JP2662066B2 - Superimposer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is used in broadcasting equipment, educational equipment, and the like, and is used to output image signals such as characters and pattern images output from a personal computer or the like, video recorders, video disk players, and the like. And a superimposer for superimposing and synthesizing a video signal output from the superimposer.

[Conventional technology]

FIG. 2 is a circuit diagram showing a conventional superimposer. In the figure, reference numeral 1 denotes a decoder circuit connected to a video signal input terminal, and 6 denotes a computer / video connected to an image signal input terminal of a personal computer or the like. Scan converter circuit (hereinafter referred to as PC / NTSC), 7 is decoder circuit 1 and PC
/ NTSC This is a video timing synthesizing circuit that takes in each output of the scan converter circuit 6 and synthesizes and outputs.

 Next, the operation will be described.

Generally, a video signal and an image signal from a personal computer or the like have different signal standards. In order to combine them, it is necessary to convert the video signal to the same standard once. Then, the video signal is obtained by modulating the RGB three primary colors and the synchronization signal into a single composite video signal.
This is an SC composite signal.
This is a special RGB signal in which the B3 primary color and the synchronization signal are separated and the frequency (synchronization frequency) of the synchronization signal is higher than that of the video signal. Therefore, in order to combine these video signals with image signals from a personal computer or the like, the video signals are converted into RGB signals,
It is necessary to match these two synchronization frequencies. Second
In the figure, a video signal is converted to an RGB signal in a decoder circuit 1, and a PC / NTSC scan converter circuit 6 converts the synchronization frequency of an image signal of a personal computer or the like to the same as the video signal. Then, the video timing synthesizing circuit 7 superimposes and synthesizes the output signal converted into the RGB signal by the decoder circuit 1 and the output signal whose synchronizing frequency is converted by the PC / NTSC scan converter circuit 6.

[Problems to be solved by the invention]

Since the conventional superimposer is configured as described above, it is necessary to develop the PC / NTSC scan converter circuit 6 for each model because the synchronization frequency of the image signal of a personal computer or the like differs depending on the model. In addition, there are some personal computers etc. whose synchronization frequency changes dynamically depending on the software used for the same model.
There were problems that the conventional configuration could not cope with.

The present invention has been made in order to solve the above-described problems, and can be applied to a personal computer or the like having a variable synchronization frequency.
It is an object of the present invention to obtain an economical superimposer that does not require modification of a / NTSC scan converter circuit or the like.

[Means for solving the problem]

A superimposer according to the present invention determines a synchronization frequency of an image signal obtained from a computer by a synchronization frequency determination circuit, and generates a timing signal corresponding to the image signal based on a determination result signal output from the synchronization frequency determination circuit. On the other hand, a video signal generated independently from the image signal is input to a decoder circuit, separated into a synchronizing signal and an RGB signal. Is converted into a signal having the same frequency as that of the computer by the timing signal output by the timing generation circuit, and when the output of the video / computer scan converter circuit and the image signal of the computer are synthesized by the computer timing synthesis circuit, Area with computer image signal It is obtained as synthesized by overwriting the image signal of the computer on the video signal.

[Action]

In the superimposer according to the present invention, the synchronization frequency of the image signal of the computer is determined by the synchronization frequency determination circuit, and based on the determination result, the timing generation circuit outputs a timing signal of the determined synchronization frequency.
Therefore, the video / computer scan converter circuit converts the video signal converted into the RGB signal by the decoder circuit into
When the video signal is always converted into a signal having the same frequency as the image signal of the computer and the video signal and the image signal of the computer are synthesized by the computer timing synthesizing circuit in accordance with the synchronization frequency, the video signal in a certain region of the image signal of the computer is Overwrites the image signal of the computer with the image signal and combines it to output to the monitor television.

(Example of the invention)

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, 1 is a decoder circuit connected to an input terminal of a video input signal, 4 is a synchronous frequency discriminating circuit connected to an input terminal of a computer such as a personal computer, and 5 is a timing generator connected to a synchronous frequency discriminating circuit. The circuit 2 is connected to the decoder circuit 1, and refers to a video / computer (hereinafter referred to as NTSC / PC) that refers to the timing signal of the timing generation circuit 5.
The scan converter circuit 3 is a computer timing synthesizing circuit for inputting the output of the NTSC / PC scan converter circuit 2 and the image signal of the computer.

Next, the operation will be described. First, the synchronization frequency determination circuit 4 determines a synchronization frequency from an image signal of a computer or the like, and determines a determination result signal (for example, 0, 1, 2, or
…) Is output. Subsequently, the timing generation circuit 5 generates a timing signal corresponding to the input image signal of the computer by an internal oscillation circuit or the like based on the determination result signal. On the other hand, the video signal is separated into three primary colors of RGB and a synchronizing signal by the decoder circuit 1 in the same manner as in the prior art.
Output to the C scan converter circuit 2. The NTSC / PC scan converter circuit 2 refers to the timing signal generated by the timing generation circuit 5 and converts the video signal converted into an RGB signal into a signal having the same synchronization frequency as the timing signal from a computer or the like. That is, the NTSC / PC scan converter circuit 2 always dynamically converts a video signal converted into an RGB signal into a signal of the same standard as a currently input image signal of a computer.

Next, the computer timing synthesizing circuit 3 is NTSC / PC
The output signal of the scan converter circuit 2 and the image signal of the computer are superimposed on the signal of the computer with priority. That is, in a certain area of the image signal of the computer, the image signal is overwritten on the video signal and synthesized. In other areas, only the video signal is displayed.

〔The invention's effect〕

As described above, according to the present invention, the synchronization frequency of the image signal obtained from the computer is determined by the synchronization frequency determination circuit, and the timing signal corresponding to the image signal is determined based on the determination result signal output from the synchronization frequency determination circuit. A video signal generated independently from the image signal is input to a decoder circuit, separated into a synchronizing signal and an RGB signal, and further divided by a video / computer scan converter circuit.
A signal is converted into a signal having the same frequency as that of the computer by the timing signal output from the timing generation circuit. When the output of the video / computer scan converter circuit and the image signal of the computer are synthesized by the computer timing synthesis circuit, However, in a certain area of the computer image signal, the computer image signal is overwritten on the video signal and synthesized.
It is compatible with personal computers with dynamically changing synchronization frequency, can be connected to many types of personal computers, etc. without modifying the internal circuit, and has the trouble of developing a PC / NTSC scan converter circuit for each model as before. This has the effect of obtaining something that can solve uneconomical effects.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a superimposer according to an embodiment of the present invention, and FIG. 2 is a block diagram showing a conventional superimposer. 1 is a decoder circuit, 2 is a video / computer scan converter circuit (NTSC / PC scan converter circuit),
3 is a computer timing synthesizing circuit, 4 is a synchronous frequency discriminating circuit, and 5 is a timing generating circuit. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

(57) [Claims] A synchronous frequency determining circuit for determining a synchronous frequency of an image signal obtained from a computer; and a timing for generating a timing signal corresponding to the image signal based on a determination result signal output from the synchronous frequency determining circuit. A generator circuit, a decoder circuit for separating a video signal obtained independently of the image signal into an RGB signal and a synchronizing signal, and the timing generating circuit outputting the synchronizing frequency of the RGB signal output by the decoder circuit A video / computer scan converter circuit for converting to the same frequency as the computer according to the timing signal, and a region where the computer image signal is present when the output of the video / computer scan converter circuit is combined with the computer image signal. So, on top of the video signal, Super-in interposer that includes a computer timing combining circuit for combining by overwriting the image signal.