JP2550954B2 - Video signal synthesizer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an image of a teloper or the like which performs so-called superimposition for superimposing and displaying a picture, a character, etc. on a screen indicated by an input video signal. The present invention relates to a signal synthesizer.

SUMMARY OF THE INVENTION The present invention provides a video signal synthesizing device such as a telopper that performs so-called superimposition for superimposing and displaying a picture, a character, and the like on a screen indicated by the input video signal. By superimposing a composite video signal having a chroma level corresponding to the burst level on the input video signal, an ACC (Automatic Cro) provided in a television receiver or a video tape recorder on the subsequent stage is superimposed.
This is to prevent the deterioration of image quality due to the operation of the (male control) circuit.

[Conventional technology]

Conventionally, for example, as shown in FIG. 2, a television tuner 31, a television camera 32, a video disc player, etc.
A video signal is supplied from various video sources such as 33 to the teloper 35 through the signal switching circuit 34, and in the teloper 35, a picture or a character is added (superimposed) to the image given by the video signal. A video system is known in which the video signal of the picture or the character is synthesized with the video signal and the synthesized image is displayed on the screen of the television receiver 36, or the video signal is recorded by the video tape recorder 37. ing.

Then, in the video signal synthesizing device such as the telopa 35,
Conventionally, a telop signal having a constant color signal level, that is, a picture or character signal to be superimposed is always added and synthesized to the input video signal regardless of the burst level of the input video signal.

Further, conventionally, in a television receiver, a video tape recorder, etc., even if the frequency characteristic of the video signal processing system fluctuates or the burst level fluctuates due to repeated dubbing, a constant color reproducibility is always kept constant. In addition, an ACC (Auto-matic Croma level Control) circuit that controls the color signal level according to the signal level of the color burst signal is built in.

[Problems to be solved by the invention]

By the way, in a television receiver or a video tape recorder having the ACC circuit built-in, as described above, an image in which a telop signal having a constant color signal level is always added and synthesized through the teloper regardless of the burst level of the input video signal When the signal is supplied, the chroma level of the superimposed telop signal rises abnormally due to the function of the ACC circuit above, and the color saturation becomes oversaturated on the television screen, or the video tape recorder. In the above, so-called overmodulation may occur.

For example, the signal level of the color burst signal in the steady state is 300 mVp-p, but if the tuning of the television tuner is not perfect, the burst level will decrease. The ACC circuit has a triple gain so that the burst level becomes a steady state when the burst level is 100 mV, for example. So 600m to this signal
If a telop signal having a chroma amplitude of Vp-p is superimposed, the chroma amplitude becomes 1800 mVp-p due to the operation of the ACC circuit of the above-mentioned television receiver or video tape recorder, resulting in excessive color saturation. And overmodulation occurs.

Therefore, in view of the above conventional problems, the present invention is
The ACC circuit provided in the television receiver or video tape recorder connected in the subsequent stage can obtain a superimposed image with extremely good color reproducibility without the chroma level of the telop signal part rising abnormally. It is an object of the present invention to provide a video signal synthesizing device having a novel configuration as described above.

[Means for solving problems]

A video signal synthesizing apparatus according to the present invention, in order to solve the above problems, carrier generation means for forming a chroma carrier from a color burst signal in an input video signal,
Demodulation means for synchronously detecting and demodulating a color signal in the input video signal by the chroma carrier, means for taking out a low frequency component of the output of the demodulation means, sample and hold means for sampling and holding the low frequency component, Synthetic signal generating means for supplying the chroma carrier and outputting a chroma signal and a luminance signal forming a synthetic video signal to be synthesized with the input video signal, and a chroma for the synthetic video signal output from the synthetic signal generating means. A chroma level control means for controlling the signal level of the signal in accordance with the output of the sample and hold means, a luminance signal supplied from the composite signal generation means, and a chroma signal supplied via the chroma level control means are added. A signal adding means for combining, an addition output signal by the signal adding means, and the input video signal are selectively output. Signal selection means, controlling the chroma level of the composite video signal according to the burst level of the input video signal, and selecting the video signal in which the image of the input video signal is combined with the image of the composite video signal. The feature is that it is output through the means.

[Action]

In the video signal synthesizing apparatus according to the present invention, a chroma carrier is formed from the color burst signal in the input video signal, and the color signal in the input video signal is synchronously detected by the chroma carrier to detect R-containing the color burst signal. The Y-axis is demodulated, the demodulated output is supplied to the sample hold means through the low-pass filter, and this hold output is supplied as the level control signal to the chroma level control means, thereby synthesizing in accordance with the burst level of the input video signal. The chroma level of the video signal is controlled, and a video signal obtained by combining the image of the input video signal with the image of the composite video signal is output.

〔Example〕

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

In the embodiment shown in the block diagram of FIG. 1, an input video signal (Sin) is supplied from a signal input terminal 1 to a signal selection circuit 11 and a bandpass filter (BPF) 2.

The BPF 2 takes out the chroma carrier component in the input video signal (Sin) and supplies it to the burst gate circuit 3 and the decoder 5. The burst gate circuit 3 extracts the color burst signal in the chroma carrier component,
It is supplied to the chroma carrier generation circuit 4. The chroma carrier generation circuit 4 uses, for example, a PLL (Phase Locked Loop) to fix the phase of the color burst signal at the chroma carrier frequency (3.58 MHz) to the chroma carrier (SC).
And the chroma carrier (SC) is formed into the decoder 5
And to the telop signal generation circuit 8. The decoder 5 demodulates the RY axis including the color burst signal by synchronously detecting the chroma carrier component with the chroma carrier (SC), and samples the demodulated output through a low pass filter (LPF) 6.・ Supply to the hold (S / H) circuit 7. The S / H circuit 7 is supplied with a burst flag pulse as a sample hold pulse, samples and holds the signal level of the color burst part of the demodulation output by the decoder 5,
The hold output is supplied to the signal level control circuit 9 as a level control signal. The telop signal generation circuit 6 also includes a chroma signal (C) and a luminance signal (Y) superimposed on the chroma carrier (SC) as a telop signal for giving a telop image to be combined with an image of the input video signal (Sin). Form. The chroma signal (C) formed by the telop signal generation circuit 8 is supplied to the signal adder 10 via the signal level control circuit 9.
The signal adder 10 adds and combines the chroma signal (C) and the luminance signal (Y), and supplies the combined output to the signal selection circuit 11 as a telop signal (Ste).

Then, the signal selection circuit 11 switches the telop signal (Ste) and the input video signal (Sin) supplied from the signal input terminal 1 according to the key signal and outputs the signal from the signal output terminal 12.

In this embodiment, the burst level of the input video signal (Sin), that is, the signal level of the color burst signal is sampled and held by the S / H circuit 7, and the signal level control circuit 9 operates using the hold output as a control signal. However, the signal level of the chroma signal (C) output from the telop signal generation circuit 6, that is, the telop signal (St
The chroma level of e) is automatically controlled by the signal level control circuit 9 according to the burst level of the input video signal (Sin). Therefore, the video signal (Sout) output from the signal selection circuit 11 through the signal output terminal 12
The input video signal (Sin) and the telop signal (Ste) both have chroma levels that correspond to the burst level, and that image is reproduced via a television receiver equipped with an ACC circuit or a video tape recorder. In such a case, a difference in color saturation due to a difference in burst level of the input video signal or deterioration in image quality due to overmodulation does not occur, and a superimposed image with extremely good color reproducibility can be obtained. Moreover, in the signal selection circuit 11, the input video signal (Sin) and the telop signal (St
Since superimposing is performed by switching between e) and, the image quality does not deteriorate on the original image part other than the telop image.

〔The invention's effect〕

As described above, in the video signal synthesizing device according to the present invention,
Since the chroma level of the composite video signal added to the input video signal is automatically controlled according to the burst level of the input video signal, the ACC provided in the television receiver or video tape recorder connected in the subsequent stage. It is possible to obtain a superimposed image with extremely good color reproducibility without causing the circuit to abnormally raise the chroma level of the composite video signal portion. Particularly, in the video signal synthesizing apparatus according to the present invention, the demodulation means for synchronously detecting and demodulating the color signal in the input video signal by the chroma carrier formed from the color burst signal in the input video signal, and the output of the demodulation means Since the noise component such as the cross color component can be removed by having the means for extracting the low-frequency component of, the accuracy of the chroma level detection is improved and the followability to the change of the chroma level is improved. It is possible to obtain a composite image with an extremely good color reproducibility by properly maintaining the chroma level of.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of a video signal synthesizing apparatus according to the present invention. FIG. 2 is a block diagram showing a configuration example of a conventional video system to which a telop is connected. 1 ... Signal input terminal 2 ... Bandpass filter 3 ... Burst gate circuit 4 ... Chroma carrier generation circuit 5 ... Decoder 7 ... Sample and hold circuit 8 ... Telop signal generation circuit 9 ... Signal level control circuit 10 …… Signal adder 11 …… Signal selection circuit 12 …… Signal output terminal

Claims (1)

(57) [Claims] 1. Carrier generation means for forming a chroma carrier from a color burst signal in an input video signal, demodulation means for synchronously detecting and demodulating a color signal in the input video signal by the chroma carrier, and the demodulation means. Means for taking out the low-frequency component of the output, sample-hold means for sample-holding the low-frequency component, and the chroma signal and the luminance signal forming the synthesized video signal supplied with the chroma carrier and synthesized with the input video signal. And a chroma level control means for controlling the signal level of the chroma signal of the synthesized video signal output from the synthesized signal generation means according to the output of the sample hold means, and the synthesized signal generation. The luminance signal supplied from the means and the chroma signal supplied via the chroma level control means. And a signal selecting means for selectively outputting the added output signal from the signal adding means and the input video signal, and adding the composite video signal according to the burst level of the input video signal. A video signal synthesizing device characterized in that a video signal obtained by synthesizing an image of the synthetic video signal with an image of the input video signal is output via the signal selecting means by controlling a chroma level.