JPH0779478B2 - Luminance signal Color signal separation device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a luminance signal / color signal separating apparatus for separating a luminance signal and a color signal from a composite color television signal.

[Conventional technology]

An existing composite power television signal, for example, an NTSC composite color television signal S, includes a luminance signal Y and two color difference signals U and V (or I and Q) as color subcarrier frequencies.
A composite signal with a color signal C that is quadrature-phase modulated by fsc and S =
Y + C = Y + USin (2πfsc t) + Vcos (2πfsc t) Here, if the frame frequency f _F (30 Hz), the field frequency f _V , and the horizontal scanning frequency f _H Becomes

Therefore, when an NTSC composite color television signal is sampled at a sampling frequency fs that is four times the color subcarrier frequency fsc, the sequence of the sampled signals is as shown in FIG. In other words, four samples are extracted in one cycle of the color subcarrier, in which the phase of the color signal C is inverted 180 degrees for each line.

In order to separate such a signal into a luminance signal Y and a color signal C,
Conventionally, a comb filter as shown in FIG. 3 is used to separate the luminance signal and the color signal. The television signal (Y-C) input in FIG. 3 is added in the adder 2 to the signal (Y + C) on the previous line delayed by the 1H delay 1. That is, as shown in FIG. 2, since the phase of the color signal is inverted 180 degrees between the current line and the previous line, the output of the adder 2 becomes 2Y and the level is changed by the next attenuator 3.
It is attenuated to 1/2 and the luminance signal Y is separated. Further, the input television signal (Y-C) is inverted by the inverter 4 and then is added to the signal (Y +) of the previous line in the adder 5.
C), the output becomes 2C, the level is attenuated to 1/2 by the attenuator 6, and the color signal C is separated.

[Problems to be solved by the invention]

The conventional luminance signal / color signal separating apparatus as described above uses the pixel information of the previous line on the assumption that the pixel information which is the sampling sequence of the composite color television signal has a strong vertical correlation. Therefore, the luminance signal and the signal of the current line are separated.

However, the conventional method as described above has a drawback in that the reproduced image is deteriorated due to color turbidity or dot interference in a region where the brightness and color of the image change drastically.

The present invention has been made in view of the above problems, and a luminance signal color capable of accurately separating a luminance signal and a color signal from a composite color television signal by using pixel information having a strong correlation on the screen. An object is to provide a signal separation device.

[Means for solving problems]

According to the present invention, in a device for sampling a composite color television signal and obtaining a pixel information signal, an arbitrary one pixel in pixels on one screen is set as a target pixel, and the target pixel is included from pixels around the target pixel. Pixel group forming means for forming a plurality of pixel groups composed of a plurality of pixels, and a pixel group having the strongest correlation between the pixels forming the pixel group among the plurality of pixel groups, the plurality of pixels forming each of the pixel groups And a separation unit that separates the luminance signal and the color signal of the target pixel by using at least a part of the plurality of pixels forming the pixel group determined by the correlation determination unit. It is a thing.

[Work]

With the above configuration, it is possible to separate the luminance signal and the color signal by using the information of the pixel group having the strongest correlation on the screen.

〔Example〕

 Hereinafter, the present invention will be described based on examples.

FIG. 1 is a diagram showing a schematic configuration of a luminance signal / color signal separation circuit as an embodiment of the present invention.

FIG. 4 is a diagram showing a block configuration of pixels for determining the correlation of pixels.

In FIG. 1, 7 to 12 are delay circuits for 2 sample periods,
3, 14 are 1H-4 sample period delay circuits (however, H is one horizontal line scanning period), 15-22 are adder / subtractors, 23-30 are absolute value converters, 31 is 1/2 level attenuator, 32-35. Is a 1/4 level attenuator, 36 to 47 are adders, 48 to 51 are subtractors, 52 is a comparison circuit,
53 is a switching circuit.

For example, when an NTSC composite color television signal is sampled at a sampling frequency fs which is four times the color subcarrier frequency fsc, the sampling points are as shown in FIG.

Referring to FIG. 4, the operation of separating the luminance signal and the color signal at the sampling point S ₃ will now be described.

In FIG. 1, when NTSC composite color television signals sampled at a sampling frequency fs which is four times the color sub-carrier frequency fsc are sequentially input, the signals are delayed by two sample period delay circuits 7 to 12 1H. The pixel information signals of the sampling points S _{1 to} S ₉ shown in FIG. 4 are simultaneously extracted by the -4 sample period delay circuits 13 and 14. In the fourth phase sample points of the pixel information signal sampling point, such as shown in FIG color signals _{S 6, S 7, S 8} , S 9 is sampled points S ₃ phase with the sampled points S _1, S ₂ , S ₄ and S ₅ are in the opposite phase with the sample point S ₃ . This is because, as described above, the NTSC composite color television signal is sampled at the sampling frequency fs which is four times the color subcarrier frequency fsc.

