JPH07181910A - Display device - Google Patents

Abstract

PURPOSE:To prevent disturbance of a screen occussing in the noninput state of a PC video signal by detecting whether or not a PC(personal computer) video signal is inputted and inhibiting the mode from being switched to a PC mode in the noninput state of the PC video signal even when a user makes a switching request in video mode. CONSTITUTION:This device is provided with a synchronizing signal presence/ absence detecting means 4 for the PC video signal. A video signal switching means 3 selects the video signal 11 inputted from a video input signal 1 when the video switching signal outputted by a NAND circuit 51 is at a high level and selects the PC video signal 12 inputted from a PC video signal input terminal 2 when at a low level. The video signal switching means 3, therefore, operates not to perform switching to the PC video signal 12 unless the PC video signal 12 is inputted even when a PC image is requested. The video signal selected by the video signal switching means 3 is amplified by a video amplifier 6 and displayed on a cathode-ray tube 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device capable of displaying video images and personal computer (hereinafter referred to as PC) images, and more particularly, switching between video images and PC images or video audio and PC audio. The present invention relates to a display device that is suitable for outputting.

[0002]

2. Description of the Related Art FIG. 8 shows a conventional system configuration of a display device having a display function of a video image and a PC image. In the figure, 1 is a video image signal input terminal, 2 is a PC image signal input terminal, 3 is an image signal switching means, and 6
Is a video amplifier, 7 is a cathode ray tube, 90 is a video / audio switching signal, 92 is a video audio signal input terminal, and 93 is P
C audio signal input terminal, 72 is audio signal switching means, 7
3 is an audio amplifier, and 74 is a speaker.

The video signal switching means 3 switches between the video video signal input from the video video signal input terminal 1 and the PC video signal input from the PC video signal input terminal 2, and the audio signal switching means 72 operates. , The video audio signal input from the video audio signal input terminal 92, and P
The PC audio signal input from the C audio signal input terminal 93 is switched.

As shown in FIG. 8, in the conventional system configuration, the video / audio switching signal 90 is supplied to both the video signal switching means 3 and the audio signal switching means 72, and the video signal switching and the audio are switched. The signal switching is performed by the same switching signal according to the switching request of the user.

As an example of such a conventional technique,
"Television Technology"; October 1989, Extra Edition (Electronic Technology Publishing Co., Ltd.), pages 26-32.

[0006]

The conventional system described above has the following problems.

As a first problem, when the user requests switching from a video mode for displaying a video image to a PC mode for displaying a PC image when the PC is not connected or the power of the PC is not turned on, The display screen is disturbed because there is no synchronization signal.

The second problem is that when the PC video signal is in a non-input state, the user erroneously changes from the video mode to the P mode.
Even if the user immediately notices an error and immediately requests to switch to the video mode after requesting to switch to the C mode, the time of the process of switching from the video mode to the PC mode and the time of the process of switching from the PC mode to the video mode. As a result, the display mode is disturbed because the video mode is not immediately returned to.

As a third problem, a PC that does not supply voice
, The output voice is also the PC voice in the PC mode, so the voice cannot be heard.

As a fourth problem, when a PC capable of reproducing audio-only software such as a compact disc (hereinafter referred to as a CD) is connected and reproduced, the PC video signal is output in the PC mode even if the PC audio is output. The display screen is disturbed because it is not present.

As a fifth problem, in the PC mode, when a high-definition television signal is input from the PC video signal input terminal and displayed on the screen, the display screen is dark in the brightness of the PC mode.

One object of the present invention is to provide a video image for preventing such a display device from causing a screen display defect that occurs when the PC video signal is not input, as in the first and second problems described above. It is to provide a signal switching means.

Another object of the present invention is that, in such a display device, the video signal switching and the audio signal switching are performed by the same switching signal as in the third and fourth problems. To prevent problems that occur in
It is to provide a video signal switching means and an audio signal switching means.

Still another object of the present invention is to prevent a problem in such a display device caused by non-identification of a standardized video signal such as a high-definition television signal as in the fifth problem. It is to provide a signal identification means.

[0015]

In order to solve the above-mentioned first problem, the present invention detects whether or not a PC is input and the PC does not input even if the user makes a switching request in the video mode. In the state, the video signal switching means does not switch to the PC mode. In addition to this, when the user makes a switching request in the PC non-input state, the fact that the PC is in the non-input state is displayed in characters on the screen.

To solve the second problem, when the video mode is switched to the PC mode and the PC is in the non-input state, the control signal supplied to the deflection circuit system is
Do not switch to the control signal for PC mode.

Further, in order to solve the third problem, it has a function of switching only the audio signal without switching the video signal.

Further, in order to solve the fourth problem, it has a function of switching only the video signal without switching the audio signal.

In order to solve the fifth problem, P
In C mode, the brightness of the display screen is normally switched to be darker than that in the video mode, but if the video signal input from the PC video signal input terminal is a high definition television signal, the brightness of the display screen is increased. To do.

[0020]

According to the means for solving the first problem, it is possible to prevent the screen from being disturbed when the PC video signal is in the non-input state. Furthermore, it is possible to inform the user that the PC is not connected.

According to the means for solving the second problem, when the user mistakenly selects the PC mode, the user can immediately return to the video mode.

According to the means for solving the third problem, when the PC which does not supply the sound is connected, the video sound can be outputted and the sound can be heard while outputting the PC video signal.

According to the means for solving the fourth problem, it is possible to reproduce audio-only software such as CD.
When C is connected and played back, a video image can be output even if PC audio is output, and it is possible to prevent screen disorder.

According to the means for solving the fifth problem, it is possible to prevent the screen from becoming dark when a high definition television signal is inputted from the PC video signal input terminal in the PC mode.

[0025]

The present invention will be described below with reference to the illustrated embodiments.

<First Embodiment> FIG. 1 is a block diagram of a display device capable of displaying a video image and a PC image according to a first embodiment of the present invention. In the figure, 1 is a video image signal input terminal, 2 is a PC image signal input terminal, 3 is a video signal switching unit, 4 is a sync signal presence / absence detecting unit, 5 is a video switching signal generating unit, 6 is a video amplifier, and 7 is A cathode ray tube, 8 is a switching request signal, 11 is a video image signal, 12 is a PC image signal, 51 is a NAND circuit, and 52 is an inverter circuit.

In this embodiment, the output of the synchronizing signal presence / absence detecting means 4 and the switching request signal 8 are inputted to the video switching signal generating means 5, and the output of the synchronizing signal presence / absence detecting means 4 and the switching request signal 8 are inputted. Thus, the output of the video switching signal generating means 5 is determined. The video switching signal generating means 5 is composed of a NAND circuit 51 and an inverter circuit 52, and the video switching signal supplied to the video signal switching means 3 passes through the output of the sync signal presence detecting means 4 and the inverter circuit 52. And a NAND with the inverted switching request signal 8.

In this embodiment, the sync signal presence / absence detecting means 4 detects the presence / absence of a sync signal of the PC video signal 12 input from the PC video signal input terminal 2, and outputs a high level when the sync signal is present. Outputs low level when there is no sync signal. Here, the fact that there is a synchronization signal means that
The video signal 12 is input, and the absence of the sync signal means that the PC is not connected to the PC video signal input terminal 2 or the power of the connected PC is not turned on. To do. The switching request signal 8 has a high level when the user requests a video image, and has a low level when the user requests a PC image. Then, the switching request signal 8 is inverted by the inverter circuit 52. The NAND circuit 51 outputs a low level only when the synchronizing signal presence / absence detecting means 4 and the inversion signal of the switching request signal 8 are at a high level at the same time. That is, the low level is output from the NAND circuit 51 only when the PC image is requested and the synchronizing signal of the PC image signal 12 is present.

The video signal switching means 3 operates when the video switching signal output from the NAND circuit 51 is at high level.
The video image signal 11 input from the video image signal input terminal 1 is selected, and when the level is low, the PC image signal 12 input from the PC image signal input terminal 2 is selected. Therefore, the video signal switching means 3 has a function of not switching to the PC video signal 12 even if the PC video is requested, unless the PC video signal 12 is input. The video signal selected by the video signal switching means 3 is amplified by the video amplifier 6 and displayed on the cathode ray tube 7.

By adopting such a configuration, when the PC is not connected or the power of the PC is not turned on, the user can display the video image from the video mode.
Even if the switching to the PC mode for displaying the PC video is requested, the display screen is not disturbed because there is no synchronization signal.

Although the case where the synchronizing signal detecting means for the PC video signal is provided has been described above, the same applies to the case where the synchronizing signal detecting means for the video picture signal is provided. The same applies to the case where the synchronizing signal detecting means for both the video image signal and the PC image signal is provided.

FIG. 2 is a diagram showing an example of the synchronizing signal presence / absence detecting means 4. In the figure, 41 is a frequency / voltage conversion circuit (hereinafter referred to as F / V conversion circuit), 42 is a comparator, and 43 is a reference voltage. In the configuration of FIG. 2, P
The frequency of the sync signal of the PC video signal input from the C video signal input terminal 2 is converted into a voltage by the F / V conversion circuit 41. In the comparator 42, the F / V conversion circuit 41
The sync signal conversion voltage output from the reference voltage 43 is compared with the reference voltage 43, and if the sync signal conversion voltage is higher than the reference voltage 23, a high level is output, and if it is low, a low level is output. Thus, if the frequency of the sync signal is below a certain level, it can be determined that there is no sync signal.

<Second Embodiment> FIG. 3 is a block diagram of a display device capable of displaying a video image and a PC image according to the second embodiment of the present invention. Are denoted by the same reference numerals, and the description thereof will be omitted to avoid duplication (this also applies to each of the following embodiments). In FIG. 3, 31 is a character multiplex processing means, 3
2 is a character display request means, 321 is a NOR circuit, and 33 is a character display request signal.

In this embodiment, a character multiplex processing means 31 and a character display requesting means 32 for supplying a character display request signal 33 to the character multiplex processing means 31 are added to the first embodiment of FIG. ing. The character display requesting means 32 is NOR
It is composed of a circuit 321. The NOR circuit 321 receives the output of the sync signal presence / absence detecting means 4 and the switching request signal 8 and outputs a high level only when two input signals are at a low level at the same time. That is, PC
Only when an image is requested and there is no PC video signal synchronizing signal, the character display requesting means 32 (NOR circuit 32
1) outputs a high level. Character multiplex processing means 31
When the character multiplex request signal 33 output from the NOR circuit 321 is at high level, the
A character (message) indicating that the video signal 12 is not input is multiplexed and output.

Therefore, in this embodiment, in addition to the effect of the first embodiment, if the PC video signal 12 is not input when the PC video is requested, it means that the PC video signal 12 is not input. The effect of being able to display is displayed.

Although the case where the PC video signal sync signal detection means is provided has been described above, the same applies to the case where the video video signal sync signal detection means is provided. The same applies to the case where the synchronizing signal detecting means for both the video image signal and the PC image signal is provided.

<Third Embodiment> FIG. 4 is a block diagram of a display device capable of displaying a video image and a PC image according to a third embodiment of the present invention. In the figure, 80 is a switching signal generating means, 81 is a control signal output means, 82 is a deflection circuit, 83 is a deflection yoke (hereinafter referred to as DY), 84 is a switching signal, 801 is a NAND circuit, 802 is an inverter circuit, 811 and 813 are memories, 812 and 81
Reference numeral 4 is a digital / analog (hereinafter referred to as D / A) converter, and 815 is a control signal switching means.

In the present embodiment, the switching signal generating means 80
Is composed of a NAND circuit 801 and an inverter circuit 802, and the switching signal 84 supplied to the control signal switching unit 81 is inverted by the output of the synchronization signal presence / absence detecting unit 4 and the inverter circuit 802. It is a NAND with 8. Further, in this embodiment, the video signal switching means 3 selects the video video signal 11 when the switching request signal 8 is at the high level, and selects the PC video signal 12 when it is at the low level. The video signal selected by the video signal switching means 3 is amplified by the video amplifier 6 and displayed on the cathode ray tube 7.

The NAND circuit 801 outputs a low level only when the sync signal presence / absence detecting means 4 and the switching request signal 8 inverted by the inverter circuit 802 are at a high level at the same time. In other words, PC video is required,
Moreover, only when there is a synchronization signal of the PC video signal 12,
A low level is output from the NAND circuit 801.

The control signal output means 81 includes a memory 811 storing video image control data, a memory 813 storing PC image control data, D / A converters 812 and 814, and a control signal switching means 815. It is configured. The video image control data stored in the memory 811 is converted from a digital signal to an analog signal by the D / A converter 812, and the PC image control data stored in the memory 813 is converted by the D / A converter 814. , Digital signals are converted to analog signals. The control signal switching means 815 selects the video image control signal output from the D / A converter 812 when the switching signal 84 output from the NAND circuit 801 is at a high level,
P output from the D / A converter 814 at low level
Select the C video control signal.

