JPH10282947A - On-screen display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an on-screen display device capable of adjusting the size and pitch of display characters according to variations in scanning speed. SOLUTION: Font data read from a font ROM are displayed on a monitor displaying video signals with different scanning speeds. In this case, this device is provided with an address generation part 1 for counting horizontal synchronizing signals inputted externally and generating read-out addresses of a font ROM 7, a register 2 for setting a predetermined count value according to the scanning speeds of video signals, and a comparison part 3 for comparing a count value counted by the address generation part 1 with the count value of the register 2. And, whenever the count value of the address generation part 1 reaches the count value of the register 2, it is configured so that the count value of the address generation part 1 is cleared and the count is newly started.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an on-screen display device for displaying characters superimposed on a video signal on a monitor.

2. Description of the Related Art As information processing equipment has become more multimedia, it is necessary to provide a monitor with an on-screen display function in order to improve the operability of these devices. However, when using a so-called multi-scan monitor that can support different scanning speeds, the conventional on-screen display mechanism makes it difficult to see the display screen because the size and occupied area of the on-screen display characters differ depending on the scanning speed. The measures are desired.

[0003]

2. Description of the Related Art FIG. 2 is a block diagram showing the overall structure of an on-screen display device for displaying on-screen characters on a multi-scan monitor. In the figure,
The image source 10 indicates a personal computer, a TV tuner, a video decoder, and the like. The control unit 11 detects the scanning speed and other attribute information of these image sources 10, and sends a control signal according to the information to the character generation unit 12 and the image generation unit. This is sent to the processing unit 13. The character generator 12 reads out and outputs font data from a built-in font ROM based on a control signal sent from the controller 11. Image processing unit 13 is an image source
The video signal sent from 10 is processed according to the control signal sent from the control unit 11. The switch unit 14 is connected to the video signal sent from the video processing unit 13 and the character generation unit 12.
The font data sent from is switched and sent to the monitor to display the video and the character in a superimposed state.

FIG. 3 is a block diagram showing a conventional character generation mechanism used in the on-screen display device, which has a function corresponding to the character generation unit 12 of the on-screen display device shown in FIG. . In the figure, reference numeral 21 denotes an address generation unit that counts the horizontal synchronization signal sent from the control unit 11 of the on-screen display device shown in FIG. 2 and generates a read address of the font ROM. A line counter 23 for counting the number of characters, 23 a digit counter for counting the number of digits of a display character, 24 a VRAM for outputting a character code and a color control signal based on signals from the line counter 22 and the digit counter 23, 25 an address generation A font ROM 26 for outputting font data specified by the read address sent from the unit 1; and a dot ROM 26 for forming characters based on the font data read from the font ROM 25 and the color control signal sent from the VRAM 24. This is a coloring section for coloring the color.

FIGS. 4 (a) and 4 (b) are diagrams for explaining a process of reading font data by the character generation mechanism. The address generation unit 21 counts the horizontal synchronization signal and the count value. 2 shows a relationship between a read address generated by the address generation unit 21 based on the read address and font data read from the font ROM 25 by the read address. The font pattern is composed of a set of many dots. Figures (a) and (b) show font patterns of type A and type B with different character sizes, each consisting of 16 dots vertically and 12 dots horizontally. In this example, 16 columns of font data are designated by a 4-bit read address. When one character is composed of 32 bits in length and 24 bits in width, 5 bits are required for the read address.

Next, the process of reading a display character string having a predetermined number of lines and digits by the above-described character generation mechanism will be described with reference to FIGS. First, prior to the generation of characters, the line counter 22 and the digit counter 23 are cleared, and the character code of the first line of the display character string specified based on the output of the cleared line counter 22 and digit counter 23 is read from the VRAM 24. It is sent to the font ROM 25.

Next, the address generator 21 starts counting the horizontal synchronization signal input from the controller 11 of the on-screen display device shown in FIG. As shown in FIG. 4, each time the count value increases sequentially from 1, the address generation unit 21 generates a read address corresponding to the count value and sends it to the font ROM 25. In the font ROM 25, the address corresponds to the read address sent. Read font data sequentially. When the count value reaches 16, the font data in the bottom row is read, and the count value of the address generation unit 21 is cleared.

When a font pattern of 32 dots per character is used, the count value is cleared when the count value reaches 32. The address generator 21 clears the count value and sends a row up signal to the row counter 22. Through the above process, the reading of the first line of the display character string is completed.

Next, the row counter 22 includes an address generator 21.
The number of lines of the display character string is advanced by one based on the line up signal sent from the VRAM 24 and the VRAM 24 is notified. The digit counter 23 informs the VRAM 24 of the number of digits advanced by one when the font data of 24 horizontal dots constituting one character is read. The VRAM 24 specifies a character code based on the number of lines and the number of digits of the display character string sent from the line counter 22 and the digit counter 23, and sends the character code to the font ROM 25.

