Delay time measurement server, delay time measurement method and program

Abstract

The purpose of this disclosure is to provide a lag time measurement server, a lag time measurement method, and a program for calculating a video display lag time without having to dispose a special device on a client side.　The disclosure of the present invention is a lag time measurement server characterized by calculating, as a video display lag time from the transmission of a video signal to a monitor until the display of video on the monitor, a video transmission lag time which is from the transmission, to the monitor, of the video signal obtained by encoding a specific video, until the receipt of a signal of a reaction to the specific video.

Description

[Technical Field]

[0001] The present disclosure relates to a technique for calculating a video display delay time until a video from a server is displayed on a client-side monitor. [Background technology]

[0002] In recent years, with the spread of remote work and online / cloud games, video-based communication has become increasingly important. In such video-based communication, video latency is an important parameter that determines the quality of experience. To facilitate smooth video-based communication during remote work, it is important to reduce the latency between remote locations. To ensure fairness in online / cloud video games, it is important to reduce the difference in video display latency between when the cloud game server transmits the video and when the video appears on each client's monitor.

[0003] Video delays include not only communication delays that occur in communication networks, but also delays that occur in video signal processing and monitors. A technology is needed to quantitatively measure and estimate these video display delay times.

[0004] One method for measuring these video display delay times is to use an LED and an optical sensor (see, for example, Non-Patent Document 1). Fig. 1 shows a conventional video delay time measurement system that uses an LED and an optical sensor. In Fig. 1, 51 is an LED, 52 is a video camera, 53 is a communication network, and 54 is a monitor. The LED 51 is photographed by the video camera 52, and the LED image is displayed on the monitor 54 via the communication network 53.

[0005] A conventional technique for measuring video delay time is shown in Figure 2. Figure 2 shows a time series of measurements using an LED and an optical sensor. In Figure 2, the signal that lights up LED 51 is represented as the LED drive signal, and the monitor display is represented as the brightness of the LED image on monitor 54. The time from when LED 51 is turned on until the LED displayed on monitor 54 starts to light up is observed as the time difference T1 from the leading edge of the LED drive signal to the rising point of the brightness of the LED image on monitor 54. This time difference T1 can be evaluated as the video display delay time.

[0006] However, in order to observe this time difference T1, the LED 51 and the monitor 54 must be installed in the same location. In cases such as cloud gaming, where the image source is installed in a center and the monitor is installed on the client side, which is remote from the center, time synchronization control is required for these devices.

[0007] A video delay time measurement system with related time synchronization control is shown in Figure 3. In Figure 3, 60 is a delay time measurement server, 53 is a communication network, 71 is a computer, and 72 is a monitor. Video is transmitted from the delay time measurement server 60 and the transmission time is stored. The computer 71 receives the transmitted video via the communication network 53. The computer 71 sends the received video to the monitor 72. The computer 71 transmits the time it received the video to the delay time measurement server 60 via the communication network 53. The delay time measurement server 60 calculates the video display delay time from the difference between the time the video was transmitted and the time the computer received the video. [Prior art documents] [Non-patent literature]

[0008] [Non-Patent Document 1] https: / / h-path.co.jp / technologies / 2-how-to-measure-latency / [Non-patent document 2] Morimoto, C., Hida, E., Shima, K. et al. Temporal Processing Instability with Millisecond Accuracy is a Cardinal Feature of Sensorimotor Impairments in Autism Spectrum Disorder: Analysis Using the synchronized Finger-Tapping Task. J Autism Dev Disord 48, 351-360 (2018). https: / / doi.org / 10.1007 / s10803-017-3334-7 Summary of the Invention [Problem to be solved by the invention]

[0009] However, in the delay time measurement system shown in Fig. 3, a time synchronization device is required to time-synchronize the computer 71 installed on the client side and the delay time measurement server 60. Adding a time synchronization device to the computer 71 installed on the client side increases the cost of the device.

[0010] Therefore, in order to solve the above-mentioned problem, the present disclosure aims to provide a delay time measurement server, a delay time measurement method, and a program that calculates video display delay time without placing a special device on the client side. [Means for solving the problem]

[0011] In order to solve the above problem, the video display delay time calculation technology disclosed herein calculates the video display delay time as the time from when a delay time measurement server transmits a specific video to when it receives a response signal for the specific video.

[0012] Specifically, the delay time measuring server of the present disclosure includes: The video transmission delay time from when a video signal encoding a specific video is transmitted to a monitor until a reaction signal for the specific video is received is calculated as a video display delay time from when the video signal is transmitted to the monitor until the video is displayed on the monitor.

[0013] Specifically, the delay time measuring server of the present disclosure includes: a video synthesis unit that encodes the specific video to generate the video signal; a video distribution unit that distributes the video signal generated by the video synthesis unit and notifies a timing of distribution of the video signal corresponding to the specific video as a transmission timing; a transmission interface that transmits the video signal distributed by the video distribution unit to the monitor via a communication network; a receiving interface for receiving the response signal via the communication network; an operation signal receiving unit that, when the receiving interface receives the response signal, notifies the timing of receiving the response signal as a reception timing; a time storage unit that stores, as a transmission time, a time when the transmission timing is notified from the video distribution unit, and stores, as a reception time, a time when the reception timing is notified from the operation signal receiving unit; a delay estimation unit that calculates, as the video display delay time, the video transmission delay time that is the difference between the transmission time and the reception time stored in the time storage unit; The present invention is characterized by comprising:

[0014] in particular, The delay time measuring server is characterized in that the specific video is a video corresponding to count zero in a countdown video.

[0015] in particular, The delay time measuring server is characterized in that the specific video is a video in which a symbol moves to a predetermined position in a moving image.

[0016] in particular, The delay time measuring server is characterized in that the specific image is an image of an object moving at a constant speed when the object reaches a predetermined position.

[0017] Specifically, the delay time measurement method of the present disclosure includes: The video transmission delay time from when a video signal encoding a specific video is transmitted to a monitor until a reaction signal for the specific video is received is calculated as a video display delay time from when the video signal is transmitted to the monitor until the video is displayed on the monitor.

[0018] Specifically, the present disclosure includes: A program for causing a computer to function as any of the above-described delay time measurement servers. Includes:

[0019] The above-disclosed inventions can be combined as much as possible. [Effects of the Invention]

[0020] According to the present disclosure, it is possible to calculate the video display delay time without disposing a special device on the client side. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a diagram illustrating a conventional video delay time measuring system. [Figure 2] FIG. 1 is a diagram illustrating a conventional technique for measuring video delay time. [Figure 3] FIG. 1 is a diagram illustrating a related video delay time measurement system. [Figure 4] 1 is a diagram illustrating a video delay time measurement system according to the present disclosure. [Figure 5] FIG. 2 is a diagram illustrating the configuration of a video delay time measuring server according to the present disclosure. [Figure 6] 10A and 10B are diagrams illustrating images used to calculate the image display delay time of the present disclosure. [Figure 7]10A and 10B are diagrams illustrating images used to calculate the image display delay time of the present disclosure. [Figure 8] 10A and 10B are diagrams illustrating images used to calculate the image display delay time of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the present disclosure is not limited to the embodiments shown below. These implementation examples are merely illustrative, and the present disclosure can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art. Note that components with the same reference numerals in this specification and drawings indicate the same components.

[0023] (Embodiment 1) The configuration of the video delay time measurement system of the present disclosure is shown in Fig. 4. In Fig. 4, reference numeral 10 denotes a delay time measurement server, 20 denotes a communication network, 31 denotes a computer, 32 denotes a monitor, and 33 denotes a controller. The video delay time measurement server 10 of the present disclosure calculates the video transmission delay time from when a video signal encoding a specific video is transmitted to the monitor 32 until a response signal to the specific video is received as the video display delay time from when the video signal is transmitted to the monitor 32 until the video is displayed on the monitor 32.

[0024] In the video delay time measurement system of the present disclosure, the delay time measurement server 10 generates a video signal by encoding a specific video and transmits the generated video signal to the monitor 32 via the communication network 20. The delay time measurement server 10 stores the transmission time t_start of the video signal. The computer 31 receives the video signal from the communication network 20 and outputs it to the monitor 32. The monitor 32 displays the specific video. The delay time from when the delay time measurement server 10 transmits the video signal to when the monitor 32 displays the specific video is defined as the video display delay time d_video.

[0025] The user on the client side observes a specific image displayed on the monitor 32, and in response to the specific image, operates a button on the controller 33. The delay time from when the monitor 32 displays the specific image until when the user on the client side operates a button on the controller 33 is defined as a reaction delay time d_reaction.

[0026] When a button is operated, the controller 33 outputs a reaction signal to the computer 31. The computer 31 transmits the reaction signal to the delay time measuring server 10 via the communication network 20. The controller 33 may transmit the reaction signal to the delay time measuring server 10 via the communication network 20 without going through the computer 31. The delay time measuring server 10 receives the reaction signal via the communication network 20. The delay time measuring server 10 stores the reception time t_fin of the reaction signal. The delay time from when the controller 33 detects a button operation to when the delay time measuring server 10 receives the reaction signal is defined as the command delay time d_command.

