JPH06292227A - Luminance signal/chrominance signal separator - Google Patents

Abstract

PURPOSE:To surely separate a luminance signal and a chrominance signal even when a tilt component is included in the luminance signal. CONSTITUTION:An inputted existing signal is given to 1H delay circuits 2, 3, in which the signal becomes a 1H delay signal and a 2H delay signal. Furthermore, three-point signal is obtained at each line by unit delay circuits 21-26 and a nine-point signal consecutive in the vertical and horizontal directions is inputted to a two-dimension logic circuit 27. The two-dimension logic circuit 27 obtains tilt correlation from the nine-point signal thereby obtaining a color degree (k). The two-dimension logic circuit 27 obtains a color signal output through the arithmetic operation of the color signal component from a DCF circuit 28 and the coefficient (k).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a luminance signal / color signal separation circuit for a color television receiver or the like.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram showing a conventional luminance signal / color signal separation circuit.

The composite video signal introduced to the input terminal 1 is delayed by 1H (H is a horizontal period) in the 1H delay circuit 2 and further delayed by 1H in the 1H delay circuit 3. Thus, the BPFs 4, 5 and 6 are supplied with the present signal a, the 1H delay signal b and the 2H delay signal c, respectively. BPF4
5 and 6 are frequency bands near the color subcarrier frequency (3.58M
The signal component of the Hz band) is passed. The signals passed through the BPFs 4 and 6 are given to the amplifiers 11 and 12, respectively, and the signals passed through the BPF 5 are inverted in polarity by the inverting amplifier 7. The outputs d, e, of these amplifier 11, inverting amplifier 7 and amplifier 12,
f is applied to the intermediate value detection circuit 10.

The intermediate value detection circuit 10 detects the intermediate value of the outputs of the amplifiers 11 and 12 and the inverting amplifier 7. These signals have the same phase for the carrier color signal components in the same horizontal period. Therefore, the intermediate value detection circuit 10 outputs the intermediate value signal h including the carrier color signal component. In addition, the intermediate value detection circuit 10 outputs the intermediate value signal h including the luminance signal component only during the period in which both the amplifiers 11 and 12 and the output of the inverting amplifier 7 include the luminance signal component.

The outputs of the amplifier 11 and the inverting amplifier 7 are given to the adder 8 and added, and the addition signal g is output to the intermediate value detection circuit 15 via the amplifier 13. Further, the outputs of the inverting amplifier 7 and the amplifier 12 are given to the adder 9, and the adder 9 outputs the addition signal i via the amplifier 14 to the intermediate value detection circuit 15. The intermediate value detection circuit 15 also has the same configuration as the intermediate value detection circuit 10, and the intermediate value detection circuit 15 detects the intermediate value of the intermediate value signal h from the intermediate value detection circuit 10 and the addition signals g, i. Since the luminance signal components of the output of the amplifier 12 and the output of the inverting amplifier 7 are in opposite phases to each other in the same horizontal period, the addition signal in the period in which the luminance signal is included in both the outputs of the amplifiers 11 and 12 and the inverting amplifier 7. g does not include the luminance signal component. Similarly, the addition signal i in this period does not include a luminance signal component. Therefore, the luminance signal component of the intermediate value signal h is deleted by the intermediate value detecting circuit 15, and the intermediate value detecting circuit 15
The intermediate value signal j output from the output terminal 18 to the output terminal 18 is a carrier color signal containing no luminance signal component.

The adder 16 uses the intermediate value signal j and the 1H delay circuit 2
And the output of. Since the phases of the carrier color signals of both are opposite to each other, the carrier color signal component is not included in the output signal 1 from the adder 16. Thus, the brightness signal is output to the output terminal 17. In this way, it is possible to reliably separate the luminance signal and the chrominance signal, and obtain a pattern having a relatively high resolution even in the vertical direction.

Further, the horizontal and vertical filtering processing of the circuit of FIG. 3 will be described in detail. The circuit of FIG. 3 has a BPF4,
A horizontal filter is constituted by 5 and 6, and a color signal component in the horizontal direction is first extracted by the horizontal filter from the input composite video signal. On the other hand, as a vertical filter, a 3-line dynamic comb filter (hereinafter,
It uses a circuit called DCF). The DCF circuit is configured by the 1H delay circuits 2 and 3 and the chain line portion 19 in FIG. After the horizontal color signal component is extracted by the horizontal filter, the vertical color signal component j is extracted by the DCF circuit. Next, the luminance signal 1 is obtained by subtracting the color signal j thus obtained from the input composite video signal. The center frequency (fsc) of the color signal
Is given by the following equation (1) in the two-dimensional frequency display.

