JP2942261B2 - Motion detection circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a composite television signal (hereinafter, referred to as a "V signal") obtained by frequency-multiplexing a chrominance signal into a high-frequency region of a luminance signal, from a luminance signal (hereinafter, referred to as "V signal"). , "Y signal" or simply "Y") and a chrominance signal (hereinafter referred to as "C signal" or simply "C") in a motion adaptive YC separation device for detecting a motion amount of a pixel signal. It relates to a detection circuit.

[Conventional technology]

A motion adaptive YC separation device using a conventional motion detection circuit
Whether the image is a still image or a moving image is locally determined, and YC separation suitable for the pixel signal of each part is performed.

In the current NTSC system, a composite signal is obtained by frequency-multiplexing a C signal in a high frequency range of a Y signal. For this reason,
The receiver requires YC separation, and the imperfect separation causes image quality deterioration such as cross color and dot crawl.

For this reason, with the development of large-capacity digital memories in recent years, it has to be equal to the vertical scanning frequency of the television signal,
Various motion adaptive YC separation devices using a delay circuit having a longer delay time (hereinafter, referred to as a “delay circuit”) have been proposed as signal processing devices for improving image quality.

FIG. 10 is a block circuit diagram showing an example of a conventional motion adaptive YC separation apparatus. In the figure, the input terminal (1) is NT
An SC type V signal (101) is input, and input terminals of an in-field YC separation circuit (4), an inter-frame YC separation circuit (5), a Y signal motion detection circuit (6), and a C signal motion detection circuit (7). Respectively. YC separation circuit in the field (4)
The YC separated Y signal Yf (102) in the field and the YC separated C signal Cf (103) in the field separated by YC by the filter in the field (not shown) are respectively provided in the Y signal mixing circuit (9). 1 input terminal and C signal mixing circuit (10)
Is input to the first input terminal. Also, the inter-frame YC separation Y signal YF (104) separated by the inter-frame YC separation circuit (5) by the inter-frame filter (not shown).
And the inter-frame YC separation C signal CF (105)
The signals are input to a second input terminal of the signal mixing circuit (9) and a second input terminal of the C signal mixing circuit (10). On the other hand, the Y signal motion amount (106) detected by the Y signal motion detection circuit (6)
Is input to one input terminal of the synthesis circuit (8), and
The C signal motion amount (107) detected by the C signal motion detection circuit (7) is input to the other input terminal of the synthesis circuit (8). The motion amount detection signal K synthesized by the synthesis circuit (8)
(108) is input to the third input terminal of the Y signal mixing circuit (9) and the third input terminal of the C signal mixing circuit (10), respectively. A motion amount detection circuit (20) including a detection circuit (7) and a synthesis circuit (8);
Is composed.

Motion adaptive YC separation Y output from Y signal mixing circuit (9)
The signal (109) is sent from the output terminal (2), and
The motion adaptive YC separation C signal (109) output from the signal mixing circuit (10) is transmitted from the output terminal (3).

 Next, the operation of this conventional example will be described.

When separating the V signal (101) by YC, the motion detection circuit (20) combines the outputs of the Y signal motion detection circuit (6) and the C signal motion detection circuit (7) with a synthesis circuit (8), and It is determined whether the signal (101) is a signal representing a still image or a signal representing motion. The Y signal motion detection circuit (6) obtains a one-frame difference of the Y signal using a one-frame delay circuit (63) and a subtractor (64), for example, as shown in FIG.
After passing through a low-pass filter (hereinafter referred to as “LPF”) (65), the absolute value circuit (66) finds its absolute value, and this nonlinear value is converted to a low-frequency component of the Y signal by a nonlinear conversion circuit (67). Is converted into a signal (106) indicating the amount of motion of. The C signal motion detection circuit (7) obtains a two-frame difference using a two-frame delay circuit (73) and a subtractor (74) as shown in FIG. 12, for example, and obtains a band-pass filter (hereinafter referred to as "BPF"). ")
After passing through, the absolute value circuit (76) finds its absolute value,
This absolute value is converted by a nonlinear conversion circuit (77) into a signal (107) indicating the amount of movement of the C signal. The synthesizing circuit (8) includes, for example, a Y signal motion amount signal (106) and a C signal motion amount signal (107).
Is configured to select and output the larger value.

