JP2558382B2 - Luminance signal / color signal separation circuit - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a luminance signal / color signal for separating a luminance signal and a color signal from an NTSC television signal used in a television receiver and a video tape recorder. It relates to a separation circuit.

[Conventional technology]

Conventionally, as a circuit that accurately separates a luminance signal and a color signal from an NTCS signal (hereinafter referred to as "Y / C separation circuit"),
The comb separation method and the logical comb separation method are widely used.

FIG. 7 is a block diagram showing the structure of a conventional comb-type separation luminance signal / color signal separation circuit.

In FIG. 7, 1 is an input terminal of 0H signal in which the input video signal is band-limited to the frequency band of color signals, and 2 and 3 are delay circuits for one horizontal scanning period (1H). 3 is connected in series. 11 is an output terminal, 24, 25,
26 is a multiplier, the input terminal of the multiplier 24 is connected to the input terminal 1, and the output terminal is connected to the adder 27. The input terminal of the multiplier 25 is connected to the output terminal of the delay circuit 2, and the output element is connected to the multiplier 27. Again multiplier
The input terminals of 26 are connected to the output terminals of the delay circuit 3, and the output terminals are connected to the output terminal 11.

Next, FIG. 8 is a waveform diagram showing an input signal and an output signal of a luminance signal / color signal separation circuit of a conventional comb separation system.

In FIG. 8, 0H is a signal in which the input video signal is band-limited to the color signal frequency band (hereinafter referred to as "0H signal"), and 1H is a signal obtained by delaying the 0H signal by one horizontal scanning period (hereinafter referred to as "1H signal"). 2H is a signal obtained by delaying the 1H signal by one horizontal period (hereinafter referred to as "2H signal") COUT is an output color signal.

Since the frequency of the color signal (fsc) and the frequency of the horizontal scanning signal (fh) have a relationship of fsc = fh (455/2), the 1H signal has the opposite phase to the 0H signal and the 2H signal, and as a result, the output The color signal has the same waveform as the 1H signal.

However, such a conventional comb-type separation Y / C separation circuit has a problem that an error occurs in the boundary region of the color signals in the vertical direction.

FIG. 9 is a waveform diagram showing an input signal and an output signal in a boundary region of color signals by a conventional comb-type separation luminance signal / color signal separation circuit.

As shown in FIG. 9, it is assumed that there are color signals in 0H and 1H but no color signals in 2H in the boundary area of the color signals. At this time, the output color signal of Cout should be the same as the 1H signal, but in this Y / C separation circuit of the comb separation system, the output color signal is 3/4 of the 1H signal. Therefore, since the luminance signal is created by subtracting the color signal from the input video signal, a pseudo luminance signal corresponding to 1/4 of the input color signal is generated.

The logical comb separation type Y / C separation circuit eliminates such an error in the boundary area of the color signal in the vertical direction, that is, the generation of the pseudo luminance signal.

This is the first Y / C separation circuit of this conventional logical comb separation method.
A description will be given based on FIG. 0 and FIG.

FIG. 10 is a block diagram showing a conventional brightness signal / color signal separation circuit of a logical comb separation system.

In FIG. 10, 1 is an input terminal of 0H signal (input video signal is band-limited to the frequency band of color signal), 2, 3
Is a delay circuit for one horizontal scanning period, 4 and 30 are multipliers, 29 is a minimum value / maximum value selection circuit, and 11 is an output terminal.

As shown in FIG. 10, the delay circuit 2 and the delay circuit 3 are connected in series. The input terminal of the delay circuit 2 is the input terminal 1
The multiplier 4 is connected to the output terminal of the delay circuit 2. The input terminal 1, the output terminal of the multiplier 4 and the output terminal of the delay circuit 3 are connected to the respective terminals 12, 13, and 14 of the minimum / maximum value selection circuit 29. The output terminal of the minimum / maximum value selection circuit 29 is connected to the input terminal of the multiplier 30.

Next, details of the minimum / maximum value selection circuit 29 will be described with reference to FIG.

In FIG. 2, 12, 13, 14 are input terminals, 15, 16, 20 are 2
Minimum value selection circuit that outputs the smaller of the two input signals, 17, 18 and 19 are maximum value selection circuits that output the larger of the two input signals, 21 is an adder, 22 is a multiplier, and 23 is an output It is a terminal.

As shown in FIG. 2, the input terminal 12 is the minimum value selection circuit 15
And an input terminal of the maximum value selection circuit 18. The input terminal 13 is connected to the inputs of the minimum value selection circuits 15 and 16 and the inputs of the maximum value selection circuits 18 and 19. The input terminal 14 is connected to the inputs of the minimum value selection circuit 16 and the maximum value selection circuit 19.
The outputs of the minimum value selection circuits 15 and 16 are the maximum value selection circuit 17
Is input to the adder 21 via the, and the outputs of the maximum value selection circuits 18 and 19 are input to the adder 21 via the minimum value selection circuit 20. The output of the adder 21 is input to the multiplier 22.

The logical comb separation type Y / C separation circuit configured as described above uses the minimum value / maximum value selection circuit 29 to determine the maximum value of the minimum value of the 0H signal and the 1H inverted signal and the minimum value of the 2H signal and the 1H inverted signal. The value is input to the adder 21, and the minimum value of the maximum value of the 0H signal and the 1H inverted signal and the maximum value of the 1H inverted signal and the 2H signal is input to the adder 21 to add them,
By inputting this added signal to the multiplier 22 and the multiplier 30, the signal whose phase of the average value is inverted is output from the output terminal 11 as a color signal. Therefore, continuous color signals as shown in FIG. Not only in the above case, but also in the boundary area of the color signal as shown in FIG. 11, the 1H signal and the output color signal have the same magnitude, and the color signal of the correct magnitude can be output.

As described above, the logical comb separation type Y / C separation circuit can eliminate the generation of the pseudo luminance signal in the boundary region of the color signal by the comb-shaped separation type Y / C separation circuit.

[Problems to be Solved by the Invention]

However, in such a conventional logical comb separation type Y / C separation circuit, a pseudo color signal is generated in the boundary area of the luminance signal. That is, as shown in FIG. 12, when there is a luminance signal in 0H and 1H but there is no luminance signal in 2H, the color signal output to the output terminal 11 should originally be zero, but the magnitude of the luminance signal is large. Pseudo-color signal of 1/2 of that was generated.

In view of the above problems, an object of the present invention is to accurately separate the luminance signal and the color signal from the NTCS signal in the boundary area of the color signal and the luminance signal without generating the pseudo luminance signal and the pseudo color signal. It is to provide a luminance signal / color signal separation circuit that can be performed.

[Means for solving the problem]

The luminance signal / color signal separation circuit of the present invention includes a logical comb color signal generation circuit, a logical comb luminance signal generation circuit, a comparison circuit, and a switching circuit.

The logical comb color signal generation circuit has the maximum value of the minimum value of 0H signal and 1H inversion signal and the minimum value of 1H inversion signal and 2H signal, and the maximum value of 0H signal and 1H inversion signal and 1H inversion signal and 2H signal. The maximum value and the minimum value signal of the signals are averaged and the phase of the logical comb color signal is inverted. Logical comb luminance signal generation circuit, 0H signal and 1H
The signal with the maximum value of the minimum value of the signal and the minimum value of the 1H signal and the 2H signal, and the maximum value of the 0H signal and the 1H signal and the 1H signal and
A logical comb luminance signal obtained by averaging the maximum value and the minimum value signal of the 2H signal is output. The comparison circuit compares the absolute value of the logical comb color signal with the absolute value of the logical comb luminance signal. The switching circuit outputs the logical comb color signal as a color signal when the absolute value of the logical comb color signal is larger than the absolute value of the logical comb brightness signal. If it is smaller than the absolute value, the signal obtained by subtracting the logical comb luminance signal from the 1H signal is output as a color signal.

[Action]

According to the configuration of the present invention, the 0H signal, the 1H inverted signal and the 2H
Input the H signal to the logical comb color signal generation circuit,
By inputting the 1H signal and the 2H signal to the logical comb luminance signal generation circuit, the logical comb color signal generation circuit outputs the logical comb color signal and the logical comb luminance signal generation circuit outputs the logical comb brightness signal. And
By comparing the absolute value of the logical comb color signal and the absolute value of the logical comb luminance signal by the comparison circuit,
If the absolute value of the logical comb color signal is larger than the absolute value of the logical comb luminance signal, the logical comb color signal is output as a color signal. Conversely, if the absolute value of the logical comb luminance signal is large, the 1H signal is output. The signal obtained by subtracting the logical comb luminance signal from is output as a color signal. That is, in the boundary area of the color signal, the logical comb color signal is output as the color signal, and in the boundary area of the luminance signal, the signal obtained by subtracting the logical comb brightness signal from the 1H signal is output as the color signal.

[Embodiment] An embodiment of the present invention will be described with reference to FIGS. 1 to 3.

FIG. 1 is a block diagram showing a luminance signal / color signal separation circuit according to an embodiment of the present invention.

In FIG. 1, reference numeral 1 is an input terminal for a 0H signal a in which an input video signal is band-limited to a color signal frequency band, and 2, 3 are delay circuits for one horizontal scanning period. Are connected in series. 4, 9 are multipliers, 5 and 6 are minimum value / maximum value selection circuits, and the minimum value / maximum value selection circuit 5 and the multiplier 9 constitute a logical comb color signal generation circuit, and the minimum value / maximum value. The selection circuit 6 becomes a logical comb luminance signal generation circuit. 7 is a comparison circuit, 10 is a switching circuit, 11
Is an output terminal, b is 1H which is obtained by delaying the 0H signal a by one horizontal scanning period.
Signal, c is a 1H inverted signal obtained by inverting the phase of 1H signal b, and d is 1H.
2H signal obtained by delaying the signal b by one horizontal scanning period is shown.

As shown in FIG. 1, the input terminal 1 is connected to the input terminal of the delay circuit 2, the minimum value / maximum value selection circuit 5 and the input terminal 12 of the minimum value / maximum value selection circuit 6. The output terminal of the delay circuit 2 has an input terminal 13 'of the minimum / maximum value selection circuit 6.
And the adder 8 are connected, and also connected to the input terminal 13 of the minimum / maximum value selection circuit 5 via the multiplier 4.
The output terminal of the delay circuit 3 is connected to the input terminal 14 of the minimum / maximum value selection circuit 5 and the minimum / maximum value selection circuit 6.
The output terminal of the minimum / maximum value selection circuit 5 is the comparison circuit 7
And the multiplier 9, and the output terminal of the minimum / maximum value selection circuit 6 is connected to the adder 8 and the comparison circuit 7. The output terminals of the multiplier 9, the adder 8 and the comparison circuit 7 are connected to the switching circuit 10.

FIG. 2 is a block diagram showing the configuration of the minimum value / maximum value selection circuit. Since the circuit configuration is the same as that of the conventional example, description thereof will be omitted. However, the input terminal of the minimum / maximum value selection circuit 5
The 1H inverted signal c is input to 13 and the 1H signal b is input to the input terminal 13 'of the minimum value / maximum value selection circuit 6.

The luminance signal / chrominance signal separation circuit configured as described above inputs the 0H signal a whose band is limited to the frequency band of the chrominance signal by the input terminal 1 and inputs the minimum value / maximum value selection circuits 5 and 6 to the input terminal 1
The 0H signal a and the 2H signal d are input to 2 and 14. In addition, the 1H inversion signal c is applied to the input terminal 13 of the minimum / maximum value selection circuit 5.
And input terminal 1 of the minimum / maximum value selection circuit 6
Input 1H signal b to 3 '.

In the minimum value / maximum value selection circuit 5 (see FIG. 2), the 0H signal a and the 1H inverted signal c are output from the minimum value selection circuit 15.
Is input to the maximum value selection circuit 17, and the minimum value B of the 1H inverted signal c and the 2H signal d from the minimum value selection circuit 16 is input to the maximum value selection circuit 17. The maximum value selection circuit 18 to 0H
The maximum value C of the signal a and the 1H inverted signal c is set to the minimum value selection circuit.
20, and the 1H inversion signal c and
The maximum value D of the 2H signal d is input to the minimum value selection circuit 20. Then, the maximum value selection circuit 17 inputs the maximum value E of the minimum value A and the minimum value B to the adder 21, and the minimum value selection circuit 20 outputs the maximum value C and the minimum value F of the maximum value D. By inputting to the adder 21, addition is performed, and by inputting to the multiplier 22 and the multiplier 9, the signals of the maximum value E and the minimum value F are averaged and the phase-inverted logical comb color signal is output. .

