JPH02192274A - Video signal processing circuit - Google Patents

Abstract

PURPOSE:To avoid the disturbance in a sub-screen by reading a sub screen signal from a sub screen generating circuit at no input of a main screen video signal and synchronizing the drive of a CRT with a sub screen video signal. CONSTITUTION:A synchronizing signal switching circuit 5 uses a signal 13 from a synchronizing signal detection circuit 2 to input sub screen horizontal and vertical signals 16, 17 from a synchronizing signal processing circuit 4 as a horizontal signal 18 and a vertical signal 19 to a sub screen generating circuit 7 and a CRT 9. When a main screen video signal is not inputted to the sub screen generating circuit 7, a sub screen signal 21 is read synchronously with the sub screen horizontal and vertical signals 16, 17, which are inputted to an RGB switching circuit 18. Thus, the disturbance in the sub screen is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a video signal processing circuit, and particularly to a picture-in-picture video signal processing circuit.

[Conventional technology]

A picture-in-picture video signal processing circuit that synthesizes and displays two or more different images by inserting a reduced sub-image into the main image in consumer image equipment such as TVs, VTRs, and VDPs. There are some that have

As shown in FIG. 2, a conventional picture-in-picture video signal processing circuit includes a first video chroma processing circuit 1 that processes a main screen video signal 10, a first synchronization signal processing circuit 3, and a sub-video chroma processing circuit 1. a second video chroma processing circuit 6 that processes the screen video signal 11 and a second synchronization signal processing circuit 4;
The second component signal 20, which is composed of a sub-screen generation circuit 7 and an RGB signal switching circuit 8 and demodulated by the second video chroma processing circuit 6, is synchronized with the output signal 16.17 of the synchronization signal processing circuit 4. After being written to the sub-screen generation circuit 7 and subjected to compression processing, it is read out in synchronization with the output signal of the synchronization signal processing circuit 3. This is because in order to insert the reduced sub-screen signal into the first component signal, it is necessary to synchronize with the main-screen video signal.

[Problem to be solved by the invention]

The conventional video signal processing circuit described above reads out the sub-screen signal in synchronization with the main-screen video signal. If the horizontal and vertical signals for the main screen are constantly changing due to noise, even if the video signal for the sub screen is input normally, if the video signal for the main screen is an empty channel, the played video on the sub screen will be distorted. , it has the disadvantage that it cannot be displayed normally.

[Means to solve the problem]

The video signal processing circuit of the present invention includes a first video chroma processing circuit that demodulates a main screen video signal and outputs a first component signal, and a second video chroma processing circuit that demodulates a sub screen video signal and outputs a first component signal.
a second video chroma processing circuit that outputs a component signal; and an RGB signal switching circuit that compresses the second component signal and inserts it into a specific area of the first component signal to form a composite signal. A picture-in-picture video signal processing circuit comprising: a synchronization detection circuit that detects a synchronization signal from the main screen video signal to detect the presence or absence of the main screen video signal; A first unit that separates the synchronization signal and generates horizontal and vertical signals for the main screen that are synchronized with the synchronization signal.
a second synchronization signal processing circuit that receives the sub-screen video signal and generates sub-screen horizontal and vertical signals; and a vertical signal, and is controlled by the output signal of the synchronization signal detection circuit, and when the main screen video signal is input, the main screen horizontal and vertical signals are output, and the main screen video signal is input. a synchronization signal switching circuit that outputs the horizontal and vertical signals for the sub-screen when the horizontal and vertical signals for the sub-screen are not input; and the synchronization signal switching circuit that inputs the second component signal in synchronization with the horizontal and vertical signals for the sub-screen and performs compression processing. and a sub-screen generation circuit that inputs a sub-screen signal to the RGB signal switching circuit, which is output in synchronization with the horizontal and vertical signals output from the RGB signal switching circuit.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

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

The main screen video signal 10 is sent to the first video chroma processing circuit 1
The first component signal 12 is demodulated and outputted as the first component signal 12, which is input to the RGB signal switching circuit 8. On the other hand, the synchronization signal detection circuit 2 detects the presence or absence of the main screen video signal 10 and inputs the synchronization detection signal 13 to the synchronization signal switching circuit 5.

Further, the first synchronization signal processing circuit 3 generates a horizontal signal 14 and a vertical signal 15 synchronized with the main screen video signal, and inputs them to the synchronization signal switching circuit 5.