Next, the address generator 21 starts a new count of the horizontal synchronizing signal and outputs the first character string of the display character string.
The same process as the reading of the line is repeated to read the display character strings on the second and subsequent lines. The read font data is sent to the coloring unit 26. The coloring section 26 adds the color control information sent from the VRAM 24 to the font data and displays the sent character string on a monitor (not shown).

[0011]

In general, a personal computer or T
Video signals output from a video source such as a V tuner have various scanning speeds. For example, a normal TV signal has a horizontal scanning frequency of 15.75 kHz, and a high-definition TV such as an EDTV has a scanning speed twice as high. Used. The personal computer uses a scanning speed of 31.5 to 120 kHz depending on the resolution. As described above, when video signals are displayed at various scanning speeds, the size and occupied area of on-screen characters displayed on the monitor are different from each other.

FIGS. 5A and 5B are diagrams showing an on-screen display area (OSD area) displayed on a monitor using the above-described on-screen display device. 24 digits 12 characters consisting of 24 horizontal dots
This shows a case in which lines are displayed. Figure (a) shows 1024 dots x
When the horizontal sync frequency is set to 68.7 kHz on a super VGA personal computer with a resolution of 768 lines, FIG.
This figure shows a case where the horizontal synchronization frequency is set to 31.5 kHz on a VGA personal computer having a resolution of 640 dots × 480 lines. The area occupied by the OSD area varies depending on the scanning speed. In the super VGA personal computer, the OSD area occupies 50% of the vertical and horizontal monitor screens, whereas in the VGA personal computer, the vertical and horizontal occupies 80% and 50%, respectively. is occupying. It can be seen that the area occupied by the OSD region increases when the scanning speed is low.

OSD due to difference in scanning speed as described above
In order to adjust the difference between the areas, a method is used in which a plurality of types of font data having different character sizes are prepared in advance in the font ROM 25, and the font data is selectively used according to the scanning speed. For example, FIGS. 4 (a) and (b)
As shown in the table, the font pattern of the type A and the font pattern of the type B smaller in size than the type A are stored in the font ROM, and when the scanning speed is low, the font pattern of the type B is used. Adjusting the size makes the screen easier to read than before.

However, in the conventional character generation mechanism, the count number cleared by the address generation unit is fixed. Therefore, all the font data corresponding to the count values 1 to 16 are read out for both the type A and type B font patterns shown in FIGS. 4 (a) and 4 (b). When a type B font pattern is read as shown in b), a blank area indicated by oblique lines is also read. Similarly, the blank area is read in the example shown in FIG. Therefore, although the character size can be adjusted, there is a problem that it is inevitable that the screen becomes hard to see due to the large gap between the displayed characters.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an on-screen display device in which both the size and character spacing of on-screen characters can be adjusted according to the difference in scanning speed.

[0016]

To solve the above-mentioned problem, an on-screen display device for displaying font data read from a font ROM on a monitor for displaying video signals having different scanning speeds is provided. An address generation unit that counts a signal to generate a read address of a font ROM; a count setting unit that sets a predetermined count value according to a scanning speed of a video signal; a count value counted by the address generation unit; A comparison unit that compares the count value of the setting unit, wherein the address generation unit clears the count value of the address generation unit and newly generates the count value each time the count value of the address generation unit reaches the count value of the count setting unit. This is achieved by an on-screen display device, which starts counting.

In the present invention, each time the count value of the address generation section reaches the count value set in the count setting section, the count value is cleared. Therefore, the font R is determined by the count value set in the count setting section.
It is possible to restrict the reading of the OM. Therefore,
If the OSD area becomes large due to a change in the scanning speed, the character size can be reduced by setting a small count value in the count setting unit. that time,
The address generation unit starts a new count immediately after the count value is cleared, and reads out the font data of the next line of the display character string. You can get the screen.

[0018]

FIG. 1 is a block diagram showing a configuration of a character generating mechanism in an on-screen display device according to an embodiment of the present invention. In the figure, reference numeral 1 denotes an address generation unit that counts the horizontal synchronization signal sent from the control unit 11 of the on-screen display device shown in FIG. 2 and generates a read address of a font ROM. Is a register that sets a predetermined count value according to the following. 3 is a comparison unit that compares the count value of the address generation unit 1 with the count value set in the register 2. 4 is a line counter that counts the number of lines of the display character string. Numeral 5 denotes a digit counter for counting the number of digits of display characters, numeral 6 denotes a line counter 4 and digit counter 5.
A VRAM 7 for outputting a character code and a color control signal based on a signal from the font ROM 7, a font ROM 7 for outputting font data specified by the read address sent from the address generation unit 1, and a font ROM 8 for reading from the font ROM 7. This is a coloring section for coloring the dots constituting the character based on the font data and the color control signal sent from the VRAM 6.

