Video transmission system, video transmission method, video transmitting device, video receiving device, and program

Abstract

A video communication system 1 comprises: a video transmission device 2 that stores a packet of video data in a transmission buffer 22 and that transmits the packet stored in the transmission buffer; a video reception device 3 that receives the packet; and an inference unit 34 that infers, from the arrival time of each packet at the video reception device 3, a characteristic of a communication path 4 between the video transmission device 2 and the video reception device 3. The video transmission device 2 transmits packets at a timing that is specified from the inverse characteristic with respect to the characteristic of the communication path 4.

Description

[Technical field]

[0001] The present invention relates to a video transmission system, a video transmission method, a video transmitting device, a video receiving device, and a program. [Background technology]

[0002] Non-patent documents 1 to 3 describe methods for transmitting uncompressed video and audio over a communication network.

[0003] Non-Patent Document 1 discloses a method for transmitting packets in which video essence is stored in a Real-time Transport Protocol (RTP) payload. In uncompressed video transmission, the number of packets per frame is constant as long as the pixel mapping method to the RTP packets and the video parameters do not change.

[0004] Non-Patent Document 2 discloses a desirable RTP packet transmission timing model for uncompressed video transmission. In the Linear model, the RTP packet transmission interval is always constant. The Gapped model is a timing model based on the Serial Digital Interface (SDI). In the Gapped model, RTP packets are transmitted at constant intervals only during a period corresponding to the effective pixels of SDI in each frame. The receiving device is designed based on the transmission timing model.

[0005] Non-Patent Document 3 discloses a complete redundant transmission (seamless protection) to deal with packet loss on a communication network. In seamless protection, the same RTP packet is sent over two different routes. The receiving side integrates the RTP packets received from the two routes based on the sequence number in the RTP header. This makes it possible to compensate for the loss of an RTP packet on one of the routes. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] SMPTE ST 2110-20:2017 Professional Media Over Managed IP Networks:Uncompressed Active Video [Non-Patent Document 2] SMPTE ST 2110-21:2017 Professional Media Over Managed IP Networks:Traffic Shaping and Delivery Timing for Video [Non-Patent Document 3] SMPTE ST 2022-7:2013 Seamless Protection Switching of SMPTE ST 2022 IP Datagrams Summary of the Invention [Problem to be solved by the invention]

[0007] However, the transmission path may affect the timing of receiving RTP packets containing video data at the receiving side. For example, delay jitter may occur due to packets being stuck in a network device on the transmission path. In order to compensate for the delay in the arrival of RTP packets caused by delay jitter, a receiving buffer with a capacity larger than the fluctuation range of the delay jitter is required. Also, when the arrival interval of RTP packets becomes short, the receiving side may not be able to take the RTP packets into the receiving buffer due to the specifications of the receiving side's hardware, etc., and may drop the RTP packets.

[0008] The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a technique capable of offsetting the effect that a transmission path has on the arrival timing of a packet containing video data. [Means for solving the problem]

[0009] A video transmission system of one embodiment of the present invention comprises a video transmitting device that stores packets of video data in a transmission buffer and transmits the packets stored in the transmission buffer, a video receiving device that receives the packets, and an estimation unit that estimates characteristics of a transmission path between the video transmitting device and the video receiving device from the arrival time of each packet at the video receiving device, and the video transmitting device transmits the packets at a timing determined from the inverse characteristics of the characteristics of the transmission path.

[0010] A video transmission method of one embodiment of the present invention includes a step of a video transmitting device storing packets of video data in a transmission buffer and transmitting the packets stored in the transmission buffer, a step of a video receiving device receiving the packets, a step of a computer estimating characteristics of a transmission path between the video transmitting device and the video receiving device from the arrival time of each packet at the video receiving device, and a step of the video transmitting device transmitting the packets at a timing determined from the inverse characteristics of the characteristics of the transmission path.

