JPH02200088A - Adaptive type contour correction system - Google Patents

Abstract

PURPOSE:To secure resolution and sharpness even when the high frequency component of a video signal is impaired by detecting the level of a burst signal inserted in the flyback period of the video signal, and adding it on the video signal on a regular line after performing the amplitude correction of a contour signal so that a detected level can be set equal to the level of a reference burst signal. CONSTITUTION:The video signal S is supplied to a Y/C separation circuit 2, a burst level detection circuit 5, and a motion detection circuit 9, respectively. A burst value is detected by the burst level detection circuit 5, and it is supplied to a control signal generation circuit 8, and control signals beta1 and beta2 corresponding to the burst value are generated. At such a case, the control signal beta1 is a signal to correct a carrier chrominance signal C separated by the Y/C separation circuit 2 to a prescribed level, and the control signal beta 2 controls the amplitude of the contour signal selected at a switch 4. In other words, the control signal beta2 corrects and outputs the contour signal to desired amplitude at a multiplier 11. In such a way, it is possible to prevent the resolution from being lowered and to secure the sharpness even when the high frequency component of brightness deteriorates.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a contour correction method for improving the sharpness of one image in a television receiver.

[Conventional technology]

Since the signal frequency of the video signal is 0 to 4.5 MHz, the resolution is limited. Therefore, in televisions, image contours are corrected (emphasized) to increase sharpness, thereby improving psychological resolution. Contour correction in the case of a television receiver is performed by extracting a contour signal from a received and separated luminance image signal and adding the contour signal to the original luminance image signal.

FIG. 3 is an example of a contour correction circuit that satisfies the above requirements.
It mainly consists of a contour signal generation circuit 37 and an adder 38 for adding the contour signal to the original image signal. Of these, the contour signal generation circuit 37 includes the delay elements 31 and 32 and the adder 3.
3, a subtracter 35, an attenuator 34, and a multiplier 36.

First, the received and separated luminance image signal YEN is input to the input terminal 3.
0. Image signal YE from this input terminal 30
N is supplied to the adder 33, and produces a delayed signal Yoz via delay elements 31 and 32 having a delay time τ, which is then supplied to the adder 33.

The adder 33 combines the delayed signal Yoz and the original signal YIN. The synthesized signal is input to an attenuator 34, which attenuates the gain to a level of 172, and outputs a signal Ys.The signal Ys and the output signal Yoz of the delay element 31 are input to a subtracter 35. In the subtracter 35, the delay element 31
The signal Ys is subtracted from the output signal Yos and output. This signal is supplied to a multiplier 36 and multiplied by a multiplication coefficient α to generate a desired image contour signal YAP and output it. Thereafter, by adding the reference main line video signal Yo and the contour signal YAP using an adder 38, it is possible to obtain an image signal Your with a luminance in which the contour portion of the image is emphasized. Then, YOUT is output from the output terminal 39.

In the contour correction configuration described above, the input terminal 30 is connected to the input terminal 30 as shown in FIG.
When a rectangular waveform video signal YiN as shown in FIG.
As shown in (b) and (c), the delayed signal Yol and the delayed signal Yox delayed by the delay times τ and 2τ are obtained. Therefore, the input signal YrN and its delayed signal Yoz are added by the adder 33, and the amplitude is reduced by 1/1 by the attenuator 34.
2, the signal Ys becomes as shown in FIG. 2(d). Then, in the subtracter 35, the signal Ys is subtracted from the delayed signal Yoi and further multiplied by the multiplication coefficient α.
An image contour signal YAP is obtained as shown in FIG.

Therefore, when the contour signal YAP is added to the reference signal Yoz by the adder 38, the output terminal 39 receives the video signal YOU with the contour portion emphasized, as shown in FIG.
T is obtained.

In this case, the delay time τ of delay elements 31 and 32 is set to 70n
When the delay time τ is set to approximately 1 to 540 nS, contour correction in the horizontal direction is performed, and when the delay time τ is set to approximately 1 to 2 horizontal scanning periods, contour correction is performed in the vertical direction. A contour correction circuit using such an algorithm is disclosed in, for example, Japanese Patent Application Laid-Open No.
It is described in No. 115113.

On the other hand, as described in JP-A No. 58-117788, when motion adaptive processing is performed using frame memory or field memory, accurate YC component M (! It is also possible to convert a scanning television signal to progressive scanning and display it, and in this case the horizontal and vertical boost frequencies of still images can be increased.

