JPH0583734A - Video signal processing circuit - Google Patents

Abstract

PURPOSE:To improve the S/N by reducing an error in the decision of a moving picture at the deterioration of C/N and making only an impulse noise inconspicuous resultingly. CONSTITUTION:A Y/C separator section 100 consists of a Y/C separator circuit (obtaining a moving picture system signal) utilizing interline correlation and a Y/C separator circuit (obtaining a still picture system signal) utilizing inter- frame correlation and a motion detection signal controls the mixing ratio of the moving picture system signal and the still picture system signal obtained from the separator circuits. In this case, the control characteristic of the mixing ratio is controlled by a setting value control signal representing the C/N level obtained from a peak detection circuit 15 and when the C/N level is deteriorated, the ratio representing the still picture mode is strengthened by the motion detection signal and erroneous decision as moving picture decision due to noise or the like is suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal processing circuit used in a video tape recorder or a television system.

[0002]

2. Description of the Related Art In a television system, a Y / C separation circuit system for separating a luminance signal and a color signal is used. There are two types of Y / C separation circuits, one of which performs separation using frame correlation and the other of which uses line correlation. A circuit utilizing frame correlation separates and derives a luminance signal and a chrominance signal by adding / subtracting the previous signal and the current signal. A circuit using line correlation separates and derives a luminance signal and a chrominance signal by adding / subtracting the signal of the previous line and the signal of the current line.

In the case of a separation circuit utilizing frame correlation,
The separation accuracy for still image signals (image signals without motion) is better than that of a separation circuit that uses line correlation. However, when a moving image signal (moving image signal) is separated, the image on the display looks like a tail. This occurs because the interval between pixels for calculation is as long as one frame. In order to compensate for this drawback, Y using line correlation is used.
A / C separation circuit is prepared, and when a moving image signal arrives, it is switched to the Y / C separation circuit based on the line correlation. This technology is, for example, literature TV technology '91 2
It is described on pages 59 and 60 of the monthly issue.

However, this three-dimensional Y / C separation circuit system can obtain good operation when processing a signal in which S / N is good and unnecessary noise is not mixed,
For example, in satellite (BS) broadcasting, when it is raining heavily,
There are many malfunctions in the determination of moving images and still images, and frame correlation Y
/ C separation and line-correlation Y / C separation are not properly switched, and the image quality is degraded. In BS broadcasting,
In the case of heavy rain, the C / N may be extremely deteriorated and impulse noise may occur on the screen. In such a case, the motion detection circuit that determines the motion of the image will erroneously determine almost all as a moving image. Then, the Y / C separation operation shifts to the line correlation Y / C separation even though the still image signal is input, and the Y / C separation operation is incompatible. This mismatch and impulse noise also overlap, making the screen very hard to see.

Since the line correlation Y / C separation is a method of extracting a chroma band component by addition processing and extracting it as a color signal, and subtracting this color signal from an original signal to extract a luminance signal, The band is narrower than the correlation Y / C separation, the S / N improvement effect is low, and the resolution of the still image portion deteriorates. Further, for example, when receiving a signal with a poor S / N (weak electric field of ground wave), it is often erroneously determined as a moving image.

[0006]

As described above, according to the system in which the frame correlation Y / C separation and the line correlation Y / C separation are combined and both separation functions are switched according to the still image and the moving image, The image / video judgment function will have a great impact on the system. If it is a conventional device,
When the electric field of BS broadcasting is weakened and the C / N is lowered to generate impulse noise on the screen, the input signal is often erroneously determined as a moving image, and the image quality is often deteriorated.

Therefore, the present invention provides a video signal processing circuit capable of reducing errors in moving image determination even when the C / N ratio is lowered, making the impulse noise and the like inconspicuous and improving the S / N ratio. The purpose is to provide.

[0008]

SUMMARY OF THE INVENTION The present invention uses the line correlation between two lines of an input video signal having n lines (n; 1, 2, 3, ...) Difference to color the input video signal. A first separation circuit for separating and deriving a signal and a luminance signal, and m frames (m; 1, 2,
3, ...) A second separation circuit for separating and deriving the input video signal into a chrominance signal and a luminance signal by utilizing frame correlation between two frames having a difference, and detecting a motion of an image of the input video signal. A motion detection means for controlling the mixing ratio of the outputs of the first and second separation circuits so that the output of the first separation circuit increases as the motion detection signal indicates the degree of motion amount determination. A means for detecting the C / N level or the S / N level of the video signal, and consequently suppressing the sensitivity of the motion determination output characteristic of the motion detection signal of the motion detecting means as the level decreases. is there.

[0009]

By the above means, when the C / N is lowered, it becomes difficult to shift to the Y / C separation operation for moving image processing, the rate of erroneous determination is reduced compared to the conventional case, and the image quality is deteriorated. Is less.

[0010]

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

FIG. 1 shows an embodiment of the present invention. A high frequency signal is introduced to the input terminal 10 from the antenna. The terminal 10 is connected to the BS tuner 11. The baseband satellite broadcast video signal demodulated by the BS tuner 11 is input to an automatic gain control circuit 12 and subjected to gain control, and then input to a low pass filter (LPF) 13 and a band pass filter (BPF) 14. To be done. Low pass filter 1
3 is for removing an unnecessary component separated from the baseband band. The bandpass filter 14 is for extracting a noise (FM triangular noise) component near 9 MHz away from the baseband.

The noise component extracted by the band-pass filter 14 is input to the peak detection circuit 15 for peak detection and output as a set value control signal. The set value control signal is used for comparison of motion detection signals, as will be described later. The level of this set value control signal represents the C / N level of the input video signal.

On the other hand, the video signal output from the low pass filter 13 is input to the Y / C separation section 100. Y
The / C separation unit 100 includes a line correlation Y / C separation unit and a frame correlation Y / C separation unit.

The line correlation Y / C separation unit will be described. The output terminal of the low-pass filter 13 is connected to a 1-line delay device 21 and a 3-line logical filter 23 having a delay amount of 1 line. 1 line delay device 21
Is further supplied to the 1-line delay device 22 and also input to the 3-line logical filter 23. The output of the 1-line delay device 22 is also input to the 3-line logical filter 23. The moving image color signal derived from the 3-line logical filter 23 is a band pass filter (BPF) 2
4 and is input to the adaptive processing circuit 27. Further, the moving image color signal derived from the 3-line logical filter 23 is passed through the horizontal logical filter 25 and the subtractor 26.
Entered in. The subtractor 26 subtracts the moving image color signal from the output signal of the 1-line delay unit 21,
The output of the adaptive processing circuit 2 is derived as a moving image luminance signal.
Input to 7.

The frame correlation Y / C separation unit will be described. The output of the 1-line delay unit 21 is the frame memory 3
1, the subtractor 33, and the subtractor 34. The output delayed by one frame in the frame memory 31 is further input to the frame memory 32 and the subtractor 32. The still image color signal is derived from the subtractor 33 by the correlation between the frames,
It is taken out through a band pass filter (BPF) 35. The still image color signal is input to the adaptive processing circuit 27. In the subtractor 34, the still image color signal is subtracted from the output of the 1-line delay device 21, and the still image luminance signal is derived and input to the adaptive processing circuit 27.

In the subtractor 36, the subtraction processing of the signals for two frames is performed, and the difference signal is input to the motion detection circuit 27. Further, the motion detection circuit 37 is also supplied with a difference signal between signals for one frame. Motion detection circuit 37
Means that the difference signal between one frame represents the motion related to the luminance signal, and the difference signal between the two frames represents the motion related to the entire band. The motion detection circuit 37 determines both difference signals by a logic circuit or the like, outputs them as motion detection signals, and inputs them to the adaptive processing circuit 27. In the adaptive processing circuit 27, moving-picture-system signals and still-picture-system signals are respectively passed through coefficient units and combined. In this case, the gains of the coefficient units are controlled in opposite directions according to the motion detection signal. When the image movement is large, the gain of the moving image counter is large and the gain of the still image counter is small.

