JPS63296593A - Luminance signal/chrominance signal separator circuit - Google Patents

Abstract

PURPOSE:To improve the picture quality by detecting the horizontal and vertical correlation by a correlation detection circuit and allowing a selection means to select a filter means having larger correlation and detecting a stripe pattern with a short period by a stripe detection circuit thereby stopping the output of the filter means. CONSTITUTION:When the horizontal correlation is large by the selection of a selection means 26 by the detection output of the correlation detection circuit 20, a chrominance signal is obtained via horizontal direction filter means 11, 12, 13, 16 and when the vertical correlation is large, a chrominance signal is obtained through the vertical filter means 10, 12, 14, 15 to reduce the production crosstalk and the vertical direction filter means is not selected in the detection of the stripe with a short period by the stripe detection circuit 40, and a selection means 26 is controlled so as not to obtain the output of the horizontal vertical filter means. Thus, the picture quality is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a luminance signal and chrominance signal separation circuit for separating a luminance signal and a chrominance signal from a standard composite color television signal.

[Conventional technology]

In the current color television standard system, brightness information and color information are sent as a frequency-multiplexed composite signal, so it is necessary for the receiver to correctly separate this information into brightness and color signals.

On the other hand, in recent years, sampling of video signals has been considered in order to improve the image quality of televisions.

For example, when an NTSC composite color television signal is synchronously sampled at a sampling frequency f that is four times the color subcarrier frequency f3c, the sampled video signal becomes as shown in Figure 3. . This takes line n as an example, and the phase of the color subcarrier is 9 between adjacent sample points on the same line, such as sample point S and adjacent sample point S.
0' different.

Focusing on this phase, sample points S1 and 82 are in opposite phases.

Sample points S1 and 83 are in phase. This sampling series is the fourth
Take a two-dimensional array as shown in the figure. In the case of the NTSC system, the phase is reversed between adjacent lines, so the sampling point S,
and 84+ sample points S2 and S6, etc., also have an antiphase relationship. In the figure, sample points in the same phase are represented by the same symbols, and out-of-phase points are represented by differences in white and black. This separates the luminance signal and chrominance signal, but if the separation is not complete, crosstalk occurs between the respective signals, resulting in image quality deterioration such as cross color and dot interference. Therefore, in the past, the Institute of Television Engineers TEBS106-1 "Improving TV picture quality through digital signal processing".

As shown in Japanese Patent Application Laid-Open No. 61-88690, a method is considered in which the correlation between sample points is taken and horizontal and vertical band pass filters are selected to separate the luminance signal and the color signal. was.

By the way, in the case of horizontal stripes, when the horizontal correlation and vertical correlation are the same, the horizontal and vertical filters are switched for each sample point due to the influence of noise, etc., causing cross color and dot interference. causing outbreaks, etc. So K
By adding a constant to the vertical difference signal, priority is given to the horizontal direction and the above interference is prevented. Of course,
In this case, priority may be given to the vertical direction by adding a constant K to the horizontal difference signal.

[Problem that the invention seeks to solve]

However, in the conventional method, vertical stripes whose repetition period is close to the color subcarrier frequency rsc of 3.58 MHz, or 1
In cases such as horizontal stripes where black and white are reversed for each line, this method cannot be distinguished and is detected as a color signal, resulting in cross-colors, which is a drawback.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a novel luminance signal/chrominance signal separation circuit that eliminates the above-mentioned drawbacks.

[Means for solving problems]

Means for achieving the above object in the present invention is provided in a luminance signal and chrominance signal separation circuit that separates a luminance signal and a chrominance signal from a composite color television signal sampled at a predetermined multiple of a color subcarrier frequency. horizontal filter means for obtaining a color signal from the sampled signal at the horizontal sampling point; vertical filter means for obtaining the color signal from the sampled signal at the vertical sampling point; The correlation in the horizontal direction is increased by a correlation detection circuit for detecting the correlation in the horizontal direction and the vertical direction of the image, a detection circuit for detecting short-period stripes in the image, and the correlation detection circuit. When a detection output is obtained, the horizontal filter means is selected to obtain a color signal, and when a detection output with a large correlation in the vertical direction is obtained, the vertical filter means is selected to obtain a color signal; When the stripe detection circuit obtains a detection output of the short-period stripes, the horizontal and vertical filter means are not selected together so that the output signals of the horizontal and vertical filter means are not obtained. The present invention relates to a luminance signal/chrominance signal separation circuit characterized by comprising a selection means.

