 3B, the priority receiver 301a and the non-priority receiver 301b are distinguished at the time when they are manufactured.
　図３Ｃは、本実施の形態の受信機３０１の他の例を示すブロック図である。図３Ｃに示す例では、製造された時点ではそれが優先受信機であるか非優先受信機であるかは特定されていない。従って、ユーザが使用の過程で受信機３０１を優先受信機３０１ａとして利用するか非優先受信機３０１ｂとして利用するかを任意に設定できる。図３Ｃに示す受信機３０１は、図３Ａに示す優先受信機３０１ａと同様に、受信部３１、復号化部３２、誤り判定部３３、コンテンツ再生部３４、受信応答生成部３５、および送信部３６を備えるとともに、更に受信応答出力設定部３７を備えている。 FIG. 3C is a block diagram illustrating another example of the receiver 301 of the present embodiment. In the example shown in FIG. 3C, it is not specified whether it is a priority receiver or a non-priority receiver at the time of manufacture. Therefore, the user can arbitrarily set whether to use the receiver 301 as the priority receiver 301a or the non-priority receiver 301b in the course of use. The receiver 301 illustrated in FIG. 3C is similar to the priority receiver 301a illustrated in FIG. 3A in that the reception unit 31, the decoding unit 32, the error determination unit 33, the content reproduction unit 34, the reception response generation unit 35, and the transmission unit 36. And a reception response output setting unit 37.
　受信応答出力設定部３７は、ユーザの操作に応じて受信応答を生成するか否かを受信応答生成部３５に設定する。即ち、受信機３０１を優先受信機３０１ａとして利用するときは、ユーザは、受信応答出力設定部３７を操作することで、受信応答を生成するように受信応答生成部３５を設定し、受信機３０１を非優先受信機３０１ｂとして利用するときは、ユーザは、受信応答出力設定部３７を操作することで、受信応答を生成しないように受信応答生成部３５を設定する。 The reception response output setting unit 37 sets, in the reception response generation unit 35, whether or not to generate a reception response according to a user operation. That is, when the receiver 301 is used as the priority receiver 301a, the user operates the reception response output setting unit 37 to set the reception response generation unit 35 so as to generate a reception response. Is used as the non-priority receiver 301b, the user operates the reception response output setting unit 37 to set the reception response generation unit 35 so as not to generate a reception response.
　以上のように、本実施の形態のマルチキャスト配信システム１によれば、送信機１０１は、優先受信機３０１ａの通信品質のみを考慮して決定された符号化レートでコンテンツを符号化してマルチキャスト配信するので、重要性の低い受信機である非優先受信機３０１ｂの通信品質が悪いために重要な受信機である優先受信機３０１ａにて十分な情報量が得られないという事態を回避できる。 As described above, according to the multicast distribution system 1 of the present embodiment, the transmitter 101 encodes content at a coding rate determined only considering the communication quality of the priority receiver 301a and distributes the multicast. Therefore, it is possible to avoid a situation in which a sufficient amount of information cannot be obtained by the priority receiver 301a which is an important receiver because the communication quality of the non-priority receiver 301b which is a less important receiver is poor.
　また、図３Ｃに示すように、ユーザの操作によってそれを優先受信機３０１ａとするか非優先受信機３０１ｂとするかを選択できる受信機３０１によれば、ユーザが必要に応じて臨機応変に優先受信機および非優先受信機を設定できる。 In addition, as shown in FIG. 3C, according to the receiver 301 that can select whether to make it a priority receiver 301a or a non-priority receiver 301b by the user's operation, the user gives priority to the case when necessary. Receiver and non-priority receiver can be set.
　なお、上記の実施の形態では、優先受信機３０１ａのみが受信応答を送信し、送信機１０１は優先受信機３０１ａのみから受信応答を受信することで、送信機１０１にて優先受信機３０１ａの通信品質のみを考慮して符号化レートを決定したが、非優先受信機３０１ｂも含めてすべての受信機３０１から受信応答を送信機１０１に送信するようにしてもよい。この場合には、受信応答中にその受信機が優先受信機であるか非優先受信機であるかを示す情報を付加する。送信機１０１は、受信応答を受信すると、その受信応答に付加された情報を参照して、その受信応答を送信した受信機が優先受信機であるか非優先受信機であるかを判断し、優先受信機から送られてきた受信応答のみを符号化レートの決定に反映させる。 In the above embodiment, only the priority receiver 301a transmits a reception response, and the transmitter 101 receives a reception response only from the priority receiver 301a, so that the transmitter 101 can communicate with the priority receiver 301a. Although the coding rate is determined considering only the quality, reception responses may be transmitted from all the receivers 301 including the non-priority receiver 301b to the transmitter 101. In this case, information indicating whether the receiver is a priority receiver or a non-priority receiver is added to the reception response. Upon receiving the reception response, the transmitter 101 refers to the information added to the reception response to determine whether the receiver that transmitted the reception response is a priority receiver or a non-priority receiver, Only the reception response sent from the priority receiver is reflected in the determination of the coding rate.
　また、送信機１０１側でどの受信機が優先受信機であるかを記憶しておき、すべての受信機から受信した受信応答のうち、優先受信機の受信応答のみを考慮して符号化レートを決定するようにしてもよい。これらの構成によっても上記と同様の効果を達成できる。 Also, which receiver is the priority receiver is stored on the transmitter 101 side, and among the reception responses received from all the receivers, only the reception response of the priority receiver is considered and the encoding rate is set. It may be determined. These configurations can achieve the same effects as described above.
（第２の実施の形態）
　次に、本発明の第２の実施の形態を説明する。図４は、第２の実施の形態の送信機１０２の構成を示すブロック図であり、図５は、第２の実施の形態の受信機３０２の構成を示すブロック図である。以下の第２～第４の実施の形態の説明において、第１の実施の形態と同一の構成については同一の符号を付してその詳細な説明は省略する。 (Second Embodiment)
Next, a second embodiment of the present invention will be described. FIG. 4 is a block diagram illustrating a configuration of the transmitter 102 according to the second embodiment, and FIG. 5 is a block diagram illustrating a configuration of the receiver 302 according to the second embodiment. In the following description of the second to fourth embodiments, the same components as those of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.
　本実施の形態は、送信機１０２側で、複数ある受信機のうちのどの受信機を優先受信機とし、どの受信機を非優先受信機とするかを指定する。このために、各受信機３０２には、個々の受信機３０２を少なくとも当該複数の受信機の中で唯一に特定するための受信機識別番号が設定されており、各受信機３０２は自己の識別番号の情報を保持している。送信機１０２は、マルチキャスト配信の対象となる複数の受信機の識別番号の情報を保持している。 In the present embodiment, on the transmitter 102 side, which receiver among the plurality of receivers is designated as a priority receiver and which receiver is designated as a non-priority receiver. For this reason, each receiver 302 is set with a receiver identification number for uniquely identifying each receiver 302 among at least the plurality of receivers, and each receiver 302 has its own identification. The number information is retained. The transmitter 102 holds information on identification numbers of a plurality of receivers that are targets of multicast distribution.
　このような状況で、ユーザは、送信機１０２を操作して、優先受信機３０２ａとなるべき受信機３０２を特定する。これにより、送信機１０２は、マルチキャスト配信の対象となる複数の受信機３０２のうちの優先受信機３０２ａとすべき受信機の識別番号を特定する。 In such a situation, the user operates the transmitter 102 to specify the receiver 302 that should be the priority receiver 302a. Thereby, the transmitter 102 specifies the identification number of the receiver that should be the priority receiver 302a among the plurality of receivers 302 that are the targets of multicast distribution.