From the pixel information signal sampling point S ₁ to S ₉ was obtained as described above, to separate the luminance signal and the color signal for each pixel block A~D shown in Figure 4. The luminance signal Y and color signal C at each pixel block are Therefore, the separation filter utilizing the above relation is used as a 1/2 level attenuator 31, a 1/4 level attenuator 32 to 35, and an adder.
36-43 and subtractors 48-51
The Y _{a to} Y _d and the color signals C _{a to} C _d are supplied to the switching circuit 57.

Here, in order to determine which of the luminance signal and the chrominance signal separated in each separation filter as described above is to be separated and output, the pixel blocks A to D are determined by the following method.
The block having the strongest correlation is discriminated, and the luminance signal and the color signal separated from the pixel information signal of the block are selected as outputs.

That is, the following operations are performed using the adder / subtractors 15-22, the absolute value converters 23-30, and the adders 44-47.

| S ₆ + S ₁ −S ₂ −S ₃ | + | S ₆ + S ₁ + S ₂ −S ₃ | = T _a | S ₁ + S ₇ −S ₃ −S ₄ | + | S ₁ −S ₇ + S ₃ −S ₄ | = T _b | S ₂ + S ₃ −S ₈ −S ₅ | + | S ₂ −S ₃ + S ₈ −S ₅ | = T _c | S ₃ + S ₄ −S ₅ −S ₉ | + | S ₃ − S ₄ + S ₅ −S ₉ | = T _{d In} the above equation, the first term represents the correlation in the vertical direction of the luminance signal and the horizontal direction of the color signal, and the second term represents the horizontal direction and the color of the luminance signal. It represents the correlation in the vertical direction of the signal. When the value is large, the correlation is weak, and when the value is small, the correlation is strong.

Then, the above calculation result is input to the comparison circuit 52, where
Of Ta to Td, the one with the smallest value is detected, and when Ta is small, Y _a , C _a , when T _b is small, Y _b , C _b , T _c is small, Y _c , When C _c and T _d are small, Y _d and C _d are output so that the comparison circuit 52 outputs a switching control signal to the switching circuit 53, and the pixel information signal at the sampling point S ₃ is a luminance signal. It is separated into color signals and output.

As described above, when the luminance signal and the color signal are separated from the composite color television signal, the optimum separation can be performed according to the vertical and horizontal correlations of the luminance signal and the color signal.

Further, in the present embodiment, the relationship of equations (1) to (4) was used to determine the strength of the correlation in each pixel block, but either the first term or the second term is used. May be calculated, and the block with the smallest result may be determined to be the block with strong correlation. In this case,
The configuration can be simplified.

Further, in this embodiment, the NTSC system composite color television signal is supplied with a sampling frequency f which is four times the color subcarrier frequency fsc.
Although the signal sampled by s is used, it can be applied to other signals such as the PAL system by changing the configuration of the pixel block.

〔The invention's effect〕

As described above, according to the present invention, it is possible to provide a luminance signal / color signal separation device capable of accurately separating a luminance signal and a color signal from a composite color television signal by using pixel information having a strong correlation on the screen. I can.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a luminance signal / color signal separation circuit as an embodiment of the present invention. FIG. 2 is a diagram showing a series of sampling signals obtained by sampling an NTSC composite color television signal at a sampling frequency fs which is four times the color subcarrier frequency fsc. FIG. 3 is a diagram showing a schematic configuration of a luminance signal / color signal separation comb type filter as a conventional example. FIG. 4 is a diagram showing the relationship between the sampling points of the sampling signal of FIG. 2 and the configuration of the pixel block. 7 to 12 ... 2 sample period delay circuit 13, 14 ... 1H-4 sample period delay circuit 15 to 22 ... adder / subtractor 23 to 30 ... absolute value converter 31 ... 1/2 level attenuator 32 to 35 ...... 1/4 level attenuator 36 to 47 …… Adder 48 to 51 …… Attenuator 52 …… Comparison circuit 53 …… Switching circuit

Claims (1)

[Claims] 1. A device for obtaining a pixel information signal by sampling a composite color television signal, wherein any one pixel among pixels on one screen is set as a target pixel, and the target pixel is selected from pixels around the target pixel. Pixel group forming means for forming a plurality of pixel groups each including a plurality of pixels, and a pixel group having a strongest correlation between pixels forming each pixel group among the plurality of pixel groups Correlation determining means for determining using a pixel, and separating means for separating a luminance signal and a color signal of the pixel of interest using at least a part of the plurality of pixels forming the pixel group determined by the correlation determining means A luminance signal / color signal separation device comprising: