Display device

Abstract

To provide a display device that can appropriately transfer information about video formats that can handle to a video source while limiting the increase in user's burden.SOLUTION: The display device can display video received from a video source. The display device includes a selection unit that selects either first identification data as identification information about formats that the display device can accept from the video source or second identification data different from the first identification data, an analysis unit that analyzes information about a video signal transmitted from the video source to the display device, and a video source control unit that causes the video source to read out the first or second identification data selected in the selection unit. The selection unit selects the first identification data when connected to the video source and selects the second identification data on the basis of analysis results of the analysis unit.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a display device. [Background technology]

[0002] In recent years, HDMI (High Definition Multimedia Interface, registered trademark) has been widely used as an interface connecting a video transmitting device (hereinafter referred to as a source device) as a video source and a video receiving device (hereinafter referred to as a sink device) that displays the video received from the source device. When a source device and a sink device are connected via HDMI, the source device reads EDID (Extended Display Identification Data) from the sink device. By reading this EDID, the source device can transmit a video signal suitable for the performance (e.g., resolution) of the sink device to the sink device.

[0003] In this regard, Patent Document 1 proposes a configuration in which, when a sink device cannot play back video, audio, etc. properly, the format data related to video, audio, etc. in the EDID is changed based on the user's remote control operation, and the source device is made to read the EDID again. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2008-158220 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the configuration described in the cited document 1, if the video signal transmitted from the source device to the sink device is not appropriate, the sink device outputs unnatural video and audio, or displays no video or audio at all. Based on such a display state, the user determines that some kind of problem has occurred and operates the remote control.

[0006] In this way, changing the EDID using the method described in Cited Document 1 is left to the user's awareness of the occurrence of a problem and the remote control operation based on that awareness. Therefore, there are cases where the user does not notice the problem immediately, or even if they do, remote control operation is required, which is not desirable for the user's viewing environment.

[0007] An aspect of the present invention provides a display device capable of appropriately transferring information about a compatible video format to a video source while suppressing an increase in the burden on a user. [Means for solving the problem]

[0008] A display device according to one embodiment of the present invention is a display device capable of displaying video received from a video source, and includes a selection unit that selects either first identification data as identification information regarding a format that the display device can accept from the video source and second identification data different from the first identification data, an analysis unit that analyzes information regarding a video signal transmitted from the video source to the display device, and a video source control unit that causes the video source to read out the first identification data or the second identification data selected by the selection unit, and the selection unit selects the first identification data when connected to the video source, and selects the second identification data based on the analysis result of the analysis unit. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a block diagram of a video display system according to a first embodiment. [Figure 2A] FIG. 2 is a conceptual diagram showing a configuration of a basic block of an EDID according to the first embodiment. [Figure 2B] FIG. 2 is a conceptual diagram showing the configuration of an extended block of EDID according to the first embodiment. [Diagram 3] FIG. 1 is a block diagram of a video display system according to a first embodiment. [Figure 4A] 5 is a timing chart of various signals when EDID is read out in the video display system according to the first embodiment. [Figure 4B] 4 is a sequence diagram showing the operations of the sink device and the source device when reading EDID in the video display system according to the first embodiment. [Figure 5A] 5 is a timing chart of various signals when EDID is read out in the video display system according to the first embodiment. [Figure 5B] 4 is a sequence diagram showing the operations of the sink device and the source device when reading EDID in the video display system according to the first embodiment. [Figure 6] 5 is a flowchart showing the operation of the sink device according to the first embodiment. [Figure 7] FIG. 11 is a block diagram of a video display system according to a second embodiment. [Figure 8A] FIG. 11 is a conceptual diagram showing the configuration of a command for acquiring the vendor name of a source device according to the second embodiment. [Figure 8B] FIG. 11 is a conceptual diagram of a source device table according to the second embodiment. [Figure 9] 10 is a timing chart of various signals when EDID is read out in a video display system according to a second embodiment. [Figure 10] 10 is a flowchart showing the operation of a sink device according to the second embodiment. [Figure 11] 13 is a flowchart showing the operation of a sink device according to the third embodiment. [Figure 12] 13 is a flowchart showing the operation of a sink device according to the fourth embodiment. [Figure 13] FIG. 13 is a conceptual diagram of an SPD packet according to modifications of the first to fourth embodiments. [Figure 14] 11 is a timing chart of various signals when EDID is read out in the video display systems according to the modifications of the first to fourth embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings, the same or equivalent elements are designated by the same reference numerals, and duplicated explanations will be omitted.

[0011] First Embodiment A display device according to a first embodiment of the present invention will be described. This embodiment relates to a method of transferring EDID to a source device when the sink device and the source device are connected via HDMI.

[0012] FIG. 1 is a block diagram of a video display system according to this embodiment, and shows only the main parts related to this embodiment. As shown in the figure, the video display system 1 includes a sink device 10 and a source device 20. The sink device 10 is a display device that receives and displays video and audio information from the source device 20 as a video source. Examples of the sink device 10 include, but are not limited to, a television receiver, a personal computer, or a display device used for digital signage. The source device 20 is a video source of a video displayed on the sink device 10, and is a video transmission device that transmits video and audio information to the sink device 10. Examples of the source device 20 include, but are not limited to, a personal computer, a game device, or a recording device such as HDR (Hard Disk Recorder). The sink device 10 and the source device 20 are connected by HDMI. Next, the sink device 10 and the source device 20 will be described in detail.

