JP2804795B2 - Motion detection circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motion detection circuit, and a composite television signal (hereinafter, referred to as a "V signal") in which a chrominance signal is frequency-multiplexed in a high frequency region of a luminance signal. A luminance signal (hereinafter referred to as “Y signal” or simply “Y”) and a chrominance signal (hereinafter referred to as “C
Signal or simply "C"), or a motion-adaptive scanning line interpolator for converting a television signal for interlaced scanning into progressive scanning. It relates to a suitable motion detection circuit.

[Conventional technology]

Many improvements have been made to motion adaptive processing to improve the image quality of current color televisions. The motion adaptation process is a process in which a motion detection circuit detects a motion of an image locally and adaptively switches between a still image process suitable for a still image and a moving image process suitable for a moving image according to the detected motion. Means The main motion adaptive processing in current color television is motion adaptive YC separation processing and motion adaptive scanning line interpolation processing.In recent years, with the development of large-capacity digital memories, it has become equal to or lower than the vertical scanning frequency of television signals. Various signal processing circuits for improving image quality using a delay circuit having the above-described delay time (hereinafter, simply referred to as “delay circuit”) have been proposed.

The motion-adaptive YC separation process separates the Y signal by taking the sum between frames and the C signal by taking the difference according to the amount of motion detected by the motion detection circuit when it is determined that the image is a still image. , Cross components such as cross color and dot crawl can be completely removed.
If it is determined that the moving image is a moving image, the in-field processing is performed to separate the Y signal and the C signal.

The motion adaptive scanning line interpolation process is for converting an interlaced signal into a sequential scanning signal. Similarly, when it is determined that the image is a still image according to the amount of motion detected by the motion detection circuit, inter-field interpolation is performed. Flicker can be removed.
If it is determined that the video is a moving image, intra-field interpolation is performed.

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

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

(2) Missing detection: A part of the moving image is determined to be a still image, and the still image is processed.

Of these erroneous motion detections, especially "missing detection" greatly impairs the image quality, and therefore a motion detection circuit has been proposed to prevent this as much as possible.

FIG. 6 is a block circuit diagram showing an example of a conventional motion detecting circuit disclosed in Japanese Patent Application Laid-Open No. 63-90987. In the figure, an NTSC analog V signal input from an input terminal 1 is converted into a digital signal by an analog / digital conversion circuit (hereinafter abbreviated as “ADC”). The 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, the first detection circuit 3 inputs the digitized V signal to the first frame memory 4 and supplies the signal delayed by one frame and the input signal of the frame memory 4 to the subtraction circuit 5, and outputs the one-frame difference signal. obtain.
The output signal of the subtraction circuit 5 is converted to a low-pass filter (hereinafter, "LP
F ") to remove the chrominance signal band to obtain the motion information of the low frequency component of the luminance signal at the output of the LPF 6. At this time, when the output of the LPF 6 is zero, it can be determined that there is stillness, and when the output is other than zero, there is a motion. Since the output signal of the LPF 6 has positive and negative polarities, it is input to the absolute value circuit 7 to determine the absolute value. The output of the absolute value circuit 7 is a conversion circuit 8
For example, the input / output characteristics are nonlinearly converted as shown in FIG. 7, and the effect of noise is removed by setting the output to zero for a low-level input.

On the other hand, the digitized V signal from the ADC 2 is input to a band-pass filter (hereinafter abbreviated as “BPF”) 9 to extract a signal in a color signal band. Due to the function of the ACC operating to keep the level of the burst signal included in the output signal of the BPF 9 constant, the variation of the color signal level due to the frequency characteristic of the transmission line was corrected in the output of the ACC amplifier circuit 10. , Almost constant signal.

Thereafter, the color signal is demodulated by the demodulation circuit 11, and the demodulation circuit 11 functions to cancel 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, an output signal of the demodulation circuit 11 and a signal obtained by delaying the output signal by two frames by the frame memories 13 and 14 are supplied to the subtraction circuit 15 to obtain a difference signal between two frames. Between the signals separated by two frames, the high-frequency components of the chrominance signal and the luminance signal have the same phase, and the difference between two frames is zero for a still image. Can be determined. Further, an absolute value circuit 16 and a 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
Is supplied to the synthesizing circuit 18 and synthesized. Thus, the motion information of the signal of the entire band of the V signal is obtained at the output of the synthesizing circuit 18. The combining circuit 18 can be realized by, for example, a method of selecting a larger one of two input signals.

The output signal of the synthesizing circuit 18 is input to the spatio-temporal filter circuit 19, and by using the motion information of surrounding pixels in a spatio-temporal manner of a certain pixel, detection error of fast motion of the object is prevented. In the spatio-temporal filter circuit 19, the output signal of the synthesis circuit 18 and the output of the spatio-temporal
After doubling (0 <α <1), the field memory 21 and the line memory 22 determine the maximum value of the signal delayed by the 262H period and the 263H period, and then the horizontal filter circuit 24 performs horizontal filtering. As a result, it is possible to refer to the motion information of a vertical pixel, a horizontal pixel, and a past pixel of a certain pixel.
Since the spatio-temporal filter circuit in this example is of a feedback type, the motion information of pixels in a range determined by the coefficient α can be referred to. For example, if α is close to 1, the referenceable range is wide, and if α is close to 0, the range is narrow.

In this example, the output of the first detection circuit 3 and the second detection circuit
The output of 12 is synthesized by the synthesizing circuit 18 to obtain the motion of the signal in the entire band of the V signal, and the motion information is filtered by the spatio-temporal filter circuit 19, thereby preventing the detection error of the fast motion of the object. In this way, the motion of the image is accurately detected.

[Problems to be solved by the invention]

The conventional motion detection circuit uses a first detection circuit that detects image motion based on a low-frequency component of a one-frame difference signal of a V signal, and a second detection circuit that uses two-frame difference between image motions. Is detected, the output signals of the two detection circuits are combined, and then a filtering process is performed by a spatio-temporal filter circuit using a field memory. FIG. 8 shows the operation of the spatiotemporal filter used in the conventional motion detection circuit.

Now, it is assumed that the output of the synthesizing 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 19, the motion amount spreads in spatio-temporal space while being multiplied by α in field units. The conventional motion detecting circuit shown in FIG. 6 has first and second detecting circuits for detecting the motions of the Y signal and the C signal, and has a spatiotemporal filter which operates as shown in FIG. Therefore, the motion information can be detected in the signal of the entire band of the V signal, and the motion of the image can be accurately detected even for an image having a small luminance difference and only a color change or an image having a fast motion. Can be.

However, for example, when shooting a scene with characters and fine patterns with a handy camera, it is erroneously determined that the image is a moving image even though it is a still image due to subtle blurring at the time of shooting, and moreover, In the filter processing by the filter circuit, there is a problem that motion detection due to the erroneous determination is spread in spatiotemporal space.

In addition, when a scene change is detected, the entire screen is detected as moving, and the detection is affected until a few fields later. In particular, even when a still image is displayed after the scene change, moving image processing is performed. There was a problem that it changed.

The present invention has been made in order to solve the above-described problems, and detects motion information of signals in the entire band of a V signal, as in a conventional motion detection circuit, and has a small luminance difference and only colors. Of course, it was possible to accurately detect the motion of an image even if it was changing or a fast-moving image, but local motion error detection or motion detection with no correlation in the time direction was performed. In such a case, an object of the present invention is to provide a motion detection circuit capable of accurately and not unnaturally detecting the motion of an image by eliminating the filtering effect of the spatiotemporal filter circuit.

[Means for solving the problem]

A motion detection circuit according to the present invention includes a first detection circuit for detecting a motion of an image based on a low-frequency component of a one-frame difference signal of a V signal, and a second detection circuit based on a two-frame difference signal. And the output signals of the two detection circuits are combined, and then the combined signal and the signal subjected to the filtering process by the spatio-temporal filter circuit using the field memory are further delayed by one field. The correlation with the signal is detected. When the correlation is large, the signal subjected to the spatio-temporal filter processing is used as motion information, and when the correlation is small, the synthesized signal is used as motion information.

[Action]

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. Further, the second detection circuit detects a motion of a signal in at least a color signal band based on the difference signal between two frames. Since the phase of the chrominance subcarrier is in-phase between signals separated by two frames, 2
Only information based on the motion of the object can be obtained from the inter-frame difference signal.

The combining circuit combines the output signals of the first detection circuit and the second detection circuit to obtain motion information of the entire band of the V signal.

The spatio-temporal filter is used to obtain the motion information of a certain pixel.
In addition to the motion information detected at the pixel, not only the motion of the surrounding pixels in the space and time, that is, the vertical, left and right, and past pixel motions is used, but also the motion information of the pixel and the spatiotemporal filter are used in the past. Performs correlation detection with past pixel motion information that has passed, uses the current pixel motion information that has passed the spatiotemporal filter if there is a correlation, and uses the current pixel that does not pass the spatiotemporal filter if there is no correlation Is used. As a result, not only the detection error in the fast motion of the object is prevented, but also the motion error detection in the still image is reduced, and the favorable motion detection without the unnaturalness at the time of the scene change is performed.