　図４に示すように、送信機１０２は、第１の実施の形態の送信機１０１の構成に加えて、優先受信機判定部１９、受信応答許可出力部２０、および受信機識別番号要求部２１を備えている。受信機識別番号要求部２１は、各受信機３０２が保持している自己の識別番号を送信するよう要求する受信機識別番号要求を生成する。この受信機識別番号要求は送信部１１によって、マルチキャストで送信される。 As shown in FIG. 4, in addition to the configuration of the transmitter 101 of the first embodiment, the transmitter 102 includes a priority receiver determination unit 19, a reception response permission output unit 20, and a receiver identification number request unit 21. It has. The receiver identification number request unit 21 generates a receiver identification number request for requesting transmission of its own identification number held by each receiver 302. This receiver identification number request is transmitted by the transmitter 11 by multicast.
　受信部１２は、受信機３０２が受信機識別番号要求に応じて送信してきた受信識別番号を受信して、優先受信機判定部１９に出力する。優先受信機判定部１９には、ユーザが指定した優先受信機３０２ａとすべき受信機の識別番号が記憶されている。優先受信機判定部１９は、受信部１２で受信した受信識別番号が優先受信機３０２ａとすべき受信機の識別番号であるか否かを判定し、その結果を受信応答許可出力部２０に出力する。 The receiving unit 12 receives the reception identification number transmitted by the receiver 302 in response to the receiver identification number request, and outputs it to the priority receiver determination unit 19. The priority receiver determination unit 19 stores the identification number of the receiver to be designated as the priority receiver 302a specified by the user. The priority receiver determination unit 19 determines whether or not the reception identification number received by the reception unit 12 is the identification number of the receiver that should be the priority receiver 302a, and outputs the result to the reception response permission output unit 20 To do.
　受信応答許可出力部２０は、受信した受信識別番号が優先受信機３０２ａとすべき受信機の識別番号である場合は、当該受信機の受信応答を許可する受信応答許可を生成する。送信部１１は、受信応答許可出力部２０で生成された受信応答許可をマルチキャストで送信する。 When the received reception identification number is the identification number of the receiver that should be the priority receiver 302a, the reception response permission output unit 20 generates a reception response permission that permits the reception response of the receiver. The transmission unit 11 transmits the reception response permission generated by the reception response permission output unit 20 by multicast.
　図５に示すように、受信機３０２は、第１の実施の形態の受信機３０１の構成に加えて、受信機識別番号要求判定部３８、受信機識別番号出力部３９、および受信応答許可判定部４０を備えている。復号化部３２は、受信部３１で受信したデータを復号化し、受信機識別番号要求判定部３８に出力する。受信機識別番号要求判定部３８は、復号化部３２で復号化されたデータに受信機識別番号要求が含まれているか否かを判定し、その結果を受信機識別番号出力部３９に出力する。 As shown in FIG. 5, in addition to the configuration of the receiver 301 of the first embodiment, the receiver 302 includes a receiver identification number request determination unit 38, a receiver identification number output unit 39, and a reception response permission determination. Part 40 is provided. The decryption unit 32 decrypts the data received by the reception unit 31 and outputs the decrypted data to the receiver identification number request determination unit 38. The receiver identification number request determination unit 38 determines whether the data decoded by the decoding unit 32 includes a receiver identification number request, and outputs the result to the receiver identification number output unit 39. .
　受信機識別番号出力部３９には、自己の受信機識別番号が記憶されている。受信機識別番号出力部３９は、受信機識別番号要求判定部３８での判定結果に従って、受信機識別番号要求がある場合には、記憶されている受信機識別番号を送信部３６に送信させる。 The receiver identification number output unit 39 stores its own receiver identification number. When there is a receiver identification number request according to the determination result in the receiver identification number request determination unit 38, the receiver identification number output unit 39 causes the transmission unit 36 to transmit the stored receiver identification number.
　受信部３１が受信応答許可を受信すると、復号化部３２はこれを復号化して受信応答許可判定部４０に出力する。受信応答許可判定部４０には、自己の受信機識別番号が記憶されている。受信応答許可判定部４０は、受信した受信応答許可において、自己の受信識別番号に対して受信応答の許可がされているか否かを判定し、その結果を受信応答出力設定部３７に出力する。 When the reception unit 31 receives the reception response permission, the decryption unit 32 decrypts it and outputs it to the reception response permission determination unit 40. The reception response permission determination unit 40 stores its own receiver identification number. The reception response permission determination unit 40 determines whether or not a reception response is permitted for its own reception identification number in the received reception response permission, and outputs the result to the reception response output setting unit 37.
　受信応答出力設定部３７は、受信応答許可判定部４０から出力された判定結果に従って、自己に対して受信応答の許可がされている場合は、受信応答を生成するよう受信応答生成部３５を設定し、自己に対して受信応答の許可がされていない場合は、受信応答を生成しないよう受信応答生成部３５を設定する。 The reception response output setting unit 37 sets the reception response generation unit 35 to generate a reception response when the reception response is permitted for itself according to the determination result output from the reception response permission determination unit 40. If the reception response is not permitted for itself, the reception response generation unit 35 is set so as not to generate the reception response.
　以上のように、本実施の形態のマルチキャスト配信システムによれば、送信機１０２にて、複数の受信機３０２のうち、優先受信機３０２ａとすべき受信機および非優先受信機３０２ｂとすべき受信機を指定することができる。これにより、例えば、本実施の形態のマルチキャスト配信システムが災害現場における状況把握のためのシステムであり、送信機１０２が、被害が生じている現場（被害現場）の状況又は人命救助の状況を撮影するカメラに備えられている場合には、次のように応用することができる。 As described above, according to the multicast distribution system of the present embodiment, at the transmitter 102, among the plurality of receivers 302, the receiver that should be the priority receiver 302a and the reception that should be the non-priority receiver 302b. You can specify the machine. Thereby, for example, the multicast distribution system according to the present embodiment is a system for grasping the situation at the disaster site, and the transmitter 102 photographs the situation at the site where the damage (damage site) occurs or the situation of lifesaving. When the camera is equipped, it can be applied as follows.
　例えば、災害現場で人命救助の作業をしている初期段階では、指揮本部のモニタ装置又は指揮責任者の携帯端末を優先受信機３０２ａと設定することで、指揮本部又は指揮責任者において確実に映像を確認することができ、作業の手順を指揮本部又は指揮責任者から指示することができる。被害現場から負傷者が救出された場合には、救急車の救急隊員の指示を仰ぐために、被害現場の送信機１０２において、救急車に設置された受信機３０２を優先受信機３０２ａとするよう指定する。この指定が優先受信機判定部１９に設定されて、上述のようにして、優先受信機３０２ａおよび非優先受信機３０２ｂが設定される。 For example, at the initial stage of lifesaving work at a disaster site, the monitoring device of the command headquarters or the mobile terminal of the commander is set as the priority receiver 302a, so that the video can be reliably displayed at the command headquarters or the commander. Can be confirmed, and the work procedure can be instructed from the command headquarters or the command manager. When an injured person is rescued from the victim site, the receiver 102 installed in the ambulance is designated as the priority receiver 302a in the transmitter 102 of the victim site in order to ask for an ambulance crew member's instruction. This designation is set in the priority receiver determination unit 19, and the priority receiver 302a and the non-priority receiver 302b are set as described above.
　このように、本実施の形態は、送信機１０２側から優先受信機３０２ａおよび非優先受信機３０２ｂを指定したい場合、特に、このマルチキャスト配信システムを利用している場面で動的に優先／非優先を変更したい場合に有効に用いられる。なお、マルチキャスト配信システムに含まれるすべての複数の受信機３０２の受信機識別番号が予め送信機１０２に記憶されている場合には、送信機１０２の受信機識別番号要求部２１および優先受信機判定部１９、受信機３０２の受信機識別番号要求判定部３８および受信機識別番号出力部３９の構成は省略することができる。 As described above, according to the present embodiment, when it is desired to designate the priority receiver 302a and the non-priority receiver 302b from the transmitter 102 side, the priority / non-priority is dynamically dynamically assigned particularly when the multicast distribution system is used. This is useful when you want to change When the receiver identification numbers of all the plurality of receivers 302 included in the multicast distribution system are stored in advance in the transmitter 102, the receiver identification number request unit 21 of the transmitter 102 and the priority receiver determination The configurations of the unit 19, the receiver identification number request determination unit 38 of the receiver 302, and the receiver identification number output unit 39 can be omitted.
