JP2020079913A - Display device, multi-display system, method for processing video signal of display device, and method for processing video signal of multi-display system - Google Patents

Abstract

To provide a display device with which it is possible to find the total number of connected apparatuses at low cost.SOLUTION: Provided is a display device connected in a first stage among a plurality of display devices connected in cascade, comprising a first video processing unit 101, a video output unit 102, a second video processing unit 103, and a counting unit 104. The first video processing unit 101 adds a display pattern to an inputted first video signal. The video output unit 102 outputs a video signal from the first video processing unit 101 to a display device that is connected in the next stage. The second video processing unit 103 inputs the video signal outputted from a display device that is connected in the last stage as a second video signal. The counting unit 104 finds the number of connected display devices on the basis of the display pattern included in the second video signal.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a display device, a multi-display system, a video signal processing method for a display device, and a video signal processing method for a multi-display system.

  In a multi-display system, a plurality of display devices are connected and a screen is constructed. When setting each device in such a system, if each device is set to the same value at the same time, the set value can be transmitted to all the devices at the same time, and thus the ID is unnecessary. However, when setting individual devices, it is necessary to individually set an ID for each device and then send a setting value for each device. Each display device forming the multi-display usually does not have a unique ID as an initial value. Therefore, the ID for each device is set after the system is constructed. The task of setting an ID for each device requires assigning an ID for each device so that the ID values do not overlap, which is a burden at the time of system installation.

  As a technique for assigning an ID to each device, Patent Document 1 discloses a system in which a plurality of electronic devices, for example, display devices are connected in cascade, and a host computer (control circuit) automatically sets an individual ID number to each electronic device. What to do is proposed. Further, Patent Document 2 proposes a method of individually assigning an ID to an electronic device by one-way communication.

International Publication No. 2013/038554 JP, 2017-158071, A

  However, the one described in Patent Document 1 is premised on bidirectional communication. Further, in the device described in Patent Document 1, each device individually communicates with the downstream. In the case of two-way communication, the establishment of communication can be confirmed, and therefore improvement in reliability can be expected. However, in bidirectional communication, the cost is high, and thus it is difficult to employ it in a display device having a low cost.

  Patent Document 2 discloses a method of individually assigning an ID to each device in one-way communication. Since the one described in Patent Document 2 uses one-way communication, the cost does not increase as compared with the two-way communication. However, Patent Document 2 does not disclose a method for obtaining the total number of connected devices. The total number of connected devices is necessary for obtaining the population parameter at the time of division in the case of division display on a plurality of display devices.

  In view of the above problems, the present invention provides a display device, a multi-display system, a video signal processing method of the display device, and a video signal processing method of the multi-display system, which can obtain the total number of connected devices at low cost. The purpose is to

  A display device according to an aspect of the present invention is a display device that is connected to a first stage of a plurality of display devices that are connected in cascade, and that adds a display pattern to an input first video signal. A video processing unit for outputting a video signal from the first video processing unit to a display device connected to the next stage, and a video signal output from a display device connected to the final stage. A second video processing unit for inputting as a second video signal and a counting unit for determining the number of connected display devices based on the display pattern included in the second video signal.

  A display device according to one embodiment of the present invention is a display device which is connected between display devices or at a final stage among a plurality of display devices which are connected in cascade, and which receives a video signal from a display device at a preceding stage. A video processing unit that adds a display pattern to the video signal and a video output unit that outputs the video signal from the video processing unit to a display device connected to the next stage or the first stage.

  A multi-display system according to an aspect of the present invention is a multi-display system including a plurality of display devices connected in cascade, wherein the plurality of display devices add a display pattern to an input first video signal. A first video processing unit, a video output unit for outputting the video signal from the first video processing unit to the display device in the next stage, and a video signal output from the display device connected to the final stage. It is configured to include a second video processing unit for inputting as the second video signal and a counting unit for determining the number of connected display devices based on the display pattern included in the second video signal. The display device connected to the first stage of the display devices adds a display pattern to the input first video signal and outputs the added first video signal to the display device of the next stage. The output video signal is input as the second video signal, the number of connected display devices is determined based on the display pattern included in the second video signal, and the display devices among the display devices are connected to each other. The display device connected to the input device receives the video signal from the display device in the previous stage, adds a display pattern to the video signal, outputs it to the display device in the next stage, and is connected to the final stage of the display devices. The display device receives the video signal from the display device in the previous stage, adds a display pattern to the video signal, and outputs the display signal to the display device connected to the first stage.