[0027] Here, because video signals use long frame lengths, digital processing of data transfer and reception processing take a long time. Video signals are often highly compressed, which means that it takes a long time to compress the video signal when transmitting and to decode the video from the received signal. It also takes a long time to display the digital video signal on a monitor. For these reasons, the video display delay time d_video becomes long. For example, the video display delay time d_video is usually around 100 milliseconds.

[0028] The reaction delay time d_reaction depends on the accuracy of human timing. According to Non-Patent Document 2, humans can synchronize the timing of periodic stimuli with an error of around 53 milliseconds. If n samples are taken as statistics, the accuracy is 53 milliseconds / n 1 / 2If 10 samples are taken, the reaction delay time d_reaction is approximately 17 milliseconds. This means that the reaction delay time d_reaction is small compared to the video display delay time d_video.

[0029] The majority of the command delay time d_command is due to transmission delay. When measured using Ping, it is usually around 10 milliseconds. This means that the command delay time d_command is shorter than the video display delay time d_video.

[0030] Since the sum of the reaction delay time d_reaction and the instruction delay time d_command is smaller than the video display delay time d_video, the video transmission delay time (t_fin-t_start) is expressed by equation (1). t_fin-t_start=d_video +(d_reaction+d_command) ≒d_video ···(1)

[0031] In other words, from equation (1), the video transmission delay time (t_fin-t_start) from when the delay time measurement server 10 transmits a video signal encoding a specific video to the monitor 32 until it receives a response signal to the specific video can be calculated as the video display delay time d_video from when the video signal is transmitted to the monitor 32 until the video is displayed on the monitor 32, as shown in equation (2). d_video=t_fin-t_start ···(2)

[0032] Here, since the command delay time d_command is approximately a fixed value t0, equation (3) may be used to more accurately calculate the video display delay time d_video. d_video=t_fin-t_start-t0 ···(3)

[0033] According to this embodiment, the video display delay time can be calculated without installing a special device on the client side.

[0034] (Embodiment 2) The configuration of the video delay time measuring server 10 of the present disclosure is shown in Fig. 5. In Fig. 5, 11 is a video synthesis unit, 12 is a video distribution unit, 13 is a transmission interface, 14 is a reception interface, 15 is an operation signal reception unit, 16 is a time holding unit, and 17 is a delay estimation unit.

[0035] The video synthesis unit 11 encodes a specific video required for measuring the video transmission delay time and generates a video signal. The video distribution unit 12 distributes the video signal generated by the video synthesis unit 11 to the transmission interface 13. At the same time, the video distribution unit 12 notifies the time holding unit 16 of the timing at which the video signal corresponding to the specific video was distributed as the transmission timing. The transmission interface 13 converts the video signal distributed by the video distribution unit 12 into a signal for communication and transmits it to the monitor 32 via the communication network 20.

[0036] The receiving interface 14 extracts a response signal of the controller 33 from the communication signal received via the communication network 20. The operation signal receiving unit 15 reads the response signal from the receiving interface 14 and recognizes that a button on the controller has been operated. At the same time, the operation signal receiving unit 15 notifies the time holding unit 16 of the timing at which the response signal was received as the reception timing. The time holding unit 16 holds the time at which the transmission timing is notified from the video distribution unit 12 as the transmission time t_start, and holds the time at which the reception timing is notified from the operation signal receiving unit 15 as the reception time t_fin. The delay estimation unit 17 calculates a video transmission delay time, which is the difference between the reception time t_fin and the transmission time t_start held by the time holding unit 16, as a video display delay time d_video.

[0037] The delay time measurement server 10 may measure the delay time several times and use the average value of the difference between the reception time t_fin and the transmission time t_start as the video display delay time d_video. By measuring the delay time several times, the reaction delay time d_reaction can be shortened. In addition, the measurement error of the reception time t_fin and the transmission time t_start can be reduced.

[0038] According to this embodiment, the delay time measurement server can calculate the video display delay time without providing a special device on the client side.

[0039] (Embodiment 3) Examples of specific video used to calculate the video display delay time of the present disclosure are shown in Figures 6 to 8. Figure 6 is an example of a countdown video. First, "Please press the button when it reaches '0'" is displayed, and the countdown proceeds in sequence. The video corresponding to count zero is the specific video. The transmission timing is the timing when the video distribution unit 12 distributes a video signal encoding the specific video to the transmission interface 13. In Figure 6, the countdown starts from "10," but the present invention is not limited to this number. Also, the countdown ends at "0," but the present invention is not limited to this number.

[0040] In the case of countdown video, the client-side user can predict the timing of operating the buttons on the controller 33, so the reaction delay time d_reaction can be shortened.

[0041] FIG. 7 is an example of a moving image with a moving symbol. First, a message is displayed saying, "Please press the button when the symbol (in FIG. 7, a star symbol) arrives here," and then the star symbol gradually approaches the circle symbol. The image when the star symbol moves to a predetermined position, i.e., the position of the circle symbol, is the specific image. The timing when the video distribution unit 12 distributes a video signal encoding the specific image to the transmission interface 13 is the transmission timing. In FIG. 7, the moving symbol is a star symbol and the predetermined position is a circle symbol, but this is not limited to these.

[0042] If the symbol is a moving image, the client user can predict the timing at which the button on the controller 33 will be operated, and therefore the reaction delay time d_reaction can be shortened.

[0043] FIG. 8 is an example of a video in which an object moves at a uniform speed. First, a message is displayed saying, "Press the button when the hand points to 12 o'clock," and then the hand rotates in sequence. The image when the hand reaches a predetermined position, i.e., the 12 o'clock position, is the specific image. The timing at which the video distribution unit 12 distributes a video signal encoding the specific image to the transmission interface 13 is the transmission timing. In FIG. 8, the object moving at a uniform speed is a rotating hand, and the predetermined position is the 12 o'clock position on a clock, but the present invention is not limited to this.

[0044] If the object is moving at a constant speed, the client user can predict the timing at which the button on the controller 33 will be operated, and therefore the reaction delay time d_reaction can be shortened.

[0045] According to this embodiment, the delay time measuring server can accurately calculate the video display delay time by using a specific video.

[0046] As described above, according to the present disclosure, it is possible to calculate the video display delay time without disposing a special device on the client side.

[0047] The delay time measuring server of the present disclosure can also be realized by a computer and a program, and the program can be recorded on a recording medium or provided via a communication network. [Industrial Applicability]

[0048] The present disclosure is applicable to the communications industry. [Explanation of symbols]

[0049] 10 Delay time measurement server 11 Video synthesis section 12 Video Distribution Department 13 Sending Interface 14 Receiving Interface 15 Operation signal receiver 16 Time holding section 17 Delay Estimation Unit 20. Communication Networks 31 Computer 32 monitors 33 Controller 51 LED 52 Video Camera 53 Communication Network 54 monitors 60 Delay time measurement server 71 Computer 72 monitors

Claims

1. A delay time measurement server that measures a video transmission delay time, including the reaction time from when a video signal encoding a specific video is sent to a monitor to when a reaction signal to the specific video is received, to when the specific video is displayed on the monitor to when a user inputs the reaction signal, and that measures the video transmission delay time as a video display delay time from when the video signal is sent to the monitor to when the video is displayed on the monitor.

2. a video synthesis unit that encodes the specific video to generate the video signal; a video distribution unit that distributes the video signal generated by the video synthesis unit and notifies a timing of distribution of the video signal corresponding to the specific video as a transmission timing; a transmission interface that transmits the video signal distributed by the video distribution unit to the monitor via a communication network; a receiving interface for receiving the response signal via the communication network; an operation signal receiving unit that, when the receiving interface receives the response signal, notifies the timing of receiving the response signal as a reception timing; a time storage unit that stores, as a transmission time, a time when the transmission timing is notified from the video distribution unit, and stores, as a reception time, a time when the reception timing is notified from the operation signal receiving unit; a delay estimation unit that calculates, as the video display delay time, the video transmission delay time that is the difference between the transmission time and the reception time stored in the time storage unit; and 2. The delay time measuring server according to claim 1, further comprising:

3. 3. The delay time measuring server according to claim 1, wherein the specific video is a video corresponding to count zero in a countdown video.

4. 3. The delay time measuring server according to claim 1, wherein the specific image is a moving image in which a symbol moves to a predetermined position.

5. 3. The delay time measuring server according to claim 1, wherein the specific image is an image of an object moving at a constant speed when the object reaches a predetermined position.

6. A delay time measurement method comprising: measuring a video transmission delay time, including the reaction time from when a video signal encoding a specific video is transmitted to a monitor until a reaction signal for the specific video is received, and from when the specific video is displayed on the monitor until a user inputs the reaction signal; and defining the video transmission delay time as a video display delay time from when the video signal is transmitted to the monitor until the video is displayed on the monitor.

7. A program for causing a computer to function as the delay time measuring server according to any one of claims 1 to 5.

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