JPS6346088A - Yc separation circuit - Google Patents

Abstract

PURPOSE:To always attain perfect YC separation and to prevent the generation of switching noise by detecting interrelation between signals supplied to each of plural comb line filters and applying weighted addition to output signals of plural comb line filters according to plural interrelation detection information. CONSTITUTION:Comb line filters are constituted respectively of 1H delay circuits 13, 14 and adders 17, 18, and adders 15, 16 and detectors 19, 20 constitute respectively detector circuits.. Variable resistors 21, 22 and a buffer amplifier 23 constitute an adder circuit that makes weighted addition. That is, when interrelation between lines n and n-1 is high, the proportion of output carrier chrominance signals becomes high, and when interrelation between lines (n) and n+1 is high, the proportion of output carrier chrominance signals becomes high. Thereby, YC separation is made perfectly by the comb line filter even in a boundary line, and as switching operation is not made, noise is not generated in the circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a YC separation circuit, and more particularly, to a YC separation circuit that uses a comb filter to separate a luminance signal and a carrier color signal.

2. Description of the Related Art Conventionally, there is a YC separation circuit that uses a comb filter to separate a luminance signal and a carrier color signal from a color video signal.

However, the comb filter is equivalent to degrading the resolution in the vertical direction, and causes color blurring, dot interference, etc. in video parts where there is no vertical line correlation.

In order to prevent these occurrences, conventional methods have been to detect line correlation in the vertical direction and use a comb filter to perform YC separation when the line correlation is high, and use a bandpass filter when the line correlation is low. There is a so-called adaptive comb filter YC separation circuit that performs YC separation based on the YC separation. Here, the adaptive form means adapting to the image.

Problems to be Solved by the Invention In the conventional adaptive comb filter YC separation circuit, it is difficult to select whether to use a comb filter or a bandpass filter based on information 1 with little correlation between two consecutive lines. cormorant. Therefore, for example, if there are two red lines followed by two white lines, there is no correlation between the red line and white line at the boundary, so a bandpass filter is used to separate the YC. Make a new appearance. Therefore, there is a problem in that the high-frequency components of the luminance signal are attenuated at the boundary line, and the luminance signal is mixed into the carrier color signal. Furthermore, there is a problem in that noise is generated on the screen due to the switching operations of the comb filter and the bandpass filter.

The present invention has been made in view of the point -F, and it is an object of the present invention to provide a VC separation circuit that always performs complete YC separation and does not generate switching noise.

In the present invention, a plurality of delay circuits of each of a plurality of comb filters are connected in cascade.

The plurality of detection circuits detect the correlation between the input signals and output signals of the plurality of delay circuits.

The adder circuit weights and adds the output signals of the plurality of comb filters in accordance with the respective output detection signals of the plurality of detection circuits to obtain a carrier color signal.

The subtracter p circuit subtracts the carrier color signal output from the adder circuit from the color video signal to obtain a luminance signal.

Operation In the present invention, the correlation between the signals supplied to each of the plurality of comb filters is detected, and the output signals of the plurality of comb filters are weighted and added in accordance with the plurality of correlation detection information.

Embodiment FIG. 1 shows a block diagram of an embodiment of the circuit of the present invention. In the figure, for example, a color video signal of the NTSC system as shown in FIG. 2(A) is input to the terminal 10.
In A), the sine wave portion shows the carrier color signal.

This color video signal is processed by a bandpass filter 11 and a delay circuit 1.
2.

The bandpass filter 11 passes the carrier color signal band, and its output signal is sent to the cascade-connected 111R extension circuit 13.
14 and are delayed by 1 to 1, respectively.

The adder 15 connects the output of the bandpass filter 11 to the IHL extension circuit 1.
3 is added to obtain a signal for determining the correlation between the line n output from the 11'' H folding circuit 13 and the next line n-1 as shown in FIG. 2(B), and the signal is supplied to the detector 19. However, the adder 16 adds the output of the one-day delay circuit 14 to the output of the one-day delay circuit 13 to determine the correlation between line n and the previous line n~+1 as shown in FIG. 2(C). Obtain the signal and use detector 2
Supply to 0. Further, the subtracter 17 subtracts the output of the bandpass filter 11 from the output of the one-day delay circuit 13, and subtracts the output of the bandpass filter 11 from the output of the one-day delay circuit 13.
) is obtained and supplied to the variable resistor 21, and the subtracter 18 outputs a 1 day delay circuit 1 from the output of the delay circuit 13.
4 is subtracted to obtain the carrier color signal shown in FIG.
14 and adders 17 and 18 each constitute a comb filter.

The detectors 19 and 20 perform envelope detection of the supplied signals and supply control signals as shown in FIGS. 2(F) and 2(G) to the blue variable resistors 21 and 22, respectively. The level of this control signal increases as the correlation between lines n and n-1 and between lines n and n+1 increases, and becomes zero level when there is complete correlation. Adder 15.16 and detector 19.20 above
and constitute a detection circuit, respectively. Variable resistance 21.22
Each has a resistance value R+ when the level of the control signal is zero.
, R2 is zero and R as the level of the control signal becomes human.
+, R2 increases. Variable resistance 21.22
The color signals passed through are commonly supplied to the buffer 7 amplifier 23, where they are mixed.

