JP3284434B2 - Motion detection circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention moves an image signal (sub-sample transmission signal) which is sub-sampled and encoded at an n-frame period (2 frame periods for a MUSE signal) like a MUSE decoder, for example. In a device that adaptively switches the interpolation process between a part and a stationary part, the present invention relates to a motion detection circuit for determining a moving part and a stationary part of the input image signal, and in particular, And a motion detection circuit adapted to adaptively control the sensitivity of the motion detection according to an image pattern.

[0002]

2. Description of the Related Art In recent years, high-definition television (HDTV) broadcasting by the MUSE system has been in full swing.
In the MUSE system, offset subsampling (decimation) is performed between fields and between frames on the encoding side. Therefore, in order to reproduce a still image on the decoding side, it is necessary to combine (interpolate between frames and between fields) from MUSE signals for four fields. However, if this still image processing is performed on a moving part, a multiplexed image is formed. Therefore, a moving part is detected from the MUSE signal, and an image is formed from the signal for one field (in the field). Insert). Therefore, the MUSE decoder needs a process (motion detection process) for discriminating between a moving image portion and a still portion.

Here, a schematic configuration and operation of the MUSE decoder will be described with reference to FIG. In FIG.
The MUSE signal S0 input from the input terminal 1 is input to the motion detection circuit 2, the moving image processing circuit 3, and the still image processing circuit 4. The moving image processing circuit 3 synthesizes an image from a signal for one field (field interpolation), and the still image processing circuit 4 synthesizes an image from a signal of four fields (frame interpolation and field interpolation). The motion detection circuit 2 detects a motion portion of the image, and controls the mixing circuit 5 with the motion detection signal. The mixing circuit 5 mixes the signal subjected to the moving image processing by the moving image processing circuit 3 and the signal subjected to the still image processing by the still image processing circuit 4 at a ratio corresponding to the amount of motion (motion detection signal) and outputs the mixed signal.

If the output of the motion detecting circuit 2 is k, the output of the moving picture processing circuit 3 is Sm, and the output of the still picture processing circuit 4 is Ss, the output y of the mixing circuit 5 is given by the following equation. y = k × Sm + (1−k) × Ss Here, k satisfies the condition of 0 ≦ k ≦ 1, and is 0 for a complete still image and 1 for a complete moving image. A detailed description of the moving image processing circuit 3, the still image processing circuit 4, and the mixing circuit 5 is omitted.

Next, the configuration and operation of the conventional motion detection circuit 2 shown in FIG. 4 will be described with reference to FIGS. By the way, in the motion detection circuit 2, it is preferable to detect a motion amount based on a difference between pixels in one frame.
In the E signal, since the sampling pattern makes one round in four fields (two frames), the same sample point does not exist in one frame, and it is difficult to detect motion. Therefore, in order to perform accurate motion detection, it is necessary to use a difference between two frames having the same sample point.

In FIG. 5, a MUSE signal S0 received from an input terminal 10 is converted into a signal S4 delayed by two frames by a two-frame delay memory 11. The subtracter 12 obtains a difference between the signal S0 of the current frame and the signal S4 of two frames before. An absolute value circuit (ABS) 13 converts the output of the subtracter 12 into an absolute value to obtain a motion detection signal Δ04 for two frames. On the other hand, the signal S0 is a high-pass filter (HPF) 1
4, where the high-frequency components are extracted. Thereafter, the absolute value circuit (ABS) 15 converts the high-frequency signal into an absolute value, thereby obtaining an edge detection signal E0. The edge detection signal E0 is input to the sensitivity control circuit 16 together with the inter-frame motion detection signal Δ04, and the sensitivity of the inter-frame motion detection signal Δ04 is controlled according to the edge detection signal E0. Thereafter, temporal expansion (fill-in) is performed by the field memories 17, 18, and 19 and the maximum value extracting circuit 20 to obtain a final motion detection signal k.

Here, the reason why the sensitivity of the motion detection signal Δ04 between two frames is controlled by the edge detection signal E0 will be described. In FIG. 6, consider the operation of motion detection when two types of objects A and B slightly move. The object A is a case where the edge of the image is large, and the object B is a case where the edge is small. Although the amplitudes of the two objects are substantially equal, the motion detection signal Δ04 between two frames causes large motion detection only at the edge portion of the object A. In this case, for example, even when there is a jitter of the sampling clock or a slight camera shake at the time of photographing with a camera, a large motion is detected, which is not preferable. Therefore, for the edge portion, control is performed so as to suppress the detection sensitivity in accordance with the magnitude of the edge detection signal E0 which is the magnitude of the edge. Incidentally, this conventional example is disclosed in Japanese Patent Application Laid-Open No. 62-17 / 1987.
No. 2877.