  A video signal processing method for a display device according to an aspect of the present invention is a video signal processing method for a display device connected to a first stage of a plurality of display devices connected in cascade, wherein A step of inputting, a step of adding a display pattern to the first video signal and the step of outputting the video signal to which the display pattern is added to a display device connected to the next stage; The method includes the steps of inputting the output video signal as a second video signal and the step of determining the number of connected display devices based on the display pattern included in the second video signal.

  A video signal processing method for a display device according to an aspect of the present invention is a video signal processing method for a display device connected between respective display devices or at a final stage among a plurality of display devices connected in cascade, And a step of adding a display pattern to the video signal and outputting the video signal to which the display pattern is added to a display device connected to the next stage or the first stage.

  A video signal processing method of a multi-display system according to an aspect of the present invention is a video signal processing method of a multi-display system including a plurality of display devices connected in cascade, and is connected to the first stage of the display devices. A display device that inputs a video signal, adds a display pattern to the video signal, and outputs the video signal to which the display pattern is added to a display device connected to the next stage; A display device connected between display devices inputs a video signal from the display device in the previous stage, adds a display pattern to the video signal, and connects the video signal to which the display pattern is added to the next stage. And the display device connected to the final stage of the display devices inputs the video signal from the display device in the previous stage, adds a display pattern to the video signal, and adds the display pattern. Outputting the video signal to the display device connected to the first stage of the display device, and the display device connected to the first stage of the display device is output from the display device connected to the last stage. Input video signal as a second video signal, and determining the number of connected display devices based on the display pattern included in the second video signal.

  According to the present invention, the total number of display devices connected to the multi-display system can be obtained from the information included in the video signal, bidirectional communication is not required, and the cost can be reduced.

It is a block diagram which shows the outline of the display apparatus which concerns on the 1st Embodiment of this invention. It is a block diagram which shows the structure of the multi display system which concerns on the 1st Embodiment of this invention. It is a figure which shows the specific example of a process when determining the total number of the display apparatuses connected in the multi display system which concerns on the 1st Embodiment of this invention. 6 is a flowchart showing a process of determining the total number of connected display devices in the multi-display system according to the first embodiment of the present invention. It is a schematic block diagram which shows the 1st basic composition of the display apparatus by this invention. It is a schematic block diagram which shows the 2nd basic composition of the display apparatus by this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an outline of a display device according to the first embodiment of the present invention.

  As shown in FIG. 1, the display device 10 according to the first exemplary embodiment of the present invention includes a first video processing unit 11, a second video processing unit 12, a video output unit 13, and a display unit 14. The controller 15 and the storage memory 16 are provided.

  The first video processing unit 11 inputs the first video signal S1 from the first video input terminal IN1. The output signal of the first video processing unit 11 is sent to the video output unit 13 and the display unit 14. The first video processing unit 11 exchanges control signals with the control unit 15 in order to analyze the first video signal S1. In addition, the first video processing unit 11 has an OSD (On Screen Display) function and can add a display pattern to the first video signal S1.

  The second video processing unit 12 inputs the second video signal S2 from the second video input terminal IN2. The second video processing unit 12 exchanges control signals with the control unit 15 in order to analyze the second video signal S2.

  The video output unit 13 outputs the video signal from the first video processing unit 11 as an output video signal S3 from the video output terminal OUT1. The display unit 14 is, for example, a liquid crystal display. The display unit 14 displays an image based on the video signal processed by the first video processing unit 11.

  The control unit 15 exchanges control signals with the first video processing unit 11 and analyzes the first video signal S1. The control unit 15 also exchanges control signals with the second video processing unit 12 and analyzes the second video signal S2. As will be described later, in this embodiment, the control unit 15 serves as a counting unit that determines the number of connected display devices based on the display pattern included in the second video signal S2.

  The storage memory 16 stores (stores) the total number of connected display devices. The total number of connected display devices can be used as the denominator of divided display.

  FIG. 2 is a block diagram showing the configuration of the multi-display system 1 according to the first embodiment of the present invention. As shown in FIG. 2, the multi-display system 1 according to the first embodiment of the present invention includes a video signal generator 20 and a plurality of display devices 10-1 to 10-N (N is an arbitrary integer). Connected and configured. As described above, the display devices 10-1 to 10-N have the first video input terminal IN1 for inputting the first video signal S1 and the second video input terminal IN2 for inputting the second video signal S2. And a video output terminal OUT1 for outputting the video signal S3.