This result is expressed in the form of a motion coefficient k (0 ≦ k ≦ 1). For example, when it is determined that the image is a complete still image, k = 0, and when the image is a complete moving image. Is given as a control signal (108) to the Y signal mixing circuit (9) and the C signal mixing circuit (10) such that k = 1.

In general, when an image is a still image, YC separation between frames using inter-frame correlation is performed, and the Y signal and C signal are separated.
Separate signals. The inter-frame YC separation circuit (5) includes a one-frame delay circuit (52) and an adder (5) as shown in FIG.
3), a 1-frame sum is obtained to extract the YF signal (104), and the subtracter (54) subtracts the YF signal (104) from the input to extract the CF signal (105).

In general, when an image is a moving image, the Y signal and the C signal are separated by performing YC separation within a field using correlation within a field. YC separation circuit in the field (4)
For example, as shown in FIG. 14, a one-line sum is obtained by using a one-line delay circuit (42) and an adder (43) to obtain a Yf signal (10
2) is extracted, and the Cf signal (103) is extracted by subtracting the Yf signal (102) from the input by the subtractor (44).

In the motion adaptive YC separation device, such an inter-frame YC separation circuit (5) and an in-field YC separation circuit (4) are juxtaposed, and a control signal (K) representing a motion coefficient k synthesized by a synthesis circuit (8). According to 108), the Y signal mixing circuit (9) performs the following operation to obtain the motion adaptive YC separated Y signal (10
9) is output.

Y = k · Yf + (1−k) YF Here, Yf: YC separated Y signal output in field (102) YF: YC separated Y signal output between frames (104). Similarly, the control signal (108) causes the C signal mixing circuit (10) to perform the following operation to output the motion adaptive YC separated C signal (110).

 C = k · Cf + (1−k) CF where: Cf: YC separated C signal output in field (103) CF: Interframe YC separated C signal output (105)

The motion adaptive Y signal (109) and the motion adaptive C signal (110) are
These are sent from the output terminal (2) and the output terminal (3), respectively.

[Problems to be solved by the invention]

A conventional motion detection circuit includes a Y signal motion detection circuit and a C signal motion detection circuit.
The Yf signal and the Cf signal by YC separation in the field,
Signal and CF by YC separation by YC separation within frame
Since each signal is configured to be mixed, Y
When the image having the vertical high frequency component and the oblique high frequency component of the signal slightly moves (for example, when the image slightly fluctuates due to the vibration of the camera or the like), the high frequency component of the V signal is Since the motion amount is detected by the Y signal motion detection circuit (6) at the same time when the motion amount is detected by the C signal motion detection circuit (7), the motion coefficient k becomes a large value. For this reason, the weight of the YC separation in the field is unnecessarily increased, so that there is a problem that the resolution is reduced and the image quality such as cross color is deteriorated.

The present invention has been made in order to solve the above-described problems, and is intended to reproduce an image having a high resolution and a small image quality deterioration such as a cross color even for an image having a high frequency of obliquely fluctuating slightly. It is an object of the present invention to obtain a motion detection circuit that can perform the motion detection.

[Means for Solving the Problems] A motion detection circuit according to the present invention comprises: means for detecting the amount of motion between frames of a target pixel of a television signal to be subjected to interlaced scanning; Means for detecting the difference between pixels in the same field at the same position as above and detecting the amount of vertical correlation in the field, and means for receiving the detected amount of motion as an input and outputting a motion amount detection signal based on a predetermined motion detection sensitivity characteristic And control means for changing at least a rising position among a rising position, a slope and an upper limit of the motion detection sensitivity characteristic based on the detected intra-field vertical correlation amount.

[Action]

The inter-frame motion amount detecting means in the present invention detects the inter-frame motion amount of the pixel of interest.