Here, the signals output from each of the subtracters 17 and 18 are S+
, 32, and the signal output from the buffer amplifier 23 is ST
Then, it is expressed as the following equation.

ST =S+ ・R2/ (R1+R2) 10S2・
R+/(R1+R2) The variable resistors 21 and 22 and the buffer amplifier 23 are an adding circuit that performs weighted addition. In other words, when the correlation between lines n and n-1 is high, the proportion of the output carrier color signal of the subtractor 17 is high, and when the correlation between lines n and n+1 is high, the proportion of the output carrier color signal of the subtractor 18 is high. becomes higher.

Therefore, for example, there are two red lines (first line, second line), then two white lines (third line,
4th line), when the second and third lines with low correlation are supplied to the cylinder reducer 17 and the first and second lines with high correlation are supplied to the Q reducer 18. The carrier color signals obtained from the first line and the second line are taken out from the buffer amplifier 23. Next, cylinder reducer 1
When the third line and the fourth line with a high correlation are supplied to the buffer amplifier 23 and the second line and the third line with a low correlation are supplied to the cylinder reducer 18, the third line and the fourth line are supplied from the buffer amplifier 23. The carrier color signals obtained from the 4 lines are extracted.

As a result, complete YC separation is performed using the comb filter even on the boundary line.

Furthermore, in the case of a monotonous increase or a monotonous decrease in the carrier color signal, the average value of the subtractors 17 and 18 is used to obtain an undistorted carrier color signal. If every line is magenta.

If green is repeated, the output will be gray, but this is almost never the case in actual images, so there is no problem.

As a result, the buffer amplifier 23 outputs the carrier color signal shown in FIG.

The delay circuit 12 delays the color video signal by a time corresponding to the delay time of the bandpass filter 11. The color video signal is further delayed for a period of 11'' in a one-day delay circuit 26, and then the carrier color signal is subtracted in a subtracter 25. As a result, a moderation signal is extracted and outputted from the terminal 27.

As described above, since no switching operation is performed in the above circuit, noise is not generated within the circuit, and it is possible to prevent a decrease in resolution in the vertical direction from color blurring and dot interference.

Further, in the above circuit, uncorrelated noise between lines is also reduced, and a noise reduction effect can be obtained.

FIG. 3 shows a block diagram of a modified example of the circuit of the present invention.

In this figure, the same parts as those in FIG.

In FIG. 3, the color video signal input to the terminal 10 is directly supplied to the 1H delay circuit 13 and the like without passing through a bandpass filter. Adder 15, 16 and buffer amplifier 2
The bandpass filters 30, 31, and 32 provided after the bandpass filter 3 are all the same as the bandpass filter 11 shown in the first diagram.

Therefore, the bandpass filter 30.31 removes the luminance signal component from the output signal of the adder 15.16, and the detector 19.20
is supplied with the same signal as in FIG. 1 for knowing the line correlation. Further, the bandpass filter 32 removes the low-frequency component of the luminance signal contained in the output signal of the Balanoa amplifier 23 and extracts only the carrier color signal, outputting it from the terminal 24 and supplying it to the tube reducer 25.

Further, the color video signal outputted from the one-day delay circuit 13 is supplied to the subtracter 25 via the delay circuit 12, where a luminance signal is extracted.

Note that high-pass filters that pass the carrier color signal band may be used instead of the bandpass filters 30 and 31, respectively.

Note that it is also possible to perform the YC separation of the J, S, P△ and one-way color video signals by using a 2-day delay circuit in place of the 11''8 delay circuits 13, 14, and 26.

Note that when the color subcarrier frequency is rsc, the delay interval 1/(2.
fsc) delay circuit may also be used. In this case, since the delay time is short, the circuit is inexpensive.

Note that in the above embodiment, YC separation is performed by detecting correlation on three consecutive lines;
is an integer of 2 or more), and may be configured similarly, and is not limited to the above embodiment.

Effects of the Invention As described above, according to the circuit of the present invention, it is possible to perform complete YC separation and to reduce the vertical resolution distortion2.
It has features such as preventing color blurring and dot interference, and since no switching is performed, no switching noise is generated, and it is also possible to reduce noise contained in color video signals. ing.

[Brief explanation of the drawing]

1 and 3 are block diagrams of an embodiment of the circuit of the present invention and a modification thereof, and FIG. 2 is a signal waveform diagram of each part of the circuit shown in FIG. 1. 11.30.31.32...Band filter, 12...
・Delay circuit, 13, 14.26...1 day delay circuit, 1
5.16...Adder, 17.18.25...Subtractor, 19.20...Detector, 21.22...Variable resistor, 23...Buffer amplifier. Patent Applicant Victor Company of Japan Co., Ltd. (G) −−−−−−−−− (H) −−−−−−−−−1 Takosha Shun

Claims (1)

[Claims] A YC separation circuit that separates a carrier color signal and a luminance signal from a color video signal using a comb filter, comprising: a plurality of comb filters in which a plurality of delay circuits are connected in cascade; a plurality of detection circuits that detect the correlation between the input signal and the output signal of the delay circuit; and weighting and adding of the output signals of the plurality of comb filters according to the detection signals output from the plurality of detection circuits. 1. A YC separation circuit comprising: an adder circuit that obtains a carrier color signal; and a subtracter circuit that obtains a luminance signal by subtracting the carrier color signal output from the adder circuit from the color video signal.