JPH0262594A - Character display device - Google Patents

Abstract

PURPOSE:To obtain a character signal superposed upon a composite video signal from the beginning by simple constitution by adding color data read out of a color ROM to carrier data by an output control part. CONSTITUTION:When color specification data of a display RAM 12 is inputted to the ROM 40, data from the ROM 40 is inputted to an output control part 41. The composite video signal, on the other hand, is inputted from an AD converter 51 to the control part 41. At the control part 41, the video signal passes through a one-bit shifter and passes through a computing element which adds the color data, so that the video signal which contains signal-colored characters is outputted to a D/A converter 51.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a character display device used in combination with or incorporated in a television receiver, a video tape recorder, or the like.

(Prior Art) In recent years, channel display and volume display in television receivers and video tape recorders are displayed directly as part of the image on the monitor screen, instead of the conventional light emitting element display or liquid crystal display. There are many methods. In addition to channel display, display contents include time, date, title, equipment handling instructions, graph display, etc.

This type of display circuit does not display the signal sent from the broadcasting station as it is, but has a function of combining a signal with the content specified by the user into a part of the video signal.

FIG. 4 shows the building blocks of an integrated circuit developed as a so-called on-screen character display circuit.

Character specification data to specify the characters and figures to be displayed, color specification data to specify the display color, size specification data to specify the size of the letters and figures, and display position. Position designation data for this purpose is input via the decoder 10.

The character generator 11 stores pattern data of various characters, figures, etc., has a ROM (read only memory), and also stores external patterns into its RAM (random access memory) via the decoder 10. It can also store data.

Character designation data and color designation data are written to a display RAM (random access memory) via a write address counter 13.

Furthermore, the data that specifies the size of characters etc. to be displayed is
Data stored in the character size register 14 and determining where on the display screen to display is stored in the position register 15.

The character designation data CHD and color designation data CRD read from the display RAM 12 are supplied to the address of the character generator 11 and the control terminal of the output control section 30, respectively. In this case, control pulses are supplied to the display RAM 12 from the position/character size control circuit 16.

On the other hand, a digital composite video signal is supplied to the input section 20 and introduced into the sync separation circuit 23 . The horizontal synchronization signal and vertical synchronization signal separated by the synchronization separation circuit 21 are supplied to reset terminals of the horizontal position counter 23 and the vertical position counter 24, respectively. Horizontal position counter 2
3 counts the output pulses of the timing generator 22, and the output pulses of the horizontal period are supplied to the clock input terminal of the vertical position counter 24.

Therefore, the horizontal position counter 23 and the vertical position counter 24
The count content represents the position information of the currently displayed display screen. The position information obtained by the horizontal position counter 23 and the vertical position counter 24 is input to the position/character size control circuit 16 and compared with the position designation data in the position register 15. The position designation data may be corrected according to the size designation data. When the position designation data matches the position information, the position/character size control circuit 16 supplies the control pulse described above to the display RAM 12 to output character designation data and color designation data. At this time, the position/character size control circuit 16 controls the control pulses given to the display RAM 12 in accordance with the size of the displayed character.

The designated color data read from the display RAM 12 is supplied to the output control section 30, and the character designated data is supplied to the character generator 11. The specified character data read from the character generator 11 is input to the output control section 30.

The output control unit 30 sets and outputs the levels of R (red), G (green), and B (blue) signals according to the contents of the character data and the contents of the designated color data. For example, if the specified color data is data specifying red, the R signal is output at the timing of, for example, a high level of the character data.

The system also includes means for controlling the background of characters and the like. The background control data is also sent to the decoder 10.
can be stored in the background control register 18 via
The background control data is supplied to the background control section 19. The background control section 19 controls the output control section 30 according to the content of the background control data, and performs, for example, color control of gaps between characters and the like. For example, if the character color is specified as red, when the character data is at a high level, an R signal is output,
When the character data is at a low level, the G signal is selected and output.

A conventional character display circuit is configured as described above.

(Problems to be Solved by the Invention) As described above, according to the conventional character display circuit, the output signals that determine the color of characters are R, G, and B signals. Therefore, if the surrounding screen on which the characters are displayed has a color similar to that of the displayed characters, there is a problem that the characters are difficult to see. In order to avoid this, it is conceivable to reduce the level of a part of the video signal on which the character signal is superimposed in advance and superimpose it at this position. However, in order to do this, it is necessary to convert the R and B signals into analog video signals using a B decoder, output them, and synthesize them into a video signal.

That is, the pedestal level of the analog video signal is stabilized in the clamp circuit 31 and inputted to the attenuator 32. Attenuator 32, R, G, B decoder 3
In response to, for example, a character signal from 4, the video signal portion on which the character signal is superimposed is attenuated, and the output video signal is input to the combining section 33. The synthesizing section 33 superimposes the character signal corresponding to the attenuated portion.

However, according to this method, the circuit configuration is complicated and the additional part is an analog part, so the position at which the character signals are synthesized tends to be inaccurate.

SUMMARY OF THE INVENTION An object of the present invention is to provide a character display device that can obtain a character signal in a form superimposed on a composite video signal from the beginning with a simple configuration, and can also make the characters easy to see.

[Structure of the Invention] (Means for Solving the Problems) The present invention includes a display RAM that stores character designation data and color designation data input from the outside, and a display RAM that stores various character data.

a character generator that outputs designated character data in response to character designation data from the display RAM; and a background for controlling the signal level of the edge of the character to be displayed and the background of the area allocated for displaying the character. a background control unit that receives control data from the outside and stores it; a display timing control unit that obtains timing for reading character designation data from the display RAM in synchronization with a synchronization signal of an input digital video signal; and an output control unit. and the output control means receives the input digital video signal, character data, and background control data, and digitally attenuates constituent data of the digital video signal corresponding to the background position of the character based on the background control data. , and the character data is superimposed on the digital video signal and output.

(Operation) With the above means, the output control section superimposes the character signal on the digital video signal with all the signals being digital. Here, the clamp level of the digital video signal is stabilized during digitization processing. Therefore, in the attenuation portion (the portion where character data is superimposed), accurate level shifting can be achieved by simple bit shifting. Furthermore, since the character data is superimposed in the digital processing section, the 11-tatami position is also accurate and the displayed characters can be easily seen.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. The difference in FIG. 1 from the conventional circuit in FIG. 3 is that a digital composite video signal is input to an output control section 41, where character data is input to f! It is configured to be folded and output. Furthermore, this output control section 41 also processes the background content of the displayed character.

A digital composite video signal from an analog-to-digital (A/D) converter 50 is supplied to the output control section 41, and if no characters are inserted, the signal is supplied to the digital-to-analog converter 51 as is. However, when a character signal is superimposed, the video signal is supplied to the digital-to-analog converter 51 as a video signal on which the character signal has been superimposed and its background processed by the above-described operation.

Further, in this embodiment, a color ROM 40 is provided to which color designation data of the display RAM 12 is supplied. This color ROM 40 stores a plurality of color burst data having different phases for at least one cycle each, and outputs various specified color data by switching and specifying a color burst to be repeatedly read out of the plurality of types of data. be able to. That is, as shown in FIG. 3, the color ROM 40 stores a plurality of types of burst data 4a, 4b, 4c, . . . , and the read data can be selectively switched. This color data is then added to the carrier data in the output control section 41.

Therefore, the character data of the digital video signal output from the output control section 41 has already been signal-colored.

Note that other parts are the same as the conventional circuit shown in FIG. 4, and are given the same reference numerals as in FIG. 4.

According to the embodiment described above, in the output control section, addition of character signals and background signal processing of the display position thereof are performed all at once, as shown in FIG. 2, for example. FIG. 2 shows the state of digital processing replaced with analog signals.

Various embodiments are possible for the output control section 41.

For example, in response to a background control signal, the video signal may be configured to pass through a 1-bit (with 6 dB attenuation) shifter, and the output of this 1-bit shifter may be configured to further pass through an arithmetic unit that adds character data. This can be achieved by doing this. Furthermore, by configuring the video signal to pass through an arithmetic unit that adds color data after that, a video signal including signal-colored characters can be obtained.

[Effects of the Invention] As described above, according to the present invention, a character signal can be obtained in a form superimposed on a composite video signal from the beginning with a simple configuration, and the characters can be made easier to see.

[Brief explanation of the drawing]

1 is a configuration explanatory diagram showing one embodiment of the present invention, FIG. 2 is a signal waveform diagram shown to explain the operation of the output control circuit of FIG. 1, and FIG. 3 is a color ROM of the color ROM of FIG. 1. An explanatory diagram of
FIG. 4 is a configuration explanatory diagram showing a conventional character display device. 10... Decoder, 11... Character generator, 12... Display ROM, 13... Write address counter, 14... Character size register, 15...
・Position register, 16...Position/character size control circuit, 18...Background register, 19...Background control unit, 2
DESCRIPTION OF SYMBOLS 1... Synchronization separation circuit, 22... Timing generator, 23... Horizontal position counter, 24... Vertical position shifter, 40... Color ROM, 41... Output control unit, 50... Analog-digital converter, 51...
Digital to analog converter. Applicant's agent Patent attorney Takehiko Suzue No. 2

Claims (1)

[Scope of Claims] A display RAM that stores character designation data and color designation data that are input from the outside; a character generator that outputs data; a background control unit that receives and stores externally input background control data for controlling the signal level of the edge of a character to be displayed and the background of an area allocated for displaying the character; , a display timing control unit that obtains the read timing of the character designation data of the display RAM in synchronization with a synchronization signal of the input digital video signal; and the input digital video signal, character data, and background control data are input, and the background control unit The present invention is characterized by comprising an output control means for digitally attenuating constituent data of the digital video signal corresponding to the background position of the character based on the data, and superimposing the character data on the digital video signal and outputting the superimposed data. character display device.