JP2500729B2 - Y / C separation circuit - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Y / C separation circuit for separating a luminance signal (Y) and a chroma signal (C) from a composite color television signal.

[0002]

2. Description of the Related Art As one of conventional Y / C separation circuits,
In the same field, the sub-carriers are inverted for each line, in other words, the sub-carrier frequency is fH / 2.
It is known to use an offset of (fH: line frequency). This is because the luminance signal is concentrated at a frequency that is an integral multiple of fH and the chroma signal is fH / 2.
Since it is concentrated at a frequency that is an integer multiple of Y, a comb filter using a 1H (H is one line period) delay element
It is considered that the / C separation can be performed, and is a combination of the band-pass filter for separating the components near the sub-carrier frequency and the above comb filter.

This two-dimensional Y / C separation circuit is conspicuously deteriorated in the case of an image having no line correlation. For example, in the case of an image in which the upper half up to a certain line on the screen is blue and the lower half below that is red, bleeding occurs at the boundary of this color.

Therefore, in the two-dimensional Y / C separation circuit, in order to reduce the deterioration of image quality as much as possible, the presence / absence of line correlation is judged from, for example, signals of three consecutive lines (through a bandpass filter), Y / depending on this judgment result
An adaptive control is needed to control the C-separation operation. For example, assuming that signals of three consecutive NTSC signals passed through a bandpass filter are T, M, and B, these signals are used, and a chroma signal (C) and a luminance signal (Y) are obtained by the following algorithm. Can be separated.

C = [M- (T + B) / 2] / 2, Y = [M + (T + B) / 2] ... C = (MT) / 2, Y = (M + T) / 2 ... C = (M−B) / 2, Y = (M + B) / 2 ...

The expression can be applied when the luminance signal and the chroma signal can be regarded as uniform, that is, when all the signals of T, M and B have a correlation in the vertical direction. If T and M are almost the same and M and B have no correlation,
If the formula is applied, T and M are uncorrelated, and M and B are approximately the same, then the formula is applied. Furthermore, T, M,
When there is no correlation between the three B signals, the following processing is performed.

(A) When the sample data of the color subcarrier one cycle apart in the signal M have substantially equal values,
The color difference signal is regarded as a transient, and C = M and Y = 0.

(B) When the sample data of the color subcarrier one cycle apart in the signal M are not substantially equal,
It is regarded as a luminance signal transient, and C = 0 and Y = M.

In addition, the NTSC subcarrier has a phase inversion between two consecutive frames. A Y / C separation circuit using a frame memory utilizing such a property is also known. Y using two frame memories
In the / C separation circuit, assuming that the corresponding signals of three consecutive frames are F ₁ , F ₂ and F _3.

C = [F ₂ − (F ₁ + F ₃ ) / 2] / 2, Y = [F ₂ + (F ₁ + F ₃ ) / 2] / 2

According to the above, Y / C separation can be performed.
In addition, in the configuration using one frame memory

C = (F ₂ −F ₁ ) / 2, Y = (F ₂ + F ₁ ) / 2

By means of Y / C separation can be performed.

Y / C using such a frame memory
The separation circuit can perform full Y / C separation when there is no motion between frames. In other words, there is a drawback that if there is motion, it will not be connected to a blurred image.

[0015]

SUMMARY OF THE INVENTION The present invention, in a two-dimensional Y / C separation circuit in which adaptive control is performed, is capable of setting the parameters necessary for adaptive control to the optimum Y / C separation. It is intended to realize a circuit. Further, the present invention is based on the fact that Y / C separation using a frame memory can perform complete separation in a still image, and when there is motion, a two-dimensional Y / C separation circuit of adaptive control is used. Therefore, it is an object of the present invention to provide a Y / C separation circuit capable of performing good Y / C separation. Furthermore, the present invention uses an unused two-dimensional Y / C separation circuit when there is no motion, and Y
/ C separation performance is compared to find the best parameter that minimizes the separation error.
This parameter is adopted when the C separation circuit is used.

