JPH0373194B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a television receiver that displays characters from a text information transmission system such as teletext and normal broadcast images on the same screen.

Development of a teletext broadcasting system (hereinafter simply referred to as teletext) that conventionally broadcasts a character signal in which character information is digitized by inserting it into a predetermined horizontal scanning period in the vertical blanking period of a television video signal. is being advanced and is being put into practical use in some areas. Various receivers that can receive such teletext have been proposed, but most of the receivers that have been proposed so far either display the text of the teletext on the entire screen, or
Alternatively, it is displayed superimposed on a part of the normal broadcast image. However, the former method is inconvenient if you want to see the broadcast image along with the text, and the latter method masks a part of the broadcast image with the text, making it difficult to see both the image and the text.

The present invention is intended to solve the above problems,
Embodiments of the present invention will be described below with reference to the drawings. still,
In the following explanation, normal television broadcasting based on the NTSC system or its broadcast screen will be simply referred to as TV or TV.
The screen on which teletext or its characters are displayed is simply referred to as a character or character screen. Also the first
In Figures 1 to 10, parts that correspond to each other or the same parts are given the same reference numerals.

A first embodiment is shown in FIGS. 1-3.

In this embodiment, as shown in FIG. 2, a TV screen 2 is displayed on the left half of the screen 1 of the receiver, and a character screen 3 is displayed on the right half.
Furthermore, the receiver according to this embodiment has the above-mentioned two-screen display (hereinafter referred to as two-screen mode), display of only TV screen 2 (hereinafter referred to as TV mode), and character screen 3.
It is possible to selectively display only text (hereinafter referred to as character mode). In any display, TV screen 2 and character screen 3
The horizontal scanning is half of the normal horizontal scanning period H, respectively.
That is, it is performed in the H/2 period.

FIG. 1 shows a circuit system for realizing each of the above displays.

In FIG. 1, a tuner 5 selects a broadcast signal in which teletext is multiplexed from signals received by an antenna 4. This broadcast signal is transmitted to the video intermediate frequency circuit 6
The signal becomes an intermediate frequency signal and is detected by the video detection circuit 7 at the next stage. The detected video signal is applied to a line conversion circuit 8, a character decoder 9, and a synchronous separation circuit 10. The line conversion circuit 8 is constructed of 1H memories 11 and 12 made of CCD or BBD and switch circuits 13, 14 and 15 as shown in the figure. The 1H memories 11 and 12 are configured to write 1H worth of video signals and then read them out at H/2. In addition, this memory 11,
12 is configured such that while writing is being performed on one side, reading on the other side is repeated twice. For this purpose, the switch circuits 13 and 14 are configured so that the a and b contacts can be switched on a H-by-H basis by operating in opposite directions. Writing is performed when the contact is switched to the a contact, and reading is performed when the contact is switched to the b contact. This reading is repeated twice every H/2. That is, the signal read from the memory 11 is applied to the a contact of the switch circuit 15, which is switched every H/2, and is returned to the memory 11 via the b contact of the switch circuit 13, where it is written again and then immediately The signal is read out and applied to the a contact of the switch circuit 15.
Similarly, the signal read from the memory 12 is applied to the B contact of the switch circuit 15, and is returned to the memory 12 via the B contact of the switch circuit 14, written again, and immediately read out to the switch circuit 15. is added to the b contact of the In order to write and read data into and from the memories 11 and 12, a write clock with a frequency of 2fc and a read clock with a frequency of 4fc are applied through the W and R contacts of switch circuits 16 and 17, which are switched in opposite directions. The video signals obtained alternately for each H from the a and b contacts of the switch circuit 15 are applied to the R, G, B decoder 18, and as a result of the known demodulation processing, the decoder 18
Three primary color signals of R, G, and B can be obtained using the NTSC system. These R, G, B signals are sent to the switch circuit 19.
It is applied to the TV contact of the switch circuit 20 which is switched every H/2.
On the other hand, in the character decoder 9, after extracting the character signal inserted in a predetermined horizontal scanning period in the vertical retrace period of the video signal, the character signal is converted to a frequency of 2f _N
decode based on the clock. As a result, from this character decoder 9, Rc having character information,
Three primary color signals of Gc and Bc are obtained. This Rc, Gc,
The Bc signal is applied to the character contacts of switch circuits 19 and 20. The synchronization separation circuit 10 separates the vertical and horizontal synchronization signals V _D and _HD of the video signal and applies them to the control circuit 21 . The control circuit 21 is synchronized with the synchronization signals V _D and _HD and sends control signals for controlling the operation timings of the switch circuits 13, 14, 15, 16, 17, 20, the RGB decoder 18, the character decoder 9, and other predetermined circuits. Output. The switch circuit 19 switches between TV, two-screen mode, and character mode depending on the selection of TV mode, two-screen mode, and character mode.
Switched to each contact point of the character. switch circuit 19
The output signal is applied to an R, G, B processor 21, subjected to necessary signal processing such as amplification, and then applied to a cathode ray tube 22. The cathode ray tube 22 is driven by a horizontal deflection circuit 23 having a horizontal scanning frequency _fH in the two-screen mode, and by a horizontal deflection circuit 24 having a horizontal scanning frequency fH in the TV mode and character mode. These changes are performed by a switch circuit 25.

Next, the operation of the above configuration will be explained.

First, in the case of TV mode, the switch circuit 19 is
The switch circuit 25 is closed to the TV contact.
Closed to character contact. This makes the character decoder 9 and the switch circuit 20 irrelevant in operation. The line conversion circuit 8 is operated at the timing described above, and the memories 11 and 12 alternately write and read video signals. As a result, a video signal of the same scanning line is obtained twice at a speed of H/2 from the switch circuit 15, and this video signal is applied to the RGB decoder 18. The demodulated R, G, and B signals are applied to the cathode ray tube 22 through the switch circuit 19 and the RGB processor 21, and are applied to the entire screen.
The TV image is displayed independently. In this case, the cathode ray tube 22 is horizontally deflected at 2f _H , so that the screen 1
In this case, as shown in FIG. 4, scanning lines with the same content, . . . , are repeatedly scanned twice every H/2. Therefore, 525 scanning lines are drawn in one field without interlaced scanning.

Next, in the character mode, the switch circuit 19 is closed to the character contact, and the switch circuit 25 is closed.
is closed to TV and text contacts. This makes the line conversion circuit 8, RGB decoder 18 and switch circuit 20 irrelevant to the operation. and Rc having character information decoded by the character decoder 9;
Gc and Bc signals are applied to the cathode ray tube 22 through a switch circuit 19 and an RGB processor 21. This causes the characters to be displayed individually on the entire screen.
In this case as well, the scanning shown in FIG. 4 is performed.

Next, in the case of 2-screen mode, switch circuit 1
9 and 25 are closed to two screen contacts. and
The R, G, and B signals obtained from the RGB decoder 18 and the Rc, Gc, and Bc signals obtained from the character decoder 9 are switched by a switch circuit 20 every H/2, and are sent to the cathode ray tube 22 through the switch circuit 19 and the RGB processor 21. added to. As a result, as shown in FIG. 2, two screen displays, the TV screen 2 and the character screen 3, are divided horizontally and displayed simultaneously. In this case, the cathode ray tube 22 is horizontally deflected at _fH , but the first half of the same scanning line contains information on the TV screen 2, and the second half contains information on the character screen 3. Therefore, 525 scanning lines are drawn in one field using interlaced scanning. In addition, in the character decoder 9,
1H worth of information written to the line memory is read out twice at a speed of H/2.

FIG. 3 shows the display timing of each signal with respect to the horizontal scanning direction of the input video signal in the TV mode, character mode, and two-screen mode described above.

FIG. 6 shows a second embodiment.

In this embodiment, as shown in FIG. 5 and FIG.
In the screen mode, the TV screen 2 and the character screen 3 are each scanned at a speed of H/4, so one scanning line is drawn at a speed of H/2. For this purpose, switch circuits 26 and 27 are connected to the R contacts of switch circuits 16 and 17, respectively, and a 4f _C clock is applied to the TV contact, and an 8f _C clock is applied to the two-screen contact. At the same time, a switch circuit 28 is connected to the character decoder 9, and 2f _N is connected to the character contact.
A clock of 4f _N is added to the 2-screen contact point. Also, the switch circuit 20
is configured to be switched every H/4.

In the above configuration, in the TV mode, the switch circuits 26 and 27 are closed to the TV contacts, and the memories 11 and 12 are read with a clock of 4f _C and written with a clock of 2f _C. Therefore,
The same operation as in the first embodiment described above is performed,
By performing the scanning shown in FIG. 4, the TV screen is displayed independently on the entire screen. Also in the character mode, the switch circuit 28 is closed to the character contact and the character decoder 9 is driven by the _2fN clock, so that the same operation as in the first embodiment is performed.
Therefore, the scanning shown in FIG. 4 is performed and the character screen is displayed alone on the entire screen.

