JPS644186B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a video signal processing device, and more particularly to a device for converting data output from a personal computer into a composite video signal that can be displayed on a CRT display or the like.

Traditionally, so-called personal computers
A device that is connected to a CRT display and displays data output from a personal computer on the CRT display is in practical use. By the way, there are cases where it is desired to display different data such as graphic data and character data in a superimposed manner on a CRT display. Therefore,
There was a strong demand for a device that would superimpose data output from two computers and display it on an ORT display.

Therefore, the main object of the present invention is to provide a video signal processing device that can satisfy the above-mentioned demands.

In summary, the present invention includes a first computer and a second computer that adjusts its internal synchronization to a horizontal synchronization signal and a vertical synchronization signal given from the first computer, and The primary color video signal and the three primary color video signals output from the second computer are superimposed, and the superimposed video signal is converted into a composite video signal.

The above-mentioned objects and other features of the present invention will become more apparent from the following detailed description with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention. In the figure, personal computer 1
Three primary color video signals R ₁ , G 1 , and B ₁ are outputted from the three primary color video signals R 1 , G ₁ , and B 1 . These signals R ₁ , G ₁ , and B ₁ are applied to one input of the adder circuit 3 . Further, a horizontal synchronization signal and a vertical synchronization signal are outputted from the personal computer 1 and given to the personal computer 2. This personal computer 2 is a computer that is externally synchronized, and the above-mentioned signal
Three primary color video signals R ₂ synchronized with R ₁ , G ₁ , B ₁ ,
Output G ₂ and B ₂ . These signals R ₂ , G ₂ , B ₂ are
It is applied to the other input of the adder circuit 3.

As shown in FIG. 2, the adder circuit 3 receives the signals R ₁ , G ₁ , B ₁ from the personal computer 1 as one input of each, and also receives the signals R ₂ , G ₂ , B ₂ from the personal computer 2. OR gates 31, 32, which receive as the other input of each
Contains 33. Therefore, the OR gate 31 outputs a signal R ₁ +R ₂ which is a superposition of the signals R ₁ and R ₂ . Also, from the OR gate 32, the signal _G1 and
A signal G ₁ +G ₂ , which is a superimposed signal with G 2 _, is output.
Further, the OR gate 33 outputs a signal B ₁ +B ₂ which is a superposition of the signals B ₁ and B ₂ . The output of the adder circuit 3 is given to an encoder circuit 4.

As shown in FIG. 3, the encoder circuit 4 includes a conversion circuit 41 that converts the three primary color signals from the addition circuit 3 into a luminance signal Y and color difference signals R-Y, R-Y;
a composite circuit 43 that converts the output of the conversion circuit 41 into a video signal that is a composite of a luminance signal and a carrier color signal;
It includes emitter followers 42a, 42b, and 42c inserted between the conversion circuit 41 and the composite circuit 43. The conversion circuit 41 receives the signal R ₁ from the addition circuit 3
Buffers 411a, 411b, 411c that can receive signals R ₂ , G ₁ -G ₂ and B ₁ -B ₁ , respectively, and signals R ₁ -
Inverters 412a, 412b, 412c receiving _R2 , _G1 - _G2 , _B1 - _B2, respectively, and buffer 4
11a to 411c and inverter 412a
412c. Further, the composite circuit 43 has a third
It includes various circuits as shown in the figure. A horizontal synchronization signal and a vertical synchronization signal from the personal computer 1 are superimposed on the output of the composite circuit 43 via an OR gate 44 . In this way, a composite video signal in which the horizontal synchronizing signal and the vertical synchronizing signal are superimposed is provided to the emitter follower 45. An NTSC composite video signal is extracted from the emitter follower 45. In addition, the composite circuit 43
The output of the R-Y, B-Y mixing circuit in the band pass filter 46 and the capacitor C
is fed back to a mixing circuit for the luminance signal and the carrier color signal. This bandpass filter 46 is provided to remove harmonic noise components from the composite video signal.

Figure 4 shows the output signal of personal computer 1.
FIG. 3 is a waveform diagram showing R ₁ , G ₁ , and B ₁ . FIG. 5 shows the output signals R ₂ , G ₂ , B ₂ of the personal computer 2.
FIG. FIG. 6 is a waveform diagram showing the output signals R ₁ +R ₂ , G ₁ +G ₂ , B ₁ +B ₂ of the adder circuit 3. Note that, for convenience of explanation, FIGS. 4 to 6 are shown so that the respective time axes correspond to each other.

The operation of an embodiment of the present invention will be described below with reference to FIGS. 1 to 6.

First, a horizontal synchronization signal and a vertical synchronization signal are provided from the personal computer 1 to the personal computer 2. Then, the personal computer 2 adjusts its internal synchronization to the applied horizontal synchronization signal and vertical synchronization signal. Therefore, the personal computers 1 and 2 output video signals of three primary colors that are synchronized with each other. Next, the output signals R ₁ , G ₁ , B ₁ of the personal computer 1 and the output signals R ₁ , G ₂ , B ₂ of the personal computer 2 are superimposed by each circuit 3 . This superimposed signal is shown in FIG. The superimposed signals R ₁ +R ₂ , G ₁ +G ₂ , B ₁ +B ₂ are converted by the encoder circuit 4 into a video signal that is a composite of a luminance signal and a carrier color signal. Furthermore, OR gate 4
The horizontal and vertical synchronization signals are superimposed via 4
It is considered to be an NTSC composite video signal. Therefore, if this composite video signal is given to a CRT display,
Data obtained by superimposing data from personal computer 1 and data from personal computer 2 is displayed.

As described above, according to the present invention, the data output from two computers are superimposed and converted into a composite video signal, so that the data output from the two computers are superimposed and displayed. be able to. Therefore, it can be used very effectively when comparing different data.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention. FIG. 2 is a circuit diagram showing details of the adder circuit 3 shown in FIG. 1. FIG. 3 is a circuit diagram showing details of the encoder circuit 4 shown in FIG. 1. FIG. 4 is a waveform diagram showing the output signal of the personal computer 1. FIG. 5 is a waveform diagram showing the output signal of the personal computer 2. As shown in FIG. FIG. 6 is a waveform diagram showing the output signal of the adder circuit 3. In the figure, 1 and 2 are personal computers, 3 is an adder circuit, and 4 is an encoder circuit.

Claims (1)

[Claims] 1. A first computer that outputs a first video signal having three primary color signals, a horizontal synchronization signal, and a vertical synchronization signal in order to display input data as an image; a second computer that outputs a second video signal having three primary color signals in synchronization with a horizontal synchronization signal and a vertical synchronization signal from the first computer in order to display the data as an image; A video signal processing device, comprising: means for superimposing the video signal of the second video signal on the second video signal; and means for converting the superimposed three primary color video signals into a composite video signal.