Μ = 3.58 MHz, ν = 525/4 cpH (1) where μ is the horizontal frequency and ν is the vertical frequency.

By adopting the DCF circuit as the vertical filter, it is possible to reduce the dot interference generated in the portion of the picture (vertical non-correlation portion) in which the color signal changes in the vertical direction. As described above, the accuracy of separation of the luminance signal and the chrominance signal in the vertical non-correlation portion (hereinafter referred to as Y / C separation) is improved as compared with the case of using only the comb filter that uses the correlation between two horizontal lines. Can be made.

However, since the diagonal component of the luminance signal cannot be discriminated, there is a problem in that Y / C separation is not reliably performed in an image containing many diagonal components and cross color is generated. This problem will be described with reference to Tables 1 and 2 below. Table 1 shows the color signal sampled at a sampling frequency of 2 fsc and the color signal amplitude at each sampling point normalized.

[0011]

[Table 1]

[Table 2] As shown in Table 1, the phase of the color signal is inverted before 1H and after 1H.

Now, the calculation mid (A, B, C) is A,
If defined as an operation for obtaining the intermediate value of B and C, the output h of the intermediate value detection circuit 10 can be expressed by the following equation (2): h = mid (d, e, f) (2) Intermediate value detection The color signal j from the circuit 15 can be represented by the following equation (3).

J = mid (h, (d + e) / 2, (e + f) / 2) (3) By applying this equation (3) to Table 1 above, a color signal when a color signal is input is obtained. Find j. The signal e is obtained by inverting the 1H delay signal in Table 1 and is the intermediate value detection circuit 10
Provides the same output as the current signal, and the intermediate value detection circuit 15 also provides the same color signal j as the current signal.

On the other hand, it is assumed that a monochrome video signal having a luminance oblique component is input through the input terminal 1. For example, it is assumed that an image in which the boundary between the black portion and the white portion is divided by a diagonally upper right line is input. Table 2 above shows the signals d, e, f of each part when such a video signal is input.
In this example, h, i, g, and j are sampled at a sampling frequency of 2fsc and their amplitudes are normalized.

In the video signals of the predetermined three lines input to the input terminal 1, the timing of changing from the black level to the white level is deviated by a predetermined period. The signals a, b, and c shown in FIG. 2 are amplitude-converted by being band-limited by the BPFs 4, 5, and 6, respectively, and the signals shown in d, e, and f of Table 2 are obtained.

These signals d, e, f are used as an intermediate value detection circuit.
Input to 10 and obtain the output h based on the above equation (2). Further, the adders 8 and 9 output the signals g and i of Table 2, respectively, and the intermediate value detection circuit 15 performs the calculation of the above equation (3) and outputs the color signal j shown in Table 2. As shown in Table 2, in the color signal j from the intermediate value detection circuit 15, a part where the amplitude is not 0 occurs. As described above, when the input video signal is black and white and originally does not include the color component, but when the luminance signal includes the oblique component, the color component is output from the output terminal 18. , Cross color will occur.

[0017]

As described above, in the above-described conventional luminance signal / color signal separation circuit, when an oblique component is included, an unnecessary color component is output. There is a problem that a pattern such as a diagonal stripe tie is displayed with added color.

It is an object of the present invention to provide a luminance signal / color signal separation circuit which can surely separate a luminance signal and a color signal even when an oblique component is included.

[0019]

Luminance signal according to the present invention
The color signal separation circuit separates the color signal component from the input composite video signal by at least one of the horizontal and vertical filters, and obtains the luminance signal by using the separated color signal component. Sampling means for sampling the input composite video signal at a predetermined sampling frequency in synchronization with a color subcarrier, and composite video signals at predetermined sampling points by the sampling means and oblique sampling which is different from the predetermined sampling point in horizontal and vertical directions. A diagonal correlation detecting means for obtaining a diagonal correlation component by obtaining an intermediate value between the point and the composite video signal, and a predetermined calculation of the diagonal correlation component and a color signal component obtained by at least one of the horizontal and vertical filters. Output by Is obtained and an output means for obtaining a signal.

[0020]

In the present invention, the diagonal correlation detecting means detects the diagonal correlation by obtaining an intermediate value between the predetermined sampling point and the composite video signal at the sampling point diagonal to the predetermined sampling point. As a result, it is possible to distinguish between the color signal component and the diagonal luminance component. The output unit switches the characteristics of the filter based on the diagonal correlation component obtained by the diagonal correlation detection unit to obtain an output color signal, thereby removing cross color.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a luminance signal / color signal separation circuit according to the present invention. In FIG. 1, the same components as those in FIG. 3 are designated by the same reference numerals.

A composite video signal is input to the input terminal 1. This composite video signal is applied to BPF4 and 1H.
It is supplied to the delay circuit 2. The 1H delay circuit 2 delays the composite video signal by 1H and supplies it to the BPF 5, the 1H delay circuit 3 and the adder 16. The 1H delay circuit 3 is the 1H delay circuit 2
The signal from is delayed by 1H and given to the BPF 6. BP
Each of F4, 5 and 6 has a pass band in the frequency band (3.58 MHz band) near the color subcarrier frequency, and the carrier color signal and 3.58 M in the introduced composite video signal.
Passes the luminance signal in the Hz band.

In the present embodiment, the passing signal (current signal) of the BPF 4 is given to the two-dimensional logic circuit 27 and also given to the two-dimensional logic circuit 27 through the series circuit of the unit delay circuits 21 and 22. The unit delay circuits 21 and 22 delay the input signal by a unit time and give it to the two-dimensional logic circuit 27. In addition, the passing signal e (1H delay signal) of the BPF 5 is set to 2
And the unit delay circuit 23,
It is given to the two-dimensional logic circuit 27 via 24 series circuits.
The unit delay circuits 23 and 24 delay the input signal by a unit time and give it to the two-dimensional logic circuit 27. Similarly, the passing signal f (2H delay signal) of the BPF 6 is given to the two-dimensional logic circuit 27 and also given to the two-dimensional logic circuit 27 through the series circuit of the unit delay circuits 25 and 26. The unit delay circuits 25 and 26 delay the input signal by a unit time and give it to the two-dimensional logic circuit 27. As a result, the two-dimensional logic circuit 27 has three consecutive predetermined three lines of video signals x1 to x3, x4 to x6, and x7 to x9 that are continuous on each line, that is, adjacent to the top, bottom, left, and right on the screen. The 9-point video signals for each of the three points are input at the same timing.

The two-dimensional logic circuit 27 discriminates the luminance oblique component by performing a predetermined calculation on these 9-point video signals, and surely extracts only the color component. That is, the two-dimensional logic circuit 27 has an oblique correlation detection circuit (not shown) for obtaining the upper right correlation and the upper left correlation from the input 9-point video signals x1 to x9. The signals x1 to x9 of 9 points are given to this diagonal correlation detection circuit. Also, the signals x2, x5,
The x8 is also given to the DCF circuit 28 which performs color separation using three lines. The DCF circuit 28 has the same configuration as the broken line portion 19 of FIG. 3, and performs the calculation shown in the above equations (2) and (3)
Outputs color signals. The DCF circuit 28 outputs signals x2, x
Color signals are separated for 5 and x8, but signals x1, x4 and x7 or signals x3, x6 and x9 at other timings are separated.
May be calculated.

As can be seen from Table 1 above, in which the color signal components of three horizontal lines are sampled and normalized, the diagonal components of the color signal are all "1" or all "-1". That is, in the color signal, the upper right correlation and the upper left correlation substantially match. On the other hand, as is clear from Table 2 above, for a luminance signal having a diagonal component, the deviation between the upper right correlation and the upper left correlation is relatively large in the vicinity of the diagonal line. In this way, by obtaining the deviation between the upper right correlation and the upper left correlation, the luminance oblique component can be discriminated.

The diagonal correlation detection circuit uses the 9-point signal x
The following equations (4) and (5) are calculated for 1 to x9 to obtain the upper right correlation DR and the upper left correlation DL.

DR = mid (x1, x5, x9) (4) DL = mid (x3, x5, x7) (5) The two-dimensional logic circuit 27 converts the diagonal correlations DR and DL into the following equation (6). By the calculation shown, a coefficient k indicating the degree of color is obtained.

K = 1-K0 │DL -DR │ ... (6) where K0 is a proportional constant.

The value of the coefficient k approaches 0 as the deviation between the upper right correlation DR and the upper left correlation DL increases. That is, k
In the case of = 0, it means that no color component is included in the vicinity of the oblique change line, that is, the video signal includes only the luminance component.

The multiplier 30 calculates the output color signal by multiplying the color signal from the DCF circuit 28 by a coefficient k, and outputs the output color signal to the output terminal 18 and the adder 16. Adder
Reference numeral 16 is adapted to subtract an output color signal from the output of the 1H delay circuit 2 and output a luminance signal to an output terminal 17.

Next, the operation of the luminance signal / color signal separation circuit thus constructed will be described with reference to Tables 3 and 4. Table 3 shows the signals of the respective parts when a color signal is input, sampled at a sampling frequency of 2 fsc and normalized, and Table 4 shows the luminance signal having an oblique component in the same manner.

[0032]

[Table 3]

[Table 4] The composite video signal input through the input terminal 1 is delayed by the 1H delay circuits 2 and 3, and the BPFs 4,5 and 5.
A current signal, a 1H delay signal and a 2H delay signal are applied to 6, respectively. The signal that has passed through the BPFs 4, 5 and 6 is given to the two-dimensional logic circuit 27 as it is and the unit delay circuit
It is delayed by 1 unit time by 21, 23 and 25 and given to the two-dimensional logic circuit 27. By the 1H delay circuits 2 and 3, the video signals of three consecutive lines are simultaneously generated by the two-dimensional logic circuit 27.
Given to. Further, the outputs of the unit delay circuits 21, 23 and 25 are delayed by one unit time by the unit delay circuits 22, 24 and 26 and given to the two-dimensional logic circuit 27. Unit delay circuits 21 to 26
As a result, continuous three-point video signals sampled at a sampling frequency of 2fsc are given to the two-dimensional logic circuit 27. In this way, the nine-point signals x1 to x9, which are three points continuous vertically and horizontally, are input to the diagonal correlation detection circuit of the two-dimensional logic circuit 27.

For these signals x1 to x9, the diagonal correlation detection circuit obtains an upper right correlation DR and an upper left correlation DL. That is, the diagonal correlation detection circuit calculates the above-mentioned expression (4) to obtain the upper right correlation DR, and calculates the above expression (5) to obtain the upper left correlation DL. Further, the two-dimensional logic circuit 27 uses the upper right correlation DR and the upper left correlation DL.
Is used to obtain the coefficient k of the above equation (6).

On the other hand, the signals x2, x5 and x8 are DCF circuits.
Also give to 28. The DCF circuit 28 separates the color signal from the video signal of three lines and outputs it to the multiplier 30. Multiplier 30 is DC
The color signal from the F circuit 28 is multiplied by the coefficient k and the output color signal is output to the output terminal 18 and the adder 16.

Now, assume that a color signal is input to the input terminal 1. In this case, the phases of the outputs of the BPFs 4, 5 and 6 are inverted around 1H as shown in Table 3 above, and the absolute values of the normalized amplitudes are all about 1. Therefore, when the operation of the equation (4) is performed on the present signal, the 1H delayed signal and the 2H delayed signal, the upper right correlation DR becomes the same as the 1H delayed signal as shown in Table 3. Similarly, the upper left correlation DL obtained by the calculation of the above equation (5)
Is the same as the 1H delayed signal. Further, when the above equation (6) is calculated with K0 = 1 using the upper right correlation DR and the upper left correlation DL, the coefficient k becomes 1 at all timings, as shown in Table 3. The multiplier 30 uses this coefficient k as the DCF
The color signal from circuit 28 is multiplied. Thus, the output terminal 18
, The color signals are accurately reproduced as shown in Table 3.

On the other hand, as shown in Table 4 above, the input terminal 1
It is assumed that a luminance signal including an oblique component is input to. When this luminance signal passes through BPFs 4, 5 and 6, the current signal, 1H delay signal and 2H delay signal shown in Table 4 above are obtained.

