JPH0691662B2 - Color TV brightness / color separation circuit - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a luminance / color separation circuit of a color television, and is particularly suitable for separating a luminance signal and a carrier color signal from an NTSC composite color television signal. It relates to a simple brightness / color separation circuit.

[Background of the Invention]

Conventionally, from a composite color television signal of NTSC system, a luminance signal (hereinafter, referred to as Y signal) and a carrier color signal (hereinafter, color (C))
As a method of separating the signal), the frame memory is used to determine the mixture ratio of the high frequency component of the difference signal between frames and the high frequency component of the difference signal between the upper and lower scanning lines having the same field to determine whether the subject moves. Is well known (see "Color Signal Separation Circuit" in JP-A-58-129892).

In the above method, when a still image with no motion of the subject, ideal Y with less dot crawling and cross color is used.
The signal and the C signal are separated. Also, good YC separation is performed even in the case of a moving image that changes drastically. However, in the case of a moving image that moves slowly, it is realized by gradually changing the mixing ratio of the YC separation used for the above still image and the moving image that changes rapidly. In the case of (for still images), Y / C
Interference easily occurs, and because the mixing ratio is changed stepwise, Y / C separation in the intermediate movement is not perfect, and there are many interferences such as dot crawling and cross color. There was a defect that became an image.

[Object of the Invention]

The object of the present invention is to eliminate such conventional drawbacks,
System color TV signal to luminance (Y) signal and color (C)
Provided is a luminance / color separation circuit capable of separating a high-quality luminance (Y) signal and color (C) signal without interference regardless of the speed of movement of a subject when separating signals. is there.

[Outline of Invention]

In order to achieve the above object, the luminance / color separation circuit of the color television of the present invention has a vertical frequency fv = fscv and a time frequency.
In the method of separating the carrier color signal and the luminance signal from the composite color television signal in which the carrier color signal modulated by the subcarrier frequency (fsc) of ft = fsct is superimposed on the luminance signal, the vertical direction with respect to the composite color television signal. Frequency (f
v) and the time-frequency (ft) two-dimensional transfer characteristic has a stop region in the vicinity of the coordinate axes of the both frequencies, and the first filter means for extracting the carrier color signal, and the two-dimensional transfer characteristic described above. Is characterized in that it has a YC separation filter having second filter means for extracting the luminance signal, each having prevention regions near the vertical frequency fv = fscv and near the time frequency ft = fsct.

Example of Invention

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 is a block diagram showing the configuration of a luminance / color (YC) separation circuit showing an embodiment of the present invention. The composite color television signal in which the color (C) signal modulated by the subcarrier frequency (sc) is superimposed on the luminance (Y) signal is sent to the YC separation circuit 2 and the motion detection circuit 3 via the input terminal 1. To be Motion detection circuit 3
Detects the motion information 3a from the color television signal and sends it to the YC separation circuit 2. The YC separation circuit 2 receives the motion information 3a, extracts the Y signal and the C signal from the color television signal,
Output terminals 4 and 5 that output high-quality Y and C signals according to the movement of the subject
Output to each.

FIG. 4 is a conceptual representation of a color television signal, which is a three-dimensional signal composed of h (horizontal axis), v (vertical axis) t (time axis). In the figure, 6 is an image represented by a signal of 1 field, 7 is a scanning line of the image, and i, (i +
1), (i + 2) ... (i + n) ... are field numbers, and the interval is 1/60 seconds, and therefore 2 fields (for example, i and (i + 1)) Complete a complete screen (1 frame).

FIG. 5 (a) is a two-dimensional (plane) representation of FIG. 4 with the vertical axis v and the time axis t. It should be noted that, in the scan line 7, Indicates the polarity of the C signal. That is, as is well known, the C signal superposed on the Y signal at the subcarrier frequency (sc) has the polarity inverted every horizontal scanning period (H), and the phase of the ○ -marked scanning line is changed. When φ, next (lower side)
of The phase at is φ + π (180 °).

FIG. 5 (b) expresses the frequency distribution of the Y signal and the C signal of the color television signal in the two dimensions of the vertical frequency v (cycle / image height) and the time frequency t (Hz). The Y signal is centered on the origin
The signal is distributed around sc. In addition, fs at this time
The coordinate of the time frequency axis ft of c is fsct, and the coordinate of the vertical frequency fv is fscv.

FIG. 2 is a block diagram of a Y / C separation circuit showing an embodiment of the present invention.