['fa problem that the invention attempts to solve]

According to the example of the contour correction circuit shown in FIG. 3 above, the contour portion of the video signal is emphasized to improve the sharpness of one image, but in a television receiver, the high frequency components of the video signal are attenuated and received. In this case, either no contour signal is obtained, or only a contour signal with a small amplitude is obtained.8 The amount of contour correction is determined by a trade-off with the noise increment accompanying contour enhancement. However, normally, contour signals with small amplitudes are treated as noise components, and coring processing is performed to stop contour correction. Therefore, if you do not perform contour correction when the amplitude is small, if the high frequency components of the video signal are attenuated due to the reception characteristics of TV radio waves, contour correction will not be performed at all, which may be inconvenient. arise.

On the other hand, motion-adaptive processing using frame memory or field memory, such as motion-adaptive Y/C separation or motion-adaptive scan line interpolation, can improve resolution for still images, but intra-field processing for moving images However, because the frequency to be boosted is high, interference due to aliasing such as dot interference and flicker occurs, and image afterimage phenomenon also occurs, resulting in deterioration of image quality. For this reason, as a method of suppressing the above-mentioned aliasing interference (image quality interference) and afterimage phenomenon, conventionally, depending on the movement of the image,
Measures are taken to reduce the amount of correction of the contour signal.

The purpose of the present invention is to prevent deterioration in the reception characteristics of television radio waves.
To ensure resolution and sharpness by automatically correcting the amplitude of a contour signal even when high frequency components of a video signal are impaired and only a small contour signal is obtained.

Another object of the present invention is to reduce the image quality disturbance and afterimage phenomenon by one amount without reducing the amount of correction for one contour signal in a moving image. , detects the burst signal level inserted in blanking period +1 (1) of the video signal, and performs amplitude correction of the contour signal so that the detected level is equal to the reference burst signal level defined by the broadcasting standard. After that, I decided to add it to the main line video No. 46.

In addition, in order to achieve the other objectives mentioned above, various types of contour signal generation circuits with different boost frequencies are provided in advance, and the characteristics of the contour signal are set so that the boost frequency of the image becomes low when the image motion is large. It was designed to change the evening sky.

[Effect]

The burst signal frequency of the video signal is 3.58 MHz.
, which matches the frequency of the carrier color signal multiplexed with the luminance signal. Since the amplitude of the carrier color signal tends to change depending on the reception conditions, television receivers detect the amplitude value of the burst signal and automatically adjust it so that the burst signal amplitude is always at a predetermined level. . On the other hand, the amplitude value of the burst signal is proportional to the amplitude value of the high frequency component of the luminance signal. Therefore, if the amplitude value of the contour signal follows the amplitude of the burst signal, the operation will be similar to the amplitude correction of the carrier color signal. This causes deterioration in reception characteristics,
Even if the high frequency components of the video signal are attenuated, the contour signal is multiplied to a desired level and added to the main signal, so the resolution and sharpness of the image are maintained.

In the contour signal generation circuit, the boost wave number of the video signal decreases as the amount of image movement increases.

It operates in the direction of switching the characteristics of the contour signal. As a result, in a moving image, the detail part (X frequency component) of the image is not emphasized, and the intermediate frequency component (for example, 1 to 2
MHz) is emphasized, so there is no interference with image quality or an increase in visual afterimage phenomena).

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to Examples.

FIG. 1 is a block diagram of an adaptive contour correction method according to an embodiment of the present invention. 1 is a composite video signal (received signal) S! demodulated to baseband. This is an input terminal for supplying. 2 is a Y/G separation circuit for separating a luminance signal Y and a carrier color signal C from a composite video signal. Reference numeral 3 denotes a contour signal generation circuit for producing various types of contour signal characteristics having different frequencies from the luminance signal Y separated by the Y/C separation circuit 2. 4 is a switch for changing the characteristics of the contour signal generated by the contour signal generation circuit 3; 5 is from the composite video signal,
This is a burst level detection circuit for detecting the amplitude of a burst signal. Reference numeral 6 denotes a control signal generation circuit that generates a control signal β1 for determining the carrier color signal level and a control signal β2 for determining the contour signal level from the detected burst signal level. 7 is a multiplier for correcting the carrier color signal C separated by the Y/C separation circuit 2 to a predetermined level. 8 is a chromaticity processing circuit for color demodulating the carrier color signal into color difference signals I, Q or (RY), (B-Y). 9 is a motion detection circuit for obtaining image motion information M from the composite video signal Sl;
10 is a control signal k for controlling switch 4
This is a threshold circuit that creates 11 is a multiplier for adjusting the level of the contour signal to a desired amplitude.