[0011] A video transmitting device of one embodiment of the present invention comprises a transmission buffer for storing packets of video data, a transmitting unit for transmitting the packets stored in the transmission buffer to a video receiving device, and a control unit for receiving from the video receiving device characteristics of a transmission path between the video transmitting device and the video receiving device estimated from the arrival time of each packet, and controlling the transmitting unit to transmit the packets at a timing determined from the inverse characteristics of the characteristics of the transmission path.

[0012] A video receiving device of one embodiment of the present invention stores packets of video data in a transmission buffer, is connected to a video transmitting device that transmits the packets stored in the transmission buffer, and is equipped with a receiving unit that receives the packets from the video transmitting device, and an estimation unit that estimates the characteristics of the transmission path between the video transmitting device and the video receiving device from the arrival time of each packet.

[0013] One aspect of the present invention is a program for causing a computer to function as the video transmitting device or the video receiving device. Effect of the Invention

[0014] According to the present invention, it is possible to provide a technique capable of offsetting the effect that a transmission path has on the arrival timing of a packet containing video data. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a diagram illustrating a system configuration of a video transmission system according to a first embodiment of the present invention, and functional blocks of a video transmitting device and a video receiving device. [Diagram 2] FIG. 2 is a sequence diagram illustrating a video transmission method in the video transmission system according to the first embodiment of the present invention. [Diagram 3] FIG. 3 is an example illustrating the ideal arrival time of a packet, the observed arrival time and the delay jitter. [Figure 4] FIG. 4 is a diagram illustrating a system configuration of a video transmission system according to a second embodiment of the present invention, and functional blocks of a video transmitting device and a video receiving device. [Diagram 5] FIG. 5 is a diagram for explaining the jitter tolerance time extended according to the third embodiment of the present invention. [Figure 6] FIG. 6 is a diagram illustrating the hardware configuration of a computer used in the video transmitting device and the video receiving device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the description of the drawings, the same parts are given the same reference numerals and the description will be omitted.

[0017] (First embodiment) (Video Transmission System) The video transmission system 1 includes a video transmitting device 2 and a video receiving device 3. The video transmitting device 2 and the video receiving device 3 are connected to each other so that they can communicate with each other via a transmission path 4. The video transmitting device 2 and the video receiving device 3 synchronize their times using Precision Time Protocol (PTP) or the like.

[0018] The video transmitting device 2 converts the video data into a plurality of packets. The video transmitting device 2 transmits the converted packets to the video receiving device 3 via a transmission path 4. The video data is the video essence to be reproduced.

[0019] The video receiving device 3 receives packets from the video transmitting device 2 via a transmission path 4. The video receiving device 3 generates video data from each received packet and plays back the generated video data.

[0020] In the first embodiment, the video transmitting device 2 includes a transmission buffer 22, and temporarily stores packets in the transmission buffer 22. The video transmitting device 2 transmits the packets stored in the transmission buffer 22 in accordance with the inverse characteristics of the characteristics of the transmission path 4 estimated in the video receiving device 3. In the first embodiment, the characteristics of the transmission path 4 are estimated from the arrival time of the packets.

[0021] In the video transmission system 1 according to the first embodiment, the video receiving device 3 calculates delay jitter as the effect that the transmission path 4 has on the arrival timing of a packet containing video data. The video receiving device 3 identifies the characteristics of the transmission path 4 from the delay jitter. The video transmitting device 2 temporarily stores the packet in the transmission buffer 22 and transmits the packet according to the inverse characteristics of the characteristics of the transmission path 4 identified by the video receiving device 3 from the delay jitter, thereby offsetting the identified characteristics of the transmission path 4. This enables the video transmission system 1 to compensate for the delay jitter in the video receiving device 3 by adjusting the transmission timing of the video transmitting device 2 using the transmission buffer 22.

[0022] The video transmitting device 2 includes a generating unit 21, a transmission buffer 22, a transmitting unit 23, and a control unit 24. The generating unit 21, the transmitting unit 23, and the control unit 24 are implemented in a CPU 901. The transmission buffer 22 is formed in a memory 902 or a storage 903. The video transmitting device 2 stores packets of video data in the transmission buffer 22, and transmits the packets stored in the transmission buffer 22.