In FIG. 2, 8, 9 and 10 are YC separation filters, which are used for a still image, a moving image that changes drastically, and a moving image that changes slowly. 11 and 12 are Y signal and C respectively
This is a signal mixing circuit, which mixes the output signals Y _{1 to} Y ₃ , C _{1 to} C ₃ of the YC separation filters 8 to 10 at the mixing ratio according to the motion information 3a, and outputs Y and C to terminals 4,5. To do.

FIG. 6 is a diagram for explaining the YC separation filter 8 of FIG. 2, in which FIG. 6 (a) is a circuit configuration diagram showing an embodiment, and FIGS. 6 (b) and (c) are Y and Y, respectively. The impulse response of the C signal and (d) and (e) of the figure show the transfer characteristics for Y ₁ and C ₁ , respectively.

In FIG. 6 (a), 13 is a frame memory that delays one frame period (525H), 14 and 21 are addition circuits, 15 is a subtraction circuit, 16 and 17 are multiplication circuits that multiply by 1/2, and 18 is a low frequency band. Pass filter (LPF), 19, 20 are band pass filters (BPF), 22,
Reference numeral 23 is a terminal to which Y ₁ and C ₁ are output, respectively. In (b) and (c) of the same figure, ⊚ indicates the scanning line of the output Y ₁ and C ₁ signals, the number in ○ indicates the load to be added (subtracted), and the negative (-) sign is Indicates that the polarities are inverted and added, that is, subtracted (the same applies hereinafter). The same figure (d),
In (e), the diagonal line to the left is the pass band, and the grid-like portion of the diagonal line is the stop band (the same applies hereinafter). The same figure (b)
of And the scanning line one frame cycle before are added by the adder circuit 14, averaged (1/2) by the multiplier circuit 16, passed through the BPF 19, and then added by the adder circuit 21. It is then averaged (1/2) in the multiplication circuit 17 and passed through the BPF 20 to become the C ₁ signal (sc is the high frequency component with the center). The transfer characteristics for the Y ₁ signal and the C ₁ signal are shown in FIGS.
It is as follows.

Here, since the frequency spectrums of the Y signal and the C signal in the still image are distributed only on the vertical frequency axis (t = 0) and t = 15 [Hz], other signal components are generated in both the Y and C signals. It can be completely blocked and an ideal Y, C separation is achieved.

FIG. 7 is a diagram for explaining the YC separation filter 9 of FIG. 2. FIG. 7A is a circuit configuration diagram showing an embodiment, and FIGS. 7B and 7C are Y and Y, respectively. The impulse response of the C signal and (d) and (e) of the same figure show the transfer characteristics for Y ₂ and C ₂ , respectively.

In FIG. 7 (a), 24 and 25 are one horizontal scanning period (1H).
Delay line memory, 26, 28, 35 adder circuit, 27, 3
0,31 is a multiplication circuit that multiplies 2 or 1/4, 29 is a subtraction circuit, 3
2 is a low-pass filter (LPF), 33 and 34 are band-pass filters (BPF), and 36 and 37 are terminals to which Y ₂ and C ₂ are output, respectively.

The scanning lines (lower side) and (upper side) in FIG. 7B are added by the adding circuit 26, and further added by the adding circuit 28. Is multiplied by 2 and added, and the multiplication circuit 30 averages (1 /
4) and after passing through BPF33, passing through LPF32 at adder circuit 35 Similarly, the addition circuit 26 adds and the subtraction circuit 29 Is subtracted from the value obtained by multiplying by 2 and the average (1 /
4) is performed and passes through the BPF 34 to become a C ₂ signal. The transfer characteristics for the Y ₂ signal and the C ₂ signal are as shown in FIGS. The Y signal and the C signal in a moving image that changes drastically are not band-limited in the time direction, that is, since the frequency spectrum of itself that spread in the time frequency (t) direction is passed, both the Y and C signals are It is possible to completely block other signal components in the vertical direction.
C separation is realized.

FIG. 1 is a diagram for explaining the YC separation filter 10 of FIG. 2, in which FIG. 1A is a circuit configuration diagram showing one embodiment, and FIGS. 1B and 1C are Y and Y, respectively. The impulse response of the C signal and (d) and (e) of the figure show the transfer characteristics for Y ₃ and C ₃ , respectively.

In FIG. 1, 38 and 39 are field memories for delaying 263H and 262H respectively, 42 and 43 are line memories for delaying 1H, 40, 44 and 51 are addition circuits, 41 and 45 are subtraction circuits, and 46 and 47 are 1 circuits. /
Multiplier circuit to multiply by 4, 48 is a low pass filter (LPF), 4
9,50 are band pass filters (BPF), 52 and 53 are Y ₃ and C respectively
₃ is the output terminal.

For the Y ₃ scanning line indicated by ⊚ in the same figure (b), the Y ₃ signal is calculated from the average value of the four scanning lines above and below the adjacent field. That is, the scanning lines (lower right) and (lower left) are added by the adder circuit 40, and further added by the adder circuit 44.
Is added with the sum of the scanning lines (upper right) and (upper left) that went 1H before, and the multiplication circuit 46 averages (1/4) and B
After passing through the PF49, the adder circuit 51 adds the scanning line ◎ passing through the LPF48 to form a Y ₃ signal. On the other hand, FIG.
The C ₃ signal for ⊚ is calculated from the line difference signal of the frame difference signals of adjacent fields. That is, scan line (lower right) Is subtracted in the subtraction circuit 41, and further in the subtraction circuit 45, the subtraction circuit 41 goes 1H before. And (upper left) are subtracted and subtracted, and the multiplication circuit 47
Averaged (1/4) at and passing through BPF50 centered on sc
It becomes a C ₃ signal. Transfer characteristics for the Y ₃ signals and C ₃ signals the figure (d), as shown in (e), the Y ₃ signal t
= 15 (Hz), v = 525/4 (cycle / image height),
On the other hand, the C ₃ signal has stopbands near t = 0 and v = 0, respectively, so that the Y signal (or C signal) in a moving image that moves slowly is interfered with by the C signal ( Alternatively, the frequency spectrum of (Y signal) can be sufficiently blocked on the time frequency t and the vertical frequency v, and Y and C separation that realizes a moving image with less afterimage (blur) is realized.

FIG. 8 is a circuit diagram showing an embodiment of the motion detecting circuit 3 and the mixing circuits 11 and 12 shown in FIG.

In FIG. 8, 54 is a frame memory for delaying 525H, 55 is a subtraction circuit, 56 is a low pass filter (LPF), 57
Is an absolute value calculation circuit, and 61 to 63 are motion coefficients k1 from the motion information 3a.
˜k3 is a conversion circuit, 64-66 are multiplication circuits by which motion coefficients k1 to k3 are multiplied, and 67 is an addition circuit.

In the motion detection circuit 3, the composite color television signal received at the input terminal 1 is delayed by the frame memory 54, and the subtraction circuit 55 calculates the difference signal between frames. Since the component of the carrier color signal is mixed with the output of the subtraction circuit 55 in addition to the motion information 3a, the LPF 56 removes the carrier color signal and outputs the luminance change signal ε between frames.

The absolute value calculation circuit 57 takes the absolute value | ε | of the above ε and sends it to the mixing circuits 11 and 12 as the motion information 3a.

In the mixing circuit 11, the conversion circuits 61, 62 and 63 convert the motion information 3a into motion coefficients k ₁ , k ₂ and k ₃ which vary between 0 and ₁ , and the multiplication circuits 64, 65 and 66 respectively generate Y ₁ , Y ₂ , Y ₃ signals are multiplied by the values of the motion coefficients k ₁ , k ₂ , k ₃ and the adder circuit 67 produces Y ₁ , Y ₂ , Y ₃ signals corresponding to the motion of the subject. The signals are mixed and output as a luminance (Y) signal. In addition, the mixing circuit 12 is similar to the above, C ₁ , C ₂ ,
Motion coefficient that changes each signal of C ₃ according to the motion of the subject
The mixed signals of k ₁ , k ₂ and k ₃ are output as the carrier color (C) signal.

FIG. 9 exemplifies the relationship between the absolute value | ε | of the luminance change signal and the motion coefficients k ₁ , k ₂ , k ₃ in FIG. 8. In FIG. 9A, the motion coefficient is gradually changed. In the example shown in FIG. 7B, the value is changed with two values of 1,0.

In FIG. 8A, | ε | = 0, that is, k ₁ = 1 and k ₂ = k ₃ = 0 in the still image portion.
Only Y ₁ and C _{1 in the} figure are output, and when 0 <| ε | <Th, Y ₁ and Y
₃ and Y, C with gradually changing the mixing ratio of C ₁ and C ₃ are output, and | ε | = Th, that is, in the image part that moves slowly
Only Y ₃ and C ₃ are output. When Th <| ε | <2Th, the mixing ratios of Y ₂ and Y ₃ and C ₂ and C ₃ are gradually changed, and 2Th | ε | Only Y ₂ and C ₂ are output.

On the other hand, in the same figure (b), when 0 | ε | <Th / 2,
When k ₁ = 1 and Y ₁ and C ₁ are Th / 2 | ε | <3Th / 2, k ₃
= 1 and Y ₃ , C ₃ is 3Th / 2 ｜ ε ｜, k ₂ = 1
Y ₂ and C ₂ are output respectively. In addition, in FIG.
The multiplying circuits 64-66 and the adding circuit 67 shown in FIG. 8 can be replaced by a switching switch.

FIG. 10 shows that the YC separation filter of FIG. 1 has a cascaded structure of a first function for calculating the sum and difference between frames and a second function for calculating the sum and difference between lines. FIG. 19A is a diagram for explaining a circuit obtained by modification, FIG. 19A is a circuit configuration diagram showing one embodiment, and FIG.
Similar to the figure, the absolute value | ε | of the brightness change signal and the motion coefficients k ₄ , k
It is a relationship diagram of ₅ .

In the figure (a), 68 and 71 are YC separation filters 69, 72 and 74 having the above-mentioned first and second functions, respectively.
Is a terminal and 70 and 73 are switching circuits.

The color television signal from the input terminal 1 is 0 in FIG.
When | ε | <Th / 2, the switching circuits 70 and 73 are switched to the (1) side and the (0) side by k ₄ = 1 and k ₅ = 0.
68 → the switch circuit 70 (1) side → the switch circuit 73 (0) through the side as the output of Y ₁ or _{C 1, Th / 2 | ε} | <3Th /
In the case of 2, since k ₄ = k ₅ = 1 passes through the YC separation filters 68 and 71, it becomes the output of Y ₃ or C ₃ , and 3Th / 2 | ε
At |, the output of Y ₂ or C ₂ that passes through only the YC separation filter 71 is obtained with k ₄ = 0 and k ₅ = 1.

FIG. 11 is a diagram for explaining a case where the YC separation circuit shown in FIG. 2 is configured in a cascade connection type as shown in FIG. 10, and FIG. 11A is a circuit configuration diagram showing one embodiment, The same figure (b),
(C) is the impulse response of the Y and C signals, respectively.

In the figure (a), 75 is a frame memory for delaying one frame, 76,84,86,90,99 are addition circuits, 77,92 are subtraction circuits, and 78,79,85,87,91,93 are multiplication circuits. Circuits, 80, 81, 94, 95 are switching circuits, 82, 83, 88, 89, 96 are line memories for delaying one line cycle, 97 is a low pass filter (LPF), 98, 100 are band pass filters (BPF) , 102 and 103 are conversion circuits.
In the circuit shown in FIG. 6A, the space between the input terminal 1 and the multiplication circuits 78 and 79 is the same as that up to the multiplication circuits 16 and 17 shown in FIG. 6A, and two outputs are provided by the switching circuits 80 and 81. When the motion coefficient k ₄ = 1, it is connected to the subsequent stage. Further, between the outputs of the switching circuits 80 and 81 and the switching circuits 94 and 95 is equivalent to the circuits up to the multiplying circuits 30 and 31 of FIG. 7 (a) described above, and the two outputs are switched as described above. The circuits 94 and 95 are connected to the subsequent stage when the motion coefficient k ₅ = 1. k ₄ = k ₅ = 1 i.e. switching circuit 80,81,94,95 are both (1) when the side becomes the Figure 6 and Figure 7 connection configuration, it is outputted to the switching circuit 94 and 95. The impulse response is shown in FIGS. 11 (b) and 11 (c) by a factor multiplied by eight.

Therefore, the color TV signal at the input terminal 1 is passed through the line memory 96 and the pass component of the LPF 97 and the switching circuits 94 and B.
By adding the addition component 99 with the passing component of PF98,
A high quality Y signal can be obtained. On the other hand, the switching circuit 95
Output of BPF100 to the horizontal subcarrier frequency sc
If a component centered at is extracted, a high quality C signal can be obtained as in the above case. The switching circuit 80, 81, 94, 9
The motion coefficients k ₄ and k 5 for controlling ₅ are the motion information 3a which is the output of the motion detection circuit 3 shown in FIG. 8 (specifically, for example, the absolute value signal | By the conversion circuits 102 and 103 which received ε |), FIG.
It is converted and created as shown in (c). Thus, the YC separation circuit shown in FIG. 2 can be realized with a simplified circuit configuration. Further, by using the circuits of FIGS. 1, 2, and 11, deterioration of image quality due to interference between Y and C signals, such as dot interference and cross color, which occur in a moving image portion that changes in a loose manner, can be avoided. it can.

〔The invention's effect〕

As described above, according to the present invention, a still image is used to separate the Y signal and the C signal from the composite color television signal.
Equipped with three types of YC separation filters suitable for a moving image that changes drastically and a moving image that changes relatively slowly. The outputs of the YC separation filters are mixed at a mixing ratio according to the motion information of the subject, and Y signals are obtained. Since the C signal is separated, the quality of the television image is improved without the image being disturbed by the degree of movement of the subject.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a YC separation filter 10 showing an embodiment of the present invention, FIG. 2 is a configuration diagram of a YC separation circuit showing an embodiment of the present invention, and FIG. 3 is a luminance / color (YC). Block diagram of separation circuit, FIG. 4 is a conceptual diagram of a color television signal, FIG. 5 is a diagram for explaining the color television signal of FIG. 4, and FIG.
FIG. 7 is a diagram for explaining the YC separation filter 8 in FIG. 7, and FIG.
FIG. 8 is a diagram for explaining the YC separation filter 9, FIG. 8 is a circuit configuration diagram showing one embodiment of the motion detection circuit 3 and the mixing circuits 11 and 12 in FIG. 2, and FIG. 9 is an absolute value signal | ε in FIG. ｜ and motion coefficient k ₁ ~
relationship diagram k _3, FIG. 10 is a circuit diagram obtained by modifying the YC separation filter of FIG. 1, FIG. 11 is a diagram illustrating a YC separation circuit which is another embodiment of the present invention. 2: YC separation circuit, 3: Motion detection circuit, 8 to 10,68,71: YC separation filter, 11, 12: Mixing circuit, 13, 54, 75: Frame memory, 14, 21, 26, 28, 35, 40,44,51,67,76,84,86,90,99: Adder circuit, 15,29,41,45,55,77,92: Subtractor circuit, 16,17,27,30,3
1,46,47,64 to 66,78,79,85,87,91,93: Multiplier circuit, 18,32,4
8,56,97: Low pass filter (LPF), 19,20,33,34,49,5
0,98,100: Bandpass filter (BPF), 24,25,42,43,82,8
3,88,89,96: Line memory, 38,39: Field memory, 5
7: Absolute value calculation circuit, 61 to 63,102,103: Conversion circuit, 70,73,8
0,81,94,95: Switching circuit.

Claims (2)

[Claims] 1. Vertical frequency fv = fscv and time frequency ft =
In a method of separating a carrier color signal and a luminance signal from a composite color television signal in which a carrier color signal modulated by a subcarrier frequency (fsc) of fsct is superimposed on a luminance signal, a vertical frequency ( The two-dimensional transfer characteristic of the fv) and the time frequency (ft) has a stop region in the vicinity of the coordinate axes of the both frequencies, and the first filter means for extracting the carrier color signal, and the two-dimensional transfer characteristic. Is near vertical frequency fv = fscv and time frequency ft
A luminance / color separation circuit for a color television having YC separation filters each having a stop region near = fsct and provided with a second filter means for extracting the brightness signal. 2. Vertical frequency fv = fscv and time frequency ft =
In a method of separating a carrier color signal and a luminance signal from a composite color television signal in which a carrier color signal modulated by a subcarrier frequency (fsc) of fsct is superimposed on a luminance signal, a vertical frequency ( The two-dimensional transfer characteristic of the fv) and the time frequency (ft) has a stop region in the vicinity of the coordinate axes of the both frequencies, and the first filter means for extracting the carrier color signal, and the two-dimensional transfer characteristic. Is near vertical frequency fv = fscv and time frequency ft
A first YC separation filter having a second filter means for extracting the luminance signal, each having a stop region in the vicinity of = fsct, and a time frequency ft for extracting the carrier color signal.
= 0 and the time frequency ft to extract the luminance signal
the second with a transfer characteristic with a stop region near and to fsct
A YC separation filter and a third YC having a transfer characteristic having a stop region near the vertical frequency fv = 0 for extracting the carrier color signal and near the vertical frequency fv = fscv for extracting the luminance signal. A color television characterized by including a separation filter, extracting a signal representing the motion of an object, and changing the mixture ratio of the carrier color signal or the luminance signal output from the three types of YC separation filters according to the motion signal. Brightness of
Color separation circuit.