JPH06339151A - Cross color reduction device in luminance signal color signal separation device - Google Patents

Abstract

(57) [Abstract] [Purpose] When a composite video signal is separated into a luminance signal and a chrominance signal, it is possible to prevent the high frequency component of the luminance signal such as a thin line from leaking into the chrominance signal. [Structure] The cross color reduction device includes a comparison circuit (1) 105,
Comparator circuit (2) 119, AND circuit (1) 112, AND circuit (2) 11
7. The logical product circuit (3) 124 and the logical product circuit (4) 118, 125 detect that the high-frequency luminance signal in the thin line portion leaks into the color signal,
In this case, the multiplier 128 suppresses this leakage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to NTSC (National
In a luminance signal color signal separation device that separates a composite signal such as a Television System Signal into component signals, a cross color reduction device in a luminance signal color signal separation device that reduces cross color that is a leak from a luminance signal to a color signal It is about.

[0002]

2. Description of the Related Art FIG. 6 is a block diagram of a conventional luminance signal / color signal separating apparatus. In FIG. 6, reference numeral 302 is a correlation detection circuit for detecting correlation in the vertical direction of signals, and 303 and 304 are 1
1H memory (1H) for delaying the horizontal period, 305 and 306 are subtractors, and 307 is a subtractor 30 according to the output of the correlation detection circuit 302.
5, 306 or a switching circuit for switching the output of 1H / 303, 308, 309 are 1/2 multipliers for subtracting the output to the switching circuit 307 from the output of 1H / 303, 310 is a high-pass filter (HPE), 311 Is a subtractor.

When an NTSC signal, for example, is input from the input terminal 301 of the conventional luminance signal / color signal separation device configured as described above, it is sequentially input to 1H.303 and 1H.304. Here, the input signal is SO1, the output of 1H · 303 is SO2, and the output of 1H · 304 is SO3. The signal currently focused on is SO2. For NTSC signals,
The color signal is modulated with the carrier color signal, and the phase of the carrier color signal is inverted for each line. Subtractor 305 is SO2
SO1 is subtracted, and the subtractor 306 subtracts SO3 from SO2. The output of the subtractor 305 is halved by the ½ multiplier 309, and the output of the subtractor 306 is halved by the ½ multiplier 308. In this way, by subtracting the signals separated by one line, the chrominance signal whose phase is inverted is preserved, and the luminance signal which is not so is attenuated. The subtractor 305 and the 1/2 multiplier 309 constitute the comb filter 1, and the subtractor 306 and the 1/2 multiplier 308
Constitutes a comb filter 2.

Here, the output of the 1/2 multiplier 309 is C1,
The output of the 1/2 multiplier 308 is C2. Switching circuit 307
In addition to C1 and C2, the signal SO2 of interest is input to. One of the three inputs is selected and the switching circuit 30
7 and the HPF 310 selects only the high frequency component including the color signal. If the switching circuit 307 uses SO
If 2 is selected, the HPF 310 extracts high frequency components, and all high frequency components become color signals. Further, when C1 or C2 is selected by the switching circuit 307, unnecessary low-frequency luminance signal components are removed from the signals separated by the comb filter. In the correlation detection circuit 302, the correlation between the signal SO2 of interest and the signal SO1 one line before and the correlation of the signal SO2 of interest and the signal SO3 one line after are examined, and when the correlation between SO1 and SO2 is strong. , The switching circuit 307 is controlled to select C1, and SO3 and SO2
If there is a strong correlation, the switching circuit 307 controls to select C2. If the correlation with the signals before and after one line is weak, the switching circuit 30 selects SO2.
Control 7

Now, the operation of this conventional luminance signal / color signal separating apparatus will be described with reference to FIGS. 7 and 8. FIG. 7 is an example of a video signal. There are colors at the top of the screen and no colors at the bottom. FIG. 8 is an enlarged view of the part where the color disappears. In FIG. 8, (a) shows the l-1 line, (b) shows the l line, and (c) shows the l + 1 line high frequency signal. Since the l-1 line and the l line have the same color, as shown in the figure, there is a carrier color signal whose phase is inverted, and since the l + 1 line has no color, there is no high frequency signal. In this case, the correlation detection circuit 302 determines that there is a strong correlation between the l line and the l-1 line, and
The switching circuit 307 is controlled so as to select C1 using the −1 line signal, and the accurate color signal shown in FIG. 8D is obtained.

