JPH08321994A - Television image compositing device - Google Patents

Abstract

PURPOSE: To composite video images even in a region where an image forming key signal is at '0' by providing a level conversion circuit slide-converting a level of a clip signal in a positive direction. CONSTITUTION: Upon the receipt of a clip signal, a level conversion circuit 1 converts a level of the received clip signal into a positive direction and provides an output of the result. A selection circuit 2 selects the signal converted by the level conversion circuit 1 or a signal not received by the level conversion circuit 1 according to an output level of the signal from the circuit 1 and provides an output of the selected signal to an adder circuit 3. The adder circuit 3 sums the selected signal and a television image composite key signal to composite video images even in a region where the image composite key signal is at '0'.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for synthesizing a television screen, and more particularly to an apparatus for synthesizing an image by using a key signal.

[0002]

2. Description of the Related Art FIG. 3 is a basic system diagram of a general mix keyer (hereinafter referred to as "MK") circuit.
FIG. 4 is a diagram showing video signals at points A to G of the circuit shown in FIG. 3.

Conventionally, when two types of video signals are combined by the MK circuit, predetermined processing is performed at each point for the video signal A and the video signal B as shown in FIGS. The combined video signal was being output.

FIG. 5 is a block diagram showing an example of a conventional television image synthesizing apparatus to which the MK circuit shown in FIG. 3 is applied.

In this conventional example, as shown in FIG. 5, a television screen synthesizing key signal and a clip signal are input, and an adding circuit 130 for performing addition and a multiplying circuit for multiplying the addition result in the adding circuit 130 by a gain signal are added. 140, a limit circuit 150 that limits and outputs the multiplication result in the multiplication circuit 140 at a certain level, and the video signal A, the video signal B, and the outputs from the limit circuit 150 are input.
It is composed of an MK circuit 160 which outputs a composite video signal.

When the above-mentioned television image synthesizing apparatus synthesizes the image signal A and the image signal B, the image is synthesized by increasing the level of the clip signal added to the television screen synthesizing key signal. Was there.

Usually, the clip signal takes only "0" or a negative value even when the level is raised for image synthesis, so that the addition result is "even if the television screen synthesis key signal is added." If the clip signal is set to a level that does not exceed 0 ", the video synthesis is not performed, but if the addition result is raised to a level higher than" 0 ", the video synthesis is performed. It has become.

[0008]

However, in the above-mentioned conventional television image synthesizing apparatus, since the level of the clip signal is only in the range from a negative value to "0", the television screen synthesizing key signal The level is
In the region of "0", the addition result does not become larger than "0" even if the clip signals are added. Therefore, no matter what value is multiplied in the multiplication circuit, the multiplication result becomes "0". However, there was a problem that the images cannot be combined.

FIG. 6 is a diagram showing an example of processed signals at respective points L to o of the television image synthesizer shown in FIG.

As shown in FIG. 6, of the television screen synthesizing key signal at point L, when the clip signal is added to the portion x of which the level is "0" (see FIG. 6).
In the case of, the clip signal is the maximum value "0")
However, it does not become larger than "0", and the multiplication circuit 1
Even when the gain signal is multiplied by 40, the output level remains "0", and the limit circuit 1
The output signal level from 50 becomes "0", and video composition is not performed for the x portion.

The present invention has been made in view of the problems of the above-mentioned conventional techniques, and video composition can be performed even in the area where the television screen composition key signal is "0". It is an object of the present invention to provide a television image synthesizing device that can be used.

[0012]

To achieve the above object, the present invention provides an addition circuit for adding a key signal for screen synthesis and a clip signal whose level is variable, and an addition result in the addition circuit. A multiplication circuit for multiplying a gain signal, a limit circuit for limiting and outputting the multiplication result in the multiplication circuit at a constant level, a first video signal and a second video signal to be combined, and an output result of the limit circuit In a television image synthesizing device having a mix keyer circuit for synthesizing the first video signal and the second video signal based on the above, and outputting a synthetic video, the level of the clip signal is slide-converted in the positive direction. It has a level conversion circuit that operates.

Further, the level conversion circuit is characterized in that the level of the clip signal is constantly converted to a positive value.

[0014]

According to the present invention configured as described above, when a clip signal having a range from a negative value to "0" is input to the level conversion circuit for screen composition, the level conversion circuit causes the screen to be displayed. Since the level of the clip signal added to the key signal for composition is increased in the positive direction, when it is subsequently added with the key signal for screen composition, the key signal for screen composition is in the "0" area. Also, the addition result is "
It is larger than 0 "and the multiplication result in the multiplication circuit thereafter does not become" 0 ", and the image synthesis is performed in all areas.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a television image synthesizing apparatus of the present invention.

In this embodiment, as shown in FIG. 1, a level conversion circuit 10 for converting the level of a clip signal, and a selection circuit 20 for selecting either a level-converted clip signal or a level-unconverted clip signal. An adding circuit 30 for adding the signal output from the selecting circuit 20 and the television screen synthesizing key signal; a multiplying circuit 40 for multiplying the addition result of the adding circuit 30 by a gain signal;
A limit circuit 50 that limits the multiplication result in the multiplication circuit 40 to a certain level and outputs the result, and an MK circuit 60 that inputs the video signal A, the video signal B, and the output from the limit circuit 50 and outputs a composite video signal. It consists of

The video synthesizing operation in the above configuration will be described below.

FIG. 2 is a diagram showing an example of processed signal waveforms at points a to g of the television image synthesizer shown in FIG.

The processed signal waveform at the point a is the waveform itself of the input clip signal, the level of the clip signal is variable, and the level is raised at a constant rate as it goes to the right in the time axis. Is represented.

The processed signal waveform at the point b is level-converted so that the level of the input clip signal is slid in the positive direction. in this case,
The maximum value of the variable clip signal is at least a positive value.

When the clip signal (the signal at the point a) is input, the level conversion circuit 10 converts the level of the input clip signal in the positive direction and outputs the signal (the signal at the point b).

B converted by the level conversion circuit 10
The signal at the point and the signal at the point a not input to the level conversion circuit 10 are selected by the selection circuit 20 according to the output level of the signal.

The addition circuit 30 adds the signal selected by the selection circuit 20 and the television screen synthesis key signal. At this time, even in the area where the television screen synthesizing key signal is "0", when the signal at the point c selected by the selection circuit 20 is at a positive level, the added signal at the point e is more than "0". Also takes a large value.

Then, in the multiplication circuit 40, the addition result of the addition circuit 30 is multiplied by the gain signal (signal at point f), and further, in the limit circuit 50,
The multiplication result is limited to a certain level and is output (signal at point g).

Thereafter, the signal output from the limit circuit 50, the video signal A, and the video signal B are combined in the MK circuit 60, and the combined video is output.

Further, there is no problem even if a level conversion circuit for raising the level of the clip signal to such a level that the minimum value takes a positive value is used.

[0028]

Since the present invention is constructed as described above, it has the following effects.

According to the first aspect of the invention, since the level conversion circuit for slidingly converting the level of the clip signal in the positive direction is provided, even if the key signal for screen combination is in the "0" area, The addition result becomes larger than "0", and the multiplication result in the subsequent multiplication circuit is "0".
It is possible to combine images in all areas.

According to the second aspect of the present invention, since the level conversion circuit is configured to convert the level of the variable clip signal so as to always take a positive value, the clip signal is purposely designed for video synthesis. Even if the level of is not raised, the signal added to the key signal has a positive value, and video can be combined.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a television image synthesizing apparatus of the present invention.

FIG. 2 is a diagram showing an example of processed signal waveforms at points a to g of the television image synthesizer shown in FIG.

FIG. 3 is a basic system diagram of a general MK circuit.

4 is a diagram showing video signals at points A to G of the circuit shown in FIG.

5 is a block diagram showing an example of a conventional television image synthesizing apparatus to which the MK circuit shown in FIG. 3 is applied.

6 is a diagram showing an example of processed signals at respective points L to o of the television image synthesizing apparatus shown in FIG.

[Explanation of symbols]

 10 level conversion circuit 20 selection circuit 30,130 addition circuit 40,140 multiplication circuit 50,150 limit circuit 60,160 MK circuit

Claims (2)

[Claims] 1. An addition circuit for adding a key signal for screen synthesis and a clip signal whose level is variable, a multiplication circuit for multiplying the addition result of the addition circuit by a gain signal, and a multiplication result of the multiplication circuit. Limit circuit for limiting and outputting a predetermined level, a first video signal and a second video signal to be combined, and the first video signal and the second video based on the output result of the limit circuit. A television image synthesizing device having a mix keyer circuit for synthesizing signals and outputting a synthesized image, characterized in that the television image synthesizing device has a level conversion circuit for slidingly converting the level of the clip signal in a positive direction. apparatus. 2. The television image synthesizing device according to claim 1, wherein the level conversion circuit performs a conversion so that the level of the clip signal is always a positive value. .