In the two-screen mode, the switch circuits 26, 27,
28 is closed to two screen contacts. As a result, the memories 11 and 12 are alternately read four times each at four times the writing speed. In this case, since the switch circuit 20 is switched every H/4, among the signals obtained from the RGB decoder 18, only the signals read out in the first and third times of each memory 11 and 12 are switched to the switch circuit 20. taken out through. Further, the character decoder 9 is driven by _4fN , and among the signals obtained from the line memory, only the signals in the periods corresponding to the second and fourth reading periods of the memories 11 and 12 are taken out from the switch circuit 20. It will be done. Therefore, from this switch circuit 20, a signal is obtained in which TV and characters are alternately successive at a rate of H/4 as shown in the two-screen mode of FIG. By this, 2 in Figure 5
A screen display is performed. In this case, 525 scanning lines are drawn in one field without interlaced scanning.

In the first embodiment shown in FIG. 2, two horizontal deflection circuits 23 and 24 are used, but in this second embodiment, only one horizontal deflection circuit 24 is used. Further, in the second embodiment, the number of scanning lines is twice the normal number in all modes of TV, text, and two screens. Further, in the second embodiment, the clock frequency of the character decoder 9 is switched between _2fN and _4fN , but in the first embodiment, there is no need for switching.

FIG. 8 shows a third embodiment.

Note that the display form in the two-screen mode of this embodiment and the timing of TV and character display in each mode are the same as in FIGS. 5 and 7.

In this embodiment, the switch circuits 29 and 30 that can be switched between the two-screen mode and the TV mode are connected to the write-side contacts W of the switch circuits 16 and 17, and the two-screen mode and TV mode are connected to the input side of the line conversion circuit 8. A switch circuit 31 that can be switched to
are connected. Then, in the two-screen mode, the video signal from the detection circuit 7 is applied to the memories 11 and 12 via the switch circuit 31, and this is alternately written 1H at a time using the f _C write clock applied via the switch circuits 29 and 30. 4f It is read using _{the C} readout clock. In this case, the writing frequency is 1/4 of the reading frequency, so when writing, the video signal is
Added to intermediate taps 1 and 12. Furthermore, in the TV mode, the switch circuits 29, 30, and 31 are switched to TV contacts, so writing is performed at _2fC and reading is performed at _4fC . The same operation as mode is performed. Furthermore, in the case of character mode, the same operations as in the first and second embodiments are performed. In addition, in the two-screen mode and the character mode, the switch circuit 28
By switching the character decoder 9, the clock of the character decoder 9 becomes _2fN or _4fN . In addition, in this example, 3
In both modes, the double scanning shown in FIG. 4 is performed.

FIG. 9 shows a fourth embodiment.

In this embodiment, two sets of line conversion circuits 8a and 8b having the same configuration as the line conversion circuit 8 described above are used for line conversion of video signals and line conversion of character signals, respectively. And 2
In the screen mode, the switch 32 is closed, and the Rc, Gc, and Bc signals from the character decoder 9 are written by the line conversion circuit 8b at a clock of _2fC and read out at a clock of _8fC . Incidentally, in the TV mode and the character mode, the same operations as in each of the previously described embodiments are performed. Further, scanning is performed in all modes as shown in FIG. 4, and the display form and operation timing are performed as shown in FIGS. 5 and 7.

FIG. 10 shows a fifth embodiment, in which a switch circuit 33 that can switch between two screens and a TV is connected to the input side of the line conversion circuit 8a, and a video signal is transferred to the line conversion circuit 8a in the two screen mode. Data is written from the intermediate tap of memories 11 and 12 using the f _C clock. The TV mode and character mode are performed in the same manner as described above, and the operations shown in FIGS. 4, 5, and 7 are performed.

In the second and third embodiments described above, the clock frequency of the character decoder 9 is changed from _2fN to _4fN in order to perform double scanning in the two-screen mode. In the embodiment, the clock frequency may be constant at _2fN .

In the first to fifth embodiments described above, in the two-screen mode, as shown in FIGS. 1 and 5,
The TV screen 2 and the text screen 3 are arranged to divide the screen 1 into two, as shown in Fig. 11A and B.
The ratio between the width a of the TV screen 2 and the width b of the character screen 3 may be changed. In that case, f _CW / f _CR + f _N0 / f _N = constant However, f _CR : Read clock frequency, f _CW : Write clock frequency, f _N : Character decoder drive frequency, f _N0 : Character screen only Driving frequency of character decoder when displaying in H period.

Therefore, f _CR and f _N or f _CW and f _N may be changed continuously or stepwise, respectively. Furthermore, in each embodiment, 525 lines per field are scanned twice in TV, text, and 2-screen modes (however, the first
In this embodiment, the number of scanning lines may be arbitrary (only for TV and character modes), scanning other than double scanning, such as 1.5x scanning, 3x scanning, etc. In that case, f _C and f _N may be changed with a certain relationship.
Further, the RGB decoder 18 in each embodiment may be arranged before the line conversion circuit 8. In that case, it is necessary to provide a line conversion circuit for each of the R, G, and B channels, but the clock frequency can be lowered. Further, each embodiment is a case where the present invention is applied to teletext broadcasting, but the present invention is a CAPTAIN that transmits character information using a telephone line.
It can also be applied to a system called

According to the present invention configured as described above, the third
In this mode, the text screen and the broadcast screen can be divided horizontally and displayed simultaneously, so the text and broadcast images can be viewed at the same time.
Unlike the superimposed display in conventional teletext receivers, the broadcast image is not masked with characters and becomes difficult to see.

In addition, in the first and second modes, the text screen or broadcast screen is displayed independently on the entire screen, and the number of scanning lines on the screen is increased, so when viewing the text screen or broadcast screen individually, You can see text or broadcast images displayed in a larger size and with improved image quality.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention, FIG. 2 is a diagram showing a screen display form in a two-screen mode in the first embodiment, and FIG. A diagram showing the operation timing in the mode, FIG. 4 is a diagram showing double scanning of the screen in the first to fifth embodiments, and FIG. 5 is a diagram showing the screen display form in the two-screen mode in the second to fifth embodiments. Figure, 6th
7 is a circuit diagram showing the second embodiment, FIG. 7 is a diagram showing the operation timing of each mode in the second to fifth embodiments, FIG. 8 is a circuit diagram showing the third embodiment, and FIG. FIG. 9 is a circuit diagram showing the fourth embodiment,
FIG. 10 is a circuit system diagram 11 showing the fifth embodiment.
The figure shows another screen display format. In addition, in the symbols used in the drawings, 1...
...Screen, 2...TV screen, 3...Text screen, 9...
...Character decoder, 11, 12...1H memory, 1
9...This is a switch circuit.

Claims (1)

[Scope of Claims] 1. A first mode configured to receive a text information signal and a television broadcast signal, and in which a character screen obtained from the text information signal is independently displayed on the entire screen; Switch means capable of selectively setting a second mode in which the broadcast screen obtained from the signal is displayed independently on the entire screen, and a third mode in which the character screen and the broadcast screen are divided horizontally and displayed simultaneously. and a plurality of memories capable of recording the television broadcast signal for one horizontal period or more, configured such that the reading speed of the television broadcast signal to the plurality of memories is higher than the writing speed of the television broadcast signal, and the third In this mode, the horizontal scanning speed during screen projection is configured to be smaller than in the second mode, and the plurality of memories are used to process the television broadcast signal and the first to third modes are processed. 1. A television receiver characterized in that the number of scanning lines on the screen in at least the first and second modes of the modes is greater than the normal number of scanning lines. 2. A first mode configured to receive a text information signal and a television broadcast signal, and in which a character screen obtained from the text information signal is displayed independently on the entire screen, and a broadcast screen obtained from the television broadcast signal. and a third mode in which the character screen and the broadcast screen are divided horizontally and displayed simultaneously on the entire screen; A plurality of memories capable of recording signals for one horizontal period or more are provided, and the readout speed of the television broadcast signal to the plurality of memories is higher than the writing speed of the television broadcast signal to the plurality of memories, and in the third mode, the above-mentioned The ratio of the reading speed to the writing speed is configured to be larger than that in the second mode, and the plurality of memories are used to process the television broadcast signal, and the mode is set to one of the first to third modes. 1. A television receiver, characterized in that the number of scanning lines on the screen in at least the first and second modes is greater than the normal number of scanning lines.