[0006]

However, the conventional luminance signal / chrominance signal separation device having the above-described structure is not shown in FIG.
When the video signal of the thin line shown in is input, the high-frequency luminance signal component of the thin line becomes as shown in FIG. In FIG. 5, (a) is a high-frequency signal of the l-1 line, (b) is a high-frequency signal of the l-line, and (c) is a high-frequency signal of the (l + 1) -th line. When the thin line in FIG. 3 is inclined, as shown in FIG.
There is no correlation between the high frequency signal of the line and the high frequency signals above and below,
The switching circuit 307 has a problem in that the signal SO2 is selected and the high-frequency luminance signals are all separated as color signals, so that cross color occurs. Further, even if the correlation detection circuit 302 is adjusted and C1 or C2 is selected by the switching circuit 307, the correlation between the l line and the upper and lower signals is weak, so that the high frequency luminance signal leaks into the color signal. However, there is a problem that cross color occurs. The present invention is to solve the above-mentioned conventional problems, and when separating a composite video signal into a luminance signal and a chrominance signal,
It is an object of the present invention to realize a cross color reduction device that prevents a wide area component of a luminance signal such as a thin line from leaking into a color signal.

[0007]

In order to achieve the above-mentioned object, the present invention delays the output of a first comparator circuit for detecting that the absolute value of a color signal is smaller than a certain threshold value. A plurality of first delay circuits, a first AND circuit that calculates a logical product of consecutive outputs of the plurality of delay circuits, and a second delay circuit that delays the output of the first delay circuit. , A plurality of third delay circuits for delaying the output of the second delay circuit, a second AND circuit for obtaining a logical product of the outputs of the third delay circuit, and a color signal having an absolute value of the color signal. A second comparator circuit for detecting that the value is larger than the value; a fourth delay circuit for delaying the output of the comparator circuit by a delay amount larger than the delay amount of the first delay circuit; and a delay of the output of the fourth delay circuit. A fifth plurality of delay circuits for causing the fifth plurality of delay circuits A third AND circuit for obtaining a logical product of the outputs of the paths, two sets of a fourth logical product circuit for obtaining a logical product of the outputs of the first, second and third logical product circuits, and the fourth logical product circuit. Is a cross color reduction device including a multiplier that multiplies the average value of one output of the AND circuit of FIG.

[0008]

The cross color reduction apparatus of the present invention detects the luminance signal leaked into the color signal by the first, second, third and fourth AND circuits and suppresses the color signal in this case. To reduce cross color.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the structure of a cross color reduction apparatus according to an embodiment of the present invention. In FIG. 1, 10
2 is an absolute value circuit that outputs the absolute value of the input signal, 103, 10
6, 107, 108, 109, 110, 113, 114, 115, 116, 121, 12
Reference numerals 2 and 123 designate a 1-clock delay circuit (1D) that delays the signal for 1 clock period, 111 designates an 8-clock delay circuit (8D) that delays the signal for 8 clock periods, and 120 designates a 7-clock delay circuit that delays the signal for 7 clock periods ( 7D), 112, 117, 12
Reference numeral 4 is a logical product circuit (1), a logical product circuit (2) and a logical product circuit (3) for calculating a logical product of four inputs. 118 and 125 are AND circuits (4) that calculate the logical product of two inputs, 104 is an adder, and 105 is a comparison circuit (1) that outputs "1" when the input signal is smaller than the threshold value (1), Reference numeral 119 is a comparator circuit (2) that outputs "1" when the input signal is greater than the threshold value (2), 126 is an inverting circuit that inverts the 1-bit input signal, 127 is an average value circuit that calculates the arithmetic mean, 128 is a multiplier, 130 is an 8 clock period delay circuit (8D-
B).

When a color signal is input from the input terminal 101 of the cross color reducing device configured as described above, the absolute value circuit 102 obtains the absolute value. This absolute value is 1D 103
Then, the addition value is obtained by adding the signal delayed by one clock period at the adder 104. The 1D 103 and the adder 104 surrounded by the broken line are a low-pass filter (LP
F). The output of the LPF is input to the comparison circuit (1) 105 and compared with the threshold value (1). The squiggle value (1) is a relatively small value. When the LPF output is smaller than the squiggle value (1), "1" is output from the comparison circuit (1) 105, and otherwise "0" is output. The output of the comparison circuit (1) 105 is 1D
・ 106,107,108,109,110,8D ・ 111,1D ・ 113,1
Input to 14, 115 and 116 in order.

Here, the output of 1D · 106 is S ₀ , 1D · 10
7 output is S ₁ , 1D · 108 output is S ₂ , 1D · 109 output is S ₃ , 1D · 110 output is S ₄ , 8D · 111 output is S
₁₂ , 1D · 113 output is S ₁₃ , 1D · 114 output is S ₁₄ ,
The output of 1D · 115 is S ₁₅ and the output of 1D · 116 is S ₁₆ . If the output of the comparison circuit (1) 105 is a signal of time t, the output of 1D · 106 is time t + 1, the output of 1D · 107 is time t + 2, the output of 1D · 108 is time t + 3, 1D · 1.
The output of 09 is time t + 4, and the output of 1D · 110 is time t +
5, 8D · 111 output is time t + 13, 1D · 113 output is time t + 14, 1D · 114 output is time t + 15, 1D · 115
Is output at time t + 16, and 1D · 116 is output at time t + 17.

The outputs of the 1Ds 106, 107, 108 and 109 are input to the logical product circuit (1) 112, and the logical product is output. 1D
The outputs of 113, 114, 115 and 116 are input to the logical product circuit (2) 117, and the logical product is output. The output of the logical product circuit (1) 112 and the output of the logical product circuit (2) 117 are input to the logical product circuit (4) 118, and the logical product is obtained. This is the signal S ₀ ,
If any of S ₁ , S ₂ , S ₃ , S ₁₂ , S ₁₃ , S ₁₄ , S ₁₅ , and S ₁₆ is “0”, the output of the AND circuit becomes “0”.
That is, the signals from time t + 1 to time t + 4 and time t + 14
When the color signal component of the signal from time t + 17 is very small, that is, when there is no color signal, the output of the AND circuit (4) 118 becomes "1".

Further, the comparison circuit (2) 119 compares the output of the LPF with the threshold value (2). The skew value (2) is a relatively large value, and when the input signal is larger than the skew value (2), the output of the comparison circuit (2) 119 becomes "1". This output is 7D / 12
0, 1D, 121, 122, 123 are input in order. 7D / 12
The output of 0 is S ₆ , the output of 1D · 121 is S ₇ , the output of 1D · 122 is S ₈ , and the output of 1D · 123 is S ₉ . When the output of the comparison circuit (2) 119 is a signal at time t, this is the same as the output time of the comparison circuit (1) 105. The output of 7D · 120 is the time t + 7, and the output of 1D · 121 is the time. The output at t + 8, 1D · 122 becomes a signal at time t + 9, and the output at 1D · 123 becomes a signal at time t + 10.

The logical product circuit (3) 124 receives the signals S ₆ , S ₇ , S ₈ ,
The logical product of S ₉ is calculated and output to the logical product circuit (4) 125.
When the signals S ₆ , S ₇ , S ₈ , and S ₉ are all “1”, that is, when the low-frequency component of the absolute value of the color signal at time t + 7, t + 8, t + 9, t + 10 is larger than the shake value (2). Yes,
When the color signal level is high, the output of the AND circuit (3) 124 becomes "1".

In the logical product circuit (4) 125, the logical product of the output of the logical product circuit (4) 118 and the output of the logical product circuit (3) 124 is calculated.
The output of the AND circuit (4) 125 becomes “1” at time t +
In the case where the color signal level is above a certain level from 7 to t + 10 and there is no color signal before and after that, the period from time t + 7 to t + 10 is one cycle of the subcarrier, and the color signal is present only during this period because the original color It is considered that the luminance signal leaks (cross color) instead of the signal. The output of the AND circuit (4) 125 is input to the inverting circuit 126 and inverted. The output of the inverting circuit 126 is input to the average value circuit 127. In the average value circuit 127,
A signal obtained by dividing the added value of the input signals in a certain period by the added number is output as an addition average value. If the output of the AND circuit (4) 125 is “1”, the output of the average value circuit 127 becomes close to “0”, and the color signal input to the multiplier 128 is input.
(Cross color in this case) is close to "0". Further, in the case of the original color signal, the output of the AND circuit (4) 125 becomes "0", and in this case, the output of the average value circuit 127 becomes "1" or becomes close to "1", and the multiplier 128 The color signal of the input signal of is output as it is. In this way, the cross color reduction circuit detects and suppresses a color signal that appears for a short period as a cross color.

FIG. 2 is a block diagram of a luminance signal / color signal separation device using a cross color reduction device according to an embodiment of the present invention. In FIG. 2, 201 is a luminance signal color signal separation device (Y / C separation device) that separates a luminance signal and a carrier color signal, 202 is a cross color reduction device (cross color suppression circuit) that suppresses cross color, and 203 is subtraction. It is a vessel. In the cross color reduction device in the luminance signal color signal separation device configured as described above, when an NTSC signal is input from the input terminal 200, the Y / C separation device 201 carries a carrier color signal (hereinafter, color signal (Abbreviated) is separated. The Y / C separation device 201 may be the conventional luminance signal / color signal separation device shown in FIG. 5 or may be a simple comb filter. Now, this color signal is input to the cross color suppression circuit 202, and unnecessary cross color components are removed. Cross color suppression circuit 20
The color signal of the output of 2 is subtracted from the NTSC signal by the subtractor 203 and output from the output terminal 204 as a luminance signal. The color signal is output from the output terminal 205. The color signal output from the cross color suppression circuit 202 is subtracted from the original signal in the subtractor 203 to obtain a luminance signal.

The operation of the cross color suppression circuit 202 is
This will be described with reference to FIGS. 3 and 4. FIG. 3 shows a case where a thin line is on the screen, and FIG. 4 (A) is an enlarged view of line 1 in FIG. FIG. 4A shows an example of the waveform, and shows the sample values of the color signal at each sample point from S ₀ to S ₁₆ . The waveform of FIG. 4B shows the low frequency component of the absolute value of the color signal (output of the adder 104). In FIG. 4 (B), each time is shown below the broken line intersecting the sample point. Further, the values of the darkness value (1) and the darkness value (2) of the inputs of the comparison circuit (1) 105 and the comparison circuit (2) 119 are also shown in FIG. 4 (B). As shown in FIG. 4 (B),
The output signal of the adder 104 from time t + 7 to time t + 10 is larger than the skew value (2), and the signal before time t + 6 and the signal after time t + 12 are smaller than the skew value (1). Therefore, when the output of the comparison circuit (1) 105 is the signal at time t + 17,
The outputs of the logical product circuit (4) 118 and the logical product circuit (3) 124 are "1", and the output of the logical product circuit (4) 125 is "1", and it is determined that the cross color is generated. Then, only in this case, the output of the inverting circuit 126 becomes "0", the output of the average value circuit 127 becomes smaller than "1", and the input terminal 101 in the multiplier 128 becomes.
The color signal further input is multiplied by a signal delayed by 8 clock periods for time adjustment to suppress the color signal (cross color). In this way, when the color signal component exists for a short period of time, it is determined that the color is cross color, and the color signal is reduced to reduce the cross color. The AND circuit
The number and positions of signals input to the (1) 112, the AND circuit (2) 117, and the AND circuit (3) 124 may have configurations other than those shown in FIG.

[0018]

As is apparent from the above embodiment, the present invention detects a high-frequency luminance signal leaking into a color signal for a short period and in that case suppresses the color signal to reduce the occurrence of cross color. It has the effect of being able to.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a cross color reduction device according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a luminance signal / color signal separation device using a cross color reduction device according to an embodiment of the present invention.

FIG. 3 is a first video signal example for explaining the operation of the cross color reduction device and the conventional embodiment in the luminance signal color signal separation device of the present invention.

FIG. 4 is a signal waveform diagram for explaining the operation of the cross color reduction device in the luminance signal color signal separation device of the present invention.

5 is an enlarged view of the video signal of FIG.

FIG. 6 is a configuration diagram of a conventional luminance signal / color signal separation device.

FIG. 7 is a signal example for explaining the operation of a conventional luminance signal / color signal separation device.

FIG. 8 is an enlarged view of the video signal of FIG.

[Explanation of symbols]

101, 200, 301 ... Input terminal, 102 ... Absolute value circuit, 10
3, 106, 107, 108, 109, 110, 113, 114, 115, 116, 12
1, 122, 123 ... 1 clock delay circuit (1D), 104 ... Adder, 105 ... Comparison circuit (1), 111 ... 8 clock delay circuit
(8D), 112 ... AND circuit (1), 117 ... AND circuit
(2), 118, 125 ... AND circuit (4), 119 ... Comparison circuit
(2), 120 ... 7 clock delay circuit (7D), 124 ... AND circuit (3), 126 ... Inversion circuit, 127 ... Average value circuit, 1
28 ... Multiplier, 129, 204, 205, 312, 313 ... Output terminal,
130 color signal 8 clock period delay circuit (8D-B), 2
01 ... Y / C separation device, 202 ... Cross color suppression circuit (cross color reduction device), 203, 305, 306, 311 ... Subtractor, 302 ... Correlation detection circuit, 303, 304 ... 1 Horizontal memory (1H), 307 ... Switching circuit, 308, 309
... 1/2 multiplier, 310 ... high-pass filter (HPE).

Claims (1)

[Claims] 1. An absolute value circuit for obtaining an absolute value of a carrier color signal, a first comparison circuit for detecting that the absolute value is smaller than a certain threshold value, and a plurality of first delay circuits for delaying the output of the comparison circuit. Delay circuit, a first AND circuit for calculating the logical product of consecutive outputs of the plurality of delay circuits, a second delay circuit for delaying the output of the first delay circuit, and a second delay circuit for delaying the output of the first delay circuit. A plurality of third delay circuits that delay the output of the delay circuit, a second AND circuit that obtains a logical product of the outputs of the third delay circuits, and an absolute value of the color signal that is larger than a certain threshold value A second comparator circuit for detecting, a fourth delay circuit for delaying the output of the comparator circuit by a larger amount than the delay amount of the first delay circuit, and a fifth plurality of circuits for delaying the output of the fourth delay circuit. AND the output of the fifth delay circuit and the delay circuit of And a second AND circuit for determining the logical product of the outputs of the first, second and third AND circuits, and 1 of the fourth AND circuit. A luminance signal including an inverting circuit for inverting one output, an average value circuit for obtaining an average value of the outputs of the inverting circuit, and a multiplication circuit for multiplying the output of the average value circuit by the color signal. A cross color reduction device in a color signal separation device.