JPH0550194B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to color television signals, especially color television signals.
The present invention relates to a circuit for extracting a luminance signal and a carrier color signal from a composite color television signal in which a carrier color signal is superimposed on a luminance signal, such as an NTSC signal.

[Prior art]

As a method for separating color signals from a composite color television signal such as an NTSC signal, the color signal is separated from the NTSC signal by a bandpass filter (BPF) centered at the subcarrier frequency (f _SC ), as used in ordinary television receivers. Carried color signal (C signal)
There is a method to extract. In this case, in order to obtain a Y signal from which the C signal has been sufficiently removed, it is necessary to widen the passband of the BPF, and the high frequency components of the luminance signal are removed, resulting in an image with reduced resolution. Therefore, it is necessary to narrow the band of the BPF, and in this case, the carrier signal remains in the luminance signal, resulting in so-called dot protection.

Interframe coding of composite color television signals and noise removal devices using frame memory require a circuit to invert the polarity of the carrier color signal of the previous frame, but the carrier color signal can be extracted using BPF. , when the polarity is reversed, the above-mentioned residual C
Since the signal components are not inverted, and the brightness high-frequency components within the BPF band are inverted, deterioration of characteristics has been a problem.

A method is also known in which a delay circuit for the horizontal scanning period (H) is prepared, a scanning line 1H before is used, and the difference signal between the scanning lines is BPF'd to extract the C signal. A different color from the original signal appeared in the horizontal stripes of the image, and a pseudo color signal appeared in the luminance signal, resulting in deterioration of image quality.

In the case of a composite color television signal in which the subject is completely stationary, a high-quality C signal without deterioration as described above can be extracted by extracting the carrier color signal from the difference signal from the signal one frame before. When the object moves, a color signal different from that of the object is extracted from the moved part, and residual color signals are also present in the luminance signal, resulting in unsightly image deterioration.

[Purpose of the invention]

The present invention was made in order to solve the above-mentioned problems, and is aimed at obtaining a high-quality color receiver that does not cause dot damage prevention, cross color, etc., or various devices that utilize high-performance inter-frame correlation. The purpose is to obtain quality luminance and color signals.

[Summary of the invention]

In order to achieve the above object, the present invention uses a memory with a capacity of one frame, so-called frame memory,
A desired phase color signal is extracted using a signal one frame period before or after the current signal and the current signal. Furthermore, by checking whether the subject is moving and changing the mixing ratio of the first and second high-frequency components, it can be applied not only to still images but also to moving images to generate high-quality color signals and even brightness signals. It's something you get.

[Embodiments of the invention]

Hereinafter, the present invention will be explained in detail with reference to Examples.

Figure 1 shows the case where the first high frequency component obtained from the sum signal of the current signal and the signal one frame period ago and the high frequency component (second high frequency component) of the current scanning line signal are used. An example is shown. In the figure, the composite color television signal input from input terminal 1 is passed through delay circuit 2 with a period of 1 frame (in the figure).
In the case of the NTSC system, the signal is delayed by 525H (H is a horizontal scanning period), and the sum signal between frames is calculated by the adder circuit 15. This sum signal is multiplied by 1/2 in a coefficient circuit 4 and then passed through a coefficient circuit 6. after that,
A subtraction circuit 16 calculates a difference signal between the output of the coefficient circuit 6 and the signal of the current scanning line. The output of the subtraction circuit is passed through a bandpass filter (BPE) 5 to extract a carrier color signal C. The obtained C signal is sent to delay circuit 1
1 (corresponding to the BPF5 calculation delay time), when the subtraction circuit 12 subtracts the input signal, the output terminal 1
3, a luminance signal Y is obtained.

In this embodiment, a part is added that changes the coefficient k depending on the presence or absence of movement of the subject. That is, the input/output signals of the frame delay circuit 2 are input to the motion detection circuit 9, and a motion information signal is obtained as an output thereof.
This controls the coefficient circuit 6 so that k approaches 1 for stationary parts, and k for large movements.
Bring it closer to 0. Therefore, the range of k is specifically expressed as 0≦k≦1.

In other words, the input signal is X, and the frame delayed output is
If X _d , the signal C in Figure 1 becomes C=(X-k(X+X _d )/2)・BPF, so the addition circuit 15 and coefficient circuit 4 combine X and
Calculate the average value of X _d , multiply it by k in the coefficient circuit 6, and subtract the signal from the current signal
By inputting it to the BPF 5, a desired C signal can be obtained. In this example, the coefficient circuit,
The number of BPFs may be one each.

FIG. 2 shows another embodiment of the present invention, that is, an embodiment in which a signal from one horizontal scan period ago is used as the second high frequency component. In the figure, by adding k times the signal that has undergone frame delay 2 and a signal obtained by multiplying the output of the 1H delay circuit 17 by (1-k) by the coefficient circuit 8 in the adding circuit 18, the current scanning line is inverted. A polar carrier color signal is derived and subtracted by a subtraction circuit 16.
is subtracted from the current signal at
Obtain the desired C signal.

In the configuration example shown in Fig. 2, if the input signal is X, the frame delay signal is X _Fd , and the lie delay signal is X _Ld , the first and second high frequency components extracted from the difference between frames and the difference between lines C ₁ and C ₂ are respectively expressed as C ₁ =1/2(X-X _Fd )·BPF C ₂ =1/2(X-X _Ld )·BPF. The carrier color signal C obtained by mixing C ₁ and C ₂ with a motion coefficient k is C=k・C ₁ +(1−k)C ₂ =k・1/2(X−X _Fd )・BPF +( 1-k)・k・1/2(X-X _Fd )・ BPF = [X-{kX _Fd + (1-k)X _Ld }]・
It can change to 1/2・BPF. The operation result in { } in the above formula is the second
Since it is obtained as the output signal of the adder circuit shown in the figure, the above equation shows the characteristics of the circuit that obtains the C signal shown in FIG. In this embodiment as well, only one BPF is required.

FIG. 3 shows a specific example of the structure of the motion detection circuit 9 shown in FIGS. 1 and 2 above. In other words, the current signal and the frame-delayed signal are input, and the color signal component of the moving part appears in the component centered on the subcarrier frequency of the sum signal of both (output of the adder circuit 19), and the color signal component of the moving part appears. The luminance signal of the moving part appears in the DC component of the output of the circuit 20. Therefore, by calculating the absolute values of the outputs of the BPF 21 and LPF 22 using the absolute value calculating circuits 23 and 24, and calculating the sum signal thereof using the adding circuit 25, a signal corresponding to the movement of the subject can be obtained. By controlling the coefficient k or (1-k) using this motion information signal, it is possible to obtain a high-quality C signal that is adapted to the motion of the subject.

[Effects of the Invention] In the above-described embodiments, the NTC method was used as the composite color television signal, but other methods can be used in the same manner. In addition, in the embodiment, the color signal is separated from the composite color television signal input to the input terminal using frame delay, but the previous frame is transferred in interframe coding, noise removal using frame delay, etc. The present invention can also be applied to a circuit that inverts the polarity of a color signal with some modifications. In other words, the output of the frame memory is taken as the current signal, and thereby 1
It is possible to separate the color signals by subtracting the signal advanced by the frame period time.

Note that in the embodiment of the present invention, the luminance signal is obtained by subtracting the extracted carrier color signal from the composite color television signal, but the present invention is not limited to this. In addition, if the input signal contains noise, terminals 13 and 1
By removing visually unimportant bands from the Y and C signals extracted in step 4 using a comb filter, it is possible to obtain high quality Y and C signals.

As explained above, according to the present invention, the luminance signal and the carrier color signal can be separated from a composite color television signal with high quality without mixing or remaining, and the color signal demodulation circuit in the television receiver can Great effects can be achieved by applying coding, noise removal, etc.

[Brief explanation of the drawing]

Both FIGS. 1 and 2 are block diagrams of an embodiment of the present invention, and FIG. 3 is a block diagram of a motion detection circuit of the above embodiment. Explanation of symbols 1...Input terminal, 2, 11, 17
...Delay circuit, 12, 15, 16, 18, 19,
20, 25... Addition (subtraction) circuit, 4, 6, 8...
Coefficient circuit, 5, 21, 22... Filter, 9...
Motion detection circuit, 13, 14... Output terminal, 23,
24... Absolute value calculation circuit.

Claims (1)

[Claims] 1. In a circuit for separating a luminance signal and a carrier chrominance signal from a composite color television signal in which a carrier chrominance signal is superimposed on a luminance signal, a first delay for delaying an input composite color television signal by one line period and one frame period, respectively. circuit, the second delay circuit, and the coefficient 1-k(0
≦k≦1); a second coefficient circuit that multiplies the output of the second delay circuit by a coefficient k;
an adder circuit that obtains the sum of the outputs of the first coefficient circuit and the second coefficient circuit; a subtractor circuit that obtains the difference between the input composite color television signal and the output of the adder circuit; a third delay circuit for delaying the input composite color television signal by a time corresponding to the calculation delay time of the bandpass filter;
a delay circuit, a subtraction circuit for obtaining the output difference of the bandpass filter, and a motion detection circuit for obtaining a signal representing the movement of a subject from the input composite color television signal; A luminance/color signal separation circuit characterized in that coefficients of a first coefficient circuit and a second coefficient circuit are respectively changed.