JPS62133886A - Luminance signal and chromaticity signal separating circuit - Google Patents

Abstract

PURPOSE:To make luminance and chromaticity separation in the same area of high correlation and separate correctly a vertical line, a horizontal line and oblique line into luminance signals and chromaticity signals, by providing a means that decides the direction intense in correlation of luminance signals. CONSTITUTION:Composite video signals 101 are applied to a delay circuit 102 of a luminance, color separation filter, and composite video signals 103-111 having specified amount of delay from the circuit 102 are inputted to multipliers 112-123 of the filter. Output of multipliers 112-123 is processed by four adders 124-127, and respective output is inputted to a switching circuit 129. Signals 103-111 from the circuit 102 are processed by subtraction and absolute value making circuits 135-138 and inputted to a minimum value selector circuit 139. The direction of high correlation of luminance signal is judged by circuits 135-138 and 139, and output of four color filters is selected and outputted by the circuit 129, and vertical lines, horizontal lines and oblique lines are separated correctly to luminance signals and chromaticity signals.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an adaptive luminance signal/chrominance signal separation filter that separates a luminance signal and chrominance signal from a color television composite signal.

[Background of the invention]

In the NTSC system, a subcarrier is used to modulate the chromaticity signal to transmit it, and the chromaticity signal is transmitted at 2.1 MHz in the 4.2% fHz video band.
It is superimposed on the 2 MHz portion from z to a. Here, there is a relationship fsc:2 fir between the subcarrier frequency fsc and the horizontal frequency f#, and the luminance signal and chromaticity signal are frequency interleaved with each other. In other words, the phase of the subcarrier is reversed at a position one line apart. Conventional luminance/chromaticity signal separation filters utilize this relationship to perform separation. In other words, the NTSC signal is transmitted for one horizontal period tH.
By delaying by (=1/fH) and adding this to the signal before the delay, the subcarrier (chromaticity signal) is canceled and only the luminance signal is obtained, and by taking the difference between the two signals, the luminance signal is obtained. The signal is canceled and only the chromaticity signal is obtained. However, this method assumes that the signals are equal one line apart, that is, that the same brightness and chromaticity exist across two lines, which generally does not hold true.

In other words, separation by this filter is performed appropriately only for screens that have small changes in the vertical direction (strong correlation).

Contrary to the above-mentioned filter, there is a method described below as an example of a filter that separates luminance and chromaticity using correlation in the horizontal direction of the screen. In other words, by delaying the Nrsc signal by a half-synchronization of the subcarrier (tsc/2C = 1/2fSC) and adding this to the signal before the delay, the subcarrier (chromaticity signal) is canceled and only the luminance signal is obtained. This method obtains only the chromaticity signal by taking the difference. In this case, it is assumed that the same luminance and chromaticity exist at positions that are half a synchronization apart on the subcarrier. Considering the band of the chromaticity signal, the I signal is 14#Hz.

Since the Q signal is o, 5 MHz, the semi-solid period of the subcarrier (
72#Hz), the chromaticity is considered to be almost constant, but since the luminance signal band is as wide as 4.2MHz, the luminance cannot be said to be constant even within this time range, and the above assumption generally does not hold. . This means that, contrary to the conventional example, only screens with small changes (strong correlation) in the horizontal direction can be accurately separated by this filter.

Furthermore, a filter that separates luminance and chromaticity by utilizing the correlation in the vertical direction and the correlation in the horizontal direction of the screen is also being considered. −
For example, 1984 Television Society National Conference 14-1
Or adaptive YC separation digital filter method 1 is mentioned. Such a filter uses the above-mentioned vertical and horizontal correlations to multiply separated luminance/chromaticity signals by weighting coefficients to produce output luminance/chromaticity signals.

However, when there is no correlation in the vertical or horizontal direction, such as with a diagonal line, there is a drawback that luminance and chromaticity cannot be separated correctly.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a luminance/chromaticity signal separation circuit that can eliminate the above-mentioned drawbacks and correctly separate luminance signals and chromaticity signals not only for vertical lines and horizontal lines but also for diagonal lines.

[Summary of the invention]

In order to achieve the above object, the present invention provides means for determining the direction in which luminance signals have a strong correlation, and performs luminance and chromaticity separation within the same region where the correlation is strong.

[Embodiments of the invention]

A concrete example of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an actual example of the 4 degree/chromaticity separation filter according to the present invention, in which 101 is a composite video signal, 102 is a delay circuit, and 103 to 111 each have a predetermined amount of delay. Composite video signal, 1
12 to 123 are multipliers, 124 to 127 are adders, 12
9 is a switching circuit, 130 is a subtracter, 131 is an output chromaticity signal, 132 is an output luminance signal, 133 and 134 are switching signals, 135 to 138 are subtraction and absolute value conversion circuits,
139 is a minimum value selection circuit.

This operation will be explained below. This embodiment basically consists of four types of chromaticity separation filters: one based on vertical correlation, one based on horizontal correlation, and two types of diagonal correlation. The correlation circuits 135 to 138 and the minimum value selection circuit 139 determine the magnitude of the correlation and select the outputs of the four chromaticity separation filters.

First, using Figure 4, it will be explained that chromaticity signals can be correctly separated in flat areas and diagonal contour areas. In Fig. 4, A-E is the composite video signal from line (t-2) to line (t+2), 1, black circle A, -
A9 etc. indicate sample points. sampling clock ba4
fscC=Vtsc). It is also assumed that the color and brightness change on the left and right sides of the dotted line.

Here, for each sample point, centering on each sample point, 3
Consider a matrix of lines x 5 dots. First, the flat portion will be explained. For example, if we focus on C7, Eo-
This includes 15 points, B, , Co, C, and D0 to D4. These points can be obtained by delay circuit 102. FIG. 2 is an explanatory diagram of the delay circuit 102, with 201 to
202 is a 1H delay circuit, 203 to 205 are 1 dot (t
6 = 1/2fsc) is a delay circuit. Also 206~
209 is a two-dot delay circuit. The nine points necessary for the present invention in the matrix are output as gold 103 to 111.

At the sample point C1, the subtraction/absolute value circuits 135 to 138 are IB, -D, 1.1CI-C31, 1, respectively.
Bo-D, l.

Find lB, -4701. Since the contour exists in the dotted line area, the 6×5 matrix centered on C1 is within the same area, and IB2 D21. IC, C51, IB6 j
)41.14-Dol are all close to 0.

Therefore, the minimum value selection circuit 139 is affected by the noise described above.
It is unclear which of the two is determined to be the minimum value, but the result is the same no matter which value is determined to be the minimum value. In other words, 1B2-
When minimizing D and l, the multipliers 112 to 114,
By the chromaticity separation filter consisting of the adder 124, pB,
, C2,Dt and 1c,−
If C8l is to be minimized, C1°c,...
multipliers 118-120 .c, to minimize 1B0-D,l. Adder 126
If +B, -D01 are to be minimized, the chromaticity separation filter consisting of multipliers 121-123 and adder 127 separates B, , C, , Do are used to diagonally separate the images, but the same chromaticity output can be obtained in both cases. If you do this operation for other points as well, you will end up with the fourth point.
It is possible to obtain a sine wave output, that is, a correct chromaticity signal, as indicated by the horizontal line in the figure.

Next, the diagonal contour will be explained. Sample point C0I
In the IC, the matrices B4-BS, C4-C8, D, ~D are evaluated. In C8, l#8-D, l
takes a value close to 0, but other L#a ”a 1.I
C5-〇? I.

1#, -D, and l take positive values. Therefore, the minimum value selection circuit 139 selects a chromaticity separation filter made up of multipliers 121 to 123 and an adder 127, and correctly performs chromaticity separation within a highly correlated region.

As mentioned above, the chromaticity signal of the 14th line can always be extracted correctly. Also, the correct chromaticity signal extracted can be extracted from the composite signal of the 14th line using the subtractor 1.
If it is subtracted at 30, a correct luminance signal can be obtained.

Next, the configuration of the minimum value selection circuit 139 will be described.

FIG. 3 is a diagram showing the minimum value selection circuit 139, and 305
, 306 is a comparison circuit for determining the size, 307゜308
309 is a selection circuit, and 309 is a determination circuit.

First, the comparison circuit 305 compares the output of the subtraction/absolute value circuit 137 and the output of the dlN-/absolute candy circuit 136, and sends the sign indicating the smaller one to the determination circuit 309 and the selection circuit 30.
7 and selects the upper 4 bits of the smaller value.
7 outputs. Similarly, the comparison circuit 306 compares the output of the subtraction/absolute value circuit 137 and the output of the subtraction/absolute value circuit 138, and sends the sign indicating the smaller one to the judgment circuit 309, and controls the selection circuit 308, The higher 4 bits of the other value are output from the selection circuit 308. Judgment circuit 309
consists of ROM, and subtraction/absolute value circuit 1!5゜1
36 1 straight 4 bits of small force output, sign indicating which is smaller, and subtraction/absolute value circuit 137° 138
The sum of the signs indicating which of the smaller output bits (1) and (1) is smaller is input as the gj lo bit. . Based on these seven human input signals, it is determined which one of the subtraction and absolute value circuits is the smallest and outputs it as a 2-pit value.

[The young fruits of invention]

As described above, the present invention enables accurate luminance/chromaticity separation not only in vertical lines and horizontal lines but also in the contours of diagonal lines, which has been difficult with conventional luminance/chromaticity separation filters.
Since it uses iJ function, dot interference and cross color interference, which were problems with conventional TV receivers, can be significantly suppressed. It is possible to improve the number of employees.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the luminance/chromaticity separation circuit according to the present invention, Fig. 2 is a block diagram showing the configuration of the delay circuit, and Fig. 3 is a block diagram showing the configuration of the delay circuit.
The figure is a block diagram showing the configuration of the minimum value selection circuit, and FIG. 4 is an fI diagram for explaining the operation. +02... Delay circuit 112-123... Multipliers 124-127/adder 129... Selection circuit 130... Subtractor 135-138... Subtraction/absolute value circuit 139...
Minimum value selection circuit, -＼ Representative patent attorney Masaru Ogawa Onyo 1 Figure blank 2 Figure 45 Figure 3g

Claims (1)

[Claims] In a luminance/chromaticity separation circuit that separates luminance signals and chromaticity signals from a digital composite color television signal, multiple directions in which separation processing is performed on a two-dimensional array consisting of multiple sample data are determined, and these multiple Luminance/chromaticity signal separation processing is performed using other sample data located in the direction and sample data targeted for the above processing.
chromaticity signal separation means, a plurality of absolute value converting means for taking the absolute value of the difference signal of the digital composite color television signal between the sample data located in the plurality of directions, and a minimum of the plurality of absolute value converting means. Luminance/color, characterized in that it is provided with a minimum value means for selecting a value and a switching means for switching and outputting the plurality of luminance/chromaticity signal separation means, and the switching means is switched by the output signal of the minimum value selection means. degree signal separation circuit.