Further, the intra-field vertical correlation detecting means detects a difference between lines adjacent to each other in the field, and detects an intra-field vertical correlation.

Now, the horizontal direction of the screen is the x axis, the vertical direction of the screen is the y axis,
Taking the t-axis, which is the time axis, in a direction perpendicular to the plane formed by the x-axis and the y-axis, a three-dimensional space-time that can be formed by the x-axis, the y-axis, and the t-axis can be considered. Further, as a frequency axis corresponding to the x-axis, the y-axis, and the t-axis, a horizontal frequency axis μ
Considering the axis, the ν axis which is a vertical frequency axis, and the f axis which is a time frequency, it is possible to consider a three-dimensional frequency space which can be constituted by μ axis, ν axis, and f axis which are orthogonal to each other.

FIG. 2A is a view of the three-dimensional frequency space viewed from the positive direction of the f-axis, and FIG. 2B is a view of the three-dimensional frequency space viewed from the positive direction of the μ-axis. The region is a region where a spectrum of an image having a small intra-field vertical correlation, which can be detected by a difference between mutually adjacent lines in the field, exists. Since the detection sensitivity control means is configured to change at least the rising position, the rising position, the slope, and the upper limit of the motion detection sensitivity according to the intra-field vertical correlation amount, when the image is a minute movement, it is determined that the image is a still image. Then, since YC separation between frames is performed, image quality deterioration can be greatly reduced.

If the image is a large-amplitude signal and moves greatly, a large frame difference occurs. Therefore, even if the intra-field vertical correlation is small, the motion detection sensitivity does not decrease, and the image is erroneously determined as a still image. There is no. On the other hand, when the image has a small amplitude, the line difference in the field takes a small value, so that it is determined that the vertical correlation in the field is large, and the motion detection sensitivity becomes high. The amount can be detected.

(Example of the invention)

Hereinafter, an embodiment of the present invention will be described. FIG. 1 is a block circuit diagram of this embodiment.

In the figure, the same reference numerals as those in FIG. 10 denote the same or corresponding parts, and (11) denotes an in-field vertical correlation detection circuit for detecting the in-field vertical correlation of the V signal.
FIG. 3 is a block circuit diagram thereof.

FIG. 4 is a block circuit diagram of the Y signal motion detection circuit (6), and FIG. 5 is a block circuit diagram of the C signal motion detection circuit (7). The conventional circuit shown in FIG. 11 and FIG. The difference between the detection circuits is that the nonlinear conversion circuits (68) and (7)
8) is provided with an input terminal for the intra-field vertical correlation detection signal l in each of the above-described embodiments, and the motion detection sensitivity is controlled by the in-field vertical correlation detection signal l.

Hereinafter, the operation of this embodiment will be described with respect to differences from the conventional example.

As shown in FIG. 3, the in-field vertical correlation detection circuit (11) receives a V signal (101) from an input terminal (21), receives a one-line delay circuit (23) and one of a subtractor (24). It is given to each input terminal. 1-line delay circuit (2
The V signal delayed by one line in 3) is applied to the other input terminal of the subtractor (24) and subtracted. Absolute value circuit (2
5) takes the absolute value of the one-line difference signal of the V signal obtained by the subtractor (24) and supplies it to the coefficient unit (26). The coefficient unit (26) sends out the in-field vertical correlation detection signal l (111) corresponding to the input absolute value from the output terminal (22).

The in-field vertical correlation detection circuit (11) configured as described above performs the frequency component in which the spectrum exists in the hatched area on the frequency space shown in FIG. 2, that is, the vertical frequency (525/4) [lph ] At the center.

