JPH03190389A - Video display device - Google Patents

Abstract

PURPOSE:To confirm the content of other broadcast simultaneously while observing one broadcast program by displaying simultaneously a video of a television broadcast and a video image subject to time compression in the horizontal direction of a teletext broadcast on a same screen. CONSTITUTION:A teletext broadcast decoder output for one horizontal period written in line memories 14, 15 is read by a memory control circuit 18 at a faster frequency than a clock frequency at write for a succeeding horizontal period and the readout signal is switched into a television video signal at a television/teletext changeover circuit 12. Thus, two patterns of a video image of a television broadcast and a video image subject to time compression in the horizontal direction of the teletext broadcast are displayed simultaneously on a display screen. Thus, while one broadcast is being observed, the content of the other broadcast is confirmed simultaneously.

Description

[Detailed Description of the Invention] Emperor's presentation ■Skin butt! The present invention relates to a video display device that simultaneously displays still images of teletext on the display screen of a television receiver.

Brown rice, barley, barley, etc. Information such as text 2 graphics (hereinafter referred to as "text information") is weighted and multiplexed onto the television signal, text information is extracted from this signal, and the text information is transmitted on the television in the home. Receivers that support teletext broadcasting, which can be viewed on TVs, have recently become popular, but these receivers generally only display television images when viewing television signals, and only display text information when viewing text information. Only the images shown are displayed on the display screen.

When viewing teletext on a conventional teletext compatible receiver, the TV/text switching circuit switches the video signal to only the teletext video signal, so only the teletext video is displayed. This is inconvenient because it is displayed on the entire display screen, making it impossible to check the images of the television broadcast at that time at the same time.

1. In order to solve the above-mentioned problem, the present invention provides a teletext compatible television receiver equipped with a teletext decoder that extracts text information superimposed on a television signal from the teletext signal. First and second line memories that store the output of the decoder for one horizontal period, and the output signal of the teletext decoder is written to the first and second line memories alternately for one horizontal period, and the writing state is A memory control circuit that reads from a line memory that is not in the line memory at a faster frequency than the clock frequency at the time of writing, and a television that switches between a normal television video signal and a horizontally time-compressed teletext video signal that is read from the line memory. A television broadcast/teletext switching circuit is provided, and the television broadcasting video and the horizontally time-compressed video of the teletext are simultaneously displayed on the same screen.

The teletext decoder output for one horizontal period written in the stop line memory is read out by the memory control circuit within the next one horizontal period at a frequency faster than the clock frequency at the time of writing, and this read signal is It is switched with the television video signal in the television/text switching circuit. Therefore, two screens, the video of the television broadcast and the horizontally time-compressed video of the text broadcast, are displayed simultaneously on the display screen.

叉”L5 FIG. 1 is a block diagram of an embodiment of the invention.

The teletext radio waves received from the antenna 1 are tuned by a tuner 2 and a channel selection circuit 3, then detected by an intermediate frequency (hereinafter referred to as rlF) detection circuit 4, guided to a teletext decoder 5, and then , are led to a video chroma deflection processing circuit 7 via a signal switching circuit 6.

The teletext decoder 5 decodes the text information multiplexed in a predetermined horizontal period of the vertical retrace period of the television video signal, and outputs the video signals R', G', , B"TV/character switching signal Y3", TV halftone. Outputting signals Y, 1' and brightness control signal Yo', guiding these signals together with blanking signal BLK to teletext output section 8, and outputting music signal S0 and guiding this to audio switching circuit 9; Reference numeral 10 denotes an audio output circuit for amplifying the output from the audio switching circuit 9, and the output of the audio output circuit 10 is guided to a speaker 11.

The teletext output section 8 outputs the video signal R.

Gl, Bl, brightness control signal Y0°, television halftone signal Y, 1. TV/character switching signal Ys', blanking signal BLK, mode switching signal n/2n for switching the display mode of character information, horizontal synchronization signal H2 writing clock r, and a display clock twice the frequency of the writing clock rs. 2ft, the video signal for teletext broadcasting, the TV halftone signal, and the TV/text switching signal necessary for displaying two screens of television broadcasting and teletext broadcasting are derived using the circuit shown in FIG. 2, which will be described later. TV signal/
The signal is led to a character switching circuit 12, and is appropriately switched with the signal from the video chroma deflection processing circuit 7, and displayed on a display device 13 such as a cathode ray tube.

