JPH074026B2 - 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 color 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 (2π fsc t) + Vcos (2π fsc t)
Becomes 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.
The luminance signal Y is separated by 1/2. Further, the input TV signal (Y-C) is inverted by the inverter 4 and then added with the signal of the previous line in the adder 5, and the output becomes 2C, and the level is attenuated to 1/2 by the attenuator 6. 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 color signal of the current line are separated.

However, in the conventional method as described above, since only the correlation of pixel information on one screen is utilized, deterioration of a reproduced image such as color turbidity or dot interference occurs in an area where the brightness and color of the image change greatly. It has the drawback of occurring.

The present invention has been falsified in view of the above problems, and it is possible to accurately separate a luminance signal and a color signal from a composite color television signal by using pixel information having a strong correlation between screens and between screens. An object is to provide a luminance signal / color signal separation device.

[Means for solving problems]

The luminance signal / color signal separation device of the present invention samples a composite color television signal to obtain a pixel information signal, and selects any one of the pixels on the current screen as a target pixel, and focuses on the target pixel. At least a pixel on the previous screen from four pixels on the previous screen having a pixel and a color signal in phase with the target pixel, one pixel on the previous screen having a color signal having an opposite phase to the target pixel, and four pixels on the current screen A pixel group forming means for forming a plurality of pixel groups having the same number of constituent pixels, and a correlation determining means for determining a pixel group having the strongest correlation between pixels forming the pixel group among the formed plurality of pixel groups. And a separation unit that separates the luminance signal and the color signal of the pixel of interest using the information signals of the pixels forming the pixel group determined by the correlation determination unit.

[Work]

With the above configuration, the luminance signal and the color signal can be separated using the pixel information having the strongest correlation between the screens.

〔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 pixel group configuration for determining the correlation of pixels.

In FIG. 1, 7 to 10 are 1H-2 sample period delay circuits (however, H is one horizontal line scanning period), 11 to 14 are 2 sample period delay circuits, and 15 is a 1F-2H period delay circuit (however, F
Is one frame scanning period), 16 to 19 are addition / subtraction circuits, 20 to 23
Is an absolute value converter, 24-35 are adders, 36-43 are 1/4 level attenuators, 44-47 are subtractors, 48 is a comparison circuit, and 49 is a switching circuit.

For example, when an NTSC composite color television signal is sampled at a sampling frequency fc that 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 subcarrier frequency fsc are sequentially input, the signals are delayed by 1H-2 sample period delay circuit 7 ... 10, 2 sample period delay circuit 11-14,
By the 1F-2H period delay circuit 15, the sampling points S ₁ ~ shown in FIG.
The pixel information signal of S ₁₀ is simultaneously extracted.

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 9} , S 10 is sampled points S ₃ phase with the sampled points S _1, S ₂ , S ₄ , S ₅ , and S ₈ are in antiphase 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.

Separating a luminance signal and a color signal for each pixel group A~D from pixel information signal sampling point S ₁ to S ₁₀ obtained are shown in FIG. 4 in the manner described above. The luminance signal Y and the color signal C in each pixel group are Since there is a relationship of 1/4 level attenuator 36-43, adder 24-35, subtractor 44-4
The luminance signals Y _{a to} Y _d and the color signals C _{a to} C obtained by
_d is supplied to the switching circuit 49.

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

That is, the following calculations are performed using the subtracters 16 to 19 and the absolute value exchangers 20 to 23.

｜ S ₈ + S ₂ −S ₇ −S ₃ ｜ ＝ Ta, | S ₈ ＋ S ₄ −S ₉ −S ₃ ｜ ＝ Tb, ｜ S ₈ ＋ S ₁ −S ₆ −S ₃ ｜ ＝ Tc, | S ₈ ＋ S ₅ −S ₁₀ −S ₃ | = Td Note that the formulas for calculating Ta to Td show the vertical and horizontal correlations that take the correlations in the time axis direction into account, and the values of each formula are large. In the case, the correlation is weak and small, the correlation is strong.

Then, the above calculation result is input to the comparison circuit 48, where
T _a through T to detect what _d smallest value out of, T _a when a small Y _a, C _a, Y _b when T _b is less, C _b, if T _c is small Y _{When c} , C _c , and T _d are small, a switching control signal is output from the comparison circuit 48 to the switching circuit 49 so that Y _d and C _d are output, and the pixel information signal at the sampling point S ₃ is the luminance signal. And 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 in consideration of the correlation between the luminance signal and the color signal in the time axis direction.

Further, in the present embodiment, a signal obtained by sampling the composite color television signal of the NTSC system with the sampling frequency fs which is four times the color subcarrier frequency fsc is used, but the PAL system is changed by changing the configuration of the pixel block. It can also be applied to other signals such as.

〔The invention's effect〕

As described above, according to the present invention, there is provided 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 between screens and between screens. Can be provided.

[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 pixel group configuration of this embodiment. 7 to 10 …… 1H-2 sample period delay circuit 11 to 14 …… 2 sample period delay circuit 15 …… 1F-2H period delay circuit 16 to 19 …… addition / subtraction circuit 20 to 23 …… absolute value converter 24 to 35 …… Adder 36〜43 …… 1/4 level attenuator 44〜47 …… Attenuator 48 …… Comparison circuit 49 …… Switching circuit

Claims (1)

[Claims] 1. When a composite color television signal is sampled and a pixel information signal is obtained, an arbitrary one of the pixels on the current screen is set as a target pixel, and the target pixel and the target pixel are centered around the target pixel. 4 pixels on the previous screen having a color signal of the same phase as that of the pixel of interest, 1 pixel on the previous screen having a color signal of the opposite phase to the pixel of interest and 4 pixels on the current screen, and at least pixels of the previous screen Pixel group forming means for forming a plurality of pixel groups having the same number, correlation determining means for determining a pixel group having the strongest correlation between pixels forming the pixel group among the formed plurality of pixel groups, and the correlation determination A luminance signal color signal separation device comprising: a separation unit that separates a luminance signal and a color signal of the pixel of interest using an information signal of a pixel forming a pixel group determined by the means.