  In addition, the number of the display devices 10-1 to 10-N is arbitrary, and the installation position thereof is also arbitrary. The plurality of display devices 10-1 to 10-N may be arranged in a line or may be arranged two-dimensionally.

  As shown in FIG. 2, when configuring the multi-display system 1, the video output terminal OUT1 of each of the display devices 10-1 to 10-N is connected to the first video input terminal IN1 of the next-stage display device, and the final display is completed. The video output terminal OUT1 of the display device 10-N in the first stage is connected to the second video input terminal IN2 of the display device 10-1 in the first stage.

  That is, the video output terminal OUT of the video signal generator 20 is connected to the first video input terminal IN1 of the first display device 10-1. The video output terminal OUT1 of the display device 10-1 is connected to the first video input terminal IN1 of the second display device 10-2. The video output terminal OUT1 of the display device 10-2 is connected to the first video input terminal IN1 of the third display device 10-3. Hereinafter, the video output terminal OUT1 of the (N-1)th display device 10-(N-1) is connected to the first video input terminal IN1 of the Nth display device 10-N. The video output terminal OUT1 of the Nth display device 10-N is connected to the second video input terminal IN2 of the first display device 10-1.

  Each of the display devices 10-1 to 10-(N-1) has a display pattern in a part of the first video signal S1 when the first video signal S1 is input to the first video input terminal IN1. If there is no display pattern, the display pattern is added to a part of the first video signal S1. If there is a display pattern, the display pattern is added to a position different from the position of the display pattern. Then, the video signal S3 is output to the first video input terminal IN1 of the next-stage display device 10-1 to 10-N. The display device 10-N outputs the video signal S3 to the second video input terminal IN2 of the display device 10-1. As a result, a display pattern is added to the video signal every time the video signal passes through each of the display devices 10-1, 10-2, 10-3,..., 10-N.

  The Nth display device 10-N outputs the video signal S3 to which the display patterns of the number corresponding to the number of the connected display devices 10-1 to 10-N are added. The Nth display device 10-N sends the video signal S3 to the second video input terminal IN2 of the first display device 10-1. The first display device 10-1 counts the number of display patterns included in the second video signal S2 input to the second video input terminal IN2. Thereby, the total number of the display devices 10-1 to 10-N connected to the multi display system 1 can be obtained.

  FIG. 3 is a specific example of processing in the case of determining the total number N of connected display devices in the multi-display system 1 according to the first embodiment of the present invention. Here, it is assumed that the multi-display system 1 is configured by the four display devices 10-1 to 10-4.

  The video signal generator 20 sends a video signal to the first video input terminal IN1 of the first display device 10-1. The video signal is composed of a video period of display information and a blank period including a synchronizing signal and a blanking line. The video signal used in this embodiment is a signal in the video period, and it is preferable not to use the signal in the blank period. This is because in the blank period, the usable area varies depending on the input signal, and depending on the route, the signal in the blank period may be reprocessed and the information in the blank period may be lost.

  The first image signal S1 is input from the image signal generator 20 to the first image input terminal IN1 of the first display device 10-1, and is output from the image output terminal OUT1 of the first display device 10-1. The generated video signal S3 is input to the first video input terminal IN1 of the second display device 10-1. Hereinafter, the video signal S3 output from the video output terminal OUT1 of the fourth display device 10-4 is input to the second video input terminal IN2 of the first display device 10-1 as the second video signal S2. At this point, the display device 10-1 determines that the display device 10-1 is the first display device because there is a video signal input to the first video input terminal IN1 and the second video input terminal IN2.

  A video signal including a background image G1 is input from the video signal generation device 20 to the first video input terminal IN1 of the first display device 10-1 as shown in the screen 51-1. When the first display device 10-1 detects that the first video signal S1 is input to the first video input terminal IN1, it determines whether a part of the first video signal S1 has a display pattern. To determine. As shown on the screen 51-1, the video signal from the video signal generator 20 is only the background image G1, and the display pattern is not included. If there is no display pattern, the display device 10-1 adds the display pattern P1 and outputs it as the video signal S3 from the video output terminal OUT1. As a result, a video signal including the background image G1 and the display pattern P1 is output from the video output terminal OUT1 of the first display device 10-1 as shown in the screen 51-2.

  The second display device 10-2 inputs the output video signal of the first display device 10-1 from the first video input terminal IN1. When the second display device 10-2 detects that the first video signal S1 from the first display device 10-1 is input to the first video input terminal IN1, the second display device 10-2 receives the first video signal S1. It is determined whether or not there is a display pattern in part of S1. As shown on the screen 51-2, the display pattern P1 is included in the output video signal from the display device 10-1. In this case, the second display device 10-2 adds the display pattern P2 to a position different from the position of the display pattern P1 and outputs it as the video signal S3 from the video output terminal OUT1. As a result, the video signal including the background image G1 and the display patterns P1 and P2 is output from the video output terminal OUT1 of the second display device 10-2 as shown in the screen 51-3.

  The third display device 10-3 inputs the output video signal of the second display device 10-2 from the first video input terminal IN1. When the third display device 10-2 detects that the first video signal S1 from the second display device 10-2 is input to the first video input terminal IN1, the first display device 10-2 receives the first video signal S1. It is determined whether or not there is a display pattern in part of S1. As shown in the screen 51-3, the display patterns P1 and P2 are included in the output video signal from the display device 10-2. In this case, the third display device 10-3 adds the display pattern P3 to a position different from the positions of the display patterns P1 and P2 and outputs it as the video signal S3 from the video output terminal OUT1. As a result, a video signal including the background image G1 and the display patterns P1, P2, and P3 is output from the video output terminal OUT1 of the third display device 10-3, as shown in the screen 51-4. ..

  The fourth display device 10-4 inputs the output video signal of the third display device 10-3 from the first video input terminal IN1. When the fourth display device 10-4 detects that the first video signal S1 is input from the third display device 10-3 to the first video input terminal IN1, the first video input terminal IN1 detects the first video signal S1. It is determined whether or not a part of the signal S1 has a display pattern. As shown in the screen 51-4, the display patterns P1, P2, and P3 are included in the output video signal from the display device 10-3. In this case, the fourth display device 10-4 adds the display pattern P4 to a position different from the positions of the display patterns P1, P2, and P3, and outputs it as the video signal S3 from the video output terminal OUT1. .. As a result, the video signal including the background image G1 and the display patterns P1, P2, P3, and P4 is output from the video output terminal OUT1 of the fourth display device 10-4 as shown in the screen 51-5. To be done.

  The first display device 10-1 inputs the output video signal of the fourth display device 10-4 from the second video input terminal IN2. The first display device 10-1 measures the number of display patterns in the second video signal S2 to obtain the total number of display devices. As shown in the screen 51-5, four patterns P1 to P4 are added to the second video signal S2 sent from the display device 10-4. As a result, the display device 10-1 determines that the total number of the display devices 10-1 to 10-N configuring the multi-display system 1 is four.

  Even if the second display device 10-2 and subsequent ones erroneously determine the presence/absence of a display pattern and add the display pattern, if the first display device 10-1 does not add the display pattern. Since the first display device 10-1 does not perform the total number determination, it is invalid.

  FIG. 4 is a flowchart showing a process of determining the total number of connected display devices 10 (10-1 to 10-N) in the multi-display system 1 according to the first embodiment of the present invention.

  (Step ST101) The control unit 15 determines whether or not the first video signal S1 is input from the first video input terminal IN1 to the first video processing unit 11. When the first video signal S1 is input (step ST101: Yes), the process proceeds to step ST102.

  (Step ST102) The control unit 15 determines whether or not a display pattern is added to the first video signal S1 from the first video input terminal IN1. If the display pattern is not added to the first video signal S1 from the first video input terminal IN1 (step ST102: No), the process proceeds to step ST103, and if the display pattern is added (step ST102). : Yes), and the process proceeds to step ST104.

  (Step ST103) The control unit 15 adds a display pattern to the first video signal S1 from the first video input terminal IN1 and advances the process to step ST105.

  (Step ST104) The control unit 15 adds a display pattern to a position different from the added pattern in the first video signal S1 from the first video input terminal IN1 and performs the process in step ST105. Proceed to.

  (Step ST105) The first video processing unit 11 sends the video signal with the added pattern to the video output unit 13, and the video output unit 13 outputs the video signal with the added pattern as the video signal S3.

