JPH1039824A - Picture signal processor and method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform the conversion of the number of scanning lines without impairing the clarity of a picture at the time of displaying the picture when the number of scanning lines is restricted by controlling when a picture signal is read out at the speed of K multiple of a writing speed and also characters of one row are expressed by N lines of horizontal scanning lines, so that all lines of the N lines of the horizontal scanning lines are read out at least one time. SOLUTION: Scanning lines to be doubled by a double-speed readout are made to be properly thinned. Here, a system displaying a teletext picture on a direct-view-type flat panel display is considered. In this case, since the number of lines of effective scanning lines is 480, a teletext picture can be contained in the display area of the display by making one line of the upper end or the lower end of the character the object of a one-time readout. The number of display scanning lines becomes 19(lines/character)×25(rows)=475(lines) because the number of scanning lines constituting one character is 19. Then, a display is performed by reading out one scanning line of the upper end of one row of a character string to be displayed one by one time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image signal processing apparatus, and more particularly to a technique for displaying an image of European teletext broadcasting on a flat panel display or the like.

[0002]

2. Description of the Related Art Television receivers using flat panel displays such as LCD panels have been commercialized. These panels usually have a limited number of horizontal scanning lines, and currently have 480 scanning lines. This is because in the display of a computer screen, a VGA (Video Graphics) having 480 effective scanning lines is used.
Array) has become the de facto standard, which is NT
This is because it is common to that of SC television broadcasting. Further, it is necessary to input image signals to these panels by converting them into a progressive scanning (non-interlaced scanning) system, instead of the interlaced scanning (interless scanning) system used in ordinary television broadcasting.

[0003] On the other hand, a case is considered where a screen of a general teletext broadcast in European television broadcast is displayed on a panel. Teletext broadcasts are broadcasts in which character information is multiplexed on a normal television image signal and sent, similarly to Japanese teletext multiplex broadcasting. This signal is composed of 250 scanning lines per field as standard. If this is to be displayed by the same non-interlace method as in the previous case, the number of scanning lines is 500 per field, and the screen to be displayed extends from the flat panel display. For this reason, a scanning line interpolation process must be performed to thin out 20 scanning lines.

[0004] However, if the scanning line interpolation processing used for a normal natural image is applied to a teletext screen, the teletext image originally having a sharp outline becomes an image blurred in the vertical direction due to linear interpolation filtering. . In addition, the conventional scanning line interpolation processing requires A / D conversion of an image signal, and a high-frequency removal filter placed in front of the A / D converter attenuates high frequency components in the horizontal direction.
This promotes blurring of the teletext image.

[0005]

As described above, when a teletext image is displayed on a flat panel display having a limited number of vertical scanning lines, the conversion of the number of scanning lines by a conventional method is as follows. There is a problem that a teletext image having a sharp outline becomes significantly unclear.

Accordingly, the present invention enables the conversion of the number of scanning lines without deteriorating the sharpness of the displayed image when displaying a teletext image on a flat panel display having a limited number of vertical scanning lines. The purpose is to do.

[0007]

An image signal processing apparatus according to the present invention converts an image signal representing a character of one line by at least N horizontal scanning lines and constituting one screen by M horizontal scanning lines. An image signal processing apparatus for converting the number of horizontal scanning lines into a number greater than M × (K−1) and less than M × K, and controls writing and reading of a field memory for converting the number of scanning lines, and a field memory. A memory controller that reads out an image signal at a speed that is K times the writing speed and that one line of characters is represented by N horizontal scanning lines in a field memory. It is characterized in that control is performed so that all of the N horizontal scanning lines are read at least once.

[0008] The image signal processing method according to the present invention comprises:
At least N horizontal scanning lines represent one line of characters, and M horizontal scanning lines are used to generate more than M × (K−1) M × K image signals using a field memory.
When converting to a smaller number of horizontal scanning lines, if the image signal is read out at K times the writing speed in the field memory and one line of characters is represented by N horizontal scanning lines, All of the N scanning lines have at least one
The time is controlled so as to be read.

In the image signal processing apparatus and method according to the present invention, the M horizontal scanning lines are converted into (K-1) times and less than K times the number of horizontal scanning lines using a field memory. At this time, all of the N scanning lines representing one line of characters are read at least once, so that image information is not lost unlike simple thinning.

