JPH0477517B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a motion detection circuit, and in particular, detects a luminance signal (hereinafter referred to as Y signal) and a carrier color signal (hereinafter referred to as C signal) from a composite video signal of NTSC system. The present invention relates to a motion detection circuit for performing a processing operation to separate images (hereinafter referred to as "abbreviated as") according to the movement of an image caused by this composite video signal.

(Prior Art) FIGS. 8a and 9b and 9a and 9b are diagrams showing an example of the spectrum of the Y signal and C signal of a composite video signal of the NTSC system, and FIGS. This is an example in which the image generated by the signal is close to a still image, and FIGS. 9a and 9b are examples in which the image is a moving image. In each figure, f ₁ represents a horizontal spatial frequency, f ₂ represents a vertical spatial frequency, and f 3 represents a temporal frequency, and in the following description, they will be abbreviated as f ₁ , f ₂ , and f ₃ , respectively.
Also, the units of f ₂ are cph (cycle per height), f ₁ , f ₃
The unit of is Hz, and the symbols Y and C indicate the spectra of the Y signal and C signal, respectively. Furthermore, f _SC is the frequency of the color subcarrier, hereinafter f _SC
It is abbreviated as

FIG. 10 is a block system diagram showing an example of a conventional Y/C separation circuit. In addition, in the same figure, F represents a one-frame delay circuit composed of a frame memory,
H each represents a 1-line delay circuit composed of a line memory.

In the figure, an NTSC composite video signal is input to an input terminal 1. 2 is a frame comb filter (hereinafter abbreviated as frame comb filter) for C signal separation that processes when the image produced by the composite video signal is a still image; this is composed of two 1-frame delay circuits F, F; It consists of an adder/subtractor, and The frequency characteristic of this frame comb filter 2 is 0.5−0.5cos (2πf ₃ /30). Figure 11 is a diagram showing the passband characteristics.
The diagonal lines in the figure represent passbands with amplitude levels of 0.5 or higher.

Here, if the image resulting from the input composite video signal is a still image with a spectrum as shown in FIG. 8a, the frame comb filter 2 described above is used.
The C signal can be separated by However, in the case of a spectrum video as shown in Figure 9a,
The above-mentioned frame comb filter 2 cannot sufficiently separate the C signal, so a line comb filter for C signal separation (hereinafter abbreviated as line comb filter) 3 shown in FIG. 10 separates the C signal. This line comb filter 3 is composed of two one-line delay circuits H, H and two adders/subtracters. The frequency characteristic of this line comb filter 3 is 0.5−0.5cos (2πf ₂ ×2/525). Figure 12 is a diagram showing the passband characteristics.
The diagonal lines in the figure represent passbands with amplitude levels of 0.5 or higher.

Reference numeral 4 in FIG. 10 denotes a one-line delay circuit, which is used to match the output of the frame comb filter 2 with the delay time of the output of the line comb filter 3.

The output of the one-line delay circuit 4 and the output of the line comb filter 3 are each supplied to a mixer 5, where they are mixed. This mixer 5 is composed of one adder and two multipliers ○×, ○×, and its function is (output of frame comb filter 2)×(1− k) + (output of line comb filter 3) x k signal.

Here, the motion coefficient k is determined by the motion detection circuit 6. When the image based on the input composite video signal is a still image, k=0 is output, and when the image has a lot of movement, k=1 is output at the maximum. Depending on the amount of movement, k=
It changes from 0 to 1 and is output.

Therefore, when k=0, the output of the frame comb filter 2 is selected and when k=1, the output of the line comb filter 3 is selected and output, and when the value of k is between 0 and 1, the output of the frame comb filter 2 is selected and output. Depending on the value of k, the output of the frame comb filter 2 and the output of the line comb filter 3 are mixed and output.

In this way, the signal output from the mixer 5 is converted from the composite video signal by the one-dimensional bandpass filter (BPF) 7 with the horizontal spatial frequency _f1 .
The signal components are separated and output from the output terminal 8.

On the other hand, the Y signal is the C signal separated from the composite video signal.
It is obtained by subtracting the signal by the subtractor 9, and this is output from the output terminal 10.

(Problems to be Solved by the Invention) In the conventional motion adaptive Y/C separation circuit described above, the motion detection circuit 6 plays an important role. That is, the quality of the processing operation for Y/C separation of the composite video signal is determined by the operation of the motion detection circuit 6. However, the conventional motion detection circuit 6 was not functionally sufficient.

The following paper describes the spectrum and processing of three-dimensional spatiotemporal frequencies regarding composite video signals. "Takahiko Fukinuki: 'Evaluating the characteristics of three-dimensional signal processing systems using a moving circular zone plate in response to the development of television technology', Nikkei Electronics, (7.1, 1985)" In view of technology,
It is an object of the present invention to provide a motion detection circuit that operates well.