The process of reading a display character string having a predetermined number of lines and a predetermined number of digits by the above-described character generation mechanism is described above with reference to FIG.
This will be described with reference to FIG. First, prior to generation of characters, the line counter 4 and the digit counter 5 are cleared, and the character code of the first line specified based on the output of the cleared line counter 4 and digit counter 5 is transmitted from the VRAM 6 to the font ROM 7. Can be In the register 2, a predetermined count value corresponding to the scanning speed sent from the control unit 11 is set.

Next, the address generator 1 starts counting the horizontal synchronization signal sent from the controller 11. As shown in FIG. 4, each time the count value increases sequentially from 1, the address generation unit 1 generates a read address corresponding to this count value and sends it to the font ROM 7. Font ROM 7
Then, the font data corresponding to the sent read address is sequentially read. The count value of the address generation unit 1 is compared with the count value set in the register 2 by the comparison unit 3.
And the count value of the address generation unit 1 is cleared. Then, a row up signal is sent from the address generation unit 1 to the row counter 4.

In the process of reading the first line of the display character string described above, if the count value 16 is set in the register 2, the comparison unit 3 sets the address generation unit 1 when the count value reaches 16. And the count value is cleared. This is the same as the reading process described in the section of the prior art.

However, when the count value 12 is set in the register 2, the count value of the address generator 1 is
When the count reaches 12, the clear signal is sent from the comparing section 3 to the address generating section 1, and the reading of the font data after the count value 13 is not performed. That is, in the conventional character generation mechanism, when the font data shown in FIG. 4B is read, the font data after the count value 13 is also read, whereas the count value is cleared to 12 in the present embodiment. The reading of the blank area of the font data is not performed.

Next, the row counter 4 stores the address
The number of lines of the display character string is advanced by one based on the line up signal sent from the VRAM 6 and the VRAM 6 is notified. The digit counter 5 advances the number of digits by one each time font data of 24 horizontal dots constituting one character is read and sends the data to the VRAM 6.
The VRAM 6 specifies a character code based on the number of lines and the number of digits sent from the line counter 4 and the digit counter 5 and sends the character code to the font ROM 7.

Next, the address generator 1 newly starts counting the horizontal synchronizing signal, and outputs the first character string of the display character string.
The same process as the reading process of the row is repeated to read the second and subsequent rows. The read font data is sent to the coloring unit 26. The coloring section 26 adds the color control information specified by the VRAM 24 to the font data and sends the character string to a monitor (not shown) to be displayed.

When the type B font pattern shown in FIG. 4B is read from the font ROM with the count value 12 set in the register 2 as described above, the blank area in the font pattern is not read. Then, the font pattern of the next line is read. Therefore, even when a font pattern having a small character size is used, there is no space between display character strings.

FIG. 6 shows an example of an on-screen display screen by the above-described character generation mechanism.
The case where the count value 20 is set in the register 2 under the same conditions as (b) is shown. As is clear from the comparison with FIG. 5B, since the length is limited to 20 dots per character, the OSD display area is reduced to be almost the same size as the OSD area shown in FIG. Since the area is not read out, it is possible to obtain an easy-to-view screen without any space between display characters.

[0027]

As described above, according to the present invention, the character size can be adjusted according to the difference in scanning speed with a simple configuration. In addition, since the character spacing can be adjusted according to the character size, the screen can be easily viewed, which is useful in displaying on-screen characters on the multi-scan monitor.

[Brief description of the drawings]

FIG. 1 is a block diagram of a character generation mechanism according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating an overall configuration of an on-screen display device.

FIG. 3 is a block diagram illustrating a configuration of a conventional character generation mechanism.

4A and 4B are diagrams for explaining a font data reading process. FIG. 4A shows a case where a type A font pattern is used, and FIG. 4B shows a case where a type B font pattern having a smaller character size than the type A is used. Is shown.

FIGS. 5A and 5B are diagrams showing examples of an on-screen display screen, wherein FIGS. 5A and 5B show cases where the scanning speeds of video signals are different.

FIG. 6 is a diagram showing an example of an on-screen display screen according to the embodiment of the present invention.

[Explanation of symbols]

1, 21 Address generation unit 7, 25 Font ROM 2 Register 8, 26 Coloring unit 3 Comparison unit 10 Video source 4, 22 line counter 11 Control unit 5, 23 digit counter 12 Character generation unit 6, 24 VRAM 13 Video processing unit 14 Switch section

Claims (1)

[Claims] 1. An on-screen display device for displaying font data read from a font ROM on a monitor displaying video signals having different scanning speeds, wherein an externally input horizontal synchronization signal is counted and a font ROM read address is counted. An address generation unit for generating a count value; a count setting unit for setting a predetermined count value according to the scanning speed of the video signal; and a comparison unit for comparing the count value counted by the address generation unit with the count value of the count setting unit. Wherein each time the count value of the address generation unit reaches the count value of the count setting unit, the address generation unit clears the count value of the address generation unit and starts a new count. On-screen display device.