FIG. 2 is a block diagram of the teletext output unit 8 which constitutes the main part of the present invention, and the present invention will be explained in more detail using this figure.

In FIG. 2, numerals 14 and 15 are line memories that store information for one horizontal period, and these memories each contain the video signal R'l G' + which is the output of the teletext decoder 5.
A switching signal Y is an AND output of the B'r brightness control signal Y o l, the television halftone signal Y, ', the television/character switching signal Y, ', and the blanking signal BLK.
□ and the respective output signals R″, G′ of the teletext decoder 5 which are led to the line memories 14 and 15.
, B', Y, °+ Y,', ysm are also led to latch circuits 16 and 17, respectively. 18 is the write clock f3 from the teletext decoder 5 and 2 of the write clock r3.
The display clock 2fj with twice the frequency is used as an input signal,
a memory control circuit that controls writing and reading of information to and from the first and second line memories 14 and 15;
The memory control circuit 18 receives a line switching signal R whose output is inverted based on the horizontal synchronizing signal H from the line switching circuit 19.
At the same time, the address and display position control circuit 20 also supplies the display position signal 8. The address and display position control circuit 20 is supplied with the write clock f, the display clock 2f, and the line switching signal R5. The control circuit 20 also controls the first and second line memories 14 and 15 by a 9-bit address bus.
, and is configured to supply control signals also to the latch circuits 16 and 17. 21 is a memory output switching circuit which selects the output of either the latch circuit 16 or 17 according to the line switching signal R8, and the memory output switching circuit 21 receives the output signals R', G' from the teletext decoder 5. ,B'',Yo'',Y,',Y
, ', the output signal 2R', 2G'', which has twice the frequency of ',
2B', 2Y,", 2Y,', 2Ys" are derived. 22 is an output signal R from the teletext decoder 5;

G", B', Y,', Yi', Ys' and the output signals 2R', 2G', 2 from the memory output switching circuit 21
B2 Yo', 2 YM', and 2 Ys' are input signals, and a mode switching signal n/2 n for switching between normal mode and two-screen mode is used as a control signal.

This is a normal mode/dual screen mode switching circuit.

Therefore, as shown in the time chart of FIG. 3, in the area of each horizontal synchronization period from N-1 to N+2 from the teletext decoder 5, video signals R', G', B", as teletext decoder signals, When the brightness control signal Y0°, the switching signal Ysm (AND output of the TV/text switching signal Y3'' and the blanking signal BLK), and the halftone signal Y,'' are output, the line memory 14 and the line memory 15 perform line switching. A line switching signal R3 generated from a horizontal synchronizing signal in circuit 19 causes one to be in the write mode and the other to be in the display mode. Now, when the line memory 14 enters the write mode during the N-1 horizontal synchronization period, the teletext decoded output of the N-1 area is stored in memory at the write clock f. On the other hand, in the N-19M region during the same horizontal synchronization period,
The line memory 15 is put into display mode by the line switching signal R8 generated from the horizontal synchronizing signal by the line switching circuit 19. In this case, the line memory 15 uses a display clock 2f! with twice the frequency of writing. The N before IH in the above NlSi area
-Read the data written in area 2. The data read from this line memo January 5 passes through the latch circuit 17 and the memory output switching circuit 21, and then goes through the normal mode/
It is guided to a two-screen mode switching circuit 22. This normal mode/dual screen mode switching circuit 22 is connected to the teletext decoder 5.
Depending on the mode switching signal n/2n, the display can be set to the normal mode in which text information is displayed on the entire display screen, or the text information can be compressed in time in the horizontal direction to display two screens at the same time as a normal television image. This is a circuit that selects the mode.

That is, when the teletext decoder 5 outputs the mode switching signal n for selecting the normal mode, the normal mode/dual screen mode switching circuit 22 is switched to the normal mode, and the output signals R', G', B from the teletext decoder 5 are
', Yo', Y14', and Ys' are output directly. When the two-screen mode switching signal 2n is output, the mode is switched to the two-screen mode, and the horizontally time-compressed output signals 2R'2G', 2B'', and 2Y0 from the memory output switching circuit 21 are output.
", 2YM', 2Ys' are derived. Normal mode/
The above output signals R'/2R', G'/2G', B'/2B'' derived from the two-screen mode switching circuit 22,
Y0°/2Y,', Ywork'/2Y,', Y,°/2Y3
° is guided to a logic circuit 23, where brightness control and level conversion are performed, and the teletext video signal R/2R
, G/2G, B/2B, TV/character switching signal Ys/2
Ys and the television halftone signal Y is output as /2YM.

If you now specify dual screen display mode, normal mode/2
Output signals 2R'2G', 2 from the screen mode switching circuit 22
B", 2YO', 2Y,', 2Y,' are guided to the logic circuit 23. In the logic circuit 23, the video signal 2R' from the normal mode/dual screen mode switching circuit 22,
2G', 2B' and brightness control signal 2Y. A logical AND is taken between the outputs and the video signals 2R', 2G'',
2B' is combined with a resistor matrix to generate a video signal 2R.
, 20, 2B, and divided into full brightness level output and half brightness level output. This situation will be explained using FIG. 4. When the teletext pattern shown on the display screen 31 is decoded by the teletext decoder circuit 5, the ! on the display screen 31! -2゛Video signal 2R'2G at position
', 2B' and the brightness control signal 2Yo'' have waveforms as shown in the figure.This video signal 2R'2G' 2B
' and the AND of the luminance signal 2Yo°, and each of these ANDs,
The video signals 2R', 2G", 2B" combined with the video signals 2R', 2G'', 2B'' by the resistor matrix become signals having outputs at full brightness level and half brightness level, as shown in the figure.

This signal output is a synchronization signal 5YNC, a TV/character switching signal 2Y, and a halftone signal 2YM that lowers the level of the normal television signal to make the characters easier to see when displaying text information in a superimposed manner, as well as the TV/text switching circuit. 12.

In the television/character switching circuit 12, the television image signal from the video chroma deflection processing circuit 7 and the teletext compressed image signal from the logic circuit 23 are switched, and the television image signal is switched horizontally to 1/2 of the horizontal area of the television image. The compressed teletext video is entered and displayed in two vertical screens on the display screen 31 of the display device 13.

As described above, the operation in the area of horizontal period N-1 is completed.

Next, when entering the 9th page area of N after one horizontal period, the line memories 14 and 15 invert their modes by the line switching signal R3. As a result, the line memory 14 enters the display mode, and the line memory 15 enters the write mode. In the same manner as described above, the line memory 15 writes information in the area N, and the line memory 14 enters the immediately preceding horizontal period. The decoded output from the teletext decoder 5 written in the N-1 area is compressed to 1/2 and outputted, and guided to the logic circuit 23. Thereafter, in the same manner as described above, r42 is displayed on the display screen 31. Display the screen.

Thereafter, similar operations are repeated for each horizontal period, and an image in which 1/2 of the television image is replaced with a still image of text information is displayed on the display screen 31.

In the above embodiment, the frequency of the display clock 2f is twice the frequency of the write clock r3, and the character information is compressed to 172 in the horizontal direction. Also, in the present invention, since a part of the television image is hidden by the teletext broadcast, it is possible to adjust the timing of generation of the display position signal, which determines the display position of the character information shown in FIG. It is also possible to reduce the impact.

Since the present invention has the above-described configuration, it is possible to view television images and text broadcast images at the same time, and there is an effect that it is possible to view one broadcast while checking the contents of the other broadcast at the same time. Although the characters of teletext broadcasts are vertically elongated, they can be displayed without degrading the quality of the characters.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a block diagram of the main parts, and FIGS. 3 and 4 are explanatory diagrams of the same operation. 5- Teletext decoder. 12... Television/character switching circuit, 13... Display device. 14, 15--Line memory, 18--Memory control circuit.

Claims (1)

[Claims] (1) In a teletext-compatible television receiver equipped with a teletext decoder that extracts text information superimposed on a television signal from a television signal, a first and second television receiver that stores the output of the teletext decoder for one horizontal period The output signal of the teletext decoder is written into the second line memory and the first and second line memories alternately for each horizontal period, and the clock frequency is faster than that of the line memory that is not in the writing state at the time of writing. A memory control circuit that reads out frequencies, a TV/character switching circuit that switches between a normal television video signal and a horizontally time-compressed teletext video signal that is read out from the line memory, is installed, and a television/character switching circuit is installed to switch between a normal television video signal that is read out by frequency, and a teletext video signal that is horizontally time-compressed and read out from the line memory. A video display device characterized by simultaneously displaying a broadcast video and a horizontally time-compressed video of a teletext broadcast.