(Means for Solving the Problems) In order to achieve the above object, the present invention solves the NTSC
In a motion detection circuit for performing a processing operation of separating a luminance signal and a carrier color signal from a composite video signal of the system in accordance with the movement of an image caused by this composite video signal, the motion detection circuit detects the difference between two frames of the composite video signal. means for passing the signal through a first low-pass filter based on a horizontal spatial frequency and outputting a first amount of motion according to the magnitude of the signal whose absolute value is taken from the output of the first low-pass filter; The signal obtained by removing the carrier color signal component from the signal detected by the one-frame difference by a two-dimensional filter using a horizontal spatial frequency and a vertical spatial frequency is passed through a second low-pass filter using a horizontal spatial frequency, and the signal is filtered through a second low-pass filter using a horizontal spatial frequency. means for detecting a second amount of motion according to the magnitude of a signal whose absolute value is taken from the output; and means for detecting the first amount of motion and the second amount of motion.
The present invention provides a motion detection circuit comprising selection means for selecting the larger of the motion amounts and outputting the selected motion amount as a detected motion amount.

(Function) In the motion detection circuit configured as described above,
The larger of the first motion amount obtained from the signal detected by the two-frame difference of the NTSC composite video signal and the second motion amount obtained from the signal detected by the one-frame difference is selected as the detected motion amount. and output it.

(Embodiment) An embodiment of the motion detection circuit according to the present invention will be described below with reference to the drawings.

When the image produced by the NTSC composite video signal is a still image, the spectrum of the Y signal is concentrated at the frequency of f ₃ =0. Therefore, motion detection involves detecting the component of the Y signal in a region where f ₃ is not zero. Therefore, as shown in the spectrum of FIG. 8a, if the C signal component is detected, it will be an erroneous detection. Therefore, in the present invention, the component (spectrum) of the Y signal is detected in a three-dimensional frequency domain excluding the region near f ₃ =0 and the center and peripheral regions of the C signal spectrum.

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

In the figure, an NTSC composite video signal is input to an input terminal 11. 12 is a two-frame difference detection circuit that detects the difference between two frames. Since the color subcarrier f _SC is in phase between two frames,
If the image generated by the composite video signal is a still image, C
The difference between the two frames of the signal becomes zero. FIG. 2 is a diagram showing the frequency characteristics of the two-frame difference detection circuit 12, and the diagonal lines in the diagram represent passbands having an amplitude level of 0.5 or more.

However, the above two-frame difference detection circuit 1
2, as shown in the frequency characteristic diagram of Fig. 2, f ₃
= No motion can be detected in the vicinity of 15Hz.

Therefore, the 1 frame difference detection circuit 13
Detect frame differences. FIG. 3 is a diagram showing the frequency characteristics of the one-frame difference detection circuit 13, and the diagonal lines in the diagram represent passbands having an amplitude level of 0.5 or more.

However, since this 1-frame difference detection circuit 13 also detects the C signal component, the output of the 1-frame difference detection circuit 13 is converted to the horizontal spatial frequency f ₁
and two-dimensional filter 1 with vertical spatial frequency f ₂
4 to remove the C signal component. FIG. 4 is a diagram showing the frequency characteristics of the two-dimensional filter 14, and the diagonal lines in the diagram represent passbands having an amplitude level of 0.5 or higher.

With the one-frame difference detection circuit 13 and the two _- dimensional filter 14 described above, it is possible to detect the Y signal spectrum in the three-dimensional frequency domain excluding the center and peripheral areas of the C signal spectrum in the vicinity of f 3 = 15Hz. Become.

However, in this case, the area from which the C signal is removed is a little too wide in the _f3 frequency direction, so the detection by the two-frame difference detection circuit 12 described above is used in combination.

15 and 16 are low pass filters (LPF),
This is to remove frequency components of f ₁ near f _SC or higher, and to improve noise resistance. FIG. 5 is a diagram showing an example of the frequency characteristics.

Moreover, 17 and 18 are absolute value circuits, which have a function of taking the absolute value of the signal detected by the two-frame difference detection circuit 12 and the one-frame difference detection circuit 13, respectively. Then, the absolute value circuit 17,1
The signals converted into absolute values at step 8 are converted into a two-frame difference motion coefficient k ₂ and a one-frame difference motion coefficient k ₁ in motion coefficient conversion circuits 19 and 20, respectively.

The input/output characteristics of the motion coefficient conversion circuits 19 and 20 are as follows:
For example, it is as shown in FIG. 6, and its output is the above-mentioned motion coefficient k (output of the motion detection circuit 6 in FIG. 10).

In FIG. 6, the part A of the input (absolute value of the two-frame or one-frame difference detection signal) is an area where the movement is very small, and k=0 is set to improve the noise resistance. Furthermore, the input C portion is a region with large motion, and k=1 is set for inputs above a certain predetermined level. Furthermore, part B of the input is an intermediate region of movement, and takes a value between k=0 and 1.

The above motion coefficient conversion circuits 19 and 20 are ROM
(Read Only Memory), and has input/output characteristics as shown in Fig. 6, and the motion coefficient k is configured in 4 bits, for example, k = 0 to 1, in 16 steps. can do.

The 2-frame differential motion coefficient k ₂ and the 1-frame differential motion coefficient k ₁ obtained by the above configuration are respectively supplied to the selection circuit 21, and the selection circuit 21 selects these motion coefficients k ₂ , k The larger _one is selected and outputted to the output terminal 22 as the detected motion coefficient k.

This motion coefficient k is supplied to the mixer 5 already explained in the Y/C separation circuit shown in FIG. 10, thereby making it possible to perform a good Y/C separation processing operation.

Here, two frame difference detection circuits 12 and 1 in the block system diagram of one embodiment of the present invention shown in FIG.
Frame difference detection circuit 13 and two-dimensional filter 1
Specific examples of each of 4 are shown in FIG. Note that the block numbers indicated by broken lines in FIG. 7 and other numbers correspond to the block numbers and other numbers in FIG. 1, respectively.

In Figure 7, F and H are frame memories, respectively.
1 represents a 1-frame delay circuit and a 1-line delay circuit made up of a line memory, and T represents a delay device for one clock, and 2T represents a delay device for two clocks. In this specific example, the clock has a frequency of 4f _SC .

The two-frame difference detection circuit 12 is composed of two one-frame delay circuits (frame memories) F, F and one subtracter, and its frequency characteristic is calculated from the difference between two frames by sin(2πf ₃ /30 ), and FIG. 2 is a diagram showing its characteristics.

The one-frame difference detection circuit 13 is composed of two one-frame delay circuits (frame memories) F and two adders/subtracters, and its frequency characteristic is 0.5-0.5cos (2πf ₃ /30 ), and FIG. 3 is a diagram showing its characteristics.

The two-dimensional filter 14 includes two one-line delay circuits (line memories) H, H, three two-clock delay circuits 2T, 2T, 2T, and five adders/subtractors.
, , and the tap gain of this two-dimensional filter 14 is as follows, where the horizontal period represents the horizontal period and the vertical period represents the vertical period.

-1/16 0 1/8 0 -1/16 1/8 0 3/4 0 1/8 -1/16 0 1/8 0 -1/16 Figure 4 shows the frequency characteristics of the two-dimensional filter 14. In the figure, the diagonal lines in the figure represent passbands with amplitude levels of 0.5 or higher.

In FIG. 7, 1-line delay devices H, 23 and 2-clock delay devices 2T, 24 are used to match the delay times of the signals supplied to the low-pass filters 15, 16 in FIG.

As described above, according to the motion detection circuit according to the embodiment of the present invention shown in FIG. 1, it is possible to perform excellent motion detection of a composite video signal.

(Effects of the Invention) As described above, according to the motion detection circuit according to the present invention, it is possible to perform a processing operation for good Y/C separation of a composite video signal, and the effect is great.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the motion detection circuit according to the present invention, and FIG. 2 is a diagram showing the characteristics of the two-frame difference detection circuit 12 constituting the present invention.
FIG. 3 is a diagram showing the characteristics of the one-frame difference detection circuit 13 constituting the present invention, FIG. 4 is a diagram showing the characteristics of the two-dimensional filter 14 constituting the present invention, and FIG. 5 is a diagram showing the characteristics of the two-dimensional filter 14 constituting the present invention. FIG. 6 is a diagram showing the characteristics of the filters 15 and 16, FIG. 6 is a diagram showing the characteristics of the motion coefficient conversion circuits 19 and 20 constituting the present invention, and FIG. 7 is a diagram showing the characteristics of the two-frame difference detection circuit 12 constituting the present invention.
FIGS. 8a and 8b are diagrams showing specific examples of the one-frame difference detection circuit 13 and the two-dimensional filter 14, respectively.
9a and 9b are diagrams showing an example of the spectrum of the Y signal and C signal of a composite video signal of the NTSC system. Figures 9a and b are diagrams showing an example of a moving image; Figure 10 is a block diagram showing an example of a conventional Y/C separation circuit; Figure 11 is a diagram showing characteristics of a frame comb filter; The figure shows the characteristics of a line comb filter. 11...Input terminal, 12...2 frame difference detection circuit, 13...1 frame difference detection circuit, 14
... Two-dimensional filter, 15, 16 ... Low pass filter (LPF), 17, 18 ... Absolute value circuit, 1
9, 20...Motion coefficient conversion circuit, 21...Selection circuit, 22...Output terminal, F...1 frame delay circuit, H...1 line delay circuit, _k1 ...1 frame differential motion coefficient, _k2 ...2-frame differential motion coefficient,
k...Detection motion coefficient, 2T...2 clock delay device.

Claims (1)

[Scope of Claims] 1. In a motion detection circuit for performing a processing operation of separating a luminance signal and a carrier color signal from an NTSC composite video signal in accordance with the movement of an image caused by the composite video signal, the composite video signal comprises: The signal detected by the difference between two frames of the signal is passed through a first low-pass filter based on the horizontal spatial frequency, and the first filter is filtered according to the magnitude of the signal whose absolute value is taken from the output of this first low-pass filter.
means for outputting the amount of movement of the composite video signal; means for outputting a second amount of movement according to the magnitude of a signal passing through a second low-pass filter and taking an absolute value from the output of the second low-pass filter; and the first amount of movement and the second movement. A motion detection circuit comprising selection means for selecting a larger amount of motion and outputting the selected motion amount as a detected motion amount.