[Effect]

In the above configuration, when the correlation in the horizontal direction is large, a 2-steep signal is obtained via the horizontal filter means, and when the correlation in the vertical direction is large, the vertical signal is selected by the selection means based on the detection output of the correlation detection circuit. In addition to obtaining a color signal through a filter means to reduce the occurrence of crosstalk, the horizontal and vertical filter means are not selected together in the short-period stripe detection circuit by the stripe detection circuit, and the horizontal and vertical filters are selected. This makes it possible to control the selection means so as not to obtain the output of the means.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings. FIG. 1 shows a luminance signal and chrominance signal separation circuit.

■ is an input terminal, 2 is the first 2 sample period delay circuit, 3 is the second 2 sample period delay circuit, 4 is the first 1-4 sample period delay circuit, 5 is the third 2 sample period delay circuit Delay circuits, 6 is a fourth 2-sample period delay circuit, 7 is a second 1-line-4-sample period delay circuit, 8 is a fifth 2-sample period delay circuit, and 9 is a sixth 2-sample period delay circuit. These are connected in series. 10 is a multiplier for inverting the phase of the output of the first two-sample period delay circuit 2 and reducing the output to 1/4; 11;
12 is a multiplier for inverting the phase of the output of the first 1 line-4 sample period delay circuit 4 and reducing it to 1/4;
A multiplier for reducing the output of the sample period delay circuit 5 to 172, 13 a multiplier for inverting the phase of the output of the fourth two sample period delay circuit 6 and reducing it to 1/4, and 14 a multiplier for reducing the output of the fourth two sample period delay circuit 6 to 1/4. This is a multiplier for inverting the phase of the output of the two-sample period delay circuit 8 and reducing it to 1/4.

The outputs of the multipliers 10, 12, and 14 are added by an adder 15 to form a vertical bandpass filter (<C-shaped filter) which is vertical filter means. The outputs of the multipliers 11, 12, and 13 are added together in an adder 16 to form a horizontal bandpass filter, which is horizontal filter means.

20 is a correlation detection circuit for detecting correlation from horizontal and vertical variation amounts, and 21 is a correlation detection circuit for subtracting the output of the multiplier 10° 14 to detect the first two-sample period delay circuit 2 and the fifth two-sample period delay circuit 2. a subtracter for obtaining the difference between the outputs of the period delay circuit 8; 22, an absolute value circuit for obtaining the absolute value of the output of the subtracter 21; 23;
is obtained by subtracting the outputs of multipliers 11 and 13 to obtain the first line -
4 samples) ■ Interval delay circuit 4 and fourth 2-sample period delay circuit 6
24 is an absolute value circuit for obtaining the absolute value of the output of the subtracter 23, and 25 is a comparator for comparing the outputs of these absolute value circuits 22 and 24. 26 is a data selector forming a selection means, terminal A is connected to a reference level generator 27, terminal B is connected to the output of the adder 15 corresponding to the output of the vertical band pass filter, and terminal B is connected to the output of the adder 15 corresponding to the output of the vertical band pass filter. C is connected to the output of the adder 16, which corresponds to the output of the horizontal bandpass filter. A color signal output terminal 29 is connected to the terminal Y of the data selector 26 via a 3.58 MHz band-pass filter. Co.

CI is a control terminal of the data selector 26, and the output of the comparator 25 is connected to the control terminal C0. Here, the selection states by the control terminals Co and CI of the data selector 26 are as shown in Table 1 below.

The first table 30 is a luminance signal output terminal, and a signal is supplied through a subtracter 31 for obtaining the difference between the output of the bandpass filter 28 and the output of the third two-sample period delay circuit 5. It has become. 32 is a compensation delay circuit for compensating for phase shift in the bandpass filter 28.

゛ 40 is a stripe detection circuit, which detects the absence of a striped pattern with a short period, and sends this detection output to the data selector 26.
The signal is supplied to the control terminal C4 of the control terminal C4. 41 is an absolute value circuit for subtracting the outputs of the third 2-sample period delay circuit 5 and the sixth 2-sample period delay circuit 9 to obtain an absolute value, and 43 is a third 2-sample period delay circuit. A subtracter 44 subtracts the outputs of the circuit 5 and the second 1-line-4 sample delay circuit 7 to obtain an absolute value, and 45 is a third 2-sample period delay circuit 5 and a second 2-sample period delay circuit 5. An absolute value circuit 47 subtracts the output of the sample period delay circuit 3 using a subtracter 46 to obtain an absolute value; This is an absolute value circuit for obtaining the absolute value by subtraction. 49 is an adder, which is an absolute value circuit 4
The output of 1.43 is added and supplied to the terminal A of the first switch circuit 50. 51 is an adder which adds the outputs of the absolute value circuits 41 and 45 and supplies the sum to the terminal B of the first switch circuit 50. 5
2 is an adder which adds the outputs of the absolute value circuits 45 and 47 and supplies the sum to the terminal A of the second switch circuit 53. 54 is an adder which adds the outputs of the absolute value circuits 43 and 47 and supplies the sum to the terminal B of the second switch circuit 53. These first. Second
Terminals Y of the switch circuits 50 and 53 are connected to comparators 54 and 55, respectively, and are compared with the dark value level of the dark value level generating circuits 56 and 57.

. Also, 1st. Control of the second switch circuit 50.53? 1■
The output of the comparator 25 of the correlation detection circuit 20 is supplied to the terminal C. This first. The operating states of the second switch circuits 50 and 53 according to the control terminal C are shown in Table 2 below.

The second table 58 is an OR circuit which supplies the outputs of the comparators 54 and 55 to the control terminal C of the data selector 26 as the detection output of the fringe detection circuit 40.

Next, the operation of the embodiment of the present invention described above will be explained with reference to FIG. In Fig. 2, for convenience of explanation, Fig. 3,
The sample points of △ and Mu in FIG. 4 are omitted. Now, when sample point S is supplied to input terminal 1, sample points S11 . S? ...
S is obtained. Therefore, the color signal C is obtained at the terminal B where the output of the vertical band pass filter is obtained and the terminal C where the output of the horizontal band pass filter is obtained. And this is data selector 26. The signal is supplied to a color signal output terminal 29 via a bandpass filter 28.

On the other hand, the luminance signal Y is the signal Y+C of the sample point S, and the color signal C
The subtracter 31 subtracts the resulting signal from the luminance signal output terminal 30.

When separating the color signal C, if the amount of change in the horizontal direction of the image is smaller than the amount of change in the vertical direction, a horizontal band-pass filter is used to separate the color signal C, and the amount of change in the vertical direction is smaller than that in the horizontal direction. This is done using a vertical band-pass filter to prevent image deterioration.

Here, the horizontal change amount, I, is DH' = l 54
S6 l, vertical direction change amount Dv is Dv = + sg
'SsI.

Therefore, the signal supplied to the C3 terminal, which will be described later, is “φ”.
Assuming that, the data selector 26 selects the terminal C signal when D+l<Dv, and selects the terminal B signal when DI4>Dv.
It is sufficient if the signal is selected. The control of this data selector 26 is based on the output of the absolute value circuit 22 in the horizontal direction, I=l54-3&l, and the absolute value circuit 2 in the vertical direction.
The output Dv=lSz-8a1 of 4 is compared by the comparator 25, and the output is made to correspond to "1" or "O" in Table 1 above. That is, when DH<Dv, the data selector 26 receives a signal of "1" from the control terminal Go and selects the terminal C, and when DH>Dv, the signal of "1" is not obtained from the control terminal C0. Terminal B is selected because it corresponds to a “0” signal.

As shown in FIG. 2A, when the image does not change drastically and is relatively uniform, the sample point S is compared to the sample point S+.

S x, S 1. Since Sq are in the same phase and their respective signal levels are the same or almost the same, the horizontal change ff1D, I.

The vertical change ff1Dv becomes zero or a value close to zero,
A horizontal bandpass filter and a vertical bandpass filter are selected as described above. In this case, both outputs have approximately the same value and no problem occurs. However, as shown in FIG. 2B, if the video signal has vertical stripes and the period is close to the color subcarrier frequency rsc of 3.58 MHz, the horizontal and vertical changes i1p++.

Since Dv are both close to zero, the outputs of the horizontal and vertical band pass filters are randomly selected due to noise or the like. On the other hand, the same applies to the case of horizontal stripes in which black and white are reversed every line as shown in FIG. 2C. Therefore, the presence or absence of a color signal cannot be determined, resulting in cross color.

However, the vertical stripes shown in FIG. 2B are detected by the stripe detection circuit 40 in FIG. 1, and the outputs of the horizontal and vertical bandpass filters are stopped by the data selector 26. This operation will be explained below. In the case of this vertical stripe, for sample point S, sample points S1, S3. S
? , S 9 are at different levels. Therefore, the adder 51 has the level STV of the first stripe.