In addition, a scanning line interpolation process is performed without affecting the sharpness of the displayed characters and without substantially affecting the proportions of the characters, so that the image is within the displayable range of the flat panel display. It becomes possible.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows an image signal processing apparatus according to the present invention used for processing teletext signals.

The output signal of the teletext decoder 2 is input to the image signal processing device 1. The output signal of the image signal processing device 1 is input to the flat panel display 3.

The image signal processing apparatus 1 includes an input interface 11, an output interface 12, a field memory 13, and a field memory controller 14.
It is composed of

The input interface 11 receives a horizontal synchronizing signal HP, a vertical synchronizing signal VP,
A system clock SCLK and R, G, B image signals are received. Although the R, G, and B image signals are originally analog signals, each of R, G, and B can take only two values because the current teletext broadcast displays eight colors. That is, the image signal can be handled as a 3-bit digital signal of 1 bit for each of R, G, and B. Therefore, the input interface 11 does not require an AD converter. However, a level conversion function is provided as needed.

A field memory controller 14 is a memory control signal FMCS for controlling the field memory 13 based on a horizontal synchronizing signal HP, a vertical synchronizing signal VP, and a system clock SCLK, and a horizontal synchronizing signal for non-interlace display. 2HP (two times the frequency of the HP) is generated.

The field memory 13 performs writing and reading of R, G and B image signals in accordance with a memory control signal FMCS.

The output interface 12 converts the R, G, and B image signals read from the field memory 13 from a logic level to a level that the flat panel display 3 can accept. here,
A DA converter is not required, as is the reason for not requiring an AD converter. Then, both the horizontal synchronizing signal 2HP and the vertical synchronizing signal VP generated by the field memory controller 14 are supplied to the flat panel display 3.

Next, the field memory controller 14
Will be described.

If the field memory controller 14 generates a memory control signal FMCS for reading out the image signal of the same scanning line on the field memory 13 twice in one period section of the horizontal synchronizing signal HP, the scanning line by double-speed reading is obtained. Although the interpolation process is possible, the screen to be displayed from the flat panel display 3 protrudes from the flat panel display 3 as described above. Therefore, it is considered to appropriately reduce the number of scanning lines doubled by double-speed reading.

Even if it says "thinning out", it actually means here that the scanning line read out twice from the field memory 13 and the scanning line read out only once coexist. Therefore, since a certain scanning line is not completely lost, no information is lost. This is a feature different from simple thinning with missing information. However,
If the reading is performed only once in a random manner, the proportions of the displayed characters will be lost. Therefore, a scanning line to be thinned out is determined in consideration of the teletext standard.

According to the teletext standard, one character of standard size is composed of ten scanning lines, and a character string of 25 lines can be displayed on one screen. That is, the display position of the character on the screen is determined. Further, according to the specification of the character font, it has been found that among the pixel areas provided for one character, one of the upper end and one of the lower end is used very little as a pixel of the character.
An excerpt of the character font specification is shown in FIG.

In "A" shown in FIG. 2A, it can be seen that one upper end and two lower ends are not used as character information. In “j” shown in FIG. 2B, one upper end is not used, but one lower end is used. However, since the information is read once as described above, information remains even if the lower end is used. In "[" shown in FIG. 2 (3), one upper end is used, but since it is read once, information remains.

From the above, if the upper end and / or lower end of a character is to be read once,
It is possible to thin out characters with little effect on the proportion of characters.

First, consider a system for displaying a teletext screen on a direct-view flat panel display. In this case, the number of effective scanning lines is 480, and the teletext screen can be accommodated in the display area by setting the upper or lower one of the characters to be read once. In this case, the number of display scanning lines is one.
Since there are nine lines, 19 [lines / characters] × 25 [lines] = 475 [lines].

FIG. 3 shows the concept of the reading method in this case. This figure shows a case where the upper one of the character strings to be displayed is read once. In addition, FIG.
2 to 3 show patterns of characters when the characters in FIGS. 2A to 2C are read out and displayed by the method in FIG. FIG.
In (1) and FIG. 2 (2), since the top one is not used as character information, the character proportions of FIGS. 4 (1) and 4 (2) have not changed. In FIG. 2 (3),
Since the top one is used as character information, FIG.
In (3), the top one is half-crushed, but no information is missing.

Next, consider a system for displaying a teletext screen on a projection type flat panel display. In the case of such a display device, the panel itself has 480 effective scanning lines, but the number of effective scanning lines is reduced to 448 due to overscan in an optical system that handles projection light. So, in this case, both the top one and the bottom one of the character,
That is, the teletext screen can be accommodated in the display area by setting the two lines to be read once. In this case, the number of scanning lines constituting one character is 18
Since it is a book, 18 [books / characters] × 25 [rows] = 450 [books].

FIG. 5 shows the concept of the reading method in this case. FIGS. 6 (1) to 6 (3) correspond to FIGS.
FIG. 6 shows a character pattern when the character of (3) is read out and displayed by the method of FIG. In FIG. 2A, one character at the upper end and one character at the lower end are not used as character information, and thus the proportion of the characters in FIG. 6A does not change. In FIG. 2 (2), one of the lower ends is used as character information, so that one of the lower ends is half-crushed, but information is not missing. Similarly, in FIG. 2 (3), since one upper end is used as character information, one upper end is half-crushed, but information is not missing.

In the above-described embodiment, characters of a standard size of European teletext broadcasting (one line is formed by ten scanning lines) are displayed on a VGA flat panel display. (800 dots in the horizontal direction and 600 dots in the vertical direction) can be similarly applied to the case of displaying on a flat panel display having a different horizontal scanning line number from the VGA.

In the teletext broadcasting standard in Europe, double-size characters (one line is formed by 20 scanning lines) are used. In this case, even if one line is lost, character information is lost. Therefore, the processing of the present invention is not required. Also,
When standard size characters and double size characters are mixed in one screen, the processing of the present invention may be performed only on the standard size characters.

[0029]

As described above, according to the present invention,
It is possible to display on a flat panel display without losing the clear character information of the European teletext broadcast, and with almost no loss of character font proportions. Moreover, the only hardware required is a field memory, a memory controller, and some interface circuits, which is very effective in terms of performance-price ratio.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a high-definition teletext signal display system to which the present invention is applied.

FIG. 2 is a specification example (excerpt) of a character font in a teletext broadcast standard.

FIG. 3 is a diagram illustrating a method of reading a scanning line from a field memory according to the present invention (when displaying on a direct-view flat panel display).

FIG. 4 is a diagram showing a pattern when characters in FIG. 2 are read out and displayed by the method in FIG. 3;

FIG. 5 is a diagram illustrating a method of reading a scanning line from a field memory according to the present invention (when displaying on a projection flat panel display).

FIG. 6 is a diagram showing a pattern when the characters in FIG. 2 are read and displayed by the method in FIG. 5;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Image signal processing apparatus, 2 ... Teletext decoder, 3
... flat panel display, 13 ... field memory, 14 ... field memory controller

Continuation of the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location H04N 7/03 H04N 7/08 A 7/035 17/04

Claims (6)

[Claims] 1. An image signal in which one screen character is represented by at least N horizontal scanning lines and one screen is constituted by M horizontal scanning lines is more than M × (K−1) and less than M × K. An image signal processing device for converting the number of horizontal scanning lines, comprising a field memory for converting the number of horizontal scanning lines, and a memory controller for controlling writing and reading of the field memory, the memory controller, In the field memory, when an image signal is read out at a speed K times the writing speed and one line of characters is represented by N horizontal scanning lines, all of the N horizontal scanning lines are at least used. An image signal processing device which controls so as to be read once. 2. The image signal processing apparatus according to claim 1, wherein N = 10, M = 250, and K = 2, and the number of horizontal scanning lines after the horizontal scanning line number conversion is 475 or 450. . 3. The image signal processing apparatus according to claim 2, wherein at least one of the first or tenth horizontal scanning lines is read once and the other scanning lines are read twice. 4. The image signal processing apparatus according to claim 1, wherein characters represented by 10 horizontal scanning lines and characters represented by 20 horizontal scanning lines are mixed in one screen. 5. The image signal processing apparatus according to claim 1, wherein the image signal is a binary signal of each of R, G, and B. 6. An image signal which represents a character of one line by at least N horizontal scanning lines and constitutes one screen by M horizontal scanning lines is represented by M × (K-1) using a field memory.
When converting the number of horizontal scanning lines to be larger than M × K, the image signal is read out at a rate of K times the writing speed in the field memory, and one line of characters is read by N horizontal scanning lines. When represented, the image signal processing method is controlled so that all of the N scanning lines are read at least once.