JPS61173291A - Superimposer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a superimposing device for simultaneously displaying a video signal from a television or VTR and a signal from a computer on the same television.

Conventional technology Conventionally, when superimposing a video signal from a TV or VTR, etc. and a signal from a computer, the TV or VT
The video signal such as R is a composite video signal that includes a synchronization signal, and the signal from the computer is R, G, B.
Signals are common.

As shown in Fig. 2, the composite video signal from the TV or VTR is input to the TV and also input to the synchronization signal extraction circuit 2 from the terminal 21, where the horizontal and vertical synchronization signals are extracted. . These two extracted synchronization signals are input to a computer (not shown) from the output terminal 22. Therefore, the R, G, and B signals from the computer will be synchronized with the above-mentioned external synchronization signal, and if these R, G, and B signals are input to the television at the same time as the above-mentioned composite video signal,
A screen with both signals synchronized will be displayed on the TV. Further, synchronization within the television set is normally achieved by the input composite video three-page signal.

On the other hand, even if this circuit is used, when only the signal from the computer is displayed on the television without superimposing, synchronization is achieved by switching and inputting the synchronization signal from the computer.

Note that elements common to those in FIG. 1 are given the same numbers, and details of the operation will be explained in FIG. 1.

As described above, whether or not to superimpose is normally determined by a command from a computer, and switching of the synchronization signal is also performed by a command from the computer.

Problems to be Solved by the Invention In the superimpose device described in the conventional example, for example, the computer issues a superimpose command and the synchronization signal to the TV is sent by itself (the computer) in the trench. If we switch from a video signal to a composite signal from a VTR, if the VTR is in operation and a composite video signal is being output from the VTR, the superimpose device will operate normally and the VTR will The composite video signal from the computer and the R, G, and B signals from the computer are superimposed on the TV, but if the VTR is not working or a normal composite video signal is not output after pressing the play switch. If the composite signal is not being output, such as when the composite signal is not being output, the R, G, and B signals from the computer will no longer be synchronized unless the synchronization signal is input to the TV, causing the TV screen to become distorted. There is a problem with putting it away.

Means for Solving the Problems In order to solve the problems shown in the conventional example, the present invention superimposes a means for detecting a composite video signal from a television, VTR, etc. and a video signal detection circuit for this video signal detection circuit. A means is provided to control the synchronization signal period change to the television by output, and when a composite video signal is detected, this composite signal is input to the television, and when a composite, 6 page video signal is not detected, Input the synchronization signal from the computer to the TV.

Effect: According to the method described above, when a composite video signal is not detected, the synchronization signal from the computer is input to the TV, which prevents the R9G and B screens from being disturbed during that time, and also prevents the composite video signal from being input. In this case, the synchronization signal to the TV will smoothly switch to a composite video signal, so the superimposed screen will also be displayed normally.

Embodiment A first embodiment of the superimposing device according to the present invention will be described below.
As shown in the figure. '1 is composite video signal and combination;
- A switching circuit for switching the synchronization signal of the computer (not shown) or the composite video signal input terminal 12 and the synchronization signal input terminal 11 from the computer (not shown), and the control from the computer (not shown). signal input terminal 13,
It has a control signal input terminal 16 from the synchronization signal monitoring device 3 and a synchronization signal 6 Beso signal output terminal 14. 2 is a synchronization signal extraction circuit 2,
It has a composite video signal input terminal 21 and a synchronization signal output terminal 22. 3 is a synchronization signal monitoring device having a synchronization signal input terminal 32 and a synchronization signal monitoring signal output terminal 31;

To further explain the operation of the superimpose circuit configured as above, R and G signals from the computer are processed without superimposing.

When displaying only the B signal, the switching circuit is connected to the synchronization signal terminal 1 from the computer according to a command from the computer.
Switch to side 1. At this time, a synchronizing signal from the computer is output from the output terminal 14. On the other hand, when performing superimposition, the switching circuit is similarly switched according to commands from the computer, but from the output terminal 14,
The synchronization signal from the computer is still being output. At this point, when the composite video signal is input to the input terminal 12, this signal is also input to the input terminal 21 of the synchronization signal sampling circuit 2, so that a synchronization signal is output from its output terminal 22, and the synchronization signal is input to the input terminal 12. The signal 7 is inputted to the input terminal 32 of the monitoring device 3 and a computer (not shown). When the synchronization signal monitoring device 3 detects a synchronization signal input, it outputs a switching circuit control signal from its output terminal 31. At this point, the output terminal 14 of the switching circuit
From there, a composite video signal will be output.

Effects of the Invention As described above, by using the superimposing device of the present invention, when there is no composite video signal, the computer automatically inputs the synchronization signal from the computer to the TV. The screen will not be distorted by the R, G, and B signals, and you can always see a synchronized screen.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a superimposing device according to an embodiment of the present invention, and FIG. 2 is a block diagram of a conventional superimposing device. DESCRIPTION OF SYMBOLS 1...Switching circuit, 2...Synchronization signal extraction circuit, 3...Synchronization signal monitoring device, 11...
...Computer synchronization signal input terminal, 12...
Composite video signal input circuit, 13... Combiator control signal input terminal, 14... Synchronous signal output terminal, 16... Synchronous signal monitoring signal input terminal, 21... ...Composite video signal input terminal, 31...Switching circuit control signal output terminal, 32.
...Sync signal input terminal. Name of agent: Patent attorney Toshio Nakao and one other person

Claims (1)

[Claims] A sync signal extraction circuit extracts a horizontal sync signal and a vertical sync signal from a television video signal, a sync signal monitoring device monitors the presence or absence of the sync signal, and a sync signal extracted by the sync signal extraction circuit and a sync signal from a computer are provided. A switching circuit is provided, which inputs a synchronizing signal from the computer to the television receiver when the television video signal is not input, externally synchronizes the computer with the television video signal, and switches between the television video signal and the television receiver. A superimposing device characterized in that output signals from a computer are simultaneously displayed on the television receiver.