（第３の実施の形態）
　次に、本発明の第３の実施の形態を説明する。図６ＡおよびＢは、本実施の形態のマルチキャスト配信システム３の全体構成を示す図である。図６ＡおよびＢには１つの優先受信機３０３ａおよび１つの非優先端末３０３ｂしか記載されていないが、それぞれ複数あってもよい。図６Ａは、優先受信機３０３ａが送信機１０３の通信範囲Ｒ外に位置している状況を示しており、図６Ｂは、優先受信機３０３ａが送信機１０３の通信範囲Ｒ内に位置している状況を示している。 (Third embodiment)
Next, a third embodiment of the present invention will be described. 6A and 6B are diagrams showing the overall configuration of the multicast distribution system 3 of the present embodiment. 6A and 6B show only one priority receiver 303a and one non-priority terminal 303b, there may be a plurality of each. 6A shows a situation where the priority receiver 303a is located outside the communication range R of the transmitter 103, and FIG. 6B shows that the priority receiver 303a is located within the communication range R of the transmitter 103. Indicates the situation.
　図７は、第３の実施の形態の送信機１０３の構成を示すブロック図である。本実施の形態では、第１の実施の形態と同様に、送信機１０３は、優先受信機３０３ａの通信品質のみを考慮して、伝送条件を調整する。本実施の形態では、伝送条件として、伝送データの再送リミット及び映像データの画質を調整する。 FIG. 7 is a block diagram illustrating a configuration of the transmitter 103 according to the third embodiment. In the present embodiment, as in the first embodiment, the transmitter 103 adjusts the transmission conditions in consideration of only the communication quality of the priority receiver 303a. In this embodiment, the transmission data retransmission limit and the image quality of video data are adjusted as transmission conditions.
　本実施の形態では、符号化部１４は、低密度パリティ検査（Ｌｏｗ Ｄｅｎｓｉｔｙ ＰａｒｉｔｙＣｈｅｃｋ：ＬＤＰＣ）符号などのブロック符号を利用して、１フレーム分の映像データを複数のサブブロックに分けて符号化する。送信パケット生成部１５は、送信パケットを生成し、送信部１１はマルチキャストで送信パケットを送信する。 In the present embodiment, the encoding unit 14 divides and encodes video data for one frame into a plurality of sub-blocks by using a block code such as a low density parity check (Low Density Parity Check: LDPC) code. . The transmission packet generation unit 15 generates a transmission packet, and the transmission unit 11 transmits the transmission packet by multicast.
　図７に示すように、送信機１０３は、第１の実施の形態の送信機１０１の構成に加えて、送信フレーム再送リミット決定部２２およびサブブロック再送リミット決定部２３を備えている。 As shown in FIG. 7, the transmitter 103 includes a transmission frame retransmission limit determination unit 22 and a sub-block retransmission limit determination unit 23 in addition to the configuration of the transmitter 101 of the first embodiment.
　送信フレーム再送リミット決定部２２は、通信品質推定部１７における受信応答の受信率に基づいて、送信フレームの再送リミット（再送上限回数）を決定する。図６Ａに示すように、優先受信機３０３ａが通信範囲Ｒ外にあって、優先受信機３０３ａからの受信応答が返ってこない場合には、送信フレーム再送リミット決定部２２及びサブブロック再送リミット決定部２３は、通常より少ない再送回数で再送を終了するよう、通常より小さい再送リミットを送信パケット生成部１５に設定する。 The transmission frame retransmission limit determination unit 22 determines a transmission frame retransmission limit (retransmission upper limit number) based on the reception rate of the reception response in the communication quality estimation unit 17. As shown in FIG. 6A, when the priority receiver 303a is outside the communication range R and the reception response from the priority receiver 303a is not returned, the transmission frame retransmission limit determination unit 22 and the sub-block retransmission limit determination unit 23 sets a retransmission limit smaller than normal in the transmission packet generation unit 15 so that retransmission is completed with a smaller number of retransmissions than usual.
　即ち送信パケット生成部１５は、受信応答判定部１６の判定結果に従って、伝送データを再送するが、このときの再送リミットを送信フレーム再送リミット決定部２２又はサブブロック再生リミット決定部２３が決定して、送信パケット生成部１５に設定する。 That is, the transmission packet generation unit 15 retransmits the transmission data according to the determination result of the reception response determination unit 16, and the transmission frame retransmission limit determination unit 22 or the sub-block reproduction limit determination unit 23 determines the retransmission limit at this time. And set in the transmission packet generator 15.
　具体的には、図６Ａに示すように、優先受信機３０３ａが送信機１０３の通信範囲Ｒ外にあって、送信機１０３にて優先受信機３０３ａからの受信応答を受信しない場合には、通信品質推定部１７は、優先受信機３０３ａからの受信応答の有無を判定し、判定結果を送信フレーム再送リミット決定部２２及びサブブロック再送リミット決定部２３に出力する。送信フレーム再送リミット決定部２２及びサブブロック再送リミット決定部２３は、通信品質推定部１７における判定結果に従って、優先受信機３０３ａから受信応答を受信していない場合には、送信パケット生成部１５に対して送信フレームの再送リミット及びサブブロックの再送リミットが小さくなるように設定する。 Specifically, as shown in FIG. 6A, when the priority receiver 303a is outside the communication range R of the transmitter 103 and the transmitter 103 does not receive a reception response from the priority receiver 303a, communication is performed. The quality estimation unit 17 determines the presence / absence of a reception response from the priority receiver 303a, and outputs the determination result to the transmission frame retransmission limit determination unit 22 and the sub-block retransmission limit determination unit 23. When the transmission frame retransmission limit determination unit 22 and the sub-block retransmission limit determination unit 23 have not received a reception response from the priority receiver 303a according to the determination result in the communication quality estimation unit 17, the transmission frame retransmission limit determination unit 22 Thus, the retransmission limit of the transmission frame and the retransmission limit of the sub-block are set to be small.
　図９は、受信機３０３から送信される受信応答のサブブロックのＡＣＫフォーマット例を示す図である。図９に示すように、サブブロックのＡＣＫフォーマットには、ＰＬＣＰヘッダ、ＭＡＣヘッダ、＃１から＃Ｎまでの各サブブロックの誤り判定結果、および誤り訂正符号ＣＲＣが含まれている。各サブブロックの誤り判定結果は、例えば、１ビットで誤りの有無を表している。通信品質推定部１７は、受信応答（ＡＣＫ）における＃１から＃Ｎまでのサブブロックのうちの誤りのあるサブブロックの比率をブロック誤り率として求める。 FIG. 9 is a diagram illustrating an ACK format example of a sub-block of a reception response transmitted from the receiver 303. As shown in FIG. 9, the ACK format of the subblock includes a PLCP header, a MAC header, an error determination result of each subblock from # 1 to #N, and an error correction code CRC. The error determination result of each sub-block represents, for example, the presence or absence of an error with 1 bit. The communication quality estimator 17 obtains the ratio of subblocks with errors among the subblocks # 1 to #N in the reception response (ACK) as the block error rate.
　また、本実施の形態では、送信機１０３は、上記の実施の形態の符号化レート決定部１８の代わりに画質決定部２４を備えている。通信品質推定部１７は、ブロック誤り率を画質決定部２４に出力する。画質決定部２４は、ブロック誤り率に基づいて、コンテンツ提供部１３に対して、映像データを生成する際の画質（フレームレートおよび解像度）を設定する。具体的には、画質決定部２４は、ブロック誤り率が高い場合には、通常の画質より低い画質で映像データを生成するようコンテンツ提供部１３を設定する。画質決定部２４は、優先受信機３０３ａから受信応答（ＡＣＫ）をしていない場合には、通常の画質で映像データを生成するようコンテンツ提供部１３を設定する。 In this embodiment, the transmitter 103 includes an image quality determination unit 24 instead of the coding rate determination unit 18 of the above embodiment. The communication quality estimation unit 17 outputs the block error rate to the image quality determination unit 24. Based on the block error rate, the image quality determination unit 24 sets the image quality (frame rate and resolution) for generating video data to the content providing unit 13. Specifically, the image quality determination unit 24 sets the content providing unit 13 to generate video data with a lower image quality than the normal image quality when the block error rate is high. When the reception response (ACK) is not received from the priority receiver 303a, the image quality determination unit 24 sets the content providing unit 13 to generate video data with normal image quality.
　このような構成によって、不感地帯（送信機１０３の通信範囲Ｒ外）にあって受信応答（ＡＣＫ又はＮＡＣＫ）が送信機１０３まで届かない受信機については、たとえそれが優先受信機３０３ａであったとしても、再送リミットを小さく設定する。また、送信機１０３は、優先受信機３０３ａが受信応答（ＡＣＫ又はＮＡＣＫ）を返してきた場合には、その受信応答の内容に基づいて、サブブロック再生リミット、送信フレーム再送リミット、およびコンテンツ提供部１３で生成する映像データの画質を自動で設定する。 With such a configuration, for a receiver that is in the dead zone (outside the communication range R of the transmitter 103) and does not receive the reception response (ACK or NACK) to the transmitter 103, it is the priority receiver 303a. However, the retransmission limit is set small. Further, when the priority receiver 303a returns a reception response (ACK or NACK), the transmitter 103, based on the content of the reception response, the sub-block reproduction limit, the transmission frame retransmission limit, and the content providing unit 13 automatically sets the image quality of the video data generated.
　図８は、第３の実施の形態の受信機３０３の構成を示すブロック図である。図８に示すように、受信機３０３は、第１の実施の形態と同様の構成を有している。受信機３０３は、第１の実施の形態と同様に、それが受信応答出力設定部３７によって優先受信機３０３ａとして設定されている場合にのみ、受信応答生成部３５にて受信応答を生成して、送信部３６にて送信機１０３に送信する。 FIG. 8 is a block diagram illustrating a configuration of the receiver 303 according to the third embodiment. As shown in FIG. 8, the receiver 303 has a configuration similar to that of the first embodiment. Similarly to the first embodiment, the receiver 303 generates a reception response in the reception response generation unit 35 only when it is set as the priority receiver 303a by the reception response output setting unit 37. The transmitter 36 transmits the data to the transmitter 103.
　本実施の形態では、誤り判定部３３は、サブブロックごとに誤りの有無を判定して、その判定結果を受信応答生成部３５に出力する。受信応答生成部３５にて生成する受信応答は、図９を参照して上記で説明した通りである。 In this embodiment, the error determination unit 33 determines the presence / absence of an error for each sub-block, and outputs the determination result to the reception response generation unit 35. The reception response generated by the reception response generation unit 35 is as described above with reference to FIG.
　このような第３の実施の形態のマルチキャスト配信システム３によれば、たとえ優先受信機であったとしても、通信が見込めない受信機については、再送信を多く繰り返すことはしない。そのため、そのような通信が見込めない優先受信機のために送信機が画質を落とし、結果として、通信可能な受信機が、通信が見込めない受信機の影響を受けて、必要以上に画質が低く抑えられた伝送データしか受信できないという事態が避けられる。 According to the multicast distribution system 3 of the third embodiment as described above, even if it is a priority receiver, a receiver that cannot expect communication is not repeatedly retransmitted. Therefore, the transmitter reduces the image quality due to the priority receiver that cannot expect such communication, and as a result, the receiver that can communicate is affected by the receiver that cannot expect communication and the image quality is lower than necessary. The situation where only the suppressed transmission data can be received is avoided.
　また、本実施の形態の送信機１０３は、ブロック符号を用いて１フレーム分の伝送データを複数のサブブロックに分けて符号化して送信するとともに、受信機３０３からのサブブロックごとの受信応答に基づいてサブブロック誤り率を求めて、サブブロックごとに再送を行うので、フレームごとの誤り率のみに基づいてフレーム単位の再送のみを行う場合と比較して、通信品質をより細かく推定することが可能であり、かつ再送オーバーヘッドを少なくできる。 In addition, the transmitter 103 according to the present embodiment divides transmission data for one frame into a plurality of sub-blocks by using a block code, transmits the data, and transmits a reception response for each sub-block from the receiver 303. Sub-block error rate is obtained based on this, and retransmission is performed for each sub-block. Therefore, communication quality can be estimated more finely than when only frame-based retransmission is performed based on only the error rate for each frame. This is possible, and retransmission overhead can be reduced.
　なお、本実施の形態の送信機１０３では、第１及び第２の実施の形態の符号化レート決定部１８の代わりに画質決定部２４を用いて、推定された通信品質に応じてコンテンツ提供部１３で生成される映像データの画質を調整する構成を採用したが、第１及び第２の実施の形態と同様に符号化レート決定部１８を採用して符号化レートを決定して符号化部１４の符号化レートを調整してもよい。この場合にも、上記と同様の効果が得られる。 Note that in the transmitter 103 according to the present embodiment, an image quality determining unit 24 is used instead of the coding rate determining unit 18 according to the first and second embodiments, and a content providing unit is used according to the estimated communication quality. Although the configuration for adjusting the image quality of the video data generated in 13 is adopted, the coding rate is determined by employing the coding rate determining unit 18 as in the first and second embodiments, and the coding unit The encoding rate of 14 may be adjusted. In this case, the same effect as described above can be obtained.
　また、第１の実施の形態の送信機１０１や第２の実施の形態の受信機１０２において、本実施の形態と同様に、符号化レート決定部１８の代わりに画質決定部２４を用いて、推定された通信品質に応じてコンテンツ提供部１３で生成される映像データの画質を調整してもよい。 Further, in the transmitter 101 of the first embodiment and the receiver 102 of the second embodiment, the image quality determination unit 24 is used instead of the coding rate determination unit 18 as in the present embodiment. The image quality of the video data generated by the content providing unit 13 may be adjusted according to the estimated communication quality.
（第４の実施の形態）
　次に、本発明の第４の実施の形態を説明する。図１０は、第４の実施の形態のマルチキャスト配信システム４の全体構成を示す図である。本実施の形態では、第１の実施の形態と同様に、送信機１０４は、優先受信機３０４ａの通信品質のみを考慮して、伝送条件を調整する。本実施の形態では、送信機１０４は、伝送条件として、フレームタイプ別の再送リミットと映像データの画質を調整する。 (Fourth embodiment)
Next, a fourth embodiment of the present invention will be described. FIG. 10 is a diagram illustrating an overall configuration of the multicast distribution system 4 according to the fourth embodiment. In the present embodiment, as in the first embodiment, the transmitter 104 adjusts the transmission conditions in consideration of only the communication quality of the priority receiver 304a. In this embodiment, transmitter 104 adjusts the retransmission limit for each frame type and the image quality of video data as transmission conditions.
　本実施の形態は、図１０に示すように、優先受信機３０４ａが、送信機１０４の通信範囲Ｒのエッジ部分に位置している場合に有効である。この場合、優先受信機３０４ａは、送信機１０４との間で通信は可能であるが、その通信品質は良好ではない。よって、例えば伝送データが映像データである場合に、高画質の映像データを送っても優先受信機３０４ａでは、高画質の映像の再生ができない。 This embodiment is effective when the priority receiver 304a is located at the edge portion of the communication range R of the transmitter 104 as shown in FIG. In this case, the priority receiver 304a can communicate with the transmitter 104, but the communication quality is not good. Therefore, for example, when the transmission data is video data, the priority receiver 304a cannot reproduce high-quality video even if high-quality video data is sent.
　映像データは、フレームレートが高いほど、また、各フレームの解像度が高いほど、画質がよくなる。即ち、フレームレートが高いほど、映像が滑らかになり、解像度が高いほど映像が鮮明になる。しかし、画質がよくなれば伝送データの量が増加して、通信品質が良好でない受信機では高画質の映像データを完全に受信できなくなる。この場合に、フレームレートを落とすか、又は解像度を落とすことで、画質を低くして伝送データの量を抑えることができる。 The video data has better image quality as the frame rate is higher and the resolution of each frame is higher. That is, the higher the frame rate, the smoother the video, and the higher the resolution, the clearer the video. However, if the image quality improves, the amount of transmission data increases, and a receiver with poor communication quality cannot completely receive high-quality video data. In this case, by reducing the frame rate or reducing the resolution, the image quality can be lowered and the amount of transmission data can be suppressed.
　また、映像データをフレーム内符号化フレーム（Ｉフレーム）およびフレーム間符号化フレーム（Ｐフレーム又はＢフレーム）を用いて符号化する場合には、映像の滑らかさと鮮明度との関係は次のようになる。即ち、フレーム内符号化フレームは、それ自体でフレームを再生できるので、フレーム内符号化フレームが確実に伝送されるということは、即ち、鮮明な映像（解像度の高い映像）の表示が確実になることを意味する。フレーム内符号化フレームの伝送を優先する場合には、フレーム間符号化フレームが抜けることがあり、それによって映像の滑らかさが損なわれる可能性はあるが、少なくともフレーム内符号化フレームの周期で解像度の高い映像を得ることができる。この意味で、フレーム内符号化フレームの伝送を優先することは、即ち解像度を優先することを意味する。 When video data is encoded using an intra-frame encoded frame (I frame) and an inter-frame encoded frame (P frame or B frame), the relationship between video smoothness and sharpness is as follows. become. That is, since the intra-frame encoded frame can be reproduced by itself, the fact that the intra-frame encoded frame is reliably transmitted means that a clear image (high resolution image) is displayed. Means that. When priority is given to transmission of intra-frame encoded frames, inter-frame encoded frames may be lost, which may impair the smoothness of the video. High image quality can be obtained. In this sense, giving priority to transmission of an intra-frame encoded frame means giving priority to resolution.
　一方、フレーム間符号化フレームは、フレーム内符号化フレームを利用して再生されるので、フレーム内符号化フレームが伝送されてさえいれば、フレーム間符号化フレームが確実に伝送されるということは、フレーム内符号化フレーム間の映像を滑らかな表示が確実になることを意味する。フレーム間符号化フレームの伝送を優先する場合には、フレーム内符号化フレームが抜けることがあり、それによって次のフレーム内符号化フレームまで映像を再生できなくなる可能性はあるが、フレーム内符号化フレームが伝送されてさえいれば、より滑らかな映像を得ることができる。この意味で、フレーム間符号化フレームの伝送を優先することは、即ちフレームレートを優先することを意味する。 On the other hand, an inter-frame encoded frame is reproduced using an intra-frame encoded frame. Therefore, as long as an intra-frame encoded frame is transmitted, the inter-frame encoded frame is transmitted reliably. This means that a smooth display of the video between the intra-frame encoded frames is ensured. When priority is given to transmission of inter-frame encoded frames, intra-frame encoded frames may be lost, which may prevent video from being reproduced until the next intra-frame encoded frame. As long as the frame is transmitted, a smoother image can be obtained. In this sense, giving priority to transmission of inter-frame encoded frames means giving priority to the frame rate.
　そこで、本実施の形態では、優先受信機３０４ａの通信品質が低く、優先受信機３０４ａにて高画質の伝送データを受信できない状況において、優先受信機３０４ａにおいて解像度を優先するかフレームレートを優先するかを任意に選択できるマルチキャスト配信システムを提供する。 Therefore, in the present embodiment, in the situation where the communication quality of the priority receiver 304a is low and high-quality transmission data cannot be received by the priority receiver 304a, the priority receiver 304a prioritizes resolution or frame rate. Provided is a multicast distribution system that can be arbitrarily selected.
　図１１は、第４の実施の形態の送信機１０４の構成を示すブロック図であり、図１２は、第４の実施の形態の受信機３０４の構成を示すブロック図である。まず、図１２を参照して、本実施の形態の受信機３０４の構成を説明する。 FIG. 11 is a block diagram illustrating a configuration of the transmitter 104 according to the fourth embodiment, and FIG. 12 is a block diagram illustrating a configuration of the receiver 304 according to the fourth embodiment. First, the configuration of the receiver 304 of the present embodiment will be described with reference to FIG.
　図１２に示すように、受信機３０４は、第１の実施の形態の受信機３０１の構成に加えて、さらに、受信応答出力設定部３７を備えている。受信応答出力設定部３７は、ユーザの操作に応じて、受信応答を生成するよう受信応答生成部３５を設定することで、受信機３０４を優先受信機とする。受信機３０４が優先受信機として設定されると、受信応答生成部３５は、誤り判定部３３による誤り判定の結果に従って受信応答を生成する。 As shown in FIG. 12, the receiver 304 is further provided with a reception response output setting unit 37 in addition to the configuration of the receiver 301 of the first embodiment. The reception response output setting unit 37 sets the reception response generation unit 35 to generate a reception response in accordance with a user operation, thereby setting the receiver 304 as a priority receiver. When the receiver 304 is set as a priority receiver, the reception response generation unit 35 generates a reception response according to the result of error determination by the error determination unit 33.
　受信機３０４は、さらに、映像パラメータ設定要求部４１を備えている。映像パラメータ設定要求部４１は、ユーザの操作に応じて映像パラメータの設定を要求する映像パラメータ設定要求を生成し、受信応答生成部３５に提供する。受信応答生成部３５は、映像パラメータ設定要求部４１にて生成された映像パラメータ設定要求を含む受信応答を生成する。送信部３６は、受信応答生成部３５にて生成された受信応答を送信機１０４に送信する。 The receiver 304 further includes a video parameter setting request unit 41. The video parameter setting request unit 41 generates a video parameter setting request for requesting the setting of the video parameter in accordance with a user operation, and provides it to the reception response generation unit 35. The reception response generation unit 35 generates a reception response including the video parameter setting request generated by the video parameter setting request unit 41. The transmission unit 36 transmits the reception response generated by the reception response generation unit 35 to the transmitter 104.
　ここで、映像パラメータには、映像の解像度およびフレームレートが含まれる。上述のように映像の画質は、解像度とフレームレートで決まる。解像度を高くするほど映像が鮮明になり、フレームレートを高くするほど映像が滑らかになるが、いずれの場合も伝送データ量が増加する。限られた伝送データ量に対して、解像度を高くしようとすれば、フレームレートは低くしなければならず、逆にフレームレートを高くする場合には、解像度は低くしなければならない。 Here, video parameters include video resolution and frame rate. As described above, the image quality of the video is determined by the resolution and the frame rate. The higher the resolution, the clearer the video, and the higher the frame rate, the smoother the video. In either case, the amount of transmitted data increases. If the resolution is to be increased with respect to the limited amount of transmission data, the frame rate must be lowered. Conversely, if the frame rate is increased, the resolution must be lowered.
　十分な量のデータを伝送できる場合には、解像度およびフレームレートともにユーザが満足いく高さを実現できるが、図１０の状況のように、通信品質が良好でない場合には、解像度を比較的高く保ってフレームレートを下げることで対応することができ、逆にフレームレートを比較的高く保って解像度を下げることで対応することもでき、さらには解像度およびフレームレートを何れも適度に下げることもできる。本実施の形態の受信機３０４では、ユーザが映像パラメータ設定要求部４１を操作することにより任意に映像パラメータを設定できる。 If a sufficient amount of data can be transmitted, the user can achieve a satisfactory resolution and frame rate, but if the communication quality is not good as in the situation of FIG. 10, the resolution is relatively high. It can be handled by lowering the frame rate while maintaining it, and conversely, it can be handled by lowering the resolution while keeping the frame rate relatively high, and further, both the resolution and the frame rate can be lowered appropriately. . In receiver 304 of the present embodiment, a user can arbitrarily set video parameters by operating video parameter setting request unit 41.
　映像パラメータ設定要求部４１は、解像度又はフレームレートの優先度合いを連続的に指定できるものであってもよいし、例えば「解像度優先」か「フレームレート優先」か「解像度およびフレームレートを同程度」（優先はなし）かを選ぶものであってもよい。優先度合いは、例えば百分率で表されてよい。例えば、解像度を７０％とした場合は、フレームレートは３０％となる。映像パラメータ設定要求には、このような優先の度合いの情報が含まれる。 The video parameter setting request unit 41 may be capable of continuously specifying the priority of resolution or frame rate. For example, “resolution priority”, “frame rate priority”, or “resolution and frame rate are about the same”. (No priority) may be selected. The priority may be expressed as a percentage, for example. For example, when the resolution is 70%, the frame rate is 30%. The video parameter setting request includes information on the degree of priority.
　次に、送信機１０４の構成を説明する。図１１に示すように、送信機１０４は、第１の実施の形態の送信機１０１の構成に加えて、さらに、映像パラメータ設定要求判定部２５およびフレームタイプ別再送リミット決定部２６を備えている。 Next, the configuration of the transmitter 104 will be described. As shown in FIG. 11, the transmitter 104 further includes a video parameter setting request determination unit 25 and a frame type-specific retransmission limit determination unit 26 in addition to the configuration of the transmitter 101 of the first embodiment. .
　映像パラメータ設定要求判定部２５は、受信部１２にて受信した受信応答に含まれる映像パラメータ設定要求の内容を判定し、判定結果を画質決定部２４に出力する。通信品質推定部１７は、受信応答の受信率や受信応答のＳ／Ｎ比に基づいて、受信機との間の通信品質を推定し、推定結果を画質決定部２４に出力する。 The video parameter setting request determination unit 25 determines the content of the video parameter setting request included in the reception response received by the reception unit 12, and outputs the determination result to the image quality determination unit 24. The communication quality estimation unit 17 estimates the communication quality with the receiver based on the reception rate of the reception response and the S / N ratio of the reception response, and outputs the estimation result to the image quality determination unit 24.
　画質決定部２４は、通信品質推定部１７による推定結果に基づいて画質を求め、その画質の範囲内で、映像パラメータ設定要求判定部２５で得られた判定結果に基づいて解像度又はフレームレートをどの程度優先するかを決定する。画質決定部２４で決定された画質および解像度又はフレームレートの優先度は、コンテンツ提供部１３に出力される。コンテンツ提供部１３は、画質決定部２４で決定された解像度及びフレームレートで映像データを生成する。 The image quality determination unit 24 obtains the image quality based on the estimation result by the communication quality estimation unit 17, and determines the resolution or frame rate based on the determination result obtained by the video parameter setting request determination unit 25 within the image quality range. Decide whether to give priority. The image quality and resolution or frame rate priority determined by the image quality determination unit 24 are output to the content providing unit 13. The content providing unit 13 generates video data at the resolution and frame rate determined by the image quality determining unit 24.
　なお、通信品質推定部１７は、受信応答のＳ／Ｎ比に加え、又は受信応答のＳ／Ｎ比に代えて、受信応答の受信率を指標として通信品質を推定してもよい。 The communication quality estimation unit 17 may estimate the communication quality using the reception rate of the reception response as an index in addition to the S / N ratio of the reception response or instead of the S / N ratio of the reception response.
　本実施の形態は、上述のように通信品質や映像パラメータ設定要求に応じてフレームレートの優先度を動的に変更しながら、コンテンツ提供部１３にて生成する映像データの画質を調整するだけでなく、通信品質や映像パラメータ設定要求に基づいて、フレームタイプごとの再送リミットも動的に変更する。このために、送信機１０４は、フレームタイプ別再送リミット決定部２６を備えている。 In this embodiment, as described above, only the image quality of the video data generated by the content providing unit 13 is adjusted while dynamically changing the priority of the frame rate according to the communication quality and the video parameter setting request. Instead, the retransmission limit for each frame type is also dynamically changed based on the communication quality and the video parameter setting request. For this purpose, the transmitter 104 includes a retransmission limit determining unit 26 for each frame type.
　符号化部１４は、コンテンツ提供部１３にて生成された映像データをフレーム内符号化フレーム（Ｉフレーム）およびフレーム間符号化フレーム（Ｐフレーム又はＢフレーム）を用いて符号化する。通信品質推定部１７による推定結果および映像パラメータ設定要求判定部２５による判定結果は、フレームタイプ別再送リミット決定部２６にも出力される。フレームタイプ別再送リミット決定部２６は、通信品質推定部１７による推定結果および映像パラメータ設定要求判定部２５による判定結果に基づいて、フレームタイプ、即ちフレーム内符号化フレームおよびフレーム間符号化フレームごとに再送リミットを決定する。 The encoding unit 14 encodes the video data generated by the content providing unit 13 using an intra-frame encoded frame (I frame) and an inter-frame encoded frame (P frame or B frame). The estimation result by the communication quality estimation unit 17 and the determination result by the video parameter setting request determination unit 25 are also output to the retransmission limit determination unit 26 by frame type. Based on the estimation result by the communication quality estimation unit 17 and the determination result by the video parameter setting request determination unit 25, the frame type retransmission limit determination unit 26 determines the frame type, that is, for each intra-frame encoded frame and inter-frame encoded frame. Determine retransmission limit.
　フレームタイプ別再送リミット決定部２６は、解像度を優先する場合は、フレーム内符号化フレームの再送リミットは大きく、フレーム間符号化フレームの再送リミットは小さくする。図１０は、このような状況を示している。再送リミットをこのように決定することで、通信品質の低い受信機は、フレーム間符号化フレームが抜けることで映像の滑らかさが損なわれる可能性はあるが、少なくともフレーム内符号化フレームの周期で解像度の高い映像を得ることができる。また、通信品質が高い受信機では、解像度およびフレームレートともに高い映像を得ることができる。 The frame type retransmission limit determination unit 26 increases the retransmission limit of the intra-frame encoded frame and decreases the retransmission limit of the inter-frame encoded frame when priority is given to the resolution. FIG. 10 shows such a situation. By determining the retransmission limit in this way, a receiver with low communication quality may lose the smoothness of the video due to the loss of the inter-frame encoded frame, but at least in the period of the intra-frame encoded frame. High resolution video can be obtained. In addition, a receiver with high communication quality can obtain images with high resolution and frame rate.
　フレームタイプ別再送リミット決定部２６は、フレームレートを優先する場合は、フレーム内符号化フレームの再送リミットは小さく、フレーム間符号化フレームの再送リミットは大きくする。再送リミットをこのように決定することで、通信品質の低い受信機は、フレーム内符号化フレームが抜けることで次のフレーム内符号化までの期間、映像が止まる可能性はあるが、フレーム内符号化フレームを受信できれば、より滑らかな映像を得ることができる。また、通信品質が高い受信機では、解像度およびフレームレートともに高い映像を得ることができる。 If the frame rate is prioritized, the frame type retransmission limit determination unit 26 decreases the retransmission limit of the intra-frame encoded frame and increases the retransmission limit of the inter-frame encoded frame. By determining the retransmission limit in this way, a receiver with low communication quality may stop video during the period until the next intra-frame encoding due to the loss of the intra-frame encoded frame. If a frame can be received, a smoother video can be obtained. In addition, a receiver with high communication quality can obtain images with high resolution and frame rate.
　本実施の形態によれば、リアルタイム性を確保しつつ、優先受信機で受信する映像の画質を、ユーザの要求に応じて設定することができる。 According to the present embodiment, it is possible to set the image quality of the video received by the priority receiver according to the user's request while ensuring the real-time property.
　以上、本発明の実施の形態を例示により説明したが、本発明の範囲はこれらに限定されるものではなく、請求項に記載された範囲内において目的に応じて変更・変形することが可能である。 The embodiments of the present invention have been described above by way of example, but the scope of the present invention is not limited to these embodiments, and can be changed or modified according to the purpose within the scope of the claims. is there.
　以上に現時点で考えられる本発明の好適な実施の形態を説明したが、本実施の形態に対して多様な変形が可能であり、そして、本発明の真実の精神と範囲内にあるそのようなすべての変形を添付の請求の範囲が含むことが意図されている。 Although the presently preferred embodiments of the present invention have been described above, various modifications can be made to the present embodiments, and such modifications are within the true spirit and scope of the present invention. It is intended that the appended claims include all modifications.
　以上のように、本発明に係るマルチキャスト配信システムは、複数の受信機に伝送データを無線でマルチキャスト配信する際に、伝送路の通信品質に合わせて受信機群に最適な伝送条件を自動調整できるという効果を有し、無線通信品質に応じて伝送データの伝送条件（符号化レート、画質、再送リミット等）を調整するマルチキャスト配信システム等として有用である。 As described above, the multicast distribution system according to the present invention can automatically adjust the optimum transmission condition for the receiver group in accordance with the communication quality of the transmission path when the transmission data is wirelessly distributed to a plurality of receivers. It is useful as a multicast distribution system or the like that adjusts transmission conditions (encoding rate, image quality, retransmission limit, etc.) of transmission data according to wireless communication quality.
　１、３、４　無線通信システム
　１０１、１０２、１０３、１０４　送信機
　１１　送信部
　１２　受信部
　１３　コンテンツ提供部
　１４　符号化部
　１５　送信パケット生成部
　１６　受信応答判定部
　１７　通信品質推定部
　１８　符号化レート決定部
　１９　優先受信機判定部
　２０　受信応答許可出力部
　２１　受信機識別番号要求部
　２２　送信フレーム再送リミット決定部
　２３　サブブロック再送リミット決定部
　２４　画質決定部
　２５　映像パラメータ設定要求判定部
　２６　フレームタイプ別再送リミット決定部
　３０１、３０２、３０３、３０４　受信機
　３０１ａ、３０３ａ、３０４ａ　優先受信機
　３０１ｂ、３０３ｂ、３０４ｂ　非優先受信機
　３１　受信部
　３２　復号化部
　３３　誤り判定部
　３４　コンテンツ再生部
　３５　受信応答生成部
　３６　送信部
　３７　受信応答出力設定部
　３８　受信機識別番号要求判定部
　３９　受信機識別番号出力部
　４０　受信応答許可判定部
　４１　映像パラメータ設定要求部 DESCRIPTION OF SYMBOLS 1, 3, 4 Wireless communication system 101,102,103,104 Transmitter 11 Transmission part 12 Reception part 13 Content provision part 14 Encoding part 15 Transmission packet generation part 16 Reception response determination part 17 Communication quality estimation part 18 Encoding rate Determination unit 19 Priority receiver determination unit 20 Reception response permission output unit 21 Receiver identification number request unit 22 Transmission frame retransmission limit determination unit 23 Sub-block retransmission limit determination unit 24 Image quality determination unit 25 Video parameter setting request determination unit 26 By frame type Retransmission limit determination unit 301, 302, 303, 304 Receiver 301a, 303a, 304a Priority receiver 301b, 303b, 304b Non-priority receiver 31 Receiver unit 32 Decoding unit 33 Error determination unit 34 Content playback unit 35 Reception response generation unit 36 Transmitter 37 Reception response output setting Unit 38 receiver identification number request determination unit 39 receiver identification number output unit 40 reception response permission determination unit 41 video parameter setting request unit

Claims (13)

  1. 　送信機と複数の受信機とを含み、前記送信機から前記複数の受信機に伝送データをマルチキャスト配信するマルチキャスト配信システムであって、
    　前記複数の受信機のうちの一部は優先受信機であり、その他は非優先受信機であり、
    　前記優先受信機は、
    　　前記送信機から受信した伝送データに対する受信応答を生成する受信応答生成部と、
    　　前記受信応答生成部にて生成された受信応答を送信機に送信する受信応答送信部と、
    　を備え、
    　前記送信機は、
    　　前記優先受信機から送信されてきた受信応答に基づいて、当該優先受信機の通信品質を推定する通信品質推定部と、
    　　前記通信品質推定部にて推定された前記優先受信機の通信品質に基づいて前記伝送データの伝送条件を決定する伝送条件決定部と、
    　　前記伝送データを送信する伝送データ送信部と、
    　を備えたことを特徴とするマルチキャスト配信システム。     A multicast distribution system including a transmitter and a plurality of receivers, and multicasting transmission data from the transmitter to the plurality of receivers,
    Some of the plurality of receivers are priority receivers, others are non-priority receivers,
    The priority receiver is:
    A reception response generator for generating a reception response to the transmission data received from the transmitter;
    A reception response transmitter for transmitting the reception response generated by the reception response generator to a transmitter;
    With
    The transmitter is
    Based on the reception response transmitted from the priority receiver, a communication quality estimation unit that estimates the communication quality of the priority receiver;
    A transmission condition determination unit that determines a transmission condition of the transmission data based on the communication quality of the priority receiver estimated by the communication quality estimation unit;
    A transmission data transmission unit for transmitting the transmission data;
    A multicast distribution system comprising:
  2. 　前記送信機は、伝送データを符号化する符号化部を備え、
    　前記伝送条件決定部は、前記伝送条件として前記符号化部における符号化レートを決定して前記符号化部に設定する符号化レート決定部であり、
    　前記符号化レート決定部は、前記優先受信機の通信品質が良好でないときに、通信品質が良好であるときよりも低い符号化レートを設定することを特徴とする請求項１に記載のマルチキャスト配信システム。     The transmitter includes an encoding unit that encodes transmission data,
    The transmission condition determination unit is an encoding rate determination unit that determines an encoding rate in the encoding unit as the transmission condition and sets the encoding rate in the encoding unit,
    The multicast distribution according to claim 1, wherein the coding rate determination unit sets a lower coding rate than when the communication quality is good when the communication quality of the priority receiver is not good. system.
  3. 　前記送信機は、伝送データとして映像データを生成するビデオ撮影部を備え、
    　前記伝送条件決定部は、前記伝送条件として前記ビデオ撮影部における画質を決定して前記ビデオ撮影部に設定する画質決定部であり、
    　前記画質決定部は、前記優先受信機の通信品質が良好でないときに、通信品質が良好であるときよりも低い画質を設定することを特徴とする請求項１に記載のマルチキャスト配信システム。     The transmitter includes a video photographing unit that generates video data as transmission data,
    The transmission condition determining unit is an image quality determining unit that determines image quality in the video shooting unit as the transmission condition and sets the image quality in the video shooting unit,
    The multicast distribution system according to claim 1, wherein the image quality determination unit sets a lower image quality when the communication quality of the priority receiver is not good than when the communication quality is good.
  4. 　前記送信機は、前記優先受信機からの受信応答の受信状況に基づいて、伝送データを再送する再送信部を備え、
    　前記伝送条件決定部は、前記伝送条件として前記再送信部における再送上限回数を決定して前記再送信部に設定する再送リミット決定部であり、
    　前記再送リミット決定部は、前記優先受信機から前記受信応答を受信しないときに、前記受信応答を受信したときよりも小さい再送上限回数を設定することを特徴とする請求項１に記載のマルチキャスト配信システム。     The transmitter includes a retransmission unit that retransmits transmission data based on a reception status of a reception response from the priority receiver,
    The transmission condition determination unit is a retransmission limit determination unit that determines the upper limit number of retransmissions in the retransmission unit as the transmission condition and sets it in the retransmission unit,
    2. The multicast delivery according to claim 1, wherein the retransmission limit determining unit sets a smaller number of retransmission upper limits than when receiving the reception response when the reception response is not received from the priority receiver. system.