[0023] A generator 21 generates packets of video data and stores the generated packets in a transmission buffer 22. The packets are packets based on a protocol for transferring video data in real time, such as RTP packets. Non-Patent Document 1, for example, is known as a method for packetizing video data into RTP packets.

[0024] The transmission buffer 22 stores the RTP packets of the video data. The transmission buffer 22 stores each RTP packet until a transmission timing controlled by the control unit 24 arrives.

[0025] The transmitting unit 23 transmits the RTP packets stored in the transmission buffer 22 to the video receiving device 3. The transmitting unit 23 transmits the packets at a timing specified by the control unit 24. Specifically, the transmitting unit 23 transmits the packets at a timing specified by the inverse characteristic of the characteristic of the transmission path 4.

[0026] The transmitting unit 23 stores the RTP packet in an arbitrary network protocol packet and transmits it to the transmission path 4. As the network protocol, User Datagram Protocol (UDP) / Internet Protocol (IP) / Ethernet may be used. Any type of transmission path may be used. A wavelength path with a dedicated wavelength may be used.

[0027] The control unit 24 receives the characteristics of the transmission path 4 from the video receiving device 3, and controls the transmission unit 23 to transmit packets at a timing specified from the inverse characteristic of the characteristics of the transmission path 4. Specifically, the control unit 24 determines the timing at which the transmission unit 23 transmits packets from the inverse characteristic of the characteristics of the transmission path 4 estimated in the video receiving device 3. Here, the inverse characteristic is a characteristic that offsets delay jitter caused by the estimated characteristics of the transmission path 4. The control unit 24 receives the characteristics of the transmission path 4 from the video receiving device 3 via the transmission path 4 or another communication network.

[0028] Any method can be used as a method for controlling the transmission timing by the control unit 24. For example, there is a method in which the control unit 24 notifies the transmission unit 23 when the transmission timing arrives, a method in which the control unit 24 notifies the transmission unit 23 of the transmission timing and the transmission unit 23 transmits according to the notified transmission timing, and the like.

[0029] The video receiving device 3 includes a receiving unit 31, a receiving buffer 32, a reproducing unit 33, and an estimating unit 34. The receiving unit 31, the reproducing unit 33, and the estimating unit 34 are implemented in a CPU 901. The receiving buffer 32 is formed in a memory 902 or a storage 903. The video receiving device 3 identifies characteristics of the transmission path 4 between the video transmitting device 2 and the video receiving device 3, estimated from the arrival time of each packet, and transmits the characteristics to the video transmitting device 2.

[0030] The receiving unit 31 receives packets from the video transmitting device 2 via the transmission path 4. The receiving unit 31 stores the received packets in the receiving buffer 32. Specifically, the receiving unit 31 extracts an RTP packet from any network protocol packet stored by the transmitting unit 23, and stores the RTP packet in the receiving buffer 32.

[0031] The receiving buffer 32 temporarily stores the RTP packets extracted by the receiving unit 31. The receiving buffer 32 records the arrival time of each packet and inputs it to the estimating unit 34. The arrival time of each packet may be measured by the receiving unit 31.

[0032] The reproduction unit 33 constructs video data from the RTP packets stored in the receiving buffer 32, and reproduces the data on a display (not shown) or the like.

[0033] The estimation unit 34 estimates the characteristics of the transmission path 4 between the video transmitting device 2 and the video receiving device 3 from the arrival time of each packet at the video receiving device 3. Here, the characteristics of the transmission path 4 are estimated from the delay jitter of each packet. The processing of the estimation unit 34 will be described in detail later.

[0034] In the embodiment of the present invention, a case will be described in which the video transmitting device 2 includes the control unit 24 and the video receiving device 3 includes the estimation unit 34, but the present invention is not limited to this. For example, the control unit 24 and the estimation unit 34 may be provided in a server capable of communicating with each of the video transmitting device 2 and the video receiving device 3. Also, either the video transmitting device 2 or the video receiving device 3 may include both the control unit 24 and the estimation unit 34. As long as the video transmitting device 2 can transmit packets with the inverse characteristics of the transmission path characteristics, the video transmission system 1 may be formed in any manner.

