JPH074025B2 - 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 (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.
The luminance signal Y is separated by 1/2. 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 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 used, deterioration of the reproduced image such as color turbidity or dot interference occurs in an area where the luminance and color of the pixel change greatly. It has the drawback of occurring.

The present invention has been falsified in view of the above-mentioned problems, and it is possible to accurately generate a luminance signal and a color signal from a composite color television signal with a simple configuration by using pixel information having a strong correlation on a screen or between screens. It is an object of the present invention to provide a luminance signal / color signal separation device that can be separated.

[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. Pixel group formation for forming a plurality of pixel groups having the same number of constituent pixels using at least pixels on the previous screen from one pixel on the previous screen and four pixels on the current screen having a color signal opposite in phase to the pixel and the pixel of interest Means, a correlation determining means for determining a pixel group having the strongest correlation between pixels forming the pixel group among the formed pixel groups, and a pixel forming the pixel group determined by the correlation determining means. It is provided with a separating means for separating the luminance signal and the color signal of the target pixel by using the information signal.

[Work]

With the above configuration, the luminance signal and the color signal can be separated by using the pixel information having the strongest correlation on the screen or 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 and 8 are 1H-2 sample period delay circuits (however, H is 1 horizontal line scanning period), 9 and 10 are 2 sample period delay circuits, and 11 are 1F-1H period delay circuits (however, F is 1 frame). (Scanning period), 12 to 23 are subtractors, 24 to 29 are absolute value converters, 30 to 41 are adders, 42 is 1/2 level attenuator, 43 to 48
Is a 1/4 level attenuator, 49 is a comparison circuit, and 50 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 a 1H-2 sample period delay circuit 7, 8, 2 sample period delay circuit 9, 10, 1F-1
The H period delay circuit 11 simultaneously extracts the pixel information signals of the sampling points S _{1 to} S ₆ shown in FIG. In the pixel information signal of the sampling point as shown in FIG. 4, the phase of the color signal is the sampling point S ₁ ,
S ₂ , S ₄ , S ₅ , and S ₆ are in anti-phase with sample 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 signals of the sampling points S _{1 to} S ₆ obtained as described above, the luminance signal and the color signal are separated for each of the pixel groups A to F shown in FIG. The luminance signal Y and the color signal C in each pixel group are Therefore, the separation filter utilizing the above relationship is used as a 1/2 level attenuator 42, a 1/4 level attenuator 43 to 48, and an adder.
30-41, subtractor 18-23, obtained luminance signal
The Y _{a to} Y _f and the color signals C _{a to} C _f are supplied to the switching circuit 50.

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 most correlation among the pixel groups A to F is obtained by the following method. Group is discriminated, and a luminance signal and a color signal separated from the pixel information signals of the group are output and selected.

That is, the following calculations are performed using the subtracters 12 to 17 and the absolute value exchangers 24 to 29.

_{| S 6 -S 1 | = T} a, | S 6 -S 5 | = Tb, | S 6 -S 2 | = T c, | S 6 -S 4 | = Td, | S 1 -S 5 | = T _e , | S ₂ −S ₄ | = Tf, Note that the formula for calculating Ta to Td shows the correlation in the vertical and horizontal directions when the correlation in the time axis direction is taken into consideration. , Tf respectively show vertical and horizontal correlations on one screen, and a large value of each equation indicates a weak correlation and a small value indicates a strong correlation.

Further, in order to obtain the correlation as described above, it is possible to discriminate a group having a strong correlation with a simple circuit configuration by using the information signal of the pixel having the same color signal.

Then, the calculation result is input to the comparison circuit 49, where
Detect the smallest value from Ta to Tf. If Ta is small, Yb, Cb is small if Ya, Ca, Tb is small, and if Yc, Cc, Td is small if Tc is small. When Yd, Cd, and Te are small, Ye, Ce, and when Tf is small, Yf and Cf are output, so that the comparison circuit 49 outputs the switching control signal to the switching circuit 50, and the sampling point S ₃ The pixel information signal in is separated into a luminance signal and a color signal 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, a luminance signal color signal capable of accurately separating a luminance signal and a color signal from a composite color television signal with a simple structure by using pixel information having a strong correlation on a screen or between screens. A separation device 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. 7,8 …… 1H-2 sample period delay circuit 9,10 …… 2 sample period delay circuit 11 …… 1F-1H period delay circuit 12-23 …… Subtractor 24 ～ 29 …… Absolute value converter 30 ～ 41 …… Adder 42 …… 1/2 level attenuator 43 to 48 …… 1/4 level attenuator 49 …… Comparison circuit 50 …… 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. And a pixel group forming means for forming a plurality of pixel groups having the same number of constituent pixels using at least pixels on the previous screen from one pixel on the previous screen and four pixels on the current screen having color signals of opposite phase. By using the correlation determining means for determining the pixel group having the strongest correlation between the pixels forming the pixel group among the plurality of pixel groups and the information signal of the pixels forming the pixel group determined by the correlation determining means 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.