FIG. 2A shows an example inside the adaptive processing circuit 27. The moving image color signal, the moving image luminance signal, the still image luminance signal, and the still image color signal are respectively counters 301, 302,
Gain control is performed at 303 and 304 according to the motion detection signal.
In this case, the gain control of the motion detection signal is supplied to the still image system via the inverter 305 so that the moving image system and the still image system have opposite directions. The moving image and still image luminance signals subjected to the gain control are added by the adder 306, and the moving image and still image color signals are added by the adder 307. The relationship between the set value control signal (representing the C / N level) and the gain control will be described below. That is, coefficient units 311 and 312 are further provided in each line of the motion detection signal (gain control signal) supplied to the moving image system and the still image system. The coefficient units 311 and 312 are gain-controlled by a set value control signal, and their gain control directions are opposite to each other. Now, it is assumed that the relationship between the gains of the coefficient units 301 and 302 of the moving image system and the image movement amount is set to the characteristic shown by the solid line in FIG. However, in this case, the gains of the coefficient units 311 and 312 based on the set value control signal are equal. Next, when the noise increases and the C / N level decreases, the gain of the coefficient unit 311 is decreased and the coefficient unit 31
The gain of 2 will be increased. Then, the motion detection signal increases the gain of the coefficient unit of the still image system and decreases the gain of the coefficient unit of the moving image system. That is, the ratio of shifting to the moving image mode is reduced, and the coefficient units 301 and 30 are reduced.
The relationship of the amount of movement with respect to 2 has a characteristic as shown by a dashed line in FIG.

As a result, in the case of a weak electric field such that C / N is lowered, or when S / N is lowered, the ratio of erroneous determination as a moving image is reduced due to noise contained in the signal, and an appropriate Y / The C separation process can be maintained. In addition, S / N for reducing impulse noise by inter-frame processing
The improvement effect also improves.

In the case of satellite broadcasting, the transmission characteristic is similar to that of light because the frequency of the broadcast wave is high. That is, the electric field strength changes depending on weather conditions such as rain. For this reason, for example, in the case of a summer evening, the electric field is weakened and the C / N is lowered, and the S
/ N deteriorates or impulse noise occurs. In such a case, in the conventional system, there are many malfunctions in motion detection and the image quality may be deteriorated. However, the use of the present invention alleviates this.

The present invention is not limited to the above-described embodiment, and the motion detection characteristic may be changed not only in accordance with the C / N level detection but also in accordance with the S / N detection. Various embodiments of the adaptive processing circuit are possible.

[0021]

As described above, the present invention has a C / N ratio.
It is possible to reduce the error in moving image determination even when it is lowered, and as a result, it is possible to make impulse noise and the like inconspicuous and improve S / N.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a specific example of the adaptive processing circuit of FIG.

[Explanation of symbols]

13 ... Low-pass filter, 14 ... Band-pass filter, 1
5 ... Peak detection circuit, 21, 22 ... 1 line delay device, 2
3 ... 3-line logical comb filter, 24, 35 ... band pass filter, 25 ... horizontal logical filter, 26, 3
3, 34 ... Subtractor, 31, 32 ... Frame memory, 27
... adaptive processing circuit.

Claims (1)

[Claims] 1. An n line of an input video signal (n; 1, 2,
3, ...) A first separation circuit for separating and deriving the input video signal into a chrominance signal and a luminance signal by using a line correlation between two lines having a difference, and m frames (m; 1, 2, 3,
...) A second separation circuit for separating and deriving the input video signal into a chrominance signal and a luminance signal using frame correlation between two frames having a difference; As the detection signal greatly indicates the degree of motion amount determination, the first and second
Motion detection means for controlling the mixing ratio of the output of the first separation circuit so as to increase the output of the first separation circuit, and the C / N level or S / N level of the input video signal is detected, and this level is reduced. Accordingly, the video signal processing circuit is further provided with means for eventually suppressing the sensitivity of the motion determination output characteristic of the motion detection signal of the motion detecting means.