JP2017009783A - Multi-display system, video display apparatus, method for preventing occurrence of display fault in video display apparatus, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of a fault due to EDID transmission trouble between video display apparatuses when a large number of video display apparatuses are daisy chained or restore from the fault without imposing a load on the user side.SOLUTION: Provided is a multi-display system in which a plurality of video display apparatuses are daisy chained, and a video supplied from a source apparatus is displayed using the plurality of video display apparatuses, the video display apparatuses having a control unit that exerts control in such a way that the video display apparatus checks a hot plug detection pin after the power is turned on, operates as a sink apparatus when the detected level is low and requests transmission of a first EDID when the detected level is high, operates as a repeater apparatus when EDID reception is successful and stands by for a first prescribed time and then stops power supply by a power supply pin when EDID reception fails, and, after restarting, requests transmission of a second EDID.SELECTED DRAWING: Figure 7

Description

  The present invention relates to a multi-display system, a video display device, a display defect occurrence prevention method and program in a video display device.

  A multi-display system that displays a single video using a plurality of display devices such as a projector and a monitor as disclosed in Patent Document 1 is known. Since the video by the multi-display system can be displayed with a larger screen and higher resolution than the video displayed on a single display device, the multi-display system is widely used in event venues, showrooms, and the like.

FIG. 1 is a diagram showing an example of a multi-display system using a projector. This system is equipped with projectors 1 to 4 (hereinafter referred to as projectors 1 to 4) connected in a daisy chain via HDMI (registered trademark: High-Definition Multimedia Interface) cable 6 and outputs video. A video output from a PC (Personal Computer: personal computer) 5 as a device to be operated (hereinafter referred to as a “source” device) is displayed on the screen 7 as one video using the projectors 1 to 4. At this time, each projector operates as a video display device that projects video (hereinafter, a sink device), but the projectors 1 to 3 relay the received video signal to another sink device connected to the back. It also operates as a device (hereinafter referred to as Repeater device). Here, the projector 1 connected to the source device 5 is referred to as a master projector, and the projectors 2 to 3 connected as repeater devices are referred to as slave projectors.
The sink device holds the information of the device itself called EDID (Extended Display Identification Data), the data corresponding to the function and the performance, and the data recorded. When connected, the EDID is transmitted to the source device. The source device refers to the EDID sent from the sink device and outputs a video signal suitable for the sink device.

FIG. 2 is a diagram showing processing in time series when the source device and the sink device are connected.
In FIG. 2, an HDMI connection procedure is described as an example. The connection process shown in FIG. 2 starts when the source device supplies +5 V to the video reception unit of the sink device connected to the source device. The + 5V supply is performed through a line dedicated to + 5V in the HDMI cable 6 that connects the source device and the sink device, and + 5V is supplied to the video reception unit in the sink device. The video receiver of the sink device starts operation with this + 5V power supply.
When the video reception unit starts operation, the sink device receives a video signal such as reading out its own EDID stored in a nonvolatile memory (for example, SRAM (Static Random Access Memory)). When preparation is completed, the HPD (Hot Plug Detect) line in the HDMI cable 6 is changed from L (= Low) to H (= High). The source device determines that a sink device capable of receiving a video signal is connected when HPD becomes H. The source device that has determined that the sink device is connected to the sink device through the DDC / CI (Display Data Channel / Command Interface) line in the HDMI cable in order to select the video signal to be output. Ask for transmission. The sink device transmits EDID in accordance with this instruction, and the source device outputs an image suitable for the sink device indicated by the received EDID. At this time, DDC and CEC (Consumer Electronics Control) are used for transmission of control signals between video display devices such as EDID. If the sink device is not turned on when this connection process is performed, the EDID recorded in the nonvolatile memory cannot be transmitted.

When a Repeater device is connected between the Source device and the Sink device, the Repeater device reads the EDID of the connected Sink device so that the video corresponding to the Sink device connected to itself is output from the Source device, Is copied to itself and notified to the source device. The connection procedure between the source device and the repeater device, the repeater device and the sink device at this time is the same as the connection procedure between the source device and the sink device. By transmitting the EDID copied from the sink device to the source device by these procedures, the source device outputs an image adapted to the sink device.
Here, when a plurality of video display devices that also serve as Repeater devices having video output terminals are daisy-chain connected even though they are sink devices that perform video display such as projectors and monitors, the video is simply displayed at the end of the connection. Operates as a sink device to display. In addition, when another sink device is connected to the output terminal, not only the video is displayed, but also a repeater device that outputs a video signal to another sink device. At this time, the determination of the sink device / repeater device is performed based on the HPD signal. Even if another sink device is connected to the output terminal and should be operated as a repeater device, if the transmission of EDID fails, the sink device operates as a sink device.

FIG. 3 is a flowchart showing an operation for determining whether the video display device is Repeater or Sink.
When the video display device is powered on, it checks the HPD signal (step S1). When it is confirmed that the HPD signal is L, it operates as a sink device (step S2). If it is confirmed in step S1 that the HPD signal is H, a signal requesting transmission of EDID is output from the output terminal (step S3). Thereafter, it is confirmed whether or not the EDID has been successfully received (step S4). When it is confirmed that the EDID has been successfully received, the device operates as a repeater device (step S5). When it is confirmed in step S4 that reception of EDID has failed, it is confirmed how many times the transmission request is made (step S6). If the EDID transmission request is the first or second time, the process returns to step S3. If the EDID transmission request is the third time, the apparatus operates as a sink device (step S7).

  Describing in accordance with the example shown in FIG. 1, if a sink device is not connected to the master projector, HPD becomes L, and the master projector operates as a sink device. Similarly, since the projector 4 in FIG. 1 is not connected to a sink device in the subsequent stage, the HPD becomes L, and it can be determined that the projector 4 is the last sink device. If another projector is connected to the subsequent stage, such as projectors 1 to 3, the latter projector determines that the HPD is H and there is a connected device, and transmits EDID according to the procedure shown in FIG. Request. At this time, if the transmission and copying of the EDID from the slave projector is successful, it operates as a Repeater device. If reading of EDID fails, NACT (Negative Acknowledgment) is returned to retry reading of EDID. Although the number of EDID transmission requests including retry varies depending on the device, it is performed approximately three times for any device, and if it still fails to read EDID, it operates as a sink device. Normally, EDID transmission succeeds during three EDID transmission requests, and an image is displayed.

JP 2003-345327 A

  When a plurality of video display devices that also serve as Repeater devices / Sink devices are connected to the source device in a daisy chain, as shown in FIG. 4, only a part of the connected video display devices (projector 1 in FIG. 4). It has been reported that a video is displayed due to the above, and that a video is not displayed by another video display device. The cause shown in Table 1 can be cited as a cause of such a video display malfunction.

  Among the causes shown in Table 1, when the signal line is disconnected as in the case where the DDC line is disconnected, the video display problem can be solved by replacing the HDMI cable. Further, when a part of the EDID data is missing, or when a checksum error or a copy error occurs, the retry is performed several times according to the HDMI standard. If retries continue to fail, the cause is that there is a problem with the transmission path, such as the influence of external noise of the same frequency as the transmission signal, or the video signal is being output from the device. There may be a problem with the device. These defects are general problems that frequently occur even when the source device and the sink device are directly connected in a one-to-one relationship. The main countermeasures against these problems are to replace the cables between video display devices, shorten the cable length, replace the device, etc., and check the connection status and the device itself. It is necessary to execute.

Another example is that the sink device fails to transmit EDID because it is booting. Originally, since the sink device sets the HPD to H after the EDID transmission preparation is completed, such a problem should not occur. However, when the daisy chain is connected, the transmission preparation is not completed and the HPD becomes H. As a result, a failure in reading the EDID often causes a video display defect.
For example, when the projectors connected in a daisy chain are turned off all at once, and then turned on again all at once, the projectors connected as shown in FIG. It has been reported that the projectors (in the case of FIG. 4, projectors 2 to 4) do not display video, but display only the video from the projector 1. This is because the power is turned on while the HPD between the projectors 1 and 2 falls to L, the voltage temporarily increases, and the projector 1 starts reading EDID because it is mistaken for H. This is a malfunction that occurred because

  The above-described problem occurs when the projector 2 is booting and the EDID stored in the nonvolatile memory such as SRAM cannot be read and cannot be transmitted to the projector 1. Since the projector 1 cannot copy the EDID of the connected projector 2, as shown in the flowchart shown in FIG. 3, the projector 1 operates not as a repeater device but as a sink device that outputs video only from the projector 1. For this reason, the projector connected after the projector 2 does not display an image, and the image displayed by the projectors 1 to 4 shown in FIG. 1 is displayed in a quarter area by the projector 1 operating as a sink device. Will be displayed. In addition, although the projector 1 and the projector 2 are shown here as an example, the same phenomenon occurs between the projectors 2 and 3 and the projectors 3 and 4 in the relationship between the Repeater / Sink device and the sink device as in the projectors 1 and 2. Can happen. In that case, the images from the projectors up to the projector 2 or 3 are displayed, respectively, and the subsequent images from the projector are not displayed. In addition, since a plurality of video display devices are connected in a daisy chain, the start timing does not match, and the EDID cannot be read within a specified time, resulting in a failure, so that the video may not be displayed.

As described above, when the projector 2 fails to read the EDID due to BOOT, the projector 1 performs the EDID reading process of the projector 2 after the BOOT of the projector 2 is completed, and if successful, the video output to the slave projector is possible. Become. However, communication using a DDC / CI line that transmits EDID and a request command thereof cannot start communication from a sink device to a higher-level repeater device or a south device. Therefore, it is necessary to send an EDID transmission request from the upper device to the lower device for rereading.
On the other hand, when a video display device to be operated as a Repeater device such as the projector 1 is operating as a sink device, it is ideal to automatically start re-reading. Since the operating projector 1 performs the operation of reading the EDID, it temporarily becomes a Repeater device. At this time, since the projector 1 is a repeater, the copy of the connected sink side EDID has not been completed, so there is no EDID, and during that time, the video by the projector 1 is not displayed. A sequence that repeats re-reading of EDID is not normally incorporated so as to prevent such video interruption. This does not stipulate that the re-reading is performed even in the certification of the video standard, and there is no problem if it can be solved by inserting and removing the cable in the certification test of the standard.

Therefore, in order to display the image normally from the state shown in FIG. 4, it is necessary for the user to physically disconnect the connection by disconnecting the cable between the two devices and perform the connection procedure again by reconnecting. . By re-connecting, the EDID is re-read by re-executing the connection procedure from the + 5V supply shown in FIG.
In addition, when video is not displayed on the sink side device because it is in the standby state or the power is not turned on, the EDID is reloaded after the start-up process is completed after the sink device is turned on. This makes it possible to display an image.

There are several causes of failures other than those shown in Table 1, but they originate from cable disconnection or equipment that does not display video after the specific video display device as shown in FIG. If it is not the cause, there are many reports that the problem can be solved by reconnecting the HDMI cable. In that case, the projector 2 is operating. Therefore, when such a video defect occurs, it is almost solved by the above-described cable reconnecting operation. In this case, however, an operation on the user side is required. A projector or the like installed on the ceiling has a problem that it is difficult not only to reconnect the cable but also the operation itself.
The present invention is intended to prevent occurrence of problems due to EDID transmission troubles between video display devices when a large number of video display devices are connected in a daisy chain, or to recover from the problems without imposing a burden on the user side.

In the multi-display system of the present invention, inter-device authentication is performed using EDID, and a plurality of video display devices are daisy chain-connected by an interface using a connector having a power supply pin and a hot plug detection pin. A multi-display system for displaying video supplied from a source device using the plurality of video display devices,
After the power is turned on, the video display device checks the pin for detecting the hot plug, and if it is Low, it operates as a sink device, and if it is High, it makes a first transmission request for the EDID. If the reception of the EDID is successful, the device operates as a repeater device. If the reception of the EDID fails, the power supply by the power supply pin is stopped after waiting for a first predetermined time. After restarting, a control unit that makes a second transmission request for the EDID is included.

The video display device according to the present invention performs inter-device authentication using EDID, and a plurality of video display devices are daisy chain-connected by an interface using a connector having a power supply pin and a hot plug detection pin. Because
After the power is turned on, the hot plug detection pin is checked. If it is Low, it operates as a sink device, and if it is High, the first transmission request for the EDID is made to receive the EDID. If it succeeds, it operates as a Repeater device, and if it fails to receive the EDID, it waits for a first predetermined time and then stops and restarts the power supply by the power supply pin. A control unit configured to request transmission of the EDID for the second time;

The display defect occurrence prevention method of the present invention performs inter-device authentication using EDID, and video in which a plurality are connected in a daisy chain by an interface using a connector having a power supply pin and a hot plug detection pin. A display failure prevention method performed in a display device,
After the power is turned on by the control unit of the video display device, the pin for detecting the hot plug is confirmed. When it is Low, it operates as a sink device, and when it is High, the first transmission request for the EDID is performed. If the reception of the EDID is successful, the device operates as a repeater device. If the reception of the EDID fails, the power supply by the power supply pin is stopped after waiting for a first predetermined time. After the restart, a second transmission request for the EDID is made.

The program of the present invention performs inter-device authentication using EDID, and is incorporated in a video display device in which a plurality of devices are connected in a daisy chain by an interface using a connector having a power supply pin and a hot plug detection pin. A program to be executed by a computer,
After powering on the video display device, the pin for hot plug detection is confirmed. When it is Low, it operates as a Sink device, and when it is High, it makes a first transmission request for the EDID, When the reception of the EDID is successful, it operates as a repeater device. When the reception of the EDID fails, the power supply by the power supply pin is stopped and resumed after waiting for a first predetermined time. Then, the computer is caused to execute a second transmission request for the EDID.

  According to the present invention, it is possible to prevent occurrence of trouble due to EDID transmission trouble between video display devices when a large number of video display devices are connected in a daisy chain, or to recover from the trouble without imposing a burden on the user side. It becomes possible.

It is a figure which shows an example of the multi-display system using a projector. It is a figure which shows the process at the time of connection of a Source apparatus and a Sink apparatus in time series. It is a flowchart which shows the operation | movement which discriminate | determines whether a video display apparatus is Repeater or Sink. It is a figure which shows the multi-display system in which the malfunction occurred. It is a block diagram which shows the internal structure of the projector 1 used by this embodiment of this invention. It is a figure which shows the connection of the input / output part of a some projector. 4 is a flowchart illustrating sequence control performed by a control unit in order to prevent occurrence of a problem in video display in the embodiment of the present invention.

In the present invention, in a system intended for multi-display, when the master projector fails to copy the EDID of the slave projector because the slave projector is booting, the slave projector is OFF or is in a standby state. In the case where the activation fails, the sequence control incorporating measures for the two cases is performed, so that multi-display is normally performed without requiring reconnection of the cable on the user side.
If the slave projector fails to transmit EDID because it is in BOOT, EDID can be transmitted after BOOT is completed. Therefore, it waits for a certain time until BOOT is completed, and then requests EDID transmission again. . This standby time differs depending on the video display device, and needs to be set in accordance with the boot time of the apparatus.
If the EDID cannot be transmitted because the slave projector is in the standby state, the slave projector is forcibly activated from the master projector side, and the EDID can be transmitted by waiting for a certain time until the BOOT is completed. It becomes.

As described in the problem to be solved in the previous section, when operating as a sink device, the master projector does not reread the EDID as a normal operation. In order to transmit EDID, it is necessary to connect and disconnect the HDMI cable and reconnect it. By disconnecting and reconnecting the HDMI cable, the connection process started from +5 V supply shown in FIG. 2 is performed. Re-execute. However, the operation of reconnecting the cable can also be performed by stopping and restarting (hereinafter referred to as OFF / ON) of the +5 V line with the cable connected. When the power supply through the + 5V line is stopped and supplied again, the connection process in which the slave projector shown in FIG. 2 sets the HPD to H is executed.
Therefore, in the video display device (Sink device) that also functions as a Repeater device, when the HPD is H, but operates as a Sink device only without operating as a Repeater device, the + 5V line is turned OFF / ON after waiting for a certain period of time. This corresponds to the case where transmission of EDID fails due to booting, and when the transmission of EDID still fails, a start command is transmitted using DDC or CEC, and the + 5V line is turned off / off again after completion of BOOT. By turning it on, video display problems are prevented.

Next, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
In the present embodiment, the occurrence of a video display malfunction when a daisy chain is connected is prevented by sequence control. For this reason, the apparatus configuration is the same as the configuration shown in FIGS. 1 and 4, and an embodiment of the present invention will be described below with reference to FIG.
Four projectors 1 to 4 are daisy chain connected to the PC 5 which is a source device. In the present embodiment, the projectors 1 to 4 are described as using lamp light sources, but the video display device in the present invention is not limited to projectors using lamp light sources. Further, an HDMI cable 6 is used for connection between the PC 5 and the master projector and between each projector. Note that although HDMI is used in this embodiment, even if an interface different from HDMI, such as DVI (Digital Visual Interface), DP (DisplayPort), is used, this It is possible to introduce sequence control similar to that of the embodiment.
In the sequence control in the present embodiment, when the slave projector connected in the latter stage is in the boot state and EDID cannot be transmitted, and the HPD is H, the slave projector is turned off or is in the standby state. In the case of the above, when the video is not displayed, etc., the + 5V line is turned OFF / ON or the power ON command is sent for rereading the EDID.

FIG. 5 is a block diagram showing the internal configuration of the projector 1 used in this embodiment. Although shown as the projector 1 in FIG. 5, the other projectors 2 to 4 constituting the multi-display system have the same configuration as the projector 1.
The projector 1 includes an input terminal (HDMI IN (in)) 11, an output terminal (HDMI OUT (out)) 12, a video transmission / reception unit 20, a video signal processing unit 30, a drive unit 40, a display unit 50, a control unit 60, a storage Part 70. The video transmission / reception unit 20 includes a reception unit (HDMI receiver (receiver)) 21 and a transmission unit (HDMI transmitter (transmitter)) 22. Each unit is connected to the control unit 60 by a bus (I2C, BUS) 61. The control unit 60 controls the operation of each unit according to the program stored in the storage unit 70. The control unit 60 is configured by a CPU (Central Processing Unit). The control unit 60 forms a computer together with the storage unit 70, and the projector 1 can be said to have a built-in computer.

The input terminal 11 is connected to the PC 5 as the source device via the HDMI cable 6 and receives a video signal and a control signal. The video signal input to the input terminal 11 is received by the receiving unit 21 of the video transmitting / receiving unit 20, and the receiving unit 21 performs serial-parallel conversion, signal level conversion, decoding of timing signals included in the control signal, and the like.
The video signal that has been subjected to processing such as conversion by the receiving unit 21 is sent to the video signal processing unit 30. The video signal processing unit 30 performs signal processing such as resolution conversion, γ correction and trapezoidal distortion correction on the video signal sent from the video transmission / reception unit 20 and sends the video signal to the drive unit 40. The drive unit 40 creates image light by driving display elements and light sources (both not shown) constituting the display unit 50 in accordance with the video signal sent from the video signal processing unit 30, and projecting the display unit 50. Image light is emitted from the lens 51. In other words, the display unit 50 forms (displays) a video corresponding to the input video signal.

Since the projectors 1 to 3 are connected to the output terminal 12 with a lower projector as a Repeater / Sink device, the input signal is sent to the output terminal 12 via the transmission unit 22 and the lower projector via the HDMI cable 6. Sent to. HDMI is used for the input terminal 11 and the output terminal 12, in addition to a video line for transmitting a video signal, a power line for supplying + 5V to a connected device, an HPD line for notifying connection, a control signal between devices, It consists of DDC / CI lines and the like for exchanging information. FIG. 6 is a diagram illustrating connection of input / output units including each line.
Connection between the devices in FIG. 6 is performed by the HDMI cable 6 as described above, but the video line notation is omitted as in FIG. For normal video display, the projectors 1 to 3 need to copy the EDID from the lower-level Repeater / Sink device as a Repeater device. As already described in the background art, the EDID transmission procedure between each device starts from + 5V supply, and the projector connected to the lower level notifies that there is a connected device by setting HPD to H. EDID transmission request and transmission are performed through the DDC / CI line. In order to display images normally with four projectors, it is necessary for the upper-level repeater device to copy the EDID of the sink device, so the EDID of the projector 4 is changed to the projector 3 by turning on the power from the lower-level device. Must be copied, and the projector 2 and the projector 1 must sequentially copy and notify the source device. In the state shown in FIG. 4, images from projectors subsequent to projector 2 including projector 2 are not displayed. This indicates that the projector 1 has failed to copy the EDID of the lower projector.

FIG. 7 is a flowchart showing the sequence control performed by the control unit 60 in order to prevent the occurrence of problems in the video display in this embodiment.
The flowchart shown in FIG. 3 shows normal sequence control for determining whether the video display device is a sink device or a repeater device, whereas in the flowchart shown in FIG. 7, the slave projector is BOOT. Countermeasure sequence control has been added to the problem that an EDID reading error occurs due to a reason such as being in the middle or in standby.

  When the projector 1 is turned on, the projector 1 checks the HPD signal (step S701). When it is confirmed that the HPD signal is L, it operates as a sink device (step S702). If it is confirmed in step S701 that the HPD signal is H, a signal requesting transmission of EDID from the output terminal 12 is output as the first EDID transmission request (step S703). Thereafter, it is confirmed whether the EDID has been successfully received (step S704). If it is confirmed that the EDID has been successfully received, the device operates as a repeater device (step S705). If it is confirmed in step S704 that reception of EDID has failed, the number of transmission requests is confirmed (step S706). When the EDID transmission request is the first or second time, the process returns to step S703, and when the EDID transmission request is the third time, the apparatus operates as a sink device (step S707). The operation so far is the same as the flowchart shown in FIG.

When operating as a sink device in step S707, the system waits for a predetermined time, in this embodiment, 30 seconds (step S708), and the + 5V line is turned OFF / ON (step S709). This is a normal sequence control when the HPD is H and it operates as a sink device, or because the slave projector is in the boot state and EDID cannot be transmitted and thus operates as a sink device. This is done as a countermeasure for the case where it happens, and is read again after waiting for a certain time.
The fixed time in step S708 can be set according to the device. Since the projector of this embodiment uses a lamp light source, it is assumed that the time from when the lamp is lit until the start-up is completed is approximately 30 seconds, and the standby time is 30 seconds. It is not always necessary to stick to this time. For example, in the case of a projector using a laser light source with a short start-up time, it can be set to about 5 seconds, and the start-up time can be set according to the equipment. is there. It waits for the completion of BOOT by waiting for the time required until the activation of the device is completed.

  After step S709, as the second EDID transmission request, a signal requesting transmission of EDID from the output terminal 12 is output (step S710). Thereafter, it is confirmed whether or not the EDID has been successfully received (step S711). When it is confirmed that the EDID has been successfully received, the device operates as a repeater device (step S712). As a result, video can be displayed by the slave projector. If it is confirmed in step S711 that reception of EDID has failed, the number of transmission requests is confirmed (step S713). If the EDID transmission request is the first or second time, the process returns to step S710, and if the EDID transmission request is the third time, a signal indicating that the power is to be turned off is output to the output terminal 12. . Specifically, a signal requesting to turn off the power is sent to the projector 2 (step S714). Next, the + 5V line is turned off (step S715), and the system waits for a predetermined time, 20 seconds in this embodiment (step S716). Thereafter, a signal indicating that the power is to be turned on is output to the output terminal 12. Specifically, a signal requesting to turn on the power is sent to the projector 2 (step S717). Next, it waits for 30 seconds in this embodiment for a certain time (step S718), and the + 5V line is turned on (step S719).

The operation in step S714 to step S719 will be described in detail.
If it is confirmed in step S713 that the EDID transmission has failed again, the slave projector may fail to start up and may be in a power-off or standby state. In order to display an image, the master projector needs to activate the slave projector itself, and the master projector sends several commands to the slave projector for restarting. This command uses, for example, DDC or CEC when connected by an HDMI cable. When executing the restart, since the power state of the slave projector is unknown at this time, first, considering the possibility that the power is on, a command to turn off the power is sent (step S714). It waits for a certain time until it is turned off (step S716). In this embodiment, since a lamp light source projector is used, the lamp is cooled before the power is turned off. Here, as an example, it is assumed that the lamp cooling time is 10 seconds, and the standby time until the power-off is completed is 20 seconds. This standby time is not limited to 20 seconds, and can be set according to the time required for powering off the device. For example, if the projector is a laser light source, the power can be turned off immediately, so it can be set to about 1 second.

In order to prevent a reading error during BOOT, the master projector turns off the + 5V line before starting the power supply of the slave projector (step S715). After the slave projector is turned off by waiting for a certain period of time after sending the power off command, the slave projector is turned on by sending a command requesting power on (step S717). After that, after waiting for a certain period of time to wait for BOOT completion (step S718), the EDID is read by turning on the + 5V line (step S719). Note that the standby time for waiting for completion of the BOOT at this time can be set in accordance with the video display device in the same manner as the standby time for completion of the previous activation. In this case, since 30 seconds are set for completion of activation by the projector of the lamp light source, 30 seconds standby is set as an example. Therefore, it can be set to about 5 seconds in a laser light source projector.
After step S719, a signal requesting transmission of EDID from the output terminal 12 is output as a third EDID transmission request (step S720). Thereafter, it is confirmed whether the EDID has been successfully received (step S721). If it is confirmed that the EDID has been successfully received, the device operates as a repeater device (step S722). As a result, video can be displayed by the slave projector. When it is confirmed in step S721 that reception of EDID has failed, it is confirmed how many times the transmission request is made (step S723). When the EDID transmission request is the first or second time, the process returns to step S720, and when the EDID transmission request is the third time, the device operates as a sink device.
In the present embodiment, as a result of making the first EDID request, the second and third requests for EDID are made in the same manner as the first EDID request even after the operation as the sink device once in step S707. By making an EDID request, it is confirmed whether the device is actually a sink device. For this reason, it is possible to prevent a device that should operate as a repeater device from operating as a sink device without imposing a burden on the user side.
Note that when the device operates as a sink device in step S707 and then operates as a repeater device by making the second and third EDID requests thereafter, the operation time as the sink device is short, and within this time The video in which the trouble as shown in FIG. 4 has occurred will be displayed. Therefore, the operation as a sink device may be omitted in step S707, and if it is confirmed in step S706 that the EDID transmission request is the third time, the process may immediately move to step S708.

1 Projector 5 PC
6 HDMI cable 11 Input terminal 12 Output terminal 20 Video transmission / reception unit 21 Reception unit 22 Transmission unit 30 Video signal processing unit 40 Drive unit 50 Display unit 51 Projection lens 60 Control unit 61 Bus 70 Storage unit

Claims (10)

A plurality of video display devices are daisy-chain connected by an interface that uses a connector having a pin for power supply and a pin for hot plug detection by performing inter-device authentication using EDID. A multi-display system for displaying video supplied from a source device,
After the power is turned on, the video display device checks the pin for detecting the hot plug. When the video display device is Low, the video display device operates as a sink device, and when the video display device is High, the video display device makes a transmission request for the first EDID. If the reception of the EDID is successful, the device operates as a repeater device. If the reception of the EDID fails, the power supply by the power supply pin is stopped after waiting for a first predetermined time. A multi-display system having a control unit that makes a transmission request for the second EDID after restarting. The multi-display system according to claim 1.
The control unit operates as a repeater device when the reception of the EDID is successful after the second EDID transmission request, and turns off the power to the interface when the reception of the EDID fails. Output a request, stop the power supply by the power supply pin, wait for a second predetermined time, then output a request to turn on the power to the interface, wait for a third predetermined time, A multi-display system that makes a transmission request for the third EDID after restarting power supply by a power supply pin. The multi-display system according to claim 2,
The control unit operates as a repeater device when receiving the EDID after the third EDID transmission request, and operates as a sink device when receiving the EDID fails. system. A video display device in which a plurality of devices are daisy-chain connected by an interface that uses a connector with a pin for power supply and a pin for hot plug detection, performing inter-device authentication using EDID,
After the power is turned on, the hot plug detection pin is checked. If it is Low, it operates as a sink device, and if it is High, it makes a first EDID transmission request and receives the EDID. If it succeeds, it operates as a Repeater device. If it fails to receive the EDID, it waits for a first predetermined time and then stops and restarts the power supply by the power supply pin. 2. A video display device having a control unit that makes a transmission request for the EDID. The video display device according to claim 4,
The control unit operates as a repeater device when the reception of the EDID is successful after the second EDID transmission request, and turns off the power to the interface when the reception of the EDID fails. Output a request, stop the power supply by the power supply pin, wait for a second predetermined time, then output a request to turn on the power to the interface, wait for a third predetermined time, A video display device which makes a transmission request for the third EDID after restarting power supply by a power supply pin. The video display device according to claim 5.
The control unit operates as a Repeater device when the EDID is successfully received after the transmission request of the third EDID, and operates as a Sink device when the reception of the EDID fails. Featured video display equipment. A method for preventing the occurrence of a display defect performed in a video display device in which a plurality of devices are daisy chain connected by an interface using a connector having a pin for power supply and a pin for hot plug detection by performing inter-device authentication using EDID Because
After the power is turned on by the control unit of the video display device, the pin for detecting the hot plug is confirmed. When it is Low, it operates as a sink device, and when it is High, the transmission request of the first EDID is performed. If the reception of the EDID is successful, the device operates as a repeater device. If the reception of the EDID fails, the power supply by the power supply pin is stopped after waiting for a first predetermined time. Then, after restarting, a display defect occurrence prevention method for requesting transmission of the second EDID. The display defect occurrence preventing method according to claim 7,
After receiving the second EDID transmission request, if the reception of the EDID is successful, it operates as a Repeater device, and if the reception of the EDID fails, outputs a request to turn off the power to the interface. The power supply by the power supply pin is stopped, and after waiting for a second predetermined time, a request to turn on the power is output to the interface, and after waiting for a third predetermined time, the power supply pin A display failure occurrence prevention method for requesting transmission of the third EDID after resuming the power supply. Performs inter-device authentication using EDID, and is executed by a computer incorporated in a video display device in which a plurality are connected in a daisy chain by an interface using a connector having a power supply pin and a hot plug detection pin A program,
After turning on the power of the video display device, the pin for hot plug detection is confirmed. When it is Low, it operates as a Sink device, and when it is High, it makes a transmission request for the first EDID, When the reception of the EDID is successful, it operates as a repeater device. When the reception of the EDID fails, the power supply by the power supply pin is stopped and resumed after waiting for a first predetermined time. And causing the computer to execute a second transmission request for the EDID. The program according to claim 9, wherein
After receiving the second EDID transmission request, if the reception of the EDID is successful, it operates as a Repeater device, and if the reception of the EDID fails, outputs a request to turn off the power to the interface. The power supply by the power supply pin is stopped, and after waiting for a second predetermined time, a request to turn on the power is output to the interface, and after waiting for a third predetermined time, the power supply pin A program for causing the computer to execute a third transmission request for the EDID after resuming the power supply.

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