JPH0483477A - Outline emphasizing circuit - Google Patents

Abstract

PURPOSE:To execute the outline emphasis of high picture quality by providing this outline emphasizing circuit with an outline component extracting circuit for a video signal and a gain control signal forming circuit for outputting a gain control signal based upon an outline component and multiplying an outline emphasis component outputted from a gain control circuit by a gain control signal. CONSTITUTION:The outline emphasizing circuit is provided with the outline extracting circuit 7 for extracting the outline component of a video signal and the gain control signal forming circuit 8 for outputting a proper gain control signal based upon the outline component and the outline emphasis component of the gain control circuit 6 is multiplied by the gain control signal alpha. Thereby, a ringing component is reduced in an outline peripheral part having large amplitude and a proper outline emphasis value can be applied to other outline part, i.e., a small amplitude outline part. Even when an input signal including a ringing component is inputted, the outline emphasis of high picture quality generating no deterioration in the picture quality can be attained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a video signal contour enhancement circuit (enhancer) in video equipment such as a television receiver.

(Summary of the Invention) The present invention relates to video signal processing, and particularly relates to the use of filters with steep cut-off characteristics to reduce image quality deterioration due to ringing when using band-limited and band-divided transmission signals. High-definition television (HD)
This is an edge enhancement circuit in a receiver such as a television (TV) or an ED television (EDTV).

Conventionally, the high-frequency component of the spatial frequency of the input signal (video signal),
For example, a method has been used in which the second-order differential component of a video signal is adjusted to an appropriate gain and then added to the original input signal. In this method, if a ringing component caused by the filter characteristics of the previous stage or the transmitting side is superimposed on the human input signal, this ringing component is also emphasized at the same time, resulting in image quality deterioration in the periphery of the contour. There was a problem that occurred. The present invention controls the magnitude and sign of an edge enhancement component to be added to a video signal in accordance with the size of the edge in the edge portion of the image and in its surrounding areas, thereby reducing the amount of information contained in the original human input signal. This enables high-quality contour enhancement that does not cause image quality deterioration due to ringing components.

(Prior art) Conventionally, the common method for edge enhancement of a video signal was to extract the spatial high-frequency component of the video signal, give it an appropriate gain, and add it to the original video signal. . This method will be briefly explained below.

FIG. 7 shows a configuration diagram of a conventional edge enhancement circuit.

The edge enhancement circuit 1 includes an edge enhancement component extraction circuit 2, a gain adjuster 3, and an adder 4. Among these, the edge emphasis component extraction circuit 2 is a circuit that extracts the edge emphasis component of the human video signal X, and outputs a signal obtained by inverting the sign of the second-order differential signal of the input video signal X, for example. Further, the gain adjuster 3 gives an appropriate gain to the edge enhancement component.

The adder 4 adds an edge enhancement component to which an appropriate gain has been added to the input video signal X, and outputs an output image signal y with enhanced edges.

(Problem to be Solved by the Invention) However, when using this method to enhance the contours of a signal whose band has been cut off by a filter having a steep cutoff characteristic, ringing is emphasized in the contour portions with large amplitudes. The drawback was that the image quality deteriorated more due to ringing than the improvement in image quality.

Actual video signals, especially signals handled by receivers, are band-limited on the transmitting side. Additionally, HDTV and HD
In a TV system, in order to transmit as much information as possible within a transmittable band, a filter having a steep cutoff characteristic is used as a band limiting filter or a band dividing filter.

For this reason, ringing having a period corresponding to the cut-off frequency is often included around the outline of the demodulated signal in the receiver.

In view of the above-mentioned points, the present invention effectively solves the problems of the prior art, and reduces the ringing component in the periphery of the contour where the amplitude is large, and at the same time reduces the ringing component in other parts, that is, the contour
It is an object of the present invention to provide an edge enhancement circuit that imparts an appropriate amount of edge enhancement to a small-amplitude edge portion, and achieves high-quality edge enhancement that does not cause image quality deterioration even for input signals including ringing. .

(Means for Solving the Problems) In order to achieve such an object, the present invention provides an edge enhancement component extraction circuit that extracts an edge enhancement component of a video signal, and a circuit that provides an appropriate gain to the edge enhancement component. An edge enhancement circuit comprising: a gain adjustment circuit that outputs a control edge enhancement signal; and an addition circuit that adds the control edge enhancement signal to the video signal; and a gain control signal generation circuit that outputs an appropriate gain control signal depending on the component, and is characterized in that the gain control signal is multiplied by the contour emphasis component of the gain adjustment circuit.

(Operation) With such a technical means, the video signal is sent to an outline emphasis circuit that extracts the outline emphasis component of the video signal and adds a control outline emphasis signal obtained by adding an appropriate gain to the outline emphasis component to the video signal. By extracting the contour component of , outputting an appropriate gain control signal based on the contour component, and multiplying the contour enhancement component by the gain m control signal, the ringing component is reduced in the periphery of the contour where the amplitude is large, and at the same time Appropriate edge enhancement can be applied to other parts, i.e., contours and small-amplitude contours, achieving high-quality edge enhancement that does not cause image quality deterioration even for input signals that include ringing. It is possible to do so.

(Example) Next, an example of the present invention will be described in detail based on the drawings.

FIG. 1 shows a schematic configuration diagram of an edge enhancement circuit which is an embodiment of the present invention. In the figure, the edge enhancement circuit 5 includes an edge enhancement component extraction circuit 2, an adder 4, and a gain adjuster (multiplier) 6.
, a contour extraction circuit 7 and a gain control signal generation circuit 8.

The contour emphasis component extraction circuit 2 is a circuit for extracting the contour emphasis component of the input video signal It is a filter.

Further, the contour extraction circuit 7 outputs, for example, the absolute value of the first differential of the human-powered video signal X. This output is input to a gain control signal generation circuit 8, which outputs a gain control signal α corresponding to three regions consisting of the contour portion, the peripheral portion of the contour, and other portions. This control signal α is multiplied by the edge enhancement component extracted by the edge enhancement component extraction circuit 2 in a multiplier 6. The gain-controlled edge enhancement signal β is added to the original input video signal X in an adder 4 to become an output image signal y with edge enhancement.

FIG. 2 shows a frequency characteristic diagram illustrating the contour enhancement operation and ringing suppression operation in FIG. 1.

In the figure, (a) shows the band of input video signal X, and (b) shows the band of input video signal X.
The figure shows an example of the characteristics of the contour emphasis component extraction circuit 2, where the contour emphasis component is the high-frequency component of the original input video signal, and the figure (C) shows an example of the characteristics of the output video signal y, where the gain of the contour emphasis component is α. This is the case. If the phase of the contour enhancement component is the same as that of the original video signal, if the gain control signal α is positive, the high frequency band will be emphasized, and if it is negative, the low frequency band will be suppressed near the upper limit of the band. It shows the characteristics. The repetition period of the ringing is approximately equal to the period of the cutoff frequency rc at the upper limit of the band. Therefore, ringing can be suppressed by the low-pass characteristic shown in FIG.

Therefore, a contour with a large ringing conspicuous amplitude is extracted, and a negative value is assigned only to the surrounding area, and an appropriate contour enhancement signal, that is, a positive value is assigned to the extracted contour and other areas. As a result, edge enhancement is performed while suppressing linking. Furthermore, by changing the gain control signal using such a configuration, it is possible to centrally control the contour enhancement operation and the ringing suppression operation.

FIG. 3 shows a schematic explanatory diagram of the contour extraction circuit in FIG. 1. In the figure, (a) is a configuration diagram thereof, and (b) is a characteristic diagram of coring processing. The contour extraction circuit 7 includes a first-order differentiation circuit 9, an absolute value circuit 10, and a coring processing circuit 1.
1, after obtaining the first derivative of the input video signal X in the first differentiation circuit 9, absolute value processing is performed in the absolute value circuit 10. For extraction, the coring processing circuit 11 outputs only those having a certain amplitude of 6 or more.

FIG. 4 shows a schematic configuration diagram of the gain control signal generation circuit in FIG. 1. The gain control signal generation circuit 8 includes a region expansion circuit 12 and a region determination circuit 13, and includes a contour extraction circuit 7.
The input signal from is branched, one is inputted as is to the area determination circuit 13, and the other is inputted to the area determination circuit 13 via the area waver circuit 12. The area determination circuit 13 uses this input signal to determine whether the image is an outline part, a peripheral part of the outline, or
The remaining portions are divided into three types of regions, and gain control amounts α■, α2. By specifying α3, the gain control signal α is generated. At this time, the gain control amount α2 is negative, and αl and α3 are positive values.

FIG. 5 shows a schematic configuration diagram of the area expanding circuit in FIG. 4. The area expanding circuit 12 has a plurality of delay circuits, four in this embodiment, and a plurality of input signals I, also five.
This circuit outputs the maximum value Q of O, 11, 12, 13, and 14, and obtains an output signal E2 obtained by expanding the input signal (contour extraction (No. 8) El) into five blocks.

FIG. 6 shows an input/output signal diagram of the area determination circuit of FIG. 4.

The input signal to the area determination circuit 13 is shown in (a).

(b) The contour extraction signal E1 and the output E2 of the area enlarging circuit 12 shown in the figure. As shown in FIG. 5, the output E2 of the region expansion circuit 12 is formed from the contour extraction signal E1. (C) The gain control signal α shown in the figure is
l, E2 and set value α1. It is generated from α2°α3 as follows.

That is, the image is classified into one of the contour, contour peripheral, and other three areas based on the contour extraction signal E1 and the area expansion circuit output E2, and then the gain control amount α1 . α2. By assigning α3, the gain control signal α is generated.

As a simple example, the following logical decision can be used.

αL: When El>0 and E2>0, α-α2: El-0 and E2>0, α3: El-
0 and E2-0, by using the gain control signal α obtained in this way, the gain α2 around the contour is set to a value around -1, thereby suppressing ringing around the contour. Gain α1. By setting α3 to a valid positive value, contour enhancement can be performed in the contour portion and other portions where there is no noticeable contour. As a result, it is possible to perform edge enhancement without deteriorating image quality due to an increase in the amplitude of ringing.

Note that the present invention is not limited to the above-mentioned embodiments, and can be implemented in other embodiments by making appropriate design changes. The same applies not only when applied vertically or diagonally.

It is also possible to consider setting a transient portion in which the gain changes continuously in each region.

(Effects of the Invention) As described above, the present invention provides an edge enhancement method that extracts an edge enhancement component of a video signal and adds a control edge enhancement signal obtained by adding an appropriate gain to the edge enhancement component to the video signal. The problems of the prior art can be effectively solved by causing a circuit to extract a contour component of the video signal, outputting an appropriate gain control signal based on the contour component, and multiplying the control signal by the gain control signal. , the ringing component is reduced in the periphery of the contour where the amplitude is large, and at the same time, the ringing component is reduced in the other portions, that is, the contour portion and the contour portion 5 which is suitable for the small amplitude contour portion! By adding J2, it is possible to perform high-quality contour enhancement without causing image quality deterioration even for input signals that include ringing.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of an embodiment of the present invention, and FIG.
3 is a schematic explanatory diagram of the contour extraction circuit in FIG. 1, and FIG. 4 is a schematic explanatory diagram of the gain control signal generation circuit in FIG. 1. , FIG. 5 is a schematic configuration diagram of the area enlarging circuit implemented in FIG. 4, FIG. 6 is an input/output signal diagram of the area determination circuit in FIG. 4, and FIG. 7 is a schematic configuration diagram of a conventional edge enhancement circuit. It is. 2... Contour enhancement component extraction circuit 4... Adder 5... Contour enhancement circuit 6... Multiplier 7... Contour extractor 8... Gain control signal generation circuit 9... Primary Differentiation circuit 10... Absolute value circuit 11.
Coring processing circuit 12...Area expansion circuit 13...Area determination circuit formula Patent attorney Hidekazu Miyoshi Figure 2 (b) Coring processing 11 Figure 3 Gain control signal generation circuit 4 Figure 5

Claims (1)

[Claims] 1) An edge enhancement component extracting circuit that extracts an edge enhancement component of a video signal, a gain adjustment circuit that outputs a control edge enhancement signal with an appropriate gain added to the edge enhancement component, and a gain adjustment circuit that outputs a control edge enhancement signal that adds an appropriate gain to the edge enhancement component; The edge enhancement circuit includes an edge extraction circuit that extracts an edge component of the video signal, and a gain control signal generation circuit that outputs an appropriate gain control signal based on the edge component, An edge enhancement circuit characterized in that the edge enhancement component of the gain adjustment circuit is multiplied by a control signal.