12 is a delay circuit for matching the phases of the video signal Y to be enhanced with the contour signal YAP, and 13 is an adder that adds the video signal Y4 that has passed through the delay circuit 12 and the contour signal YAP. . 14 is Yo with contour emphasis
Demodulated color difference signal 1. Q or (RY
), (B-Y), the three primary color signals of the image (
This is a matrix circuit that obtains red 2 R2 green: G, blue 2 B).

Composite video signal S1 demodulated to baseband
By adding Y to the input terminal 1, the video signal S1 becomes Y
/C separation circuit 2, burst level detection circuit 5, and motion detection circuit 9, respectively.

First, the video signal SL supplied to the Y/C separation circuit 2 is separated into a luminance signal Y and a carrier color signal C here. The luminance signal Y separated and outputted by the Y/C separation circuit 2 is supplied to a single contour signal generation circuit 3 and a delay circuit 12. @ In the contour signal generation circuit 3, from the input luminance signal Y, a contour signal Yst of the luminance signal Y and a contour signal Ysz having characteristics different from this are generated and outputted.6 The contour signal generation method is based on the conventional technology. In order to generate contour signals with different characteristics, which may be the same as the method described above, it is sufficient to vary the delay time τ of the delay element used when extracting the contour signal, and then to generate contour signals Yst and Yst with different characteristics. Ys2 is added to the changeover switch 4, and Ysx and Y
sz is selected.

Next, regarding the video signal Ss supplied to the motion detection circuit 9, the motion detection circuit 9 performs signal processing to obtain image motion information from the video signal S1.
In the case of motion detection of an SC composite signal, this is because the phase of the carrier color signal multiplexed with the luminance signal is inverted every frame.

By creating a one-frame difference signal of the composite signal and passing the one-frame difference signal through a low-pass filter, the motion signal (
(low-frequency components of motion) are obtained. In addition, if a composite two-frame difference signal is obtained, a motion signal of the entire band can also be obtained. That is, in the motion detection circuit 9, the above-mentioned means are performed. As a result, the extracted motion signal M is supplied to a threshold circuit 10, where a control signal k is obtained for switching the characteristics of the contour signal depending on the amount of motion of the image. When the amount of motion is large, a contour signal with a lower image boost frequency is selected as the contour signal.

When a moving piece is small, a contour signal with a higher boost frequency for one image is selected. Furthermore, since it is necessary to change the delay time of the delay circuit 12 depending on the characteristics of the contour signal, the control signal is also a control signal for switching and correcting the delay time of the delay circuit 12.

Now, regarding the video signal SL supplied to the burst level detection circuit 5, a color burst signal is extracted from the input video signal SL. The burst signal specified by the broadcasting standard has a frequency of 3.58M.
Hz and an amplitude of 0.286 Vp-p. Originally, the burst signal is inserted as a reference signal for determining the hue and saturation when color demodulating the carrier color signal. However, if we pay attention to the amplitude of the burst signal, the amplitude changes not only for each color signal, but also for the high frequency component of the luminance signal (3,58
It also shows the deterioration status of the MHz component. therefore,
The burst level detection circuit wI5 detects a burst value and supplies it to the control signal generation circuit 6, which generates control signals β1 and β2 according to the burst value. Here, the control signal β
1 is the carrier color signal C separated by the Y/C separation circuit 2
The control signal β2 is used to correct the contour signal (Y s s or Y
This is for controlling the amplitude of sz). Therefore, the control signal β1 generated by the control signal generation circuit 6 is supplied to the control terminal of the multiplier 7, and the level is corrected so that the carrier color signal C becomes a predetermined value. The color signal is input to the chromaticity processing circuit 8, where it is color-demodulated into color difference signals I, Q or (RY), (B-Y) signals, which are then supplied to the matrix circuit 14. On the other hand, the control signal β2 generated by the control signal generation circuit 6 is supplied to the control terminal of the multiplier 11 to generate a contour signal (Yst or Ysz).
is corrected to the desired amplitude and output. And multiplier 11
By adding the contour signal YAP output from the adder 13 with the luminance signal Y4 passed through the delay circuit 12,
Contour-enhanced luminance signal Your (=Y4+YA
P) is obtained.