[0016]

According to the present invention, in a Y / C separation circuit for separating a luminance signal and a chroma signal from a composite color television signal, the correlation of different lines is detected, and Y is detected according to this detection output. / C separation operation that switches the operation of the / C separation, and the error of the Y / C separation is evaluated from the luminance output and the chroma output, and the reference value for determining the presence or absence of line correlation is sequentially changed to perform the separation. A signal generation circuit that selectively gives a reference value that minimizes the error, a frame memory and a separation circuit that performs Y / C separation by calculating composite color television signals of different frames obtained from this frame memory, and a composite color A motion detection circuit that detects the motion of the television signal, and the detection of this motion detection circuit, when there is no motion, extracts the Y / C separation output of the separation circuit and No. generating circuit is operated, the detection of the motion detection circuit, when the motion is present, the adaptive 2-D Y /
While taking out the output separated by the C separation circuit,
It is a Y / C separation circuit having a control circuit for stopping the reference value changing operation of the signal generation circuit.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the overall construction of an embodiment of the present invention, in which 1 is a digitized N, for example.
Input terminal for TSC composite color television signal,
Reference numeral 2 is a Y / C separation circuit using a frame memory, and 3 is an adaptive control type two-dimensional Y / C separation circuit. These two Y
The luminance signal (Y) and the chroma signal (C) output from the / C separation circuits 2 and 3 are supplied to the selector 4. The output of one Y / C separation circuit is selected by this selector 4 and is taken out to the output terminals 5Y and 5C.

Of the signals of three consecutive frames of the Y / C separation circuit 2, the signal F ₁ of the first frame and the signal F ₃ of the last frame are supplied to the motion detection circuit 6. This motion detection circuit 6 generates a detection signal whose level changes depending on the presence or absence of motion. The selector 4 is controlled by this detection signal. That is, when there is no motion, the selector 4 selects the output of the Y / C separation circuit 2 using the frame memory, and when there is motion, the two-dimensional Y / C
The selector 4 selects the output of the C separation circuit 3. A reference value γ for detection is supplied from the terminal 7 to the motion detection circuit 6.

The luminance signal and the chroma signal output from the Y / C separation circuit 3 are also supplied to the separation evaluation circuit 8.
The output of the separation evaluation circuit 8 is supplied to the reference value generation circuit 9. The separation evaluation circuit 8 detects the separation error of the two-dimensional Y / C separation circuit 3, and the reference value generation circuit 9 generates a reference value ε that minimizes this separation error. In addition, the separation evaluation is
This is done only when there is no movement and the Y / C separation circuit 2 is used, so the detection signal of the movement detection circuit 6 is supplied to the reference value generation circuit 9 for its control.

FIG. 2 shows an example of the Y / C separation circuit 2 using a frame memory. The digital composite color television signal from the input terminal 1 is supplied to the frame memory 10, and the output of the frame memory 10 is supplied to the frame memory 11. The frame memories 10 and 11 take out the signals F ₁ , F ₂ and F _{3 of} three consecutive frames and supply them to the adder circuit 15 via the multipliers 12, 13 and 14, respectively. The coefficient of the multiplier 12 is 1/4, the coefficient of the multiplier 13 is 1/2, and the coefficient of the multiplier 14 is 1/4.

The output of the adder circuit 15 is taken out as a chroma signal, phase-inverted and supplied to the adder circuit 16. The signal F ₂ is supplied to the adder circuit 16, and the output of the adder circuit 16 is taken out as the luminance signal Y. The delay of the Y / C separation circuit 2 using the frame memories 10 and 11 coincides with the time of the signal F ₂ . Therefore, the signal F ₂ is taken out to the terminal 17 and supplied to the two-dimensional Y / C separation circuit 3.

FIG. 3 shows an example of the structure of the motion detection circuit 6. The signal F ₃ supplied to the input terminal 1 and the phase-inverted version of the signal F ₁ output from the frame memory 11 are supplied to the addition circuit 18, and the difference between them (δ = F ₃ −F ₁ ).
Is calculated, and the difference component is supplied to the comparison circuit 19,
The reference value γ from the terminal 7 is compared. When (δ <γ), it is detected that there is no motion, and when (δ> γ),
Motion is detected. As described above, the selector 4 is switched by this detection signal.

As the Y / C separation circuit 2 using a frame memory, a structure using one frame memory 10 can be used as shown in FIG. Signals F _{1 of} different frames obtained by the frame memory 10,
The luminance signal output is obtained by supplying F ₂ to the adder circuit 20 and halving the output of this adder circuit 20 by the multiplier 21. Also, the phase-inverted signal F ₁ and the signal F ₂ are supplied to the adder circuit 22, and the output of the adder circuit 22 is halved by the multiplier 23 to obtain a chroma signal output.

An example of the adaptive control type two-dimensional Y / C separation circuit 3 is shown in FIG. In FIG. 5, a digital composite color television signal is supplied to an input terminal designated by 17. Reference numeral 25 denotes a bandpass filter for passing the band of the chroma signal. The output of the bandpass filter 25 is supplied to the series connection of the 1H (1 horizontal section) delay circuit 26 and the 1H delay circuit 27, The signals B, M, and T extracted from these stages are multiplied by the multipliers 28, 29, and 30.
Are supplied to the correlation determination circuit 31 as shown in broken lines. A predetermined coefficient, for example, 1/2 is supplied to the multipliers 28, 29, 30 and the output thereof is supplied to the adder circuit 36 via the switch circuits 33, 34, 35. The switch circuits 33, 34 and 35 are controlled by the judgment output of the correlation judgment circuit 31. Then, the output of the adder circuit 36 is taken out as a chroma signal. Further, the composite color television signal is supplied to the adder circuit 39 via the delay circuit 37 and the 1H delay circuit 38 for correcting the delay in the band pass filter 25. An antiphase chroma signal C is added to the adder circuit 39, and its output is taken out as a luminance signal.

The above-mentioned correlation judging circuit 31 judges the presence / absence of correlation using the absolute values of the three signals, and controls the switch circuits 28, 29, 30 according to the result of this judgment. I am doing a lot of processing.

When | T | ≈ | M | ≈ | B |
Based on the formula, C = [M- (T + B) / 2] / 2, Y = [M + (T + B) / 2] / 2

When only | T | ≈ | M | holds, C = (MT) / 2 and Y = (M + T) / 2 based on the equations.

When only | M | ≈ | B | holds, C = (M−B) / 2 and Y = (M + B) / 2 based on the equations.

[T] |, | M |, | B |

(A) When the sample data of the color subcarriers separated by one cycle in the signal M have substantially equal values, it is regarded as a transient of the color difference signal and C = M and Y = 0.

(B) When the sample data of the color subcarrier one cycle apart in the signal M are not substantially equal,
It is regarded as a luminance signal transient, and C = 0 and Y = M.

In the correlation judgment circuit 31 described above, the judgment reference value ε is supplied from the terminal 32. For example (| T |-| M
When the relation of | <ε) is established, (| T | ≈ | M |)
It is said.

The adaptive control type two-dimensional Y / C separation circuit 3 described above performs correlation judgment by comparing absolute values. Unlike this method, the chroma signal levels of adjacent lines in the same field are the same and the phase is 180 degrees.
The applicant of the present application has proposed a method of determining that there is a correlation if the states are different from each other, and determining that there is no correlation otherwise. FIG. 6 shows the procedure for determining the presence or absence of this correlation. It is determined whether or not the absolute value of the sum (or the difference) of the signals of adjacent lines is smaller than the reference value ε.
If this relationship is established, it is determined that there is a correlation, and if not, it is determined that there is no correlation.

FIG. 7 shows the configuration of the two-dimensional Y / C separation circuit 3 which performs such a correlation determination. Basically, a Y / C separation circuit similar to that of FIG. 5 is configured, and a correlation determination circuit 31 surrounded by a broken line makes the determination shown in FIG.

The operation circuit 40 of the correlation determining circuit 31 is | M
The calculation of + T |
Is to sequentially perform the operation of | M + B | for each sample. These operation outputs are level comparison circuits 42 and 4.
3 and is compared with the reference value ε from the terminal 32.
The comparison outputs a, a * of the level comparison circuits 42 and 43,
b, b *, (* means inverted output)
This corresponds to the one shown in the flow chart of FIG. 6, and ab, a
Four judgment outputs a * b *, ab *, and a * b are formed. The meaning of each of the determination outputs is that an output that becomes a high level when | M + T |> ε holds, a * that outputs a high level otherwise, and | M + B |> ε holds. The output that is high level when the output is on is b, and the output that is high level otherwise is on b *.

Ab. . . There is no correlation between the signals T, M, B of the three lines. a * b *. . . There is a correlation between any of the signals T, M, and B. ab *. . . There is a correlation between the signals T and M. a * b. . . There is a correlation between the signals M and T.

The above-mentioned judgment outputs are the AND gates 48, 4
9, 50, 51. The output of the AND gate 48 is supplied to the AND gate 52, and the AND gate 49,
The signal passed through 50, 51 and 52 is supplied to the OR gate 53, and the chroma signal C appears from this OR gate 53.

In the comparison operation of the level comparison circuits 42 and 43 described above, when the same comparison result continuously occurs with respect to a plurality of sample data, the comparison result is checked so as not to be affected by noise or the like. You may make it effective.

Further, the adder circuits 54 and 55 form the difference signals M-B and M-T, and the divider circuits 56 and 57 divide the difference signals into 1/2 to obtain (M-B) / 2, (M-
Each signal of T) / 2 is formed, and further, the addition circuit 58 and the division circuit 59 form a signal of [M− (T + B) / 2] / 2. These division circuits 56, 57 and 5
The respective outputs of 9 are supplied to the AND gates 49, 50 and 51 described above.

The signal M appearing at the output of the 1H delay circuit 26 is supplied to the AND gate 52 and also to the delay circuit 60 and the arithmetic circuit 61. This delay circuit 60
Let M'be the output of
′ | Is calculated and its output is supplied to the level comparison circuit 62 and compared with the reference signal R from the terminal 63. The delay circuit 60 has a delay amount of one cycle of the color subcarrier, and M ′ is a signal one cycle before M. When the levels of the signals M and M ′ are almost equal (| MM−M ′ |
When <R), the level comparison circuit 62 generates a comparison output that becomes high level, and otherwise becomes low level.
This is supplied to the AND gate 48. Therefore, a
When b is high and it is determined that there is no correlation between the three signals, and when the levels of M and M ′ are approximately equal,
The signal M is taken out as a chroma output through the AND gate 52 and the OR gate 53, and the luminance signal Y from the adder circuit 39 is set to 0. Similarly, when it is determined that there is no correlation between the three signals, and when the levels of M and M ′ are not substantially equal, the AND gate 52 is turned off, the chroma signal C is set to 0, and The luminance signal Y is the signal M.

Further, when the output a * b * of the judgment circuit 31 is at a high level, the output of the division circuit 59 is selected as a chroma signal, and when the judgment output ab * is at a high level, the output of the division circuit 56. Is selected as the chroma signal and the judgment output a *
The output of the divider circuit 57 is selected when b is high.

In the above description, the presence or absence of correlation is determined by using the signals of three adjacent lines in the same field, but the presence or absence of correlation is determined by using the signals of four adjacent lines. It may be used for determination.

As shown in FIG. 1, the separation / evaluation circuit 8 synthesizes the outputs of the two-dimensional Y / C separation circuit 3 by the addition circuit 64 to form a composite color television signal, and outputs the phase-inverted signal. The separation error β is detected by supplying the signal F ₁ of the first frame extracted from the T / C separation circuit 2 using the frame memory to the addition circuit 65.
The composite color television signal obtained by synthesizing the output of the Y / C separation circuit 2 is the signal F ₂ of the _second frame. However, since there is no movement, if the operation of the two-dimensional Y / C separation circuit 3 is good, (F ₁ ≈F ₂ ) and the separation error β becomes extremely small.

This separation error β is generated for each sample data of the digitized signal, and is passed through the square circuit 66 and the digital integration circuit 67 of the ROM configuration. The digital integrating circuit 67 includes a register 68 and an adding circuit 69, and is configured to add the data input from the adding circuit 69 and fed back from the register 68. An effective value of the separation error β is generated from this digital integration circuit 67.

The reference value generating circuit 9 includes registers 70, 7
1, 72, 73, a comparison circuit 74, a memory 75 for storing a plurality of reference values, a selector 76, and a control circuit 77. The detection signal of the motion detection circuit 6 is supplied to the selector 76 and the control circuit 77. Selector 76
Selects the reference value read from the memory 75 when there is no movement and supplies it to the two-dimensional Y / C separation circuit 3, and selects the reference value stored in the register 72 when there is movement and selects 2
It is supplied to the dimension Y / C separation circuit 3. In addition, the control circuit 77
Captures data for each register, and the memory 75
Control the read operation of.

When there is no movement, the control circuit 77 reads out from the memory 75 a reference value .epsilon. Which changes sequentially for each frame, for example, and supplies it to the two-dimensional Y / C separation circuit 3 via the selector 76. . An error β of Y / C separation performed using the reference value at this time is detected by the separation evaluation circuit 8. The effective value of this error β for one frame is taken into the register 70. The register 70 fetches the separation error value slightly before the timing when the next reference value is read from the memory 75 and stores it.

The register 71 stores the minimum separation error value corresponding to each of the past reference values. That is, the new separation error value from the register 70 and the register 7
The minimum value stored in 1 is compared by the comparison circuit 74, and this is taken into the register 71 only when the new separation error value becomes smaller. This register 71 is initially filled with a large value to start the evaluation of a series of reference values. When the content of the register 71 is updated as described above, the reference value appearing in the selector 76 is stored in the register 73.

By performing the above-mentioned operation for each of the series of reference values, the minimum separation error value is stored in the register 71, and the reference value that causes this minimum separation error value is stored in the register 73. It is in the state of being.
Then, the contents of the register 73 are transferred to the register 72,
When there is movement, the selector 76 selects the reference value stored in the register 72. Using the reference value ε, the two-dimensional Y / C separation circuit 3 determines the correlation as described above. Therefore, the reference value ε
Is to optimize the separation operation of the two-dimensional Y / C separation circuit 3.

[0049]

[0050]

Further, the separation evaluation circuit and the reference value generation circuit may be constructed using a microcomputer.

Further, the present invention can be applied to a PAL system color television signal.

[0053]

According to the present invention, the reference value used for determining the correlation and the band parameter of the bandpass filter can be automatically set to a value that minimizes the separation error. It is possible to realize a two-dimensional Y / C separation circuit that can be controlled to be digitalized. Further, according to the present invention, in which the two-dimensional Y / C separation circuit and the Y / C separation circuit using the frame memory are combined and both are selectively used according to the presence or absence of motion, blurring may occur. None and two-dimensional Y
It is possible to perform Y / C separation in which the insufficient Y / C separation by the / C separation circuit is eliminated.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a block diagram of an example of a Y / C separation circuit using a frame memory.

FIG. 3 is a block diagram of an example of a motion detection circuit.

FIG. 4 is a block diagram of another example of a Y / C separation circuit using a frame memory.

FIG. 5 is a block diagram of an example of a two-dimensional Y / C separation circuit.

FIG. 6 is a flowchart used to describe a two-dimensional Y / C separation circuit.

FIG. 7 is a block diagram used to describe a two-dimensional Y / C separation circuit.

[Explanation of symbols]

 1 Digital composite color television signal input terminal 2 Y / C separation circuit using frame memory 3 Two-dimensional Y / C separation circuit 5Y Luminance signal output terminal 5C Chroma signal output terminal 6 Motion detection circuit 8 Separation evaluation circuit 9 Reference value generating circuit 10 frame memory 11 frame memory 25 bandpass filter 26 1H delay circuit 27 1H delay circuit 31 correlation determination circuit 32 input terminal for reference value of correlation determination

Claims (2)

(57) [Claims] 1. A Y / C separation circuit for separating a luminance signal and a chroma signal from a composite color television signal, detects the correlation of different lines, and outputs Y according to the detection output.
/ C separation operation is switched to an adaptive two-dimensional Y / C separation circuit, the Y / C separation error is evaluated from the luminance output and the chroma output, and the reference value for judging the presence or absence of the line correlation is sequentially changed. Signal generation circuit for selectively giving a reference value that minimizes the separation error, and a separation circuit for performing Y / C separation by calculating a frame memory and a composite color television signal of different frames obtained from the frame memory. A motion detection circuit for detecting the motion of the composite color television signal, and when the motion detection circuit detects no motion, the Y / C separation output of the separation circuit is taken out and the signal generation circuit is When the motion is detected by the motion detecting circuit, the output separated by the adaptive two-dimensional Y / C separating circuit is taken out, and A Y / C separation circuit comprising: a control circuit for stopping the reference value changing operation of the signal generation circuit. 2. The signal generating circuit is the two-dimensional Y / C.
Detecting the separation error by combining the outputs of the separation circuit to form the composite color television signal and adding the phase-inverted signal and the signal of the first frame extracted from the separation circuit. The Y / C separation circuit according to claim 1, wherein