[0013] First, a description will be given of the sink device 10. As shown in Fig. 1, the sink device 10 includes an EDID transmission / reception unit 11, an EDID data selection unit 12, an EDID buffer 13, a video synchronization signal analysis unit 14, an HPD control unit 15, and an HDMI control unit 16.

[0014] The EDID data selection unit 12 is a selection unit that selects either the first identification data or the second identification data as identification information related to a video format that the sink device 10 can accept from the source device 20. More specifically, the EDID data selection unit 12 includes a selector 30 and a memory 31.

[0015] The memory 31 holds first and second identification data as the above-mentioned identification information. This identification information is, for example, EDID, which is identification data unique to a device. The memory 31 holds EDID_A as the first identification data, and further holds EDID_B as the second identification data. In this example, EDID_A and EDID_B are EDID1.3 (VESA E-EDID Standard Release A Revision 1) conforming to the VESA (registered trademark, Video Electronics Standards Association) standard, and each includes a basic block block0 (128 bytes) conforming to the VESA standard and one (or more) CTA (Consumer Technology Association) extended block block1 (128 bytes). EDID_A describes functions defined in the HDMI2.x standard (x is zero or a positive integer). On the other hand, EDID_B describes functions defined in the HDMI1.x standard. Details of EDID will be described later.

[0016] The selector 30 selects either EDID_A or EDID_B held in the memory 31 in accordance with an instruction from the HDMI control unit 16 .

[0017] The EDID buffer 13 temporarily holds either EDID_A or EDID_B selected by the selector 30.

[0018] The EDID transmission / reception unit 11 receives an EDID read request from the source device 20. In response to the EDID read request, the EDID transmission / reception unit 11 transfers either EDID_A or EDID_B stored in the EDID buffer to the source device 20 via a DDC (Display Data Channel) line of the HDMI.

[0019] The video synchronization signal analysis unit 14 is an analysis unit that analyzes information about the video signal transmitted from the source device 20 to the sink device 10. That is, the video synchronization signal analysis unit 14 analyzes information about the resolution and refresh rate of the video transmitted from the source device 20 to the sink device 10, and determines whether the sink device 10 can display the video.

[0020] That is, the source device 20 transmits a video signal including horizontal / vertical synchronization signals and a pixel clock to the sink device 10 via a Transmission Minimized Differential Signaling (TMDS) / Fixed Rate Link (FRL) line.

[0021] Then, the video synchronization signal analysis unit 14 calculates the resolution and refresh rate of the video based on the horizontal / vertical synchronization signals and the pixel clock, and determines whether or not the video can be displayed on the sink device 10. Then, the video synchronization signal analysis unit 14 transmits the determination result to the HDMI control unit 16.

[0022] When the source device 20 is connected to the sink device 10 via HDMI, the HDMI control unit 16 causes the selector 30 to select EDID_A, and further commands the HPD control unit 15 to transmit an HPD signal (second signal) to the source device 20. When the video synchronization signal analysis unit 14 determines that the video signal is not appropriate, the HDMI control unit 16 causes the selector 30 to select EDID_B, and further commands the HPD control unit 15 to resend an HPD (Hot Plug Detect) signal. In other words, the selector 30 selects EDID_B based on the analysis result in the video synchronization signal analysis unit 14.

[0023] In this example, the video synchronization signal analysis unit 14 determines whether or not the video signal is appropriate for the sink device 10. However, the video synchronization signal analysis unit 14 may determine only whether or not the synchronization signal is appropriate, and the HDMI control unit 16 may determine whether or not the video signal is appropriate based on the result of this determination. This also applies to the following embodiments.

[0024] The HPD control unit 15 is a video source control unit that causes the source device 20 to read out EDID_A or EDID_B selected by the EDID data selection unit 12. That is, in accordance with a command from the HDMI control unit 16, the HPD control unit 15 first transmits an HPD signal to the source device 20 to prompt the source device 20 to read out EDID_A, and when EDID_B is selected by the EDID data selection unit 12, transmits an HPD signal again to the source device 20 to prompt the source device 20 to read out EDID_B.

[0025] Next, the source device 20 will be described. As described above, the source device 20 is a device (video source) that outputs video and audio to the sink device 10. When the source device 20 is connected to the sink device 10 via HDMI, it supplies a power supply voltage of, for example, +5V to the sink device 10 via a power supply line. Furthermore, when the source device 20 receives the above-mentioned HPD signal from the sink device 10, it reads out the EDID from the sink device 10 and transfers optimal video and audio signals for the sink device 10 to the sink device 10 based on the read EDID via a TMDS (Transmission Minimized Differential Signaling) / FRL (Fixed Rate Link) line.

[0026] Next, a brief description will be given of the configurations of the above-described EDID_A and EDID_B. Figures 2A and 2B are conceptual diagrams of information held by EDID_A and EDID_B, where Figure 2A shows a basic block block0 and Figure 2B shows a CTA extension block block1.

[0027] First, the basic block block0 will be described with reference to Fig. 2A. The basic block block0 describes the minimum specifications of the sink device 10. Specifically, as shown in Fig. 2A, the basic block block0 has 128 bytes of data, of which the first 8 bytes are a Header, and the data from the ninth byte onwards are, in order, Vender / Product ID (ID for identifying the sink device), EDID Structure Version / Revision, Basic Display Parameters and Features (basic information of the sink device: display size, compatible functions, etc.), Color Characteristic (chromaticity information of the display), Established Timings and Standard Timing Identification (corresponding video signal information), Detailed Timing Description #1 (corresponding video signal information), Detailed Timing Description #2-#4 or Monitor Descriptor (monitor name, etc.), Extension Flag (the number of subsequent CTA extension blocks), and Check Sum.