[0035] A video transmission method according to an embodiment of the present invention will be described with reference to Fig. 2. In the example shown in Fig. 2, a video transmitting device 2 first transmits packets sequentially. After the characteristics of a transmission path 4 are estimated in a video receiving device 3, the video transmitting device 2 transmits packets according to the inverse characteristics of the estimated characteristics.

[0036] First, in step S1, the video transmitting device 2 generates a plurality of RTP packets from video data. The video transmitting device 2 stores each of the generated RTP packets in the transmission buffer 22. In step S2, the video transmitting device 2 sequentially transmits the RTP packets stored in the transmission buffer 22 to the video receiving device 3. In step S3, the RTP packets are transmitted from the video transmitting device 2 to the video receiving device 3.

[0037] In step S4, the video receiving device 3 stores the received RTP packets in the receiving buffer 32. In step S5, the video receiving device 3 generates video data from the received RTP packets and plays back the video data.

[0038] In step S6, the video receiving device 3 estimates the characteristics of the transmission path 4 from the arrival time of each RTP packet. In step S7, the video receiving device 3 transmits the estimated characteristics of the transmission path 4 to the video transmitting device 2.

[0039] In step S8, the video transmitting device 2 transmits the RTP packet at a timing specified by the inverse characteristic of the characteristic of the transmission path 4 transmitted in step S6. In step S9, the RTP packet is transmitted from the video transmitting device 2 to the video receiving device 3.

[0040] According to such a video transmission system 1, RTP packets are transmitted from the video transmitting device 2 to the video receiving device 3 according to the inverse characteristics of the characteristics of the transmission path. The video transmission system 1 suppresses delay jitter and RTP packet drops occurring in the video receiving device 3. Furthermore, the video transmission system 1 can smooth the arrival timing of RTP packets in the video receiving device 3.

[0041] An example of a method for estimating the characteristics of the transmission path 4 will be described. The estimation unit 34 acquires the arrival time at the video receiving device 3 for the RTP packet group to be estimated. The estimation target is, for example, a packet group constituting one frame of video data. As another example, the estimation target may be a packet group received within a predetermined time period, such as one second.

[0042] Let T be the sequence of ideal packet arrival times of the packet group to be estimated. IDEAL Let (k) be the index of the RTP packet in the frame, 0≦k≦N-1, where N is the number of packets to be estimated. The ideal arrival time of the RTP packet is determined from the transmission timing model.

[0043] If the arrival time of the first RTP packet to be estimated is 0, then T IDEAL (k)=C*k, where C is the ideal RTP packet transmission interval based on the transmission timing model.

[0044] Let T be the sequence of arrival times of each RTP packet of the packet group to be estimated observed at the video receiving device 3. OBSERVED (k). The delay jitter T JITTER (k) is T JITTER (k)=T OBSERVED (k)-T IDEAL The result is (k).

[0045] Figure 3 shows the T IDEAL (k), T OBSERVED (k), T JITTER In the example shown in FIG. IDEAL (k) is expressed as 2*k, which is a net increase. In contrast, T OBSERVED (k) is T IDEAL There is a delay for (k).

[0046] The estimation unit 34 specifies the estimated delay jitter pattern J(k) as the characteristic of the transmission path 4. JITTER The delay jitter pattern obtained by averaging T(k) may be used as J(k). JITTER A delay jitter pattern predicted from (k) by deep learning or the like may be adopted as J(k). The estimation unit 34 transmits the estimated characteristics of the transmission path 4 to the video transmission device 2.

[0047] Next, a method for identifying the transmission timing of an RTP packet will be described. The control unit 24 of the video transmitting device 2 acquires the characteristics of the transmission path 4 estimated by the video receiving device 3. The control unit 24 determines the transmission timing T CONTROL (k) is T CONTROLThe control unit 24 controls the transmission timing of the subsequent packet of the estimation target estimated by the estimation unit 34. The control unit 24 controls the transmission timing of the packet of the frame that is transmitted after the frame estimated by the estimation unit 34.

[0048] The estimation unit 34 performs the above estimation at the start of transmission of the RTP packet, and CONTROL Alternatively, the estimation unit 34 may perform estimation at any time during operation, and T CONTROL (k) may be dynamically changed. In the case of an on-demand estimation, the estimation unit 34 may estimate periodically. Alternatively, the estimation unit 34 may monitor the magnitude of the delay jitter in the video receiving device 3 and estimate when the reference value exceeds a threshold. JITTER The L1 norm or L2 norm of (k) may be used.

[0049] This is expected to smooth the arrival intervals of RTP packets observed in the receiving buffer 32, and to prevent RTP packets from being dropped. It is also expected to reduce the receiving buffer size required to absorb delay jitter. Furthermore, the smaller buffer size is expected to reduce delays, contribute to reducing the required memory device capacity, and reduce costs and mounting area.

[0050] (Second embodiment) A video transmission system 6 according to a second embodiment will be described with reference to FIG. 4. The video transmission system 1 according to the first embodiment specifies the characteristics of the transmission path 4 from the delay jitter of the packets, whereas the video transmission system 6 according to the second embodiment calculates the RTP packet arrival time difference of seamless protection as the influence of the first transmission path 9 and the second transmission path 10 on the arrival timing of the packets containing video data. The video transmission system 6 specifies the characteristics of the first transmission path 9 and the second transmission path 10 from the arrival time difference of the RTP packets. The second embodiment will be described focusing on the differences from the first embodiment.

[0051] The video transmission system 6 includes a video transmitting device 7 and a video receiving device 8. The video transmitting device 7 and the video receiving device 8 are connected to each other via a first transmission path 9 and a second transmission path 10 so as to be able to communicate with each other.

[0052] In the second embodiment, the video transmitting device 7 includes a transmission buffer 72, and temporarily stores packets in the transmission buffer 72. The video transmitting device 7 transmits packets stored in the transmission buffer 72 according to the inverse characteristics of the characteristics of the first transmission path 9 and the second transmission path 10 estimated in the video receiving device 3, thereby canceling out the identified characteristics of the first transmission path 9 and the second transmission path 10. The characteristics of the first transmission path 9 and the second transmission path 10 are estimated from the arrival time difference between the packet received from the first transmission path 9 and the packet received from the second transmission path 10.

[0053] The video transmitting device 7 includes a generating unit 71, a transmission buffer 72, a first transmitting unit 73, a second transmitting unit 74, and a control unit 75. The generating unit 71, the first transmitting unit 73, the second transmitting unit 74, and the control unit 75 are implemented in a CPU 901. The transmission buffer 72 is formed in a memory 902 or a storage 903. The video transmitting device 7 stores packets of video data in the transmission buffer 72, and transmits the packets stored in the transmission buffer 72 to each of the first transmission path 9 and the second transmission path 10.

[0054] The generating unit 71 generates RTP packets of the video data, and stores the generated RTP packets in the transmission buffer 72 .

[0055] The transmission buffer 72 stores the RTP packets of the video data. The transmission buffer 72 stores each RTP packet until the transmission timing controlled by the control unit 24 for each of the first transmission unit 73 and the second transmission unit 74. The transmission buffer 72 stores one RTP packet for each sequence number. This one RTP packet is stored in the transmission buffer 72 until it is transmitted to the video receiving device 8 by each of the first transmission unit 73 and the second transmission unit 74.

[0056] The first transmitting unit 73 and the second transmitting unit 74 transmit the RTP packets stored in the transmission buffer 22 to the video receiving device 3. The first transmitting unit 73 transmits the RTP packets via the first transmission path 9. The second transmitting unit 74 transmits the RTP packets via the second transmission path 10. The first transmitting unit 73 and the second transmitting unit 74 transmit the packets at a timing designated by the control unit 75. Specifically, the first transmitting unit 73 and the second transmitting unit 74 transmit the packets to the transmission path with the earlier arrival time after a time according to the arrival time difference has elapsed since the first transmitting unit 73 and the second transmitting unit 74 transmitted the packets to the transmission path with the later arrival time.

