JPH01194780A - Line-number converting method - Google Patents

Abstract

PURPOSE:To prevent the vertical swaying of a picture in cast the number of lines is converted by setting lines to be thinned out or read twice in positions apart from each other for 1-H (horizontal period) or 2-H. CONSTITUTION:In case of converting an odd-number-field of input TV signals to that of output TV signals, and in case of converting an even-number-field of input TV signals to that of output TV signals, the operation is made 'mode 1'. But in case of converting an odd-number-field of input TV signals to an even-number-field of output TV signals, and in case an even-number-field of input TV signals is converted to an odd-number-field of output TV signals, the operation is made 'mode 2'. In case of converting the number of lines from 625 to 525 by in-field interpolation, the input lines are thinned out. And the positions of these lines to be thinned out are made identical or close to each other between the mode 1 and mode 2, so that, the vertical swaying of a picture in case the mode 1 and the mode 2 are alternately repeated can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of converting the number of lines of a television signal using a memory.

[Summary of the invention]

The present invention uses memory to thin out or read certain lines of the input television signal twice, and performs intra-field line interpolation to produce an output television signal with a different number of lines than that of the human-powered television signal. In the method for converting the number of lines that form By setting the positions of the lines for thinning out or double reading in the two modes to be the same or close to each other in the vertical direction, vertical shaking of the screen can be improved.

[Conventional technology]

The NTSC system is (525 lines/60 fields), and the PAL and SECAM systems are (625 lines/150 fields).
2. Description of the Related Art A system conversion device is known for converting a system (AL system or SECAM system) or (PAL system or SECAM system→NTSC system). In the case of format conversion, it is necessary to convert the number of fields and lines.

Conversion of the number of lines using memory has conventionally been performed using the configuration shown in FIG. In FIG. 3, 1 is an input terminal to which an input television signal converted into a digital signal is supplied, and 2 is a field memory. For example, when the input television signal is of the PAL system, a specific line is not read in the field memory 2, so that an output television signal in which 625 lines are converted to 525 lines is obtained from the field memory 2.

The output signal of this field memory 2 is supplied to an IH (IH: 1 horizontal period) delay circuit 3, and the output signal of the IH delay circuit 3 is supplied to a coefficient circuit 4.

Further, a signal that does not go through the IH delay circuit 3 is supplied to the coefficient circuit 5. The coefficient circuit 4 is a circuit that multiplies by a coefficient k,
The coefficient circuit 5 is a circuit that multiplies by a coefficient (1-k). The output signals of these coefficient circuits 4 and 5 are added in an adder circuit 6 and taken out to an output terminal 7. A control circuit 8 is provided to control writing and reading of the field memory 2 and to set coefficients.

As mentioned above, if the memory is smaller than one field, interpolation between fields is impossible, so interpolation within fields as shown in FIG. 4 is performed. In FIG. 4, Ll to L7 indicate the lines of the input television signal (PAL system), when converting the odd field of the input television signal to the odd field of the output television signal, and the lines of the even field of the input television signal. The case where the field is converted into an even field of the output television signal is called mode 1. Furthermore, the case where the odd field of the input television signal is converted into the even field of the output television signal, and the case where the even field of the input television signal is converted into the odd field of the output television signal are referred to as mode 2.

In mode 1, lines L1-L7 to lines 21-25 are
is formed. For example, line I11 is (k=1/4)
and is formed by interpolation of (1/4 L 2 +3/4 L 1 ). In the case of mode 2, as shown on the right side of FIG. 4, the sequence of mode 1 is set to appear in reverse phase, and lines 21 to 115 are formed from lines L1 to L7. For example, line i1 is (
k - 3/4), and (3/4L 2 + 1/4 L
1) is formed by interpolation. In this example, the interpolation coefficient is a step.

In the field memory 2, the line that is not read is L6 (6n+6th line) in mode 1, and L3 (6n+3rd line) in mode 2. Contrary to the above, in the case of conversion from the NTSC system to the PAL system, a line is set in the field memory 2 to be read twice.

[Problem that the invention seeks to solve]

In the case of conversion from PAL system to NTSC system, changes in odd/even numbers in the output side field and changes in odd/even numbers in the input side field are as shown in Figure 5, and the above mode 1 and mode 2 will appear alternately every 6 fields. In the case of the conventional line number conversion, as shown in FIG. 6, after stopping the reading of the 6n+3 line in mode 2 until stopping reading the 61st+6 line in mode 1,
A difference of one line occurs between the pairs of lines to be read.

Therefore, when mode 1 and mode 2 are repeated alternately, on the output side, the next 61st line from the 6n+3th line
Up to the +6 line, signals located far apart on IH can be seen on the same line. Therefore, when viewing the output image on a monitor, the entire screen appears to be shaking in the vertical direction, and this frequency is 57.

This vertical shaking is easily noticeable and is unfavorable in terms of image quality.

Therefore, an object of the present invention is to provide a line number conversion method that can prevent vertical shaking of the screen.

[Means for solving problems]

The present invention uses a memory to thin out or read a specific line of a human-powered television signal twice, and performs intra-field line interpolation to produce an output television signal with a different number of lines than the input television signal. In the line number conversion method that forms , the positions of the thinned out or double read lines are the same or vertically close in the two modes.

[Effect]

Mode 1 is used to convert odd fields of an input television signal into odd fields of an output television signal, and to convert even fields of an input television signal to even fields of an output television signal. Mode 2 is defined as the case where an odd field of an input television signal is converted into an even field of an output television signal, and the case where an even field of an input television signal is converted into an odd field of an output television signal. When converting 625 lines to 525 lines by intra-field interpolation, the input lines are thinned out. By setting the positions of the thinned lines to be the same or close to each other in mode 1 and mode 2, mode 1
When Mode 2 and Mode 2 are alternately repeated, it is possible to prevent the screen from shaking in the vertical direction.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. The cause of the vertical screen shaking that occurs in the conventional line number conversion method is that the line to be thinned out or read twice is not the same line in mode 1 and mode 2. However, in line interpolation, the desirable conditions are: (1) The spatial position of the line to be interpolated is between the two base lines (no extrapolation);

■The line to be interpolated and the pair of two original lines have a (1:1) correspondence (two lines will not be interpolated from the same pair).

Therefore, the line to be thinned out or read twice cannot be set to the same line in mode 1 and mode 2.

Therefore, in this embodiment, the lines to be thinned out or read twice are set at positions IH or 2H apart.

FIG. 1 shows an example in which the present invention is applied to line number conversion (from PAL system to NTSC system). In Figure 1,
L1 to L7 indicate lines of input television signals (PAL system). The case where odd fields of the input television signal are converted to odd fields of the output television signal and the case where even fields of the input television signal are converted to even fields of the output television signal are referred to as mode 1. Furthermore, the case where the odd field of the input television signal is converted into the even field of the output television signal, and the case where the even field of the input television signal is converted into the odd field of the output television signal are referred to as mode 2.

In mode 1, the sequence of coefficients shown on the left in FIG.
is formed. That is, the coefficient k is (0, 1/4.2/4.
2/4.2/4). For example, line 21 is (
k=0) and is formed by interpolation of (4/4 L 1 ). In the case of mode 2, as shown on the right side in FIG. 1, from lines L1 to L7 to line! 1 to 15 are formed. That is, the coefficient k is (2/4.3/4.4/4
．． 2/4.2/4). For example, line 21
is (k=2/4), and (2/4L 2 +2/4
L 1 ) is formed by interpolation of L 1 ). In this example, the interpolation coefficient is the ward step.

In the field memory, by not reading, the line to be thinned out is L6 (6n+) in mode 1.
6th line), and in the case of mode 2, L5 (6th line + 5th line)
line) and set at a distance from IH.

FIG. 2 shows another example. In the example shown in FIG. 2, the coefficient k
When is mode 1, (0, 1/4.2/4°3/4
．． In mode 2, the coefficient k changes in the sequence of (3/4.3/4.2/4.1/4.2/4).
) changes in sequence. In the example shown in FIG. 2, the line to be thinned out is L6 (6n+6th line) in the first mode.
line), and in the case of mode 2, it is set as L4 (6n+4th line), which is set 2H apart.

Unlike the above-mentioned embodiments, the present invention is based on (NTSC system →
This method can also be applied to line number conversion for PAL format. Further, in order to improve the picture quality, a television system with a large number of lines has been proposed. Since the number of lines varies, for example, 1050, 1125, 1250, etc., the present invention can also be applied to conversion of the number of lines between these systems.

〔Effect of the invention〕

According to this invention, it is possible to improve the vertical shaking of the screen that occurs when the results of interpolation from IH-shifted lines appear at the same position in mode 1 and mode 2.

[Brief explanation of the drawing]

FIG. 1 is a route map showing an example of the line interpolation method according to the present invention, FIG. 2 is a route map showing another example of the line interpolation method according to the present invention, and FIG. 3 is a route map to which the present invention can be applied. A block diagram of an example of a line number conversion device, Figure 4 is a route map used to explain the conventional line number conversion method, and Figures 5 and 6 are route diagrams used to explain the problems of the conventional line number conversion method. It is. Explanation of main symbols in the drawings L1-L7: Input lines, 21-! 5: Output line, 3: IH delay circuit, 4
．． 5: Coefficient circuit. Agent Patent Attorney Tadashi Sugiura Tomokazu 1. A row, Figure 1, line number sound) Moxibustion 1 eye l each Figure 3 line, ``t-1?'+ -112 6n+1 0-1111 6n+2 0-1111110 6n+1 Kura Ryo) Mushita 4 min block Figure 6 ← White - ht-rz→ Ox

Claims (1)

[Claims] Using a memory, a particular line of the input television signal is thinned out or read twice, and a number of lines different from that of the input television signal is output by line interpolation within the field. In the method for converting the number of lines for forming a television signal, the above thinning or twice is performed for each of two modes determined by the correspondence between the odd and even fields of the input television signal and the odd and even fields of the output television signal. A method for converting the number of lines, characterized in that reading lines are set, and the positions of the thinning or double reading lines are the same or close to each other in the vertical direction in the two modes.