Apparatus for receiving character multiplex broadcasting

A character multiplex broadcasting receiving apparatus is provided for reducing and displaying a plurality of character figure images including header information and text information. In the invention, to simultaneously display a plurality of character figure images, division signals are formed from a horizontal pulse, a vertical pulse, and a clock pulse (chrominance subcarrier frequency f.sub.sc .times.4) to designate areas on the CRT. Either and animation image (television image) or a character image to display character figure information is designated for each divided picture plane and a plurality of character figure images are simultaneously displayed.

BACKGROUND OF THE INVENTION 
The present invention relates to an apparatus for receiving a character 
multiplex broadcast in which when a character image is reduced and 
divisionally displayed on a cathode ray tube (CRT), a superimposing 
control to decide whether the image displayed on the divided screen is a 
television image or a character image can be executed every divided 
screen, and both of the television image and the character image can be 
simultaneously mixedly displayed on the CRT. 
In recent years, a new media of character broadcasting has been put into 
practical use and has become gradually widespread. Various kinds of 
additional functions are being examined to increase the use of character 
broadcasting. 
FIG. 1 shows a schematic block diagram of a character multiplex receiving 
decoder (hereinafter, simply referred to as a decoder). In the diagram, 
reference numeral 1 denotes a central processing unit (CPU) to process 
various kinds of data of the decoder. Reference numeral 2 denotes a read 
only memory (ROM) in which a program to execute the processing procedure 
in the CPU 1 is stored; 3 indicates a random access memory (RAM) for 
working of the CPU 1; 4 an extracting section for extracting a character 
signal from a video signal and supplying the same to the CPU 1; 5 a system 
control section to generate various kinds of control signals which are 
necessary to control each block; 6 a display control section for storing 
the received character signal into a video RAM 7 or for reading out the 
character signal from the video RAM 7 and outputting the same to a display 
terminal; and 8 a Kanji (Chinese character) ROM to store a font (pattern) 
of a character which was encoded and designated in the character signal. 
The code encoded in accordance with a predetermined code system (for 
instance, Japanese Industrial Standard (JIS)) is supplied from the CPU 1 
and added as an address into the Kanji ROM 8 and a pattern output 
corresponding to the code is read out of the Kanji ROM 8 and written into 
the video RAM 7. By reading out the pattern output from the video RAM 7 
and outputting it to the CRT, the character is displayed on the CRT 
screen. 
FIG. 2 is a block diagram of a decoding section as a part of the display 
control section 6 in FIG. 1. 
In the diagram, reference numeral 9 denotes a selector to switch and output 
one of a raster information signal to designate the background color of 
the whole screen and a character figure information signal when a 
character figure picture plane is displayed on the CRT. Reference numeral 
10 denotes a detecting circuit to detect the presence or absence of the 
character figure information signal to generate a switching signal which 
is necessary when the selector 9 performs the switching operation; 11 
indicates a detecting circuit to obtain a YM signal which is necessary to 
execute the superimposing display; and 12 a detecting circuit to similarly 
obtain a YS signal. Reference numeral 13 denotes a register to output an 
indication signal to indicate whether a character figure image to be 
displayed is an image to be superimposed or not on the basis of the 
control of the CPU 1. Reference numerals 14 and 15 denote AND gates which 
are opened only when the indication signal to indicate the superimposing 
display was input from the register 13. 
The operation of the display control section of the above-mentioned 
character multiplex receiving decoder will now be described hereinbelow. 
In the character multiplex broadcasting, in general, sixteen colors 
comprising eight colors each with two gradations can be displayed. 
Therefore, all of the colors can be designated by 4-bit data and the 
following table shows the relationship among the 4-bit data and the 
display colors. 
______________________________________ 
Ri B G R color 
______________________________________ 
0 0 0 0 0 black 
1 0 0 0 1 red 
2 0 0 1 0 green 
3 0 0 1 1 yellow 
4 0 1 0 0 blue 
5 0 1 0 1 pink 
6 0 1 1 0 light blue 
7 0 1 1 1 white 
8 1 0 0 0 transparent 
9 1 0 0 1 1/2 red 
10 1 0 1 0 1/2 green 
11 1 1 0 0 1/2 yellow 
12 1 1 0 0 1/2 blue 
13 1 1 0 1 1/2 pink 
14 1 1 1 0 1/2 light 
blue 
15 1 1 1 1 1/2 white 
______________________________________ 
In the above table, the color is set in a manner such that when the color 
data is "8" or more, that is, when the bit of Ri is set to "1", the 
luminance of the color which is expressed by the other three bits is 
reduced into the half. Although the color data "8" denotes black of 1/2, 
such a color does not actually exist; therefore, the transparent color is 
set in such a case. In other words, if the information indicative of color 
data "8" exists in the character figure information signal, the color at 
such a position is displayed as a raster color. Namely, the character/ 
figure is displayed as a transparent image. On the other hand, in the 
superimposing display mode, a television signal is displayed in place of 
the raster color display. Therefore, in the superimposing display mode, by 
designating "8" for both of the raster color and character background 
color (writing "8" into the video RAM), the superimposed display of both 
of the character and the television signal can be executed. The YS signal 
is used to realize such an operation control. Further, since 1/2 white 
(gray color) in the superimposed mode is difficult to see, the YM signal 
is used to execute an operation control so as to reduce the luminance 
level of the television image only in the superimposing display mode. 