That is, when the switching to the PC video is requested, the video signal switching means 3 switches to the PC video signal 12 according to the request, but the control signal switching means 815.
Operates so as not to switch to the PC control signal unless the PC video signal 12 is input. The control signal selected by the control signal switching unit 815 is supplied to the deflection circuit 82.

With such a configuration, when the PC video signal is in a non-input state, the user mistakenly requests the switching from the video mode to the PC mode and immediately notices the mistake and immediately switches to the video mode. , You can immediately return to video mode.

Although the case where the synchronizing signal detecting means for the PC video signal is provided has been described above, the same applies to the case where the synchronizing signal detecting means for the video picture signal is provided. The same applies to the case where the synchronizing signal detecting means for both the video image signal and the PC image signal is provided.

<Fourth Embodiment> FIG. 5 is a block diagram of a display device capable of displaying a video image and a PC image according to a fourth embodiment of the present invention. In the figure, 90 is an image
Voice switching signal, 91 is voice switching request signal, 92
Is a video audio signal input terminal, 93 is a PC audio signal input terminal, 94 is an audio switching signal generating means, and 941 is Exc.
a positive-OR (hereinafter referred to as Ex-OR) circuit,
Reference numeral 95 is a voice switching signal, 72 is a voice signal switching means, 73 is an audio amplifier, and 74 is a speaker.

In this embodiment, the voice switching signal generating means 94 is composed of the Ex-OR circuit 941.
The audio switching signal 95 supplied to the audio signal switching means 72 is Ex-OR of the video / audio switching signal 90 and the audio switching request signal 91. The video / audio switching signal 90 requests video video / audio at a high level and requests PC video / audio at a low level. A video / audio switching signal 90 is supplied to the video signal switching means 3, and when the video / audio switching signal 90 is at a high level, a video video signal input from the video video signal input terminal 1 is selected and a low signal is selected. When the level is set, the PC video signal input from the PC video signal input terminal 2 is selected. The video signal selected by the video signal switching means 3 is
It is amplified by the video amplifier 6 and displayed on the cathode ray tube 7.

The audio switching request signal 91 is set to a high level when requesting switching of only audio, and is cleared to a low level when the video / audio switching signal 90 is switched. Video / audio switching signal 9
0 and voice switching request signal 91 are connected to the input E
The x-OR circuit 941 outputs a low level if the two input signals have the same level, and outputs a high level if the two input signals have different levels. That is, when the audio switching request signal 91 is low level, the same level as the video / audio switching signal 90 is output, but when it is high level, the inverted level of the video / audio switching signal 90 is output. The audio signal switching means 72 selects a video audio signal when the audio switching signal 95 output from the Ex-OR circuit 941 is at a high level, and selects a PC audio signal when it is at a low level.

Therefore, in the normal case where the audio switching is not required, the audio is selected according to the video / audio switching signal 90, but when the audio switching is requested, only the audio is switched. Audio signal switching means 7
The audio signal selected in 2 is output to the speaker 74 via the audio amplifier 73.

With such a configuration, it is possible to output video sound while outputting the PC video signal, and to hear the sound even when a PC that does not supply sound is connected.

<Fifth Embodiment> FIG. 6 is a block diagram of a display device capable of displaying a video image and a PC image according to a fifth embodiment of the present invention. In the figure, 96 is a video switching signal, 97 is a video switching signal generating means, 971.
Is an Ex-OR circuit, and 98 is a video switching request signal.

In this embodiment, the video switching signal generating means 97 is composed of an Ex-OR circuit 971.
The video switching signal to the video signal switching means 3 is Ex-OR of the video / audio switching signal 90 and the video switching request signal 98. Video / audio switching signal 9
0 requests video / audio at a high level and requests PC video / audio at a low level. A video / audio switching signal 90 is supplied to the audio signal switching means 72, and when the video / audio switching signal 90 is at a high level,
The video audio signal input from the video audio signal input terminal 92 is selected, and when the level is low, the PC audio signal input from the PC audio signal input terminal 93 is selected. The audio signal selected by the audio signal switching means 72 is output to the speaker 74 via the audio amplifier 73.