  (Step ST106) The control unit 15 determines whether or not the second video signal S2 is input to the second video processing unit 12 from the second video input terminal IN2. When the second video signal S2 is input (step ST106: Yes), the process proceeds to step ST107. If the second video signal S2 is not input (step ST106: No), the process ends.

  (Step ST107) The control unit 15 measures the number of display patterns in the second video signal S2. From the number of display patterns in the second video signal S2, the total number of connected display devices 10 (10-1 to 10-N) can be determined. When the number of desired display patterns in the second video signal S2 is measured, the process ends.

  As described above, in the embodiment of the present invention, the display device 10 (10-1 to 10-N) can independently analyze the first video signal S1 and the second video signal S2. What can be used is used. By configuring the multi-display system 1 using such display devices 10 (10-1 to 10-N), the display device 10-1 connected to the multi-display system 1 without using bidirectional communication. The total number of -10-N can be determined.

  It should be noted that the display pattern added in each of the display devices 10-1 to 10-N described above is assumed to have a size of about (8×8) vertical pixels or (16×16) pixels. Currently, the video signal mainly used has the lowest resolution and has (640×480) pixels. Therefore, if a display pattern of (8×8) pixels is used, for example, 80 display patterns can be arranged in the horizontal direction in order from the upper left. If a display pattern of (16×16) pixels is used, 40 display patterns can be arranged in the horizontal direction. In the case of a multi-display system including dozens of display devices, the total number can be sufficiently expressed by arranging the display patterns in a horizontal row. When the total number of display devices further increases, the display patterns may be arranged in one horizontal row, and the display patterns may be arranged in the same manner from the left row in the same manner from the left.

  The display pattern added by each of the display devices 10-1 to 10-N may be the same for all of the display devices 10-1 to 10-N, or each display device 10-1 to 10-N. It may be different for each N. If the display patterns added by the respective display devices 10-1 to 10-N are the same, the presence or absence of the display pattern can be detected from the video signal by matching with the predetermined pattern. Even if the display patterns added in the respective display devices 10-1 to 10-N are different from each other, by determining the conditions capable of specifying the display pattern such as the size and position of the display pattern to be added, It is possible to determine the presence or absence of the display pattern based on the. If the display pattern to be added is different for each of the display devices 10-1 to 10-N, the information about the respective display devices 10-1 to 10-N is included in each display pattern and the first device is displayed. It can be transmitted to the display device 10-1.

  Further, it is desirable that the display pattern be easily distinguishable from the background image. Further, as the display pattern, it is preferable that adjacent pixels have different colors and a large gradation difference, because it is easy to distinguish from the input video signal which becomes the background image.

  Further, in the above-described embodiment, among the video signals, the signal in the blank period is not used and only the signal in the video period is used. As a result, even if the signal in the blank period is reprocessed or the information in the blank period is missing, it does not hinder the determination result of the total number. Further, since only the signal in the video period is used, general-purpose products can be used as the first video processing unit 11 and the second video processing unit 12, and the cost can be reduced.

  FIG. 5 is a schematic block diagram showing the first basic configuration of the display device according to the present invention. A display device 100 according to the present invention is a display device that is connected to the first stage of a plurality of display devices that are connected in cascade, and includes a first video processing unit 101, a video output unit 102, and a second video. The processing unit 103 and the counting unit 104 are provided. The first video processing unit 101 adds a display pattern to the input first video signal. The video output unit 102 outputs the video signal from the first video processing unit 101 to the display device connected to the next stage. The second video processing unit 103 inputs the video signal output from the display device connected at the final stage as the second video signal. The counting unit 104 calculates the number of connected display devices based on the display pattern included in the second video signal.

  FIG. 6 is a schematic block diagram showing a second basic configuration of the display device according to the present invention. The display device 200 according to the present invention is a display device that is connected between each display device or at a final stage among a plurality of display devices that are connected in cascade, and includes a video processing unit 201 and a video output unit 202. The video processing unit 201 inputs the video signal from the display device in the previous stage and adds a display pattern to the video signal. The video output unit 202 outputs the video signal from the video processing unit 201 to the display device connected to the next stage or the first stage.