From the character figure information signal, either one of the character 
figure information signal and the raster information signal is selected by 
the selector 9 on the basis of a detection output signal of the detecting 
circuit 10, so that the final R, G, and B signals are derived. On the 
other hand, in the superimposing display mode, the superimposing display 
mode is designated to the register 13 by the CPU 1 and the gates 14 and 15 
are opened, thereby obtaining the YM and YS signals. 
Although not shown, the R, G, B, and Ri signals are converted into analog 
signals by simple D/A converters and are synthesized with the television 
signal together with the YM and YS signals. 
The operation of the character multiplex receiving decoder constructed as 
mentioned above will now be briefly explained hereinbelow. 
If the figure information in the character signal extracted from the video 
signal by the character signal extracting section 4 has been subjected to 
compression or the like by the process of the CPU 1, the expanding process 
is executed and, thereafter, the expanded figure information is input to 
the display control section 6. Or, in the case of the encoded character 
information, the Kanji ROM 8 is accessed in accordance with the code of 
such character information and the pattern read out of the ROM 8 is input 
to the display control section 6. The display control section 6 stores the 
figure information or pattern into the video RAM 7 in accordance with the 
input. The display control section 6 simultaneously reads out the display 
data from the video RAM 7 and provides an output of the R, G, and B 
signals through a decoding section in FIG. 2. 
In addition to the ordinary character broadcasting receiving and displaying 
operations as mentioned above, as an additional function, as shown in FIG. 
3B, there is considered what is called a picture-in-picture mode in which 
the display area of the character picture plane data is reduced and is 
displayed by synthesizing onto the ordinary television screen. For 
instance, the screen in which the ordinary character picture plane area 
comprises 248 dots in the lateral direction and 204 lines in the vertical 
direction is reduced into the picture plane area comprising 124 
dots.times.102 lines whose size is 1/4 of the ordinary screen and the 
display is executed on the reduced area. If the ordinary television 
picture plane data is displayed as the main data and the character picture 
plane data is displayed as a size of 1/4 at the corner of the main 
television picture plane area, both of them can be simultaneously seen. On 
the other hand, if character picture plane data which the user wants to 
see in detail is input, such data can be soon exchanged and displayed in 
the main picture plane area in place of the main television picture plane 
data. Further, as shown in FIG. 3C, the character picture plane data of 
four picture planes can be also simultaneously displayed. In such a case, 
the amount of information able to be displayed is increased, thus 
improving the overall usefulness of the system. 
In general, in the case of displaying the character picture plane data on 
the CRT, a display memory is assigned so as to cover the whole display 
area. Since the character picture plane data in which the display area is 
reduced uses a part of the display memory, each time the reduced display 
is executed in a part of the television image, the rewriting operation 
must be performed so as to generate the YS signal from the display memory 
in the other area. Unfortunately, the program required to execute the 
above data processing is complex and development costs are significant. 
On the other hand, in the case of simultaneously displaying four reduced 
picture planes, if the superimposing display mode is designated for either 
one of them, a similar problem occurs. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a character multiplex 
broadcasting receiving apparatus with a data simplified processing program 
for reducing and displaying received character picture plane data. 
Another object of the invention is to provide a receiving apparatus with a 
simplified program which is used to simultaneously display character 
picture plane data of a plurality of picture planes which were data 
processed so as to reduce the display areas and to display any of the 
picture planes in the superimposed display mode. 
To accomplish the above objects, a character multiplex broadcasting 
receiving apparatus of the invention is constructed in a manner such that 
when the reduced character image is displayed in a part of a television 
image, if character image data which is displayed in an area other than 
the area whose display position is designated is input, a YS signal is 
automatically generated, and on the other hand, when the superimposed 
display mode is designated for either one of a plurality of picture 
planes, a control signal to perform the transparent display as a raster 
information signal is output from a control signal register corresponding 
to each picture plane. 
With the above construction of the invention, even if the additional 
function for the reduction display is provided, the control similar to the 
ordinary character broadcasting display can be executed on a divided 
picture plane unit basis. The time and cost of development time of control 
program software and the data processing burden can be reduced.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
An embodiment of the present invention will be described hereinbelow with 
reference to the drawings. FIG. 4 is a block diagram of an RGB decoding 
section in a character multiplex broadcasting receiving apparatus in an 
embodiment of the invention. 
In the diagram, reference numerals 9 to 15 denote the same parts and 
components as those shown in FIG. 2. Reference numeral 16 indicates a 
division signal generating section for receiving a horizontal signal H, a 
vertical signal V, and a clock signal CLK obtained by frequency dividing a 
chrominance subcarrier frequency signal and for generating division 
signals .circle.A, .circle.B, and .circle.C which are necessary to 
perform the reduction display. Reference numeral 17 denotes a dividing 
position signal generating section to obtain a dividing position 
designation signal corresponding to each display position in FIG. 3C from 
the division signals obtained from the division signal generating section 
16. Reference numeral 18 denotes a quadrant designating register to 
designate a display position (quadrant) in the case of performing the 
picture-in-picture display; 19 indicates a super-position designating 
register which is necessary in the multi-display mode and generates a 
control signal so that the superimposing display mode can be designated in 
correspondence to each display block shown in FIG. 3C; and 20 represents a 
control signal generating section for receiving the above various kinds of 
designation and control signals and for generating a superimpose 
designation signal in correspondence to each dividing position. 
Reference numeral 21 denotes a raster control circuit to forcedly set the 
raster information signal to the data corresponding to "8" in the above 
table by the superimpose designation signal obtained by the control signal 
generating section 20. Reference numeral 22 indicates an OR gate to 
similarly forcedly switch the YS signal to the television image signal. 
The operation of the RGB decoder constructed as mentioned above will now be 
described hereinbelow. 
The ordinary character broadcast displaying operation is similar to that in 
the conventional apparatus. The multi-display mode will be first explained 
hereinbelow. 
In the multi-screen display mode as shown in FIG. 3C, the picture plane is 
not always limited to the character picture plane but there are also a 
title service and a superimposing display. In the case where they are 
designated, the apparatus must execute those instructions. In the 
multi-screen display mode, it is arbitrarily necessary to control the 
character picture plane (text) display or the superimposing display. 
The division signal generating section 16 obtains signals as shown in FIG. 
5 from the CLK (display clock or the like), H (horizontal pulse), and V 
(vertical pulse). .circle.A denotes the signal which has the same period 
as the horizontal pulse H and is the division signal to designate either 
the left half (0) or the right half (1) on the display screen. That is, 
either the display areas of "1", "3", "5", and "7" or the display areas of 
"2", "4", "6", and "8" in FIG. 3C are designated. .circle.B indicates the 
signal synchronized with the vertical pulse V and similarly designates 
either the display areas (0) of "1", "2", "5", and "6" or the display 
areas (1) of "3", "4", "7", and "8". .circle.C likewise designates either 
the header sections (0) of "1", "2", "3", and "4" or the text sections (1) 
of "5", "6", " 7", and "8". The signal .circle.D in FIG. 5 denotes a 
display area in the vertical direction. 
The dividing position signal generating section 17 generates signals 
corresponding to the dividing positions indicated by the division signals 
.circle.A, .circle.B, and .circle.C. Those signals are indicated by the 
super-position designating register 19 to generate a control signal in 
correspondence to each divided screen to indicate the superimposing 
position. If 1 (header 1) and 5 (text 1) show the superimposing display, 
the signal corresponding thereto is generated. The dividing position 
signal generated from the dividing position signal generating section 17 
is controlled by the control signal generating section 20. A 
super-switching signal is generated at only the indicated dividing 
position. 
To set the superimposing display mode, it is fundamentally sufficient to 
set the raster information signal to the color data "8". Therefore, the 
output of the super-control signal generating section 20 is input to the 
raster control section 21 and the raster information signal is forcedly 
set to the data value "8". Thus, the raster is set into the superimposing 
mode at only the designated dividing position. 
However, in such a case, since the above circuit is commonly used together 
with the ordinary circuit, it is necessary that the text/super switching 
register 13 is set into the superimposing display mode. 
The operation in the picture-in-picture display mode will now be described. 
In the above case, the super-position designating register 19 is not used 
but the quadrant designating register 18 is used. The picture-in-picture 
system intends to reduce and display a character picture plane at the 
designated quadrant position on the television image. It will be 
inconvenient if the character picture plane is displayed at a position 
other than the designated position. In the picture-in-picture display 
mode, the image data to be reduced and displayed is stored in the memory 
which is commonly used to store the ordinary character picture plane data. 
Therefore, according to the conventional method, it is necessary to erase 
the contents of memory other than the designated quadrant. However, the 
data processes or the like in such a case are troublesome. Therefore, the 
quadrant designating register 18 is used and the superimposing signal is 
generated at the divided screen position other than the designated 
quadrant. The superimposing signal is transmitted through the OR gate 22 
and the YS signal is forcedly set to "0". Due to this, even if any 
character image exists in the quadrant other than the designated quadrant, 
it is not displayed and there is no need to erase the content of the 
memory. It is also possible to construct the detecting circuits 10 and 12 
in a manner such that the input data is inverted by an inverter or the 
like and "0" is detected. On the other hand, it is also obviously possible 
to commonly use the registers 13 and 18 or the like. 
As described above, according to the present invention, in the case of 
performing the reduction display in the multi-display or 
picture-in-picture display, the processes to erase and rewrite the memory 
content can be omitted. If reduction data is preliminarily prepared, they 
can be instantaneously exchanged or the like and the burden on the program 
software processes can be lightened.