JPH0638650B2 - Color TV receiver - Google Patents

Description

The present invention relates to a color television which records a television video signal in a video memory, reads it out, synthesizes it with a parent screen video signal, and displays it on a television screen. It concerns the improvement of the John receiver.

[Conventional technology]

Generally, in a television receiver, for example, there are times when it is desired to monitor an image of a VTR or the like while watching a television program. In order to realize this kind of function, in a conventional device, a video signal to be monitored is stored in a video memory, and the video signal is combined with the main screen video signal and displayed. At this time, the video signal stored in the video memory is read and displayed in accordance with the sync signal of the parent screen video signal.

[Problems to be solved by the invention]

Since the conventional color television receiver is configured as described above, for example, when the playback image of the VTR is used as the parent screen and the television broadcast program is used as the child screen and two screens are displayed, the tape can be rewound or fast forwarded. When the VTR reproduction signal is null, there is a problem that the monitor output image of the small screen is out of synchronization and cannot be displayed normally.

The present invention has been made in view of the above problems, and an object of the present invention is to obtain a color television receiver capable of displaying an image of a sub-screen normally even when there is no main-screen video signal. .

[Means for solving problems]

The color television receiver according to the present invention has a function of time-compressing a sub-picture image signal by digital processing including horizontal and vertical thinning processing according to the sub-picture size and storing it in a memory. In addition to a signal processing unit consisting of a combination of an A / D converter and memory control, a local sync signal generator for generating the same sync signal for the parent screen video signal, and a local sync signal generator based on the input level of the parent screen video signal A detection circuit for detecting the presence or absence, when the absence of a signal is detected by the detection circuit, instead of the parent screen video signal,
In addition to this, the deflection circuit is operated by the completely independent local synchronizing signal, and at the same time, the reading operation from the memory of the sub-picture image signal is synchronized.

[Action]

According to the present invention, when the detection circuit for detecting the presence / absence of the parent screen video signal detects that the parent screen video signal is absent, instead of the synchronization signal of the parent screen video signal, it is independent of this. The horizontal and vertical synchronizing signals of the local synchronizing signal generator, that is, the composite synchronizing signal is operated to input the composite synchronizing signal to the image amplifying circuit of the parent screen system while operating the horizontal and vertical deflection circuits, and the reading of the image signal for the child screen from the image memory is performed. Since the operation is synchronized, this level is not limited to when the main screen video signal is not actually present, but when the level of the main screen video signal is low and the presence / absence detection circuit detects that there is no signal. The brightness level of the main screen is controlled by the DC level between the horizontal and vertical signal pulses of the local sync signal generator without being affected by the unstable sync signal of the small main screen video signal. Child screen display state can be excellently display the kept at a certain, yet can be performed well channel search of the child screen in this state according to.

〔Example〕

 Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a television receiver having a dual-screen display function according to an embodiment of the present invention, in which the tuner section, the detection section, and the audio section are omitted.

In the figure, 1 is a signal presence / absence detection circuit for detecting the presence / absence of a parent screen video signal input, 2 is a local synchronization signal generator for generating the same synchronization signal as the parent screen video signal, and 3 is the signal presence / absence detection circuit 1 Switch for switching between the main screen video signal A and the sync signal L of the local sync signal generator 2 to the video amplifier circuit 4 (signal selection circuit), and 5 for amplifying the video signal. A sync separation circuit that separates the sync signal C from the output B of the circuit 4 and inputs the sync signal C to the deflection circuit 8 and the memory control circuit 17, 13 is a video amplification circuit that amplifies the sub-picture video signal, and 14 is the sub-screen video signal D
From the video amplifier circuit 13 to receive the output E of the video amplifier circuit 13 and to sample in a horizontal and vertical direction according to the size of the sub-screen 20. 16 is an A / D converter. A video memory that stores the digital video signal F that is the output of the D / D converter 15, and 18 is a video memory 16
An A / D converter for converting the digital video signal M read by the signal N of the memory control circuit 17 into an analog signal, and 6 is the output B or D of the video amplification circuit 4 depending on the signal I of the memory control circuit 17. / A
Switches for selecting the output J of the converter 18 and inputting one of them to the video output circuit 7, 9 and 10 are the video output circuit 7
Of the deflection circuit 8 and the output of the deflection circuit 8 as inputs, and a deflection yoke and a cathode ray tube for displaying an image.

Next, the operation will be described.

The parent screen video signal A is supplied to the video amplifier circuit 4 through the switch circuit 3, and its output signal B is supplied to the cathode ray tube 10 through the switch circuit 6 and the video output circuit 7. Further, the signal B is also supplied to the sync separation circuit 5, and the output of the horizontal / vertical sync signal C is guided to the deflection circuit 8 to generate a sawtooth current for driving the deflection yoke 9. In this way, the TV image of the parent screen is displayed on the cathode ray tube.