On the other hand, in the minimum value / maximum value selection circuit 6, the minimum value selection circuit
The minimum value A of the 0H signal a and the 1H signal b from 15 is input to the maximum value selection circuit 17, and the minimum value selection circuit 16 outputs the 1H signal b and
The minimum value B of the 2H signal d is input to the maximum value selection circuit 17. Further, the maximum value selection circuit 18 inputs the maximum value C of the 0H signal a and the 1H signal b to the minimum value selection circuit 20, and the maximum value selection circuit 19 outputs the maximum value D of the 1H signal b and the 2H signal d to the minimum value selection circuit.
Enter in 20. Then, the maximum value selection circuit 17 outputs the minimum value A
And the signal of the maximum value E of the minimum value B are input to the adder 21,
Further, the signals of the minimum value F of the maximum value C and the maximum value D from the minimum value selection circuit 20 are input to the adder 21 to add and the maximum value E and the minimum value F are input to the multiplier 22. The averaged logical comb luminance signal is output.

Then, the comparison circuit 7 outputs the absolute value and the minimum value of the logical comb color signal output from the minimum / maximum value selection circuit 5.
The magnitude of the logical comb luminance signal output from the maximum value selection circuit 6 is compared with the absolute value. The absolute value of the logical comb color signal output from the minimum / maximum value selection circuit 5 is the minimum value /
When it is larger than the absolute value of the logical comb luminance signal output from the maximum value selection circuit 6, the contact of the switching circuit 10 is switched to the multiplier 9 side to output the logical comb color signal from the output terminal 11 as a color signal. On the contrary, when the absolute value of the logical comb color signal output from the minimum / maximum value selection circuit 5 is smaller than the absolute value of the logical comb luminance signal output from the minimum / maximum value selection circuit 6, switching is performed. By switching the contact of the circuit 10 to the adder 8 side, a signal obtained by subtracting the logical comb luminance signal from the 1H signal b is output as a color signal.

FIG. 3 is a waveform diagram showing an input signal and an output signal in the boundary region of the luminance signal by the luminance signal / color signal separation circuit of one embodiment of the present invention.

As shown in FIG. 3, when the same luminance signal is present in 0H and 1H and there is no luminance signal in 2H, the logical comb color signal becomes a signal half the size of the 1H signal. The luminance signal has the same magnitude as the 1H signal. In this case, the absolute value of the logical comb luminance signal becomes larger than the absolute value of the logical comb color signal, so the switching circuit 10 falls to the adder 8 side and the output color signal becomes zero. become. That is, in the boundary area of the luminance signal, a signal obtained by subtracting the logical comb luminance signal from the 1H signal is output as a color signal. Therefore, unlike the conventional logical comb separation type Y / C separation circuit, the pseudo color signal shown in FIG. 12 does not occur.

On the other hand, in the boundary area of the color signal, the logical comb color signal is output as the color signal.

FIG. 4 is a diagram showing the frequency characteristics of the output signal of the luminance signal / color signal separation circuit of one embodiment of the present invention, and FIG. 5 is the frequency of the output signal of the conventional comb-shaped separation type luminance signal / color signal separation circuit. FIG. 6 is a diagram showing the characteristic, and FIG. 6 is a diagram showing the frequency characteristic of the output signal of the luminance signal / color signal separation circuit of the conventional logical comb separation system.

4, 5, and 6, the solid line X shows the frequency characteristic of the color signal output, and the broken line Y shows the frequency characteristic of the luminance signal output. The horizontal axis is the frequency axis, where 0 is the center frequency of the color signal, and 1 and -1 are frequencies that are (1/2) fh away from the color signal frequency (the center frequency of the luminance signal). ) Is shown. The vertical axis is decibel display.

Comparing these FIG. 4, FIG. 5 and FIG. 6, the frequency characteristic of the output signal of the luminance signal / color signal of the embodiment shown in FIG. And the chrominance signal X in the vicinity of the center frequencies 1 and −1 of the luminance signal are large. On the other hand, the frequency characteristic of the output signal by the luminance signal / color signal separation circuit of the conventional logical comb separation system shown in FIG.
The luminance signal Y has a large attenuation in the vicinity of the center frequency 0, while the color signal X has a small attenuation in the vicinity of the center frequencies 1 and −1 of the luminance signal Y. Further, the frequency characteristic of the output signal by the conventional comb-type separation luminance signal / color signal separation circuit shown in FIG. 5 is as follows: attenuation of the luminance signal Y near the center frequency 0 of the color signal X and center frequency of the luminance signal Y 1, The attenuation of the color signal X near -1 is small. As described above, the difference in the frequency characteristics of the output signals of the luminance signal / color signal separation circuit between the embodiment and the conventional example is due to the pseudo signal in the boundary region between the color signal and the luminance signal in the vertical direction by each of the luminance signal / color signal separation circuits. It is clear that it corresponds to the degree of occurrence.

〔The invention's effect〕

According to the brightness signal / color signal separation circuit of the present invention, in the boundary area of the color signal, the logical comb color signal output from the logical comb color signal generation circuit is output as the color signal, and in the boundary area of the brightness signal, By outputting the signal obtained by subtracting the logical comb luminance signal, which is the output of the logical comb luminance signal generation circuit, from the 1H signal as the color signal, the generation of the pseudo color signal and the pseudo luminance signal in the boundary area of the color signal and the luminance signal is eliminated. , It is possible to accurately separate the luminance signal and the color signal from the NTCS signal.

[Brief description of drawings]

FIG. 1 is a block diagram showing a luminance signal / color signal separation circuit according to an embodiment of the present invention, FIG. 2 is a block diagram showing a configuration of a minimum value / maximum value selection circuit, and FIG. 3 is an embodiment of the present invention. FIG. 4 is a waveform diagram showing the input signal and the output signal in the boundary region of the luminance signal by the luminance signal / color signal separation circuit of the example, FIG. 4 is a diagram showing the frequency characteristic of the output signal of the luminance signal / color signal separation circuit, FIG. 5 is a diagram showing frequency characteristics of output signals of a conventional comb-type separation luminance signal / color signal separation circuit, and FIG. 6 is a diagram showing frequency characteristics of output signals of the same luminance signal / color signal separation circuit. FIG. 8 is a block diagram showing a configuration of a conventional comb-type separation luminance signal / color signal separation circuit, FIG. 8 is a waveform diagram showing input signals and output signals of the same luminance signal / color signal separation circuit, and FIG. 9 is the same. Input in the color signal boundary area by the luminance signal / color signal separation circuit No. and waveform diagram showing an output signal, the
FIG. 10 is a block diagram showing a luminance signal / color signal separation circuit of a conventional logical comb separation method, and FIG. 11 is a waveform showing an input signal and an output signal in a color signal boundary region by the same luminance signal / color signal separation circuit. FIG. 12 and FIG. 12 are waveform diagrams showing the input signal and the output signal in the boundary region of the luminance signal by the luminance signal / color signal separation circuit. a ... 0H signal, b ... 1H signal, c ... 1H inverted signal, d ...
… 2H signal, 7 …… Comparison circuit, 10 …… Switching circuit

Claims (1)

(57) [Claims] 1. A 0H signal in which an input video signal is band-limited to a frequency band of a color signal, a 1H signal obtained by delaying the 0H signal by one horizontal scanning period, a 1H inversion signal obtained by inverting the phase of the 1H signal, and the 1H signal. A luminance signal / color signal separation circuit comprising an output circuit for outputting a 2H signal delayed by one horizontal scanning period, the minimum value of the 0H signal and the 1H inversion signal, the 1H inversion signal and the 2H signal. The minimum value and the maximum value signal, the maximum value of the 0H signal and the 1H inversion signal and the minimum value signal of the 1H inversion signal and the maximum value of the 2H signal are averaged, and the phase is inverted. A logical comb color signal generation circuit that outputs a logical comb color signal, a maximum value signal of the minimum value of the 0H signal and the 1H signal and the minimum value of the 1H signal and the 2H signal, and the 0H signal and the 1H Maximum value of the signal and the 1H signal and the above A logical comb luminance signal generation circuit that outputs a logical comb luminance signal obtained by averaging the maximum value and the minimum value signal of the 2H signal, and the magnitude of the absolute value of the logical comb color signal and the absolute value of the logical comb luminance signal. If the absolute value of the logical comb color signal is larger than the absolute value of the logical comb luminance signal, the logical comb color signal is output as a color signal, and the absolute value of the logical comb color signal is When the value is smaller than the absolute value of the logical comb luminance signal, the luminance signal / chrominance signal separation is provided with a switching circuit that outputs a signal obtained by subtracting the logical comb luminance signal from the 1H signal as a color signal. circuit.