The in-field vertical correlation detection signal l (111) is input from the input terminal (63) of the Y signal motion detection circuit (6) and the input terminal (73) of the C signal motion detection circuit (7), and is input to the nonlinear conversion circuit (68). ) And (78) are controlled.
The input / output characteristics of the two nonlinear conversion circuits (68) and (78) are configured to have variable characteristics as shown in FIG. 6, for example. That is, the characteristic a indicates the characteristic when the in-field vertical correlation detection signal l (111) is the minimum, and the characteristic a changes until the input level from the absolute value circuits (66) and (67) reaches the value of A. The output levels of the quantity detection signals (112) and (113) are 0
(That is, the frame correlation is high and the motion amount is zero), and as the value becomes larger than A, the output level gradually increases (ie, the inter-frame correlation gradually decreases and the motion amount gradually increases), and the final As the level of the vertical correlation detection signal 1 (111) in the field increases, the output start point A shifts to the right as shown by the characteristics b, c, d, and the absolute value circuit (66) , (76) is adjusted so that it is not determined that there is a motion unless there is a large input.

The Y signal motion detection circuit (6) detects the motion amount of the Y signal from the V signal (101) with the input / output characteristics shown in FIG. 6 and outputs a Y signal motion detection signal (112). The signal motion detection circuit (7) outputs a C signal motion amount detection signal (113).
Is output.

The synthesizing circuit (8) receives the input Y signal motion detection signal (11
2) and the C signal motion amount detection signal (113), the one having the larger value is selected and output as the control signal (114) for the motion coefficient kl.

The Y signal mixing circuit (9) and the C signal mixing circuit (10) receive the control signal (114) and calculate Y = kl · Yf + (1-kl) YF C = kl · cf + (1-Kl) CF Then, a motion-adaptive YC separation Yl signal (115) without a decrease in resolution due to a minute movement of an image and a motion-adaptive YC separation Cl signal (11
6) is output from the output terminals (2) and (3), respectively.

Note that, in the above embodiment, even if image degradation such as cross color of an image having a vertical high frequency component is allowed, if it is desired to prevent a decrease in resolution due to a double image or the like as much as possible,
Coefficient unit (26) in vertical correlation detection circuit (11) in the field
The input / output characteristics may be set to a low gain as shown by the characteristic e in FIG. 7. Conversely, if it is desired to minimize the deterioration of the image quality due to cross color or the like even when the double image is allowed. The gain may be set high as in the input / output characteristic f shown in FIG.

The input / output characteristics of the coefficient unit (26) are fixed, and the input / output characteristics of the nonlinear conversion circuit (68) in the Y signal motion detection circuit (6) and the nonlinear conversion circuit in the C signal motion detection circuit (7) are set. The input / output characteristic of (78) is changed to the input / output characteristic g in FIG.
Alternatively, by changing as h, the same effect as changing the characteristics of the coefficient unit (26) can be obtained. In addition,
The input / output characteristics g and h shown in FIG. 8 do not necessarily have to change all of the rising points B and C, the slope, and the saturation level as in this example. It goes without saying that a combination may be used.

Also, the input / output characteristics of the nonlinear conversion circuits (68) and (78) in the Y signal motion detection circuit (6) and the C signal motion detection circuit (7) do not suddenly change depending on the pixel position.
A buffer circuit (12) as shown in FIG. 9 may be inserted after the nonlinear conversion circuits (68) and (78). The buffer circuit (12) converts the Y signal motion detection signal (112) input from the input terminal (31) to a smoothing circuit (3
3) The signal is changed to a smooth signal through 3), and if necessary, the number of bits is reduced by a clip circuit (34) for reducing the number of bits, and the signal is input from the output terminal (32) to the synthesis circuit (8). Thus, malfunction due to noise or the like can be reduced.

In the above embodiment, the Y signal motion detecting circuit (6) detects the amount of motion between one frame of the Y signal, and the C signal motion detecting circuit (7) detects the amount of motion between two frames of the C signal. The composition circuit (8) selects the larger one of the motion amount detection signals and outputs the selected signal as the control signal kl (114).
Depending on the purpose, only one of the motion detection circuits may be provided, and the other motion detection circuit and the synthesizing circuit (8) may be omitted.

Also, in the above embodiment, the in-field correlation detection circuit (11) is configured to detect the correlation with the pixel in the vertical direction one line before, but it is not necessarily limited to one line before, but it is not necessarily two lines or two lines. The configuration for detecting the correlation with the pixels on the previous line may be used, and the configuration for detecting the average correlation with the pixels on the plurality of lines may be used.

〔The invention's effect〕

As described above, according to the present invention, since the control means for changing at least the rising position among the rising position, the slope, and the upper limit of the motion detection sensitivity according to the intra-field vertical correlation amount is provided, when the intra-field vertical correlation is small. In addition, by lowering the motion detection sensitivity, there is an effect that it is possible to perform a motion-adaptive YC separation that causes a reduction in resolution due to minute motion of an image and a little deterioration in image quality such as cross color.

[Brief description of the drawings]

FIG. 1 is a block circuit diagram of one embodiment of the present invention, FIG. 2 is a diagram showing a frequency region detected by a vertical correlation detection circuit in a field of this embodiment, and FIG. 3 is a vertical circuit in a field of this embodiment. FIG. 4 is a block circuit diagram of the Y signal motion detection circuit of this embodiment, and FIG.
FIG. 6 is a block diagram of a C signal motion detecting circuit of this embodiment. FIG. 6 is a diagram showing characteristics of the nonlinear conversion circuit of this embodiment. FIG. 7 is a block diagram showing a vertical correlation detecting circuit in a field of this embodiment. FIG. 8 is a diagram showing an example of input / output characteristics of a coefficient unit, FIG. 8 is a diagram showing another example of characteristics of the nonlinear conversion circuit of this embodiment, FIG. 9 is a block circuit diagram of a buffer circuit of this embodiment, and FIG. FIG. 11 is a block circuit diagram of a conventional motion-adaptive YC separating apparatus using a conventional motion detecting circuit, FIG. 11 is a block circuit diagram of this conventional Y-signal motion detecting circuit, and FIG. FIG. 13 is a block circuit diagram of the YC separation circuit between frames according to the prior art and one embodiment of the present invention shown in FIG. 1, and FIG.
It is a block circuit diagram of a separation circuit. (6)… Y signal motion detection circuit, (7)… C signal motion detection circuit, (8)… synthesis circuit, (11)… vertical correlation detection circuit in the field, (20)… motion detection circuit ,(twenty three)
... 1-line delay circuit, (24), (64), (74) ... Subtractor, (25), (66), (76) ... Absolute value circuit, (26)
…… Coefficient unit, (63) …… 1 frame delay circuit, (65)…
... LPF, (68), (78) ... Non-linear conversion circuit, (75) ...
... BPF. In the drawings, the same reference numerals indicate the same or corresponding parts.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yao Politics, Baba Zujo, Nagaokakyo-shi, Kyoto Prefecture Mitsubishi Electric Corporation Electronic Product Development Laboratory (72) Inventor Yoshiteru Suzuki, 1 Baba Zhou, Nagaokakyo-shi, Kyoto Mitsubishi (72) Inventor Yutaka Taguchi 1 Baba Zoshosho, Nagaokakyo-shi, Kyoto, Japan In-house Electronic Products Development Laboratory (72) Inventor Kazumio Nakagawa Totsuka-ku, Yokohama-shi, Kanagawa 292 Yoshida-cho, Hitachi, Ltd., Home Appliance Research Laboratory, Inc. (72) Inventor Sadao Kubota 292 Yoshida-cho, Totsuka-ku, Yokohama, Kanagawa, Japan 292 Hitachi Appliances, Ltd. Home Appliance Research Laboratories (56) Reference JP-A-62-76889 (JP, A) JP-A 63-131794 (JP, A)

Claims (1)

(57) [Claims] 1. A means for detecting a motion amount between frames of a target pixel of a television signal to be subjected to interlaced scanning, and a difference between the target pixel and a pixel in the same field at a position near the vertical direction thereof. Means for detecting and detecting the amount of vertical correlation in the field; means for inputting the detected amount of motion as an input and outputting a motion amount detection signal based on predetermined motion detection sensitivity characteristics; A control circuit for changing at least a rising position among a rising position, a slope and an upper limit of the detection sensitivity characteristic.