JPH04103291A - Luminance signal chrominance signal separator circuit - Google Patents

Abstract

PURPOSE:To eliminate the generation of a pseudo chrominance signal and a pseudo luminance signal at a border area by using a logical comb chrominance signal as a chrominance signal at a border area of the chrominance signal and using a signal resulting from subtracting a logical comb luminance signal from a 1H signal at a border area of the luminance area as the chrominance signal and outputting the result. CONSTITUTION:A signal resulting from band-limiting an input video signal to a frequency band of a chrominance signal (OH signal), an inversed signal resulting from retarding the OH signal by one horizontal scanning period (1H signal), and a signal resulting from retarding the 1H signal by one horizontal scanning period (2H signal) are fed to a logical comb chrominance signal generating circuit 5, and the OH signal, the 1H signal and the 2H signal are fed to a logical comb luminance signal generating circuit 6, and a logical comb chrominance signal and a logical comb luminance signal are respectively outputted. Then a comparator circuit 7 compares them, and outputs the logical comb chrominance signal when the absolute value of the logical comb chrominance signal is larger than that the logical comb luminance signal and outputs a signal resulting from subtracting the logical comb luminance signal from the 1H signal as a chrominance signal when the absolute value of the logical comb luminance signal is larger than that of the logical comb chrominance signal. Thus, a pseudo chrominance signal and a pseudo luminance signal are not generated at a border area.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a luminance signal/chrominance signal that separates a luminance signal and a chrominance signal from an NTSC television signal used in television receivers and video tape recorders. It concerns a separation circuit.

[Conventional technology]

Conventionally, a comb separation method and a logical comb separation method have been widely used as circuits for accurately separating luminance signals and color signals from NTC3 signals (hereinafter referred to as rY/C separation circuit J).

FIG. 7 is a block diagram showing the configuration of a conventional comb-shaped separation type luminance signal/chrominance signal separation circuit.

In FIG. 7, 1 is an input terminal for the 0H signal which band-limits the input video signal to the frequency band of the color signal, 2.3 is a delay circuit for one horizontal scanning period (1H);
and delay circuit 3 are connected in series. 11 is an output terminal,
24, 25, and 26 are multipliers, the input terminal of multiplier 24 is connected to input terminal 1, and the output terminal is connected to adder 27.
connected to. Further, the input terminal of the multiplier 25 is connected to the output terminal of the delay circuit 2, and the output terminal is connected to the multiplier 27. Further, the input terminal of the multiplier 26 is connected to the output terminal of the delay circuit 3, and the output terminal is connected to the output terminal 11.

Next, FIG. 8 is a waveform diagram showing input signals and output signals of a luminance signal/chrominance signal separation circuit using a conventional comb separation method.

In FIG. 8, 0H is a signal obtained by band-limiting the input video signal to the frequency band of the color signal (hereinafter referred to as r0H signal).

), 1H is a signal obtained by delaying the 0H signal by one horizontal scanning period (
Hereinafter referred to as "r1H signal". ), 2H is a 1H multiplied signal delayed by one horizontal period (hereinafter referred to as "r2H signal").
, C0UT indicate output color signals.

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

However, such a conventional Y/C separation circuit using a comb-type separation method has a problem in that errors occur in the boundary area of color signals in the vertical direction.

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

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

A Y/C separation circuit using a logical comb separation method eliminates such errors in the vertical color signal boundary area, that is, the generation of pseudo luminance signals.

This conventional logical comb separation type Y/C separation circuit will be explained based on FIGS. 10 and 2.

FIG. 10 is a block diagram showing a conventional logical comb separation type luminance signal/chrominance signal separation circuit.

In FIG. 10, 1 is an input terminal for the 0H signal (a signal obtained by band-limiting the input video signal to the frequency band of the color signal), 2
．． 3 is a delay circuit for l horizontal scanning period, 4.30 is a multiplier, 29 is a minimum value/maximum value selection circuit, and 11 is an output terminal.

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

Further, the output terminal of the minimum value/maximum value selection circuit 29 is connected to the input terminal of a multiplier 30.

Next, details of the minimum value/maximum value selection circuit 29 will be explained based on FIG. 2.

In FIG. 2, 12, 13.14 are input terminals, 15.
16.20 is a minimum value selection circuit that outputs the smaller of the two input signals; 17. 18. 19 is a maximum value selection circuit that outputs the larger of two input signals, 21 is an adder, 22 is a multiplier, and 23 is an output terminal.

As shown in FIG. 2, the input terminal 12 is connected to the minimum value selection circuit 1.
5 and the input terminal of the maximum value selection circuit 18.

Input terminal 13 is connected to the input of minimum value selection circuit 15.16 and to the input of maximum value selection circuit 18.19. The input terminal 14 is connected to a minimum value selection circuit 16 and a maximum value selection circuit 19.
connected to the input of and minimum value selection circuit 15.16
The outputs of the maximum value selection circuits 18 and 19 are input to the adder 21 via the maximum value selection circuit 17, 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 this adder 21 is input to a multiplier 22.

The Y/C separation circuit of the logical comb separation method configured in this way uses the minimum value/maximum value selection circuit 29 to select the maximum value between 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 inputted to the adder 21, and this added signal is added. Multiplication is calculator 2
2 and the multiplication are input to the calculator 30, and a signal with the phase of the average value inverted is output from the output terminal 11 as a color signal. As shown in FIG. 11, even in the boundary area of the color signal, the size is the same as that of the 1H times signal output color signal, and a color signal of the correct size can be output.

In this way, the logical comb separation type Y/C separation circuit can eliminate the generation of pseudo luminance signals in the boundary areas of color signals caused by the comb separation type Y/C separation circuit.

[Problem to be solved by the invention]

However, in such a conventional logical comb separation type Y/C separation circuit, a false color signal is generated in the boundary area of the luminance signal. In other words, as shown in Fig. 12, if 0H and 1H have a luminance signal, but 2H does not have a luminance signal, the color signal output to the output terminal 11 should be zero, but the magnitude of the luminance signal A false color signal of 1/2 of the size was generated.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to accurately separate a luminance signal and a chrominance signal from an NTC8 signal without generating a pseudo-luminance signal or a pseudo-color signal in the boundary area between the chrominance signal and the luminance signal. The object of the present invention is to provide a luminance signal/chrominance signal separation circuit that is capable of separating a luminance signal and a color signal.

[Means to solve the problem]

The luminance signal/chrominance 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 generates a signal of the maximum value between the minimum value of the 0H signal and the 1H inverted signal, the minimum value of the 1H inverted signal and the 2H signal, the maximum value of the 0H signal and the 1H inverted signal, the 1H inverted signal, and the 2H inverted signal. The maximum signal value and the minimum value signal are averaged, and a logical comb color signal whose phase is inverted is output. The logical comb brightness signal generation circuit is 0
The signal of the maximum value between the minimum value of the H signal and 1H times signal and the minimum value of the 1H times signal and 2H signal, and the signal of the minimum value of the maximum value of the 0H signal and 1H times signal and the maximum value of the 1H times signal and 2H signal outputs a logical comb luminance signal that is the average of the The comparison circuit compares the absolute value of the logical comb color signal and 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, and 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 value, 1H
A signal obtained by subtracting the logical comb luminance signal from the doubled signal is output as a color signal.

[Effect]

According to the configuration of the present invention, the 0H signal, the 1H inverted signal, and the 2H signal are input to the logical comb color signal generation circuit,
By inputting the H signal, 1H times signal, and 2H signal to the logical comb brightness signal generation circuit, the logical comb color signal generation circuit outputs the logical comb color signal, and the logical comb brightness signal generation circuit outputs the logical comb brightness signal. do. Then, by comparing the absolute value of the logical comb color signal and the absolute value of the logical comb luminance signal using a 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, and conversely, when the absolute value of the logical comb luminance signal is large, a signal obtained by subtracting the logical comb luminance signal from the 1H signal is output as the color signal. In other words, 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,
A signal obtained by subtracting the logical comb luminance signal from the 1H multiplied signal is output as a color signal.

〔Example〕

An embodiment of the present invention will be described based on FIGS. 1 to 3.

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

In Fig. 1, 1 is an input terminal for a 0H multiplied signal obtained by band-limiting the input video signal to the color signal frequency band, and 2 and 3 are 1
This is a delay circuit for the horizontal scanning period, and the delay circuit 2 and the delay circuit 3 are connected in series.

4.9 is a multiplier, 5 and 6 are minimum value/maximum value selection circuits, the minimum value/maximum value selection circuit 5 and the multiplier 9 constitute a logical comb color signal generation circuit, and The value/maximum value selection circuit 6 becomes a logical comb luminance signal generation circuit.

7 is a comparison circuit, lO is a switching circuit, 11 is an output terminal, and b is a 1H times signal C which is the 0H times signal delayed by one horizontal scanning period.
d indicates a 1HH signal obtained by inverting the phase of the H times signal, and d indicates a 2H signal obtained by delaying the 1H times signal by one horizontal scanning period.

As shown in FIG. 1, the input terminal 1 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 are connected to the input terminal l. The output terminal of the delay circuit 2 is connected to the input terminal 13 of the minimum value/maximum value selection circuit 6.
' and the adder 8 are connected, and the multiplier is connected to the input terminal 13 of the minimum value/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 value/maximum value selection circuit 5 and the minimum value/maximum value selection circuit 6. Further, the output terminal of the minimum value/maximum value selection circuit 5 is connected to a comparator circuit 7 and a multiplier 9, and the output terminal of the minimum value/maximum value selection circuit 6 is connected to an adder 8 and a comparison circuit 7. And the multiplication is the calculator 9. The output terminals of adder 8 and comparison circuit 7 are connected to switching circuit 10.

FIG. 2 is a block diagram showing the configuration of the minimum value/maximum value selection circuit, and since the circuit configuration is the same as that of the conventional example, a description thereof will be omitted. However, input terminal 1 of minimum value/maximum value selection circuit 5
3, a 1H anti-inversion signal tone is inputted, and an input terminal 13 of the minimum value/maximum value selection circuit 6 is inputted with a 1H times signal.

The luminance signal/chrominance signal separation circuit configured in this manner inputs the 0H multiplied signal band-limited to the frequency band of the color signal through the input terminal 1, and inputs the 0H multiplied signal band-limited to the frequency band of the color signal through the input terminals 12 and 14 of the minimum value/maximum value selection circuits 5 and 6. The 0H multiplied signal and the 2H signal d are input to the 0H signal and the 2H signal d. Further, a 1H anti-inverted signal tone is inputted to the input terminal 13 of the minimum value/maximum value selection circuit 5, and a 1H times signal is inputted to the input terminal 13' of the minimum value/maximum value selection circuit 6.

Then, in the minimum value/maximum value selection circuit 5 (see Fig. 2),
The minimum value A of the 0H multiplied signal and the 1H anti-inversion signal tone is input from the minimum value selection circuit 15 to the maximum value selection circuit 17, and the minimum value B of the 1H anti-inversion signal tone and the 2H signal d is inputted from the minimum value selection circuit 16 to the maximum value. It is input to the selection circuit 17. Further, the 0H times signal and the 1H anti-inverted signal tone maximum value C are input from the maximum value selection circuit 18 to the minimum value selection circuit 20, and the maximum value selection circuit 19
The maximum values of the 1H anti-inversion signal tone and the 2H signal d are input to the minimum value selection circuit 20. And maximum value selection circuit 1
7 to the maximum value E of the minimum value A and the minimum value B to the adder 2! and input the maximum value C from the minimum value selection circuit 20.
By inputting the signals of the minimum value F and the maximum value to the adder 21, the signals of the maximum value E and the minimum value F are averaged. and outputs a logical comb color signal with the phase reversed.

On the other hand, in the minimum value/maximum value selection circuit 6, the minimum value selection circuit 1
The minimum value A of the 0H times signal and the 1H times signal d is inputted from the minimum value selection circuit 16 to the maximum value selection circuit 17.
Enter. Also, the maximum value C of the 0H times signal and the 1H times signal is input from the maximum value selection circuit 18 to the minimum value selection circuit 20, and the maximum value C of the 1H times signal and 2H signal d is inputted from the maximum value selection circuit 19 to the minimum value selection circuit. Enter 20.

Then, the signal of the maximum value E of the minimum value A and the minimum value B is inputted from the maximum value selection circuit 17 to the adder 21, and the signal of the maximum value C and the minimum value F between the maximum values is inputted from the minimum value selection circuit 20. The maximum value E and the minimum value F are added by inputting the input to the adder 21, and the maximum value E and the minimum value F
Outputs the averaged logical comb luminance signal.

Then, the comparison circuit 7 selects the minimum value/maximum value selection circuit 5.
The absolute value of the logical comb color signal output from the logical comb color signal is compared with the absolute value of the logical comb luminance signal output from the minimum value/maximum value selection circuit 6.

When the absolute value of the logical comb color signal that is the output of the minimum value/maximum value selection circuit 5 is larger than the absolute value of the logical comb luminance signal that is the output of the minimum value/maximum value selection circuit 6, the contact of the switching circuit 10 By switching the multiplier to the calculator 9 side, the logical comb color signal is output as a color signal from the output terminal 11, and conversely, the absolute value of the logical comb color signal output from the minimum value/maximum value selection circuit 5 is the minimum. If the absolute value is smaller than the absolute value of the Logical Comb luminance signal output from the value/maximum value selection circuit 6, the contact of the switching circuit 10 is switched to the adder 8 side, and a signal obtained by subtracting the Ron Calcom luminance signal from the 1H times signal is obtained. Output as a color signal.

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

As shown in Fig. 3, if the same luminance signal is present in 0H and 1H and there is no luminance signal in 2H, the logical comb color signal will be a signal with the magnitude of 1H times the signal 1/2, but the logical comb The brightness signal has the same magnitude as the 1H times signal, and in this case, the absolute value of the logical comb brightness 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 times signal is output as a color signal. Therefore, unlike the Y/C separation circuit of the conventional logical comb separation method, the false color signal shown in FIG. 12 is not generated.

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/chrominance signal separation circuit according to an embodiment of the present invention, and FIG. 5 is a diagram showing the frequency characteristics of the output signal of the luminance signal/chrominance signal separation circuit of the conventional comb-shaped separation method. FIG. 6 is a diagram showing the frequency characteristics of the output signal of the luminance signal/color signal separation circuit of the conventional logical comb separation method.

In FIGS. 4, 5, and 6, a solid line X indicates the frequency characteristic of the color signal output, and a broken line Y indicates the frequency characteristic of the luminance signal output. The horizontal axis is the frequency axis, and 0 on this frequency axis indicates the center frequency of the color signal, and 1 and -1 indicate frequencies (1/2) fh away from the frequency of the color signal, respectively.
(center frequency of the luminance signal). The vertical axis is expressed in decibels.

Comparing these figures 4, 5 and 6, it is found that
The frequency characteristics of the output signals of the luminance signal and color signal of the embodiment shown in the figure are the attenuation of the luminance signal Y near the center frequency θ of the color signal X and the attenuation of the luminance signal Y around the center frequency 1. The attenuation of the color signal X near -1 is large. On the other hand, the frequency characteristics of the output signal from the luminance signal/chrominance signal separation circuit of the conventional logical comb separation method shown in FIG.
The attenuation of the luminance signal Y near the center frequency 0 is large, whereas the attenuation of the color signal X near the center frequency 11 of the luminance signal Y is small. Further, the frequency characteristics of the output signal from the conventional comb-shaped separation type luminance signal/chrominance signal separation circuit shown in FIG. 5 include attenuation of the luminance signal Y near the center frequency θ of the color signal 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/chrominance signal separation circuits of the embodiment and the conventional example is due to the difference in the frequency characteristics of the output signals of the luminance signal/chrominance signal separation circuits of each luminance signal/chrominance signal separation circuit due to the generation of pseudo signals in the vertical direction chrominance signal and luminance signal boundary areas. It is clear that this corresponds to the degree of occurrence.

(Effects of the Invention) According to the luminance signal/chrominance signal separation circuit of the present invention, in the boundary region of the color signal, the logical comb color signal which is the output of the logical comb color signal generation circuit is output as the color signal, and the luminance signal In the boundary area between the color signal and the brightness signal, a signal obtained by subtracting the logical comb brightness signal, which is the output of the logical comb brightness signal generation circuit, from the 1H signal is output as a color signal. It is possible to eliminate the generation of a luminance signal and separate the luminance signal and color signal from the NTC8 signal with high accuracy.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a luminance signal/chrominance signal separation circuit according to an embodiment of the present invention, FIG. 2 is a block diagram showing the configuration of a minimum value/maximum value selection circuit, and FIG. 3 is an embodiment of the present invention. Figure 4 is a waveform diagram showing the input and output signals in the boundary area of the luminance signal by the luminance signal/chrominance signal separation circuit of the example. Figure 5 is a diagram showing the frequency characteristics of the output signal of the luminance signal/chrominance signal separation circuit of the conventional comb-shaped separation method, Figure 6 is a diagram showing the frequency characteristics of the output signal of the same luminance signal/chrominance signal separation circuit, and Figure 7 The figure is a block diagram showing the configuration of a conventional comb-shaped separation method luminance signal/chrominance signal separation circuit, Figure 8 is a waveform diagram showing the input and output signals of the luminance signal/chrominance signal separation circuit, and Figure 9 is the same. FIG. 10 is a waveform diagram showing the input and output signals in the chrominance signal boundary region by the luminance signal/chrominance signal separation circuit; FIG. 10 is a block diagram showing the luminance signal/chrominance signal separation circuit of the conventional logical comb separation method; FIG. 11 is the same luminance signal
A waveform diagram showing the input signal and output signal in the boundary area of the color signal by the color signal separation circuit, and FIG. 12 is a waveform diagram showing the input signal and output signal in the boundary area of the luminance signal by the luminance signal/chrominance signal separation circuit. It is a diagram. a...0H signal, b...1H times signal C...1H inverted signal, d...2H signal, 7... Comparison circuit, 10.
...Switching time Figure 1 Figure C Wa Amiichi Figure 1

Claims (1)

[Claims] 0 in which the input video signal is band-limited to the frequency band of the color signal.
H signal and 1H signal delayed by one horizontal scanning period from this 0H signal.
A signal, a 1H inverted signal obtained by inverting the phase of this 1H signal,
A luminance signal/chrominance signal separation circuit comprising an output circuit that outputs a 2H signal obtained by delaying the 1H signal by one horizontal scanning period, the luminance signal/chrominance signal separation circuit comprising: a minimum value of the 0H signal and the 1H inverted signal;
Average the signal of the maximum value between the minimum value of the H inversion signal and the 2H signal, and the minimum value of the maximum value of the 0H signal and the 1H inversion signal, and the maximum value of the 1H inversion signal and the 2H signal. a logical comb color signal generation circuit that outputs a logical comb color signal with a phase inverted; , a logical comb brightness signal generation circuit that outputs a logical comb brightness signal that is an average of the maximum value of the 0H signal and the 1H signal and the minimum value of the maximum value of the 1H signal and the 2H signal; a comparison circuit that compares the absolute value of the color signal with the absolute value of the logical comb luminance signal, and when the absolute value of the logical comb color signal is greater than the absolute value of the logical comb luminance signal, The color signal is output as a color signal, and when the absolute value of the logical comb color signal is smaller than the absolute value of the logical comb luminance signal, a signal obtained by subtracting the logical comb luminance signal from the 1H signal is output as the color signal. A luminance signal/chrominance signal separation circuit characterized by comprising a switching circuit.