JPH0250578A - Vertical contour emphasizing circuit - Google Patents

Abstract

PURPOSE:To obtain the effect of a contour emphasis even in an enlarged picture by providing a first vertical contour correcting means to extract a high frequency component in a vertical direction and a second vertical contour correcting means to have a filtering characteristics to extract the 1/2 frequency component, and suitably using the characteristic of the vertical contour emphasizing means between the enlarged picture and the other picture. CONSTITUTION:A/C-converted input digital video signals pass through one-line delay circuits 4a to 4d, obtain sampling values at five sampling points on a longitudinal straight line on a screen, and constitute vertical contour correcting circuits 5a and 5b in two systems. The second vertical contour correcting circuit 5b has the filtering characteristic to extract the 1/2 frequency component of the frequencies to be emphasized at the time of the normal picture. Contour correcting signals 106 and 107 are sent to a switching circuit 7 together with a control signal 108, the switching circuit 7 switches the first or second vertical contour correcting signal by the control signal 108, and a vertical correcting signal 109 is added to an original signal 103 to be outputted as a vertical contour emphasis signal 101. Thus, even in the enlarged picture, the effect of the contour emphasis can be obtained in the same way as the normal picture.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a vertical contour emphasizing circuit, and particularly to a vertical contour emphasizing circuit for a television signal sampled in synchronization with a horizontal scanning frequency in a television receiver having an enlargement function. It is related to.

[Conventional technology]

FIG. 2 is a block diagram showing an example of the configuration of a conventional vertical edge enhancement circuit. In FIG. 0, a digital video signal is input to an input terminal 1. In FIG. The input digital video signal 201 is sequentially applied to one-line delay circuits 4e and 4f. The input digital video signal 201 and the outputs 202 and 203 of the 1-line delay circuits 4e and 4f are applied to the vertical contour correction circuit 5C. Output 204 of vertical contour correction circuit 5C
is applied to one input of the adder circuit 6b, and the output 202 of the one-line delay circuit 4e is applied to the other input of the adder circuit 6b. The output 205 of the adder circuit 6b is applied to the output terminal 3 as a vertical contour emphasis signal.

Next, the operation of the vertical contour emphasizing circuit will be explained.

The input digital video signal 201 is sent to a 1-line delay circuit 4e.
. The vertical contour correction circuit 5c has filter characteristics expressed by the following transfer function using 2 transformation.

G(2)=(-1/4)(1-z-')''where z-L represents one line delay.

The above-mentioned filter characteristic is a characteristic for extracting a vertical high-frequency component, that is, a contour signal in a vertical direction.

The output 204 of the vertical contour correction circuit 5C is added to the original signal 202 and output as a vertical contour enhancement signal 205.

(Problems to be Solved by the Invention) In the above conventional technology, there is no problem with normal images, but in the case of enlarged images, the same frequency components as normal are filtered out, even though the frequency has become lower. There was a problem in that the normal contour enhancement effect could not be obtained because of the processing.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a vertical contour enhancement circuit that can perform optimal contour enhancement even on enlarged images.

[Means to solve the problem]

The vertical contour enhancement circuit according to the present invention includes a means for delaying an input digital video signal to simultaneously obtain a sample point of interest to be contour-enhanced and a sample point that forms a line-straight line on the screen, and the values of these sample points. , the first vertical contour correction means extracts and outputs high frequency components in the vertical direction with the same configuration as the conventional one, and the first vertical contour correction means has a ratio of 1/
A second vertical contour correction means having a filter characteristic for extracting two frequency components is provided. The output of the vertical contour correction means is selected to perform vertical contour enhancement.

[Effect]

In the present invention, the characteristics of the vertical edge enhancement circuit are used differently for enlarged images and other images, so that the effect of edge enhancement can be obtained in enlarged images as well as in normal images.

〔Example〕

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

FIG. 1 is a schematic block diagram showing a vertical edge enhancement circuit according to an embodiment of the present invention. In FIG. 0, 1 is an input terminal to which a digital video signal is applied. The input digital video signal 101 is sent to one-line delay circuits 4a and 4b.
, 4c, and 4d sequentially. The first vertical contour correction circuit 5a includes outputs 102, 103, 1 of the one-line delay circuits 4a, 4b, 4c among the outputs of the one-line delay circuit.
04 is given. In addition, a second vertical contour correction circuit 5b
is given an input signal 101 and outputs 103 and 105 of the one-line delay circuits 4b and 4d.