[0028] Of the above data, Detailed Timing Description #1 and #2 indicate the resolution and refresh rate supported by the sink device 10. In general, Detailed Timing Description #1 has the highest priority for the sink device 10. Note that in this specification, for the sake of simplicity, the relationship between the resolution and the refresh rate may be expressed as "resolution / refresh rate."

[0029] Next, the CTA extension block block1 will be described with reference to Fig. 2B. As shown in the figure, the first 4 bytes of the 128 bytes of data are the CTA Extension Header, which includes a Tag ("0X02") and a Revision Number. After the CTA Extension Header are the Data Block Collection, Detailed Timing Descriptor, the final address is a Checksum, and the space between the final Detailed Timing Descriptor and the Checksum is filled with "00h".

[0030] In the above-mentioned CTA extension block block 1, a data block is described in the data block collection to indicate the video / audio signals and HDMI functions supported by the sink device 10 (EDID_A indicates a function compliant with HDMI 2.x, and EDID_B indicates a function compliant with HDMI 1.x).

[0031] Next, the operation of the video display system 1 configured as above will be described, focusing particularly on EDID transfer. Fig. 3 is a simplified diagram of the video display system 1 shown in Fig. 1, and shows signals transmitted and received between the sink device 10 and the source device 20 when the sink device 10 and the source device 20 are connected by HDMI.

[0032] 3, when sink device 10 and source device 20 are connected by HDMI, a voltage of +5V is transferred from source device 20 to sink device 10 via the HDMI power line. Then, in sink device 10, in response to the supply of a voltage of +5V, HPD control unit 15 outputs an HPD signal to source device 20 under command of HDMI control unit 16. In response to receiving the HPD signal, source device 20 reads out EDID held in EDID buffer 13 from sink device 10. Thereafter, source device 20 determines a video format to be output based on the EDID, and transmits a video signal in the determined video format to sink device 10.

[0033] The above operation will be described in more detail below. As an example, the sink device 10 according to this embodiment holds EDID_A conforming to the HDMI2.x (e.g., HDMI2.1) standard and EDID_B conforming to the HDMI1.x (e.g., HDMI1.4) standard. In the initial state (the state immediately after the sink device 10 is connected to the source device 20 via HDMI), the HDMI control unit 16 causes the selector 30 to select EDID_A. Therefore, EDID_A is held in the EDID buffer 13.

[0034] At this time, if the source device 20 does not support the HDMI 2.x standard but supports the HDMI 1.x standard, the source device 20 may not correctly recognize some information (information related to functions defined in the HDMI 2.x standard) in the read EDID_A, and may misrecognize the information of EDID_A. Then, the source device 20 may transmit to the sink device 10 a video signal that cannot be displayed on the sink device 10, or may transmit to the sink device 10 a video signal with a low resolution that is not expected in the sink device 10. Therefore, the sink device 10 according to the present embodiment judges whether the video signal transmitted from the source device 20 is appropriate, in other words, whether the source device 20 has misrecognized the information of EDID_A, based on the analysis result of the video synchronization signal analysis unit 14. Then, if the video signal transmitted from the source device 20 is not appropriate, in other words, if the source device 20 has misrecognized the EDID_A, the HDMI control unit 16 causes the selector 30 to select EDID_B. Then, the HPD control unit 15 transmits the HPD signal again to cause the source device 20 to read out EDID_B.

[0035] First, a case where the source device 20 complies with the HDMI 2.x standard will be described with reference to Fig. 4A and Fig. 4B. Fig. 4A is a timing chart of signals transmitted and received between the sink device 10 and the source device 20, and Fig. 4B is a sequence diagram showing a flow of processing between the sink device 10 and the source device 20.

[0036] As shown in the figure, at time t1, the source device 20 turns on the power supply for HDMI, thereby supplying +5V to the sink device 10 via the power line. Then, at time t2, the HPD control unit 15 of the sink device 10 turns on the HPD signal. That is, the HPD control unit 15 outputs the HPD signal, and the HPD signal is changed from the "L" level to the "H" level. The change of the HPD signal to the "H" level is used as a trigger for the source device 20 to start reading out EDID_A from the sink device 10 at time t3. The DDC line is used for transmitting and receiving the EDID.

[0037] First, the source device 20 reads the 1st to 128th bytes of EDID_A, i.e., basic block block0, from the EDID buffer 13 of the sink device 10. As a result, the source device 20 obtains the minimum specification information of the sink device 10. Next, the source device 20 reads the 129th to 256th bytes of EDID_A, i.e., CTA extended block block1, from the EDID buffer 13 of the sink device 10. As a result, the source device 20 recognizes that the sink device 10 supports video signals such as 8K / 60Hz, 4K / 120Hz, and 4K / 144Hz, and has HDMI2.x functions.

[0038] By reading the CTA extension block block1, the source device 20 detects that the sink device 10 supports HDMI2.x and also supports video of 8K / 60Hz, 4K / 120Hz, and 4K / 144Hz. Therefore, after time t5, the source device 20 transmits video signals and audio signals of these resolutions and refresh rates (for example, 4K / 144Hz) to the sink device 10 via the TMDS / FRL line. The source device 20 also transmits these video signals and audio signals to the sink device 10 via the TMDS / FRL line.

[0039] When the video signal is transmitted to the sink device 10, the video synchronization signal analysis unit 14 analyzes, for example, the horizontal / vertical synchronization signals and the pixel clock, and determines whether the received video signal can be reproduced. In this example, the source device 20 is compatible with the HDMI 2.x standard and can correctly recognize EDMI_A. Therefore, a video signal such as 4K / 144Hz described in the CTA extension block block 1 of EDID_A is transmitted to the sink device 10. This video signal is a signal that can be reproduced correctly in the sink device 10. The video synchronization signal analysis unit 14 recognizes this by analyzing the horizontal / vertical synchronization signals and the pixel clock, and determines that the video signal can be reproduced, in other words, that a proper video signal is being received, and transmits the determination result to the HDMI control unit 16.

[0040] When the HDMI control unit 16 receives the determination result from the video synchronization signal analysis unit 14, it causes the selector 30 to continue selecting EDID_A. Then, the sink device 10 reproduces 4K video and audio signals with a refresh rate of 120 Hz or 144 Hz.

[0041] Next, a case will be described where the source device 20 does not support HDMI 2.x, but supports the HDMI 1.x standard such as HDMI 1.4. Fig. 5A is a timing chart of signals transmitted and received between the sink device 10 and the source device 20, and Fig. 5B is a sequence diagram showing the flow of processing between the sink device 10 and the source device 20, which correspond to Fig. 4A and Fig. 4B described above, respectively.

[0042] As shown in the figure, the operation from time t1 to t4 is as described in Figures 4A and 4B. However, what is different from the case of Figures 4A and 4B is that the source device 20 cannot correctly recognize EDID_A. That is, in this example, since the source device does not support the HDMI 2.x standard, there is a possibility that it cannot correctly recognize EDID_A that supports the HDMI 2.x standard. Therefore, at time t5, the source device 20 transmits a video signal and an audio signal to the sink device 10 via the TMDS / FRL line based on the EDID_A read during the period from time t3 to t4, but this video signal is a signal with a resolution / refresh rate that cannot display a video on the sink device 10, for example.

[0043] Therefore, the video synchronization signal analysis unit 14 determines that the video signal transmitted from the source device 20 during the period from time t5 to t6 is not appropriate, and transmits this determination result to the HDMI control unit 16. Then, the HDMI control unit 16 commands the HPD control unit 15 to turn off the HPD signal based on the determination result of the video synchronization signal analysis unit 14. As a result, at time t7, the HPD control unit 15 changes the HPD signal from the "H" level to the "L" level. As the HPD signal has been changed to the "L" level, the source device 20 detects that the connection with the sink device 10 has been disconnected, and temporarily stops transmitting and receiving signals to and from the sink device 10. For example, the source device 20 does not transmit a video signal or the like to the sink device 10.

[0044] Furthermore, the HDMI control unit 16 commands the selector 30 to select EDID_B based on the analysis result of the video synchronization signal analysis unit 14. In response to this command, the selector 30 selects EDID_B that complies with the HDMI 1.x standard and stores it in the EDID buffer 13. Then, in response to a command from the HDMI control unit 16, the HPD control unit 15 turns on the HPD signal again at time t8. That is, the HPD control unit 15 changes the HPD signal from the "H" level to the "L" level at time t7, and then retransmits the HPD signal from the "L" level to the "H" level at time t8, causing the source device 20 to read out EDID_B.

[0045] In response to the output of the HPD signal, the source device 20 detects the reconnection with the sink device 10 and resumes reading the EDID from the sink device 10. That is, the source device 20 reads the EDID from the sink device 10 during the period from time t9 to t10. At this time, the EDID that is read is EDID_B held in the EDID buffer 13.

[0046] The source device 20 first reads the 1st to 128th bytes of EDID_B, i.e., the basic block block0, from the EDID buffer 13 of the sink device 10. The source device 20 then reads the 129th to 256th bytes of EDID_B, i.e., the CTA extension block block1, from the EDID buffer 13 of the sink device 10. This enables the source device 20 to recognize that the sink device 10 is compatible with HDMI1.x and supports 4K video with a refresh rate of 30 Hz or full HD video with a refresh rate of 60 Hz. Therefore, from time t11 onwards, the sink device 10 is compatible with HDMI1.x and transmits 4K / 30 Hz or full HD / 60 Hz video and audio signals to the sink device 10, which then plays them back.

[0047] 6 is a flowchart showing the flow of processing of the sink device 10 when performing the above operation. As shown in the figure, first, in step S10, the selector 30 selects EDID_A conforming to the HDMI 2.x standard according to an instruction from the HDMI control unit 16, and sets this in the EDID buffer 13 as the initial EDID of the sink device 10. In step S11, the sink device 10 is connected to the source device 20 by HDMI. More specifically, as described above, a power supply voltage of +5V is supplied from the source device 20 to the sink device 10. Furthermore, in step S12, the HPD control unit 15 outputs an HPD signal according to an instruction from the HDMI control unit 16. In step S13, the EDID held in the EDID buffer 13 of the sink device 10 is read out to the source device 20 via the DDC line. In step S14, the source device 20 transmits a video signal according to the read EDID, and the sink device 10 receives it.