The video switching request signal 98 goes to a high level when a video only switching request is made.
When the voice switching signal 90 is switched, it is cleared to a low level. The Ex-OR circuit 971 connected to the inputs of the video / audio switching signal 90 and the video switching request signal 98 outputs a low level when the two input signals have the same level, and outputs a high level when the two input signals have different levels. To do. That is, when the video switching request signal 98 is low level, the same level as the video / audio switching signal 90 is output, but when it is high level, the inverted level of the video / audio switching signal 90 is output. The video signal switching means 3 selects the video audio signal when the video switching signal 96 output from the Ex-OR circuit 971 is at high level, and selects the PC audio signal when at low level.

Therefore, the video signal switching means 3 normally selects the video according to the video / audio switching signal 90 when the video switching is not required, but when the video switching is requested, only the video is switched. The video signal selected by the video signal switching means 3 is amplified by the video amplifier 6 and displayed on the cathode ray tube 7.

With such a configuration, when a PC capable of reproducing audio-only software such as a CD is connected and reproduced, a video image can be output even if PC audio is output, and the screen is disturbed. Can be prevented.

<Sixth Embodiment> FIG. 7 is a block diagram of a display device capable of displaying a video image and a PC image according to a sixth embodiment of the present invention. In the figure, 20 is a video signal identifying means, 21 is a video circuit, and 22 is a luminance switching signal generating means.

In this embodiment, the discrimination result of the video signal discrimination means 20 and the selection signal 8 are inputted to the luminance switching signal generating means 22, and the switching signal outputted from the luminance switching signal generating means 22 is inputted to the video circuit 21. Supplied. The respective video signals input from the video video signal input terminal 1 and the PC video signal input terminal 2 are supplied to the video signal switching means 3, and the video signal switching means 3 selects the selection signal 8
Either one of the two video signals supplied by is selected and output to the video circuit 21. The video circuit 21 performs a predetermined signal processing on the input video signal and outputs it to the cathode ray tube 7.

On the other hand, the video signal identifying means 20 identifies whether the video signal input from the PC video signal input terminal 2 is a high definition television signal. Examples of the identification method include a method of detecting whether or not an input video signal having the same frequency as that of the high-definition television signal is interlaced, and if the interlace is regarded as a high-definition television signal. The switching signal supplied from the luminance switching signal generating means 22 to the video circuit 21 is generated from the identification result of the video signal identifying means 20 and the selection signal 8. The luminance signal processing performed in the video circuit 21 is the selection signal 8
Thus, when the video image signal is selected and when the PC image signal is selected, predetermined luminance signal processing is performed.

The luminance signal during the PC image display is normally set to be darker than that in the video image display. However, when the identification result of the image signal identifying means 20 is judged to be a high definition television signal, With the switching signal output from the luminance switching signal generating means 22, the luminance signal processing is performed so that the brightness becomes equivalent to that of the video image display. That is,
By providing an identifying means for a video signal having a specific signal specification such as a standardized high-definition television signal, when a specific video signal is identified, specific signal processing is performed and output conditions are suitable. To work.

With such a configuration, it is possible to prevent the screen from becoming dark when a high-definition television signal is input from the PC video signal input terminal in the PC mode.

The case where the video signal identification means for the PC video signal is provided to identify the high definition television signal has been described above, but the same applies to the identification of a specific video signal. Further, the case where the control target is the luminance signal has been described, but the same applies to other control targets. The same applies to the case where the image identification means for the video image signal is provided, and the same applies when the image signal identification means for both the video image signal and the PC image signal is provided.

[0060]

As described above, according to the present invention, in a display device having a display function of a video image and a PC image, it is possible to prevent a screen display problem that occurs when the PC image signal is not input. .

In addition to video, video audio and PC
In a display device capable of outputting audio, it is possible to prevent a problem caused by switching the video signal and the audio signal with the same switching signal.

When displaying a PC image, normally,
Although the brightness is set to be dark, when the input signal from the PC video signal input terminal is identified as a high-definition television signal, the brightness can be automatically increased to make it easier to see. As described above, by providing the identifying means for the video signal having the unique signal specification such as the standardized high definition television signal, the output condition can be optimized when the specific video signal is identified. You can

[Brief description of drawings]

FIG. 1 is a configuration diagram of a display device capable of displaying a video image and a PC image according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing an example of sync signal presence / absence detection means in FIG.

FIG. 3 is a configuration diagram of a display device capable of displaying a video image and a PC image according to a second embodiment of the present invention.

FIG. 4 is a configuration diagram of a display device capable of displaying a video image and a PC image according to a third embodiment of the present invention.

FIG. 5 is a configuration diagram of a display device capable of displaying a video image and a PC image according to a fourth embodiment of the present invention.

FIG. 6 is a configuration diagram of a display device capable of displaying a video image and a PC image according to a fifth embodiment of the present invention.

FIG. 7 is a configuration diagram of a display device capable of displaying a video image and a PC image according to a sixth embodiment of the present invention.

FIG. 8 is a configuration diagram of a display device capable of displaying a video image and a PC image according to a conventional example.

[Explanation of symbols]

 1 Video video signal input terminal 2 PC video signal input terminal 3 Video signal switching means 4 Sync signal presence / absence detection means 6 Video amplifier 20 Video signal identification means 21 Video circuit 72 Audio signal switching means 73 Audio amplifier 81 Control signal output means 82 Deflection circuit 92 Video audio signal input terminal 93 PC audio signal input terminal

Claims (5)

[Claims] 1. A video signal input terminal, a personal computer video signal input terminal, a video signal switching means, and a video amplifier, wherein the video signal switching means inputs a video input from the video video signal input terminal. A display device for selecting one of a video signal and a personal computer video signal input from the personal computer video signal input terminal and supplying the video amplifier to the video amplifier. , Having a sync signal detecting means for detecting the presence or absence of a sync signal for at least one of the video signals,
A display device, wherein a video switching signal supplied to the video signal switching means is generated from a selection signal corresponding to a switching request from a user and a detection signal output from the synchronization signal detecting means. 2. A video image signal input terminal, a personal computer video signal input terminal, a video signal switching means, a video amplifier, a control signal output means, and a deflection circuit, the video signal switching means comprising: The video signal input from the video signal input terminal or the personal computer video signal input from the personal computer video signal input terminal selects either one and supplies it to the video amplifier. A display device for selecting one of a video image control signal stored in the control signal output means and a personal computer image control signal and supplying the selected video signal to the deflection circuit. Signal and at least one of the personal computer video signal Has a synchronization signal detection means for detecting the presence or absence of a synchronizing signal for the image signal,
The switching signal supplied to the control signal output means is generated from the selection signal corresponding to the switching request of the user and the detection signal output from the synchronization signal detection means, and the synchronization signal for video display requested by the selection signal is The display device, wherein the control signal output means has a function of not switching to the requested video control signal when the synchronization signal detection means determines that there is no such signal. 3. A video image signal input terminal, a personal computer video signal input terminal, a video signal switching means, a video amplifier, a video audio signal input terminal, a personal computer audio signal input terminal, and an audio signal switching means. And an audio amplifier, and the video signal switching means selects one of a video video signal input from the video video signal input terminal and a personal computer video signal input from the personal computer video signal input terminal. And supplies the video signal to the video amplifier, and the audio signal switching means selects either one of the video audio signal input from the video audio signal input terminal and the personal computer audio signal input from the personal computer audio signal input terminal. Select the ode A display device supplied to a bio-amplifier, wherein the display device has a function of switching the audio signal switching means without switching the video signal switching means. 4. A video image signal input terminal, a personal computer video signal input terminal, a video signal switching means, a video amplifier, a video audio signal input terminal, a personal computer audio signal input terminal, and an audio signal switching means. And an audio amplifier, and the video signal switching means selects one of a video video signal input from the video video signal input terminal and a personal computer video signal input from the personal computer video signal input terminal. And supplies the video signal to the video amplifier, and the audio signal switching means selects either one of the video audio signal input from the video audio signal input terminal and the personal computer audio signal input from the personal computer audio signal input terminal. Select the ode A display device supplied to a bio-amplifier, wherein the display device has a function of switching the video signal switching means without switching the audio signal switching means. 5. A video image signal input terminal, a personal computer video signal input terminal, a video signal switching means, and a video circuit, wherein the video signal switching means inputs a video input from the video video signal input terminal. A display device which selects one of a video signal and a personal computer video signal input from the personal computer video signal input terminal and supplies the video circuit with the selected video signal. A display device characterized in that the signal specification of an input video signal is identified for at least one of the video signals, and if the signal specification matches a predetermined specification, predetermined signal processing is performed.