[0008]

However, according to the above-described control method of the motion detection sensitivity in the conventional motion detection circuit, the sensitivity is uniformly reduced in a portion having a large edge regardless of the degree of motion. The motion detection is likely to be insufficient for a part where the intensity is high, and a problem arises in that part that a multiple image is formed. Conversely, if the sensitivity control for the edge portion is relaxed, the edge portion is undesirably processed as a moving image in the case of minute movement such as jitter or camera shake. Originally, even for large moving parts, even if the edge is large, there is no need to lower the sensitivity, and video processing should be performed.On the other hand, extremely small movements such as jitter and camera shake should be extremely sensitive. And still image processing should be performed. Therefore, if the sensitivity of motion detection is controlled only by the size of the edge as in the conventional method, there is a solution only to a method of setting an appropriate compromise, and accurate motion detection cannot be expected. In particular,
In the image of the edge part, the image quality difference when the erroneous determination is made is extremely different (multiple image obstacles when a moving image is processed as a still image and aliasing interference when a still image is processed as a moving image become remarkable), so that more accurate Motion detection is required.

SUMMARY OF THE INVENTION The present invention has been made in view of such a problem, and an object of the present invention is to provide a motion detection circuit capable of more accurately detecting motion at an edge portion of an image.

[0010]

Means for Solving the Problems The present invention for solving the problems of the prior art described above, (a) a motion detecting circuit used in the subsample transmission signals apparatus for decoding an input image signal To n
(N is an integer of 1 or more) delay means (1
1) and an n-frame motion to obtain an n-frame motion detection signal (Δ04) based on the absolute value of the difference between the input image signal (S0) and the n-frame delay signal (S4) obtained by the delay means. A first high-pass filter (1) for extracting a high-frequency component (H0) of the input image signal in a motion detection circuit having detection means (12, 13);
And 4) a second high pass filter for extracting high-frequency components (H4) of the n-frame delayed signal (21), the n full
Level variable hand that changes the level of the inter-frame motion detection signal
And a level (16, 22), wherein the level varying means is
The output of the first high-pass filter and the second high-pass filter
When the absolute value of the difference from the output of the filter is small, the n
Raising the level of the inter-frame motion detection signal,
The output of the pass filter and the output of the second high-pass filter
When the absolute value of the difference from the force is large,
Providing a motion detection circuit, characterized in that lowering the level of the detection signal, using the device for decoding (b) sub-samples the transmission signal
A motion detection circuit for converting an input image signal into n
(N is an integer of 1 or more) Delay means 11 for delaying a frame
And the input image signal (S0) and the delay means
Of the difference from the obtained n-frame delayed signal (S4)
To obtain a motion detection signal (Δ04) for n frames based on the value n
Motion having inter-frame motion detection means (12, 13)
In a detection circuit, a high frequency component of the input image signal
A first high-pass filter for extracting (H0) (14)
And extracting a high-frequency component (H4) of the n-frame delayed signal
A second high-pass filter (21),
Level varying means for varying the level of the motion detection signal
(16, 22), wherein the level varying means is
A sensitivity control circuit for controlling the sensitivity of the motion detection signal for n frames.
Path (16) and the output of said first and second high-pass filters.
A control signal for controlling the sensitivity control circuit by force
A control signal generating circuit (22) for generating
Controlling the control signal generation circuit to the output of the first high-pass filter;
Absolute value of the difference between the force and the output of the second high-pass filter
First means (221, 223) for determining
Output of a high-pass filter and said second high-pass filter
The edge amount of the image signal by at least one of
Second means (222, 224, 225) for determining
As the output of the first means increases, the second means
And third means (226) for reducing the level of the output of
A motion detection circuit characterized by being provided and provided .

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a motion detection circuit according to the present invention will be described with reference to the accompanying drawings. FIG. 1 is a block diagram showing an embodiment of the motion detection circuit of the present invention, FIG. 2 is a block diagram showing a specific configuration of the logic circuit in FIG. 1, and FIG. 3 explains the operation of the motion detection circuit of the present invention. FIG. In FIG. 1, the same portions as those in FIG. 5 are denoted by the same reference numerals.

In FIG. 1, a MUSE signal S0 input from an input terminal 10 is converted into a signal S4 delayed by two frames by a two-frame delay memory 11. The subtracter 12 obtains a difference between the signal S0 of the current frame and the signal S4 of two frames before. An absolute value circuit (ABS) 13 converts the output of the subtracter 12 into an absolute value to obtain a motion detection signal Δ04 for two frames. The signal S output from the two-frame delay memory 11
4 is also input to a high-pass filter (HPF) 21, where high-frequency components are extracted and input to a logic circuit 22.

On the other hand, the signal S0 is a high-pass filter (HP
F) 14 is also input, where the high frequency component is extracted.
This high-frequency signal is input to the logic circuit 22. The logic circuit 22 generates a control signal E04 for controlling the sensitivity of motion detection by the sensitivity control circuit 16 from the outputs of the HPFs 14 and 21 as described later. This control signal E04
Is input to the sensitivity control circuit 16 together with the inter-frame motion detection signal Δ04, and the sensitivity of the inter-frame motion detection signal Δ04 is controlled according to the control signal E04. Thereafter, temporal expansion (fill-in) is performed by the field memories 17, 18, and 19 and the maximum value extracting circuit 20 to obtain a final motion detection signal k.

Here, the logic circuit 22 will be described. The logic circuit 22 is a circuit for generating a control signal E04 for controlling the sensitivity from the difference between the patterns and the size of the edge from both the output signal H0 of the HPF 14 and the output signal H4 of the HPF 21. This is to detect the degree of movement, whether it is a minute movement such as jitter or camera shake, or a movement that changes rapidly. Since the main purpose of the HPF 14 and the HPF 21 is to detect the gradient of the waveform, a simple differential filter is sufficient.

The logic circuit 22 is configured, for example, as shown in FIG. The logic circuit 22 outputs the signal H
The absolute value of the difference between 0 and the signal H4 is obtained, and the amount of the edge is controlled according to the magnitude. That is, in FIG.
And the signal H4 are input to the subtraction circuit 221, and the signal H4 is subtracted from the signal H0. The output of the subtraction circuit 221 is converted into an absolute value by an absolute value circuit 223. This output is
04H. On the other hand, the signals H0 and H4 are converted to absolute values by absolute value circuits 222 and 224, respectively. As a result, the edge amounts of the signal S0 of the current frame and the signal S4 two frames before are obtained. Absolute value circuits 222, 224
Is input to the maximum value extracting circuit 225, and the larger one of these two values is selected and output. This output is designated as H04. In this embodiment, the edge amount of the image signal is obtained by using both the signal S0 of the current frame and the signal S4 of two frames before, but either one may be used. In this case, the maximum value extraction circuit 225 can be omitted.

The signal Δ0 output from the absolute value circuit 223
4H and the signal H04 output from the maximum value extracting circuit 225
Is input to the sensitivity control circuit 226. Sensitivity control circuit 22
6 controls the signal H04 by the signal Δ04H. That is, the sensitivity control circuit 226 controls the sensitivity so as to lower the level of the signal H04 when the signal Δ04H is large, and conversely, increases (or simply does not lower) the level of the signal H04 when the signal Δ04H is small. I do. As a result, when the signal Δ04H is large, the control signal E04 becomes small. Conversely, when the signal Δ04H is small, the control signal E0 becomes small.
4 is larger (or not smaller). The output of the sensitivity control circuit 226 is input to the sensitivity control circuit 16 in FIG. 1 as a control signal E04. Then, the sensitivity control circuit 16
When the input control signal E04 is large, the level of the motion detection signal Δ04 between two frames is lowered to lower the sensitivity of motion detection, and when the control signal E04 is small, the motion detection signal Δ0
4 to increase the sensitivity of motion detection,
Output as

The state of a series of these processes will be described with reference to FIG. FIG. 3 shows the signals S0, S0 in FIG. 1 or FIG.
S4, Δ04, H0, H4, Δ04H, H04, E0
4, K04. FIG. 3 shows a case where the movement of the edge portion of the object A is minute and the movement of the edge portion of the object C is quick. When the movement of the edge portion is very small like the object A, the difference between the waveforms of the signal H0 and the signal H4 (Δ04H) is small, but when the object is moving quickly like the object C, the signal H0 and the signal The difference between the waveforms of H4 (Δ04H) is large. These two objects A and C are substantially equal in magnitude with respect to the signal H04, but the signal Δ
The magnitude of the signal E04 controlled by 04H is clearly different. In this example, the signal K04 after the sensitivity control is small for the object A with a small movement and large for the object C with a strong movement.

As described above, according to the present invention, unlike the conventional motion detection sensitivity control method in the conventional motion detection circuit that uniformly controls the motion detection sensitivity only by the magnitude of the edge, the difference between the edge waveforms is detected. , The degree of motion can be reflected, and as a result, more accurate motion detection becomes possible. Further, it is possible to alleviate the problem that a still image is motion-detected during fade-in and fade-out. 1 and 2 is merely an embodiment of the present invention, and the difference between the high-frequency signal of the current frame and the signal n frames past this signal is used for controlling the motion detection sensitivity. The configuration is not limited to these configurations.

As described above, in the motion detection circuit of the present invention,
Motion detection at the edge portion of the image can be performed more accurately. Since aliasing obstruction that occurs when processing a minute motion in a moving image or multiple image failure when a violently moving part is processed in a still image appears remarkably in the edge portion of the image,
The sensitivity control method according to the present invention, which utilizes the change in the pattern of the edge portion, is particularly effective. According to the configuration shown in FIG. 1, the increase in the number of circuits from the conventional configuration is negligible, and the cost does not increase in recent IC integration technology.

[0020]

As described in detail above, the motion detection circuit of the present invention comprises a first high-pass filter for extracting a high-frequency component of an input image signal, and a high-frequency component of an n-frame delay signal. a second high pass filter for extracting, n frame
Level varying means for varying the level of the motion detection signal between
And the level varying means is provided with a first high-pass filter.
Of the difference between the output of the second filter and the output of the second high-pass filter
When the value is small, the level of the motion detection signal
The output of the first high-pass filter and the second high-pass
When the absolute value of the difference from the filter output is large, n frames
The level of the inter-unit motion detection signal is reduced . Also, the level varying means is used to detect the motion detection signal for n frames.
And a first and second high-pass filter.
Control for controlling the sensitivity control circuit by the output of the filter
A control signal generation circuit that generates a signal
Signal generation circuit, the output of the first high-pass filter and the second
A first method for calculating an absolute value of a difference from an output of a high-pass filter
Means, an output of the first high-pass filter and a second high-pass filter.
The image signal by at least one of the outputs of the over-filter
The second means for determining the edge amount of
As the level of the output of the second means decreases,
Third means are provided. Therefore, it is possible to detect the degree of movement whether the image is moving violently or whether it is a minute movement due to the influence of jitter or the like, and it is possible to perform more accurate sensitivity control of the motion detection sensitivity using the detection result. .

[Brief description of the drawings]

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

FIG. 2 is a block diagram showing a specific configuration of a logic circuit 22 in FIG.

FIG. 3 is a waveform chart for explaining the operation of the present invention.

FIG. 4 is a block diagram illustrating a schematic configuration of a MUSE decoder.

FIG. 5 is a block diagram showing a conventional example.

FIG. 6 is a waveform chart for explaining the operation of the conventional example.

[Explanation of symbols]

 11 two-frame delay memory (delay means) 12 subtractor (n-frame motion detection means) 13 absolute value circuit (n-frame motion detection means) 14 high-pass filter (first high-pass filter) 16 sensitivity control circuit 17 to Reference Signs List 19 field memory 20 maximum value extraction circuit 21 high-pass filter (second high-pass filter) 22 logic circuit (control signal generation circuit)

Claims (2)

(57) [Claims] 1. A motion detecting circuit for use in an apparatus for decoding a sub-sample transmission signal, comprising: delay means for delaying an input image signal by n (n is an integer of 1 or more) frames; And a n-frame motion detecting means for obtaining an n-frame motion detecting signal based on an absolute value of a difference between the n-frame delayed signal obtained by the delay means and the n-frame delayed signal. A first high-pass filter for extracting a component, a second high-pass filter for extracting a high-frequency component of the n-frame delay signal, and a level varying a level of the n-frame motion detection signal.
And a level varying unit , wherein the level varying unit is provided with the first high-pass filter.
The absolute difference between the output and the output of the second high-pass filter
When the value is small, the level of the motion detection signal
The output of the first high-pass filter and the
2 When the absolute value of the difference from the output of the high-pass filter is large
Wherein the level of the motion detection signal for n frames is reduced . 2. An apparatus for decoding a sub-sample transmission signal.
Is a motion detection circuit used for
(N is an integer of 1 or more) frame delay means
Obtained by the input image signal and the delay means.
N frames by the absolute value of the difference from the
And n-frame motion detection means for obtaining a motion detection signal between frames.
A first detection circuit for extracting a high-frequency component of the input image signal.
A bandpass filter and a second high- pass filter for extracting a high-frequency component of the n-frame delayed signal.
A band-pass filter and a level for varying the level of the n-frame motion detection signal.
And a level change means for detecting the n-frame inter-frame motion detection signal.
A sensitivity control circuit for controlling the sensitivity of the
The sensitivity control circuit is controlled by the output of the bandpass filter.
And a control signal generating circuit for generating a control signal for
The control signal generating circuit is connected to the output of the first high-pass filter and the second high-pass filter.
First means for determining the absolute value of the difference from the output of the overfilter
And the output of the first high-pass filter and the second high-pass filter.
The image signal by at least one of the outputs of the over-filter
A second means for calculating the edge amount of the second hand, and the second hand as the output of the first means increases.
Third means for reducing the output level of the stage.
A motion detection circuit characterized in that the motion detection circuit is implemented.