〔Example〕

 Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention. In FIG. 1, the same parts as those in FIG. 6 are denoted by the same reference numerals. The description up to the first detection circuit 3 for obtaining the difference between one frame and the second detection circuit 12 for obtaining the difference between two frames is the same as in FIG. Further, the first synthesizing circuit 18 for synthesizing the output signals of the two types of detection circuits operates in the same manner as the synthesizing circuit 18 in FIG.

The output signal of the first synthesizing circuit 18 is input to the spatio-temporal filter 19, the first input terminal of the comparator 27, and the first input terminal of the second synthesizing circuit 28. In the spatiotemporal filter 16, the output signal of the synthesis circuit 18 and the output of the spatiotemporal filter circuit 19 are multiplied by α (0 <α <
After 1), the first field memory 21 and the line memory 22 determine the maximum value with the signal delayed for the 262H period and the 263H period, and then the horizontal filter circuit 24 performs horizontal filtering. On the other hand, the output signal of the line memory 22 is also input to the second field memory 26, and is output from the second field memory 26 as a signal delayed by 525H from the output signal of the first synthesizing circuit 18.

The output signal of the second field memory 26 is input to a second input terminal of the comparator 27. The output signal of the spatiotemporal filter 19 is input to a 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 18 and the output signal of the spatio-temporal filter 19 are input to the third input terminal. It is synthesized according to the signal. The output signal of the second synthesis circuit 28 is output from the output terminal 25 as a motion detection amount.

In FIG. 1, the comparator 27 and the second synthesizing circuit 28 can be realized by, for example, a configuration as shown in FIG. 2 (a). 2A, an output signal of the first combining circuit 18 of FIG. 1 is input to a first input terminal 29. Also, the second input terminal
The output signal of the spatiotemporal filter 19 is input to 30. Further, an output signal of the second field memory 26 is input to the third input terminal 31. Signals input from the input terminals 29 and 30 are input to two input terminals of a subtractor 32 constituting the comparator 27. The signal subtracted by the subtractor 32 is converted into an absolute value by an absolute value circuit 33, and is further subjected to a non-linear conversion by a conversion circuit 34, for example, as shown in FIG. In FIG. 5A, the horizontal axis is the axis representing the magnitude of the input signal of the conversion circuit 34, and the vertical axis is the axis representing the magnitude of the output signal of the conversion circuit 34. As described above, it is preferable that the lower limit of the output signal be Q and the upper limit be P.

The signal input from the first input terminal 29 is
It is input to a first input terminal of a subtraction circuit 35 and a first input terminal of an adder circuit 37 which constitute 28. The signal input from the third input terminal 31 is input to the second input terminal of the subtraction circuit 35,
The signal at the first input is reduced. The subtracted signal is a coefficient multiplier
36, and k times (0 <k <
1) is done. The value of k of the coefficient unit 36 is controlled so that k = 1 when the output is Q and k = 0 when P is output in FIG. 5 (a), and the output is the second input terminal of the adder 37. Is input to The added signal is output from the output terminal 25 as a signal synthesized by correlation between the signal of one frame before passing through the spatiotemporal filter and the current motion amount.

Further, the comparator 27 and the second synthesizing circuit 28 in FIG. 1 can also be realized by a configuration as shown in FIG. 2 (b). In FIG. 2B, the combining circuit 28 is constituted by a switch circuit 38 controlled by the output of the comparator 27. 2 (b) conversion circuit
As shown in FIG. 5 (b), the input / output characteristic of the output 34 takes either a value of P or Q. When the output is P, the signal input from the first input terminal 29 is output. The signal input from the third input terminal 31 is switched and output.

FIG. 3 shows circuit operations after the spatiotemporal filter when the comparator 27 and the second combining circuit 28 in FIG. 1 are configured as shown in FIG. 2 (b). First combining circuit as in FIG.
Assume that the output of 18 takes the value A at only one point on a certain scanning line in n fields as shown in FIG. 3 (b). At this time, the output signal of the spatiotemporal filter 19 is further multiplied by α in the coefficient circuit 20 and is delayed by one frame period in the field memories 21 and 26 and the line memory 22, so that an output as shown in FIG. . Further, as described above, the output of the first synthesis circuit 18 is as shown in FIG. 3 (b). From the results of FIGS. 3A and 3B, the correlation between the output of the first synthesizing circuit 18 and the output of the second field memory 26 for each field is as shown in FIG. 3C. Since the output of the spatiotemporal filter 19 is as shown in FIG. 3D, the final output is as shown in FIG. 3E depending on the presence or absence of the correlation shown in FIG. 3C. If this result is drawn in the same manner as in FIG. 8, the result is as shown in FIG. 4. If there is no correlation between the motion amounts of the pixels separated by one frame period, the motion amounts of two fields including the current field are output. But after that, it is not stretched into space-time.

In the above embodiment, the second detection circuit is realized by obtaining a difference between two frames of the demodulated color signal.
As shown in FIG. 9, the same effect can be obtained by obtaining the difference between one frame and the difference between two frames from the digitized V signal. Here, in this circuit, the first detection circuit for obtaining the difference signal between one frame of the V signal is not only a circuit composed of 13,5 to 8 for calculating the difference between the current signal and the signal of one frame before, but also one circuit. A second circuit for obtaining a difference signal between two frames consisting of 13 to 17 and obtaining the difference signal between two frames by using a circuit consisting of 14, 39 to 42 for taking the difference between the signal before the frame and the signal two frames before. By inputting the signal to the synthesizing circuit 18 together with the output of the detection circuit, it is possible to minimize the influence of the time-direction shift between the one-frame difference signal and the two-frame difference signal as much as possible.

〔The invention's effect〕

As described above, according to the present invention, the first detection circuit for detecting the motion of the image based on the low-frequency component of the one-frame difference signal of the V signal, and the second detection circuit based on the two-frame difference signal are used. After detecting the motion of the image with the detection circuit of (1) and synthesizing the output signals of the two detection circuits, the synthesized signal and the signal subjected to the filter processing by the spatio-temporal filter circuit using the field memory are further divided into one. Since the correlation with the field-delayed signal is detected, and when the correlation is large, the signal subjected to the spatio-temporal filter processing is used as the motion information, and when the correlation is small, the synthesized signal is used as the motion information. As with the motion detection circuit, it is of course possible to accurately detect the motion of an image even when the luminance difference is small and only the color is changing, or for a fast-moving image. Detection or If the correlation between the direction there is no motion detected has been made, there is an effect that it is possible to accurately, yet not unnatural detect motion.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a motion detecting circuit according to the present invention, FIG. 2 is a block diagram showing two types of embodiments of a comparator and a second synthesizing circuit according to the present invention, and FIG. FIG. 4 is a diagram showing a relationship between an input signal and an output signal of a second synthesizing circuit according to the present invention, FIG. 4 is a diagram showing an output signal of a motion detecting circuit according to the present invention, and FIG. 5 is a diagram showing conversion characteristics of a comparator according to the present invention. FIG. 6, FIG. 6 is a block diagram showing an example of a conventional motion detecting circuit, FIG. 7 is a diagram showing input / output characteristics of a conversion circuit of the conventional motion detecting circuit, and FIG. 8 constitutes a comparator according to the present invention. FIG. 9 is a diagram showing input / output characteristics of a conversion circuit, and FIG. 9 is a block diagram showing another embodiment of the motion detection circuit according to the present invention. 1 ... V signal input, 2 ... ADC, 3 ... first motion detection circuit, 4 ... first frame memory, 5, 15, 32, 35, 39 ...
… Subtraction circuit, 6,40… LPF, 7,16,33,41 …… Absolute value circuit, 8,17,34,42 …… Conversion circuit, 9… BPF, 10… ACC amplification circuit, 11 ... color demodulation circuit, 12 ... second motion detection circuit, 13 ... second frame memory, 14 ... third frame memory, 18 ... first synthesis circuit, 19 ... spatio-temporal filter, 20: first coefficient circuit, 21: first field memory, 22: line memory, 23: maximum value selection circuit, 24
… Horizontal filter, 25… motion detection amount output terminal, 26… second field memory, 27… comparator, 28… second synthesis circuit, 29, 30, 31… motion amount input terminal, 36 ... second coefficient circuit, 37 ... addition circuit, 38 ... switch circuit. In the drawings, the same reference numerals indicate the same or corresponding parts.

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H04N 11/04 H04N 9/77-9/78

Claims (1)

(57) [Claims] 1. A motion detecting circuit for inputting a composite television signal obtained by frequency-multiplexing a color signal into a high-frequency region of a luminance signal and detecting a motion of an image, comprising the steps of: A first detection circuit for detecting a motion of an image based on a low-frequency component of the one-frame difference signal; Means for obtaining a difference signal, a second detection circuit for detecting a motion of an image based on the difference signal between two frames, and an output signal of the first detection circuit and the output signal of the second detection circuit; A combining circuit; and a spatio-temporal filter circuit for adaptively controlling the output signal and a signal obtained by performing a filtering process for temporally and spatially expanding the output signal based on the output signal of the combining circuit by an inter-frame correlation of the output signal. When A motion detection circuit comprising: