JPH0377495A - Movement detecting circuit - Google Patents

Abstract

PURPOSE:To detect the movement of a picture accurately without unnatural state by invalidating a filter processing effect by a time space filter circuit when local movement error detection or movement detection without no correlation in time direction takes place. CONSTITUTION:A detection circuit 3 detects the movement of a luminance signal low frequency component based on the low frequency component of a one frame difference signal and a detection circuit 12 detects the movement of the signal of a color signal band based on a two inter-frame difference signal. The correlation between a signal resulting from synthesis of two output signals and a signal subjected to filter processing by a time space filter circuit 19 employing a field memory 26 and further subjected to one field delay by a field memory 26 is detected and when the correlation is large, the signal subjected to time space filter processing is used as movement information and when the correlation is small, the synthesized signal is used as movement information. Thus, not only detection mistake in a fast movement of an object is prevented but also movement mis-detection in a still picture is decreased and excellent movement detection without unnatural scene change is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a motion detection circuit, and the present invention relates to a motion detection circuit that detects a composite television broadcast signal (a composite television broadcast signal) in which a color signal is frequency-multiplexed into a high frequency region of a luminance signal.
a motion adaptive YC separation device for separating a luminance signal (hereinafter referred to as "V signal") from a luminance signal (hereinafter referred to as "Y signal" or simply "Y") and a color signal (hereinafter referred to as "C signal" or simply rcu); The present invention also relates to a motion detection circuit suitable for use in motion detection in a motion adaptive scanning line interpolation device for converting a television broadcast signal that performs interlaced scanning to progressive scanning.

[Conventional technology]

Many improvements have been made to motion adaptive processing to improve the picture quality of current color television programmers. Motion adaptive processing is a process in which a motion detection circuit locally detects image movement and adaptively switches between still image processing suitable for still images and video processing suitable for moving images according to the detected movement. The main motion adaptive processing in current color televisions includes motion adaptive YC separation processing and motion adaptive scanning line interpolation processing.In recent years, with the development of large-capacity digital memories, the vertical scanning frequency of television signals has increased. Various signal processing circuits have been proposed for improving image quality using delay circuits (hereinafter simply referred to as "delay circuits") having delay times equal to or greater than that.

Motion adaptive YC separation processing separates the Y signal by calculating the sum between frames and the C signal by calculating the difference if the image is determined to be a still image, depending on the amount of movement detected by the motion detection circuit. This allows cross component components such as cross color and dot crawl to be completely removed.

If it is determined that the image is a moving image, intra-field processing is performed to separate the Y signal and C signal.

The purpose of motion adaptive scanning line interpolation processing is to convert an interlaced signal into a sequential scanning signal. Similarly, if it is determined that the image is a still image according to the amount of motion detected by the motion detection circuit, interfield interpolation is performed to convert the line Flicker can be removed. Also, if it is determined that the image is a moving image, intra-field interpolation is performed.

In the above-described motion adaptive processing, the motion detection accuracy of the motion detection circuit greatly affects the quality of the reproduced image. Erroneous motion detection can be classified into the following two types.

(1) Erroneous detection: A part of a still image is determined to be a moving image and processed as a moving image.

(2) Missed detection: A part of the video is determined to be a still image and processed as a still image.

Among these erroneous motion detections, "missed detection" in particular greatly impairs image quality, so motion detection circuits have been proposed to prevent this as much as possible.

FIG. 6 is a block circuit diagram showing an example of a conventional motion detection circuit disclosed in Japanese Patent Application Laid-Open No. 63-90987. In the figure, an NTSC analog V signal input from input terminal 1 is converted to an analog-to-digital converter (rA
(abbreviated as DCJ) into a digital signal. This digitized V signal is input to the first detection circuit 3 to detect the movement of the low frequency component of the luminance signal. First detection circuit 3
First, the DigiMole V signal is stored in the first frame memory 4.
Signal delayed by 1 frame manually and frame memory 4
The input signal of (2) is supplied to the subtraction circuit 5 to obtain an inter-frame difference signal. The output signal of the subtraction circuit 5 is passed through a low-pass filter (
(hereinafter abbreviated as rLPFJ) 6 to remove the color signal band, motion information of the low frequency component of the luminance signal is obtained from the output of the LPF 6. At this time, it can be determined that the object is stationary when the output of the LPF 6 is zero, and that there is movement when the output is other than zero. Since the output signal of this LPF 6 has positive and negative polarities, it is input to an absolute value circuit 7 to obtain the absolute value. The output of the absolute value circuit 7 is converted non-linearly by the conversion circuit 8 with input/output characteristics as shown in FIG. ing.

On the other hand, the digimole V signal from the ADC 2 is input to a bandpass filter C (abbreviated as rBPF) 9, and a signal in the color signal band is extracted.The level of the burst signal included in the output signal of this BPF 9 is kept constant. A that operates like
Due to the function of the CC, the output of the ACC amplifier circuit 10 obtains a nearly constant signal in which fluctuations in the color signal level due to the frequency characteristics of the transmission path are corrected.

Thereafter, the demodulation circuit 11 demodulates the color signal, and the demodulation circuit 11 works to cancel out the inversion of the phase of the color subcarrier between frames. The output signal of the demodulation circuit 11 is input to the second detection circuit 12 to detect the movement of the signal in the color signal band. First, the output signal of the demodulation circuit 11 is input to the second frame memory 13 and delayed by one frame, and then input to the third frame memory 14 and further delayed by one frame.

Next, the output signal of the demodulation circuit 11 and a signal obtained by delaying this output signal by two frames by the frame memories 13 and 14 are supplied to the subtraction circuit 15 to obtain a two-frame difference signal.

The high-frequency components of the chrominance signal and luminance signal are both in phase between signals that are two frames apart, and in the case of a still image, two
Since the inter-frame difference is zero, it can be determined that there is movement when the two-frame difference signal is other than zero. Further, the absolute value circuit 16 and the conversion circuit 17 operate similarly to the absolute value circuit 7 and the conversion circuit 8, respectively.

The output signal of the first detection circuit 3 and the second detection circuit 12
The output signal is supplied to the combining circuit 18 to generate the output signal. As a result, signal movement information of the entire band of the ■ signal is obtained at the output of the combining circuit 18. The synthesis circuit 8 can be realized, for example, by selecting the larger of two input signals.

The output signal of the synthesis circuit 18 is input to the spatio-temporal filter circuit 19, and movement information of spatio-temporally surrounding pixels of a certain pixel is also used to prevent mistakes in detecting fast movements of objects. In the spatio-temporal filter circuit 19, the synthesis circuit 1
The maximum value of the output signal of 8 and the signal delayed by 262HwI and 263HM by the field memory 21 and line memory 22 after multiplied by α (0 < α × 1) by the coefficient circuit 20 is obtained from the output of the spatio-temporal filter circuit 19. After that, the horizontal filter circuit 24 performs filter processing in the horizontal direction. This allows the top and bottom of a certain pixel.

You can refer to left/right and past pixel movement information. Since the spatiotemporal filter circuit in this example has a feedback type configuration, it is possible to refer to the motion information of pixels within the range determined by the coefficient α.For example, if α is close to i, the referenceable range is wide, and if α is close to O, the range is narrow. Become.

In this example, the output of the first detection circuit 3 and the output of the second detection circuit 1
By combining the outputs of 2 and 2 in a synthesis circuit 18, the movement of the entire band of the V signal is obtained, and this movement information is filtered in a spatio-temporal filter circuit 19, thereby preventing mistakes in detecting fast movements of objects. However, as described above, the movement of the image is accurately detected.

[Problem B to be Solved by the Invention] The conventional motion detection circuit has a first detection circuit that detects the motion of an image based on the low frequency component of the one-frame difference signal of the V signal, and a first detection circuit that detects the motion of the image based on the difference between two frames. The second detection circuit detects the motion of the image, and after the output signals of the two detection circuits reach the bottom, filter processing is performed by a spatio-temporal filter circuit using a field memory. FIG. 8 shows the operation of a spatio-temporal filter used in a conventional motion detection circuit.

Suppose now that the output of the synthesis circuit 18 takes the value A at only one point on the scanning line represented by . in n fields.

When this output is input to the spatio-temporal filter 9, the amount of motion is multiplied by α in field units and spreads in space and time. The conventional motion detection circuit shown in FIG. 6 detects the motion of the Y signal and C signal. Since it has a second detection circuit and a spatiotemporal filter that operates as shown in Figure 8, it is possible to detect motion information in the entire signal band;
It is also possible to accurately detect image movement even for images with small brightness differences (only the color changes) or images that move quickly.

However, for example, when shooting a scene with text or detailed patterns using a handheld camera, slight blurring during shooting may cause parts of the image to be mistakenly judged to be moving images, even though they are still images. There is a problem in that the motion detection caused by the erroneous judgment spreads in space and time due to the filter processing performed by the spatial filter circuit.

In addition, when a scene change occurs, the entire screen is detected as motion, and this detection affects several fields later, so even if the scene change is a still image, video processing is performed, and then still image processing is gradually performed. The problem was that it was changing.

This invention was made to solve the above-mentioned problems, and as with conventional motion detection circuits, it detects motion information of signals in the entire signal band, and also detects signal motion information with small brightness differences and only colors. Although it is possible to accurately detect image movement even in images that are changing or fast-moving, there are times when local motion errors are detected or motion is detected that has no correlation in the temporal direction. In some cases, it is an object of the present invention to provide a motion detection circuit that can accurately and unnaturally detect the motion of an image by eliminating the filtering effect of the spatio-temporal filter circuit.

[Means to solve the problem]

The motion detection circuit according to the present invention includes a first detection circuit that detects the motion of an image based on the low frequency component of the inter-frame difference signal of the V signal, and a second detection circuit that detects the motion of an image based on the inter-frame difference signal of the V signal. After detecting the movement of the image using the circuit ε and combining the output signals of the two detection circuits, the combined signal and the signal filtered by the spatio-temporal filter circuit using field memory are further delayed by one field. When the correlation is large, the signal subjected to spatiotemporal filter processing is used as motion information, and when the correlation is small, the combined signal is used as motion information.

[Effect]

The first detection circuit detects the movement of the low frequency component of the luminance signal based on the low frequency component of the one-frame difference signal. Also,
The second detection circuit detects signal movement in at least the color signal band based on the two-frame difference signal. Since the phases of the color subcarriers are in phase between the signals separated by two frames, only information based on the movement of the object can be obtained from the difference signal between the two frames.

The synthesis circuit synthesizes the output signals of the first detection circuit and the second detection circuit, and obtains motion information of the entire band of the signal.

In order to obtain motion information for a certain pixel, a spatiotemporal filter simply uses the motion information detected at that pixel as well as the motions of pixels spatiotemporally surrounding that pixel, that is, vertical, horizontal, horizontal, and past pixels. Detects the correlation between the motion information of that pixel and the motion information of past pixels that have passed through the spatio-temporal filter, and if there is a correlation, uses the motion information of the current pixel that has passed the spatio-temporal filter. If there is no correlation, motion information of the current pixel that does not pass through the spatio-temporal filter is used. This not only prevents detection errors when the object is moving quickly, but also reduces erroneous motion detection in still images, and performs good motion detection without any unnaturalness when changing scenes.

〔Example〕

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

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

In FIG. 1, the same parts as in FIG. 6 are given the same reference numerals. Furthermore, the explanations up to the first detection circuit 3 for determining the difference between one frame and the second detection circuit 12 for determining the difference between two frames are the same as those in FIG. 6, and will therefore be omitted. Furthermore, the first synthesis circuit 18 for synthesizing the output signals of the two types of detection circuits operates in the same manner as the synthesis circuit 18 in FIG.

The output signal of the first synthesis circuit 18 is transmitted to one spatiotemporal filter, the first input terminal of the comparator 27, and the first input terminal of the second synthesis circuit 28.
262H is input by the first field memory 21 and the line memory 22 after
Find the maximum value of the period and the signal delayed by 263H period,
After that, horizontal filter processing is performed by the horizontal filter circuit 24. Meanwhile, the output signal of the line memory 22 is also input to the second field memory 26, and is delayed by a period of 525H with respect to the output signal of the tenth synthesis circuit 18. It is output from the second field memory 26 as a signal.

The output signal of the second field memory 26 is input to the second input of the comparator 27. Further, the output signal of the spatio-temporal filter 19 is input to the second input terminal of the second synthesis circuit 28 . The output signal of the comparator 27 is input to the third input terminal of the second synthesis circuit 28, and the output signal of the first synthesis circuit 1 and the output signal of the spatio-temporal filter 19 are input to the third input terminal of the second synthesis circuit 28.
are synthesized according to the input signals of This second synthesis circuit 2
The output signal No. 8 is outputted from the output terminal 25 as a motion detection amount.

In FIG. 1, the comparator 27 and the second combining circuit 28 can be realized, for example, with a configuration as shown in FIG. 2(a). In FIG. 2(a), the output signal of the first synthesis circuit 18 in FIG. 1 is input to the first input @29. Further, the output signal of the spatio-temporal filter 19 is input to the second input terminal 30 . Furthermore, the output signal - of the second field memory 26 is input to the third input terminal 31 . The signals input from the input terminals 29 and 30 are input to the two input terminals of the subtracter 32 that constitutes the comparator 27. The signal subtracted by the subtracter 32 is converted into an absolute value by an absolute value circuit 33, and then converted to an absolute value by a conversion circuit 3.
4, nonlinear transformation is performed, for example, as shown in FIG. 5(a).

In FIG. 5(a), the horizontal axis represents the magnitude of the input signal of the conversion circuit 34, and the vertical axis represents the magnitude of the output signal of the conversion circuit 34. In FIG. In this way, the lower limit of the output signal is Q
, the upper limit should be limited to P.

The signal inputted from the first input terminal 29 is also inputted to the first input terminal of the subtracting circuit 35 and the first input terminal of the adding circuit 37, which constitute the combining circuit 28.

Further, the signal input from the third input terminal 31 is input to the subtraction circuit 3.
5, and reduces the signal at the first input terminal. The subtracted signal is input to the coefficient multiplier 36 and multiplied by the output of the comparator 27 (0<k<1). Coefficient unit 3
The value of k in 6 is 1 when the output is Q in Figure 5(a).
, P, and the output thereof is input to the second input terminal of the adder circuit 37. The added signal is output from the output end 25 as a signal synthesized by the correlation between the signal of one frame before passing through the spatio-temporal filter and the current amount of motion.

Furthermore, the comparator 27 and the second combining circuit 28 in FIG.
This can also be realized with a configuration as shown in Figure 2).

In FIG. 2), the synthesis circuit 28 is constituted by a switch circuit 38 controlled by the output of the comparator 27. Figure 2(b)
The input/output characteristics of the conversion circuit 34 are as shown in FIG. At this time, the signal input from the third input terminal 31 is switched and output.

The comparator 27 and the second combining circuit 2 in FIG.
FIG. 3 shows the circuit operation after the spatio-temporal filter when configured as shown in FIG. Assume that, similarly to FIG. 8, the output of the first combining circuit 18 takes the value A at only one point on a certain scanning line within n fields, as shown in FIG. 3(b). At this time, the output signal of the spatio-temporal filter 19 is further multiplied by the coefficient circuit 20 and delayed by one frame period in the field memories 21, 26 and line memory 22, so that the output signal as shown in FIG. 3(a) is obtained. Become. Further, as described above, the output of the first synthesis circuit 18 is as shown in FIG. 3(b). Third
From the results shown in FIGS. 3(a) and 3(b), the correlation between the output of the first combining circuit 18 and the output of the second field memory 26 for each field is as shown in FIG. 3(C). Since the output of the spatio-temporal filter 19 is as shown in FIG. 3 ((to)), the final output is as shown in FIG.
If this result is drawn in the same manner as in Fig. 8, it will become as shown in Fig. 4. If there is no correlation in the amount of motion with pixels separated by one frame period, two fields including the current field will be drawn. The amount of movement is output, but after that it is not expanded in space and time.

In the above embodiment, the second detection circuit was realized by obtaining the difference between two frames of demodulated color signals, but as shown in FIG. 9, the second detection circuit was realized by obtaining the difference between two frames.

A similar effect can be obtained by obtaining the difference between two frames from the DigiMole V signal. Here in this circuit,
■The first detection circuit that obtains the difference signal between one frame of the signal,
Take the difference between the current signal and the signal one frame ago 13.5
In addition to the circuit consisting of ~8, we also use a circuit consisting of 14.39~42 that takes the difference between the signal one frame before and the signal two frames ago, and the output of both circuits is 13~17.
By inputting it to the synthesis circuit 18 together with the output of the second detection circuit that obtains the two-frame difference signal, the influence of the time-direction deviation between the one-frame difference signal and the two-frame difference signal can be minimized. ing.

〔Effect of the invention〕

As described above, according to the present invention, the first method detects the movement of an image based on the low frequency component of the one-frame difference signal of the signal.
The motion of the image is detected by a detection circuit and a second detection circuit based on the difference signal between two frames, and after combining the output signals of the two detection circuits, the combined signal and the field memory are combined. The correlation between the signal filtered by the spatio-temporal filter circuit used and the signal delayed by l field is detected, and when the correlation is large, the spatio-temporally filtered signal is used as motion information, and when the correlation is small, the signal processed by the spatio-temporal filter is used as motion information. Since it is configured to use the synthesized signal as motion information, it can detect image movement even for images with small brightness differences and only changing colors or fast-moving images, just like conventional motion detection circuits. In addition to accurately detecting motion, it is also effective in detecting motion accurately and without unnaturalness even when local motion detection or motion detection that has no correlation in the temporal direction is performed. be.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of a motion detection circuit according to the present invention, FIG. 2 is a block diagram showing two types of embodiments of a comparator and a second synthesis circuit according to the present invention, and FIG. FIG. 4 is a diagram showing the relationship between the input signal and output signal of the second synthesis circuit according to the invention, FIG. 4 is a diagram showing the output signal of the motion detection circuit according to the invention, and FIG. 5 is a diagram showing the conversion characteristics of the comparator according to the invention. 6 is a block diagram showing an example of a conventional motion detection circuit, FIG. 7 is a diagram showing input/output characteristics of a conversion circuit of the conventional motion detection circuit, and FIG. 8 is a diagram configuring a comparator according to the present invention. FIG. 9, which is a diagram showing the input/output characteristics of the conversion circuit, is a block diagram showing another embodiment of the motion detection circuit according to the present invention. l... ■ Signal input, 2... ADC13... First motion detection circuit, 4... First frame memory, 5, 1
5゜32.35.39--Subtraction circuit, 6.4O-LP
F. 7.16.33.41... Absolute value circuit, 8,1734
．． 42--conversion circuit, 9-B P F, 10-ACC
11... Color demodulation circuit, 12... Second motion detection circuit, 13... Second frame memory, 14
...Third frame memory, 18...First synthesis circuit, 19...Space-time filter, 2o...First coefficient circuit, 21...First field memory, 22...・
Line memory, 23... Maximum value selection circuit, 24...
Horizontal filter, 25...Motion detection amount output end, 26...
・Second field memory, 27... Comparator, 28.
. . . second synthesis circuit, 29, 30. 31 . . . motion amount large end, 36 . . . second coefficient circuit, 37 . Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] (1) In a motion detection circuit that inputs a composite television signal in which the color signal is frequency-multiplexed into the high frequency region of the luminance signal and detects the motion of an image, the composite color television signal is input and the difference between one frame is detected. a first detection circuit having means for obtaining a signal and detecting image movement based on the low frequency component of the one-frame difference signal; and a first detection circuit that receives the composite color television signal and receives a two-frame difference signal. a second detection circuit that detects the movement of an image based on the difference signal between the two frames; and a synthesis circuit that synthesizes the output signals of the first detection circuit and the second detection circuit. and a spatio-temporal filter circuit that adaptively controls a filtered signal based on the output signal of the synthesis circuit to spatio-temporally expand the output signal and the output signal by inter-frame correlation of the output signal. A motion detection circuit characterized by being provided.