The outputs 106 and 107 of the vertical contour correction circuits 5a and 5b are:
It is applied to the switch circuit 7 together with the control signal 108 input from the input terminal 3. The control signal 108 is a signal that controls the switch circuit 7 depending on whether the input video signal is an enlarged signal or not. The output 109 of the switch circuit 7 is applied as a vertical contour correction signal to one input of the adder circuit 6a, and the output 103 of the one-line delay circuit 4b is applied to the other input of the adder circuit 6a. Addition circuit 6
The output 1)0 of a is sent to the output terminal 2 as a vertical contour emphasis signal.

Next, the operation will be explained.

When the input video signal to the input terminal is an enlarged image (here, it is assumed to be 2 times enlarged), each line before enlargement is scanned twice as shown in FIG. Therefore, when an enlarged image signal is input, in order to achieve the same contour enhancement effect as when a normal signal that has not been enlarged is input, it is necessary to enhance the contour using sample points spaced two lines apart. Filter processing is required to extract a frequency component that is half the frequency that is emphasized in the case of a normal image. This will be explained below using FIG.

The A/D-converted input digital video signal passes through one-line delay circuits 4a, 4b, 4c, and 4d, and sample values at five sample points between lines on the screen are obtained. Two systems of vertical contour correction circuits are constructed based on these sample points.

The first vertical contour correction circuit 5a includes a one-line delay circuit 4a.
, 4b, 4c have filter characteristics expressed by the following transfer function.

F, (z) = (-1/4) (1-z-')"2nd
The vertical contour correction circuit 5b receives the input digital video signal 1.
01 and the outputs 103, 1 of the 1-line delay circuits 4b and 4d.
05, it has filter characteristics expressed by the following transfer function.

Ft (2)= (-1/4) (1z-")"
The contour correction signals 106 and 107 are sent to the switch circuit 7 together with the control signal 108. The control signal 108 is a signal that controls the switch circuit 7 depending on whether the input digital video signal is an enlarged video signal or not. Control signal 1
08, the switch circuit 7 switches the first or second vertical contour correction signal as follows.

Enlarged image: Select the second vertical contour correction signal Other than the above: Select the first vertical contour correction signal The vertical contour correction signal 109 selected and output by the switch circuit 7 is added to the original signal 103 to produce a vertical contour emphasis signal. It is output as 101.

〔Effect of the invention〕

As described above, according to the vertical contour emphasizing circuit according to the present invention, the characteristics of the vertical contour emphasizing circuit are switched between enlarged images and other images. It has the effect of increasing emphasis.

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram showing an example of a vertical edge enhancement circuit according to an embodiment of the present invention, FIG. 2 is a schematic block diagram showing an example of a conventional vertical edge enhancement circuit, and FIG. 3 is an enlarged image from a normal image. FIG. 6 is a diagram showing an arrangement of sample points when scanning is changed to . 1.3 is an input terminal, 2 is an output terminal, 4a to 4d are one-line delay circuits, 5a and 5b are first . In the second vertical contour correction circuit, 6a is an adder circuit, and 7 is a switch circuit. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] (1) Input a digital video signal sampled at a predetermined frequency synchronized with the horizontal scanning frequency so that each sampling point is arranged in a grid on the screen, and emphasize the vertical high frequency components from the digital video signal. A vertical contour enhancement circuit comprising: a delay means for delaying the digital video signal to simultaneously obtain sample values of five sample points across five lines arranged vertically on the screen; and the five samples. When the points are the first, second, third, fourth, and fifth sample points from the top, the sample values of the second, third, and fourth sample points are input, and the high frequency in the vertical direction is a first vertical contour correction means that extracts and outputs a component; and a second vertical contour correction means that receives the sample values of the first, third, and fifth sample points as input, and extracts and outputs a high frequency component in the vertical direction. vertical contour correction means; a switch circuit that switches and outputs the outputs of the first and second vertical contour correction means depending on whether the digital video signal is an enlarged image; 1. A vertical contour emphasizing circuit comprising: an adding circuit that adds a video signal and outputs a vertical contour emphasizing signal.