5TVI = I 5l-3sl + l S7-35
1, and the level s'rvz of the second adjacent stripe to the adder 54 is 5TVz = 13l-3SI + l59-3SI
obtained as. On the other hand, since the correlation in the vertical direction is detected by the correlation detection circuit 20, the first and second switch circuits 50.53 select the terminal B, and the 5TV1.5TV
2 (No. 8 level) is supplied to comparators 54 and 55. If at least one of the signal levels is greater than the dark value, the comparators 54 and 55 send out a detection output indicating that there is a vertical stripe in the output of the OR circuit 58. Therefore, , the data selector 26 selects the terminal A and sends the reference level to the terminal Y when a signal of "1" is supplied to the control terminal C1.Therefore, there is no color signal C and only the luminance signal is sent to each output terminal 30. supplied to

In addition, in the case of horizontal stripes shown in FIG. 2C, the stripe detection circuit 4
0, the presence of horizontal stripes is detected, and the data selector 26 stops the outputs of the horizontal and vertical bandpass filters, as in the case of vertical stripes described above. This means that the adder 49 has the first fringe level STH, 5THI = 1 3l-3SI + l S:
+-3sl, and the level 5TH2 of the second stripe adjacent to the first is 5THz = l S? 3SI + l Sq
Obtained as Ssl. On the other hand, since the horizontal correlation is detected by the correlation detection circuit 20, the first and second switch circuits 50 and 53 select the terminal A, and STH, .
The signal level of S'TH, is supplied to comparators 54 and 55. The comparators 54 and 55 detect that the value is larger than the threshold value and send out a detection output in the form of horizontal stripes. Since the control terminal C1 is "1", the data selector 26 selects the terminal A, stops transmitting the color signal, and transmits only the luminance signal.

〔Effect of the invention〕

According to the present invention, the correlation detection circuit detects horizontal and vertical correlations, and the selection means operates to select the filter means with a larger correlation to obtain a color signal, thereby eliminating cross colors due to crosstalk, etc. In addition, the stripe detection circuit detects the presence or absence of a striped pattern with a short period and controls the selection means so that when there is a striped pattern, the output of the filter means is not obtained. The brightness signal has improved image quality because it does not affect the brightness signal.

A color signal separation circuit can be provided. Further, according to the present invention, since the luminance signal 9 and the sudden signal can be separated within the field, a special field memory is required.

It also has the effect that a motion compensation circuit is not required and the circuit can be made inexpensive.

[Brief explanation of drawings]

Fig. 1 shows a luminance signal 2 sudden signal separation circuit showing an embodiment of the present invention, and Fig. 2 shows an arrangement on a screen of a sampled signal sequence of an NTSC system composite color television signal to provide an explanation of the invention. Figure A is for the case where the image changes are uniform, Figure B is for the case of vertical stripes with a short period, Figure 0 is for the case of horizontal stripes for each line, four times, and Figure 3 is for the case of NTSC system composite color. FIG. 4 is an explanatory diagram showing sampling points when sampling a television signal. FIG. 4 is an explanatory diagram showing the arrangement of the sampled signal sequence on the screen in FIG. 1... Input terminal 2... First 2 sample period delay circuit 3... Second 2 sample period delay circuit 4... First 1 line-4 sample period delay circuit 5...
Third 2-sample period delay circuit 6...Fourth 2-sample period delay circuit 7...Second 1-line-4-sample period delay circuit 8...
Fifth two-sample period delay circuit 9...Sixth two-sample period delay circuit 20...Correlation detection circuit 26...Data selector (selection means) 27...Reference level generator 29...Color Signal output terminal 30... Forest signal output terminal 40... Stripe detection circuit

Claims (1)

[Claims] A luminance signal and chrominance signal separation circuit separates a luminance signal and a chrominance signal from a composite color television signal sampled at a predetermined multiple of the color subcarrier frequency. horizontal filter means for obtaining a signal, vertical filter means for obtaining a color signal from the signal of the sampled vertical sampling points, and detecting correlation in the horizontal and vertical directions of the sampled image. a correlation detection circuit for detecting short-period stripes in an image; a detection circuit for detecting short-period stripes in an image; and a detection circuit for selecting the horizontal filter means when the correlation detection circuit obtains a detection output with a large correlation in the horizontal direction. to obtain a color signal, and when a detection output with a large correlation in the vertical direction is obtained, the vertical filter means is selected to obtain a color signal, and the stripe detection circuit detects the short-period stripes. and a selection means for not selecting both the horizontal and vertical filter means and not obtaining output signals of the horizontal and vertical filter means when output is obtained. Signal and color signal separation circuit.