[0057] The control unit 75 receives the characteristics of the first transmission path 9 and the second transmission path 10 from the video receiving device 8, and controls the first transmission unit 73 and the second transmission unit 74 to transmit packets at timings specified by the inverse characteristics of the characteristics of the first transmission path 9 and the second transmission path 10. Here, the characteristics of the first transmission path 9 and the second transmission path 10 are the difference in arrival time when the video transmitting device 7 simultaneously transmits RTP packets with the same sequence number to the video receiving device 8. The inverse characteristics are characteristics that cancel out delays when RTP packets with the same sequence number are transmitted via the first transmission path 9 and the second transmission path 10, respectively. Specifically, the control unit 24 determines the timings at which the first transmission unit 73 and the second transmission unit 74 transmit their packets so that RTP packets with the same sequence number arrive at the video receiving device 8 simultaneously. The control unit 75 receives the characteristics from the video receiving device 8 via the first transmission path 9, the second transmission path 10, or other communication networks.

[0058] The video receiving device 8 includes a first receiving unit 81, a second receiving unit 82, a first receiving buffer 83, a second receiving buffer 84, a reproduction unit 85, and an estimation unit 86. The first receiving unit 81, the second receiving unit 82, the reproduction unit 85, and the estimation unit 86 are implemented in a CPU 901. The first receiving buffer 83 and the second receiving buffer 84 are formed in a memory 902 or a storage 903. The video receiving device 8 complements and reproduces packets received from the first transmission path 9 and the second transmission path 10, respectively. The video receiving device 8 transmits to the video transmitting device 7 the characteristics of the first transmission path 9 and the second transmission path 10 between the video transmitting device 2 and the video receiving device 3, which are estimated from the arrival time difference of each packet.

[0059] The first receiving unit 81 receives the RTP packets from the first transmission line 9. The first receiving unit 81 stores the received RTP packets in the first receiving buffer 83.

[0060] The second receiving unit 82 receives the RTP packets from the second transmission line 10. The second receiving unit 82 stores the received RTP packets in a second receiving buffer 84.

[0061] The reproduction unit 85 constructs video data from the RTP packets stored in the first receiving buffer 83 and the second receiving buffer 84, and reproduces the video data on a display (not shown) or the like. The reproduction unit 85 integrates two RTP packets having the same sequence number, compensates for the loss of an RTP packet, and reproduces the video data.

[0062] The estimation unit 86 estimates the characteristics of the first transmission path 9 and the second transmission path 10 between the video transmitting device 2 and the video receiving device 3 from the arrival time of each packet at the video receiving device 3. Here, the characteristics of the transmission path 4 are estimated from the arrival time difference between the packet received from the first transmission path 9 and the packet received from the second transmission path 10.

[0063] The following is an example of a method for estimating the arrival time difference of RTP packets in the estimation unit 86 of the video receiving device 8. The estimation unit 86 can identify RTP packets that transmit the same video essence between two routes by referring to the sequence number of the RTP header.

[0064] For a pair of corresponding RTP packets, if the packet arrival time on the first transmission path 9 side is T1 and the packet arrival time on the second transmission path 10 side is T2, the arrival time difference is calculated as T2-T1. If the value is positive, the RTP packet on the second transmission path 10 side is delayed. If the value is negative, the RTP packet on the first transmission path 9 side is delayed.

[0065] The estimation unit 86 transmits the estimated value D of the arrival time difference to the control unit 75 of the video transmission device 7. To reduce the effect of delay jitter, the average value of T2-T1 may be adopted as D.

[0066] Next, a method for identifying the transmission timing of an RTP packet will be described. When the control unit 75 of the video transmission device 7 receives the estimated value D of the RTP packet arrival time difference, the control unit 75 sets a fixed delay in the first transmission unit 73 or the second transmission unit 74. If D is positive, the first transmission unit 73 delays transmission to the first transmission path 9 by D after the second transmission unit 74 sends it to the second transmission path 10. If D is negative, the second transmission unit 74 delays transmission to the second transmission path 10 by |D| after the first transmission unit 73 sends it to the first transmission path 9.

[0067] In general, in seamless protection transmission, differences in the arrival times of RTP packets may occur due to differences in path length. In seamless protection, waiting is required on the receiving side to integrate RTP packets, but if the arrival time difference is too large, buffer overflow may occur. In order to prevent buffer overflow, it is necessary to make the receiving buffer large.

[0068] In contrast, in the video transmission system 6 according to the second embodiment, the transmission timing by the video transmitting device 7 is adjusted so that RTP packets with the same sequence number arrive at the video receiving device 8 at the same time. This makes it possible to reduce the waiting time for the RTP packets at the video receiving device 8.

[0069] In the second embodiment, the reducible buffer size is estimated. Note that this buffer size is the sum of the reducible buffer sizes for the transmission buffer 72, the first reception buffer 83, and the second reception buffer 84. As a premise, the maximum jitter allowable time in the reception buffer is Δ. Δ is a given value, which is a design parameter of the video receiving device. Also, the arrival time difference of RTP packets is D. D is a value determined by the first transmission path 9 and the second transmission path 10. Also, the bit rate per video is R. R is a value determined by the video format.

[0070] First, in a typical video transmission system using seam protection, when delay jitter and arrival time difference are absorbed only by the receiving buffer, the required buffer size is 2R*(Δ+D) to ensure an absorbing capacity in both the first receiving buffer and the second receiving buffer. On the other hand, in the second embodiment, the required transmission buffer size is R*D, the required receiving buffer size is 2R*Δ for both the first receiving buffer 83 and the second receiving buffer 84, and the total required buffer size is R*(2Δ+D). Therefore, in the video transmission system 6 according to the second embodiment, it is possible to reduce the buffer size by R*D.

[0071] (Third embodiment) In the third embodiment, the video transmitting device 7 and the video receiving device 8 are implemented by programs that realize the respective functions in hardware of the same specifications that includes an FPGA (Field Programmable Gate Array). The hardware includes an FPGA, a memory, and a communication device, and may further include a CPU, a storage device, an input device, and an output device. By making the hardware of the same specifications function as either the video transmitting device 7 or the video receiving device 8 at the installation site, it is expected that the cost at the installation site can be reduced.

[0072] In the third embodiment, the buffer size of the transmission buffer 72 of the video transmitting device 7 and the total buffer size of the first receiving buffer 83 and the second receiving buffer 84 of the video receiving device 8 are the same M.

[0073] Let R be the bit rate per video, D be the arrival time difference of RTP packets, and Δ be the allowable jitter time.

[0074] When D≦M / R, the transmission buffer 72 absorbs the difference in arrival times of RTP packets, and the first reception buffer 83 and the second reception buffer 84 absorb the delay jitter. In this case, Δ=M / (2R).

[0075] When D>M / R, the transmission buffer 72 absorbs the RTP packet arrival time difference, and the first reception buffer 83 and the second reception buffer 84 absorb the residual error of the RTP arrival time difference and delay jitter. In this case, Δ=(3M) / (2R)-D.

[0076] On the other hand, when the RTP packet arrival time difference and delay jitter are absorbed only by the first receiving buffer 83 and the second receiving buffer 84, the tolerable jitter time Δ that can be absorbed is Δ=M / (2R)-D, where D≦M / (2R).

[0077] Therefore, the jitter tolerance time extended by the third embodiment is the region corresponding to the difference between the solid line and the broken line in FIG.

[0078] Each of the video transmitting devices 2, 7 and the video receiving devices 3, 8 of the present embodiment described above uses, for example, a general-purpose computer system including a CPU (Central Processing Unit, processor) 901, a memory 902, a storage 903 (HDD: Hard Disk Drive, SSD: Solid State Drive), a communication device 904, an input device 905, and an output device 906. In this computer system, the CPU 901 executes a program loaded on the memory 902, thereby realizing each function of the video transmitting devices 2, 7 and the video receiving devices 3, 8.

[0079] Each of the video transmitting devices 2, 7 and the video receiving devices 3, 8 may be implemented in one computer or in multiple computers. Also, each of the video transmitting devices 2, 7 and the video receiving devices 3, 8 may be a virtual machine implemented in a computer.

[0080] The programs of the video transmitting devices 2, 7 and the video receiving devices 3, 8 can be stored on a computer-readable recording medium such as a HDD, SSD, USB (Universal Serial Bus) memory, CD (Compact Disc), or DVD (Digital Versatile Disc), or can be distributed via a network.

[0081] The present invention is not limited to the above-described embodiment, and various modifications are possible within the scope of the present invention. [Explanation of symbols]

[0082] 1. Video transmission system 2, 7 Video transmission device 3, 8 Video receiving device 4, 9, 10 Transmission lines 21, 71 generation part 22, 72 transmit buffer 23, 73, 74 Transmitter 24, 75 Control section 31, 81, 82 Receiver 32, 83, 84 receive buffers 33, 85 Playback section 34, 86 Estimation part 901 CPU 902 Memory 903 Storage 904 Communication equipment 905 Input Device 906 Output Device

Claims

1. a video transmitting device that stores packets of video data in a transmission buffer and transmits the packets stored in the transmission buffer; A video receiving device for receiving the packets; an estimation unit that estimates characteristics of a transmission path between the video transmitting device and the video receiving device from an arrival time of each packet at the video receiving device; the video transmitting device transmits the packets at a timing specified by an inverse characteristic of the characteristic of the transmission path; The characteristic is estimated from the delay jitter of each packet; The estimation unit estimates a delay jitter pattern specified from each delay jitter of each packet of each packet group. Video transmission system.

2. the video transmission device transmits packets of the video data to each of a first transmission path and a second transmission path; the video receiving device complements the video data using the packets received from the first transmission path and the second transmission path, the estimation unit estimates the characteristic from an arrival time difference between a packet received from the first transmission path and a packet received from the second transmission path; The video transmitting device transmits a packet to the transmission path having a slower arrival time and then transmits the packet to the transmission path having an earlier arrival time after a time period according to the arrival time difference has elapsed.

2. The video transmission system according to claim 1.

3. The video transmitting device and the video receiving device are each implemented by a program that realizes each function in hardware having the same specifications and including an FPGA; A total buffer size obtained by adding together a buffer size of a transmission buffer on the video transmitting device side, a buffer size of a first reception buffer for storing packets received on the first transmission path on the video receiving device side, and a buffer size of a second reception buffer for storing packets received on the second transmission path on the video receiving device side is the same. The video transmission system according to claim 2 .

4. a video transmitting device storing packets of video data in a transmission buffer and transmitting the packets stored in the transmission buffer; a video receiving device receiving the packets; A computer estimates characteristics of a transmission path between the video transmitting device and the video receiving device from an arrival time of each packet at the video receiving device; a step of the video transmitting device transmitting the packet at a timing specified by an inverse characteristic of the characteristic of the transmission path; Equipped with The characteristic is estimated from the delay jitter of each packet; The video transmission method, in which the estimating step estimates a delay jitter pattern specified from each delay jitter of each packet of each packet group.

5. a transmission buffer for storing packets of video data; a transmitting unit that transmits the packets stored in the transmission buffer to a video receiving device; A control unit that receives from the video receiving device the characteristics of a transmission path between the video transmitting device and the video receiving device, estimated from the arrival time of each packet, and controls the transmitting unit to transmit the packets at a timing specified by the inverse characteristic of the characteristics of the transmission path. Equipped with A video transmission device, wherein the characteristic is a delay jitter pattern estimated from the delay jitter of each packet and specified from each delay jitter of each packet of each packet group.

6. storing packets of video data in a transmission buffer and connecting to a video transmission device that transmits the packets stored in the transmission buffer; a receiving unit for receiving the packets from the video transmitting device; an estimation unit that estimates characteristics of a transmission path between the video transmitting device and the video receiving device from the arrival time of each packet; Equipped with The characteristic is estimated from the delay jitter of each packet; The estimation unit estimates a delay jitter pattern specified from each delay jitter of each packet of each packet group.

7. A program for causing a computer to function as the video transmitting device according to claim 5 or the video receiving device according to claim 6.

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