For these signals, the above equation (4),
Performing the calculation of (5), the upper right correlation DR and the upper left correlation DL
Ask for. As shown in Table 4, the upper right correlation DR is 1H.
It becomes the same as the delayed signal, and the upper left correlation DL becomes 0 at all timings. Furthermore, if K0 = 0, then the above equation (6)
The coefficient k is obtained by the calculation of As shown in Table 4, the coefficient k becomes 0 at the timing when the upper right correlation DR becomes 1 and -1, and becomes 1 at other timings.

On the other hand, the DCF circuit 28 uses the above equation (2),
The color signal is obtained by the calculation of (3). As described above, this color signal is cross-colored due to the oblique luminance component (third and fourth sampling points from the left in Table 4). However, in the multiplier 30, the color signal and the coefficient k
When multiplied by, the coefficient k is 0 at this sampling point, so that the output color signal becomes 0 at all timings, as shown in Table 4. In this way, even if a luminance signal including an oblique component is input, cross color is prevented from occurring.

In this embodiment, for convenience of explanation, the coefficient k is set to 0 or 1 by using the normalized values as the color signal and the luminance signal, but in reality, the coefficient k depends on each signal component. It can take other values. In this case, the output color signal m changes in a slope according to the value of k.

As described above, in this embodiment, the upper right correlation DR and the upper left correlation DL are obtained by using the video signals of 9 points vertically and horizontally adjacent to each other, and the luminance component is discriminated from the deviation between them. To obtain the coefficient k indicating the degree of the color signal. By changing the ratio of the color component and the luminance component according to the obtained coefficient k, it is possible to prevent the oblique component of the luminance signal from appearing in the color signal output. In this way, sure Y
/ C can be separated, and cross color can be prevented from occurring even when a video signal having an oblique pattern is input.

FIG. 2 is a block diagram showing another embodiment of the present invention. 2, the same components as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted.

This embodiment differs from the embodiment of FIG. 1 in that a switch 31 is provided in place of the multiplier 30, and the switch 31 is controlled by the two-dimensional logic circuit 27. In the embodiment of FIG. 1, the color signal output is obtained by multiplying the output of the DCF circuit 28 by the coefficient k. However, assuming that the constant K0 is 1, the value of the coefficient k is 1.
Or it becomes 0, so this multiplication is 1 at the output of the DCF circuit 28.
It is equivalent to multiplying the bit coefficient k, that is, controlling the output of the DCF circuit 28 by a switch.

That is, the calculation of the color signal output = (output of the DCF circuit 28) × k is equivalent to the control employing the logic shown in the following equation (7) when the coefficient k is quantized by 1 bit. is there.

If (k> Th) then color signal output = 0 else color signal output = output of DCF circuit 28 (7) In the embodiment configured in this way, the coefficient k from the two-dimensional logic circuit 27 is If 1, switch 31 is D
Output terminal of CF circuit 28 is selected and output as color signal output
18 and adder 16. On the contrary, when the coefficient k is 0, the switch 31 outputs 0. That is, even in this case,
The same results as in Tables 3 and 4 above are obtained.

Also in this embodiment, the cross color can be removed as in the embodiment of FIG.

[0046]

As described above, according to the present invention, the luminance signal and the chrominance signal can be reliably separated even when the oblique component is included.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a luminance signal / color signal separation circuit according to the present invention.

FIG. 2 is a block diagram showing another embodiment of the present invention.

FIG. 3 is a block diagram showing a conventional luminance signal / color signal separation circuit.

[Explanation of symbols]

2, 3 ... 1H delay circuit, 21-26 ... Unit delay circuit, 27 ... 2
Dimensional logic circuit, 28 ... DCF circuit, 30 ... Multiplier

Claims (1)

[Claims] 1. A luminance signal / color signal separation circuit for separating a color signal component from an input composite video signal by at least one of a horizontal filter and a vertical filter and obtaining a luminance signal using the separated color signal component, Sampling means for sampling the input composite video signal at a predetermined sampling frequency in synchronization with the color subcarrier, and a composite video signal at a predetermined sampling point by this sampling means and diagonal sampling points which are different from the predetermined sampling point horizontally and vertically. A diagonal correlation component for obtaining a diagonal correlation component by obtaining an intermediate value with the composite video signal, and a predetermined calculation of the diagonal correlation component and the color signal component obtained by at least one of the horizontal and vertical filters. Output color A luminance signal / color signal separation circuit, comprising: