JPH0846925A - Motion detection circuit for picture signal - Google Patents

Abstract

PURPOSE:To obtain a motion detection circuit which can generate a highly precise motion detection signal for a picture having the change of brightness in a time base when viewed by a whole screen and having a part different in brightness in the same screen on motion detection based on a frame differential signal. CONSTITUTION:A threshold processor 105 compares the inputted frame differential signal and a threshold and outputs still/motion detection signals. An average luminance detector 107 detects the average luminance of the present screen. An average luminance detector 106, a subtracter 108 and an absolute value calculator 110 detect one frame difference of average luminance and adaptively and variably control the threshold based on average luminance and one frame difference.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image signal motion detection circuit for generating a motion detection signal for controlling a motion adaptive signal processing circuit by a digitized image signal.

More specifically, when a motion detection signal is generated by comparing the frame difference signal with a threshold value based on the frame difference signal, the threshold value is adaptively switched according to the brightness of the image to obtain the motion detection signal. The present invention relates to a motion detection circuit for an image signal that is generated.

[0003]

2. Description of the Related Art Generally, a motion adaptive process in which a motion of an image is detected from an image signal of a current color television and the signal process is switched between a motion image and a still image by controlling the detected motion detection signal. To improve the image quality. The main motion adaptive processing includes motion adaptive YC separation and motion adaptive scan line interpolation, both of which are effective in improving image quality.

In the motion adaptive YC separation, when the motion of the image is small, the Y signal (luminance signal) is separated by taking the sum between the frames, and the C signal (chroma signal) is separated by the difference between the frames. Is a process for completely separating the Y component and the C component and removing the components such as cross color and cross luminance. Further, when the image movement is large, adaptive processing for performing YC separation is performed in the in-field processing.

Motion-adaptive scanning line interpolation means that when an interpolated scan line is generated for converting an image of an interlaced signal into an image of a non-interlaced signal, when the image motion is small, interpolation is performed between fields, When there is a large amount of motion, it is the process of performing interpolation within the field.

FIG. 5 is a block diagram showing an example of a conventional motion detection circuit for generating a motion detection signal for performing such signal processing. The image signal output from the signal source 500 is input to the frame memory 501 and the subtractor 502. The subtractor 502 generates a frame difference signal which is the difference between the signal of the current image from the signal source 500 and the signal from the frame memory 501 one frame before, and the absolute value calculator 503 processes the absolute value of the frame difference signal. I do. The absolute value of the frame difference signal output from the absolute value calculator 503 is input to the filter processor 504 and filtered in the spatiotemporal direction to prevent omission or false detection.
It is input to the threshold processor 505. Threshold processor 5
In 05, the input signal (absolute value of the frame difference signal) is compared with a fixed threshold value, that is, static / moving determination is performed, and as a result, a motion detection signal is output. To be done.

This motion detection circuit can output a highly accurate motion detection signal when the brightness of the entire screen is constant in the time direction. However, for example, in a scene that changes from daytime to nighttime or a scene in which the lighting is turned on / off, the motion detection accuracy decreases. That is, even if the size and amount of movement of the background and the moving object are constant, the magnitude of the absolute value of the frame difference signal becomes smaller in a dark scene such as a night scene than in a bright scene such as a day scene. Therefore, if the threshold value set by the threshold value processor 505 is fixed for a bright scene, the accuracy of motion detection in a dark scene is lowered, and conversely, the threshold value set is fixed for a dark scene. If so, the accuracy of motion detection in a bright scene will decrease. In addition, in a scene where the brightness of the entire screen changes abruptly, such as lighting ON / OFF, it is determined that the entire screen moves.

[0008]

Even if the size and the amount of movement of the background and the moving object are constant, the absolute value of the frame difference signal in a dark scene such as a night scene is smaller than that in a bright scene such as a day scene. However, as described above, in the conventional technique, the amount of motion detected based on the frame difference signal is thresholded by a fixed threshold, so that the time is There is a problem that accurate motion detection cannot be performed for an image whose brightness is not constant in the direction.

Further, there is a problem that an image having a sudden change in the brightness of the entire screen such as lighting ON / OFF is erroneously determined to be in motion.

Further, in the threshold processing with a fixed threshold value, a scene having different brightness parts in the same screen, for example, a brightness part such as a sunlit part and a shaded part or a room and the outside of a window, is brightened. In different scenes, there is a problem that motion detection with low accuracy is performed in a part of the screen.

The present invention was devised in view of such circumstances, and in motion detection based on a frame difference signal, an image in which the brightness changes in the time direction in the entire screen or the same screen is seen. It is an object of the present invention to provide a motion detection circuit that can generate a highly accurate motion detection signal even for an image having portions with different brightness.

[0012]

A motion detection circuit for an image signal according to the present invention compares a frame difference signal of an input image signal with a threshold value and outputs the result as a motion detection signal. Processing means, means for detecting the average luminance of the entire screen of the image signal, means for detecting one frame difference of the average luminance of the entire screen of the image signal, or means for detecting the average of the frame difference signals. The threshold value of the threshold value processing means is adaptively switched based on the output of any one of the detection means.

Further, the image signal may be divided into a plurality of blocks, and the average luminance, one frame difference of the average luminance, or the average of the frame difference signals may be detected for each block.

[0014]

Since the threshold value of the threshold value processing means is adaptively switched on the basis of the detected average luminance, one frame difference of the average luminance and the average of the frame difference signals,
It is possible to generate a motion detection signal that does not reduce the motion detection accuracy for images of various brightness and for images in which the brightness of the screen changes in the time direction.

Further, by dividing the image signal into a plurality of blocks and detecting each block, the motion detection can be performed without deteriorating the motion detection accuracy even for an image having a different brightness in the same screen. It becomes possible to generate a signal.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of a motion detection circuit for an image signal of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 is a block diagram showing the arrangement of a motion detection circuit for image signals according to the first embodiment. In the figure, 100 is a signal source that emits a digitized image signal, 101 is a frame memory that stores the image signal in 1-frame units, 102 is the current image signal from the signal source 100 and 1 frame from the frame memory 101. A subtracter that takes the difference from the previous image signal, 103 is an absolute value calculator that takes the absolute value of the frame difference signal input from the subtractor 102, 104 is a filter processor, 109 is a delay device, and 105 is the frame difference signal. A threshold value processor that performs thresholding by comparing the absolute value of
Reference numeral 106 denotes a first average luminance detector that detects the average luminance of the image signal of one frame before read from the frame memory 101, and 107 denotes a second average luminance that detects the average luminance of the current image signal input from the signal source 100. Luminance detector, 108
Is a subtractor that takes the difference between the average luminance of the current screen from the second average luminance detector 107 and the average luminance of one frame before from the first average luminance detector 106, and 110 is the difference of the average luminance by one frame. It is an absolute value calculator that takes an absolute value. The delay unit 109 delays the frame difference signal by the delay amount of the first average luminance detector 106 or the second average luminance detector 107 and the subtractor 108. The threshold value in the threshold value processor 105 is the second average luminance detector 10
It is adapted to change adaptively according to the average brightness of the current screen from 7 and the one-frame difference of the average brightness from the absolute value calculator 110.

The digital image signal output from the signal source 100 is input to the frame memory 101 and the subtractor 102. The subtractor 102 takes the difference between the image signal of the current screen from the signal source 100 and the image signal of the previous frame from the frame memory 101, and outputs it as a frame difference signal to the absolute value calculator 103. The absolute value calculator 103 performs absolute value processing on the frame difference signal, and the signal of the absolute value of the frame difference signal is filtered by the filter processor 104.
Is input to and filtered in the spatiotemporal direction to prevent omission or false detection. The output signal from the filter processor 104 is delayed by a delay device 109 for a predetermined time and input to the threshold processor 105.

The digital image signal from the signal source 100 is also input to the second average brightness detector 107, the average of the brightness of the entire current screen is calculated and output to the subtractor 108 and the threshold value processor 105. . The image signal from the frame memory 101 is also input to the first average luminance detector 106,
The average luminance of the entire screen one frame before is calculated and output to the subtractor 108. The subtractor 108 calculates the difference between the average brightness signal of the current screen and the average brightness of the screen one frame before (one frame difference of the average brightness), and the absolute value calculator 110 performs absolute value processing. Absolute value calculator 1
The absolute value of the average luminance difference from 10 for one frame is output to the threshold value processor 105.

In the threshold value processor 105, the input signal (absolute value of the frame difference signal) is compared with the threshold value as in the conventional example, and the comparison result is output as a motion detection signal. The threshold value at is not a fixed value as in the conventional example, but is set to the average brightness of the current screen input from the second average brightness detector 107 and the one-frame difference of the average brightness input from the absolute value calculator 110. The value can be changed based on the value.

The method of setting the variable threshold will be described below.

First, the control mechanism for setting the variable threshold value based on the average brightness of the current screen from the second average brightness detector 107 will be described. Regarding the absolute value of the frame difference signal that is the basis of the motion detection signal, even if the size and the amount of movement of the background and the moving object are constant, the absolute value of a dark scene such as a night scene is compared to a bright scene like a day scene. The absolute value becomes small. Therefore, it is necessary to adaptively change the threshold according to the brightness of the current screen.

In FIG. 2, the output of the threshold processor 105 is static /
In the case of dynamic binary output, that is, when the variable threshold is one with respect to the output of the delay device 109, an example of setting the variable threshold by the input signal of the average luminance of the current screen will be shown. As shown in FIG. 2, when the average brightness of the current screen is small, that is, when the entire screen is dark, the threshold value is set to a small value, and when the average brightness of the current screen is large, that is, when the entire screen is bright, the threshold value is set. Control to set a large value.

Next, the control mechanism for setting the variable threshold value by the one-frame difference of the average brightness from the absolute value calculator 110 will be described. The output from the absolute value calculator 110 is
It is the absolute value of the one-frame difference of the average luminance of the entire screen, that is, the amount of change in the brightness of the entire screen between frames. For example, when the lighting is turned on / off in an indoor scene, conventional motion detection determines that the entire screen is in motion. Therefore, in order to prevent such an erroneous determination, it is necessary to adaptively control the variable threshold value of the threshold value processor 105 when the change amount of the brightness of the entire screen between frames is large.

FIG. 3 shows an example of setting a variable threshold value based on the amount of change in screen brightness, that is, the difference in average luminance by one frame. As shown in FIG. 3, the control is performed such that the threshold value is set to a large value as the amount of change in screen brightness increases. By controlling the variable threshold value in this way, it is possible to generate a highly accurate motion detection signal even in a scene such as lighting ON / OFF.

(Second Embodiment) Next, a motion detection circuit for an image signal according to a second embodiment will be described. The block diagram of this embodiment is FIG. 1 similarly to the first embodiment.

In the above-described first embodiment, the average brightness is detected by the first average brightness detector 106 and the second average brightness detector 107 over the entire screen, and the threshold value processor 105 is operated.
The variable threshold setting of is controlled on a screen-by-screen basis.
In the second embodiment, one screen is divided into several blocks, the average brightness is detected for each block, and the setting of the variable threshold is adaptively controlled.

The second embodiment has the same effect as that of the first embodiment, and further, an image having a portion having different brightness in one screen, for example, a sunlit portion and a shaded portion are displayed. It is possible to generate a highly accurate motion detection signal even for an object or an image having different brightness such as the inside of a room and the outside of a window.

(Third Embodiment) Next, a motion detection circuit for an image signal according to a third embodiment will be described. FIG. 4 is a block diagram showing the arrangement of a motion detection circuit for image signals according to the third embodiment. 4, the same parts as those in FIG. 1 of the first embodiment are designated by the same reference numerals. That is, 100 is a signal source, 10
1 is a frame memory, 102 is a subtractor, 103 is an absolute value calculator, 104 is a filter processor, 109 is a delay device, 1
Reference numeral 05 is a threshold value processor, and 107 is an average brightness detector for inputting a digital image signal from the signal source 100 to detect the average brightness of the entire screen and outputting it to the threshold value processor 105. An average brightness difference detector 111 receives the frame difference signal output from the subtractor 102 and detects the average (average brightness difference) of the frame differences of the entire screen.

The signal output from the average brightness difference detector 111 is the same signal as the output of the absolute value calculator 110 of the first embodiment. That is, the average luminance difference detector 111 detects and outputs the one-frame difference in average luminance. The average signal of the frame differences output from the average luminance difference detector 111 is input to the threshold value processor 105, and the setting of the variable threshold value is controlled as shown in FIG.

As in the first embodiment, the variable threshold of the threshold processor 105 is adaptively set according to the average luminance of the current screen output from the average luminance detector 107.

In the third embodiment, the illumination is turned on / off by controlling the variable threshold value as in the first embodiment.
It is possible to generate a highly accurate motion detection signal even in a scene such as OFF. In addition, this third embodiment is
Subtractor 108 and absolute value calculator 11 in the configuration diagram of FIG.
This is a configuration in which 0 is reduced, and there is an advantage that the circuit scale can be smaller than that of the first embodiment.

(Fourth Embodiment) An image signal motion detection circuit according to the fourth embodiment will be described below. The block diagram of this embodiment is FIG. 4 similarly to the third embodiment.

In the above third embodiment, the average luminance detector 1
07 and the average brightness difference detector 111 detect the average brightness on the entire screen and control the setting of the variable threshold value of the threshold value processor 105 on a screen-by-screen basis. Divides one screen into several blocks,
The average luminance detector 107 and the average luminance difference detector 111 detect the average luminance for each block and adaptively control the setting of the variable threshold.

In the fourth embodiment, similar to the second embodiment, in addition to having the same effect as the first embodiment, a portion having different brightness is formed in one screen. It is possible to generate a highly accurate motion detection signal even for an image that is included, for example, an image having a sunlit portion and a shaded portion, or an image having different brightness such as inside a room and outside a window. Further, the fourth embodiment has a configuration in which the subtractor 108 and the absolute value calculator 110 in the configuration diagram of FIG. 1 are reduced, and has the advantage that the circuit scale can be smaller than that of the second embodiment. is there.

(Fifth Embodiment) Next, an image signal motion detection circuit according to a fifth embodiment will be described. The block diagram of this embodiment is FIG. 4 similarly to the third embodiment.

The fifth embodiment is the average brightness difference detector 111.
The average brightness difference is detected by the entire screen, but the average brightness is detected by the average brightness detector 107 in block units, and the setting of the variable threshold value of the threshold value processor 105 is controlled in block units. is there.

In the fifth embodiment, similar to the fourth embodiment, the same effect as the first embodiment is obtained, and in addition, a portion having different brightness is formed in one screen. It is possible to generate a highly accurate motion detection signal even for an image that is included, for example, an image having a sunlit portion and a shaded portion, or an image having different brightness such as inside a room and outside a window. Further, the fifth embodiment has a configuration in which the subtractor 108 and the absolute value calculator 110 in the configuration diagram of FIG. 1 are reduced similarly to the fourth embodiment, and the circuit scale is larger than that of the second embodiment. Has the advantage of being small.

(Sixth Embodiment) Next, an image signal motion detection circuit according to the sixth embodiment will be described. The block diagram of this embodiment is FIG. 4 similarly to the third embodiment.

In the sixth embodiment, the average luminance detector 107 detects the average luminance over the entire screen, but the average luminance difference detector 111 detects the average luminance difference in block units, and the threshold in block units. It controls the setting of the variable threshold value of the value processor 105.

In the sixth embodiment, similarly to the third embodiment, it is possible to generate a highly accurate motion detection signal for an image in which the brightness of the entire screen changes in the time direction. The circuit scale can be reduced as compared with the first embodiment shown in FIG.

(Various Embodiments) The threshold value processor 10 is based on the average brightness of the current screen detected by the average brightness detector 107.
5 represents that the threshold value is changed, and that the threshold value is changed by one frame difference of the average brightness generated by the average brightness detector 106, the subtractor 108 and the absolute value calculator 110. When the threshold is varied by the average of the frame difference signals detected by the luminance difference detector 111, and the detection of each block for each is represented by ',', '. The following are included as examples of the present invention. That is, only only only'only 'only'only' (first embodiment) '+' (second embodiment) + (third embodiment) '+' (fourth embodiment) '+ ( Fifth embodiment) + '(sixth embodiment) is an embodiment of the present invention. These correspond to claims 1 to 12 in that order.

[0043]

Since the threshold value of the threshold value processing means is adaptively varied according to the detected average luminance, one frame difference of the average luminance, and the average of the frame difference signals, images of various brightness are obtained. On the other hand, a highly accurate motion detection signal can be generated for an image in which the screen brightness changes in the time direction.

Further, by dividing the image signal into a plurality of blocks and detecting each block, it is possible to generate a highly accurate motion detection signal even for an image having portions with different brightness in the same screen. it can.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an image signal motion detection circuit according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of threshold value setting by average brightness input in the threshold value processor of FIG.

FIG. 3 is an explanatory diagram of threshold value setting by inputting an average luminance change amount in the threshold value processor of FIG.

FIG. 4 is a block diagram showing a configuration of an image signal motion detection circuit according to a third embodiment of the present invention.

FIG. 5 is a block diagram showing a configuration of an image signal motion detection circuit according to a conventional example.

[Explanation of symbols]

 100 ... Signal source 101 ... Frame memory 102 ... Subtractor 103 ... Absolute value calculator 104 ... Filter processor 105 ... Threshold processor 106 ... First average brightness detector 107 ... 2 average brightness detector 108 ... subtractor 109 ... delay device 110 ... absolute value calculator 111 ... average brightness difference detector

Claims (12)

[Claims] 1. A threshold value processing means for comparing a frame difference signal of an input image signal with a threshold value and outputting the result as a motion detection signal, and a means for detecting an average luminance of the entire screen of the image signal. A motion detection circuit for an image signal, which is configured to adaptively switch the threshold value of the threshold value processing means based on the output of the average brightness detection means. 2. A threshold value processing means for comparing a frame difference signal of an input image signal with a threshold value and outputting the result as a motion detection signal, and one frame difference of the average luminance of the entire screen of the image signal. And a means for detecting the difference between the threshold values of the threshold value processing means based on the output of the detection means of the one-frame difference of the average brightness. Image signal motion detection circuit. 3. A threshold value processing means for comparing a frame difference signal of an input image signal with a threshold value and outputting the result as a motion detection signal; and a means for detecting an average of the frame difference signal. A motion detection circuit for an image signal, which is configured to adaptively switch the threshold of the threshold processing means based on the output of the average detection means of the frame difference signal. 4. Threshold processing means for comparing a frame difference signal of an input image signal with a threshold value and outputting the result as a motion detection signal, and dividing the image signal into a plurality of blocks And a means for detecting an average luminance for each block, and is configured to adaptively switch the threshold value of the threshold value processing means based on the output of the average luminance detection means for each block. Characteristic image signal motion detection circuit. 5. Threshold processing means for comparing a frame difference signal of an input image signal with a threshold value and outputting the result as a motion detection signal, and dividing the image signal into a plurality of blocks Means for detecting a one-frame difference in average luminance for each block, and adaptively switches the threshold value of the threshold value processing means on the basis of the output of the one-frame difference in average luminance for each block. An image signal motion detection circuit having the above structure. 6. A threshold value processing means for comparing a frame difference signal of an input image signal with a threshold value and outputting the result as a motion detection signal, and the image signal is divided into a plurality of blocks. Means for detecting the average of the frame difference signals for each block, and adaptively switching the threshold of the threshold processing means based on the output of the means for detecting the average of the frame difference signals for each block. An image signal motion detection circuit having the above-mentioned configuration. 7. Threshold processing means for comparing a frame difference signal of an input image signal with a threshold value and outputting the result as a motion detection signal, and means for detecting an average luminance of the entire screen of the image signal. And a means for detecting a one-frame difference in average luminance of the entire screen of the image signal, and outputs two outputs, that is, an output of the average luminance detecting means and an output of the one-frame difference detecting average luminance. A motion detection circuit for an image signal, characterized in that the threshold value of the threshold value processing means is adaptively switched based on the above. 8. Threshold processing means for comparing a frame difference signal of an input image signal with a threshold value and outputting the result as a motion detection signal, and dividing the image signal into a plurality of blocks An average brightness for each block, and a unit for detecting a difference of one frame of the average brightness for each block, and an output of the detection unit of the average brightness of each block and one frame of the average brightness of each block. A motion detection circuit for an image signal, characterized in that the threshold value of the threshold value processing means is adaptively switched based on two outputs, that is, the output of the difference detection means. 9. A threshold processing means for comparing a frame difference signal of an input image signal with a threshold value and outputting the result as a motion detection signal, and a means for detecting an average luminance of the entire screen of the image signal. And a means for detecting an average of the frame difference signal, and the threshold processing based on two outputs of an output of the average brightness detection means and an output of the frame difference signal average detection means. An image signal motion detection circuit characterized in that the threshold value of the means is adaptively switched. 10. Threshold processing means for comparing a frame difference signal of an input image signal with a threshold value and outputting the result as a motion detection signal, and dividing the image signal into a plurality of blocks A means for detecting the average luminance for each block, and a means for detecting the average of the frame difference signal for each block, the output of the average luminance detection means for each block and the average of the frame difference signal for each block The image signal motion detection circuit is configured to adaptively switch the threshold value of the threshold value processing means based on the two outputs of the detection means and the output of the detection means. 11. Threshold processing means for comparing a frame difference signal of an input image signal with a threshold value and outputting the result as a motion detection signal, and means for detecting the average luminance of the entire screen of the image signal. And a means for dividing the image signal into a plurality of blocks and detecting an average of the frame difference signals for each of the blocks, the output of the average brightness detecting means and the average of the frame difference signals for each block. A motion detection circuit for an image signal, characterized in that the threshold value of the threshold value processing means is adaptively switched based on two outputs of the detection means. 12. Threshold processing means for comparing a frame difference signal of an input image signal with a threshold value and outputting the result as a motion detection signal, and an image signal divided into a plurality of blocks. A means for detecting the average luminance for each, and a means for detecting the average of the frame difference signal, between the output of the average luminance detection means for each block and the output of the average detection means of the frame difference signal A motion detecting circuit for an image signal, wherein the threshold value of the threshold value processing means is adaptively switched based on two outputs.