JPH0437269A - Video switching circuit - Google Patents

Abstract

PURPOSE:To take precedence of a front side slave picture over a rear side slave picture by controlling a control signal of a circuit inserting a slave picture connecting to a post-stage with a control signal of a circuit connecting to a pre-stage. CONSTITUTION:When a control signal YS1 is outputted from a video slave picture generating circuit 3, a base current flows through resistors 9, 10 and transistors(TRs) 7, 8 are conductive. The control signals YS2, YM outputted from a slave picture generating circuit 5 of a teletext use to control a teletext slave picture insertion circuit 4 cannot control the teletext slave picture insertion circuit 4 connecting to ground via resistors 11, 12 and a video slave picture insertion circuit 2 connecting to the pre-stage takes precedence over the teletext slave picture insertion circuit 4 connecting to the post-stage when the video slave pattern and the teletext slave pattern are overlapped. Thus, the operation of the pre-stage slave picture insertion circuit takes precedence over the post- stage slave picture insertion circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a video switching circuit for a television receiver equipped with a small screen generation circuit for multiplexing video and text.

2. Description of the Related Art An example of a conventional video switching circuit will be described below with reference to the drawings.

FIG. 9 is a block diagram of a conventional video switching circuit.

In FIG. 9, 1 is a video chroma circuit for television images, 2 is a video sub-screen insertion circuit that inserts a video sub-screen into the television image, and 3 is a video sub-screen generation circuit that generates a video sub-screen. 4 is a character screen insertion circuit that inserts a character multiplexed sub screen into a television image, 5 is a character screen insertion circuit that generates a character multiplexed sub screen, and 6 is a CRT image that is inserted into the television image. This displays the sub-screen signal that is displayed.

A conventional video switching circuit configured as described above will be explained.

A television video signal is demodulated by a video chroma circuit 1. A video sub-screen generated by a video sub-screen generating circuit 3 is inserted into the video of the television by a video sub-screen inserting circuit 2 in the demodulated signal.

Next, the character multiplexed child screen generated by the character multiplexed child screen generating circuit 5 is inserted into the television video by the character multiplexed child screen insertion circuit 4. The television image into which a sub-screen with multiple images and text is inserted is displayed on the cathode ray tube 6. The image projected on the cathode ray tube 6 is as shown in FIG. 10, where a sub-screen of the image appears on top of the television image, and a sub-screen with multiple characters appears above it.

The video-chroma circuit 1 is commonly used and outputs color difference or primary colors. Video sub-screen insertion circuit 2
The character sub-screen insertion circuit 4 mainly uses I as shown in FIG.
C, and switches between the television video signal and the small screen signal.

The control signals include signals Ys1 and YS2 for switching, and a signal YM which is unique to teletext broadcasting and reduces the brightness of the television image to about half in order to make it easier to read when superimposing subtitles and the like. The video sub-screen generation circuit 3 demodulates a video signal from television or satellite broadcasting using a video chroma circuit (not shown) similar to the video chroma circuit 1, and then generates a digital signal using a memory (not shown). Through processing, it is compressed and displayed as ``ha'' or %. The character sub-screen generation circuit 6 is equipped with a character generator for small characters for sub-screens in addition to the character generator originally included in a normal teletext demodulator. Video and text sub-screen signals are in primary colors.

Problems to be Solved by the Invention However, in the above configuration, the circuits for inserting the sub-screens into the television image are connected in tandem, so when two sub-screens overlap, the circuits are connected in tandem. There was a problem in that the child screen with multiple characters always appeared preferentially on the screen.

In view of this point, the present invention has been developed so that, in a circuit for inserting sub-screens connected in series, the sub-screen connected to the front side is preferentially raised, or when two sub-screens overlap, the sub-screens are overlapped. To provide a video switching circuit capable of displaying a television video by disabling the other parts.

Means for Solving the Problems In order to solve the above-mentioned problems, the video switching circuit of the present invention includes a circuit connected to the front side of a circuit for inserting child screens connected in series. Further, in claims 3 and 4, each of the circuits for inserting child screens connected in series has a circuit for controlling the control signal of the circuit connected to the rear side with the control signal of the circuit connected to the rear side. The present invention is characterized in that the front side controls the control signal of the rear side circuit, and the rear side controls the control signal of the front side circuit.

Effect The present invention is based on the above-described configuration, and in claims 1 and 2,
By controlling the rear control signal with the front control signal of a circuit that inserts child screens connected in tandem, the operation of the rear control signal is prohibited while the front control signal is being output. The child screen on the front side takes priority over the child screen on the rear side.

Further, in claims 3 and 4, in the circuits for inserting child screens connected in series, the front side is controlled by the control signal of the rear side, and the rear side is controlled by the control signal of the front side by the control signal of each circuit. While one control signal is being output, the control signal on the other side can be prohibited, and when two sub-screens overlap and both control signals are being output, both control signals will be prohibited. On the screen, you can see the television image where the sub-screens overlap.

Embodiment FIG. 1 shows a block diagram of a video switching circuit in a first embodiment (corresponding to claim 1) of the present invention.

In FIG. 1, numerals 7 and 8 are transistors that control the control signal of the teletext sub-screen using the control signal of the video sub-screen. 9 and 1o are resistors that limit the base current of the transistor 7.8. 11.12 is the transistor 7.
This is a resistor that limits the outflow current of the control signal of the small screen generation circuit 4 for teletext broadcasting, which is controlled by 8.

The operation of the video switching circuit of this embodiment configured as described above will be described below with reference to FIGS. 1 and 2.

First, FIG. 2 shows the video and control signals when the video sub-screen and the teletext sub-screen overlap on the television screen. A control signal (Y
s,) is output, a base current flows through the resistor 9°1o, and the transistor 7°8 becomes conductive. Then, a control signal (Ys2.YM) output from the teletext sub-screen generating circuit 6 and controlling the text sub-screen insertion circuit 4 is transmitted to the resistor 11.1.
2, it becomes impossible to control the character sub-screen insertion circuit 4, and when the video sub-screen and text sub-screen overlap, the video sub-screen connected to the front side of the character sub-screen insertion circuit 4 connected to the rear side becomes Screen insertion circuit 2 has priority.

As described above, according to this embodiment, by providing a circuit that controls the rear side control signal with the front side control signal of the circuit that inserts the child screens connected in series, the rear side child screen insertion circuit 4 The operation of the small screen insertion circuit 2 on the front side can be prioritized.

FIG. 3 shows a block diagram of a video switching circuit in a second embodiment (corresponding to claim 2) of the present invention.

In FIG. 3, 15 is a transistor that controls the control signal of the video sub-screen with the control signal of the teletext sub-screen; 16 is a resistor that limits the base current of the transistor 15;
7 is a resistor 18, 1 which is controlled by the transistor 15 and limits the outflow current of the control signal of the video small screen generation circuit 3;
Reference numeral 9 denotes a diode that takes the logical sum of two control signals of the teletext small screen generation circuit 5.

The operation of the video switching circuit of this embodiment configured as described above will be explained below with reference to FIGS. 3 and 4.

First, FIG. 4 shows the video and control signals when the video sub-screen and the teletext sub-screen overlap on the television screen. A control signal (Y
s2. When YM) is damaged, a base current flows through the diodes 18 and 19 and the resistor 16, and the transistor 15 becomes conductive. Then, the control signal (Ys1) output from the video sub-screen generation circuit 3 and controlling the video sub-screen insertion circuit 2 is grounded via the resistor 17, and the video sub-screen insertion circuit 2 cannot be controlled, and the video sub-screen and character Where the screens overlap, the character sub-screen insertion circuit 4 connected to the front side is given priority over the video sub-screen insertion circuit 2 connected to the rear side.

As described above, according to this embodiment, it is necessary to provide a circuit that controls the control signal on the rear side with the control signal on the front side of the circuit for inserting the child screens connected in series, and the circuit for inserting the child screen on the rear side. It is possible to give priority to the operation of the child screen insertion circuit 4 located earlier than the child screen insertion circuit 2.

FIG. 5 shows a block diagram of a video switching circuit in a third embodiment (corresponding to claim 3) of the present invention. In Fig. 5, transistor 7°8, resistor 9, 10, 1
1.12 has the same function as the first embodiment (see FIG. 1). Transistor 15, resistor 16.17, diode 1
8.19 works the same as the second embodiment (see Figure 3).

The operation of the video switching circuit of this embodiment configured as described above will be described below with reference to FIGS. 5 and 6.

FIG. 6 shows the video and control signals when the video sub-screen and the teletext sub-screen overlap on the television screen. Control signal (YB2) from video sub-screen generation circuit 3
When output, transistor 7. is outputted via resistor 8.1°.
8 conducts. Then, a control signal (Y
B2. YM) is grounded through resistors 11 and 12, and the character sub-screen insertion circuit 4 cannot be controlled. Further, when the control signal (YB2.YM) is applied from the character child screen generating circuit 5, the transistor 16 becomes conductive via the diodes 18, 19 and the resistor 16. Then, pressure is applied from the video sub-screen generation circuit 3, and a control signal (
YB2) is grounded through the resistor 17, making it impossible to control the video sub-screen insertion circuit 2, and where the video sub-screen and text sub-screen overlap, neither control signal can control it, and the television image is output as is. be done.

As described above, according to this embodiment, by providing a circuit that mutually controls the front control signal and the rear control signal of the circuit that inserts the serially connected child screens, it is possible to prevent the child screens from overlapping each other. Sometimes, mutual control signals can be controlled to compress the television image.

FIG. 7 shows a block diagram of a video switching circuit in a fourth embodiment (corresponding to claim 4) of the present invention, in which the video sub-screen generation circuit 2 and the character sub-screen generation circuit 4 of the third embodiment are shown.
FIG. 8 shows the video and control signals when the video sub-screen and the teletext sub-screen overlap on the television screen. Since both the operation and effect are the same as those of the third embodiment, a description thereof will be omitted.

In addition, in the first embodiment (see FIG. 1), the third embodiment (see FIG. 5), and the fourth embodiment (see FIG. 7), the resistors 9 and 10 are connected in parallel with each other. A capacitor may be added to increase the speed.

Further, in the second embodiment (see FIG. 2) and the third and fourth embodiments, a capacitor may be added in parallel with the resistor 16 to speed up switching.

Effects of the Invention As described above, according to the video switching circuit of claims 1 and 2 of the present invention, the control signal of the circuit connected to the front side of the circuit for inserting the child screens connected in series can be connected to the rear side. By providing a circuit that controls the control signal of the circuit that is connected, the front control signal can control the rear control signal,
By prohibiting the operation of the rear control signal while the front control signal is being output, it is possible to give priority to the front sub-screen over the rear sub-screen. According to the video switching circuits of claims 3 and 4, among the circuits for inserting child screens connected in series, the front side is the control signal of the rear side circuit, and the rear side is the control signal of the front side circuit. By providing a circuit that controls the front side and the rear side, the control signal of each circuit
The rear side can control the front side's control signal, and while the signal is being output, the control on one side is controlled by the other side. 8 can be prohibited, and while the sub-screens overlap and both control signals are output, both controls will be prohibited, and the area where the sub-screens overlap will be prohibited on the screen. It is possible to display images of John, and its practical effects are great.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a video switching circuit according to the first embodiment of the present invention, FIG. 2 is a schematic diagram for explaining the operation of FIG. 1, and FIG. 3 is a block diagram of the video switching circuit according to the second embodiment of the present invention. 4 is a schematic diagram for explaining the operation of FIG. 3, FIG. 6 is a block diagram of the video switching circuit in the third embodiment of the present invention, and FIG. 6 is a schematic diagram for explaining the operation of FIG. Schematic diagram, 7th
The figure is a block diagram of the video switching circuit in the fourth embodiment of the present invention, FIG. 8 is a schematic diagram for explaining the operation of FIG. 7,
Fig. 9 is a block diagram of a conventional video switching circuit, Fig. 1o is a schematic diagram for explaining the operation of Fig. 9, and Fig. 11 is a block diagram of a conventional video switching circuit.
FIG. 2 is a specific configuration diagram of a character sub-screen insertion circuit. 1...Video chroma circuit, 2...Video sub-screen insertion circuit, 3...Video sub-screen generation circuit, 4...Character sub-screen insertion circuit , 6...
Character sub-screen generation circuit, 6... Braun tube, 7
, 8, 15...-transistor, 9, 10, 11.
12, 16.17... Resistance, 18.19...
···diode. Name of agent: Patent attorney Shigetaka Awano et al.16 Figure 7V

Claims (4)

[Claims] (1) A television receiver is equipped with a sub-screen generation circuit for text multiplex signals and a sub-screen generation circuit for video signals, and a circuit for inserting each sub-screen signal into the television image is installed in a sub-screen generation circuit for text multiplex signals. The circuit for inserting the sub-screen signal is connected in series so that it follows, and when the sub-screens overlap on the screen of the television receiver, the sub-screen of the video signal is inserted into the television image. A video switching circuit which inserts a character multiplexed child screen using the first control signal and which controls a second control signal to preferentially display the aforementioned video signal child screen on the subsequently connected character multiplexed child screen. . (2) The television receiver is equipped with a sub-screen generation circuit for character multiplex signals and a sub-screen generation circuit for video signals, and a circuit for inserting each sub-screen signal into the television image. The circuit for inserting the sub-screen signal is connected in tandem so that it follows the circuit for inserting the character-multiplexed sub-screen signal, and when the sub-screens overlap on the screen of the television receiver, The first control signal inserts a sub-screen of a video signal into the video. The second control signal is used to insert the sub-screen of a video signal into the video signal. Video switching circuit that preferentially displays images on the sub-screen. (3) The television receiver is equipped with a sub-screen generation circuit for character multiplex signals and a sub-screen generation circuit for video signals, and a circuit for inserting each sub-screen signal into the television image is installed in a character multiplex signal generator. The circuit for inserting the sub-screen signal is connected in series so that it follows, and when the sub-screens overlap on the screen of the television receiver, the sub-screen of the video signal is inserted into the television image. A video switching circuit controls the first control signal and a second control signal for inserting a character multiplexed sub-screen, and projects a television image at the location where each sub-screen overlaps. (4) The television receiver is equipped with a sub-screen generating circuit for character multiplex signals and a sub-screen generating circuit for video signals, and a circuit for inserting each sub-screen signal into the television image. The circuit for inserting the sub-screen signal is connected in series so that it follows, and when the sub-screens overlap on the screen of the television receiver, the sub-screen of the video signal is inserted into the television image. A video switching circuit controls the first control signal and a second control signal for inserting a character multiplexed sub-screen, and projects a television image at the location where each sub-screen overlaps.