  All or part of the multi-display system 1 in the above-described embodiment may be realized by a computer. In that case, the program for realizing this function may be recorded in a computer-readable recording medium, and the program recorded in this recording medium may be read by a computer system and executed. The “computer system” mentioned here includes an OS and hardware such as peripheral devices. Further, the “computer-readable recording medium” refers to a portable medium such as a flexible disk, a magneto-optical disk, a ROM, a CD-ROM, or a storage device such as a hard disk built in a computer system. Further, the "computer-readable recording medium" means to hold a program dynamically for a short time like a communication line when transmitting the program through a network such as the Internet or a communication line such as a telephone line. In this case, a volatile memory inside a computer system that serves as a server or a client in that case may hold a program for a certain period of time. Further, the program may be for realizing some of the functions described above, or may be one that can realize the functions described above in combination with a program already recorded in the computer system, It may be realized using a programmable logic device such as FPGA.

  Although the embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and includes a design and the like within a range not departing from the gist of the present invention.

10, 10-1, 10-2,... Display device, 11... First video processing unit, 12... Second video processing unit, 13... Video output unit, 14... Display unit, 15... Control unit, 20... Video signal generator

Claims (7)

A display device connected to the first stage of a plurality of display devices connected in cascade,
A first video processing unit for adding a display pattern to the input first video signal;
A video output unit for outputting the video signal from the first video processing unit to a display device connected to the next stage;
A second video processing unit for inputting a video signal output from a display device connected to the final stage as a second video signal;
A counting unit for determining the number of connected display devices based on a display pattern included in the second video signal;
A display device including. A display device connected between each display device or at the final stage among a plurality of display devices connected in cascade,
A video processing unit for inputting a video signal from the display device in the preceding stage and adding a display pattern to the video signal;
A video output unit that outputs the video signal from the video processing unit to a display device connected to the next stage or the first stage,
A display device including.   The display device according to claim 2, wherein if the display pattern is already included in the video signal, the video processing unit adds a new display pattern to a position different from the display pattern already included. A multi-display system comprising a plurality of display devices connected in cascade,
The plurality of display devices include a first image processing unit that adds a display pattern to the input first image signal, and an image that outputs the image signal from the first image processing unit to the display device in the next stage. Based on an output section, a second video processing section for inputting a video signal output from a display device connected to the final stage as a second video signal, and a display pattern included in the second video signal. It is configured to include a counting unit that determines the number of connected display devices,
The display device connected to the first stage of the display devices adds a display pattern to the input first video signal and outputs it to the display device of the next stage, and outputs from the display device connected to the last stage. The video signal to be input is input as the second video signal, and the number of connected display devices is calculated based on the display pattern included in the second video signal,
The display device connected between the display devices of the display device, input the video signal from the display device of the previous stage, add a display pattern to the video signal, and output to the display device of the next stage,
The display device connected to the final stage of the display devices receives a video signal from the display device in the previous stage, adds a display pattern to the video signal, and outputs the multi-display to the display device connected to the first stage. Display system. A video signal processing method for a display device connected to a first stage of a plurality of display devices connected in cascade,
Inputting a first video signal,
Adding a display pattern to the first video signal, and outputting the video signal to which the display pattern is added to a display device connected to the next stage;
Inputting a video signal output from a display device connected to the final stage as a second video signal;
Determining the number of connected display devices based on the display pattern included in the second video signal. A video signal processing method of a display device connected between each display device or a final stage among a plurality of display devices connected in cascade,
A step of inputting a video signal from the display device in the previous stage,
A step of adding a display pattern to the video signal and outputting the video signal to which the display pattern is added to a display device connected to the next stage or the final stage;
Video signal processing method for a display device including the. A video signal processing method for a multi-display system comprising a plurality of display devices connected in cascade,
A display device connected to the first stage of the display devices inputs a video signal, adds a display pattern to the video signal, and outputs the video signal added with the display pattern to a display device connected to the next stage. The process of
A display device connected between the display devices of the display devices inputs the video signal from the display device of the previous stage, adds a display pattern to the video signal, and outputs the video signal to which the display pattern is added to the next stage. Output to a display device connected to
A display device connected to the final stage of the display devices inputs the video signal from the display device in the previous stage, adds a display pattern to the video signal, and displays the video signal to which the display pattern has been added. Outputting to a display device connected to the first stage of the device,
The display device connected to the first stage of the display devices inputs the video signal output from the display device connected to the final stage as a second video signal, and is included in the second video signal. And a step of determining the number of connected display devices based on a display pattern.

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