JP2827717B2 - Video signal synthesizer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal synthesizing apparatus for synthesizing two video signals, and more particularly to a video signal synthesizing apparatus capable of monitoring a synthesized video signal at the completion of synthesis.

[0002]

2. Description of the Related Art Conventionally, a video signal synthesizing device of this kind, as shown in FIG. 3, for example, performs a predetermined superimposing process and outputs a synthesized video signal So1 as a synthesized circuit 2.
1 and the synthesized video signal S when the superimpose process is completed.
and a synthesizing circuit 22 that outputs o2.

Here, when the video signal Si2 is superimposed on the input video signal Si1, the key signal generation circuit 23 is controlled by the control circuit 24, and the video signal Si2 is superimposed.
2 generate key signals K1 and K2, respectively. The synthesizing circuits 21 and 22 superimpose the video signal Si2 on the video signal Si1 in accordance with the key signals K1 and K2, and send out them as synthesized video signals So1 and So2.

In this case, the key signal generation circuit 23 changes with time and finally changes the key signal K2 at the time of completion of the superimposing process and the key signal K2 so that a predetermined superimposing process is executed. A matching key signal K1 is generated.

[0005]

In the conventional video signal synthesizing apparatus described above, a separate synthesizing circuit is provided in order to generate a synthesized video signal upon completion of the superimposing process. For this reason, there is a problem that the circuit scale becomes large and the size cannot be reduced.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a video signal synthesizing apparatus capable of monitoring in advance a synthesized video signal at the time of completion of superimposing processing using one synthesizing circuit.

[0007]

Video signal synthesizing apparatus of the present invention According to an aspect of the case the first and second video signals in accordance with a key signal
A synthesizing circuit, a key signal generating circuit for generating the key signal from the second video signal, a delay circuit for applying a predetermined delay to the first video signal, an output signal of the delay circuit, and the synthesizing circuit. a switching circuit for selecting one of the output signal of the circuit, a control circuit for controlling said key signal generating circuit and said switching circuit, monitoring output terminal connected to an output terminal <br/> of the combining circuit When, a synthesizing output terminal connected to an output terminal <br/> of said switching circuit, said control circuit,
Before the synthesizing process starts, the key signal generation circuit is controlled to
If the key signal is set to the state at the time of completion of the combining process,
Controlling the switching circuit to output the output signal of the delay circuit.
And then, at the start of the synthesis process, the key signal
To zero once, and controlling the switching circuit to
The output signal of the synthesis circuit is selected, and then the key signal
The configured so that varied as predetermined composite processing is executed.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention. Here, the synthesizing circuit 11 superimposes the video signal Si2 on the video signal Si1 in accordance with the key signal K to generate a synthesized video signal So, and sends it to the switching circuit 14 and the monitoring output terminal 17. The delay circuit 12 gives the same delay as the delay time generated in the synthesis circuit 11. The key signal generation circuit 13 generates a key signal K from the video signal Si2 under the control of the control circuit 15. Switching circuit 14
Is controlled by the control circuit 15 to select one of the synthesized video signal So from the synthesizing circuit 11 and the output signal of the delay circuit 12, and sends it to the synthesizing output terminal 16.

Next, the operation will be described.

Now, it is assumed that the video signals Si1 and Si2 are images as shown in FIGS. 2 (a) and 2 (b), for example.

First, at the stage before the start of the superimposing process, the key signal K is, as shown in FIG.
Generated in the state when the superimpose process is completed. Therefore, as for the composite video signal So output from the composite circuit 11, a video at the time of completion of the superimposing process is generated and transmitted to the monitoring output terminal 17, as shown in FIG.
That is, at the stage before the start of the superimposition processing, the video at the time of completion of the superimposition processing can be monitored from the monitoring output terminal 17. On the other hand, in this state, the switching circuit 14 has selected the output signal of the delay circuit 12,
Accordingly, as shown in FIG. 2C, the video of the video signal Si1 is transmitted to the composite output terminal 16 as it is.

At the start of the superimposing process, the key signal K temporarily becomes zero, and at the same time, the switching circuit 14
Is switched to the combining circuit 11 side. Therefore, the composite output terminal 1
The video of the video signal Si1 is sent to the monitor output terminal 6 and the monitoring output terminal 17 as it is before the start of the superimposing process. Thereafter, the key signal K changes with time so that a predetermined superimpose process is executed, and finally enters a state at the time of completion of the superimpose process. Therefore, a video signal on which a predetermined superimpose process has been performed is transmitted to the composite output terminal 16.

[0014]

As described above, according to the present invention, a switching circuit for selecting one of an input video signal and a video signal synthesized by a synthesizing circuit is provided, and the output of this switching circuit is synthesized and output. Connect the output of the synthesizing circuit to the output terminal for monitoring, control the switching circuit before starting the synthesizing process, select the input video signal, and generate the key signal when the synthesizing process is completed. To send the video signal at the time of completion of the synthesizing process to the monitoring output terminal.
At the start of the synthesis process, the key signal is temporarily set to zero,
By controlling the switching circuit to select the synthesized video signal and changing the key signal so that a predetermined synthesizing process is executed, before the synthesizing process is started, when the synthesizing process is completed via the monitoring output terminal, You can monitor the video. Therefore, the combined video signal at the completion of the combining process can be monitored in advance by one combining circuit.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a diagram for explaining the operation of the present embodiment.

FIG. 3 is a block diagram illustrating an example of a conventional video signal combining device.

[Explanation of symbols]

 Reference Signs List 11 synthesis circuit 12 delay circuit 13 key signal generation circuit 14 switching circuit 15 control circuit 16 synthesis output terminal 17 monitoring output terminal K key signal Si1, Si2 video signal So synthesized video signal

Claims (1)

(57) [Claims] A synthesizing circuit for synthesizing first and second video signals in accordance with a key signal; a key signal generating circuit for generating the key signal from the second video signal; and a first video signal a delay circuit for giving a predetermined delay to the switching circuit for selecting one of the output signal of the output signal and the synthesis circuit of the delay circuit, said key signal generating circuit
A control circuit for controlling the pre-said switching circuit, the combining circuit
A monitoring output terminal connected to the output terminal of the
And a composite output terminal connected to the output terminal, the control
The circuit controls the key signal generation circuit before the synthesis process starts
So that the key signal is in the state at the time of completion of the combining process.
Control the switching circuit and output the delay circuit.
Force signal, and then, at the start of the synthesis process,
Once the key signal is set to zero, the switching circuit is controlled
To select an output signal of the synthesis circuit, and thereafter,
A video signal synthesizing device that changes a key signal so that a predetermined synthesizing process is executed .