On the other hand, the decoded video signal D which is the sub-picture video signal is amplified by the video amplifier circuit 13, and its output signal E is A / D converter 1.
5, the data is sampled in a horizontal and vertical direction in accordance with the size of the sub-screen and converted into a digital signal E. The simplification clock H at this time is synchronized with the horizontal / vertical synchronization signal G separated from the sub-screen video signal by the synchronization separation circuit 14. Then, the write control signal N is supplied from the memory control circuit 17 to the video memory 16, whereby the digital video signal F
Are stored in the video memory 16. Then, the reading is performed by the read control signal N from the memory control 17. The read control signal N is created in accordance with the horizontal / vertical sync signal C from the sync separation circuit 5 of the parent screen in order to superimpose and display the child screen 20 on the parent screen 30. The read signal M is converted into an analog signal J by the D / A converter 18 and output to the 2 side of the switch circuit 6. The switch 6 is connected to the contact 2 side by the signal I from the memory control circuit 17 during the memory reading period, so that the child screen 20 is superimposed on the parent screen 30 as shown in FIG. It is displayed on 10.

Next, when the parent screen video signal A is not input, this is detected by the signal presence / absence detection circuit 1, and the switch 3 is switched to the local synchronization signal generator 2 side by the detection signal K. As a result, the horizontal / vertical synchronization signal L of the local synchronization signal generator 2, that is, the composite synchronization signal, is input to the memory control 17 and the deflection circuit 8 via the synchronization separation circuit 5. Then, the digital video signal M for the small screen is read from the video memory 16 based on the horizontal / vertical synchronizing signal L, and the small screen is normally displayed based on the synchronizing signal L.

As described above, according to the present embodiment, since the horizontal / vertical synchronizing signal C necessary for displaying the small screen is obtained from the local synchronizing signal generator when there is no main screen image signal, the small screen can be displayed without being disturbed. . Further, since the horizontal / vertical synchronizing signal obtained from the local synchronizing signal generating circuit 1 is independent of the horizontal / vertical synchronizing signal of the parent screen video signal A, the level of the parent screen video signal is small and its presence / absence is detected. Even when the circuit detects that there is no signal, the small screen can be displayed well without being affected by the unstable sync signal of the small-sized main screen video signal.

Furthermore, since the local sync signal is a signal independent of the sync signal of the sub-picture video signal, a certain luminance depending on the display state of the parent screen with no signal, that is, the direct current level between the horizontal and vertical sync pulses. In the level display state, the child screen channel search can be favorably performed without disturbing the non-signal state parent screen.

〔The invention's effect〕

As described above, according to the color television receiver of the present invention, when the parent screen video signal is no longer input, instead of the synchronizing signal of the parent screen video signal, a local synchronization independent of this is performed. While the horizontal and vertical deflection circuits of the signal generator, that is, the composite sync signal are operated, the composite sync signal is input to the video amplification circuit of the parent screen system and the operation of reading the video signal for the child screen from the video memory is performed. Since the synchronization is made, it is not limited to when the parent screen video signal is not actually present, and when the level of the parent screen video signal is low and the presence / absence detection circuit detects that there is no signal, the parent signal with this level is low. The brightness level of the parent screen is adjusted to the DC level between the horizontal and vertical sync signal pulses of the local sync signal generator without being affected by the unstable sync signal of the screen video signal. While keeping constant in the can be satisfactorily display the child screen, moreover there is an effect that can be favorably performed without disturbing the main screen of the no-signal state channel search of the child screen in this state.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a television receiver according to an embodiment of the present invention, and FIG. 2 is a diagram showing a state in which a child screen is fitted and displayed on a parent screen. 1 ... Signal presence / absence detection circuit, 2 ... Local sync signal generator,
3 ... switch (signal selection circuit), 5 ... sync separation circuit, 16 ... video memory, 17 ... memory control circuit, 20 ... sub-screen, 30 ... parent screen. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (1)

[Claims] Claim: What is claimed is: 1. A color television receiver equipped with a function for displaying a parent-child two-screen on a television screen by inserting the child-screen video signal into the parent-screen video signal by time-axis compression. A local sync signal generator that generates the same sync signal as the signal, a signal presence detection circuit that detects the presence or absence of the parent screen video signal, and a sync signal that is separated from the parent screen video signal when a signal is detected And a signal selection circuit for selecting a sync signal from the local sync signal generator when no signal is detected, a deflection circuit driven by the selected sync signal, and a sub-screen video signal for the sub-screen. A signal processing means for sampling in accordance with the size and compressing in the horizontal and vertical directions on the time axis, a video memory for storing the time axis compressed sub-picture video signal, and A color television receiver comprising: control means for controlling reading of a sub-picture video signal from the picture memory and display of a combined picture.