  5. 　前記送信機は、１フレーム分の伝送データを複数のサブブロックに分けて符号化する符号化部を備え、
    　前記再送リミット決定部は、前記伝送条件として前記再送信部におけるフレーム単位の再送上限回数を決定して前記再送信部に設定するフレーム再送リミット決定部及び前記伝送条件として前記再送信部におけるサブブロック単位の再送上限回数を決定して前記再送信部に設定するサブブロック再送リミット決定部を含み、
    　前記フレーム再送リミット決定部及び前記サブブロック再送リミット決定部は、それぞれ前記優先受信機から前記受信応答を受信しないときに、前記受信応答を受信したときよりも小さい再送上限回数を設定することを特徴とする請求項４に記載のマルチキャスト配信システム。     The transmitter includes an encoding unit that encodes transmission data for one frame by dividing it into a plurality of sub-blocks,
    The retransmission limit determination unit determines a frame unit retransmission upper limit count in the retransmission unit as the transmission condition and sets the retransmission limit determination unit in the retransmission unit, and a subblock in the retransmission unit as the transmission condition Including a sub-block retransmission limit determination unit that determines the upper limit number of retransmissions of a unit and sets it in the retransmission unit,
    The frame retransmission limit determination unit and the sub-block retransmission limit determination unit each set a lower retransmission upper limit than when the reception response is received when the reception response is not received from the priority receiver. The multicast distribution system according to claim 4.
  6. 　前記通信品質推定部は、前記受信応答に含まれるサブブロック誤り率に基づいて、前記優先受信機の通信品質を推定することを特徴とする請求項５に記載のマルチキャスト配信システム。 The multicast distribution system according to claim 5, wherein the communication quality estimation unit estimates the communication quality of the priority receiver based on a sub-block error rate included in the reception response.
  7. 　前記優先受信機は、
    　　映像の解像度およびフレームレートの何れを優先するかを示す映像パラメータ設定要求を生成する映像パラメータ設定要求部と、
    　　前記映像パラメータ設定要求を送信する前記映像パラメータ設定要求送信部と、
    　をさらに備え、
    　前記送信機は、
    　　伝送データとして映像データを生成するビデオ撮影部と、
    　　前記映像データをフレーム内符号化フレーム及びフレーム間符号化フレームを用いて符号化する符号化部と、
    　　前記優先受信機より受信した前記映像パラメータ設定要求に基づいて、映像の解像度およびフレームレートの何れを優先するかを判定する映像パラメータ設定要求判定部と、
    　をさらに備え、
    　前記伝送条件決定部は、前記伝送条件として前記再送信部における再送上限回数をフレームタイプ別に決定して前記再送信部に設定するフレームタイプ別再送リミット決定部であり、
    　前記フレームタイプ別再送リミット決定部は、前記映像パラメータ設定要求判定部にて解像度を優先すると判定したときに、前記フレーム内符号化フレームの再送上限回数を前記フレーム間符号化フレームの再送上限回数よりも大きく設定することを特徴とする請求項４に記載のマルチキャスト配信システム。     The priority receiver is:
    A video parameter setting request unit for generating a video parameter setting request indicating which of the video resolution and the frame rate has priority;
    The video parameter setting request transmission unit for transmitting the video parameter setting request;
    Further comprising
    The transmitter is
    A video shooting unit that generates video data as transmission data;
    An encoding unit that encodes the video data using an intra-frame encoded frame and an inter-frame encoded frame;
    Based on the video parameter setting request received from the priority receiver, a video parameter setting request determination unit that determines which of the video resolution and frame rate is prioritized;
    Further comprising
    The transmission condition determining unit is a retransmission limit determining unit for each frame type that determines, as the transmission condition, a retransmission upper limit number in the retransmission unit for each frame type and sets in the retransmission unit,
    The retransmission limit determining unit for each frame type determines the upper limit number of retransmissions of the intra-frame encoded frame from the upper limit number of retransmissions of the inter-frame encoded frame when the video parameter setting request determination unit determines that resolution is prioritized. The multicast distribution system according to claim 4, wherein a larger value is set.
  8. 　前記複数の受信機のうちの前記優先受信機及び前記非優先受信機のいずれもが、前記受信応答生成部と、受信応答を生成するか否かを前記受信応答生成部に設定する受信応答出力設定部とを備え、
    　前記優先受信機となるべき受信機の前記受信応答出力設定部は、受信応答を生成するよう前記受信応答生成部に設定をし、前記非優先受信機となるべき受信機の前記受信応答出力設定部は、受信応答を生成しないよう前記受信応答生成部に設定をすることを特徴とする請求項１ないし７のいずれかに記載のマルチキャスト配信システム。     The priority response receiver and the non-priority receiver of the plurality of receivers set the reception response generation unit and the reception response generation unit to set whether or not to generate a reception response. A setting unit,
    The reception response output setting unit of the receiver to be the priority receiver sets the reception response generation unit to generate a reception response, and the reception response output setting of the receiver to be the non-priority receiver The multicast distribution system according to claim 1, wherein the unit sets the reception response generation unit so as not to generate a reception response.
  9. 　前記受信応答出力設定部は、ユーザの操作に応じて受信応答を生成するか否かを前記受信応答生成部に設定することを特徴とする請求項７に記載のマルチキャスト配信システム。 The multicast delivery system according to claim 7, wherein the reception response output setting unit sets whether or not to generate a reception response according to a user operation in the reception response generation unit.
  10. 　前記送信機は、前記複数の受信機のうちの前記優先受信機の受信応答を許可する受信応答許可を出力する受信応答許可出力部をさらに備え、
    　前記受信応答出力設定部は、受信応答許可にて自らが前記優先受信機として受信応答を許可されている場合に、受信応答を生成するよう前記受信応答生成部に設定し、自己に対して受信応答の許可がされていない場合は、受信応答を生成しないよう前記受信応答生成部に設定することを特徴とする請求項９に記載のマルチキャスト配信システム。     The transmitter further includes a reception response permission output unit that outputs a reception response permission that permits a reception response of the priority receiver among the plurality of receivers,
    The reception response output setting unit sets the reception response generation unit to generate a reception response when the reception response is permitted as a priority receiver by the reception response permission, and receives the response to itself. 10. The multicast distribution system according to claim 9, wherein when the response is not permitted, the reception response generation unit is set not to generate a reception response.
  11. 　前記送信機は、
    　　前記複数の受信機が各々保持している自己の識別番号を送信するよう要求する受信機識別番号要求部と、
    　　前記複数の受信機のうちの前記優先受信機とすべき受信機の識別番号が記憶されており、前記受信機識別番号要求部による要求に応じて前記複数の受信機の各々から送信された受信識別番号を受信して、前記優先受信機とすべき受信機を判定する優先受信機判定部と、
    　をさらに備え、
    　前記受信応答許可出力部は、前記優先受信機判定部にて優先受信機とすべきと認定された受信機に対して受信応答を許可する受信応答許可を出力することを特徴とする請求項１０に記載のマルチキャスト配信システム。     The transmitter is
    A receiver identification number requesting unit for requesting transmission of its own identification number held by each of the plurality of receivers;
    An identification number of a receiver to be used as the priority receiver among the plurality of receivers is stored, and received from each of the plurality of receivers in response to a request by the receiver identification number request unit A priority receiver determination unit that receives an identification number and determines a receiver to be the priority receiver;
    Further comprising
    11. The reception response permission output unit outputs a reception response permission that permits a reception response to a receiver that is determined to be a priority receiver by the priority receiver determination unit. The multicast distribution system described in 1.
  12. 　請求項１ないし１１のいずれかに記載のマルチキャスト配信システムにおける前記送信機。 The transmitter in the multicast distribution system according to any one of claims 1 to 11.
  13. 　請求項８ないし１１のいずれかに記載のマルチキャスト配信システムにおける前記受信機。
          The receiver in the multicast distribution system according to any one of claims 8 to 11.
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