Therefore, when looking at the frequency characteristics of the contour-enhanced luminance signal You out, for example, as shown in curves (a) or (b) in FIG. 2, the characteristics are such that a specific frequency and its vicinity are boosted.

In the same time, the vertical axis shows the gain, while the horizontal axis shows both the horizontal frequency fu [Hzl] and the vertical spatial frequency fu [TV main]. In addition, (a) in the same figure shows the characteristics when a still image or an image has a small amount of movement, and (b) in the same figure shows the characteristics when the amount of motion of the image is small.
This is the characteristic when moving images.

The contour-enhanced or 111 signal Your is the chromaticity-processed color signal [I, Q or (RY), (B-Y)
] are supplied to the matrix circuit 14, where they are converted into video signals of three primary color signals (R, G, B).

It is displayed on the television screen dIJ.

In addition, in this example, the characteristics of the contour signal were explained by switching between two types according to the movement of the image, but it goes without saying that the characteristics of the contour No. By doing so, it is also possible to adaptively switch contour enhancement. Furthermore, if the correction amount of the contour signal YAP increases depending on the reception situation, an increase in noise is expected. Therefore, if a noise reducer is added after the multiplier 11 to the contour signal YAP, The noise components generated can be suppressed.

Therefore, according to this embodiment, even if the high-frequency component of brightness deteriorates due to reception characteristics, amplitude correction is automatically performed, so that it is possible to prevent a decrease in resolution and a lack of sharpness. Further, by switching the boost frequency according to the movement of the image, it is possible to suppress image quality disturbance and visual afterimage phenomenon.

〔Effect of the invention〕

According to the present invention, even when high-frequency components of brightness deteriorate due to reception characteristics, the degree of deterioration can be grasped by detecting the burst signal level, and the amplitude of the contour signal can be adaptively adjusted according to the degree of deterioration. Since automatic adjustment can be performed, it is possible to prevent a decrease in resolution and ensure image sharpness.

Further, by varying the frequency to be boosted depending on the amount of image movement, there is an effect of suppressing image quality disturbance and afterimage phenomenon. In particular, in moving images, the intermediate frequency of the video signal is boosted, giving the image sharpness.

Furthermore, as the amount of contour correction increases, noise also increases, but in combination with a noise reducer, it is possible to suppress the noise associated with contour correction.

[Brief explanation of the drawing]

FIG. 1 is a circuit block diagram showing an embodiment of the adaptive contour correction method of the present invention, FIG. 2 is a frequency characteristic diagram after contour correction that changes according to the amount of image movement obtained by the embodiment of the present invention, Figure 3 is a circuit block diagram of a conventional contour correction device.
FIG. 4 is an operational waveform diagram of FIG. 3. 1... Input terminal, 2... Y/C separation circuit, 3, 37
... Contour signal generation circuit, 4... Changeover switch,
5... Burst level detection circuit, 6... Control signal generation circuit, 7.11, 34.36... Multiplier, 8...
Chromaticity processing circuit, 9...Motion detection circuit, 10...Threshold circuit, 12...Delay circuit, 13, 33, 3
8... Adder. 14... Matrix circuit, 31.32... Delay element, 35... Subtractor, 39... Output terminal, YAP...
- Contour signal, Yoυding...contour emphasis signal. Tomi 1 Figure Vine Figure ■ Figure B Fossa Figure Shima

Claims (1)

[Claims] 1. In a method for performing contour correction on a luminance signal separated from a composite video signal demodulated to baseband, the amplitude value of a burst signal is detected from the composite video signal, and the amplitude value is A control signal is generated according to the brightness signal, and the amplitude of the contour signal extracted from the separated luminance signal is corrected using the control signal so that the burst signal amplitude becomes a predetermined value. An adaptive contour correction method that performs the following. 2. A contour signal generation circuit is provided that generates many types of contour signals with different characteristics from an input image signal, detects the motion of the input image, and generates a control signal proportional to the amount of motion; The adaptive contour correction method according to claim 1, wherein the contour signal generating circuit outputs a contour signal having a characteristic that the boost frequency of the image decreases as the control signal increases. .