[0048] In step S15, the video synchronization signal analysis unit 14 judges whether the video signal received in step S14 is a signal that can be displayed on the sink device 10. As described above, this judgment can be made by, for example, analyzing the horizontal / vertical synchronization signals and the pixel clock. Then, in step S15, if the video signal is a signal that cannot be displayed (NO in step S15), in step S19, the HDMI control unit 16 causes the HPD control unit 15 to reset the HPD signal. Furthermore, in step S20, the HDMI control unit 16 causes the selector 30 to select EDID_B and store it in the EDID buffer 13, thereby changing the EDID of the sink device 10 from EDID_A conforming to HDMI2.x to EDID_B conforming to HDMI1.x. Then, the process returns to step S12, and the HPD control unit 15 sets the output of the HPD signal and causes the source device 20 to read out EDID_B. These steps S19 and S20 correspond to the cases described in FIG. 5A and FIG. 5B.

[0049] In step S15, if the video signal is a signal that can be displayed (YES in step S15), in step S16, the sink device 10 displays a video based on the video signal received in step S14.

[0050] Thereafter, in step S17, the connection with the source device 20 is disconnected. Then, in step S18, the HDMI control unit 16 changes the EDID of the sink device 10 back to EDID_A as necessary (if it has been changed to EDID_B).

[0051] As described above, in this embodiment, the memory 31 of the sink device 10 holds two EDIDs (EDID_A and EDID_B) corresponding to different functions in the HDMI standard. The video synchronization signal analysis unit 14 analyzes information about the video signal transmitted from the source device 20, and the selector 30 selects EDID_B based on the analysis result of the video synchronization signal analysis unit 14. More specifically, the video synchronization signal analysis unit 14 determines whether the video signal is appropriate for the sink device 10 based on a synchronization signal (for example, a horizontal / vertical synchronization signal and a pixel clock) transmitted together with the video signal, in other words, whether the sink device 10 can display video based on the synchronization signal and the video signal. Then, when the video signal is not appropriate, in other words, when the sink device 10 cannot display video, the selector 30 selects EDID_B. Therefore, the source device 20 can transmit video information in an appropriate format to the sink device 10.

[0052] For example, in the example of FIG. 5A, in the case of a video display system in which the source device 20 does not read EDID_B from time t9 to t10, the source device 20 transmits a signal in a video format conforming to the HDMI 2.x standard described in EDID_A to the sink device 10. However, since the source device 20 does not conform to the HDMI 2.x standard but conforms to the HDMI 1.x standard, there is a possibility that the source device 20 cannot correctly recognize the information related to the HDMI 2.x standard described in EDID_A. In this way, when the source device 20 erroneously recognizes the EDID, the source device 20 may transmit a video signal to the sink device 10 in a format (e.g., resolution or refresh rate) that cannot be displayed or played by the sink device 10. As a result, the sink device 10 cannot display the video even if it receives the video signal from the source device 20, and a warning message such as "Video signal is not being input" is displayed on the display of the sink device 10, which reduces usability for the user.

[0053] However, in this embodiment, the memory 31 of the EDID data selection unit 12 holds not only EDID_A corresponding to the HDMI 2.x standard, but also EDID_B corresponding to the HDMI 1.x standard. Furthermore, when the video synchronization signal analysis unit 14 determines that the video signal is not appropriate, EDID_B is selected as the EDID of the sink device 10. Then, the sink device 10 outputs the HPD signal again to make the source device 20 read EDID_B. This allows the source device 20 to correctly recognize the EDID, and transmits to the sink device 10 a video signal that conforms to the HDMI 1.x standard and has a format that can be played back by the sink device 10. The switching from EDID_A to EDID_B is performed in response to the analysis result of the video signal by the video synchronization signal analysis unit 14, without requiring the user to operate a remote control or the like. As a result, the user can view the video received from the source device 20 without recognizing that the video signal format has been switched, and without being notified that the video is not displayed.

[0054] <Second embodiment> Next, a display device according to a second embodiment of the present invention will be described. In this embodiment, when the display device described in the first embodiment is reconnected to a source device previously connected via HDMI, the previously used EDID is selected. Only the differences from the first embodiment will be described below.

[0055] 7 is a block diagram of a video display system according to the present embodiment. As shown in the figure, a sink device 10 according to the present embodiment further includes a source device information detection unit 17 in addition to the configuration of FIG. 1 described in the first embodiment.

[0056] When the sink device 10 is HDMI-connected to the source device 20, the source device information detection unit 17 acquires information about the source device 20 from the source device 20. As an example, the source device information detection unit 17 transmits a signal to the source device 20 requesting information about the source device 20, and receives information transmitted from the source device 20 in response to this signal. The information about the source device 20 is, for example, the vendor name and / or product name of the source device 20. Upon acquiring this information, the source device information detection unit 17 transmits it to the HDMI control unit 16.

[0057] Furthermore, the memory 31 according to this embodiment holds a source device table in addition to EDID_A and EDID_B. The source device table holds the relationship between information capable of identifying a sink device previously connected via HDMI and the EDID (i.e., EDID_A or EDID_B) used when the sink device was connected. The information capable of identifying the sink device is, for example, the vendor name and / or product name of the source device 20 received by the source device information detection unit 17 described above. The source device table may be held in a memory separate from the memory 31.

[0058] When the source device 20 is connected to the sink device 10 via HDMI, the HDMI control unit 16 reads out the source device table from the memory 3. If the source device table does not exist in the memory 31, the HDMI control unit 16 generates the source device table. Then, the HDMI control unit 16 checks whether the information on the source device 20 received from the source device information detection unit 17, i.e., the vendor name and / or product name of the source device 20, is recorded in the read source device table. If it is recorded, the HDMI control unit 16 commands the selector 30 to select the EDID (EDID_A or EDID_B) recorded in association with the source device 20. That is, if the source device 20 is recorded in the source device table, the EDID recorded in association with the source device 20 is set as the EDID of the sink device 10. On the other hand, if the information on the source device 20 connected to the sink device 10 is not recorded in the source device table, the EDID is selected by the method described in the first embodiment, and the HDMI control unit 16 associates the selected EDID with the information on the source device 20, records it in the source device table, and holds it in the memory 31.

[0059] The other configurations are similar to those of the first embodiment, so the description will be omitted.

[0060] In the above configuration, the source device information detection unit 17 can use a command (Give Vendor Command) for requesting information from the source device 20 using a CEC (Consumer Electronics Control) line as a command for reading out information about the source device 20. Fig. 8A shows an overview of the Give Vendor Command defined in the High-Definition Multimedia Specification.

[0061] As shown in the figure, by receiving a Give Vendor Command in which Give Device Vendor ID is set as the Opcode of the command, the source device 20 returns the Device Vendor ID assigned to the source device 20 to the sink device 10. The Device Vendor ID is a unique ID assigned to each vendor, and by receiving this information, the HDMI control unit 16 of the sink device 10 can recognize the vendor name of the source device 20. Note that by setting Vendor Command, Vendor Command with ID, and Vendor Remote Button Down as the Opcode of the Give Vendor Command, detailed vendor information such as that shown in FIG. 8A can be obtained.

[0062] Fig. 8B is a conceptual diagram of a source device table held in memory 31. As shown in the figure, the source device table records Device Vendor IDs indicating the vendor names of source devices 20 previously connected to the sink device 10, and the EDIDs used corresponding to the Device Vendor IDs. For example, in the example of Fig. 8B, it can be seen that a source device 20 with a vendor name corresponding to a Device Vendor ID of "0x0001" was previously connected to the sink device 10, and EDID_A was used at that time, EDID_B was used for a source device 20 with a vendor name corresponding to a Device Vendor ID of "0x002F", and EDID_A was used for a source device 20 with a vendor name corresponding to a Device Vendor ID of "0x0800".

[0063] The above operation will be described in more detail below. Fig. 9 is a timing chart of various signals when the source device 20 is HDMI connected to the sink device 10, and corresponds to Fig. 4A and Fig. 4B described in the first embodiment.

[0064] As shown in the figure, at time t1, source device 20 supplies +5V to sink device 10 via the power line, and at time t2, HPD control unit 15 of sink device 10 turns on the HPD signal. Then, in this example, at time t3 before source device 20 reads EDID, source device information detection unit 17 of sink device 10 issues, for example, the Give Vendor Command described above and transmits it to source device 20 via the CEC line. Then, at time t5, in response to the Give Vendor Command, source device 20 transmits a Device Vendor ID to sink device 10 via the CEC line.

[0065] The source device information detection unit 17 that has received the Device Vendor ID transmits it to the HDMI control unit 16. The HDMI control unit 16 then reads the source device table from the memory 31, and checks whether the sink device 10 is registered in the source device table. In this example, it is assumed that the received Device Vendor ID is registered in the source device table, and the corresponding EDID is EDID_B. Then, the HDMI control unit 16 causes the selector 30 to select EDID_B.

[0066] The operation thereafter is the same as that at time t9 described in Fig. 5A. That is, as shown in Fig. 9, in the period from time t7 to time t8, the source device 20 reads out EDID_B, and at time t11, transmits a video signal having a resolution defined in HDMI1.x to the sink device 10 via the TMDS / FRL line.

[0067] If the Device Vendor ID received at time t5 is not registered in the source device table, the operations from time t3 onwards described in FIG. 5A in the first embodiment are executed from time t7 onwards.

[0068] Fig. 10 is a flowchart showing the flow of processing of the sink device 10 when performing the above operation. The differences from Fig. 5 described in the first embodiment are as follows. After step S12, the source device information detection unit 17 of the sink device 10 reads out information about the source device 20 in step S30. After step S30, in step S31, the HDMI control unit 16 determines, based on the information read out in step S30 and the information in the source device table, whether the source device 20 connected in step S11 is a source device connecting to the sink device 10 for the first time. If it is determined in step S31 that the source device is not the first to be connected to the sink device 10 but is a source device that was previously connected (NO in step S31), then in step S32 the HDMI control unit 16 commands the selector 30 to select the same EDID as in the previous connection. After step S32, similarly to steps S13 and S14, the source device 20 reads the EDID of the sink device, transmits a video signal to the sink device 10, and proceeds to the process of step S16. In step S31, if it is determined that the source device is connected to the sink device 10 for the first time (YES in step S31), the process from step S15 onwards is carried out as in the first embodiment.

[0069] According to this embodiment, when sink device 10 first connects to source device 20 via HDMI, the sink device 10 holds information about the source device (for example, vendor name and product name) and the EDID used in the source device table. Then, when connecting to source device 20, before the source device 20 reads the EDID, the sink device 10 determines whether the source device has previously connected via HDMI based on the information read by source device information detection unit 17 and the information in the source device table. If it is registered that an HDMI connection has been made in the past, the sink device 10 sets the EDID used at that time as the EDID of the sink device 10.

[0070] This allows the sink device 10 to set an appropriate EDID for the source device 20 without waiting for the EDID to be read or for a video signal to be transmitted from the source device 20. This allows the connection time to be shortened when connecting via HDMI to the same source device 20 for the second or subsequent times.

[0071] <Third embodiment> Next, a display device according to a third embodiment of the present invention will be described. In this embodiment, in the display device described in the above first embodiment, whether or not the EDID is appropriate for the source device 20 is determined based on whether or not the video signal transmitted from the source device 20 is a signal expected by the sink device 10. Only the points different from the first embodiment will be described below.

[0072] The configuration and operation of the sink device 10 according to this embodiment are almost the same as those of the first embodiment. This embodiment differs from the first embodiment in the analysis method in the video synchronization signal analysis unit 14. The video synchronization signal analysis unit 14 according to this embodiment determines whether or not the resolution and / or refresh rate of the video signal received from the source device 20 is a value assumed by the sink device 10 during the period from time t5 to t6 described in FIG. 5A.

[0073] As described in FIG. 2A and FIG. 2B, the Detailed Timing Description #1-#2 of the basic block block0 of EDID_A and the Data block collection of the CTA extension block block1 describe the resolution and maximum refresh rate that the sink device 10 can support. Therefore, the video synchronization signal analyzer 14 receives a video signal from the source device 20 and determines whether the resolution of the received video signal is appropriate based on the resolution described in EDID_A. More specifically, if the resolution and / or refresh rate of the received video signal is not described in EDID_A, or if it is described but is the minimum resolution / refresh rate, for example, VGA (640×480), it determines that the received video signal is not appropriate and transmits the result to the HDMI control unit 16. Other operations are the same as those in the first embodiment.

[0074] 11 is a flowchart showing a process flow of the sink device 10 when the source device 20 is connected to the sink device 10. The difference from FIG. 5 described in the first embodiment is that in step S40 instead of step S15, the video synchronization signal analysis unit 14 judges whether or not the video signal received from the source device 20 is a signal expected by the sink device 10. As described above, this judgment method is based on the resolution and / or refresh rate of the video signal and the resolution and / or refresh rate described in EDID_A. If the video signal is a signal expected by the sink device 10, the process proceeds to step S16, and if not, the process proceeds to step S19, where the EDID of the sink device 10 is switched from EDID_A to EDID_B, and the source device 20 reads the EDID from the sink device 10 again.

[0075] As described above, whether or not the video signal received from the source device 20 is appropriate for the sink device 10, in other words, whether or not EDID_A is appropriate for the source device 20, can be determined based on the resolution and / or refresh rate of the received video signal, as described in the first embodiment. Furthermore, if the source device 20 erroneously recognizes the EDID and transmits an inappropriate video signal to the sink device 10, it does not necessarily mean that the video cannot be displayed, and for example, a low-quality video with a very low resolution such as VGA that is not expected by the user (sink device) may be displayed. However, according to this embodiment, the occurrence of such a situation can be suppressed.

[0076] <Fourth embodiment> Next, a display device according to a fourth embodiment of the present invention will be described. This embodiment is a combination of the second and third embodiments. Only the differences from the second embodiment will be described below.

[0077] The configuration and operation of the sink device 10 according to this embodiment are almost the same as those of the second embodiment. This embodiment differs from the second embodiment in that, like the third embodiment, the video synchronization signal analyzer 14 determines whether or not the resolution and / or refresh rate of the video signal received from the source device 20 is a value assumed by the sink device 10. The method of determination is the same as that of the third embodiment.

[0078] Fig. 12 is a flowchart showing a flow of processing of the sink device 10 when the source device 20 is connected to the sink device 10. The difference from Fig. 10 described in the second embodiment is that in step S40 instead of step S15, the video synchronization signal analyzer 14 determines whether or not the video signal received from the source device 20 is a signal expected by the sink device 10, as described in the third embodiment.

[0079] As described above, the method of determining whether or not the video signal received from the source device 20 is appropriate for the sink device 10, in other words, whether or not EDID_A is appropriate for the source device 20, which has been described in the third embodiment, can also be applied to the second embodiment.

[0080] <Modifications, etc.> The above-described embodiment is merely an example, and various modifications are possible. For example, in the above-described embodiment, as a method for determining whether the video signal received from the source device 20 is appropriate for the sink device 10, in other words, whether EDID_A is appropriate for the source device 20, the first and second embodiments have been described with respect to a case in which whether the video signal can be played back and displayed is determined based on the resolution and / or refresh rate. In the third and fourth embodiments, a method for determining whether the resolution and / or refresh rate of the video signal are described in the EDID or the priority is higher than a predetermined priority has been described. However, the determination method is not limited to these, and is not limited to any method that can determine whether the relationship between the sink device 10 and EDID_A is appropriate.

[0081] In the second embodiment, the Give Vendor Command is used as an example of a method for obtaining information about the source device 20. However, the method is not limited to this as long as it can obtain information that can determine whether the source device 20 has been HDMI-connected to the sink device 10 in the past. For example, a source product description (SPD) packet may be used to obtain the vendor name and product name. The SPD packet is transmitted from the source device 20 to the sink device 10 via the TMDS / FRL line together with a video signal. FIG. 13 shows an overview of information held by the SPD packet. As shown in the figure, the 1st to 8th bytes of the SPD packet hold the vendor name of the source device 20, and the 9th to 24th bytes hold the product name. Therefore, the sink device 10 can determine whether the source device 20 has been connected in the past by analyzing the SPD packet.

[0082] Fig. 14 is a timing chart of various signals corresponding to Fig. 5 described in the first embodiment. As shown in the figure, the difference from the first embodiment is that, for example, the video synchronization signal analysis unit 14 or the source device information detection unit 17 receives a video signal at times t5 to t6 and analyzes an SPD packet included in the video signal. Then, based on the vendor name and product name obtained by analyzing the SPD packet and the information registered in the source device table, it is determined whether the source device 20 has been connected via HDMI in the past. That is, in the first and third embodiments, it is possible to determine whether a video signal is appropriate or not based on the information held in the SPD packet.

[0083] In the above embodiment, the case where one CTA extension block is provided has been described as an example, but two or more CTA extension blocks, block1 and block2, may be provided. If information that can be used to determine whether EDID_A is appropriate for the source device 20 is included in the CTA extension block block2, the information may be used. In the above embodiment, the case where both EDID_A and EDID_B are EDID1.4 has been described as an example, but, for example, EDID_A may conform to EDID1.4 and EDID_B may conform to EDID1.0, or both may conform to EDID1.0.

[0084] Furthermore, in the above embodiment, the memory 31 holds two EDIDs, EDID_A and EDID_B. However, three or more EDIDs may be held. For example, EDIDs that precisely correspond to the HDMI standards may be prepared, such as EDID_A that corresponds to the HDMI 2.1 standard, EDID_B that corresponds to the HDMI 2.0 standard, EDID_C that corresponds to the HDMI 1.4 standard, and EDID_D that corresponds to the HDMI 1.3 standard.

[0085] In the above embodiment, an example has been described in which two EDIDs, EDID_A and EDID_B, are stored in advance in the memory 31. However, the memory 31 may not store EDID_B. In this case, when it becomes necessary to change the EDID, for example in step S20 of Fig. 6, the HDMI control unit 16 may read EDID_A from the memory 31, generate EDID_B based on EDID_A, and store this in the EDID buffer 13. In this case, the selector 30 is not necessary.

[0086] Furthermore, in the above embodiment, the sink device 10 and the source device 20 are connected by HDMI, and an example of EDID that is read by the source device 20 at that time has been described. However, the above embodiment is not limited to HDMI EDID. In other words, the above embodiment can be applied to all cases where multiple devices are connected by wire or wirelessly, and when at least one device reads information from the other device, the data that can be supported by the device is limited. In other words, on the device side from which information is read, multiple pieces of data to be read may be prepared, for example, for each standard or performance, and appropriate data may be read using the method described in the above embodiment.

[0087] Although several embodiments of the present invention have been described above, the present invention is not limited to the above-mentioned forms and can be modified as appropriate. The above configurations can be replaced with substantially similar configurations, configurations that provide similar functions and effects, or configurations that can achieve similar purposes. [Explanation of symbols]

[0088] 1...video display system, 10...sink device, 11...EDID transmission / reception unit, 12...EDID data selection unit, 13...EDID buffer, 14...video synchronization signal analysis unit, 15...HPD control unit, 16...HDMI control unit, 17...source device information detection unit, 20...source device

Claims

1. A display device capable of displaying an image received from a video source, comprising: a selection unit that selects either first identification data as identification information related to a format that the display device can accept from the video source, or second identification data different from the first identification data; an analysis unit that analyzes information about a video signal transmitted from the video source to the display device; an image source control unit that causes the image source to read out the first identification data or the second identification data selected by the selection unit; Equipped with The display device, wherein the selection unit selects the first identification data when connected to the video source, and selects the second identification data based on an analysis result by the analysis unit.

2. The analysis unit determines whether the video signal is appropriate for the display device based on a synchronization signal transmitted together with the video signal from the video source; The display device according to claim 1 , wherein the selection section selects the second identification data when the analysis section determines that the video signal is inappropriate.

3. The display device according to claim 2 , wherein the analysis section determines that the video signal is inappropriate when the display device cannot display an image based on the synchronization signal and the video signal.

4. The analyzer determines whether the video signal is appropriate for the display device based on a resolution of the video signal received from the video source; The display device according to claim 1 , wherein the selection section selects the second identification data when the analysis section determines that the video signal is inappropriate.

5. The display device according to claim 4 , wherein the analysis section determines that the video signal is inappropriate when a resolution of the video signal received from the video source does not match resolution information included in the first identification data.

6. A video source information detection unit that detects information about the video source, The display device according to any one of claims 1 to 5, wherein when it is determined based on the information detected by the video source information detection unit that the video source was previously connected to the display device, the selection unit selects the identification information used when the video source was previously connected.

7. The display device according to claim 6 , wherein the image source information detector transmits a first signal to the image source requesting information about the image source before the identification information is read by the image source.

8. the selection unit includes a memory and a selector; the memory holds the first identification data and the second identification data; the selector selects the first identification data from the memory, and the video source control unit causes the video source to read the first identification data; The display device of claim 1, wherein the analysis unit determines whether the video signal is appropriate for the display device based on a signal indicating information about the video signal transmitted from the video source, and if it is determined to be inappropriate, the selector selects the second identification data from the memory, and the video source control unit causes the video source to read out the second identification data.

9. The display device according to claim 1 , wherein the first identification data and the second identification data are Extended Display Identification Data (EDID), which is identification data unique to a device.

10. 9. The display device according to claim 1, wherein the image source control unit transmits, when the second identification data is selected by the selection unit, a second signal to the image source to prompt the image source to read out the second identification data.

11. The display device according to claim 10 , wherein the second signal is a Hot Plug Detect (HPD) signal.

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