Similarly, the sub-screen video signal 11 is input to the second synchronization signal processing circuit 4 and the second video chroma processing circuit 6. The synchronization signal processing circuit 4 generates a horizontal signal 16 and a vertical signal 17 synchronized with the sub-screen video signal 11 and inputs them to the synchronization signal switching circuit 5. The synchronization signal switching circuit 5 generates a signal 13 from the synchronization signal detection circuit 2. Therefore, when the main screen video signal is input, the main screen horizontal and vertical signals 14.15 from the synchronization signal processing circuit 3 are input, or when there is no signal, the sub screen horizontal and vertical signals 16.1 from the synchronization signal processing circuit 4 are input.
7 is input to the sub-screen generation circuit 7 and CRT 9 as a horizontal signal 18 and a vertical signal 19.

The sub-screen generation circuit 7 writes and compresses the sub-screen component signal 20 from the video chroma processing circuit 6 in synchronization with the horizontal and vertical signals 14 and 15 for the main screen, and then converts it to the main screen when the main screen video signal is input. The sub-screen signal 21 is read out in synchronization with the horizontal and vertical signals 14.15 for the sub-screen, or in synchronization with the horizontal and vertical signals 16.17 for the sub-screen when the main screen video signal is not input, and is input to the RGB switching circuit 8. .

The RGB signal switching circuit 8 switches between the component signal 12 and the sub-screen signal 21 according to the main-sub-screen switching signal 22 from the sub-screen generation circuit 7, and converts the main-sub-screen composite signal 23 into CR.
Input to T9.

〔Effect of the invention〕

As explained above, the present invention enables the main screen video signal to be changed by synchronizing the readout of the subscreen signal from the subscreen generation circuit and the driving of the CRT with the subscreen video signal when the main screen video signal is unattended. Even in the case of unattended operation, stable synchronization can be obtained and the sub-screen can be displayed normally without any disturbance.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a block diagram showing an example of a conventional video signal processing circuit. DESCRIPTION OF SYMBOLS 1... First video chroma processing circuit, 2... Synchronization signal detection circuit, 3... First synchronization signal processing circuit, 4...
- Second synchronization signal processing circuit, 5... Synchronization signal switching circuit, 6... Second video chroma processing circuit, 7... Sub-screen generation circuit, 8... RGB signal switching circuit, 9.・・C
RT, 10... Video signal for main screen, 11... Video signal for sub screen, 12... First component signal, 1
3...Synchronization detection signal, 14...Horizontal signal for main screen,
15... Vertical signal for main screen, 16... Horizontal signal for sub-screen 17... Vertical signal for sub-screen, 18... Horizontal signal, one... Vertical signal, 20... Second Component signals 21...Sub-screen signal, 22... Main-sub-screen switching signal, 23... Main-sub-screen composite signal.

Claims (1)

[Claims] A first video chroma processing circuit that demodulates a main screen video signal and outputs a first component signal, and a second video chroma processing circuit that demodulates a sub screen video signal and outputs a second component signal. and an RGB signal switching circuit that compresses the second component signal and inserts it into a specific area of the first component signal to form a composite signal. , a synchronization detection circuit that detects a synchronization signal from the main screen video signal to detect the presence or absence of the main screen video signal; and a main screen that separates the synchronization signal from the main screen video signal and synchronizes with the synchronization signal. a first synchronous signal processing circuit that generates horizontal and vertical signals for the main screen; a second synchronous signal processing circuit that receives the sub-screen video signal and generates horizontal and vertical signals for the main screen; The horizontal and vertical signals and the horizontal and vertical signals for the sub-screen are input and controlled by the output signal of the synchronization signal detection circuit, and when the video signal for the main screen is input, the horizontal and vertical signals for the main screen are input. a synchronization signal switching circuit that outputs the horizontal and vertical signals for the sub-screen when the main screen video signal is not input; and a synchronization signal switching circuit that inputs the second component signal in synchronization with the horizontal and vertical signals for the sub-screen. A video signal characterized in that it includes a sub-screen generation circuit that inputs into the RGB signal switching circuit a sub-screen signal that is output in synchronization with the horizontal and vertical signals output from the synchronization signal switching circuit after compression processing. processing circuit.